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Sample records for field asymmetric ion

  1. High sensitivity field asymmetric ion mobility spectrometer

    Science.gov (United States)

    Chavarria, Mario A.; Matheoud, Alessandro V.; Marmillod, Philippe; Liu, Youjiang; Kong, Deyi; Brugger, Jürgen; Boero, Giovanni

    2017-03-01

    A high sensitivity field asymmetric ion mobility spectrometer (FAIMS) was designed, fabricated, and tested. The main components of the system are a 10.6 eV UV photoionization source, an ion filter driven by a high voltage/high frequency n-MOS inverter circuit, and a low noise ion detector. The ion filter electronics are capable to generate square waveforms with peak-to-peak voltages up to 1000 V at frequencies up to 1 MHz with adjustable duty cycles. The ion detector current amplifier has a gain up to 1012 V/A with an effective equivalent input noise level down to about 1 fA/Hz1/2 during operation with the ion filter at the maximum voltage and frequency. The FAIMS system was characterized by detecting different standard chemical compounds. Additionally, we investigated the use of a synchronous modulation/demodulation technique to improve the signal-to-noise ratio in FAIMS measurements. In particular, we implemented the modulation of the compensation voltage with the synchronous demodulation of the ion current. The analysis of the measurements at low concentration levels led to an extrapolated limit of detection for acetone of 10 ppt with an averaging time of 1 s.

  2. Field Asymmetric Waveform Ion Mobility Spectrometry Studies of Proteins: Dipole Alignment in Ion Mobility Spectrometry?

    Energy Technology Data Exchange (ETDEWEB)

    Shvartsburg, Alexandre A.; Bryskiewicz, Tadeusz; Purves, Randy; Tang, Keqi; Guevremont, Roger; Smith, Richard D.

    2006-11-02

    Approaches to characterization and separation of ions involving their mobilities in gases were developed since 1960-s. Conventional ion mobility spectrometry (IMS) measures the absolute mobility and the field asymmetric waveform IMS (FAIMS) exploits the difference between mobilities at high and low electric fields. However, all previous work was based on the orientationally averaged cross-sections Ωavg between ions and buffer gas molecules. Virtually all large ions are electric dipoles that will be oriented by a sufficiently strong electric field. At typical FAIMS conditions, that must happen for dipole moments > ~400 Debye, found for many macroions including most proteins above ~30 kDa. Mobilities of aligned dipoles depend on directional cross-sections Ωdir (rather than Ωavg), which should have a major effect on FAIMS separation parameters. Here we study the FAIMS behavior of ESI-generated ions for ten proteins up to ~70 kDa. Those above 29 kDa exhibit a strong increase of mobility at high field, which is consistent with predicted ion dipole alignment. This effect expands the FAIMS peak capacity by an order of magnitude, allowing separation of up to ~102 distinct protein conformers and revealing information about Ωdir and ion dipole moment that is of potential utility for structural characterization. Possible means to extend the dipole alignment to smaller ions are discussed.

  3. Isotope separation using high-field asymmetric waveform ion mobility spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Barnett, David A.; Purves, Randy W.; Guevremont, Roger E-mail: roger.guevremont@nrc.ca

    2000-08-01

    A new apparatus for gas-phase separation of stable elemental isotopes at atmospheric pressure is described. A gaseous mixture of chloride isotopes was generated using electrospray ionization and introduced into the analyzer region of a high-field asymmetric waveform ion mobility spectrometer (FAIMS). The ion current exiting the FAIMS was sampled into a quadrupole mass spectrometer for isotope identification.

  4. Separation and identification of isomeric glycopeptides by high field asymmetric waveform ion mobility spectrometry.

    Science.gov (United States)

    Creese, Andrew J; Cooper, Helen J

    2012-03-01

    The analysis of intact glycopeptides by mass spectrometry is challenging due to the numerous possibilities for isomerization, both within the attached glycan and the location of the modification on the peptide backbone. Here, we demonstrate that high field asymmetric wave ion mobility spectrometry (FAIMS), also known as differential ion mobility, is able to separate isomeric O-linked glycopeptides that have identical sequences but differing sites of glycosylation. Two glycopeptides from the glycoprotein mucin 5AC, GT(GalNAc)TPSPVPTTSTTSAP and GTTPSPVPTTST(GalNAc)TSAP (where GalNAc is O-linked N-acetylgalactosamine), were shown to coelute following reversed-phase liquid chromatography. However, FAIMS analysis of the glycopeptides revealed that the compensation voltage ranges in which the peptides were transmitted differed. Thus, it is possible at certain compensation voltages to completely separate the glycopeptides. Separation of the glycopeptides was confirmed by unique reporter ions produced by supplemental activation electron transfer dissociation mass spectrometry. These fragments also enable localization of the site of glycosylation. The results suggest that glycan position plays a key role in determining gas-phase glycopeptide structure and have implications for the application of FAIMS in glycoproteomics.

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

    Science.gov (United States)

    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.

  6. Asymmetrical field emitter

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  8. High-field asymmetric waveform ion mobility spectrometry with solvent vapor addition: a potential greener bioanalytical technique.

    Science.gov (United States)

    Tsai, Chia-Wei; Yost, Richard A; Garrett, Timothy J

    2012-06-01

    Green chemistry is a way to avoid threats to human health and the environment in chemical processes, including analytical methodology. According to the 12 principles provided by ACS Green Chemistry Institute, first described by Anastas and Warner, prevention of waste generation should be first considered as an alternative to ways of treating waste. Therefore, analytical techniques that may reduce solvent waste are of great interest towards greener analysis. High-field asymmetric waveform ion mobility spectrometry (FAIMS) utilizes electrical fields to achieve separation, post an ionization source, and could provide an alternative method for separation and reduce solvent use in comparison with traditional HPLC methodologies. In this article, the operational principles and developments of FAIMS will be discussed, including the advantages of adding solvent vapor to the carrier gas. In addition, applications and challenges of implementing FAIMS technology will also be discussed.

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

    Science.gov (United States)

    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.

  10. Detection of Potato Storage Disease via Gas Analysis: A Pilot Study Using Field Asymmetric Ion Mobility Spectrometry

    Directory of Open Access Journals (Sweden)

    Massimo Rutolo

    2014-08-01

    Full Text Available 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.

  11. High-field asymmetric waveform ion mobility spectrometry for determining the location of in-source collision-induced dissociation in electrospray ionization mass spectrometry.

    Science.gov (United States)

    Xia, Yuan-Qing; Jemal, Mohammed

    2009-09-15

    The understanding and control of the in-source collision-induced dissociation (CID) of analytes is important for the accurate LC-MS/MS quantitation of drugs and metabolites in biological samples. Accordingly, it was of interest to us to establish whether such in-source CID takes place after and/or before the orifice of an electrospray ionization (ESI) mass spectrometer. A high-field asymmetric waveform ion mobility spectrometry (FAIMS) system that is physically located between the sprayer and the orifice of a mass spectrometer can serve as an ion filter to control ions entering the orifice of the mass spectrometer. In such a configuration, FAIMS could conceivably be used to determine if the in-source CID of an analyte occurs after and/or before the mass spectrometer orifice. We demonstrated this capability of FAIMS using ifetroban acylglucuronide metabolite as a model compound. Under the conditions used, the results showed that the in-source CID conversion of the acylglucuronide metabolite to its parent drug ifetroban occurred almost entirely after the orifice of the mass spectrometer, with the conversion upstream of the orifice accounting for only 5.6% of the conversion. Under the circumstance, the term "post-orifice CID" rather than "in-source CID" may be more appropriate in describing such a dissociation occurring in the front end of a mass spectrometer.

  12. Determination of melamine in milk and dairy products by microchip-based high-field asymmetric ion mobility spectrometry combined with solid-phase extraction.

    Science.gov (United States)

    Zhao, Wei-jun; Wang, Yonghuan; Li, Juan; Li, Ling-feng; Wang, Qi; Han, Ke; Zhang, Yuang; Li, Xin; Li, Peng; Luo, Jikui; Wang, Xiaozhi

    2015-12-01

    This article presents a method for sensitive, fast and quantitative determination of melamine in milk and dairy products using high-field asymmetric ion mobility spectrometry (FAIMS). The solid-phase extraction (SPE) technology was used for purification after the sample was extracted by organic solvents, and followed by the analysis of FAIMS. The measurement parameters and variables that affect the FAIMS detection have been investigated, and optimum conditions have been obtained as follows: the carrier gas flow rate is 1.6 L min(-1), the headspace sampler temperature is 150 °C, the pressure is 1 atm, and the humidity is 2.0 g m(-3). The results showed that the SPE-FAIMS method can detect melamine in samples with a concentration down to 0.1 mg kg(-1). The ion intensity has a linear relationship with melamine concentration in the range from 0.3 mg L(-1) to 25 mg L(-1), with a good linearity of 0.9975. The limits of detection (LOD) and limits of quantification (LOQ) are 0.1 mg kg(-1) and 0.3 mg kg(-1) in milk and dairy products, respectively, and the relative standard deviation is less than 8.0%. The results demonstrated that FAIMS has great potential as a powerful tool for food analysis and safety inspection.

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

    Science.gov (United States)

    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.

  14. New electric field in asymmetric magnetic reconnection.

    Science.gov (United States)

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

    2013-09-27

    We present a theory and numerical evidence for the existence of a previously unexplored in-plane electric field in collisionless asymmetric magnetic reconnection. This electric field, dubbed the "Larmor electric field," is associated with finite Larmor radius effects and is distinct from the known Hall electric field. Potentially, it could be an important indicator for the upcoming Magnetospheric Multiscale mission to locate reconnection sites as we expect it to appear on the magnetospheric side, pointing earthward, at the dayside magnetopause reconnection site.

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

    Directory of Open Access Journals (Sweden)

    Nihar R. Pradhan

    2016-01-01

    Full Text Available 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.

  16. Magnetic Field and Force Calculations for ATLAS Asymmetrical Structure

    CERN Document Server

    Nessi, Marzio

    2001-01-01

    Magnetic field distortion in the assymetrical ATLAS structure are calculated. Magnetic forces in the system are estimated. 3D magnetic field simulation by the Opera3D code for symmetrical and asymmetrical systems is used.

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

    Science.gov (United States)

    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.

  18. The experimental study of acoustic field in an asymmetric borehole

    Institute of Scientific and Technical Information of China (English)

    LINWeijun; ZHANGChengyu; ZHANGHailan; WANGXiuming

    2003-01-01

    The acoustic field in an asymmetric borehole was investigated by recording and comparing the waveforms with different offset in both axial symmetric borehole and axial asymmetric borehole. The two-dimensional spectrum in wave-number and frequency domain was also calculated and compared with the result of numeric simulation with 2.5-D finite difference method, and a consistent result was obtained. This work provides an accurate verification of our investigation of asymmetric borehole with 2.5-D finite difference method.

  19. Estimation of electric conductivity of the quark gluon plasma via asymmetric heavy-ion collisions

    CERN Document Server

    Hirono, Yuji; Hirano, Tetsufumi

    2012-01-01

    We show that in asymmetric heavy-ion collisions, especially off-central Cu+Au collisions, a sizable strength of electric field directed from Au nucleus to Cu nucleus is generated in the overlapping region, because of the difference in the number of electric charges between the two nuclei. This electric field would induce an electric current in the matter created after the collision, which result in a dipole deformation of the charge distribution. The directed flow parameters $v_1^{\\pm}$ of charged particles turn out to be sensitive to the charge dipole and provide us with information about electric conductivity of the quark gluon plasma.

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

    Science.gov (United States)

    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).

  1. Vinylimidazole-Based Asymmetric Ion Pair Comonomers: Synthesis, Polymerization Studies and Formation of Ionically Crosslinked PMMA

    NARCIS (Netherlands)

    Jana, S.; Vasantha, V.A.; Stubbs, L.P.; Parthiban, A.; Vancso, G.J.

    2013-01-01

    Vinylimidazole-based asymmetric ion pair comonomers (IPCs) which are free from nonpolymerizable counter ions have been synthesized, characterized and polymerized by free radical polymerization (FRP), atom transfer radical polymerization (ATRP), and reversible addition-fragmentation chain transfer (R

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

    Science.gov (United States)

    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

  3. Scaling of triple differential cross-sections for asymmetric (, 2) process on helium isoelectronic ions by fast electrons

    Indian Academy of Sciences (India)

    M K Srivastava

    2005-01-01

    A simple scaling law is obtained for asymmetric (, 2) process on helium isoelectronic ions by fast electrons. It is based on treating the targets as having one active electron moving in the effective Coulomb field of the atomic core with an effective charge ' = − 5/8. This effective charge is also used in the description of the scattered and ejected electrons. The model has been tested against other available (, 2) results on helium in asymmetric geometry. The scaling law is found to work reasonably well for fast incident electrons and becomes increasingly accurate as target increases.

  4. Asymmetric ion track nanopores for sensor technology. Reconstruction of pore profile from conductometric measurements

    Science.gov (United States)

    Apel, Pavel Yu; Blonskaya, Irina V.; Orelovitch, Oleg L.; Sartowska, Bozena A.; Spohr, Reimar

    2012-06-01

    We reconstruct the profile of asymmetric ion track nanopores from an algorithm developed for conductometric measurements of symmetric nanopores. The validity of the reconstruction is supported by FESEM observations. Our analysis reveals that asymmetric pores fabricated by one-sided etching are funnel-like and not conical. The analysis provides the constriction diameter and the pore profile as a function of etching time. The reconstruction of the pore profile defines the starting conditions of asymmetric nanopores at breakthrough. The deviation from the conical shape is most pronounced at the pore tip. This critical zone dominates transport properties relevant to ion conductance, selectivity, current rectification, resistive pulse sensing and biosensors. The classical cone approximation used until now underestimates the tip diameter by a factor of two. As transport processes in nanopores depend in a highly nonlinear way on the constriction diameter the presented reconstruction must be taken into account when studying ionic and molecular transport processes in asymmetric pores.

  5. Population Mixing in Asymmetric Magnetic Reconnection with a Guide Field.

    Science.gov (United States)

    Hesse, M; Chen, L J; Liu, Y-H; Bessho, N; Burch, J L

    2017-04-07

    We investigate how population mixing leads to structured electron distribution functions in asymmetric guide-field magnetic reconnection based on particle-in-cell simulations. The change of magnetic connectivity patches populations from different inflow regions to form multicomponent distributions in the exhaust, illustrating the direct consequence of the breaking and rejoining of magnetic flux tubes. Finite Larmor radius (FLR) effects of electrons accelerated by the perpendicular electric fields result in crescent-type nongyrotropic distributions. A new type of nongyrotropy is found to be caused by the combined effects of the FLR and velocity dispersion of electrons accelerated by the parallel electric field. The patching together of populations and the effects of acceleration and the FLR form the first steps of mixing in the exhaust and separatrix regions.

  6. Asymmetric field-aligned currents in the conjugate hemispheres

    Science.gov (United States)

    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.

  7. Intrinsic potential of cell membranes: opposite effects of lipid transmembrane asymmetry and asymmetric salt ion distribution

    DEFF Research Database (Denmark)

    Gurtovenko, Andrey A; Vattulainen, Ilpo

    2009-01-01

    Using atomic-scale molecular dynamics simulations, we consider the intrinsic cell membrane potential that is found to originate from a subtle interplay between lipid transmembrane asymmetry and the asymmetric distribution of monovalent salt ions on the two sides of the cell membrane. It turns out......Cl saline solution and the PE leaflet is exposed to KCl, the outcome is that the effects of asymmetric lipid and salt ion distributions essentially cancel one another almost completely. Overall, our study highlights the complex nature of the intrinsic potential of cell membranes under physiological...

  8. Analysis of liposomes using asymmetrical flow field-flow fractionation

    DEFF Research Database (Denmark)

    Kuntsche, Judith; Decker, Christiane; Fahr, Alfred

    2012-01-01

    Liposomes composed of dipalmitoylphosphatidylcholine and dipalmitoylphosphatidylglycerol were analyzed by asymmetrical flow field-flow fractionation coupled with multi-angle laser light scattering. In addition to evaluation of fractionation conditions (flow conditions, sample mass, carrier liquid......), radiolabeled drug-loaded liposomes were used to determine the liposome recovery and a potential loss of incorporated drug during fractionation. Neither sample concentration nor the cross-flow gradient distinctly affected the size results but at very low sample concentration (injected mass 5 μg) the fraction...... of larger vesicles was underestimated. Imbalance in the osmolality between the inner and outer aqueous phase resulted in liposome swelling after dilution in hypoosmotic carrier liquids. In contrast, liposome shrinking under hyperosmotic conditions was barely visible. The liposomes themselves eluted...

  9. Indexes of Indoor Thermal Environment with Asymmetrical Radiant Field

    Institute of Scientific and Technical Information of China (English)

    钟珂; 刘加平; 亢燕铭

    2004-01-01

    The main features of top-floor rooms with natural ventilation are identified by investigating indoor thermal environment in summer season. One is high indoor air temperature, for this reason the indoor climate is far beyond the thermal comfort standard; the other is the inhomogeneous temperature distribution of the inner wall surfaces, and high temperature of the inner surface of the roof causes much scorching to the head of occupant. This is the characteristic of such rooms.Both features mentioned above should be considered comprehensively for thc evaluation of indoor thermal environment of the top-floor rooms with asymmetric radiant field. In order to characterize the indoor thermal environment of the rooms, the heat stress index, HSI and radiant heat flux reaching human head, QR should be introduced simultaneously as thermal indexes for the indoor climate evaluation. The application of the indexes to a topfloor room is presented and analyzed.

  10. Effects of a Guide Field on the Larmor Electric Field and Upstream Electron Temperature Anisotropy in Collisionless Asymmetric Magnetic Reconnection

    Science.gov (United States)

    Ek-In, Surapat; Malakit, Kittipat; Ruffolo, David; Shay, Michael A.; Cassak, Paul A.

    2017-08-01

    We perform the first study of the properties of the Larmor electric field (LEF) in collisionless asymmetric magnetic reconnection in the presence of an out-of-plane (guide) magnetic field for different sets of representative upstream parameters at Earth’s dayside magnetopause with an ion temperature greater than the electron temperature (the ion-to-electron temperature ratio fixed at 2) using two-dimensional particle-in-cell simulations. We show that the LEF does persist in the presence of a guide field. We study how the LEF thickness and strength change as a function of guide field and the magnetospheric temperature and reconnecting magnetic field strength. We find that the thickness of the LEF structure decreases, while its magnitude increases when a guide field is added to the reconnecting magnetic field. The added guide field makes the Larmor radius smaller, so the scaling with the magnetospheric ion Larmor radius is similar to that reported for the case without a guide field. Note, however, that the physics causing the LEF is not well understood, so future work in other parameter regimes is needed to fully predict the LEF for arbitrary conditions. We also find that a previously reported upstream electron temperature anisotropy arises in the vicinity of the LEF region both with and without a guide field. We argue that the generation of the anisotropy is linked to the existence of the LEF. The LEF can be used in combination with the electron temperature anisotropy as a signature to effectively identify dayside reconnection sites in observations.

  11. Sodium chlorite as an efficient oxidant and hydroxy ion pump in osmium-catalyzed asymmetric dihydroxylation.

    Science.gov (United States)

    Junttila, Mikko H; Hormi, Osmo E O

    2004-07-09

    Sodium chlorite is an efficient stoichiometric oxidant in Sharpless asymmetric dihydroxylation. One sodium chlorite provides the reaction with the stoichiometric number of electrons and hydroxide ions needed to dihydroxylate two olefins without the consumption of any additional base. 100% conversion in sodium chlorite asymmetric dihydroxylation of styrene was achieved twice as fast as in the established Sharpless K(3)[Fe(CN)(6)] dihydroxylation. Even internal olefins were dihydroxylated fast with sodium chlorite without hydrolysis aids. Eight olefins were dihydroxylated to corresponding vicinal diols with yields and ees as good as those reported in the literature for other similar processes.

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

    Science.gov (United States)

    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.

  13. Directed Orientation of Asymmetric Composite Dumbbells by Electric Field Induced Assembly

    NARCIS (Netherlands)

    Nagao, D.; Sugimoto, M.; Okada, A.; Ishii, H.; Konno, M.; Imhof, A.; van Blaaderen, A.

    2012-01-01

    Assembly and directed orientation of anisotropic particles with an external ac electric field in a range from 1 kHz to 2 MHz were studied for asymmetric composite dumbbells incorporating a silica, titania, or titania/silica (titania:silica = 75:25 vol %) sphere. The asymmetric composite dumbbells,

  14. Directed Orientation of Asymmetric Composite Dumbbells by Electric Field Induced Assembly

    NARCIS (Netherlands)

    Nagao, D.; Sugimoto, M.; Okada, A.; Ishii, H.; Konno, M.; Imhof, A.; van Blaaderen, A.

    2012-01-01

    Assembly and directed orientation of anisotropic particles with an external ac electric field in a range from 1 kHz to 2 MHz were studied for asymmetric composite dumbbells incorporating a silica, titania, or titania/silica (titania:silica = 75:25 vol %) sphere. The asymmetric composite dumbbells, w

  15. Attraction between neutral dielectrics mediated by multivalent ions in an asymmetric ionic fluid

    Science.gov (United States)

    Kanduč, Matej; Naji, Ali; Forsman, Jan; Podgornik, Rudolf

    2012-11-01

    We study the interaction between two neutral plane-parallel dielectric bodies in the presence of a highly asymmetric ionic fluid, containing multivalent as well as monovalent (salt) ions. Image charge interactions, due to dielectric discontinuities at the boundaries, as well as effects from ion confinement in the slit region between the surfaces are taken fully into account, leading to image-generated depletion attraction, ion correlation attraction, and steric-like repulsive interactions. We investigate these effects by employing a combination of Monte Carlo simulation methods, including explicit-ion simulations (where all electrostatic interactions are simulated explicitly) and implicit-ion simulations (where monovalent ions are replaced by an effective screened electrostatic potential between multivalent ions), as well as an approximate analytical theory. The latter incorporates strong ion-image charge correlations, which develop in the presence of high valency ions in the mixture. We show that the implicit-ion simulations and the proposed analytical theory can describe the explicit simulation results on a qualitative level, while excellent quantitative agreement can be obtained for sufficiently large monovalent salt concentrations. The resultant attractive interaction between the neutral surfaces is shown to be significant, as compared with the usual van der Waals interactions between semi-infinite dielectrics, and can thus play an important role at the nano scale.

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

    Science.gov (United States)

    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.

  17. Tomographic imaging of asymmetric molecular orbitals with a two-color multicycle laser field

    CERN Document Server

    Qin, Meiyan; Zhang, Qingbin; Lu, Peixiang

    2013-01-01

    We theoretically demonstrate a scheme for tomographic reconstruction of asymmetric molecular orbitals based on high-order harmonic generation with a two-color multicycle laser field. It is shown that by adjusting the relative phase of the two fields, the returning electrons can be forced to recollide from one direction for all the orientations of molecules. Thus the reconstruction of the asymmetric orbitals can be carried out with multicycle laser field. This releases the stringent requirement of a single-cycle pulse with a stabilized and controllable carrier-envelop phase for the tomographic imaging of asymmetric molecular orbitals.

  18. 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.

    Science.gov (United States)

    Lyczko, Jadwiga; Beach, Daniel; Gabryelski, Wojciech

    2015-10-01

    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.

  19. The effects of intense laser field and applied electric and magnetic fields on optical properties of an asymmetric quantum well

    Energy Technology Data Exchange (ETDEWEB)

    Restrepo, R.L., E-mail: pfrire@eia.edu.co [Department of Physics, Cumhuriyet University, 58140 Sivas (Turkey); Escuela de Ingeniería de Antioquia-EIA, Envigado (Colombia); Grupo de Materia Condensada-UdeA, Instituto de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia-UdeA, Calle 70 No. 52-21, Medellín (Colombia); Ungan, F.; Kasapoglu, E. [Department of Physics, Cumhuriyet University, 58140 Sivas (Turkey); Mora-Ramos, M.E. [Facultad de Ciencias, Universidad Autonóma del Estado de Morelos, Ave. Universidad 1001, CP 62209, Cuernavaca, Morelos (Mexico); Morales, A.L.; Duque, C.A. [Grupo de Materia Condensada-UdeA, Instituto de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia-UdeA, Calle 70 No. 52-21, Medellín (Colombia)

    2015-01-15

    This paper presents the results of the theoretical study of the effects of non-resonant intense laser field and electric and magnetic fields on the optical properties (the linear and third-order nonlinear refractive index and absorption coefficients) in an asymmetric quantum well. The electric field and intense laser field are applied along the growth direction of the asymmetric quantum well and the magnetic field is oriented perpendicularly. To calculate the energy and the wave functions of the electron in the asymmetric quantum well, the effective mass approximation and the method of envelope wave function are used. The asymmetric quantum well is constructed by using different aluminium concentrations in both right and left barriers. The confinement in the quantum well is changed drastically by either the effect of electric and magnetic fields or by the application of intense laser field. The optical properties are calculated using the compact density matrix approach. The results show that the effect of the intense laser field competes with the effects of the electric and magnetic fields. Consequently, peak position shifts to lower photon energies due to the effect of the intense laser field and it shifts to higher photon energies by the effects of electric and magnetic fields. In general, it is found that the concentration of aluminum, electric and magnetic fields and intense laser field are external agents that modify the optical responses in the asymmetric quantum well.

  20. Fermion localization on asymmetric two-field thick branes

    Energy Technology Data Exchange (ETDEWEB)

    Zhao Zhenhua; Liu Yuxiao; Li Haitao, E-mail: zhaozhh09@lzu.c, E-mail: liuyx@lzu.edu.c, E-mail: liht07@lzu.c [Institute of Theoretical Physics, Lanzhou University, Lanzhou 730000 (China)

    2010-09-21

    In this paper we investigate the localization of fermions on asymmetric thick branes generated by two scalars {phi} and {chi}. In order to trap fermions on the asymmetric branes with kink-like warp factors, the couplings with the background scalars {eta}{Psi}-barF({chi},{phi}){Psi} are introduced, where F({chi}, {phi}) is a function of {phi} and {chi}. We find that the coupling {eta}{Psi}-bar{sub {chi}{phi}{Psi}} does not support the localization of four-dimensional fermions on the branes. While, for the case {eta}{Psi}-bar{sub {chi}{Psi}} +{eta}'{Psi}-bar{sub {phi}{Psi}} , which is the kink-fermion coupling corresponding to one-scalar-generated brane scenarios, the zero mode of left-handed fermions could be trapped on the branes under some conditions.

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

    Science.gov (United States)

    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.

  2. Laser ion source with solenoid field

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  4. Field ion source development for neutron generators

    Science.gov (United States)

    Bargsten Johnson, B.; Schwoebel, P. R.; Holland, C. E.; Resnick, P. J.; Hertz, K. L.; Chichester, D. L.

    2012-01-01

    An ion source based on the principles of electrostatic field desorption is being developed to improve the performance of existing compact neutron generators. The ion source is an array of gated metal tips derived from field electron emitter array microfabrication technology. A comprehensive summary of development and experimental activities is presented. Many structural modifications to the arrays have been incorporated to achieve higher tip operating fields, while lowering fields at the gate electrode to prevent gate field electron emission which initiates electrical breakdown in the array. The latest focus of fabrication activities has been on rounding the gate electrode edge and surrounding the gate electrode with dielectric material. Array testing results have indicated a steady progression of increased array tip operating fields with each new design tested. The latest arrays have consistently achieved fields beyond those required for the onset of deuterium desorption (˜20 V/nm), and have demonstrated the desorption of deuterium at fields up to 36 V/nm. The number of ions desorbed from an array has been quantified, and field desorption of metal tip substrate material from array tips has been observed for the first time. Gas-phase field ionization studies with ˜10,000 tip arrays have achieved deuterium ion currents of ˜50 nA. Neutron production by field ionization has yielded ˜10 2 n/s from ˜1 mm 2 of array area using the deuterium-deuterium fusion reaction at 90 kV.

  5. Field ion source development for neutron generators

    Energy Technology Data Exchange (ETDEWEB)

    Bargsten Johnson, B. [University of New Mexico, Albuquerque, NM 87131 (United States); Schwoebel, P.R., E-mail: schwoebel@chtm.unm.edu [University of New Mexico, Albuquerque, NM 87131 (United States); Holland, C.E. [SRI International, Menlo Park, CA 94025 (United States); Resnick, P.J. [Sandia National Laboratories, Albuquerque, NM 87123 (United States); Hertz, K.L. [Sandia National Laboratories, Livermore, CA 94551 (United States); Chichester, D.L. [Idaho National Laboratory, Idaho Falls, ID 83415 (United States)

    2012-01-21

    An ion source based on the principles of electrostatic field desorption is being developed to improve the performance of existing compact neutron generators. The ion source is an array of gated metal tips derived from field electron emitter array microfabrication technology. A comprehensive summary of development and experimental activities is presented. Many structural modifications to the arrays have been incorporated to achieve higher tip operating fields, while lowering fields at the gate electrode to prevent gate field electron emission which initiates electrical breakdown in the array. The latest focus of fabrication activities has been on rounding the gate electrode edge and surrounding the gate electrode with dielectric material. Array testing results have indicated a steady progression of increased array tip operating fields with each new design tested. The latest arrays have consistently achieved fields beyond those required for the onset of deuterium desorption ({approx}20 V/nm), and have demonstrated the desorption of deuterium at fields up to 36 V/nm. The number of ions desorbed from an array has been quantified, and field desorption of metal tip substrate material from array tips has been observed for the first time. Gas-phase field ionization studies with {approx}10,000 tip arrays have achieved deuterium ion currents of {approx}50 nA. Neutron production by field ionization has yielded {approx}10{sup 2} n/s from {approx}1 mm{sup 2} of array area using the deuterium-deuterium fusion reaction at 90 kV.

  6. Field Ion Source Development for Neutron Generators

    Energy Technology Data Exchange (ETDEWEB)

    B. Bargsten Johnson; P. R. Schwoebel; C. E. Holland; P. J. Resnick; K. L. Hertz; D. L. Chichester

    2012-01-01

    An ion source based on the principles of electrostatic field desorption is being developed to improve the performance of existing compact neutron generators. The ion source is an array of gated metal tips derived from field electron emitter array microfabrication technology. A comprehensive summary of development and experimental activities is presented. Many structural modifications to the arrays have been incorporated to achieve higher tip operating fields, while lowering fields at the gate electrode to prevent gate field electron emission which initiates electrical breakdown in the array. The latest focus of fabrication activities has been on rounding the gate electrode edge and surrounding the gate electrode with dielectric material. Array testing results have indicated a steady progression of increased array tip operating fields with each new design tested. The latest arrays have consistently achieved fields beyond those required for the onset of deuterium desorption ({approx}20 V/nm), and have demonstrated the desorption of deuterium at fields up to 36 V/nm. The number of ions desorbed from an array has been quantified, and field desorption of metal tip substrate material from array tips has been observed for the first time. Gas-phase field ionization studies with {approx}10,000 tip arrays have achieved deuterium ion currents of {approx}50 nA. Neutron production by field ionization has yielded {approx}10{sup 2} n/s from {approx}1 mm{sup 2} of array area using the deuterium-deuterium fusion reaction at 90 kV.

  7. Supercontinuous high harmonic generation from asymmetric molecules in the presence of a terahertz field

    Institute of Scientific and Technical Information of China (English)

    Du Hong-Chuan; Wang Hui-Qiao; Hu Bi-Tao

    2011-01-01

    We have investigated high-order harmonic generation from asymmetric molecules. It is found that supercontinuous high harmonics, which are produced from asymmetric molecules by significantly steering the ionization, are broken down when the electric field of the 5-fs driving laser pulse is increased to 0.16 a.u.The high harmonic generation from asymmetric molecules with the presence of a terahertz field is also investigated. This reveals that the terahertz controlled laser pulse significantly increases the energy difference between photons, emitted from the ejected electrons,in the first and second halves of the optical cycle at the centre of the driving laser pulse. In this way, a 200-eV broadbandsupercontinuum can be produced in the plateau, from which a 60-as pulse with a bandwidth of 60 eV can be directly obtained with a minor post-pulse.

  8. Non-axisymmetric reflectors concentrating radiation from an asymmetric heliostat field onto a circular absorber

    Energy Technology Data Exchange (ETDEWEB)

    Spirkl, W.; Timinger, A.; Muschaweck, J. [Ludwig-Maximilians-Universitaet, Munich (Germany). Sektion Physik; Ries, H. [Paul Scherrer Institute, Villigen (Switzerland); Kribus, A. [Weizmann Institute of Science, Rehovot (Israel). Environmental Sciences and Energy Research Dept.

    1998-07-01

    In solar tower plants, where a rotationally symmetric field of heliostats surrounds the tower, an axisymmetric secondary concentrator such as a compound parabolic concentrator (CPC) or a tailored concentrator or a cone is the obvious choice. For locations at higher latitudes, however, the reflecting area of the heliostats may be used more efficiently if the field of heliostats is located opposite to the sun as seen from the tower. Then the field is asymmetric with regard to the tower. In the case of an asymmetric field, an axisymmetric concentrator necessarily has a concentration significantly lower than the upper limit. Furthermore, the area on the ground from which a tilted axisymmetric concentrator accepts radiation is an ellipse, including also heliostats very distant to the tower producing a large image of the sun. For these reasons we investigate asymmetric secondaries. From the shape of the edge ray reflectors constructed for rays in the central south-north plane we conclude that a skew cone reflector might be appropriate for the field, and optimize its free parameters by means of ray tracing. Asymmetric concentrators may increase the concentration by up to 25% at the same efficiency compared to optimized axisymmetric CPC or cone reflectors. (author)

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

    DEFF Research Database (Denmark)

    Löschner, Katrin; Navratilova, Jana; Legros, Samuel

    2013-01-01

    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 es...

  10. Density dependent hadron field theory for asymmetric nuclear matter and exotic nuclei

    NARCIS (Netherlands)

    Hofmann, F. Keil; Lenske, H.

    2001-01-01

    Published in: Phys. Rev. C 64 (2001) , pp.034314 citations recorded in [Science Citation Index] Abstract: The density dependent relativistic hadron field (DDRH) theory is applied to strongly asymmetric nuclear matter and finite nuclei far off stability. A new set of in-medium meson-nucleon vertices

  11. Characterization of enzymatically synthesized amylopectin analogs via asymmetrical flow field flow fractionation

    NARCIS (Netherlands)

    Ciric, Jelena; Rolland-Sabate, Agnes; Guilois, Sophie; Loos, Katja

    2014-01-01

    Asymmetrical flow field flow fractionation (AF4), when coupled with multi-angle laser light scattering (MALLS), is a very powerful technique for determination of the macromolecular structure of high molar mass (branched) polysaccharides. AF4 is a size fractionation technique just as size exclusion c

  12. Asymmetric flow field-flow fractionation in the field of nanomedicine.

    Science.gov (United States)

    Wagner, Michael; Holzschuh, Stephan; Traeger, Anja; Fahr, Alfred; Schubert, Ulrich S

    2014-06-01

    Asymmetric flow field-flow fractionation (AF4) is a widely used and versatile technique in the family of field-flow fractionations, indicated by a rapidly increasing number of publications. It represents a gentle separation and characterization method, where nonspecific interactions are reduced to a minimum, allows a broad separation range from several nano- up to micrometers and enables a superior characterization of homo- and heterogenic systems. In particular, coupling to multiangle light scattering provides detailed access to sample properties. Information about molar mass, polydispersity, size, shape/conformation, or density can be obtained nearly independent of the used material. In this Perspective, the application and progress of AF4 for (bio)macromolecules and colloids, relevant for "nano" medical and pharmaceutical issues, will be presented. The characterization of different nanosized drug or gene delivery systems, e.g., polymers, nanoparticles, micelles, dendrimers, liposomes, polyplexes, and virus-like-particles (VLP), as well as therapeutic relevant proteins, antibodies, and nanoparticles for diagnostic usage will be discussed. Thereby, the variety of obtained information, the advantages and pitfalls of this emerging technique will be highlighted. Additionally, the influence of different fractionation parameters in the separation process is discussed in detail. Moreover, a comprehensive overview is given, concerning the investigated samples, fractionation parameters as membrane types and buffers used as well as the chosen detectors and the corresponding references. The perspective ends up with an outlook to the future.

  13. Optimization and performance of an optically asymmetrical heliostat field

    Energy Technology Data Exchange (ETDEWEB)

    Romero, M.; Fernandez, V. [CIEMAT, Centro de Investigacion Energica Medioambiental y Technologia, DER (Spain); Sanchez, M. [Commission Europeenne, DG XII, Bruxelles (Belgium)

    1999-03-01

    The recent trend of integrating CRS into hybrid plants with combined cycles is creating a new situation, since the solar field is forced to make use of sites near gas pipelines and industrial areas. Land there becomes a significant portion of plant cost and constraints lead to some particular problems for layout optimization and subsequent optical performance. The COLON SOLAR heliostat field represented a real challenge during the design phase, because of the important restrictions stemming from the available site. Field optimization required adapting the existing codes to the COLON SOLAR site, since the field is not oriented to the North, is narrower than required and presents a number of restrictions associated with industrial pipelines and electrical grids (both aerial and buried) found on the site. Flux distributions on the absorber surface obtained with HELIOS and DELSOL3 demonstrated that in any given situation the centroid shifted about 25 to the East because of the higher number of heliostats to the West. The influence of such peculiarities in the field on design and the minimization of their effect on plant performance are discussed. (authors)

  14. Highly enantioselective asymmetric autocatalysis using chiral ruthenium complex-ion-exchanged synthetic hectorite as a chiral initiator.

    Science.gov (United States)

    Kawasaki, Tsuneomi; Omine, Toshiki; Suzuki, Kenta; Sato, Hisako; Yamagishi, Akihiko; Soai, Kenso

    2009-03-21

    The synthetic hectorite containing intercalated chiral Delta- and Lambda-tris(1,10-phenanthroline)ruthenium(II) ions acts as a heterogeneous chiral catalyst in the enantioselective addition of diisopropylzinc to pyrimidine-5-carbaldehyde to afford, in combination with asymmetric autocatalytic amplification of enantiomeric excess, 5-pyrimidyl alkanol with high enantiomeric excess.

  15. Ion Plasma Responses to External Electromagnetic Fields

    NARCIS (Netherlands)

    Naus, H.W.L.

    2010-01-01

    The response of ion plasmas to external radiation fields is investigated in a quantum mechanical formalism.We focus on the total electric field within the plasma. For general bandpass signals three frequency regions can be distinguished in terms of the plasma frequency. For low frequencies, the exte

  16. How does an asymmetric magnetic field change the vertical structure of a hot accretion flow?

    Science.gov (United States)

    Samadi, M.; Abbassi, S.; Lovelace, R. V. E.

    2017-09-01

    This paper explores the effects of large-scale magnetic fields in hot accretion flows for asymmetric configurations with respect to the equatorial plane. The solutions that we have found show that the large-scale asymmetric magnetic field can significantly affect the dynamics of the flow and also cause notable outflows in the outer parts. Previously, we treated a viscous resistive accreting disc in the presence of an odd symmetric B-field about the equatorial plane. Now, we extend our earlier work by taking into account another configuration of large-scale magnetic field that is no longer symmetric. We provide asymmetric field structures with small deviations from even and odd symmetric B-field. Our results show that the disc's dynamics and appearance become different above and below the equatorial plane. The set of solutions also predicts that even a small deviation in a symmetric field causes the disc to compress on one side and expand on the other. In some cases, our solution represents a very strong outflow from just one side of the disc. Therefore, the solution may potentially explain the origin of one-sided jets in radio galaxies.

  17. Second-harmonic generation in asymmetric quantum dots in the presence of a static magnetic field

    Institute of Scientific and Technical Information of China (English)

    Li Xue-Chao; Wang An-Min; Wang Zhao-Liang; Yang Yang

    2012-01-01

    The second-harmonic generation (SHG) coefficient in an asymmetric quantum dot (QD) with a static magnetic field is theoretically investigated.Within the framework of the effective-mass approximation,we obtain the confined wave functions and energies of electrons in the QD.We also obtain the SHG coefficient by the compact-density-matrix approach and the iterative method.The numerical results for the typical GaAs/AlGaAs QD show that the SHG coefficient depends strongly on the magnitude of magnetic field,parameters of the asymmetric potential and the radius of the QD.The resonant peak shifts with the magnetic field or the radius of the QD changing.

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

    Science.gov (United States)

    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

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

    Energy Technology Data Exchange (ETDEWEB)

    Dorville, Nicolas, E-mail: nicolas.dorville@lpp.polytechnique.fr; Belmont, Gérard; Aunai, Nicolas; Dargent, Jérémy; Rezeau, Laurence [LPP, Ecole Polytechnique, CNRS, UPMC, Université Paris Sud, Palaiseau (France)

    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

  20. Photocatalysis-triggered ion rectification in artificial nanochannels based on chemically modified asymmetric TiO2 nanotubes.

    Science.gov (United States)

    Hu, Ziying; Zhang, Qianqian; Gao, Jun; Liu, Zhaoyue; Zhai, Jin; Jiang, Lei

    2013-04-16

    Ion rectification is one of the important characteristics of biological ion channels. Inspired by the function of biological ion channels, creation of artificial nanochannels that show analogous ion rectification characteristics has attracted a great interest recently. Herein, we demonstrate a new type of artificial solid-state nanochannel with ion rectification characteristics. The creation of artificial nanochannels includes the formation of asymmetric TiO2 nanotubes by electrochemical anodization of Ti metal, followed by chemical modification with octadecyltrimethoxysilane (OTS) molecules. The carboxylic groups are introduced onto the tip side of TiO2 nanotubes via photocatalytic decomposition of OTS molecules by TiO2 photocatalysis under ultraviolet light. When the radius of tip side of TiO2 nanotubular channels is comparable to the thickness of electric double layer, the negatively charged surface in neutral electrolyte in combination with the asymmetric pore geometry contributes to the ion rectification characteristics. Compared with previous artificial nanochannels, our new type of artificial nanochannel is more facile to fabricate and behaves as a diode that rectifies the ion transport, which also shows some other potential applications, such as sensor and separation materials.

  1. Optical absorption in asymmetric double quantum wells driven by two intense terahertz fields

    Institute of Scientific and Technical Information of China (English)

    Wu Hong-Wei; Mi Xian-Wu

    2013-01-01

    Optical absorption is investigated for asymmetric double quantum wells driven by a resonant terahertz field and a varied terahertz field,both polarized along the growth direction.Rich nonlinear dynamics of the replica peak and the Autler-Townes splitting of various dressed states are systematically studied in undoped asymmetric double quantum wells by taking account of multiple factors,such as the frequency of the varied terahertz field and the strength of the resonant terahertz field.Each electron subband splits into two dressed states when the resonant terahertz field is applied in the absence of the varied terahertz field,the optical absorption spectrum shows the first-order Autler-Townes splitting of the electron subbands.When a varied terahertz field is added into the resonant system,the replica peak and the second-order Autler-Townes splitting of the dressed states near the band edge respectively emerge when the varied terahertz field is non-resonant and resonant with these dressed states.Wben the strength of the resonant terahertz field is increased,the first-order Autler-Townes double peaks and the replica peak in the optical absorption spectrum shift with the shifts of the dressed states.The presented results have potential applications in electro-optical devices.

  2. Asymmetry of the ion diffusion region Hall electric and magnetic fields during guide field reconnection: observations and comparison with simulations.

    Science.gov (United States)

    Eastwood, J P; Shay, M A; Phan, T D; Øieroset, M

    2010-05-21

    In situ measurements of magnetic reconnection in the Earth's magnetotail are presented showing that even a moderate guide field (20% of the reconnecting field) considerably distorts ion diffusion region structure. The Hall magnetic and electric fields are asymmetric and shunted away from the current sheet; an appropriately scaled particle-in-cell simulation is found to be in excellent agreement with the data. The results show the importance of correctly accounting for the effects of the magnetic shear when attempting to identify and study magnetic reconnection diffusion regions in nature.

  3. Rotation effect on peristaltic transport of a Jeffrey fluid in an asymmetric channel with gravity field

    Directory of Open Access Journals (Sweden)

    A.M. Abd-Alla

    2016-06-01

    Full Text Available In this paper, the peristaltic flow of a Jeffrey fluid in an asymmetric rotating channel is studied under long wavelength and low Reynolds number assumptions are investigated. Closed form expressions for the pressure gradient, pressure rise, stream function, axial velocity and shear stress on the channel walls have been computed numerically. The effects of the ratio of relaxation to retardation times, time-mean flow, rotation, the phase angle and the gravity field on the pressure gradient, pressure rise, streamline, axial velocity and shear stress are discussed in detail and shown graphically. The results indicate that the effect of the ratio of relaxation to retardation times, time-mean flow, rotation, the phase angle and the gravitational field are very pronounced in the phenomena. Comparison was made with the results obtained in the asymmetric channel and symmetric channel.

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

    Science.gov (United States)

    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.

  5. Asymmetrical flow field-flow fractionation in the study of water-soluble macromolecules

    OpenAIRE

    Yohannes, Gebrenegus

    2007-01-01

    Asymmetrical flow field-flow fractionation (AsFlFFF) was constructed, and its applicability to industrial, biochemical, and pharmaceutical applications was studied. The effect of several parameters, such as pH, ionic strength, temperature and the reactants mixing ratios on the particle sizes, molar masses, and the formation of aggregates of macromolecules was determined by AsFlFFF. In the case of industrial application AsFlFFF proved to be a valuable tool in the characterization of the hydrod...

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

    OpenAIRE

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

    2013-01-01

    Asymmetric flow field-flow fractionation (AF4) 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 ...

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

    Science.gov (United States)

    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.

  8. Investigation of electron localization in harmonic emission from asymmetric molecular ion

    Institute of Scientific and Technical Information of China (English)

    张彩萍; 苗向阳

    2015-01-01

    We theoretically investigate the electron localization around two nuclei in harmonic emission from asymmetric molec-ular ion. The results show that the ionization process of electron localized around one nucleus competes with its transfer process to the other nucleus. By increasing the initial vibrational level, more electrons localized around the nucleus D+tend to transfer to the nucleus He2+so that the ionizations of electrons localized around the nucleus He2+increase. In this case, the difference in harmonic efficiency between HeH2+and HeD2+decreases while the difference in harmonic spectral structure increases. The evident minimum can be observed in the harmonic spectrum of HeH2+ compared with that in the spectral structure of HeD2+, which is due to the strong interference of multiple recombination channels originating from two nuclei. Time-dependent nuclear probability density, electron-nuclear probability density, double-well model, and time-frequency maps are presented to explain the underlying mechanisms.

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

    Science.gov (United States)

    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.

  10. Theoretical description of mixed-field orientation of asymmetric top molecules: a time-dependent study

    CERN Document Server

    Omiste, Juan J

    2016-01-01

    We present a theoretical study of the mixed-field-orientation of asymmetric top molecules in tilted static electric field and non-resonant linearly polarized laser pulse by solving the time-dependent Schr\\"odinger equation. Within this framework, we compute the mixed-field orientation of a state selected molecular beam of benzonitrile (C$_7$H$_5$N) and compare with the experimental observations [J. L. Hansen et al., Phys. Rev. A 83, 023406 (2011)], and with our previous time-independent descriptions [J. J. Omiste et al., Phys. Chem. Chem. Phys. 13, 18815 (2011)]. For an excited rotational state, we investigate the field-dressed dynamics for several field configurations as those used in the mixed-field experiments. The non-adiabatic phenomena and their consequences on the rotational dynamics are analyzed in detail.

  11. Robustness of the filamentation instability for asymmetric plasma shells collision in arbitrarily oriented magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Bret, A. [ETSI Industriales, Universidad de Castilla-La Mancha, 13071 Ciudad Real, Spain and Instituto de Investigaciones Energticas y Aplicaciones Industriales, Campus Universitario de Ciudad Real, 13071 Ciudad Real (Spain)

    2013-10-15

    The filamentation instability triggered when two counter streaming plasma shells overlap appears to be the main mechanism by which collisionless shocks are generated. It has been known for long that a flow aligned magnetic field can completely suppress this instability. In a recent paper [Phys. Plasmas 18, 080706 (2011)], it was demonstrated in two dimensions that for the case of two cold, symmetric, relativistically colliding shells, such cancellation cannot occur if the field is not perfectly aligned. Here, this result is extended to the case of two asymmetric shells. The filamentation instability appears therefore as an increasingly robust mechanism to generate shocks.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  15. On the Electron Agyrotropy during Rapid Asymmetric Magnetic Island Coalescence in Presence of a Guide Field

    CERN Document Server

    Cazzola, Emanuele; Goldman, Martin V; Newman, David L; Markidis, Stefano; Lapenta, Giovanni

    2016-01-01

    We present an analysis of the properties of the electron velocity distribution during island coalescence in asymmetric reconnection with and without guide field. In a previous study, three main domains were identified, in the case without guide field, as X-, D- and M-regions featuring different reconnection evolutions {Cazzola et al. 2015). These regions are also identified here in the case with guide field. We study the departure from isotropic and gyrotropic behavior by means of different robust detection algorithms proposed in the literature. While in the case without guide field these metrics show an overall agreement, when the guide field is present a discrepancy in the agyrotropy within some relevant regions is observed, such as at the separatrices and inside magnetic islands. Moreover, in light of the new observations from the Multiscale MagnetoSpheric mission, an analysis of the electron velocity phase-space in these domains is presented.

  16. Rotational dynamics of an asymmetric top molecule in parallel electric and non-resonant laser fields

    CERN Document Server

    Omiste, Juan J

    2013-01-01

    We present a theoretical study of the rotational dynamics of asymmetry top molecules in parallel electric field and non-resonant linearly polarized laser pulses. The time-dependent Schr\\"odinger equation is solved within the the rigid rotor approximation. Using the benzonitrile molecule as prototype, we investigate the field-dressed dynamics for experimentally accessible field configurations and compare these results to the adiabatic predictions. We show that for an asymmetric top molecule in parallel fields, the formation of the pendular doublets and the avoided crossings between neighboring levels are the two main sources of non-adiabatic effects. We also provide the field parameters under which the adiabatic dynamics would be achieved.

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

    Science.gov (United States)

    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.

  18. Transport of ions and biomolecules through single asymmetric nanopores in polymer films

    Science.gov (United States)

    Schiedt, Birgitta; Healy, Ken; Morrison, Alan P.; Neumann, Reinhard; Siwy, Zuzanna

    2005-07-01

    Single conical nanopores in polymer foils show 'rectifying' diode-like current-voltage (I-V) characteristics, with preferential cation flow in the direction from the narrow to the wide opening [P. Apel, Y.E. Korchev, Z. Siwy, R. Spohr, M. Yoshida, Nucl. Instr. and Meth. B 184 (2001) 337-346, Z. Siwy, D. Dobrev, R. Neumann, C. Trautmann, K. Voss, Appl. Phys. A 76 (2003) 781-785]. To produce single-pore membranes, we irradiated polymer films (polyethylene terephthalate and polyimide) with single heavy ions (using kinetic energies in the GeV range) and subsequently performed asymmetric chemical track-etching. The resulting conical pores had narrow openings of 4-20 nm. The I-V curves of these pores were measured in aqueous KCl solutions of various concentrations and pH values, and it was found that both parameters influence the rectification properties of the pores. For decreasing concentrations, down to 0.1 M, the degree of rectification increases, as predicted by a recently proposed model [Z. Siwy, A. Fulinski, Phys. Rev. Lett. 89 (2002) 198103], however, as the concentration decreases further, the rectification unexpectedly begins to decrease again. We suspect that this is due to conformation changes occurring in the pore. Also, our results have shown that the pores exhibit a non-classical conductance versus electrolyte concentration characteristic, having elevated conductances at low concentrations, for which we propose an explanation based on surface conductivity. Finally, we present an application of the polyimide conical nanopores as single-molecule DNA sensors, with results demonstrating their ability to detect individual plasmid DNA molecules.

  19. Ions in a binary asymmetric dipolar mixture: mole fraction dependent Born energy of solvation and partial solvent polarization structure.

    Science.gov (United States)

    Kashyap, Hemant K; Biswas, Ranjit

    2007-11-14

    Mean spherical approximation (MSA) for electrolyte solution has been extended to investigate the role of partial solvent polarization densities around an ion in a completely asymmetric binary dipolar mixture. The differences in solvent diameters, dipole moments, and ionic size are incorporated systematically within the MSA framework in the present theory for the first time. In addition to the contributions due to difference in dipole moments, the solvent-solvent and ion-solvent size ratios are found to significantly affect the nonideality in binary dipolar mixtures. Subsequently, the theory is used to investigate the role of ion-solvent and solvent-solvent size ratios in determining the nonideality in Born free energy of solvation of a unipositive rigid ion in alcohol-water and dimethyl sulfoxide-acetonitrile mixtures, where the solvent components are represented only by their molecular diameters and dipole moments. Nonideality in Born free energy of solvation in such simplified mixtures is found to be stronger for smaller ions. The slope of the nonideality for smaller alkali metal ions in methanol-water mixture is found to be opposite to that for larger ion, such as quaternary tertiary butyl ammonium ion. For ethanol-water mixtures, the slopes are in the same direction for all the ions studied here. These results are in qualitative agreement with experiments, which is surprising as the present MSA approach does not include the hydrogen bonding and hydrophobic interactions present in the real mixtures. The calculated partial polarization densities around a unipositive ion also show the characteristic deviation from ideality and reveal the microscopic origin of the ion and solvent size dependent preferential solvation. Also, the excess free energy of mixing (in the absence of any ion) for these binary mixtures has been calculated and a good agreement between theory and experiment has been found.

  20. Magnetic Field and Gravity Effects on Peristaltic Transport of a Jeffrey Fluid in an Asymmetric Channel

    Directory of Open Access Journals (Sweden)

    A. M. Abd-Alla

    2014-01-01

    Full Text Available In this paper, the peristaltic flow of a Jeffrey fluid in an asymmetric channel has been investigated. Mathematical modeling is carried out by utilizing long wavelength and low Reynolds number assumptions. Closed form expressions for the pressure gradient, pressure rise, stream function, axial velocity, and shear stress on the channel walls have been computed numerically. Effects of the Hartmann number, the ratio of relaxation to retardation times, time-mean flow, the phase angle and the gravity field on the pressure gradient, pressure rise, streamline, axial velocity, and shear stress are discussed in detail and shown graphically. The results indicate that the effect of Hartmann number, ratio of relaxation to retardation times, time-mean flow, phase angle, and gravity field are very pronounced in the peristaltic transport phenomena. Comparison was made with the results obtained in the presence and absence of magnetic field and gravity field.

  1. Effect of induced magnetic field on peristaltic flow of a micropolar fluid in an asymmetric channel

    CERN Document Server

    Shit, G C; Ng, E Y K; 10.1002/cnm.1397

    2010-01-01

    Of concern in this paper is an investigation of peristaltic transport of a physiological fluid in an asymmetric channel under long wave length and low-Reynolds number assumptions. The flow is assumed to be incompressible, viscous, electrically conducting micropolar fluid and the effect of induced magnetic field is taken into account. Exact analytical solutions obtained for the axial velocity, microrotation component, stream line pattern, magnetic force function, axial-induced magnetic field as well as the current density distribution across the channel. The flow phenomena for the pumping characteristics, trapping and reflux are also investigated. The results presented reveal that the velocity decreases with the increase of magnetic field as well as the coupling parameter. Moreover, the trapping fluid can be eliminated by the application of an external magnetic field. Thus, the study bears the promise of important applications in physiological systems.

  2. Large field of view computed laminography with the asymmetric rotational scanning geometry

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    X-ray computed laminography(CL)is used in the fields of industrial inspection and medical imaging.It can provide the internal structure three-dimensional(3D)information of a region of the objects nondestructively.It is important to the clinical diagnosis and the quality control of flat objects like printed circuit boards,aircraft wings and satellite solar panels.With the restriction that the imaging region must be within the X-ray beam formed by the X-ray source and the detector,the imaging field of view of CL is limited by the size of detector.A new CL method with an asymmetric rotational cone-beam scanning geometry,called large field of view CL,is presented to overcome the existing disadvantage.It can extend the imaging region when the imaging spatial resolution keeps the same as that of the conventional CL.It can also improve the imaging spatial resolution when the imaging region keeps the same as that of the conventional CL.The asymmetric configuration can be achieved by offsetting the detector from the conventional symmetric configuration.It does not,however,require new detectors and X-ray source nor alter the scanning mechanical system.The filtered back-projection(FBP)reconstruction algorithm and the data truncation smoothing functions have been deduced to reconstruct the images directly from the data acquired with this asymmetric configuration.We performed numerical studies and experiments to demonstrate and validate the proposed approach. Results in these studies and experiments confirm that the proposed method can enlarge the imaging region and improve the spatial resolution.The proposed approach may find applications in the CL system with the rotational scanning geometry.

  3. Dose calculation for asymmetric fields and irregular fields with multileaf collimators. Approximation of tissue-maximum ratio and field factor using modified Day`s calculation method

    Energy Technology Data Exchange (ETDEWEB)

    Nakata, Manabu; Okada, Takashi; Komai, Yoshinori; Nohara, Hiroki [Kyoto Univ. (Japan). Hospital

    1996-08-01

    Modern linear accelerators have four independent jaws and multileaf collimators (MLC) of 1 cm width at the isocenter. Asymmetric fields defined by such independent jaws and irregular multileaf collimated fields can be used to match adjacent fields or to spare the spinal cord in external photon beam radiotherapy. We have developed a new approximate algorithm for depth dose calculations at the collimator rotation axis. The program is based on Clarkson`s principle, and uses a more accurate modification of Day`s method for asymmetric fields. Using this method, tissue-maximum ratios (TMR) and field factors of ten kinds of asymmetric fields and ten different irregular multileaf collimated fields were calculated and compared with the measured data for 6 MV and 15 MV photon beams. The dose accuracy with the general A/Pe method was about 3%, however, with the new modified Day`s method, accuracy was within 1.7% for TMR and 1.2% for field factors. The calculated TMR and field factors were found to be in good agreement with measurements for both the 6 MV and 15 MV photon beams. (author)

  4. Dual-Material Surrounding-Gate Metal-Oxide-Semiconductor Field Effect Transistors with Asymmetric Halo

    Institute of Scientific and Technical Information of China (English)

    LI Zun-Chao

    2009-01-01

    Asymmetrical halo and dual-material gate structure are used in the sub-100 nm surrounding-gate metal-oxide-semiconductor field effect transistor (MOSFET) to improve the performance. Using three-region parabolic po-tential distribution and universal boundary condition, analytical surface potential and threshold voltage models of the novel MOSFET are developed based on the solution of Poisson's equation. The performance of the MOS-FET is examined by the analytical models and the 3D numerical device simulator Davinci. It is shown that the novel MOSFET can suppress short channel effect and improve carrier transport efficiency. The derived analytical models agree well with Davinci.

  5. Adiabatic field-free alignment of asymmetric top molecules with an optical centrifuge

    CERN Document Server

    Korobenko, A

    2015-01-01

    We use an optical centrifuge to align asymmetric top $\\mathrm{SO_2}$ molecules by adiabatically spinning their most polarizable O-O axis. The effective centrifugal potential in the rotating frame confines sulfur atoms to the plane of the laser-induced rotation, leading to the planar molecular alignment which persists after the molecules are released from the centrifuge. Periodic appearance of the full three-dimensional alignment, typically observed only with linear and symmetric top molecules, is also detected. Together with strong in-plane centrifugal forces, which bend the molecules by up to 10 degrees, permanent field-free alignment offers new ways of controlling molecules with laser light.

  6. Asymmetric flow field-flow fractionation of superferrimagnetic iron oxide multicore nanoparticles

    DEFF Research Database (Denmark)

    Dutz, Silvio; Kuntsche, Judith; Eberbeck, Dietmar

    2012-01-01

    . This classification was carried out by means of asymmetric flow field-flow fractionation (AF4). A clear increase of the particle size with increasing elution time was confirmed by multi-angle laser light scattering coupled to the AF4 system, dynamic light scattering and Brownian diameters determined...... size distributed MCNP fluid classified by AF4 show a strong correlation between hydrodynamic diameter and magnetic properties. Thus we state that AF4 is a suitable technology for reproducible size dependent classification of magnetic multicore nanoparticles suspended as ferrofluids....

  7. Ground state properties of La isotopes in reflection asymmetric relativistic mean field theory

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The ground state properties of La isotopes are investigated with the reflection asymmetric relativistic mean field(RAS-RMF) model.The calculation results of binding energies and the quadrupole moments are in good agreements with the experiment.The calculation results indicate the change of the quadrupole deformation with the nuclear mass number.The "kink" on the isotope shifts is observed at A = 139 where the neutron number is the magic number N = 82.It is also found that the octupole deformations may exist in the La isotopes with mass number A ~ 145-155.

  8. Ground state properties of La isotopes in reflection asymmetric relativistic mean field theory

    Institute of Scientific and Technical Information of China (English)

    WANG Nan; GUO Lu

    2009-01-01

    The ground state properties of La isotopes are investigated with the reflection asymmetric relativistic mean field (RAS-RMF) model.The calculation results of binding energies and the quadrupole moments are in good agreements with the experiment.The calculation results indicate the change of the quadrupole deformation with the nuclear mass number.The "kink" on the isotope shifts is observed at A=139 where the neutron number is the magic number N=82.It is also found that the octupole deformations may exist in the La isotopes with mass number A~ 145-155.

  9. Recycling asymmetric hydrogenation catalysts by their immobilisation onto ion-exchange resins.

    Science.gov (United States)

    Barbaro, Pierluigi; Bianchini, Claudio; Giambastiani, Giuliano; Oberhauser, Werner; Bonzi, Laura Morassi; Rossi, Filippo; Dal Santo, Vladimiro

    2004-06-21

    New systems based on cationic chiral phosphine-rhodium complexes anchored to a commercial cation-exchange gel-type resin showed high efficiency and easy recycling in the asymmetric hydrogenation of prochiral olefins.

  10. Directed orientation of asymmetric composite dumbbells by electric field induced assembly.

    Science.gov (United States)

    Nagao, Daisuke; Sugimoto, Maki; Okada, Ayako; Ishii, Haruyuki; Konno, Mikio; Imhof, Arnout; van Blaaderen, Alfons

    2012-04-24

    Assembly and directed orientation of anisotropic particles with an external ac electric field in a range from 1 kHz to 2 MHz were studied for asymmetric composite dumbbells incorporating a silica, titania, or titania/silica (titania:silica = 75:25 vol %) sphere. The asymmetric composite dumbbells, which were composed of a polymethylmethacrylate (PMMA)-coated sphere (core-shell part) and a polystyrene (PSt) lobe, were synthesized with a soap-free emulsion polymerization to prepare PMMA-coated inorganic spheres and another soap-free emulsion polymerization to form a polystyrene (PSt) lobe from the PMMA-coated inorganic spheres. The composite dumbbells dispersed in water were directly observed with optical microscopy. The dumbbells incorporating a silica sphere oriented parallel to an electric field in the whole frequency range and they formed a pearl chain structure at a high frequency of 2 MHz. The titania-incorporated dumbbells formed chain structures, in which they contacted their core-shell parts and oriented perpendicularly to a low-frequency (kHz) field, whereas they oriented parallel to a high-frequency (MHz) field. Since the alignment of dumbbells in the chains depends not only on the interparticle forces but also on the torque that the induced dipoles in the dumbbells experience in the electric field, the orientation of dumbbells perpendicular to the electric field was the case dominated by the interparticle force, whereas the other orientation was the case dominated by the torque. The present experiments show that the incorporation of inorganic dumbbells is an effective way to control the assembled structure and orientation with an electric field.

  11. Measurement of the Charge Reduction and Asymmetrical Interaction Force Created by the Ion Wakefield in a Dusty Plasma

    Science.gov (United States)

    Chen, Mudi; Yousefi, Razieh; Kong, Jie; Qiao, Ke; Carmona-Reyes, Jorge; Matthews, Lorin; Hyde, Truell

    2014-10-01

    The manner in which the ion wakefield forms has strong implications on the structure, stability and dynamics of a complex plasma. The majority of vertically aligned, ordered dust particle structures observed in a complex plasma result from a combination of the ion wakefield and the external confinement. The ion wakefield is also responsible for other interesting phenomena, such as the reduction in charge seen for a down-stream particle in a vertically aligned dust particle chain and the asymmetrical interaction force between the up-stream and down-stream particles. Unfortunately, few experimental measurements of these phenomena are available. In this experiment, one dimensional (1-D) dust particle structures (i.e., particle chains) are formed in a GEC RF reference cell within a glass box sitting on the powered, lower electrode. The charge reduction on the downstream particle and the asymmetric interaction force are examined using an externally produced DC bias applied to the lower electrode and a diode pumped solid state laser (Coherent VERDI) for perturbation.

  12. Integrated field emission array for ion desorption

    Energy Technology Data Exchange (ETDEWEB)

    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.

  13. Integrated field emission array for ion desorption

    Energy Technology Data Exchange (ETDEWEB)

    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.

  14. Integrated field emission array for ion desorption

    Science.gov (United States)

    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.

  15. Coexistence of phases in asymmetric nuclear matter under strong magnetic fields

    CERN Document Server

    Aguirre, R

    2014-01-01

    The equation of state of nuclear matter is strongly affected by the presence of a magnetic field. Here we study the equilibrium configuration of asymmetric nuclear matter for a wide range of densities, isospin composition, temperatures and magnetic fields. Special attention is paid to the low density and low temperature domain, where a thermodynamical instability exists. Neglecting fluctuations of the Coulomb force, a coexistence of phases is found under such conditions, even for extreme magnetic intensities. We describe the nuclear interaction by using the non--relativistic Skyrme potential model within a Hartree--Fock approach. We found that the coexistence of phases modifies the equilibrium configuration, masking most of the manifestations of the spin polarized matter. However, the compressibility and the magnetic susceptibility show clear signals of this fact. Thermal effects are significative for both quantities, mainly out of the coexistence region.

  16. Self-organization model on receptive field of neuron with asymmetric time window of synaptic modification

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The spatial-temporal response properties of some simple neurons in visual pathway arise basically prior to birth. In the absence of visual experience, how do these neurons develop in visual system? Based on Wimbauer network with delay, a four-layer feed-forward network model is proposed, which is characterized by modifying the Hebb learning rule through introducing the asymmetric time window of synaptic modification found recently in neurobiology. The model can not only generate by self-organization more diversified spatial-temporal response characteristics of neuronal receptive field than earlier models but also provide some explanations for the possible mechanism underlying the development of receptive fields of contrast polarity sensitive neurons found in visual system of vertebrate. Thus the proposed model may be more widely applicable than Linsker model and Wimbauer model.

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

    Science.gov (United States)

    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.

  18. Scaling of cross-sections for asymmetric (, 3) process on helium-like ions by fast electrons

    Indian Academy of Sciences (India)

    M K Srivastava

    2004-11-01

    An approximate simple scaling law is obtained for asymmetric (, 3) process on helium-like ions for double ionization by fast electrons. It is based on the equation $(Z'^{3} /)$ exp$[−Z' (r_{1} + r_{2})]$, $Z' = Z − (5/16)$ for ground state wave function of helium- like ions and $Z'^{2}$ scaling of energies. The scaling law is found to work very well if the lower energy electron is ejected along the momentum transfer direction and the other one is ejected in the opposite direction. It also works quite well if this electron is ejected within about 90° of the momentum transfer direction with the other electron going in the opposite direction. The scaling law becomes increasingly accurate as the target nuclear charge and the energy increase.

  19. Design of Magnetic Field System for Calutron Ion Source Set

    Institute of Scientific and Technical Information of China (English)

    REN; Xiu-yan; ZENG; Zi-qiang

    2013-01-01

    The Calutron ion source is the most important equipment of EMIS,and the structure of the ion source is more complicated.Because the parameter of each part is interrelate,as experiment and test set,It is very convenient to adjust the parameter of ion source and make the ion source get a good quality.Magnetic field system is the leading and necessary auxiliary equipment of the Calutron ion source

  20. Polycrystalline silicon ion sensitive field effect transistors

    Science.gov (United States)

    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.

  1. Factors affecting measurement of channel thickness in asymmetrical flow field-flow fractionation.

    Science.gov (United States)

    Dou, Haiyang; Jung, Euo Chang; Lee, Seungho

    2015-05-01

    Asymmetrical flow field-flow fractionation (AF4) has been considered to be a useful tool for simultaneous separation and characterization of polydisperse macromolecules or colloidal nanoparticles. AF4 analysis requires the knowledge of the channel thickness (w), which is usually measured by injecting a standard with known diffusion coefficient (D) or hydrodynamic diameter (dh). An accurate w determination is a challenge due to its uncertainties arising from the membrane's compressibility, which may vary with experimental condition. In the present study, influence of factors including the size and type of the standard on the measurement of w was systematically investigated. The results revealed that steric effect and the particles-membrane interaction by van der Waals or electrostatic force may result in an error in w measurement.

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

    Directory of Open Access Journals (Sweden)

    David eMüller

    2015-07-01

    Full Text Available 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 scale-down 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.

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

    Science.gov (United States)

    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.

  4. Standard and nonstandard nematic electrohydrodynamic convection in the presence of asymmetric ac electric fields.

    Science.gov (United States)

    Low, Jonathan; Hogan, S John

    2008-10-01

    In planar nematic electrohydrodynamic convection (EHC), a microscopic liquid crystal cell is driven by a homogeneous ac electric field, which, if strong enough, causes the fluid to destabilize into a regular pattern-forming state. We consider asymmetric electric fields E(t)=E(t+T) not equal-E(t+T2) , which leads to the possibility of three different types of instabilities at onset: conductive, dielectric, and subharmonic. The first two are already well known as they are easily produced when the system is driven by symmetric electric fields; the third can only occur when the electric field symmetry is broken. We present theoretical results on EHC using linear stability analysis and Floquet theory. We consider rigid and free boundary conditions, extending the model to two Fourier modes in the vertical plane, the inclusion of flexoelectricity, and using standard (nematic electric conductivity sigma_{a}>0 and dielectric anisotorpy _{a}conduction and subharmonic regimes disappear and only the dielectric threshold exists.

  5. A systematic investigation of quaternary ammonium ions as asymmetric phase-transfer catalysts. Application of quantitative structure activity/selectivity relationships.

    Science.gov (United States)

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

    2011-06-01

    Although 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.

  6. Field applications of ion-mobility spectrometry

    Science.gov (United States)

    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.

  7. Divergent Field Annular Ion Engine Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The proposed work investigates an approach that would allow an annular ion engine geometry to achieve ion beam currents approaching the Child-Langmuir limit. In this...

  8. Asymmetric focusing study from twin input power couplers using realistic rf cavity field maps

    Directory of Open Access Journals (Sweden)

    Colwyn Gulliford

    2011-03-01

    Full Text Available Advanced simulation codes now exist that can self-consistently solve Maxwell’s equations for the combined system of an rf cavity and a beam bunch. While these simulations are important for a complete understanding of the beam dynamics in rf cavities, they require significant time and computing power. These techniques are therefore not readily included in real time simulations useful to the beam physicist during beam operations. Thus, there exists a need for a simplified algorithm which simulates realistic cavity fields significantly faster than self-consistent codes, while still incorporating enough of the necessary physics to ensure accurate beam dynamics computation. To this end, we establish a procedure for producing realistic field maps using lossless cavity eigenmode field solvers. This algorithm incorporates all relevant cavity design and operating parameters, including beam loading from a nonrelativistic beam. The algorithm is then used to investigate the asymmetric quadrupolelike focusing produced by the input couplers of the Cornell ERL injector cavity for a variety of beam and operating parameters.

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

    Science.gov (United States)

    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.

  10. Ionic force field optimization based on single-ion and ion-pair solvation properties

    CERN Document Server

    Fyta, Maria; Dzubiella, Joachim; Vrbka, Lubos; Netz, Roland R

    2009-01-01

    Molecular dynamics simulations of ionic solutions depend sensitively on the force fields employed for the ions. To resolve the fine differences between ions of the same valence and roughly similar size and in particular to correctly describe ion-specific effects, it is clear that accurate force fields are necessary. In the past, optimization strategies for ionic force fields either considered single-ion properties (such as the solvation free energy at infinite dilution or the ion-water structure) or ion-pair properties (in the form of ion-ion distribution functions). In this paper we investigate strategies to optimize ionic force fields based on single-ion and ion-pair properties simultaneously. To that end, we simulate five different salt solutions, namely CsCl, KCl, NaI, KF, and CsI, at finite ion concentration. The force fields of these ions are systematically varied under the constraint that the single-ion solvation free energy matches the experimental value, which reduces the two-dimensional $\\{\\sigma,\\e...

  11. Asymmetric Diketopyrrolopyrrole Conjugated Polymers for Field-Effect Transistors and Polymer Solar Cells Processed from a Nonchlorinated Solvent.

    Science.gov (United States)

    Ji, Yunjing; Xiao, Chengyi; Wang, Qiang; Zhang, Jianqi; Li, Cheng; Wu, Yonggang; Wei, Zhixiang; Zhan, Xiaowei; Hu, Wenping; Wang, Zhaohui; Janssen, René A J; Li, Weiwei

    2016-02-01

    Newly designed asymmetric diketopyrrolopyrrole conjugated polymers with two different aromatic substituents possess a hole mobility of 12.5 cm(2) V(-1) s(-1) in field-effect transistors and a power conversion efficiency of 6.5% in polymer solar cells, when solution processed from a nonchlorinated toluene/diphenyl ether mixed solvent.

  12. Asymmetric flow field-flow fractionation as a new approach to analyse iron-(hydr)oxide nanoparticles in soil extracts

    NARCIS (Netherlands)

    Regelink, I.C.; Weng, L.P.; Koopmans, G.F.; Riemsdijk, van W.H.

    2013-01-01

    Iron-(hydr)oxide nanoparticles are important for the sequestration of organic carbon because of their small size and consequently large specific surface area. Therefore, there is an increasing interest in analytical techniques such as asymmetric flow field-flow fractionation (AF4) that allow for a d

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

    NARCIS (Netherlands)

    Lavrijsen, R.; Hartmann, D. M. F.; van den Brink, Ton; Yin, Y.; Barcones, B.; Duine, R. A.|info:eu-repo/dai/nl/304830127; Verheijen, M. A.; Swagten, H. J. M.; Koopmans, B.

    2015-01-01

    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

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

    NARCIS (Netherlands)

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

    2015-01-01

    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

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

    Science.gov (United States)

    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

  16. Asymmetric fission and evaporation of C{sub 60}{sup r+} (r = 2-4) fullerene ions in ion-C{sub 60} collisions: I. Proton results

    Energy Technology Data Exchange (ETDEWEB)

    Rentenier, A; Bordenave-Montesquieu, A; Moretto-Capelle, P; Bordenave-Montesquieu, D [LCAR-IRSAMC, UMR 5589 Universite Paul Sabatier-CNRS, 118 rte de Narbonne, 31062 Toulouse Cedex (France)

    2004-06-28

    A quantitative description of the asymmetric fission (AF) of C{sub 60}{sup r+} fullerene ions (r = 2-4), using a multistop coincidence technique between both fragment ions, is presented. Charged light fragment (LF) and heavy fragment (HF) size distributions are discussed together with the corresponding averaged sizes. Complete AF distributions are reported for the first time for C{sub 60}{sup 2+} ions. Simple dependences of the more probable channels and averaged fragment sizes on the partner size are found and discussed. The LF ones are not very sensitive to the parent fullerene ion charge r and vary linearly with the HF size at least for the largest ones. On the other hand the HF ones present an oscillating dependence against the LF size, the odd-numbered LFs being correlated to a smaller HF size, and depend on r. In the comparison of branching ratios between AF and the competing pure neutral evaporation channel, some emphasis is given to the behaviour of the unimolecular processes with r which are compared with the evolution of the activation energies and fission barriers. From a close examination of the individual HF distributions the production mechanisms of odd-n fragments are discussed, and the most probable dissociation channels of even-numbered C{sub n}{sup +} excited carbon clusters identified. Finally, an analysis of the neutral channels is also presented for the first time, the total neutral mass N (in carbon units) being deduced from the mass conservation law. Surprising similarities between the charged LF- and N-distributions are found. AF processes are also identified where light neutrals and ions play a symmetrical role. These findings lead us to suggest that a concerted emission of ions and heavy neutrals is probably a fission mechanism to be considered to understand the AF process of the C{sub 60} molecule in addition to the often assumed multistep fragmentation cascade scheme.

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

    Science.gov (United States)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Thopan, P.; Suwannakachorn, D.; Tippawan, U. [Plasma and Beam Physics Research Facility, Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Yu, L.D., E-mail: yuld@thep-center.org [Plasma and Beam Physics Research Facility, Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Thailand Center of Excellence in Physics, Commission on Higher Education, 328 Si Ayutthaya Road, Bangkok 10400 (Thailand)

    2015-12-15

    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.

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

    Science.gov (United States)

    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.

  20. The effect of reconnection electric field on crescent and U-shaped distribution functions in asymmetric reconnection with no guide field

    Science.gov (United States)

    Bessho, N.; Chen, L.-J.; Hesse, M.; Wang, S.

    2017-07-01

    Electron distribution functions in the electron diffusion region in asymmetric reconnection without a guide field are studied by means of theory and 2-dimensional particle-in-cell (PIC) simulations. The effect of the reconnection electric field on crescent-shaped distribution functions is to broaden the thickness of the crescent. We express the thickness of the crescent as a function of field strengths, the distance from the X-line, and the time electrons spend executing meandering orbits. The electron distribution at the reconnection X-line exhibits a U-shaped structure with an opening angle in the direction of the reconnection electric field. We predict the opening angle of the U-shaped distribution by considering acceleration of the meandering electrons by the reconnection electric field. Results from particle tracing in PIC simulations and theoretical analysis agree. The above predictions provide guidance to interpret measurements by spacecraft from electron diffusion regions in asymmetric reconnection.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  3. Probing and quantifying DNA-protein interactions with asymmetrical flow field-flow fractionation.

    Science.gov (United States)

    Ashby, Jonathan; Schachermeyer, Samantha; Duan, Yaokai; Jimenez, Luis A; Zhong, Wenwan

    2014-09-05

    Tools capable of measuring binding affinities as well as amenable to downstream sequencing analysis are needed for study of DNA-protein interaction, particularly in discovery of new DNA sequences with affinity to diverse targets. Asymmetrical flow field-flow fractionation (AF4) is an open-channel separation technique that eliminates interference from column packing to the non-covalently bound complex and could potentially be applied for study of macromolecular interaction. The recovery and elution behaviors of the poly(dA)n strand and aptamers in AF4 were investigated. Good recovery of ssDNAs was achieved by judicious selection of the channel membrane with consideration of the membrane pore diameter and the radius of gyration (Rg) of the ssDNA, which was obtained with the aid of a Molecular Dynamics tool. The Rg values were also used to assess the folding situation of aptamers based on their migration times in AF4. The interactions between two ssDNA aptamers and their respective protein components were investigated. Using AF4, near-baseline resolution between the free and protein-bound aptamer fractions could be obtained. With this information, dissociation constants of ∼16nM and ∼57nM were obtained for an IgE aptamer and a streptavidin aptamer, respectively. In addition, free and protein-bound IgE aptamer was extracted from the AF4 eluate and amplified, illustrating the potential of AF4 in screening ssDNAs with high affinity to targets. Our results demonstrate that AF4 is an effective tool holding several advantages over the existing techniques and should be useful for study of diverse macromolecular interaction systems. Copyright © 2014 Elsevier B.V. All rights reserved.

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

    Science.gov (United States)

    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.

  5. Evaluation of collapsed cone convolution superposition (CCCS algorithms in prowess treatment planning system for calculating symmetric and asymmetric field size

    Directory of Open Access Journals (Sweden)

    Tamer Dawod

    2015-01-01

    Full Text Available Purpose: This work investigated the accuracy of prowess treatment planning system (TPS in dose calculation in a homogenous phantom for symmetric and asymmetric field sizes using collapse cone convolution / superposition algorithm (CCCS. Methods: The measurements were carried out at source-to-surface distance (SSD set to 100 cm for 6 and 10 MV photon beams. Data for a full set of measurements for symmetric fields and asymmetric fields, including inplane and crossplane profiles at various depths and percentage depth doses (PDDs were obtained during measurements on the linear accelerator.Results: The results showed that the asymmetric collimation dose lead to significant errors (up to approximately 7% in dose calculations if changes in primary beam intensity and beam quality. It is obvious that the most difference in the isodose curves was found in buildup and the penumbra regions. Conclusion: The results showed that the dose calculation using Prowess TPS based on CCCS algorithm is generally in excellent agreement with measurements.

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

    Science.gov (United States)

    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.

  7. Probing surface electric field noise with a single ion

    CERN Document Server

    Daniilidis, N; Bolloten, G; Ramm, M; Ransford, A; Ulin-Avila, E; Talukdar, I; Häffner, H

    2013-01-01

    We report room-temperature electric field noise measurements combined with in-situ surface characterization and cleaning of a microfabricated ion trap. We used a single-ion electric field noise sensor in combination with surface cleaning and analysis tools, to investigate the relationship between electric field noise from metal surfaces in vacuum and the composition of the surface. These experiments were performed in a novel setup that integrates ion trapping capabilities with surface analysis tools. We find that surface cleaning of an aluminum-copper surface significantly reduces the level of electric field noise, but the surface does not need to be atomically clean to show noise levels comparable to those of the best cryogenic traps. The post-cleaning noise levels are low enough to allow fault-tolerant trapped-ion quantum information processing on a microfabricated surface trap.

  8. Primary amine/CSA ion pair: A powerful catalytic system for the asymmetric enamine catalysis

    KAUST Repository

    Liu, Chen

    2011-05-20

    A novel ion pair catalyst containing a chiral counteranion can be readily derived by simply mixing cinchona alkaloid-derived diamine with chiral camphorsulfonic acid (CSA). A mixture of 9-amino(9-deoxy)epi-quinine 8 and (-)-CSA was found to be the best catalyst with matching chirality, enabling the direct amination of α-branched aldehydes to proceed in quantitative yields and with nearly perfect enantioselectivities. A 0.5 mol % catalyst loading was sufficient to catalyze the reaction, and a gram scale enantioselective synthesis of biologically important α-methyl phenylglycine has been successfully demonstrated. © 2011 American Chemical Society.

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

    Science.gov (United States)

    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.

  10. Zero-field optical manipulation of magnetic ions in semiconductors.

    Science.gov (United States)

    Myers, R C; Mikkelsen, M H; Tang, J-M; Gossard, A C; Flatté, M E; Awschalom, D D

    2008-03-01

    Controlling and monitoring individual spins is desirable for building spin-based devices, as well as implementing quantum information processing schemes. As with trapped ions in cold gases, magnetic ions trapped on a semiconductor lattice have uniform properties and relatively long spin lifetimes. Furthermore, diluted magnetic moments in semiconductors can be strongly coupled to the surrounding host, permitting optical or electrical spin manipulation. Here we describe the zero-field optical manipulation of a few hundred manganese ions in a single gallium arsenide quantum well. Optically created mobile electron spins dynamically generate an energy splitting of the ion spins and enable magnetic moment orientation solely by changing either photon helicity or energy. These polarized manganese spins precess in a transverse field, enabling measurements of the spin lifetimes. As the magnetic ion concentration is reduced and the manganese spin lifetime increases, coherent optical control and readout of single manganese spins in gallium arsenide should be possible.

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

    Science.gov (United States)

    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.

  12. Peristaltic flow of a couple stress fluid under the effect of induced magnetic field in an asymmetric channel

    Energy Technology Data Exchange (ETDEWEB)

    Nadeem, Sohail; Akram, Safia [Quaid-i-Azam University, Department of Mathematics, Islamabad (Pakistan)

    2011-01-15

    The present paper investigates the peristaltic transport of a couple stress fluid in an asymmetric channel with the effect of the induced magnetic field. The exact solutions of momentum and the magnetic field equations have been calculated under the assumptions of long wave length and low but finite Reynolds number. The expression for pressure rise has been computed numerically using mathematics software Mathematica. The graphical results have been presented to discuss the physical behavior of various physical parameters of interest. Finally, the trapping phenomena have been discussed for various physical parameters. (orig.)

  13. Ion recognition: application of symmetric and asymmetric schiff bases and their complexes for the fabrication of cationic and anionic membrane sensors to determine ions in real samples.

    Science.gov (United States)

    Faridbod, Farnoush; Ganjali, Mohammad Reza; Dinarvand, Rassoul; Norouzi, Parviz

    2007-08-01

    Schiff base compounds refer to the branch of supra-molecules and can be used as sensing material in the construction of potentiometric ion selective electrodes (ISEs). This relatively modern field has been subject to extensive research in the period of 1999-2007 when more than 100 ISEs employing Schiff bases were constructed. The quantitative high-throughput detection of 29 cations and 7 anions has been demonstrated in various scientific branches, such as biomedicine, pharmacy, biochemistry, pharmacology, environmental chemistry, food technology, and agriculture. This review discusses Schiff base compounds and their applications in the design and development of ion selective sensors and microsensors.

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

    Science.gov (United States)

    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.

  15. Effect of radiation and magnetic field on peristaltic transport of nanofluids through a porous space in a tapered asymmetric channel

    Energy Technology Data Exchange (ETDEWEB)

    Kothandapani, M., E-mail: mkothandapani@gmail.com [Department of Mathematics, University College of Engineering Arni, (A Constituent College of Anna University Chennai), Arni 632326, Tamil Nadu (India); Prakash, J., E-mail: prakashjayavel@yahoo.co.in [Department of Mathematics, Arulmigu Meenakshi Amman College of Engineering, Vadamavandal 604410, Tamil Nadu (India)

    2015-03-15

    Theoretical analyses on the effect of radiation and MHD on the peristaltic flow of a nanofluid through a porous medium in a two dimensional tapered asymmetric channel has been made. The nanofluid is assumed to be electrically conducting in the presence of a uniform magnetic field. The transport equation accounts the both Brownian motion and thermophoresis along with the radiation reaction. The problem has been further simplified with the authentic assumptions of long wavelength and small Reynolds number. The analytical expressions obtained for the axial velocity, stream function, temperature field, nanoparticle fraction field and pressure gradient provide satisfactory explanation. Influence of various parameters on the flow characteristics have been discussed with the help of graphical results. The trapping phenomenon has also been discussed in detail. - Highlights: • Combine effect of thermal radiation and MHD on the peristaltic flow of a Newtonian nanofluid are discussed. • This work may be first attempt dealing the study of Newtonian nanofluid flow in the porous tapered asymmetric channel. • The velocity, stream function, temperature field and nanoparticle fraction field provide satisfactory explanation with help of graphs.

  16. Solar Wind Electric Fields in the Ion Cyclotron Frequency Range

    CERN Document Server

    Kellogg, P J; Mozer, F S; Horbury, T S; Reme, H

    2006-01-01

    Measurements of fluctuations of electric fields in the frequency range from a fraction of one Hz to 12.5 Hz are presented, and corrected for the Lorentz transformation of magnetic fluctuations to give the electric fields in the plasma frame. The electric fields are large enough to provide the dominant force on the ions of the solar wind in the region near the ion cyclotron frequency of protons, larger than the force due to magnetic fluctuations. They provide sufficient velocity space diffusion or heating to counteract conservation of magnetic moment in the expanding solar wind to maintain nearly isotropic velocity distributions.

  17. Atom probe field ion microscopy of high resistivity materials

    Energy Technology Data Exchange (ETDEWEB)

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

    1998-02-01

    Over the last 30 years the atom probe has proved to be a powerful tool for studying nanometer-sized compositional fluctuations in a wide range of metallic alloys but has had only limited applications to semiconductors and ceramics. One of the primary reasons for this difference is the higher resistivity of semiconducting and ceramic specimens. Because of this high resistivity, the high voltage field evaporation pulse is attenuated before it reaches the apex of the specimen thereby making the pulse ineffective for field evaporation. Experiments have demonstrated that both variants of the voltage-pulsed atom probe (i.e., those instruments in which the field evaporation pulse is applied directly to the specimen and those in which the negative pulse is applied to a counter electrode in front of the specimen) are equally affected. In this overview, the limits of applicability of the voltage-pulsed atom probe to high resistivity materials are examined. In this study, a wide range of materials have been examined to determine whether field ion microscopy and voltage-pulsed field evaporation can be achieved and the results are summarized in the report. Field ion microscopy including dc field evaporation was possible for all materials except bulk ceramic insulators and glasses. Field ion microscopy requires some conductivity both to achieve a high electric field at the apex of the specimen, and also to support the field ion current. In contrast, voltage-pulsed field evaporation requires transmission of the pulse to the apex of the specimen. All metallic alloys including high resistance alloys and metallic glasses were successfully field evaporated with a voltage pulse. Specimens that were produced from bulk material of several conducting ceramics including MoSi, TiB and TiC were also successfully field evaporated with a voltage pulse.

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

    Science.gov (United States)

    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.

  19. Study on neutron radiation field of carbon ions therapy

    CERN Document Server

    Xu, Jun-Kui; Li, Wu-Yuan; Yan, Wei-Wei; Chen, Xi-Meng; Mao, Wang; Pang, Cheng-Guo

    2015-01-01

    Carbon ions offer significant advantages for deep-seated local tumors therapy due to their physical and biological properties. Secondary particles, especially neutrons caused by heavy ion reactions should be carefully considered in treatment process and radiation protection. For radiation protection purposes, the FLUKA Code was used in order to evaluate the radiation field at deep tumor therapy room of HIRFL in this paper. The neutron energy spectra, neutron dose and energy deposition of carbon ion and neutron in tissue-like media was studied for bombardment of solid water target by 430MeV/u C ions. It is found that the calculated neutron dose have a good agreement with the experimental date, and the secondary neutron dose may not exceed one in a thousand of the carbon ions dose at Bragg peak area in tissue-like media.

  20. Two-photon interaction between trapped ions and cavity fields

    CERN Document Server

    Semião, F L

    2006-01-01

    In this paper, we generalize the ordinary two-photon Jaynes-Cummings model (TPJCM) by considering the atom (or ion) to be trapped in a simple harmonic well. A typical setup would be an optical cavity containing a single ion in a Paul trap. Due to the inclusion of atomic vibrational motion, the atom-field coupling becomes highly nonlinear what brings out quite different behaviors for the system dynamics when compared to the ordinary TPJCM. In particular, we derive an effective two-photon Hamiltonian with dependence on the number operator of the ion's center-of-mass motion. This dependence occurs both in the cavity induced Stark-shifs and in the ion-field coupling, and its role in the dynamics is illustrated by showing the time evolution of the probability of occupation of the electronic levels for simple initial preparations of the state of the system.

  1. Adiabatic asymmetric scattering of atoms in the field of a standing wave

    CERN Document Server

    Hakobyan, M V; Ishkhanyan, A M

    2015-01-01

    A model of the asymmetric coherent scattering process (caused by initial atomic wave-packet splitting in the momentum space) taking place at the large detuning and adiabatic course of interaction for an effective two-state system interacting with a standing wave of laser radiation is discussed. We show that the same form of initial wave-packet splitting may lead to different, in general, diffraction patterns for opposite, adiabatic and resonant, regimes of the standing-wave scattering. We show that the scattering of the Gaussian wave packet in the adiabatic case presents refraction (a limiting form of the asymmetric scattering) in contrast to the bi-refringence (the limiting case of the high-order narrowed scattering) occurring in the resonant scattering.

  2. Strong-field relativistic processes in highly charged ions

    Energy Technology Data Exchange (ETDEWEB)

    Postavaru, Octavian

    2010-12-08

    In this thesis we investigate strong-field relativistic processes in highly charged ions. In the first part, we study resonance fluorescence of laser-driven highly charged ions in the relativistic regime by solving the time-dependent master equation in a multi-level model. Our ab initio approach based on the Dirac equation allows for investigating highly relativistic ions, and, consequently, provides a sensitive means to test correlated relativistic dynamics, bound-state quantum electrodynamic phenomena and nuclear effects by applying coherent light with x-ray frequencies. Atomic dipole or multipole moments may be determined to unprecedented accuracy by measuring the interference-narrowed fluorescence spectrum. Furthermore, we investigate the level structure of heavy hydrogenlike ions in laser beams. Interaction with the light field leads to dynamic shifts of the electronic energy levels, which is relevant for spectroscopic experiments. We apply a fully relativistic description of the electronic states by means of the Dirac equation. Our formalism goes beyond the dipole approximation and takes into account non-dipole effects of retardation and interaction with the magnetic field components of the laser beam. We predicted cross sections for the inter-shell trielectronic recombination (TR) and quadruelectronic recombination processes which have been experimentally confirmed in electron beam ion trap measurements, mainly for C-like ions, of Ar, Fe and Kr. For Kr{sup 30}+, inter-shell TR contributions of nearly 6% to the total resonant photorecombination rate were found. (orig.)

  3. MMS observations of plasma wave and electron energization in the electron diffusion region of asymmetric reconnection with strong guide field

    Science.gov (United States)

    Xiao, Chijie; Zhao, Siqi; Shi, Mijie; Pu, Zuyin; Wang, Xiaogang

    2016-10-01

    Here we report an asymmetric reconnection event with strong guide field observed by Magnetospheric Multiscale Mission (MMS) on the dayside magnetopause. In this event there are multiple wave modes, such as electron Alfvenic mode, broadband waves between the lower-hybrid and electron cyclotron frequencies, exist in the vicinity of the electron diffusion region and the separatrix. And the electron velocity distribution functions show that bi-stream electrons with low energy (processes are investigated and comparison with some 3D numerical simulation results. This work was supported by NSFC (Grants 41274168 and 11375053).

  4. Magnetic field effect in photodetachment from negative ion in electric field near metal surface

    Institute of Scientific and Technical Information of China (English)

    Tang Tian-Tian; Wang De-Hua; Huang Kai-Yun; Wang Shan-Shan

    2011-01-01

    Based on the closed-orbit theory, the magnetic field effect in the photodetachment of negative ion in the electric field near a metal surface is studied for the first time. The results show that the magnetic field can produce a significant effect on the photodetachment of negative ion near a metal surface. Besides the closed orbits previously found by Du et al. for the H-in the electric field near a metal surface (J. Phys. B 43 035002 (2010)), some additional closed orbits are produced due to the effect of magnetic field. For a given ion-surface distance and an electric field strength, the cross section depends sensitively on the magnetic field strength. As the magnetic field strength is very small, its influence can be neglected. With the increase of the magnetic field strength, the number of the closed orbits increases greatly and the oscillation in the cross section becomes much more complex. Therefore we can control the photodetachment cross section of the negative ion by changing the magnetic field strength. We hope that our results may guide future experimental studies for the photodetachment process of negative ion in the presence of external fields and surfaces.

  5. 3DFD Simulation of Asymmetric Wave Field by Side-wall Acoustic Tool in Open and Cased Wells

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    We developed a parallelized scheme of 3D finite difference (3DFD) with non-uniform staggered grid to simulate the eccentric borehole acoustic field with side-wall acoustic logging tools in open and cased wells. Higher accuracy and lower computation cost were achieved with this scheme for modeling such an asymmetric wave field generated by a high frequency source near or on the borehole wall. We also modeled the cases with and without considering the effects of the tool body. The simulation results demonstrated that the logging tool body would attenuate the direct waves but have only little influence on the interface waves in such a borehole condition. The effects of the tool body on the wave field were significant only when the contrast of the elastic properties between tool body and borehole fluid was large.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  8. Irradiation of graphene field effect transistors with highly charged ions

    Science.gov (United States)

    Ernst, P.; Kozubek, R.; Madauß, L.; Sonntag, J.; Lorke, A.; Schleberger, M.

    2016-09-01

    In this work, graphene field-effect transistors are used to detect defects due to irradiation with slow, highly charged ions. In order to avoid contamination effects, a dedicated ultra-high vacuum set up has been designed and installed for the in situ cleaning and electrical characterization of graphene field-effect transistors during irradiation. To investigate the electrical and structural modifications of irradiated graphene field-effect transistors, their transfer characteristics as well as the corresponding Raman spectra are analyzed as a function of ion fluence for two different charge states. The irradiation experiments show a decreasing mobility with increasing fluences. The mobility reduction scales with the potential energy of the ions. In comparison to Raman spectroscopy, the transport properties of graphene show an extremely high sensitivity with respect to ion irradiation: a significant drop of the mobility is observed already at fluences below 15 ions/μm2, which is more than one order of magnitude lower than what is required for Raman spectroscopy.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  11. $H_{2}^{+}$ ion in strong magnetic field an accurate calculation

    CERN Document Server

    López, J C; Turbiner, A V

    1997-01-01

    Using a unique trial function we perform an accurate calculation of the ground state $1\\sigma_g$ of the hydrogenic molecular ion $H^+_2$ in a constant uniform magnetic field ranging $0-10^{13}$ G. We show that this trial function also makes it possible to study the negative parity ground state $1\\sigma_u$.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  14. PSYCHOLOGICAL PROBLEMS AND STRESS FACED BY SOLDIERS WHO OPERATE IN ASYMMETRIC WARFARE ENVIRONMENTS: EXPERIENCES IN THE FIELD

    Directory of Open Access Journals (Sweden)

    Giuseppe CAFORIO

    2014-10-01

    Full Text Available This article deals with the problems of anxiety, stress and psychological discomfort that can affect soldiers sent on asymmetric warfare operations. It is based on secondary analysis of the data of two important field researches whose results have recently (2013 been published. Although the two researches adopted different methodologies, the testimonies are fully comparable and show that soldiers from different countries and cultures display common or similar reactions when they are placed in the stress conditions that the asymmetric environment involves. The approach of the paper is drawn up in such a way as to make the reader a participating observer of the reality of such missions. It is therefore centered on the personal testimonies of the soldiers interviewed in the two researches, testimonies reported just as they are, in their simplicity and, often, drama, with comments by the author kept to a minimum in order to give readers ample opportunity to evaluate and interpret the reported texts on their own. The research data, drawn from the declarations of those directly concerned, reveal the existence of a problem of psychological distress resulting from deployment in asymmetric warfare situations that is in part different in the causes of the problems resulting from deployment in traditional combat and affects percentages of participating soldiers that are not high but definitely significant. The highest incidence appears to be constituted by problems relating to reintegration into normal social and working life upon returning from the mission. This is followed in percentage terms by anxiety situations relating to life far from the family, due in large part to a sense of powerlessness for the scant possibility of managing family situations that may have cropped up or already existed beforehand.

  15. Asymmetric fission and evaporation of C{sub 60}{sup r+} (r = 2-4) fullerene ions in ion-C{sub 60} collisions: II. Dependence on collisional processes?

    Energy Technology Data Exchange (ETDEWEB)

    Rentenier, A; Bordenave-Montesquieu, A; Moretto-Capelle, P; Bordenave-Montesquieu, D [LCAR-IRSAMC, UMR 5589 Universite Paul Sabatier-CNRS, 118 rte de Narbonne, 31062 Toulouse Cedex (France)

    2004-06-28

    In this paper, a quantitative comparison of our experimental data for the asymmetrical fission (AF) and neutral evaporation of the C{sub 60} molecule under proton impact (part I) is made with data published by other authors and often obtained in rather different collisional systems. The comparison with multicharged ions for which more quantitative data are available is focused on. It is demonstrated that size distributions of fragments, averaged fragment sizes, branching ratios between AF and evaporation or between AF channels, are common to all the collisional systems. Differences only appear when the comparison includes the undissociated stable fullerene ion signals.

  16. Single-ion microwave near-field quantum sensor

    Science.gov (United States)

    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.

  17. Ion Colliders

    CERN Document Server

    Fischer, W

    2014-01-01

    High-energy ion colliders are large research tools in nuclear physics to study the Quark-Gluon-Plasma (QGP). The range of collision energy and high luminosity are important design and operational considerations. The experiments also expect flexibility with frequent changes in the collision energy, detector fields, and ion species. Ion species range from protons, including polarized protons in RHIC, to heavy nuclei like gold, lead and uranium. Asymmetric collision combinations (e.g. protons against heavy ions) are also essential. For the creation, acceleration, and storage of bright intense ion beams, limits are set by space charge, charge change, and intrabeam scattering effects, as well as beam losses due to a variety of other phenomena. Currently, there are two operating ion colliders, the Relativistic Heavy Ion Collider (RHIC) at BNL, and the Large Hadron Collider (LHC) at CERN.

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

    CERN Document Server

    Gault, Baptiste; Ashton, Michael V; Sinnott, Susan B; Chiaramonti, Ann N; Moody, Michael P; Schreiber, Daniel K

    2015-01-01

    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 modelling of ion trajectories, and the application of density-functional theory (DFT) simulations to derive molecular ion energetics. It is demonstrated that the direct thermal emission of neutral molecules is extremely unlikely. However, neutrals can still...

  19. Emission characteristics of AuSiBe field ion sources

    Energy Technology Data Exchange (ETDEWEB)

    Drandarov, N.; Georgieva, St.; Nikolov, B.; Donchev, T. (Bylgarska Akademiya na Naukite, Sofia (Bulgaria). Inst. po Elektronika)

    A ribbon type AuSiBe alloy field ion source, which combines the advantages of both hairpin type sources and reservoir type sources, has been constructed. The current-voltage characteristics of this source have been investigated. Hysteresis and four differentiated emission regions have been observed for them. By means of scanning electronic microscopy, it has been established that this complicated behaviour of the I-V curves and the angular distribution of the extracted ions are associated with the shape of the emitting surface. The mass spectrum of the emitted ions has been determined by means of an E x B mass filter. Considerable emission of Au[sup +], AuBe[sub 3][sup 2+], Si[sup 2+], Be[sup 2+], AuBe[sub 3][sup +], Be[sup +], Si[sup +], and Au[sup 2+] has been observed. (author).

  20. Ion and impurity transport in turbulent, anisotropic magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Negrea, M; Petrisor, I [Department of Physics, Association Euratom-MEdC, Romania, University of Craiova, A.I. Cuza str. 13, Craiova (Romania); Isliker, H; Vogiannou, A; Vlahos, L [Section of Astrophysics, Astronomy and Mechanics, Department of Physics, University of Thessaloniki, Association Euratom-Hellenic Republic, 541 24 Thessaloniki (Greece); Weyssow, B [Physique Statistique-Plasmas, Association Euratom-Etat Belge, Universite Libre de Bruxelles, Campus Plaine, Bd. du Triomphe, 1050 Bruxelles (Belgium)

    2011-08-15

    We investigate ion and impurity transport in turbulent, possibly anisotropic, magnetic fields. The turbulent magnetic field is modeled as a correlated stochastic field, with Gaussian distribution function and prescribed spatial auto-correlation function, superimposed onto a strong background field. The (running) diffusion coefficients of ions are determined in the three-dimensional environment, using two alternative methods, the semi-analytical decorrelation trajectory (DCT) method, and test-particle simulations. In a first step, the results of the test-particle simulations are compared with and used to validate the results obtained from the DCT method. For this purpose, a drift approximation was made in slab geometry, and relatively good qualitative agreement between the DCT method and the test-particle simulations was found. In a second step, the ion species He, Be, Ne and W, all assumed to be fully ionized, are considered under ITER-like conditions, and the scaling of their diffusivities is determined with respect to varying levels of turbulence (varying Kubo number), varying degrees of anisotropy of the turbulent structures and atomic number. In a third step, the test-particle simulations are repeated without drift approximation, directly using the Lorentz force, first in slab geometry, in order to assess the finite Larmor radius effects, and second in toroidal geometry, to account for the geometric effects. It is found that both effects are important, most prominently the effects due to toroidal geometry and the diffusivities are overestimated in slab geometry by an order of magnitude.

  1. Trapped-Ion Quantum Logic with Global Radiation Fields

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  3. Optomechanical Entanglement Between an Ion and an Optical Cavity Field

    Science.gov (United States)

    Bhattacherjee, Aranya B.

    2016-04-01

    I study an optomechanical system in which the mechanical motion of a single trapped ion is coupled to a cavity field for the realization of a strongly quantum correlated two-mode system. I show that for large pump intensities the steady state photon number exhibits bistable behaviour. I further analyze the occurrence of normal mode splitting (NMS) due to mixing of the fluctuations of the cavity field and the fluctuations of the ion motion which indicates a coherent energy exchange. I also find that in the parameter regime where NMS exists, the steady state of the system shows continuous variable entanglement. Such a two-mode optomechanical system can be used for the realization of continuous variable quantum information interfaces and networks.

  4. Asymmetrical flow field-flow fractionation with on-line detection for drug transfer studies: a feasibility study

    DEFF Research Database (Denmark)

    Hinna, A.; Steiniger, F.; Hupfeld, S.

    2014-01-01

    Knowledge about drug retention within colloidal carriers is of uppermost importance particularly if drug targeting is anticipated. The aim of the present study was to evaluate asymmetrical flow field-flow fractionation (AF4) with on-line UV/VIS drug quantification for its suitability to determine...... both release and transfer of drug from liposomal carriers to a model acceptor phase consisting of large liposomes. The hydrophobic porphyrin 5,10,15,20-tetrakis(4-hydroxyphenyl)21H,23H-porphine (p-THPP), a fluorescent dye with an absorbance maximum in the visible range and structural similarity...... channel geometries. Drug quantification by on-line absorbance measurements was established by comprehensive evaluation of the size-dependent turbidity contribution in on-line UV/VIS detection and by comparison with off-line results obtained for the respective dye-loaded donor formulations (dissolved...

  5. Transient flickering behavior in fringe-field switching liquid crystal mode analyzed by positional asymmetric flexoelectric dynamics.

    Science.gov (United States)

    Lee, Dong-Jin; Shim, Gyu-Yeop; Choi, Jun-Chan; Park, Ji-Sub; Lee, Joun-Ho; Baek, Ji-Ho; Choi, Hyun Chul; Ha, Yong Min; Ranjkesh, Amid; Kim, Hak-Rin

    2015-12-28

    We analyzed a transient blinking phenomenon in a fringe-field switching liquid crystal (LC) mode that occurred at the moment of frame change even in the optimized DC offset condition for minimum image flicker. Based on the positional dynamic behaviors of LCs by using a high-speed camera, we found that the transient blink is highly related to the asymmetric responses of the splay-bend transitions caused by the flexoelectric (FE) effect. To remove the transient blink, the elastic property adjustment of LCs was an effective solution because the FE switching dynamics between the splay-enhanced and bend-enhanced deformations are highly dependent on the elastic constants of LCs, which is the cause of momentary brightness drop.

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

    Science.gov (United States)

    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.

  7. Comparison of Miniaturized and Conventional Asymmetrical Flow Field-Flow Fractionation (AF4 Channels for Nanoparticle Separations

    Directory of Open Access Journals (Sweden)

    Zengchao You

    2017-03-01

    Full Text Available The performance of a miniaturized channel for the separation of polymer and metal nanoparticles (NP using Asymmetrical Flow Field-Flow Fractionation (AF4 was investigated and compared with a conventional AF4 system. To develop standard separation methods, experimental parameters like cross flow, gradient profile and injection time were varied and optimized. Corresponding chromatographic parameters were calculated and compared. Our results indicate that the chromatographic resolution in the miniaturized channel is lower, whereas significantly shorter analyses time and less solvent consumption were obtained. Moreover, the limit of detection (LOD and limit of quantification (LOQ obtained from hyphenation with a UV-detector are obviously lower than in a conventional channel, which makes the miniaturized channel interesting for trace analysis.

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

    Science.gov (United States)

    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.

  9. Dosimetric study of field junction in adjacent beams using asymmetric collimators and MLC

    Institute of Scientific and Technical Information of China (English)

    Ahmed Zaki; Hosnya Abu-Zeid; Hada Ashry; Khaled EL Shahat

    2014-01-01

    Adjacent treatment fields are commonly employed in external beam radiation therapy, such as the mantle and inverted-Y fields for the treatment of Hodgkin’s disease. In some cases, the adjacent fields are orthogonal, such as the cra-niospinal fields used in the treatment of meduloblastoma. Another example is the irradiation of head and neck tumors when the lateral neck fields are placed adjacent to the anterior supraclavicular field. In each of these situations, there is a possibility of introducing very large dosage errors across the junction. Consequently, this region is at risk for tumor recurrence if it is underdosed or severe complications if it is overdosed. Four milimeter overlap and gap resulted in an unacceptable dose in homogeneity in the junction. As a result of this study, the magnitudes of hot and cold spots might be clinicaly acceptable for 3 mm gap between photon fields.

  10. Two-dimensional hydrogen negative ion in a magnetic field

    Institute of Scientific and Technical Information of China (English)

    Xie Wen-Fang

    2004-01-01

    Making use of the adiabatic hyperspherical approach, we report a calculation for the energy spectrum of the ground and low-excited states of a two-dimensional hydrogen negative ion H- in a magnetic field. The results show that the ground and low-excited states of H- in low-dimensional space are more stable than those in three-dimensional space and there may exist more bound states.

  11. Strain evolution in Si substrate due to implantation of MeV ion observed by extremely asymmetric x-ray diffraction

    Science.gov (United States)

    Emoto, T.; Ghatak, J.; Satyam, P. V.; Akimoto, K.

    2009-08-01

    We studied the strain introduced in a Si(111) substrate due to MeV ion implantation using extremely asymmetric x-ray diffraction and measured the rocking curves of asymmetrical 113 diffraction for the Si substrates implanted with a 1.5 MeV Au2+ ion at fluence values of 1×1013, 5×1013, and 1×1014/cm2. The measured curves consisted of a bulk peak and accompanying subpeak with an interference fringe. The positional relationship of the bulk peak to the subpeak and the intensity variation of those peaks with respect to the wavelengths of the x rays indicated that crystal lattices near the surface were strained; the lattice spacing of surface normal (111) planes near the surface was larger than that of the bulk. Detailed strain profiles along the depth direction were successfully estimated using a curve-fitting method based on Darwin's dynamical diffraction theory. Comparing the shapes of resultant strain profiles, we found that a strain evolution rapidly occurred within a depth of ˜300 nm at fluence values between 1×1013 and 5×1013/cm2. This indicates that formation of the complex defects progressed near the surface when the fluence value went beyond a critical value between 1×1013 and 5×1013/cm2 and the defects brought a large strain to the substrate.

  12. Asymmetric active nano-particles for directive near-field radiation

    DEFF Research Database (Denmark)

    Arslanagic, Samel; Thorsen, Rasmus O.

    2016-01-01

    In this work, we demonstrate the potential of cylindrical active coated nano-particles with certain geometrical asymmetries for the creation of directive near-field radiation. The particles are excited by a near-by magnetic line source, and their performance characteristics are reported in terms...... of radiated power, near-field and power flow distributions as well as the far-field directivity....

  13. Electric field effects on resonance structures in negative ion photodetachment

    Science.gov (United States)

    Slonim, V. Z.; Greene, C. H.

    1991-12-01

    The photodetachment of negative ions in a static electric field exhibits some new characteristic features and has beer considered in various theortical approaches.1 Most of them, however, neglect the short-range interaction between the escaping electron and the atomic core, and must be modified to describe various resonant effects. Experiments2 have shown very rich resonant structure in a dc-field, which can be attributed to the mixing of different excited states in the negative ion, to competition between elastic and inelastic decay channels, and to tunneling effects induced by the field. It is known that various resonant structures in Photoprocesses can be successfully described within standard multichannel quantum defect theory (MQDT). We present a modified MQDT frame transformation approach to extend the standard method to long-range potentials with nonspherical symmetry. In our treatment both the electron-field and electron-atom interactions are treated nonperturbatively and on an equal footing. The resulting theoretical calculations are compared with experimental data on field-modified H? photodetachment in the vicinity of the n = 2 resonances.

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

    Science.gov (United States)

    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.

  15. Excitation of radial ion motion in an rf-only multipole ion guide immersed in a strong magnetic field gradient.

    Science.gov (United States)

    Beu, Steven C; Hendrickson, Christopher L; Marshall, Alan G

    2011-03-01

    Radiofrequency (rf) multipole ion guides are widely used to transfer ions through the strong magnetic field gradient between source and analyzer regions of external source Fourier transform ion cyclotron resonance mass spectrometers. Although ion transfer as determined solely by the electric field in a multipole ion guide has been thoroughly studied, transfer influenced by immersion in a strong magnetic field gradient has not been as well characterized. Recent work has indicated that the added magnetic field can have profound effects on ion transfer, ultimately resulting in loss of ions initially contained within the multipole. Those losses result from radial ejection of ions due to transient cyclotron resonance that occurs when ions traverse a region in which the magnetic field results in an effective cyclotron frequency equal to the multipole rf drive frequency divided by the multipole order (multipole order is equal to one-half the number of poles). In this work, we describe the analytical basis for ion resonance in a rf multipole ion guide with superposed static magnetic field and compare with results of numerical trajectory simulations. © American Society for Mass Spectrometry, 2011

  16. Enhanced ion acoustic lines due to strong ion cyclotron wave fields

    Directory of Open Access Journals (Sweden)

    H. Bahcivan

    2008-07-01

    Full Text Available The Fast Auroral Snapshot Explorer (FAST satellite detected intense and coherent 5–20 m electric field structures in the high-latitude topside auroral ionosphere between the altitudes of 350 km and 650 km. These electric fields appear to belong to electrostatic ion cyclotron (EIC waves in terms of their frequency and wavelengths. Numerical simulations of the response of an electron plasma to the parallel components of these fields show that the waves are likely to excite a wave-driven parallel ion acoustic (IA instability, through the creation of a highly non-Maxwellian electron distribution function, which when combined with the (assumed Maxwellian ion distribution function provides inverse Landau damping. Because the counter-streaming threshold for excitation of EIC waves is well below that for excitation of IA waves (assuming Maxwellian statistics our results suggest a possible two step mechanism for destabilization of IA waves. Combining this simulation result with the observational fact that these EIC waves share a common phenomenology with the naturally enhanced IA lines (NEIALS observed by incoherent scatter radars, especially that they both occur near field-aligned currents, leads to the proposition that this two-step mechanism is an alternative path to NEIALS.

  17. Origin of Asymmetric Solvation Effects for Ions in Water and Organic Solvents Investigated Using Molecular Dynamics Simulations: The Swain Acity-Basity Scale Revisited.

    Science.gov (United States)

    Reif, Maria M; Hünenberger, Philippe H

    2016-08-25

    The asymmetric solvation of ions can be defined as the tendency of a solvent to preferentially solvate anions over cations or cations over anions, at identical ionic charge magnitudes and effective sizes. Taking water as a reference, these effects are quantified experimentally for many solvents by the relative acity (A) and basity (B) parameters of the Swain scale. The goal of the present study is to investigate the asymmetric solvation of ions using molecular dynamics simulations, and to connect the results to this empirical scale. To this purpose, the charging free energies of alkali and halide ions, and of their hypothetical oppositely charged counterparts, are calculated in a variety of solvents. In a first set of calculations, artificial solvent models are considered that present either a charge or a shape asymmetry at the molecular level. The solvation asymmetry, probed by the difference in charging free energy between the two oppositely charged ions, is found to encompass a term quadratic in the ion charge, related to the different solvation structures around the anion and cation, and a term linear in the ion charge, related to the solvation structure around the uncharged ion-sized cavity. For these simple solvent models, the two terms are systematically counteracting each other, and it is argued that only the quadratic term should be retained when comparing the results of simulations involving physical solvents to experimental data. In a second set of calculations, 16 physical solvents are considered. The theoretical estimates for the acity A are found to correlate very well with the Swain parameters, whereas the correlation for B is very poor. Based on this observation, the Swain scale is reformulated into a new scale involving an asymmetry parameter Σ, positive for acitic solvents and negative for basitic ones, and a polarity parameter Π. This revised scale has the same predictive power as the original scale, but it characterizes asymmetry in an

  18. Experimental Measurement of Asymmetric Fluctuations of Poloidal Magnetic Field in Damavand Tokomak at Different Plasma Currents

    Science.gov (United States)

    Moslehi-Fard, Mahmoud; Alinejad, Naser; Rasouli, Chapar; Sadigzadeh, Asghar

    2012-08-01

    Toroidal and Poloidal magnetic fields have an important effect on the tokomak topology. Damavand Tokomak is a small size tokomak characterized with k = 1.2, B t = 1T, R 0 = 36 cm, maximum plasma current is about 35 KA with a discharge time of 21 ms. In this experimental work, the variation of poloidal magnetic field on the torodial cross section is measured and analyzed. In order to measure the polodial magnetic field, 18 probes were installed on the edge of tokomak plasma with ∆θ = 18°, while a limiter was installed inside the torus. Plasma current, I p, induces a polodial magnetic field, B p, smaller than the torodial magnetic field B t. Magnetic lines B produced as a combination of B t and B p, are localized on the nested toroidal magnetic surfaces. The presence of polodial magnetic field is necessary for particles confinement. Mirnov oscillations are the fluctuations of polodial magnetic field, detected by magnetic probes. Disrupted instability in Tokomak typically starts with mirnov oscillations which appear as fluctuations of polodial magnetic field and is detected by magnetic probes. Minor disruptions inside the plasma can contain principal magnetic islands and their satellites can cause the annihilation of plasma confinement. Production of thin layer of turbulent magnetic field lines cause minor disruption. Magnetic limiter may cause the deformation of symmetric equilibrium configuration and chaotic magnetic islands reveal in plasma occurring in thin region of chaotic field lines close to their separatrix. The width of this chaotic layer in the right side of poloidal profile of Damavand Tokomak is smaller than the width in the left side profile because of Shafranov displacement. Ergodic region in the left side of profile develops a perturbation on the magnetic polodial field lines, B p, that are greater in magnitude than that in the right side, although the values of B p on the left side are smaller than that on the right side of the profile. The Left

  19. 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

    NARCIS (Netherlands)

    Helsper, J.P.F.G.; Peters, R.J.B.; Bemmel, M.E.M. van; Rivera, Z.E.H.; Wagner, S.; Kammer, F. von der; Tromp, P.C.; Hofmann, T.; Weigel, S.

    2016-01-01

    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 (IC

  20. Solenoidal Fields for Ion Beam Transport and Focusing

    Energy Technology Data Exchange (ETDEWEB)

    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

  1. Performance of a rectangular secondary concentrator with an asymmetric heliostat field

    Energy Technology Data Exchange (ETDEWEB)

    Kribus, A.; Huleihil, M.; Ben-Mair, R. [Weizmann Inst. of Science, Environmental Sciences and Energy Research Dept., Rehovot (Israel); Timinger, A. [Ludwig-Maximilians Univ. Muenchen, Sektion Physik, Muenchen (Germany)

    2000-07-01

    Secondary concentrators with non-regular cross section have been proposed to permit additional degrees of freedom in heliostat field design, free of the limitations imposed by conventional rotationally symmetric concentrators. A new class of concentrators with a rectangular cross section was found by numerical optimisation for heliostat fields having an elliptic contour with high eccentricity. An example of such a rectangular concentrator was constructed and tested at the Weizmann Institute, where the heliostat field has a strong asymmetry and is poorly suited for symmetric (having regular cross section) concentrators. The performance of the new concentrator has been tested using calorimetric and radiometric measurements. The tests were carried out for several heliostats, located in representative positions relative to the predicted acceptance contours of the concentrator. The results of the tests show an agreement with the prediction, and validate the new design for use with highly eccentric fields. A more general conclusion is the validation of the approach of optimising faceted secondary concentrators with flexible geometry to match heliostat fields having a wide range of possible contours. (Author)

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  5. Plasma physics on auroral field lines - The formation of ion conic distributions

    Science.gov (United States)

    Ashour-Abdalla, M.; Okuda, H.

    1983-01-01

    The formation of the conical distribution function and the acceleration of ions on aurora field lines are considered. Ion cyclotron waves were assumed to be excited by drifting electrons associated with the return current in the auroral zone. A theoretical analysis of ion cyclotron waves is given, and a simulation model is described. Simulation results are presented. The heating of ions and the evolution of ion cyclotron waves on auroral field lines and in the magnetosphere are discussed.

  6. Individual-Ion Addressing with Microwave Field Gradients

    Science.gov (United States)

    2013-04-22

    MW. Near the center of the trap BMW can be approxi- mated for ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi x2 þ z2 p & 3 m by a y-independent x-z...resonance by BMW while the field strength is minimal at the position of qubit 1. The qubit transition is driven by Bk, the component of BMW parallel...configuration B. After applying BMW for duration TMW the positions are switched back to configuration A and the qubit states of both ions are detected [Fig

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  9. Fragmentation of negative ions in a strong laser field

    Science.gov (United States)

    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.

  10. Experimental study of the free surface velocity field in an asymmetrical confluence

    Science.gov (United States)

    Creelle, Stephan; Mignot, Emmanuel; Schindfessel, Laurent; De Mulder, Tom

    2017-04-01

    The hydrodynamic behavior of open channel confluences is highly complex because of the combination of different processes that interact with each other. To gain further insights in how the velocity uniformization between the upstream channels and the downstream channel is proceeding, experiments are performed in a large scale 90 degree angled concrete confluence flume with a chamfered rectangular cross-section and a width of 0.98m. The dimensions and lay-out of the flume are representative for a prototype scale confluence in e.g. drainage and irrigation systems. In this type of engineered channels with sharp corners the separation zone is very large and thus the velocity difference between the most contracted section and the separation zone is pronounced. With the help of surface particle tracking velocimetry the velocity field is recorded from upstream of the confluence to a significant distance downstream of the confluence. The resulting data allow to analyze the evolution of the incoming flows (with a developed velocity profile) that interact with the stagnation zone and each other, causing a shear layer between the two bulk flows. Close observation of the velocity field near the stagnation zone shows that there are actually two shear layers in the vicinity of the upstream corner. Furthermore, the data reveals that the shear layer observed more downstream between the two incoming flows is actually one of the two shear layers next to the stagnation zone that continues, while the other shear layer ceases to exist. The extensive measurement domain also allows to study the shear layer between the contracted section and the separation zone. The shear layers of the stagnation zone between the incoming flows and the one between the contracted flow and separation zone are localized and parameters such as the maximum gradient, velocity difference and width of the shear layer are calculated. Analysis of these data shows that the shear layer between the incoming flows

  11. Analytical possibilities of highly focused ion beams in biomedical field

    Science.gov (United States)

    Ren, M. Q.; Ji, X.; Vajandar, S. K.; Mi, Z. H.; Hoi, A.; Walczyk, T.; van Kan, J. A.; Bettiol, A. A.; Watt, F.; Osipowicz, T.

    2017-09-01

    At the Centre for Ion Beam Applications (CIBA), a 3.5 MV HVEE Singletron™ accelerator serves to provide MeV ion beams (mostly protons or He+) to six state-of-the-art beam lines, four of which are equipped with Oxford triplet magnetic quadrupole lens systems. This facility is used for a wide range of research projects, many of which are in the field of biomedicine. Here we presented a discussion of currently ongoing biomedical work carried out using two beamlines: The Nuclear Microscopy (NM) beamline is mainly used for trace elemental quantitative mapping using a combination of Particle Induced X-ray Emission (PIXE), to measure the trace elemental concentration of inorganic elements, Rutherford Backscattering Spectrometry (RBS), to characterise the organic matrix, and Scanning Transmission Ion Microscopy (STIM) to provide information on the lateral areal density variations of the specimen. Typically, a 2.1 MeV proton beam, focused to 1-2 μm spot size with a current of 100 pA is used. The high resolution single cell imaging beamline is equipped with direct STIM to image the interior structure of single cells with proton and alpha particles of sub-50 nm beam spot sizes. Simultaneously, forward scattering transmission ion microscopy (FSTIM) is utilized to generate images with improved contrast of nanoparticles with higher atomic numbers, such as gold nanoparticles, and fluorescent nanoparticles can be imaged using Proton Induced Fluorescence (PIF). Lastly, in this facility, RBS has been included as an option if required to determine the depth distribution of nanoparticles in cells, albeit with reduced spatial resolution.

  12. Calcium Ion Detection Using Miniaturized InN-based Ion Sensitive Field Effect Transistors

    Directory of Open Access Journals (Sweden)

    Kun-Wei Kao

    2012-03-01

    Full Text Available An Ultrathin (~10 nm InN ion sensitive field effect transistor (ISFET with gate regions functionalized with phosphotyrosine (p-Tyr is proposed to detect calcium ions (Ca2+ in aqueous solution. The ISFET was miniaturized to a chip size of 1.1 mm by 1.5 mm and integrated at the tip of a hypodermic injection needle (18 G for real-time and continuous monitoring. The sensor shows a current variation ratio of 1.11% with per decade change of Ca2+ and a detection limit of 10-6 M. The response time of 5 sec. reveals its great potential for accomplishing fast detection in chemical and physiological sensing applications. The sensor would be applied in medical diagnosis and used to monitor continuous and real-time variations of Ca2+ levels in human blood in the near future.

  13. The Onset of Ion Heating During Magnetic Reconnection with a Strong Guide Field

    CERN Document Server

    Drake, J F

    2014-01-01

    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 $\\alpha$ 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 ...

  14. Analysis of liposomes using asymmetrical flow field-flow fractionation: separation conditions and drug/lipid recovery.

    Science.gov (United States)

    Kuntsche, Judith; Decker, Christiane; Fahr, Alfred

    2012-08-01

    Liposomes composed of dipalmitoylphosphatidylcholine and dipalmitoylphosphatidylglycerol were analyzed by asymmetrical flow field-flow fractionation coupled with multi-angle laser light scattering. In addition to evaluation of fractionation conditions (flow conditions, sample mass, carrier liquid), radiolabeled drug-loaded liposomes were used to determine the liposome recovery and a potential loss of incorporated drug during fractionation. Neither sample concentration nor the cross-flow gradient distinctly affected the size results but at very low sample concentration (injected mass 5 μg) the fraction of larger vesicles was underestimated. Imbalance in the osmolality between the inner and outer aqueous phase resulted in liposome swelling after dilution in hypoosmotic carrier liquids. In contrast, liposome shrinking under hyperosmotic conditions was barely visible. The liposomes themselves eluted completely (lipid recoveries were close to 100%) but there was a loss of incorporated drugs during separation with a strong dependence on the octanol-water partition coefficient of the drug. Whereas corticosterone (partition coefficient ~2) was washed out more or less completely (recovery about 2%), loss of temoporfin (partition coefficient ~9) was only minor (recovery about 80%). All fractionations were well repeatable under the experimental conditions applied in the present study.

  15. Monitoring the Erosion of Hydrolytically-Degradable Nanogels via Multiangle Light Scattering Coupled to Asymmetrical Flow Field-Flow Fractionation

    Science.gov (United States)

    Smith, Michael H.; South, Antoinette B.; Gaulding, Jeffrey C.; Lyon, L. Andrew

    2009-01-01

    We describe the synthesis and characterization of degradable nanogels that display bulk erosion under physiologic conditions (pH = 7.4, 37 °C). Erodible poly(N-isopropylmethacrylamide) nanogels were synthesized by copolymerization with N,O-(dimethacryloyl)hydroxylamine, a cross-linker previously used in the preparation of non-toxic and biodegradable bulk hydrogels. To monitor particle degradation, we employed multiangle light scattering and differential refractometry detection following asymmetrical flow field-flow fractionation. This approach allowed the detection of changes in nanogel molar mass and topology as a function of both temperature and pH. Particle erosion was evident from both an increase in nanogel swelling and a decrease in scattering intensity as a function of time. Following these analyses, the samples were recovered for subsequent characterization by direct particle tracking, which yields hydrodynamic size measurements and enables number density determination. Additionally, we confirmed the conservation of nanogel stimuli-responsivity through turbidity measurements. Thus, we have demonstrated the synthesis of degradable nanogels that erode under conditions and on timescales that are relevant for many drug delivery applications. The combined separation and light scattering detection method is demonstrated to be a versatile means to monitor erosion and should also find applicability in the characterization of other degradable particle constructs. PMID:20000662

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

    Science.gov (United States)

    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.

  17. Influence of applied electric field on the absorption coefficient and subband distances in asymmetrical AIN/GaN coupled double quantum wells

    Institute of Scientific and Technical Information of China (English)

    Cen Long-Bin; Shen Bo; qin Zhi-Xin; Zhang Guo-Yi

    2009-01-01

    The influence of applied electric fields on the absorption coefficient and subband distances in asymmetrical AlN/GaN coupled double quantum wells (CDQWs) has been investigated by solving Schrodinger and Poisson equations self-consistently. It is found that the absorption coefficient of the intersubband transition (ISBT) between the ground state and the third excited state (1odd -2even) can be equal to zero when the electric fields are applied in asymmetrical A1N/GaN CDQWs,which is related to applied electric fields induced symmetry recovery of these states. Meanwhile,the energy distances between 1odd -2even and 1even - 2even subbands have different relationships from each other with the increase of applied electric fields due to the different polarization-induced potential drops between the lett and the right wells. The results indicate that an electrical-optical modulator operated within the opto-communication wavelength range can be realized in spite of the strong polarization-induced electric fields in asymmetrical AIN/GaN CDQWs.

  18. On the use of asymmetric PSF on NIR images of crowded stellar fields

    CERN Document Server

    Fiorentino, Giuliana; Iannicola, Giacinto; Bono, Giuseppe; Monelli, Matteo; Testa, Vincenzo; Arcidiacono, Carmelo; Faccini, Marco; Gilmozzi, Roberto; Xompero, Marco; Briguglio, Runa

    2014-01-01

    We present data collected using the camera PISCES coupled with the Firt Light Adaptive Optics (FLAO) mounted at the Large Binocular Telescope (LBT). The images were collected using two natural guide stars with an apparent magnitude of R<13 mag. During these observations the seeing was on average ~0.9". The AO performed very well: the images display a mean FWHM of 0.05 arcsec and of 0.06 arcsec in the J- and in the Ks-band, respectively. The Strehl ratio on the quoted images reaches 13-30% (J) and 50-65% (Ks), in the off and in the central pointings respectively. On the basis of this sample we have reached a J-band limiting magnitude of ~22.5 mag and the deepest Ks-band limiting magnitude ever obtained in a crowded stellar field: Ks~23 mag. J-band images display a complex change in the shape of the PSF when moving at larger radial distances from the natural guide star. In particular, the stellar images become more elongated in approaching the corners of the J-band images whereas the Ks-band images are more ...

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

    Science.gov (United States)

    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.

  20. Asymmetrical flow field-flow fractionation with multi-angle light scattering detection for the analysis of structured nanoparticles.

    Science.gov (United States)

    Zattoni, Andrea; Rambaldi, Diana Cristina; Reschiglian, Pierluigi; Melucci, Manuela; Krol, Silke; Garcia, Ana Maria Coto; Sanz-Medel, Alfredo; Roessner, Dierk; Johann, Christoph

    2009-12-25

    Synthesis and applications of new functional nanoparticles are topics of increasing interest in many fields of nanotechnology. Chemical modifications of inorganic nanoparticles are often necessary to improve their features as spectroscopic tracers or chemical sensors, and to increase water solubility and biocompatibility for applications in nano-biotechnology. Analysis and characterization of structured nanoparticles are then key steps for their synthesis optimization and final quality control. Many properties of structured nanoparticles are size-dependent. Particle size distribution analysis then provides fundamental analytical information. Asymmetrical flow field-flow fractionation (AF4) with multi-angle light scattering (MALS) detection is able to size-separate and to characterize nanosized analytes in dispersion. In this work we focus on the central role of AF4-MALS to analyze and characterize different types of structured nanoparticles that are finding increasing applications in nano-biotechnology and nanomedicine: polymer-coated gold nanoparticles, fluorescent silica nanoparticles, and quantum dots. AF4 not only size-fractionated these nanoparticles and measured their hydrodynamic radius (r(h)) distribution but it also separated them from the unbound, relatively low-M(r) components of the nanoparticle structures which were still present in the sample solution. On-line MALS detection on real-time gave the gyration radius (r(g)) distribution of the fractionated nanoparticles. Additional information on nanoparticle morphology was then obtained from the r(h)/r(g) index. Stability of the nanoparticle dispersions was finally investigated. Aggregation of the fluorescent silica nanoparticles was found to depend on the concentration at which they were dispersed. Partial release of the polymeric coating from water-soluble QDs was found when shear stress was induced by increasing flowrates during fractionation.

  1. Investigation of zinc oxide particles in cosmetic products by means of centrifugal and asymmetrical flow field-flow fractionation.

    Science.gov (United States)

    Sogne, Vanessa; Meier, Florian; Klein, Thorsten; Contado, Catia

    2017-09-15

    The dimensional characterization of insoluble, inorganic particles, such as zinc oxide ZnO, dispersed in cosmetic or pharmaceutical formulations, is of great interest considering the current need of declaring the possible presence of nanomaterials on the label of commercial products. This work compares the separation abilities of Centrifugal- and Asymmetrical Flow Field-Flow Fractionation techniques (CF3 and AF4, respectively), equipped with UV-vis, MALS and DLS detectors, in size sorting ZnO particles, both as pristine powders and after their extraction from cosmetic matrices. ZnO particles, bare and superficially modified with triethoxycaprylyl silane, were used as test materials. To identify the most suitable procedure necessary to isolate the ZnO particles from the cosmetic matrix, two O/W and two W/O emulsions were formulated on purpose. The suspensions, containing the extracted particles ZnO, were separated by both Field-Flow Fractionation (FFF) techniques to establish a common analysis protocol, applicable for the analysis of ZnO particles extracted from three commercial products, sold in Europe for the baby skin care. Key aspects of this study were the selection of an appropriate dispersing agent enabling the particles to stay in stable suspensions (>24h)and the use of multiple detectors (UV-vis, MALS and DLS) coupled on-line with the FFF channels, to determine the particle dimensions without using the retention parameters. Between the two FFF techniques, CF3 revealed to be the most robust one, able to sort all suspensions created in this work. Copyright © 2017 Elsevier B.V. All rights reserved.

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

    Science.gov (United States)

    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+.

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

    Energy Technology Data Exchange (ETDEWEB)

    Hajmirzaheydarali, M.; Sadeghipari, M.; Akbari, M.; Shahsafi, A.; Mohajerzadeh, S., E-mail: mohajer@ut.ac.ir [Thin Film and Nanoelectronics Lab, Nanoelectronics Center of Excellence, School of Electrical and Computer Engineering, University of Tehran, Tehran 143957131 (Iran, Islamic Republic of)

    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.

  4. Electron-ion-ion coincidence experiments for photofragmentation of polyatomic molecules using pulsed electric fields: treatment of random coincidences

    CERN Document Server

    Pruemper, G

    2007-01-01

    In molecular photofragmentation processes by soft X-rays, a number of ionic fragments can be produced, each having a different abundance and correlation with the emitted electron kinetic energy. For investigating these fragmentation processes, electron-ion and electron-ion-ion coincidence experiments, in which the kinetic energy of electrons are analyzed using an electrostatic analyzer while the mass of the ions is analyzed using a pulsed electric field, are very powerful. For such measurements, however, the contribution of random coincidences is substantial and affects the data in a non-trivial way. Simple intuitive subtraction methods cannot be applied. In the present paper, we describe these electron-ion and electron-ion-ion coincidence experiments together with a subtraction method for the contribution from random coincidences. We provide a comprehensive set of equations for the data treatment, including equations for the calculation of error-bars. We demonstrate the method by applying it to the fragmenta...

  5. Computer simulation of the emission process of some field emission alloy ion sources

    Energy Technology Data Exchange (ETDEWEB)

    Georgieva, S.; Vichev, R.; Drandarov, N. [Bulgarian Academy of Sciences, Sofia (Bulgaria)

    1996-10-01

    The ion emission process from InGa, AuBe and AuSi field emission alloy ion sources (LAIS) is simulated. Field strength is calculated using the SOC model. Paraxial source size, beam spot size, energy and angular distributions are estimated. The effects on the emission characteristics of Coulomb interaction between ions are investigated, and the strong influences of ion mass and charge are also shown. (Author).

  6. Optimizing direct intense-field laser acceleration of ions

    Energy Technology Data Exchange (ETDEWEB)

    Harman, Zoltan [Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg (Germany); ExtreMe Matter Institute EMMI, Planckstrasse 1, D-64291 Darmstadt (Germany); Salamin, Yousef I. [Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg (Germany); Department of Physics, American University of Sharjah, POB 26666, Sharjah (United Arab Emirates); Galow, Benjamin J.; Keitel, Christoph H. [Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg (Germany)

    2011-11-15

    The dynamics of ion acceleration in tightly focused laser beams is investigated in relativistic simulations. Studies are performed to find the optimal parameters which maximize the energy gain, beam quality, and flux. The exit ionic kinetic energy and its uncertainty are improved and the number of accelerated particles is increased by orders of magnitude over our earlier results, especially when working with a longer laser wavelength. Laser beams of powers of 0.1-10 petawatts and focused to subwavelength spot radii are shown to directly accelerate protons and bare nuclei of helium, carbon, and oxygen from a few to several hundred MeV/nucleon. Variation of the volume of the initial ionic ensemble, as well as the introduction of a pulse shape on the laser fields, have been investigated and are shown to influence the exit particle kinetic energies only slightly.

  7. Fractionation and Characterization of High Aspect Ratio Gold Nanorods Using Asymmetric-Flow Field Flow Fractionation and Single Particle Inductively Coupled Plasma Mass Spectrometry

    OpenAIRE

    Nguyen, Thao M; Jingyu Liu; Vincent A. Hackley

    2015-01-01

    Gold nanorods (GNRs) are of particular interest for biomedical applications due to their unique size-dependent longitudinal surface plasmon resonance band in the visible to near-infrared. Purified GNRs are essential for the advancement of technologies based on these materials. Used in concert, asymmetric-flow field flow fractionation (A4F) and single particle inductively coupled mass spectrometry (spICP-MS) provide unique advantages for fractionating and analyzing the typically complex mixtur...

  8. Characterization of Silver Nanoparticles under Environmentally Relevant Conditions Using Asymmetrical Flow Field-Flow Fractionation (AF4.

    Directory of Open Access Journals (Sweden)

    Min-Hee Jang

    Full Text Available The development of methods to monitor manufactured nanomaterials in the environment is one of the crucial areas for the assessment of their risk. More specifically, particle size analysis is a key element, because many properties of nanomaterial are size dependent. The sizing of nanomaterials in real environments is challenging due to their heterogeneity and reactivity with other environmental components. In this study, the fractionation and characterization of a mixture of polyvinylpyrrolidone-coated silver nanoparticles (PVP-AgNPs of three different sizes were investigated using asymmetrical flow field-flow fractionation (AF4 coupled with UV-Vis spectrophotometry. In particular, the effects of electrolyte composition and natural organic matter (NOM on the particle size and stability were evaluated. The fractogram peaks (i.e., stability of three different AgNPs decreased in the presence of both 10 mM NaCl and 10 mM CaCl2, while increased with increasing concentration of humic acid (HA. In addition, the hydrodynamic diameters of AgNPs in both electrolytes slightly increased with an increase of HA concentration, suggesting the adsorption (coating of HA onto the particle surface. It is also interesting to note that an increase in the particle size depended on the types of electrolyte, which could be explained by the conformational characteristics of the adsorbed HA layers. Consistent these results, AgNPs suspended in lake water containing relatively high concentration of organic carbon (TOC showed higher particle stability and larger particle size (i.e., by approximately 4 nm than those in river water. In conclusion, the application of AF4 coupled with highly sensitive detectors could be a powerful method to characterize nanoparticles in natural waters.

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

    Science.gov (United States)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

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

    Science.gov (United States)

    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.

  14. Field-effect ion-transport devices with carbon nanotube channels: schematics and simulations

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ju Yul; Kang, Jeong Won; Byun, Ki Ryang; Kang, Eu Seok; Hwang, Ho Jung [Chung-Ang University, Seoul (Korea, Republic of); Lee, Jun Ha; Lee, Hoong Joo [Sangmyung University, Chonan (Korea, Republic of); Kwon, Oh Keun [Semyung University, Jecheon (Korea, Republic of); Kim, Young Min [Chung-Cheong University, Cheongwon (Korea, Republic of)

    2004-08-15

    We investigated field-effect ion-transport devices based on carbon nanotubes by using classical molecular dynamics simulations under applied external force fields, and we present model schematics that can be applied to the nanoscale data storage devices and unipolar ionic field-effect transistors. As the applied external force field is increased, potassium ions rapidly flow through the nanochannel. Under low external force fields, thermal fluctuations of the nanochannels affect tunneling of the potassium ions whereas the effects of thermal fluctuations are negligible under high external force fields. Since the electric current conductivity increases when potassium ions are inserted into fullerenes or carbon nanotubes, the field effect due to the gate, which can modify the position of the potassium ions, changes the tunneling current between the drain and the source.

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

    Science.gov (United States)

    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.

  16. Asymmetric Flow-Field Flow Fractionation Hyphenated ICP-MS as an Alternative to Cloud Point Extraction for Quantification of Silver Nanoparticles and Silver Speciation: Application for Nanoparticles with a Protein Corona.

    Science.gov (United States)

    Mudalige, Thilak K; Qu, Haiou; Linder, Sean W

    2015-07-21

    Production and application of nanoparticles in consumer products is at an all-time high due to the emerging field of nanotechnology. Direct detection and quantification of trace levels of nanoparticles within consumer products is very challenging and problematic. Although multiple methodologies are available for this purpose, each method has its own set of limitations. Herein, we developed an analytical platform consisting of asymmetric flow-field flow fractionation (AF4) coupled with inductively coupled plasma mass spectroscopy (ICP-MS) for the speciation and quantification of silver ions and silver nanoparticles at the ng/kg level (ppt). AF4 is utilized to concentrate the nanoparticles, and ICP-MS acts as the detector. The protein corona that forms upon exposure of nanoparticles to bovine serum albumin was utilized as a nanoparticle stabilization and AF4 recovery enhancement mechanism. Speciation of silver ions and nanoparticles was achieved with the assistance of penicillamine as a complexation ligand. The effect of nanoparticle size, surface coating, and ionization state toward the detection and quantification of the developed methodology was evaluated. The detection limit was found to be 4 ng/kg with the application of a 5 mL sample loop. Further application of this developed methodology on environmentally relevant samples was demonstrated by the analysis of Arkansas River water spiked with silver nanoparticles and nanoparticle spiked into humic acid solution (50 mg/L) at an environmentally relevant level.

  17. Asymmetric fission and evaporation of C{sup r+}{sub 60} (r = 2-4) fullerene ions in ion-C{sub 60} collisions: III. Universal behaviour of fission

    Energy Technology Data Exchange (ETDEWEB)

    Bordenave-Montesquieu, D; Bordenave-Montesquieu, A; Rentenier, A; Moretto-Capelle, P [LCAR-IRSAMC, UMR 5589 Universite Paul Sabatier-CNRS, 118 rte de Narbonne, 31062 Toulouse Cedex (France)

    2005-04-14

    The behaviour of the asymmetrical fission (AF) scheme (correlated ion distributions) against the collision conditions is investigated using H{sup +}{sub x} (x = 1-3) and He{sup +} projectiles in the 1-130 keV collision energy range. The present work is an extension of our recent publications on this topic using 11 keV protons (Rentenier et al 2004 J. Phys. B: At. Mol. Opt. Phys. 37 2429 and 2455). The threshold for AF is observed at 2 keV proton energy corresponding to a maximum deposited energy equal to about 41 eV. The main result concerns the fragment distributions resulting from AF of C{sup r+}{sub 60} ions, and secondary dissociation of even-n C{sup +}{sub n} fragments, which are both found to remain independent of the projectile species and collision velocity. These findings indicate that they are insensitive to the internal energy distributions of the parent ions. In addition, a contribution of binary collisions between the projectile and individual carbon atoms of the C{sub 60} molecule to AF is identified in the C{sup +}{sub 1} production at the lowest collision velocities, the so-called impulsive fragmentation.

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

    Science.gov (United States)

    Alterations in calcium ion activity by ELF and RF electromagnetic fieldsIntroductionCalcium 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...

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

    Science.gov (United States)

    Alterations in calcium ion activity by ELF and RF electromagnetic fieldsIntroductionCalcium 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...

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  2. 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.

    Science.gov (United States)

    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

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

    Science.gov (United States)

    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.

  4. Modification of semiconductor materials using laser-produced ion streams additionally accelerated in the electric fields

    Science.gov (United States)

    Rosinski, M.; Badziak, B.; Parys, P.; Wołowski, J.; Pisarek, M.

    2009-03-01

    The laser-produced ion stream may be attractive for direct ultra-low-energy ion implantation in thin layer of semiconductor for modification of electrical and optical properties of semiconductor devices. Application of electrostatic fields for acceleration and formation of laser-generated ion stream enables to control the ion stream parameters in broad energy and current density ranges. It also permits to remove the useless laser-produced ions from the ion stream designed for implantation. For acceleration of ions produced with the use of a low fluence repetitive laser system (Nd:glass: 2 Hz, pulse duration: 3.5 ns, pulse energy:˜0.5 J, power density: 10 10 W/cm 2) in IPPLM the special electrostatic system has been prepared. The laser-produced ions passing through the diaphragm (a ring-shaped slit in the HV box) have been accelerated in the system of electrodes. The accelerating voltage up to 40 kV, the distance of the diaphragm from the target, the diaphragm diameter and the gap width were changed for choosing the desired parameters (namely the energy band of the implanted ions) of the ion stream. The characteristics of laser-produced Ge ion streams were determined with the use of precise ion diagnostic methods, namely: electrostatic ion energy analyser and various ion collectors. The laser-produced and post-accelerated Ge ions have been used for implantation into semiconductor materials for nanocrystal fabrication. The characteristics of implanted samples were measured using AES.

  5. MAGNETIC FIELD GRADIENT EFFECTS ON ION FLUX BEHAVIORS IN ECR PLASMA SOURCES

    Institute of Scientific and Technical Information of China (English)

    1998-01-01

    The available electron cyclotron resonance plasma source has been simulated in two-dimensional configuration space (z, r) and three-dimensional velocity space (Vz, Vr Vθ). The simulation is focused on the magnetic field gradient effects on ion flux behaviors in electron cyclotron resonance plasma sources. The simulation results show that, when the magnetic field gradients increase, electron temperature, plasma density, ionization rate, and ion flux in Zdirection would decrease, while ion energy and plasma potential would increase.

  6. Investigation of the Decelerating Field of an Electron Multiplier under Negative Ion Impact

    DEFF Research Database (Denmark)

    Larsen, Elfinn; Kjeldgaard, K.

    1973-01-01

    The effect of the decelerating field of an electron multiplier towards negative ions was investigated under standard mass spectrometric conditions. Diminishing of this decelerating field by changing of the potential of the electron multiplier increased the overall sensitivity to negative ions...... by a factor of 100. The secondary electron emission coefficient for the negative halogen ions relative to I− were measured on CuBe at the kinetic energies 1.0 and 1.5 keV....

  7. Field ionization characteristics of an ion source array for neutron generators

    Energy Technology Data Exchange (ETDEWEB)

    Bargsten Johnson, B.; Schwoebel, P. R. [University of New Mexico, Albuquerque, New Mexico 87131 (United States); Resnick, P. J. [Sandia National Laboratories, Albuquerque, New Mexico 87123 (United States); Holland, C. E. [SRI International, Menlo Park, California 94025 (United States); Hertz, K. L. [Sandia National Laboratories, Livermore, California 94551 (United States); Chichester, D. L. [Idaho National Laboratory, Idaho Falls, Idaho 83415 (United States)

    2013-11-07

    A new deuterium ion source is being developed to improve the performance of existing compact neutron generators. The ion source is a microfabricated array of metal tips with an integrated gate (i.e., grid) and produces deuterium ions by field ionizing (or field desorbing) a supply of deuterium gas. Deuterium field ion currents from arrays at source temperatures of 77 K and 293 K are studied. Ion currents from single etched-wire tips operating under the same conditions are used to help understand array results. I-F characteristics of the arrays were found to follow trends similar to those of the better understood single etched-wire tip results; however, the fields achieved by the arrays are limited by electrical breakdown of the structure. Neutron production by field ionization at 293 K was demonstrated for the first time from microfabricated array structures with integrated gates.

  8. Field ionization characteristics of an ion source array for neutron generators

    Energy Technology Data Exchange (ETDEWEB)

    B. Bargsten Johnson; P. R. Schwoebel; P. J. Resnick; C. E. Holland; L. Hertz; D. L. Chichester

    2013-11-01

    A new deuterium ion source is being developed to improve the performance of existing compact neutron generators. The ion source is a microfabricated array of metal tips with an integrated gate (i.e., grid) and produces deuterium ions by field ionizing (or field desorbing) a supply of deuterium gas. Deuterium field ion currents from arrays at source temperatures of 77?K and 293?K are studied. Ion currents from single etched-wire tips operating under the same conditions are used to help understand array results. I-F characteristics of the arrays were found to follow trends similar to those of the better understood single etched-wire tip results; however, the fields achieved by the arrays are limited by electrical breakdown of the structure. Neutron production by field ionization at 293?K was demonstrated for the first time from microfabricated array structures with integrated gates.

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

    Energy Technology Data Exchange (ETDEWEB)

    Nakamura, T., E-mail: tsubasa@oshima-k.ac.jp; Wada, H.; Furuse, M. [National Institute of Technology, Oshima College, 1091-1 Komatsu, Suouoshima, Oshima, Yamaguchi 742-2193 (Japan); Asaji, T. [National Institute of Technology, Toyama College, 13 Hongo, Toyama 939-8630 (Japan)

    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.

  10. Field ionization characteristics of an ion source array for neutron generators

    Science.gov (United States)

    Bargsten Johnson, B.; Schwoebel, P. R.; Resnick, P. J.; Holland, C. E.; Hertz, K. L.; Chichester, D. L.

    2013-11-01

    A new deuterium ion source is being developed to improve the performance of existing compact neutron generators. The ion source is a microfabricated array of metal tips with an integrated gate (i.e., grid) and produces deuterium ions by field ionizing (or field desorbing) a supply of deuterium gas. Deuterium field ion currents from arrays at source temperatures of 77 K and 293 K are studied. Ion currents from single etched-wire tips operating under the same conditions are used to help understand array results. I-F characteristics of the arrays were found to follow trends similar to those of the better understood single etched-wire tip results; however, the fields achieved by the arrays are limited by electrical breakdown of the structure. Neutron production by field ionization at 293 K was demonstrated for the first time from microfabricated array structures with integrated gates.

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

    Science.gov (United States)

    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.

  12. Ion rotational velocity of a field-reversed configuration plasma measured by neutral beam probe spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ito, Y.; Tanjyo, M.; Ohi, S.; Goto, S.; Ishimura, T.

    1987-01-01

    The ion rotational angular velocity ..cap omega.. and the ion temperature T/sub i/ of a translated field-reversed configuration (FRC) plasma are measured using neutral beam probe spectroscopy. The value of ..cap omega.. is --(1.0--1.2) x ..cap omega..* at the onset time of the n = 2 rotational instability, where ..cap omega..* is the ion diamagnetic frequency for a rigid-rotor equilibrium. The ion rotational direction is the same as the ion diamagnetic direction. The value of ..cap omega.. is smaller than the angular frequency ..omega../sub re/ of the n = 2 instability, which can yield experimental evidence of the ion kinetic effects on the n = 2 instability in the FRC plasma. When the octupole field is applied to the plasma in order to suppress the n = 2 deformation, ..cap omega.. is slightly reduced. The ion temperature T/sub i/ is --70 eV at the onset time of the n = 2 instability.

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

    Science.gov (United States)

    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.

  14. Electromagnetic fields and anomalous transports in heavy-ion collisions-a pedagogical review.

    Science.gov (United States)

    Huang, Xu-Guang

    2016-07-01

    The hot and dense matter generated in heavy-ion collisions may contain domains which are not invariant under P and CP transformations. Moreover, heavy-ion collisions can generate extremely strong magnetic fields as well as electric fields. The interplay between the electromagnetic field and triangle anomaly leads to a number of macroscopic quantum phenomena in these P- and CP-odd domains known as anomalous transports. The purpose of this article is to give a pedagogical review of various properties of the electromagnetic fields, the anomalous transport phenomena, and their experimental signatures in heavy-ion collisions.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

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

    Science.gov (United States)

    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.

  17. Effect of upward ion on field-aligned currents in the near-earth magnetotail

    Institute of Scientific and Technical Information of China (English)

    ZHANG; LingQian; LIU; ZhenXing; MA; ZhiWei; SHEN; Chao; ZHOU; XuZhi; ZHANG; XianGuo

    2007-01-01

    A 3-dimensional resistive MHD simulation was carried out to study the effect of the upward ions on the field-aligned currents (FACs) in the near-earth magnetotail. The simulation results show that the up-flow ions originating from the nightside auroral oval would drift into the center plasma sheet along the magnetic field lines in the plasma sheet boundary, and have an important effect on the field-aligned currents. The main conclusions include that: 1) the upward-ions mainly affect the field- aligned currents in the near-earth magnetotail (inside 15 Re); 2) the generated FACs in the near-earth region have two types, i.e., Region 1 FAC in the high-latitude and Region 2 FAC in the low-latitude; 3) FACs increase with the enhancement of the upward ion flux; 4) with the same flux of the upward ions, FACs enhance with the increase of the velocity of the up-flow ions; 5) the intensification of FACs is also closely related with the latitude of the upward ions, and the ions from the closed field line region generate larger FACs; 6) the generation of FACs is closely related with By created by the upward ions.

  18. Ion mobility sensor system

    Science.gov (United States)

    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.

  19. 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

    DEFF Research Database (Denmark)

    Löschner, Katrin; Harrington, Chris F.; Kearney, Jacque-Lucca;

    2015-01-01

    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 (AF4) coupled...... and give an indication of particle size, providing useful pathological indices. As such, the methods indicate a new way forward for in vivo investigation of the processes which lead to tissue necrosis and hip loosening in patients with MoM hip replacements....

  20. Asymmetric structures of field-aligned currents and convection of ionospheric plasma controlled by the IMF azimuthal component and season of year

    DEFF Research Database (Denmark)

    Lukianova, R. Yu.; Kozlovsky, A.; Christiansen, Freddy

    2010-01-01

    We present the results of using the statistical model of field-aligned currents (FACs) based on satellite data and the numerical model of the electric potential distribution in order to detect the asymmetric part in FAC structures and ionospheric plasma convection controlled by the IMF azimuthal (B...... y ) component at different seasons of the year. These structures can be identified by plotting diagrams, which represent differences in corresponding maps for opposite signs of IMF B y . Circular near-pole current symmetric about the noon meridian and corresponding convection vortices around...

  1. Photodetachment of negative ion in a gradient electric field near a metal surface

    Institute of Scientific and Technical Information of China (English)

    Liu Tian-Qi; Wang De-Hun; Han Cai; Liu Jiang; Liang Dong-Qi; Xie Si-Cheng

    2012-01-01

    Based on closed-orbit theory,the photodetachment of Hˉ in a gradient electric field near a metal surface is studied.It is demonstrated that the gradient electric field has a significant influence on the photodetachment of negative ions near a metal surface.With the increase of the gradient of the electric field,the oscillation in the photodetachment cross section becomes strengthened.Besides,in contrast to the photodetachment of Hˉ near a metal surface in a uniform electric field,the oscillating amplitude and the oscillating region in the cross section of a gradient electric field also become enlarged.Therefore,we can use the gradient electric field to control the photodetachment of negative ions near a metal surface.We hope that our results will be useful for understanding the photodetachment of negative ions in the vicinity of surfaces,cavities,and ion traps.

  2. Cold asymmetrical fermion superfluids

    Energy Technology Data Exchange (ETDEWEB)

    Caldas, Heron

    2003-12-19

    The recent experimental advances in cold atomic traps have induced a great amount of interest in fields from condensed matter to particle physics, including approaches and prospects from the theoretical point of view. In this work we investigate the general properties and the ground state of an asymmetrical dilute gas of cold fermionic atoms, formed by two particle species having different densities. We have show in a recent paper, that a mixed phase composed of normal and superfluid components is the energetically favored ground state of such a cold fermionic system. Here we extend the analysis and verify that in fact, the mixed phase is the preferred ground state of an asymmetrical superfluid in various situations. We predict that the mixed phase can serve as a way of detecting superfluidity and estimating the magnitude of the gap parameter in asymmetrical fermionic systems.

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

    Energy Technology Data Exchange (ETDEWEB)

    Deards, C. L. [Lockheed Martin, 1011 Lockheed Way, Palmdale, California 93599 (United States); Hoffman, A. L.; Steinhauer, L. C. [Redmond Plasma Physics Laboratory, University of Washington, 14700 NE 95th Street, Suite 100, Redmond, Washington 98052 (United States)

    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.

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

    Science.gov (United States)

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

    2011-11-01

    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.

  5. 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

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Shailesh, E-mail: shailesh.sharma6@mail.dcu.ie [Dublin City University, Glasnevin, Dublin 9 (Ireland); Impedans Limited, Chase House, City Junction Business Park, Northern Cross, D17 AK63, Dublin 17 (Ireland); Gahan, David, E-mail: david.gahan@impedans.com; Scullin, Paul; Doyle, James; Lennon, Jj; Hopkins, M. B. [Impedans Limited, Chase House, City Junction Business Park, Northern Cross, D17 AK63, Dublin 17 (Ireland); Vijayaraghavan, Rajani K.; Daniels, Stephen [Dublin City University, Glasnevin, Dublin 9 (Ireland)

    2016-04-15

    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.

  6. 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.

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  8. Generation of elliptically polarized nitrogen-ion laser fields using two-color femtosecond laser pulses

    CERN Document Server

    Li, Ziting; Chu, Wei; Xie, Hongqiang; Yao, Jinping; Li, Guihua; Qiao, Lingling; Wang, Zhanshan; Cheng, Ya

    2015-01-01

    We experimentally investigate generation of molecular nitrogen-ion lasers with two femtosecond laser pulses at different wavelengths. The first pulse serves as the pump which ionizes the nitrogen molecules and excites the molecular ions to excited electronic states. The second pulse serves as the probe which leads to stimulated emission from the excited molecular ions. We observe that changing the angle between the polarization directions of the two pulses gives rise to elliptically polarized molecular nitrogen-ion laser fields, which is interpreted as a result of strong birefringence of the gain medium near the wavelengths of the molecular nitrogen-ion laser.

  9. Ablation plasma transport using multicusp magnetic field for laser ion source

    Science.gov (United States)

    Takahashi, K.; Umezawa, M.; Uchino, T.; Ikegami, K.; Sasaki, T.; Kikuchi, T.; Harada, N.

    2016-05-01

    We propose a plasma guiding method using multicusp magnetic field to transport the ablation plasma keeping the density for developing laser ion sources. To investigate the effect of guiding using the magnetic field on the ablation plasma, we demonstrated the transport of the laser ablation plasma in the multicusp magnetic field. The magnetic field was formed with eight permanent magnets and arranged to limit the plasma expansion in the radial direction. We investigated the variation of the plasma ion current density and charge distribution during transport in the magnetic field. The results indicate that the plasma is confined in the radial direction during the transport in the multicusp magnetic field.

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

    Science.gov (United States)

    Fyta, Maria; Netz, Roland R

    2012-03-28

    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.

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

    Science.gov (United States)

    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. Electron-ion-ion coincidence experiments for photofragmentation of polyatomic molecules using pulsed electric fields: Treatment of random coincidences

    Energy Technology Data Exchange (ETDEWEB)

    Pruemper, G. [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980 8577 (Japan)]. E-mail: pruemper@tagen.tohoku.ac.jp; Ueda, K. [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980 8577 (Japan)

    2007-05-01

    In molecular photofragmentation processes by soft X-rays, a number of ionic fragments can be produced, each having a different abundance and correlation with the kinetic energy of the emitted electron. For investigating these fragmentation processes, electron-ion and electron-ion-ion coincidence experiments, in which the kinetic energy of electrons are analyzed using an electrostatic analyzer while the mass of the ions is analyzed using a pulsed electric field, are very powerful. For such measurements, however, the contribution of random coincidences is substantial and affects the data in a non-trivial way. Simple intuitive subtraction methods cannot be applied. In the present paper, we describe these electron-ion and electron-ion-ion coincidence experiments together with a subtraction method for the contribution from random coincidences. We provide a comprehensive set of equations for the data treatment, including equations for the calculation of error-bars. We demonstrate the method by applying it to the fragmentation of free CF{sub 3}SF{sub 5} molecules.

  13. Acceleration of hydrogen ions and conic formation along auroral field lines

    Energy Technology Data Exchange (ETDEWEB)

    Okuda, H.; Ashour-Abdalla, M.

    1982-05-01

    Electrostatic ion cyclotron turbulence and the formation of ion conics at low altitudes (approx. = 1500 km) along auroral field lines have been investigated analytically and by plasma numerical simulations. Ion cyclotron waves are assumed to be driven unstable by the up-going cold ionospheric electrons associated with the downward auroral current. When the electron drift speed is comparable to the electron thermal speed, it is found that the large amplitude, e phi/T/sub e/ approx. = 1, coherent, ..omega.. = ..cap omega../sub i/, ion cyclotron waves shoudl exist along auroral field lines at low altitudes extending approx. = 500 to 1000 km. Ion conics are associated with the cyclotron turbulence and the ion bulk temperature is found to increase a factor of 10 of the initial ionospheric temperature, while the temperature of the high energy tail can be as much as a factor of 100 of the ionospheric temperature. Theory and simulations agree well.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  16. Molecular dynamics simulations of ion irradiation of a surface under an electric field

    Energy Technology Data Exchange (ETDEWEB)

    Parviainen, S., E-mail: stefan.parviainen@iki.fi; Djurabekova, F.

    2014-11-15

    The presence of high electric fields may affect significantly the process of sputtering of metal surfaces by energetic ions, especially in the vicinity of rough surface features. The effect can be significant if the energy of ions is fairly low. Moreover, the nanosized rough surface features – invisible to a naked eye, both intrinsic ones due to technological processing of surfaces and those forming because of sputtering – may affect the topology of surface erosion under ion bombardment. In this work we study by means of concurrent electrodynamics–molecular dynamics the sputtering yield of Cu{sup +} ions hitting a flat Cu surface or a nanosized Cu protrusion as a function of both ion energy and electric field strength. The results show that the sputtering yield is significantly enhanced in the presence of an electric field in both cases.

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

    Energy Technology Data Exchange (ETDEWEB)

    Saleem, H. [Department of Space Science, Institute of Space Technology, 1-Islamabad Highway, Islamabad (Pakistan); Theoretical Research Institute, Pakistan Academy of Sciences, 3-Constitution Avenue G-5/3, Islamabad (Pakistan); Ali, S. [Theoretical Research Institute, Pakistan Academy of Sciences, 3-Constitution Avenue G-5/3, Islamabad (Pakistan); National Centre for Physics (NCP) at Quaid-i-Azam University Campus, Shahdra Valley Road, Islamabad 44000 (Pakistan); Haque, Q. [Theoretical Research Institute, Pakistan Academy of Sciences, 3-Constitution Avenue G-5/3, Islamabad (Pakistan); National Centre for Physics (NCP) at Quaid-i-Azam University Campus, Shahdra Valley Road, Islamabad 44000 (Pakistan); Theoretical Physics Division, PINSTECH, P.O. Nilore, Islamabad (Pakistan)

    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.

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

    Science.gov (United States)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Yamazaki, Takao; Watanabe, Yusuke; Kanya, Reika [Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Yamanouchi, Kaoru, E-mail: kaoru@chem.s.u-tokyo.ac.jp [Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); NANOQUINE, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)

    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.

  20. Modification of semiconductor materials using laser-produced ion streams additionally accelerated in the electric fields

    Energy Technology Data Exchange (ETDEWEB)

    Rosinski, M. [Institute of Plasma Physics and Laser Microfusion, P.O. Box 49, Hery Street 23, 00-908 Warsaw (Poland)], E-mail: rosinski@ifpilm.waw.pl; Badziak, B.; Parys, P.; Wolowski, J. [Institute of Plasma Physics and Laser Microfusion, P.O. Box 49, Hery Street 23, 00-908 Warsaw (Poland); Pisarek, M. [Warsaw University of Technology, Material Science and Engineering Faculty, Warsaw (Poland)

    2009-03-01

    The laser-produced ion stream may be attractive for direct ultra-low-energy ion implantation in thin layer of semiconductor for modification of electrical and optical properties of semiconductor devices. Application of electrostatic fields for acceleration and formation of laser-generated ion stream enables to control the ion stream parameters in broad energy and current density ranges. It also permits to remove the useless laser-produced ions from the ion stream designed for implantation. For acceleration of ions produced with the use of a low fluence repetitive laser system (Nd:glass: 2 Hz, pulse duration: 3.5 ns, pulse energy:{approx}0.5 J, power density: 10{sup 10} W/cm{sup 2}) in IPPLM the special electrostatic system has been prepared. The laser-produced ions passing through the diaphragm (a ring-shaped slit in the HV box) have been accelerated in the system of electrodes. The accelerating voltage up to 40 kV, the distance of the diaphragm from the target, the diaphragm diameter and the gap width were changed for choosing the desired parameters (namely the energy band of the implanted ions) of the ion stream. The characteristics of laser-produced Ge ion streams were determined with the use of precise ion diagnostic methods, namely: electrostatic ion energy analyser and various ion collectors. The laser-produced and post-accelerated Ge ions have been used for implantation into semiconductor materials for nanocrystal fabrication. The characteristics of implanted samples were measured using AES.

  1. Knowledge Representation of Ion-Sensitive Field-Effect Transistor Voltage Response for Potassium Ion Concentration Detection in Mixed Potassium/Ammonium Ion Solutions

    Directory of Open Access Journals (Sweden)

    Wan F.H. Abdullah

    2010-01-01

    Full Text Available Problem statement: The Ion-Sensitive Field-Effect Transistor (ISFET is a metal-oxide field-effect transistor-based sensor that reacts to ionic activity at the electrolye/membrane/gate interface. The ionic sensor faces issue of selectivity from interfering ions that contribute to the sensor electrical response in mixed solutions. Approach: We present the training data collection of ISFET voltage response for the purpose of post-processing stage neural network supervised learning. The role of the neural network is to estimate the main ionic activity from the interfering ion contribution in mixed solutions given time-independent input voltages. In this work, potassium ion (K+ and ammonium ion (NH4+ ISFET response data are collected with readout interface circuit that maintains constant voltage and current bias levels to the ISFET drain-source terminals. Sample solutions are prepared by keeping the main ion concentration fixed while the activity of an interfering ion varied based on the fixed interference method. Results: Sensor demonstrates linear relationship to the ion concentration within detection limit but has low repeatability of 0.52 regression factor and 0.16 mean squared error between similarly repeated measurements. We find that referencing the voltage response to the sensor response in DIW prior to measurement significantly improves the repeatability by 15.5% for correlation and 98.3% for MSE. Demonstration of multilayer perceptron feed-forward neural network estimation of ionic concentration from the data collection shows a recognition of >0.8 regression factor. Conclusion: Time-independent DC voltage response of ISFET of the proposed setup can be used as training data for neural network supervised learning for the estimation of K+ in mixed K+/NH4+ solutions.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2008-05-30

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

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

    Science.gov (United States)

    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

  4. Catalytic Asymmetric Bromocyclization of Polyenes.

    Science.gov (United States)

    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.

  5. Field structure and electron life times in the MEFISTO electron cyclotron resonance ion source

    Energy Technology Data Exchange (ETDEWEB)

    Bodendorfer, M. [EPFL - Ecole Polytechnique Federale de Lausanne (Switzerland); University of Berne, Institute of Physics, Space Research and Planetary Sciences, Siedlerstrasse 5, 3012 Berne (Switzerland)], E-mail: michael.bodendorfer@space.unibe.ch; Altwegg, K. [University of Berne, Institute of Physics, Space Research and Planetary Sciences, Siedlerstrasse 5, 3012 Berne (Switzerland); Shea, H. [EPFL - Ecole Polytechnique Federale de Lausanne (Switzerland); Wurz, P. [University of Berne, Institute of Physics, Space Research and Planetary Sciences, Siedlerstrasse 5, 3012 Berne (Switzerland)

    2008-03-15

    The complex magnetic field of the permanent magnet electron cyclotron resonance (ECR) ion source MEFISTO located at the University of Berne has been numerically simulated. For the first time the magnetized volume qualified for electron cyclotron resonance at 2.45 GHz and 87.5 mT has been analyzed in highly detailed 3D simulations with unprecedented resolution. New results were obtained from the numerical simulation of 25,211 electron trajectories. The evident characteristic ion sputtering trident of hexapole confined ECR ion sources has been identified with the field and electron trajectory distribution. Furthermore, unexpected long electron trajectory lifetimes were found.

  6. Field structure and electron life times in the MEFISTO electron cyclotron resonance ion source

    Science.gov (United States)

    Bodendorfer, M.; Altwegg, K.; Shea, H.; Wurz, P.

    2008-03-01

    The complex magnetic field of the permanent magnet electron cyclotron resonance (ECR) ion source MEFISTO located at the University of Berne has been numerically simulated. For the first time the magnetized volume qualified for electron cyclotron resonance at 2.45 GHz and 87.5 mT has been analyzed in highly detailed 3D simulations with unprecedented resolution. New results were obtained from the numerical simulation of 25,211 electron trajectories. The evident characteristic ion sputtering trident of hexapole confined ECR ion sources has been identified with the field and electron trajectory distribution. Furthermore, unexpected long electron trajectory lifetimes were found.

  7. Modulation of electrical mobility in Au ion irradiated titanium oxide with crystal field splitting

    Science.gov (United States)

    Park, Hyun-Woo; Jun, Byung-Hyuk; Choi, Dukhyun; Chung, Kwun-Bum

    2016-11-01

    Electrical modulation of radio frequency (RF) sputtered TiO2- x films were investigated as a function of Au swift heavy ion irradiation dose at room temperature. The prepared TiO2- x films were irradiated with 130 MeV Au swift heavy ion in the range from 1 × 1011 to 5 × 1012 ions/cm2. As the Au ion irradiation dose increased up to 1 × 1012 ions/cm2, the electrical mobility of TiO2- x films were dramatically increased 3.07 × 102 cm2 V-1 s-1 without the change of carrier concentration. These changes in electrical properties of Au irradiated TiO2- x film, are related to the modification of electronic structure such as crystal field splitting of Ti 3d orbital hybridization and sub-band edge states below the conduction band as a function of Au swift heavy ion irradiation dose.

  8. Analyzing the influence of PEG molecular weight on the separation of PEGylated gold nanoparticles by asymmetric-flow field-flow fractionation.

    Science.gov (United States)

    Hansen, Matthew; Smith, Mackensie C; Crist, Rachael M; Clogston, Jeffrey D; McNeil, Scott E

    2015-11-01

    Polyethylene glycol (PEG) is an important tool for increasing the biocompatibility of nanoparticle therapeutics. Understanding how these potential nanomedicines will react after they have been introduced into the bloodstream is a critical component of the preclinical evaluation process. Hence, it is paramount that better methods for separating, characterizing, and analyzing these complex and polydisperse formulations are developed. We present a method for separating nominal 30-nm gold nanoparticles coated with various molecular weight PEG moieties that uses only phosphate-buffered saline as the mobile phase, without the need for stabilizing surfactants. The optimized asymmetric-flow field-flow fractionation technique using in-line multiangle light scattering, dynamic light scattering, refractive index, and UV-vis detectors allowed successful separation and detection of a mixture of nanoparticles coated with 2-, 5-, 10-, and 20-kDa PEG. The particles coated with the larger PEG species (10 and 20 kDa) were eluted at times significantly earlier than predicted by field-flow fractionation theory. This was attributed to a lower-density PEG shell for the higher molecular weight PEGylated nanoparticles, which allows a more fluid PEG surface that can be greater influenced by external forces. Hence, the apparent particle hydrodynamic size may fluctuate significantly depending on the overall density of the stabilizing surface coating when an external force is applied. This has considerable implications for PEGylated nanoparticles intended for in vivo application, as nanoparticle size is important for determining circulation times, accumulation sites, and routes of excretion, and highlights the importance and value of the use of secondary size detectors when one is working with complex samples in asymmetric-flow field-flow fractionation.

  9. Photodetachment of H$^−$ ion in crossed gradient electric and magnetic fields

    Indian Academy of Sciences (India)

    DEHUA WANG; SHAOHAO CHENG

    2016-11-01

    We study the photodetachment of H$^−$ ion in crossed gradient electric and magnetic fields and put forward an analytical formula for calculating the photodetachment cross-section. Compared to the photodetachmentof H$^−$ ion in a gradient electric field, the Hamiltonian of the detached electron has three degrees of freedom, which makes the dynamical behaviour of the detached electron complex. Photodetachment cross-section for variousexternal fields and the laser polarization are calculated and displayed. A comparison with the photodetachment cross-section in crossed uniform electric and magnetic fields or in a single gradient electric field has been made.The agreement of our results with the above two special cases suggests the correctness of our calculation. Our study may have some potential applications in the photodetachment microscopy experiment or in ion detection.

  10. Ion-sensitive field effect transistors for pH and potassium ion concentration sensing: towards detection of myocardial ischemia

    Science.gov (United States)

    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.

  11. Electron transferring from titanium ion irradiated carbon nanotube arrays into vacuum under low applied fields

    Science.gov (United States)

    Deng, Jian-hua; Ping, Zhao-xia; Zheng, Rui-ting; Cheng, Guo-an

    2011-05-01

    Field emission characteristics of carbon nanotube arrays synthesized by thermal chemical vapor deposition on iron ion pre-bombarded silicon substrate are enhanced by titanium ion irradiation. A pronounced degradation of turn-on electric field of 0.305 V/μm and threshold field, of which the lowest value is only 1.054 V/μm, about 0.482 V/μm at the dose of 5 × 10 16 ions/cm 2 is as an expression of this enhancement. Scanning electron microscopy, Raman spectroscopy, x-ray photoelectron spectroscopy, Photoelectron spectrometer and transmission electron microscopy are measured for comparison before and after the Ti ion irradiation of the carbon nanotube arrays, and the results reveal that the formation of carbon nanorod/nanotube heterostructure during ion irradiation plays a dominative role in the promotion of the field emission properties. However, high-dose irradiating transaction on carbon nanotube arrays will exert repulsive effects on the field emission characteristics for the introduction of severe structural damage. Additionally, the longtime eminent stability behaviors under high applied fields have provided a possibility for the potential application of field emission flat panel display or electron emitters based on carbon nanotube arrays.

  12. Nonthermal ions and associated magnetic field behavior at a quasi-parallel earth's bow shock

    Science.gov (United States)

    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.

  13. Synthesis of nanowires via helium and neon focused ion beam induced deposition with the gas field ion microscope.

    Science.gov (United States)

    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.

  14. Perspective on the Role of Negative Ions and Ion-Ion Plasmas in Heavy Ion Fusion Science, Magnetic Fusion Energy, and Related Fields

    Energy Technology Data Exchange (ETDEWEB)

    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.

  15. Perspective on the Role of Negative Ions and Ion-Ion Plasmas in Heavy Ion Fusion Science, Magnetic Fusion Energy, and Related Fields

    Energy Technology Data Exchange (ETDEWEB)

    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.

  16. Perspective on the Role of Negative Ions and Ion-Ion Plasmas in Heavy Ion Fusion Science, Magnetic Fusion Energy,and Related Fields

    Energy Technology Data Exchange (ETDEWEB)

    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.

  17. Explicit Compact Surface-Potential and Drain-Current Models for Generic Asymmetric Double-Gate Metal-Oxide-Semiconductor Field-Effect Transistors

    Science.gov (United States)

    Zhu, Zhaomin; Zhou, Xing; Chandrasekaran, Karthik; Rustagi, Subhash C.; See, Guan Huei

    2007-04-01

    In this paper, explicit surface potentials for undoped asymmetric-double-gate (a-DG) metal-oxide-semiconductor field-effect transistors (MOSFETs) suitable for compact model development are presented for the first time. The model is physically derived from Poisson’s equation in each region of operation and adopted in a unified regional approach. The proposed model is physically scalable with oxide/channel thicknesses and has been verified with generic implicit solutions for independent gate biases as well as for different gate/oxide materials. The model is extendable to silicon-on-insulator (SOI) and symmetric-DG (s-DG) MOSFETs. Finally, a continuous, explicit drain-current equation has been derived on the basis of the developed explicit surface-potential solutions.

  18. Co-elution effects can influence molar mass determination of large macromolecules with asymmetric flow field-flow fractionation coupled to multiangle light scattering.

    Science.gov (United States)

    Perez-Rea, Daysi; Zielke, Claudia; Nilsson, Lars

    2017-07-14

    Starch and hence, amylopectin is an important biomacromolecule in both the human diet as well as in technical applications. Therefore, accurate and reliable analytical methods for its characterization are needed. A suitable method for analyzing macromolecules with ultra-high molar mass, branched structure and high polydispersity is asymmetric flow field-flow fractionation (AF4) in combination with multiangle light scattering (MALS) detection. In this paper we illustrate how co-elution of low quantities of very large analytes in AF4 may cause disturbances in the MALS data which, in turn, causes an overestimation of the size. Furthermore, it is shown how pre-injection filtering of the sample can improve the results. Copyright © 2017 Elsevier B.V. All rights reserved.

  19. Detection and characterization of silver nanoparticles in chicken meat by asymmetric flow field flow fractionation with detection by conventional or single particle ICP-MS

    DEFF Research Database (Denmark)

    Löschner, Katrin; Navratilova, Jana; Købler, Carsten;

    2013-01-01

    A method of analysis of silver nanoparticles (AgNPs) in chicken meat was developed. The homogenized chicken meat sample, which was spiked with AgNPs, was subjected to enzymolysis by Proteinase K for 40 min at 37 °C. Transmission electron microscopy and inductively coupled plasma mass spectrometry...... of the AgNPs took place during the sample preparation stage. The digestate was injected into the asymmetric flow field flow fractionation (AF(4)) -ICP-MS system, which enabled fractionation of nanoparticles from the remaining meat matrix, and resulted in one large peak in the fractograms as well as two...... (ICP-MS) in single particle mode were used to characterize the number-based size distribution of AgNPs in the meat digestate. Because similar size distributions were found in the meat digestate and in the aqueous suspension of AgNPs used for spiking the meat, it was shown that no detectable dissolution...

  20. Asymmetric flow-field flow fractionation-multidetection coupling for assessing colloidal copper in drain waters from a Bordeaux wine-growing area.

    Science.gov (United States)

    El Hadri, Hind; Lespes, Gaëtane; Chéry, Philippe; Potin-Gautier, Martine

    2014-02-01

    The objective of this study was to show that on-line asymmetric flow-field flow fractionation (AFFFF)-multidetection coupling is useful for studying environmental colloids in a qualitative and quantitative way. The utility of the technique was illustrated by assessing the colloidal fraction of the copper that was extracted from the soil, transferred to an aqueous phase and then transported by drain waters in a wine-growing area. To determine the size and composition of the colloids, AFFFF was coupled to UV, multi-angle light scattering and inductively coupled plasma mass spectrometry detectors. Colloidal copper represents between 20 and 60% of the total copper in the sub 450 nm of drain waters. Copper is mainly associated with organic-rich colloids with a size below 10 nm. It is also found in organo-mineral populations (as clay or (oxy)hydroxides), with sizes ranging between 10 and 450 nm.

  1. Electric field modulation of the membrane potential in solid-state ion channels.

    Science.gov (United States)

    Guan, Weihua; Reed, Mark A

    2012-12-12

    Biological ion channels are molecular devices that allow a rapid flow of ions across the cell membrane. Normal physiological functions, such as generating action potentials for cell-to-cell communication, are highly dependent on ion channels that can open and close in response to external stimuli for regulating ion permeation. Mimicking these biological functions using synthetic structures is a rapidly progressing yet challenging area. Here we report the electric field modulation of the membrane potential phenomena in mechanically and chemically robust solid-state ion channels, an abiotic analogue to the voltage-gated ion channels in living systems. To understand the complex physicochemical processes in the electric field regulated membrane potential behavior, both quasi-static and transient characteristics of converting transmembrane ion gradients into electric potential are investigated. It is found that the transmembrane potential can be adequately tuned by an external electrical stimulation, thanks to the unique properties of the voltage-regulated selective ion transport through a nanoscale channel.

  2. External-field shifts in precision spectroscopy of hydrogen molecular ions

    Energy Technology Data Exchange (ETDEWEB)

    Bakalov, Dimitar, E-mail: dbakalov@inrne.bas.bg [INRNE, Bulgarian Academy of Sciences (Bulgaria); Korobov, Vladimir [Joint Institute for Nuclear Research (Russian Federation); Schiller, Stephan [Heinrich-Heine-Universitat Dusseldorf, Institut fur Experimentalphysik (Germany)

    2015-08-15

    The Effective Hamiltonian of the hydrogen molecular ions is a convenient tool for the evaluation of the shift of the energy levels of the ro-vibrational states and the frequencies of the transitions between them, due to external electric and magnetic fields. Using the Effective Hamiltonian, composite frequencies of suppressed susceptibility to external fields are constructed.

  3. Enhanced electron field emission from carbon nanotubes irradiated by energetic C ions.

    Science.gov (United States)

    Sun, Peng-Cheng; Deng, Jian-Hua; Cheng, Guo-An; Zheng, Rui-Ting; Ping, Zhao-Xia

    2012-08-01

    The field emission performance and structure of the vertically aligned multi-walled carbon nanotube arrays irradiated by energetic C ion with average energy of 40 keV have been investigated. During energetic C ion irradiation, the curves of emission current density versus the applied field of samples shift firstly to low applied fields when the irradiation doses are less than 9.6 x 10(16) cm(-2), and further increase of dose makes the curves reversing to a high applied field, which shows that high dose irradiation in carbon nanotube arrays makes their field emission performance worse. After energetic ion irradiation with a dose of 9.6 x 1016 cm(-2), the turn-on electric field and the threshold electric field of samples decreased from 0.80 and 1.13 V/microm to 0.67 and 0.98 V/microm respectively. Structural analysis of scanning electron microscopy, transmission electron microscopy and Raman spectroscopy indicates that the amorphous carbon nanowire/carbon nanotube hetero nano-structures have been fabricated in the C ion irradiated carbon nanotubes. The enhancement of electron field emission is due to the formation of amorphous carbon nanowires at the tip of carbon nanotube arrays, which is an electron emitting material with low work function.

  4. Atom probe field ion microscopy and related topics: A bibliography 1993

    Energy Technology Data Exchange (ETDEWEB)

    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.

  5. Ion Viscosity Mediated by Tangled Magnetic Fields: An Application to Black Hole Accretion Disks

    Science.gov (United States)

    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

  6. Influence of tail-like magnetic field on O+ ion distribution in the Martian magnetosphere

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Based on the comparison with the Earth, using the LB magneticfield model, the distribution of O+ ion originating from the ionosphere in the Martian magnetosphere is theoretically studied under different conditions of the tail-like magnetic field. The results show that the tail-like magnetic field has influence on the O+ ion flux in the Martian magnetotail: (ⅰ) the O+ ion flux in the Martian tail will increase if the tail-like magnetic field increases; when the tail-like magnetic field increases from 5 nT to 20 nT, the O+ ion flux increases 3 times in the region of 2.8 Rm in the Martian tail; and (ⅱ) the O+ ion flux decreases with increasing intrinsic moment; when the intrinsic moment increases about 5 times, the flux decreases to one fourth in the region of 2.8 Rm in the Martian tail. According to the data on the O+ ion flux and theoretical result in this paper, the deduced Martian intrinsic moment is about 2×1021 Gcm3. This is consistent with the most recent observation by the USA satellite MGS.

  7. [Negative air ions generated by plants upon pulsed electric field stimulation applied to soil].

    Science.gov (United States)

    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.

  8. Behavior of moving plasma in solenoidal magnetic field in a laser ion source

    Energy Technology Data Exchange (ETDEWEB)

    Ikeda, S., E-mail: ikeda.s.ae@m.titech.ac.jp [Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, Yokohama, Kanagawa 226-8502 (Japan); Nishina Center for Accelerator-Based Science, RIKEN, Wako, Saitama 351-0108 (Japan); Takahashi, K. [Department of Electrical Engineering, Nagaoka University of Technology, Nagaoka, Niigata 940-2137 (Japan); Okamura, M. [Collider-Accelerator Department, Brookhaven National Laboratory, Upton, New York 11973-5000 (United States); Horioka, K. [Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, Yokohama, Kanagawa 226-8502 (Japan)

    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.

  9. Behavior of moving plasma in solenoidal magnetic field in a laser ion source

    Science.gov (United States)

    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.

  10. Asymmetric Ashes

    Science.gov (United States)

    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

  11. Enhancement of Ar sup 8 sup + ion beam intensity from RIKEN 18 GHz electron cyclotron resonance ion source by optimizing the magnetic field configuration

    CERN Document Server

    Higurashi, Y; Kidera, M; Kase, M; Yano, Y; Aihara, T

    2003-01-01

    We successfully produced a 1.55 emA Ar sup 8 sup + ion beam using the RIKEN 18 GHz electron cyclotron resonance ion source at a microwave power of 700 W. To produce such an intense beam, we optimized the minimum magnetic field of mirror magnetic field and plasma electrode position. (author)

  12. Controlling trapping potentials and stray electric fields in a microfabricated ion trap through design and compensation

    CERN Document Server

    Doret, S Charles; Wright, Kenneth; Volin, Curtis; Killian, Tyler; Ozakin, Arkadas; Denison, Douglas; Hayden, Harley; Pai, C -S; Slusher, Richart E; Harter, Alexa W

    2012-01-01

    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/eleme...

  13. Toroidal mode driven by ion temperature gradients and magnetic-field curvature

    Energy Technology Data Exchange (ETDEWEB)

    Olla, P.

    1986-11-01

    The effect of magnetic-field curvature on the ion-mixing mode is studied in a collisionless-plasma regime. A simple plane model with an external gravity-simulating magnetic curvature is adopted. A dispersion relation which connects the ion-mixing mode to the ubiquitous mode is obtained. It is found that, within the limitations of the present local model, an inhomogeneous plasma can support fluctuations with frequencies larger than those expected in an analysis which disregards the effect of magnetic curvature. The instability threshold of this mode, which depends on the ion temperature gradient, is lowered. The effect of gravity on the ion response influences the quasi-linear ion heat transport.

  14. Observations of diverging field-aligned ion flow with the ESR

    Directory of Open Access Journals (Sweden)

    S. C. Buchert

    2004-03-01

    Full Text Available We report on observations of a diverging ion flow along the geomagnetic field that is often seen at the EISCAT Svalbard radar. The flow is upward above the peak of the electron density in the F-region and downward below the peak. We estimate that in such events mass transport along the field line is important for the ionization balance, and that the shape of the F-layer and its ion composition should be strongly influenced by it. Diverging flow typically occurs when there are signatures of direct entry of sheath plasma to the ionosphere in the form of intense soft particle precipitation, and we suggest that it is caused by the ionization and ionospheric electron heating associated with this precipitation. On average, 30% of all events with ion upflow also show significant ion downflow below.

    Key words.Ionosphere (polar ionosphere; ionization mechanism; plasma temperature and density

  15. Orientation-dependent ionization yields from strong-field ionization of fixed-in-space linear and asymmetric top molecules

    DEFF Research Database (Denmark)

    Hansen, Jonas Lerche; Holmegaard, Lotte; Nielsen, Jens Hedegaard

    2012-01-01

    The yield of strong-field ionization, by a linearly polarized probe pulse, is studied experimentally and theoretically as a function of the relative orientation between the laser field and the molecule. Experimentally, carbonyl sulphide (OCS), benzonitrile and naphthalene molecules are aligned in...

  16. Ideal 3D asymmetric concentrator

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Botella, Angel [Departamento Fisica Aplicada a los Recursos Naturales, Universidad Politecnica de Madrid, E.T.S.I. de Montes, Ciudad Universitaria s/n, 28040 Madrid (Spain); Fernandez-Balbuena, Antonio Alvarez; Vazquez, Daniel; Bernabeu, Eusebio [Departamento de Optica, Universidad Complutense de Madrid, Fac. CC. Fisicas, Ciudad Universitaria s/n, 28040 Madrid (Spain)

    2009-01-15

    Nonimaging optics is a field devoted to the design of optical components for applications such as solar concentration or illumination. In this field, many different techniques have been used for producing reflective and refractive optical devices, including reverse engineering techniques. In this paper we apply photometric field theory and elliptic ray bundles method to study 3D asymmetric - without rotational or translational symmetry - concentrators, which can be useful components for nontracking solar applications. We study the one-sheet hyperbolic concentrator and we demonstrate its behaviour as ideal 3D asymmetric concentrator. (author)

  17. Fast ion confinement and stability in a neutral beam injected reversed field pinch

    Energy Technology Data Exchange (ETDEWEB)

    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. [University of Wisconsin, Madison, Wisconsin 53706 (United States); Belykh, V.; Davydenko, V. I.; Ivanov, A. A.; Polosatkin, S. V.; Tsidulko, Y. A. [Budker Institute of Nuclear Physics, Novosibirsk (Russian Federation); Lin, L. [University of California, Los Angeles, California 90095 (United States); Liu, D. [University of California, Irvine, California 92697 (United States); 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.

  18. Ion-sensitive field effect transistors using carbon nanotubes as the transducing layer.

    Science.gov (United States)

    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.

  19. Balancing the Interactions of Ions, Water, and DNA in the Drude Polarizable Force Field

    OpenAIRE

    Savelyev, Alexey; MacKerell, Alexander D.

    2014-01-01

    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...

  20. The Chrial Magnetic Wave and Strong Field Effects in Heavy Ion Collisions

    CERN Document Server

    Liao, Jinfeng

    2013-01-01

    A number of recent progresses in the study of strong field effects in heavy ion collisions are discussed here: 1) the Chiral Magnetic Wave (CMW) and its experimental manifestation via splitting of positive/negative pions' elliptic flow; 2) the event-by-event azimuthal fluctuations of strong EM fields and its correlations with matter geometry; 3) a new mechanism for generating axial current in external electric field, the Chiral Electric Separation Effect (CESE).

  1. Contributions to the cross shock electric field at supercritical perpendicular shocks: Impact of the pickup ions

    CERN Document Server

    Yang, Zhongwei; Yang, Huigen; Hu, Hongqiao; Zhang, Beichen; Zhang, Qinhe; Liu, Ruiyuan

    2012-01-01

    A particle-in-cell code is used to examine contributions of the pickup ions (PIs) and the solar wind ions (SWs) to the cross shock electric field at the supercritical, perpendicular shocks. The code treats the pickup ions self-consistently as a third component. Herein, two different runs with relative pickup ion density of 25% and 55% are presented in this paper. Present preliminary results show that: (1) in the low percentage (25%) pickup ion case, the shock front is nonstationary. During the evolution of this perpendicular shock, a nonstationary foot resulting from the reflected solar wind ions is formed in front of the old ramp, and its amplitude becomes larger and larger. At last, the nonstationary foot grows up into a new ramp and exceeds the old one. Such a nonstationary process can be formed periodically. hen the new ramp begins to be formed in front of the old ramp, the Hall term mainly contributed by the solar wind ions becomes more and more important. The electric field Ex is dominated by the Hall t...

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

    CERN Document Server

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

    2016-01-01

    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. 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 {\\AA}) as compared to the forbidden lines of the same ion (17.05 {\\AA} and 17.10 {\\AA}). The presence and radial dependence of the cooling flow was investigated through spectral modeling. In addition, a parallel analysis with deep Chandra Advances CCD Imaging Spectrometer (ACIS) data was conducted to gain additional information about the thermodynamical properties of the IGM. We find that the plasma at the group center to the north shows efficient Fe xvii ion resonant scattering, wheras no resonant scattering was detected at the south side. The regions featuring resona...

  3. High-field magnetization of rare-earth ions in scandium

    DEFF Research Database (Denmark)

    Roeland, L. W.; Touborg, P.

    1978-01-01

    The magnetic moments of Tb, Dy, or Er ions in dilute Sc single-crystal alloys have been measured in fields up to 280 × 105 A/m (350 kOe). The Zeeman energies in this high field are comparable to the total crystal-field splittings. This gives rise to characteristic features in the magnetization...... curves. The crystal-field parameters obtained previously from experiments in low fields and the Zeeman interaction give a satisfactory quantitative acount of the experimental results....

  4. Determination of lead ion removal from a flowing electrolyte in the presence of a magnetic field using Raman spectroscopy.

    Science.gov (United States)

    Rodríguez, Rogelio; Rangel, Domingo; Vargas, Susana; González, Maykel; Malagon, Karla; Quintanilla, Francisco

    2015-11-01

    The authors report on the development of a new, noninvasive method to efficiently remove metal ions in aqueous solution flowing in a tube and to quantify the concentrations of those ions. Such a technique could be used to remove toxic ions in the interiors of arteries and veins in patients intoxicated by the ingestion of metal ions. A magnetic field is applied to an aqueous electrolyte flowing in a specially designed rectangular cell in order to deflect the ion trajectories and concentrate them at one side of a cell. Once the ions are concentrated, they can be removed. Raman spectroscopy is used to promptly determine the concentration of the removed lead ions. It is possible to increase, on one side of the cell, the ion concentration by more than 80% with respect to the average concentration; the removed ions were taken from this high concentration region. This approach is a rapid, efficient, and noninvasive method for the removal of ions in aqueous solution. Raman spectroscopy was found to be a suitable technique to determine the amount of removed ions. The results indicate that the ion concentration can be increased more than 80% in a region where they can be removed. The increment in the ion concentration produced by the deflection due to the magnetic field, together with the use of Raman spectroscopy, allows for a rapid analysis of the removed ions without any previous preparation. The proposed method is a potentially useful method for metal ion separation of interest in the medical physics field.

  5. 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

    Science.gov (United States)

    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...

  6. The direct injection of intense ion beams from a high field electron cyclotron resonance ion source into a radio frequency quadrupole.

    Science.gov (United States)

    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.

  7. The direct injection of intense ion beams from a high field electron cyclotron resonance ion source into a radio frequency quadrupole

    Energy Technology Data Exchange (ETDEWEB)

    Rodrigues, G., E-mail: gerosro@gmail.com; Kanjilal, D.; Roy, A. [Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi (India); Becker, R. [Institut fur Angewandte Physik der Universitaet, D-60054 Frankfurt/M (Germany); Hamm, R. W. [R and M Technical Enterprises, Inc., 4725 Arlene Place, Pleasanton, California 94566 (United States); Baskaran, R. [Indira Gandhi Centre for Atomic Research, Kalpakkam, Tamilnadu (India)

    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.

  8. The direct injection of intense ion beams from a high field electron cyclotron resonance ion source into a radio frequency quadrupole

    Science.gov (United States)

    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.

  9. Multiply Charged Negative Ions of Hydrogen Induced by Superintense Laser Fields

    Energy Technology Data Exchange (ETDEWEB)

    van Duijn, E.; Gavrila, M.; Muller, H.G. [FOM--Institute for Atomic and Molecular Physics, Kruislaan 407, 1098 SJ Amsterdam (The Netherlands)

    1996-10-01

    Using the high-frequency Floquet theory of laser-atom interactions we predict that in superintense fields a proton can bind more than two electrons. For linear polarization, a self-consistent solution of the structure equation shows that H{sup 2{minus}} becomes bound for {alpha}{sub 0}=155 a.u. The fields and frequencies needed for binding H{sup 2{minus}} are within reach of lasers under construction. By choosing appropriately polarized bichromatic radiation, the production of more highly charged negative ions also lies within experimental reach. The ions are (adiabatically) stabilized against ionization, from their very appearance. {copyright} {ital 1996 The American Physical Society.}

  10. Relation between stabilization energy, crystal field coefficient and themagnetic exchange interaction for Tb3+ ion

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xiangmu; MA Wenjuan; CUI Shuwen; WANG Lihua

    2006-01-01

    Based on a single ion model, Hamiltonian of the simplest form about magnetocrystalline anisotropy for Tb3+ ion was solved by using the numerical method. The relation between the stabilization energy, crystal field coefficient B20 and the magnetic exchange interaction was studied as temperature approaches to 0K. The results show that the stabilization energy contributed by Tb3+ is linear with crystal field coefficient B20 approximately, but it is insensitive to the change of magnetic exchange interaction for the strong magnetic substancessuch as TbCo5, Tb2Co17 and Tb2Fe14B compounds.

  11. Field structure and electron life times in the MEFISTO Electron Cyclotron Resonance Ion Source

    CERN Document Server

    Bodendorfer, Michael; Shea, Herbert; Wurz, Peter

    2008-01-01

    The complex magnetic field of the permanent-magnet electron cyclotron resonance (ECR) ion source MEFISTO located at the University of Bern have been numerically simulated. For the first time the magnetized volume qualified for electron cyclotron resonance at 2.45 GHz and 87.5 mT has been analyzed in highly detailed 3D simulations with unprecedented resolution. New results were obtained from the numerical simulation of 25211 electron trajectories. The evident characteristic ion sputtering trident of hexapole confined ECR sources has been identified with the field and electron trajectory distribution. Furthermore, unexpected long electron trajectory lifetimes were found.

  12. Atoms and Ions Interacting with Particles and Fields: Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Robicheaux, Francis [Auburn Univ., AL (United States)

    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.

  13. Zero-magnetic-field spin-splitting and the warping in the valence band of highly p-doped asymmetric AlGaAs/GaAs quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Hirmer, Michael; Hirmer, M.; Schuh, D.; Wegscheider, W.; Korn, T.; Schueller, C. [Institut fuer Experimentelle Physik, Universitaet Regensburg, 93040 Regensburg (Germany)

    2011-07-01

    Zero-Magnetic-Field-Spin-Splitting (ZMFSS) in 2D quantum wells (QW) induced by the structure inversion asymmetry, and its control, are of major importance for both fundamental research and spintronic applications. In hole systems, the asymmetry leads to a ZMFSS of the heavy hole (HH) states in third order of the in-plane wave vector k. In our experiments, we focus on highly p-doped asymmetric AlGaAs/GaAs QW. We utilize electronic intersubband Raman measurements in backscattering geometry. In all samples we observe a low-energy spin-density excitation (SDE) with energies in the range of 0-3 meV. Samples with higher hole density show a two-component SDE. Comparing these excitation energies to 8 band k.p calculations of the valence subbands, the SDE can be interpreted as an intersubband excitation of the spin-split HH ground state, reflecting directly the ZMFSS. The two components can be attributed to different HH dispersions in different crystallographic directions, the so-called warping. We found that the observed spin splitting increases systematically with increasing hole density p, or by an external electric field. Measurements of the Shubnikov de Haas oscillations showed similar results.

  14. Influence of induced magnetic field and heat transfer on the peristaltic motion of a Jeffrey fluid in an asymmetric channel: Closed form solutions

    Energy Technology Data Exchange (ETDEWEB)

    Akram, Safia, E-mail: safia_akram@yahoo.com [Department of Humanities and Basic Sciences, Military College of Signals, National University of Sciences and Technology, Rawalpindi 46000 (Pakistan); Department of Mathematics, Quaid-i-Azam University 45320, Islamabad 44000 (Pakistan); Nadeem, S. [Department of Mathematics, Quaid-i-Azam University 45320, Islamabad 44000 (Pakistan)

    2013-02-15

    We discuss the peristaltic motion of a two dimensional Jeffrey fluid in an asymmetric channel under the effects of induced magnetic field and heat transfer. The problem is simplified by using long wave length and low Reynolds approximations. Exact and closed form Adomian solutions are presented. Expressions for the velocity, stream function, magnetic force function, temperature, pressure gradient and pressure rise are computed. The results of pertinent parameters are discussed. Finally, the trapping phenomena for different wave shapes are discussed. It is observed that the pressure rise for sinusoidal wave is less than trapezoidal wave and greater than triangular in a Jeffrey fluid. - Highlights: Black-Right-Pointing-Pointer The effects of induced magnetic field and heat transfer in peristaltic motion of a two dimensional Jeffrey fluid are discussed. Black-Right-Pointing-Pointer In this paper exact and closed form Adomian solutions are presented. Black-Right-Pointing-Pointer Different wave shapes are considered to observe the behavior of pressure rise and trapping phenomena.

  15. Ion confinement and transport in a toroidal plasma with externally imposed radial electric fields

    Science.gov (United States)

    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.

  16. The Asymmetrical Relationship with Respondents and Local Colleagues - Some Points on the Art of Doing Field Work

    DEFF Research Database (Denmark)

    Wangel, Arne

    2003-01-01

    While the epistemological aspects of cross-cultural research are extensively discussed in general terms by ethnographers and other social scientists, little attention is paid to the specific patterns of interests and expectations involved. Drawing upon previous field work in Malaysia and also upon...

  17. Characterization of Colloidal Phosphorus Species in Drainage Waters from a Clay Soil Using Asymmetric Flow Field-Flow Fractionation

    NARCIS (Netherlands)

    Regelink, I.C.; Koopmans, G.F.; Salm, van der C.; Weng, L.P.; Riemsdijk, van W.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

  18. Characterization of ultrahigh-molecular weight cationic polyacrylamide using frit-inlet asymmetrical flow field-flow fractionation and multi-angle light scattering.

    Science.gov (United States)

    Woo, Sohee; Lee, Ju Yong; Choi, Woonjin; Moon, Myeong Hee

    2016-01-15

    In this study, frit inlet asymmetrical flow field-flow fractionation (FlFFF) with multi-angle light scattering (MALS) and differential refractive index (DRI) detection is utilized for size separation, determination of molecular weight (MW), and conformation of ultrahigh-MW (10(7)-10(9) g/mol) cationic polyacrylamides (C-PAMs), a class of water-soluble copolymers based on acrylamide and vinyl-type comonomers with quaternary ammonium cations that are widely used in wastewater treatment and in paper industries. Linear and branched C-PAM copolymers prepared in two different polymerization methods (solution and emulsion) from varying amounts of crosslinking agent and initiator were size fractionated by FlFFF with field-programming. It was found experimentally that the linear copolymers from both polymerization methods were less than 10(8) g/mol in MW with compact, nearly spherical structures, while the branched C-PAM copolymers from the emulsion polymerization showed a significant increase in average MW up to ∼ 10(9)g/mol, which was about 20-fold greater than those from the solution method, and the branched copolymers had more compact or shrunken conformations. While both linear and branched copolymers less than 10(8) g/mol MW were well resolved in an increasing order of MW (normal mode), it was noted that branched copolymers prepared through emulsion polymerization exhibited significantly larger MWs of 10(8-)10(9) g/mol and eluted in the steric/hyperlayer mode, in which the elution order is reversed in an extreme run condition (strong initial field strength followed by a fast field decay during programming).

  19. 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.

    Science.gov (United States)

    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

  20. New Statistical Multiparticle Approach to the Acceleration of Electrons by the Ion Field in Plasmas

    Directory of Open Access Journals (Sweden)

    Eugene Oks

    2010-01-01

    Full Text Available The phenomenon of the acceleration of the (perturbing electrons by the ion field (AEIF significantly reduces Stark widths and shifts in plasmas of relatively high densities and/or relatively low temperature. Our previous analytical calculations of the AEIF were based on the dynamical treatment: the starting point was the ion-microfield-caused changes of the trajectories and velocities of individual perturbing electrons. In the current paper, we employ a statistical approach: the starting point is the electron velocity distribution function modified by the ion microfield. The latter had been calculated by Romanovsky and Ebeling in the multiparticle description of the ion microfield. The result shows again the reduction of the electron Stark broadening. Thus two totally different analytical approaches (dynamical and statistical agree with each other and therefore disprove the corresponding recent fully-numerical simulations by Stambulchik et al. that claimed an increase of the electron Stark broadening.

  1. Ion Source for Neutral beam injection meant for plasma and magnetic field diagnostics

    Energy Technology Data Exchange (ETDEWEB)

    Vainionpaa, Jaakko Hannes; Leung, Ka Ngo; Gough, Richard A.; Kwan, Joe W.; Levinton, Fred

    2007-06-01

    At the Lawrence Berkeley National Laboratory (LBNL) a diagnostic neutral beam injection system for measuring plasma parameters, flow velocity, and local magnetic field is being developed. The systems is designed to have a 90 % proton fraction and small divergence with beam current at 5-6 A and a pulse length of {approx}1 s occurring once every 1-2 min. The ion source needs to generate uniform plasma over a large (8 cm x 5 cm) extraction area. For this application, we have compared RF driven multicusp ion sources operating with either an external or an internal antenna in similar ion source geometry. The ion beam will be made of an array of six sheet-shaped beamlets. The design is optimized using computer simulation programs.

  2. Orientation-dependent ionization yields from strong-field ionization of fixed-in-space linear and asymmetric top molecules

    CERN Document Server

    Hansen, Jonas L; Nielsen, Jens H; Stapelfeldt, Henrik; Dimitrovski, Darko; Madsen, Lars Bojer

    2011-01-01

    The yield of strong-field ionization, by a linearly polarized probe pulse, is studied experimentally and theoretically, as a function of the relative orientation between the laser field and the molecule. Experimentally, carbonyl sulfide, benzonitrile and naphthalene molecules are aligned in one or three dimensions before being singly ionized by a 30 fs laser pulse centered at 800 nm. Theoretically, we address the behaviour of these three molecules. We consider the degree of alignment and orientation and model the angular dependence of the total ionization yield by molecular tunneling theory accounting for the Stark shift of the energy level of the ionizing orbital. For naphthalene and benzonitrile the orientational dependence of the ionization yield agrees well with the calculated results, in particular the observation that ionization is maximized when the probe laser is polarized along the most polarizable axis. For OCS the observation of maximum ionization yield when the probe is perpendicular to the intern...

  3. Small-scale ion flux and magnetic field fluctuations in solar wind, foreshock and magnetosheath

    Institute of Scientific and Technical Information of China (English)

    N. N. Shevyrev; Du Jian; G. N. Zastenker; Wang Chi; P. E. Eigesa

    2007-01-01

    We have continued investigation of waves in the regions of undisturbed solar wind, foreshock and magnetosheath. The analysis of ion flux and magnetic field variations with the time interval l-240s was performed in the regions above. Very large variation in such a time interval can be considered the common feature of the foreshock and magnetosheath. The results of case and statistical studies showed that the level of relative variations of ion flux and magnetic field magnitude in foreshock is about 3 times larger than in undisturbed solar wind. Variations of these parameters in the magnetosheath topologically connected with the quasi-parallel bow shock are about two times larger than those behind the quasi-perpendicular. We also compared the results from Interball-1 data analysis with those from statistical analysis of cluster magnetic field measurements. The magnetic field variations obtained from the different satellite data coincide with each other very well not only in quality but also in quantity.

  4. Thermal photon production from gluon fusion induced by magnetic fields in relativistic heavy-ion collisions

    CERN Document Server

    Ayala, Alejandro; Dominguez, C A; Hernandez, L A

    2016-01-01

    We compute the production of thermal photons in relativistic heavy-ion collisions by gluon fusion in the presence of an intense magnetic field, and during the early stages of the reaction. This photon yield is an excess over calculations that do not consider magnetic field effects. We add this excess to recent hydrodynamic calculations that are close to describing the experimental transverse momentum distribution in RHIC and LHC. We then show that with reasonable values for the temperature, magnetic field strength, and strong coupling constant, our results provide a very good description of such excess. These results support the idea that the origin of at least some of the photon excess observed in heavy-ion experiments may arise from magnetic field induced processes.

  5. Thermal ion imagers and Langmuir probes in the Swarm electric field instruments

    Science.gov (United States)

    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.

  6. Concepts of magnetic filter fields in powerful negative ion sources for fusion

    Energy Technology Data Exchange (ETDEWEB)

    Kraus, W., E-mail: kraus@ipp.mpg.de; Fantz, U.; Heinemann, B.; Wünderlich, D. [Max Planck Institute for Plasma Physics, Boltzmannstr. 2, 85748 Garching (Germany)

    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.

  7. Field-enhanced ion transport in solids: Reexamination with molecular dynamics simulations

    Science.gov (United States)

    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.

  8. Vacuum and magnetic field constraints in a H -/light ion synchrotron

    Science.gov (United States)

    Arduini, G.; Martin, R. L.; Rossi, S.; Silari, M.

    1994-08-01

    Acceleration of H - ions in a synchrotron imposes severe restrictions on the level of residual pressure in the vacuum chamber and the maximum magnetic field in the magnets of the ring. Significant vacuum requirements are also imposed by the acceleration of ions. This paper discusses these two aspects of the design of a combined H -/light ion synchrotron for radiation therapy. The fractional loss of the accelerated beam induced by the two processes is evaluated on the basis of a general treatment of the physics of these phenomena. The values of the vacuum and magnetic field necessary for normal operation of the machine are specified and a discussion is given of the behaviour of the above quantities as a function of several parameters such as beam energy, composition and pressure of the residual gas in the vacuum chamber and beam extraction time.

  9. Specimen preparation and atom probe field ion microscopy of BSCCO-2212 superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Larson, D.J. [Wisconsin Univ., Madison, WI (United States). Mater. Sci. Program]|[Applied Superconductivity Center, Univ. of Wisconsin, Madison, WI (United States); Camus, P.P. [Applied Superconductivity Center, Univ. of Wisconsin, Madison, WI (United States)]|[Wisconsin Univ., Madison, WI (United States). Dept. of Materials Sciences and Engineering; Vargas, J.L. [Applied Superconductivity Center, Univ. of Wisconsin, Madison, WI (United States); Kelly, T.F. [Wisconsin Univ., Madison, WI (United States). Mater. Sci. Program]|[Applied Superconductivity Center, Univ. of Wisconsin, Madison, WI (United States)]|[Wisconsin Univ., Madison, WI (United States). Dept. of Materials Sciences and Engineering; Miller, M.K. [Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.

    1996-09-01

    Field ion specimens of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub x} (BSCCO) high temperature superconductor (HTS) materials have been prepared using a combination of three different preparation techniques: the method of sharp shards, electropolishing and ion milling. Field ion microscopy (FIM) has demonstrated that samples which exhibit the ``striped``-image contrast characteristic of HTS materials can be successfully fabricated using this combination. FIM images have been obtained which show the striped-image contrast much clearer than any previously published images of Pb-free BSCCO. Preliminary atom probe (AP) chemical analysis of the material was also performed. Analytical electron microscopy was used to confirm the existence of both the correct crystallographic structure and nominal composition in the near-apex region of the specimen after preparation and FIM. (orig.).

  10. Ion motion in salt water flowing under a transverse magnetic field

    Directory of Open Access Journals (Sweden)

    De Luca R.

    2012-10-01

    Full Text Available The problem of ion motion in an electrolyte solution flowing in a thin rectangular duct with velocity VE in the presence of a transverse magnetic field B0 is studied by means of classical mechanics and electrodynamics. Because of Lorentz force on the ions in the electrolyte solution, a so called Faraday voltage appears at the electrodes orthogonal to both the field B0 and the velocity VE. The dynamics of positive and negative ions (cations and anions, respectively in this classical system is studied by taking into account the viscosity of the fluid and the process of charge accumulation on the opposite walls of the duct. Hydrogen production is seen to take place at one of the electrodes when salt water is taken as the flowing electrolyte.

  11. A trapped ion with time-dependent frequency interaction with a laser field

    Energy Technology Data Exchange (ETDEWEB)

    MartInez, J M Vargas; Moya-Cessa, H [INAOE, Apartado Postal 51 y 216, 72000 Puebla (Mexico)

    2004-06-01

    We analyse the problem of a trapped ion with time-dependent frequency interacting with a laser field. By using a set of unitary time-dependent transformations we show that this system is equivalent to the interaction between a quantized field and a double level with time-dependent interaction parameters. In passing, we show that in the on-resonance case different vibrational transitions may be achieved by using time-dependent parameters.

  12. Photodetachment microscopy of a hydrogen negative ion in an electric field near a metal surface

    Institute of Scientific and Technical Information of China (English)

    Tang Tian-Tian; Wang De-Hua; Wang Shan-Shan

    2012-01-01

    According to the semi-classical theory,we study the photodetachment microscopy of H- in the electric field near a metal surface.During the photodetachment,the electron is photo-detached by a laser and the electron is drawn toward a position-sensitive detector.The electron flux distribution is measured as a function of position.Two classical paths lead the ion to any point in the classically allowed region on the detector,and waves traveling along these paths produce an interference pattern.If the metal surface perpendicular to the electric field is added,we find that the interference pattern is related not only to the electron energy and the electric-field strength,but also to the ion-surface distance.In addition,the laser polarization also has a great influence on the electron flux distribution.We present calculations predicting the interference pattern that may be seen in experiment.We hope that our study can provide a new nnderstanding of the electron flux distribution of negative ions in an external field and surface,and can guide future experimental research on negative ion photo-detachment microscopy.

  13. The ion-sensitive field effect transistor in rapid acid-base titrations

    NARCIS (Netherlands)

    Bos, M.; Bergveld, P.; Veen-Blaauw, van A.M.W.

    1979-01-01

    Ion-sensitive field effect transistors (ISFETs) are used as the pH sensor in rapid acid—base titrations. Titration speeds at least five times greater than those with glass electrodes are possible for accuracies better than ±1%.

  14. On the bonding and the electric field gradient of the uranyl ion

    NARCIS (Netherlands)

    de Jong, WA; Visscher, L; Nieuwpoort, WC

    1999-01-01

    Molecular properties of the uranyl ion ([UO2](2+)) are studied using both a non-relativistic and a relativistic method. Inclusion of relativity leads to a bond length expansion and makes the electric field gradient (EFG) at the uranium nucleus strongly dependent on the U-O bond distance, The non-rel

  15. Observation of increased ion cyclotron resonance signal duration through electric field perturbations.

    Science.gov (United States)

    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

  16. Systematically Asymmetric Heliospheric Magnetic Field: Evidence for a Quadrupole Mode and Non-Axisymmetry with Polarity Flip-Flops

    Science.gov (United States)

    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.

  17. The Asymmetrical Relationship with Respondents and Local Colleagues - Some Points on the Art of Doing Field Work

    DEFF Research Database (Denmark)

    Wangel, Arne

    2003-01-01

    While the epistemological aspects of cross-cultural research are extensively discussed in general terms by ethnographers and other social scientists, little attention is paid to the specific patterns of interests and expectations involved. Drawing upon previous field work in Malaysia and also upo...... universally applicable. Their purpose is to inspire a discussion on how to develop new approaches in relating to respondents and local colleagues, by which the negotiation of co-operation based on mutual interest and shared benefits is given priority....

  18. Transverse eV ion heating by random electric field fluctuations in the plasmasphere

    Science.gov (United States)

    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.

  19. Transverse eV Ion Heating by Random Electric Field Fluctuations in the Plasmasphere

    Science.gov (United States)

    Artemyev, A. V.; Mourenas, D.; Agapitov, O. V.; Blum, L.

    2017-01-01

    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 approx. 0.3 eV could potentially explain the observations.

  20. Electron cyclotron resonance heating by magnetic filter field in a negative hydrogen ion source

    Energy Technology Data Exchange (ETDEWEB)

    Kim, June Young, E-mail: beacoolguy@snu.ac.kr; Cho, Won-Hwi; Dang, Jeong-Jeung; Chung, Kyoung-Jae, E-mail: jkjlsh1@snu.ac.kr; Hwang, Y. S. [Department of Nuclear Engineering, Seoul National University, Seoul 151-742 (Korea, Republic of)

    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.

  1. Nanofriction in cold ion traps.

    Science.gov (United States)

    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.

  2. Improvement of penning ion sources

    CERN Document Server

    Bizyukov, A A; Kashaba, A Y; Sereda, K N

    2000-01-01

    It is shown that the loss of a longitudinal symmetry of magnetic field distribution in respect to the centre of the Penning discharge system causes change of electrostatic potential distribution in the discharge gap leads to appearance of asymmetry of current magnitude to the cathodes of the Penning cell,change of magnitude of current density and energy distribution of the ion beam extracted in a longitudinal direction.The use of an inhomogeneous magnetic field which is longitudinally asymmetrical concerning electrodes of the system allows to increase current efficiency of Penning ion sources from 0,2 to 0,55.

  3. IonCCD Detector for Miniature Sector-Field Mass Spectrometer : Investigation of Peak Shape and Detector Surface Artifacts Induced by keV Ion Detection

    NARCIS (Netherlands)

    Hadjar, Omar; Schlatholter, Thomas; Davila, Stephen; Catledge, Shane A.; Kuhn, Ken; Kassan, Scott; Kibelka, Gottfried; Cameron, Chad; Verbeck, Guido F.

    2011-01-01

    A recently described ion charge coupled device detector IonCCD (Sinha and Wadsworth, Rev. Sci. Instrum. 76(2), 2005; Hadjar, J. Am. Soc. Mass Spectrom. 22(4), 612-624, 2011) is implemented in a miniature mass spectrometer of sector-field instrument type and Mattauch-Herzog (MH)-geometry (Rev. Sci. I

  4. IonCCD Detector for Miniature Sector-Field Mass Spectrometer : Investigation of Peak Shape and Detector Surface Artifacts Induced by keV Ion Detection

    NARCIS (Netherlands)

    Hadjar, Omar; Schlatholter, Thomas; Davila, Stephen; Catledge, Shane A.; Kuhn, Ken; Kassan, Scott; Kibelka, Gottfried; Cameron, Chad; Verbeck, Guido F.

    2011-01-01

    A recently described ion charge coupled device detector IonCCD (Sinha and Wadsworth, Rev. Sci. Instrum. 76(2), 2005; Hadjar, J. Am. Soc. Mass Spectrom. 22(4), 612-624, 2011) is implemented in a miniature mass spectrometer of sector-field instrument type and Mattauch-Herzog (MH)-geometry (Rev. Sci.

  5. Multivariate DoE Optimization of Asymmetric Flow Field Flow Fractionation Coupled to Quantitative LC-MS/MS for Analysis of Lipoprotein Subclasses

    Directory of Open Access Journals (Sweden)

    Zsuzsanna Kuklenyik

    2015-02-01

    Full Text Available In this report we demonstrate a practical multivariate design of experiment (DoE approach for asymmetric flow field-flow fractionation (AF4 method optimization using separation of lipoprotein subclasses as an example. First, with the aid of commercially available software, we built a full factorial screening design where the theoretical outcomes were calculated by applying established formulas that govern AF4 channel performance for a 5–35 nm particle size range of interest for lipid particles. Second, using the desirable ranges of instrumental parameters established from theoretical optimization, we performed fractional factorial DoE for AF4 separation of pure albumin and ferritin with UV detection to narrow the range of instrumental parameters and allow optimum size resolution while minimizing losses from membrane immobilization. Third, the optimal range of conditions were tested using response surface DoE for sub-fractionation of high and low density lipoproteins (HDL and LDL in human serum, where the recovery of the analytes were monitored by fraction collection and isotope-dilution LC-MS/MS analysis of each individual fraction for cholesterol and apolipoproteins (ApoA-1 and ApoB-100. Our results show that DoE is an effective tool in combining AF4 theoretical knowledge and experimental data in finding the most optimal set of AF4 instrumental parameters for quantitative coupling with LC-MS/MS measurements.

  6. Gate-controlled zero-magnetic-field spin splitting in the valence band of asymmetric AlGaAs/GaAs quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Hirmer, Michael; Hirmer, Marika; Schuh, Dieter; Wegscheider, Werner; Korn, Tobias; Schueller, Christian [Institut fuer Experimentelle und Angewandte Physik, Universitaet Regensburg (Germany)

    2010-07-01

    Zero-magnetic-field-spin-splitting (ZMFSS) in two-dimensional quantum wells (QW) induced by the structure inversion asymmetry, and its control, are of major importance for both fundamental research and spintronic applications, due to its influence on the dynamics and manipulation of the spin. In hole systems the asymmetry leads to a ZMFSS of the heavy hole (HH) states in third order of the in-plane wave vector k {sub parallel}. In our experiments, we focus on highly p-doped asymmetric 2D AlGaAs/GaAs quantum wells (QW). with different QW widths and spacer thicknesses and the manipulation of the Rashba spin splitting via top gates. We utilize electronic intersubband Raman measurements in backscattering geometry at 4.2 K. Using polarization selection rules, one can distinguish between charge-density excitation (CDE, polarized spectra) and spin-density excitation (SDE, depolarized spectra) in the Raman spectra. In all samples we observe a low-energy SDE with excitation energies in the range of 0-2 meV. Comparing these excitation energies to 8 band k.p calculations of the valence subbands, the SDE can be interpreted as an intersubband excitation of the spin-split HH ground state, reflecting directly the ZMFSS.

  7. Characterization of the molar mass distribution of macromolecules in beer for different mashing processes using asymmetric flow field-flow fractionation (AF4) coupled with multiple detectors.

    Science.gov (United States)

    Choi, Jaeyeong; Zielke, Claudia; Nilsson, Lars; Lee, Seungho

    2017-07-01

    The macromolecular composition of beer is largely determined by the brewing and the mashing process. It is known that the physico-chemical properties of proteinaceous and polysaccharide molecules are closely related to the mechanism of foam stability. Three types of "American pale ale" style beer were prepared using different mashing protocols. The foam stability of the beers was assessed using the Derek Rudin standard method. Asymmetric flow field-flow fractionation (AF4) in combination with ultraviolet (UV), multiangle light scattering (MALS) and differential refractive index (dRI) detectors was used to separate the macromolecules present in the beers and the molar mass (M) and molar mass distributions (MD) were determined. Macromolecular components were identified by enzymatic treatments with β-glucanase and proteinase K. The MD of β-glucan ranged from 10(6) to 10(8) g/mol. In addition, correlation between the beer's composition and foam stability was investigated (increased concentration of protein and β-glucan was associated with increased foam stability).

  8. Characterization of oxidized tannins: comparison of depolymerization methods, asymmetric flow field-flow fractionation and small-angle X-ray scattering.

    Science.gov (United States)

    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.

  9. Fractionation and Characterization of High Aspect Ratio Gold Nanorods Using Asymmetric-Flow Field Flow Fractionation and Single Particle Inductively Coupled Plasma Mass Spectrometry

    Directory of Open Access Journals (Sweden)

    Thao M. Nguyen

    2015-07-01

    Full Text Available Gold nanorods (GNRs are of particular interest for biomedical applications due to their unique size-dependent longitudinal surface plasmon resonance band in the visible to near-infrared. Purified GNRs are essential for the advancement of technologies based on these materials. Used in concert, asymmetric-flow field flow fractionation (A4F and single particle inductively coupled mass spectrometry (spICP-MS provide unique advantages for fractionating and analyzing the typically complex mixtures produced by common synthetic procedures. A4F fractions collected at specific elution times were analyzed off-line by spICP-MS. The individual particle masses were obtained by conversion of the ICP-MS pulse intensity for each detected particle event, using a defined calibration procedure. Size distributions were then derived by transforming particle mass to length assuming a fixed diameter. The resulting particle lengths correlated closely with ex situ transmission electron microscopy. In contrast to our previously reported observations on the fractionation of low-aspect ratio (AR GNRs (AR < 4, under optimal A4F separation conditions the results for high-AR GNRs of fixed diameter (≈20 nm suggest normal, rather than steric, mode elution (i.e., shorter rods with lower AR generally elute first. The relatively narrow populations in late eluting fractions suggest the method can be used to collect and analyze specific length fractions; it is feasible that A4F could be appropriately modified for industrial scale purification of GNRs.

  10. Importance of material matching in the calibration of asymmetric flow field-flow fractionation: material specificity and nanoparticle surface coating effects on retention time

    Science.gov (United States)

    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.

  11. Enzymatic determination of cholesterol and triglycerides in serum lipoprotein profiles by asymmetrical flow field-flow fractionation with on-line, dual detection.

    Science.gov (United States)

    Rambaldi, Diana Cristina; Reschiglian, Pierluigi; Zattoni, Andrea; Johann, Christoph

    2009-11-03

    Alterations of lipoproteins (LPs) and related lipid levels in blood serum are correlated to the risk of coronary artery disease (CAD). Fast, possibly automated methods to obtain complete, multi-parametric LP profiles are therefore welcome to be developed for routine, clinical analysis practice. In this work, asymmetrical flow field-flow fractionation (AF4) with on-line, dual post-fractionation reaction detection (PFRD) is applied to develop a method for single-run, simultaneous quantification of cholesterol (CHOL) and triglycerides (TGs) in each fractionated LP class. The enzymatic reagents used for the post-fractionation reaction are available as commercial kits for certified, standard clinical protocols for the analysis of CHOL and TGs in serum. Using CHOL and glycerol as reference standards, a new procedure is applied to optimize the experimental conditions for PFRD-based, quantitative analysis. Upon optimized PFRD and AF4 conditions, results obtained for the determination of total CHOL (TC), TGs, HDL-cholesterol (HDL-C), and LDL-cholesterol (LDL-C) in a set of serum samples from healthy donors are found in agreement with the values provided by a clinical laboratory. The intra-day and inter-day precisions of the method were found always lower than 10% (CV). When the method was applied to serum samples from patients affected by sepsis, differences in CHOL and TG profiles between patients and healthy donors were observed.

  12. Size separations of starch of different botanical origin studied by asymmetrical-flow field-flow fractionation and multiangle light scattering.

    Science.gov (United States)

    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.

  13. Rational design of ion force fields based on thermodynamic solvation properties.

    Science.gov (United States)

    Horinek, Dominik; Mamatkulov, Shavkat I; Netz, Roland R

    2009-03-28

    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 (H(3)O(+)) 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

  14. Storm-Time Strong Field-Aligned Ion Upflow in Region of the SED Plume

    Institute of Scientific and Technical Information of China (English)

    YUAN Zhi-Gang; DENG Xiao-Hua; WANG Jing-Fang

    2008-01-01

    report the observations from the GPS TEC and DMSP F-13 satellites showing that very strong upward field-aligned (FA) ion velocity and flux in the outer region of the storm-enhanced density (SED) occurred in the event of the geomagnetic storm on 29-31 May 2003. By a method of coordinate transformation, upward FA ion velocities in excess of 250m/s are obtained from the observations of the DMSP F-13 satellite. Further, an FA ion flux is estimated to be about 4.5×1013ions/m2s in the dusk sector. The estimated FA ion velocity and flux provide a powerful direct proof to support the scenario that there is a strong coupling of particles between the ionosphere and plasmasphere in the region of the SED plume. In the process, FA ion flux transports from the ionosphere to the plasmasphere in the region of the SED plume. Therefore, the plume of SED in the ionosphere provides an important source to the enhanced density of O+ in the storm-time plasmasphere.

  15. Generation of energetic negative ions from clusters using intense laser fields

    Science.gov (United States)

    Rajeev, R.; Madhu Trivikram, T.; Rishad, K. P. M.; Narayanan, V.; Krishnamurthy, M.

    2013-04-01

    Intense laser fields are known to induce strong ionization in atoms. In nanoclusters, ionization is only stronger, resulting in very high charge densities that lead to Coulomb explosion and emission of accelerated highly charged ions. In such a strongly ionized system, it is neither conceivable nor intuitive that energetic negative ions can originate. Here we demonstrate that in a dense cluster ensemble, where atomic species of positive electron affinity are used, it is indeed possible to generate negative ions with energy and ion yield approaching that of positive ions. It is shown that the process behind such a strong charge reduction is extraneous to the ionization dynamics of single clusters within the focal volume. Normal and well-known charge transfer reactions are insufficient to explain the observations. Our analysis reveals the formation of a manifold of Rydberg excited clusters around the focal volume that facilitate orders of magnitudes more efficient electron transfer. This phenomenon, which involves an active role of laser-heated electrons, comprehensively explains the formation of copious accelerated negative ions from the nano-cluster plasma.

  16. Optical field ionization of atoms and ions using ultrashort laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Fittinghoff, D.N.

    1993-12-01

    This dissertation research is an investigation of the strong optical field ionization of atoms and ions by 120-fs, 614-run laser pulses and 130-fs, 800-nm laser pulses. The experiments have shown ionization that is enhanced above the predictions of sequential tunneling models for He{sup +2}, Ne{sup +2} and Ar{sup +2}. The ion yields for He{sup +l}, Ne{sup +l} and Ar{sup +l} agree well with the theoretical predictions of optical tunneling models. Investigation of the polarization dependence of the ionization indicates that the enhancements are consistent with a nonsequential ionization mechanism in which the linearly polarized field drives the electron wavefunction back toward the ion core and causes double ionization through inelastic e-2e scattering. These investigations have initiated a number of other studies by other groups and are of current scientific interest in the fields of high-irradiance laser-matter interactions and production of high-density plasmas. This work involved: (1) Understanding the characteristic nature of the ion yields produced by tunneling ionization through investigation of analytic solutions for tunneling at optical frequencies. (2) Extensive characterization of the pulses produced by 614-nm and 800-ran ultrashort pulse lasers. Absolute calibration of the irradiance scale produced shows the practicality of the inverse problem--measuring peak laser irradiance using ion yields. (3) Measuring the ion yields for three noble gases using linear, circular and elliptical polarizations of laser pulses at 614-nm and 800-nm. The measurements are some of the first measurements for pulse widths as low as 120-fs.

  17. Relativistic heavy ion collisions with realistic non-equilibrium mean fields

    CERN Document Server

    Fuchs, C; Wolter, H H

    1996-01-01

    We study the influence of non-equilibrium phase space effects on the dynamics of heavy ion reactions within the relativistic BUU approach. We use realistic Dirac-Brueckner-Hartree-Fock (DBHF) mean fields determined for two-Fermi-ellipsoid configurations, i.e. for colliding nuclear matter, in a local phase space configuration approximation (LCA). We compare to DBHF mean fields in the local density approximation (LDA) and to the non-linear Walecka model. The results are further compared to flow data of the reaction Au on Au at 400 MeV per nucleon measured by the FOPI collaboration. We find that the DBHF fields reproduce the experiment if the configuration dependence is taken into account. This has also implications on the determination of the equation of state from heavy ion collisions.

  18. Radiofrequency hydrogen ion source with permanent magnets providing axial magnetic field.

    Science.gov (United States)

    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.

  19. Radiofrequency hydrogen ion source with permanent magnets providing axial magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Oikawa, Kohei, E-mail: oikawa@ecei.tohoku.ac.jp; Saito, Yuta; Komizunai, Shota; Takahashi, Kazunori; Ando, Akira [Department of Electrical Engineering, Tohoku University, Sendai 980-8579 (Japan)

    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.

  20. Novel quantum phenomena induced by strong magnetic fields in heavy-ion collisions

    CERN Document Server

    Hattori, Koichi

    2016-01-01

    The relativistic heavy-ion collisions create both hot quark-gluon matter and strong magnetic fields, and provide an arena to study the interplay between quantum chromodynamics (QCD) and quantum electrodynamics (QED). In recent years, it has been shown that such an interplay can generate a number of interesting quantum phenomena in hadronic and quark-gluon matter. In this short review, we first discuss some properties of the magnetic fields in heavy-ion collisions and then give an overview of the magnetic-field induced novel quantum effects. In particular, we focus on the magnetic effect on the heavy-flavor mesons, and the heavy quark transports, and also the phenomena closely related to chiral anomaly.

  1. Chaotic behavior of collective ion dynamics in the presence of an external static magnetic field

    Science.gov (United States)

    Poria, Swarup; Ghosh, Samiran

    2016-06-01

    The two-dimensional nonlinear collective ion dynamics in the presence of external magnetic field in an electron-ion plasma is investigated. The analysis is performed for traveling plane waves to elucidate the various aspects of the phase-space dynamics. The presence of magnetic field makes the dynamics of the nonlinear wave complex with a complicated phase-space behavior. Thus, the nonlinear wave supports a wide class of nonlinear structures viz., single soliton, multi-soliton, periodic, and quasi-periodic oscillations depending on the values of M (Mach number) and Ω (the ratio of ion gyro-frequency to the ion plasma frequency). The computational results predict the chaotic behavior of the nonlinear wave and the transition to chaos takes place when Ω ≳ 0.35 depending on the direction of propagation and the value of M. The amplitude of the wave depends on the obliqueness of the propagation and Mach number, whereas the magnetic field changes the dispersion properties of the wave.

  2. Harmonic analysis and field quality improvement of an HTS quadrupole magnet for a heavy ion accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Zhan; Wei, Shaoqing; Lee, Sang Jin [Uiduk University, Gyeongju (Korea, Republic of); Jo, Hyun Chul; Kim, Do Gyun; Kim, Jong Won [Rare Isotope Science Project, Institute for Basic Science, Daejeon (Korea, Republic of)

    2016-06-15

    In recent years, the iron-dominated high-temperature superconductor (HTS) quadrupole magnets are being developed for heavy ion accelerators. Field analyses for iron-dominated quadrupole magnets were based on the normal-conducting (NC) quadrupole magnet early in the development for accelerators. Some conclusions are still in use today. However, the magnetic field of iron-dominated HTS quadrupole magnets cannot fully follow these conclusions. This study established an HTS quadrupole magnet model and an NC quadrupole magnet model, respectively. The harmonic characteristics of two magnets were analyzed and compared. According to the comparison, the conventional iron-dominated quadrupole magnets can be designed for maximum field gradient; the HTS quadrupole magnet, however, should be considered with varying field gradient. Finally, the HTS quadrupole magnet was designed for the changing field gradient. The field quality of the design was improved comparing with the result of the previous study. The new design for the HTS quadrupole magnet has been suggested.

  3. Modelling radiation fields of ion beams in tissue-like materials

    Energy Technology Data Exchange (ETDEWEB)

    Burigo, Lucas Norberto

    2014-07-16

    Fast nuclei are ionizing radiation which can cause deleterious effects to irradiated cells. The modelling of the interactions of such ions with matter and the related effects are very important to physics, radiobiology, medicine and space science and technology. A powerful method to study the interactions of ionizing radiation with biological systems was developed in the field of microdosimetry. Microdosimetry spectra characterize the energy deposition to objects of cellular size, i.e., a few micrometers. In the present thesis the interaction of ions with tissue-like media was investigated using the Monte Carlo model for Heavy-Ion Therapy (MCHIT) developed at the Frankfurt Institute for Advanced Studies. MCHIT is a Geant4-based application intended to benchmark the physical models of Geant4 and investigate the physical properties of therapeutic ion beams. We have implemented new features in MCHIT in order to calculate microdosimetric quantities characterizing the radiation fields of accelerated nucleons and nuclei. The results of our Monte Carlo simulations were compared with recent experimental microdosimetry data. In addition to microdosimetry calculations with MCHIT, we also investigated the biological properties of ion beams, e.g. their relative biological effectiveness (RBE), by means of the modified Microdosimetric-Kinetic model (MKM). The MKM uses microdosimetry spectra in describing cell response to radiation. MCHIT+MKM allowed us to study the physical and biological properties of ion beams. The main results of the thesis are as follows: MCHIT is able to describe the spatial distribution of the physical dose in tissue-like media and microdosimetry spectra for ions with energies relevant to space research and ion-beam cancer therapy; MCHIT+MKM predicts a reduction of the biological effectiveness of ions propagating in extended medium due to nuclear fragmentation reactions; We predicted favourable biological dose-depth profiles for monoenergetic helium and

  4. On the role of magnetic field in photon excess in heavy ion collisions

    CERN Document Server

    Tuchin, Kirill

    2014-01-01

    Synchrotron photon spectrum in heavy-ion collisions is computed taking into account the spatial and temporal structure of magnetic field. It is found that a significant fraction of photon excess in heavy-ion collisions in the region $k_\\bot=1-3$GeV can be attributed to the synchrotron radiation. Azimuthal anisotropy of the synchrotron photon spectrum is characterized by the Fourier coefficients $v_2=4/7$ and $v_4=1/10$ that are independent of photon momentum and centrality.

  5. Creation and recovery of a W(111) single atom gas field ion source.

    Science.gov (United States)

    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.

  6. Ion-cage interpretation for the structural and dynamic changes of ionic liquids under an external electric field.

    Science.gov (United States)

    Shi, Rui; Wang, Yanting

    2013-05-01

    In many applications, ionic liquids (ILs) work in a nonequilibrium steady state driven by an external electric field. However, how the electric field changes the structure and dynamics of ILs and its underlying mechanism still remain poorly understood. In this paper, coarse-grained molecular dynamics simulations were performed to investigate the structure and dynamics of 1-ethyl-3-methylimidazolium nitrate ([EMIm][NO3]) under a static electric field. The ion cage structure was found to play an essential role in determining the structural and dynamic properties of the IL system. With a weak or moderate electric field (0-10(7) V/m), the external electric field is too weak to modify the ion cage structure in an influential way and thus the changes of structural and dynamic properties are negligible. With a strong electric field (10(7)-10(9) V/m) applied, ion cages expand and deform apparently, leading to the increase of ion mobility and self-diffusion coefficient with electric field, and the self-diffusion of ions along the electric field becomes faster than the other two directions due to the anisotropic deformation of ion cages. In addition, the Einstein relation connecting diffusion and mobility breaks down at strong electric fields, and it also breaks down for a single ion species even at moderate electric fields (linear-response region).

  7. Interaction modes between asymmetrically and oppositely charged rods.

    Science.gov (United States)

    Antila, Hanne S; Van Tassel, Paul R; Sammalkorpi, Maria

    2016-02-01

    The interaction of oppositely and asymmetrically charged rods in salt-a simple model of (bio)macromolecular assembly-is observed via simulation to exhibit two free energy minima, separated by a repulsive barrier. In contrast to similar minima in the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, the governing mechanism includes electrostatic attraction at large separation, osmotic repulsion at close range, and depletion attraction near contact. A model accounting for ion condensation and excluded volume is shown to be superior to a mean-field treatment in predicting the effect of charge asymmetry on the free-energy profile.

  8. Plasma and Energetic Particle Behaviors During Asymmetric Magnetic Reconnection at the Magnetopause

    Science.gov (United States)

    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.

  9. Characterization of cationic polymers by asymmetric flow field-flow fractionation and multi-angle light scattering-A comparison with traditional techniques.

    Science.gov (United States)

    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.

  10. Energy loss of ions by electric-field fluctuations in a magnetized plasma.

    Science.gov (United States)

    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.

  11. Isolated attosecond pulses generation from coherent superposition state of helium ion in static electric fields and spatial nonhomogeneous fields

    Science.gov (United States)

    Liu, Hao; Zhang, Zhengzhong; Wu, Yangjiang; Jiang, Shicheng; Yu, Chao

    2016-09-01

    We present a systematic study of high-order harmonic generation (HHG) from helium ion with the initial state prepared as a coherent superposition of electronic ground state and an excited state. As a result, the conversion efficiency of the harmonic spectrum is significantly enhanced. When we add a static electric field in fundamental field, the supercontinuum region of the harmonic spectrum is distinctly extended and an isolated 100 as pulse can be generated. Moreover, we use a spatial nonhomogeneous field to increase the cutoff energy in high-order harmonic generation spectrum, which can be extended to about 700 eV, and an isolated 50 as pulse can be obtained directly by the superposition of the supercontinuum harmonics.

  12. Ion field-evaporation from ionic liquids infusing carbon xerogel microtips

    Energy Technology Data Exchange (ETDEWEB)

    Perez-Martinez, C. S., E-mail: carlita@mit.edu; Lozano, P. C. [Department of Aeronautics and Astronautics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

    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.

  13. Temperature Field Analysis and Thermal Dissipation Structure Optimization of Lithium-ion Battery Pack in PEVs

    Directory of Open Access Journals (Sweden)

    Hu Jianjun

    2014-01-01

    Full Text Available Aimed to achieve good thermal stability of lithium batteries in electric vehicles under the conditions of high-power. This study established a three-dimensional, transient heat dissipation model for Lithium-ion battery package in the three-dimensional Cartesian coordinate system based on theoretical knowledge of thermodynamics and heat transfer. With the help of the numerical simulation theoretical of CFD, the flow and temperature field of force air cooling Lithium-ion battery pack was simulated with the heat source obtained from dynamic performance simulations of Pure Electric Vehicles (PEVs under 15% climbing conditions. For the issues of high temperature rise and large temperature difference, optimal programs to improve the cooling effect of Lithium-ion battery pack were proposed. Simulation results indicate that the optimal measures make heat dissipation well and temperature distribution uniform, which satisfies the application requirement in PEVs.

  14. A compact broadband ion beam focusing device based on laser-driven megagauss thermoelectric magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Albertazzi, B., E-mail: bruno.albertazzi@polytechnique.edu [LULI, École Polytechnique, CNRS, CEA, UPMC, 91128 Palaiseau (France); INRS-EMT, Varennes, Québec J3X 1S2 (Canada); Graduate School of Engineering, Osaka University, Suita, Osaka 565-087 (Japan); D' Humières, E. [CELIA, Universite de Bordeaux, Talence 33405 (France); Department of Physics, University of Nevada, Reno, Nevada 89557 (United States); Lancia, L.; Antici, P. [Dipartimento SBAI, Universita di Roma “La Sapienza,” Via A. Scarpa 16, 00161 Roma (Italy); Dervieux, V.; Nakatsutsumi, M.; Romagnani, L.; Fuchs, J., E-mail: Julien.fuchs@polytechnique.fr [LULI, École Polytechnique, CNRS, CEA, UPMC, 91128 Palaiseau (France); Böcker, J.; Swantusch, M.; Willi, O. [Institut für Laser- und Plasmaphysik, Heinrich-Heine-Universität, Düsseldorf D-40225 (Germany); Bonlie, J.; Cauble, B.; Shepherd, R. [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States); Breil, J.; Feugeas, J. L.; Nicolaï, P.; Tikhonchuk, V. T. [CELIA, Universite de Bordeaux, Talence 33405 (France); Chen, S. N. [LULI, École Polytechnique, CNRS, CEA, UPMC, 91128 Palaiseau (France); Lawrence Livermore National Laboratory, Livermore, California 94551 (United States); Sentoku, Y. [Department of Physics, University of Nevada, Reno, Nevada 89557 (United States); 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.

  15. 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

    Energy Technology Data Exchange (ETDEWEB)

    Kirichok, A. V., E-mail: sandyrcs@gmail.com; Kuklin, V. M.; Pryimak, A. V. [Institute for High Technologies, V.N. Karazin Kharkiv National University, 4 Svobody Sq., Kharkiv 61022 (Ukraine); Zagorodny, A. G. [Bogolyubov Institute for Theoretical Physics, 14-b, Metrolohichna str., Kiev 03680 (Ukraine)

    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.

  16. 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

    Science.gov (United States)

    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.

  17. Capability of the free-ion eigenstates for crystal-field splitting

    CERN Document Server

    Mulak, Jacek

    2011-01-01

    Any electron eigenstate |\\Psi>of the paramagnetic ion open-shell is characterized by the three independent multipole asphericities A_{k}= for k=2,4 and 6 related to the second moments of the relevant crystal-field splittings by \\sigma_{k}^{2}=]A_{k}^{2}S_{k}^{2}, where S_{k}^{2}=]\\sum_{q}|B_{kq}|^{2}. The A_{k} can serve as a reliable measure of the state |\\Psi>capability for the splitting produced by the k-rank component of the crystal-field Hamiltonian and allow one to verify any fitted crystal-field parameter set directly comparing the calculated and the experimental second moments of the relevant crystal-field splittings. We present the multipole characteristics A_{k} for the extensive set of eigenstates from the lower parts of energy spectra of the tripositive 4f^{N} ions applying in the calculations the advanced eigenfunctions of the free lanthanide ions obtained based on the M. Reid f-shell programs. Such amended asphericities are compared with those achieved for the simplified Russell-Saunders states....

  18. Plasma expansion across a transverse magnetic field in a negative hydrogen ion source for fusion

    Science.gov (United States)

    Fantz, U.; Schiesko, L.; Wünderlich, D.

    2014-08-01

    High power negative hydrogen ion sources operating at 0.3 Pa are a key component of the neutral beam injection systems for the international fusion experiment ITER. To achieve the required large ion current at a tolerable number of co-extracted electrons the source is equipped with a magnetic filter field (up to 10 mT). The IPP prototype source (1/8 of the area of the ITER source) has been equipped with a flexible magnetic filter frame to perform filter field studies (position, polarity, strength). Axial profiles of the plasma parameters are measured with two Langmuir probes, positioned in the upper and the lower half of the expansion chamber. In addition to the expected decrease in electron temperature and density a vertical drift develops the direction depending on the polarity of the field. Without field no drift is observed. The drift is less pronounced in caesium seeded discharges and almost vanishes in deuterium, indicating an influence of the ion mass on the drift. A comparison with results from a half-size ITER source reveals that the plasma is much more uniform in the large source.

  19. Three-body fragmentation of triatomic molecular ions in a strong laser field

    Science.gov (United States)

    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.

  20. High accuracy calculation of the hydrogen negative ion in strong magnetic fields

    Institute of Scientific and Technical Information of China (English)

    Zhao Ji-Jun; Wang Xiao-Feng; Qiao Hao-Xue

    2011-01-01

    Using a full configuration-interaction method with Hylleraas-Gaussian basis function, this paper investigates the 110+, 11(-1)+ and l1(-2)+ states of the hydrogen negative ion in strong magnetic fields. The total energies, electron detachment energies and derivatives of the total energy with respect to the magnetic field are presented as functions of magnetic field over a wide range of field strengths. Compared with the available theoretical data, the accuracy for the energies is enhanced significantly. The field regimes 3 <γ< 4 and 0.02 < 7< 0.05, in which the l1(-l)+ and l1(-2)+states start to become bound, respectively, are also determined based on the calculated electron detachment energies.

  1. Shocklets, SLAMS, and Field-Aligned Ion Beams in the Terrestrial Foreshock

    Science.gov (United States)

    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.

  2. Relationship between ion concentration of ferrofluid and response signals of magnetic nanoparticles against ac magnetic fields

    Science.gov (United States)

    Oda, Shoya; Kitamoto, Yoshitaka

    2017-05-01

    Harmonic components of magnetic signals from ferrofluids excited by alternating magnetic fields are studied in view of applications to liquid sensing. The harmonic signals from ferrofluids of iron-oxide magnetic nanoparticles excited at the field strength of 100 mTp-p and the frequency range from 1510-6500 Hz are detected by a pickup coil and are processed with a lock-in amplifier. The harmonic signal exhibits a minimum in the frequency dependence at a frequency, which is correlated to the magnetic relaxation. The minimum frequency is decreased and the minimum value is increased with the increase of the ion concentration; the frequency dependence around the minimum frequency exhibits characteristic features depending on the ion concentration. The features are originated from polydispersity in the aggregation formed in the ferrofluids at higher ion concentration, and are different from the frequency characteristics depending on the viscosity. This magnetic relaxometry using the harmonic signals is useful for ion sensing in liquids without the influence of viscosity.

  3. Relationship between ion concentration of ferrofluid and response signals of magnetic nanoparticles against ac magnetic fields

    Directory of Open Access Journals (Sweden)

    Shoya Oda

    2017-05-01

    Full Text Available Harmonic components of magnetic signals from ferrofluids excited by alternating magnetic fields are studied in view of applications to liquid sensing. The harmonic signals from ferrofluids of iron-oxide magnetic nanoparticles excited at the field strength of 100 mTp-p and the frequency range from 1510−6500 Hz are detected by a pickup coil and are processed with a lock-in amplifier. The harmonic signal exhibits a minimum in the frequency dependence at a frequency, which is correlated to the magnetic relaxation. The minimum frequency is decreased and the minimum value is increased with the increase of the ion concentration; the frequency dependence around the minimum frequency exhibits characteristic features depending on the ion concentration. The features are originated from polydispersity in the aggregation formed in the ferrofluids at higher ion concentration, and are different from the frequency characteristics depending on the viscosity. This magnetic relaxometry using the harmonic signals is useful for ion sensing in liquids without the influence of viscosity.

  4. Modelling of Ion Transport in Solids with a General Bond Valence Based Force-Field

    Directory of Open Access Journals (Sweden)

    S. Adams

    2010-12-01

    Full Text Available Empirical bond length - bond valence relations provide insight into the link between structure of and ion transport in solid electrolytes. Building on our earlier systematic adjustment of bond valence (BV parameters to the bond softness, here we discuss how the squared BV mismatch can be linked to the absolute energy scale and used as a general Morse-type interaction potential for analyzing low-energy pathways in ion conducting solid or mixed conductors either by an energy landscape approach or by molecular dynamics (MD simulations. For a wide range of Lithium oxides we could thus model ion transport revealing significant differences to an earlier geometric approach. Our novel BV-based force-field has also been applied to investigate a range of mixed conductors, focusing on cathode materials for lithium ion battery (LIB applications to promote a systematic design of LIB cathodes that combine high energy density with high power density. To demonstrate the versatility of the new BV-based force-field it is applied in exploring various strategies to enhance the power performance of safe low cost LIB materials (LiFePO4, LiVPO4F, LiFeSO4F, etc..

  5. Fourier Transfrom Ion Cyclotron Resonance Mass Spectrometry at High Magnetic Field

    Science.gov (United States)

    Marshall, Alan G.

    1998-03-01

    At high magnetic field (9.4 tesla at NHMFL), Fourier transform ion cyclotron resonance mass spectrometry performance improves dramatically: mass resolving power, axialization efficiency, and scan speed (each proportional to B), maximum ion mass, dynamic range, ion trapping period, kinetic energy, and electron self-cooling rate for sympathetic cooling (each proportional to B^2), and ion coalescence tendency (proportional 1/B^2). These advantages may apply singly (e.g., unit mass resolution for proteins of >100,000 Da), or compound (e.g., 10-fold improvement in S/N ratio for 9.4 T vs. 6 T at the same resolving power). Examples range from direct determination of molecular formulas of diesel fuel components by accurate mass measurement (=B10.1 ppm) to protein structure and dynamics probed by H/D exchange. This work was supported by N.S.F. (CHE-93-22824; CHE-94-13008), N.I.H. (GM-31683), Florida State University, and the National High Magnetic Field Laboratory in Tallahassee, FL.

  6. Aharonov-Bohm Effect in the Photodetachment Microscopy of Hydrogen Negative Ions in an Electric Field

    Science.gov (United States)

    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.

  7. Implementing Silicon Nanoribbon Field-Effect Transistors as Arrays for Multiple Ion Detection

    Directory of Open Access Journals (Sweden)

    Ralph L. Stoop

    2016-05-01

    Full Text Available 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. Ion acoustic wave instabilities and nonlinear structures associated with field-aligned flows in the F-region ionosphere

    Science.gov (United States)

    Saleem, H.; Ali Shan, S.; Haque, Q.

    2016-11-01

    It is shown that the inhomogeneous field-aligned flow of heavier ions into the stationary plasma of the upper ionosphere produces very low frequency (of the order of a few Hz) electrostatic unstable ion acoustic waves (IAWs). This instability is an oscillatory instability unlike D'Angelo's purely growing mode. The growth rate of the ion acoustic wave (IAW) corresponding to heavier ions is due to shear flow and is larger than the ion Landau damping. However, the ion acoustic waves corresponding to non-flowing lighter ions are Landau damped. It is found that even if D'Angelo's instability condition is satisfied, the unstable mode develops its real frequency in this coupled system. Hence, the shear flow of one type of ions in a bi-ion plasma system produces ion acoustic wave activity. If the density non-uniformity is taken into account, then the drift wave becomes unstable. The coupled nonlinear equations for stationary ions "a," flowing ions "b," and inertialess electrons are also solved using the small amplitude limit. The solutions predict the existence of the order of a few kilometers electric field structures in the form of solitons and vortices, which is in agreement with the satellite observations.

  9. Data including GROMACS input files for atomistic molecular dynamics simulations of mixed, asymmetric bilayers including molecular topologies, equilibrated structures, and force field for lipids compatible with OPLS-AA parameters

    DEFF Research Database (Denmark)

    Róg, Tomasz; Orłowski, Adam; Llorente, Alicia

    2016-01-01

    In this Data in Brief article we provide a data package of GROMACS input files for atomistic molecular dynamics simulations of multicomponent, asymmetric lipid bilayers using the OPLS-AA force field. These data include 14 model bilayers composed of 8 different lipid molecules. The lipids present ...... (md.mdp). The data is associated with the research article "Interdigitation of Long-Chain Sphingomyelin Induces Coupling of Membrane Leaflets in a Cholesterol Dependent Manner" (Róg et al., 2016) [3]....

  10. Mass transport model of ions within biofilms under the effect of external field

    Institute of Scientific and Technical Information of China (English)

    WANG Jun; TANG Xue-xi

    2006-01-01

    A mass transport model was developed to predict the transport rate of ions within biofilms, which was experimentally verified using the fluxes ofNH4+ and Ca2+ through the heterotrophic biofilms with the thickness varying from 230 to 1430 μm under the effect of external field in the range of-20 V/m to 60 V/m. It is found that the result predicted by the model is in agreement with the experimentally obtained one, with the error less than 5 percent for the thin biofilms. The error increases with the increase of the biofilm thickness. The transport rate of ions caused by electric migration is affected by the charges, field strength, and biofilm thickness and so on.

  11. Optical properties of 3d-ions in crystals spectroscopy and crystal field analysis

    CERN Document Server

    Brik, Mikhail

    2013-01-01

    "Optical Properties of 3d-Ions in Crystals: Spectroscopy and Crystal Field Analysis" discusses spectral, vibronic and magnetic properties of 3d-ions in a wide range of crystals, used as active media for solid state lasers and potential candidates for this role. Crystal field calculations (including first-principles calculations of energy levels and absorption spectra) and their comparison with experimental spectra, the Jahn-Teller effect, analysis of vibronic spectra, materials science applications are systematically presented. The book is intended for researchers and graduate students in crystal spectroscopy, materials science and optical applications. Dr. N.M. Avram is an Emeritus Professor at the Physics Department, West University of Timisoara, Romania; Dr. M.G. Brik is a Professor at the Institute of Physics, University of Tartu, Estonia.

  12. Sternheimer Factors and Electric-Field-Gradient Hyperpolarisabilities for Ions in Crystals

    Science.gov (United States)

    Fowler, P. W.; Kelly, H. M.

    1994-02-01

    Analytic coupled Hartree-Fock calculations of the electric field gradient response properties y (the Sternheimer shielding factor) and e (the dipole-dipole-electric field gradient hyperpolarisability) have been carried out on anions in clusters that simulate that crystal environment. The systems studied are F- in LiF and NaF, Cl- in LiCl and NaCl, O2-in MgO, S2- in MgS, and H- in LiH. Both properties show large reductions from free-ion values and significant variation with lattice parameter, and the results indicate that damped values of anion Sternheimer factors will be necessary in accurate simulation of N Q R data or modelling of properties of ion-pairs.

  13. Characteristics of a high brightness gaseous field ion source employing tungsten-carbon doped NiAl needles

    Energy Technology Data Exchange (ETDEWEB)

    Mousa, Marwan S., E-mail: mmousa@mutah.edu.jo [Department of Physics, Mu' tah University, P.O. Box 7, Al-Karak (Jordan)

    2011-05-15

    We report on the characterization of a high brightness gaseous field ion source using an emitter made of a NiAl needle containing tiny spherical tungsten-carbon precipitates. By field evaporation of such a multiphase alloy, a surface protrusion is formed out of a precipitate, which can act as a small source size field ion emitter. The emission current-voltage characteristics of this emitter were recorded for a variety of parameters. The results obtained suggest that its application as a stable ion source is possible even on long term operation. -- Research highlights: {yields} High brightness gaseous field ion source of precipitation hardened NiAl+W+C emitter. {yields} Emission current-voltage characteristics are recorded for a variety of parameters. {yields} Very small virtual source sizes and energy spreads can be attained. {yields} Results suggest that application as long term stable ion source is possible.

  14. 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.

    Science.gov (United States)

    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.

  15. Feasibility of asymmetrical flow field-flow fractionation as a method for detecting protective antigen by direct recognition of size-increased target-captured nanoprobes.

    Science.gov (United States)

    Shin, Kayeong; Choi, Jaeyeong; Cho, Jun-Haeng; Yoon, Moon-Young; Lee, Seungho; Chung, Hoeil

    2015-11-27

    Asymmetrical flow field-flow fractionation (AF4) was evaluated as a potential analytical method for detection of a protective antigen (PA), an Anthrax biomarker. The scheme was based on the recognition of altered AF4 retention through the generation of the size-increased Au nanoparticle probes as a result of PA binding, in which a PA-selective peptide was conjugated on the probe surface. In the visible absorption-based AF4 fractograms, the band position shifted to a longer retention time as the PA concentration increased due to the presence of probe bound with PAs. The shift was insignificant when the concentration was relatively low at 84.3pM. To improve sensitivity, two separate probes conjugated with two different peptides able to bind on different PA epitopes were used together. The band shift then became distinguishable even at 84.3pM of PA sample. The formation of larger PA-probe inter-connected species using the dual-probe system was responsible for the enhanced band shift. In parallel, the feasibility of surface-enhanced Raman scattering (SERS) as a potential AF4 detection method was also evaluated. In the off-line SERS fractogram constructed using fractions collected during AF4 separation, a band shift was also observed for the 84.3pM PA sample, and the band intensity was higher when using the dual-probe system. The combination of AF4 and SERS is promising for the detection of PA and will become a potential tool if the reproducibility of SERS measurement is improved.

  16. Combining asymmetrical flow field-flow fractionation with on- and off-line fluorescence detection to examine biodegradation of riverine dissolved and particulate organic matter.

    Science.gov (United States)

    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.

  17. Far-field constant-gradient laser accelerator of electrons in an ion channel

    CERN Document Server

    Khudik, Vladimir; Shvets, Gennady

    2016-01-01

    We predict that electrons in an ion channel can gain ultra-relativistic energies by simultaneously interacting with a laser pulse and, counter-intuitively, with a decelerating electric field. The crucial role of the decelerating field is to maintain high-amplitude betatron oscillations, thereby enabling constant rate energy flow to the electrons via the direct laser acceleration mechanism. Multiple harmonics of the betatron motion can be employed. Injecting electrons into a decelerating phase of a laser wakefield accelerator is one practical implementation of the scheme.

  18. Field-ion microscopy observation of single-walled carbon nanotubes

    Institute of Scientific and Technical Information of China (English)

    张兆祥; 张耿民; 杜民; 金新喜; 侯士敏; 孙建平; 顾镇南; 赵兴钰; 刘惟敏; 吴锦雷; 薛增泉

    2002-01-01

    Field-ion microscopy (FIM), a tool for surface analysis with atomic resolution, has been employed to observethe end structure of single-walled carbon nanotubes (SWCNTs). FIM images revealed the existence of open SWCNTends. Amorphous carbon atoms were also observed to occur around SWCNTs and traditional field evaporation failedto remove them. Heat treatment was found to be efficacious in altering the end structures of SWCNT bundles. Carbonand oxygen atoms released from heated tungsten filament are believed to be responsible for the decoration imposed onthe SWCNT ends.

  19. Ion heating, burnout of the HF field and ion sound generation under the development of a modulation instability of an intense Langmuir wave in a plasma

    CERN Document Server

    Kirichok, A V; Pryimak, A V; Zagorodny, A G

    2015-01-01

    The development of one-dimensional parametric instabilities of intense long-wave plasma waves is considered in terms of the so-called hybrid models, when electrons are treated as a fluid and ions are 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 (LF) 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. Reduced absorption of the HF field leads to the retardation of the HF field burnout within plasma density cavities and to the broadening of the HF spectrum. At the same time, the i...

  20. Azimuthally fluctuating magnetic field and its impacts on observables in heavy-ion collisions

    Energy Technology Data Exchange (ETDEWEB)

    Bloczynski, John [Physics Department and Center for Exploration of Energy and Matter, Indiana University, 2401 N Milo B. Sampson Lane, Bloomington, IN 47408 (United States); Huang, Xu-Guang, E-mail: xuhuang@indiana.edu [Physics Department and Center for Exploration of Energy and Matter, Indiana University, 2401 N Milo B. Sampson Lane, Bloomington, IN 47408 (United States); Zhang, Xilin [Physics Department and Center for Exploration of Energy and Matter, Indiana University, 2401 N Milo B. Sampson Lane, Bloomington, IN 47408 (United States); Liao, Jinfeng [Physics Department and Center for Exploration of Energy and Matter, Indiana University, 2401 N Milo B. Sampson Lane, Bloomington, IN 47408 (United States); RIKEN BNL Research Center, Bldg. 510A, Brookhaven National Laboratory, Upton, NY 11973 (United States)

    2013-01-29

    The heavy-ion collisions can produce extremely strong transient magnetic and electric fields. We study the azimuthal fluctuation of these fields and their correlations with the also fluctuating matter geometry (characterized by the participant plane harmonics) using event-by-event simulations. A sizable suppression of the angular correlations between the magnetic field and the 2nd and 4th harmonic participant planes is found in very central and very peripheral collisions, while the magnitudes of these correlations peak around impact parameter b{approx}8-10 fm for RHIC collisions. This can lead to notable impacts on a number of observables related to various magnetic field induced effects, and our finding suggests that the optimal event class for measuring them should be that corresponding to b{approx}8-10 fm.

  1. Electric field simulation and measurement of a pulse line ion accelerator

    Institute of Scientific and Technical Information of China (English)

    SHEN Xiao-Kang; ZHANG Zi-Min; CAO Shu-Chun; ZHAO Hong-Wei; WANG Bo; SHEN Xiao-Li; ZHAO Quan-Tang; LIU Ming; JING Yi

    2012-01-01

    An oil dielectric helical pulse line to demonstrate the principles of a Pulse Line Ion Accelerator (PL1A) 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.

  2. Ions confined in spherical dielectric cavities modeled by a splitting field-theory

    Energy Technology Data Exchange (ETDEWEB)

    Lue, Leo, E-mail: leo.lue@strath.ac.uk [Department of Chemical and Process Engineering, University of Strathclyde, James Weir Building, 75 Montrose Street, Glasgow G1 1XJ (United Kingdom); Linse, Per [Physical Chemistry, Department of Chemistry, Lund University, P.O. Box 124, S-221 00 Lund (Sweden)

    2015-04-14

    The properties of ions confined within spherical dielectric cavities are examined by a splitting field-theory and Monte Carlo simulations. Three types of cavities are considered: one possessing a uniform surface charge density, one with a uniform volume charge density, and one containing mobile ions. In all cases, mobile counterions are present within the dielectric sphere. The splitting theory is based on dividing the electrostatic interaction into long- and short-wavelength contributions and applying different approximations on the two contributions. The splitting theory works well for the case where the dielectric constant of the confining sphere is equal to or less than that of the medium external to the sphere. Nevertheless, by extending the theory with a virial expansion, the predictions are improved. However, when the dielectric constant of the confining sphere is greater than that of the medium outside the sphere, the splitting theory performs poorly, only qualitatively agreeing with the simulation data. In this case, the strong-coupling expansion does not seem to work well, and a modified mean-field theory where the counterions interact directly with only their own image charge gives improved predictions. The splitting theory works best for the system with a uniform surface charge density and worst for the system with a uniform volume charge density. Increasing the number of ions within the sphere, at a fixed radius, tends to increase the ion density near the surface of the sphere and leads to a depletion region in the sphere interior; however, varying the ion number does not lead to any qualitative changes in the performance of the splitting theory.

  3. The neon gas field ion source-a first characterization of neon nanomachining properties

    Energy Technology Data Exchange (ETDEWEB)

    Livengood, Richard H., E-mail: richard.h.livengood@intel.com [Intel Corporation, Intel Architecture Group, Santa Clara, CA (United States); Tan, Shida; Hallstein, Roy [Intel Corporation, Intel Architecture Group, Santa Clara, CA (United States); Notte, John; McVey, Shawn; Faridur Rahman, F.H.M. [Carl Zeiss SMT, Nano Technology Systems Division, Peabody, MA (United States)

    2011-07-21

    At the Charged Particle Optics Conference (CPO7) in 2006, a novel trimer based helium gas field ion source (GFIS) was introduced for use in a new helium ion microscope (HIM), demonstrating the novel source performance attributes and unique imaging applications of the HIM (Hill et al., 2008 ; Livengood et al., 2008). Since that time there have been numerous enhancements to the HIM source and platform demonstrating resolution scaling into the sub 0.5 nm regime (Scipioni et al., 2009 ; Pickard et al., 2010). At this Charged Particle Optics Conference (CPO8) we will be introducing a neon version of the trimer-GFIS co-developed by Carl Zeiss SMT and Intel Corporation. The neon source was developed as a possible supplement to the gallium liquid metal ion source (LMIS) used today in most focused ion beam (FIB) systems (Abramo et al., 1994 ; Young et al.,1998). The neon GFIS source has low energy spread ({approx}1 eV) and a small virtual source size (sub-nanometer), similar to that of the helium GFIS. However neon does differ from the helium GFIS in two significant ways: neon ions have high sputtering yields (e.g. 1 Si atom per incident ion at 20 keV); and have relatively shallow implant depth (e.g. 46 nm in silicon at 20 keV). Both of these are limiting factors for helium in many nanomachining applications. In this paper we will present both simulation and experimental results of the neon GFIS used for imaging and nanomachining applications.

  4. Experimental study of the dependence of beam current on injection magnetic field in 6.4 GHz ECR ion source

    Indian Academy of Sciences (India)

    G S Taki; P R Sarma; D K Chakraborty; R K Bhandari; P K Ray

    2006-09-01

    The ion current from an electron cyclotron resonance (ECR) heavy ion source depends on the confining axial and radial magnetic fields. Some efforts were made by earlier workers to investigate magnetic field scaling on the performance of the ECR source. In order to study the dependence of the ion current on the injection magnetic field in the 6.4 GHz ECR source, we have measured the current by varying the peak injection field and have inferred that the variation of the current is exponential up to our maximum design injection field of 7.5 kG. An attempt has been made to understand this exponential nature on the basis of ion confinement time.

  5. Critical Properties of Mixed Ising Spin System with Different Trimodal Transverse Fields in the Presence of Single-Ion Anisotropy

    Institute of Scientific and Technical Information of China (English)

    CHEN Qiang; YAN Shi-Lei

    2006-01-01

    Within the framework of an effective field approximation, the effects of single-ion anisotropy and different trimodal transverse fields of two sublattices on the critical properties of the mixed spin-1/2 and spin-1 Ising system are investigated on the simple cubic lattice. A smaller single-ion anisotropy can magnify magnetic ordering phases and a larger one can depress magnetic ordering phase for T-Ω1/2 space at low temperatures, while a smaller single-ion anisotropy can hardly change the value of critical transverse field for T-Ω1 space. On the other hand, influences of two different trimodal transverse fields concentrations on tricritical points and magnetic ordering phases take on some interesting results in T-D space. The main reason comes from the common action of single-ion anisotropy, different transverse fields and two trimodal distributions.

  6. Electric field gradients from first-principles and point-ion calculations

    Science.gov (United States)

    Stoll, E. P.; Meier, P. F.; Claxton, T. A.

    2002-02-01

    Point-ion models have been extensively used to determine ``hole numbers'' at copper and oxygen sites in high-temperature superconducting cuprate compounds from measured nuclear quadrupole frequencies. The present study assesses the reliability of point-ion models to predict electric field gradients accurately and also the implicit assumption that the values can be calculated from the ``holes'' and not the total electronic structure. First-principles cluster calculations using basis sets centered on the nuclei have enabled the determination of the charge- and spin-density distribution in the CuO2 plane. The contributions to the electric field gradients and the magnetic hyperfine couplings are analyzed in detail. In particular they are partitioned into regions in an attempt to find a correlation with the most commonly used point-ion model, the Sternheimer equation, which depends on the two parameters R and γ. Our most optimistic objective was to find expressions for these parameters, which would improve our understanding of them, but although estimates of the R parameter were encouraging, the method used to obtain the γ parameter indicated that the two parameters may not be independent. The problem seems to stem from the covalently bonded nature of the CuO2 planes in these structures which severely questions using the Sternheimer equation for such crystals, since its derivation is heavily reliant on the application of perturbation theory to predominantly ionic structures. Furthermore, it is shown that the complementary contributions of electrons and holes in an isolated ion cannot be applied to estimates of electric field gradients at copper and oxygen nuclei in cuprates.

  7. Effects of Slip Condition, Variable Viscosity and Inclined Magnetic Field on the Peristaltic Motion of a Non-Newtonian Fluid in an Inclined Asymmetric Channel

    Directory of Open Access Journals (Sweden)

    A. Afsar Khan

    2016-01-01

    Full Text Available The peristaltic motion of a third order fluid due to asymmetric waves propagating on the sidewalls of a inclined asymmetric channel is discussed. The key features of the problem includes longwavelength and low-Reynolds number assumptions. A mathematical analysis has been carried out to investigate the effect of slip condition, variable viscosity and magnetohydrodynamics (MHD. Followed by the nondimensionalization of the nonlinear governing equations along with the nonlinear boundary conditions, a perturbation analysis is made. For the validity of the approximate solution, a numerical solution is obtained using the iterative collocation technique.

  8. Field Observation of the Green Ocean Amazon. Neutral Cluster Air Ion Spectrometer (NAIS) Final Campaign Summary

    Energy Technology Data Exchange (ETDEWEB)

    Petaja, T. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Backman, J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Manninen, H. E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Wimmer, D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2016-03-01

    The neutral cluster and air ion spectrometer (NAIS) was deployed to the T3 site for Intensive Operations Periods 1 and 2 (IOP1 and IOP2). The NAIS is an instrument that measures aerosol particle and ion number size distributions in the mobility diameter range of 0.8 to 42 nm, corresponding to electrical mobility range between 3.2 and 0.0013 cm2 V-1 s-1. New particle formation (NPF) events were detected using the NAIS at the T3 field site during IOP1 and IOP2. Secondary NPF is a globally important source of aerosol number. To fully explain atmospheric NPF and subsequent growth, we need to directly measure the initial steps of the formation processes in different environments, including rain forest. Particle formation characteristics, such as formation and growth rates, were used as indicators of the relevant processes and participating compounds in the initial formation. In a case of parallel ion and neutral cluster measurements, we estimated the relative contribution of ion-induced and neutral nucleation to the total particle formation.

  9. An Angular Overlap Model for Cu(II) Ion in the AMOEBA Polarizable Force Field.

    Science.gov (United States)

    Xiang, Jin Yu; Ponder, Jay W

    2014-01-01

    An extensible polarizable force field for transition metal ion was developed based on AMOEBA and the angular overlap model (AOM) with consistent treatment of electrostatics for all atoms. Parameters were obtained by fitting molecular mechanics (MM) energies to various ab initio gas-phase calculations. The results of parameterization were presented for copper (II) ion ligated to water and model fragments of amino acid residues involved in the copper binding sites of type 1 copper proteins. Molecular dynamics (MD) simulations were performed on aqueous copper (II) ion at various temperatures, as well as plastocyanin (1AG6) and azurin (1DYZ). Results demonstrated that the AMOEBA-AOM significantly improves the accuracy of classical MM in a number of test cases when compared to ab initio calculations. The Jahn-Teller distortion for hexa-aqua copper (II) complex was handled automatically without specifically designating axial and in-plane ligands. Analyses of MD trajectories resulted in a 6-coordination first solvation shell for aqueous copper (II) ion and a 1.8ns average residence time of water molecules. The ensemble average geometries of 1AG6 and 1DYZ copper binding sites were in general agreement with X-ray and previous computational studies.

  10. The Study of State-Selected Ion-Molecule Reactions using the Vacuum Ultraviolet Pulsed Field Ionization-Photoion Technique

    Science.gov (United States)

    2006-01-01

    challenges of improving the kinetic energy resolu- Very recently, high-level time-dependent quantum mechani - tion in ion-molecule collisional experiments...2006) Copyright 2006 American Institute of Physics 14. ABSTRACT This paper presents the methodology to generate beams of ions in single quantum states...in single quantum states for bimolecular ion-molecule reaction dynamics studies using pulsed field ionization (PFI) of atoms or molecules in high-n

  11. Hydration free energies of cyanide and hydroxide ions from molecular dynamics simulations with accurate force fields

    Science.gov (United States)

    Lee, M.W.; Meuwly, M.

    2013-01-01

    The evaluation of hydration free energies is a sensitive test to assess force fields used in atomistic simulations. We showed recently that the vibrational relaxation times, 1D- and 2D-infrared spectroscopies for CN(-) in water can be quantitatively described from molecular dynamics (MD) simulations with multipolar force fields and slightly enlarged van der Waals radii for the C- and N-atoms. To validate such an approach, the present work investigates the solvation free energy of cyanide in water using MD simulations with accurate multipolar electrostatics. It is found that larger van der Waals radii are indeed necessary to obtain results close to the experimental values when a multipolar force field is used. For CN(-), the van der Waals ranges refined in our previous work yield hydration free energy between -72.0 and -77.2 kcal mol(-1), which is in excellent agreement with the experimental data. In addition to the cyanide ion, we also study the hydroxide ion to show that the method used here is readily applicable to similar systems. Hydration free energies are found to sensitively depend on the intermolecular interactions, while bonded interactions are less important, as expected. We also investigate in the present work the possibility of applying the multipolar force field in scoring trajectories generated using computationally inexpensive methods, which should be useful in broader parametrization studies with reduced computational resources, as scoring is much faster than the generation of the trajectories.

  12. Experiments with low energy ion beam transport into toroidal magnetic fields

    CERN Document Server

    Joshi, N; Meusel, O; Ratzinger, U

    2016-01-01

    The stellarator-type storage ring for accumulation of multi- Ampere proton and ion beams with energies in the range of $100~AkeV$ to $1~AMeV$ is designed at Frankfurt university. The main idea for beam confinement with high transversal momentum acceptance was presented in EPAC2006. This ring is typically suited for experiments in plasma physics and nuclear astrophysics. The accumulator ring with a closed longitudinal magnetic field is foreseen with a strength up to $6-8~T$. The experiments with two room temperature 30 degree toroids are needed. The beam transport experiments in toroidal magnetic fields were first described in EPAC2008 within the framework of a proposed low energy ion storage ring. The test setup aims on developing a ring injection system with two beam lines representing the main beam line and the injection line. The primary beam line for the experiments was installed and successfully commissioned in 2009. A special diagnostics probe for \\textit{"in situ"} ion beam detection was installed.This...

  13. Kinetic energies of charged fragments resulting from multifragmentation and asymmetric fission of the C{sub 60} molecule in collisions with monocharged ions (2-130 keV)

    Energy Technology Data Exchange (ETDEWEB)

    Rentenier, A; Bordenave-Montesquieu, D; Moretto-Capelle, P; Bordenave-Montesquieu, A [Laboratoire CAR-IRSAMC, UMR 5589 CNRS - Universite Paul Sabatier, 118 Route de Narbonne, 31062 Toulouse Cedex (France)

    2003-04-28

    Multifragmentation and asymmetric fission (AF) of the C{sub 60} molecule induced by H{sup +}, H{sub 2}{sup +}, H{sub 3}{sup +} and He{sup +} ions at medium collision energies (2-130 keV) are considered. Momenta and kinetic energies of C{sub n}{sup +} fragment ions (n = 1- 12) are deduced from an analysis of time-of-flight spectra. In multifragmentation processes, momenta are found to be approximately constant when n > 2, a behaviour which explains that the most probable kinetic energy, as well as the width of the kinetic energy distributions, is found to be inversely proportional to the fragment size n; both momenta and kinetic energies are independent of the velocity and nature of the projectile, and hence of the energy deposit. A specific study of the AF shows that the kinetic energies of C{sub 2}{sup +}, C{sub 4}{sup +} and C{sub 6}{sup +} fragments are also independent of the collision velocity and projectile species; a quantitative agreement is found with values deduced from kinetic energy release measurements by another group in electron impact experiments, and the observed decrease when the mass of the light fragment increases is also reproduced. A quantitative comparison of AF and multifragmentation for the n = 2, 4 and 6 fragment ions shows that kinetic energies in AF exceed that in multifragmentation, a result which explains the oscillations observed when momenta or kinetic energies of fragments are plotted against the n-value. The AF yield is also found to scale with the energy deposit in the collision velocity range extending below the velocity at the maximum of the electronic stopping power; except for protons, it remains negligible with respect to multifragmentation as soon as the total energy deposit exceeds about 100 eV.

  14. Particle Yields in Heavy Ion Collisions and the Influence of Strong Magnetic Fields

    Directory of Open Access Journals (Sweden)

    M. G. de Paoli

    2014-01-01

    Full Text Available It is expected that the magnetic fields in heavy ion collisions are very high. In this work, we investigate the effects of a strong magnetic field on particle ratios within a thermal model of particle production. We model matter as a free gas of baryons and mesons under the influence of an external magnetic field varying from zero to 30mπ2 through an  χ2 fitting to some data sets of the STAR experiment. For this purpose, we use the Dirac, Rarita-Schwinger, Klein-Gordon, and Proca equations subject to magnetic fields in order to obtain the energy expressions and the degeneracy for spin 1/2, spin 3/2, spin 0, and spin 1 particles, respectively. Our results show that, if the magnetic field can be considered as slowly varying and leaves its signature on the particle yields, a field of the order of 6mπ2 produces an improved fitting to the experimental data as compared to the calculations without magnetic field.

  15. Particle Production in Strong Electromagnetic Fields in Relativistic Heavy-Ion Collisions

    Directory of Open Access Journals (Sweden)

    Kirill Tuchin

    2013-01-01

    Full Text Available I review the origin and properties of electromagnetic fields produced in heavy-ion collisions. The field strength immediately after a collision is proportional to the collision energy and reaches ~mπ2 at RHIC and ~10mπ2 at LHC. I demonstrate by explicit analytical calculation that after dropping by about one-two orders of magnitude during the first fm/c of plasma expansion, it freezes out and lasts for as long as quark-gluon plasma lives as a consequence of finite electrical conductivity of the plasma. Magnetic field breaks spherical symmetry in the direction perpendicular to the reaction plane, and therefore all kinetic coefficients are anisotropic. I examine viscosity of QGP and show that magnetic field induces azimuthal anisotropy on plasma flow even in spherically symmetric geometry. Very strong electromagnetic field has an important impact on particle production. I discuss the problem of energy loss and polarization of fast fermions due to synchrotron radiation, consider photon decay induced by magnetic field, elucidate J/ψ dissociation via Lorentz ionization mechanism, and examine electromagnetic radiation by plasma. I conclude that all processes in QGP are affected by strong electromagnetic field and call for experimental investigation.

  16. Influence of the Ion Source Operating Conditions on the Characteristics of a Prism Mass Spectrometer With Inhomogeneous Magnetic Field

    Directory of Open Access Journals (Sweden)

    P.O. Kuzema

    2010-01-01

    Full Text Available The influence of magnetic field focusing the electron beam in ion source of mass spectrometer on the analytical characteristics of the instrument has been studied. The range of current of ion source's focusing electromagnet providing the optimal performance of the mass spectrometer has been determined.

  17. A large Bradbury Nielsen ion gate with flexible wire spacing based on photo-etched stainless steel grids and its characterization applying symmetric and asymmetric potentials

    Science.gov (United States)

    Brunner, T.; Mueller, A. R.; O'Sullivan, K.; Simon, M. C.; Kossick, M.; Ettenauer, S.; Gallant, A. T.; Mané, E.; Bishop, D.; Good, M.; Gratta, G.; Dilling, J.

    2012-01-01

    Bradbury Nielsen gates are well known devices used to switch ion beams and are typically applied in mass or mobility spectrometers for separating beam constituents by their different flight or drift times. A Bradbury Nielsen gate consists of two interleaved sets of electrodes. If two voltages of the same amplitude but opposite polarity are applied the gate is closed, and for identical (zero) potential the gate is open. Whereas former realizations of the device employ actual wires resulting in difficulties with winding, fixing and tensioning them, our approach is to use two grids photo-etched from a metallic foil. This design allows for simplified construction of gates covering large beam sizes up to at least 900\\,mm$^2$ with variable wire spacing down to 250\\,\\textmu m. By changing the grids the wire spacing can be varied easily. A gate of this design was installed and systematically tested at TRIUMF's ion trap facility, TITAN, for use with radioactive beams to separate ions with different mass-to-charge ratios by their time-of-flight.

  18. Simulations of ion acceleration at non-relativistic shocks: ii) magnetic field amplification and particle diffusion

    CERN Document Server

    Caprioli, Damiano

    2014-01-01

    We use large hybrid (kinetic ions-fluid electrons) simulations to study ion acceleration and generation of magnetic turbulence due to the streaming of energetic particles that are self-consistently accelerated at non-relativistic shocks. When acceleration is efficient (at quasi-parallel shocks), we find that the magnetic field develops transverse components and is significantly amplified in the pre-shock medium. The total amplification factor is larger than 10 for shocks with Mach number $M=100$, and scales with the square root of $M$. We find that in the shock precursor the energy spectral density of excited magnetic turbulence is proportional to spectral energy distribution of accelerated particles at corresponding resonant momenta, in good agreement with the predictions of quasilinear theory of diffusive shock acceleration. We discuss the role of Bell's instability, which is predicted and found to grow faster than resonant instability in shocks with $M\\gtrsim 30$. Ahead of these strong shocks we distinguis...

  19. Photoelectron angular distributions from photodetachment of negative ions in strong laser fields

    Energy Technology Data Exchange (ETDEWEB)

    Bai Lihua; Liu Yuheng; Cui Tingting; Wang Yan; Zhang Huifang; Deng Dongmei [Department of Physics, Shanghai University, Shanghai 200444 (China); Ren Xianghe, E-mail: lhbai@163.com [Institute of Advance Energy, Kyoto University, Gokasho, Uji, Kyoto, 611-0011 (Japan)

    2011-02-01

    Using a nonperturbative scattering theory, the photoelectron angular distributions (PADs) of negative ions irradiated by intense laser fields are studied. Various PADs are obtained. Similar to that of atoms, PADs of negative ions show main lobes and jet-like structures. Here, the main lobe means the formation of the detached photoelectrons around the direction of laser polarization, while the jet-like structure means a peaked-out formation of photoelectrons emitted from the waist between the two main lobes. For a set of above-threshold-detachment peaks, with one-more-photon absorption, the number of the jet-like structures is not always increased by one, which verifies that the jet-like structures are irrelevant to photoelectron angular momentum.

  20. Fast electron generation by Coulomb scattering on spatially correlated ions in a strong laser field

    CERN Document Server

    Bauch, S

    2009-01-01

    Electrons colliding with spatially fixed ions in strong laser fields are investigated by solving the time-dependent Schr\\"odinger equation. Considering first simple one-dimensional model systems, the mechanisms and energy spectra of fast electrons are analyzed, starting from collisions on a single ion. By using these electrons as projectiles for a second and third collision, the maximum possible energy obtained can be significantly increased. We then generalize the analysis to 2D systems where additional angular degrees of freedom lead to a drastic loss of efficiency. This problem can be overcome by introducing external confinements, which allow to focus the electrons and increase the intensity of high-energy electrons.

  1. Stochastic ion heating by an electrostatic wave in a sheared magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Gell, Y.; Nakach, R.

    1980-08-01

    Effects of the shear of the magnetic field on the stochastic acceleration of ions due to an electrostatic wave with a frequency in the lower-hybrid range are considered. An appropriate Hamiltonian formalism is used to analyze the equations of motion numerically and theoretically. The surface of section method is used to visualize the solutions and to compare these with the theoretical predictions. From this analysis it appears that there exists an upper adiabatic barrier for the stochastic region which seems to be responsible for the formation of a hot tail in the ion velocity distribution. In addition to lowering the threshold for the onset of stochasticity, the effect of shear is to shift the tail structure to lower values of the velocities. Consequently, these results might help to improve the efficiency of heating by external radiation in the lower-hybrid frequency range.

  2. Behavior of leaching and precipitation of weathering crust ion-absorbed type by magnetic field

    Institute of Scientific and Technical Information of China (English)

    QIU Tingsheng; FANG Xihui; CUI Lifeng; FANG Yanxi

    2008-01-01

    With weathering crust Ion-Absorbed Type Rare Earth (IATRE) ores in southern Jiangxi as an example, rare earth percolation leaching and leaching solution precipitation process research were carried out under conditions of magnetic field. The effect on the rare earth leaching process such as magnetic field strength, magnetization time, magnetization manner, and other factors were discussed. The effect on the mother rare earth liquor sedimentation rate, purity, and crystallization behavior such as magnetic field strength, magnetization time, and magnetization manner were investigated. Leaching and precipitation mechanism of magnetization on IATRE were analyzed. The results showed that the magnetic treatment can improve leaching rate of weathering crust IATRE and the sedimentation rate, and reduce consumption of reagents.

  3. Influence of Chiral Mean Field on Kaon In-plane Flow in Heavy Ion Collisions

    Institute of Scientific and Technical Information of China (English)

    ZHENG Yu-Ming; FUCHS Christian; FAESSLER Amand; SHEKHTER Kirril; SRISAWAD Pornrad; KOBDAJ Chinorat; YAN Yu-Peng

    2004-01-01

    The influence of the chiral mean field on the K+ in-plane flow in heavy ion collisions at SIS energy is investigated within covariant kaon dynamics. For the kaon mesons inside the nuclear medium a quasi-particle picture including scalar and vector fields is adopted and compared to the standard treatment with a static potential. It is confirmed that a Lorentz force from spatial component of the vector field provides an important contribution to the inmedium kaon dynamics and strongly counterbalances the influence of the vector potential on the K+ in-plane flow. The calculated results show that the new FOPI data can be reasonably described using the Brown & Rho parametrization,which partly takes into account the correction of higher order contributions in the chiral expansion. This indicates that one can abstract the information on the kaon potential in a nuclear medium from the analysis of the K+ in-plane flow.

  4. Electromagnetic fields with electric and chiral magnetic conductivities in heavy ion collisions

    Science.gov (United States)

    Li, Hui; Sheng, Xin-li; Wang, Qun

    2016-10-01

    We derive an analytic formula for electric and magnetic fields produced by a moving charged particle in a conducting medium with the electric conductivity σ and the chiral magnetic conductivity σχ. We use the Green's function method and assume that σχ is much smaller than σ . The compact algebraic expressions for electric and magnetic fields without any integrals are obtained. They recover the Lienard-Wiechert formula at vanishing conductivities. Exact numerical solutions are also found for any values of σ and σχ and are compared with analytic results. Both numerical and analytic results agree very well for the scale of high-energy heavy ion collisions. The spacetime profiles of electromagnetic fields in noncentral Au+Au collisions have been calculated based on these analytic formula as well as exact numerical solutions.

  5. Electromagnetic fields with electric and chiral magnetic conductivities in heavy ion collisions

    CERN Document Server

    Li, Hui; Wang, Qun

    2016-01-01

    We derive analytic formula for electric and magnetic fields produced by a moving charged particle in a conducting medium with the electric conductivity \\sigma and the chiral magnetic conductivity \\sigma_{\\chi}. We use the Green function method and assume that \\sigma_{\\chi} is much smaller than \\sigma. The compact algebraic expressions for electric and magnetic fields without any integrals are obtained. They recover the Lienard-Wiechert formula at vanishing conductivities. Exact numerical solutions are also found for any values of \\sigma and \\sigma_{\\chi} and are compared to analytic results. Both numerical and analytic results agree very well for the scale of high energy heavy ion collisions. The space-time profiles of electromagnetic fields in non-central Au+Au collisions have been calculated based on these analytic formula as well as exact numerical solutions.

  6. Influence of tail-like magnetic field on O+ ion distribution in the Martian magnetosphere

    Institute of Scientific and Technical Information of China (English)

    SHI; Jiankui

    2001-01-01

    [1]Gallagher, J. J., Simpson, J. A., Search for trapped electrons and a magnetic moment at Mars by Mariner IV, Science, 1965, 149: 1233—1239.[2]Russell, C. T., The magnetic field of Mars: Mars 3 evidence reexamined, Geophys. Res. Lett., 1978, 5: 81—86.[3]Riedler, W., Schwingenschun, K., Lichtenegger, H. et al., Interaction of solar wind with the planet Mars: Phobos 2 magnetic field observations, Planet. Space Sci., 1991, 39: 75—81.[4]Gringauz, K. I., What was known about the Martian magnetosphere before Phobos-2 mission, Planet. Space Sci., 1991, 39: 73—74.[5]Acuna, M. H., Connerney, J. E. P., Wasilewski, P. et al., Magnetic field and plasma observations at Mars: Initial results of the Mars global surveyor mission, Science, 1998, 279: 1676—1680.[6]Mohlmann, D., Riedler. W., Rustenbuch, J. et al., The question of an internal Martian magnetic field, Planet. Space Sci., 1991, 39: 83—88.[7]Shi, J. K., Liu, Z. X., Zhang, T. L., A theoretical study on the O+ ions of the Martian magnetosphere, Chin Astron Astrophys., 1999, 23: 377—383.[8]Rosenbauer, H., Shutte, N., Apathy, I. et al., Ions of Martian origin and plasma sheet in the Martian magnetotail: Initial results of TAUS experiment, Nature, 1989, 341: 612—614.[9]Lundin, R., Zakharov, A., Pelinen, R. et al., ASPERA/Phobos measurements of the ion outflow from the Martian ionosphere, Geophy. Res. Lett., 1990, 17: 873—876.[10]Verigin, M. I., Shutte, N. M., Galeev, A. A. et al., Ions of planetary origin in the Martian magnetosphere (Phobos 2 / TAUS experiment), Planet. Space Sci., 1991, 39: 131—137.[11]Lundin, R., Zakharov, A., Pelinen, R. et al., First measurements of the ionospheric plasma escape from Mars, Nature, 1989, 341: 609—612.[12]Lammer, H., Bauer, S. J., Nonthermal atmospheric escape from Mars and Titan, J. Geophys. Res., 1991, 96: 1819—1826.[13]Haider, S. A., O+ escape in the polar ion exosphere of Mars, Adv. Space Res., 1995, 16: 49

  7. Asymmetrical flow field-flow fractionation coupled to inductively coupled plasma mass spectrometry for sizing SeNPs for packaging applications

    Science.gov (United States)

    Palomo-Siguero, María; Vera, Paula; Echegoyen, Yolanda; Nerin, Cristina; Cámara, Carmen; Madrid, Yolanda

    2017-06-01

    This paper describes the application of Asymmetrical Flow Field-Flow Fractionation (AF4) coupled to diode array detector (DAD) and inductively coupled plasma mass spectrometry (AF4-UV-ICP-MS) to characterize selenium nanoparticles (SeNPs) in an aqueous acrylic adhesive to be used in a multilayer food packaging material. SeNPs were synthesized using a solution-phase approach based on the reduction of selenite with ascorbic acid in presence of different stabilizers compatible with food industry such as polysaccharides (chitosan (poly(D-glucosamine) and hydroxyethylcellulose (HEC)) and non-ionic surfactants (Triton X-100 (t-octylphenoxypolyethoxyethanol), 2,4,7,9-tetramethyl 5decyne-4,7-diol ethoxylate, and isotridecanol ethoxylate). Several parameters such as pH, ascorbic acid and stabilizers concentration, and compatibility of the stabilizer with the adhesive were evaluated. SeNPs suspensions with spherical morphology were obtained except when isotridecanol ethoxylate was employed which provides SeNPs with a nanorod morphology. AF4-DAD-ICP-MS was further applied for sizing the different SeNPs preparations. DAD was used as detector for selecting the best AF4 separation conditions before coupling to ICP-MS to ensure unequivocal identification of NPs. AF4 calibration with polystyrene latex (PSL) beads of known sizes allowed size determination of the different SeNPs. The following estimated hydrodynamic sizes (expressed as the mean ± standard deviation, n = 6 replicates) were found: chitosan-SeNPs- (26 ± 3 nm), TritonX100-SeNPs (22 ± 10 nm) HEC- SeNPs (91 ± 8 nm) and 2,4,7,9-tetramethyl 5decyne-4,7-diol ethoxylate- SeNPs (59 ± 4 nm). The proposed methodology was successfully applied to the characterization in terms of size of aqueous acrylic adhesives containing SeNPs Results from AF4-ICP-MS and TEM shown that only those SeNPs obtained with non-ionic surfactants and HEC were compatible with the adhesive. The results reported here evidence the usefulness of AF4-ICP

  8. Quantum Theory of Radical-Ion-Pair Recombination: A New Physical Paradigm for Low-Magnetic-Field Effects

    OpenAIRE

    Kominis, I. K.

    2008-01-01

    A new paradigm emerging in the description of magnetic-sensitive radical-ion-pair recombination reactions is presented. This paradigm is founded on the realization that the recombination process of radical-ion pairs is a continuous quantum measurement. In the regime of low magnetic fields we describe the appearance of purely quantum phenomena, that fade away as the magnetic field increases. We will analyze the magnetic sensitivity of these reactions under this perspective and bridge the new f...

  9. Comment on "Ion distribution function in a plasma with uniform electric field" [Phys. Plasmas 19, 113703 (2012)].

    Science.gov (United States)

    Mustafaev, Alex; Sukhomlinov, Vladimir; Timofeev, Nikolay

    2016-08-01

    The comparison between experimental data of ion distribution function at the parent gas plasma obtained by the authors and results of calculations presented by Lampe et al. are considered. It is shown that the experimental and calculated angular distributions of ions in the case at least of argon differ considerably. The analysis of Lampe et al. assumptions showed that the main reasons of these discrepancies were the assumptions of ion distribution function independence on field orientation and independence of charge exchange cross-section on the relative velocity of ion and atom.

  10. In vitro evaluation of flexible pH and potassium ion-sensitive organic field effect transistor sensors

    Science.gov (United States)

    Ji, Taeksoo; Rai, Pratyush; Jung, Soyoun; Varadan, Vijay K.

    2008-06-01

    Acute myocardial ischemia is a state of trauma of the heart muscle caused by occlusion of oxygenated blood supply. It is accompanied by an increase in potassium and hydrogen ion concentrations in the heart muscles. A flexible substrate based ion-sensitive field effect transistor (ISFET) has been designed to measure the concentration of potassium and hydrogen ions with high specificity. Double exponential smoothing technique was used to calculate background noise and explain the dependence of drain current on reference voltage and ion concentration in saturation mode of the ISFET.

  11. Zero-field splitting of 4T2 term for 3d3 ions in tetragonal symmetry

    Indian Academy of Sciences (India)

    Qun Wei; Qi-Ming Xu

    2009-04-01

    By taking into account slight interactions, i.e. spin-spin, spin-other-orbit and orbit-orbit interactions, in addition to spin-orbit interaction, the zero-field splitting of 4T2 state for 3d3 ions at tetragonal symmetry has been studied. The convergence of the approximation perturbation formula of 4T2 state for 3d3 ions at tetragonal symmetry has been investigated, and the contributions to zero-field splitting arising from magnetic interaction and tetragonal crystal field are discussed. It is found that there exists combined mechanism between magnetic interactions and tetragonal crystal field.

  12. Interaction of charged amino-acid side chains with ions: an optimization strategy for classical force fields.

    Science.gov (United States)

    Kahlen, Jens; Salimi, Leila; Sulpizi, Marialore; Peter, Christine; Donadio, Davide

    2014-04-10

    Many well-established classical biomolecular force fields, fitted on the solvation properties of single ions, do not necessarily describe all the details of ion pairing accurately, especially for complex polyatomic ions. Depending on the target application, it might not be sufficient to reproduce the thermodynamics of ion pairing, but it may also be necessary to correctly capture structural details, such as the coordination mode. In this work, we analyzed how classical force fields can be optimized to yield a realistic description of these different aspects of ion pairing. Given the prominent role of the interactions of negatively charged amino-acid side chains and divalent cations in many biomolecular systems, we chose calcium acetate as a benchmark system to devise a general optimization strategy that we applied to two popular force fields, namely, GROMOS and OPLS-AA. Using experimental association constants and first-principles molecular dynamics simulations as a reference, we found that small modifications of the van der Waals ion-ion interaction parameters allow a systematic improvement of the essential thermodynamic and structural properties of ion pairing.

  13. On-chip asymmetric microcavity optomechanics.

    Science.gov (United States)

    Soltani, Soheil; Hudnut, Alexa W; Armani, Andrea M

    2016-12-26

    High quality factor (Q) optical resonators have enabled rapid growth in the field of cavity-enhanced, radiation pressure-induced optomechanics. However, because research has focused on axisymmetric devices, the observed regenerative excited mechanical modes are similar. In the present work, a strategy for fabricating high-Q whispering gallery mode microcavities with varying degrees of asymmetry is developed and demonstrated. Due to the combination of high optical Q and asymmetric device design, two previously unobserved modes, the asymmetric cantilever and asymmetric crown mode, are demonstrated with sub-mW thresholds for onset of oscillations. The experimental results are in good agreement with computational modeling predictions.

  14. Asymmetric information and macroeconomic dynamics

    Science.gov (United States)

    Hawkins, Raymond J.; Aoki, Masanao; Roy Frieden, B.

    2010-09-01

    We show how macroeconomic dynamics can be derived from asymmetric information. As an illustration of the utility of this approach we derive the equilibrium density, non-equilibrium densities and the equation of motion for the response to a demand shock for productivity in a simple economy. Novel consequences of this approach include a natural incorporation of time dependence into macroeconomics and a common information-theoretic basis for economics and other fields seeking to link micro-dynamics and macro-observables.

  15. First-principles calculation of crystal field parameters of Dy ions substituted for Nd in Nd-Fe-B magnets

    Energy Technology Data Exchange (ETDEWEB)

    Tanaka, S; Moriya, H; Tsuchiura, H; Sakuma, A [Department of Applied Physics, Tohoku University, Sendai 980-8579 (Japan); Divis, M [Department of Condensed Matter, Charles University, FMF, Prague (Czech Republic); Novak, P, E-mail: tanaka@olive.apph.tohoku.ac.jp [Institute of Physics of ASCR, Cukrovarnicka 10, 162 53 Prague 6 (Czech Republic)

    2011-01-01

    We study the electronic structures of crystalline Nd{sub 2}Fe{sub 14}B, Dy{sub 2}Fe{sub 14}B and Dy-doped Nd-Fe-B, and estimate the crystal field parameter A{sup 0}{sub 2}(r{sup 2}) of the rare earth ions of these systems based on the first principles calculations. We find that the crystal field of the Dy ions is appreciably insensitive to its crystallographic location than that of Nd ions.

  16. Shocklets, SLAMS, and field-aligned ion beams in the terrestrial foreshock

    CERN Document Server

    Wilson, L B; 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). We show that the SLAMS are acting like a local quasi-perpendicular shock reflecting ions to produce the FABs. Previous FAB observations reported the source as the quasi-perpendicular bow shock. The SLAMS exhibit a foot-like magnetic enhancement with a leading magnetosonic whistler train, consistent with previous observations. The FABs are found to have T_b ~ 80-850 eV, V_b/V_sw ~ 1-2, T_{b,perp}/T{b,para} ~ 1-10, and n_b/n_i ~ 0.2-14%. Strong ion and electron heating are observed within the series of shocklets and SLAMS increasing by factors \\geq 5 and \\geq 3, respectively. Both the core and halo electron components show strong perpendicular heating inside the feature.

  17. Drift-kink instability induced by beam ions in field-reversed configurations

    Energy Technology Data Exchange (ETDEWEB)

    Nishimura, Kazumi; Horiuchi, Ritoku; Sato, Tetsuya [National Inst. for Fusion Science, Toki, Gifu (Japan)

    1999-04-01

    The drift-kink instability in field-reversed configurations with a beam component is investigated by means of a three-dimensional particle simulation. The unstable mode with the toroidal mode number n=4 grows with the rate {gamma} {approx} 0.1 - 1.0{omega}{sub ci} for a strong beam current and deforms the plasma profile along the beam orbit in the vicinity of the field-null line. This mode is nonlinearly saturated as a result of the relaxation of current profile. Both the saturation level and the growth rate tend to increase as the ratio of the beam current to the plasma current I{sub b}/I{sub p} increases. It is also found that there is a threshold value of the beam velocity {upsilon}{sub b} {approx} {upsilon}{sub Ti} (ion thermal velocity) for the excitation of the instability. (author)

  18. Effects of external magnetic field on oblique propagation of ion acoustic cnoidal wave in nonextensive plasma

    Science.gov (United States)

    Farhad Kiyaei, Forough; Dorranian, Davoud

    2017-01-01

    Effects of the obliqueness and the strength of external magnetic field on the ion acoustic (IA) cnoidal wave in a nonextensive plasma are investigated. The reductive perturbation method is employed to derive the corresponding KdV equation for the IA wave. Sagdeev potential is extracted, and the condition of generation of IA waves in the form of cnoidal waves or solitons is discussed in detail. In this work, the domain of allowable values of nonextensivity parameter q for generation of the IA cnoidal wave in the plasma medium is considered. The results show that only the compressive IA wave may generate and propagate in the plasma medium. Increasing the strength of external magnetic field will increase the frequency of the wave and decrease its amplitude, while increasing the angle of propagation will decrease the frequency of the wave and increase its amplitude.

  19. Correlated electron-ion collisions in a strong laser field; Korrelierte Elektron-Ion-Stoesse in starken Laserfeldern

    Energy Technology Data Exchange (ETDEWEB)

    Ristow, T.

    2007-12-17

    Electron-ion-collisions in plasmas in the presence of an ultra-short intensive laser pulse can cause high energy transfers to the electrons. During the collision the oscillation energy of the electron in the laser field is changed into drift energy. In this regime, multi-photon processes, known from the ionization of neutral atoms (Above-Threshold Ionization), and successive, so called correlated collisions, are important. The subject of the thesis is a study of binary Coulomb collisions in strong laser fields. The collisions are treated both in the context of classical Newtonian mechanics and in the quantum-mechanical framework by the Schroedinger equation. In the classical case a simplified instantaneous collision model and a complete dynamical treatment are discussed. Collisions can be treated instantaneously, if the ratio of the impact parameter to the quiver amplitude is small. The energy distributions calculated in this approximation show an elastic peak and a broad plateau due to rescattered electrons. At incident velocities smaller than the quiver velocity, correlated collisions are observed in the electron trajectories of the dynamical model. This effect leads to characteristic momentum distributions of the electrons, that are explicitly calculated and compared with the results of the instantaneous model. In addition, the time-dependence of the collisions is discussed in the framework of a singular perturbation theory. The complete description of the Coulomb scattering requires a quantum-mechanical description. A time-dependent method of wave-packet scattering is used and the corresponding time-dependent three-dimensional Schroedinger equation is solved by an implicit ADImethod on a spatial grid. The momentum and the energy distributions of the scattered electrons are calculated by the Fourier transformation of the wavefunction. A comparison of the scattering from a repulsive and an attractive potential is used to distinguish between simple collisions and

  20. Sensing small neurotransmitter-enzyme interaction with nanoporous gated ion-sensitive field effect transistors.

    Science.gov (United States)

    Kisner, Alexandre; Stockmann, Regina; Jansen, Michael; Yegin, Ugur; Offenhäusser, Andreas; Kubota, Lauro Tatsuo; Mourzina, Yulia

    2012-01-15

    Ion-sensitive field effect transistors with gates having a high density of nanopores were fabricated and employed to sense the neurotransmitter dopamine with high selectivity and detectability at micromolar range. The nanoporous structure of the gates was produced by applying a relatively simple anodizing process, which yielded a porous alumina layer with pores exhibiting a mean diameter ranging from 20 to 35 nm. Gate-source voltages of the transistors demonstrated a pH-dependence that was linear over a wide range and could be understood as changes in surface charges during protonation and deprotonation. The large surface area provided by the pores allowed the physical immobilization of tyrosinase, which is an enzyme that oxidizes dopamine, on the gates of the transistors, and thus, changes the acid-base behavior on their surfaces. Concentration-dependent dopamine interacting with immobilized tyrosinase showed a linear dependence into a physiological range of interest for dopamine concentration in the changes of gate-source voltages. In comparison with previous approaches, a response time relatively fast for detecting dopamine was obtained. Additionally, selectivity assays for other neurotransmitters that are abundantly found in the brain were examined. These results demonstrate that the nanoporous structure of ion-sensitive field effect transistors can easily be used to immobilize specific enzyme that can readily and selectively detect small neurotransmitter molecule based on its acid-base interaction with the receptor. Therefore, it could serve as a technology platform for molecular studies of neurotransmitter-enzyme binding and drugs screening.

  1. Floquet calculation of harmonic generation from hydrogen molecular ions in strong monochromatic laser fields

    CERN Document Server

    Tsogbayar, Ts

    2014-01-01

    We present Floquet calculations of high harmonic generation (HHG) for the lowest two electronic states of the $\\mbox{H}_2^+$ ion by strong continuous-wave laser fields. We solve the non-Hermitian matrix problem to get accurate solutions to the periodic time-dependent Schr\\"odinger equation (TDSE) by applying a pseudospectral representation combined with a complex absorbing potential method. This represents an alternative approach to direct TDSE solutions to obtain the harmonic spectra for the ion. We compare our HHG rates for the lower and upper states of $\\mbox{H}^{+}_{2}$, which correspond to the gerade and ungerade ground states in the field-free case, with previously obtained results in the literature. We show that the enhancement of the ionization rates at the critical internuclear separation $R_{c}\\approx 8\\,au$ plays some role in the appearance of very strong harmonic orders $n=5-11$ at $\\lambda = 1064\\,nm$ and $n=5-9$ at $\\lambda = 800\\,nm$ and intensity $I=10^{14}\\,W/cm^{2}$.

  2. In-house validation of a method for determination of silver nanoparticles in chicken meat based on asymmetric flow field-flow fractionation and inductively coupled plasma mass spectrometric detection

    DEFF Research Database (Denmark)

    Löschner, Katrin; Navratilova, Jana; Grombe, Ringo

    2015-01-01

    spectrometric detection (AF4-ICP-MS) was applied for quantitative analysis of silver nanoparticles (AgNPs) in a chicken meat matrix following enzymatic sample preparation. For the first time an analytical validation of nanoparticle detection in a food matrix by AF4-ICP-MS has been carried out and the results......Nanomaterials are increasingly used in food production and packaging, and validated methods for detection of nanoparticles (NPs) in foodstuffs need to be developed both for regulatory purposes and product development. Asymmetric flow field-flow fractionation with inductively coupled plasma mass...

  3. Accurate Size and Size-Distribution Determination of Polystyrene Latex Nanoparticles in Aqueous Medium Using Dynamic Light Scattering and Asymmetrical Flow Field Flow Fractionation with Multi-Angle Light Scattering

    Directory of Open Access Journals (Sweden)

    Shinichi Kinugasa

    2012-01-01

    Full Text Available Accurate determination of the intensity-average diameter of polystyrene latex (PS-latex by dynamic light scattering (DLS was carried out through extrapolation of both the concentration of PS-latex and the observed scattering angle. Intensity-average diameter and size distribution were reliably determined by asymmetric flow field flow fractionation (AFFFF using multi-angle light scattering (MALS with consideration of band broadening in AFFFF separation. The intensity-average diameter determined by DLS and AFFFF-MALS agreed well within the estimated uncertainties, although the size distribution of PS-latex determined by DLS was less reliable in comparison with that determined by AFFFF-MALS.

  4. First steps towards a generic sample preparation scheme for inorganic engineered nanoparticles in a complex matrix for detection, characterization, and quantification by asymmetric flow-field flow fractionation coupled to multi-angle light scattering and ICP-MS

    DEFF Research Database (Denmark)

    Wagner, Stephan; Legros, Samuel; Löschner, Katrin

    2015-01-01

    The applicability of a multi-step generic procedure to systematically develop sample preparation methods for the detection, characterization, and quantification of inorganic engineered nanoparticles (ENPs) in a complex matrix was successfully demonstrated. The research focused on the optimization...... content by asymmetric flow-field flow fractionation coupled to a multi-angle light scattering detector and an inductively coupled plasma mass spectrometer. Following the proposed generic procedure SiO2-ENPs were separated from a tomato soup. Two potential sample preparation methods were tested these being...

  5. Plasma sheet stretching accompanied by field aligned energetic ion fluxes observed by the MUADU instrument aboard TC-2

    Institute of Scientific and Technical Information of China (English)

    Lu Li; S.MCKENNA-LAWLOR; S.BARABASH; LIU ZhenXing; CAO JinBin; J.BALAZ; K.KUDELA; T.L.ZHANG; C.M.CARR

    2007-01-01

    The NUADU(NeUtral Atom Detector Unit)instrument aboard TC-2 recorded 4π solid angle images of charged particles(E>180 keV)spiraling around the magnetic field lines in the near-Earth plasma sheet (at~-7 RE,equatorial dawn-to-night side)during a geomagnetic storm(Dst=-219 nT)on August 24,2005.Energetic ion beam events characterized by symmetrical,ring-like,solid angle distributions around ambient magnetic field lines were observed during a 34-minute traversal of the plasma sheet by the TC-2 spacecraft.Also,observations during these multiple crossings of the plasma sheet were monitored by the magnetometer experiment(FGM)aboard the same spacecraft.During each crossing,a whistler-mode chorus enhancement was observed in the anisotropic area by the TC-2 low frequency electromagnetic wave detector(LFEW/TC-2)at a frequency just above that of the local lower hybrid wave.A comparison of the ion pitch angle distribution(PAD)map with the ambient magnetic field shows that an enhancement in the field aligned energetic ion flux was accompanied by tailward stretching of the magnetic field lines in the plasma sheet.In contrast,the perpendicular ion-flux enhancement was accompanied by a signature indicating the corresponding shrinkage of the magnetic field lines in the plasma sheet.Since both parallel ion-flux and perpendicular ion-flux enhancements occurred intermittently,the data were interpreted to imply a dynamical,oscillatory process of the magnetic field line(stretching and shrinking)in the near-Earth plasma sheet,which might have acted to help establish an interaction region in this area which would support continuous aurora-substorm triggering during the ongoing magnetic storm.The whistler-mode chorus may have been produced due to ion gyro-resonance during particle pitch angle diffusion after the plasma sheet compression.

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

    Science.gov (United States)

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

    2014-10-07

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

  7. Asymmetric GaAs n-type double δ-doped quantum wells as a source of intersubband-related nonlinear optical response: Effects of an applied electric field

    Energy Technology Data Exchange (ETDEWEB)

    Rodríguez-Magdaleno, K.A.; Martínez-Orozco, J.C.; Rodríguez-Vargas, I. [Unidad Académica de Física, Universidad Autónoma de Zacatecas, Calz. Solidaridad Esq. Paseo a La Bufa S/N. C.P. 98060 Zacatecas (Mexico); Mora-Ramos, M.E. [Facultad de Ciencias, Universidad Autónoma del Estado de Morelos, Av. Universidad 1001, CP 62209 Cuernavaca, Morelos (Mexico); Física Teórica y Aplicada, Escuela de Ingeniería de Antioquia, AA 7516 Medellín (Colombia); Grupo de Materia Condensada-UdeA, Instituto de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia UdeA, Calle 70 No. 52-21, Medellín (Colombia); Duque, C.A., E-mail: cduque@fisica.udea.edu.co [Grupo de Materia Condensada-UdeA, Instituto de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia UdeA, Calle 70 No. 52-21, Medellín (Colombia)

    2014-03-15

    In this work, the conduction band electron states and the associated intersubband-related linear and nonlinear optical absorption coefficient and relative refractive index change are calculated for an asymmetric double n-type δ-doped quantum well in a GaAs-matrix. The effects of an external applied static electric field are included. Values of the two-dimensional impurities density (N{sub 2d}) of each single δ-doped quantum well are taken to vary within the range of 1.0×10{sup 12} to 7.0×10{sup 12} cm{sup −2}, consistent with the experimental data growth regime. The optical responses are reported as a function of the δ-doped impurities density and the applied electric field. It is shown that single electron states and the related optical quantities are significantly affected by the structural asymmetry of the double δ-doped quantum well system. In addition, a brief comparison with the free-carrier-related optical response is presented. -- Highlights: • Nonlinear optics in asymmetric double n-type δ-doped quantum well in a GaAs-matrix. • The system is considered under external applied electric field in growth direction. • The 2D impurity density is consistent with the experimental data growth regime. • The optical quantities are significantly affected by the structural asymmetry of the system.

  8. Effects of an induced electric field on \\pi^{-}/\\pi^{+} ratio in heavy-ion collisions

    CERN Document Server

    Wei, Gao-Feng; Cao, Xin-Wei; Zhang, Yun-Liang

    2016-01-01

    Using an isospin- and momentum-dependent transport model, we examine the effects of an electric field induced by a variable magnetic field on the \\pi^{-}/\\pi^{+} ratio in central to peripheral heavy-ion collisions at beam energies of 400 and 1500MeV/nucleon. It is shown that while the induced electric field does not affect the total multiplicities of both $\\pi^{-}$ and $\\pi^{+}$ mesons at both the lower beam energy of 400MeV/nucleon and the higher beam energy of 1500MeV/nucleon, it reduces (enhances) the emission of $\\pi^{-}$ ($\\pi^{+}$) mesons in midrapidity, but enhances (reduces) the emission of $\\pi^{-}$ ($\\pi^{+}$) mesons in forward and backward rapidities especially for the more peripheral collisions at the lower beam energy because of the rapidly transient variable magnetic field at more peripheral collisions and longer reaction duration time at the lower beam energy. These findings indicate that the total \\pi^{-}/\\pi^{+} ratio is still a precisely reliable probe of symmetry energy at both the lower an...

  9. Photon and dilepton spectra from nonlinear QED effects in supercritical magnetic fields induced by heavy-ion collisions

    CERN Document Server

    Hattori, Koichi

    2015-01-01

    We discuss properties of photons in extremely strong magnetic fields induced by the relativistic heavy-ion collisions. We investigate the vacuum birefringence, the real-photon decay, and the photon splitting which are all forbidden in the ordinary vacuum, but become possible in strong magnetic fields. These effects potentially give rise to anisotropies in photon and dilepton spectra.

  10. Beyond the Nernst-limit with dual-gate ZnO ion-sensitive field-effect transistors

    NARCIS (Netherlands)

    Spijkman, M.; Smits, E.C.P.; Cillessen, J.F.M.; Biscarini, F.; Blom, P.W.M.; Leeuw, D.M. de

    2011-01-01

    The sensitivity of conventional ion-sensitive field-effect transistors (ISFETs) is limited to 59 mV/pH, which is the maximum detectable change in electrochemical potential according to the Nernst equation. Here we demonstrate a transducer based on a ZnO dual-gate field-effect transistor that breache

  11. 2D profile of poloidal magnetic field diagnosed by a laser-driven ion-beam trace probe (LITP)

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Xiaoyi; Xiao, Chijie, E-mail: cjxiao@pku.edu.cn; Chen, Yihang; Xu, Tianchao; Lin, Chen [State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing 100871 (China); Wang, Long [Institute of Physics, Chinese Academy of Sciences, P.O. Box 603, Beijing 100190 (China); Xu, Min [Center for Fusion Science of Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041 (China); Yu, Yi [School of Nuclear Science and Technology, University of Science and Technology of China, Hefei 230026 (China)

    2016-11-15

    Based on large energy spread of laser-driven ion beam (LIB), a new method, the Laser-driven Ion-beam Trace Probe (LITP), was suggested recently to diagnose the poloidal magnetic field (B{sub p}) and radial electric field (E{sub r}) in toroidal devices. Based on another property of LIB, a wide angular distribution, here we suggested that LITP could be extended to get 2D B{sub p} profile or 1D profile of both poloidal and radial magnetic fields at the same time. In this paper, we show the basic principle, some preliminary simulation results, and experimental preparation to test the basic principle of LITP.

  12. Research of the Effects of Electron Focused Electric Field upon an Enhanced Glow Discharge Plasma Ion Implantation

    Institute of Scientific and Technical Information of China (English)

    LI Liu-he; WU Yong-qin; ZHANG Yan-hua; CAI Xun; CHU Paul K

    2004-01-01

    A new Enhanced Glow Discharge Plasma Ion Implantation methods are introduced, in which the plasma are produced by the self glow discharge excitated by high negative voltage bias. The electric field is designed to a electron focusing mode by using a small area hollow anode and a large area sample holder cathode. The pattern of equipotentials of the electric field are calculated through finite-element method. By using the special electron-focusing field, the self glow discharge are enhanced and provide denser ions to implanted into the substrate.

  13. 2D profile of poloidal magnetic field diagnosed by a laser-driven ion-beam trace probe (LITP)

    Science.gov (United States)

    Yang, Xiaoyi; Xiao, Chijie; Chen, Yihang; Xu, Tianchao; Lin, Chen; Wang, Long; Xu, Min; Yu, Yi

    2016-11-01

    Based on large energy spread of laser-driven ion beam (LIB), a new method, the Laser-driven Ion-beam Trace Probe (LITP), was suggested recently to diagnose the poloidal magnetic field (Bp) and radial electric field (Er) in toroidal devices. Based on another property of LIB, a wide angular distribution, here we suggested that LITP could be extended to get 2D Bp profile or 1D profile of both poloidal and radial magnetic fields at the same time. In this paper, we show the basic principle, some preliminary simulation results, and experimental preparation to test the basic principle of LITP.

  14. Time-resolved ion energy distribution measurements using an advanced neutral particle analyzer on the MST reversed-field pinch.

    Science.gov (United States)

    Eilerman, S; Anderson, J K; Reusch, J A; Liu, D; Fiksel, G; Polosatkin, S; Belykh, V

    2012-10-01

    An advanced neutral particle analyzer (ANPA) capable of simultaneously measuring hydrogen and deuterium ions of energies up to 45 keV has recently been developed for use on the Madison Symmetric Torus. The charge-to-mass separation allows for separate analysis of bulk deuterium ions and hydrogen ions injected with a 1 MW, 25 keV neutral beam. Orientation of the ANPA allows sampling of different regions of ion velocity space; a radial viewport favors collection of ions with high v(perpendicular)∕|v| while a recently installed tangential viewport favors ions with high v(||)∕|v|, such as those from the core-localized fast ion population created by the neutral beam. Signals are observed in the ANPA's highest energy channels during periodic magnetic reconnection events, which are drivers of anisotropic, non-Maxwellian ion energization in the reversed-field pinch. ANPA signal strength is dependent on the background neutral density, which also increases during magnetic reconnection events, so careful analysis must be performed to identify the true change in the ion distribution. A Monte Carlo neutral particle tracing code (NENE) is used to reconstruct neutral density profiles based on D(α) line emission, which is measured using a 16-chord filtered photodiode array.

  15. Electric field and ion density anomalies in the mid latitude ionosphere: Possible connection with earthquakes?

    Science.gov (United States)

    Gousheva, M. N.; Glavcheva, R. P.; Danov, D. L.; Hristov, P. L.; Kirov, B. B.; Georgieva, K. Y.

    2008-07-01

    The problem of earthquake prediction has stimulated the search for a correlation between seismic activity and ionospherical anomalies. We found observational evidence of possible earthquake effects in the near-equatorial and low latitude ionosphere; these ionospheric anomalies have been proposed by Gousheva et al. [Gousheva, M., Glavcheva, R., Danov, D., Angelov P., Hristov, P., Influence of earthquakes on the electric field disturbances in the ionosphere on board of the Intercosmos-Bulgaria-1300 satellite. Compt. Rend. Acad. Bulg. Sci. 58 (8) 911-916, 2005a; Gousheva, M., Glavcheva, R., Danov, D., Angelov, P., Hristov, P., Kirov, B., Georgieva, K., Observation from the Intercosmos-Bulgaria-1300 satellite of anomalies associated with seismic activity. In: Poster Proceeding of 2nd International Conference on Recent Advances in Space Technologies: Space in the Service of Society, RAST '2005, June 9-11, Istanbul, Turkey, pp. 119-123, 2005b; Gousheva, M., Glavcheva, R., Danov, D., Angelov, P., Hristov, P., Kirov, B., Georgieva, K., Satellite monitoring of anomalous effects in the ionosphere probably related to strong earthquakes. Adv. Space Res. 37 (4), 660-665, 2006]. This paper presents new results from observations of the quasi-static electric field and ion density on board INTERCOSMOS-BULGARIA-1300 satellite in the mid latitude ionosphere above sources of moderate earthquakes. Data from INTERCOSMOS-BULGARIA-1300 satellite and seismic data (World Data Center, Denver, Colorado, USA) for magnetically quiet and medium quiet days are juxtaposed in time-space domain. For satellite's orbits in the time period 15.09-01.10.1981 an increase in the horizontal and vertical components of the quasi-static electric field and fluctuations of the ion density are observed over zones of forthcoming seismic events. Some similar post effects are observed too. The emphasis of this paper is put on the anomalies which specify the mid latitude ionosphere. The obtained results contain

  16. Terahertz metamaterial with asymmetric transmission

    CERN Document Server

    Singh, R; Menzel, C; Rockstuhl, C; Azad, A K; Cheville, R A; Lederer, F; Zhang, W; Zheludev, N I

    2009-01-01

    We show for the first time that a planar metamaterial, an array of coupled metal split-ring resonators with a unit cell lacking mirror symmetry, exhibits asymmetric transmission of terahertz radiation propagating through it in opposite directions. This intriguing effect, that is compatible with Lorentz reciprocity and time-reversal, depends on a directional difference in conversion efficiency of the incident circularly polarized wave into one of opposite handedness, that is only possible in lossy low-symmetry planar chiral metamaterials. We show that asymmetric transmission is linked to excitation of enantiomerically sensitive plasmons, these are induced charge-field excitations that depend on the mutual handedness of incident wave and metamaterial pattern. Various bands of positive, negative and zero phase and group velocities have been identified indicating the opportunity to develop polarization sensitive negative index and slow light media based on such metamaterials.

  17. On the dynamics of Cu ions injection into low-k nanoporous materials under oscillating applied fields

    Science.gov (United States)

    Borja, Juan; Plawsky, Joel. L.; Lu, T.-M.; Gill, William N.

    2013-01-01

    Cu injection into low-k dielectrics was studied using oscillating bipolar field experiments coupled with a mass transport model. Cu/SiCOH/Si structures were stressed using an oscillating square bipolar applied field at 200 °C. Breakdown was defined experimentally as the time it takes for the leakage current to exceed 1 × 10-5 A under given stress conditions. Time to failure was found to depend on field oscillating frequency and amplitude of the applied field. It was determined that ion solubility primarily affects the magnitude of lifetime enhancement, while mobility affects its onset in the frequency domain. Overtime, the local field generated by the accumulation of Cu ions during bias temperature stress resists the action of the oscillating field thus inhibiting the ability to sweep ions from cathode to anode through reversal of the applied field and thereby limits the observed lifetime enhancement. Predictions from the model match trends for experimental data involving transport of Cu ions into SiCOH.

  18. Kinetic signatures of the region surrounding the X line in asymmetric (magnetopause) reconnection

    Science.gov (United States)

    Shay, M. A.; Phan, T. D.; Haggerty, C. C.; Fujimoto, M.; Drake, J. F.; Malakit, K.; Cassak, P. A.; Swisdak, M.

    2016-05-01

    Kinetic particle-in-cell simulations are used to identify signatures of the electron diffusion region (EDR) and its surroundings during asymmetric magnetic reconnection. A "shoulder" in the sunward pointing normal electric field (EN > 0) at the reconnection magnetic field reversal is a good indicator of the EDR and is caused by magnetosheath electron meandering orbits in the vicinity of the X line. Earthward of the X line, electrons accelerated by EN form strong currents and crescent-shaped distribution functions in the plane perpendicular to B. Just downstream of the X line, parallel electric fields create field-aligned crescent electron distribution functions. In the immediate upstream magnetosheath, magnetic field strength, plasma density, and perpendicular electron temperatures are lower than the asymptotic state. In the magnetosphere inflow region, magnetosheath ions intrude resulting in an Earthward pointing electric field and parallel heating of magnetospheric particles. Many of the above properties persist with a guide field of at least unity.

  19. CMISTARK: Python package for the Stark-effect calculation and symmetry classification of linear, symmetric and asymmetric top wavefunctions in dc electric fields

    CERN Document Server

    Chang, Yuan-Pin; Sartakov, Boris; Küpper, Jochen

    2013-01-01

    The Controlled Molecule Imaging group (CMI) at the Center for Free Electron Laser Science (CFEL) has developed the CMIstark software to calculate, view, and analyze the energy levels of adiabatic Stark energy curves of linear, symmetric top and asymmetric top molecules. The program exploits the symmetry of the Hamiltonian to generate fully labeled adiabatic Stark energy curves. CMIstark is written in Python and easily extendable, while the core numer- ical calculations make use of machine optimized BLAS and LAPACK routines. Calculated energies are stored in HDF5 files for convenient access and programs to extract ASCII data or to generate graphical plots are provided.

  20. Hydration of the cyanide ion: an ab initio quantum mechanical charge field molecular dynamics study.

    Science.gov (United States)

    Moin, Syed Tarique; Hofer, Thomas S

    2014-12-21

    This paper presents an ab initio quantum mechanical charge field molecular dynamics simulation study of the cyanide anion (CN(-)) in aqueous solution where hydrogen bond formation plays a dominant role in the hydration process. Preferential orientation of water hydrogens compared to oxygen atoms was quantified in terms of radial, angular as well as coordination number distributions. All structural results indicate that the water hydrogens are attracted towards CN(-) atoms, thus contributing to the formation of the hydration layer. Moreover, a clear picture of the local arrangement of water molecules around the ellipsoidal CN(-) ion is provided via angular-radial distribution and spatial distribution functions. Apart from the structural analysis, the evaluation of water dynamics in terms of ligand mean residence times and H-bond correlation functions indicates the weak structure making capacity of the CN(-) ion. The similar values of H-bond lifetimes obtained for the NHwat and CHwat bonds indicate an isokinetic behaviour of these H-bonds, since there is a very small difference in the magnitude of the lifetimes. On the other hand, the H-bond lifetimes between water molecules of the hydration shell, and between solute and solvent evidence the slightly stable hydration of the CN(-). Overall, the H-bonding dominates in the hydration process of the cyanide anion enabling it to become soluble in the aqueous environment associated to chemical and biological processes.

  1. Atom probe field ion microscope study of the range and diffusivity of helium in tungsten

    Energy Technology Data Exchange (ETDEWEB)

    Wagner, A.

    1978-08-01

    A time-of-flight (TOF) atom-probe field-ion microscope (FIM) specifically designed for the study of defects in metals is described. With this automated system 600 TOF min/sup -1/ can be recorded and analyzed. Performance tests of the instrument demonstrated that (1) the seven isotopes of molybdenum and the five isotopes of tungsten can be clearly resolved; and (2) the concentration and spatial distribution of all constitutents present at levels greater than 0.05 at. % in a W--25 at. % Re, Mo--1.0 at. % Ti, Mo--1.0 at. % Ti--0.08 at. % Zr (TZM), a low swelling stainless steel (LS1A) and a metallic glass (Metglas 2826) can be measured. The effect of the rate of field evaporation on the quantitative atom probe analysis of a Mo--1.0 at. % Ti alloy and a Mo--1.0 at. % Ti--0.08 at. % Zr alloy was investigated. As the field evaporation rate increased the measured Ti concentration was found to also increase. A simple qualitative model was proposed to explain the observation. The spatial distribution of titanium in a fast neutron irradiated Mo--1.0 at. % Ti alloy has been investigated. No evidence of Ti segregation to the voids was detected nor has any evidence of significant resolution of Ti from the TiC precipitates been detected. A small amount of segregation of carbon to a void was detected.

  2. Vibrational analysis of ferrocyanide complex ion based on density functional force field

    Energy Technology Data Exchange (ETDEWEB)

    Park, Sun Kyung; Lee, Choong Keun; Lee, Nam Soo [Chungbuk National Univ., Cheongju (Korea, Republic of); Lee, Sang Ho [The University of Michigan, Ann Arbor (United States)

    2002-02-01

    Vibrational properties of ferrocyanide complex ion, [Fe(CN){sub 6}]{sup 4-}, have been studied based on the force constants obtained from the density functional calculations at B3LYP/6-31G level by means of the normal mode analysis using new bond angle and linear angle internal coordinates recently developed. Vibrations of ferrocyanide were manipulated by twenty-three symmetry force constants. The angled bending deformations of C-Fe-C, the linear bending deformations of Fe-C{identical_to}N and the stretching vibrations of Fe-C have been quantitatively assigned to the calculated frequencies. The force constants in the internal coordinates employed in the modified Urey-Bradley type potential were evaluated on the density functional force field applied, and better interaction force constants in the internal coordinates have been proposed. The valence force constants in the general quadratic valence force field were also given. The stretch-stretch interaction and stretch-bending interaction constants are not sensitive to the geometrical displacement in the valence force field.

  3. Design of electric-field assisted surface plasmon resonance system for the detection of heavy metal ions in water

    Directory of Open Access Journals (Sweden)

    Htet Htet Kyaw

    2015-10-01

    Full Text Available Surface Plasmon Resonance (SPR sensors are widely used in diverse applications. For detecting heavy metal ions in water, surface functionalization of the metal surface is typically used to adsorb target molecules, where the ionic concentration is detected via a resonance shift (resonance angle, resonance wavelength or intensity. This paper studies the potential of a possible alternative approach that could eliminate the need of using surface functionalization by the application of an external electric field in the flow channel. The exerted electrical force on the ions pushes them against the surface for enhanced adsorption; hence it is referred to as “Electric-Field assisted SPR system”. High system sensitivity is achieved by monitoring the time dynamics of the signal shift. The ion deposition dynamics are discussed using a derived theoretical model based on ion mobility in water. On the application of an appropriate force, the target ions stack onto the sensor surface depending on the ionic concentration of target solution, ion mass, and flow rate. In the experimental part, a broad detection range of target cadmium ions (Cd2+ in water from several parts per million (ppm down to a few parts per billion (ppb can be detected.

  4. Design of electric-field assisted surface plasmon resonance system for the detection of heavy metal ions in water

    Energy Technology Data Exchange (ETDEWEB)

    Kyaw, Htet Htet [Department of Physics, College of Science, Sultan Qaboos University, P. O. Box 36, Al-Khoud 123 (Oman); Boonruang, Sakoolkan, E-mail: sakoolkan.boonruang@nectec.or.th, E-mail: waleed.m@bu.ac.th [Photonics Technology Laboratory, National Electronics and Computer Technology Center (NECTEC), 112 Thailand Science Park, PathumThani 12120 (Thailand); Mohammed, Waleed S., E-mail: sakoolkan.boonruang@nectec.or.th, E-mail: waleed.m@bu.ac.th [Center of Research in Optoelectronics, Communication and Control Systems (BUCROCCS), School of Engineering, Bangkok University, PathumThani 12120 (Thailand); Dutta, Joydeep [Functional Materials Division, School of Information and Communication Technology, KTH Royal Institute of Technology, Isafjordsgatan 22, SE-164 40 Kista, Stockholm (Sweden)

    2015-10-15

    Surface Plasmon Resonance (SPR) sensors are widely used in diverse applications. For detecting heavy metal ions in water, surface functionalization of the metal surface is typically used to adsorb target molecules, where the ionic concentration is detected via a resonance shift (resonance angle, resonance wavelength or intensity). This paper studies the potential of a possible alternative approach that could eliminate the need of using surface functionalization by the application of an external electric field in the flow channel. The exerted electrical force on the ions pushes them against the surface for enhanced adsorption; hence it is referred to as “Electric-Field assisted SPR system”. High system sensitivity is achieved by monitoring the time dynamics of the signal shift. The ion deposition dynamics are discussed using a derived theoretical model based on ion mobility in water. On the application of an appropriate force, the target ions stack onto the sensor surface depending on the ionic concentration of target solution, ion mass, and flow rate. In the experimental part, a broad detection range of target cadmium ions (Cd{sup 2+}) in water from several parts per million (ppm) down to a few parts per billion (ppb) can be detected.

  5. Ion shell distributions as free energy source for plasma waves on auroral field lines mapping to plasma sheet boundary layer

    Directory of Open Access Journals (Sweden)

    A. Olsson

    2004-06-01

    Full Text Available Ion shell distributions are hollow spherical shells in velocity space that can be formed by many processes and occur in several regions of geospace. They are interesting because they have free energy that can, in principle, be transmitted to ions and electrons. Recently, a technique has been developed to estimate the original free energy available in shell distributions from in-situ data, where some of the energy has already been lost (or consumed. We report a systematic survey of three years of data from the Polar satellite. We present an estimate of the free energy available from ion shell distributions on auroral field lines sampled by the Polar satellite below 6 RE geocentric radius. At these altitudes the type of ion shells that we are especially interested in is most common on auroral field lines close to the polar cap (i.e. field lines mapping to the plasma sheet boundary layer, PSBL. Our analysis shows that ion shell distributions that have lost some of their free energy are commonly found not only in the PSBL, but also on auroral field lines mapping to the boundary plasma sheet (BPS, especially in the evening sector auroral field lines. We suggest that the PSBL ion shell distributions are formed during the so-called Velocity Dispersed Ion Signatures (VDIS events. Furthermore, we find that the partly consumed shells often occur in association with enhanced wave activity and middle-energy electron anisotropies. The maximum downward ion energy flux associated with a shell distribution is often 10mWm-2 and sometimes exceeds 40mWm-2 when mapped to the ionosphere and thus may be enough to power many auroral processes. Earlier simulation studies have shown that ion shell distributions can excite ion Bernstein waves which, in turn, energise electrons in the parallel direction. It is possible that ion shell distributions are the link between the X-line and the auroral wave activity and electron

  6. RBSPICE measurement of ion loss during the 2015 March storm: Adiabatic response to the geomagnetic field change

    Science.gov (United States)

    Soto-Chavez, A. R.; Lanzerotti, L. J.; Gerrard, A.; Kim, H.; Bortnik, J.; Manweiler, J. W.

    2016-10-01

    A strongly energy-dependent ring current ion loss was measured by the Radiation Belt Storm Probes Ion Composition Experiment (RBSPICE) instrument on the Van Allen Probes A spacecraft in the local evening sector during the 17 March 2015 geomagnetic storm. The ion loss is found to be energy dependent where only ions with energies measured above ˜ 150 keV have a significant drop in intensity. At these energies the ion dynamics are principally controlled by variations of the geomagnetic field which, during magnetic storms, exhibits large-scale variations on time scales from minutes to hours. Here we show that starting from ˜19:10 UTC on 17 March the geomagnetic field increased from 220 to 260 nT on a time scale of about an hour as captured by RBSPICE-A close to spacecraft apogee, L = 6.1 and magnetic local time (MLT) = 21.85 h (GSM coordinates X =- 4.89, Y = 3.00, and Z =- 0.73). We demonstrate the relationship between this large geomagnetic field increase and the dropouts of the ≳ 150 keV ring current ions.

  7. Population Redistribution among Multiple Electronic States of Molecular Nitrogen Ions in Strong Laser Fields

    CERN Document Server

    Yao, Jinping; Chu, Wei; Zeng, Bin; Wu, Chengyin; Lu, Ruifeng; Li, Ziting; Xie, Hongqiang; Li, Guihua; Yu, Chao; Wang, Zhanshan; Jiang, Hongbing; Gong, Qihuang; Cheng, Ya

    2015-01-01

    We carry out a combined theoretical and experimental investigation on the population distributions in the ground and excited states of tunnel ionized N2 molecules at various driver wavelengths in the near- and mid-infrared range. Our results reveal that efficient couplings (i.e., population exchanges) between the ground state and the excited states occur in strong laser fields. The couplings result in the population inversion between the ground and the excited states at the wavelengths near 800 nm, which is verified by our experiment by observing the amplification of a seed at ~391 nm. The result provides insight into the mechanism of free-space nitrogen ion lasers generated in remote air with strong femtosecond laser pulses.

  8. Fluctuations of the initial color fields in high energy heavy ion collisions

    CERN Document Server

    Epelbaum, Thomas

    2013-01-01

    In the Color Glass Condensate approach to the description of high energy heavy ion collisions, one needs to superimpose small random Gaussian distributed fluctuations to the classical background field, in order to resum the leading secular terms that result from the Weibel instability, that would otherwise lead to pathological results beyond leading order. In practical numerical simulations, one needs to know this spectrum of fluctuations at a proper time $\\tau \\ll Q_s^{-1}$ shortly after the collision, in the Fock-Schwinger gauge $\\ma{A}^\\tau=0$. In this paper, we derive these fluctuations from first principles, by solving the Yang-Mills equations linearized around the classical background, with plane wave initial conditions in the remote past. We perform the intermediate steps in light-cone gauge, and we convert the results to the Fock-Schwinger gauge at the end. We obtain simple and explicit formulas for the fluctuation modes.

  9. Chiral electric field in relativistic heavy-ion collisions at energies available at the BNL Relativistic Heavy Ion Collider and at the CERN Large Hadron Collider

    Science.gov (United States)

    Zhong, Yang; Yang, Chun-Bin; Cai, Xu; Feng, Sheng-Qin

    2016-08-01

    It has been proposed that electric fields may lead to chiral separation in quark-gluon plasma (QGP). This is called the chiral electric separation effect. The strong electromagnetic field and the QCD vacuum can both be completely produced in off-central nuclear-nuclear collision. We use the Woods-Saxon nucleon distribution to calculate the electric field distributions of off-central collisions. The chiral electric field spatial distribution at Relativistic Heavy-Ion Collider (RHIC) and Large Hadron Collider (LHC) energy regions are systematically studied in this paper. The dependence of the electric field produced by the thermal quark in the central position with different impact parameters on the proper time with different collision energies in the RHIC and LHC energy regions are studied in this paper. Supported by National Natural Science Foundation of China (11375069, 11435054, 11075061, 11221504) and Key Laboratory Foundation of Quark and Lepton Physics (Hua-Zhong Normal University)(QLPL2014P01)

  10. Effect of a static magnetic fields and fluoride ions on the antioxidant defense system of mice fibroblasts.

    Science.gov (United States)

    Kurzeja, Ewa; Synowiec-Wojtarowicz, Agnieszka; Stec, Małgorzata; Glinka, Marek; Gawron, Stanisław; Pawłowska-Góral, Katarzyna

    2013-07-18

    The results of studies on the biological influence of magnetic fields are controversial and do not provide clear answers regarding their impact on cell functioning. Fluoride compounds are substances that influence free radical processes, which occur when the reactive forms of oxygen are present. It is not known whether static magnetic fields (SMF) cause any changes in fluoride assimilation or activity. Therefore, the aim of this work was to determine the potential relationship between magnetic field exposure to, and the antioxidant system of, fibroblasts cultured with fluoride ions. Three chambers with static magnetic fields of different intensities (0.4, 0.6, and 0.7 T) were used in this work. Fluoride ions were added at a concentration of 0.12 mM, which did not cause the precipitation of calcium or magnesium. The results of this study show that static magnetic fields reduce the oxidative stress caused by fluoride ions and normalize the activities of antioxidant enzymes, including superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT). Static magnetic fields modify the energy state of fibroblasts, causing an increase in the ATP concentration and a decrease in the MDA concentration. These results suggest that exposure to fluoride and an SMF improves the tolerance of cells to the oxidative stress induced by fluoride ions.

  11. Diffusive Transport Particle Simulations of Cold and Hot Ions Under Northward Interplanetary Magnetic Field

    Science.gov (United States)

    Mata, W.; Wang, C.; Lemon, C. L.; Lyons, L. R.

    2013-12-01

    The main difference seen in the plasma sheet between northward interplanetary magnetic field (NIMF) and southward interplanetary magnetic field (SIMF) intervals is that the plasma sheet is colder and denser during NIMF [e.g., Terasawa et al., 1997]. The basic processes responsible for these changes in the plasma sheet during NIMF and SIMF are not fully understood. The plasma sheet densities increase gradually following a northward turning of the IMF [Wing et al., 2005], and the density change is associated with a < ~1 keV cold population near the flanks. Observations also show a large variation in density across the tail with higher densities near the flanks than at midnight [e.g., Wing and Newell.,2002; Wang et al., 2006], which suggests that there are transport processes that allow the cold particles access to the midnight sector from the flanks. It has been proposed [e.g., Terasawa et al., 1997; Antonova, 2006] that diffusion may transport cold particles from the flanks deep into the plasma sheet. Diffusive particle transport results from fluctuations in the plasma sheet flow in the presence of a spatial gradient in the particle number. In this study we add electric and magnetic field perturbations to the background Tsyganenko 2001 (T01) magnetic field and Weimer 2000 electric potential with the superposition of different waves to determine whether diffusive transport can account for the gradual cooling and densification of the plasma sheet during NIMF. We follow the guiding center drift and full particle drift, where appropriate, of over 20,000 protons with arbitrary pitch angles and energies from 32 eV-30 keV in the simulation region from X = -10 to -50 and |Y| < 20 RE .We then obtain particle distributions by mapping the phase space densities to realistic source distributions based on THEMIS and Geotail observations and compute the resulting plasma moments. We investigate if diffusion can transport colder ions more efficiently than the hotter ions from the

  12. Generation of large-amplitude electric field and subsequent enhancement of O+ ion flux in the inner magnetosphere during substorms

    Science.gov (United States)

    Nakayama, Y.; Ebihara, Y.; Tanaka, T.

    2015-06-01

    Energetic O+ ions are rapidly enhanced in the inner magnetosphere because of abrupt intensification of the dawn-to-dusk electric field and significantly contribute to the ring current during substorms. Here we examine the generation mechanism of the dawn-to-dusk electric field that accelerates the O+ ions and the spatial and temporal evolution of the differential flux of the O+ ions by using a test particle simulation in the electric and magnetic fields that are provided by a global magnetohydrodynamics (MHD) simulation. In the MHD simulation, strong dawn-to-dusk electric field appears in the near-Earth tail region by a joint action of the earthward tension force and pileup of magnetic flux near an onset of substorm expansion. The peak of the electric field is ~9-13 mV/m and is located ~1-2 RE earthward of the peak of the plasma bulk speed because of the pileup. O+ ions coming from the lobe are accelerated from ~eV to >100 keV in ~10 min. The reconstructed flux of the O+ ions shows that at ~7 RE near midnight, the flux has a peak near a few tens of keV and the flux below ~10 keV is small. This structure, called a "void" structure, is consistent with the Polar observation and can be regarded as a manifestation of the acceleration of unmagnetized ions perpendicular to the magnetic field. In the inner magnetosphere (at 6.0 RE), reconstructed energy-time spectrograms show the nose dispersion structure that is also consistent with satellite observations.

  13. Thermodynamic Properties of Random Transverse Field Mixed Spin System in the Presence of Single-Ion Anisotropy

    Institute of Scientific and Technical Information of China (English)

    ZHANGYa-Nan; YANShi-Lei

    2003-01-01

    We study the thermodynamic properties of random transverse field mixed spin system in the presence of single-ion anisotropy on a square lattice. By making use of the effective field theory and a cutting approximation, the detailed phase diagrams are described and some interesting results are found under trimodal random transverse field distribution. A small single-ion anisotropy can magnify magnetic ordering region at low temperatures and existence of a large transverse field can assist the occurrence of reentrant phenomena. With increasing disorder, second-order phase transitions are shown to change into first-order phase transitions. The trajectory of the tricritical point in the phase space as a function of disorder is presented. These indicate a strong correlation with the corresponding to trimodal transverse field distribution.

  14. Kinetic signatures of the region surrounding the X-line in asymmetric (magnetopause) reconnection

    CERN Document Server

    Shay, M A; Haggerty, C C; Fujimoto, M; Drake, J F; Malakit, K; Cassak, P A; Swisdak, M

    2016-01-01

    Kinetic particle-in-cell simulations are used to identify signatures of the electron diffusion region (EDR) and its surroundings during asymmetric magnetic reconnection. A "shoulder" in the sunward pointing normal electric field (EN > 0) at the reconnection magnetic field reversal is a good indicator of the EDR, and is caused by magnetosheath electron meandering orbits in the vicinity of the x-line. Earthward of the X-line, electrons accelerated by EN form strong currents and crescent-shaped distribution functions in the plane perpendicular to B. Just downstream of the X-line, parallel electric fields create field-aligned crescent electron distribution functions. In the immediate upstream magnetosheath, magnetic field strength, plasma density, and perpendicular electron temperatures are lower than the asymptotic state. In the magnetosphere inflow region, magnetosheath ions intrude resulting in an Earthward pointing electric field and parallel heating of magnetospheric particles. Many of the above properties p...

  15. Accurate One-Centre Method for Hydrogen Molecule Ions in Strong Magnetic Field

    Institute of Scientific and Technical Information of China (English)

    ZHANG Yue-Xia; KANG Shuai; SHI Ting-Yun

    2008-01-01

    An accurate one-centre method for the hydrogen molecule ion is tested. The slow convergence and singularities at the nuclear positions that are problems in the general one-centre method are solved well by employing the optimal radial and angular B-spline basis. Therefore, the accuracy of the one-centre method is improved observably. For the ground state of the H+2 in the free field, 7×10-8 accuracy is obtained, which rivals the best one-centre calculation before. As a test, the nuclear distances and the total energies of the 1σg,u, 1πu, 1δg,u and 2σg states of the H+2 for the magnetic field strength B = 1a.u. are also obtained. Compared to other results, five-digit accuracy at least can be arrived even for the antibonding states 1σu and 1δu, whose equilibrium distances R is very large.

  16. Force field development for actinyl ions via quantum mechanical calculations: an approach to account for many body solvation effects.

    Science.gov (United States)

    Rai, Neeraj; Tiwari, Surya P; Maginn, Edward J

    2012-09-06

    Advances in computational algorithms and methodologies make it possible to use highly accurate quantum mechanical calculations to develop force fields (pair-wise additive intermolecular potentials) for condensed phase simulations. Despite these advances, this approach faces numerous hurdles for the case of actinyl ions, AcO2(n+) (high-oxidation-state actinide dioxo cations), mainly due to the complex electronic structure resulting from an interplay of s, p, d, and f valence orbitals. Traditional methods use a pair of molecules (“dimer”) to generate a potential energy surface (PES) for force field parametrization based on the assumption that many body polarization effects are negligible. We show that this is a poor approximation for aqueous phase uranyl ions and present an alternative approach for the development of actinyl ion force fields that includes important many body solvation effects. Force fields are developed for the UO2(2+) ion with the SPC/Fw, TIP3P, TIP4P, and TIP5P water models and are validated by carrying out detailed molecular simulations on the uranyl aqua ion, one of the most characterized actinide systems. It is shown that the force fields faithfully reproduce available experimental structural data and hydration free energies. Failure to account for solvation effects when generating PES leads to overbinding between UO2(2+) and water, resulting in incorrect hydration free energies and coordination numbers. A detailed analysis of arrangement of water molecules in the first and second solvation shell of UO2(2+) is presented. The use of a simple functional form involving the sum of Lennard-Jones + Coulomb potentials makes the new force field compatible with a large number of available molecular simulation engines and common force fields.

  17. Ion acoustic instability of HPT particles, FAC density, anomalous resistivity and parallel electric field in the auroral region

    Indian Academy of Sciences (India)

    C S Jayasree; G Renuka; C Venugopal

    2003-12-01

    During the magnetic storm of 21st March 1990, the DE-1 spacecraft encountered the auroral region at high invariant latitude at altitudes ranging from a few thousand kilometers in the ionosphere to many earth radii in the magnetosphere. The magnetic field perturbations interpretable as field aligned current (FAC) layers and the electrostatic turbulence possibly due to electrostatic ion acoustic instability driven by these currents are shown. The critical drift velocity of Hot Plasma Torus (HPT) electrons and the growth rate of ion acoustic wave as a function of electron to ion temperature ratio (/) for low and high current densities and energy of HPT electrons are found out. The intense FAC destabilizes the ion acoustic wave and the resultant electrostatic turbulence creates an anomalous resistivity. The current driven resistivity produces parallel electric field and high power dissipation. The anomalous resistivity , potential differnece along the auroral field lines ∥, intensity of electric field turbulence ∥ and power produced per unit volume are computed. It is found that the change in westward magnetic perturbation increases ∥; ; ∥ ;∥ and . Hence HPT electrons are heated and accelerated due to power dissipation during magnetically active periods in the auroral region. Concerning, applications, such HPT electrons can be used in particle accelerators like electron ring accelerator, smokatron etc.

  18. SPP-associated dual left-handed bands and field enhancement in metal-dielectric-metal metamaterial perforated by asymmetric cross hole arrays.

    Science.gov (United States)

    Ding, P; Liang, E J; Hu, W Q; Zhou, Q; Zhang, L; Yuan, Y X; Xue, Q Z

    2009-02-16

    Dual-band left-handed transmissions in the near infrared frequencies through the metal-dielectric-metal metamaterial perforated with an array of asymmetric cross holes are demonstrated. It is shown that the left-handed bands originate from the SPP-associated magnetic response excited by different polarized light and their frequencies can be tuned by the arm's length or width of the cross-gaps. The structures are further optimized at 1.064 microm laser light excitation for elucidating the mechanism and possible application in surface enhanced Raman spectroscopy in sandwiched architectures. This study provides valuable information for the design of compact optical devices with dual left-handed bands in a single structure and may also pave the way toward stable and reproducible substrate design for surface enhanced Raman spectroscopy.

  19. Analysis techniques for diagnosing runaway ion distributions in the reversed field pinch

    Science.gov (United States)

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

    2016-11-01

    An advanced neutral particle analyzer (ANPA) on the Madison Symmetric Torus measures deuterium ions of energy ranges 8-45 keV with an energy resolution of 2-4 keV and time resolution of 10 μs. Three different experimental configurations measure distinct portions of the naturally occurring fast ion distributions: fast ions moving parallel, anti-parallel, or perpendicular to the plasma current. On a radial-facing port, fast ions moving perpendicular to the current have the necessary pitch to be measured by the ANPA. With the diagnostic positioned on a tangent line through the plasma core, a chord integration over fast ion density, background neutral density, and local appropriate pitch defines the measured sample. The plasma current can be reversed to measure anti-parallel fast ions in the same configuration. Comparisons of energy distributions for the three configurations show an anisotropic fast ion distribution favoring high pitch ions.

  20. 多回直流输电线路的离子流场计算%Ion Flow Field Calculation of Multi-circuit DC Transmission Lines

    Institute of Scientific and Technical Information of China (English)

    李伟; 张波; 何金良

    2008-01-01

    An upwind finite element (FE) based algorithm to calculate the ion flow field in the vicinity of multi-circuit DC transmission lines is described. The initial value estimation and boundary condition are optimized, so details of the transmission lines such as bundle conductors and ground wires can be taken into account in the simulation model. Comparison between measured and computed ground level total electrical field and ion current density shows satisfactory agreement. The ion flow field of a ±500 kV HVDC Project with bipolar lines on the same tower is simulated. The total electrical field and ion current density on ground level are compared among different line arrangements.

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

    Science.gov (United States)

    Pfeifer, Kent B; Rumpf, Arthur N

    2005-08-15

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

  2. Information entropy of a time-dependent three-level trapped ion interacting with a laser field

    Science.gov (United States)

    Abdel-Aty, Mahmoud

    2005-10-01

    Trapped and laser-cooled ions are increasingly used for a variety of modern high-precision experiments, frequency standard applications and quantum information processing. Therefore, in this communication we present a comprehensive analysis of the pattern of information entropy arising in the time evolution of an ion interacting with a laser field. A general analytic approach is proposed for a three-level trapped-ion system in the presence of the time-dependent couplings. By working out an exact analytic solution, we conclusively analyse the general properties of the von Neumann entropy and quantum information entropy. It is shown that the information entropy is affected strongly by the time-dependent coupling and exhibits long time periodic oscillations. This feature attributed to the fact that in the time-dependent region Rabi oscillation is time dependent. Using parameters corresponding to a specific three-level ionic system, a single beryllium ion in a RF-(Paul) trap, we obtain illustrative examples of some novel aspects of this system in the dynamical evolution. Our results establish an explicit relation between the exact information entropy and the entanglement between the multi-level ion and the laser field. We show that different nonclassical effects arise in the dynamics of the ionic population inversion, depending on the initial states of the vibrational motion/field and on the values of Lamb-Dicke parameter η.

  3. Non-modal theory of the kinetic ion temperature gradient driven instability of plasma shear flows across the magnetic field

    Science.gov (United States)

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

    2016-06-01

    The temporal evolution of the kinetic ion temperature gradient driven instability and of the related anomalous transport of the ion thermal energy of plasma shear flow across the magnetic field is investigated analytically. This instability develops in a steady plasma due to the inverse ion Landau damping and has the growth rate of the order of the frequency when the ion temperature is equal to or above the electron temperature. The investigation is performed employing the non-modal methodology of the shearing modes which are the waves that have a static spatial structure in the frame of the background flow. The solution of the governing linear integral equation for the perturbed potential displays that the instability experiences the non-modal temporal evolution in the shearing flow during which the unstable perturbation becomes very different from a canonical modal form. It transforms into the non-modal structure with vanishing frequency and growth rate with time. The obtained solution of the nonlinear integral equation, which accounts for the random scattering of the angle of the ion gyro-motion due to the interaction of ions with ensemble of shearing waves, reveals similar but accelerated process of the transformations of the perturbations into the zero frequency structures. It was obtained that in the shear flow the anomalous ion thermal conductivity decays with time. It is a strictly non-modal effect, which originates from the temporal evolution of the shearing modes turbulence.

  4. Focussed ion beam machined cantilever aperture probes for near-field optical imaging.

    Science.gov (United States)

    Jin, E X; Xu, X

    2008-03-01

    Near-field optical probe is the key element of a near-field scanning optical microscopy (NSOM) system. The key innovation in the first two NSOM experiments (Pohl et al., 1984; Lewis et al., 1984) is the fabrications of a sub-wavelength optical aperture at the apex of a sharply pointed transparent probe tip with a thin metal coating. This paper discusses the routine use of focussed ion beam (FIB) to micro-machine NSOM aperture probes from the commercial silicon nitride cantilevered atomic force microscopy probes. Two FIB micro-machining approaches are used to form a nanoaperture of controllable size and shape at the apex of the tip. The FIB side slicing produces a silicon nitride aperture on the flat-end tips with controllable sizes varying from 120 nm to 30 nm. The FIB head-on drilling creates holes on the aluminium-coated tips with sizes down to 50 nm. Nanoapertures in C and bow tie shapes can also be patterned using the FIB head-on milling method to possibly enhance the optical transmission. A transmission-collection NSOM system is constructed from a commercial atomic force microscopy to characterize the optical resolution of FIB-micro-machined aperture tips. The optical resolution of 78 nm is demonstrated by an aperture probe fabricated by FIB head-on drilling. Simultaneous topography imaging can also be realized using the same probe. By mapping the optical near-field from a bow-tie aperture, optical resolution as small as 59 nm is achieved by an aperture probe fabricated by the FIB side slicing method. Overall, high resolution and reliable optical imaging of routinely FIB-micro-machined aperture probes are demonstrated.

  5. Spontaneous baryogenesis from asymmetric inflaton

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, Fuminobu [Tohoku Univ., Sendai (Japan). Dept. of Physics; Tokyo Univ., Chiba (Japan). Kavli IPMU (WPI), UTIAS; Yamada, Masaki [Tokyo Univ., Chiba (Japan). Kavli IPMU (WPI), UTIAS; Tokyo Univ., Chiba (Japan). Inst. for Cosmic Ray Research; DESY Hamburg (Germany)

    2015-10-15

    We propose a variant scenario of spontaneous baryogenesis from asymmetric inflaton based on current-current interactions between the inflaton and matter fields with a non-zero B-L charge. When the inflaton starts to oscillate around the minimum after inflation, it may lead to excitation of a CP-odd component, which induces an effective chemical potential for the B-L number through the current-current interactions. We study concrete inflation models and show that the spontaneous baryogenesis scenario can be naturally implemented in the chaotic inflation in supergravity.

  6. Fully differential cross sections for ion-atom impact ionization in the presence of a laser field

    Energy Technology Data Exchange (ETDEWEB)

    Ciappina, M F [Max Planck Institute for the Physics of Complex Systems, Noethnitzer Str 38, D-01187, Dresden (Germany)

    2007-11-14

    We study fully differential cross sections (FDCS) for single ionization of helium by ion impact in the presence of a laser field. The field is assumed to have linear polarization, to be weak compared to the typical atomic field, and we use a frequency corresponding to a CO{sub 2} laser. We employ the continuum distorted wave-eikonal initial state (CDW-EIS) to describe our FDCS in the laser background. Analysing our numerical results we explore the dependence of the FDCS on the laser field properties as well as on the ionized electron parameters.

  7. Electrical conduction of ion tracks in tetrahedral amorphous carbon: temperature, field and doping dependence and comparison with matrix data

    Science.gov (United States)

    Krauser, J.; Gehrke, H.-G.; Hofsäss, H.; Amani, J.; Trautmann, C.; Weidinger, A.

    2015-12-01

    This paper gives an extended overview of the electrical properties of ion tracks in hydrogen-free tetrahedral amorphous carbon (ta-C) with a sp3 bond fraction of about 80%. The films were grown by mass selected ion beam deposition of 100 eV 12C+ ions. The ion tracks are generated by irradiation of ta-C films with uranium ions of 1 GeV kinetic energy. Along the ion path a conversion from diamond-like (sp3) carbon to graphite-like (sp2) carbon takes place. Topography and current measurements of individual ion tracks were performed by atomic force microscopy at ambient temperature. The temperature dependence of the electric conductivity was studied between 15 and 390 K by means of 0.28 mm2 large contact pads averaging over about 107 tracks. For each sample and at each temperature the conductivity as a function of the applied electrical field (non-ohmic behaviour) was measured separately and the data were extrapolated to field zero. In this way, the zero-field conductivity was determined independent from the field dependence. In spite of large differences in the absolute values, the temperature dependence of the zero-field conductivities is found to be very similar in shape for all samples. The conductivities follow a {T}-{1/4} law up to temperatures slightly below room temperature. At higher temperatures a transport mechanism based on over-barrier hopping dominates with an activation energy of about 220 meV for tracks and 260 meV for the ta-C matrix. The field dependence measurements show that the deviation of the I-V characteristics from ohmic behaviour decreases with increasing zero-field conductivity. We also tested Cu-doped ta-C samples and found that they conduct significantly better than pure ta-C. However, the doping also increases the zero-field conductivity resulting in a weaker contrast between the track and matrix. The data are interpreted within the so-called ‘barrier model’ where the electrons are assumed to move fairly freely in well-conducting sp2

  8. Surface-electrode trap with an integrated permanent magnet for generating a magnetic-field gradient at trapped ions

    Science.gov (United States)

    Kawai, Yuji; Shimizu, Kenji; Noguchi, Atsushi; Urabe, Shinji; Tanaka, Utako

    2017-01-01

    We report on a surface-electrode trap with SmCo magnets arranged in a quadrupole configuration underneath the trap electrode. Because the distance between the magnets and the trapped ions can be as little as several hundred micrometers, a large magnetic field is produced without any heat management. The magnetic-field gradient was measured using the Zeeman splitting of a single trapped 40Ca+ ion at several positions, and a field gradient of 36 T m-1 was obtained. Such a field gradient is useful for the generation of a state-dependent force, which is important for quantum simulation and/or quantum gate operation using radio-frequency or microwave radiation.

  9. Thermodynamic Properties of Random Transverse Field Mixed Spin System in the Presence of Single-Ion Anisotropy

    Institute of Scientific and Technical Information of China (English)

    ZHANG Ya-Nan; YAN Shi-Lei

    2003-01-01

    We study the thermodynamic properties of random transverse field mixed spin system in the presence ofsingle-ion anisotropy on a square lattice. By making use of the effective field theory and a cutting approximation, thedetailed phase diagrams are described and some interesting results are found under trimodal random transverse fielddistribution. A smallsingle-ion anisotropy can magnify magnetic ordering region at low temperatures and existence ofa large transverse field can assist the occurrence of reentrant phenomena. With increasing disorder, second-order phasetransitions are shown to change into first-order phase transitions. The trajectory of the tricritical point in the phasespace as a function of disorder is presented. These indicate a strong correlation with the corresponding to trimodaltransverse field distribution.

  10. Surface-electrode trap with an integrated permanent magnet for generating a magnetic-field gradient at trapped ions

    CERN Document Server

    Kawai, Yuji; Noguchi, Atsushi; Urabe, Shinji; Tanaka, Utako

    2016-01-01

    We report on a surface-electrode trap with SmCo magnets arranged in a quadrupole configuration underneath the trap electrode. Because the distance between the magnets and the trapped ions can be as little as several hundred micrometers, a large magnetic field is produced without any heat management. The magnetic-field gradient was measured using the Zeeman splitting of a single trapped $^{40}$Ca$^+$ ion at several positions, and a field gradient of 36 T/m was obtained. Such a field gradient is useful for the generation of a state-dependent force, which is important for quantum simulation and/or quantum gate operation using radio-frequency or microwave radiation.

  11. Crystal field effects on interionic distance in cubic MgO crystal doped with Fe{sup 2+} ions

    Energy Technology Data Exchange (ETDEWEB)

    Ivascu, S.; Gruia, A.S. [Faculty of Physics, West University of Timisoara, Bd. V. Parvan 4, 300223-Timisoara (Romania); Avram, N.M., E-mail: avram@physics.uvt.ro [Faculty of Physics, West University of Timisoara, Bd. V. Parvan 4, 300223-Timisoara (Romania); Academy of Romanian Scientists, Independentei 54, 050094-Bucharest (Romania)

    2014-10-01

    The exchange charge model of crystal field was applied to determine the dependence of the crystal field strength 10Dq on interionic distances R between the Fe{sup 2+} impurity ion and O{sup 2−} ligands in cubic MgO:Fe{sup 2+}. The obtained results were extrapolated by the power law and was shown that 10Dq depends on R as 1/R{sup n}, with n=6.3486. The deviations of these values from the value n=5 (predicted by the simple point charge model of crystal field) is explained by the covalent and exchange effects between impurity ion and ligands; the contribution of these effects into the total crystal field strength was considered separately. The 10Dq functions obtained as a result of our calculations were used for estimations of the electron–vibrational constants, Huang–Rhys parameters, and Jahn–Teller stabilization energy, and compared with available literature data.

  12. Crystal field effects on interionic distance in cubic MgO crystal doped with Fe2+ ions

    Science.gov (United States)

    Ivascu, S.; Gruia, A. S.; Avram, N. M.

    2014-10-01

    The exchange charge model of crystal field was applied to determine the dependence of the crystal field strength 10Dq on interionic distances R between the Fe2+ impurity ion and O2- ligands in cubic MgO:Fe2+. The obtained results were extrapolated by the power law and was shown that 10Dq depends on R as 1/R, with n=6.3486. The deviations of these values from the value n=5 (predicted by the simple point charge model of crystal field) is explained by the covalent and exchange effects between impurity ion and ligands; the contribution of these effects into the total crystal field strength was considered separately. The 10Dq functions obtained as a result of our calculations were used for estimations of the electron-vibrational constants, Huang-Rhys parameters, and Jahn-Teller stabilization energy, and compared with available literature data.

  13. Asymmetric bilayer graphene nanoribbon MOSFETs for analog and digital electronics

    Science.gov (United States)

    Dinarvand, A.; Ahmadi, V.; Darvish, Gh.

    2016-05-01

    In this paper, a new structure was proposed for bilayer graphene nanoribbon field-effect transistor (BGNFET) mainly to enhance the electrical characteristics in analog and digital applications. The proposed device uses two metallic gates on the top and bottom of a bilayer graphene nanoribbon, which is surrounded by SiO2 and connected to heavily doped source/drain contacts. Electrical properties of the proposed device were explored using fully self-consistent solution of Poisson and Schrödinger equations based on the nonequilibrium Green's function (NEGF) formalism. Significant improvements in the electrical behavior was seen in the simulation results for gates asymmetrically biased. The comparison with graphene nanoribbon FET showed that the proposed structure benefited from higher intrinsic voltage gain and cut-off frequency and improved switching characteristics such as delay and Ion/Ioff ratio.

  14. PH MEASUREMENTS WITH AN ION SENSITIVE FIELD-EFFECT TRANSISTOR IN THE MOUTH OF PATIENTS WITH XEROSTOMIA

    NARCIS (Netherlands)

    VISCH, LL; BERGVELD, P; LAMPRECHT, W; SGRAVENMADE, EJ

    A transistor pH electrode (ion sensitive field effect transistor), placed in the upper dentures of eleven xerostomia patients and five healthy volunteers, was used to register pH changes in five-, six- and seven-day-old dental plaque. A mouth rinse with a 10% sucrose solution caused a pH fall of

  15. Scrape-off layer ion temperature measurements at the divertor target in MAST by retarding field energy analyser

    CERN Document Server

    Elmore, S; Kirk, A; Thornton, A J; Harrison, J R; Tamain, P; Kocan, M; Bradley, J W

    2013-01-01

    Knowledge of the ion temperature (Ti) is of key importance for determining heat fluxes to the divertor and plasma facing components, however data regarding this is limited compared to electron temperature (Te) data. Ti measurements at the divertor target, between edge-localised modes (inter-ELM) H-mode, have been made using a novel retarding field energy analyser (RFEA).

  16. Sawtooth control in JET with ITER relevant low field side resonance ion cyclotron resonance heating and ITER-like wall

    NARCIS (Netherlands)

    Graves, J. P.; Lennholm, M.; Chapman, I.T.; Lerche, E.; Reich, M.; Alper, B.; Bobkov, V.; Dumont, R.; Faustin, J. M.; Jacquet, P.; Jaulmes, F.; Johnson, T.; Keeling, D. L.; Liu, Y. Q.; Nicolas, T.; Tholerus, S.; Blackman, T.; Carvalho, I. S.; Coelho, R.; Van Eester, D.; Felton, R.; Goniche, M.; Kiptily, V.; Monakhov, I.; Nave, M. F. F.; von Thun, Perez; Sabot, R.; Sozzi, C.; Tsalas, M.

    2015-01-01

    New experiments at JET with the ITER-like wall show for the first time that ITER-relevant low field side resonance first harmonic ion cyclotron resonance heating (ICRH) can be used to control sawteeth that have been initially lengthened by fast particles. In contrast to previous (Graves et al 2012

  17. Oxidative response of human monocytes and macrophages cultured under low oxygen culture conditions to ion parametric resonance magnetic fields.

    Science.gov (United States)

    INTRODUCTION One proposed mechanism of action of electromagnetic fields (EMFs) on biological systems is the Ion Parametric Resonance (IPR) model, which has been experimentally validated in neuronal PC-12 cells [1, 2]. It proposes that when applied EMFs are tuned to resonate with...

  18. Expansion of a plasma across a transverse magnetic field in a negative hydrogen ion source for fusion

    Science.gov (United States)

    Fantz, Ursel; Schiesko, Loic; Wünderlich, Dirk

    2012-10-01

    Negative ion sources are a key component of the neutral beam injection systems for the international fusion experiment ITER. To achieve the required ion current of 40 A at a tolerable amount of co-extracted electrons (electron to ion ratio below one) the source is separated into a plasma generation region and an expansion chamber equipped with a magnetic filter field (up to 10 mT). The field is needed for: (1) cooling the electrons down and thus minimize the H^- destruction by collisions, (2) to reduce the co-extracted electron current, and (3) to enhance the extraction probability for the surface produced negative ions. The area of the ITER source will be approximately 1m width and 2 m height, the IPP prototype source is a 1/8-size source. The recently installed flexible magnetic filter frame allows for systematic filter field studies (strength, position, polarity). Two Langmuir probes have been used to measure the plasma parameters simultaneously in axial direction. The profiles in the upper and lower part of the expansion chamber show beside the expected electron temperature and density decrease a drop in the plasma potential and a drift depending on the polarity, which vanishes when removing the filter field. The data interpretation is supported by modeling activities.

  19. In-Plane Electrical Connectivity and Near-Field Concentration of Isolated Graphene Resonators Realized by Ion Beams.

    Science.gov (United States)

    Luo, Weiwei; Cai, Wei; Xiang, Yinxiao; Wu, Wei; Shi, Bin; Jiang, Xiaojie; Zhang, Ni; Ren, Mengxin; Zhang, Xinzheng; Xu, Jingjun

    2017-08-01

    Graphene plasmons provide great opportunities in light-matter interactions benefiting from the extreme confinement and electrical tunability. Structured graphene cavities possess enhanced confinements in 3D and steerable plasmon resonances, potential in applications for sensing and emission control at the nanoscale. Besides graphene boundaries obtained by mask lithography, graphene defects engineered by ion beams have shown efficient plasmon reflections. In this paper, near-field responses of structured graphene achieved by ion beam direct-writing are investigated. Graphene nanoresonators are fabricated easily and precisely with a spatial resolution better than 30 nm. Breathing modes are observed in graphene disks. The amorphous carbons around weaken the response of edge modes in the resonators, but meanwhile render the isolated resonators in-plane electrical connections, where near-fields are proved gate-tunable. The realization of gate-tunable near-fields of graphene 2D resonators opens up tunable near-field couplings with matters. Moreover, graphene nonconcentric rings with engineered near-field confinement distributions are demonstrated, where the quadrupole plasmon modes are excited. Near-field mappings reveal concentrations at the scale of 3.8×10-4λ02 within certain zones which can be engineered. The realization of electrically tunable graphene nanoresonators by ion beam direct-writing is promising for active manipulation of emission and sensing at the nanoscale. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Thomson scattering measurements from asymmetric interpenetrating plasma flows

    Energy Technology Data Exchange (ETDEWEB)

    Ross, J. S., E-mail: ross36@llnl.gov; Moody, J. D.; Fiuza, F.; Ryutov, D.; Divol, L.; Huntington, C. M.; Park, H.-S. [Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94551 (United States)

    2014-11-15

    Imaging Thomson scattering measurements of collective ion-acoustic fluctuations have been utilized to determine ion temperature and density from laser produced counter-streaming asymmetric flows. Two foils are heated with 8 laser beams each, 500 J per beam, at the Omega Laser facility. Measurements are made 4 mm from the foil surface using a 60 J 2ω probe laser with a 200 ps pulse length. Measuring the electron density and temperature from the electron-plasma fluctuations constrains the fit of the multi-ion species, asymmetric flows theoretical form factor for the ion feature such that the ion temperatures, ion densities, and flow velocities for each plasma flow are determined.