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Sample records for resonance enhanced neutron

  1. Neutron elastic backscattering with resonance enhancement

    SciTech Connect

    Gomberg, H.J.; McEllistrem, M.T.

    1993-12-31

    Reliable detection of explosives and narcotics depends on generating signatures of compounds which characterize them. Major explosives and also alkaloid narcotics contain unique concentrations of Carbon, Oxygen, and Nitrogen which provide specific elemental ratios and chemical signatures. Neutron-induced reaction methods are rapid and non-invasive means of probing container interiors for special element-ratio signatures which signal the presence of significant amounts of contraband. Among these reactions the highest probabilities occur for neutron from different light elements, allowing determination of relative abundance of these elements. The authors have already demonstrated signature for simulated explosives and simulated narcotics in experimental tests at 1-4 MeV at the University of Kentucky accelerator labs. Intensities of neutron scatter at angles near 150{degrees} from three different elements, C, N, and O, were determined. Fast neutron time-of-flight detection methods enabled measurement of neutron energies, and thus separation of scattering from the different elements. Making measurements on and off strong resonances for specific elements, increases PFD and reduces PFA. Measurements illustrating this resonance enhancement technique will be presented.

  2. Neutron resonance averaging

    SciTech Connect

    Chrien, R.E.

    1986-10-01

    The principles of resonance averaging as applied to neutron capture reactions are described. Several illustrations of resonance averaging to problems of nuclear structure and the distribution of radiative strength in nuclei are provided. 30 refs., 12 figs.

  3. Neutron resonance averaging with filtered beams

    SciTech Connect

    Chrien, R.E.

    1985-01-01

    Neutron resonance averaging using filtered beams from a reactor source has proven to be an effective nuclear structure tool within certain limitations. These limitations are imposed by the nature of the averaging process, which produces fluctuations in radiative intensities. The fluctuations have been studied quantitatively. Resonance averaging also gives us information about initial or capture state parameters, in particular the photon strength function. Suitable modifications of the filtered beams are suggested for the enhancement of non-resonant processes.

  4. Laser generated neutron source for neutron resonance spectroscopy

    SciTech Connect

    Higginson, D. P.; Bartal, T.; McNaney, J. M.; Swift, D. C.; Hey, D. S.; Le Pape, S.; Mackinnon, A.; Kodama, R.; Tanaka, K. A.; Mariscal, D.; Beg, F. N.; Nakamura, H.; Nakanii, N.

    2010-10-15

    A neutron source for neutron resonance spectroscopy has been developed using high-intensity, short-pulse lasers. This technique will allow robust measurement of interior ion temperature of laser-shocked materials and provide insight into material equation of state. The neutron generation technique uses laser-accelerated protons to create neutrons in LiF through (p,n) reactions. The incident proton beam has been diagnosed using radiochromic film. This distribution is used as the input for a (p,n) neutron prediction code which is validated with experimentally measured neutron yields. The calculation infers a total fluence of 1.8x10{sup 9} neutrons, which are expected to be sufficient for neutron resonance spectroscopy temperature measurements.

  5. Neutron-Resonance Capture Analysis of Materials

    SciTech Connect

    Postma, H.; Bode, P.; Blaauw, M.; Corvi, F.

    1999-11-14

    Epithermal neutron activation analysis is a well-established approach to improve the sensitivity for certain elements by suppressing the activation of interfering elements. If epithermal neutrons of a given energy could be selected, the signal-to-noise ratio might be further improved by taking advantage of resonance capture. This reaction occurs mainly by intermediate and heavy nuclei. Moreover, most of these reactions take place with epithermal or fast neutrons. Intense epithermal neutrons are available as ''white'' beams at accelerator-driven neutron sources. Neutron resonance capture offers interesting analytical opportunities. Low-Z elements have little capture of epithermal neutrons and are thus virtually absent in the time-of-flight spectrum. Relatively large objects can be placed in the neutron beam and analyzed nondestructively. The induced radioactivity is relatively low. If an element has several stable isotopes, each of these isotopes can be recognized by its specific resonances. This would allow for multitracer studies with several isotopically labeled compounds. Different from mass spectrometry, the sample remains intact and can be used for further studies after analysis. Applications may be in the field of archaeology, metallurgy, and certification of reference materials.

  6. NBS work on neutron resonance radiography

    SciTech Connect

    Schrack, R.A.

    1987-01-01

    NBS has been engaged in a wide-ranging program in Neutron Resonance Radiography utilizing both one- and two-dimensional position-sensitive neutron detectors. The ability to perform a position-sensitive assay of up to 16 isotopes in a complex matrix has been demonstrated for a wide variety of sample types, including those with high gamma activity. A major part of the program has been the development and application of the microchannel-plate-based position-sensitive neutron detector. This detector system has high resolution and sensitivity, together with adequate speed of response to be used with neutron time-of-flight techniques. This system has demonstrated the ability to simultaneously image three isotopes in a sample with no interference.

  7. The pygmy dipole resonance in neutron-rich nuclei

    NASA Astrophysics Data System (ADS)

    Quang Hung, Nguyen; Kiet, Hoang Anh Tuan; Duc, Huynh Ngoc; Thi Chuong, Nguyen

    2016-06-01

    The pygmy dipole resonance (PDR), which has been observed via the enhancement of the electric dipole strength E1 of atomic nuclei, is studied within a microscopic collective model. The latter employs the Hartree-Fock (HF) method with effective nucleon-nucleon interactions of the Skyrme types plus the random-phase approximation (RPA). The results of the calculations obtained for various even-even nuclei such as 16-28O, 40-58Ca, 100-120Sn, and 182-218Pb show that the PDR is significantly enhanced when the number of neutrons outside the stable core of the nucleus is increased, that is, in the neutron-rich nuclei. As the result, the relative ratio between the energy weighted sum of the strength of the PDR and that of the GDR (giant dipole resonance) does not exceed 4%. The collectivity of the PDR and GDR states will be also discussed.

  8. Enhanced NIF neutron activation diagnostics

    SciTech Connect

    Yeamans, C. B.; Bleuel, D. L.; Bernstein, L. A.

    2012-10-15

    The NIF neutron activation diagnostic suite relies on removable activation samples, leading to operational inefficiencies and a fundamental lower limit on the half-life of the activated product that can be observed. A neutron diagnostic system measuring activation of permanently installed samples could remove these limitations and significantly enhance overall neutron diagnostic capabilities. The physics and engineering aspects of two proposed systems are considered: one measuring the {sup 89}Zr/{sup 89m}Zr isomer ratio in the existing Zr activation medium and the other using potassium zirconate as the activation medium. Both proposed systems could improve the signal-to-noise ratio of the current system by at least a factor of 5 and would allow independent measurement of fusion core velocity and fuel areal density.

  9. Resonance effects in neutron scattering lengths

    SciTech Connect

    Lynn, J.E.

    1989-06-01

    The nature of neutron scattering lengths is described and the nuclear effects giving rise to their variation is discussed. Some examples of the shortcomings of the available nuclear data base, particularly for heavy nuclei, are given. Methods are presented for improving this data base, in particular for obtaining the energy variation of the complex coherent scattering length from long to sub-/angstrom/ wave lengths from the available sources of slow neutron cross section data. Examples of this information are given for several of the rare earth nuclides. Some examples of the effect of resonances in neutron reflection and diffraction are discussed. This report documents a seminar given at Argonne National Laboratory in March 1989. 18 refs., 18 figs.

  10. Doping explosive materials for neutron radiographic enhancement.

    NASA Technical Reports Server (NTRS)

    Golliher, K. G.

    1971-01-01

    Discussion of studies relating to the selection of doping materials of high neutron absorption usable for enhancing the neutron radiographic imaging of explosive mixtures, without interfering with the proper chemical reaction of the explosives. The results of the studies show that gadolinium oxide is an excellent material for doping explosive mixtures to enhance the neutron radiographic image.

  11. Hadronic resonances enhanced by thresholds

    NASA Astrophysics Data System (ADS)

    Caramés, T. F.; Valcarce, A.

    2016-07-01

    We present a neat example of a meson-baryon system where the vicinity of two different thresholds enhances the binding of a hadronic resonance, a pentaquark. As a consequence the pattern of states may change when moving among different flavor sectors, what poses a warning on naive extrapolations to heavy flavor sectors based on systematic expansions. For this purpose we simultaneously analyze the N D bar and NB two-hadron systems looking for possible bound states or resonances. When a resonance is controlled by a coupled-channel effect, going to a different flavor sector may enhance or diminish the binding. This effect may, for example, generate significant differences between the charmonium and bottomonium spectra above open-flavor thresholds or pentaquark states in the open-charm and open-bottom sectors.

  12. Characterization of nuclear material by Neutron Resonance Transmission Analysis

    NASA Astrophysics Data System (ADS)

    Paradela, C.; Alaerts, G.; Becker, B.; Heyse, J.; Kopecky, S.; Moens, A.; Mondelaers, W.; Schillebeeckx, P.; Wynants, R.; Harada, H.; Kitatani, F.; Koizumi, M.; Tsuchiya, H.

    2016-11-01

    The use of Neutron Resonance Transmission Analysis for the characterization of nuclear materials is discussed. The method, which relies on resonance structures in neutron-induced reaction cross sections, can be applied as a non-destructive method to characterise complex nuclear materials such as melted fuel resulting from a severe nuclear accident. Results of a demonstration experiment at the GELINA facility reveal that accurate data can be obtained at a compact facility even in the case of strong overlapping resonances.

  13. Neutron Resonance Spin Determination Using Multi-Segmented Detector DANCE

    SciTech Connect

    Baramsai, B.; Mitchell, G. E.; Chyzh, A.; Dashdorj, D.; Walker, C.; Agvaanluvsan, U.; Becvar, F.; Krticka, M.; Bredeweg, T. A.; Couture, A.; Haight, R. C.; Jandel, M.; Keksis, A. L.; O'Donnell, J. M.; Rundberg, R. S.; Ullmann, J. L.; Vieira, D. J.; Wouters, J. M.

    2011-06-01

    A sensitive method to determine the spin of neutron resonances is introduced based on the statistical pattern recognition technique. The new method was used to assign the spins of s-wave resonances in {sup 155}Gd. The experimental neutron capture data for these nuclei were measured with the DANCE (Detector for Advanced Neutron Capture Experiment) calorimeter at the Los Alamos Neutron Science Center. The highly segmented calorimeter provided detailed multiplicity distributions of the capture {gamma}-rays. Using this information, the spins of the neutron capture resonances were determined. With these new spin assignments, level spacings are determined separately for s-wave resonances with J{sup {pi}} = 1{sup -} and 2{sup -}.

  14. A detector system for neutron resonance capture imaging

    NASA Astrophysics Data System (ADS)

    Perelli Cippo, E.; Borella, A.; Gorini, G.; Kockelmann, W.; Pietropaolo, A.; Postma, H.; Rhodes, N. J.; Schillebeeckx, P.; Schooneveld, E. M.; Tardocchi, M.; Wynants, R.; Ancient Charm Collaboration

    2010-11-01

    Neutron resonance capture analysis (NRCA) is used in the Ancient Charm project to determine element concentrations in cultural heritage objects. NRCA employs gamma-ray detectors to determine time-of-flight spectra that reveal the resonance structure in neutron induced reaction cross sections. One of the objectives is to produce a high-detection efficient NRCA system capable of mapping element distributions. The detection system is described together with the results of neutron beam tests at the time-of-flight facility GELINA and at the pulsed neutron spallation source ISIS (UK).

  15. Prompt Fission Neutron Emission in Resonance Fission of 239Pu

    NASA Astrophysics Data System (ADS)

    Hambsch, Franz-Josef; Varapai, Natallia; Zeinalov, Shakir; Oberstedt, Stephan; Serot, Olivier

    2005-05-01

    The prompt neutron emission probability from neutron-induced fission in the resonance region is being investigated at the time-of-flight facility GELINA of the IRMM. A double Frisch-gridded ionization chamber is used as a fission-fragment detector. For the data acquisition of both the fission-fragment signals as well as the neutron detector signals the fast digitization technique has been applied. For the neutron detection, large-volume liquid scintillation detectors from the DEMON collaboration are used. A specialized data analysis program taking advantage of the digital filtering technique has been developed to treat the acquired data. Neutron multiplicity investigations for actinides, especially in resonance neutron-induced fission, are rather scarce. They are, however, important for reactor control and safety issues as well as for understanding the basic physics of the fission process. Fission yield measurements on both 235U and 239Pu without prompt neutron emission coincidence have shown that fluctuation of the fission-fragment mass distribution exists from resonance to resonance, larger in the case of 235U. To possibly explain these observations, the question now is whether the prompt neutron multiplicity shows similar fluctuations with resonance energy.

  16. Neutron Resonance Spectroscopy for the Analysis of Materials and Objects

    SciTech Connect

    Borella, A.; Lampoudis, C.; Schillebeeckx, P.; Kopecky, S.; Postma, H.; Moxon, M.

    2009-12-02

    The presence of resonances in neutron induced reaction cross sections is the basis of the Neutron Resonance Capture (NRCA) and Transmission (NRTA) Analysis techniques. Since resonances can be observed at neutron energies which are specific for each nuclide, they can be used as fingerprints to identify and quantify elements in materials and objects. Both NRCA and NRTA are fully non-destructive methods which determine the bulk elemental composition, do not require any sample preparation and result in a negligible residual activation. In this text we review the technique and present an analysis procedures including one based on a more methodological approach which relies on a full Resonance Shape Analysis (RSA) and accounts directly for the neutron self-shielding, multiple scattering, Doppler broadening and instrumental resolution.

  17. Resonant shattering of neutron star crusts.

    PubMed

    Tsang, David; Read, Jocelyn S; Hinderer, Tanja; Piro, Anthony L; Bondarescu, Ruxandra

    2012-01-01

    The resonant excitation of neutron star (NS) modes by tides is investigated as a source of short gamma-ray burst (SGRB) precursors. We find that the driving of a crust-core interface mode can lead to shattering of the NS crust, liberating ∼10{46}-10{47}  erg of energy seconds before the merger of a NS-NS or NS-black-hole binary. Such properties are consistent with Swift/BAT detections of SGRB precursors, and we use the timing of the observed precursors to place weak constraints on the crust equation of state. We describe how a larger sample of precursor detections could be used alongside coincident gravitational wave detections of the inspiral by Advanced LIGO class detectors to probe the NS structure. These two types of observations nicely complement one another, since the former constrains the equation of state and structure near the crust-core boundary, while the latter is more sensitive to the core equation of state. PMID:22304251

  18. Ultrasonic signal enhancement by resonator techniques

    NASA Technical Reports Server (NTRS)

    Heyman, J. S.

    1973-01-01

    Ultrasonic resonators increase experimental sensitivity to acoustic dispersion and changes in attenuation. Experimental sensitivity enhancement line shapes are presented which were obtained by modulating the acoustic properties of a CdS resonator with a light beam. Small changes in light level are made to produce almost pure absorptive or dispersive changes in the resonator signal. This effect is due to the coupling of the ultrasonic wave to the CdS conductivity which is proportional to incident light intensity. The resonator conductivity is adjusted in this manner to obtain both dispersive and absorptive sensitivity enhancement line shapes. The data presented verify previous thoretical calculations based on a propagating wave model.

  19. Enhancement of Magnetic Resonance Imaging with Metasurfaces.

    PubMed

    Slobozhanyuk, Alexey P; Poddubny, Alexander N; Raaijmakers, Alexander J E; van den Berg, Cornelis A T; Kozachenko, Alexander V; Dubrovina, Irina A; Melchakova, Irina V; Kivshar, Yuri S; Belov, Pavel A

    2016-03-01

    It is revealed that the unique properties of ultrathin metasurface resonators can improve magnetic resonance imaging dramatically. A metasurface formed when an array of metallic wires is placed inside a scanner under the studied object and a substantial enhancement of the radio-frequency magnetic field is achieved by means of subwavelength manipulation with the metasurface, also allowing improved image resolution. PMID:26754827

  20. Estimation of neutron energy for first resonance from absorption cross section for thermal neutrons

    NASA Technical Reports Server (NTRS)

    Bogart, Donald

    1951-01-01

    Examination of published data for some 52 isotopes indicates that the neutron energy for which the first resonance occurs is related to the magnitude of the thermal absorption cross section. The empirical relation obtained is in qualitative agreement with the results of a simplified version of the resonance theory of the nucleus of Breit-Wigner.

  1. Novel detectors for fast-neutron resonance radiography

    NASA Astrophysics Data System (ADS)

    Vartsky, D.; Mor, I.; Goldberg, M. B.; Bar, D.; Feldman, G.; Dangendorf, V.; Tittelmeier, K.; Weierganz, M.; Bromberger, B.; Breskin, A.

    2010-11-01

    We describe the concept and properties of a time-resolved integrative optical neutron (TRION) detector, a novel high spatial resolution neutron imaging system in the energy range of 1-10 MeV, for fast-neutron resonance radiography (FNRR), with multiple-energy TOF-spectrometry capability. Two generations of TRION detectors have already demonstrated their suitability for detecting small quantities of thin-sheet explosives. TRION holds promise for fully automatic detection and identification of standard and improvised explosives concealed in luggage and cargo, by determining the density distribution of light elements such as C, N and O.

  2. Possibility of generating a 4-neutron resonance with a T =3 /2 isospin 3-neutron force

    NASA Astrophysics Data System (ADS)

    Hiyama, E.; Lazauskas, R.; Carbonell, J.; Kamimura, M.

    2016-04-01

    We consider the theoretical possibility of generating a narrow resonance in the 4-neutron system as suggested by a recent experimental result. To that end, a phenomenological T =3 /2 3-neutron force is introduced, in addition to a realistic N N interaction. We inquire what the strength should be of the 3 n force to generate such a resonance. The reliability of the 3-neutron force in the T =3 /2 channel is examined, by analyzing its consistency with the low-lying T =1 states of 4H,4He, and 4Li and the 3H+n scattering. The ab initio solution of the 4 n Schrödinger equation is obtained using the complex scaling method with boundary conditions appropriate to the four-body resonances. We find that to generate narrow 4 n resonant states a remarkably attractive 3 N force in the T =3 /2 channel is required.

  3. Bandwidth enhancement of dielectric resonator antennas

    NASA Technical Reports Server (NTRS)

    Lee, Richard Q.; Simons, Rainee N.

    1993-01-01

    An experimental investigation of bandwidth enhancement of dielectric resonator antennas (DRA) using parasitic elements is reported. Substantial bandwidth enhancement for the HE(sub 11delta) mode of the stacked geometry and for the HE(sub 13delta) mode of the coplanar collinear geometry was demonstrated. Excellent radiation patterns for the HE(sub 11delta) mode were also recorded.

  4. Ultracold Neutrons - Quantum Bouncing Ball Resonates

    SciTech Connect

    Greene, G. L.

    2011-01-01

    Spectroscopic techniques typically probe the interaction between matter and electromagnetic fields. An experiment now demonstrates that transitions between quantum states of neutrons can be brought about by mechanically vibrating a mirror, an approach that may lead to sensitive tests of gravity laws.

  5. Epithermal Neutron Source for Neutron Resonance Spectroscopy (NRS) using High Intensity, Short Pulse Lasers

    SciTech Connect

    Higginson, D P; McNaney, J M; Swift, D C; Bartal, T; Hey, D S; Pape, S L; Mackinnon, A; Mariscal, D; Nakamura, H; Nakanii, N; Beg, F N

    2010-04-22

    A neutron source for neutron resonance spectroscopy (NRS) has been developed using high intensity, short pulse lasers. This measurement technique will allow for robust measurements of interior ion temperature of laser-shocked materials and provide insight into equation of state (EOS) measurements. The neutron generation technique uses protons accelerated by lasers off of Cu foils to create neutrons in LiF, through (p,n) reactions with {sup 7}Li and {sup 19}F. The distribution of the incident proton beam has been diagnosed using radiochromic film (RCF). This distribution is used as the input for a (p,n) neturon prediction code which is compared to experimentally measured neutron yields. From this calculation, a total fluence of 1.8 x 10{sup 9} neutrons is infered, which is shown to be a reasonable amount for NRS temperature measurement.

  6. Neutron capture in s-wave resonances of nickel-64

    SciTech Connect

    Wisshak, K.; Fabbri, F.; Kappeler, F.; Macklin, R.L.; Reffo, G.

    1984-05-01

    The neutron capture widths of the s-wave resonances at 13.9 and 33.8 keV in /sup 64/Ni have been determined using a setup with extremely low neutron sensitivity completely different from all previous experiments on this isotope. This feature is important because these resonances exhibit a very large scattering-to-capture ratio. A pulsed 3-MV Van de Graaff accelerator and a kinematically collimated neutron beam, produced via the /sup 7/Li(p,n) reaction, was used in the experiments. Capture gamma rays were observed by three Moxon-Rae detectors with a graphite, a bismuth-graphite, and a bismuth converter, respectively. The samples were positioned at a neutron flight path of only 6 to 8 cm. Thus, events due to capture of resonance-scattered neutrons in the detectors or in surrounding materials are completely discriminated by their additional time of flight. The short flight path and the high neutron flux at the sample position allowed for a signal-to-background ratio of approximately unity even for the broad resonance at 33.8 keV. The data obtained with the individual detectors were corrected for the efficiency of the different converter materials. For that purpose, detailed theoretical calculations of the capture gamma-ray spectra of the measured isotope and of gold, which was used as a standard, were performed. The final radiative widths are GAMMA..gamma.. (13.9 keV) = 1.01 + or - 0.07 eV and GAMMA..gamma.. (33.8 keV) = 1.16 + or - 0.08 eV, considerably smaller than the rough estimates obtained in previous work.

  7. Monostable array-enhanced stochastic resonance.

    PubMed

    Lindner, J F; Breen, B J; Wills, M E; Bulsara, A R; Ditto, W L

    2001-05-01

    We present a simple nonlinear system that exhibits multiple distinct stochastic resonances. By adjusting the noise and coupling of an array of underdamped, monostable oscillators, we modify the array's natural frequencies so that the spectral response of a typical oscillator in an array of N oscillators exhibits N-1 different stochastic resonances. Such families of resonances may elucidate and facilitate a variety of noise-mediated cooperative phenomena, such as noise-enhanced propagation, in a broad class of similar nonlinear systems. PMID:11414887

  8. Trampoline metamaterial: Local resonance enhancement by springboards

    NASA Astrophysics Data System (ADS)

    Bilal, Osama R.; Hussein, Mahmoud I.

    2013-09-01

    We investigate the dispersion characteristics of locally resonant elastic metamaterials formed by the erection of pillars on the solid regions in a plate patterned by a periodic array of holes. We show that these solid regions effectively act as springboards leading to an enhanced resonance behavior by the pillars when compared to the nominal case of pillars with no holes. This local resonance amplification phenomenon, which we define as the trampoline effect, is shown to cause subwavelength bandgaps to increase in size by up to a factor of 4. This outcome facilitates the utilization of subwavelength metamaterial properties over exceedingly broad frequency ranges.

  9. Evaluation of Neutron Resonance Cross Section Data at GELINA

    NASA Astrophysics Data System (ADS)

    Schillebeeckx, P.; Becker, B.; Capote, R.; Emiliani, F.; Guber, K.; Heyse, J.; Kauwenberghs, K.; Kopecky, S.; Lampoudis, C.; Massimi, C.; Mondelaers, W.; Moxon, M.; Noguere, G.; Plompen, A. J. M.; Pronyaev, V.; Siegler, P.; Sirakov, I.; Trkov, A.; Volev, K.; Zerovnik, G.

    2014-05-01

    Over the last decade, the EC-JRC-IRMM, in collaboration with other institutes such as INRNE Sofia (BG), INFN Bologna (IT), ORNL (USA), CEA Cadarache (FR) and CEA Saclay (FR), has made an intense effort to improve the quality of neutron-induced cross section data in the resonance region. These improvements relate to both the infrastructure of the facility and the measurement setup, and the data reduction and analysis procedures. As a result total and reaction cross section data in the resonance region with uncertainties better than 0.5 % and 2 %, respectively, can be produced together with evaluated data files for both the resolved and unresolved resonance region. The methodology to produce full ENDF compatible files, including covariances, is illustrated by the production of resolved resonance parameter files for 241Am, Cd and W and an evaluation for 197Au in the unresolved resonance region.

  10. Neutron resonance spin-echo upgrade at the three-axis spectrometer FLEXX.

    PubMed

    Groitl, F; Keller, T; Quintero-Castro, D L; Habicht, K

    2015-02-01

    We describe the upgrade of the neutron resonance spin-echo setup at the cold neutron triple-axis spectrometer FLEXX at the BER II neutron source at the Helmholtz-Zentrum Berlin. The parameters of redesigned key components are discussed, including the radio frequency (RF) spin-flip coils, the magnetic shield, and the zero field coupling coils. The RF-flippers with larger beam windows allow for an improved neutron flux transfer from the source to the sample and further to the analyzer. The larger beam cross sections permit higher coil inclination angles and enable measurements on dispersive excitations with a larger slope of the dispersion. Due to the compact design of the spin-echo units in combination with the increased coil tilt angles, the accessible momentum-range in the Larmor diffraction mode is substantially enlarged. In combination with the redesigned components of the FLEXX spectrometer, including the guide, the S-bender polarizer, the double focusing monochromator, and a Heusler crystal analyzer, the count rate increased by a factor of 15.5, and the neutron beam polarization is enhanced. The improved performance extends the range of feasible experiments, both for inelastic scattering on excitation lifetimes in single crystals, and for high-resolution Larmor diffraction. The experimental characterization of the instrument components demonstrates the reliable performance of the new neutron resonance spin-echo option, now available for the scientific community at FLEXX. PMID:25725891

  11. Neutron resonance spin-echo upgrade at the three-axis spectrometer FLEXX

    SciTech Connect

    Groitl, F. Quintero-Castro, D. L.; Habicht, K.; Keller, T.

    2015-02-15

    We describe the upgrade of the neutron resonance spin-echo setup at the cold neutron triple-axis spectrometer FLEXX at the BER II neutron source at the Helmholtz-Zentrum Berlin. The parameters of redesigned key components are discussed, including the radio frequency (RF) spin-flip coils, the magnetic shield, and the zero field coupling coils. The RF-flippers with larger beam windows allow for an improved neutron flux transfer from the source to the sample and further to the analyzer. The larger beam cross sections permit higher coil inclination angles and enable measurements on dispersive excitations with a larger slope of the dispersion. Due to the compact design of the spin-echo units in combination with the increased coil tilt angles, the accessible momentum-range in the Larmor diffraction mode is substantially enlarged. In combination with the redesigned components of the FLEXX spectrometer, including the guide, the S-bender polarizer, the double focusing monochromator, and a Heusler crystal analyzer, the count rate increased by a factor of 15.5, and the neutron beam polarization is enhanced. The improved performance extends the range of feasible experiments, both for inelastic scattering on excitation lifetimes in single crystals, and for high-resolution Larmor diffraction. The experimental characterization of the instrument components demonstrates the reliable performance of the new neutron resonance spin-echo option, now available for the scientific community at FLEXX.

  12. Wavelength-selected Neutron Pulses Formed by a Spatial Magnetic Neutron Spin Resonator

    NASA Astrophysics Data System (ADS)

    Gösselsberger, C.; Bacak, M.; Gerstmayr, T.; Gumpenberger, S.; Hawlik, A.; Hinterleitner, B.; Jericha, E.; Nowak, S.; Welzl, A.; Badurek, G.

    We present a novel type of spatial magnetic neutron spin resonator whose time and wavelength resolution can be de- coupled from each other by means of a travelling wave mode of operation. Combined with a pair of highly efficient polarisers such a device could act simultaneously as monochromator and chopper, able to produce short neutron pulses, whose wavelength, spectral width and duration could be varied almost instantaneously by purely electronic means with- out any mechanical modification of the experimental setup. To demonstrate the practical feasibility of this technique we have designed and built a first prototype resonator consisting of ten individually switchable modules which allows to produce neutron pulses in the microsecond regime. It was installed at a polarised 2.6 Å neutron beamline at the 250 kW TRIGA research reactor of the Vienna University of Technology where it could deliver pulses of 55 μs duration, which is about three times less than the passage time of the neutrons through the resonator itself. In order to further improve the achievable wavelength resolution to about 3% a second prototype resonator, consisting of 48 individual modules with optimised field homogeneity and enlarged beam cross-section of 6 × 6 cm2 was developed. We present the results of first measurements which demonstrate the successful operation of this device.

  13. The resonant detector and its application to epithermal neutron spectroscopy

    NASA Astrophysics Data System (ADS)

    Gorini, G.; Perelli-Cippo, E.; Tardocchi, M.; Andreani, C.; D'Angelo, A.; Pietropaolo, A.; Senesi, R.; Imberti, S.; Bracco, A.; Previtali, E.; Pessina, G.; Rhodes, N. J.; Schooneveld, E. M.

    2004-08-01

    New perspectives for epithermal neutron spectroscopy are being opened by the development of the resonant detector (RD) and its use on inverse geometry time of flight spectrometers at spallation sources. The RD was first proposed in the 1980s and was recently brought to a performance level exceeding conventional neutron-sensitive Li-glass scintillator detectors. It features a photon counter coupled to a neutron analyzer foil. Resonant neutron absorption in the foil results in the emission of prompt gamma rays that are detected in the photon counter. The dimensions of the RD set the spatial resolution that can be achieved, ranging from a fraction of a cm to several cm. It can thus be tailored to the construction of detector arrays of different geometry. The main results of the research on this kind of detector are reported leading to the present optimized RD design based on a combination of YAP scintillation photon counter and uranium or gold analyzer foils. This detector has already been selected for application in the upgrade of the VESUVIO spectrometer on ISIS. A special application is the Very Low Angle Detector (VLAD) bank, which will extend the kinematical region for neutron scattering to low momentum transfer (<10 Å -1) whilst still keeping energy transfer >1 eV, thus allowing new experimental studies in condensed matter systems. The first results of tests made with prototype VLAD detectors are presented, confirming the usefulness of the RD for measurements at scattering angles as low as 2-5°.

  14. Hafnium Resonance Parameter Analysis Using Neutron Capture and Transmission Experiments

    SciTech Connect

    MJ Trbovich; DP Barry; RE Slovacck; Y Danon; RC Block; JA Burke; NJ Drindak; G Leinweber; RV Ballad

    2004-10-13

    The focus of this work is to determine resonance parameters for stable hafnium isotopes in the 0.005-200 eV region, with special emphasis on the overlapping {sup 176}Hf and {sup 178}Hf resonances near 8 eV. The large neutron cross section of hafnium, combined with its corrosion resistance and excellent mechanical properties, make it a useful material for controlling nuclear reactions. Experiments measuring neutron capture and transmission were performed at the Rensselaer Polytechnic Institute (RPI) electron linear accelerator (LINAC) using the time of flight method. {sup 6}Li glass scintillation detectors were used for transmission experiments at flight path lengths of 15 and 25 m. Capture experiments were done using a sixteen section NaI(Tl) multiplicity detector at a flight path length of 25 m. These experiments utilized various thicknesses of metallic and isotopically-enriched liquid samples. The liquid samples were designed to provide information on the {sup 176}Hf and {sup 178}Hf contributions to the 8 eV doublet without saturation. Data analysis was done using the R-matrix Bayesian code SAMMY version M6 beta. SAMMY is able to account for experimental resolution effects for each of the experimental setups at the RPI LINAC, and also can correct for multiple scattering effects in neutron capture yield data. The combined capture and transmission data analysis yielded resonance parameters for all hafnium isotopes from 0.005-200 eV. Resonance integrals were calculated along with errors for each hafnium isotope using the NJOY [1] and INTER [2] codes. The isotopic resonance integrals calculated were significantly different than previously published values; however the calculated elemental hafnium resonance integral changed very little.

  15. Hafnium Resonance Parameter Analysis using Neutron Capture and Transmission Experiments

    SciTech Connect

    Trbovich, Michael J.; Barry, Devin P.; Burke, John A.; Drindak, Noel J.; Leinweber, Greg; Ballad, Robert V.; Slovacek, Rudy E.; Danon, Yaron; Block, Robert C.

    2005-05-24

    The focus of this work is to determine resonance parameters for stable hafnium isotopes in the 0.005-200 eV region, with special emphasis on the overlapping 176Hf and 178Hf resonances near 8 eV. The large neutron cross section of hafnium, combined with its corrosion resistance and excellent mechanical properties, make it a useful material for controlling nuclear reactions.Experiments measuring neutron capture and transmission were performed at the Rensselaer Polytechnic Institute (RPI) electron linear accelerator (LINAC) using the time of flight method. 6Li glass scintillation detectors were used for transmission experiments at flight path lengths of 15 and 25 m. Capture experiments were done using a sixteen-section NaI(Tl) multiplicity detector at a flight path length of 25 m. These experiments utilized various thicknesses of metallic and isotopically enriched liquid samples. The liquid samples were designed to provide information on the 176Hf and 178Hf contributions to the 8-eV doublet without saturation.Data analysis was done using the R-matrix Bayesian code SAMMY version M6 beta. SAMMY is able to account for experimental resolution effects for each of the experimental setups at the RPI LINAC, and also can correct for multiple scattering effects in neutron capture yield data. The combined capture and transmission data analysis yielded resonance parameters for all hafnium isotopes from 0.005-200 eV. Resonance integrals were calculated along with errors for each hafnium isotope using the NJOY and INTER codes. The isotopic resonance integrals calculated were significantly different than previously published values; however the calculated elemental hafnium resonance integral changed very little.

  16. Time Delay in Neutron-Alpha Resonant Scattering

    SciTech Connect

    Hoop, Bernard; Hale, Gerald M.

    2011-10-24

    Time delay analysis of neutron-alpha resonant scattering cross sections supports characterization of the lowest 3/2{sup +} level in {sup 5}He as fundamentally an n-{alpha} resonance on the second Riemann energy sheet of both n-{alpha} and deuteron-{sup 3}H channels, with an associated shadow pole on a different unphysical sheet that, through its associated zero on the physical sheet, contributes to the large {sup 4}He(n,d){sup 3}H cross section.

  17. Enhancement of artificial magnetism via resonant bianisotropy.

    PubMed

    Markovich, Dmitry; Baryshnikova, Kseniia; Shalin, Alexander; Samusev, Anton; Krasnok, Alexander; Belov, Pavel; Ginzburg, Pavel

    2016-01-01

    All-dielectric "magnetic light" nanophotonics based on high refractive index nanoparticles allows controlling magnetic component of light at nanoscale without having high dissipative losses. The artificial magnetic optical response of such nanoparticles originates from circular displacement currents excited inside those structures and strongly depends on geometry and dispersion of optical materials. Here an approach for enhancing of magnetic response via resonant bianisotropy effect is proposed and analyzed. The key mechanism of enhancement is based on electric-magnetic interaction between two electrically and magnetically resonant nanoparticles of all-dielectric dimer. It was shown that proper geometrical arrangement of the dimer in respect to the incident illumination direction allows flexible control over all vectorial components of the magnetic moment, tailoring the latter in the dynamical range of 100% and delivering enhancement up to 36% relative to performances of standalone spherical particles. The proposed approach provides pathways for designs of all-dielectric metamaterials and metasurfaces with strong magnetic responses. PMID:26941126

  18. Enhancement of artificial magnetism via resonant bianisotropy

    NASA Astrophysics Data System (ADS)

    Markovich, Dmitry; Baryshnikova, Kseniia; Shalin, Alexander; Samusev, Anton; Krasnok, Alexander; Belov, Pavel; Ginzburg, Pavel

    2016-03-01

    All-dielectric “magnetic light” nanophotonics based on high refractive index nanoparticles allows controlling magnetic component of light at nanoscale without having high dissipative losses. The artificial magnetic optical response of such nanoparticles originates from circular displacement currents excited inside those structures and strongly depends on geometry and dispersion of optical materials. Here an approach for enhancing of magnetic response via resonant bianisotropy effect is proposed and analyzed. The key mechanism of enhancement is based on electric-magnetic interaction between two electrically and magnetically resonant nanoparticles of all-dielectric dimer. It was shown that proper geometrical arrangement of the dimer in respect to the incident illumination direction allows flexible control over all vectorial components of the magnetic moment, tailoring the latter in the dynamical range of 100% and delivering enhancement up to 36% relative to performances of standalone spherical particles. The proposed approach provides pathways for designs of all-dielectric metamaterials and metasurfaces with strong magnetic responses.

  19. Scissors Mode of 162 Dy Studied from Resonance Neutron Capture

    DOE PAGESBeta

    Baramsai, B.; Bečvář, F.; Bredeweg, T. A.; Haight, R. C.; Jandel, M.; Kroll, J.; Krtička, M.; Mitchell, G. E.; O’Donnell, J. M.; Rundberg, R. S.; et al

    2015-05-28

    Multi-step cascade γ-ray spectra from the neutron capture at isolated resonances of 161Dy nucleus were measured at the LANSCE/DANCE time-of-flight facility in Los Alamos National Laboratory. The objectives of this experiment were to confirm and possibly extend the spin assignment of s-wave neutron resonances and get new information on photon strength functions with emphasis on the role of the M1 scissors mode vibration. The preliminary results show that the scissors mode plays a significant role in all transitions between accessible states of the studied nucleus. The photon strength functions describing well our data are compared to results from 3He-induced reactions,more » (n,γ) experiments on Gd isotopes, and (γ,γ’) reactions.« less

  20. Scissors Mode of 162Dy Studied from Resonance Neutron Capture

    NASA Astrophysics Data System (ADS)

    Baramsai, B.; Bečvář, F.; Bredeweg, T. A.; Haight, R. C.; Jandel, M.; Kroll, J.; Krtička, M.; Mitchell, G. E.; O'Donnell, J. M.; Rundberg, R. S.; Ullmann, J. L.; Valenta, S.; Wilhelmy, J. B.

    2015-05-01

    Multi-step cascade γ-ray spectra from the neutron capture at isolated resonances of 161Dy nucleus were measured at the LANSCE/DANCE time-of-flight facility in Los Alamos National Laboratory. The objectives of this experiment were to confirm and possibly extend the spin assignment of s-wave neutron resonances and get new information on photon strength functions with emphasis on the role of the M1 scissors mode vibration. The preliminary results show that the scissors mode plays a significant role in all transitions between accessible states of the studied nucleus. The photon strength functions describing well our data are compared to results from 3He-induced reactions, (n,γ) experiments on Gd isotopes, and (γ,γ') reactions.

  1. Influence of neutron surface on E1 resonance properties

    NASA Astrophysics Data System (ADS)

    Goncharova, N. G.; Tretyakova, T. Yu.; Fedorov, N. A.

    2016-01-01

    The E1 strength distributions in even-even Si isotopes were calculated in the "particle-core coupling" version of the shell model taking into account the fragmentation of the hole configuration among the states of the daughter nuclei. The comparison of calculated strength distributions in different isotopes of the same element shows the peculiarities of a neutron surface influence on the E1 resonance fragmentation.

  2. Neutron Resonance Densitometry for Particle-like Debris of Melted Fuel

    NASA Astrophysics Data System (ADS)

    Harada, H.; Kitatani, F.; Koizumi, M.; Takamine, J.; Kureta, M.; Tsutiya, H.; Iimura, H.; Seya, M.; Becker, B.; Kopecky, S.; Schillebeeckx, P.

    2014-04-01

    Neutron Resonance Densitometry (NRD) is proposed for the quantification of nuclear materials in particle-like debris of melted fuel from the reactors of the Fukushima Daiichi nuclear power plant. The method is based on a combination of neutron resonance transmission analysis (NRTA) and neutron resonance capture analysis (NRCA). It uses the neutron time-of-flight (TOF) technique with a pulsed white neutron source and a neutron flight path as short as 5 m. The spectrometer for NRCA is made of LaBr3(Ce) detectors. The achievable uncertainty due to only counting statistics is less than 1 % to determine Pu and U isotopes.

  3. Hafnium Resonance Parameter Analysis Using Neutron Capture and Transmission Experiments

    SciTech Connect

    Trbovich, M J; Barry, D P; Slovacek, R E; Danon, Y; Block, R C; Francis, N C; Lubert, M; Burke, J A; Drindak, N J; Lienweber, G; Ballad, R

    2007-02-06

    The focus of this work is to determine the resonance parameters for stable hafnium isotopes in the 0.005 - 200 eV region, with special emphasis on the overlapping {sup 176}Hf and {sup 178}Hf resonances near 8 eV. Accurate hafnium cross sections and resonance parameters are needed in order to quantify the effects of hafnium found in zirconium, a metal commonly used in reactors. The accuracy of the cross sections and the corresponding resonance parameters used in current nuclear analysis tools are rapidly becoming the limiting factor in reducing the overall uncertainty on reactor physics calculations. Experiments measuring neutron capture and transmission are routinely performed at the Rensselaer Polytechnic Institute (RPI) LINAC using the time-of flight technique. {sup 6}Li glass scintillation detectors were used for transmission experiments at flight path lengths of 15 and 25 m, respectively. Capture experiments were performed using a sixteen section NaI multiplicity detector at a flight path length of 25 m. These experiments utilized several thicknesses of metallic and isotope-enriched liquid Hf samples. The liquid Hf samples were designed to provide information on the {sup 176}Hf and {sup 178}Hf contributions to the 8 eV doublet without saturation. Data analyses were performed using the R-matrix Bayesian code SAMMY. A combined capture and transmission data analysis yielded resonance parameters for all hafnium isotopes from 0.005 - 200 eV. Additionally, resonance integrals were calculated, along with errors for each hafnium isotope, using the NJOY and INTER codes. The isotopic resonance integrals calculated were significantly different than previous values. The {sup 176}Hf resonance integral, based on this work, is approximately 73% higher than the ENDF/B-VI value. This is due primarily to the changes to resonance parameters in the 8 eV resonance, the neutron width presented in this work is more than twice that of the previous value. The calculated elemental

  4. Resonantly-enhanced axion-photon regeneration

    SciTech Connect

    Mueller, Guido; Sikivie, Pierre; Tanner, David B.; Bibber, Karl van

    2010-08-30

    A resonantly-enhanced photon-regeneration experiment to search for the axion or axion-like particles is discussed. Photons enter a strong magnetic field and some are converted to axions; the axions can pass through an opaque wall and some may convert back to photons in a second high-field region. The photon regeneration is enhanced by employing matched Fabry-Perot optical cavities, with one cavity within the axion generation magnet and the second within the photon regeneration magnet. The optics for this experiment are discussed, with emphasis on the alignment of the two cavities.

  5. Plasmon resonance enhanced multicolour photodetection by graphene

    PubMed Central

    Liu, Yuan; Cheng, Rui; Liao, Lei; Zhou, Hailong; Bai, Jingwei; Liu, Gang; Liu, Lixin; Huang, Yu; Duan, Xiangfeng

    2012-01-01

    Graphene has the potential for high-speed, wide-band photodetection, but only with very low external quantum efficiency and no spectral selectivity. Here we report a dramatic enhancement of the overall quantum efficiency and spectral selectivity that enables multicolour photodetection, by coupling graphene with plasmonic nanostructures. We show that metallic plasmonic nanostructures can be integrated with graphene photodetectors to greatly enhance the photocurrent and external quantum efficiency by up to 1,500%. Plasmonic nanostructures of variable resonance frequencies selectively amplify the photoresponse of graphene to light of different wavelengths, enabling highly specific detection of multicolours. Being atomically thin, graphene photodetectors effectively exploit the local plasmonic enhancement effect to achieve a significant enhancement factor not normally possible with traditional planar semiconductor materials. PMID:22146398

  6. Enhanced reaction rates in NDP analysis with neutron scattering

    SciTech Connect

    Downing, R. Gregory

    2014-04-15

    Neutron depth profiling (NDP) makes accessible quantitative information on a few isotopic concentration profiles ranging from the surface into the sample a few micrometers. Because the candidate analytes for NDP are few, there is little interference encountered. Furthermore, neutrons have no charge so mixed chemical states in the sample are of no direct concern. There are a few nuclides that exhibit large probabilities for neutron scattering. The effect of neutron scattering on NDP measurements has not previously been evaluated as a basis for either enhancing the reaction rates or as a source of measurement error. Hydrogen is a common element exhibiting large neutron scattering probability found in or around sample volumes being analyzed by NDP. A systematic study was conducted to determine the degree of signal change when neutron scattering occurs during analysis. The relative signal perturbation was evaluated for materials of varied neutron scattering probability, concentration, total mass, and geometry. Signal enhancements up to 50% are observed when the hydrogen density is high and in close proximity to the region of analysis with neutron beams of sub thermal energies. Greater signal enhancements for the same neutron number density are reported for thermal neutron beams. Even adhesive tape used to position the sample produces a measureable signal enhancement. Because of the shallow volume, negligible distortion of the NDP measured profile shape is encountered from neutron scattering.

  7. Epithermal neutron formation for boron neutron capture therapy by adiabatic resonance crossing concept

    NASA Astrophysics Data System (ADS)

    Khorshidi, A.; Ghafoori-Fard, H.; Sadeghi, M.

    2014-05-01

    Low-energy protons from the cyclotron in the range of 15-30 MeV and low current have been simulated on beryllium (Be) target with a lead moderator around the target. This research was accomplished to design an epithermal neutron beam for Boron Neutron Capture Therapy (BNCT) using the moderated neutron on the average produced from 9Be target via (p, xn) reaction in Adiabatic Resonance Crossing (ARC) concept. Generation of neutron to proton ratio, energy distribution, flux and dose components in head phantom have been simulated by MCNP5 code. The reflector and collimator were designed in prevention and collimation of derivation neutrons from proton bombarding. The scalp-skull-brain phantom consisting of bone and brain equivalent material has been simulated in order to evaluate the dosimetric effect on the brain. Results of this analysis demonstrated while the proton energy decreased, the dose factor altered according to filters thickness. The maximum epithermal flux revealed using fluental, Fe and bismuth (Bi) filters with thicknesses of 9.4, 3 and 2 cm, respectively and also the epithermal to thermal neutron flux ratio was 103.85. The potential of the ARC method to replace or complement the current reactor-based supply sources of BNCT purposes.

  8. Extracting Neutron Structure Functions in the Resonance Region

    SciTech Connect

    Yonatan Kahn

    2009-07-01

    A new iterative method is presented for extracting neutron structure functions from inclusive structure functions of nuclei, focusing specifically on the resonance region. Unlike earlier approaches, this method is applicable to both spin-averaged and spin-dependent structure functions. We show that in numerical tests, this method is able to reproduce known input functions of nearly arbitrary shape after only 5–10 iterations. We illustrate the method on extractions of F2n and g1,2n from data, and discuss the treatment of systematic errors from this extraction procedure.

  9. Cyclotron line resonant transfer through neutron star atmospheres

    NASA Technical Reports Server (NTRS)

    Wang, John C. L.; Wasserman, Ira M.; Salpeter, Edwin E.

    1988-01-01

    Monte Carlo methods are used to study in detail the resonant radiative transfer of cyclotron line photons with recoil through a purely scattering neutron star atmosphere for both the polarized and unpolarized cases. For each case, the number of scatters, the path length traveled, the escape frequency shift, the escape direction cosine, the emergent frequency spectra, and the angular distribution of escaping photons are investigated. In the polarized case, transfer is calculated using both the cold plasma e- and o-modes and the magnetic vacuum perpendicular and parallel modes.

  10. Collinear Resonance Ionization Spectroscopy of Neutron-Deficient Francium Isotopes

    NASA Astrophysics Data System (ADS)

    Flanagan, K. T.; Lynch, K. M.; Billowes, J.; Bissell, M. L.; Budinčević, I.; Cocolios, T. E.; de Groote, R. P.; De Schepper, S.; Fedosseev, V. N.; Franchoo, S.; Garcia Ruiz, R. F.; Heylen, H.; Marsh, B. A.; Neyens, G.; Procter, T. J.; Rossel, R. E.; Rothe, S.; Strashnov, I.; Stroke, H. H.; Wendt, K. D. A.

    2013-11-01

    The magnetic moments and isotope shifts of the neutron-deficient francium isotopes Fr202-205 were measured at ISOLDE-CERN with use of collinear resonance ionization spectroscopy. A production-to-detection efficiency of 1% was measured for Fr202. The background from nonresonant and collisional ionization was maintained below one ion in 105 beam particles. Through a comparison of the measured charge radii with predictions from the spherical droplet model, it is concluded that the ground-state wave function remains spherical down to Fr205, with a departure observed in Fr203 (N=116).

  11. Collinear resonance ionization spectroscopy of neutron-deficient francium isotopes.

    PubMed

    Flanagan, K T; Lynch, K M; Billowes, J; Bissell, M L; Budinčević, I; Cocolios, T E; de Groote, R P; De Schepper, S; Fedosseev, V N; Franchoo, S; Garcia Ruiz, R F; Heylen, H; Marsh, B A; Neyens, G; Procter, T J; Rossel, R E; Rothe, S; Strashnov, I; Stroke, H H; Wendt, K D A

    2013-11-22

    The magnetic moments and isotope shifts of the neutron-deficient francium isotopes (202-205)Fr were measured at ISOLDE-CERN with use of collinear resonance ionization spectroscopy. A production-to-detection efficiency of 1% was measured for (202)Fr. The background from nonresonant and collisional ionization was maintained below one ion in 10(5) beam particles. Through a comparison of the measured charge radii with predictions from the spherical droplet model, it is concluded that the ground-state wave function remains spherical down to (205)Fr, with a departure observed in (203)Fr (N=116). PMID:24313482

  12. Enhancement of artificial magnetism via resonant bianisotropy

    PubMed Central

    Markovich, Dmitry; Baryshnikova, Kseniia; Shalin, Alexander; Samusev, Anton; Krasnok, Alexander; Belov, Pavel; Ginzburg, Pavel

    2016-01-01

    All-dielectric “magnetic light” nanophotonics based on high refractive index nanoparticles allows controlling magnetic component of light at nanoscale without having high dissipative losses. The artificial magnetic optical response of such nanoparticles originates from circular displacement currents excited inside those structures and strongly depends on geometry and dispersion of optical materials. Here an approach for enhancing of magnetic response via resonant bianisotropy effect is proposed and analyzed. The key mechanism of enhancement is based on electric-magnetic interaction between two electrically and magnetically resonant nanoparticles of all-dielectric dimer. It was shown that proper geometrical arrangement of the dimer in respect to the incident illumination direction allows flexible control over all vectorial components of the magnetic moment, tailoring the latter in the dynamical range of 100% and delivering enhancement up to 36% relative to performances of standalone spherical particles. The proposed approach provides pathways for designs of all-dielectric metamaterials and metasurfaces with strong magnetic responses. PMID:26941126

  13. Anisotropic Elastic Resonance Scattering model for the Neutron Transport equation

    SciTech Connect

    Mohamed Ouisloumen; Abderrafi M. Ougouag; Shadi Z. Ghrayeb

    2014-11-24

    The resonance scattering transfer cross-section has been reformulated to account for anisotropic scattering in the center-of-mass of the neutron-nucleus system. The main innovation over previous implementations is the relaxation of the ubiquitous assumption of isotropic scattering in the center-of-mass and the actual effective use of scattering angle distributions from evaluated nuclear data files in the computation of the angular moments of the resonant scattering kernels. The formulas for the high order anisotropic moments in the laboratory system are also derived. A multi-group numerical formulation is derived and implemented into a module incorporated within the NJOY nuclear data processing code. An ultra-fine energy mesh cross section library was generated using these new theoretical models and then was used for fuel assembly calculations with the PARAGON lattice physics code. The results obtained indicate a strong effect of this new model on reactivity, multi-group fluxes and isotopic inventory during depletion.

  14. Scissors mode of Gd nuclei studied from resonance neutron capture

    SciTech Connect

    Kroll, J.; Baramsai, B.; Becker, J. A.; and others

    2012-10-20

    Spectra of {gamma} rays following the neutron capture at isolated resonances of stable Gd nuclei were measured. The objectives were to get new information on photon strength of {sup 153,155-159}Gd with emphasis on the role of the M1 scissors-mode vibration. An analysis of the data obtained clearly indicates that the scissors mode is coupled not only to the ground state, but also to all excited levels of the nuclei studied. The specificity of our approach ensures unbiasedness in estimating the sumed scissors-mode strength {Sigma}B(M1){up_arrow}, even for odd product nuclei, for which conventional nuclear resonance fluorescence measurements yield only limited information. Our analysis indicates that for these nuclei the sum {Sigma}B(M1){up_arrow} increases with A and for {sup 157,159}Gd it is significantly higher compared to {sup 156,158}Gd.

  15. Phonon Properties of Materials from Neutron Resonance Doppler Broadening Measurements

    NASA Astrophysics Data System (ADS)

    Eric Lynn, J.

    2002-12-01

    At low temperatures the Doppler broadened widths of neutron resonances are strongly affected by the phonon characteristics of the material used for making the cross-section measurement. The Doppler width can be expressed in terms of the moments of the phonon spectrum carried by the atomic species with the resonant cross-section. Cross-section measurements made with tungsten and tantalum metals are reviewed here and compared with phonon information obtained by other methods. Applications of the method to a plutonium-gallium alloy and to some lanthanum barium cuprates are described briefly. We discuss possible extensions of the technique and how an epithermal flight path at the SNS may be advantageous.

  16. Resonantly enhanced four-wave mixing

    DOEpatents

    Begley, Richard F.; Kurnit, Norman A.

    1978-01-01

    A method and apparatus for achieving large susceptibilities and long interaction lengths in the generation of new wavelengths in the infrared spectral region. A process of resonantly enhanced four-wave mixing is employed, utilizing existing laser sources, such as the CO.sub.2 laser, to irradiate a gaseous media. The gaseous media, comprising NH.sub.3, CH.sub.3 F, D.sub.2, HCl, HF, CO, and H.sub.2 or some combination thereof, are of particular interest since they are capable of providing high repetition rate operation at high flux densities where crystal damage problems become a limitation.

  17. Space Time Reversal Experiment by Use of Pulsed Neutron Ramsey Resonance

    SciTech Connect

    Masuda, Y.; Jeong, S. C.; Watanabe, Y.; Skoy, V.; Ino, T.

    2007-06-13

    We have developed a pulsed neutron Ramsey resonance for a T-violation experiment on polarized neutron transmission through a polarized nuclear target. Two separated oscillatory fields were placed in a pulsed neutron beam line, which were synchronized with a neutron pulse for precision neutron spin manipulation. We observed neutron Larmor precession between the two oscillatory fields as a function of a neutron time of flight (TOF). We modulated the phase of the second oscillatory field with respect to the first oscillatory field. The effect of the phase modulation was found in a neutron intensity modulation as a function of the TOF. From the neutron intensity modulation, the neutron spin direction as well as the neutron velocity between the two oscillatory fields was precisely obtained.

  18. Resonant cavity enhanced multi-analyte sensing

    NASA Astrophysics Data System (ADS)

    Bergstein, David Alan

    Biological research and medicine increasingly depend on interrogating binding interactions among small segments of DNA, RNA, protein, and bio-specific small molecules. Microarray technology, which senses the affinity for target molecules in solution for a multiplicity of capturing agents fixed to a surface, has been used in biological research for gene expression profiling and in medicine for molecular biomarker detection. Label-free affinity sensing is preferable as it avoids fluorescent labeling of the target molecules, reducing test cost and variability. The Resonant Cavity Imaging Biosensor (RCIB) is a label-free optical inference based technique introduced that scales readily to high throughput and employs an optical resonant cavity to enhance sensitivity by a factor of 100 or more. Near-infrared light centered at 1512.5 nm couples resonantly through a cavity constructed from Si/SiO2 Bragg reflectors, one of which serves as the binding surface. As the wavelength is swept 5 nm, an Indium-Gallium-Arsenide digital camera monitors cavity transmittance at each pixel with resolution 128 x 128. A wavelength shift in the local resonant response of the optical cavity indicates binding. Positioning the sensing surface with respect to the standing wave pattern of the electric field within the cavity, one can control the sensitivity of the measurement to the presence of bound molecules thereby enhancing or suppressing sensitivity where appropriate. Transmitted intensity at thousands of pixel locations are recorded simultaneously in a 10 s, 5 nm scan. An initial proof-of-principle setup was constructed. A sample was fabricated with 25, 100 mum wide square regions, each with a different density of 1 mum square depressions etched 12 nm into the S1O 2 surface. The average depth of each etched region was found with 0.05 nm RMS precision when the sample remains loaded in the setup and 0.3 nm RMS precision when the sample is removed and replaced. Selective binding of the protein

  19. Monte Carlo Code System for Calculation of Multiple Scattering of Neutrons in the Resonance Region.

    Energy Science and Technology Software Center (ESTSC)

    1983-01-25

    Version 00 MCRTOF systematically calculates capture and scattering probabilities for neutrons incident on a material disk, with neutron cross sections calculated from the resonance parameters. Capture, front and rear face scattering, transmission, etc., probabilities are obtained from the average destinations of the incident neutrons.

  20. Ultra high resolution neutron scattering: Neutron Resonance Spin-Echo and Larmor Diffraction

    NASA Astrophysics Data System (ADS)

    Walters, Andrew; Keller, Thomas; Keimer, Bernhard

    2012-02-01

    The TRISP spectrometer at the FRM II neutron source near Munich, Germany, is a unique world-leading neutron scattering instrument which employs the Neutron Resonance Spin-Echo technique (NRSE). Linewidths of dispersive excitations with energy transfers up to 50 meV can be measured with an energy resolution in the μeV range without the restrictive flux limitations that normally apply to high resolution neutron triple-axis spectrometers. Pioneering studies on the electron-phonon interaction in elemental superconductorsootnotetextP. Aynajian et al., Science 319 1509 (2008) and the lifetimes of magnetic excitations in archetypal magnetic systems will be reviewed.ootnotetextS. Bayrakci et al., Science 312 1928 (2006) The instrument can also be used as a Larmor diffractometer, enabling d-spacings to be measured with a resolution of δdd ˜10-6, i.e. more than one order of magnitude more sensitive than conventional diffraction techniques.ootnotetextC. Pfleiderer et al., Science 316 1871 (2007) Ongoing and future NRSE and Larmor diffraction projects will be outlined, especially in regard to prospective studies which will take full advantage of the new low temperature and high pressure sample environment capabilities now available at TRISP.

  1. Enhancing the Detector for Advanced Neutron Capture Experiments

    NASA Astrophysics Data System (ADS)

    Couture, A.; Mosby, S.; Baramsai, B.; Bredeweg, T. A.; Jandel, M.; Macon, K.; O'Donnell, J. M.; Rusev, G.; Taddeucci, T. N.; Ullmann, J. L.; Walker, C. L.

    2015-05-01

    The Detector for Advanced Neutron Capture Experiments (DANCE) has been used for extensive studies of neutron capture, gamma decay, photon strength functions, and prompt and delayed fission-gamma emission. Despite these successes, the potential measurements have been limited by the data acquisition hardware. We report on a major upgrade of the DANCE data acquisition that simultaneously enables strait-forward coupling to auxiliary detectors, including high-resolution high-purity germanium detectors and neutron tagging array. The upgrade will enhance the time domain accessible for time-of-flight neutron measurements as well as improve the resolution in the DANCE barium fluoride crystals for photons.

  2. Enhancing the detector for advanced neutron capture experiments

    DOE PAGESBeta

    Couture, A.; Mosby, S.; Baramsai, B.; Bredeweg, T. A.; Jandel, M.; Macon, K.; O’Donnell, J. M.; Rusev, G.; Taddeucci, T. N; Ullmann, J. L.; et al

    2015-05-28

    The Detector for Advanced Neutron Capture Experiments (DANCE) has been used for extensive studies of neutron capture, gamma decay, photon strength functions, and prompt and delayed fission-gamma emission. Despite these successes, the potential measurements have been limited by the data acquisition hardware. We report on a major upgrade of the DANCE data acquisition that simultaneously enables strait-forward coupling to auxiliary detectors, including high-resolution high-purity germanium detectors and neutron tagging array. The upgrade will enhance the time domain accessible for time-of-flight neutron measurements as well as improve the resolution in the DANCE barium fluoride crystals for photons.

  3. Spoof localized surface plasmons on ultrathin textured MIM ring resonator with enhanced resonances.

    PubMed

    Zhou, Yong Jin; Xiao, Qian Xun; Yang, Bao Jia

    2015-01-01

    We numerically demonstrate that spoof localized surface plasmons (LSPs) resonant modes can be enhanced based on ultrathin corrugated metal-insulator-metal (MIM) ring resonator. Further enhancement of the LSPs modes has been achieved by incorporating an efficient and ease-of-integration exciting method. Quality factors of resonance peaks have become much larger and multipolar resonances modes can be easily observed on the textured MIM ring resonator excited by a microstrip line. Experimental results validate the high-efficiency excitation and resonance enhancements of spoof LSPs modes on the MIM ring resonator in the microwave frequencies. We have shown that the fabricated resonator is sensitive to the variation of both the dielectric constant and the thickness of surrounding materials under test. The spoof plasmonic resonator can be used as key elements to provide many important device functionalities such as optical communications, signal processing, and spectral engineering in the plasmonic integration platform. PMID:26420668

  4. Spoof localized surface plasmons on ultrathin textured MIM ring resonator with enhanced resonances

    PubMed Central

    Zhou, Yong Jin; Xiao, Qian Xun; Jia Yang, Bao

    2015-01-01

    We numerically demonstrate that spoof localized surface plasmons (LSPs) resonant modes can be enhanced based on ultrathin corrugated metal-insulator-metal (MIM) ring resonator. Further enhancement of the LSPs modes has been achieved by incorporating an efficient and ease-of-integration exciting method. Quality factors of resonance peaks have become much larger and multipolar resonances modes can be easily observed on the textured MIM ring resonator excited by a microstrip line. Experimental results validate the high-efficiency excitation and resonance enhancements of spoof LSPs modes on the MIM ring resonator in the microwave frequencies. We have shown that the fabricated resonator is sensitive to the variation of both the dielectric constant and the thickness of surrounding materials under test. The spoof plasmonic resonator can be used as key elements to provide many important device functionalities such as optical communications, signal processing, and spectral engineering in the plasmonic integration platform. PMID:26420668

  5. Antiferromagnetic resonance excitation by terahertz magnetic field resonantly enhanced with split ring resonator

    SciTech Connect

    Mukai, Y.; Hirori, H.; Yamamoto, T.; Kageyama, H.; Tanaka, K.

    2014-07-14

    Excitation of antiferromagnetic resonance (AFMR) in a HoFeO{sub 3} crystal combined with a split ring resonator (SRR) is studied using terahertz (THz) electromagnetic pulses. The magnetic field in the vicinity of the SRR is induced by the incident THz electric field component and excites spin oscillations that correspond to the AFMR, which are directly probed by the Faraday rotation of the polarization of a near-infrared probe pulse. The good agreement of the temperature-dependent magnetization dynamics with the calculation using the two-lattice Landau-Lifshitz-Gilbert equation confirms that the AFMR is excited by the THz magnetic field, which is enhanced at the SRR resonance frequency by a factor of 20 compared to the incident magnetic field.

  6. Reconstruction of Material Elemental Composition Using Fast Neutron Resonance Radiography

    NASA Astrophysics Data System (ADS)

    Mor, Ilan; Dangendorf, Volker; Reginatto, Marcel; Kaufmann, Frank; Vartsky, David; Brandis, Michal; Bar, Doron; Goldberg, Mark B.

    Fast neutron resonance radiography (FNRR) is an imaging method that exploits characteristic cross-section structures (peaks and troughs) of certainelements in the energy-range of 1-10 MeV to identify materials in a large volume object. In FNRR, the neutron energy spectrum transmitted through an object carries information about the elemental composition of thatobject. The principal elements present in most explosives are: carbon, oxygen, nitrogen andhydrogen. Explosives are characterized by high fractions of nitrogen and oxygen as well as low fractions of carbon and hydrogencompared to benign materials. Detection of explosives in cargo employing FNRRis based on determination of the local areal densities of these four elements and their ratios. In our measurements, the transmission spectrum is usually divided in 100 - 500 energy bins, representing 100 - 500 linear equations containing four unknown areal densities of HCNO. This is an overdetermined problem, which allows us to derive not only the fourexpectation values of their areal densitiesbut theirprobability distribution as well. For this purpose, a model was formulated and implemented within a software package which performs Bayesian analysis of complex statistical models using Markov chain Monte-Carlo (MCMC). This model was tested successfully both on simulated and experimental data. This work will describe the model and the outcome of elemental ratios reconstruction for several materials from experimental data.

  7. Film adhesive enhances neutron radiographic images

    NASA Technical Reports Server (NTRS)

    Reed, M. W.

    1978-01-01

    Resolution of neutron radiographic images of thermally conductive film is increased by replacing approximately 5 percent of aluminum powder, which provides thermal conductivity, with gadolinium oxide. Oxide is also chemically stable.

  8. Neutron decay of 15C resonances by measurements of neutron time-of-flight

    NASA Astrophysics Data System (ADS)

    Cavallaro, M.; Agodi, C.; Assié, M.; Azaiez, F.; Cappuzzello, F.; Carbone, D.; de Séréville, N.; Foti, A.; Pandola, L.; Scarpaci, J. A.; Sgouros, O.; Soukeras, V.; Tropea, S.

    2016-06-01

    The neutron decay of the resonant states of light neutron-rich nuclei is an important and poorly explored property, useful to extract valuable nuclear structure information. In the present paper the neutron decay of the 15C resonances populated via the two-neutron transfer reaction 13C(18O,16On ) at 84-MeV incident energy is reported for the first time using an innovative technique which couples the MAGNEX magnetic spectrometer and the EDEN neutron detector array. Experimental data show that the resonances below the one-neutron emission threshold decay to the 14C ground state via one-neutron emission with an almost 100 % total branching ratio, whereas the recently observed 15C giant pairing vibration at 13.7 MeV mainly decays via two-neutron emission.

  9. Neutron absorbers and detector types for spent fuel verification using the self-interrogation neutron resonance densitometry

    NASA Astrophysics Data System (ADS)

    Rossa, Riccardo; Borella, Alessandro; Labeau, Pierre-Etienne; Pauly, Nicolas; van der Meer, Klaas

    2015-08-01

    The Self-Interrogation Neutron Resonance Densitometry (SINRD) is a passive non-destructive assay (NDA) technique that is proposed for the direct measurement of 239Pu in a spent fuel assembly. The insertion of neutron detectors wrapped with different neutron absorbing materials, or neutron filters, in the central guide tube of a PWR fuel assembly is envisaged to measure the neutron flux in the energy region close to the 0.3 eV resonance of 239Pu. In addition, the measurement of the fast neutron flux is foreseen. This paper is focused on the determination of the Gd and Cd neutron filters thickness to maximize the detection of neutrons within the resonance region. Moreover, several detector types are compared to identify the optimal condition and to assess the expected total neutron counts that can be obtained with the SINRD measurements. Results from Monte Carlo simulations showed that ranges between 0.1-0.3 mm and 0.5-1.0 mm ensure the optimal conditions for the Gd and Cd filters, respectively. Moreover, a 239Pu fission chamber is better suited to measure neutrons close to the 0.3 eV resonance and it has the highest sensitivity to 239Pu, in comparison with a 235U fission chamber, with a 3He proportional counter, and with a 10B proportional counter. The use of a thin Gd filter and a thick Cd filter is suggested for the 239Pu and 235U fission chambers to increase the total counts achieved in a measurement, while a thick Gd filter and a thin Cd filter are envisaged for the 3He and 10B proportional counters to increase the sensitivity to 239Pu. We concluded that an optimization process that takes into account measurement time, filters thickness, and detector size is needed to develop a SINRD detector that can meet the requirement for an efficient verification of spent fuel assemblies.

  10. Enhancing Neutron Beam Production with a Convoluted Moderator

    SciTech Connect

    Iverson, Erik B; Baxter, David V; Muhrer, Guenter; Ansell, Stuart; Gallmeier, Franz X; Dalgliesh, Robert; Lu, Wei; Kaiser, Helmut

    2014-10-01

    We describe a new concept for a neutron moderating assembly resulting in the more efficient production of slow neutron beams. The Convoluted Moderator, a heterogeneous stack of interleaved moderating material and nearly transparent single-crystal spacers, is a directionally-enhanced neutron beam source, improving beam effectiveness over an angular range comparable to the range accepted by neutron beam lines and guides. We have demonstrated gains of 50% in slow neutron intensity for a given fast neutron production rate while simultaneously reducing the wavelength-dependent emission time dispersion by 25%, both coming from a geometric effect in which the neutron beam lines view a large surface area of moderating material in a relatively small volume. Additionally, we have confirmed a Bragg-enhancement effect arising from coherent scattering within the single-crystal spacers. We have not observed hypothesized refractive effects leading to additional gains at long wavelength. In addition to confirmation of the validity of the Convoluted Moderator concept, our measurements provide a series of benchmark experiments suitable for developing simulation and analysis techniques for practical optimization and eventual implementation at slow neutron source facilities.

  11. Array enhanced stochastic resonance: Implications for signal processing

    SciTech Connect

    Inchiosa, M.E.; Bulsara, A.R.; Lindner, J.F.; Meadows, B.K.; Ditto, W.L.

    1996-06-01

    In computer simulations, we enhance the response of a {open_quote}{open_quote}stochastic resonator{close_quote}{close_quote} by coupling it into an array of identical resonators. We relate this array enhanced stochastic resonance (AESR) to the global spatiotemporal dynamics of the array and show how noise and coupling cooperate to organize spatial order, temporal periodicity, and peak output signal-to-noise ratio. We consider the application of AESR to signal processing. {copyright} {ital 1996 American Institute of Physics.}

  12. Enhanced neutron imaging detector using optical processing

    SciTech Connect

    Hutchinson, D.P.; McElhaney, S.A.

    1992-08-01

    Existing neutron imaging detectors have limited count rates due to inherent property and electronic limitations. The popular multiwire proportional counter is qualified by gas recombination to a count rate of less than 10{sup 5} n/s over the entire array and the neutron Anger camera, even though improved with new fiber optic encoding methods, can only achieve 10{sup 6} cps over a limited array. We present a preliminary design for a new type of neutron imaging detector with a resolution of 2--5 mm and a count rate capability of 10{sup 6} cps pixel element. We propose to combine optical and electronic processing to economically increase the throughput of advanced detector systems while simplifying computing requirements. By placing a scintillator screen ahead of an optical image processor followed by a detector array, a high throughput imaging detector may be constructed.

  13. Neutron strength functions: the link between resolved resonances and the optical model

    SciTech Connect

    Moldauer, P.A.

    1980-01-01

    Neutron strength functions and scattering radii are useful as energy and channel radius independent parameters that characterize neutron scattering resonances and provide a connection between R-matrix resonance analysis and the optical model. The choice of R-matrix channel radii is discussed, as are limitations on the accuracies of strength functions. New definitions of the p-wave strength function and scattering radius are proposed. For light nuclei, where strength functions display optical model energy variations over the resolved resonances, a doubly reduced partial neutron width is introduced for more meaningful statistical analyses of widths. The systematic behavior of strength functions and scattering radii is discussed.

  14. Overhauser-enhanced magnetic resonance elastography.

    PubMed

    Salameh, Najat; Sarracanie, Mathieu; Armstrong, Brandon D; Rosen, Matthew S; Comment, Arnaud

    2016-05-01

    Magnetic resonance elastography (MRE) is a powerful technique to assess the mechanical properties of living tissue. However, it suffers from reduced sensitivity in regions with short T2 and T2 * such as in tissue with high concentrations of paramagnetic iron, or in regions surrounding implanted devices. In this work, we exploit the longer T2 * attainable at ultra-low magnetic fields in combination with Overhauser dynamic nuclear polarization (DNP) to enable rapid MRE at 0.0065 T. A 3D balanced steady-state free precession based MRE sequence with undersampling and fractional encoding was implemented on a 0.0065 T MRI scanner. A custom-built RF coil for DNP and a programmable vibration system for elastography were developed. Displacement fields and stiffness maps were reconstructed from data recorded in a polyvinyl alcohol gel phantom loaded with stable nitroxide radicals. A DNP enhancement of 25 was achieved during the MRE sequence, allowing the acquisition of 3D Overhauser-enhanced MRE (OMRE) images with (1.5 × 2.7 × 9) mm(3) resolution over eight temporal steps and 11 slices in 6 minutes. In conclusion, OMRE at ultra-low magnetic field can be used to detect mechanical waves over short acquisition times. This new modality shows promise to broaden the scope of conventional MRE applications, and may extend the utility of low-cost, portable MRI systems to detect elasticity changes in patients with implanted devices or iron overload. Copyright © 2016 John Wiley & Sons, Ltd. PMID:26915977

  15. SUGGEL: A Program Suggesting the Orbital Angular Momentum of a Neutron Resonance from the Magnitude of its Neutron Width

    SciTech Connect

    Oh, S.Y.

    2001-02-02

    The SUGGEL computer code has been developed to suggest a value for the orbital angular momentum of a neutron resonance that is consistent with the magnitude of its neutron width. The suggestion is based on the probability that a resonance having a certain value of g{Gamma}{sub n} is an l-wave resonance. The probability is calculated by using Bayes' theorem on the conditional probability. The probability density functions (pdf's) of g{Gamma}{sub n} for up to d-wave (l=2) have been derived from the {chi}{sup 2} distribution of Porter and Thomas. The pdf's take two possible channel spins into account. This code is a tool which evaluators will use to construct resonance parameters and help to assign resonance spin. The use of this tool is expected to reduce time and effort in the evaluation procedure, since the number of repeated runs of the fitting code (e.g., SAMMY) may be reduced.

  16. Magnetic symmetries in neutron and resonant x-ray Bragg diffraction patterns of four iridium oxides

    NASA Astrophysics Data System (ADS)

    Lovesey, S. W.; Khalyavin, D. D.; Manuel, P.; Chapon, L. C.; Cao, G.; Qi, T. F.

    2012-12-01

    The magnetic properties of Sr2IrO4, Na2IrO3, Sr3Ir2O7 and CaIrO3 are discussed, principally in the light of experimental data in recent literature for Bragg intensities measured in x-ray diffraction with enhancement at iridium L-absorption edges. The electronic structure factors we report, which incorporate parity-even and acentric entities, serve the immediate purpose of making full use of crystal and magnetic symmetry to refine our knowledge of the magnetic properties of the four iridates from resonant x-ray diffraction data. They also offer a platform on which to interpret future investigations, using dichroic signals, resonant x-ray diffraction and neutron diffraction, for example, as well as ab initio calculations of electronic structure. Unit-cell structure factors, suitable for x-ray Bragg diffraction enhanced by an electric dipole-electric dipole (E1-E1) event, reveal exactly which iridium multipoles are visible, e.g., a magnetic dipole parallel to the crystal c-axis (z-axis) and an electric quadrupole with yz-like symmetry in the specific case of CaIrO3. Magnetic space-groups are assigned to Sr2IrO4, Sr3Ir2O7 and CaIrO3, namely, PIcca, PAban and Cm‧cm‧, respectively, in the Belov-Neronova-Smirnova notation. The assignment for Sr2IrO4 is possible because of our new high-resolution neutron diffraction data, gathered on a powder sample. In addition, the new data are used to show that the ordered magnetic moment of an Ir4+ ion in Sr2IrO4 does not exceed 0.29(4) μB. Na2IrO3 has two candidate magnetic space-groups that are not resolved with currently available resonant x-ray data.

  17. Supernova matter at subnuclear densities as a resonant Fermi gas: enhancement of neutrino rates.

    PubMed

    Bartl, A; Pethick, C J; Schwenk, A

    2014-08-22

    At low energies nucleon-nucleon interactions are resonant and therefore supernova matter at subnuclear densities has many similarities to atomic gases with interactions dominated by a Feshbach resonance. We calculate the rates of neutrino processes involving nucleon-nucleon collisions and show that these are enhanced in mixtures of neutrons and protons at subnuclear densities due to the large scattering lengths. As a result, the rate for neutrino pair bremsstrahlung and absorption is significantly larger below 10(13) g cm(-3) compared to rates used in supernova simulations. PMID:25192083

  18. Ultraviolet Resonant Raman Enhancements in the Detection of Explosives

    SciTech Connect

    Short Jr., Billy Joe

    2009-06-01

    Raman-based spectroscopy is potentially militarily useful for standoff detection of high explosives. Normal (non-resonance) and resonance Raman spectroscopies are both light scattering techniques that use a laser to measure the vibrational spectrum of a sample. In resonance Raman, the laser is tuned to match the wavelength of a strong electronic absorbance in the molecule of interest, whereas, in normal Raman the laser is not tuned to any strong electronic absorbance bands. The selection of appropriate excitation wavelengths in resonance Raman can result in a dramatic increase in the Raman scattering efficiency of select band(s) associated with the electronic transition. Other than the excitation wavelength, however, resonance Raman is performed experimentally the same as normal Raman. In these studies, normal and resonance Raman spectral signatures of select solid high explosive (HE) samples and explosive precursors were collected at 785 nm, 244 nm and 229 nm. Solutions of PETN, TNT, and explosive precursors (DNT & PNT) in acetonitrile solvent as an internal Raman standard were quantitatively evaluated using ultraviolet resonance Raman (UVRR) microscopy and normal Raman spectroscopy as a function of power and select excitation wavelengths. Use of an internal standard allowed resonance enhancements to be estimated at 229 nm and 244 nm. Investigations demonstrated that UVRR provided ~2000-fold enhancement at 244 nm and ~800-fold improvement at 229 nm while PETN showed a maximum of ~25-fold at 244 nm and ~190-fold enhancement at 229 nm solely from resonance effects when compared to normal Raman measurements. In addition to the observed resonance enhancements, additional Raman signal enhancements are obtained with ultraviolet excitation (i.e., Raman scattering scales as !4 for measurements based on scattered photons). A model, based partly on the resonance Raman enhancement results for HE solutions, is presented for estimating Raman enhancements for solid HE samples.

  19. Experimental evaluation of the twofold electromagnetic enhancement theory of surface-enhanced resonance Raman scattering

    SciTech Connect

    Yoshida, Ken-ichi; Itoh, Tamitake; Biju, Vasudevanpillai; Ishikawa, Mitsuru; Ozaki, Yukihiro

    2009-02-15

    We examined an electromagnetic (EM) theory of surface-enhanced resonance Raman scattering (SERRS) using single Ag nanoaggregates. The SERRS-EM theory is characterized by twofold EM enhancement induced by the coupling of plasmon resonance with both excitation and emission of Raman scattering plus fluorescence. The total emission cross-section spectra of enhanced Raman scattering and enhanced fluorescence were calculated using the following parameters: the spectrum of enhancement factor induced by plasmon resonance, resonance Raman scattering overlapped with fluorescence, and excitation wavelengths. The calculations well agreed with experimental total emission cross-section spectra, thus providing strong indications that the SERRS-EM theory is quantitatively correct.

  20. A neutron resonance capture analysis experimental station at the ISIS spallation source.

    PubMed

    Pietropaolo, Antonino; Gorini, Giuseppe; Festa, Giulia; Reali, Enzo; Grazzi, Francesco; Schooneveld, Erik M

    2010-09-01

    Neutron resonance capture analysis (NRCA) is a nuclear technique that is used to determine the elemental composition of materials and artifacts (e.g., bronze objects) of archaeological interest. NRCA experiments are mostly performed at the GELINA facility in Belgium, a pulsed neutron source operating with an electron linear accelerator. Very intense fluxes of epithermal neutrons are also provided by spallation neutron sources, such as the ISIS spallation neutron source in the United Kingdom. In the present study, the suitability of the Italian Neutron Experimental Station (INES) beam line for NRCA measurements is assessed using a compact (n, γ) resonance detector made of a Yttrium-Aluminum-Perovskite (YAP) scintillation crystal coupled with a silicon photomultiplier (SiPM) readout. The measurements provided a qualitative recognition of the composition of the standard sample, a lower limit for the sensitivity for NRCA for almost-in-traces elements, and an estimation of the relative isotopic concentration in the sample. PMID:20828445

  1. LETTER TO THE EDITOR: Enhancement of neutron radiation dose by the addition of sulphur-33 atoms

    NASA Astrophysics Data System (ADS)

    Porras, I.

    2008-04-01

    The use of neutrons in radiotherapy allows the possibility of producing nuclear reactions in a specific target inserted in the medium. 10B is being used to induce reactions (n, α), a technique called boron neutron capture therapy. I have studied the possibility of inducing a similar reaction using the nucleus of 33S, for which the reaction cross section presents resonances for keV neutrons, the highest peak occurring at 13.5 keV. Here shown, by means of Monte Carlo simulation of point-like sources of neutrons in this energy range, is an enhancement effect on the absorbed dose in water by the addition of 33S atoms. In addition to this, as the range of the alpha particle is of the order of a mammalian cell size, the energy deposition via this reaction results mainly inside the cells adjacent to the interaction site. The main conclusion of the present work is that the insertion of these sulphur atoms in tumoral cells would enhance the effect of neutron irradiation in the keV range.

  2. Using the {delta}{sub 3} statistic to test for missed levels in neutron resonance data

    SciTech Connect

    Mulhall, Declan

    2009-03-31

    The {delta}{sub 3}(L) statistic is studied as a possible tool to detect missing levels in the neutron resonance data of odd-A nuclei. A {delta}{sub 3}(L) analysis of neutron resonance data is compared with the results of a maximum likelihood method applied to the level spacing distribution. The {delta}{sub 3}(L) statistic compares favorably with the level spacing distribution as a tool to gauge the completeness of the data.

  3. Tailored Asymmetry for Enhanced Coupling to WGM Resonators

    NASA Technical Reports Server (NTRS)

    Mohageg, Makan; Maleki, Lute

    2008-01-01

    Coupling of light into and out of whispering- gallery-mode (WGM) optical resonators can be enhanced by designing and fabricating the resonators to have certain non-axisymmetric shapes (see figure). Such WGM resonators also exhibit the same ultrahigh values of the resonance quality factor (Q) as do prior WGM resonators. These WGM resonators are potentially useful as tunable narrow-band optical filters having throughput levels near unity, high-speed optical switches, and low-threshold laser resonators. These WGM resonators could also be used in experiments to investigate coupling between high-Q and chaotic modes within the resonators. For a WGM resonator made of an optically nonlinear material (e.g., lithium niobate) or another material having a high index of refraction, a prism made of a material having a higher index of refraction (e.g., diamond) must be used as part of the coupling optics. For coupling of a beam of light into (or out of) the high-Q resonator modes, the beam must be made to approach (or recede from) the resonator at a critical angle determined by the indices of refraction of the resonator and prism materials. In the case of a lithium niobate/diamond interface, this angle is approximately 22 .

  4. Resonance Analysis and Evaluation of the Uranium -235 Neutron-Induced Cross-Sections

    NASA Astrophysics Data System (ADS)

    Leal, Luiz Carlos

    Neutron cross sections of fissile nuclei are of considerable interest for the understanding of parameters such as resonance absorption, resonance escape probability, resonance self-shielding, and the dependence of the reactivity on temperature. In the present study, new techniques for the evaluation of the ^{235}U neutron cross sections are described. The Reich-Moore formalism of the Bayesian computer code SAMMY was used to perform consistent R-matrix multilevel analyses of the selected neutron cross-section data. The Delta_3 -statistics of Dyson and Mehta, along with high -resolution data and the spin-separated fission cross-section data, have provided the possibility of developing a new methodology for the analysis and evaluation of neutron -nucleus cross-sections. The result of the analysis consists of a set of resonance parameters which describe the ^{235}U neutron cross sections up to 500 eV. The set of resonance parameters obtained through a R-matrix analysis are expected to satisfy statistical properties which lead to information on the nuclear structure. The resonance parameters were tested and showed good agreement with the theory. It is expected that the parametrization of the ^{235}U neutron cross sections obtained in this dissertation represents the current state of art in data as well as in theory and, therefore, can be of direct use in reactor calculations.

  5. Design of a boron neutron capture enhanced fast neutron therapy assembly

    NASA Astrophysics Data System (ADS)

    Wang, Zhonglu

    The use of boron neutron capture to boost tumor dose in fast neutron therapy has been investigated at several fast neutron therapy centers worldwide. This treatment is termed boron neutron capture enhanced fast neutron therapy (BNCEFNT). It is a combination of boron neutron capture therapy (BNCT) and fast neutron therapy (FNT). It is believed that BNCEFNT may be useful in the treatment of some radioresistant brain tumors, such as glioblastoma multiforme (GBM). A boron neutron capture enhanced fast neutron therapy assembly has been designed for the Fermilab Neutron Therapy Facility (NTF). This assembly uses a tungsten filter and collimator near the patient's head, with a graphite reflector surrounding the head to significantly increase the dose due to boron neutron capture reactions. The assembly was designed using Monte Carlo radiation transport code MCNP version 5 for a standard 20x20 cm2 treatment beam. The calculated boron dose enhancement at 5.7-cm depth in a water-filled head phantom in the assembly with a 5x5 cm2 collimation was 21.9% per 100-ppm 10B for a 5.0-cm tungsten filter and 29.8% for a 8.5-cm tungsten filter. The corresponding dose rate for the 5.0-cm and 8.5-cm thick filters were 0.221 and 0.127 Gy/min, respectively; about 48.5% and 27.9% of the dose rate of the standard 10x10 cm2 fast neutron treatment beam. To validate the design calculations, a simplified BNCEFNT assembly was built using four lead bricks to form a 5x5 cm2 collimator. Five 1.0-cm thick 20x20 cm2 tungsten plates were used to obtain different filter thicknesses and graphite bricks/blocks were used to form a reflector. Measurements of the dose enhancement of the simplified assembly in a water-filled head phantom were performed using a pair of tissue-equivalent ion chambers. One of the ion chambers is loaded with 1000-ppm natural boron (184-ppm 10B) to measure dose due to boron neutron capture. The measured dose enhancement at 5.0-cm depth in the head phantom for the 5.0-cm thick

  6. Design of a boron neutron capture enhanced fast neutron therapy assembly

    SciTech Connect

    Wang, Zhonglu

    2006-08-01

    The use of boron neutron capture to boost tumor dose in fast neutron therapy has been investigated at several fast neutron therapy centers worldwide. This treatment is termed boron neutron capture enhanced fast neutron therapy (BNCEFNT). It is a combination of boron neutron capture therapy (BNCT) and fast neutron therapy (FNT). It is believed that BNCEFNT may be useful in the treatment of some radioresistant brain tumors, such as glioblastoma multiform (GBM). A boron neutron capture enhanced fast neutron therapy assembly has been designed for the Fermilab Neutron Therapy Facility (NTF). This assembly uses a tungsten filter and collimator near the patient's head, with a graphite reflector surrounding the head to significantly increase the dose due to boron neutron capture reactions. The assembly was designed using Monte Carlo radiation transport code MCNP version 5 for a standard 20x20 cm{sup 2} treatment beam. The calculated boron dose enhancement at 5.7-cm depth in a water-filled head phantom in the assembly with a 5x5 cm{sup 2} collimation was 21.9% per 100-ppm {sup 10}B for a 5.0-cm tungsten filter and 29.8% for a 8.5-cm tungsten filter. The corresponding dose rate for the 5.0-cm and 8.5-cm thick filters were 0.221 and 0.127 Gy/min, respectively; about 48.5% and 27.9% of the dose rate of the standard 10x10 cm{sup 2} fast neutron treatment beam. To validate the design calculations, a simplified BNCEFNT assembly was built using four lead bricks to form a 5x5 cm{sup 2} collimator. Five 1.0-cm thick 20x20 cm{sup 2} tungsten plates were used to obtain different filter thicknesses and graphite bricks/blocks were used to form a reflector. Measurements of the dose enhancement of the simplified assembly in a water-filled head phantom were performed using a pair of tissue-equivalent ion chambers. One of the ion chambers is loaded with 1000-ppm natural boron (184-ppm {sup 10}B) to measure dose due to boron neutron capture. The measured dose enhancement at 5.0-cm depth in

  7. Neutron resonances in the compound nucleus: Parity nonconservation to dynamic temperature measurements

    SciTech Connect

    Yuan, V.W.

    1997-08-01

    Experiments using epithermal neutrons that interact to form compound-nuclear resonances serve a wide range of scientific applications. Changes in transmission which are correlated to polarization reversal in incident neutrons have been used to study parity nonconservation in the compound nucleus for a wide range of targets. The ensemble of measured parity asymmetries provides statistical information for the extraction of the rms parity-violating mean-square matrix element as a function of mass. Parity nonconservation in neutron resonances can also be used to determine the polarization of neutron beams. Finally the motion of target atoms results in an observed temperature-dependent Doppler broadening of resonance line widths. This broadening can be used to determine temperatures on a fast time scale of one microsecond or less.

  8. Subwavelength resonant antennas enhancing electromagnetic energy harvesting

    NASA Astrophysics Data System (ADS)

    Oumbe Tekam, Gabin; Ginis, Vincent; Seetharamdoo, Divitha; Danckaert, Jan

    2016-04-01

    In this work, an electromagnetic energy harvester operating at microwave frequencies is designed based on a cut- wire metasurface. This metamaterial is known to contain a quasistatic electric dipole resonator leading to a strong resonant electric response when illuminated by electromagnetic fields.1 Starting from an equivalent electrical circuit, we analytically design the parameters of the system to tune the resonance frequency of the harvester at the desired frequency band. Subsequently, we compare these results with numerical simulations, which have been obtained using finite elements numerical simulations. Finally, we optimize the design by investigating the best arrangement for energy harvesting by coupling in parallel and in series many single layers of cut-wire metasurfaces. We also discuss the implementation of different geometries and sizes of the cut-wire metasurface for achieving different center frequencies and bandwidths.

  9. Investigating Prompt Fission Neutron Emission from 235U(n,f) in the Resolved Resonance Region

    NASA Astrophysics Data System (ADS)

    Göök, Alf; Hambsch, Franz-Josef; Oberstedt, Stephan

    2016-03-01

    Investigations of prompt emission in fission is of importance in understanding the fission process in general and the sharing of excitation energy among the fission fragments in particular. Experimental activities at IRMM on prompt neutron emission from fission in response to OECD/NEA nuclear data requests is presented in this contribution. Main focus lies on currently on-going investigations of prompt neutron emission from the reaction 235U(n,f) in the region of the resolved resonances. For this reaction strong fluctuations of fission fragment mass distributions and mean total kinetic energy have been observed [Nucl. Phys. A 491, 56 (1989)] as a function of incident neutron energy in the resonance region. In addition fluctuations of prompt neutron multiplicities were also observed [Phys. Rev. C 13, 195 (1976)]. The goal of the present study is to verify the current knowledge of prompt neutron multiplicity fluctuations and to study correlations with fission fragment properties.

  10. Neutron Induced Capture Reaction Studies in the Resonance Region at GELINA

    SciTech Connect

    Schillebeeckx, Peter; Borella, A.; Kopecky, S.; Mihailescu, L. C.; Siegler, P.; Sirakov, I.; Massimi, C.; Moxon, M.; Ware, T.

    2009-01-28

    The neutron time-of-flight facility GELINA installed at the IRMM Geel (B) has been designed to study neutron-induced reactions in the resonance region. It is a multi-user facility, providing a pulsed white neutron source, with a neutron energy range between 10 meV and 20 MeV and a time resolution of 1 ns. The research program concentrates on cross section data needs for nuclear energy applications. In this paper efforts to improve the quality of cross section data for neutron induced capture reactions in the resolved and unresolved resonance region are presented together with examples of cross section data to support the development of advanced reactor concepts and to optimize the use of present nuclear power plants.

  11. Neutron Cross Section Processing Methods for Improved Integral Benchmarking of Unresolved Resonance Region Evaluations

    NASA Astrophysics Data System (ADS)

    Walsh, Jonathan A.; Forget, Benoit; Smith, Kord S.; Brown, Forrest B.

    2016-03-01

    In this work we describe the development and application of computational methods for processing neutron cross section data in the unresolved resonance region (URR). These methods are integrated with a continuous-energy Monte Carlo neutron transport code, thereby enabling their use in high-fidelity analyses. Enhanced understanding of the effects of URR evaluation representations on calculated results is then obtained through utilization of the methods in Monte Carlo integral benchmark simulations of fast spectrum critical assemblies. First, we present a so-called on-the-fly (OTF) method for calculating and Doppler broadening URR cross sections. This method proceeds directly from ENDF-6 average unresolved resonance parameters and, thus, eliminates any need for a probability table generation pre-processing step in which tables are constructed at several energies for all desired temperatures. Significant memory reduction may be realized with the OTF method relative to a probability table treatment if many temperatures are needed. Next, we examine the effects of using a multi-level resonance formalism for resonance reconstruction in the URR. A comparison of results obtained by using the same stochastically-generated realization of resonance parameters in both the single-level Breit-Wigner (SLBW) and multi-level Breit-Wigner (MLBW) formalisms allows for the quantification of level-level interference effects on integrated tallies such as keff and energy group reaction rates. Though, as is well-known, cross section values at any given incident energy may differ significantly between single-level and multi-level formulations, the observed effects on integral results are minimal in this investigation. Finally, we demonstrate the calculation of true expected values, and the statistical spread of those values, through independent Monte Carlo simulations, each using an independent realization of URR cross section structure throughout. It is observed that both probability table

  12. Second harmonic generation and enhancement in microfibers and loop resonators

    NASA Astrophysics Data System (ADS)

    Gouveia, Marcelo A.; Lee, Timothy; Ismaeel, Rand; Ding, Ming; Broderick, Neil G. R.; Cordeiro, Cristiano M. B.; Brambilla, Gilberto

    2013-05-01

    We model and experimentally investigate second harmonic generation in silica microfibers and loop resonators, in which the second order nonlinearity arises from the glass-air surface dipole and bulk multipole contributions. In the loop resonator, the recirculation of the pump light on resonance is used to increase the conversion. The effect of the loop parameters, such as coupling and loss, is theoretically studied to determine their influence on the resonance enhancement. Experimentally, microfibers were fabricated with diameters around 0.7 μm to generate the intermodally phase matched second harmonic with an efficiency up to 4.2 × 10-8 when pumped with 5 ns 1.55 μm pulses with a peak power of 90 W. After reconfiguring the microfiber into a 1 mm diameter loop, the efficiency was resonantly enhanced by 5.7 times.

  13. Resonant enhancement of Raman scattering in metamaterials with hybrid electromagnetic and plasmonic resonances

    NASA Astrophysics Data System (ADS)

    Guddala, Sriram; Narayana Rao, D.; Ramakrishna, S. Anantha

    2016-06-01

    A tri-layer metamaterial perfect absorber of light, consisting of (Al/ZnS/Al) films with the top aluminum layer patterned as an array of circular disk nanoantennas, is investigated for resonantly enhancing Raman scattering from C60 fullerene molecules deposited on the metamaterial. The metamaterial is designed to have resonant bands due to plasmonic and electromagnetic resonances at the Raman pump frequency (725 nm) as well as Stokes emission bands. The Raman scattering from C60 on the metamaterial with resonantly matched bands is measured to be enhanced by an order of magnitude more than C60 on metamaterials with off-resonant absorption bands peaking at 1090 nm. The Raman pump is significantly enhanced due to the resonance with a propagating surface plasmon band, while the highly impedance-matched electromagnetic resonance is expected to couple out the Raman emission efficiently. The nature and hybridization of the plasmonic and electromagnetic resonances to form compound resonances are investigated by numerical simulations.

  14. Isotopic molybdenum total neutron cross section in the unresolved resonance region

    SciTech Connect

    Bahran, R.; Barry, D.; Block, R.; Leinweber, G.; Rapp, M.; Daskalakis, A.; Blain, E.; Williams, D.; McDermott, B.; Leal, L.; Danon, Y.

    2015-08-04

    Accurate isotopic molybdenum nuclear data are important because molybdenum can exist in nuclear reactor components including fuel, cladding, or as a high yield fission product. High-resolution time-of-flight neutron transmission measurements on highly enriched isotopic metallic samples of 95Mo, 96Mo, 98Mo, and 100Mo were performed in the resonance energy range from 1 to 620 keV. The measurements were taken with the newly developed modular 6Li-glass transmission detector positioned at the 100-m experimental flight station. For the unresolved energy region (URR), new comprehensive methods of analysis were developed and validated in order to obtain accurate neutron total cross-section data from the measurement by correcting for background and transmission enhancement effects. Average parameters and fits to the total cross section for 95Mo were obtained using the Hauser-Feshbach statistical model code FITACS, which is currently incorporated into the SAMMY code. Moreover, fits to the experimental data deviate from the current evaluated nuclear data file/B-VII.1 isotopic Mo evaluations by several percent in the URR.

  15. Isotopic molybdenum total neutron cross section in the unresolved resonance region

    DOE PAGESBeta

    Bahran, R.; Barry, D.; Block, R.; Leinweber, G.; Rapp, M.; Daskalakis, A.; Blain, E.; Williams, D.; McDermott, B.; Leal, L.; et al

    2015-08-04

    Accurate isotopic molybdenum nuclear data are important because molybdenum can exist in nuclear reactor components including fuel, cladding, or as a high yield fission product. High-resolution time-of-flight neutron transmission measurements on highly enriched isotopic metallic samples of 95Mo, 96Mo, 98Mo, and 100Mo were performed in the resonance energy range from 1 to 620 keV. The measurements were taken with the newly developed modular 6Li-glass transmission detector positioned at the 100-m experimental flight station. For the unresolved energy region (URR), new comprehensive methods of analysis were developed and validated in order to obtain accurate neutron total cross-section data from the measurementmore » by correcting for background and transmission enhancement effects. Average parameters and fits to the total cross section for 95Mo were obtained using the Hauser-Feshbach statistical model code FITACS, which is currently incorporated into the SAMMY code. Moreover, fits to the experimental data deviate from the current evaluated nuclear data file/B-VII.1 isotopic Mo evaluations by several percent in the URR.« less

  16. Isotopic molybdenum total neutron cross section in the unresolved resonance region

    NASA Astrophysics Data System (ADS)

    Bahran, R.; Barry, D.; Block, R.; Leinweber, G.; Rapp, M.; Daskalakis, A.; Blain, E.; Williams, D.; McDermott, B.; Leal, L.; Danon, Y.

    2015-08-01

    Accurate isotopic molybdenum nuclear data are important because molybdenum can exist in nuclear reactor components including fuel, cladding, or as a high yield fission product. High-resolution time-of-flight neutron transmission measurements on highly enriched isotopic metallic samples of 95Mo , 96Mo , 98Mo , and 100Mo were performed in the resonance energy range from 1 to 620 keV . The measurements were taken with the newly developed modular 6Li -glass transmission detector positioned at the 100-m experimental flight station. In the unresolved energy region (URR), new comprehensive methods of analysis were developed and validated in order to obtain accurate neutron total cross-section data from the measurement by correcting for background and transmission enhancement effects. Average parameters and fits to the total cross section for 95Mo were obtained using the Hauser-Feshbach statistical model code fitacs, which is currently incorporated into the sammy code. The fits to the experimental data deviate from the current evaluated nuclear data file/B-VII.1 isotopic Mo evaluations by several percent in the URR.

  17. Resonant Raman scattering from silicon nanoparticles enhanced by magnetic response.

    PubMed

    Dmitriev, Pavel A; Baranov, Denis G; Milichko, Valentin A; Makarov, Sergey V; Mukhin, Ivan S; Samusev, Anton K; Krasnok, Alexander E; Belov, Pavel A; Kivshar, Yuri S

    2016-05-01

    Enhancement of optical response with high-index dielectric nanoparticles is attributed to the excitation of their Mie-type magnetic and electric resonances. Here we study Raman scattering from crystalline silicon nanoparticles and reveal that magnetic dipole modes have a much stronger effect on the scattering than electric modes of the same order. We demonstrate experimentally a 140-fold enhancement of the Raman signal from individual silicon spherical nanoparticles at the magnetic dipole resonance. Our results confirm the importance of the optically-induced magnetic response of subwavelength dielectric nanoparticles for enhancing light-matter interactions. PMID:27113352

  18. Enhanced vibrational energy harvesting using nonlinear stochastic resonance

    NASA Astrophysics Data System (ADS)

    McInnes, C. R.; Gorman, D. G.; Cartmell, M. P.

    2008-12-01

    Stochastic resonance has seen wide application in the physical sciences as a tool to understand weak signal amplification by noise. However, this apparently counter-intuitive phenomenon does not appear to have been exploited as a tool to enhance vibrational energy harvesting. In this note we demonstrate that by adding periodic forcing to a vibrationally excited energy harvesting mechanism, the power available from the device is apparently enhanced over a mechanism without periodic forcing. In order to illustrate this novel effect, a conceptually simple, but plausible model of such a device is proposed to explore the use of stochastic resonance to enhance vibrational energy harvesting.

  19. Neutron unbound resonances cataloged by isotope and invariant mass measurements for nuclei Z = 1-12

    NASA Astrophysics Data System (ADS)

    Havens, Elizabeth; Finck, Joseph; Gueye, Paul; Thoennessen, Michael; MoNA Collaboration

    2015-10-01

    Prior to 2014, no comprehensive study had been undertaken to compile experimental results from neutron unbound spectroscopy using invariant mass measurements, gamma resolutions and half-lives. Through the collaborative efforts of Central Michigan University, Hampton University and the NSCL, a project was initiated to catalog all unbound resonances in light nuclei (Z = 1-12). Unbound resonances were characterized by having a confirmed neutron decay branch and/or an energy level greater than the neutron binding energy listed for that isotope, according to either the NNDC's ENSDF or XUNDL and the referred journals therein. This was initially compiled in July 2014 and presented in October of that year. Recent discoveries and updates to NNDC have added ten isotopes and their resonances. Additionally, various corrections to previously compiled resonances have been made and equivalent evaluated and unevaluated invariant mass measurements have been consolidated into single entries. The neutron separation energy is noted for each isotope. The isotopes in which unbound resonances occur have been identified and, if known, each unbound resonance's gamma resolution, half-life, method of production and journal reference were also determined.

  20. Some Nuclear Techniques in Experimental Magnetism: Mössbauer Effect, Neutron Scattering and Nuclear Magnetic Resonance

    NASA Astrophysics Data System (ADS)

    Piecuch, Michel

    The goal of this chapter is to present three traditional methods for the study of magnetic properties : Mössbauer effect, neutron diffraction and nuclear magnetic resonance. It begins by recalling the basic properties of atomic nuclei and describing the hyperfine interactions between the nucleus and its surrounding. Then, the recoilless absorption of γ-rays by crystal, the Mössbauer effect is presented, we discuss the main parameters measured and show one example of application. Next we present neutron interactions with matter, the interaction of neutrons with the atomic nucleus and the interaction of the neutron magnetic moment with the magnetic moment of electrons. The use of polarized neutron and the inelastic scattering of neutrons are also discussed. The comparison between neutron experiments and synchrotron radiation techniques is briefly reviewed. One example of the use of neutron scattering in the domain of thin film magnetism is shown. Finally, we present the basic theory of nuclear magnetic resonance and one application of this technique to the study of Co/Cu multilayers.

  1. A Drabkin-type spin resonator as tunable neutron beam monochromator

    NASA Astrophysics Data System (ADS)

    Piegsa, F. M.; Ries, D.; Filges, U.; Hautle, P.

    2015-09-01

    A Drabkin-type spin resonator was designed and successfully implemented at the multi-purpose beam line BOA at the spallation neutron source SINQ at the Paul Scherrer Institute. The device selectively acts on the magnetic moment of neutrons within an adjustable velocity band and hence can be utilized as a tunable neutron beam monochromator. Several neutron time-of-flight (TOF) spectra have been recorded employing various settings in order to characterize its performance. In a first test application the velocity dependent transmission of a beryllium filter was determined. In addition, we demonstrate that using an exponential current distribution in the spin resonator coil the side-maxima in the TOF spectra usually associated with a Drabkin setup can be strongly suppressed.

  2. Neutron resonance spin flippers: Static coils manufactured by electrical discharge machining

    SciTech Connect

    Martin, N.; Kredler, L.; Häußler, W.; Wagner, J. N.; Dogu, M.; Fuchs, C.; Böni, P.

    2014-07-15

    Radiofrequency spin flippers (RFSF) are key elements of Neutron Resonance Spin Echo (NRSE) spectrometers, which allow performing controlled manipulations of the beam polarization. We report on the design and test of a new type of RFSF which originality lies in the new manufacturing technique for the static coil. The largely automated procedure ensures reproducible construction as well as an excellent homogeneity of the neutron magnetic resonance condition over the coil volume. Two salient features of this concept are the large neutron window and the closure of the coil by a μ-metal yoke which prevents field leakage outside of the coil volume. These properties are essential for working with large beams and enable new applications with coils tilted with respect to the beam axis such as neutron Larmor diffraction or the study of dispersive excitations by inelastic NRSE.

  3. Optimized {gamma}-Multiplicity Based Spin Assignments of s-Wave Neutron Resonances

    SciTech Connect

    Becvar, F.; Koehler, Paul Edward; Krticka, Milan; Mitchell, G. E.; Ullmann, J. L.

    2011-01-01

    The multiplicity of -ray emission following neutron capture at isolated resonances carries valuable information on the resonance spin. Several methods utilizing this information have been developed. The latest method was recently introduced for analyzing the data from time-of-flight measurements with 4 -calorimetric detection systems. The present paper describes a generalization of this method. The goal is the separation of the -emission yields belonging to the two neutron capturing state spins of isolated (or even unresolved) s-wave neutron resonances on targets with non-zero spin. The formalism for performing this separation is described and then tested on artificially generated data. This new method was applied to the -multiplicity data obtained for the 147Sm(n, )148Sm reaction using the DANCE detector system at the LANSCE facility at Los Alamos National Laboratory. The analyzing power of the upgraded method is supported by combined dicebox and geant4 simulations of the fluctuation properties of the multiplicity distributions.

  4. Primary gamma transitions in 173,174Yb in neutron capture at isolated resonances

    NASA Astrophysics Data System (ADS)

    Telezhnikov, S. A.; Granja, C.; Hiep, H. T.; Honzátko, J.; Králík, M.; Montero-Cabrera, M.-E.; Pospíšil, S.

    2005-12-01

    Gamma transitions in 174Yb were investigated in radiative neutron capture at 23 isolated and additional 7 partially resolved summed resonances of 173Yb. The time-of-flight technique was used on an enriched target at the IBR-30 reactor at JINR Dubna. A total of 77 primary gamma transitions are reported populating levels in 174Yb up to 2.8 MeV in the spin-parity range 1,2,3,4. Spin and parity assignments of neutron resonances and of populated levels are proposed. In addition to these results, seven primary gamma transitions in 173Yb were also observed from neutron capture at three isolated resonances of 172Yb.

  5. Thermoelectric effect enhanced by resonant states in graphene

    NASA Astrophysics Data System (ADS)

    Inglot, M.; Dyrdał, A.; Dugaev, V. K.; Barnaś, J.

    2015-03-01

    Thermoelectric effects in graphene are considered theoretically with particular attention paid to the role of resonant scattering on impurities. Using the T -matrix method we calculate the impurity resonant states and the momentum relaxation time due to scattering on impurities. The Boltzmann kinetic equation is used to determine the thermoelectric coefficients. It is shown that the resonant impurity states near the Fermi level give rise to a resonant enhancement of the Seebeck coefficient and figure of merit Z T . The Wiedemann-Franz ratio deviates from that known for ordinary metals, where this ratio is constant and equal to the Lorentz number. This deviation appears for small chemical potentials and in the vicinity of the resonant states. In the limit of a constant relaxation time, this ratio has been calculated analytically for μ =0 .

  6. Stochastic resonance enhanced by dichotomic noise in a bistable system

    SciTech Connect

    Rozenfeld, Robert; Neiman, Alexander; Schimansky-Geier, Lutz

    2000-09-01

    We study linear responses of a stochastic bistable system driven by dichotomic noise to a weak periodic signal. We show that the effect of stochastic resonance can be greatly enhanced in comparison with the conventional case when dichotomic forcing is absent, that is, both the signal-to-noise ratio and the spectral power amplification reach much greater values than in the standard stochastic resonance setup. (c) 2000 The American Physical Society.

  7. Resonant Raman scattering from silicon nanoparticles enhanced by magnetic response

    NASA Astrophysics Data System (ADS)

    Dmitriev, Pavel A.; Baranov, Denis G.; Milichko, Valentin A.; Makarov, Sergey V.; Mukhin, Ivan S.; Samusev, Anton K.; Krasnok, Alexander E.; Belov, Pavel A.; Kivshar, Yuri S.

    2016-05-01

    Enhancement of optical response with high-index dielectric nanoparticles is attributed to the excitation of their Mie-type magnetic and electric resonances. Here we study Raman scattering from crystalline silicon nanoparticles and reveal that magnetic dipole modes have a much stronger effect on the scattering than electric modes of the same order. We demonstrate experimentally a 140-fold enhancement of the Raman signal from individual silicon spherical nanoparticles at the magnetic dipole resonance. Our results confirm the importance of the optically-induced magnetic response of subwavelength dielectric nanoparticles for enhancing light-matter interactions.Enhancement of optical response with high-index dielectric nanoparticles is attributed to the excitation of their Mie-type magnetic and electric resonances. Here we study Raman scattering from crystalline silicon nanoparticles and reveal that magnetic dipole modes have a much stronger effect on the scattering than electric modes of the same order. We demonstrate experimentally a 140-fold enhancement of the Raman signal from individual silicon spherical nanoparticles at the magnetic dipole resonance. Our results confirm the importance of the optically-induced magnetic response of subwavelength dielectric nanoparticles for enhancing light-matter interactions. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr07965a

  8. Resonantly Enhanced Pair Production in a Simple Diatomic Model

    NASA Astrophysics Data System (ADS)

    Fillion-Gourdeau, François; Lorin, Emmanuel; Bandrauk, André D.

    2013-01-01

    A new mechanism for the production of electron-positron pairs from the interaction of a laser field and a fully ionized diatomic molecule in the tunneling regime is presented. When the laser field is turned off, the Dirac operator has resonances in both the positive and the negative energy continua while bound states are in the mass gap. When this system is immersed in a strong laser field, the resonances move in the complex energy plane: the negative energy resonances are pushed to higher energies while the bound states are Stark shifted [F. Fillion-Gourdeau , J. Phys. A 45, 215304 (2012)JPHAC50305-4470]. It is argued here that there is a pair production enhancement at the crossing of resonances by looking at a simple one-dimensional model: the nuclei are modeled simply by Dirac delta potential wells while the laser field is assumed to be static and of finite spatial extent. The average rate for the number of electron-positron pairs produced is evaluated and the results are compared to the one and zero nucleus cases. It is shown that positrons are produced by the resonantly enhanced pair production mechanism, which is analogous to the resonantly enhanced ionization of molecular physics. This phenomenon could be used to increase the number of pairs produced at low field strength, allowing the study of the Dirac vacuum.

  9. Enhancement of Spin-transfer torque switching via resonant tunneling

    SciTech Connect

    Chatterji, Niladri; Tulapurkar, Ashwin A.; Muralidharan, Bhaskaran

    2014-12-08

    We propose the use of resonant tunneling as a route to enhance the spin-transfer torque switching characteristics of magnetic tunnel junctions. The proposed device structure is a resonant tunneling magnetic tunnel junction based on a MgO-semiconductor heterostructure sandwiched between a fixed magnet and a free magnet. Using the non-equilibrium Green's function formalism coupled self consistently with the Landau-Lifshitz-Gilbert-Slonczewski equation, we demonstrate enhanced tunnel magneto-resistance characteristics as well as lower switching voltages in comparison with traditional trilayer devices. Two device designs based on MgO based heterostructures are presented, where the physics of resonant tunneling leads to an enhanced spin transfer torque thereby reducing the critical switching voltage by up to 44%. It is envisioned that the proof-of-concept presented here may lead to practical device designs via rigorous materials and interface studies.

  10. Pygmy dipole resonance as a constraint on the neutron skin of heavy nuclei

    SciTech Connect

    Piekarewicz, J.

    2006-04-15

    The isotopic dependence of the isovector Pygmy dipole response in tin is studied within the framework of the relativistic random-phase approximation. Regarded as an oscillation of the neutron skin against the isospin-symmetric core, the pygmy dipole resonance may place important constraints on the neutron skin of heavy nuclei and, as a result, on the equation of state of neutron-rich matter. The present study centers around two questions. First, is there a strong correlation between the development of a neutron skin and the emergence of low-energy isovector dipole strength? Second, could one use the recently measured Pygmy dipole resonance in {sup 130}Sn and {sup 132}Sn to discriminate among theoretical models? For the first question we found that although a strong correlation between the neutron skin and the Pygmy dipole resonance exists, a mild anticorrelation develops beyond {sup 120}Sn. The answer to the second question suggests that models with overly large neutron skins--and thus stiff symmetry energies--are in conflict with experiment.

  11. Neutron cross section covariances in the resonance region: 52Cr, 56Fe, 58Ni

    SciTech Connect

    Oblozinsky, P.; Cho, Y.-S.; Mattoon, C.M.; Mughabghab, S.F.

    2010-08-03

    We evaluated covariances for neutron capture and elastic scattering cross sections on major structural materials, {sup 52}Cr, {sup 56}Fe and {sup 58}Ni, in the resonance region which extends beyond 800 keV for each of them. Use was made of the recently developed covariance formalism based on kernel approximation along with data in the Atlas of Neutron Resonances. The data of most interest for AFCI applications, elastic scattering cross section uncertainties at energies above about few hundred keV, are on the level of about 12% for {sup 52}Cr, 7-8% for {sup 56}Fe and 5-6% for {sup 58}Ni.

  12. NEUTRON STARS WITH SMALL RADII-THE ROLE OF {Delta} RESONANCES

    SciTech Connect

    Schuerhoff, Torsten; Schramm, Stefan; Dexheimer, Veronica

    2010-11-20

    Recent neutron star observations suggest that the masses and radii of neutron stars may be smaller than previously considered, which would disfavor a purely nucleonic equation of state (EoS). In our model, we use a flavor SU(3) sigma model that includes {Delta} resonances and hyperons in the EoS. We find that if the coupling of the {Delta} resonances to the vector mesons is slightly smaller than that of the nucleons, we can reproduce both the measured mass-radius relationship and the extrapolated EoS.

  13. Dynamic neutron scattering on incoherent systems using efficient resonance spin flip techniques

    SciTech Connect

    Häussler, Wolfgang; Kredler, Lukas

    2014-05-15

    We have performed numerical ray-tracing Monte-Carlo-simulations of incoherent dynamic neutron scattering experiments. We intend to optimize the efficiency of incoherent measurements depending on the fraction of neutrons scattered without and with spin flip at the sample. In addition to conventional spin echo, we have numerically and experimentally studied oscillating intensity techniques. The results point out the advantages of these different spin echo variants and are an important prerequisite for neutron resonance spin echo instruments like RESEDA (FRM II, Munich), to choose the most efficient technique depending on the scattering vector range and the properties of the sample system under study.

  14. Prompt Gamma Emission in Resonance Neutron Induced Fission of 239Pu

    NASA Astrophysics Data System (ADS)

    Ruskov, I.; Kopatch, Yu. N.; Panteleev, Ts.; Skoy, V. R.; Shvetsov, V. N.; Dermendjiev, E.; Janeva, N.; Pikelner, L. B.; Grigoriev, Yu. V.; Mezentseva, Zh. V.; Ivanov, I.

    The scientific interest in the resonance neutron induced capture and fission reactions on 239Pu is continuously rising during the last decade. From a practical point of view, this is because more precise data on capture and fission cross sections, fission fragment mass and kinetic energy distributions, variation of prompt fission neutron and gamma yields in the resonance neutron region, are needed for the modelling of new generation nuclear power plants and for nuclear spent fuel and waste transmutation. From a heuristic and fundamental point of view, such a research improves our knowledge and understanding of the fission phenomena itself. To achieve these goals more powerful neutron sources and more precise fission product detectors have to be used. At the Joint Institute for Nuclear Research (JINR) Frank Laboratory of Neutron Physics (FLNP), where already half a century the thermal and resonance neutron induced nuclear reactions are studied, a new electron accelerator driven white spectrum pulsed neutron source IREN has been built and successfully tested. The improved characteristics of this facility, in comparison with those of the former pulse neutron fast reactor IBR-30, will allow measuring some of the neutron-nuclear reaction data with better precision and accuracy. A new experimental setup for detecting gamma rays (and neutrons) has been designed and is under construction. It will consist of 2 rings (arrays) of 12 NaI(Tl) detectors each (or 1 array of 24 detectors) with variable ring diameter and distance between both rings. Such a setup will make possible not only to measure the multiplicity, energy and angular anisotropy of prompt fission gammas, but also to separate the contribution of prompt fission neutrons by their longer time-of-flight from the fissile target to the detectors. The signals from all the 24 detectors will be recorded simultaneously in digitized form and will be stored on the hard disk of the personal computer for further off

  15. Measurement of neutron total cross-section and resonance parameters of xenon

    NASA Astrophysics Data System (ADS)

    Skoy, V. R.; Wang, T. F.; Kim, G. N.; Oh, Y. D.; Cho, M. H.; Ko, I. S.; Namkung, W.

    2009-07-01

    We measured the neutron total cross-sections of natural xenon in the neutron energy region from 0.1 to 40 eV by using the time-of-flight method at the Pohang neutron facility, which consists of an electron linear accelerator, a water-cooled tantalum target with a water moderator, and a 12-m long time-of-flight path. A 6Li-ZnS(Ag) scintillator with a diameter of 12.5 cm and a thickness of 1.6 cm was used as a neutron detector. Notch filters composed of Co, In, Cd were used to estimate the background level and to calculate the neutron flight path length. The present measurement was compared with the existing experimental and the evaluated data. The resonance parameters of Xe isotopes were obtained from the transmission ratio by using the SAMMY code and were compared with other previous results.

  16. Resonance neutron capture by Ne-(20, 22) in stellar environments

    NASA Astrophysics Data System (ADS)

    Winters, R. R.; Macklin, R. L.

    1988-06-01

    The neutron capture cross sections were measured over the neutron energy range 2.5-200 keV of Ne-(20, 22) at the Oak Ridge Electron Linear Accelerator using enriched samples at high pressures. The cross sections, averaged using a Maxwell-Boltzmann distribution weighting function for a range of temperatures thought to be appropriate for the sites of s-process stellar nucleosynthesis, are small. For example, the Maxwellian-averaged Ne-22(n, gamma) cross section for kT = 30 keV derived from the present work is smaller than 0.27 mbarn. This result increases the calculated net neutron production from Ne-22 by reducing the importance of Ne-22(n, gamma) as a neutron poison in s-process calculations. The number of neutrons per Fe-56 seed available for s-process stellar nucleosynthesis appears sufficient to account for the observed abundances of the s-elements for A in the range of 60-90.

  17. Roles of deformation and neutron excess on the giant monopole resonance in neutron-rich Zr isotopes

    SciTech Connect

    Yoshida, Kenichi

    2010-09-15

    We investigate the roles of deformation on the giant monopole resonance (GMR), particularly the mixing of the giant quadrupole resonance (GQR) and the effects of the neutron excess in the well-deformed nuclei around {sup 110}Zr and in the drip-line nuclei around {sup 140}Zr by means of the deformed quasiparticle-random-phase approximation employing the Skyrme and the local-pairing energy-density functionals. It is found that the isoscalar (IS) GMR has a two-peak structure, the lower peak of which is associated with the mixing between the ISGMR and the K{sup {pi}=}0{sup +} component of the ISGQR. The transition strength of the lower peak of the ISGMR grows as the neutron number increases. In the drip-line nuclei, the neutron excitation is dominant over the proton excitation. We find that for an isovector (IV) excitation the GMR has a four-peak structure due to the mixing of the IS and IV modes as well as the mixing of the K{sup {pi}=}0{sup +} component of the IVGQR. In addition to the GMR, we find that the threshold strength is generated by neutrons only.

  18. Production of tritium, neutrons, and heat based on the transmission resonance model (TRM) for cold fusion

    NASA Astrophysics Data System (ADS)

    Bush, Robert T.

    1991-05-01

    The TRM has recently been successful in fitting calorimetric data having interesting nonlinear structure. The model appears to provide a natural description for electrolytic cold fusion in terms of ``fractals''. Extended to the time dimension, the model can apparently account for the phenomenon of heat ``bursts''. The TRM combines a transmission condition involving quantized energies and an engergy shift of a Maxwell-Boltzmann energy distribution of deuterons at the cathodic surface that appears related to the concentration overpotential (hydrogen overvoltage). The model suggest three possible regimes vis-a-vis tritium production in terms of this energy shift, and indicates why measurable tritium production in the electrolytic case will tend to be the exception rather than the rule in absence of a recipe: Below a shift of approximately 2.8 meV there is production of both tritium and measureable excess heat, with the possibility of accounting for the Bockris curve indicating about a 1% correlation between excess heat and tritium. However, over the large range from about 2.8 meV to 340 meV energy shift there is a regime of observable excess heat production but little, and probably no measurable, tritium production. The third regime is more hypothetical: It begins at an energy shift of about 1 keV and extends to the boundaries of ``hot'' fusion at about 10 keV. A new type of nucelar reaction, trint (for transmission resonance-induced neutron transfer), is suggested by the model leading to triton and neutron production. A charge distribution ``polarization conjecture'' is the basis for theoretical derivation for the low-energy limit for an energy-dependent branching ratio for D-on-D. When the values of the parameters are inserted, this expression yields an estimate for the ratio of neutron-to-triton production of about 1.64×10-9. The possibility of some three-body reactions is also suggested. A comparison of the TRM's transmission energy levels for palladium deuteride

  19. Thermal neutron capture and resonance integral cross sections of 45Sc

    NASA Astrophysics Data System (ADS)

    Van Do, Nguyen; Duc Khue, Pham; Tien Thanh, Kim; Thi Hien, Nguyen; Kim, Guinyun; Kim, Kwangsoo; Shin, Sung-Gyun; Cho, Moo-Hyun; Lee, Manwoo

    2015-11-01

    The thermal neutron cross section (σ0) and resonance integral (I0) of the 45Sc(n,γ)46Sc reaction have been measured relative to that of the 197Au(n,γ)198Au reaction by means of the activation method. High-purity natural scandium and gold foils without and with a cadmium cover of 0.5 mm thickness were irradiated with moderated pulsed neutrons produced from the Pohang Neutron Facility (PNF). The induced activities in the activated foils were measured with a high purity germanium (HPGe) detector. In order to improve the accuracy of the experimental results the counting losses caused by the thermal (Gth) and resonance (Gepi) neutron self-shielding, the γ-ray attenuation (Fg) and the true γ-ray coincidence summing effects were made. In addition, the effect of non-ideal epithermal spectrum was also taken into account by determining the neutron spectrum shape factor (α). The thermal neutron cross-section and resonance integral of the 45Sc(n,γ)46Sc reaction have been determined relative to the reference values of the 197Au(n,γ)198Au reaction, with σo,Au = 98.65 ± 0.09 barn and Io,Au = 1550 ± 28 barn. The present thermal neutron cross section has been determined to be σo,Sc = 27.5 ± 0.8 barn. According to the definition of cadmium cut-off energy at 0.55 eV, the present resonance integral cross section has been determined to be Io,Sc = 12.4 ± 0.7 barn. The present results are compared with literature values and discussed.

  20. Manganese-Enhanced Magnetic Resonance Imaging (MEMRI)

    PubMed Central

    Massaad, Cynthia A.; Pautler, Robia G.

    2012-01-01

    The use of manganese ions (Mn2+) as an MRI contrast agent was introduced over 20 years ago in studies of Mn2+ toxicity in anesthetized rats (1). Manganese-enhanced MRI (MEMRI) evolved in the late nineties when Koretsky and associates pioneered the use of MEMRI for brain activity measurements (2) as well as neuronal tract tracing (3). Currently, MEMRI has three primary applications in biological systems: (1) contrast enhancement for anatomical detail, (2) activity-dependent assessment and (3) tracing of neuronal connections or tract tracing. MEMRI relies upon the following three main properties of Mn2+: (1) it is a paramagnetic ion that shortens the spin lattice relaxation time constant (T1) of tissues, where it accumulates and hence functions as an excellent T1 contrast agent; (2) it is a calcium (Ca2+) analog that can enter excitable cells, such as neurons and cardiac cells via voltage-gated Ca2+ channels; and (3) once in the cells Mn2+ can be transported along axons by microtubule-dependent axonal transport and can also cross synapses trans-synaptically to neighboring neurons. This chapter will emphasize the methodological approaches towards the use of MEMRI in biological systems. PMID:21279601

  1. Coupled Electromagnetic Resonators for Enhanced Communications and Telemetry

    NASA Technical Reports Server (NTRS)

    Dimmock, John O.

    2005-01-01

    Future NASA missions will require the collection of an increasing quantity and quality of data which, in turn, will place increasing demands on advanced sensors and advanced high bandwidth telemetry and communications systems. The capabilities of communication and telemetry systems depend, among other factors, on the stability, controllability and spectral purity of the carrier wave. These, in turn, depend on the quality of the oscillator, or resonator, or the Q of the system. Recent work on high Q optical resonators has indicated that the Q, or quality factor, of optical microsphere resonators can be substantially enhanced by coupling several such resonators together.1-3 In addition to the possibility of enhanced Q and increased energy storage capacity, the coupled optical resonators indicate that a wide variety of interesting and potentially useful phenomena such as induced transparency and interactive mode splitting can be observed depending critically on the morphology and configuration of the microresonators. The purpose of this SFFP has been to examine several different coupled electromagnetic oscillator configurations in order to evaluate their potential for enhanced electromagnetic communications.

  2. Enhancing Eu(3+) magnetic dipole emission by resonant plasmonic nanostructures.

    PubMed

    Hussain, Rabia; Kruk, Sergey S; Bonner, Carl E; Noginov, Mikhail A; Staude, Isabelle; Kivshar, Yuri S; Noginova, Natalia; Neshev, Dragomir N

    2015-04-15

    We demonstrate the enhancement of magnetic dipole spontaneous emission from Eu3+ ions by an engineered plasmonic nanostructure that controls the electromagnetic environment of the emitter. Using an optical microscope setup, an enhancement in the intensity of the Eu3+ magnetic dipole emission was observed for emitters located in close vicinity to a gold nanohole array designed to support plasmonic resonances overlapping with the emission spectrum of the ions. PMID:25872041

  3. Enhancement of polarizabilities of cylinders with cylinder-slab resonances.

    PubMed

    Xiao, Meng; Huang, Xueqin; Liu, H; Chan, C T

    2015-01-01

    If an object is very small in size compared with the wavelength of light, it does not scatter light efficiently. It is hence difficult to detect a very small object with light. We show using analytic theory as well as full wave numerical calculation that the effective polarizability of a small cylinder can be greatly enhanced by coupling it with a superlens type metamaterial slab. This kind of enhancement is not due to the individual resonance effect of the metamaterial slab, nor due to that of the object, but is caused by a collective resonant mode between the cylinder and the slab. We show that this type of particle-slab resonance which makes a small two-dimensional object much "brighter" is actually closely related to the reverse effect known in the literature as "cloaking by anomalous resonance" which can make a small cylinder undetectable. We also show that the enhancement of polarizability can lead to strongly enhanced electromagnetic forces that can be attractive or repulsive, depending on the material properties of the cylinder. PMID:25641391

  4. Multiple pulse resonantly enhanced laser plasma wakefield acceleration

    SciTech Connect

    Corner, L.; Walczak, R.; Nevay, L. J.; Dann, S.; Hooker, S. M.; Bourgeois, N.; Cowley, J.

    2012-12-21

    We present an outline of experiments being conducted at Oxford University on multiple-pulse, resonantly-enhanced laser plasma wakefield acceleration. This method of laser plasma acceleration uses trains of optimally spaced low energy short pulses to drive plasma oscillations and may enable laser plasma accelerators to be driven by compact and efficient fibre laser sources operating at high repetition rates.

  5. Distribution of total radiation widths for neutron resonances of Pt isotopes

    NASA Astrophysics Data System (ADS)

    Koehler, P. E.; Bečvář, F.; Krtička, M.

    2015-05-01

    High quality neutron capture and transmission data were measured on isotopically enriched 192,194,195,196Pt and natural Pt samples at ORELA. R-matrix analysis of this data revealed resonance parameters for 159, 413, 423, 258, and 11 neutron resonances for neutron energies below 5.0, 16.0, 7.5, 16.0, and 5.0 keV for 192,194,195,196,198Pt+n, respectively. Earlier analysis of data on reduced neutron widths, Γ0n, showed that the distributions of Γ0n for 192,194Pt deviate significantly from the Porter-Thomas distribution (PTD) predicted by random matrix theory. In this contribution we report on preliminary results of the analysis of distribution of total radiation widths, Γγ, in 192,194,195,196Pt+n reactions. Comparison of experimental data with predictions made within the nuclear statistical model indicates that standard models of Photon Strength Functions (PSFs) and Nuclear Level Density predict Γγ distributions which are too narrow. We found that satisfactory agreement between experimental and simulated distributions can be obtained only by a strong suppression of the PSFs at low γ-ray energies and/or by violation of the usual assumption that primary transitions from neutron resonances follow the PTD. The shape of PSFs needed for reproduction of our Γγ data also nicely reproduces spectra from several (n,γ) experiments on the neighbor nuclide 198Au.

  6. Cyclotron resonant scattering in gamma-ray bursts - Line strengths and signature of neutron star rotation

    NASA Technical Reports Server (NTRS)

    Lamb, D. Q.; Wang, J. C. L.; Wasserman, I.

    1992-01-01

    We explain the relative line strengths in gamma-ray bursts in terms of cyclotron resonant scattering. We describe the line signature of neutron star rotation and discuss the possibility that variations seen in the strengths and widths of the lines in GB780325 and GB870303 are due to rotation.

  7. Doubly-Resonant Fabry-Perot Cavity for Power Enhancement of Burst-Mode Picosecond Ultraviolet Pulses

    SciTech Connect

    Abudureyimu, Reheman; Huang, Chunning; Liu, Yun

    2015-01-01

    We report on a first experimental demonstration of locking a doubly-resonant Fabry-Perot cavity to burst-mode picosecond ultraviolet (UV) pulses by using a temperature controlled dispersion compensation method. This technique will eventually enable the intra cavity power enhancement of burst-mode 402.5MHz/50ps UV laser pulses with a MW level peak power required for the laser assisted H- beam stripping experiment at the Spallation Neutron Source.

  8. Neutron Resonance Parameters and Covariance Matrix of 239Pu

    SciTech Connect

    Derrien, Herve; Leal, Luiz C; Larson, Nancy M

    2008-08-01

    In order to obtain the resonance parameters in a single energy range and the corresponding covariance matrix, a reevaluation of 239Pu was performed with the code SAMMY. The most recent experimental data were analyzed or reanalyzed in the energy range thermal to 2.5 keV. The normalization of the fission cross section data was reconsidered by taking into account the most recent measurements of Weston et al. and Wagemans et al. A full resonance parameter covariance matrix was generated. The method used to obtain realistic uncertainties on the average cross section calculated by SAMMY or other processing codes was examined.

  9. Enhancing surface plasmon resonances of metallic nanoparticles by diatom biosilica.

    PubMed

    Ren, Fanghui; Campbell, Jeremy; Wang, Xiangyu; Rorrer, Gregory L; Wang, Alan X

    2013-07-01

    Diatoms are single-celled algaes that make photonic-crystal-like silica shells or frustules with hierarchical micro- & nano-scale features consisting of two-dimensional periodic pores. This article reports the use of diatom frustules as an integration platform to enhance localized surface plasmon resonances of self-assembled silver nanoparticles (NPs) on the surface of diatom frustules. Theoretical and experimental results show enhanced localized surface plasmons due to the coupling with the guided-mode resonances of the frustules. We observed 2 × stronger optical extinction and over 4 × higher sensitivity of surface-enhanced Raman scattering of Rhodmine 6G from the NPs-on-diatom than the NPs-on-glass structure. PMID:23842317

  10. Neutron Capture and Transmission Measurements and Resonance Parameter Analysis of Samarium

    SciTech Connect

    G. Leinweber; J.A. Burke; H.D. Knox; N.J. Drindak; D.W. Mesh; W.T. Haines; R.V. Ballad; R.C. Block; R.E. Slovacek; C.J. Werner; M.J. Trbovich; D.P. Barry; T. Sato

    2001-07-16

    The purpose of the present work is to accurately measure the neutron cross sections of samarium. The most significant isotope is {sup 149}Sm, which has a large neutron absorption cross section at thermal energies and is a {sup 235}U fission product with a 1% yield. Its cross sections are thus of concern to reactor neutronics. Neutron capture and transmission measurements were performed by the time-of-flight technique at the Rensselaer Polytechnic institute (RPI) LINAC facility using metallic and liquid Sm samples. The capture measurements were made at the 25 meter flight station with a multiplicity-type capture detector, and the transmission total cross-section measurements were performed at 15- and 25-meter flight stations with {sup 6}Li glass scintillation detectors. Resonance parameters were determined by a combined analysis of six experiments (three capture and three transmission) using the multi-level R-matrix Bayesian code SAMMY version M2. The significant features of this work are as follows. Dilute samples of samarium nitrate in deuterated water (D{sub 2}O) were prepared to measure the strong resonances at 0.1 and 8 eV without saturation. Disk-shaped spectroscopic quartz cells were obtained with parallel inner surfaces to provide a uniform thickness of solution. The diluent feature of the SAMMY program was used to analyze these data. The SAMMY program also includes multiple scattering corrections to capture yield data and resolution functions specific to the RPI facility. Resonance parameters for all stable isotopes of samarium were deduced for all resonances up to 30 eV. Thermal capture cross-section and capture resonance integral calculations were made using the resultant resonance parameters and were compared to results obtained using resonance parameters from ENDF/B-VI updated through release 3. Extending the definition of the capture resonance integral to include the strong 0.1 eV resonance in {sup 149}Sm, present measurements agree within estimated

  11. Plasmon resonance enhanced mechanical detection of ligand binding

    SciTech Connect

    Ariyaratne, Amila; Zocchi, Giovanni

    2015-01-05

    Small molecule binding to the active site of enzymes typically modifies the mechanical stiffness of the enzyme. We exploit this effect, in a setup which combines nano-mechanics and surface plasmon resonance (SPR) enhanced optics, for the label free detection of ligand binding to an enzyme. The large dynamic range of the signal allows to easily obtain binding curves for small ligands, in contrast to traditional SPR methods which rely on small changes in index of refraction. Enzyme mechanics, assessed by nano-rheology, thus emerges as an alternative to electronic and spin resonances, assessed by traditional spectroscopies, for detecting ligand binding.

  12. Neutron intensity modulation and time-focusing with integrated Larmor and resonant frequency techniques

    SciTech Connect

    Zhao, Jinkui Hamilton, William A.; Robertson, J. L.; Crow, Lowell; Lee, Sung-Woo; Kang, Yoon W.

    2015-09-14

    The analysis of neutron diffraction experiments often assumes that neutrons are elastically scattered from the sample. However, there is growing evidence that a significant fraction of the detected neutrons is in fact inelastically scattered, especially from soft materials and aqueous samples. Ignoring these inelastic contributions gives rise to inaccurate experimental results. To date, there has been no simple method with broad applicability for inelastic signal separation in neutron diffraction experiments. Here, we present a simple and robust method that we believe could be suited for this purpose. We use two radio frequency resonant spin flippers integrated with a Larmor precession field to modulate the neutron intensity and to encode the inelastic scattering information into the neutron data. All three components contribute to the spin encoding. The Larmor field serves several additional purposes. Its usage facilitates neutron time-focusing, eliminates the need for stringent magnetic shielding, and allows for compact setups. The scheme is robust, simple, and flexible. We believe that, with further improvements, it has the potential of adding inelastic signal discrimination capabilities to many existing diffraction instruments in the future.

  13. High yield neutron generator based on a high-current gasdynamic electron cyclotron resonance ion source

    NASA Astrophysics Data System (ADS)

    Skalyga, V.; Izotov, I.; Golubev, S.; Sidorov, A.; Razin, S.; Strelkov, A.; Tarvainen, O.; Koivisto, H.; Kalvas, T.

    2015-09-01

    In present paper, an approach for high yield compact D-D neutron generator based on a high current gasdynamic electron cyclotron resonance ion source is suggested. Results on dense pulsed deuteron beam production with current up to 500 mA and current density up to 750 mA/cm2 are demonstrated. Neutron yield from D2O and TiD2 targets was measured in case of its bombardment by pulsed 300 mA D+ beam with 45 keV energy. Neutron yield density at target surface of 109 s-1 cm-2 was detected with a system of two 3He proportional counters. Estimations based on obtained experimental results show that neutron yield from a high quality TiD2 target bombarded by D+ beam demonstrated in present work accelerated to 100 keV could reach 6 × 1010 s-1 cm-2. It is discussed that compact neutron generator with such characteristics could be perspective for a number of applications like boron neutron capture therapy, security systems based on neutron scanning, and neutronography.

  14. Neutron intensity modulation and time-focusing with integrated Larmor and resonant frequency techniques

    NASA Astrophysics Data System (ADS)

    Zhao, Jinkui; Hamilton, William A.; Lee, Sung-Woo; Robertson, J. L.; Crow, Lowell; Kang, Yoon W.

    2015-09-01

    The analysis of neutron diffraction experiments often assumes that neutrons are elastically scattered from the sample. However, there is growing evidence that a significant fraction of the detected neutrons is in fact inelastically scattered, especially from soft materials and aqueous samples. Ignoring these inelastic contributions gives rise to inaccurate experimental results. To date, there has been no simple method with broad applicability for inelastic signal separation in neutron diffraction experiments. Here, we present a simple and robust method that we believe could be suited for this purpose. We use two radio frequency resonant spin flippers integrated with a Larmor precession field to modulate the neutron intensity and to encode the inelastic scattering information into the neutron data. All three components contribute to the spin encoding. The Larmor field serves several additional purposes. Its usage facilitates neutron time-focusing, eliminates the need for stringent magnetic shielding, and allows for compact setups. The scheme is robust, simple, and flexible. We believe that, with further improvements, it has the potential of adding inelastic signal discrimination capabilities to many existing diffraction instruments in the future.

  15. High yield neutron generator based on a high-current gasdynamic electron cyclotron resonance ion source

    SciTech Connect

    Skalyga, V.; Sidorov, A.; Izotov, I.; Golubev, S.; Razin, S.; Strelkov, A.; Tarvainen, O.; Koivisto, H.; Kalvas, T.

    2015-09-07

    In present paper, an approach for high yield compact D-D neutron generator based on a high current gasdynamic electron cyclotron resonance ion source is suggested. Results on dense pulsed deuteron beam production with current up to 500 mA and current density up to 750 mA/cm{sup 2} are demonstrated. Neutron yield from D{sub 2}O and TiD{sub 2} targets was measured in case of its bombardment by pulsed 300 mA D{sup +} beam with 45 keV energy. Neutron yield density at target surface of 10{sup 9} s{sup −1} cm{sup −2} was detected with a system of two {sup 3}He proportional counters. Estimations based on obtained experimental results show that neutron yield from a high quality TiD{sub 2} target bombarded by D{sup +} beam demonstrated in present work accelerated to 100 keV could reach 6 × 10{sup 10} s{sup −1} cm{sup −2}. It is discussed that compact neutron generator with such characteristics could be perspective for a number of applications like boron neutron capture therapy, security systems based on neutron scanning, and neutronography.

  16. Enhancement of polarizabilities of cylinders with cylinder-slab resonances

    PubMed Central

    Xiao, Meng; Huang, Xueqin; Liu, H.; Chan, C. T.

    2015-01-01

    If an object is very small in size compared with the wavelength of light, it does not scatter light efficiently. It is hence difficult to detect a very small object with light. We show using analytic theory as well as full wave numerical calculation that the effective polarizability of a small cylinder can be greatly enhanced by coupling it with a superlens type metamaterial slab. This kind of enhancement is not due to the individual resonance effect of the metamaterial slab, nor due to that of the object, but is caused by a collective resonant mode between the cylinder and the slab. We show that this type of particle-slab resonance which makes a small two-dimensional object much “brighter” is actually closely related to the reverse effect known in the literature as “cloaking by anomalous resonance” which can make a small cylinder undetectable. We also show that the enhancement of polarizability can lead to strongly enhanced electromagnetic forces that can be attractive or repulsive, depending on the material properties of the cylinder. PMID:25641391

  17. Neutron Capture and Transmission Measurements and Resonance Parameter Analysis of Samarium

    SciTech Connect

    Leinweber, G.; Burke, J.A.; Knox, H.D.; Drindak, N.J.; Mesh, D.W.; Haines, W.T.; Ballad, R.V.; Block, R.C.; Slovacek, R.E.; Werner, C.J.; Trbovich, M.J.; Barry, D.P.; Sato, T.

    2002-09-15

    The purpose of the present work is to measure the neutron cross sections of samarium accurately. The most significant isotope is {sup 149}Sm, which has a large neutron absorption cross section at thermal energies and is a {sup 235}U fission product with a 1% yield. Its cross sections are thus of concern to reactor neutronics.Neutron capture and transmission measurements were performed by the time-of-flight technique at the Rensselaer Polytechnic Institute (RPI) LINAC facility using metallic and liquid Sm samples. The capture measurements were made at the 25-m flight station with a multiplicity-type capture detector, and the transmission total cross-section measurements were performed at 15- and 25-m flight stations with {sup 6}Li glass scintillation detectors. Resonance parameters were determined by a combined analysis of six experiments (three capture and three transmission) using the multilevel R-matrix Bayesian code SAMMY version M2.The significant features of this work are as follows. Dilute samples of samarium nitrate in deuterated water (D{sub 2}O) were prepared to measure the strong resonances at 0.1 and 8 eV without saturation. Disk-shaped spectroscopic quartz cells were obtained with parallel inner surfaces to provide a uniform thickness of solution. The diluent feature of the SAMMY program was used to analyze these data. The SAMMY program also includes multiple-scattering corrections to capture yield data and resolution functions specific to the RPI facility.Resonance parameters for all stable isotopes of samarium were deduced for all resonances up to 30 eV. Thermal capture cross-section and capture resonance integral (RI) calculations were made using the resultant resonance parameters and were compared to results obtained using resonance parameters from ENDF/B-VI updated through release 3. Extending the definition of the capture RI to include the strong 0.1-eV resonance in {sup 149}Sm, present measurements agree within estimated uncertainties with ENDF

  18. Cavity-enhanced resonant tunneling photodetector at telecommunication wavelengths

    SciTech Connect

    Pfenning, Andreas Hartmann, Fabian; Langer, Fabian; Höfling, Sven; Kamp, Martin; Worschech, Lukas

    2014-03-10

    An AlGaAs/GaAs double barrier resonant tunneling diode (RTD) with a nearby lattice-matched GaInNAs absorption layer was integrated into an optical cavity consisting of five and seven GaAs/AlAs layers to demonstrate cavity enhanced photodetection at the telecommunication wavelength 1.3 μm. The samples were grown by molecular beam epitaxy and RTD-mesas with ring-shaped contacts were fabricated. Electrical and optical properties were investigated at room temperature. The detector shows maximum photocurrent for the optical resonance at a wavelength of 1.29 μm. At resonance a high sensitivity of 3.1×10{sup 4} A/W and a response up to several pA per photon at room temperature were found.

  19. Evaluation of Silicon Neutron Resonance Parameters in the Energy Range Thermal to 1800 keV

    SciTech Connect

    Derrien, H.

    2002-09-30

    The evaluation of the neutron cross sections of the three stable isotopes of silicon in the energy range thermal to 20 MeV was performed by Hetrick et al. for ENDF/B-VI (Evaluated Nuclear Data File). Resonance parameters were obtained in the energy range thermal to 1500 keV from a SAMMY analysis of the Oak Ridge National Laboratory experimental neutron transmission data. A new measurement of the capture cross section of natural silicon in the energy range 1 to 700 keV has recently been performed at the Oak Ridge Electron Linear Accelerator. Results of this measurement were used in a SAMMY reevaluation of the resonance parameters, allowing determination of the capture width of a large number of resonances. The experimental data base is described; properties of the resonance parameters are given. For the first time the direct neutron capture component has been taken into account from the calculation by Rauscher et al. in the energy range from thermal to 1 MeV. Results of benchmark calculations are also given. The new evaluation is available in the ENDF/B-VI format.

  20. Evaluation of silicon neutron resonance parameters in the thermal to 1800 keV energy range.

    PubMed

    Derrien, H; Leal, L C; Guber, K H; Larson, N M

    2005-01-01

    Because silicon is a major constituent of concrete and soil, neutron and gamma ray information on silicon is important for reactor shielding and criticality safety calculations. Therefore, much effort was put into the ENDF/B-VI evaluation for the three stable isotopes of silicon. The neutron capture cross section of natural silicon was recently measured at the Oak Ridge Electron Linear Accelerator (ORELA) in the energy range 1-700 keV. Using the ENDF/B-VI evaluation for initial values, a new evaluation of the resonance parameters was performed by adding the results of the ORELA capture measurements to the experimental database. The computer code SAMMY was used for the analysis of the experimental data; the new version of SAMMY allows accurate calculations of the self-shielding and multiple scattering effects in the capture measurements. The accuracy of the radiative capture widths of the resonances was improved by this analysis. Accurate values of the s-, p- and d-wave neutron strength functions were also obtained. Although the resonance capture component of the present evaluation is 2-3 times smaller than that in ENDF/B-VI, the total capture cross section is much larger, at least for energies >250 keV, because the direct capture component contributes values of the same order of magnitude as the resonance component. The direct component was not taken into account in the ENDF/B-VI evaluation and was calculated for the first time in the present evaluation. PMID:16381717

  1. Spin and parity assignments for {sup 94,95}Mo neutron resonances

    SciTech Connect

    Sheets, S. A.; Agvaanluvsan, U.; Becker, J. A.; Parker, W. E.; Wu, C. Y.; Becvar, F.; Krticka, M.; Bredeweg, T. A.; Haight, R. C.; Jandel, M.; O'Donnell, J. M.; Reifarth, R.; Rundberg, R. S.; Ullmann, J. L.; Vieira, D. J.; Wouters, J. M.; Wilhelmy, J. B.; Mitchell, G. E.; Sharapov, E. I.; Tomandl, I.

    2007-12-15

    The {gamma} rays following the {sup 94,95}Mo(n,{gamma}) reactions were measured as a function of incident neutron energy by the time-of-flight method with the DANCE (Detector for Advanced Neutron Capture Experiments) array of 160 BaF{sub 2} scintillation detectors at the Los Alamos Neutron Science Center. The targets were enriched samples: 91.59% {sup 94}Mo and 96.47% {sup 95}Mo. The {gamma}-ray multiplicities and energy spectra for different multiplicities were measured in s- and p-wave resonances up to E{sub n}=10 keV for {sup 94}Mo and up to E{sub n}=2 keV for {sup 95}Mo. Definite spins and parities were assigned in {sup 96}Mo for about 60% of the resonances, and tentative spins and parities were assigned for the remaining resonances. In {sup 95}Mo the parities were determined for the observed resonances, confirming previously known assignments.

  2. Para-Hydrogen-Enhanced Gas-Phase Magnetic Resonance Imaging

    SciTech Connect

    Bouchard, Louis-S.; Kovtunov, Kirill V.; Burt, Scott R.; Anwar,M. Sabieh; Koptyug, Igor V.; Sagdeev, Renad Z.; Pines, Alexander

    2007-02-23

    Herein, we demonstrate magnetic resonance imaging (MRI) inthe gas phase using para-hydrogen (p-H2)-induced polarization. A reactantmixture of H2 enriched in the paraspin state and propylene gas is flowedthrough a reactor cell containing a heterogenized catalyst, Wilkinson'scatalyst immobilized on modified silica gel. The hydrogenation product,propane gas, is transferred to the NMR magnet and is spin-polarized as aresult of the ALTADENA (adiabatic longitudinal transport and dissociationengenders net alignment) effect. A polarization enhancement factor of 300relative to thermally polarized gas was observed in 1D1H NMR spectra.Enhancement was also evident in the magnetic resonance images. This isthe first demonstration of imaging a hyperpolarized gaseous productformed in a hydrogenation reaction catalyzed by a supported catalyst.This result may lead to several important applications, includingflow-through porous materials, gas-phase reaction kinetics and adsorptionstudies, and MRI in low fields, all using catalyst-free polarizedfluids.

  3. Neutron total cross section and resonance parameters of /sup 231/Pa

    SciTech Connect

    Hussein, A.R.Z.; Harvey, J.A.; Hill, N.W.; Patterson, J.R.

    1981-08-01

    Time-of-flight measurements of the neutron total cross section of /sup 231/Pa were carried out, in the energy range 0.01 to 10,000 eV, on two sample thicknesses using the Oak Ridge Electron Linear Accelerator as the pulsed neutron source. The multilevel R matrix code MULTI, which includes instrumental resolution and the Doppler broadening, has been used to fit the data. The resonance parameters obtained from the present multilevel R matrix analysis of /sup 231/Pa transmission data from 0.03 to 120 eV are given. 14 refs.

  4. Resonance enhancement of spin-polarized electron emission

    SciTech Connect

    Gerchikov, L. G. Mamaev, Yu. A.; Yashin, Yu. P.; Vasiliev, D. A.; Kuz'michev, V. V.; Ustinov, V. M.; Zhukov, A. E.; Vasiliev, A. P.; Mikhrin, V. S.

    2009-04-15

    Resonance enhancement of the quantum yield of polarized electrons from photocathodes based on strained short-period semiconductor superlattices is studied. The superlattice is a constituent of a Fabry-Perot optical cavity formed by the outer surface of the photocathode and the distributed Bragg reflector. An increase in the quantum yield by an order of magnitude is observed in the wavelength region corresponding to the maximum degree of polarization of photoemission.

  5. The Search for Missing Resonances: the Neutron Anomaly

    SciTech Connect

    Jaegle, Igal

    2011-10-24

    We report the observation of a narrow structure in the invariant mass spectrum of the {eta}-neutron pairs produced in the reaction {gamma}d{yields}{eta}n(p) which is absent in the {eta}-proton pairs produced in the reaction {gamma}d{yields}{eta}p(n). These results are obtained from a liquid deuterium target, the data sample was collected with the Crystal Barrel and TAPS detectors at the electron accelerator ELSA. This structure is also seen in preliminary analyses of the data samples taken by the Crystal Ball and TAPS detectors at the electron accelerator MAMI with a liquid deuterium target and a liquid helium 3 target ruling out a nuclear effect. We report the measurements of the position and width of this narrow structure in the invariant mass spectrum at W{approx_equal}1665 MeV and with a FWHM of {Gamma} = 25 MeV.

  6. New measurement of neutron capture resonances in Bi209

    NASA Astrophysics Data System (ADS)

    Domingo-Pardo, C.; Abbondanno, U.; Aerts, G.; Álvarez-Pol, H.; Alvarez-Velarde, F.; Andriamonje, S.; Andrzejewski, J.; Assimakopoulos, P.; Audouin, L.; Badurek, G.; Baumann, P.; Bečvář, F.; Berthoumieux, E.; Calviño, F.; Cano-Ott, D.; Capote, R.; Albornoz, A. Carrillo De; Cennini, P.; Chepel, V.; Chiaveri, E.; Colonna, N.; Cortes, G.; Couture, A.; Cox, J.; Dahlfors, M.; David, S.; Dillman, I.; Dolfini, R.; Dridi, W.; Duran, I.; Eleftheriadis, C.; Embid-Segura, M.; Ferrant, L.; Ferrari, A.; Ferreira-Marques, R.; Fitzpatrick, L.; Frais-Koelbl, H.; Fujii, K.; Furman, W.; Gallino, R.; Goncalves, I.; Gonzalez-Romero, E.; Goverdovski, A.; Gramegna, F.; Griesmayer, E.; Guerrero, C.; Gunsing, F.; Haas, B.; Haight, R.; Heil, M.; Herrera-Martinez, A.; Igashira, M.; Isaev, S.; Jericha, E.; Kadi, Y.; Käppeler, F.; Karamanis, D.; Karadimos, D.; Kerveno, M.; Ketlerov, V.; Koehler, P.; Konovalov, V.; Kossionides, E.; Krtička, M.; Lamboudis, C.; Leeb, H.; Lindote, A.; Lopes, I.; Lozano, M.; Lukic, S.; Marganiec, J.; Marques, L.; Marrone, S.; Mastinu, P.; Mengoni, A.; Milazzo, P. M.; Moreau, C.; Mosconi, M.; Neves, F.; Oberhummer, H.; Oshima, M.; O'Brien, S.; Pancin, J.; Papachristodoulou, C.; Papadopoulos, C.; Paradela, C.; Patronis, N.; Pavlik, A.; Pavlopoulos, P.; Perrot, L.; Plag, R.; Plompen, A.; Plukis, A.; Poch, A.; Pretel, C.; Quesada, J.; Rauscher, T.; Reifarth, R.; Rosetti, M.; Rubbia, C.; Rudolf, G.; Rullhusen, P.; Salgado, J.; Sarchiapone, L.; Savvidis, I.; Stephan, C.; Tagliente, G.; Tain, J. L.; Tassan-Got, L.; Tavora, L.; Terlizzi, R.; Vannini, G.; Vaz, P.; Ventura, A.; Villamarin, D.; Vincente, M. C.; Vlachoudis, V.; Vlastou, R.; Voss, F.; Walter, S.; Wendler, H.; Wiescher, M.; Wisshak, K.

    2006-08-01

    The neutron capture cross section of Bi209 has been measured at the CERN n_TOF facility by employing the pulse-height-weighting technique. Improvements over previous measurements are mainly because of an optimized detection system, which led to a practically negligible neutron sensitivity. Additional experimental sources of systematic error, such as the electronic threshold in the detectors, summing of γ-rays, internal electron conversion, and the isomeric state in bismuth, have been taken into account. γ-Ray absorption effects inside the sample have been corrected by employing a nonpolynomial weighting function. Because Bi209 is the last stable isotope in the reaction path of the stellar s-process, the Maxwellian averaged capture cross section is important for the recycling of the reaction flow by α decays. In the relevant stellar range of thermal energies between kT=5 and 8 keV our new capture rate is about 16% higher than the presently accepted value used for nucleosynthesis calculations. At this low temperature an important part of the heavy Pb-Bi isotopes are supposed to be synthesized by the s-process in the He shells of low mass, thermally pulsing asymptotic giant branch stars. With the improved set of cross sections we obtain an s-process fraction of 19±3% of the solar bismuth abundance, resulting in an r-process residual of 81±3%. The present (n,γ) cross-section measurement is also of relevance for the design of accelerator driven systems based on a liquid metal Pb/Bi spallation target.

  7. Lanthanide luminescence enhancements in porous silicon resonant microcavities.

    PubMed

    Jenie, S N Aisyiyah; Pace, Stephanie; Sciacca, Beniamino; Brooks, Robert D; Plush, Sally E; Voelcker, Nicolas H

    2014-08-13

    In this paper, the covalent immobilization and luminescence enhancement of a europium (Eu(III)) complex in a porous silicon (pSi) layer with a microcavity (pSiMC) structure are demonstrated. The alkyne-pendant arm of the Eu(III) complex was covalently immobilized on the azide-modified surface via ligand-assisted "click" chemistry. The design parameters of the microcavity were optimized to obtain an efficient luminescence-enhancing device. Luminescence enhancements by a factor of 9.5 and 3.0 were observed for Eu(III) complex bound inside the pSiMC as compared to a single layer and Bragg reflector of identical thickness, respectively, confirming the increased interaction between the immobilized molecules and the electric field in the spacer of the microcavity. When comparing pSiMCs with different resonance wavelength position, luminescence was enhanced when the resonance wavelength overlapped with the maximum emission wavelength of the Eu(III) complex at 614 nm, allowing for effective coupling between the confined light and the emitting molecules. The pSiMC also improved the spectral color purity of the Eu(III) complex luminescence. The ability of a pSiMC to act as an efficient Eu(III) luminescence enhancer, combined with the resulting sharp linelike emission, can be exploited for the development of ultrasensitive optical biosensors. PMID:25032481

  8. Neutron capture cross section measurements for 238U in the resonance region at GELINA

    NASA Astrophysics Data System (ADS)

    Kim, H. I.; Paradela, C.; Sirakov, I.; Becker, B.; Capote, R.; Gunsing, F.; Kim, G. N.; Kopecky, S.; Lampoudis, C.; Lee, Y.-O.; Massarczyk, R.; Moens, A.; Moxon, M.; Pronyaev, V. G.; Schillebeeckx, P.; Wynants, R.

    2016-06-01

    Measurements were performed at the time-of-flight facility GELINA to determine the 238U(n, γ) cross section in the resonance region. Experiments were carried out at a 12.5 and 60m measurement station. The total energy detection principle in combination with the pulse height weighting technique was applied using C6D6 liquid scintillators as prompt γ-ray detectors. The energy dependence of the neutron flux was measured with ionisation chambers based on the 10B(n, α) reaction. The data were normalised to the isolated and saturated 238U resonance at 6.67 eV. Special procedures were applied to reduce bias effects due to the weighting function, normalization, dead time and background corrections, and corrections related to the sample properties. The total uncertainty due to the weighting function, normalization, neutron flux and sample characteristics is about 1.5%. Resonance parameters were derived from a simultaneous resonance shape analysis of the GELINA capture data and transmission data obtained previously at a 42m and 150m station of ORELA. The parameters of resonances below 500 eV are in good agreement with those resulting from an evaluation that was adopted in the main data libraries. Between 500 eV and 1200 eV a systematic difference in the neutron width is observed. Average capture cross section data were derived from the experimental capture yield in the energy region between 3.5 keV and 90 keV. The results are in good agreement with an evaluated cross section resulting from a least squares fit to experimental data available in the literature prior to this work. The average cross section data derived in this work were parameterised in terms of average resonance parameters and included in a least squares analysis together with other experimental data reported in the literature.

  9. Neutron Stars with Delta-Resonances in the Walecka and Zimanyi-Moszkowski Models

    SciTech Connect

    Fong, C. T.; Oliveira, J. C. T.; Duarte, S. B.

    2010-11-12

    In the present work we have obtained the equation of state of the highly asymmetric dense stellar matter focusing on the delta resonance formation. We extended the nonlinear Walecka (NLW) and Zimanyi-Moszkowski (ZM) models to accommodate in the context of the relativistic mean field approximation the Rarita-Schwinger field for the spin 3/2 resonances. With the constructed stellar matter equations of state we solve numerically the TOV equation (Tolman-Oppenheimer-Volkoff) in order to determine the internal structure of neutron stars, and discuss the obtained masses versus radii diagram.

  10. Mirror and Bragg reflections of neutrons at a nuclear resonance: (Final technical report)

    SciTech Connect

    Batigun, C.M.; Brugger, R.M.

    1987-01-01

    These experiments have observed the mirror reflection and Bragg diffraction of neutrons at the energy of a low lying nuclear resonance of /sup 115/In. The reflector was a mirror of In metal with the resonance at 1.457 eV. The mirror reflection for different angles of incidence has been measured and sets of data showing the relative reflectivities have been obtained. For the Bragg diffraction, the crystal was a wafer of InP and several examples of Bragg reflections near 1.455 eV were measured. 4 refs., 12 figs.

  11. Ergodicity of the {delta}{sub 3} statistic and purity of neutron resonance data

    SciTech Connect

    Mulhall, Declan; Huard, Zachary; Zelevinsky, Vladimir

    2007-12-15

    The {delta}{sub 3}(L) statistic characterizes the fluctuations of the number of levels as a function of the length of the spectral interval. It is studied as a possible tool to indicate the regular or chaotic nature of the underlying dynamics and to detect missing levels and the mixing of sequences of levels of different symmetry, particularly in neutron resonance data. The relation between the ensemble average and the average over different fragments of a given realization of spectra is considered. A useful expression for the variance of {delta}{sub 3}(L) that accounts for finite sample size is discussed. An analysis of neutron resonance data presents the results consistent with a maximum likelihood method applied to the level spacing distribution.

  12. Introduction to theory and analysis of resolved (and unresolved) neutron resonances via SAMMY

    SciTech Connect

    Larson, N.M.

    1998-07-01

    Neutron cross-section data are important for two distinct purposes: first, they provide insight into the nature of matter, thus assisting in the understanding of fundamental physics; second, they are needed for practical applications (e.g., for calculating when and how a reactor will become critical, or how much shielding is needed for storage of nuclear materials, and for medical applications). Neutron cross section data in the resolved-resonance region are generally obtained by time-of-flight experiments, which must be carefully analyzed if they are to be properly understood and utilized. In this paper, important features of the analysis process are discussed, with emphasis on the particular technique used in the analysis code SAMMY. Other features of the code are also described; these include such topics as calculation of group cross sections (including covariance matrices), generation and fitting of integral quantities, and extensions into the unresolved-resonance region and higher-energy regions.

  13. Introduction to the Theory and Analysis of Resolved (and Unresolved) Neutron Resonances via SAMMY

    SciTech Connect

    Larson, N.

    2000-03-13

    Neutron cross-section data are important for two purposes: First, they provide insight into the nature of matter, increasing our understanding of fundamental physics. Second, they are needed for practical applications (e.g., for calculating when and how a reactor will become critical, or how much shielding is needed for storage of nuclear materials, or for medical applications). Neutron cross section data in the resolved-resonance region are generally obtained by time-of-flight experiments, which must be carefully analyzed if they are to be properly understood and utilized. In this report, important features of the analysis process are discussed, with emphasis on the particular techniques used in the analysis code SAMMY. Other features of the code are also described; these include such topics as calculation of group cross sections (including covariance matrices), generation and fitting of integral quantities, and extensions into the unresolved-resonance region and higher-energy regions.

  14. Introduction to the theory and analysis of resolved (and unresolved) neutron resonances via SAMMY

    SciTech Connect

    Larson, N.M.

    1998-02-01

    Neutron cross-section data are important for two distinct purposes: First, they provide insight into the nature of matter, thus assisting in the understanding of fundamental physics. Second, they are needed for practical applications (e.g., for calculating when and how a reactor will become critical, or how much shielding is needed for storage of nuclear materials, and for medical applications). Neutron cross section data in the resolved-resonance region are generally obtained by time-of-flight experiments, which must be carefully analyzed if they are to be properly understood and utilized. In this paper, important features of the analysis process are discussed, with emphasis on the particular techniques used in the analysis code SAMMY. Other features of the code are also described; these include such topics as calculation of group cross sections (including covariance matrices), generation and fitting of integral quantities, and extensions into the unresolved-resonance region and higher energy regions.

  15. Scissors Mode of 162 Dy Studied from Resonance Neutron Capture

    SciTech Connect

    Baramsai, B.; Bečvář, F.; Bredeweg, T. A.; Haight, R. C.; Jandel, M.; Kroll, J.; Krtička, M.; Mitchell, G. E.; O’Donnell, J. M.; Rundberg, R. S.; Ullmann, J. L.; Valenta, S.; Wilhelmy, J. B.

    2015-05-28

    Multi-step cascade γ-ray spectra from the neutron capture at isolated resonances of 161Dy nucleus were measured at the LANSCE/DANCE time-of-flight facility in Los Alamos National Laboratory. The objectives of this experiment were to confirm and possibly extend the spin assignment of s-wave neutron resonances and get new information on photon strength functions with emphasis on the role of the M1 scissors mode vibration. The preliminary results show that the scissors mode plays a significant role in all transitions between accessible states of the studied nucleus. The photon strength functions describing well our data are compared to results from 3He-induced reactions, (n,γ) experiments on Gd isotopes, and (γ,γ’) reactions.

  16. Evolution of the pygmy dipole resonance in nuclei with neutron excess

    SciTech Connect

    Co', G.; Donno, V. De; Maieron, C.; Anguiano, M.; Lallena, A. M.

    2009-07-15

    The electric dipole excitation of various nuclei is calculated with a Random Phase Approximation phenomenological approach. The evolution of the strength distribution in various groups of isotopes of oxygen, calcium, zirconium, and tin is studied. The neutron excess produces E1 strength in the low-energy region. Indexes to measure the collectivity of the excitation are defined. We studied the behavior of proton and neutron transition densities to determine the isoscalar or isovector nature of the excitation. We observed that in medium-heavy nuclei the low-energy E1 excitation has characteristics rather different than those exhibited by the giant dipole resonance. This new type of excitation can be identified as a pygmy dipole resonance.

  17. Laminography using resonant neutron attenuation for detection of drugs and explosives

    NASA Astrophysics Data System (ADS)

    Loveman, R. A.; Feinstein, R. L.; Bendahan, J.; Gozani, T.; Shea, P.

    1997-02-01

    Resonant neutron attenuation has been shown to be usable for assaying elements which constitute explosives, cocaine, and heroin. By careful analysis of attenuation measurements, the determination of the presence or absence of explosives can be determined. Simple two dimensional radiographic techniques only give results for areal density and consequently will be limited in their effectiveness. Classical tomographic techniques are both computationally very intensive and place strict requirements on the quality and amount of data acquired. These requirements and computations take time and are likely to be very difficult to perform in real time. Simulation studies described in this article have shown that laminographic image reconstruction can be used effectively with resonant neutron attenuation measurements to interrogate luggage for explosives or drugs. The design of the system described in this article is capable of pseudo-three dimensional image reconstruction of all of the elemental densities pertinent to explosive and drug detection.

  18. Neutron capture in s-wave resonances of iron-56, nickel-58, and nickel-60

    SciTech Connect

    Wisshak, K.; Fabbri, F.; Kappeler, F.; Reffo, G.

    1984-02-01

    The neutron capture widths of s-wave resonances in /sup 56/Fe (27.7 keV), /sup 58/Ni (15.4 keV), and /sup 60/Ni (12.5 keV) have been determined using a setup completely different from previous experiments. A pulsed 3-MV Van de Graaff accelerator and a kinematically collimated neutron beam, produced via the /sup 7/Li(p,n) reaction, were used in the experiments. Capture gamma rays were observed by three Moxon-Rae detectors with graphite, bismuth-graphite, and bismuth converters, respectively. The samples were positioned at a neutron flight path of only 9 cm. Thus, events due to capture of resonance-scattered neutrons in the detectors or in surrounding materials are completely discriminated by their additional time of flight. The high neutron flux at the sample position allowed the use of very thin samples (0.15 to 0.45 mm), avoiding large multiple scattering corrections. The data obtained with the individual detectors were corrected for the efficiency of the respective converter materials. For that purpose, detailed theoretical calculations of the capture gamma-ray spectra of the measured isotopes and of gold, which was used as a standard, were performed. The final results are GAMMA /SUB lg/ (27.7 keV, /sup 56/Fe) = 1.06 + or - 0.05 eV; GAMMA..gamma..(15.4 keV, /sup 58/Ni) = 1.53 + or - 0.10 eV; and GAMMA..gamma..(12.5 keV, /sup 60/Ni) = 2.92 + or - 0.19 eV. The accuracy obtained with the present experimental method represents an improvement by a factor 3 to 6 compared to previous experiments. The investigated s-wave resonances contribute 10 to 40% to the total capture rate of the respective isotopes in a typical fast reactor.

  19. Evidence for a narrow N{sup *}(1685) resonance in quasifree Compton scattering on the neutron

    SciTech Connect

    Kuznetsov, V.; Polyakov, M. V.; Bellini, V.; Giusa, A.; Mammoliti, F.; Randieri, C.; Russo, G.; Sperduto, M. L.; Boiko, T.; Chebotaryov, S.; Dho, H.-S.; Kim, W.; Milman, E.; Ni, A.; Gervino, G.; Ghio, F.; Kim, A.; Perevalova, I. A.; Vall, A. N.; Sutera, C. M.

    2011-02-15

    The study of quasifree Compton scattering on the neutron in the energy range of E{sub {gamma}}=0.75-1.5 GeV is presented. The data reveal a narrow peak at W{approx}1.685 GeV. This result, being considered in conjunction with the recent evidence for a narrow structure at W{approx}1.68 GeV in {eta} photoproduction on the neutron, suggests the existence of a nucleon resonance with unusual properties: a mass M{approx}1.685 GeV, a narrow width {Gamma}{<=}30 MeV, and the much stronger photoexcitation on the neutron than on the proton.

  20. Gamma-ray cascade transitions from resonant neutron capture in Cd-111 and Cd-113

    SciTech Connect

    Rusev, Gencho Y.

    2012-08-27

    A neutron-capture experiment on {sup nat}Cd has been carried out at DANCE. Multiple-fold coincidence {gamma}-ray spectra have been collected from J=0, 1 resonances in {sup 111}Cd and {sup 113}Cd. The cascades ending at the ground state can be described by the SLO model while the cascades ending at the 2+ states are better reproduced by the mixed SLO+KMF model.

  1. Resonance Enhanced Multi-photon Spectroscopy of DNA

    NASA Astrophysics Data System (ADS)

    Ligare, Marshall Robert

    For over 50 years DNA has been studied to better understand its connection to life and evolution. These past experiments have led to our understanding of its structure and function in the biological environment but the interaction of DNA with UV radiation at the molecular level is still not very well understood. Unique mechanisms in nucleobase chromaphores protect us from adverse chemical reactions after UV absorption. Studying these processes can help develop theories for prebiotic chemistry and the possibility of alternative forms of DNA. Using resonance enhanced multi-photon spectroscopic techniques in the gas phase allow for the structure and dynamics of individual nucleobases to be studied in detail. Experiments studying different levels of structure/complexity with relation to their biological function are presented. Resonant IR multiphoton dissociation spectroscopy in conjunction with molecular mechanics and DFT calculations are used to determine gas phase structures of anionic nucleotide clusters. A comparison of the identified structures with known biological function shows how the hydrogen bonding of the nucleotides and their clusters free of solvent create favorable structures for quick incorporation into enzymes such as DNA polymerase. Resonance enhanced multi-photon ionization (REMPI) spectroscopy techniques such as resonant two photon ionization (R2PI) and IR-UV double resonance are used to further elucidate the structure and excited state dynamics of the bare nucleobases thymine and uracil. Both exhibit long lived excited electronic states that have been implicated in DNA photolesions which can ultimately lead to melanoma and carcinoma. Our experimental data in comparison with many quantum chemical calculations suggest a new picture for the dynamics of thymine and uracil in the gas phase. A high probability of UV absorption from a vibrationally hot ground state to the excited electronic state shows that the stability of thymine and uracil comes from

  2. A simple method for the analysis of neutron resonance capture spectra

    SciTech Connect

    Clarijs, Martijn C.; Bom, Victor R.; Eijk, Carel W. E. van

    2009-03-15

    Neutron resonance capture analysis (NRCA) is a method used to determine the bulk composition of various kinds of objects and materials. It is based on analyzing direct capture resonance peaks. However, the analysis is complicated by scattering followed by capture effects in the object itself. These effects depend on the object's shape and size. In this paper the new Delft elemental analysis program (DEAP) is presented which can automatically and quickly analyze multiple NRCA spectra in a practical and simple way, yielding the elemental bulk composition of an object, largely independent of its shape and size. The DEAP method is demonstrated with data obtained with a Roman bronze water tap excavated in Nijmegen (The Netherlands). DEAP will also be used in the framework of the Ancient Charm project as data analysis program for neutron resonance capture imaging (NRCI) experiments. NRCI provides three-dimensional visualization and quantification of the internal structure of archaeological objects by performing scanning measurements with narrowly collimated neutron beams on archaeological objects in computed tomography based experimental setups. The large amounts (hundreds to thousands) of spectra produced during a NRCI experiment can automatically and quickly be analyzed by DEAP.

  3. Experimental benchmark of MCNPX calculations against self-interrogation neutron resonance densitometry (SINRD) fresh fuel measurements

    SciTech Connect

    Menlove, Howard O; Swinhoe, Martyn T; La Fleur, Adrienne M; Charlton, William S; Lee, S Y; Tobin, S J

    2010-01-01

    We have investigated the use of Self-Interrogation Neutron Resonance Densitometry (SINRD) to measure the {sup 235}U concentration in a PWR 15 x 15 fresh LEU fuel assembly in air. Different measurement configurations were simulated in Monte Carlo N-Particle eXtended transport code (MCNPX) and benchmarked against experimental results. The sensitivity of SINRD is based on using the same fissile materials in the fission chambers as are present in the fuel because the effect of resonance absorption lines in the transmitted flux is amplified by the corresponding (n,j) reaction peaks in fission chamber. Due to the low spontaneous fission rate of {sup 238}U (i.e. no curium in the fresh fuel), {sup 252}Cf sources were used to self-interrogate the fresh fuel pins. The resonance absorption of these neutrons in the fresh fuel pins can be measured using {sup 235}U fission chambers placed adjacent to the assembly. We used ratios of different fission chambers to reduce the number of unknowns we are trying measure because the neutron source strength and detector-fuel assembly coupling cancel in the ratios. The agreement between MCNPX results and experimental measurements confirms the accuracy of the MCNPX models used. The development of SINRD to measure the fissile content in spent fuel is important to the improvement of nuclear safeguards and material accountability. Future work includes the use of this technique to measure the fissile content in LWR spent fuel in water.

  4. Enhanced stress durability of nano resonators with scandium doped electrodes

    SciTech Connect

    Nuessl, R.; Jewula, T.; Binninger, C.; Drozd, R.; Ruile, W.; Beckmeier, D.; Sulima, T.; Eisele, I.; Hansch, W.

    2010-11-15

    To explore mechanical stress durability of thin aluminum-scandium (AlSc) films, 0.86 GHz nano resonators with AlSc electrodes have been manufactured. Four different samples have been prepared altering the Sc content in the alloy between 0.0% and 2.5%. A final lift-off step accomplished manufacture procedure of the devices. The resonators have been operated with heavy load to determine power durability. The resonators with AlSc electrodes show increased power durability compared to conventional Al metallized devices. Texture and grain structure of all films have been investigated by means of electron backscatter diffraction (EBSD) and atomic force microscopy (AFM). Material fatigue of electrodes has been visualized by scanning electron microscopy (SEM). The refined grain structure of these alloys can explain the enhanced mechanical stress durability of AlSc electrodes. - Research Highlights: {yields}Enhanced power durability of SAW devices with Sc doped electrodes. {yields}Refined grain structure of Sc doped Al films. {yields}Sudden device breakdown of highly Sc doped devices.

  5. Experimental Resonance Enhanced Multiphoton Ionization (REMPI) studies of small molecules

    NASA Technical Reports Server (NTRS)

    Dehmer, J. L.; Dehmer, P. M.; Pratt, S. T.; Ohalloran, M. A.; Tomkins, F. S.

    1987-01-01

    Resonance enhanced multiphoton ionization (REMPI) utilizes tunable dye lasers to ionize an atom or molecule by first preparing an excited state by multiphoton absorption and then ionizing that state before it can decay. This process is highly selective with respect to both the initial and resonant intermediate states of the target, and it can be extremely sensitive. In addition, the products of the REMPI process can be detected as needed by analyzing the resulting electrons, ions, fluorescence, or by additional REMPI. This points to a number of exciting opportunities for both basic and applied science. On the applied side, REMPI has great potential as an ultrasensitive, highly selective detector for trace, reactive, or transient species. On the basic side, REMPI affords an unprecedented means of exploring excited state physics and chemistry at the quantum-state-specific level. An overview of current studies of excited molecular states is given to illustrate the principles and prospects of REMPI.

  6. Enhancement of resonant absorption through excitation of SPR

    NASA Astrophysics Data System (ADS)

    Giulietti, Danilo; Calcagno, L.; Curcio, Alessandro; Cutroneo, M.; Galletti, Mario; Skala, J.; Torrisi, L.; Zimbone, M.

    2016-09-01

    In this experiment the absorption of the laser radiation impinging on polymeric films with Au nanoparticles implanted in surface was studied. By varying the polarization and the incidence angle of the laser radiation on target, the role in the laser absorption of both excitation of surface plasmons and excitation of electronic plasma waves at critical density through resonant absorption was highlighted. In conditions of p-polarized laser irradiations at 1015 W /cm2 intensity, resonant absorption can be induced in films enhancing proton and ion acceleration. Plasma on-line diagnostics is based on SiC detectors. Measurements of kinetic energy of accelerated ions indicate a significant increment using p-polarized laser light with respect to no-polarized light irradiation.

  7. Magnetic field dependence of the neutron spin resonance in CeB6

    NASA Astrophysics Data System (ADS)

    Portnichenko, P. Y.; Demishev, S. V.; Semeno, A. V.; Ohta, H.; Cameron, A. S.; Surmach, M. A.; Jang, H.; Friemel, G.; Dukhnenko, A. V.; Shitsevalova, N. Yu.; Filipov, V. B.; Schneidewind, A.; Ollivier, J.; Podlesnyak, A.; Inosov, D. S.

    2016-07-01

    In zero magnetic field, the famous neutron spin resonance in the f -electron superconductor CeCoIn5 is similar to the recently discovered exciton peak in the nonsuperconducting CeB6. A magnetic field splits the resonance in CeCoIn5 into two components, indicating that it is a doublet. Here we employ inelastic neutron scattering (INS) to scrutinize the field dependence of spin fluctuations in CeB6. The exciton shows a markedly different behavior without any field splitting. Instead, we observe a second field-induced magnon whose energy increases with field. At the ferromagnetic zone center, however, we find only a single mode with a nonmonotonic field dependence. At low fields, it is initially suppressed to zero together with the antiferromagnetic order parameter, but then reappears at higher fields inside the hidden-order phase, following the energy of an electron spin resonance (ESR). This is a unique example of a ferromagnetic resonance in a heavy-fermion metal seen by both ESR and INS consistently over a broad range of magnetic fields.

  8. Broadband quantum efficiency enhancement in high index nanowire resonators.

    PubMed

    Yang, Yiming; Peng, Xingyue; Hyatt, Steven; Yu, Dong

    2015-05-13

    Light trapping in subwavelength semiconductor nanowires (NWs) offers a promising approach to simultaneously reducing material consumption and enhancing photovoltaic performance. Nevertheless, the absorption efficiency of a NW, defined by the ratio of optical absorption cross section to the NW diameter, lingers around 1 in existing NW photonic devices, and the absorption enhancement suffers from a narrow spectral width. Here, we show that the absorption efficiency can be significantly improved in NWs with higher refractive indices, by an experimental observation of up to 350% apparent external quantum efficiency in lead sulfide NW resonators, a 3-fold increase compared to Si NWs. Furthermore, broadband absorption enhancement is achieved in single tapered NWs, where light of various wavelengths is absorbed at segments with different diameters. Overall, the single NW Schottky junction solar cells benefit from optical resonance, near bandgap open circuit voltage, and long minority carrier diffusion length, demonstrating power conversion efficiency comparable to Si and III-V single NW coaxial p-n junction cells but with much simpler fabrication processes. PMID:25919358

  9. Splitting of the isovector giant dipole resonance in neutron-rich spherical nuclei

    SciTech Connect

    Kolomietz, V.M.; Magner, A.G.; Shlomo, S.

    2006-02-15

    The well-known splitting of the isovector giant dipole resonance is traditionally explained as a phenomenon of the nuclear isospin asymmetry (isospin splitting model) or the nuclear deformation. We suggest a new mechanism of the splitting of the giant multipole resonances in spherical neutron-rich nuclei resulting from the interplay of the isovector and isoscalar sounds with different velocities. Our approach is based on the collisional Landau kinetic theory and can be used for description of the splitting phenomena for both the isoscalar and the isovector modes in a wide region of nuclear masses A{approx}40-240. For the isovector dipole modes, the evaluated values of the splitting energy, the relative strength of the main and satellite resonance peaks, and the contribution to the energy-weighted sum rule are in agreement with experimental data.

  10. Resonantly enhanced Bragg-scattering spectroscopy of an atomic transition

    NASA Astrophysics Data System (ADS)

    Yang, Xudong; Qiao, Cuifang; Li, Chuanliang; Chen, Fenghua

    2016-07-01

    A novel resonantly enhanced Bragg-scattering (REBS) spectroscopy from a population difference grating (PDG) is reported. The PDG is formed by a standing-wave (SW) pump field, which periodically modulates the space population distributions of two levels in the 87Rb D1 line. Then, a probe beam, having identical frequency and orthogonal polarization with the SW pump field, is Bragg-scattered by the PDG. The research achievement shows that the Bragg-scattered light is strongest at an atomic transition, and forms an REBS spectrum with a high signal-to-noise ratio and sub-natural linewidth. The observed REBS can be applied in precise frequency measurements.

  11. Enabling Explosives and Contraband Detection with Neutron Resonant Attenuation. Year 1 of 3 Summary

    SciTech Connect

    Sweany, Melinda

    2015-10-01

    Material Identification by Resonant Attenuation is a technique that measures the energy-dependent attenuation of 1-10 MeV neutrons as they pass through a sample. Elemental information is determined from the neutron absorption resonances unique to each element. With sufficient energy resolution, these resonances can be used to categorize a wide range of materials, serving as a powerful discrimination technique between explosives, contraband, and other materials. Our proposed system is unique in that it simultaneously down-scatters and time tags neutrons in scintillator detectors oriented between a d-T generator and sample. This allows not only for energy measurements without pulsed neutron beams, but for sample interrogation over a large range of relevant energies, vastly improving scan times. Our system’s core advantage is a potential breakthrough ability to provide detection discrimination of threat materials by their elemental composition (e.g. water vs. hydrogen peroxide) without opening the container. However, several technical and computational challenges associated with this technique have yet to be addressed. There are several open questions: what is the sensitivity to different materials, what scan times are necessary, what are the sources of background, how do each of these scale as the detector system is made larger, and how can the system be integrated into existing scanning technology to close current detection gaps? In order to prove the applicability of this technology, we will develop a validated model to optimize the design and characterize the uncertainties in the measurement, and then test the system in a real-world scenario. This project seeks to perform R&D and laboratory tests that demonstrate proof of concept (TRL 3) to establishing an integrated system and evaluating its performance (TRL 4) through both laboratory tests and a validated detector model. The validated model will allow us to explore our technology’s benefits to explosive

  12. sup 56 Fe resonance parameters for neutron energies up to 850 keV

    SciTech Connect

    Perey, C.M.; Perey, F.G.; Harvey, J.A.; Hill, N.W.; Larson, N.M.

    1990-12-01

    High-resolution neutron measurements for {sup 56}Fe-enriched iron targets were made at the Oak Ridge Electron Linear Accelerator (ORELA) in transmission below 20 MeV and in differential elastic scattering below 5 MeV. Transmission measurements were also performed with a natural iron target below 160 keV. The transmission data were analyzed from 5 to 850 keV with the multilevel R-matrix code SAMMY which uses Bayes' theorem for the fitting process. This code provides energies and neutron widths of the resonances inside the 5- to 850-keV energy region, as well as possible parameterization for resonances external to the analyzed region to describe the smooth cross section from a few eV to 850 keV. The resulting set of resonance parameters yields the accepted values for the thermal total and capture cross sections. The differential elastic-scattering data at several scattering angles were compared to theoretical calculations from 40 to 850 keV using the R-matrix code RFUNC based on the Blatt-Biedenharn formalism. Various combinations of spin and parity were tried to predict cross sections for the well defined {ell} > 0 resonances; comparison of these predictions with the data allowed us to determine the most likely spin and parity assignments for these resonances. The results of a capture data analysis by Corvi et al. (COR84), from 2 to 350 keV, were combined with our results to obtain the radiation widths of the resonances below 350 keV observed in transmission, capture, and differential elastic-scattering experiments.

  13. Polarization enhanced Nuclear Quadrupole Resonance with an atomic magnetometer

    NASA Astrophysics Data System (ADS)

    Malone, Michael W.; Barrall, Geoffrey A.; Espy, Michelle A.; Monti, Mark C.; Alexson, Dimitri A.; Okamitsu, Jeffrey K.

    2016-05-01

    Nuclear Quadrupole Resonance (NQR) has been demonstrated for the detection of 14-N in explosive compounds. Application of a material specific radio-frequency (RF) pulse excites a response typically detected with a wire- wound antenna. NQR is non-contact and material specific, however fields produced by NQR are typically very weak, making demonstration of practical utility challenging. For certain materials, the NQR signal can be increased by transferring polarization from hydrogen nuclei to nitrogen nuclei using external magnetic fields. This polarization enhancement (PE) can enhance the NQR signal by an order of magnitude or more. Atomic magnetometers (AM) have been shown to improve detection sensitivity beyond a conventional antenna by a similar amount. AM sensors are immune to piezo-electric effects that hamper conventional NQR, and can be combined to form a gradiometer for effective RF noise cancellation. In principle, combining polarization enhancement with atomic magnetometer detection should yield improvement in signal-to-noise ratio that is the product of the two methods, 100-fold or more over conventional NQR. However both methods are even more exotic than traditional NQR, and have never been combined due to challenges in operating a large magnetic field and ultra-sensitive magnetic field sensor in proximity. Here we present NQR with and without PE with an atomic magnetometer, demonstrating signal enhancement greater than 20-fold for ammonium nitrate. We also demonstrate PE for PETN using a traditional coil for detection with an enhancement factor of 10. Experimental methods and future applications are discussed.

  14. Exploiting material softening in hard PZTs for resonant bandwidth enhancement

    NASA Astrophysics Data System (ADS)

    Leadenham, S.; Moura, A.; Erturk, A.

    2016-04-01

    Intentionally designed nonlinearities have been employed by several research groups to enhance the frequency bandwidth of vibration energy harvesters. Another type of nonlinear resonance behavior emerges from the piezoelectric constitutive behavior for high excitation levels and is manifested in the form of softening stiffness. This material nonlinearity does not result in the jump phenomenon in soft piezoelectric ceramics, e.g. PZT-5A and PZT-5H, due to their large internal dissipation. This paper explores the potential for wideband energy harvesting using a hard (relatively high quality factor) PZT-8 bimorph by exploiting its material softening. A wide range of base excitation experiments conducted for a set of resistive electrical loads confirms the frequency bandwidth enhancement.

  15. Gadolinium-enhanced magnetic resonance angiography in brain death

    NASA Astrophysics Data System (ADS)

    Luchtmann, M.; Beuing, O.; Skalej, M.; Kohl, J.; Serowy, S.; Bernarding, J.; Firsching, R.

    2014-01-01

    Confirmatory tests for the diagnosis of brain death in addition to clinical findings may shorten observation time required in some countries and may add certainty to the diagnosis under specific circumstances. The practicability of Gadolinium-enhanced magnetic resonance angiography to confirm cerebral circulatory arrest was assessed after the diagnosis of brain death in 15 patients using a 1.5 Tesla MRI scanner. In all 15 patients extracranial blood flow distal to the external carotid arteries was undisturbed. In 14 patients no contrast medium was noted within intracerebral vessels above the proximal level of the intracerebral arteries. In one patient more distal segments of the anterior and middle cerebral arteries (A3 and M3) were filled with contrast medium. Gadolinium-enhanced MRA may be considered conclusive evidence of cerebral circulatory arrest, when major intracranial vessels fail to fill with contrast medium while extracranial vessels show normal blood flow.

  16. Imaging of surfaces by surface plasmon resonance and surface plasmon resonance-enhanced fluorescence

    NASA Astrophysics Data System (ADS)

    Thariani, Rahber A.

    An instrument system capable of concurrent imaging of surfaces by surface plasmon resonance microscopy (SPRM) and surface plasmon resonance-enhanced fluorescence (SPRF) is presented. A conventional laser pointer is adopted as a light source, and a reflective diffuser coupled to an acoustic transducer is used to remove speckle artifacts due to coherent beam interference. Both SPRM and SPRF systems are characterized, and a careful choice of widely available, inexpensive, off-the-shelf components allows the entire system to be constructed at low cost. A model streptavidin-biotin system is explored utilizing the different modalities of the instrument. Applications of the system include mobile, cost-effective point-of-care diagnostics system and research laboratories in resource-limited settings where cost efficacy is a prime concern.

  17. Image enhancement using MCNP5 code and MATLAB in neutron radiography.

    PubMed

    Tharwat, Montaser; Mohamed, Nader; Mongy, T

    2014-07-01

    This work presents a method that can be used to enhance the neutron radiography (NR) image for objects with high scattering materials like hydrogen, carbon and other light materials. This method used Monte Carlo code, MCNP5, to simulate the NR process and get the flux distribution for each pixel of the image and determines the scattered neutron distribution that caused image blur, and then uses MATLAB to subtract this scattered neutron distribution from the initial image to improve its quality. This work was performed before the commissioning of digital NR system in Jan. 2013. The MATLAB enhancement method is quite a good technique in the case of static based film neutron radiography, while in neutron imaging (NI) technique, image enhancement and quantitative measurement were efficient by using ImageJ software. The enhanced image quality and quantitative measurements were presented in this work. PMID:24583508

  18. Polarized Nuclei: From Fundamental Nuclear Physics To Applications In Neutron Scattering and Magnetic Resonance Imaging

    SciTech Connect

    Brandt, B. van den; Hautle, P.; Konter, J. A.; Kurdzesau, F.; Piegsa, F. M.; Urrego-Blanco, J.-P.

    2008-02-06

    The methods of dynamically polarizing nuclei (DNP) have not only lead to the development of increasingly sophisticated polarized targets with which the role of spin in nuclear and particle interactions is investigated, but have also opened new possibilities in neutron science by exploiting the strong spin dependence of the neutron scattering. Very recently NMR and MRI have been a driving force behind a surge of interest in DNP methods, considering its tremendous potential for sensitivity enhancement. An overview of our current projects with dynamically polarized nuclei is given.

  19. Resonance neutron-capture cross sections of stable magnesium isotopes and their astrophysical implications

    NASA Astrophysics Data System (ADS)

    Massimi, C.; Koehler, P.; Bisterzo, S.; Colonna, N.; Gallino, R.; Gunsing, F.; Käppeler, F.; Lorusso, G.; Mengoni, A.; Pignatari, M.; Vannini, G.; Abbondanno, U.; Aerts, G.; Álvarez, H.; Álvarez-Velarde, F.; Andriamonje, S.; Andrzejewski, J.; Assimakopoulos, P.; Audouin, L.; Badurek, G.; Barbagallo, M.; Baumann, P.; Bečvář, F.; Belloni, F.; Bennett, M.; Berthoumieux, E.; Calviani, M.; Calviño, F.; Cano-Ott, D.; Capote, R.; Carrapiço, C.; Carrillo de Albornoz, A.; Cennini, P.; Chepel, V.; Chiaveri, E.; Cortes, G.; Couture, A.; Cox, J.; Dahlfors, M.; David, S.; Dillmann, I.; Dolfini, R.; Domingo-Pardo, C.; Dridi, W.; Duran, I.; Eleftheriadis, C.; Embid-Segura, M.; Ferrant, L.; Ferrari, A.; Ferreira-Marques, R.; Fitzpatrick, L.; Frais-Koelbl, H.; Fujii, K.; Furman, W.; Goncalves, I.; González-Romero, E.; Goverdovski, A.; Gramegna, F.; Griesmayer, E.; Guerrero, C.; Haas, B.; Haight, R.; Heil, M.; Herrera-Martinez, A.; Herwig, F.; Hirschi, R.; Igashira, M.; Isaev, S.; Jericha, E.; Kadi, Y.; Karadimos, D.; Karamanis, D.; Kerveno, M.; Ketlerov, V.; Konovalov, V.; Kopecky, S.; Kossionides, E.; Krtička, M.; Lampoudis, C.; Leeb, H.; Lederer, C.; Lindote, A.; Lopes, I.; Losito, R.; Lozano, M.; Lukic, S.; Marganiec, J.; Marques, L.; Marrone, S.; Martínez, T.; Mastinu, P.; Mendoza, E.; Milazzo, P. M.; Moreau, C.; Mosconi, M.; Neves, F.; Oberhummer, H.; O'Brien, S.; Oshima, M.; Pancin, J.; Papachristodoulou, C.; Papadopoulos, C.; Paradela, C.; Patronis, N.; Pavlik, A.; Pavlopoulos, P.; Perrot, L.; Pigni, M. T.; Plag, R.; Plompen, A.; Plukis, A.; Poch, A.; Praena, J.; Pretel, C.; Quesada, J.; Rauscher, T.; Reifarth, R.; Rockefeller, G.; Rosetti, M.; Rubbia, C.; Rudolf, G.; Salgado, J.; Santos, C.; Sarchiapone, L.; Sarmento, R.; Savvidis, I.; Stephan, C.; Tagliente, G.; Tain, J. L.; Tarrío, D.; Tassan-Got, L.; Tavora, L.; Terlizzi, R.; Vaz, P.; Ventura, A.; Villamarin, D.; Vlachoudis, V.; Vlastou, R.; Voss, F.; Walter, S.; Wendler, H.; Wiescher, M.; Wisshak, K.

    2012-04-01

    We have measured the neutron capture cross sections of the stable magnesium isotopes 24,25,26Mg in the energy range of interest to the s process using the neutron time-of-flight facility n_TOF at CERN. Capture events from a natural metal sample and from samples enriched in 25Mg and 26Mg were recorded using the total energy method based on C62H6 detectors. Neutron resonance parameters were extracted by a simultaneous resonance shape analysis of the present capture data and existing transmission data on a natural isotopic sample. Maxwellian-averaged capture cross sections for the three isotopes were calculated up to thermal energies of 100 keV and their impact on s-process analyses was investigated. At 30 keV the new values of the stellar cross section for 24Mg, 25Mg, and 26Mg are 3.8±0.2 mb, 4.1±0.6 mb, and 0.14±0.01 mb, respectively.

  20. R-MATRIX RESONANCE ANALYSIS AND STATISTICAL PROPERTIES OF THE RESONANCE PARAMETERS OF 233U IN THE NEUTRON ENERGY RANGE FROM THERMAL TO 600 eV

    SciTech Connect

    Leal, L.C.

    2001-02-27

    The R-matrix resonance analysis of experimental neutron transmission and cross sections of {sup 233}U, with the Reich-Moore Bayesian code SAMMY, was extended up to the neutron energy of 600 eV by taking advantage of new high resolution neutron transmission and fission cross section measurements performed at the Oak Ridge Electron Linear Accelerator (ORELA). The experimental data base is described. In addition to the microscopic data (time-of-flight measurements of transmission and cross sections), some experimental and evaluated integral quantities were included in the data base. Tabulated and graphical comparisons between the experimental data and the SAMMY calculated cross sections are given. The ability of the calculated cross sections to reproduce the effective multiplication factors k{sub eff} for various thermal, intermediate, and fast systems was tested. The statistical properties of the resonance parameters were examined and recommended values of the average s-wave resonance parameters are given.

  1. Boron neutron capture enhancement (BNCE) of fast neutron irradiation for glioblastoma: increase of thermal neutron flux with heavy material collimation, a theoretical evaluation.

    PubMed

    Paquis, P; Pignol, J P; Lonjon, M; Brassart, N; Courdi, A; Chauvel, P; Grellier, P; Chatel, M

    1999-01-01

    Despite the fact that fast neutron irradiation of glioblastoma has shown on autopsies an ability to sterilize tumors, no therapeutic windows have been found for these particles due to their toxicity toward normal brain. Therefore, the Boron Neutron Capture Enhancement (BNCE) of fast neutron beam has been suggested. This paper addresses the problem of fast neutron beam collimation, which induces a dramatic decrease of the thermal neutron flux in the depth of the tissues when smaller irradiation fields are used. Thermoluminescent dosimeter TLD-600 and TLD-700 were used to determine the thermal neutron flux within a Plexiglas phantom irradiated under the Nice Biomedical Cyclotron p(60)+Be(32) fast neutron beam. A BNCE of 4.6% in physical dose was determined for a 10 x 10 cm2 field, and of 10.4% for a 20 x 20 cm2 one. A Dose Modification Factor of 1.19 was calculated for CAL 58 glioblastoma cells irradiated thanks to the larger field. In order to increase the thermal flux in depth while shaping the beam, heavy material collimation was studied with Monte Carlo simulations using coupled FLUKA and MCNP-4A codes. The use of 20 cm width lead blocks allowed a 2 fold thermal neutron flux increase in the depth of the phantom, while shielding the fast neutron beam with a fast neutron dose transmission of 23%. Using the DMF of 1.19, a BNCE of 40% was calculated in the beam axis. This enhancement might be sufficient to open, at least theoretically, a therapeutic window. PMID:10222419

  2. Spin and Parity Assignment of Neutron Resonances using Gamma-ray Multiplicity

    SciTech Connect

    Agvaanluvsan, U.; Mitchell, G. E.; Baramsai, B.; Chyzh, A.; Walker, C.; Dashdorj, D.; Becker, J. A.; Parker, W. E.; Sleaford, B.; Wu, C. Y.; Bredeweg, T. A.; Couture, A.; Haight, R. C.; Jandel, M.; Rundberg, R. S.; Ullmann, J. L.; Vieira, D. J.; Wouters, J. M.; Krticka, M.; Becvar, F.

    2009-03-31

    Decay gamma rays following neutron capture on various isotopes are collected by the Detector for Advanced Neutron Capture Experiments (DANCE) array, which is located at flight path 14 at the Lujan Neutron Scattering Center at Los Alamos National Laboratory. The high segmentation (160 detectors) and close packing of the detector array enable gamma-ray multiplicity measurements. The calorimetric properties of the DANCE array coupled with the neutron time-of-flight technique enables one to gate on a specific resonance of a given isotope in the time-of-flight spectrum and obtain the summed energy spectrum for that isotope. The singles gamma-ray spectrum for each multiplicity can be separated by their DANCE cluster multiplicity. The multiplicity distribution contains the signatures of spin and parity of the capture state. Under suitable circumstances where the difference between spins of the initial (capture) and final (ground) state is large enough, the signatures in the multiplicity distribution can be used in improving the spin assignment of the initial state. The spin assignment is applied with varying degree of success to difference isotopes and description of this application for {sup 95}Mo, {sup 151,153}Eu, and {sup 155,157}Gd is reviewed briefly.

  3. The effects of boron on the electron paramagnetic resonance spectra of alanine irradiated with thermal neutrons

    SciTech Connect

    Ciesielski, B.; Wielopolski, L.

    1995-10-01

    The effects of boric acid admixture on the intensity and line structure of EPR spectra of free radicals produced in alanine by thermal neutrons are presented. The EPR signal enhancement, up to a factor of 40 depending on the boron concentration, is related to additional energy deposition in alanine crystals by the disintegration products resulting from the capture of a thermal neutron by boron, {sup 10}B(n,{alpha}){sup 7}Li. The changes in the shape of the EPR spectra observed by changing the microwave power are due to the differences in the microwave power saturation of the free radicals produced by a low-LET radiation and those produced by the high-LET components of the radiation after the neutron capture reaction. 27 refs., 4 figs., 2 tabs.

  4. A Search for Nonstandard Neutron Spin Interactions using Dual Species Xenon Nuclear Magnetic Resonance

    NASA Astrophysics Data System (ADS)

    Bulatowicz, Michael; Larsen, Michael; Mirijanian, James; Fu, Changbo; Yan, Haiyang; Smith, Erick; Snow, Mike; Walker, Thad

    2012-06-01

    NMR measurements using polarized noble gases can constrain possible exotic spin-dependent interactions involving nucleons. A differential measurement insensitive to magnetic field fluctuations can be performed using a mixture of two polarized species with different ratios of nucleon spin to magnetic moment. We used the NMR cell test station at Northrop Grumman Corporation (NGC) (developed to evaluate dual species xenon vapor cells for the Nuclear Magnetic Resonance Gyroscope) to search for NMR frequency shifts of xenon-129 and xenon-131 when a non-magnetic zirconia rod is modulated near the NMR cell. We simultaneously excited both Xe isotopes and detected free-induction-decay transients. In combination with theoretical calculations of the neutron spin contribution to the nuclear angular momentum, the measurements put a new upper bound on possible monopole-dipole interactions of the neutron for ranges around 1mm. This work is supported by the NGC Internal Research and Development (IRAD) funding, the Department of Energy, and the NSF.

  5. Surface plasmon enhanced interfacial electron transfer and resonance Raman, surface-enhanced resonance Raman studies of cytochrome C mutants

    SciTech Connect

    Zheng, Junwei

    1999-11-08

    Surface plasmon resonance was utilized to enhance the electron transfer at silver/solution interfaces. Photoelectrochemical reductions of nitrite, nitrate, and CO{sub 2} were studied on electrochemically roughened silver electrode surfaces. The dependence of the photocurrent on photon energy, applied potential and concentration of nitrite demonstrates that the photoelectrochemical reduction proceeds via photoemission process followed by the capture of hydrated electrons. The excitation of plasmon resonances in nanosized metal structures resulted in the enhancement of the photoemission process. In the case of photoelectrocatalytic reduction of CO{sub 2}, large photoelectrocatalytic effect for the reduction of CO{sub 2} was observed in the presence of surface adsorbed methylviologen, which functions as a mediator for the photoexcited electron transfer from silver metal to CO{sub 2} in solution. Photoinduced reduction of microperoxidase-11 adsorbed on roughened silver electrode was also observed and attributed to the direct photoejection of free electrons of silver metal. Surface plasmon assisted electron transfer at nanostructured silver particle surfaces was further determined by EPR method.

  6. Unexpected Enhancements and Reductions of RF Resonance Strengths

    SciTech Connect

    Leonova, M. A.; Krisch, A. D.; Morozov, V. S.; Raymond, R. S.; Sivers, D. W.; Wong, V. K.; Gebel, R.; Lehrach, A.; Lorentz, B.; Maier, R.; Prasuhn, D.; Schnase, A.; Stockhorst, H.; Hinterberger, F.; Ulbrich, K.

    2007-06-13

    We analyzed all available data on spin-flipping stored beams of protons, deuterons and electrons. We first calculated the rf-induced spin resonance strength ratio {epsilon}FS/*{epsilon}Bdl; the {epsilon}FS was obtained by fitting the measured polarization data to the modified Froissart-Stora equation, while *{epsilon}Bdl was calculated using the {integral}Bdl of the rf dipole or rf solenoid. We found that {epsilon}FS/*{epsilon}Bdl was often 7 times lower than predicted for deuterons, and 12 to 170 times higher than predicted for protons. We studied these discrepancies with vertically polarized beams of 2.1 GeV/c protons and 1.85 GeV/c deuterons stored in the COSY ring in Juelich, Germany. These studies involved flipping their polarization direction, by sweeping the frequency of a water-cooled ferrite rf dipole, of typically {integral}Bdlrms = 0.60 {+-} 0.3 T{center_dot}mm, through an rf-induced spin resonance.We studied the dependence of {epsilon}FS/*Bdl on the beam size, the momentum spread and the distance from the nearest 1st-order intrinsic spin resonance for both protons and deuterons, and on the frequency sweep range {delta}f for deuterons. We observed no measurable dependence of {epsilon}FS/*Bdl on the beam's size or momentum spread for either protons or deuterons. When we varied the vertical betatron tune {nu}y near a 1st-order intrinsic spin resonance, we observed a strong enhancement of {epsilon}FS/*{epsilon}Bdl with a hyperbolic dependence on the distance from the 1st-order intrinsic spin resonance for both protons and deuterons. This explained much of the proton discrepancy, but did not explain the deuteron's very small {epsilon}FS/*{epsilon}Bdl. All early deuteron data had small {delta}f values of 100-200 Hz; however, when {delta}f was increased from 100 to 3000 Hz, in four steps, there was no dependence of {epsilon}FS/*{epsilon}Bdl on {delta}f Thus, this anomalously small {epsilon}FS/*{epsilon}Bdl ratio may be due to some unexpected behavior of

  7. Observation of enhanced nuclear stability near the 162 neutron shell

    SciTech Connect

    Lougheed, R.W.; Moody, K.J.; Wild, J.F.; Hulet, E.K.; McQuaid, J.H.; Lazarev, Yu.A.; Lobanov, Yu.V.; Oganessian, Yu.Ts.; Utyonkov, V.K.; Abdullin, F.Sh.; Buklanov, G.V.; Gikal, B.N.; Iliev, S.; Mezentsev, A.N.; Polyakov, A.N.; Sedykh, I.M.; Shirokovsky, I.V.; Subbotin, V.G.; Sukhov, A.M.; Tsyganov, Yu.S.; Zhuchko, V.E.

    1993-09-22

    In bombardments of {sup 248}Cm with {sup 22}Ne the authors discovered two new isotopes, {sup 265}106 and {sup 266}106, by establishing genetic links between {alpha} decays of the 106 nuclides and SF or {alpha} decays of the daughter (grand-daughter) nuclides. For {sup 266}106 they measured E{sub {alpha}}=8.62{+-}0.06 MeV followed by the SF decay of {sup 262}104 for which they measured a half-life value of 1.2{sup +1.0}{sub {minus}0.5} s. For {sup 265}106 they measured E{sub {alpha}}=8.82{+-}0.06 MeV. They estimated {alpha} half-lives of 10-30 s for {sup 266}106 and 2-30 s for {sup 265}106 with SF branches of {approximately}50% or less. The decay properties of {sup 266}106 indicate a large enhancement in the SF stability of this N=160 nuclide and confirm the existence of the predicted neutron-deformed shell N=162.

  8. {sup 10}Li low-lying resonances populated by one-neutron transfer

    SciTech Connect

    Cavallaro, M. Agodi, C.; Carbone, D.; Cunsolo, A.; De Napoli, M.; Cappuzzello, F.; Bondì, M.; Davids, B.; Galinski, N.; Ruiz, C.; Davinson, T.; Sanetullaev, A.; Foti, A.; Kanungo, R.; Lenske, H.; Orrigo, S. E. A.

    2015-10-15

    The {sup 9}Li + {sup 2}H → {sup 10}Li + {sup 1}H one-neutron transfer reaction has been performed at 100 MeV incident energy at TRIUMF using a {sup 9}Li beam delivered by the ISAC-II facility. A setup based on double-sided silicon strip detectors has been used in order to detect and identify the outgoing {sup 9}Li produced by the {sup 10}Li breakup at forward angles and the recoil protons emitted at backward angles. The {sup 10}Li low-lying resonances, whose energies, widths and configurations are still unclear, have been populated with significant statistics.

  9. 10Li low-lying resonances populated by one-neutron transfer

    NASA Astrophysics Data System (ADS)

    Cavallaro, M.; De Napoli, M.; Cappuzzello, F.; Agodi, C.; Bondı, M.; Carbone, D.; Cunsolo, A.; Davids, B.; Davinson, T.; Foti, A.; Galinski, N.; Kanungo, R.; Lenske, H.; Orrigo, S. E. A.; Ruiz, C.; Sanetullaev, A.

    2015-10-01

    The 9Li + 2H → 10Li + 1H one-neutron transfer reaction has been performed at 100 MeV incident energy at TRIUMF using a 9Li beam delivered by the ISAC-II facility. A setup based on double-sided silicon strip detectors has been used in order to detect and identify the outgoing 9Li produced by the 10Li breakup at forward angles and the recoil protons emitted at backward angles. The 10Li low-lying resonances, whose energies, widths and configurations are still unclear, have been populated with significant statistics.

  10. Nuclear Poincaré cycle synchronizes with the incident de Broglie wave to predict regularity in neutron resonance energies

    NASA Astrophysics Data System (ADS)

    Ohkubo, Makio

    2016-06-01

    In observed neutron resonances, long believed to be a form of quantum chaos, regular family structures are found in the s-wave resonances of many even-even nuclei in the tens keV to MeV region [M.Ohkubo, Phys. Rev. C 87, 014608(2013)]. Resonance reactions take place when the incident de Broglie wave synchronizes with the Poincaré cycle of the compound nucleus, which is composed of several normal modes with periods that are time quantized by inverse Fermi energy. Based on the breathing model of the compound nucleus, neutron resonance energies in family structures are written by simple arithmetic expressions using Sn and small integers. Family structures in observed resonances of 40Ca+n and 37Cl+n are described as simple cases. A model for time quantization is discussed.

  11. Abrupt change in radiation-width distribution for 147Sm neutron resonances.

    PubMed

    Koehler, P E; Reifarth, R; Ullmann, J L; Bredeweg, T A; O'Donnell, J M; Rundberg, R S; Vieira, D J; Wouters, J M

    2012-04-01

    We obtained the total radiation widths of s-wave resonances through an R-matrix analysis of (147)Sm(n,γ) cross sections. Distributions of these widths differ markedly for resonances below and above E(n)=300 eV, which is in stark contrast to long-established theory. We show that this change, as well as a similar change in the neutron-width distribution reported previously, is reflected in abrupt increases in both the average (147)Sm(n,γ) cross section and fluctuations about the average near 300 eV. Such effects could have important consequences for applications such as nuclear astrophysics and nuclear criticality safety. PMID:22540788

  12. Tagged Neutron Source for API Inspection Systems with Greatly Enhanced Spatial Resolution

    SciTech Connect

    2012-06-04

    We recently developed induced fission and transmission imaging methods with time- and directionally-tagged neutrons offer new capabilities for characterization of fissile material configurations and enhanced detection of special nuclear materials (SNM). An Advanced Associated Particle Imaging (API) generator with higher angular resolution and neutron yield than existing systems is needed to fully exploit these methods.

  13. Resonant enhanced multiphoton ionization studies of atomic oxygen

    NASA Technical Reports Server (NTRS)

    Dixit, S. N.; Levin, D.; Mckoy, V.

    1987-01-01

    In resonant enhanced multiphoton ionization (REMPI), an atom absorbs several photons making a transition to a resonant intermediate state and subsequently ionizing out of it. With currently available tunable narrow-band lasers, the extreme sensitivity of REMPI to the specific arrangement of levels can be used to selectively probe minute amounts of a single species (atom) in a host of background material. Determination of the number density of atoms from the observed REMPI signal requires a knowledge of the multiphoton ionization cross sections. The REMPI of atomic oxygen was investigated through various excitation schemes that are feasible with available light sources. Using quantum defect theory (QDT) to estimate the various atomic parameters, the REMPI dynamics in atomic oxygen were studied incorporating the effects of saturation and a.c. Stark shifts. Results are presented for REMPI probabilities for excitation through various 2p(3) (4S sup o) np(3)P and 2p(3) (4S sup o) nf(3)F levels.

  14. Optomechanical Enhancement of Doubly Resonant 2D Optical Nonlinearity.

    PubMed

    Yi, Fei; Ren, Mingliang; Reed, Jason C; Zhu, Hai; Hou, Jiechang; Naylor, Carl H; Johnson, A T Charlie; Agarwal, Ritesh; Cubukcu, Ertugrul

    2016-03-01

    Emerging two-dimensional semiconductor materials possess a giant second order nonlinear response due to excitonic effects while the monolayer thickness of such active materials limits their use in practical nonlinear devices. Here, we report 3300 times optomechanical enhancement of second harmonic generation from a MoS2 monolayer in a doubly resonant on-chip optical cavity. We achieve this by engineering the nonlinear light-matter interaction in a microelectro-mechanical system enabled optical frequency doubling device based on an electrostatically tunable Fabry-Perot microresonator. Our versatile optomechanical approach will pave the way for next generation efficient on-chip tunable light sources, sensors, and systems based on molecularly thin materials. PMID:26854706

  15. Light-emitting diodes enhanced by localized surface plasmon resonance

    PubMed Central

    2011-01-01

    Light-emitting diodes [LEDs] are of particular interest recently as their performance is approaching fluorescent/incandescent tubes. Moreover, their energy-saving property is attracting many researchers because of the huge energy crisis we are facing. Among all methods intending to enhance the efficiency and intensity of a conventional LED, localized surface plasmon resonance is a promising way. The mechanism is based on the energy coupling effect between the emitted photons from the semiconductor and metallic nanoparticles fabricated by nanotechnology. In this review, we describe the mechanism of this coupling effect and summarize the common fabrication techniques. The prospect, including the potential to replace fluorescent/incandescent lighting devices as well as applications to flat panel displays and optoelectronics, and future challenges with regard to the design of metallic nanostructures and fabrication techniques are discussed. PMID:21711711

  16. Applications of Manganese-Enhanced Magnetic Resonance Imaging in Neuroscience

    NASA Astrophysics Data System (ADS)

    McCreary, J. Keiko

    Manganese-Enhanced Magnetic Resonance Imaging (MEMRI) has proven itself to be a beneficial technique in the field of Neuroscience. This thesis applies MEMRI to studies in neuroscience by first establishing the limitations concerning the use of MEMRI in live rats. Experiment 1 used an osmotic pump for manganese (Mn) delivery to the lateral ventricles for acquisition of anatomical images using MEMRI. From my knowledge, this was the first method demonstrating slow infusion of Mn to the lateral ventricles. In Experiment 2, MEMRI was used for volumetric analysis the whole brain and hippocampus of prenatally stressed rats. To my knowledge, this study was the first to investigate the effect of generational prenatal stress on the structure of a rat's brain using MEMRI and histology. Additionally, Experiment 2 investigated the use of a subcutaneous osmotic pump to deliver Mn for MEMRI. A summary on the use of MEMRI in Neuroscience concludes this thesis, with a discussion on the methods used and related technical considerations.

  17. Light-emitting diodes enhanced by localized surface plasmon resonance

    NASA Astrophysics Data System (ADS)

    Gu, Xuefeng; Qiu, Teng; Zhang, Wenjun; Chu, Paul K.

    2011-12-01

    Light-emitting diodes [LEDs] are of particular interest recently as their performance is approaching fluorescent/incandescent tubes. Moreover, their energy-saving property is attracting many researchers because of the huge energy crisis we are facing. Among all methods intending to enhance the efficiency and intensity of a conventional LED, localized surface plasmon resonance is a promising way. The mechanism is based on the energy coupling effect between the emitted photons from the semiconductor and metallic nanoparticles fabricated by nanotechnology. In this review, we describe the mechanism of this coupling effect and summarize the common fabrication techniques. The prospect, including the potential to replace fluorescent/incandescent lighting devices as well as applications to flat panel displays and optoelectronics, and future challenges with regard to the design of metallic nanostructures and fabrication techniques are discussed.

  18. Light-emitting diodes enhanced by localized surface plasmon resonance.

    PubMed

    Gu, Xuefeng; Qiu, Teng; Zhang, Wenjun; Chu, Paul K

    2011-01-01

    Light-emitting diodes [LEDs] are of particular interest recently as their performance is approaching fluorescent/incandescent tubes. Moreover, their energy-saving property is attracting many researchers because of the huge energy crisis we are facing. Among all methods intending to enhance the efficiency and intensity of a conventional LED, localized surface plasmon resonance is a promising way. The mechanism is based on the energy coupling effect between the emitted photons from the semiconductor and metallic nanoparticles fabricated by nanotechnology. In this review, we describe the mechanism of this coupling effect and summarize the common fabrication techniques. The prospect, including the potential to replace fluorescent/incandescent lighting devices as well as applications to flat panel displays and optoelectronics, and future challenges with regard to the design of metallic nanostructures and fabrication techniques are discussed. PMID:21711711

  19. Electronic Resonance Enhancement in Raman and CARS Spectroscopy: Surface Enhanced Scattering of Highly Fluorescent Molecules

    NASA Astrophysics Data System (ADS)

    Lawhead, Carlos; Ujj, Laszlo

    2015-03-01

    Surface enhanced Raman spectroscopy (SERS) is an extremely useful tool in increasing sensitivity of Raman spectroscopy; this technique significantly increases the signal from vibrational resonances which can overcome background fluoresces. Silver nanoparticles coated substrates and the silver nanoparticles in solution were used on a variety of fluorescent molecules in order to overcome sample complexities and measure the vibrational spectra. The possible enhancement of SERS using a coherent Raman (CARS) method was investigated, but enhancement factors due to Surface Enhanced CARS have yet to be verified. The instrument used was developed in the University of West Florida Physics Department utilized the second harmonic of a Nd:YAG laser to provide the excitation wavelength at 532 nm and is capable of both transmission and reflection Raman measurements. Special thanks to the UWF Office of Undergraduate Research.

  20. Neutron physics of the Re/Os clock. III. Resonance analyses and stellar (n,gamma) cross sections of {sup 186,187,188}Os

    SciTech Connect

    Fujii, K.; Abbondanno, U.; Belloni, F.; Milazzo, P. M.; Moreau, C.; Mosconi, M.; Kaeppeler, F.; Audouin, L.; Dillmann, I.; Heil, M.; Plag, R.; Voss, F.; Walter, S.; Wisshak, K.; Mengoni, A.; Domingo-Pardo, C.; Aerts, G.; Andriamonje, S.; Berthoumieux, E.; Dridi, W.

    2010-07-15

    Neutron resonance analyses have been performed for the capture cross sections of {sup 186}Os, {sup 187}Os, and {sup 188}Os measured at the n{sub T}OF facility at cern. Resonance parameters have been extracted up to 5, 3, and 8 keV, respectively, using the sammy code for a full R-matrix fit of the capture yields. From these results average resonance parameters were derived by a statistical analysis to provide a comprehensive experimental basis for modeling of the stellar neutron capture rates of these isotopes in terms of the Hauser-Feshbach statistical model. Consistent calculations for the capture and inelastic reaction channels are crucial for the evaluation of stellar enhancement factors to correct the Maxwellian averaged cross sections obtained from experimental data for the effect of thermally populated excited states. These factors have been calculated for the full temperature range of current scenarios of s-process nucleosynthesis using the combined information of the experimental data in the region of resolved resonances and in the continuum. The consequences of this analysis for the s-process component of the {sup 187}Os abundance and the related impact on the evaluation of the time duration of galactic nucleosynthesis via the Re/Os cosmochronometer are discussed.

  1. Dynamic measurement of temperature in detonating PBX 9502 using neutron resonance spectroscopy

    SciTech Connect

    Funk, D.J.; Rabie, R.; Mace, J.

    1997-09-01

    Accurate temperature measurements in dynamic systems have been pursued for decades and have usually relied on optical techniques. These approaches are generally hampered by insufficient information regarding the emissivity of the system under study, particularly when looking at detonating energetic materials. This results from the complex chemical change that the detonating system is undergoing, from neat organic crystals with discrete set of electronic states and molecular vibrations embedded in a binder, to gas phase products, with a different set of discrete states. Typically, when making an optical measurement, one makes the grey body approximation and measures the photon flux at a few discrete bands to extract a temperature from the light emission. We are developing NRS techniques to measure temperature in dynamic systems and overcome the limitations of optical systems. Many elements have neutron resonances with narrow enough intrinsic Breit-Wigner (Lorentzian) widths such that the resonance is substantially broadened by atomic motion even at room temperature. Thus, accurate measurement of the Doppler contribution allows one to infer the material temperature, and for the conditions achieved using standard high explosives, the probe itself is not perturbed by the high temperature and pressure. Moreover, since the opacity of energetic materials to neutrons is much less than it is to infrared, visible, or ultraviolet light, we probe the internal temperature, in contrast to measuring the surface temperature through a laser or an emission technique. Also, NRS is much less affected by the opacity of soot or other particulate than are optical methods.

  2. A Second Look at Neutron Resonance Transmission Analysis as a Spent Fuel NDA Technique

    SciTech Connect

    James W .Sterbentz; David L. Chichester

    2011-07-01

    Many different nondestructive analysis techniques are currently being investigated as a part of the United States Department of Energy's Next Generation Safeguards Initiative (NGSI) seeking methods to quantify plutonium in spent fuel. Neutron Resonance Transmission Analysis (NRTA) is one of these techniques. Having first been explored in the mid-1970s for the analysis of individual spent-fuel pins a second look, using advanced simulation and modeling methods, is now underway to investigate the suitability of the NRTA technique for assaying complete spent nuclear fuel assemblies. The technique is similar to neutron time-of-flight methods used for cross-section determinations but operates over only the narrow 0.1-20 eV range where strong, distinguishable resonances exist for both the plutonium (239, 240, 241,242Pu) and uranium (235,236,238U) isotopes of interest in spent fuel. Additionally, in this energy range resonances exists for six important fission products (99Tc, 103Rh, 131Xe, 133Cs, 145Nd, and 152Sm) which provide additional information to support spent fuel plutonium assay determinations. Initial modeling shows excellent agreement with previously published experimental data for measurements of individual spent-fuel pins where plutonium assays were demonstrated to have a precision of 2-4%. Within the simulation and modeling analyses of this project scoping studies have explored fourteen different aspects of the technique including the neutron source, drift tube configurations, and gross neutron transmission as well as the impacts of fuel burn up, cooling time, and fission-product interferences. These results show that NRTA may be a very capable experimental technique for spent-fuel assay measurements. The results suggest sufficient transmission strength and signal differentiability is possible for assays through up to 8 pins. For an 8-pin assay (looking at an assembly diagonally), 64% of the pins in a typical 17 ? 17 array of a pressurized water reactor fuel

  3. Demonstration of a single-crystal reflector-filter for enhancing slow neutron beams

    NASA Astrophysics Data System (ADS)

    Muhrer, G.; Schönfeldt, T.; Iverson, E. B.; Mocko, M.; Baxter, D. V.; Hügle, Th.; Gallmeier, F. X.; Klinkby, E. B.

    2016-09-01

    The cold polycrystalline beryllium reflector-filter concept has been used to enhance the cold neutron emission of cryogenic hydrogen moderators, while suppressing the intermediate wavelength and fast neutron emission at the same time. While suppressing the fast neutron emission is often desired, the suppression of intermediate wavelength neutrons is often unwelcome. It has been hypothesized that replacing the polycrystalline reflector-filter concept with a single-crystal reflector-filter concept would overcome the suppression of intermediate wavelength neutrons and thereby extend the usability of the reflector-filter concept to shorter but still important wavelengths. In this paper we present the first experimental data on a single-crystal reflector-filter at a reflected neutron source and compare experimental results with hypothesized performance. We find that a single-crystal reflector-filter retains the long-wavelength benefit of the polycrystalline reflector-filter, without suffering the same loss of important intermediate wavelength neutrons. This finding extends the applicability of the reflector-filter concept to intermediate wavelengths, and furthermore indicates that the reflector-filter benefits arise from its interaction with fast (background) neutrons, not with intermediate wavelength neutrons of potential interest in many types of neutron scattering.

  4. New mechanism of phase enhancement in neutron interferometry and ``exotic'' interactions

    NASA Astrophysics Data System (ADS)

    Gudkov, Vladimir

    2009-10-01

    The possibility to search for anomalous ``gravitational'' interactions in neuron interferometric experiments has been recently considered for cold [1] and ultra cold [2] neutrons, where it was shown a very large contribution to the phase of neutron wave function from these anomalous interactions. To understand the origin of this phase enhancement, we consider one dimensional Schr"odinger equation which describes neutron propagation through materials. It is shown that in many cases this Schr"odinger equation can be transformed into Hill's equation, and/or, under some conditions, into Heun's and Mathieu's equations. The asymptotic solution of the considered equations shows that the contribution of weak exotic interactions to the phase of propagated neutrons is accumulated with a distance exponentially rather than linearly. This can lead to rather large enhancement factor for a contribution of these interactions into neutron phase. Using perturbation theory approach, one can see that this enhanced phase is also proportional to the value of neutron wavelength. This explains why one can see the phase enhancement only with very cold neutrons. [4pt] [1] G. L. Greene and V. Gudkov, Phys. Rev. C 75, 015501 (2007).[0pt] [2] V. Gudkov, H. M. Shimizu and G. L. Greene, NIM A (2009), in press.

  5. Neutron Cross section Covariances in the Resonance region: 50,53Cr, 54,57Fe and 60Ni

    SciTech Connect

    Oblozinsky, P.; Cho,Y.-S.; Mattoon,C.M.; Mughabghab,S.F.

    2010-11-23

    We evaluated covariances in the neutron resonance region for capture and elastic scattering cross sections on minor structural materials, {sup 50,53}Cr, {sup 54,57}Fe and {sup 60}Ni. Use was made of the recently developed covariance formalism based on kernel approximation along with data in the Atlas of Neutron Resonances. Our results of most interest for advanced fuel cycle applications, elastic scattering cross section uncertainties at energies around 100 keV, are on the level of about 7-10%.

  6. Acoustic Resonance Spectroscopy (ARS) Munition Classification System enhancements. Final report

    SciTech Connect

    Vela, O.A.; Huggard, J.C.

    1997-09-18

    Acoustic Resonance Spectroscopy (ARS) is a non-destructive evaluation technology developed at the Los Alamos National Laboratory (LANL). This technology has resulted in three generations of instrumentation, funded by the Defense Special Weapons Agency (DSWA), specifically designed for field identification of chemical weapon (CW) munitions. Each generation of ARS instrumentation was developed with a specific user in mind. The ARS1OO was built for use by the U.N. Inspection Teams going into Iraq immediately after the Persian Gulf War. The ARS200 was built for use in the US-Russia Bilateral Chemical Weapons Treaty (the primary users for this system are the US Onsite Inspection Agency (OSIA) and their Russian counterparts). The ARS300 was built with the requirements of the Organization for the Prohibition of Chemical Weapons (OPCW) in mind. Each successive system is an improved version of the previous system based on learning the weaknesses of each and, coincidentally, on the fact that more time was available to do a requirements analysis and the necessary engineering development. The ARS300 is at a level of development that warrants transferring the technology to a commercial vendor. Since LANL will supply the computer software to the selected vendor, it is possible for LANL to continue to improve the decision algorithms, add features where necessary, and adjust the user interface before the final transfer occurs. This paper describes the current system, ARS system enhancements, and software enhancements. Appendices contain the Operations Manual (software Version 3.01), and two earlier reports on enhancements.

  7. NEUTRON-ENHANCED CALORIMETRY FOR HADRONS (NECH): FINAL REPORT

    SciTech Connect

    Andrew Stroud, Lee Sawyer

    2012-08-31

    We present the results of a project to apply scintillator technology recently developed at Louisiana Tech University to hadronic calorimetry. In particular, we developed a prototype calorimeter module incorporating scintillator embedded with metal oxide nanoparticles as the active layers. These metal oxide nanoparticles of gadolinium oxide, have high cross-sections for interactions with slow neutrons. As a part fo this research project, we have developed a novel method for producing plastic scintillators with metal oxide nanoparticles evenly distributed through the plastic without aggregation.We will test the performance of the calorimeter module in test beam and with a neutron source, in order to measure the response to the neutron component of hadronic showers. We will supplement our detector prototyping activities with detailed studies of the effect of neutron component on the resolution of hadronic energy measurements, particular in the next generation of particle flow calorimeters.

  8. Recent Advances in Neutron Physics

    ERIC Educational Resources Information Center

    Feshbach, Herman; Sheldon, Eric

    1977-01-01

    Discusses new studies in neutron physics within the last decade, such as ultracold neutrons, neutron bottles, resonance behavior, subthreshold fission, doubly radiative capture, and neutron stars. (MLH)

  9. Reaction rate of the 13C(α,n)16O neutron source using the ANC of the -3 keV resonance measured with the THM

    NASA Astrophysics Data System (ADS)

    La Cognata, M.; Spitaleri, C.; Trippella, O.; Kiss, G. G.; Rogachev, G. V.; Mukhamedzhanov, A. M.; Avila, M.; Guardo, G. L.; Koshchiy, E.; Kuchera, A.; Lamia, L.; Puglia, S. M. R.; Romano, S.; Santiago, D.; Spartà, R.

    2016-01-01

    The s-process is responsible of the synthesis of most of the nuclei in the mass range 90 ≤ A ≤ 208. It consists in a series of neutron capture reactions on seed nuclei followed by β-decays, since the neutron accretion rate is slower than the β-decay rate. Such small neutron flux is supplied by the 13C(α,n)16O reaction. It is active inside the helium-burning shell of asymptotic giant branch stars, at temperatures < 108 K, corresponding to an energy interval of 140-230 keV. In this region, the astrophysical S (E)-factor is dominated by the -3 keV sub-threshold resonance due to the 6.356 MeV level in 17O. In this work, we have applied the Trojan Horse Method (THM) to the 13C(6Li,n16O)d quasi-free reaction to extract the 6.356 MeV level resonance parameters, in particular the asymptotic normalization coefficient . A preliminary analysis of a partial data set has lead to , slightly larger than the values in the literature. However, the deduced 13C(α, n)16O reaction rate is in agreement with most results in the literature at ˜ 108 K, with enhanced accuracy thanks to our innovative approach merging together ANC and THM.

  10. Double resonance surface enhanced Raman scattering substrates: an intuitive coupled oscillator model.

    PubMed

    Chu, Yizhuo; Wang, Dongxing; Zhu, Wenqi; Crozier, Kenneth B

    2011-08-01

    The strong coupling between localized surface plasmons and surface plasmon polaritons in a double resonance surface enhanced Raman scattering (SERS) substrate is described by a classical coupled oscillator model. The effects of the particle density, the particle size and the SiO2 spacer thickness on the coupling strength are experimentally investigated. We demonstrate that by tuning the geometrical parameters of the double resonance substrate, we can readily control the resonance frequencies and tailor the SERS enhancement spectrum. PMID:21934853

  11. A workshop on enhanced national capability for neutron scattering

    SciTech Connect

    Hurd, Alan J; Rhyne, James J; Lewis, Paul S

    2009-01-01

    This two-day workshop will engage the international neutron scattering community to vet and improve the Lujan Center Strategic Plan 2007-2013 (SP07). Sponsored by the LANL SC Program Office and the University of California, the workshop will be hosted by LANSCE Professor Sunny Sinha (UCSD). Endorsement by the Spallation Neutron Source will be requested. The discussion will focus on the role that the Lujan Center will play in the national neutron scattering landscape assuming full utilization of beamlines, a refurbished LANSCE, and a 1.4-MW SNS. Because the Lujan Strategic Plan is intended to set the stage for the Signature Facility era at LANSCE, there will be some discussion of the long-pulse spallation source at Los Alamos. Breakout groups will cover several new instrument concepts, upgrades to present instruments, expanded sample environment capabilities, and a look to the future. The workshop is in keeping with a request by BES to update the Lujan strategic plan in coordination with the SNS and the broader neutron community. Workshop invitees will be drawn from the LANSCE User Group and a broad cross section of the US, European, and Pacific Rim neutron scattering research communities.

  12. The upgraded cold neutron triple-axis spectrometer FLEXX - enhanced capabilities by new instrumental options

    NASA Astrophysics Data System (ADS)

    Habicht, Klaus; Lucía Quintero-Castro, Diana; Toft-Petersen, Rasmus; Kure, Mathias; Mäde, Lucas; Groitl, Felix; Le, Manh Duc

    2015-01-01

    The upgrade of the cold neutron triple axis spectrometer FLEXX, a work-horse instrument for inelastic neutron scattering matching the sample environment capabilities at Helmholtz-Zentrum Berlin, has been successfully accomplished. Experiments confirmed an order of magnitude gain in flux now allowing for intensity demanding options to be fully exploited at FLEXX. In this article, we describe the layout and design of two newly available FLEXX instrument options in detail. The new Heusler analyzer gives an increase of the detected polarized neutron flux due to its superior focusing properties, significantly improving the feasibility of future polarized and neutron resonance spin echo experiments. The MultiFLEXX option provides simultaneous access to large regions in wavevector and energy space for inelastic excitations thus adding mapping capabilities to the spectrometer.

  13. Enhancement of Otolith Specific Ocular Responses Using Vestibular Stochastic Resonance

    NASA Technical Reports Server (NTRS)

    Fiedler, Matthew; De Dios, Yiri E.; Esteves, Julie; Galvan, Raquel; Wood, Scott; Bloomberg, Jacob; Mulavara, Ajitkumar

    2011-01-01

    Introduction: Astronauts experience disturbances in sensorimotor function after spaceflight during the initial introduction to a gravitational environment, especially after long-duration missions. Our goal is to develop a countermeasure based on vestibular stochastic resonance (SR) that could improve central interpretation of vestibular input and mitigate these risks. SR is a mechanism by which noise can assist and enhance the response of neural systems to relevant, imperceptible sensory signals. We have previously shown that imperceptible electrical stimulation of the vestibular system enhances balance performance while standing on an unstable surface. Methods: Eye movement data were collected from 10 subjects during variable radius centrifugation (VRC). Subjects performed 11 trials of VRC that provided equivalent tilt stimuli from otolith and other graviceptor input without the normal concordant canal cues. Bipolar stochastic electrical stimulation, in the range of 0-1500 microamperes, was applied to the vestibular system using a constant current stimulator through electrodes placed over the mastoid process behind the ears. In the VRC paradigm, subjects were accelerated to 216 deg./s. After the subjects no longer sensed rotation, the chair oscillated along a track at 0.1 Hz to provide tilt stimuli of 10 deg. Eye movements were recorded for 6 cycles while subjects fixated on a target in darkness. Ocular counter roll (OCR) movement was calculated from the eye movement data during periods of chair oscillations. Results: Preliminary analysis of the data revealed that 9 of 10 subjects showed an average increase of 28% in the magnitude of OCR responses to the equivalent tilt stimuli while experiencing vestibular SR. The signal amplitude at which performance was maximized was in the range of 100-900 microamperes. Discussion: These results indicate that stochastic electrical stimulation of the vestibular system can improve otolith specific responses. This will have a

  14. Demonstration of a Single-Crystal Reflector-Filter for Enhancing Slow Neutron Beams

    DOE PAGESBeta

    Muhrer, Guenter; Schönfeldt, Troels; Iverson, Erik B.; Mocko, Michal; Baxter, David V.; Hügle, Thomas; Gallmeier, Franz X.; Klinkby, Esben

    2016-06-14

    The cold polycrystalline beryllium reflector-filter concept has been used to enhance the cold neutron emission of cryogenic hydrogen moderators, while suppressing the intermediate wavelength and fast neutron emission at the same time. While suppressing the fast neutron emission is often desired, the suppression of intermediate wavelength neutrons is often unwelcome. It has been hypothesized that replacing the polycrystalline reflector-filter concept with a single-crystal reflector-filter concept would overcome the suppression of intermediate wavelength neutrons and thereby extend the usability of the reflector-filter concept to shorter but still important wavelengths. In this paper we present the first experimental data on a single-crystalmore » reflector-filter and compare experimental results with hypothesized performance. We find that a single-crystal reflector-filter retains the long-wavelength benefit of the polycrystalline reflector-filter, without suffering the same loss of important intermediate wavelength neutrons. Ultimately, this finding extends the applicability of the reflector-filter concept to intermediate wavelengths, and furthermore indicates that the reflector-filter benefits arise from its interaction with fast (background) neutrons, not with intermediate wavelength neutrons of potential interest in many types of neutron scattering.« less

  15. Demonstration of a Single-Crystal Reflector-Filter for Enhancing Slow Neutron Beams

    SciTech Connect

    Muhrer, Guenter; Schönfeldt, Troels; Iverson, Erik B; Mocko, Michal; Baxter, David V; Hügle, Thomas; Gallmeier, Franz X; Klinkby, Esben

    2016-01-01

    The cold polycrystalline beryllium reflector-filter concept has been used to enhance the cold neutron emission of cryogenic hydrogen moderators, while suppressing the intermediate wavelength and fast neutron emission at the same time. While suppressing the fast neutron emission is often desired, the suppression of intermediate wavelength neutrons is often unwelcome. It has been hypothesized that replacing the polycrystalline reflector-filter concept with a single-crystal reflector-filter concept would overcome the suppression of intermediate wavelength neutrons and thereby extend the usability of the reflector-filter concept to shorter but still important wavelengths. In this paper we present the first experimental data on a single-crystal reflector-filter and compare experimental results with hypothesized performance. We find that a single-crystal reflector-filter retains the long-wavelength benefit of the polycrystalline reflector-filter, without suffering the same loss of important intermediate wavelength neutrons. This finding extends the applicability of the reflector-filter concept to intermediate wavelengths, and furthermore indicates that the reflector-filter benefits arise from its interaction with fast (background) neutrons, not with intermediate wavelength neutrons of potential interest in many types of neutron scattering.

  16. Surface plasmon resonance prism coupler for enhanced circular dichroism sensing.

    PubMed

    Phan, Quoc-Hung; Lo, Yu-Lung; Huang, Chih-Ling

    2016-06-13

    A novel method for enhanced circular dichroism (CD) detection is proposed based on a surface plasmon resonance (SPR) prism coupler and a polarization scanning ellipsometry technique. An analytical model is derived to extract the CD and degree of polarization (DOP) properties of optical samples with and without scattering effects, respectively. The validity of the analytical model is confirmed by means of numerical simulations. The simulation results show that the proposed detection method has a sensitivity of 10-5~10-6 RIU (refractive index unit) for refractive indices in the range of 1.32~1.36 and 1.3100~1.3118. The practical feasibility of the proposed method is demonstrated by the experimental results for the sensitivity of the CD with the chlorophyllin samples with/without scattering effect. It is shown that for both types of sample, the extracted CD value increases linearly with the chlorophyll concentration over the considered range. In general, the results obtained in this study show that the measured CD response is highly sensitive to the polarization scanning angle. Consequently, the potential of polarization scanning ellipsometry for high-resolution CD detection is confirmed. PMID:27410300

  17. Manganese-enhanced magnetic resonance microscopy of mineralization

    USGS Publications Warehouse

    Chesnick, I.E.; Todorov, T.I.; Centeno, J.A.; Newbury, D.E.; Small, J.A.; Potter, K.

    2007-01-01

    Paramagnetic manganese (II) can be employed as a calcium surrogate to sensitize magnetic resonance microscopy (MRM) to the processing of calcium during bone formation. At high doses, osteoblasts can take up sufficient quantities of manganese, resulting in marked changes in water proton T1, T2 and magnetization transfer ratio values compared to those for untreated cells. Accordingly, inductively coupled plasma mass spectrometry (ICP-MS) results confirm that the manganese content of treated cell pellets was 10-fold higher than that for untreated cell pellets. To establish that manganese is processed like calcium and deposited as bone, calvaria from the skull of embryonic chicks were grown in culture medium supplemented with 1 mM MnCl2 and 3 mM CaCl2. A banding pattern of high and low T2 values, consistent with mineral deposits with high and low levels of manganese, was observed radiating from the calvarial ridge. The results of ICP-MS studies confirm that manganese-treated calvaria take up increasing amounts of manganese with time in culture. Finally, elemental mapping studies with electron probe microanalysis confirmed local variations in the manganese content of bone newly deposited on the calvarial surface. This is the first reported use of manganese-enhanced MRM to study the process whereby calcium is taken up by osteoblasts cells and deposited as bone. ?? 2007 Elsevier Inc. All rights reserved.

  18. Image fusion for dynamic contrast enhanced magnetic resonance imaging

    PubMed Central

    Twellmann, Thorsten; Saalbach, Axel; Gerstung, Olaf; Leach, Martin O; Nattkemper, Tim W

    2004-01-01

    Background Multivariate imaging techniques such as dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) have been shown to provide valuable information for medical diagnosis. Even though these techniques provide new information, integrating and evaluating the much wider range of information is a challenging task for the human observer. This task may be assisted with the use of image fusion algorithms. Methods In this paper, image fusion based on Kernel Principal Component Analysis (KPCA) is proposed for the first time. It is demonstrated that a priori knowledge about the data domain can be easily incorporated into the parametrisation of the KPCA, leading to task-oriented visualisations of the multivariate data. The results of the fusion process are compared with those of the well-known and established standard linear Principal Component Analysis (PCA) by means of temporal sequences of 3D MRI volumes from six patients who took part in a breast cancer screening study. Results The PCA and KPCA algorithms are able to integrate information from a sequence of MRI volumes into informative gray value or colour images. By incorporating a priori knowledge, the fusion process can be automated and optimised in order to visualise suspicious lesions with high contrast to normal tissue. Conclusion Our machine learning based image fusion approach maps the full signal space of a temporal DCE-MRI sequence to a single meaningful visualisation with good tissue/lesion contrast and thus supports the radiologist during manual image evaluation. PMID:15494072

  19. Superparamagnetic nanoparticles for enhanced magnetic resonance and multimodal imaging

    NASA Astrophysics Data System (ADS)

    Sikma, Elise Ann Schultz

    Magnetic resonance imaging (MRI) is a powerful tool for noninvasive tomographic imaging of biological systems with high spatial and temporal resolution. Superparamagnetic (SPM) nanoparticles have emerged as highly effective MR contrast agents due to their biocompatibility, ease of surface modification and magnetic properties. Conventional nanoparticle contrast agents suffer from difficult synthetic reproducibility, polydisperse sizes and weak magnetism. Numerous synthetic techniques and nanoparticle formulations have been developed to overcome these barriers. However, there are still major limitations in the development of new nanoparticle-based probes for MR and multimodal imaging including low signal amplification and absence of biochemical reporters. To address these issues, a set of multimodal (T2/optical) and dual contrast (T1/T2) nanoparticle probes has been developed. Their unique magnetic properties and imaging capabilities were thoroughly explored. An enzyme-activatable contrast agent is currently being developed as an innovative means for early in vivo detection of cancer at the cellular level. Multimodal probes function by combining the strengths of multiple imaging techniques into a single agent. Co-registration of data obtained by multiple imaging modalities validates the data, enhancing its quality and reliability. A series of T2/optical probes were successfully synthesized by attachment of a fluorescent dye to the surface of different types of nanoparticles. The multimodal nanoparticles generated sufficient MR and fluorescence signal to image transplanted islets in vivo. Dual contrast T1/T2 imaging probes were designed to overcome disadvantages inherent in the individual T1 and T2 components. A class of T1/T2 agents was developed consisting of a gadolinium (III) complex (DTPA chelate or DO3A macrocycle) conjugated to a biocompatible silica-coated metal oxide nanoparticle through a disulfide linker. The disulfide linker has the ability to be reduced

  20. Exploration of Adiabatic Resonance Crossing Through Neutron Activator Design for Thermal and Epithermal Neutron Formation in (99)Mo Production and BNCT Applications.

    PubMed

    Khorshidi, Abdollah

    2015-10-01

    A feasibility study was performed to design thermal and epithermal neutron sources for radioisotope production and boron neutron capture therapy (BNCT) by moderating fast neutrons. The neutrons were emitted from the reaction between (9)Be, (181)Ta, and (184)W targets and 30 MeV protons accelerated by a small cyclotron at 300 μA. In this study, the adiabatic resonance crossing (ARC) method was investigated by means of (207)Pb and (208)Pb moderators, graphite reflector, and boron absorber around the moderator region. Thermal/epithermal flux, energy, and cross section of accumulated neutrons in the activator were examined through diverse thicknesses of the specified regions. Simulation results revealed that the (181)Ta target had the highest neutron yield, and also tungsten was found to have the highest values in both surface and volumetric flux ratio. Transmutation in the (98)Mo sample through radiative capture was investigated for the natural lead moderator. When the sample radial distance from the target was increased inside the graphite region, the production yield had the greatest value of activity. The potential of the ARC method is a replacement or complements the current reactor-based supply sources of BNCT purposes. PMID:26397967

  1. Measurement of the thermal neutron capture cross section and the resonance integral of radioactive Hf182

    NASA Astrophysics Data System (ADS)

    Vockenhuber, C.; Bichler, M.; Wallner, A.; Kutschera, W.; Dillmann, I.; Käppeler, F.

    2008-04-01

    The neutron capture cross sections of the radioactive isotope Hf182 (t1/2=8.9×106 yr) in the thermal and epithermal energy regions have been measured by activation at the TRIGA Mark-II reactor of the Atomic Institute of the Austrian Universities in Vienna, Austria, and subsequent γ-ray spectroscopy of Hf183. High values for the thermal (kT=25 meV) cross section σ0=133±10 b and for the resonance integral I0=5850±660 b were found. Additionally, the absolute intensities of the main γ-ray transitions in the decay of Hf182 have been considerably improved.

  2. Neutron-skin thickness from the study of the anti-analog giant dipole resonance

    SciTech Connect

    Krasznahorkay, A.; Stuhl, L.; Csatlos, M.; Algora, A.; and others

    2012-10-20

    The {gamma}-decay of the anti-analog of the giant dipole resonance (AGDR) to the isobaric analog state has been measured following the p({sup 124}Sn,n) reaction at a beam energy of 600 MeV/nucleon. The energy of the transition was also calculated with state-of-the-art self-consistent relativistic random-phase approximation (RPA) and turned out to be very sensitive to the neutronskin thickness ({Delta}R{sub pn}). By comparing the theoretical results with the measured one, the {Delta}R{sub pn} value for {sup 124}Sn was deduced to be 0.21 {+-} 0.07 fm, which agrees well with the previous results. The present method offers new possibilities for measuring the neutron-skin thicknesses of very exotic isotopes.

  3. Neutron total cross-sections and resonance parameters of Mo and Ta

    NASA Astrophysics Data System (ADS)

    Moinul Haque Meaze, A. K. M.; Devan, K.; Lee, Y. S.; Oh, Y. D.; Kim, G. N.; Son, D.

    2007-02-01

    Experimental results of transmissions for the samples of natural molybdenum with thickness 0.0192 atoms/barn and for the four samples of natural tantalum with thickness 0.0222, 0.0111, 0.0055 and 0.0025 atoms/barn are presented in this work. Measurements were carried out at the Pohang Neutron Facility which consists of a 100 MeV Linac, water-cooled tantalum target, and 12 m flight path length. Effective total cross-sections were extracted from the transmission data, and resonance parameters were obtained by using the code SAMMY. The present measurements were compared with other measurements and with the evaluated nuclear data file ENDF/B-VI.8.

  4. Neutron yield enhancement in laser-induced deuterium-deuterium fusion using a novel shaped target.

    PubMed

    Zhao, J R; Zhang, X P; Yuan, D W; Chen, L M; Li, Y T; Fu, C B; Rhee, Y J; Li, F; Zhu, B J; Li, Yan F; Liao, G Q; Zhang, K; Han, B; Liu, C; Huang, K; Ma, Y; Li, Yi F; Xiong, J; Huang, X G; Fu, S Z; Zhu, J Q; Zhao, G; Zhang, J

    2015-06-01

    Neutron yields have direct correlation with the energy of incident deuterons in experiments of laser deuterated target interaction [Roth et al., Phys. Rev. Lett. 110, 044802 (2013) and Higginson et al., Phys. Plasmas 18, 100703 (2011)], while deuterated plasma density is also an important parameter. Experiments at the Shenguang II laser facility have produced neutrons with energy of 2.45 MeV using d (d, n) He reaction. Deuterated foil target and K-shaped target were employed to study the influence of plasma density on neutron yields. Neutron yield generated by K-shaped target (nearly 10(6)) was two times higher than by foil target because the K-shaped target results in higher density plasma. Interferometry and multi hydro-dynamics simulation confirmed the importance of plasma density for enhancement of neutron yields. PMID:26133837

  5. Neutron yield enhancement in laser-induced deuterium-deuterium fusion using a novel shaped target

    SciTech Connect

    Zhao, J. R.; Chen, L. M. Li, Y. T.; Li, F.; Zhu, B. J.; Li, Yan. F.; Liao, G. Q.; Huang, K.; Ma, Y.; Li, Yi. F.; Zhang, X. P.; Fu, C. B.; Yuan, D. W.; Zhang, K.; Han, B.; Zhao, G.; Rhee, Y. J.; Liu, C.; Xiong, J.; Huang, X. G.; and others

    2015-06-15

    Neutron yields have direct correlation with the energy of incident deuterons in experiments of laser deuterated target interaction [Roth et al., Phys. Rev. Lett. 110, 044802 (2013) and Higginson et al., Phys. Plasmas 18, 100703 (2011)], while deuterated plasma density is also an important parameter. Experiments at the Shenguang II laser facility have produced neutrons with energy of 2.45 MeV using d (d, n) He reaction. Deuterated foil target and K-shaped target were employed to study the influence of plasma density on neutron yields. Neutron yield generated by K-shaped target (nearly 10{sup 6}) was two times higher than by foil target because the K-shaped target results in higher density plasma. Interferometry and multi hydro-dynamics simulation confirmed the importance of plasma density for enhancement of neutron yields.

  6. Further Evaluation of the Neutron Resonance Transmission Analysis (NRTA) Technique for Assaying Plutonium in Spent Fuel

    SciTech Connect

    J. W. Sterbentz; D. L. Chichester

    2011-09-01

    This is an end-of-year report (Fiscal Year (FY) 2011) for the second year of effort on a project funded by the National Nuclear Security Administration's Office of Nuclear Safeguards (NA-241). The goal of this project is to investigate the feasibility of using Neutron Resonance Transmission Analysis (NRTA) to assay plutonium in commercial light-water-reactor spent fuel. This project is part of a larger research effort within the Next-Generation Safeguards Initiative (NGSI) to evaluate methods for assaying plutonium in spent fuel, the Plutonium Assay Challenge. The second-year goals for this project included: (1) assessing the neutron source strength needed for the NRTA technique, (2) estimating count times, (3) assessing the effect of temperature on the transmitted signal, (4) estimating plutonium content in a spent fuel assembly, (5) providing a preliminary assessment of the neutron detectors, and (6) documenting this work in an end of the year report (this report). Research teams at Los Alamos National Laboratory (LANL), Lawrence Berkeley National Laboratory (LBNL), Pacific Northwest National Laboratory (PNNL), and at several universities are also working to investigate plutonium assay methods for spent-fuel safeguards. While the NRTA technique is well proven in the scientific literature for assaying individual spent fuel pins, it is a newcomer to the current NGSI efforts studying Pu assay method techniques having just started in March 2010; several analytical techniques have been under investigation within this program for two to three years or more. This report summarizes work performed over a nine month period from January-September 2011 and is to be considered a follow-on or add-on report to our previous published summary report from December 2010 (INL/EXT-10-20620).

  7. Two Coils Resonant Ramsey’s Method for the Measurement of Time Reversal Invariance Violation in Neutron Transmission

    PubMed Central

    Loukachevitch, V. V.; Aldushchenkov, A. V.

    2005-01-01

    It is proposed within the framework of Ramsey’s method to register two-dimensional spectra, depending on the neutron phase and neutron energy, for measuring parity (P) and time (T) violating amplitudes of the interaction of polarized neutrons with polarized 139La nuclei in region of the p-wave resonance. The form of the phase spectrum and corresponding expressions for the asymmetries are obtained on the basis of a formalism of a spin density matrix. It is shown that the ratio of the P,T,-violating to P-violating imaginary amplitudes can be obtained from the measurements of the neutron phase spectrum with polarized and unpolarized 139La target. PMID:27308169

  8. Hands-on resonance-enhanced photoacoustic detection

    NASA Astrophysics Data System (ADS)

    Euler, Manfred

    2001-10-01

    The design of an improved photoacoustic converter cell using kitchen equipment is described. It operates by changing manually the Helmholtz resonance frequency of bottles by adjusting the distance between the bottleneck and the outer ear. The experiment helps to gain insights in ear performance, in photoacoustic detection methods, in resonance phenomena and their role for detecting small periodic signals in the presence of noise.

  9. Combining Neutron and Magnetic Resonance Imaging to Study the Interaction of Plant Rootsand Soil

    NASA Astrophysics Data System (ADS)

    Oswald, Sascha E.; Tötzke, Christian; Haber-Pohlmeier, Sabina; Pohlmeier, Andreas; Kaestner, Anders P.; Lehmann, Eberhard

    The soil in direct vicinity of the roots, the root-soil interface or so called rhizosphere, is heavily modified by the activity of roots, compared to bulk soil, e.g. in respect to microbiology and soil chemistry. It has turned out that the root-soil interface, though small in size, also plays a decisive role in the hydraulics controlling the water flow from bulk soil into the roots. A promising approach for the non-invasive investigation of water dynamics, water flow and solute transport is the combination of the two imaging techniques magnetic resonance imaging (MRI) and neutron imaging (NI). Both methods are complementary, because NI maps the total proton density, possibly amplified by NI tracers, which usually corresponds to total water content, and is able to detect changes and spatial patterns with high resolution. On the other side, nuclear magnetic resonance relaxation times reflect the interaction between fluid and matrix, while also a mapping of proton spin density and thus water content is possible. Therefore MRI is able to classify different water pools via their relaxation times additionally to the water distribution inside soil as a porous medium. We have started such combined measurements with the approach to use the same samples and perform tomography with each imaging method at different location and short-term sample transfer.

  10. The pygmy quadrupole resonance and neutron-skin modes in 124Sn

    NASA Astrophysics Data System (ADS)

    Spieker, M.; Tsoneva, N.; Derya, V.; Endres, J.; Savran, D.; Harakeh, M. N.; Harissopulos, S.; Herzberg, R.-D.; Lagoyannis, A.; Lenske, H.; Pietralla, N.; Popescu, L.; Scheck, M.; Schlüter, F.; Sonnabend, K.; Stoica, V. I.; Wörtche, H. J.; Zilges, A.

    2016-01-01

    We present an extensive experimental study of the recently predicted pygmy quadrupole resonance (PQR) in Sn isotopes, where complementary probes were used. In this study, (α ,α‧ γ) and (γ ,γ‧) experiments were performed on 124Sn. In both reactions, Jπ =2+ states below an excitation energy of 5 MeV were populated. The E2 strength integrated over the full transition densities could be extracted from the (γ ,γ‧) experiment, while the (α ,α‧ γ) experiment at the chosen kinematics strongly favors the excitation of surface modes because of the strong α-particle absorption in the nuclear interior. The excitation of such modes is in accordance with the quadrupole-type oscillation of the neutron skin predicted by a microscopic approach based on self-consistent density functional theory and the quasiparticle-phonon model (QPM). The newly determined γ-decay branching ratios hint at a non-statistical character of the E2 strength, as it has also been recently pointed out for the case of the pygmy dipole resonance (PDR). This allows us to distinguish between PQR-type and multiphonon excitations and, consequently, supports the recent first experimental indications of a PQR in 124Sn.

  11. Resonant states of the neutron-rich Λ hypernucleus He7Λ

    NASA Astrophysics Data System (ADS)

    Hiyama, E.; Isaka, M.; Kamimura, M.; Myo, T.; Motoba, T.

    2015-05-01

    The structure of the neutron-rich Λ hypernucleus, He7Λ is studied within the framework of an α +Λ +n +n four-body cluster model. We predict second 3 /2+ and 5 /2+ states, corresponding to a 0 s Λ coupled to the second 2+ state of 6He, as narrow resonant states with widths of Γ ˜1 MeV to be at 0.03 and 0.07 MeV with respect to the α +Λ +n +n threshold. From a separate estimate of the differential cross section for the 7Li (γ ,K+) He7Λ reaction, we suggest a possibility to observe these states at the Thomas Jefferson National Accelerator Facility (JLab) in the future. We also calculate the second 2+ state of 6He as a resonant state within the framework of an α +n +n three-body cluster model. Our result is 2.81 MeV with Γ =4.63 MeV with respect to the α +n +n threshold. This energy position is ˜1 MeV higher, and with a much broader decay width, than the recent SPIRAL data. We suggest that an experiment at JLab to search for the second 3 /2+ and 5 /2+ states of He7Λ would provide an opportunity to confirm the second 2+ state of the core nucleus 6He.

  12. Enhanced dynamic electron paramagnetic resonance imaging of in vivo physiology

    NASA Astrophysics Data System (ADS)

    Redler, Gage

    It is well established that low oxygen concentration (hypoxia) in tumors strongly affects their malignant state and resistance to therapy. The importance of tumor oxygenation status has led to increased interest in the development of robust oxygen imaging modalities. One such method is electron paramagnetic resonance imaging (EPRI). EPRI has provided a non-invasive, quantitative imaging modality with sensitivity deep in tissues, capable of investigating static oxygen concentration (pO2) in vivo and has helped to corroborate the correlation between chronic states of hypoxia and tumor malignancy. However, when studying the complicated physiology of a living animal, the situation tends to be inherently dynamic. It has been found that in certain tumor regions there may exist steady states of hypoxia, or chronic hypoxia, whereas in other regions there may exist transient states of hypoxia, or acute hypoxia. It has been postulated that the negative prognostic implications associated with hypoxic tumors may be amplified for acutely hypoxic tumors. However, controversial data and a current lack in methods with the capability to noninvasively image tumor pO2 in vivo with sufficient spatial, temporal, and pO 2 resolution preclude definitive conclusions on the relationships between the different forms of hypoxia and the differences in their clinical implications. A particularly promising oxygen imaging modality that can help to study both chronic and acute hypoxia and elucidate important physiological and clinical differences is rapid Dynamic EPRI. The focus of this work is the development of methods enabling Dynamic EPRI of in vivo physiology as well as its potential applications. This work describes methods which enhance various aspects of EPRI in order to establish a more robust Dynamic EPRI capable of noninvasively studying and quantifying acute hypoxia in vivo. These enhancements are achieved through improvements that span from methods for the acquisition of individual

  13. Super defect inside photonic crystal ring resonator to enhance Q factor

    NASA Astrophysics Data System (ADS)

    Sreenivasulu, Tupakula; Kolli, Venkateswara Rao; Tarimala, Badrinarayana; Hegde, Gopalkrishna; Sangineni, Mohan; Talabattula, Srinivas

    2016-03-01

    A design is proposed to enhance the quality factor of a photonic crystal ring resonator. A super defect is employed inside the ring resonator, which consists of variation of hole dimensions inside the ring resonator in such a way that the radiation field components of the resonant nanocavity are forced to get cancelled in order to reduce radiation loss. After this forced cancellation, the improved Q factor is calculated as 18,000. This photonic crystal ring resonator can be used for sensing applications like force sensing, pressure sensing, biochemical sensing, and communication applications like demultiplexing.

  14. Dynamics of hydrogenated amorphous silicon flexural resonators for enhanced performance

    NASA Astrophysics Data System (ADS)

    Mouro, J.; Chu, V.; Conde, J. P.

    2016-04-01

    Hydrogenated amorphous silicon thin-film flexural resonators with sub-micron actuation gaps are fabricated by surface micromachining on glass substrates. Experimentally, the resonators are electrostatically actuated and their motion is optically detected. Three different configurations for the electrostatic excitation force are used to study the dynamics of the resonators. In the first case, a dc voltage (Vdc) is added to an ac voltage with variable excitation frequency (Vac(ω)) and harmonic, superharmonic, and subharmonic resonances of different orders are observed. The second case consists on mixing the dc voltage (Vdc) with an ac voltage applied at a fixed frequency of twice the natural frequency of the resonator (V(2ω0)). High-amplitude parametric resonance is excited at the natural frequency of the system, ω0. This configuration allows a separation between the frequencies of the excitation and the mechanical motion. Finally, in the third case, the dc voltage (Vdc) is combined with both ac voltages, Vac(ω) and V(2ω0), and parametric resonance is excited and emerges from the fundamental harmonic resonance peak. The single-degree-of-freedom equation of motion is modeled and discussed for each case. The nonlinearity inherent to the electrostatic force is responsible for modulating the spring constant of the system at different frequencies, giving rise to parametric resonance. These equations of motion are simulated in the time and frequency domains, providing a consistent explanation of the experimentally observed phenomena. A wide variety of possible resonance modes with different characteristics can be used advantageously in MEMS device design.

  15. Video enhancement of X-ray and neutron radiographs

    NASA Technical Reports Server (NTRS)

    Vary, A.

    1973-01-01

    System was devised for displaying radiographs on television screen and enhancing fine detail in picture. System uses analog-computer circuits to process television signal from low-noise television camera. Enhanced images are displayed in black and white and can be controlled to vary degree of enhancement and magnification of details in either radiographic transparencies or opaque photographs.

  16. Design, status and first operations of the spallation neutron source polyphase resonant converter modulator system

    SciTech Connect

    Reass, W. A.; Apgar, S. E.; Baca, D. M.; Doss, James D.; Gonzales, J.; Gribble, R. F.; Hardek, T. W.; Lynch, M. T.; Rees, D. E.; Tallerico, P. J.; Trujillo, P. B.; Anderson, D. E.; Heidenreich, D. A.; Hicks, J. D.; Leontiev, V. N.

    2003-01-01

    The Spallation Neutron Source (SNS) is a new 1.4 MW average power beam, 1 GeV accelerator being built at Oak Ridge National Laboratory. The accelerator requires 15 converter-modulator stations each providing between 9 and 11 MW pulses with up to a 1 .I MW average power. The converter-modulator can be described as a resonant 20 kHz polyphase boost inverter. Each converter modulator derives its buss voltage from a standard substation cast-core transformer. Each substation is followed by an SCR pre-regulator to accommodate voltage changes from no load to full load, in addition to providing a soft-start function. Energy storage is provided by self-clearing metallized hazy polypropylene traction capacitors. These capacitors do not fail short, but clear any internal anomaly. Three 'H-Bridge' IGBT transistor networks are used to generate the polyphase 20 kHz transformer primary drive waveforms. The 20 kHz drive waveforms are time-gated to generate the desired klystron pulse width. Pulse width modulation of the individual 20 lcHz pulses is utilized to provide regulated output waveforms with DSP based adaptive feedforward and feedback techniques. The boost transformer design utilizes nanocrystalline alloy that provides low core loss at design flux levels and switching frequencies. Capacitors are used on the transformer secondary networks to resonate the leakage inductance. The transformers are wound for a specific leakage inductance, not turns ratio. This design technique generates multiple secondary volts per turn as compared to the primary. With the appropriate tuning conditions, switching losses are minimized. The resonant topology has the added benefit of being deQed in a klystron fault condition, with little energy deposited in the arc. This obviates the need of crowbars or other related networks. A review of these design parameters, operational performance, production status, and OWL installation and performance to date will be presented.

  17. Neutron capture therapy: a comparison between dose enhancement of various agents, nanoparticles and chemotherapy drugs.

    PubMed

    Khosroabadi, Mohsen; Ghorbani, Mahdi; Rahmani, Faezeh; Knaup, Courtney

    2014-09-01

    The aim of this study is to compare dose enhancement of various agents, nanoparticles and chemotherapy drugs for neutron capture therapy. A (252)Cf source was simulated to obtain its dosimetric parameters, including air kerma strength, dose rate constant, radial dose function and total dose rates. These results were compared with previously published data. Using (252)Cf as a neutron source, the in-tumour dose enhancements in the presence of atomic (10)B, (157)Gd and (33)S agents; (10)B, (157)Gd, (33)S nanoparticles; and Bortezomib and Amifostine chemotherapy drugs were calculated and compared in neutron capture therapy. Monte Carlo code MCNPX was used for simulation of the (252)Cf source, a soft tissue phantom, and a tumour containing each capture agent. Dose enhancement for 100, 200 and 500 ppm of the mentioned media was calculated. Calculated dosimetric parameters of the (252)Cf source were in agreement with previously published values. In comparison to other agents, maximum dose enhancement factor was obtained for 500 ppm of atomic (10)B agent and (10)B nanoparticles, equal to 1.06 and 1.08, respectively. Additionally, Bortezomib showed a considerable dose enhancement level. From a dose enhancement point of view, media containing (10)B are the best agents in neutron capture therapy. Bortezomib is a chemotherapy drug containing boron and can be proposed as an agent in boron neutron capture therapy. However, it should be noted that other physical, chemical and medical criteria should be considered in comparing the mentioned agents before their clinical use in neutron capture therapy. PMID:24961208

  18. Using the {delta}{sub 3} statistic to test for missed levels in mixed sequence neutron resonance data

    SciTech Connect

    Mulhall, Declan

    2009-09-15

    The {delta}{sub 3}(L) statistic is studied as a tool to detect missing levels in the neutron resonance data where two sequences are present. These systems are problematic because there is no level repulsion, and the resonances can be too close to resolve. {delta}{sub 3}(L) is a measure of the fluctuations in the number of levels in an interval of length L on the energy axis. The method used is tested on ensembles of mixed Gaussian orthogonal ensemble spectra, with a known fraction of levels (x%) randomly depleted, and can accurately return x. The accuracy of the method as a function of spectrum size is established. The method is used on neutron resonance data for 11 isotopes with either s-wave neutrons on odd-A isotopes, or p-wave neutrons on even-A isotopes. The method compares favorably with a maximum likelihood method applied to the level spacing distribution. Nuclear data ensembles were made from 20 isotopes in total, and their {delta}{sub 3}(L) statistics are discussed in the context of random matrix theory.

  19. A Monte Carlo simulation to study a design of a gamma-ray detector for neutron resonance densitometry

    NASA Astrophysics Data System (ADS)

    Tsuchiya, H.; Harada, H.; Koizumi, M.; Kitatani, F.; Takamine, J.; Kureta, M.; Iimura, H.

    2013-11-01

    Neutron resonance densitometry (NRD) has been proposed to quantify nuclear materials in melted fuel (MF) that will be removed from the Fukushima Daiichi nuclear power plant. The problem is complex due to the expected presence of strong neutron absorbing impurities such as 10B and high radiation field that is mainly caused by 137Cs. To identify the impurities under the high radiation field, NRD is based on a combination of neutron resonance transmission analysis (NRTA) and neutron resonance capture analysis (NRCA). We investigated with Geant4 the performance of a gamma-ray detector for NRCA in NRD. The gamma-ray detector has a well shape, consisting of cylindrical and tube type LaBr3 scintillators. We show how it measures 478 keV gamma rays derived from 10B(n, αγ) reaction in MF under a high 137Cs-radiation environment. It was found that the gamma-ray detector was able to well suppress the Compton edge of 662-keV gamma rays of 137Cs and had a high peak-to-Compton continuum ratio, by using the tube type scintillator as a back-catcher detector. Then, we demonstrate that with this ability, detection of 478-keV gamma rays from 10B is accomplished in realistic measuring time.

  20. Surface-enhanced resonance hyper-Raman scattering and surface-enhanced resonance Raman scattering of dyes adsorbed on silver electrode and silver colloid: a comparison study

    NASA Astrophysics Data System (ADS)

    Li, Wu-Hu; Li, Xiao-Yuan; Yu, Nai-Teng

    1999-10-01

    Surface-enhanced resonance hyper-Raman scattering (SERHRS) and surface-enhanced resonance Raman scattering (SERRS) of three dyes, rhodamine 6G, crystal violet and basic fuchsin, are studied comparatively on electrochemically roughened silver electrode and silver colloid, respectively. All three dyes show a better SERHRS efficiency on the silver colloid than on the silver electrode, a phenomenon just opposite to what we have recently observed for pyridine and pyrazine [Chem. Phys. Lett. 305 (1999) 303]. These results suggest that the efficiency of SEHRS depends not only on the active surfaces employed (colloidal metals versus roughened electrodes) but also on the types of the adsorbed molecules.

  1. Enhanced plasmonic Fano-like resonances in multilayered nanoellipsoid

    NASA Astrophysics Data System (ADS)

    Khan, Adnan Daud

    2016-04-01

    Plasmonic Fano-like resonances, which arise from the destructive interference of bright and dark plasmon modes, are theoretically investigated in gold-silica-gold multilayered nanoellipsoid. It is found that the higher-order Fano resonances with sharp modulation depth can be achieved in the symmetric case by simply varying the structural parameters of the nanoparticle. Moreover, for the generation of unique multiple Fano-like resonances, two types of symmetry-breaking conception are also introduced: first by offsetting the inner metal core from its central position and then by relaxing the rotational symmetry of the nanoparticle. The multiple plasmonic Fano-like resonances make the proposed nanostructure highly suitable for plasmon line shaping, electromagnetic-induced transparency, and slow light applications.

  2. Diffusive transport enhancement by isolated resonances and distribution tails growth in hadronic beams

    SciTech Connect

    Gerasimov, A.

    1990-12-06

    The escape rates and evolution of a distribution of particles are considered for a 2-D model of transverse motion of particles in hadronic storage rings, when nonlinear resonances and external diffusion are present. Dynamic enhancement of diffusion inside separatrices can develop under a certain geometry of resonance oscillations and relatively wide resonances, leading to the fast growth of distribution tails and escape rates. The phenomenon is absent in 1-D. 10 refs., 4 figs.

  3. Gamma Emission Spectra from Neutron Resonances in 234,236,238U Measured Using the Dance Detector at Lansce

    NASA Astrophysics Data System (ADS)

    Ullmann, J. L.; Bredeweg, T. A.; Couture, A. J.; Haight, R. C.; Jandel, M.; Kawano, T.; Keksis, A. L.; O'Donnell, J. M.; Rundberg, R. S.; Vieira, D. J.; Wouters, J. M.; Wilhelmy, J. B.; Wu, C. Y.; Becker, J. A.; Chyzh, A.; Baramsai, B.; Mitchell, G. E.; Krticka, M.

    2013-03-01

    An accurate knowledge of the radiative strength function and level density is needed to calculate of neutron-capture cross sections. An additional constraint on these quantities is provided by measurements of γ-ray emission spectra following capture. We present γ-emission spectra from several neutron resonances in 234,236,238U, measured using the DANCE detector at LANSCE. The measurements are compared to preliminary calculations of the cascade. It is observed that the generalized Lorentzian form of the E1 strength function cannot reproduce the shape of the emission spectra, but a better description is made by adding low-lying M1 Lorentzian strength.

  4. Enhanced γ -Ray Emission from Neutron Unbound States Populated in β Decay

    NASA Astrophysics Data System (ADS)

    Tain, J. L.; Valencia, E.; Algora, A.; Agramunt, J.; Rubio, B.; Rice, S.; Gelletly, W.; Regan, P.; Zakari-Issoufou, A.-A.; Fallot, M.; Porta, A.; Rissanen, J.; Eronen, T.; ńystö, J.; Batist, L.; Bowry, M.; Bui, V. M.; Caballero-Folch, R.; Cano-Ott, D.; Elomaa, V.-V.; Estevez, E.; Farrelly, G. F.; Garcia, A. R.; Gomez-Hornillos, B.; Gorlychev, V.; Hakala, J.; Jordan, M. D.; Jokinen, A.; Kolhinen, V. S.; Kondev, F. G.; Martínez, T.; Mendoza, E.; Moore, I.; Penttilä, H.; Podolyák, Zs.; Reponen, M.; Sonnenschein, V.; Sonzogni, A. A.

    2015-08-01

    Total absorption spectroscopy is used to investigate the β -decay intensity to states above the neutron separation energy followed by γ -ray emission in Br,8887 and 94Rb. Accurate results are obtained thanks to a careful control of systematic errors. An unexpectedly large γ intensity is observed in all three cases extending well beyond the excitation energy region where neutron penetration is hindered by low neutron energy. The γ branching as a function of excitation energy is compared to Hauser-Feshbach model calculations. For 87Br and 88Br the γ branching reaches 57% and 20%, respectively, and could be explained as a nuclear structure effect. Some of the states populated in the daughter can only decay through the emission of a large orbital angular momentum neutron with a strongly reduced barrier penetrability. In the case of neutron-rich 94Rb the observed 4.5% branching is much larger than the calculations performed with standard nuclear statistical model parameters, even after proper correction for fluctuation effects on individual transition widths. The difference can be reconciled by introducing an enhancement of 1 order of magnitude in the photon strength to neutron strength ratio. An increase in the photon strength function of such magnitude for very neutron-rich nuclei, if it proves to be correct, leads to a similar increase in the (n ,γ ) cross section that would have an impact on r process abundance calculations.

  5. Enhanced γ -Ray Emission from Neutron Unbound States Populated in β Decay

    DOE PAGESBeta

    Tain, J. L.; Valencia, E.; Algora, A.; Agramunt, J.; Rubio, B.; Rice, S.; Gelletly, W.; Regan, P.; Zakari-Issoufou, A. -A.; Fallot, M.; et al

    2015-08-01

    Total absorption spectroscopy was used to investigate the β -decay intensity to states above the neutron separation energy followed by γ -ray emission in 87,88Br and 94Rb. Accurate results were obtained thanks to the careful control of systematic errors. An unexpectedly large γ intensity was observed in all three cases extending well beyond the excitation energy region where neutron penetration is hindered by low neutron energy. The γ branching as a function of excitation energy was compared to Hauser-Feshbach model calculations. For 87Br and 88Br the branching reaches 57% and 20% respectively, and could be explained as a nuclear structuremore » effect. Some of the states populated in the daughter can only decay through the emission of a large orbital angular momentum neutron with a strongly reduced barrier penetrability. In the case of neutron-rich 94Rb the observed 4.5% branching is much larger than the calculations performed with standard nuclear statistical model parameters, even after proper correction for fluctuation effects on individual transition widths. The difference can be reconciled introducing an enhancement of one order-of-magnitude in the photon strength to neutron strength ratio. An increase in the photon strength function of such magnitude for very neutron-rich nuclei, if it proved to be correct, leads to a similar increase in the (n, γ) cross section that would have an impact on r process abundance calculations.« less

  6. Unified studies of chemical bonding structures and resonant scattering in light neutron-excess systems, 10,12Be.

    PubMed

    Ito, Makoto; Ikeda, Kiyomi

    2014-09-01

    The generalized two-center cluster model (GTCM), which can treat covalent, ionic and atomic configurations in general systems with two inert cores plus valence nucleons, is formulated in the basis of the microscopic cluster model. In this model, the covalent configurations constructed by the molecular orbital (MO) method and the atomic (or ionic) configuration obtained by the valence bonding (VB) method can be handled in a consistent manner. The GTCM is applied to the light neutron-rich system (10,12)Be = α + α + Xn (X = 2, 4). The continuous and smooth changes of the neutron orbits from the covalent MO states to the ionic VB states are clearly observed in the adiabatic energy surfaces (AESs), which are the energy curves obtained with a variation of the α-α distance. The energy levels obtained from the AESs nicely reproduce the recent observations over a wide energy region. The individual spectra are characterized in terms of chemical-bonding-like structures, such as the covalent MO or ionic VB structures, according to analysis of their intrinsic wave functions. From the analysis of AESs, the formation of the mysterious 0(2)(+) states in (10,12)Be, which have anomalously small excitation energies in comparison to a naive shell-model prediction, is investigated. A large enhancement in a monopole transition from a ground MO state to an ionic α + (6,8)He VB state is found, which seems to be consistent with a recent observation. In the unbound region, the structure problem, which handles the total system of α + α + Xn (X = 2, 4) as a bound or quasi-bound state, and the reaction problem, induced by the collision of an asymptotic VB state of α + (6,8)He, are combined by the GTCM. The properties of unbound resonant states are discussed in close connection to the reaction mechanism, and some enhancement factors originating from the properties of the intrinsic states are predicted in the reaction observables. PMID:25222183

  7. Progress on performance assessment of ITER enhanced heat flux first wall technology after neutron irradiation

    NASA Astrophysics Data System (ADS)

    Hirai, T.; Bao, L.; Barabash, V.; Chappuis, Ph; Eaton, R.; Escourbiac, F.; Giqcuel, S.; Merola, M.; Mitteau, R.; Raffray, R.; Linke, J.; Loewenhoff, Th; Pintsuk, G.; Wirtz, M.; Boomstra, D.; Magielsen, A.; Chen, J.; Wang, P.; Gervash, A.; Safronov, V.

    2016-02-01

    ITER first wall (FW) panels are irradiated by energetic neutrons during the nuclear phase. Thus, an irradiation and high heat flux testing programme is undertaken by the ITER organization in order to evaluate the effects of neutron irradiation on the performance of enhanced heat flux (EHF) FW components. The test campaign includes neutron irradiation (up to 0.6-0.8 dpa at 200 °C-250 °C) of mock-ups that are representative of the final EHF FW panel design, followed by thermal fatigue tests (up to 4.7 MW m-2). Mock-ups were manufactured by the same manufacturing process as proposed for the series production. After a pre-irradiation thermal screening, eight mock-ups will be selected for the irradiation campaigns. This paper reports the preparatory work of HHF tests and neutron irradiation, assessment results as well as a brief description of mock-up manufacturing and inspection routes.

  8. Surface plasmon resonance enhanced upconversion luminescence in aqueous media for TNT selective detection.

    PubMed

    Tu, Nina; Wang, Leyu

    2013-07-18

    We present a novel report on a surface plasmon resonance enhanced upconversion luminescence strategy in aqueous media for highly sensitive and selective detection of 2,4,6-trinitrotoluene (TNT). PMID:23739225

  9. Resonance modes, cavity field enhancements, and long-range collective photonic effects in periodic bowtie nanostructures

    SciTech Connect

    Hsueh, Chun-Hway; Li, Jia-Han; Hatab, Nahla A.; Gu, Baohua

    2011-01-01

    The discovery of single-molecule sensitivity via surfaceenhanced Raman scattering on resonantly excited noble metal nanoparticles has brought an increasing interest in its applications to the molecule detection and identification. Periodic gold bowtie nanostructures have recently been shown to give a large enhancement factor sufficient for single molecule detection. In this work, we simulate the plasmon resonance for periodic gold bowtie nanostructures. The difference between the dipole and the quadrupole resonances is described by examining the magnitude and phase of electric field, the bound surface charge, and the polarization. The gap size dependence of the field enhancement can be interpreted by considering cavity field enhancement. Also, additional enhancement is obtained through the long-range collective photonic effect when the bowtie array periodicity matches the resonance wavelength.

  10. Noise-enhanced Parametric Resonance in Perturbed Galaxies

    NASA Astrophysics Data System (ADS)

    Sideris, Ioannis V.; Kandrup, Henry E.

    2004-02-01

    This paper describes how parametric resonances associated with a galactic potential subjected to relatively low-amplitude, strictly periodic time-dependent perturbations can be impacted by pseudo-random variations in the pulsation frequency, modeled as colored noise. One aim thereby is to allow for the effects of a changing oscillation frequency as the density distribution associated with a galaxy evolves during violent relaxation. Another is to mimic the possible effects of internal substructures, satellite galaxies, and/or a high-density environment. The principal conclusions are that allowing for a variable frequency does not vitiate the effects of parametric resonance, and that, in at least some cases, such variations can increase the overall importance of parametric resonance associated with systematic pulsations. In memory of Professor H. E. Kandrup, a brilliant scientist, excellent teacher, and good friend. His genius and sense of humor will be greatly missed.

  11. Neutron capture in the 1. 15-keV resonance of /sup 56/Fe using Moxon-Rae detectors

    SciTech Connect

    Corvi, F.; Bastian, C.; Wisshak, K.

    1986-08-01

    The capture area in the 1.15-keV neutron resonance of /sup 56/Fe was measured with Moxon-Rae detectors with converters of bismuth, bismuth-graphite, and graphite. The data were normalized to gold capture at 4.91 eV using the saturated resonance method. Two separate measurements were performed: the first with the detector axis at 120 deg with respect to the neutron beam direction and the second with the axis at 90 deg. The average of the results over the three detectors is gGAMMA/sub n/GAMMA..gamma../sub / GAMMA=(64.9 + .2.4) MeV for the 120-deg run and gGAMMAn/GAMMA..gamma../GAMMA=(63.5 + .2.1) MeV for the 90-deg run. These values are 14 to 16% larger than the corresponding one from transmission data. No reason is found for such a discrepancy.

  12. Cross-phase modulation enhancement via a resonating cavity: semiclassical description

    NASA Astrophysics Data System (ADS)

    Martínez-Rincón, Julián; Howell, John C.

    2016-06-01

    We evaluate the advantages of performing cross-phase modulation (XPM) on a very-far-off-resonance atomic system. We consider a ladder system with a weak (few-photon level) control coherent field imparting a conditional nonlinear phase shift on a probe beam. We find that by coupling to an optical resonator the optimal XPM is enhanced proportional to the finesse of the resonator by a factor of $F/4\\pi$. We present a semi-classical description of the system and show that the phenomenon is optimal in the self-defined condition of off-resonance-effective-cooperativity equal to one.

  13. Quantification of background enhancement in breast magnetic resonance imaging

    PubMed Central

    Klifa, C; Suzuki, S; Aliu, S; Singer, L; Wilmes, L; Newitt, D; Joe, B; Hylton, N

    2011-01-01

    Purpose To present a novel technique for measuring tissue enhancement in breast fibroglandular tissue regions on contrast-enhanced breast MR images aimed at quantifying the enhancement of breast parenchyma, also known as “background enhancement”. Materials and Methods Our quantitative method for measuring breast MRI background enhancement was evaluated in a population of 16 healthy volunteers. We also demonstrate the use of our new technique in the case study of one subject classified as high risk for developing breast cancer who underwent 3 months of tamoxifen therapy. Results We obtained quantitative measures of background enhancement in all cases. The high-risk patient exhibited a 37% mean reduction in background enhancement with treatment. Conclusion Our quantitative method is a robust and promising tool that may allow investigators to quantify and document the potential adverse effect of background enhancement on diagnostic accuracy in larger populations. PMID:21509883

  14. Near-field enhanced ultraviolet resonance Raman spectroscopy using aluminum bow-tie nano-antenna.

    PubMed

    Li, Ling; Fang Lim, Shuang; Puretzky, Alexander A; Riehn, Robert; Hallen, H D

    2012-09-10

    An aluminum bow-tie nano-antenna is combined with the resonance Raman effect in the deep ultraviolet to dramatically increase the sensitivity of Raman spectra to a small volume of material, such as benzene used here. We further demonstrate gradient-field Raman peaks for several strong infrared modes. We achieve a gain of [Formula: see text] in signal intensity from the near field enhancement due to the surface plasmon resonance in the aluminum nanostructure. The on-line resonance enhancement contributes another factor of several thousands, limited by the laser line width. Thus, an overall gain of hundreds of million is achieved. PMID:23066168

  15. Enhanced acoustoelectric coupling in acoustic energy harvester using dual Helmholtz resonators.

    PubMed

    Peng, Xiao; Wen, Yumei; Li, Ping; Yang, Aichao; Bai, Xiaoling

    2013-10-01

    In this paper, enhanced acoustoelectric transduction in an acoustic energy harvester using dual Helmholtz resonators has been reported. The harvester uses a pair of cavities mechanically coupled with a compliant perforated plate to enhance the acoustic coupling between the cavity and the plate. The experimental results show that the volume optimization of the second cavity can significantly increase the generated electric voltage up to 400% and raise the output power to 16 times as large as that of a harvester using a single Helmholtz resonator at resonant frequencies primarily related to the plate. PMID:24081260

  16. Neutron emission spectroscopy results for internal transport barrier and mode conversion ion cyclotron resonance heating experiments at JET

    SciTech Connect

    Giacomelli, L.; Hjalmarsson, A.; Hellesen, C.; Conroy, S.; Sunden, E. Andersson; Ericsson, G.; Johnson, M. Gatu; Sjoestrand, H.; Weiszflog, M.; Kaellne, J.; Tardocchi, M.; Gorini, G.

    2008-10-15

    The effect of ion cyclotron resonance heating (ICRH) on ({sup 3}He)D plasmas at JET was studied with the time of flight optimized rate (TOFOR) spectrometer dedicated to 2.5 MeV dd neutron measurements. In internal transport barrier (ITB) plasma experiments with large {sup 3}He concentrations (X({sup 3}He)>15%) an increase in neutron yield was observed after the ITB disappeared but with the auxiliary neutral beam injection and ICRH power still applied. The analysis of the TOFOR data revealed the formation of a high energy (fast) D population in this regime. The results were compared to other mode conversion experiments with similar X({sup 3}He) but slightly different heating conditions. In this study we report on the high energy neutron tails originating from the fast D ions and their correlation with X({sup 3}He) and discuss the light it can shed on ICRH-plasma power coupling mechanisms.

  17. Pure surface plasmon resonance enhancement of the first hyperpolarizability of gold core-silver shell nanoparticles.

    PubMed

    Abid, Jean-Pierre; Nappa, Jérôme; Girault, Hubert H; Brevet, Pierre-François

    2004-12-22

    We report the optical second harmonic (SH) response from gold core-silver shell nanoparticles supported at a liquid-liquid interface in the spectral region where the second harmonic generation (SHG) frequency is resonant with the surface plasmon (SP) resonance excitation of the nanoparticles. We compare these results with that obtained by classical linear optical absorption spectroscopy and show that the nonlinear optical response is dominated by the SP resonance enhancement with negligible contributions from the interband transitions. As a result, the SH spectrum exhibits two clear SP resonance bands attributed to the two SP resonances of the composite nanostructure formed by the gold core-silver shell nanoparticles. Absolute values of the hyperpolarizabilities are measured by hyper Rayleigh scattering (HRS) and compared that of pure gold nanoparticles. The hyperpolarizability measured at a harmonic energy of 3.0 eV, enhanced through excitation of the high energy SP resonance of the nanoparticle, increases with the silver content whereas the hyperpolarizability measured at a harmonic energy of 2.4 eV, enhanced through the excitation of the low energy SP resonance of the nanoparticle, decreases because of the shift of this resonance away from the harmonic frequency. The hyperpolarizability determined by HRS and the square root of the SHG intensities, scaling with the nanoparticle hyperpolarizability, have similar trends with respect to the silver content indicative of closely related adsorption properties yielding similar surface concentrations at the liquid-liquid interface. PMID:15606279

  18. Beam current enhancement of microwave plasma ion source utilizing double-port rectangular cavity resonator.

    PubMed

    Lee, Yuna; Park, Yeong-Shin; Jo, Jong-Gab; Yang, J J; Hwang, Y S

    2012-02-01

    Microwave plasma ion source with rectangular cavity resonator has been examined to improve ion beam current by changing wave launcher type from single-port to double-port. The cavity resonators with double-port and single-port wave launchers are designed to get resonance effect at TE-103 mode and TE-102 mode, respectively. In order to confirm that the cavities are acting as resonator, the microwave power for breakdown is measured and compared with the E-field strength estimated from the HFSS (High Frequency Structure Simulator) simulation. Langmuir probe measurements show that double-port cavity enhances central density of plasma ion source by modifying non-uniform plasma density profile of the single-port cavity. Correspondingly, beam current from the plasma ion source utilizing the double-port resonator is measured to be higher than that utilizing single-port resonator. Moreover, the enhancement in plasma density and ion beam current utilizing the double-port resonator is more pronounced as higher microwave power applied to the plasma ion source. Therefore, the rectangular cavity resonator utilizing the double-port is expected to enhance the performance of plasma ion source in terms of ion beam extraction. PMID:22380295

  19. Beam current enhancement of microwave plasma ion source utilizing double-port rectangular cavity resonator

    SciTech Connect

    Lee, Yuna; Park, Yeong-Shin; Jo, Jong-Gab; Yang, J. J.; Hwang, Y. S.

    2012-02-15

    Microwave plasma ion source with rectangular cavity resonator has been examined to improve ion beam current by changing wave launcher type from single-port to double-port. The cavity resonators with double-port and single-port wave launchers are designed to get resonance effect at TE-103 mode and TE-102 mode, respectively. In order to confirm that the cavities are acting as resonator, the microwave power for breakdown is measured and compared with the E-field strength estimated from the HFSS (High Frequency Structure Simulator) simulation. Langmuir probe measurements show that double-port cavity enhances central density of plasma ion source by modifying non-uniform plasma density profile of the single-port cavity. Correspondingly, beam current from the plasma ion source utilizing the double-port resonator is measured to be higher than that utilizing single-port resonator. Moreover, the enhancement in plasma density and ion beam current utilizing the double-port resonator is more pronounced as higher microwave power applied to the plasma ion source. Therefore, the rectangular cavity resonator utilizing the double-port is expected to enhance the performance of plasma ion source in terms of ion beam extraction.

  20. Enhanced Tidal Dissipation via Resonance Locking in Heartbeat Stars

    NASA Astrophysics Data System (ADS)

    Fuller, Jim; Hambleton, Kelly Marie; thompson, susan; Kurtz, Don

    2015-08-01

    Heartbeat stars are eccentric binary stars in short period orbits, whose light curves are shaped by tidal distortion, reflection, and Doppler beaming. Over 150 heartbeat stars have been identified in Kepler data thus far, and some exhibit tidally excited oscillations that provide new opportunities for understanding the physics of tidal dissipation within stars. KIC 8164262 is a particlularly interesting heartbeat star with a large amplitude tidally excited oscillation whose frequency is precisely 229 times the orbital frequency. We demonstrate that the high-amplitude tidally excited oscillation in KIC 8164262 is unlikely to occur due to a chance resonance with a stellar oscillation mode. Instead, the oscillation is likely excited via resonance locking, in which a stellar oscillation mode is resonantly excited for an extended period of time. We show that the mode’s frequency, amplitude, and phase are consistent with this hypothesis. Resonance locking allows the mode to generate efficient tidal dissipation (we calculate an effective tidal quality factor of Q ˜ 2×10^4), such that tidal orbital decay/circularization proceeds on a stellar evolution time scale.

  1. SYNTHESIS AND FABRICATION OF MO-W COMPONENTS FOR NEUTRON RESONANCE SPECTROSCOPY TEMPERATURE MEASUREMENT

    SciTech Connect

    S. BINGERT; P. DESCH; E. TRUJILLO

    1999-09-01

    A Molybdenum--{sup 182}Tungsten (Mo-{sup 182}W) alloy was specified for an application that would ultimately result in the measurement of temperature and particle velocity during the steady state time following the shock loading of various materials. The {sup 182}W isotope provides a tag for the analysis of neutron resonance line shape from which the temperature may be calculated. The material was specified to have 1.8 atom percent W, with W-rich regions no larger than 1 {micro}m in size. Both the composition and W distribution were critical to the experiment. Another challenge to the processing was the very small quantity of {sup 182}W material available for the synthesis of the alloy. Therefore, limited fabrication routes were available for evaluation. Several synthesis and processing routes were explored to fabricate the required alloy components. First, precipitation of W onto Mo powder using ammonium metatungstate was investigated for powder synthesis followed by uniaxial hot pressing. Second, mechanical alloying (MA) followed by hot isostatic pressing (HIP) and warm forging was attempted. Finally, arc-melting techniques followed by either hot rolling or crushing the alloyed button into powder and consolidation were pursued. The results of the processing routes and characterization of the materials produced will be discussed.

  2. A theoretical framework for absorption (dichroism) and the resonance-enhanced scattering of x-rays by magnetic materials: I

    NASA Astrophysics Data System (ADS)

    Lovesey, Stephen W.; Balcar, Ewald

    1996-12-01

    The scattering length common to the attenuation coefficient and cross-sections for the resonance-enhanced scattering of x-rays suffers from a dependence on a spectrum of virtual, intermediate states which contain next to no useful information about the environment of the atoms. It is the dependence of the scattering length on intermediate states that sets the x-ray techniques apart from neutron scattering and other techniques which directly probe properties of magnetic materials, and limits the usefulness of physical intuition in the interpretation of empirical x-ray data. As a step toward a legible interpretation, in a language of standard atomic variables, an investigation is reported of a modified scattering length constructed to possess a structure similar to the scattering length for magnetic neutron scattering, namely, it has the mathematical structure of a spherical tensor operator, to which all Racah's methods for electrons in an open valence shell can be applied. In the process of reaching this goal, the influence of the intermediate states on the scattering length is reduced by summing over a limited set of quantum numbers for the intermediate states. Topics covered in the investigation include the attenuation coefficient for x-rays passing through a foil of magnetic material, dichroism, and the cross-sections for resonance-enhanced elastic (Bragg) and inelastic scattering of x-rays by magnetic materials. The treatment of polarization in the primary beam admits states of partial polarization, described by a Stokes vector. Both jj-coupling and Russell - Saunders coupling schemes for the valence states are explored.

  3. Design and construction of the RPI enhanced thermal neutron target and thermal cross-section measurements of rare earth isotopes

    SciTech Connect

    Danon, Y.

    1993-12-31

    In order to perform thermal cross section measurements the neutron flux in the RPI linac facility had to be increased. A new Enhanced Thermal Target (ETT) was designed, constructed and used. The thermal flux of the new target was up to six times higher than the previous RPI Bounce Target (BT). The ETT was also designed to be coupled to a cold moderator that will give an additional flux increase in the MeV energy region. Design calculations for the cold moderator including neutronics and cryogenics are also presented. The ETT was used for transmission measurements of rare earth metal samples of Ho, Er and Tm and enriched oxide samples of {sup 166}Er{sub 2}O{sub 3} and {sup 167}Er{sub 2}O{sub 3} in the energy range from 0.001 eV to 20 eV. The measurements were done with a 15 meter time-of-flight spectrometer and provide high quality data in the thermal and subthermal region as well as in the low energy resonance region. These measurements allowed a systematic study of paramagnetic scattering for the materials with Z = 67, 68 and 69 for which the paramagnetic scattering has the strongest effect. The paramagnetic scattering was inferred from the total cross section and compared to theoretical results and other experiments.

  4. Surface plasmon resonance imaging by holographic enhanced mapping.

    PubMed

    Mandracchia, B; Pagliarulo, V; Paturzo, M; Ferraro, P

    2015-04-21

    We designed, constructed and tested a holographic surface plasmon resonance (HoloSPR) objective-based microscope for simultaneous amplitude-contrast and phase-contrast surface plasmon resonance imaging (SPRi). SPRi is a widely spread tool for label-free detection of changes in refractive index and concentration, as well as mapping of thin films. Currently, most of the SPR sensors rely on the detection of amplitude or phase changes of light. Despite the high sensitivities achieved so far, each technique alone has a limited detection range with optimal sensitivity. Here we use a high numerical aperture objective that avoids all the limitations due to the use of a prism-based configuration, yielding highly magnified and distortion-free images. Holographic reconstructions of SPR images and real-time kinetic measurements are presented to show the capability of HoloSPR to provide a versatile imaging method for high-throughput SPR detection complementary to conventional SPR techniques. PMID:25816225

  5. Resonance-induced sensitivity enhancement method for conductivity sensors

    NASA Technical Reports Server (NTRS)

    Tai, Yu-Chong (Inventor); Shih, Chi-yuan (Inventor); Li, Wei (Inventor); Zheng, Siyang (Inventor)

    2009-01-01

    Methods and systems for improving the sensitivity of a variety of conductivity sensing devices, in particular capacitively-coupled contactless conductivity detectors. A parallel inductor is added to the conductivity sensor. The sensor with the parallel inductor is operated at a resonant frequency of the equivalent circuit model. At the resonant frequency, parasitic capacitances that are either in series or in parallel with the conductance (and possibly a series resistance) is substantially removed from the equivalent circuit, leaving a purely resistive impedance. An appreciably higher sensor sensitivity results. Experimental verification shows that sensitivity improvements of the order of 10,000-fold are possible. Examples of detecting particulates with high precision by application of the apparatus and methods of operation are described.

  6. Assessing the Feasibility of Using Neutron Resonance Transmission Analysis (NRTA) for Assaying Plutonium in Spent Fuel Assemblies

    SciTech Connect

    D. L. Chichester; J. W. Sterbentz

    2012-07-01

    Neutron resonance transmission analysis (NRTA) is an active-interrogation nondestructive assay (NDA) technique capable of assaying spent nuclear fuel to determine plutonium content. Prior experimental work has definitively shown the technique capable of assaying plutonium isotope composition in spent-fuel pins to a precision of approximately 3%, with a spatial resolution of a few millimeters. As a Grand Challenge to investigate NDA options for assaying spent fuel assemblies (SFAs) in the commercial fuel cycle, Idaho National Laboratory has explored the feasibility of using NRTA to assay plutonium in a whole SFA. The goal is to achieve a Pu assay precision of 1%. The NRTA technique uses low-energy neutrons from 0.1-40 eV, at the bottom end of the actinide-resonance range, in a time-of-flight arrangement. Isotopic composition is determined by relating absorption of the incident neutrons to the macroscopic cross-section of the actinides of interest in the material, and then using this information to determine the areal density of the isotopes in the SFA. The neutrons used for NRTA are produced using a pulsed, accelerator-based neutron source. Distinguishable resonances exist for both the plutonium (239,240,241,242Pu) and uranium (235,236,238U) isotopes of interest in spent fuel. Additionally, in this energy range resonances exists for six important fission products (99Tc, 103Rh, 131Xe, 133Cs, 145Nd, and 152Sm) which provide additional information to support spent fuel plutonium assay determinations. Based on extensive modeling of the problem using Monte Carlo-based simulation codes, our preliminary results suggest that by rotating an SFA to acquire four symmetric views, sufficient neutron transmission can be achieved to assay a SFA. In this approach multiple scan information for the same pins may also be unfolded to potentially allow the determination of plutonium for sub-regions of the assembly. For a 17 ? 17 pressurized water reactor SFA, a simplistic preliminary

  7. Thermal enhancement and stochastic resonance of polaron ratchets.

    PubMed

    Brizhik, L S; Eremko, A A; Piette, B M A G; Zakrzewski, W J

    2014-06-01

    We study the ratchet drift of large polarons (solitons) in molecular diatomic chains induced by unbiased time periodic electric fields at nonzero temperature below its critical value. We show that, at a nonzero temperature, the critical value of the intensity of the electric field above which the ratchet phenomenon takes place is lower than at zero temperature for the same frequency of the field. We show that there is a range of temperatures for which the polaron drift is larger than that at zero temperature. We also show that temperature decreases the value of the lowest critical period of the field. And, finally, we demonstrate that there is a stochastic resonance in a polaron ratchet, namely that there is an optimal temperature at which the polaron drift is a maximum. The values of the stochastic resonance temperature, the lowest critical values of the field intensity, and its period depend on various parameters of the system and, in particular, on the anisotropy of the chain parameters. This temperature induced decrease of the critical value of the field intensity and its period, as well as the stochastic resonance itself, may be important for practical applications of the ratchet phenomenon in systems involving conducting polymers and other low-dimensional materials. They may also be important in some biological macromolecules where the ratchet phenomenon could take place in biomotors and energy and/or charge transport. PMID:25019849

  8. Thermal enhancement and stochastic resonance of polaron ratchets

    NASA Astrophysics Data System (ADS)

    Brizhik, L. S.; Eremko, A. A.; Piette, B. M. A. G.; Zakrzewski, W. J.

    2014-06-01

    We study the ratchet drift of large polarons (solitons) in molecular diatomic chains induced by unbiased time periodic electric fields at nonzero temperature below its critical value. We show that, at a nonzero temperature, the critical value of the intensity of the electric field above which the ratchet phenomenon takes place is lower than at zero temperature for the same frequency of the field. We show that there is a range of temperatures for which the polaron drift is larger than that at zero temperature. We also show that temperature decreases the value of the lowest critical period of the field. And, finally, we demonstrate that there is a stochastic resonance in a polaron ratchet, namely that there is an optimal temperature at which the polaron drift is a maximum. The values of the stochastic resonance temperature, the lowest critical values of the field intensity, and its period depend on various parameters of the system and, in particular, on the anisotropy of the chain parameters. This temperature induced decrease of the critical value of the field intensity and its period, as well as the stochastic resonance itself, may be important for practical applications of the ratchet phenomenon in systems involving conducting polymers and other low-dimensional materials. They may also be important in some biological macromolecules where the ratchet phenomenon could take place in biomotors and energy and/or charge transport.

  9. Analysis of experimental measurements of PWR fresh and spent fuel assemblies using Self-Interrogation Neutron Resonance Densitometry

    NASA Astrophysics Data System (ADS)

    LaFleur, Adrienne M.; Menlove, Howard O.

    2015-05-01

    Self-Interrogation Neutron Resonance Densitometry (SINRD) is a new NDA technique that was developed at Los Alamos National Laboratory (LANL) to improve existing nuclear safeguards measurements for LWR fuel assemblies. The SINRD detector consists of four fission chambers (FCs) wrapped with different absorber filters to isolate different parts of the neutron energy spectrum and one ion chamber (IC) to measure the gross gamma rate. As a result, two different techniques can be utilized using the same SINRD detector unit and hardware. These techniques are the Passive Neutron Multiplication Counter (PNMC) method and the SINRD method. The focus of the work described in this paper is the analysis of experimental measurements of fresh and spent PWR fuel assemblies that were performed at LANL and the Korea Atomic Energy Research Institute (KAERI), respectively, using the SINRD detector. The purpose of these experiments was to assess the following capabilities of the SINRD detector: 1) reproducibility of measurements to quantify systematic errors, 2) sensitivity to water gap between detector and fuel assembly, 3) sensitivity and penetrability to the removal of fuel rods from the assembly, and 4) use of PNMC/SINRD ratios to quantify neutron multiplication and/or fissile content. The results from these simulations and measurements provide valuable experimental data that directly supports safeguards research and development (R&D) efforts on the viability of passive neutron NDA techniques and detector designs for partial defect verification of spent fuel assemblies.

  10. Power enhancement of burst-mode UV pulses using a doubly-resonant optical cavity

    SciTech Connect

    Rahkman, Abdurahim; Notcutt, Mark; Liu, Yun

    2015-11-24

    We report a doubly-resonant enhancement cavity (DREC) that can realize a simultaneous enhancement of two incoming laser beams at different wavelengths and different temporal structures. The double-resonance condition is theoretically analyzed and different DREC locking methods are experimentally investigated. Simultaneous locking of a Fabry-Perot cavity to both an infrared (IR, 1064 nm) and its frequency tripled ultraviolet (UV, 355 nm) pulses has been demonstrated by controlling the frequency difference between the two beams with a fiber optic frequency shifter. The DREC technique opens a new paradigm in the applications of optical cavities to power enhancement of burst-mode lasers with arbitrary macropulse width and repetition rate.

  11. Aggregation-Induced Resonance Raman Optical Activity (AIRROA): A New Mechanism for Chirality Enhancement.

    PubMed

    Zajac, Grzegorz; Kaczor, Agnieszka; Pallares Zazo, Ana; Mlynarski, Jacek; Dudek, Monika; Baranska, Malgorzata

    2016-05-01

    Raman optical activity (ROA) spectroscopy is hampered by low sensitivity, with limited possibilities for enhancing the signal. In the present study, we report a new mechanism whereby chirality is enhanced using the resonance resulting from supramolecular aggregation. We have named this mechanism aggregation-induced resonance Raman optical activity (AIRROA). As an example, we study J-aggregates of astaxanthin (AXT), which show strong absorption of circularly polarized light in the range of ROA excitation. The implications of aggregation-induced signal enhancement for chiroptical spectroscopy are discussed. PMID:27057926

  12. A band enhanced metamaterial absorber based on E-shaped all-dielectric resonators

    NASA Astrophysics Data System (ADS)

    Li, Liyang; Wang, Jun; Du, Hongliang; Wang, Jiafu; Qu, Shaobo; Xu, Zhuo

    2015-01-01

    In this paper, we propose a band enhanced metamaterial absorber in microwave band, which is composed of high-permittivity E-shaped dielectric resonators and metallic ground plate. The E-shaped all-dielectric structure is made of high-temperature microwave ceramics with high permittivity and low loss. An absorption band with 1 GHz bandwidth for both TE and TM polarizations are observed. Moreover, the absorption property is stable under different incident angles. The band enhanced absorption is caused by different resonant modes which lie closely in the absorption band. Due to the enhanced localized electric/magnetic fields at the resonant frequencies, strong absorptions are produced. Our work provides a new method of designing high-temperature and high-power microwave absorbers with band enhanced absorption.

  13. Electron doping evolution of the neutron spin resonance in NaFe1 -xCoxAs

    NASA Astrophysics Data System (ADS)

    Zhang, Chenglin; Lv, Weicheng; Tan, Guotai; Song, Yu; Carr, Scott V.; Chi, Songxue; Matsuda, M.; Christianson, A. D.; Fernandez-Baca, J. A.; Harriger, L. W.; Dai, Pengcheng

    2016-05-01

    Neutron spin resonance, a collective magnetic excitation coupled to superconductivity, is one of the most prominent features shared by a broad family of unconventional superconductors including copper oxides, iron pnictides, and heavy fermions. In this paper, we study the doping evolution of the resonances in NaFe1 -xCoxAs covering the entire superconducting dome. For the underdoped compositions, two resonance modes coexist. As doping increases, the low-energy resonance gradually loses its spectral weight to the high-energy one but remains at the same energy. By contrast, in the overdoped regime we only find one single resonance, which acquires a broader width in both energy and momentum but retains approximately the same peak position even when Tc drops by nearly a half compared to optimal doping. These results suggest that the energy of the resonance in electron overdoped NaFe1 -xCoxAs is neither simply proportional to Tc nor the superconducting gap but is controlled by the multiorbital character of the system and doped impurity scattering effect.

  14. Electron doping evolution of the neutron spin resonance in NaFe1-xCoxAs

    DOE PAGESBeta

    Zhang, Chenglin; Song, Yu; Carr, Scott Victor; Chi, Songxue; Christianson, Andrew D.; Matsuda, Masaaki; Fernandez-Baca, Jaime A.; Dai, Pengcheng; Lv, Weicheng; Tan, Guotai; et al

    2016-05-31

    Neutron spin resonance, a collective magnetic excitation coupled to superconductivity, is one of the most prominent features shared by a broad family of unconventional superconductors including copper oxides, iron pnictides, and heavy fermions. In this paper, we study the doping evolution of the resonances in NaFe1–xCoxAs covering the entire superconducting dome. For the underdoped compositions, two resonance modes coexist. As doping increases, the low-energy resonance gradually loses its spectral weight to the high-energy one but remains at the same energy. By contrast, in the overdoped regime we only find one single resonance, which acquires a broader width in both energymore » and momentum but retains approximately the same peak position even when Tc drops by nearly a half compared to optimal doping. Furthermore, these results suggest that the energy of the resonance in electron overdoped NaFe1–xCoxAs is neither simply proportional to Tc nor the superconducting gap but is controlled by the multiorbital character of the system and doped impurity scattering effect.« less

  15. Observation of large enhancements of charge exchange cross sections with neutron-rich carbon isotopes

    NASA Astrophysics Data System (ADS)

    Tanihata, I.; Terashima, S.; Kanungo, R.; Ameil, F.; Atkinson, J.; Ayyad, Y.; Cortina-Gil, D.; Dillmann, I.; Estradé, A.; Evdokimov, A.; Farinon, F.; Geissel, H.; Guastalla, G.; Janik, R.; Knoebel, R.; Kurcewicz, J.; Litvinov, Yu. A.; Marta, M.; Mostazo, M.; Mukha, I.; Nociforo, C.; Ong, H. J.; Pietri, S.; Prochazka, A.; Scheidenberger, C.; Sitar, B.; Strmen, P.; Takechi, M.; Tanaka, J.; Toki, H.; Vargas, J.; Winfield, J. S.; Weick, H.

    2016-04-01

    Production cross sections of nitrogen isotopes from high-energy (˜ 950 MeV per nucleon) carbon isotopes on hydrogen and carbon targets have been measured for the first time for a wide range of isotopes (A = 12 to 19). The fragment separator FRS at GSI was used to deliver C-isotope beams. The cross sections of the production of N-isotopes were determined by charge measurements of forward-going fragments. The cross sections show a rapid increase with the number of neutrons in the projectile. Since the production of nitrogen is mostly due to charge-exchange (Cex) reactions below the proton separation energies, the present data suggests a concentration of Gamow-Teller and/or Fermi transition strength at low excitation energies for neutron-rich carbon isotopes. It was also observed that the Cex cross sections were enhanced much more strongly for neutron-rich isotopes in the C-target data.

  16. Delayed Myocardial Enhancement in Cardiac Magnetic Resonance Imaging

    PubMed Central

    Franco, Arie; Javidi, Saeed; Ruehm, Stefan G

    2015-01-01

    Delayed myocardial enhancement MRI is a highly valuable but non-specific imaging technique that is ancillary in the diagnosis of a variety of diseases including myocardial viability, cardiomyopathy, myocarditis and other infiltrative myocardial processes. The lack of specificity stems from the wide variety of differential diagnoses that may present with overlapping patterns of delayed enhancement. Many of these differential diagnoses have been presented and discussed in this article. PMID:26622933

  17. Resonance-enhanced waveguide-coupled silicon-germanium detector

    NASA Astrophysics Data System (ADS)

    Alloatti, L.; Ram, R. J.

    2016-02-01

    A photodiode with 0.55 ± 0.1 A/W responsivity at a wavelength of 1176.9 nm has been fabricated in a 45 nm microelectronics silicon-on-insulator foundry process. The resonant waveguide photodetector exploits carrier generation in silicon-germanium within a microring which is compatible with high-performance electronics. A 3 dB bandwidth of 5 GHz at -4 V bias is obtained with a dark current of less than 20 pA.

  18. Harmonic trap resonance enhanced synthetic atomic spin-orbit coupling

    NASA Astrophysics Data System (ADS)

    Wu, Ling-Na; Luo, Xinyu; Xu, Zhi-Fang; Ueda, Masahito; Wang, Ruquan; You, Li

    2016-05-01

    The widely adopted scheme for synthetic atomic spin-orbit coupling (SOC) is based on the momentum sensitive Raman coupling, which is easily implemented in one spatial dimension. Recently, schemes based on pulsed or periodically modulating gradient magnetic field (GMF) were proposed and the main characteristic features have subsequently been demonstrated. The present work reports an experimental discovery and the associated theoretical understanding of tuning the SOC strength synthesized with GMF through the motional resonance of atomic center-of-mass in a harmonic trap. In some limits, we observe up to 10 times stronger SOC compared to the momentum impulse from GMF for atoms in free space.

  19. Electrofocusing-enhanced localized surface plasmon resonance biosensors

    NASA Astrophysics Data System (ADS)

    Zhang, Jinling; Wang, Yi; Wong, Ten It; Liu, Xiaohu; Zhou, Xiaodong; Liedberg, Bo

    2015-10-01

    Localized surface plasmon resonance (LSPR) biosensors typically suffer from diffusion limited mass transport and nonspecific adsorption upon detection of biomolecules in real biofluids. We employ here a peptide-modified plasmonic gold nanohole (AuNH) array for real-time detection of human troponin I (cTnI). Applying a negative electric bias on the AuNH sensor chip enables us to attract and concentrate cTnI at the sensor surface, while repelling other proteins thus decreasing interferences due to nonspecific adsorption.Localized surface plasmon resonance (LSPR) biosensors typically suffer from diffusion limited mass transport and nonspecific adsorption upon detection of biomolecules in real biofluids. We employ here a peptide-modified plasmonic gold nanohole (AuNH) array for real-time detection of human troponin I (cTnI). Applying a negative electric bias on the AuNH sensor chip enables us to attract and concentrate cTnI at the sensor surface, while repelling other proteins thus decreasing interferences due to nonspecific adsorption. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr03373j

  20. Enhanced optical transmission and Fano resonance through a nanostructured metal thin film

    PubMed Central

    Xiao, Bo; Pradhan, Sangram K.; Santiago, Kevin C.; Rutherford, Gugu N.; Pradhan, Aswini K.

    2015-01-01

    Artificial and engineered nanostructures expand the degrees of freedom with which one can manipulate the intricate interplay of light and matter. Certain nanostructural arrangements in the excited state enable the efficient electromagnetic coupling of propagating light with localized fields. Here, we demonstrate that light transmitted through a nanostructured metal thin film without any apertures can be significantly enhanced. Distinct asymmetric Fano resonances are observed in the zero-order transmission spectra using an incoherent light source. The transmission efficiency surpasses that of a metal thin film with the same area and thickness at the resonance maxima. The transmission minima and the sharp resonance maxima bear a strong resemblance to the extraordinary optical transmission observed in sub-wavelength nanohole array structures The resonance wavelength closely matches the nanostructural periodicity. The sensitivity of the resonances to the surrounding medium and the transmission efficiency demonstrate the potential for use in energy harvesting, imaging, optical processing and sensing applications. PMID:25981974

  1. Enhanced optical transmission and Fano resonance through a nanostructured metal thin film

    NASA Astrophysics Data System (ADS)

    Xiao, Bo; Pradhan, Sangram K.; Santiago, Kevin C.; Rutherford, Gugu N.; Pradhan, Aswini K.

    2015-05-01

    Artificial and engineered nanostructures expand the degrees of freedom with which one can manipulate the intricate interplay of light and matter. Certain nanostructural arrangements in the excited state enable the efficient electromagnetic coupling of propagating light with localized fields. Here, we demonstrate that light transmitted through a nanostructured metal thin film without any apertures can be significantly enhanced. Distinct asymmetric Fano resonances are observed in the zero-order transmission spectra using an incoherent light source. The transmission efficiency surpasses that of a metal thin film with the same area and thickness at the resonance maxima. The transmission minima and the sharp resonance maxima bear a strong resemblance to the extraordinary optical transmission observed in sub-wavelength nanohole array structures The resonance wavelength closely matches the nanostructural periodicity. The sensitivity of the resonances to the surrounding medium and the transmission efficiency demonstrate the potential for use in energy harvesting, imaging, optical processing and sensing applications.

  2. Intercalation between antitumor anthracyclines and DNA as probed by resonance and surface-enhanced Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Smulevich, G.; Mantini, A. R.; Casu, M.; Marzocchi, M. P.

    1991-05-01

    The antiturnor anthracyclincs, idarubicin (IDA ), adrianiycin (ADM), epirubicin (EPI), carminomycin (CAR) and 1 1-deoxycarminornycin (DCM), whose siructural formula includes a substituted hydroxyanthraquirionc chrornophore and a sugar residue, form intercalation complexes with DNA. The stacking interaction between the chromophore and the base-pairs of DNA gives rise to noticeable ciTects on resonance Raman (RR) and surface-enhanced resonance Raman (SERRS) scattering as well as on the absorption (ABS), its second derivative (D2) and fluorescence emission (FEM) spectra.

  3. Concepts and Engineering Aspects of a Neutron Resonance Spin-Echo Spectrometer for the National Institute of Standards and Technology Center for Neutron Research.

    PubMed

    Cook, Jeremy C

    2014-01-01

    Following a brief introduction, the Neutron Resonance Spin-Echo (NRSE) principle is discussed classically in Sec. 2. In Sec. 3, two idealized 4-coil NRSE spectrometers are discussed (one using single π-flipper coil units and one using paired "bootstrap" coils); some idealized (exact π-flip) expressions are given for the spin-echo signal and some theoretical limitations are discussed. A more quantum mechanical discussion of NRSE is presented in Sec. 4 and additional theory related to the spin-echo signal, including wavelength-dependence, is given is Sec. 5. Factors affecting the instrumental resolution are discussed in Sec. 6. In Sec. 7, a variety of engineering issues are assessed in the context of challenging performance goals for a NIST Center for Neutron Research (NCNR) NRSE spectrometer. In Sec. 8, some Monte Carlo simulations are presented that examine the combined influences of spectrometer imperfections on the NRSE signal. These are compared with analytical predictions developed in previous sections. In Sec. 9, possible alternatives for a NCNR NRSE spectrometer configuration are discussed together with a preliminary assessment of the spectrometer neutron guide requirements. A summary of some of the useful formulas is given in Appendix A. PMID:26601027

  4. Concepts and Engineering Aspects of a Neutron Resonance Spin-Echo Spectrometer for the National Institute of Standards and Technology Center for Neutron Research

    PubMed Central

    Cook, Jeremy C.

    2014-01-01

    Following a brief introduction, the Neutron Resonance Spin-Echo (NRSE) principle is discussed classically in Sec. 2. In Sec. 3, two idealized 4-coil NRSE spectrometers are discussed (one using single π-flipper coil units and one using paired “bootstrap” coils); some idealized (exact π-flip) expressions are given for the spin-echo signal and some theoretical limitations are discussed. A more quantum mechanical discussion of NRSE is presented in Sec. 4 and additional theory related to the spin-echo signal, including wavelength-dependence, is given is Sec. 5. Factors affecting the instrumental resolution are discussed in Sec. 6. In Sec. 7, a variety of engineering issues are assessed in the context of challenging performance goals for a NIST Center for Neutron Research (NCNR) NRSE spectrometer. In Sec. 8, some Monte Carlo simulations are presented that examine the combined influences of spectrometer imperfections on the NRSE signal. These are compared with analytical predictions developed in previous sections. In Sec. 9, possible alternatives for a NCNR NRSE spectrometer configuration are discussed together with a preliminary assessment of the spectrometer neutron guide requirements. A summary of some of the useful formulas is given in Appendix A. PMID:26601027

  5. Anisotropic neutron spin resonance in superconducting BaFe{sub 1.9}Ni{sub 0.1}As{sub 2}.

    SciTech Connect

    Lipscombe, O. J.; Harriger, L. W.; Freeman, P. G.; Enderle, M.; Zhang, C.; Wang, M.; Egami, T.; Hu, J.; Xiang, T.; Norman, M. R.; Dai, P.; Materials Science Division; Univ. of Tennessee at Knoxville; Inst. Laue-Langevin; ORNL; Purdue Univ.; Chinese Academy of Sciences

    2010-01-01

    We use polarized inelastic neutron scattering to show that the neutron spin resonance below T{sub c} in superconducting BaFe{sub 1.9}Ni{sub 0.1}As{sub 2} (T{sub c} = 20 K) is purely magnetic in origin. Our analysis further reveals that the resonance peak near 7 meV only occurs for the planar response. This challenges the common perception that the spin resonance in the pnictides is an isotropic triplet excited state of the singlet Cooper pairs, as our results imply that only the S{sub 001} = {+-} 1 components of the triplet are involved.

  6. High-sensitivity pesticide detection using particle-enhanced resonant Raman scattering

    NASA Astrophysics Data System (ADS)

    Ranjan, Bikas; Saito, Yuika; Verma, Prabhat

    2016-03-01

    The use of pesticides in agriculture has raised concerns, as even a small residual of pesticide on food can be harmful. It is therefore of great importance to develop a robust technique to detect tiny amounts of pesticides. Although Raman spectroscopy is frequently used for chemical identification, it is not suitable for extremely low molecular concentrations. We propose a technique called particle-enhanced resonant Raman spectroscopy to detect extremely low concentrations of pesticides, where gold nanoparticles of desired plasmonic resonance are synthesized to match the resonance in Raman scattering. We successfully demonstrated the detection of extremely low amounts of pesticides on oranges.

  7. Resonance-enhanced vibrational excitation in electron scattering from O/sub 2/ multilayer films

    SciTech Connect

    Sanche, L.; Michaud, M.

    1981-10-05

    Electron-impact intramolecular vibrational and vibronic excitation of disordered multilayer O/sub 2/ films is studied with primary energies varying from 2 to 20 eV. The intensity of the v = 1 to v = 4 vibrational modes of ground state O/sub 2/ exhibits a broad resonance as a function of electron energy. At the resonance maximum the vibrational intensities are enhanced by one to two orders of magnitude. The resonance appears to be derived from gas-phase O/sub 2/-quasibound states.

  8. Reactive lymphoid hyperplasia of the liver: Perinodular enhancement on contrast-enhanced computed tomography and magnetic resonance imaging

    PubMed Central

    Sonomura, Tetsuo; Anami, Shinpei; Takeuchi, Taizo; Nakai, Motoki; Sahara, Shinya; Tanihata, Hirohiko; Sakamoto, Kazuki; Sato, Morio

    2015-01-01

    We report the case of a 69-year-old woman with reactive lymphoid hyperplasia (RLH) of the liver. She underwent partial hepatectomy under a preoperative diagnosis of hepatocellular carcinoma; however, histopathological analysis revealed RLH. The liver nodule showed the imaging feature of perinodular enhancement in the arterial dominant phase on contrast-enhanced computed tomography and magnetic resonance imaging, which could be a useful clue for identifying RLH in the liver. Histologically, the perinodular enhancement was compatible with prominent sinusoidal dilatation surrounding the liver nodule. PMID:26074715

  9. Reactive lymphoid hyperplasia of the liver: Perinodular enhancement on contrast-enhanced computed tomography and magnetic resonance imaging.

    PubMed

    Sonomura, Tetsuo; Anami, Shinpei; Takeuchi, Taizo; Nakai, Motoki; Sahara, Shinya; Tanihata, Hirohiko; Sakamoto, Kazuki; Sato, Morio

    2015-06-01

    We report the case of a 69-year-old woman with reactive lymphoid hyperplasia (RLH) of the liver. She underwent partial hepatectomy under a preoperative diagnosis of hepatocellular carcinoma; however, histopathological analysis revealed RLH. The liver nodule showed the imaging feature of perinodular enhancement in the arterial dominant phase on contrast-enhanced computed tomography and magnetic resonance imaging, which could be a useful clue for identifying RLH in the liver. Histologically, the perinodular enhancement was compatible with prominent sinusoidal dilatation surrounding the liver nodule. PMID:26074715

  10. Combined use of FLUKA and MCNP-4A for the Monte Carlo simulation of the dosimetry of 10B neutron capture enhancement of fast neutron irradiations.

    PubMed

    Pignol, J P; Cuendet, P; Brassart, N; Fares, G; Colomb, F; M'Bake Diop, C; Sabattier, R; Hachem, A; Prevot, G

    1998-06-01

    Boron neutron capture enhancement (BNCE) of the fast neutron irradiations use thermal neutrons produced in depth of the tissues to generate neutron capture reactions on 10B within tumor cells. The dose enhancement is correlated to the 10B concentration and to thermal neutron flux measured in the depth of the tissues, and in this paper we demonstrate the feasibility of Monte Carlo simulation to study the dosimetry of BNCE. The charged particle FLUKA code has been used to calculate the primary neutron yield from the beryllium target, while MCNP-4A has been used for the transport of these neutrons in the geometry of the Biomedical Cyclotron of Nice. The fast neutron spectrum and dose deposition, the thermal flux and thermal neutron spectrum in depth of a Plexiglas phantom has been calculated. The thermal neutron flux has been compared with experimental results determined with calibrated thermoluminescent dosimeters (TLD-600 and TLD-700, respectively, doped with 6Li or 7Li). The theoretical results were in good agreement with the experimental results: the thermal neutron flux was calculated at 10.3 X 10(6) n/cm2 s1 and measured at 9.42 X 10(6) n/cm2 s1 at 4 cm depth of the phantom and with a 10 cm X 10 cm irradiation field. For fast neutron dose deposition the calculated and experimental curves have the same slope but different shape: only the experimental curve shows a maximum at 2.27 cm depth corresponding to the build-up. The difference is due to the Monte Carlo simulation which does not follow the secondary particles. Finally, a dose enhancement of, respectively, 4.6% and 10.4% are found for 10 cm X 10 cm or 20 cm X 20 cm fields, provided that 100 micrograms/g of 10B is loaded in the tissues. It is anticipated that this calculation method may be used to improve BNCE of fast neutron irradiations through collimation modifications. PMID:9650176

  11. Neutron flow between nuclei as the principal enhancement mechanism in heavy-ion subbarrier fusion

    SciTech Connect

    Stelson, P.H.

    1988-01-01

    The observed enhanced cross sections for heavy-ion fusion are interpreted with a model in which the near barrier cross sections are dominated by neck formation initiated by neutron flow between the colliding nuclei. The collective properties of the colliding nuclei are then interpreted as a modulation of the thresholds for neck formation and dominate the cross sections in the region far below the barrier. 12 refs., 12 figs., 2 tabs.

  12. Highly enhanced transverse plasmon resonance and tunable double Fano resonances in gold@titania nanorods

    NASA Astrophysics Data System (ADS)

    Ruan, Qifeng; Fang, Caihong; Jiang, Ruibin; Jia, Henglei; Lai, Yunhe; Wang, Jianfang; Lin, Hai-Qing

    2016-03-01

    Gold nanorods have attracted intensive interest owing to their localized surface plasmon resonance properties and enormous potential applications. The transverse plasmon of Au nanorods is usually weaker than the longitudinal one, hampering certain plasmonic applications. Herein we report on the intensification of the transverse plasmon resonance by coating TiO2 onto Au nanorods. The transverse plasmon mode of the resultant Au@TiO2 nanorods with a sufficiently thick shell can be comparable to or even stronger than the longitudinal one in intensity. Moreover, both the transverse and longitudinal plasmon resonances of the Au@TiO2 nanorods exhibit an asymmetric line shape on their scattering spectra. Electrodynamic simulations and analyses based on a coupled oscillator model suggest that the asymmetric line shape originates from the coupling between the Au core and TiO2 shell. Apart from the shell thickness, the plasmonic properties of the Au@TiO2 nanorods can also be tuned by the dimension of the Au nanorod core. In addition, the polarization-dependent light scattering from the individual Au@TiO2 nanorods has also been investigated. These results will be of high importance for understanding the interactions between noble metals and semiconductors in plasmonic hybrid nanosystems, and for designing novel plasmonic nanostructures with desired optical properties and functions.Gold nanorods have attracted intensive interest owing to their localized surface plasmon resonance properties and enormous potential applications. The transverse plasmon of Au nanorods is usually weaker than the longitudinal one, hampering certain plasmonic applications. Herein we report on the intensification of the transverse plasmon resonance by coating TiO2 onto Au nanorods. The transverse plasmon mode of the resultant Au@TiO2 nanorods with a sufficiently thick shell can be comparable to or even stronger than the longitudinal one in intensity. Moreover, both the transverse and longitudinal

  13. Multifold Enhancement of Third-Harmonic Generation in Dielectric Nanoparticles Driven by Magnetic Fano Resonances.

    PubMed

    Shorokhov, Alexander S; Melik-Gaykazyan, Elizaveta V; Smirnova, Daria A; Hopkins, Ben; Chong, Katie E; Choi, Duk-Yong; Shcherbakov, Maxim R; Miroshnichenko, Andrey E; Neshev, Dragomir N; Fedyanin, Andrey A; Kivshar, Yuri S

    2016-08-10

    Strong Mie-type magnetic dipole resonances in all-dielectric nanostructures provide novel opportunities for enhancing nonlinear effects at the nanoscale due to the intense electric and magnetic fields trapped within the individual nanoparticles. Here we study third-harmonic generation from quadrumers of silicon nanodisks supporting high-quality collective modes associated with the magnetic Fano resonance. We observe nontrivial wavelength and angular dependencies of the generated harmonic signal featuring a multifold enhancement of the nonlinear response in oligomeric systems. PMID:27403664

  14. Neutron Capture by Cadmium: Thermal Cross Sections and Resonance Integrals of ^106,108,110,112,114,116Cd

    NASA Astrophysics Data System (ADS)

    Gicking, Allison M.; Krane, Kenneth S.

    2011-10-01

    The neutron capture cross sections of the stable, even-mass Cd isotopes (A = 106, 108, 110, 112, 114, and 116) have been previously measured in sources of natural abundance or low enrichment, often making the results uncertain owing to the large absorption cross section of naturally occurring ^113Cd. Ambiguities in values of the isomeric branching ratios have also contributed to uncertainties in previous results. We have remeasured the Cd neutron capture cross sections using samples of greater than 90% isotopic enrichment irradiated in the OSU TRIGA reactor. Gamma-ray emission spectra were analyzed to determine the effective resonance integrals and thermal cross sections leading to eight radioactive ground and isomeric states in the Cd isotopes.

  15. Enhancing the low frequency THz resonances (< 1 THz) of organic molecules via electronegative atom substitution

    NASA Astrophysics Data System (ADS)

    Dash, Jyotirmayee; Ray, Shaumik; Pesala, Bala

    2015-03-01

    Terahertz (THz) technology is an active area of research with various applications in non-intrusive imaging and spectroscopy. Very few organic molecules have significant resonances below 1 THz. Understanding the origin of low frequency THz modes in these molecules and their absence in other molecules could be extremely important in design and engineering molecules with low frequency THz resonances. These engineered molecules can be used as THz tags for anti-counterfeiting applications. Studies show that low frequency THz resonances are commonly observed in molecules having higher molecular mass and weak intermolecular hydrogen bonds. In this paper, we have explored the possibility of enhancing the strength of THz resonances below 1 THz through electronegative atom substitution. Adding an electronegative atom helps in achieving higher hydrogen bond strength to enhance the resonances below 1 THz. Here acetanilide has been used as a model system. THz-Time Domain Spectroscopy (THz-TDS) results show that acetanilide has a small peak observed below 1 THz. Acetanilide can be converted to 2-fluoroacetanilide by adding an electronegative atom, fluorine, which doesn't have any prominent peak below 1 THz. However, by optimally choosing the position of the electronegative atom as in 4-fluoroacetanilide, a significant THz resonance at 0.86 THz is observed. The origin of low frequency resonances can be understood by carrying out Density Functional Theory (DFT) simulations of full crystal structure. These studies show that adding an electronegative atom to the organic molecules at an optimized position can result in significantly enhanced resonances below 1 THz.

  16. Anomalous fluctuations of s-wave reduced neutron widths of 192,194Pt resonances

    SciTech Connect

    Koehler, Paul Edward; Becvar, F.; Krticka, Milan; Harvey, John A; Guber, Klaus H

    2010-01-01

    We obtained an unprecedentedly large number of s-wave neutron widths through R-matrix analysis of neutron cross-section measurements on enriched Pt samples. Careful analysis of these data rejects the validity of the Porter-Thomas distribution with a statistical significance of at least 99.997%.

  17. Magnetic resonance imaging and contrast enhancement. Scientific report

    SciTech Connect

    Swenberg, C.E.; Movius, E.G.

    1988-01-01

    Chapters II through VI of this report discuss: Relaxation of Nuclear Spins; Echo Techniques; Basic Imaging Pulse Sequences; Partial Saturation Recovery; Inversion Recovery; Spin Echo; Effects of Pulse Sequence on Image Contrast; Contrast Agents; Theoretical Aspects; Pharmacokinetics and Toxicity; and Physiological Rationale for Agent Selection. One of the major goals in all medical imaging techniques is to maximize one's ability to visualize and differentiate adjacent tissue regions in the body on the basis of differences in anatomy, physiology, or various pathological processes. Magnetic resonance (MR) imaging offers distinct advantages over conventional x-ray imaging because of the possibility of selecting specific pulse sequences that can differentiate adjacent structures on the basis of differences in proton density, T/sub 1/ or T/sub 2/ relaxation rates, or flow. As a result of applying these various pulse sequences, numerous images have been obtained of the brain and other organs that demonstrate considerably more-detailed anatomical structure than had previously been available with computerized tomography, ultrasound, or nuclear medicine techniques. In some situations it is clearly superior, such as in the diagnosis of multiple sclerosis.

  18. Enhancement of non-resonant dielectric cloaks using anisotropic composites

    SciTech Connect

    Takezawa, Akihiro Kitamura, Mitsuru

    2014-01-15

    Cloaking techniques conceal objects by controlling the flow of electromagnetic waves to minimize scattering. Herein, the effectiveness of homogenized anisotropic materials in non-resonant dielectric multilayer cloaking is studied. Because existing multilayer cloaking by isotropic materials can be regarded as homogenous anisotropic cloaking from a macroscopic view, anisotropic materials can be efficiently designed through optimization of their physical properties. Anisotropic properties can be realized in two-phase composites if the physical properties of the material are within appropriate bounds. The optimized anisotropic physical properties are identified by a numerical optimization technique based on a full-wave simulation using the finite element method. The cloaking performance measured by the total scattering width is improved by about 2.8% and 25% in eight- and three-layer cylindrical cloaking materials, respectively, compared with multilayer cloaking by isotropic materials. In all cloaking examples, the optimized microstructures of the two-phase composites are identified as the simple lamination of two materials, which maximizes the anisotropy. The same performance as published for eight-layer cloaking by isotropic materials is achieved by three-layer cloaking using the anisotropic material. Cloaking with an approximately 50% reduction of total scattering width is achieved even in an octagonal object. Since the cloaking effect can be realized using just a few layers of the laminated anisotropic dielectric composite, this may have an advantage in the mass production of cloaking devices.

  19. Contrast-enhanced dynamic magnetic resonance nephrography in healthy dogs.

    PubMed

    Fonseca-Matheus, J M; Pérez-García, C C; Ginja, M M D; Altónaga, J R; Orden, M A; Gonzalo-Orden, J M

    2011-09-01

    Twenty-three healthy mixed-breed male adult dogs were examined using serial magnetic resonance (MR) renograms. The images were obtained using a dynamic gradient-echo, fast SPGR, T1-weighted sequence and low doses of gadolinium chelates (0.025 mmol/kg). Time-intensity curves were obtained to assess typical urinary excretion parameters, namely, time to vascular peak (TVP), time to vascular drop (TVD), time to glomerular peak (TGP), parenchymal phase length (PPL), gradient of parenchymal phase (GPP) and pattern of excretory segment. The mean TVP, TVD, TGP and PPL were 31.6±11.8, 43.4±11.2, 154.0±36.2 and 115.2±37.7s, respectively. The GPP was 24.1±8.6% of signal intensity per min. The excretory segment was concave in all cases, and at the end of the examination, 87.1% of kidneys had shown a reduction in signal intensity of 50%. This MR nephrography protocol can provide adequate time-intensity curve parameters for the urinary system of dogs, offers excellent anatomical detail, and represents an alternative to radionuclide nephrography. PMID:20810295

  20. Enhancement of non-resonant dielectric cloaks using anisotropic composites

    NASA Astrophysics Data System (ADS)

    Takezawa, Akihiro; Kitamura, Mitsuru

    2014-01-01

    Cloaking techniques conceal objects by controlling the flow of electromagnetic waves to minimize scattering. Herein, the effectiveness of homogenized anisotropic materials in non-resonant dielectric multilayer cloaking is studied. Because existing multilayer cloaking by isotropic materials can be regarded as homogenous anisotropic cloaking from a macroscopic view, anisotropic materials can be efficiently designed through optimization of their physical properties. Anisotropic properties can be realized in two-phase composites if the physical properties of the material are within appropriate bounds. The optimized anisotropic physical properties are identified by a numerical optimization technique based on a full-wave simulation using the finite element method. The cloaking performance measured by the total scattering width is improved by about 2.8% and 25% in eight- and three-layer cylindrical cloaking materials, respectively, compared with multilayer cloaking by isotropic materials. In all cloaking examples, the optimized microstructures of the two-phase composites are identified as the simple lamination of two materials, which maximizes the anisotropy. The same performance as published for eight-layer cloaking by isotropic materials is achieved by three-layer cloaking using the anisotropic material. Cloaking with an approximately 50% reduction of total scattering width is achieved even in an octagonal object. Since the cloaking effect can be realized using just a few layers of the laminated anisotropic dielectric composite, this may have an advantage in the mass production of cloaking devices.

  1. Design of the radiation shielding for the time of flight enhanced diagnostics neutron spectrometer at Experimental Advanced Superconducting Tokamak

    SciTech Connect

    Du, T. F.; Chen, Z. J.; Peng, X. Y.; Yuan, X.; Zhang, X.; Hu, Z. M.; Cui, Z. Q.; Xie, X. F.; Ge, L. J.; Li, X. Q.; Zhang, G. H.; Chen, J. X.; Fan, T. S.; Gorini, G.; Nocente, M.; Tardocchi, M.; Hu, L. Q.; Zhong, G. Q.; Lin, S. Y.; Wan, B. N.

    2014-11-15

    A radiation shielding has been designed to reduce scattered neutrons and background gamma-rays for the new double-ring Time Of Flight Enhanced Diagnostics (TOFED). The shielding was designed based on simulation with the Monte Carlo code MCNP5. Dedicated model of the EAST tokamak has been developed together with the emission neutron source profile and spectrum; the latter were simulated with the Nubeam and GENESIS codes. Significant reduction of background radiation at the detector can be achieved and this satisfies the requirement of TOFED. The intensities of the scattered and direct neutrons in the line of sight of the TOFED neutron spectrometer at EAST are studied for future data interpretation.

  2. Measurement of thermal neutron cross section and resonance integral for the {sup 170}Er(n,{gamma}){sup 171}Er reaction by using a {sup 55}Mn monitor

    SciTech Connect

    Yuecel, Haluk; Budak, M. Gueray; Karadag, Mustafa

    2007-09-15

    The thermal neutron cross section and the resonance integral of the reaction {sup 170}Er(n,{gamma}){sup 171}Er were measured by the Cd-ratio method using a {sup 55}Mn monitor as single comparator. Analytical grade MnO{sub 2} and Er{sub 2}O{sub 3} powder samples with and without a cylindrical 1 mm Cd shield box were irradiated in an isotropic neutron field obtained from three {sup 241}Am-Be neutron sources. The induced activities in the samples were measured with a 120.8% relative efficiency p-type HPGe detector. The correction factors for gamma-ray attenuation (F{sub g}), thermal neutron self-shielding (G{sub th}), and resonance neutron self-shielding (G{sub epi}) effects, and the epithermal neutron spectrum shape factor ({alpha}) were taken into account. The thermal neutron cross section for the (n,{gamma}) reaction in {sup 170}Er has been determined to be 8.00 {+-} 0.56 b, relative to that of the {sup 55}Mn monitor. However, some previously reported experimental results compared to the present result show a large discrepancy ranging from 8.3 to 86%. The present result is, in general, in good agreement with the recently measured values by 9%. According to the definition of Cd cut-off energy at 0.55 eV, the resonance integral obtained is 44.5 {+-} 4.0 b, which is determined relative to the reference integral value of the {sup 55}Mn monitor by using cadmium ratios. The existing experimental data for the resonance integral are distributed between 18 and 43 b. The present resonance integral value agrees only with the measurement of 43 {+-} 5 b by Gillette [Thermal Cross Section and Resonance Integral Studies, ORNL-4155, 15 (1967)] within uncertainty limits.

  3. Surface-Enhanced Raman Scattering Using Silica Whispering-Gallery Mode Resonators

    NASA Technical Reports Server (NTRS)

    Anderson, Mark S.

    2013-01-01

    The motivation of this work was to have robust spectroscopic sensors for sensitive detection and chemical analysis of organic and molecular compounds. The solution is to use silica sphere optical resonators to provide surface-enhanced spectroscopic signal. Whispering-gallery mode (WGM) resonators made from silica microspheres were used for surface-enhanced Raman scattering (SERS) without coupling to a plasmonic mechanism. Large Raman signal enhancement is observed by exclusively using 5.08-micron silica spheres with 785-nm laser excitation. The advantage of this non-plasmonic approach is that the active substrate is chemically inert silica, thermally stable, and relatively simple to fabricate. The Raman signal enhancement is broadly applicable to a wide range of molecular functional groups including aliphatic hydrocarbons, siloxanes, and esters. Applications include trace organic analysis, particularly for in situ planetary instruments that require robust sensors with consistent response.

  4. Quantitative evaluation of blinking in surface enhanced resonance Raman scattering and fluorescence by electromagnetic mechanism

    NASA Astrophysics Data System (ADS)

    Itoh, Tamitake; Iga, Mitsuhiro; Tamaru, Hiroharu; Yoshida, Ken-ichi; Biju, Vasudevanpillai; Ishikawa, Mitsuru

    2012-01-01

    We analyze blinking in surface enhanced resonance Raman scattering (SERRS) and surface enhanced fluorescence (SEF) of rhodamine 6G molecules as intensity and spectral instability by electromagnetic (EM) mechanism. We find that irradiation of intense NIR laser pulses induces blinking in SERRS and SEF. Thanks to the finding, we systematically analyze SERRS and SEF from stable to unstable using single Ag nanoparticle (NP) dimers. The analysis reveals two physical insights into blinking as follows. (1) The intensity instability is inversely proportional to the enhancement factors of decay rate of molecules. The estimation using the proportionality suggests that separation of the molecules from Ag NP surfaces is several angstroms. (2) The spectral instability is induced by blueshifts in EM enhancement factors, which have spectral shapes similar to the plasmon resonance. This analysis provides us with a quantitative picture for intensity and spectral instability in SERRS and SEF within the framework of EM mechanism.

  5. Enhanced Analysis Techniques for an Imaging Neutron and Gamma Ray Spectrometer

    NASA Astrophysics Data System (ADS)

    Madden, Amanda C.

    The presence of gamma rays and neutrons is a strong indicator of the presence of Special Nuclear Material (SNM). The imaging Neutron and gamma ray SPECTrometer (NSPECT) developed by the University of New Hampshire and Michigan Aerospace corporation detects the fast neutrons and prompt gamma rays from fissile material, and the gamma rays from radioactive material. The instrument operates as a double scatter device, requiring a neutron or a gamma ray to interact twice in the instrument. While this detection requirement decreases the efficiency of the instrument, it offers superior background rejection and the ability to measure the energy and momentum of the incident particle. These measurements create energy spectra and images of the emitting source for source identification and localization. The dual species instrument provides superior detection than a single species alone. In realistic detection scenarios, few particles are detected from a potential threat due to source shielding, detection at a distance, high background, and weak sources. This contributes to a small signal to noise ratio, and threat detection becomes difficult. To address these difficulties, several enhanced data analysis tools were developed. A Receiver Operating Characteristic Curve (ROC) helps set instrumental alarm thresholds as well as to identify the presence of a source. Analysis of a dual-species ROC curve provides superior detection capabilities. Bayesian analysis helps to detect and identify the presence of a source through model comparisons, and helps create a background corrected count spectra for enhanced spectroscopy. Development of an instrument response using simulations and numerical analyses will help perform spectra and image deconvolution. This thesis will outline the principles of operation of the NSPECT instrument using the double scatter technology, traditional analysis techniques, and enhanced analysis techniques as applied to data from the NSPECT instrument, and an

  6. Gold and aluminum based surface plasmon resonance biosensors: sensitivity enhancement

    NASA Astrophysics Data System (ADS)

    Biednov, Mykola; Lebyedyeva, Tetyana; Shpylovyy, Pavlo

    2015-05-01

    In this work we considered Gold and Aluminum thin films coated with additional dielectric layers as sensing platforms. Operation of these sensors is based on measuring shift in the position of the reflectivity dip in angular reflectivity spectrum of the sample. Shift can be caused by changes in the refraction index of either liquid that interacts with sensors surface (refractometric measurements) or thin adjacent biolayer on top of the sensor due to immobilization of the target molecules (biosensing). Calculations based on Fresnel equations and transfer matrix formalism allowed us to make comprehensive analysis of the angular sensitivity, shape of the reflectivity dip and dynamic range of the sensors with different dielectric coatings. Calculations were performed for both cases of bio and refractometric sensing. Results showed different dependence of the sensitivity of Au an Al based sensors upon refraction index of the dielectric coating. For Au-based surface Plasmon resonance sensor up to two times increased sensitivity can be achieved using dielectric coating with high refraction index 2.3 of proper thickness. For sensors based on aluminum we were able to achieve 50% increased angular sensitivity. At the same time width of the reflectivity dip increased proportionally to the optical thickness of the dielectric coating. For estimating sensors quality we analyzed ratio of the angular sensitivity to the width of the reflectivity dip. This ratio decreased with increase in optical thickness of the dielectric, however angular sensitivity of the sensor increased significantly. Deposition of the additional dielectric layer with high refraction index such as Niobium Oxide can also improve chemical and mechanical stability of the sensor.

  7. Enhanced multicolor fluorescence in bioimaging using deep-ultraviolet surface plasmon resonance

    NASA Astrophysics Data System (ADS)

    Kikawada, Masakazu; Ono, Atsushi; Inami, Wataru; Kawata, Yoshimasa

    2014-06-01

    Enhanced multicolor fluorescence has been achieved using deep-ultraviolet surface plasmon resonance (DUV-SPR) on an aluminum thin film using the Kretschmann configuration. The film thickness and the incident angle of the light were optimized by calculations using the Fresnel equations. The presence of a surface oxide layer was also considered in the calculations. Experimental measurements showed that DUV-SPR led to a strong enhancement of the fluorescence intensity from both quantum dots and dye-labeled cells.

  8. Dual-band-enhanced Transmission through a Subwavelength Aperture by Coupled Metamaterial Resonators

    PubMed Central

    Guo, Yunsheng; Zhou, Ji

    2015-01-01

    In classical mechanics, it is well known that a system consisting of two identical pendulums connected by a spring will steadily oscillate with two modes: one at the fundamental frequency of a single pendulum and one in which the frequency increases with the stiffness of the spring. Inspired by this physical concept, we present an analogous approach that uses two metamaterial resonators to realize dual-band-enhanced transmission of microwaves through a subwavelength aperture. The metamaterial resonators are formed by the periodically varying and strongly localized fields that occur in the two metal split-ring resonators, which are placed gap-to-gap on either side of the aperture. The dual-band frequency separation is determined by the coupling strength between the two resonators. Measured transmission spectra, simulated field distributions, and theoretical analyses verify our approach. PMID:25634496

  9. Figure of merit enhancement of surface plasmon resonance sensors using absentee layer.

    PubMed

    Chen, Zhaoyang; Zhao, Xin; Lin, Chengyou; Chen, Shujing; Yin, Liang; Ding, Yingchun

    2016-09-01

    By adding an absentee layer on the top of the metallic layer, the figure of merit (FOM) of a surface plasmon resonance (SPR) sensor with Kretschmann configuration was enhanced, without changing the resonance angle and the reflectance at the resonance angle. Comparing with a traditional SPR sensor, the FOM of the SPR sensor with an absentee layer composed of either 1367 nm thick KCl or 235 nm thick Si3N4 can be improved by 5.53% or 11.41%, respectively. The enhancement of the FOM should be attributed to the faster decrease of the full width at half-maximum than the sensitivity after an absentee layer was applied in the SPR sensor. PMID:27607256

  10. Enhanced actuation of nanocrystalline diamond microelectromechanical disk resonators with AlN layers

    NASA Astrophysics Data System (ADS)

    Yoshikawa, Taro; Reusch, Markus; Holc, Katarzyna; Iankov, Dimitre; Zuerbig, Verena; Zukauskaite, Agne; Nebel, Christoph E.; Ambacher, Oliver; Lebedev, Vadim

    2016-04-01

    A great potential of the use of aluminum nitride (AlN) to enhance the actuation of nanocrystalline diamond (NCD) microelectromechanical system disk resonators is revealed. A disk resonator with a unimorph (AlN/NCD) structure is fabricated by depositing a c-axis oriented AlN on a capacitive NCD disk resonator. The unimorph resonator is piezoelectrically actuated with flexural whispering gallery modes with a relatively large electrode gap spacing, i.e., the spacing which is greater than 1 μm, although this is not possible for the capacitive NCD disk resonator. This result is explained by a finite element method simulation where the piezoelectric actuation turns out to be more effective than the capacitive actuation when the electrode gap spacing is >0.8 μm. The simulation also shows that the electrode gap spacing required for the capacitive actuation to be more effective than the piezoelectric actuation exponentially decreases when the resonator dimension is scaled down for higher frequency operations. Our study indicates that the use of AlN is promising to decrease impedance levels of NCD disk resonators especially for their higher frequency operations.

  11. Resonance Enhanced Multi-Photon Ionization (rempi) and Double Resonance Uv-Uv and Ir-Uv Spectroscopic Investigation Isocytosine

    NASA Astrophysics Data System (ADS)

    Lee, Seung Jun; Min, Ahreum; Ahn, Ahreum; Moon, Cheol Joo; Choi, Myong Yong; Ishiuchi, Shun-Ichi; Miyazaki, Mitsuhiko; Fujii, Masaaki

    2013-06-01

    Isocytosine(iC), 2-aminouracil, is a non-natural nucleobase and its functional group's positions resemble those of guanine; therefore, its spectroscopic investigation is worthy of attention especially for the natural/unnatural base pairs with guanine and isoguanine. In this study, resonance enhanced multi-photon ionization (REMPI) and UV/IR-UV double resonance spectra of iC in the gas phase are presented. The collaboration work between Tokyo Institute of Technology, Japan and Gyeongsang National University, Korea using laser ablation and thermal evaporation, respectively, for producing jet-cooled iC is presented and discussed. The REMPI spectrum of iC monomers is recorded in the spectral range of 35000 to 36400cm-1, showing very congested π-π* vibronic bands. UV-UV hole burning spectroscopy is further conducted to investigate the conformational landscapes of iC monomers. Moreover, the presence of free OH band from IR-UV double resonance spectroscopy in combination with quantum chemical calculations convinces that the iC monomer in free-jet expansion experiment is an enol tautomer. However, a possible presence of a keto tautomer of iC may be provided by employing a pico-second experiment on iC.

  12. Evidence of Spin Resonance Signal in Oxygen Free Superconducting CaFe0.88Co0.12AsF: An Inelastic Neutron Scattering Study

    NASA Astrophysics Data System (ADS)

    Price, Stephen; Su, Yixi; Xiao, Yinguo; Adroja, Devashibhai T.; Guidi, Tatiana; Mittal, Ranjan; Nandi, Shibabrata; Matsuishi, Satoru; Hosono, Hideo; Brückel, Thomas

    2013-10-01

    The spin excitation spectrum of optimally doped superconducting CaFe0.88Co0.12AsF (Tc˜ 22 K) was studied by means of time-of-flight (ToF) inelastic neutron scattering experiments on a powder sample for temperatures above and below Tc and energies up to 15 meV. In the superconducting state, the spin resonance signal is observed as an enhancement of spectral weight of particle hole excitations of approximately 1.5 times relative to normal state excitations. The resonance energy ER˜ 7 meV scales to Tc via 3.7 kBTc which is in reasonable agreement to the scaling relation reported for other Fe-based compositions. For energies below 5 meV the spectrum of spin flip particle hole excitations in the superconducting state exhibits a strong reduction in spectral weight, indicating the opening of the spin gap. Nonetheless, a complete suppression of magnetic response cannot be observed. In contrast, the normal state spin excitations are not gapped and strongly two dimensional spin fluctuations persist up to temperatures at least as high as 150 K.

  13. Simultaneous resonant enhanced multiphoton ionization and electron avalanche ionization in gas mixtures

    SciTech Connect

    Shneider, Mikhail N.; Zhang Zhili; Miles, Richard B.

    2008-07-15

    Resonant enhanced multiphoton ionization (REMPI) and electron avalanche ionization (EAI) are measured simultaneously in Ar:Xe mixtures at different partial pressures of mixture components. A simple theory for combined REMPI+EAI in gas mixture is developed. It is shown that the REMPI electrons seed the avalanche process, and thus the avalanche process amplifies the REMPI signal. Possible applications are discussed.

  14. Nonlinear standing wave excitation by series resonance-enhanced harmonics in low pressure capacitive discharges

    NASA Astrophysics Data System (ADS)

    Lieberman, M. A.; Lichtenberg, A. J.; Kawamura, Emi; Marakhtanov, A. M.

    2015-09-01

    It is well known that standing waves having radially center-high rf voltage profiles exist in high frequency capacitive discharges. It is also known that in radially uniform discharges, the capacitive sheath nonlinearities excite strong nonlinear series resonance harmonics that enhance the electron power deposition. In this work, we consider the coupling of the series resonance-enhanced harmonics to the standing waves. A one-dimensional, asymmetric radial transmission line model is developed incorporating the wave and nonlinear sheath physics and a self-consistent dc potential. The resulting coupled pde equation set is solved numerically to determine the discharge voltages and currents. A 10 mT argon base case is chosen with plasma density 2 ×1016 m-3, gap width 2 cm and conducting electrode radius 15 cm, driven by a high frequency 500 V source with source resistance 0.5 ohms. We find that nearby resonances lead to an enhanced ratio of 4.5 of the electron power per unit area on axis, compared to the average. The radial dependence of electron power with frequency shows significant variations, with the central enhancement and sharpness of the spatial resonances depending in a complicated way on the harmonic structure. Work supported by DOE Fusion Energy Science Contract DE-SC000193 and by a gift from the Lam Research Corporation.

  15. Enhanced fluorescent resonant energy transfer of DNA conjugates complexed with surfactants and divalent metal ions.

    PubMed

    Oh, Taeseok; Choi, Jae-Young; Heller, Michael J

    2016-04-21

    Dimerization and resultant quenching of donor and acceptor dyes conjugated on DNA causes loss of fluorescent resonant energy transfer (FRET) efficiency. However, when complexed with surfactants and divalent metal ions, sheathing effects insulate and shield the DNA structures, reducing dimerization and quenching which leads to significant enhancement of FRET efficiency. PMID:26985458

  16. Resonance enhancement in the accelerator transmutation of 1.3-day {sup 232}Pa and 2.1-day {sup 238}Np

    SciTech Connect

    Moore, M. S.; Danon, Y.

    1995-09-15

    The suggestion that the transmutation of actinide waste into fission products might best be done with thermalized spallation neutrons and odd-odd target materials such as {sup 238}Np has been studied. During the 1993 LAMPF/PSR cycle, we measured the fission cross section of 1.3-day {sup 232}Pa and 2.1-day {sup 238}Np from 0.01 eV to 40 keV at the LANSCE facility, and have carried out a preliminary resonance analysis of the observed structure and of the thermal region, with a 1/v representation above a few eV. In the present study, we calculate the reaction rates of these two species and {sup 247}Cm in a 'resonance reactor', an accelerator-driven assembly whose slowing-down properties are well known. Our model is a 1.8 m{sup 3} block of lead with a helium-cooled tungsten target in the center, i.e., the Rensselaer Intense Neutron Source (RINS). We include the effects of adding moderator outside an idealized lead slowing-down assembly, giving resonance enhancement factors for {sup 232}Pa and {sup 238}Np, and present parameters for the accelerator required to drive such an assembly to accomplish actinide burnup of these species.

  17. No enhancement of fusion probability by the neutron halo of 6He

    NASA Astrophysics Data System (ADS)

    Raabe, R.; Sida, J. L.; Charvet, J. L.; Alamanos, N.; Angulo, C.; Casandjian, J. M.; Courtin, S.; Drouart, A.; Durand, D. J. C.; Figuera, P.; Gillibert, A.; Heinrich, S.; Jouanne, C.; Lapoux, V.; Lepine-Szily, A.; Musumarra, A.; Nalpas, L.; Pierroutsakou, D.; Romoli, M.; Rusek, K.; Trotta, M.

    2004-10-01

    Quantum tunnelling through a potential barrier (such as occurs in nuclear fusion) is very sensitive to the detailed structure of the system and its intrinsic degrees of freedom. A strong increase of the fusion probability has been observed for heavy deformed nuclei. In light exotic nuclei such as 6He, 11Li and 11Be (termed `halo' nuclei), the neutron matter extends much further than the usual nuclear interaction scale. However, understanding the effect of the neutron halo on fusion has been controversial-it could induce a large enhancement of fusion, but alternatively the weak binding energy of the nuclei could inhibit the process. Other reaction channels known as direct processes (usually negligible for ordinary nuclei) are also important: for example, a fragment of the halo nucleus could transfer to the target nucleus through a diminished potential barrier. Here we study the reactions of the halo nucleus 6He with a 238U target, at energies near the fusion barrier. Most of these reactions lead to fission of the system, which we use as an experimental signature to identify the contribution of the fusion and transfer channels to the total cross-section. At energies below the fusion barrier, we find no evidence for a substantial enhancement of fusion. Rather, the (large) fission yield is due to a two-neutron transfer reaction, with other direct processes possibly also involved.

  18. Observation of low-lying resonances in the quasicontinuum of 195,196Pt and enhanced astrophysical reaction rates

    DOE PAGESBeta

    Giacoppo, F.; Bello Garrote, F. L.; Eriksen, T. K.; Görgen, A.; Guttormsen, M.; Hagen, T. W.; Larsen, A. C.; Kheswa, B. V.; Klintefjord, M.; Koehler, P. E.; et al

    2015-05-28

    An excess of strength on the low-energy tail of the giant dipole resonance recently has been observed in the γ-decay from the quasicontinuum of 195,196Pt. The nature of this phenomenon is not yet fully investigated. If this feature is present also in the γ-ray strength of the neutron-rich isotopes, it can affect the neutron-capture reactions involved in the formation of heavy-elements in stellar nucleosynthesis. The experimental level density and γ-ray strength function of 195,196Pt are presented together with preliminary calculations of the corresponding neutron-capture cross sections.

  19. Cardiac sarcoidosis evaluated with gadolinium-enhanced magnetic resonance and contrast-enhanced 64-slice computed tomography.

    PubMed

    Smedema, Jan-Peter; Truter, Rene; de Klerk, Petra A; Zaaiman, Leonie; White, Leonie; Doubell, Anton F

    2006-09-20

    Sarcoidosis is a multi-system granulomatous disorder of unknown etiology with symptomatic cardiac involvement in up to 7% of patients. The clinical features of sarcoid heart disease include congestive heart failure, arrhythmias, conduction disturbances, and sudden death. We evaluated the value of contrast-enhanced multi-detector computed tomography in delineating myocardial scar and granulomatous inflammation by comparing our findings with gadolinium magnetic resonance in a patient diagnosed with cardiac sarcoidosis. PMID:16257460

  20. A triple-resonance Raman chip for simultaneous enhancement of Stokes and anti-Stokes lines utilizing both localized and non-localized plasmonic resonance

    NASA Astrophysics Data System (ADS)

    Lin, Jiao; Zhang, Yuan; Lee, El-Hang; He, Sailing

    2015-10-01

    In this paper we report a triple-resonance surface-enhanced Raman scattering (SERS) chip that is able to provide simultaneous field enhancement for both the Stokes and anti-Stokes lines. The structure consists of an array of periodic gold bowties placed on the surface of a uniform gold film. It can support two localized surface plasmonic resonances (LSPRs): an electric dipole binding resonance (EDBR) and a magnetic dipole resonance (MDR). A third field enhancement peak is obtained by utilizing the strong interaction between the non-localized surface plasmonic resonance (non-localized SPR) and the LSPR, which greatly raises the field enhancement for the non-localized SPR. In addition, a gold strip-line resonator is incorporated to further enhance the local field intensity. Consequently, the field enhancement of the three peaks are all increased. Compared with the same structure without strip, the periodic bowtie-strip compound structure on gold film can gain as much as ∼22.8 times and ∼3.6 times larger Raman intensity enhancement simultaneously for both the Stokes and anti-Stokes lines.

  1. Development of self-interrogation neutron resonance densitometry (sinrd) to measure the fissile content in nuclear fuel

    NASA Astrophysics Data System (ADS)

    LaFleur, Adrienne Marie

    The development of non-destructive assay (NDA) capabilities to directly measure the fissile content in spent fuel is needed to improve the timely detection of the diversion of significant quantities of fissile material. Currently, the International Atomic Energy Agency (IAEA) does not have effective NDA methods to verify spent fuel and recover continuity of knowledge in the event of a containment and surveillance systems failure. This issue has become increasingly critical with the worldwide expansion of nuclear power, adoption of enhanced safeguards criteria for spent fuel verification, and recent efforts by the IAEA to incorporate an integrated safeguards regime. In order to address these issues, the use of Self-Interrogation Neutron Resonance Densitometry (SINRD) has been developed to improve existing nuclear safeguards and material accountability measurements. The following characteristics of SINRD were analyzed: (1) ability to measure the fissile content in Light Water Reactors (LWR) fuel assemblies and (2) sensitivity and penetrability of SINRD to the removal of fuel pins from an assembly. The Monte Carlo Neutral Particle eXtended (MCNPX) transport code was used to simulate SINRD for different geometries. Experimental measurements were also performed with SINRD and were compared to MCNPX simulations of the experiment to verify the accuracy of the MCNPX model of SINRD. Based on the results from these simulations and measurements, we have concluded that SINRD provides a number of improvements over current IAEA verification methods. These improvements include: (1) SINRD provides absolute measurements of burnup independent of the operator's declaration. (2) SINRD is sensitive to pin removal over the entire burnup range and can verify the diversion of 6% of fuel pins within 3o from LWR spent LEU and MOX fuel. (3) SINRD is insensitive to the boron concentration and initial fuel enrichment and can therefore be used at multiple spent fuel storage facilities. (4) The

  2. Comparative study of resonance Raman and surface-enhanced resonance Raman chlorophyll a spectra using soret and red excitation

    SciTech Connect

    Thomas, L.L.; Kim, Jaeho; Cotton, T.M. )

    1990-12-05

    Surface-enhanced resonance Raman scattering (SERRS) spectra are reported for chlorophyll a adsorbed on a silver electrode at 298 and 77 K with 406.7-, 457.9-, 514.5-, and 647.1-nm excitation. Submerging the electrode in degassed water at 298 K was found to improve the spectral quality by minimizing sample heating and photooxidation. Spectral intensities and peak resolutions were greater at all excitation wavelengths at liquid nitrogen temperature. Most significantly, roughened silver at the low temperature quenched the fluorescence accompanying red excitation and minimized sample photooxidation, resulting in richly detailed SERRS spectra of chlorophyll a. The close correspondence between chlorophyll a resonance Raman (RR) and SERRS spectra suggests that an electromagnetic mechanism is the major source of the surface enhancement, rather than a chemical mechanism (e.g. a charge-transfer complex between chlorophyll a and the metal). The spectral similarities, together with the presence of the MgN{sub 4} vibration band in the SERRS spectra, also provide evidence that structural alterations (e.g. cleavage of ring V or loss of Mg) do not occur in chlorophyll a after adsorption at the electrode surface. A distinctive SERRS spectrum was obtained for each excitation wavelength. Selective excitation within the various electronic transitions can thus be utilized to verify assignments of the vibrational modes of chlorophyll a and to monitor its interactions and photochemical behavior in biomimetic systems.

  3. Enhanced RF to DC converter with LC resonant circuit

    NASA Astrophysics Data System (ADS)

    Gabrillo, L. J.; Galesand, M. G.; Hora, J. A.

    2015-06-01

    Presented in this paper is an experimental comparison of the conventional and proposed design circuit of a radio frequency (RF) energy harvesting. RF to DC energy harvester simply consists of antenna and rectifier block for receiving electromagnetic radiation signal and to produce a DC voltage, respectively. In addition to this conventional circuit, the proposed design includes LC tank circuit as receiving block of a well-designed antenna radio frequency receiver. Proper choice of an antenna type, realizing of point contact Germanium diodes as rectifier and correct design values for the LC passive components, greatly improved the measurement of the maximum output power, giving approximately a 100% increase compared to the conventional method. Experimental results of the enhanced RF to DC converter measured a maximum output power of 1.80 mWat a distance of 77.84 meters from a TV signal tower operating at 165 MHz.Thus, the harvested signal was enough to supply a low power wireless device applications without battery maintenance.

  4. Evaluations of the new LiF-scintillator and optional brightness enhancement films for neutron imaging

    NASA Astrophysics Data System (ADS)

    Iikura, H.; Tsutsui, N.; Nakamura, T.; Katagiri, M.; Kureta, M.; Kubo, J.; Matsubayashi, M.

    2011-09-01

    Japan Atomic Energy Agency has developed the neutron scintillator jointly with Chichibu Fuji Co., Ltd. In this study, we evaluated the new ZnS(Ag):Al/ 6Li scintillator developed for neutron imaging. It was confirmed that the brightness increased by about double while maintaining equal performance for the spatial resolution as compared with a conventional scintillator. High frame-rate imaging using a high-speed video camera system and this new scintillator made it possible to image beyond 10 000 frames per second while still having enough brightness. This technique allowed us to obtain a high-frame-rate visualization of oil flow in a running car engine. Furthermore, we devised a technique to increase the light intensity of reception for a camera by adding brightness enhancement films on the output surface of the scintillator. It was confirmed that the spatial resolution degraded more than double, but the brightness increased by about three times.

  5. Order of magnitude enhancement in neutron emission with deuterium-krypton admixture operation in miniature plasma focus device

    SciTech Connect

    Verma, Rishi; Lee, P.; Lee, S.; Springham, S. V.; Tan, T. L.; Rawat, R. S.; Krishnan, M.

    2008-09-08

    The effect of varied concentrations of deuterium-krypton (D{sub 2}-Kr) admixture on the neutron emission of a fast miniature plasma focus device was investigated. It was found that a judicious concentration of Kr in D{sub 2} can significantly enhance the neutron yield. The maximum average neutron yield of (1{+-}0.27)x10{sup 4} n/shot for pure D{sub 2} filling at 3 mbars was enhanced to (3.14{+-}0.4)x10{sup 5} n/shot with D{sub 2}+2% Kr admixture operation, which represents a >30-fold increase. More than an order of magnitude enhancement in the average neutron yield was observed over the broader operating range of 1-4 mbars for D{sub 2}+2% Kr and D{sub 2}+5% Kr admixtures.

  6. Simulated Performance of the Integrated Passive Neutron Albedo Reactivity and Self-Interrogation Neutron Resonance Densitometry Detector Designed for Spent Fuel Measurement at the Fugen Reactor in Japan

    SciTech Connect

    Ulrich, Timothy J. II; Lafleur, Adrienne M.; Menlove, Howard O.; Swinhoe, Martyn T.; Tobin, Stephen J.; Seya, Michio; Bolind, Alan M.

    2012-07-16

    An integrated nondestructive assay instrument, which combined the Passive Neutron Albedo Reactivity (PNAR) and the Self-Interrogation Neutron Resonance Densitometry (SINRD) techniques, is the research focus for a collaborative effort between Los Alamos National Laboratory (LANL) and the Japanese Atomic Energy Agency as part of the Next Generation Safeguard Initiative. We will quantify the anticipated performance of this experimental system in two physical environments: (1) At LANL we will measure fresh Low Enriched Uranium (LEU) assemblies for which the average enrichment can be varied from 0.2% to 3.2% and for which Gd laced rods will be included. (2) At Fugen we will measure spent Mixed Oxide (MOX-B) and LEU spent fuel assemblies from the heavy water moderated Fugen reactor. The MOX-B assemblies will vary in burnup from {approx}3 GWd/tHM to {approx}20 GWd/tHM while the LEU assemblies ({approx}1.9% initial enrichment) will vary from {approx}2 GWd/tHM to {approx}7 GWd/tHM. The estimated count rates will be calculated using MCNPX. These preliminary results will help the finalization of the hardware design and also serve a guide for the experiment. The hardware of the detector is expected to be fabricated in 2012 with measurements expected to take place in 2012 and 2013. This work is supported by the Next Generation Safeguards Initiative, Office of Nuclear Safeguards and Security, National Nuclear Security Administration.

  7. Fundamentals of a modified model of the distribution of neutron-resonance widths and results of its application in the mass-number range of 35 {<=} A {<=} 249

    SciTech Connect

    Sukhovoj, A. M. Khitrov, V. A.

    2013-01-15

    A modified model is developed for describing the distribution of random resonance width for any nuclei. The model assumes the coexistence in a nucleus of one or several partial radiative and neutron amplitudes for respective resonance widths, these amplitudes differing in their parameters. Also, it is assumed that amplitude can be described by a Gaussian curve characterized by a nonzero mean value and a variance not equal to unity and that their most probable values can be obtained with the highest reliability from approximations of cumulative sums of respective widths. An analysis of data for 157 sets of neutron widths for 0 {<=} l {<=} 3 and for 56 sets of total radiative widths has been performed to date. The basic result of this analysis is the following: both for neutron and for total radiative widths, the experimental set of resonance width can be represented with a rather high probability in the form of a superposition of k {<=} 4 types differing in mean amplitude parameters.

  8. Manganese-Enhanced Magnetic Resonance Imaging of Traumatic Brain Injury

    PubMed Central

    Talley Watts, Lora; Shen, Qiang; Deng, Shengwen; Chemello, Jonathan

    2015-01-01

    Abstract Calcium dysfunction is involved in secondary traumatic brain injury (TBI). Manganese-enhanced MRI (MEMRI), in which the manganese ion acts as a calcium analog and a MRI contrast agent, was used to study rats subjected to a controlled cortical impact. Comparisons were made with conventional T2 MRI, sensorimotor behavior, and immunohistology. The major findings were: (1) Low-dose manganese (29 mg/kg) yielded excellent contrast with no negative effects on behavior scores relative to vehicle; (2) T1-weighted MEMRI was hyperintense in the impact area at 1–3 h, hypointense on day 2, and markedly hypointense with a hyperintense area surrounding the core on days 7 and/or 14, in contrast to the vehicle group, which did not show a biphasic profile; (3) in the hyperacute phase, the area of hyperintense T1-weighted MEMRI was larger than that of T2 MRI; (4) glial fibrillary acidic protein staining revealed that the MEMRI signal void in the impact core and the hyperintense area surrounding the core on day 7 and/or 14 corresponded to tissue cavitation and reactive gliosis, respectively; (5) T2 MRI showed little contrast in the impact core at 2 h, hyperintense on day 2 (indicative of vasogenic edema), hyperintense in some animals but pseudonormalized in others on day 7 and/or 14; (6) behavioral deficit peaked on day 2. We concluded that MEMRI detected early excitotoxic injury in the hyperacute phase, preceding vasogenic edema. In the subacute phase, MEMRI detected contrast consistent with tissue cavitation and reactive gliosis. MEMRI offers novel contrasts of biological processes that complement conventional MRI in TBI. PMID:25531419

  9. /sup 187/Os + n resonance parameters in the interval 27-500 eV neutron energies

    SciTech Connect

    Winters, R.R.; Carlton, R.F.; Harvey, J.A.; Hill, N.W.

    1982-01-01

    The neutron total cross section for /sup 187/Os, in the energy range, 27 eV to 500 eV, has been measured at the ORELA facility by the neutron time-of-flight technique, utilizing a 2.0 gm osmium sample (n = 0.008401 Os-nuclei/barn) enriched to 70.38% /sup 187/Os. Measurements were performed at a 80 m flight station with an energy resolution, ..delta..E/E, of 0.1% using a /sup 6/Li glass scintillator. Resolved resonances have been analyzed by a Reich-Moore multilevel code (SAMMY) to obtain parameters for 85 resonances up to 500 eV. Preliminary determinations of the level spacing (5 eV) and s-wave strength function (3.9 x 10/sup -4/) for /sup 187/Os are in agreement with recent analyses of the osmium isotopes, made in connection with the use of the Re/Os chronometer for estimating the duration of stellar nucleosynthesis.

  10. Contrast enhanced-magnetic resonance imaging as a surrogate to map verteporfin delivery in photodynamic therapy

    NASA Astrophysics Data System (ADS)

    Samkoe, Kimberley S.; Bryant, Amber; Gunn, Jason R.; Pereira, Stephen P.; Hasan, Tayyaba; Pogue, Brian W.

    2013-12-01

    The use of in vivo contrast-enhanced magnetic resonance (MR) imaging as a surrogate for photosensitizer (verteporfin) dosimetry in photodynamic therapy of pancreas cancer is demonstrated by correlating MR contrast uptake to ex vivo fluorescence images on excised tissue. An orthotopic pancreatic xenograft mouse model was used for the study. A strong correlation (r=0.57) was found for bulk intensity measurements of T1-weighted gadolinium enhancement and verteporfin fluorescence in the tumor region of interest. The use of contrast-enhanced MR imaging shows promise as a method for treatment planning and photosensitizer dosimetry in human photodynamic therapy (PDT) of pancreas cancer.

  11. Power enhancement of burst-mode UV pulses using a doubly-resonant optical cavity

    DOE PAGESBeta

    Rahkman, Abdurahim; Notcutt, Mark; Liu, Yun

    2015-11-24

    We report a doubly-resonant enhancement cavity (DREC) that can realize a simultaneous enhancement of two incoming laser beams at different wavelengths and different temporal structures. The double-resonance condition is theoretically analyzed and different DREC locking methods are experimentally investigated. Simultaneous locking of a Fabry-Perot cavity to both an infrared (IR, 1064 nm) and its frequency tripled ultraviolet (UV, 355 nm) pulses has been demonstrated by controlling the frequency difference between the two beams with a fiber optic frequency shifter. The DREC technique opens a new paradigm in the applications of optical cavities to power enhancement of burst-mode lasers with arbitrarymore » macropulse width and repetition rate.« less

  12. Efficiency enhancement of coupled-cavity TWT's through cavity resonance tapering

    NASA Technical Reports Server (NTRS)

    Connolly, D. J.

    1979-01-01

    The paper examines efficiency enhancement of coupled-cavity traveling-wave tube (TWT) through cavity resonance tapering. Beam-wave resynchronization through circuit velocity reduction is used for TWT efficiency enhancement, with circuit velocity reduction in coupled cavity TWT's accomplished through period tapering. However, the amount of the latter is limited by the stability considerations, so that beyond a critical value of velocity reduction, the tube may be subject to zero drive oscillations originating in the velocity taper region. The coupled-cavity resonance tapering allows the velocity reduction to continue beyond the limit of stable period tapering, and it is accomplished by a gradual reduction in the cavity resonance frequency, with the period and the circuit bandwidth unchanged. The advantages of cavity resonance tapering vs period tapering are discussed, and test data are presented with the results of large-signal computer calculations. It is shown that cavity resonance tapering can produce efficiencies as period tapering without incurring the same risk of lower band-edge oscillations.

  13. Engineered absorption enhancement and induced transparency in coupled molecular and plasmonic resonator systems.

    PubMed

    Adato, Ronen; Artar, Alp; Erramilli, Shyamsunder; Altug, Hatice

    2013-06-12

    Coupled plasmonic resonators have become the subject of significant research interest in recent years as they provide a route to dramatically enhanced light-matter interactions. Often, the design of these coupled mode systems draws intuition and inspiration from analogies to atomic and molecular physics systems. In particular, they have been shown to mimic quantum interference effects, such as electromagnetically induced transparency (EIT) and Fano resonances. This analogy also been used to describe the surface-enhanced absorption effect where a plasmonic resonance is coupled to a weak molecular resonance. These important phenomena are typically described using simple driven harmonic (or linear) oscillators (i.e., mass-on-a-spring) coupled to each other. In this work, we demonstrate the importance of an essential interdependence between the rate at which the system can be driven by an external field and its damping rate through radiative loss. This link is required in systems exhibiting time-reversal symmetry and energy conservation. Not only does it ensure an accurate and physically consistent description of resonant systems but leads directly to interesting new effects. Significantly, we demonstrate this dependence to predict a transition between EIT and electromagnetically induced absorption that is solely a function of the ratio of the radiative to intrinsic loss rates in coupled resonator systems. Leveraging the temporal coupled mode theory, we introduce a unique and intuitive picture that accurately describes these effects in coupled plasmonic/molecular and fully plasmonic systems. We demonstrate our approach's key features and advantages analytically as well as experimentally through surface-enhanced absorption spectroscopy and plasmonic metamaterial applications. PMID:23647070

  14. Resonance Raman enhancement optimization in the visible range by selecting different excitation wavelengths

    NASA Astrophysics Data System (ADS)

    Wang, Zhong; Li, Yuee

    2015-09-01

    Resonance enhancement of Raman spectroscopy (RS) has been used to significantly improve the sensitivity and selectivity of detection for specific components in complicated environments. Resonance RS gives more insight into the biochemical structure and reactivity. In this field, selecting a proper excitation wavelength to achieve optimal resonance enhancement is vital for the study of an individual chemical/biological ingredient with a particular absorption characteristic. Raman spectra of three azo derivatives with absorption spectra in the visible range are studied under the same experimental conditions at 488, 532, and 633 nm excitations. Universal laws in the visible range have been concluded by analyzing resonance Raman (RR) spectra of samples. The long wavelength edge of the absorption spectrum is a better choice for intense enhancement and the integrity of a Raman signal. The obtained results are valuable for applying RR for the selective detection of biochemical constituents whose electronic transitions take place at energies corresponding to the visible spectra, which is much friendlier to biologial samples compared to ultraviolet.

  15. Combined dielectric and plasmon resonance for giant enhancement of Raman scattering

    NASA Astrophysics Data System (ADS)

    Kukushkin, V. I.; Grishina, Ya. V.; Egorov, S. V.; Solov'ev, V. V.; Kukushkin, I. V.

    2016-04-01

    Combined dielectric/metal resonators for colossal enhancement of inelastic light scattering are developed and their properties are investigated. It is shown that a record enhancement factor of 2 × 108 can be obtained using these structures. The dielectric resonators are fabricated on Si/SiO2 substrates where periodic arrays of square 10- to 200-nm-high dielectric pillars are produced via electron-beam lithography and plasma etching. The lateral size a of the pillars varies between 50 and 1500 nm, and their period in the array is 2 a. To make a combined dielectric/metal resonator, a nanostructured layer of silver is deposited onto the fabricated periodic dielectric structure by thermal evaporation. It is established that, for a fixed height of the dielectric pillars, the Raman scattering enhancement factor experiences pronounced oscillations as a function of the period (and size) of the pillars. It is shown that these oscillations are determined by the modes of the dielectric resonator and governed by the relation between the excitation laser wavelength and the planar size of the dielectric pillars.

  16. Single-molecular surface-enhanced resonance Raman scattering as a quantitative probe of local electromagnetic field: The case of strong coupling between plasmonic and excitonic resonance

    NASA Astrophysics Data System (ADS)

    Itoh, Tamitake; Yamamoto, Yuko S.; Tamaru, Hiroharu; Biju, Vasudevanpillai; Wakida, Shin-ichi; Ozaki, Yukihiro

    2014-05-01

    We investigate electromagnetic coupling between plasmonic and molecular electronic resonances using single-molecular surface-enhanced resonance Raman scattering (SERRS) from single silver nanoparticle dimers. When dimers exhibit SERRS activity, their elastic light scattering spectra show two lines, which are temporally closing toward each other. The higher energy line eventually disappears at the time of SERRS quenching. A coupled-oscillator model composed of plasmonic and molecular electronic resonances consistently reproduces the above interesting results by decreasing coupling energy, indicating that SERRS can be a quantitative probe for strong coupling between the two resonances.

  17. Enhanced sensitivity of surface plasmon resonance phase-interrogation biosensor by using oblique deposited silver nanorods

    NASA Astrophysics Data System (ADS)

    Chung, Hung-Yi; Chen, Chih-Chia; Wu, Pin Chieh; Tseng, Ming Lun; Lin, Wen-Chi; Chen, Chih-Wei; Chiang, Hai-Pang

    2014-09-01

    Sensitivity of surface plasmon resonance phase-interrogation biosensor is demonstrated to be enhanced by oblique deposited silver nanorods. Silver nanorods are thermally deposited on silver nanothin film by oblique angle deposition (OAD). The length of the nanorods can be tuned by controlling the deposition parameters of thermal deposition. By measuring the phase difference between the p and s waves of surface plasmon resonance heterodyne interferometer with different wavelength of incident light, we have demonstrated that maximum sensitivity of glucose detection down to 7.1 × 10-8 refractive index units could be achieved with optimal deposition parameters of silver nanorods.

  18. A resonant scanning dipole-antenna probe for enhanced nanoscale imaging.

    PubMed

    Neumann, Lars; van 't Oever, Jorick; van Hulst, Niek F

    2013-11-13

    We present a scanning antenna probe that provides 35 nm optical hotspots with a 16-fold excitation enhancement. A resonant optical antenna, tuned to operation in the visible, is carved into the aluminum-coated scanning probe. The antenna resonances, field localization, excitation, and polarization response are probed in the near-field by scanning over single fluorescent nanobeads. At the same time, the distance-dependent coupling of the emission to the antenna mode is mapped. Good agreement with theory is obtained. The presented scanning antenna approach is useful for both nanoscale plasmonic mode imaging and (bio)imaging. PMID:24124987

  19. Enhanced sensitivity of surface plasmon resonance phase-interrogation biosensor by using oblique deposited silver nanorods.

    PubMed

    Chung, Hung-Yi; Chen, Chih-Chia; Wu, Pin Chieh; Tseng, Ming Lun; Lin, Wen-Chi; Chen, Chih-Wei; Chiang, Hai-Pang

    2014-01-01

    Sensitivity of surface plasmon resonance phase-interrogation biosensor is demonstrated to be enhanced by oblique deposited silver nanorods. Silver nanorods are thermally deposited on silver nanothin film by oblique angle deposition (OAD). The length of the nanorods can be tuned by controlling the deposition parameters of thermal deposition. By measuring the phase difference between the p and s waves of surface plasmon resonance heterodyne interferometer with different wavelength of incident light, we have demonstrated that maximum sensitivity of glucose detection down to 7.1 × 10(-8) refractive index units could be achieved with optimal deposition parameters of silver nanorods. PMID:25258602

  20. Enhanced electromechanical coupling of a nanomechanical resonator to coupled superconducting cavities

    PubMed Central

    Li, Peng-Bo; Li, Hong-Rong; Li, Fu-Li

    2016-01-01

    We investigate the electromechanical coupling between a nanomechanical resonator and two parametrically coupled superconducting coplanar waveguide cavities that are driven by a two-mode squeezed microwave source. We show that, with the selective coupling of the resonator to the cavity Bogoliubov modes, the radiation-pressure type coupling can be greatly enhanced by several orders of magnitude, enabling the single photon strong coupling to be reached. This allows the investigation of a number of interesting phenomena such as photon blockade effects and the generation of nonclassical quantum states with electromechanical systems. PMID:26753744

  1. Quality-Factor Enhancement of Nanoelectromechanical Systems by Capacitive Driving Beyond Resonance

    NASA Astrophysics Data System (ADS)

    Barois, T.; Perisanu, S.; Poncharal, P.; Vincent, P.; Purcell, S. T.; Ayari, A.

    2016-07-01

    Nanoelectromechanical systems are considered as ultrasensitive devices for mass and force detection. Capacitive actuation is widely used in these devices but is known to degrade the quality factor of the resonator due to dc electrostatic damping. We report the enhancement of the quality factor of SiC vibrating nanowires detected nano-optomechanically and electrically by applying an ac capacitive driving at a frequency above both the resonance frequency and the electrical cutoff frequency. Self-oscillations are demonstrated for optimal conditions. We develop an analytical model of the phenomenon and show that it can lead to an improvement of the force sensitivity.

  2. Cavity Self-Stabilization and Enhancement of Laser Gyroscopes by (Coupled) Optical Resonators

    NASA Technical Reports Server (NTRS)

    Smith, David D.

    2006-01-01

    We analyze the effect of a highly dispersive element placed inside a modulated optical cavity on the frequency and amplitude of the modulation to determine the conditions for cavity self-stabilization and enhanced gyroscopic sensitivity. Hence, we model cavity rotation or instability by an arbitrary AM/FM modulation, and the dispersive element as a phase and amplitude filter. We find that anomalous dispersion may be used to self-stabilize a laser cavity, provided the magnitude of the group index of refraction is smaller than the phase index of refraction in the cavity. The optimal stabilization is found to occur when the group index is zero. Group indices with magnitudes larger than the phase index (both normal and anomalous dispersion) are found to enhance the sensitivity of a laser gyroscope to rotation. Furthermore, our results indicate that atomic media, even coherent superpositions in multilevel atoms, are not useful for these applications, because the amplitude and phase filters work against one another, i.e., decreasing the modulation frequency increases its amplitude and vice versa, with one exception: negative group indices whose magnitudes are larger than the phase index result in negative, but enhanced, beat frequencies. On the other hand, for optical resonators the dispersion reversal associated with critical coupling enables the amplitude and phase filters to work together under a greater variety of circumstances than for atomic media. We find that for single over-coupled resonators, or in the case of under-coupled coupled-resonator-induced absorption, the absorption and normal dispersion on-resonance increase the contrast and frequency of the beat-note, respectively, resulting in a substantial enhancement of the gyroscopic response. Moreover, for cavity self-stabilization, we propose the use of a variety of coupled-resonator induced transparency that is accompanied by anomalous dispersion.

  3. Water distribution in a sorption enhanced methanation reactor by time resolved neutron imaging.

    PubMed

    Borgschulte, A; Delmelle, R; Duarte, R B; Heel, A; Boillat, P; Lehmann, E

    2016-06-29

    Water adsorption enhanced catalysis has been recently shown to greatly increase the conversion yield of CO2 methanation. However, the joint catalysis and adsorption process requires new reactor concepts. We measured the spatial water distribution in a model fixed bed reactor using time resolved neutron imaging. Due to the high neutron attenuation coefficient of hydrogen, the absorbed water in the sorption catalyst gives a high contrast allowing us to follow its formation and map its distribution. At the same time, the product gas was analysed by FTIR-gas analysis. The measurements provided crucial insights into the future design of sorption reactors: during the sorption enhanced reaction, a reaction front runs through the reactor. Once the extension of the reaction front reaches the exhaust, the conversion rate of sorption enhanced methanation decreases. The existence of a reaction front running through the reactor is prerequisite for a high conversion rate. We give a simple model of the experimental results, in particular the conditions, under which a reaction front is established. In particular the latter effect must be taken into account for the dimensions of a large scale reactor. PMID:26791100

  4. Plasma focus sources: Supplement to the neutron resonance radiography workshop proceedings

    SciTech Connect

    Nardi, V.; Brzosko, J.

    1989-01-01

    Since their discovery, plasma focus discharges have been recognized as very intense pulsed sources of deuterium-deuterium (D-D) or deuterium-tritium (D-T) fusion-reaction neutrons, with outstanding capabilities. Specifically, the total neutron emission/shot, YN, and the rate of neutron emission, Y/sub n/, of an optimized plasma focus (PF) are higher than the corresponding quantities observed in any other type of pinched discharge at the same level of powering energy W/sub 0/. Recent developments have led to the concept and experimental demonstration of an Advanced Plasma Focus System (APF) that consists of a Mather-geometry plasma focus in which field distortion elements (FDEs) are inserted in the inter-electrode gap for increasing the neutron yield/shot, Y/sub n/. The FDE-induced redistribution of the plasma current increases Y/sub n/ by a factor approx. =5-10 above the value obtained without FDEs under otherwise identical conditions of operation of the plasma focus. For example, an APF that is fed by a fast capacitor bank with an energy, W/sub 0/ = 6kJ, and voltage, V/sub 0/ = 16.5 kV provides Y/sub n/ /congruent/ 4 /times/ 10/sup 9/ D-D neutrons/shot (pure D/sub 2/ filling) and Y/sub n/ = 4 /times/ 10/sup 11/ D-T neutrons/shot (filling is 50% deuterium and 50% tritium). The FDE-induced increase of Y/sub n/ for fixed values of (W/sub 0/, V/sub 0/), the observed scaling law Y/sub n/ /proportional to/ W/sub 0//sup 2/ for optimized plasma focus systems, and our experience with neutron scattering in bulk objects lead us to the conclusion that we can use an APF as a source of high-intensity neutron pulses (10/sup 14/ n/pulse) in the field off neutron radiography (surface and bulk) with a nanosecond or millisecond time resolution.

  5. Nonlinear standing wave excitation by series resonance-enhanced harmonics in low pressure capacitive discharges

    NASA Astrophysics Data System (ADS)

    Lieberman, M. A.; Lichtenberg, A. J.; Kawamura, E.; Marakhtanov, A. M.

    2015-10-01

    It is well-known that standing waves having radially center-high rf voltage profiles exist in high frequency capacitive discharges. It is also known that in radially uniform discharges, the capacitive sheath nonlinearities excite strong nonlinear series resonance harmonics that enhance the electron power deposition. In this work, we consider the coupling of the series resonance-enhanced harmonics to the standing waves. A one-dimensional, asymmetric radial transmission line model is developed incorporating the wave and nonlinear sheath physics and a self-consistent dc potential, for both conducting and insulating electrode surfaces. The resulting coupled pde equation set is solved numerically to determine the discharge voltages and currents. A 10 mTorr argon plasma is chosen with density 2× {{10}16} m-3, gap width 2 cm and conducting electrode radius 15 cm, driven by a 500 V rf source with resistance 0.5 Ω . We examine a set of frequencies from near 30 MHz up to frequencies more than three times as high. For most frequencies, no harmonics correspond exactly with the series or spatial resonances, which is the generic situation. Nevertheless, nearby resonances lead to a significantly enhanced ratio of the electron power per unit area on axis, compared to the average. Nearly similar results are found for insulating electrodes. Strong effects are seen for varying source resistance: high (50 Ω ) resistance damps out most of the harmonic activity, while zero source resistance leads to a non-steady discharge with bias voltage relaxation oscillations. Stronger harmonic effects are seen for an increased radius of 30 cm, as lower harmonics become spatially resonant at lower frequencies. The radial dependence of electron power with frequency showed significant variations, with the central enhancement and sharpness of the spatial resonances depending in a complicated way on the amplitudes of the nearby series resonance current harmonics and the phase relations among

  6. Maximizing the electromagnetic and chemical resonances of surface-enhanced Raman scattering for nucleic acids.

    PubMed

    Freeman, Lindsay M; Pang, Lin; Fainman, Yeshaiahu

    2014-08-26

    Although surface-enhanced Raman spectroscopy (SERS) has previously been performed with nucleic acids, the measured intensities for each nucleic acid have varied significantly depending on the SERS substrate and excitation wavelength. We have demonstrated that the charge-transfer (CT) mechanism, also known as the chemical enhancement of SERS, is responsible for the discrepancies previously reported in literature. The electronic states of cytosine and guanine attached to silver atoms are computationally calculated and experimentally measured to be in the visible range, which leads to a resonance Raman effect at the corresponding maximum wavelengths. The resulting SERS measurements are in good agreement with the simulated values, in which cytosine-silver shows stronger enhancement at 532 nm and guanine-silver shows stronger enhancement at 785 nm. An atomic layer of aluminum oxide is deposited on substrates to prevent charge-transfer, and corresponding measurements show weaker Raman signals caused by the suppression of the chemical resonance. These findings suggest the optimal SERS signal can be achieved by tuning the excitation wavelength to match both the electromagnetic and chemical resonances, paving the way for future single molecule detection of nucleic acids other than adenine. PMID:25065837

  7. Enhancement of the epithermal neutron beam at the Brookhaven Medical Research Reactor

    SciTech Connect

    Liu, Hungyuan B.; Brugger, R.M.; Rorer, D.C.

    1992-12-31

    Improvements for the Brookhaven Medical Research Reactor (BMRR) epithermal neutron beam have been evaluated by MCNP calculations and measurements. Different dosimetric measurements have been made after one fuel element was in place of the graphite stringer in the core. Measurements show an 18% increase of beam intensity without reducing the beam quality. These results are consistent with the predictions of an MCNP calculation. Major changes to enhance the beam include rearranging the fuel elements in the core, placing aluminum pellets in the moderator tank C, redesigning the moderator assembly, replacing the outer bismuth by lead plus 0.05% atomic number density of {sup 6}Li, and modifying the irradiation port to accommodate an air indentation. The MCNP calculated values for the present and new designs were compared to demonstrate the improvements. The results show that the epithermal flux can be increased by 80% at the irradiation port. The neutron dose per epithermal neutron can be reduced by 30%. The beam directionality can be improved by 7%.

  8. Enhancement of the epithermal neutron beam at the Brookhaven Medical Research Reactor

    SciTech Connect

    Liu, Hungyuan B.; Brugger, R.M.; Rorer, D.C.

    1992-01-01

    Improvements for the Brookhaven Medical Research Reactor (BMRR) epithermal neutron beam have been evaluated by MCNP calculations and measurements. Different dosimetric measurements have been made after one fuel element was in place of the graphite stringer in the core. Measurements show an 18% increase of beam intensity without reducing the beam quality. These results are consistent with the predictions of an MCNP calculation. Major changes to enhance the beam include rearranging the fuel elements in the core, placing aluminum pellets in the moderator tank C, redesigning the moderator assembly, replacing the outer bismuth by lead plus 0.05% atomic number density of [sup 6]Li, and modifying the irradiation port to accommodate an air indentation. The MCNP calculated values for the present and new designs were compared to demonstrate the improvements. The results show that the epithermal flux can be increased by 80% at the irradiation port. The neutron dose per epithermal neutron can be reduced by 30%. The beam directionality can be improved by 7%.

  9. Neutron total and capture cross section measurements and resonance parameter analysis of tungsten from 0.01 eV to 200 eV

    SciTech Connect

    Werner, C.J.; Block, R.C.; Slovacek, R.E.; Overberg, M.E.; Moretti, B.E.; Burke, J.A.; Leinweber, G.; Drindak, N.J.

    1998-06-15

    Natural tungsten metal was measured using neutron time-of-flight spectroscopy at the Rensselaer Polytechnic Institute (RPI) Gaerttner Laboratory linear accelerator to determine the tungsten resonance parameters. Three separate measurements were performed: transmission, capture, and self-indication. Previous measurements did not employ all three experiment types and used less sophisticated methods. The current work improves on the published tungsten data base and reduces resonance parameter uncertainties.

  10. Gd-EOB-DTPA-enhanced magnetic resonance imaging for bile duct intraductal papillary mucinous neoplasms

    PubMed Central

    Ying, Shi-Hong; Teng, Xiao-Dong; Wang, Zhao-Ming; Wang, Qi-Dong; Zhao, Yi-Lei; Chen, Feng; Xiao, Wen-Bo

    2015-01-01

    AIM: To investigate gadolinium-ethoxybenzyl-diethylenetriamine-pentaacetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance imaging (MRI) of intraductal papillary mucinous neoplasms of the bile duct (IPMN-B). METHODS: The imaging findings of five cases of IPMN-B which were pathologically confirmed at our hospital between March 2012 and May 2013 were retrospectively analyzed. Three of these cases were diagnosed by duodenal endoscopy and biopsy pathology, and two cases were diagnosed by surgical pathology. All five patients underwent enhanced and non-enhanced computed tomography (CT), magnetic resonance cholangiopancreatography, and Gd-EOB-DTPA-enhanced MRI; one case underwent both Gd-EOB-DTPA-enhanced MRI and positron emission tomography-CT. The clinical data and imaging results for these cases were compared and are presented. RESULTS: Conventional imaging showed diffuse dilatation of bile ducts and multiple intraductal polypoid and papillary neoplasms or serrated changes along the bile ducts. In two cases, Gd-EOB-DTPA-enhanced MRI revealed dilated biliary ducts and intraductal tumors, as well as filling defects caused by mucin in the dilated bile ducts in the hepatobiliary phase. Gd-EOB-DTPA-enhanced MRI in one case clearly showed a low-signal tumor in the hepatobiliary phase, similar to what was seen by positron emission tomography-CT. In two patients, routine inspection was unable to discern whether the lesions were inflammation or tumors. However, Gd-EOB-DTPA-enhanced MRI revealed a pattern of gradual enhancement during the hepatobiliary phase, and the signal intensity of the lesions was lower than the surrounding liver parenchyma, suggesting tissue inflammation in both cases, which were confirmed by surgical pathology. CONCLUSION: Gd-EOB-DTPA-enhanced MRI reveals the intraductal mucin component of IPMN-B in some cases and the extent of tumor infiltration beyond the bile ducts in invasive cases. PMID:26167082

  11. Evaluated 182,183,184,186W Neutron Cross Sections and Covariances in the Resolved Resonance Region

    SciTech Connect

    Pigni, Marco T; Leal, Luiz C

    2015-01-01

    Oak Ridge National Laboratory (ORNL) has recently completed the resonance parameter evaluation of four tungsten isotopes, i.e., 182,183,184,186W, in the neutron energy range of thermal up to several keV. This nuclear data work was performed with support from the US Nuclear Criticality Safety Program (NCSP) in an effort to provide improved tungsten cross section and covariance data for criticality safety analyses. The evaluation methodology uses the Reich-Moore approximation of the R-matrix formalism of the code SAMMY to fit high-resolution measurements performed in 2010 and 2012 at the Geel linear accelerator facility (GELINA), as well as other experimental data sets on natural tungsten available in the EXFOR library. In the analyzed energy range, this work nearly doubles the resolved resonance region (RRR) present in the latest US nuclear data library ENDF/B-VII.1. In view of the interest in tungsten for distinct types of nuclear applications and the relatively homogeneous distribution of the isotopic tungsten—namely, 182W(26.5%), 183W(14.31%), 184W(30.64%), and 186W(28.43%) - the completion of these four evaluations represents a significant contribution to the improvement of the ENDF library. This paper presents an overview of the evaluated resonance parameters and related covariances for total and capture cross sections on the four tungsten isotopes.

  12. Neutron resonance parameters of /sup 79/Br and /sup 81/Br up to 15 keV

    SciTech Connect

    Ohkubo, M.; Kawarasaki, Y.; Mizumoto, M.

    1980-09-01

    Resonance parameters of separated isotopes of bromine were measured using TOF spectrometer of Japan Atomic Energy Research Institute linear accelerator. Transmission and capture measurements were made with /sup 6/Li-glass and Moxon-Rae detectors, on separated isotopes (approx. 98%) of /sup 79/Br and /sup 81/Br. Resonance analyses were made on transmission data with an area analysis code, and on capture data with a Monte-Carlo program CAFIT. For /sup 79/Br gGAMMA/sup 0//sub n/ values for 156 levels below 10 keV are obtained, and for /sup 81/Br 100 levels below 15 keV. Strength functions are obtained: for /sup 79/Br S/sub O/ = (1.27 +- 0.14) x10/sup -4/ below 10 keV, and for /sup 81/Br S/sub O/ = (0.86 +- 0.14)10/sup -4/ below 15 keV. Intermediate structures are observed in the resonances of /sup 81/Br showing clusters of levels at 1.2, 10, 11.5, and 14 keV, where the sum of gGAMMA/sup 0//sub n/ vs. neutron energy shows steep rises.

  13. Quantitative evaluation of proteins with bicinchoninic acid (BCA): resonance Raman and surface-enhanced resonance Raman scattering-based methods.

    PubMed

    Chen, Lei; Yu, Zhi; Lee, Youngju; Wang, Xu; Zhao, Bing; Jung, Young Mee

    2012-12-21

    A rapid and highly sensitive bicinchoninic acid (BCA) reagent-based protein quantitation tool was developed using competitive resonance Raman (RR) and surface-enhanced resonance Raman scattering (SERRS) methods. A chelation reaction between BCA and Cu(+), which is reduced by protein in an alkaline environment, is exploited to create a BCA-Cu(+) complex that has strong RR and SERRS activities. Using these methods, protein concentrations in solutions can be quantitatively measured at concentrations as low as 50 μg mL(-1) and 10 pg mL(-1). There are many advantages of using RR and SERRS-based assays. These assays exhibit a much wider linear concentration range and provide an additional one (RR method) to four (SERRS method) orders of magnitude increase in detection limits relative to UV-based methods. Protein-to-protein variation is determined using a reference to a standard curve at concentrations of BSA that exhibits excellent recoveries. These novel methods are extremely accurate in detecting total protein concentrations in solution. This improvement in protein detection sensitivity could yield advances in the biological sciences and medical diagnostic field and extend the applications of reagent-based protein assay techniques. PMID:23099478

  14. Lorentz force in water: evidence that hydronium cyclotron resonance enhances polymorphism.

    PubMed

    D'Emilia, E; Giuliani, L; Lisi, A; Ledda, M; Grimaldi, S; Montagnier, L; Liboff, A R

    2015-01-01

    There is an ongoing question regarding the structure forming capabilities of water at ambient temperatures. To probe for different structures, we studied effects in pure water following magnetic field exposures corresponding to the ion cyclotron resonance of H3O(+). Included were measurements of conductivity and pH. We find that under ion cyclotron resonance (ICR) stimulation, water undergoes a transition to a form that is hydroxonium-like, with the subsequent emission of a transient 48.5 Hz magnetic signal, in the absence of any other measurable field. Our results indicate that hydronium resonance stimulation alters the structure of water, enhancing the concentration of EZ-water. These results are not only consistent with Del Giudice's model of electromagnetically coherent domains, but they can also be interpreted to show that these domains exist in quantized spin states. PMID:25020009

  15. Toward an Enhancement of the Photoactivity of Multiphotochromic Dimers Using Plasmon Resonance: A Theoretical Study.

    PubMed

    Fihey, Arnaud; Le Guennic, Boris; Jacquemin, Denis

    2015-08-01

    Building dimers of organic photochromic compounds paves the way to multifunctional switches, but such architectures often undergo partial photoreactivity only. Combining photochromism of molecules and plasmon resonance of gold nanoparticles (NPs) is known to affect the photochromism of monomers, yet the impact on multimers remains unknown. Here we propose a theoretical study of dimers of dithienylethenes by the mean of a hybrid calculation scheme (discrete-interaction model/quantum mechanics). We aim to assess how the optical properties of multiphotochromes are tuned by the influence of the plasmon resonances. We show that, for a typical chemisorption orientation on the NP, the absorption bands responsible for the photochromism are significantly enhanced for both the doubly open and mixed closed-open isomers of the dyad, hinting that plasmon resonance could be used to boost the generally poor photoactivity of dithienylethene dyads. PMID:26267018

  16. Analysis of the Ground-Level Enhancements on 14 July 2000 and 13 December 2006 Using Neutron Monitor Data

    NASA Astrophysics Data System (ADS)

    Mishev, A.; Usoskin, I.

    2016-04-01

    On the basis of neutron monitor data, we estimate the energy spectrum, anisotropy axis direction, and pitch-angle distribution of solar energetic particles during two major ground-level enhancements (GLE 59 on 14 July 2000 and GLE 70 on 13 December 2006). For the analysis we used a newly computed neutron monitor yield function. The method consists of several consecutive steps: definition of the asymptotic viewing cones of neutron monitor stations considered for the data analysis by computing the cosmic ray particle propagation in a model magnetosphere with the MAGNETOCOSMICS code, computing the neutron monitor model responses, and deriving the solar energetic particle characteristics on the basis of inverse problem solution. The pitch-angle distribution and rigidity spectrum of high-energy protons are obtained as a function of time in the course of ground-level enhancements. A comparison with previously reported results is performed and reasonable agreement is achieved. A discussion of the obtained results is included.

  17. Parity violation in {sup 232}Th neutron resonances above 250 eV

    SciTech Connect

    Sharapov, E. I.; Bowman, J. D.; Crawford, B. E.; Delheij, P. P. J.; Frankle, C. M.; Iinuma, M.; Knudson, J. N.; Lowie, L. Y.; Lynch, J. E.; Masaike, A.

    2000-02-01

    The analysis of parity nonconservation (PNC) measurements performed on {sup 232}Th by the TRIPLE Collaboration has been extended to include the neutron energy range of 250 to 1900 eV. Below 250 eV all ten statistically significant parity violations have the same sign. However, at higher energies PNC effects of both signs were observed in the transmission of longitudinally polarized neutrons through a thick thorium target. Although the limited experimental energy resolution precluded analysis in terms of the longitudinal asymmetry, parity violations were observed and the cross section differences for positive and negative neutron helicities were obtained. For comparison, a similar analysis was performed on the data below 250 eV, for which longitudinal asymmetries were obtained previously. For energies below 250 eV, the p-wave neutron strength functions for the J=1/2 and J=3/2 states were extracted: S{sub 1/2}{sup 1}=(1.68{+-}0.61)x10{sup -4} and S{sub 3/2}{sup 1}=(0.75{+-}0.18)x10{sup -4}. The data provide constraints on the properties of local doorway states proposed to explain the PNC sign effect in thorium. (c) 2000 The American Physical Society.

  18. Neutron-Absorbing Coatings for Safe Storage of Fissile Materials with Enhanced Shielding & Criticality Safety

    SciTech Connect

    Choi, J; Farmer, J; Lee, C; Fischer, L; Boussoufi, M; Liu, B; Egbert, H

    2007-07-03

    Neutron-absorbing Fe-based amorphous-metal coatings have been developed that are more corrosion resistant than other criticality-control materials, including Al-B{sub 4}C composites, borated stainless steels, and Ni-Cr-Mo-Gd alloys. The presence of relatively high concentration of boron in these coatings not only enhances its neutron-absorption capability, but also enables these coatings to exist in the amorphous state. Exceptional corrosion resistance has been achieved with these Fe-based amorphous-metal alloys through additions of chromium, molybdenum, and tungsten. The addition of rare earth elements such as yttrium has lowered the critical cooling rate of these materials, thereby rendering them more easily processed. Containers used for the storage of nuclear materials, and protected from corrosion through the application of amorphous metal coatings, would have greatly enhanced service lives, and would therefore provide greater long-term safety. Amorphous alloy powders have been successfully produced in multi-ton quantities with gas atomization, and applied to several half-scale spent fuel storage containers and criticality control structures with the high-velocity oxy-fuel (HVOF) thermal spray process. Salt fog testing and neutron radiography of these prototypes indicates that such an approach is viable for the production of large-scale industrial-scale facilities and containers. The use of these durable neutron-absorbing materials to coat stainless steel containers and storage racks, as well as vaults, hot-cell facilities and glove boxes could substantially reduce the risk of criticality in the event of an accident. These materials are particularly attractive for shielding applications since they are fire proof. Additionally, layers of other cold and thermal sprayed materials that include carbon and/or carbides can be used in conjunction with the high-boron amorphous metal coatings for the purpose of moderation. For example, various carbides, including boron

  19. Enhancing ferromagnetic resonance absorption for very thin insulating magnetic films with spin plasmonics

    SciTech Connect

    Chui, S. T.

    2015-05-14

    We consider enhancing the ferromagnetic resonance (FMR) absorption of very thin insulating magnetic films by placing it on top of a dielectric. We find that the signal is enhanced by at least an order of magnitude due to a new nonreciprocal interface resonance that is a mixture of the magnetic surface plasmon mode and a wave guide mode. This resonance occurs over a wide range of thicknesses of the dielectric that is still much less than the wavelength and is made possible by the negative magnetic susceptibility of the magnetic layer. The line width of absorption is reduced by an order of magnitude less than the Gilbert damping parameter. At some frequency, the group velocity of this resonance is negative. Experimentally, very thin yttrium iron garnet (YIG) films are grown on a Gadolinium Gallium Garnet (GGG) substrate which can be considered the dielectric. Our model applies to experiments performed in the YIG/GGG system. Indeed, our picture resolves the disagreement on the magnitude of the spin diffusion lengths obtained with the FMR and the Brillouin scattering techniques. It also provides for a way to make new adaptive thin film miniaturized photonic nonreciprocal devices with low loss.

  20. Surface-enhanced resonance Raman spectroscopy of iron-dopamine complexes

    NASA Astrophysics Data System (ADS)

    Kowalchyk, Will K.; Davis, Kevin L.; Morris, Michael D.

    1995-01-01

    Surface-enhanced resonance Raman spectroscopy (SERRS) at silver colloids is used to detect the catecholamines, 3-hydroxytyramine (dopamine) and 3,4-dihydroxyphenylacetic acid (DOPAC), in a modified Ringer's solution. Catecholamines form very strong complexes with iron(III) in solution ( Kf > 10 40) and exhibit a broad ligand-to-metal charge-transfer (LMCT) absorption in the visible (˜ 500 nm). Resonance enhancement is achieved by excitation at 532 nm from a frequency doubled Nd:YAG laser with high quality spectra attainable in 1 s. Maximum SERRS signal is observed when basic buffer is added to a dopamine sample containing 50 × 10 -6 M ferric ion. Dopamine concentrations in the nanomolar (resting level) range are obtained using this technique.

  1. Resonance-enhanced collective effect in a triangle arrangement of Rydberg atoms with anisotropic interactions

    NASA Astrophysics Data System (ADS)

    Qian, Jing

    2016-08-01

    We investigate the collective excitation effect in a scheme where three identical Rydberg atoms are arranged in an equilateral triangular lattice. By using a static electric field polarizing the atomic dipoles, the dipole-dipole interactions between two Rydberg atoms are essentially anisotropic and can even disappear in the several special resonance cases. For that fact, we observe collectively enhanced excitation probability of single Rydberg atom in resonant areas in the case of strong blockade, and that of double or triple Rydberg atoms in the case of partial blockade. To give more evidences for this collective excitation enhancement, we study the two-body quantum correlation between three Rydberg atoms, as well as the dependence of the blockade radius on the length of triangle sides, which present a good agreement with the excitation properties.

  2. Enhanced light emission from carbon nanotubes integrated in silicon micro-resonator

    NASA Astrophysics Data System (ADS)

    Noury, Adrien; Le Roux, Xavier; Vivien, Laurent; Izard, Nicolas

    2015-08-01

    Single-walled carbon nanotubes are considered a fascinating nanomaterial for photonic applications and are especially promising for efficient light emitters in the telecommunication wavelength range. Furthermore, their hybrid integration with silicon photonic structures makes them an ideal platform to explore their intrinsic properties. Here we report on the strong photoluminescence enhancement from carbon nanotubes integrated in silicon ring resonator circuits under two pumping configurations: surface-illuminated pumping at 735 nm and collinear pumping at 1.26 μ {{m}}. Extremely efficient rejection of the non-resonant photoluminescence was obtained. In the collinear approach, an emission efficiency enhancement by a factor of 26 has been demonstrated in comparison with the classical pumping scheme. This demonstration paves the way for the development of integrated light sources in silicon based on carbon nanotubes.

  3. Double resonant enhancement in the neutrinoless double-electron capture of 190Pt

    NASA Astrophysics Data System (ADS)

    Eibach, M.; Bollen, G.; Gulyuz, K.; Izzo, C.; Redshaw, M.; Ringle, R.; Sandler, R.; Valverde, A. A.

    2016-07-01

    Background: The observation of neutrinoless double-β transitions would indicate physics beyond the standard model as the lepton number conservation is violated. For a complete degeneracy in the energy of the initial and final states, the neutrinoless double-electron capture is resonantly enhanced. This shortens the half-life to similar orders of magnitude as the neutrinoless double-β decay and expands the set of nuclei for the search of neutrinoless double-β transitions as the observation of either process would be equally likely. Purpose: To clearly identify transitions that are resonantly enhanced, among other parameters the total energy of the decay, Qɛ ɛ, needs to be measured very precisely. Of the 12 initially identified candidates, the last remaining decay without a precise Qɛ ɛ was 190Pt(0 ν ɛ ɛ )190Os . Method: The Qɛ ɛ value was determined with the Penning trap mass spectrometer LEBIT by measuring the ratio of the cyclotron frequencies of +190Pt and +190Os in a 9.4-T superconducting magnet. Result: The Qɛ ɛ value was determined to be 1401.57(47) keV with an uncertainty reduction of an order of magnitude compared to its previously known value. The absolute value is shifted by 17.17(623) keV relative to the previously accepted one. Furthermore, the mass value of 190Pt was found to be shifted by more than three standard deviations. In addition we improved the mass values for Os,190186 and 194Pt. Conclusion: Transitions to the two nuclear excited states of 190Os with 1326.9(5) and 1387.00(2) keV energy were identified to be resonantly enhanced within a 1 σ uncertainty. The significantly reduced uncertainty of Qɛ ɛ confirmed the potential for a resonantly enhanced transition.

  4. Surface-irregularity-enhanced subband resonance of semiconductors. I. General theory

    SciTech Connect

    Nee, T.W.

    1984-03-15

    The intersubband resonance absorption enhanced by the insulator-semiconductor interfacial irregularities in a metal-insulator-semiconductor system is investigated theoretically. The line shape of absorption spectrum is calculated microscopically. It is shown that the perpendicular excitation can be effectively generated by electric fields parallel to the surface due to the localized electromagnetic waves scattered by the surface irregularities. The general spectra for both isotropic and anisotropic surface scattering models are calculated and discussed.

  5. Enhancing photonic spin Hall effect via long-range surface plasmon resonance.

    PubMed

    Tan, Xiao-Jie; Zhu, Xiao-Song

    2016-06-01

    We presented the significant enhancement of the photonic spin Hall effect by taking advantage of long-range surface plasmon resonance (LRSPR). The influence of the thicknesses of metal and dielectric layers in the insulator-metal-insulator structure which supports LRSPR was investigated. Under the optimal parameter setup, the largest transverse separation with a 632.8 nm incident Gaussian beam reaches 7.85 μm, which is much larger than previous reported values. PMID:27244393

  6. Resonance enhancement of harmonics in metal plasmas using tunable mid-infrared pulses

    NASA Astrophysics Data System (ADS)

    Ganeev, R. A.; Odžak, S.; Milošević, D. B.; Suzuki, M.; Kuroda, H.

    2016-07-01

    The tuning of odd and even high-order harmonics along the resonances of laser-produced plasmas using an optical parametric amplifier of white-light continuum radiation (1250–1400 nm)and its second harmonic is reported. We demonstrate the enhancement of tunable harmonics in the regions of 27, 38, and 47 nm using tin, antimony, and chromium plasmas and discuss the theoretical model of this phenomenon.

  7. Plasmonic coupled modes in metal-dielectric multilayer structures: Fano resonance and giant field enhancement.

    PubMed

    Sekkat, Zouheir; Hayashi, Shinji; Nesterenko, Dmitry V; Rahmouni, Anouar; Refki, Siham; Ishitobi, Hidekazu; Inouye, Yasushi; Kawata, Satoshi

    2016-09-01

    We provide an overview of Fano resonance and plasmon induced transparency (PIT) as well as on plasmons coupling in planar structures, and we discuss their application in sensing and enhanced spectroscopy. Metal-insulator-metal (MIM) structures, which are known to support symmetric and anti-symmetric surface plasmon polaritons (SPPs) arising from the coupling between two SPPs at the metal-insulator interfaces, exhibit anticrossing behavior of the dispersion relations arising from the coupling of the symmetric SPP and the metal/air SPP. Multilayer structures, formed by a metal film and a high-index dielectric waveguide (WG), separated by a low-index dielectric spacer layer, give narrow resonances of PIT and Fano line shapes. An optimized Fano structure shows a giant field intensity enhancement value of 106 in air at the surface of the high-index dielectric WG. The calculated field enhancement factor and the figure of merit for the sensitivity of the Fano structure in air can be 104 times as large as those of the conventional surface plasmon resonance and WG sensors. PMID:27607617

  8. Capture of a neutron to excited states of a {sup 9}Be nucleus taking into account resonance at 622 keV

    SciTech Connect

    Dubovichenko, S. B.

    2013-10-15

    Radiative capture of a neutron to the ground and excited states of the 9Be nucleus is considered using the potential cluster model with forbidden states and with classification of cluster states by the Young schemes taking into account resonance at 622 keV for thermal and astrophysical energies.

  9. Neutron Resonance Parameters of 238U and the Calculated Cross Sections from the Reich-Moore Analysis of Experimental Data in the Neutron Energy Range from 0 keV to 20 keV

    SciTech Connect

    Derrien, H

    2005-12-05

    The neutron resonance parameters of {sup 238}U were obtained from a SAMMY analysis of high-resolution neutron transmission measurements and high-resolution capture cross section measurements performed at the Oak Ridge Electron Linear Accelerator (ORELA) in the years 1970-1990, and from more recent transmission and capture cross section measurements performed at the Geel Linear Accelerator (GELINA). Compared with previous evaluations, the energy range for this resonance analysis was extended from 10 to 20 keV, taking advantage of the high resolution of the most recent ORELA transmission measurements. The experimental database and the method of analysis are described in this report. The neutron transmissions and the capture cross sections calculated with the resonance parameters are compared with the experimental data. A description is given of the statistical properties of the resonance parameters and of the recommended values of the average parameters. The new evaluation results in a slight decrease of the effective capture resonance integral and improves the prediction of integral thermal benchmarks by 70 pcm to 200 pcm.

  10. Nuclear magnetic resonance study of Gd-based nanoparticles to tag boron compounds in boron neutron capture therapy

    SciTech Connect

    Corti, M.; Bonora, M.; Borsa, F.; Bortolussi, S.; Protti, N.; Santoro, D.; Stella, S.; Altieri, S.; Zonta, C.; Clerici, A. M.; Cansolino, L.; Ferrari, C.; Dionigi, P.; Porta, A.; Zanoni, G.; Vidari, G.

    2011-04-01

    We report the investigation of new organic complexes containing a magnetic moment (Gd-based molecular nanomagnets), which can serve the double purpose of acting as boron neutron capture therapy (BNCT) agents, and at the same time act as contrast agents to detect the molecule in the tissue by a proton magnetic resonance imaging (MRI). We also explore the possibility of monitoring the concentration of the BNCT agent directly via proton and boron NMR relaxation. The absorption of {sup 10}B-enriched molecules inside tumoral liver tissues has been shown by NMR measurements and confirmed by {alpha} spectroscopy. A new molecular Gd-tagged nanomagnet and BNCT agent (GdBPA) has been synthesized and characterized measuring its relaxivity R{sub 1} between 10 kHz and 66 MHz, and its use as a contrast agent in MRI has been demonstrated. The NMR-based evidence of the absorption of GdBPA into living tumoral cells is also shown.

  11. Nuclear magnetic resonance study of Gd-based nanoparticles to tag boron compounds in boron neutron capture therapy

    NASA Astrophysics Data System (ADS)

    Corti, M.; Bonora, M.; Borsa, F.; Bortolussi, S.; Protti, N.; Santoro, D.; Stella, S.; Altieri, S.; Zonta, C.; Clerici, A. M.; Cansolino, L.; Ferrari, C.; Dionigi, P.; Porta, A.; Zanoni, G.; Vidari, G.

    2011-04-01

    We report the investigation of new organic complexes containing a magnetic moment (Gd-based molecular nanomagnets), which can serve the double purpose of acting as boron neutron capture therapy (BNCT) agents, and at the same time act as contrast agents to detect the molecule in the tissue by a proton magnetic resonance imaging (MRI). We also explore the possibility of monitoring the concentration of the BNCT agent directly via proton and boron NMR relaxation. The absorption of 10B-enriched molecules inside tumoral liver tissues has been shown by NMR measurements and confirmed by α spectroscopy. A new molecular Gd-tagged nanomagnet and BNCT agent (GdBPA) has been synthesized and characterized measuring its relaxivity R1 between 10 kHz and 66 MHz, and its use as a contrast agent in MRI has been demonstrated. The NMR-based evidence of the absorption of GdBPA into living tumoral cells is also shown.

  12. Measurement of the thermal neutron capture cross section and the resonance integral of radioactive {sup 182}Hf

    SciTech Connect

    Vockenhuber, C.; Bichler, M.; Wallner, A.; Kutschera, W.; Dillmann, I.; Kaeppeler, F.

    2008-04-15

    The neutron capture cross sections of the radioactive isotope {sup 182}Hf (t{sub 1/2}=8.9x10{sup 6} yr) in the thermal and epithermal energy regions have been measured by activation at the TRIGA Mark-II reactor of the Atomic Institute of the Austrian Universities in Vienna, Austria, and subsequent {gamma}-ray spectroscopy of {sup 183}Hf. High values for the thermal (kT=25 meV) cross section {sigma}{sub 0}=133{+-}10 b and for the resonance integral I{sub 0}=5850{+-}660 b were found. Additionally, the absolute intensities of the main {gamma}-ray transitions in the decay of {sup 182}Hf have been considerably improved.

  13. The perturbation of backscattered fast neutrons spectrum caused by the resonances of C, N and O for possible use in pyromaterial detection

    NASA Astrophysics Data System (ADS)

    Abedin, Ahmad Firdaus Zainal; Ibrahim, Noorddin; Zabidi, Noriza Ahmad; Abdullah, Abqari Luthfi Albert

    2015-04-01

    Neutron radiation is able to determine the signature of land mine detection based on backscattering energy spectrum of landmine. In this study, the Monte Carlo simulation of backscattered fast neutrons was performed on four basic elements of land mine; hydrogen, nitrogen, oxygen and carbon. The moderation of fast neutrons to thermal neutrons and their resonances cross-section between 0.01 eV until 14 MeV were analysed. The neutrons energies were divided into 29 groups and ten million neutrons particles histories were used. The geometries consist of four main components: neutrons source, detectors, landmine and soil. The neutrons source was placed at the origin coordinate and shielded with carbon and polyethylene. Americium/Beryllium neutron source was placed inside lead casing of 1 cm thick and 2.5 cm height. Polyethylene was used to absorb and disperse radiation and was placed outside the lead shield of width 10 cm and height 7 cm. Two detectors were placed between source with distance of 8 cm and radius of 1.9 cm. Detectors of Helium-3 was used for neutron detection as it has high absorption cross section for thermal neutrons. For the anomaly, the physical is in cylinder form with radius of 10 cm and 8.9 cm height. The anomaly is buried 5 cm deep in the bed soil measured 80 cm radius and 53.5 cm height. The results show that the energy spectrum for the four basic elements of landmine with specific pattern which can be used as indication for the presence of landmines.

  14. The perturbation of backscattered fast neutrons spectrum caused by the resonances of C, N and O for possible use in pyromaterial detection

    SciTech Connect

    Abedin, Ahmad Firdaus Zainal Ibrahim, Noorddin; Zabidi, Noriza Ahmad; Abdullah, Abqari Luthfi Albert

    2015-04-29

    Neutron radiation is able to determine the signature of land mine detection based on backscattering energy spectrum of landmine. In this study, the Monte Carlo simulation of backscattered fast neutrons was performed on four basic elements of land mine; hydrogen, nitrogen, oxygen and carbon. The moderation of fast neutrons to thermal neutrons and their resonances cross-section between 0.01 eV until 14 MeV were analysed. The neutrons energies were divided into 29 groups and ten million neutrons particles histories were used. The geometries consist of four main components: neutrons source, detectors, landmine and soil. The neutrons source was placed at the origin coordinate and shielded with carbon and polyethylene. Americium/Beryllium neutron source was placed inside lead casing of 1 cm thick and 2.5 cm height. Polyethylene was used to absorb and disperse radiation and was placed outside the lead shield of width 10 cm and height 7 cm. Two detectors were placed between source with distance of 8 cm and radius of 1.9 cm. Detectors of Helium-3 was used for neutron detection as it has high absorption cross section for thermal neutrons. For the anomaly, the physical is in cylinder form with radius of 10 cm and 8.9 cm height. The anomaly is buried 5 cm deep in the bed soil measured 80 cm radius and 53.5 cm height. The results show that the energy spectrum for the four basic elements of landmine with specific pattern which can be used as indication for the presence of landmines.

  15. Single protein sensing with asymmetric plasmonic hexamer via Fano resonance enhanced two-photon luminescence

    NASA Astrophysics Data System (ADS)

    Deng, Hai-Dong; Chen, Xing-Yu; Xu, Yi; Miroshnichenko, Andrey E.

    2015-12-01

    Fano resonances in plasmonic systems have been proved to facilitate various sensing applications in the nanoscale. In this work, we propose an experimental scheme to realize a single protein sensing by utilizing its two-photon luminescence enhanced by a plasmonic Fano resonance system. The asymmetric gold hexamer supporting polarization-dependent Fano resonances and plasmonic modes without in-plane rotational symmetry is used as a referenced spatial coordinate for bio-sensing. We demonstrate via the full-vectorial three-dimensional simulation that the moving direction and the spatial location of a protein can be detected via its two-photon luminescence, which benefits from the resonant near-field interaction with the electromagnetic hot-spots. The sensitivity to changes in position of our method is substantially better compared with the conventional linear sensing approach. Our strategy would facilitate the sensing, tracking and imaging of a single biomolecule in deep sub-wavelength scale and with a small optical extinction cross-section.Fano resonances in plasmonic systems have been proved to facilitate various sensing applications in the nanoscale. In this work, we propose an experimental scheme to realize a single protein sensing by utilizing its two-photon luminescence enhanced by a plasmonic Fano resonance system. The asymmetric gold hexamer supporting polarization-dependent Fano resonances and plasmonic modes without in-plane rotational symmetry is used as a referenced spatial coordinate for bio-sensing. We demonstrate via the full-vectorial three-dimensional simulation that the moving direction and the spatial location of a protein can be detected via its two-photon luminescence, which benefits from the resonant near-field interaction with the electromagnetic hot-spots. The sensitivity to changes in position of our method is substantially better compared with the conventional linear sensing approach. Our strategy would facilitate the sensing, tracking and

  16. Determination of Resonance Parameters and their Covariances from Neutron Induced Reaction Cross Section Data

    SciTech Connect

    Schillebeeckx, P.; Becker, B.; Danon, Y.; Guber, K.; Harada, H.; Heyse, J.; Junghans, A.R.; Kopecky, S.; Massimi, C.; Moxon, M.C.; Otuka, N.; Sirakov, I.; Volev, K.

    2012-12-15

    Cross section data in the resolved and unresolved resonance region are represented by nuclear reaction formalisms using parameters which are determined by fitting them to experimental data. Therefore, the quality of evaluated cross sections in the resonance region strongly depends on the experimental data used in the adjustment process and an assessment of the experimental covariance data is of primary importance in determining the accuracy of evaluated cross section data. In this contribution, uncertainty components of experimental observables resulting from total and reaction cross section experiments are quantified by identifying the metrological parameters involved in the measurement, data reduction and analysis process. In addition, different methods that can be applied to propagate the covariance of the experimental observables (i.e. transmission and reaction yields) to the covariance of the resonance parameters are discussed and compared. The methods being discussed are: conventional uncertainty propagation, Monte Carlo sampling and marginalization. It is demonstrated that the final covariance matrix of the resonance parameters not only strongly depends on the type of experimental observables used in the adjustment process, the experimental conditions and the characteristics of the resonance structure, but also on the method that is used to propagate the covariances. Finally, a special data reduction concept and format is presented, which offers the possibility to store the full covariance information of experimental data in the EXFOR library and provides the information required to perform a full covariance evaluation.

  17. Interference of fission amplitudes of neutron resonances and T-odd asymmetry for various prescission third particles in the ternary fission of nuclei

    SciTech Connect

    Kadmensky, S. G.; Bunakov, V. E.; Kadmensky, S. S.

    2011-12-15

    Differential cross sections for reactions of the true ternary fission of nuclei that was induced by cold polarized neutrons were constructed with allowance of the effect that Coriolis interaction and the interference between fission amplitudes of neutron resonances excited in fissile nuclei upon incidentneutron capture by target nuclei exerted on angular distributions of prescission third particles (alpha particles, neutrons, or photons). It is shown that T -odd TRI- and ROT-type asymmetries for prescission alpha particles are associated with, respectively, the odd and even components of the Coriolis interaction-perturbed amplitude of angular distributions of particles belonging to the types indicated above. These asymmetries have angular distributions differing from each other and stemming from a nontrivial dependence of these components on the neutron-resonance spins J{sub s} and their projections K{sub s} onto the symmetry axis of the nucleus involved. It is shown that angular distributions of prescission photons and neutrons from reactions of the ternary fission of nuclei that is induced by cold polarized neutrons are determined by the effect of Coriolis forces exclusively. Therefore, the emerging T-odd asymmetries have a character of a ROT-type asymmetry and are universal for all target nuclei.

  18. Calculating broad neutron resonances in a cut-off Woods-Saxon potential

    NASA Astrophysics Data System (ADS)

    Baran, Á.; Noszály, Cs.; Salamon, P.; Vertse, T.

    2015-07-01

    In a cut-off Woods-Saxon (CWS) potential with realistic depth S -matrix poles being far from the imaginary wave number axis form a sequence where the distances of the consecutive resonances are inversely proportional with the cut-off radius value, which is an unphysical parameter. Other poles lying closer to the imaginary wave number axis might have trajectories with irregular shapes as the depth of the potential increases. Poles being close repel each other, and their repulsion is responsible for the changes of the directions of the corresponding trajectories. The repulsion might cause that certain resonances become antibound and later resonances again when they collide on the imaginary axis. The interaction is extremely sensitive to the cut-off radius value, which is an apparent handicap of the CWS potential.

  19. Observations of magnetospheric ionization enhancements using upper-hybrid resonance noise band data from the RAE-1 satellite

    NASA Technical Reports Server (NTRS)

    Mosier, S. R.

    1975-01-01

    Noise bands associated with the upper-hybrid resonance were used to provide direct evidence for the existence of regions of enhanced density in the equatorial magnetosphere near L = 2. Density enhancements ranging from several percent to as high as 45 percent are observed with radial dimensions of several hundred kilometers. The enhancement characteristics strongly suggest their identification as magnetospheric whistler ducts.

  20. Effect of diameter of nanoparticles and capture cross-section library on macroscopic dose enhancement in boron neutron capture therapy

    PubMed Central

    Farhood, Bagher

    2014-01-01

    Purpose The aim of this study is evaluation of the effect of diameter of 10B nanoparticles and various neutron capture cross-section libraries on macroscopic dose enhancement in boron neutron capture therapy (BNCT). Material and methods MCNPX Monte Carlo code was used for simulation of a 252Cf source, a soft tissue phantom and a tumor containing 10B nanoparticles. Using 252Cf as a neutron source, macroscopic dose enhancement factor (MDEF) and total dose rate in tumor in the presence of 100, 200, and 500 ppm of 10B nanoparticles with 25 nm, 50 nm, and 100 nm diameters were calculated. Additionally, the effect of ENDF, JEFF, JENDL, and CENDL neutron capture cross-section libraries on MDEF was evaluated. Results There is not a linear relationship between the average MDEF value and nanoparticles’ diameter but the average MDEF grows with increased concentration of 10B nanoparticles. There is an increasing trend for average MDEF with the tumor distance. The average MDEF values were obtained the same for various neutron capture cross-section libraries. The maximum and minimum doses that effect on the total dose in tumor were neutron and secondary photon doses, respectively. Furthermore, the boron capture related dose component reduced in some extent with increase of diameter of 10B nanoparticles. Conclusions Based on the results of this study, it can be concluded that from physical point of view, various nanoparticle diameters have no dominant effect on average MDEF value in tumor. Furthermore, it is concluded that various neutron capture cross-section libraries are resulted to the same macroscopic dose enhancements. However, it is predicted that taking into account the biological effects for various nanoparticle diameters will result in different dose enhancements. PMID:25834582

  1. Simultaneous and Direct Measurement of the Neutron - Branching Ratio of URANIUM-238 in the Region of the Giant Quadrupole Resonance.

    NASA Astrophysics Data System (ADS)

    Countryman, Peter John

    We have measured the coincidence cross-sections ^{238}U(alpha, alpha'{rm n| f} ) and ^{238}U( alpha,alpha'f), and inclusive cross-sections ^{238} U(alpha,alpha') using the 120 MeV alpha particle beam at the Lawrence Berkeley Laboratory's 88-Inch Cyclotron. The (alpha, alpha'{rm n| f} ) experiment simultaneously measured the cross-sections for ^{238}U(alpha, alpha'f) and ^{238 }U(alpha,alpha' {rm n| f}) at theta _{alpha'} ~ 17^circ, a local maximum for the angular distributions of the isoscalar giant quadrupole and monopole resonances (GQ_0R and GM _0R). The branching ratio Gamma _{rm n}/Gamma_{ rm f} obtained from this experiment is therefore not subject to many of the systematic errors which go into the individual cross-sections. The energy of the scattered alpha-particle (E _{alpha'}) and the neutron time-of-flight were measured for each event. Fission events were detected using a large solid-angle array, so that the fission neutrons could be removed from the neutron decay spectra. This enabled us to make the first measurement of the neutron decay from an actinide nucleus. Inelastic scattering cross-sections are presented for the range of excitation energy from 0. to 20. MeV. In a separate experiment, the cross-section {rm d^2sigma(alpha,alpha 'rm f)}over {rm d Omega_{alpha'}{dE}_{alpha'} } was measured for uranium at seven scattering angles in the range theta_{alpha '} = 7^circ -21^{circ}. We extracted the transition strength as a function of excitation energy for the GQ_0R and GM _0R. In (alpha,alpha 'f), we find 25% of the L = 2 energy-weighted sum-rule (from 8 to 12 MeV), and 50% of the L = 0 sum-rule (12 to 16 MeV). The strength agrees well with a recent (e,e^'f) experiment. We used the strengths extracted from the ( alpha,alpha'f) experiment along with the (alpha,alpha' {n| f}) data to place limits on (Gamma_{rm n }/Gamma_{rm f}) _{rm GQR} and ( Gamma_{rm n}/Gamma_ {rm f})_{rm GMR}. We obtained (Gamma_ {rm n}/Gamma_{rm f})_{rm GQR} = 6 +/- 4 (statistical

  2. Angular-anisotropy coefficients for fragment originating from the resonance-neutron-induced fission of {sup 235}U oriented nuclei

    SciTech Connect

    Tambovtsev, D. I.

    2008-04-15

    Statistical distributions of the coefficients measured for the angular distribution of fragments originating from the fission of {sup 235}U oriented nuclei that was induced by resonance neutrons obtained by using booster targets at the electron accelerator in Harwell and at a pulsed reactor in Dubna were approximated by a curve that was calculated under the assumption of a normal distribution of partial-wave fission amplitudes. A cutoff from below at a level of one-half of the average partial-wave width was introduced in this distribution. The calculation was performed with allowance for the K = 0, 1 and 2 channels for J = 3 and the K = 1 and 2 channels for J =4. The contributions of the K channels to the total probability were in the ratio 0.15 : 0.53 : 0.32 for J = 3 and in the ratio 0.625 : 0.375 for J = 4. A strong suppression of the K = 0 channel in the J = 3 spin subsystem in contrast to the situation observed in photofission can be interpreted as an indication of the possible partial conservation of K in resonance states formed from the entrance channel, which features only maximum values of K equal to J and J - 1.

  3. Tunable multiple plasmon resonances and local field enhancement of nanocrescent/nanoring structure

    NASA Astrophysics Data System (ADS)

    Wang, Bin-Bing; Zhou, Jun; Chen, Dong; Fang, Yun-Tuan; Chen, Ming-Yang

    2015-08-01

    According to the plasmon hybridization theory, the plasmon resonance characteristics of the gold nanocrescent/nanoring (NCNR) structure are systematically investigated by the finite element method. It is found that the extinction spectra of NCNR structure exhibit multiple plasmon resonance peaks, which could be attributed to the result of the plasmon couplings between the multipolar plasmon modes of nanocrescent and the dipolar, quadrupolar, hexapolar, octupolar, decapolar plasmon modes of nanoring. By changing the geometric parameters, the intense and separate multiple plasmon resonance peaks are obtained and can be tuned in a wide wavelength range. It is further found that the plasmon coupling induces giant multipole electric field enhancements around the tips of the nanocrescent. The tunable and intense multiple plasmon resonances of NCNR structure may provide effective applications in multiplex biological sensing. Project supported by the National Natural Science Foundation of China (Grant Nos. 61275153 and 61320106014), the Natural Science Foundation of Zhejiang Province, China (Grant No. LY12A04002), the Natural Science Foundation of Ningbo City, China (Grant Nos. 2010D10018 and 2012A610107), and the K. C. Wong Magna Foundation of Ningbo University, China.

  4. Synchronization and array-enhanced resonances in delayed coupled neuronal network with channel noise.

    PubMed

    Chen, Jianchun; Ding, Shaojie; Li, Hui; He, Guolong; Zhang, Xuejuan

    2014-09-01

    This paper studies the combined effect of transmission delay and channel fluctuations on population behaviors of an excitatory Erdös-Rényi neuronal network. First, it is found that the network reaches a perfect spatial temporal coherence at a suitable membrane size. Such a coherence resonance is stimulus-free and is array-enhanced. Second, the presence of transmission delay can induce intermittent changes of the population dynamics. Besides, two resonant peaks of the population firing rate are observed as delay changes: one is at τd≈7ms for all membrane areas, which reflects the resonance between the delayed interaction and the intrinsic period of channel kinetics; the other occurs when the transmission delay equals to the mean inter-spike intervals of the population firings in the absence of delay, which reflects the resonance between the delayed interaction and the firing period of the non-delayed system. Third, concerning the impact of network topology and population size, it is found that decreasing the connection probability does not change the range of transmission delay but broadens the range of synaptic coupling that supports population neurons to generate action potentials synchronously and temporally coherently. Furthermore, there exists a critical connection probability that distinguishes the population dynamics into an asynchronous and synchronous state. All the results we obtained are based on networks of size N = 500, which are shown to be robust to further increasing the population size. PMID:25273211

  5. Resonance enhanced electron impact excitation for P-like Cu XV

    NASA Astrophysics Data System (ADS)

    Li, Shuang; Yan, Jun; Li, Chuan-Ying; Huang, Min; Chen, Chong-Yang

    2015-11-01

    Employing both the Dirac R-matrix and the relativistic distorted wave with independent process and isolated resonance approaches, we report resonance enhanced electron impact excitation data (specifically, effective collision strengths) among the lowest 41 levels from the n = 3 configurations of Cu XV. The results show that the latter approach can obtain resonance contributions reasonably well for most excitations of Cu XV, though a comparison between the two approaches shows that the close-coupling effects are truly significant for rather weak excitations, especially for two-electron excitations from the 3s3p4 to 3s23p23d configuration. Resonance contributions are significant (more than two orders of magnitude) for many excitations and dramatically influence the line intensity ratios associated with density diagnostics. Project supported by the National Natural Science Foundation of China (Grant Nos. 11076009 and 11374062), the Chinese Association of Atomic and Molecular Data, the Chinese National Fusion Project for ITER (Grant No. 2015GB117000), and the Leading Academic Discipline Project of Shanghai, China (Grant No. B107).

  6. Enhancing the Surface Sensitivity of Metallic Nanostructures Using Oblique-Angle-Induced Fano Resonances

    PubMed Central

    Lee, Kuang-Li; Chang, Chia-Chun; You, Meng-Lin; Pan, Ming-Yang; Wei, Pei-Kuen

    2016-01-01

    Surface sensitivity is an important factor that determines the minimum amount of biomolecules detected by surface plasmon resonance (SPR) sensors. We propose the use of oblique-angle-induced Fano resonances caused by two-mode coupling or three-mode coupling between the localized SPR mode and long-range surface plasmon polariton modes to increase the surface sensitivities of silver capped nanoslits. The results indicate that the coupled resonance between the split SPR (−kSPR) and cavity modes (two-mode coupling) has a high wavelength sensitivity for small-angle incidence (2°) due to its short decay length. Additionally, three-mode coupling between the split SPR (−kSPR), substrate (+kSub) and cavity modes has a high intensity sensitivity for large-angle incidence due to its short decay length, large resonance slope and enhanced transmission intensity. Compared to the wavelength measurement, the intensity measurement has a lower detectable (surface) concentration below 1 ng/ml (0.14 pg/mm2) and is reduced by at least 3 orders of magnitude. In addition, based on the calibration curve and current system noise, a theoretical detection limit of 2.73 pg/ml (0.38 fg/mm2) can be achieved. Such a surface concentration is close to that of prism-based SPR with phase measurement (0.1–0.2 fg/mm2 under a phase shift of 5 mdeg). PMID:27609431

  7. Enhancing the Surface Sensitivity of Metallic Nanostructures Using Oblique-Angle-Induced Fano Resonances.

    PubMed

    Lee, Kuang-Li; Chang, Chia-Chun; You, Meng-Lin; Pan, Ming-Yang; Wei, Pei-Kuen

    2016-01-01

    Surface sensitivity is an important factor that determines the minimum amount of biomolecules detected by surface plasmon resonance (SPR) sensors. We propose the use of oblique-angle-induced Fano resonances caused by two-mode coupling or three-mode coupling between the localized SPR mode and long-range surface plasmon polariton modes to increase the surface sensitivities of silver capped nanoslits. The results indicate that the coupled resonance between the split SPR (-kSPR) and cavity modes (two-mode coupling) has a high wavelength sensitivity for small-angle incidence (2°) due to its short decay length. Additionally, three-mode coupling between the split SPR (-kSPR), substrate (+kSub) and cavity modes has a high intensity sensitivity for large-angle incidence due to its short decay length, large resonance slope and enhanced transmission intensity. Compared to the wavelength measurement, the intensity measurement has a lower detectable (surface) concentration below 1 ng/ml (0.14 pg/mm(2)) and is reduced by at least 3 orders of magnitude. In addition, based on the calibration curve and current system noise, a theoretical detection limit of 2.73 pg/ml (0.38 fg/mm(2)) can be achieved. Such a surface concentration is close to that of prism-based SPR with phase measurement (0.1-0.2 fg/mm(2) under a phase shift of 5 mdeg). PMID:27609431

  8. Correction: Enhanced photoresponse in dye-sensitized solar cells via localized surface plasmon resonance through highly stable nickel nanoparticles

    NASA Astrophysics Data System (ADS)

    Rahman, Md. Mahbubur; Im, Sang Hyuk; Lee, Jae-Joon

    2016-03-01

    Correction for `Enhanced photoresponse in dye-sensitized solar cells via localized surface plasmon resonance through highly stable nickel nanoparticles' by Md. Mahbubur Rahman et al., Nanoscale, 2016, DOI: 10.1039/c5nr08155f.

  9. Correction: Enhanced photoresponse in dye-sensitized solar cells via localized surface plasmon resonance through highly stable nickel nanoparticles.

    PubMed

    Rahman, Md Mahbubur; Im, Sang Hyuk; Lee, Jae-Joon

    2016-04-14

    Correction for 'Enhanced photoresponse in dye-sensitized solar cells via localized surface plasmon resonance through highly stable nickel nanoparticles' by Md. Mahbubur Rahman et al., Nanoscale, 2016, DOI: 10.1039/c5nr08155f. PMID:26991406

  10. Sensitivity Enhancement of Transition Metal Dichalcogenides/Silicon Nanostructure-based Surface Plasmon Resonance Biosensor

    NASA Astrophysics Data System (ADS)

    Ouyang, Qingling; Zeng, Shuwen; Jiang, Li; Hong, Liying; Xu, Gaixia; Dinh, Xuan-Quyen; Qian, Jun; He, Sailing; Qu, Junle; Coquet, Philippe; Yong, Ken-Tye

    2016-06-01

    In this work, we designed a sensitivity-enhanced surface plasmon resonance biosensor structure based on silicon nanosheet and two-dimensional transition metal dichalcogenides. This configuration contains six components: SF10 triangular prism, gold thin film, silicon nanosheet, two-dimensional MoS2/MoSe2/WS2/WSe2 (defined as MX2) layers, biomolecular analyte layer and sensing medium. The minimum reflectivity, sensitivity as well as the Full Width at Half Maximum of SPR curve are systematically examined by using Fresnel equations and the transfer matrix method in the visible and near infrared wavelength range (600 nm to 1024 nm). The variation of the minimum reflectivity and the change in resonance angle as the function of the number of MX2 layers are presented respectively. The results show that silicon nanosheet and MX2 layers can be served as effective light absorption medium. Under resonance conditions, the electrons in these additional dielectric layers can be transferred to the surface of gold thin film. All silicon-MX2 enhanced sensing models show much better performance than that of the conventional sensing scheme where pure Au thin film is used, the highest sensitivity can be achieved by employing 600 nm excitation light wavelength with 35 nm gold thin film and 7 nm thickness silicon nanosheet coated with monolayer WS2.

  11. Nanomaterials enhanced surface plasmon resonance for biological and chemical sensing applications.

    PubMed

    Zeng, Shuwen; Baillargeat, Dominique; Ho, Ho-Pui; Yong, Ken-Tye

    2014-05-21

    The main challenge for all electrical, mechanical and optical sensors is to detect low molecular weight (less than 400 Da) chemical and biological analytes under extremely dilute conditions. Surface plasmon resonance sensors are the most commonly used optical sensors due to their unique ability for real-time monitoring the molecular binding events. However, their sensitivities are insufficient to detect trace amounts of small molecular weight molecules such as cancer biomarkers, hormones, antibiotics, insecticides, and explosive materials which are respectively important for early-stage disease diagnosis, food quality control, environmental monitoring, and homeland security protection. With the rapid development of nanotechnology in the past few years, nanomaterials-enhanced surface plasmon resonance sensors have been developed and used as effective tools to sense hard-to-detect molecules within the concentration range between pmol and amol. In this review article, we reviewed and discussed the latest trend and challenges in engineering and applications of nanomaterials-enhanced surface plasmon resonance sensors (e.g., metallic nanoparticles, magnetic nanoparticles, carbon-based nanomaterials, latex nanoparticles and liposome nanoparticles) for detecting "hard-to-identify" biological and chemical analytes. Such information will be viable in terms of providing a useful platform for designing future ultrasensitive plasmonic nanosensors. PMID:24549396

  12. Sensitivity Enhancement of Transition Metal Dichalcogenides/Silicon Nanostructure-based Surface Plasmon Resonance Biosensor

    PubMed Central

    Ouyang, Qingling; Zeng, Shuwen; Jiang, Li; Hong, Liying; Xu, Gaixia; Dinh, Xuan-Quyen; Qian, Jun; He, Sailing; Qu, Junle; Coquet, Philippe; Yong, Ken-Tye

    2016-01-01

    In this work, we designed a sensitivity-enhanced surface plasmon resonance biosensor structure based on silicon nanosheet and two-dimensional transition metal dichalcogenides. This configuration contains six components: SF10 triangular prism, gold thin film, silicon nanosheet, two-dimensional MoS2/MoSe2/WS2/WSe2 (defined as MX2) layers, biomolecular analyte layer and sensing medium. The minimum reflectivity, sensitivity as well as the Full Width at Half Maximum of SPR curve are systematically examined by using Fresnel equations and the transfer matrix method in the visible and near infrared wavelength range (600 nm to 1024 nm). The variation of the minimum reflectivity and the change in resonance angle as the function of the number of MX2 layers are presented respectively. The results show that silicon nanosheet and MX2 layers can be served as effective light absorption medium. Under resonance conditions, the electrons in these additional dielectric layers can be transferred to the surface of gold thin film. All silicon-MX2 enhanced sensing models show much better performance than that of the conventional sensing scheme where pure Au thin film is used, the highest sensitivity can be achieved by employing 600 nm excitation light wavelength with 35 nm gold thin film and 7 nm thickness silicon nanosheet coated with monolayer WS2. PMID:27305974

  13. Noise Enhances Action Potential Generation in Mouse Sensory Neurons via Stochastic Resonance

    PubMed Central

    Onorato, Irene; D'Alessandro, Giuseppina; Di Castro, Maria Amalia; Renzi, Massimiliano; Dobrowolny, Gabriella; Musarò, Antonio; Salvetti, Marco; Limatola, Cristina; Crisanti, Andrea; Grassi, Francesca

    2016-01-01

    Noise can enhance perception of tactile and proprioceptive stimuli by stochastic resonance processes. However, the mechanisms underlying this general phenomenon remain to be characterized. Here we studied how externally applied noise influences action potential firing in mouse primary sensory neurons of dorsal root ganglia, modelling a basic process in sensory perception. Since noisy mechanical stimuli may cause stochastic fluctuations in receptor potential, we examined the effects of sub-threshold depolarizing current steps with superimposed random fluctuations. We performed whole cell patch clamp recordings in cultured neurons of mouse dorsal root ganglia. Noise was added either before and during the step, or during the depolarizing step only, to focus onto the specific effects of external noise on action potential generation. In both cases, step + noise stimuli triggered significantly more action potentials than steps alone. The normalized power norm had a clear peak at intermediate noise levels, demonstrating that the phenomenon is driven by stochastic resonance. Spikes evoked in step + noise trials occur earlier and show faster rise time as compared to the occasional ones elicited by steps alone. These data suggest that external noise enhances, via stochastic resonance, the recruitment of transient voltage-gated Na channels, responsible for action potential firing in response to rapid step-wise depolarizing currents. PMID:27525414

  14. Noise Enhances Action Potential Generation in Mouse Sensory Neurons via Stochastic Resonance.

    PubMed

    Onorato, Irene; D'Alessandro, Giuseppina; Di Castro, Maria Amalia; Renzi, Massimiliano; Dobrowolny, Gabriella; Musarò, Antonio; Salvetti, Marco; Limatola, Cristina; Crisanti, Andrea; Grassi, Francesca

    2016-01-01

    Noise can enhance perception of tactile and proprioceptive stimuli by stochastic resonance processes. However, the mechanisms underlying this general phenomenon remain to be characterized. Here we studied how externally applied noise influences action potential firing in mouse primary sensory neurons of dorsal root ganglia, modelling a basic process in sensory perception. Since noisy mechanical stimuli may cause stochastic fluctuations in receptor potential, we examined the effects of sub-threshold depolarizing current steps with superimposed random fluctuations. We performed whole cell patch clamp recordings in cultured neurons of mouse dorsal root ganglia. Noise was added either before and during the step, or during the depolarizing step only, to focus onto the specific effects of external noise on action potential generation. In both cases, step + noise stimuli triggered significantly more action potentials than steps alone. The normalized power norm had a clear peak at intermediate noise levels, demonstrating that the phenomenon is driven by stochastic resonance. Spikes evoked in step + noise trials occur earlier and show faster rise time as compared to the occasional ones elicited by steps alone. These data suggest that external noise enhances, via stochastic resonance, the recruitment of transient voltage-gated Na channels, responsible for action potential firing in response to rapid step-wise depolarizing currents. PMID:27525414

  15. Resonant antenna probes for tip-enhanced infrared near-field microscopy.

    PubMed

    Huth, Florian; Chuvilin, Andrey; Schnell, Martin; Amenabar, Iban; Krutokhvostov, Roman; Lopatin, Sergei; Hillenbrand, Rainer

    2013-03-13

    We report the development of infrared-resonant antenna probes for tip-enhanced optical microscopy. We employ focused-ion-beam machining to fabricate high-aspect ratio gold cones, which replace the standard tip of a commercial Si-based atomic force microscopy cantilever. Calculations show large field enhancements at the tip apex due to geometrical antenna resonances in the cones, which can be precisely tuned throughout a broad spectral range from visible to terahertz frequencies by adjusting the cone length. Spectroscopic analysis of these probes by electron energy loss spectroscopy, Fourier transform infrared spectroscopy, and Fourier transform infrared near-field spectroscopy corroborates their functionality as resonant antennas and verifies the broad tunability. By employing the novel probes in a scattering-type near-field microscope and imaging a single tobacco mosaic virus (TMV), we experimentally demonstrate high-performance mid-infrared nanoimaging of molecular absorption. Our probes offer excellent perspectives for optical nanoimaging and nanospectroscopy, pushing the detection and resolution limits in many applications, including nanoscale infrared mapping of organic, molecular, and biological materials, nanocomposites, or nanodevices. PMID:23362918

  16. Sensitivity Enhancement of Transition Metal Dichalcogenides/Silicon Nanostructure-based Surface Plasmon Resonance Biosensor.

    PubMed

    Ouyang, Qingling; Zeng, Shuwen; Jiang, Li; Hong, Liying; Xu, Gaixia; Dinh, Xuan-Quyen; Qian, Jun; He, Sailing; Qu, Junle; Coquet, Philippe; Yong, Ken-Tye

    2016-01-01

    In this work, we designed a sensitivity-enhanced surface plasmon resonance biosensor structure based on silicon nanosheet and two-dimensional transition metal dichalcogenides. This configuration contains six components: SF10 triangular prism, gold thin film, silicon nanosheet, two-dimensional MoS2/MoSe2/WS2/WSe2 (defined as MX2) layers, biomolecular analyte layer and sensing medium. The minimum reflectivity, sensitivity as well as the Full Width at Half Maximum of SPR curve are systematically examined by using Fresnel equations and the transfer matrix method in the visible and near infrared wavelength range (600 nm to 1024 nm). The variation of the minimum reflectivity and the change in resonance angle as the function of the number of MX2 layers are presented respectively. The results show that silicon nanosheet and MX2 layers can be served as effective light absorption medium. Under resonance conditions, the electrons in these additional dielectric layers can be transferred to the surface of gold thin film. All silicon-MX2 enhanced sensing models show much better performance than that of the conventional sensing scheme where pure Au thin film is used, the highest sensitivity can be achieved by employing 600 nm excitation light wavelength with 35 nm gold thin film and 7 nm thickness silicon nanosheet coated with monolayer WS2. PMID:27305974

  17. Guided-mode-resonance-enhanced measurement of thin-film absorption.

    PubMed

    Wang, Yifei; Huang, Yin; Sun, Jingxuan; Pandey, Santosh; Lu, Meng

    2015-11-01

    We present a numerical and experimental study of a guided-mode-resonance (GMR) device for detecting surface-bound light-absorbing thin films. The GMR device functions as an optical resonator at the wavelength strongly absorbed by the thin film. The GMR mode produces an evanescent field that results in enhanced optical absorption by the thin film. For a 100-nm-thick lossy thin film, the GMR device enhances its absorption coefficients over 26 × compared to a conventional glass substrate. Simulations show the clear quenching effect of the GMR when the extinction coefficient is greater than 0.01. At the resonant wavelength, the reflectance of the GMR surface correlates well with the degree of optical absorption. GMR devices are fabricated on a glass substrate using a surface-relief grating and a titanium-dioxide coating. To analyze a visible absorbing dye, the reflection coefficient of dye-coated GMR devices was measured. The GMR-based method was also applied to detecting acid gases, such as hydrochloric vapor, by monitoring the change in absorption in a thin film composed of a pH indicator, bromocresol green. This technique potentially allows absorption analysis in the visible and infrared ranges using inexpensive equipment. PMID:26561126

  18. Gadolinium-DTPA enhanced magnetic resonance imaging of bone cysts in patients with rheumatoid arthritis.

    PubMed Central

    Gubler, F M; Algra, P R; Maas, M; Dijkstra, P F; Falke, T H

    1993-01-01

    OBJECTIVES--To examine the contents of intraosseous cysts in patients with rheumatoid arthritis (RA) through the signal intensity characteristics on gadolinium-DTPA (Gd-DTPA) enhanced magnetic resonance imaging. METHODS--The hand or foot joints of nine patients with the cystic form of RA (where the initial radiological abnormality consisted of intraosseous cysts without erosions) were imaged before and after intravenous administration of Gd-DTPA. A 0.6 unit, T1 weighted spin echo and T2* weighted gradient echo were used to obtain images in at least two perpendicular planes. RESULTS--Most cysts showed a low signal intensity on the non-enhanced T1 weighted (spin echo) images and a high signal intensity on the T2* weighted (gradient echo) images, consistent with a fluid content. No cyst showed an enhancement of signal intensity on the T1 weighted images after intravenous administration of Gd-DTPA, whereas synovium hyperplasia at the site of bony erosions did show an increased signal intensity after Gd-DTPA. Magnetic resonance imaging detected more cysts (as small as 2 mm) than plain films, and the cysts were located truly intraosseously. In six patients no other joint abnormalities were identified by magnetic resonance imaging; the three other patients also showed, after Gd-DTPA administration, an enhanced synovium at the site of bony erosions. CONCLUSIONS--It is suggested that intraosseous bone cysts in patients with RA do not contain hyperaemic synovial proliferation. The bone cysts in patients with the cystic form of RA may be the only joint abnormality. Images PMID:8257207

  19. Diode-laser-based near-resonantly enhanced flow visualization in shock tunnels.

    PubMed

    Hruschka, Robert; O'Byrne, Sean; Kleine, Harald

    2008-08-20

    Two new near-resonantly enhanced flow visualization techniques suitable for hypersonic low-density flows in shock or arc tunnels have been developed using seeded lithium (Li) metal as the refractivity-enhancing species. Two semiconductor lasers, single-longitudinal-mode and multimode, are compared with respect to their suitability as light sources for the technique. Transient wake-flow structures around a cylinder and a model of a planetary entry vehicle are visualized to demonstrate the capabilities of this comparatively inexpensive and simple visualization system. The images show flow features which are undetectable with conventional schlieren, shadowgraph, or interferometry techniques. Furthermore, the effect of density inhomogeneities along the line-of-sight outside the region of interest can be reduced by enhancing the refractivity only in selected parts of the flowfield. PMID:18716640

  20. Brain nuclear magnetic resonance imaging enhanced by a paramagnetic nitroxide contrast agent: preliminary report. [Dogs

    SciTech Connect

    Brasch, R.C.; Nitecki, D.E.; Brant-Zawadzki, M.; Enzmann, D.R.; Wesbey, G.E.; Tozer, T.N.; Tuck, L.D.; Cann, C.E.; Fike, J.R.; Sheldon, P.

    1983-11-01

    Contrast-enhancing agents for demonstrating abnormalities of the blood-brain barrier may extend the diagnostic utility of proton nuclear magnetic resonance (NMR) imaging. TES, a nitroxide stable free radical derivative, was tested as a central nervous system contrast enhancer in dogs with experimentally induced unilateral cerebritis or radiation cerebral damage. After intravenous injection of TES, the normal brain showed no change in NMR appearance, but areas of disease demonstrated a dramatic increase (up to 45%) in spin-echo intensity and a decrease in T/sub 1/, relaxation times. The areas of disease defined by TES enhancement were either not evident on the nonenhanced NMR images or were better defined after contrast administration. In-depth tests of toxicity, stability, and metabolism of this promising NMR contrast agent are now in progress.

  1. Enhancement of Resonant Energy Transfer Due to an Evanescent Wave from the Metal.

    PubMed

    Poudel, Amrit; Chen, Xin; Ratner, Mark A

    2016-03-17

    The high density of evanescent modes in the vicinity of a metal leads to enhancement of the near-field Förster resonant energy transfer (FRET) rate. We present a classical approach to calculate the FRET rate based on the dyadic Green's function of an arbitrary dielectric environment and consider the nonlocal limit of material permittivity in the case of the metallic half-space and thin film. In a dimer system, we find that the FRET rate is enhanced due to shared evanescent photon modes bridging a donor and an acceptor. Furthermore, a general expression for the FRET rate for multimer systems is derived. The presence of a dielectric environment and the path interference effect enhance the transfer rate, depending on the combination of distance and geometry. PMID:26913686

  2. Performance enhancement of organic photovoltaic devices enabled by Au nanoarrows inducing surface plasmonic resonance effect.

    PubMed

    Li, Shujun; Li, Zhiqi; Zhang, Xinyuan; Zhang, Zhihui; Liu, Chunyu; Shen, Liang; Guo, Wenbin; Ruan, Shengping

    2016-09-21

    The surface plasmon resonance (SPR) effect of metal nanoparticles is widely employed in organic solar cells to enhance device performance. However, the light-harvesting improvement is highly dependent on the shape of the metal nanoparticles. In this study, the significantly enhanced performance upon incorporation of Au nanoarrows in solution-processed organic photovoltaic devices is demonstrated. Incorporating Au nanoarrows into the ZnO cathode buffer layer results in superior broadband optical absorption improvement and a power conversion efficiency of 7.82% is realized with a 27.3% enhancement compared with the control device. The experimental and theoretical results indicate that the introduction of Au nanoarrows not only increases optical trapping by the SPR effect but also facilitates exciton generation, dissociation, and charge transport inside the thin film device. PMID:27531663

  3. Transmission enhancement through deep subwavelength apertures using connected split ring resonators.

    PubMed

    Ates, Damla; Cakmak, Atilla Ozgur; Colak, Evrim; Zhao, Rongkuo; Soukoulis, C M; Ozbay, Ekmel

    2010-02-15

    We report astonishingly high transmission enhancement factors through a subwavelength aperture at microwave frequencies by placing connected split ring resonators in the vicinity of the aperture. We carried out numerical simulations that are consistent with our experimental conclusions. We experimentally show higher than 70,000-fold extraordinary transmission through a deep subwavelength aperture with an electrical size of lambda/31 x lambda/12 (width x length), in terms of the operational wavelength. We discuss the physical origins of the phenomenon. Our numerical results predict that even more improvements of the enhancement factors are attainable. Theoretically, the approach opens up the possibility for achieving very large enhancement factors by overcoming the physical limitations and thereby minimizes the dependence on the aperture geometries. PMID:20389408

  4. Giant electric field enhancement in split ring resonators featuring nanometer-sized gaps.

    PubMed

    Bagiante, S; Enderli, F; Fabiańska, J; Sigg, H; Feurer, T

    2015-01-01

    Today's pulsed THz sources enable us to excite, probe, and coherently control the vibrational or rotational dynamics of organic and inorganic materials on ultrafast time scales. Driven by standard laser sources THz electric field strengths of up to several MVm(-1) have been reported and in order to reach even higher electric field strengths the use of dedicated electric field enhancement structures has been proposed. Here, we demonstrate resonant electric field enhancement structures, which concentrate the incident electric field in sub-diffraction size volumes and show an electric field enhancement as high as ~14,000 at 50 GHz. These values have been confirmed through a combination of near-field imaging experiments and electromagnetic simulations. PMID:25623373

  5. Enhancement of VUV and EUV generation by field-controlled resonance structures of diatomic molecules

    NASA Astrophysics Data System (ADS)

    Heslar, John; Telnov, Dmitry A.; Chu, Shih-I.

    2016-05-01

    Below- and near-threshold harmonic generation provides a potential approach to achieve a high conversion efficiency of vacuum-ultraviolet and extreme-ultraviolet sources for the advancement of spectroscopy. Here we perform an all-electron time-dependent density functional theory (TDDFT) study for the nonperturbative treatment of below- and near-threshold harmonic generation of CO and N2 diatomic molecules subject to short near-infrared laser pulses and aligned parallel to the laser field polarization. We find that with the use of different driving laser pulse shapes we can control and enhance harmonic generation through the excited state resonance structures. Our analysis reveals several novel features where the HHG signal is enhanced, boosting the conversion efficiency on the microscopic level. Depending on the pulse shape, the enhancement can reach 5 to 7 orders of magnitude as compared to the reference sine-squared laser pulse of the same duration. This work was partially supported by DOE.

  6. Resonant charge relaxation as a likely source of the enhanced thermopower in FeSi

    NASA Astrophysics Data System (ADS)

    Sun, Peijie; Wei, Beipei; Menzel, Dirk; Steglich, Frank

    2014-12-01

    The enhanced thermopower of the correlated semiconductor FeSi is found to be robust against the sign of the relevant charge carriers. At T ≈70 K, the position of both the high-temperature shoulder of the thermopower peak and the nonmagnetic-enhanced paramagnetic crossover, the Nernst coefficient ν assumes a large maximum and the Hall mobility μH diminishes to below 1 cm2/V s. These cause the dimensionless ratio ν /μH —a measure of the energy dispersion of the charge scattering time τ (ɛ ) —to exceed that of classical metals and semiconductors by two orders of magnitude. Concomitantly, the resistivity exhibits a hump and the magnetoresistance changes its sign. Our observations hint at a resonant scattering of the charge carriers at the magnetic crossover, imposing strong constraints on the microscopic interpretation of the robust thermopower enhancement in FeSi.

  7. Highly sensitive detection of melamine based on gemini surfactant using enhanced resonance Rayleigh scattering signals

    NASA Astrophysics Data System (ADS)

    Wang, Peng; Dong, Jiang Xue; Li, Nian Bing; Luo, Hong Qun

    2013-02-01

    We present here a resonance Rayleigh scattering (RRS) spectrum method for the determination of melamine at the nanogram level using a gemini surfactant (disodium 4-dodecyl-2,4'-oxydibenzenesulfonate, DDOF). It was found that DDOF could react with cationic melamine to form an ion-association complex, which induced the enhancement of RRS intensity and the appearance of a new RRS spectrum in acetate buffer (pH 3.6). The RRS spectral characteristics of the melamine-DDOF system, the optimum conditions of the reaction, and the influencing factors have been investigated. Under optimum conditions, the enhanced RRS intensity was proportional to the concentration of melamine in the range of 0.38-6.30 μg/mL. The method has high sensitivity, and the detection limit for melamine is 8.48 ng/mL. Furthermore, the reaction mechanism and the reasons of RRS enhancement were evaluated.

  8. Cooling enhancement in optical refrigeration by non-resonant optical cavities

    NASA Astrophysics Data System (ADS)

    Farfan, B. G.; Gragossian, A.; Symonds, G.; Ghasemkhani, M. R.; Albrecht, A. R.; Sheik-Bahae, M.; Epstein, R. I.

    2016-05-01

    We present a study of cooling enhancement in optical refrigerators by the implementation of advanced non-resonant optical cavities. Cavity designs have been studied to maximize pump light-trapping to improve absorption and thereby increase the efficiency of optical refrigeration. The approaches of non-resonant optical cavities by Herriott-cell and totalinternal- reflection were studied. Ray-tracing simulations and experiments were performed to analyze and optimize the different light-trapping configurations. Light trapping was studied for laser sources with high quality beams and for beams with large divergences, roughly corresponding to the output from fiber lasers and from diode lasers, respectively. We present a trade-off analysis between performance, reliability, and manufacturability.

  9. Subwavelength acoustic focusing by surface-wave-resonance enhanced transmission in doubly negative acoustic metamaterials

    SciTech Connect

    Zhou, Xiaoming; Badreddine Assouar, M. Oudich, Mourad

    2014-11-21

    We present analytical and numerical analyses of a yet unseen lensing paradigm that is based on a solid metamaterial slab in which the wave excitation source is attached. We propose and demonstrate sub-diffraction-limited acoustic focusing induced by surface resonant states in doubly negative metamaterials. The enhancement of evanescent waves across the metamaterial slab produced by their resonant coupling to surface waves is evidenced and quantitatively determined. The effect of metamaterial parameters on surface states, transmission, and wavenumber bandwidth is clearly identified. Based on this concept consisting of a wave source attached on the metamaterial, a high resolution of λ/28.4 is obtained with the optimum effective physical parameters, opening then an exciting way to design acoustic metamaterials for ultrasonic focused imaging.

  10. Ferromagnetic resonance shifts from electric fields: Field-enhanced screening charge in ferromagnet/ferroelectric multilayers

    NASA Astrophysics Data System (ADS)

    Gunawan, V.; Stamps, R. L.

    2012-03-01

    We calculate standing spin wave frequencies in a multilayer which unit cell is a trilayer comprised of a ferromagnet, a ferroelectric, and a normal metal. An applied voltage enhances the polarization of the ferroelectric and increases the magnetic moment at one interface through spin polarization and charge transfer. We show that the induced surface magnetism results in shifts of resonance and standing spin wave mode frequencies. A new resonance peak is predicted, associated with a strongly localized surface moment. Estimates are provided using parameters appropriate to the ferroelectric BaTiO3 and four different ferromagnetic metals, including a Heusler alloy (Fe, CrO2, permalloy, and Co2MnGe). The calculations use an entire-cell effective-medium approximation that takes into account the polarization profile in the ferroelectric. The metallic ferromagnetic electrode is treated as a real metal, and the depolarization field is included in the determination of polarization in the ferroelectric.

  11. Single molecule surface enhanced resonance Raman scattering (SERRS) of the enhanced green fluorescent protein (EGFP)

    NASA Astrophysics Data System (ADS)

    Hofkens, Johan; De Schryver, Frans C.; Cotlet, Mircea; Habuchi, Satoshi

    2004-06-01

    One of the most intriguing findings in single molecule spectroscopy (SMS) is the observation of Raman spectra of individual molecules, despite the small cross section of the transitions involved. The observation of the spectra can be explained by the surface enhanced Raman scattering (SERRS) effect. At the single-molecule level, the SERRS-spectra recorded as a function of time reveal inhomogeneous behaviour such as on/off blinking, spectral diffusion, intensity fluctuations of vibrational line, and even splitting of some lines within the spectrum of one molecule. Single-molecule SERRS (SM-SERRS) spectroscopy opens up exciting opportunities in the field of biophysics and biomedical spectroscopy. The first example of single protein SERRS was performed on hemoglobin. However, the possibility of extracting the heme group by silver sols can not be excluded. Here we report on SM-SERRS spectra of enhanced green fluorescent protein (EGFP) in which the chromophore is kept in the protein. The time series of SM-SERRS spectra suggest the conversion of the EGFP chromophore between the deprotonated and the protonated form. Autocorrelation analysis of SM-SERRS trajectory reveals the presence of fast dynamics taking place in the protein. Our findings show the potential of the technique to study structural dynamics of protein molecules.

  12. Double-maximum enhancement of signal-to-noise ratio gain via stochastic resonance and vibrational resonance.

    PubMed

    Duan, Fabing; Chapeau-Blondeau, François; Abbott, Derek

    2014-08-01

    This paper studies the signal-to-noise ratio (SNR) gain of a parallel array of nonlinear elements that transmits a common input composed of a periodic signal and external noise. Aiming to further enhance the SNR gain, each element is injected with internal noise components or high-frequency sinusoidal vibrations. We report that the SNR gain exhibits two maxima at different values of the internal noise level or of the sinusoidal vibration amplitude. For the addition of internal noise to an array of threshold-based elements, the condition for occurrence of stochastic resonance is analytically investigated in the limit of weak signals. Interestingly, when the internal noise components are replaced by high-frequency sinusoidal vibrations, the SNR gain displays the vibrational multiresonance phenomenon. In both considered cases, there are certain regions of the internal noise intensity or the sinusoidal vibration amplitude wherein the achieved maximal SNR gain can be considerably beyond unity for a weak signal buried in non-Gaussian external noise. Due to the easy implementation of sinusoidal vibration modulation, this approach is potentially useful for improving the output SNR in an array of nonlinear devices. PMID:25215715

  13. Photoproduction of π0 mesons off neutrons in the nucleon resonance region.

    PubMed

    Dieterle, M; Keshelashvili, I; Ahrens, J; Annand, J R M; Arends, H J; Bantawa, K; Bartolome, P A; Beck, R; Bekrenev, V; Braghieri, A; Branford, D; Briscoe, W J; Brudvik, J; Cherepnya, S; Demissie, B; Downie, E J; Drexler, P; Fil'kov, L V; Fix, A; Glazier, D I; Hamilton, D; Heid, E; Hornidge, D; Howdle, D; Huber, G M; Jaegle, I; Jahn, O; Jude, T C; Käser, A; Kashevarov, V L; Kondratiev, R; Korolija, M; Kruglov, S P; Krusche, B; Kulbardis, A; Lisin, V; Livingston, K; MacGregor, I J D; Maghrbi, Y; Mancell, J; Manley, D M; Marinides, Z; Martinez, M; McGeorge, J C; McNicoll, E; Mekterovic, D; Metag, V; Micanovic, S; Middleton, D G; Mushkarenkov, A; Nefkens, B M K; Nikolaev, A; Novotny, R; Oberle, M; Ostrick, M; Oussena, B; Pedroni, P; Pheron, F; Polonski, A; Prakhov, S N; Robinson, J; Rosner, G; Rostomyan, T; Schumann, S; Sikora, M H; Sober, D; Starostin, A; Supek, I; Thiel, M; Thomas, A; Unverzagt, M; Watts, D P; Werthmüller, D; Witthauer, L

    2014-04-11

    Precise angular distributions have been measured for the first time for the photoproduction of π0 mesons off neutrons bound in the deuteron. The effects from nuclear Fermi motion have been eliminated by a complete kinematic reconstruction of the final state. The influence of final-state-interaction effects has been estimated by a comparison of the reaction cross section for quasifree protons bound in the deuteron to the results for free protons and then applied as a correction to the quasifree neutron data. The experiment was performed at the tagged photon facility of the Mainz Microtron MAMI with the Crystal Ball and TAPS detector setup for incident photon energies between 0.45 and 1.4 GeV. The results are compared to the predictions from reaction models and partial-wave analyses based on data from other isospin channels. The model predictions show large discrepancies among each other and the present data will provide much tighter constraints. This is demonstrated by the results of a new analysis in the framework of the Bonn-Gatchina coupled-channel analysis which included the present data. PMID:24765945

  14. Investigations of the Space Parity Violation and Interference Effects in the Fragment Angular Distributions of 235U, 233U, and 239Pu Fission by Resonance Neutrons

    NASA Astrophysics Data System (ADS)

    Sokolov, V. E.; Gagarski, A. M.; Guseva, I. S.; Golosovskaya, S. P.; Krasnoshchokova, I. S.; Petrov, G. A.; Petrova, V. I.; Petukhov, A. K.; Pleva, Yu. S.; Alfimenkov, V. P.; Chernikov, A. N.; Lason, L.; Mareev, Yu. D.; Novitski, V. V.; Pikelner, L. B.; Pikelner, T. L.; Tsulaya, M. I.

    2005-05-01

    Investigations of the space parity nonconserving (PNC) asymmetry of 233U, 235U, and 239Pu fission fragment emission and parity conserving (PC) interference effects of left-right and forward-backward asymmetries were carried out on the neutron beams of the reactor IBR-30 (JINR, Dubna) over the range of neutron energies from 0.02 eV to about 100 eV. All experimental results obtained have been found to be in a good mutual accordance within the frames of modern theoretical conceptions about the mechanisms of PNC and PC effects forming in fission process induced by slow neutrons. In case of the P-even interference effects of asymmetry the evident mutual well-marked irregularities in their neutron energy dependencies up to about 100 eV were observed. It is connected with the interference of s, p-resonances at fission compound stage according to modern theory. As a remarkable result of the PNC effect measurements the resonance behavior of the PNC asymmetry coefficients in the low neutron energy region (En < 2 eV) was observed. Unfortunately, the statistical accuracy of the PNC effect measurements is not enough for observation of these resonance effects in other cases of more high energies. Results of simultaneous analysis of all three asymmetry effects for all three nuclei are presented. The satisfactory combined description of the experimental points is received. As a result of theoretical evaluation of these data main parameters and the estimates of nuclear matrix elements of the weak interaction for some p-resonances in the low energy range were extracted.

  15. Magnetic field enriched surface enhanced resonance Raman spectroscopy for early malaria diagnosis

    NASA Astrophysics Data System (ADS)

    Yuen, Clement; Liu, Quan

    2012-01-01

    Hemozoin is a by-product of malaria infection in erythrocytes, which has been explored as a biomarker for early malaria diagnosis. We report magnetic field-enriched surface-enhanced resonance Raman spectroscopy (SERRS) of β--hematin crystals, which are the equivalent of hemozoin biocrystals in spectroscopic features, by using magnetic nanoparticles with iron oxide core and silver shell (Fe3O4@Ag). The external magnetic field enriches β--hematin crystals and enhances the binding between β--hematin crystals and magnetic nanoparticles, which provides further improvement in SERRS signals. The magnetic field-enriched SERRS signal of β--hematin crystals shows approximately five orders of magnitude enhancement in the resonance Raman signal, in comparison to about three orders of magnitude improvement in the SERRS signal without the influence of magnetic field. The improvement has led to a β--hematin detection limit at a concentration of 5 nM (roughly equivalent to 30 parasites/μl at the early stages of malaria infection), which demonstrates the potential of magnetic field-enriched SERRS technique in early malaria diagnosis.

  16. Dual V-type resonators to enhance beam quality of Yb:YAG thin-disk lasers.

    PubMed

    Kazemi, Shahram; Mahdieh, Mohammad Hossein; Aghaie, Mohammad

    2016-04-01

    In this paper, the operating characteristics of a Yb:YAG thin-disk laser using double V-type resonators are reported. The laser maintained stable performance by independently activating either the main or the auxiliary V-type resonator depending on the pumping laser power. Experimental investigations revealed that by reducing the dynamic range in which the main resonator was used for stability and instead employing the auxiliary resonator, the laser beam quality factor M2 could be reduced from 40.2 to 32.3, representing a beam quality enhancement of approximately 20%. PMID:27139657

  17. Application of polarized neutron reflectometry and x-ray resonant magnetic reflectometry for determining the inhomogeneous magnetic structure in Fe/Gd multilayers.

    SciTech Connect

    Kravtsov, E. A.; Haskel, D.; te Velthuis, S. G. E.; Jiang, J. S.; Kirby, B. J.

    2010-01-01

    The evolution of the magnetic structure of multilayer [Fe (35 {angstrom})/Gd (50 {angstrom}){sub 5}] with variation in temperature and an applied magnetic field was determined using a complementary approach combining polarized neutron and X-ray resonant magnetic reflectometry. Self-consistent simultaneous analysis of X-ray and neutron spectra allowed us to determine the elemental and depth profiles in the multilayer structure with unprecedented accuracy, including the identification of an inhomogeneous intralayer magnetic structure with near-atomic resolution.

  18. Utilizing resonant magnetic perturbations to enhance neoclassical tearing mode stabilization by rf current

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoguang; Zhang, Xiaodong; Yu, Qingquan; Wu, Bin; Zhu, Sizheng; Wang, Jinfang; Zhang, Yang; Wang, Xiaojing

    2015-09-01

    A new method to stabilize the rotating neoclassical tearing mode (NTM) by using both the rf current drive and the static resonant magnetic perturbation (RMP) is investigated. When a non-uniform mode rotation is induced by the RMP, the stabilization of NTM by the rf current is found to be enhanced if the RMP phase has a half period difference from that of the rf wave deposition along the helical angle. The required rf current for mode stabilization is reduced by about one third if an appropriate RMP amplitude is applied.

  19. New electronic states of NH and ND observed by resonance enhanced multiphoton ionization spectroscopy

    NASA Technical Reports Server (NTRS)

    Johnson, Russell D., III; Hudgens, Jeffrey W.

    1990-01-01

    Resonance Enhanced MultiPhoton Ionization (REMPI) spectra of NH and ND, which reveal four new electronic states are presented. Transitions from NH a 1 delta to 3s and 3p Rydberg states in both NH and ND have been observed and rotationally analyzed. The transitions were observed in the wavelength range of 258 to 288 nm. The state assignments are: e 1 pi (3s sigma) at 82857/cm, f 1 pi (3p sigma) at 86378/cm, g 1 delta (3p pi) at 88141/cm and h 1 sigma (3p pi) at 89151/cm.

  20. Resonance enhanced laser mass spectrometry for process- and environmental-analysis: Applications and perspectives

    NASA Astrophysics Data System (ADS)

    Zimmermann, Ralf; Heger, Hans Jörg; Dorfner, Ralph; Boesl, Ulrich; Kettrup, Antonius

    1998-12-01

    Laser induced Resonance-Enhanced Multi-Photon Ionization Time-Of-Flight Mass Spectrometry (REMPI TOFMS) is a highly selective as well as sensitive analytical technique, well suited for species selective, on-line monitoring of trace-substances. In this contribution some analytical applications of a mobile REMPI-TOFMS are presented. This includes REMPI-TOMS on-line analysis of coffee roasting gas and waste incineration flue gas as well as headspace measurements of pulp processing lye or rapid analysis of polycyclic aromatic hydrocarbons from soil samples via thermal desorption.

  1. Resonance enhanced laser mass spectrometry for process- and environmental-analysis: Applications and perspectives

    SciTech Connect

    Zimmermann, Ralf; Dorfner, Ralph; Kettrup, Antonius; Heger, Hans Joerg; Boesl, Ulrich

    1998-12-16

    Laser induced Resonance-Enhanced Multi-Photon Ionization Time-Of-Flight Mass Spectrometry (REMPI TOFMS) is a highly selective as well as sensitive analytical technique, well suited for species selective, on-line monitoring of trace-substances. In this contribution some analytical applications of a mobile REMPI-TOFMS are presented. This includes REMPI-TOMS on-line analysis of coffee roasting gas and waste incineration flue gas as well as headspace measurements of pulp processing lye or rapid analysis of polycyclic aromatic hydrocarbons from soil samples via thermal desorption.

  2. Resonance

    NASA Astrophysics Data System (ADS)

    Perozzi, E.; Murdin, P.

    2000-11-01

    A resonance in CELESTIAL MECHANICS occurs when some of the quantities characterizing the motion of two or more celestial bodies can be considered as commensurable, i.e. their ratio is close to an integer fraction. In a simplified form, this can be expressed as ...

  3. Spin disorder in maghemite nanoparticles investigated using polarized neutrons and nuclear resonant scattering

    NASA Astrophysics Data System (ADS)

    Herlitschke, M.; Disch, S.; Sergueev, I.; Schlage, K.; Wetterskog, E.; Bergström, L.; Hermann, R. P.

    2016-04-01

    The manuscript reports the investigation of spin disorder in maghemite nanoparticles of different shape by a combination of polarized small-angle neutron scattering (SANSPOL) and nuclear forward scattering (NFS) techniques. Both methods are sensitive to magnetization on the nanoscale. SANSPOL allows for investigation of the particle morphology and spatial magnetization distribution and NFS extends this nanoscale information to the atomic scale, namely the orientation of the hyperfine field experienced by the iron nuclei. The studied nanospheres and nanocubes with diameters of 7.4 nm and 10.6 nm, respectively, exhibit a significant spin disorder. This effect leads to a reduction of the magnetization to 44% and 58% of the theoretical maghemite bulk value, observed consistently by both techniques.

  4. Spin disorder in maghemite nanoparticles investigated using polarized neutrons and nuclear resonant scattering

    DOE PAGESBeta

    Herlitschke, Marcus; Disch, Sabrina; Sergueev, I.; Schlage, Kai; Wetterskog, Erik; Bergstrom, Lennart; Hermann, Raphael P.

    2016-01-01

    The manuscript reports the investigation of spin disorder in maghemite nanoparticles of different shape by a combination of polarized small-angle neutron scattering (SANSPOL) and nuclear forward scattering (NFS) techniques. Both methods are sensitive to magnetization on the nanoscale. SANSPOL allows for investigation of the particle morphology and spatial magnetization distribution and NFS extends this nanoscale information to the atomic scale, namely the orientation of the hyperfine field experienced by the iron nuclei. The studied nanospheres and nanocubes with diameters of 7.4nm and 10.6 nm, respectively, exhibit a significant spin disorder. This effect leads to a reduction of the magnetization tomore » 44% and 58% of the theoretical maghemite bulk value, observed consistently by both techniques.« less

  5. Progesterone and testosterone studies by neutron scattering and nuclear magnetic resonance methods and quantum chemistry calculations

    NASA Astrophysics Data System (ADS)

    Szyczewski, A.; Hołderna-Natkaniec, K.; Natkaniec, I.

    2004-05-01

    Inelastic incoherent neutron scattering spectra of progesterone and testosterone measured at 20 and 290 K were compared with the IR spectra measured at 290 K. The Phonon Density of States spectra display well resolved peaks of low frequency internal vibration modes up to 1200 cm -1. The quantum chemistry calculations were performed by semiempirical PM3 method and by the density functional theory method with different basic sets for isolated molecule, as well as for the dimer system of testosterone. The proposed assignment of internal vibrations of normal modes enable us to conclude about the sequence of the onset of the torsion movements of the CH 3 groups. These conclusions were correlated with the results of proton molecular dynamics studies performed by NMR method. The GAUSSIAN program had been used for calculations.

  6. Spin disorder in maghemite nanoparticles investigated using polarized neutrons and nuclear resonant scattering

    SciTech Connect

    Herlitschke, Marcus; Disch, Sabrina; Sergueev, I.; Schlage, Kai; Wetterskog, Erik; Bergstrom, Lennart; Hermann, Raphael P.

    2016-01-01

    The manuscript reports the investigation of spin disorder in maghemite nanoparticles of different shape by a combination of polarized small-angle neutron scattering (SANSPOL) and nuclear forward scattering (NFS) techniques. Both methods are sensitive to magnetization on the nanoscale. SANSPOL allows for investigation of the particle morphology and spatial magnetization distribution and NFS extends this nanoscale information to the atomic scale, namely the orientation of the hyperfine field experienced by the iron nuclei. The studied nanospheres and nanocubes with diameters of 7.4nm and 10.6 nm, respectively, exhibit a significant spin disorder. This effect leads to a reduction of the magnetization to 44% and 58% of the theoretical maghemite bulk value, observed consistently by both techniques.

  7. Effects of Resonance in Quasi-periodic Oscillators of Neutron Star Binaries

    NASA Astrophysics Data System (ADS)

    Titarchuk, Lev

    2002-10-01

    Using a large quantity of Rossi X-Ray Timing Explorer data presented in the literature, I offer a detailed investigation into the accuracy of the quasi-periodic oscillation (QPO) frequency determination. The QPO phenomenon seen in X-ray binaries is possibly a result of the resonance of the intrinsic (eigen) oscillations and harmonic driving forces of the system. I show that the resonances, in the presence of the damping of oscillations, occur at frequencies that are systematically and randomly shifted with respect to the eigenfrequencies of the system. The shift value strongly depends on the damping rate that is measured by the half-width of the QPO feature. Taking into account this effect, I analyze the QPO data for four Z sources, Scorpius X-1, GX 340+0, GX 5-1, and GX 17+2, and two atoll sources, 4U 1728-34 and 4U 0614+09. The transition-layer model (TLM) predicts the existence of the invariant quantity δ, an inclination angle of the magnetospheric axis with respect to the normal to the disk. I calculate δ and the error bars of δ using the resonance shift, and I find that the inferred δ-values are consistent with constants for these four Z sources, in which horizontal-branch oscillation and kilohertz frequencies have been detected and correctly identified. It is shown that the inferred δ are in the range between 5.5d and 6.5d. I conclude that the TLM seems to be compatible with the data.

  8. Electrical noise modulates perception of electrical pulses in humans: sensation enhancement via stochastic resonance.

    PubMed

    Iliopoulos, Fivos; Nierhaus, Till; Villringer, Arno

    2014-03-01

    Although noise is usually considered to be harmful for signal detection and information transmission, stochastic resonance (SR) describes the counterintuitive phenomenon of noise enhancing the detection and transmission of weak input signals. In mammalian sensory systems, SR-related phenomena may arise both in the peripheral and the central nervous system. Here, we investigate behavioral SR effects of subliminal electrical noise stimulation on the perception of somatosensory stimuli in humans. We compare the likelihood to detect near-threshold pulses of different intensities applied on the left index finger during presence vs. absence of subliminal noise on the same or an adjacent finger. We show that (low-pass) noise can enhance signal detection when applied on the same finger. This enhancement is strong for near-threshold pulses below the 50% detection threshold and becomes stronger when near-threshold pulses are applied as brief trains. The effect reverses at pulse intensities above threshold, especially when noise is replaced by subliminal sinusoidal stimulation, arguing for a peripheral direct current addition. Unfiltered noise applied on longer pulses enhances detection of all pulse intensities. Noise applied to an adjacent finger has two opposing effects: an inhibiting effect (presumably due to lateral inhibition) and an enhancing effect (most likely due to SR in the central nervous system). In summary, we demonstrate that subliminal noise can significantly modulate detection performance of near-threshold stimuli. Our results indicate SR effects in the peripheral and central nervous system. PMID:24353303

  9. Neutron Imaging Developments at LANSCE

    NASA Astrophysics Data System (ADS)

    Nelson, Ron; Hunter, James; Schirato, Richard; Vogel, Sven; Swift, Alicia; Ickes, Tim; Ward, Bill; Losko, Adrian; Tremsin, Anton

    2015-10-01

    Neutron imaging is complementary to x-ray imaging because of its sensitivity to light elements and greater penetration of high-Z materials. Energy-resolved neutron imaging can provide contrast enhancements for elements and isotopes due to the variations with energy in scattering cross sections due to nuclear resonances. These cross section differences exist due to compound nuclear resonances that are characteristic of each element and isotope, as well as broader resonances at higher energies. In addition, multi-probe imaging, such as combined photon and neutron imaging, is a powerful tool for discerning properties and features in materials that cannot be observed with a single probe. Recently, we have demonstrated neutron imaging, both radiography and computed tomography, using the moderated (Lujan Center) and high-energy (WNR facility) neutron sources at LANSCE. Flat panel x-ray detectors with suitable scintillator-converter screens provide good sensitivity for both low and high neutron energies. Micro-Channel-Plate detectors and iCCD scintillator camera systems that provide the fast time gating needed for energy-resolved imaging have been demonstrated as well. Examples of recent work will be shown including fluid flow in plants and imaging through dense thick objects. This work is funded by the US Department of Energy, National Nuclear Security Administration, and performed by Los Alamos National Security LLC under Contract DE-AC52-06NA25396.

  10. Enhancement of squeezing in resonance fluorescence of a driven quantum dot close to a graphene sheet

    NASA Astrophysics Data System (ADS)

    Fang, Wei; Wu, Qing-lin; Wu, Shao-ping; Li, Gao-xiang

    2016-05-01

    We investigate squeezing of the resonance fluorescence of a laser-driven quantum dot (QD) close to a graphene sheet. The coupling between the QD and the surface plasmon around the graphene sheet is frequency dependent in the terahertz region, which can be adjusted by the laser intensity. Distinct decay rates in different transition channels of dressed QDs can be achieved due to the tailored photon reservoir, which can be used to improve the squeezing. It is found that increases in both the dephasing rate and the environmental temperature are harmful to the squeezing. Meanwhile, an enhancement in the QD-plasmon coupling strength may reduce the fragility of squeezing against the decoherence process. Additionally, in the strong light-matter coupling region, squeezing can be largely enhanced by tuning the strength of the pump field and its detuning from the QD.

  11. Enhancement of VUV and EUV generation by field-controlled resonance structures of diatomic molecules

    NASA Astrophysics Data System (ADS)

    Heslar, John; Telnov, Dmitry A.; Chu, Shih-I.

    2016-06-01

    Below- and near-threshold harmonic generation provides a potential approach to achieve a high conversion efficiency of vacuum-ultraviolet and extreme-ultraviolet sources for the advancement of spectroscopy. Here, we perform a time-dependent density functional theory study for the nonperturbative treatment of below- and near-threshold harmonic generation of CO and N2 diatomic molecules subject to short near-infrared laser pulses and aligned parallel to the laser field polarization. We find that with the use of different driving laser pulse shapes, we can control and enhance harmonic generation through the excited-state resonance structures. Depending on the pulse shape, the enhancement can reach five to seven orders of magnitude as compared to the reference sine-squared laser pulse of the same duration. The results for different driving laser intensities are also presented and discussed in detail.

  12. Resonance-enhanced two-photon ionization of ions by Lyman alpha radiation in gaseous nebulae.

    PubMed

    Johansson, S; Letokhov, V

    2001-01-26

    One of the mysteries of nebulae in the vicinity of bright stars is the appearance of bright emission spectral lines of ions, which imply fairly high excitation temperatures. We suggest that an ion formation mechanism, based on resonance-enhanced two-photon ionization (RETPI) by intense H Lyman alpha radiation (wavelength of 1215 angstroms) trapped inside optically thick nebulae, can produce these spectral lines. The rate of such an ionization process is high enough for rarefied gaseous media where the recombination rate of the ions formed can be 10(-6) to 10(-8) per second for an electron density of 10(3) to 10(5) per cubic centimeter in the nebula. Under such conditions, the photo-ions formed may subsequently undergo further RETPI, catalyzed by intense He i and He ii radiation, which also gets enhanced in optically thick nebulae that contain enough helium. PMID:11158669

  13. Selective enhancement of topologically induced interface states in a dielectric resonator chain

    PubMed Central

    Poli, Charles; Bellec, Matthieu; Kuhl, Ulrich; Mortessagne, Fabrice; Schomerus, Henning

    2015-01-01

    The recent realization of topological phases in insulators and superconductors has advanced the search for robust quantum technologies. The prospect to implement the underlying topological features controllably has given incentive to explore optical platforms for analogous realizations. Here we realize a topologically induced defect state in a chain of dielectric microwave resonators and show that the functionality of the system can be enhanced by supplementing topological protection with non-hermitian symmetries that do not have an electronic counterpart. We draw on a characteristic topological feature of the defect state, namely, that it breaks a sublattice symmetry. This isolates the state from losses that respect parity-time symmetry, which enhances its visibility relative to all other states both in the frequency and in the time domain. This mode selection mechanism naturally carries over to a wide range of topological and parity-time symmetric optical platforms, including couplers, rectifiers and lasers. PMID:25833814

  14. Ultrasensitive Biosensors Using Enhanced Fano Resonances in Capped Gold Nanoslit Arrays

    NASA Astrophysics Data System (ADS)

    Lee, Kuang-Li; Huang, Jhih-Bin; Chang, Jhih-Wei; Wu, Shu-Han; Wei, Pei-Kuen

    2015-02-01

    Nanostructure-based sensors are capable of sensitive and label-free detection for biomedical applications. However, plasmonic sensors capable of highly sensitive detection with high-throughput and low-cost fabrication techniques are desirable. We show that capped gold nanoslit arrays made by thermal-embossing nanoimprint method on a polymer film can produce extremely sharp asymmetric resonances for a transverse magnetic-polarized wave. An ultrasmall linewidth is formed due to the enhanced Fano coupling between the cavity resonance mode in nanoslits and surface plasmon resonance mode on periodic metallic surface. With an optimal slit length and width, the full width at half-maximum bandwidth of the Fano mode is only 3.68 nm. The wavelength sensitivity is 926 nm/RIU for 60-nm-width and 1,000-nm-period nanoslits. The figure of merit is up to 252. The obtained value is higher than the theoretically estimated upper limits of the prism-coupling SPR sensors and the previously reported record high figure-of-merit in array sensors. In addition, the structure has an ultrahigh intensity sensitivity up to 48,117%/RIU.

  15. Ultrasensitive Biosensors Using Enhanced Fano Resonances in Capped Gold Nanoslit Arrays

    PubMed Central

    Lee, Kuang-Li; Huang, Jhih-Bin; Chang, Jhih-Wei; Wu, Shu-Han; Wei, Pei-Kuen

    2015-01-01

    Nanostructure-based sensors are capable of sensitive and label-free detection for biomedical applications. However, plasmonic sensors capable of highly sensitive detection with high-throughput and low-cost fabrication techniques are desirable. We show that capped gold nanoslit arrays made by thermal-embossing nanoimprint method on a polymer film can produce extremely sharp asymmetric resonances for a transverse magnetic-polarized wave. An ultrasmall linewidth is formed due to the enhanced Fano coupling between the cavity resonance mode in nanoslits and surface plasmon resonance mode on periodic metallic surface. With an optimal slit length and width, the full width at half-maximum bandwidth of the Fano mode is only 3.68 nm. The wavelength sensitivity is 926 nm/RIU for 60-nm-width and 1,000-nm-period nanoslits. The figure of merit is up to 252. The obtained value is higher than the theoretically estimated upper limits of the prism-coupling SPR sensors and the previously reported record high figure-of-merit in array sensors. In addition, the structure has an ultrahigh intensity sensitivity up to 48,117%/RIU. PMID:25708955

  16. Resonant enhancement of the transversal Kerr effect in the InMnAs layers

    NASA Astrophysics Data System (ADS)

    Gan'shina, E. A.; Golik, L. L.; Kovalev, V. I.; Kun'kova, Z. E.; Temiryazev, A. G.; Danilov, Yu A.; Vikhrova, O. V.; Zvonkov, B. N.; Rubacheva, A. D.; Tcherbak, P. N.; Vinogradov, A. N.; Zhigalina, O. M.

    2010-10-01

    Spectral dependences of the transversal Kerr effect (TKE) as well as of the real and imaginary parts of the permittivity of InMnAs layers were studied. Pulsed laser ablation of Mn and InAs targets was used to form the layers on GaAs(100) substrates. Spectra of the optical constants and TKE depended substantially on layer fabrication conditions and testified to the presence of MnAs inclusions in the samples. The cross-sectional transmission electron microscopy revealed the presence of inclusions of size 10-40 nm in the layers. At room temperature a strong resonant band was observed in the TKE spectra of the InMnAs layers in the energy range of 0.5-2.2 eV. In this band the TKE was comparable in magnitude but opposite in sign to that in the strong ferromagnetic MnAs. The resonant character of the TKE spectra was explained by excitation of surface plasmons in the MnAs nanoclusters embedded in the InMnAs semiconductor host. Modelling the TKE spectra for (InAs)1 - X:(MnAs)X nanocomposites in the effective-medium approximation (Maxwell-Garnett approximation) confirmed the assumption on the plasmon mechanism of the resonant enhancement of the transversal Kerr effect in the InMnAs layers.

  17. Ultrasensitive biosensors using enhanced Fano resonances in capped gold nanoslit arrays.

    PubMed

    Lee, Kuang-Li; Huang, Jhih-Bin; Chang, Jhih-Wei; Wu, Shu-Han; Wei, Pei-Kuen

    2015-01-01

    Nanostructure-based sensors are capable of sensitive and label-free detection for biomedical applications. However, plasmonic sensors capable of highly sensitive detection with high-throughput and low-cost fabrication techniques are desirable. We show that capped gold nanoslit arrays made by thermal-embossing nanoimprint method on a polymer film can produce extremely sharp asymmetric resonances for a transverse magnetic-polarized wave. An ultrasmall linewidth is formed due to the enhanced Fano coupling between the cavity resonance mode in nanoslits and surface plasmon resonance mode on periodic metallic surface. With an optimal slit length and width, the full width at half-maximum bandwidth of the Fano mode is only 3.68 nm. The wavelength sensitivity is 926 nm/RIU for 60-nm-width and 1,000-nm-period nanoslits. The figure of merit is up to 252. The obtained value is higher than the theoretically estimated upper limits of the prism-coupling SPR sensors and the previously reported record high figure-of-merit in array sensors. In addition, the structure has an ultrahigh intensity sensitivity up to 48,117%/RIU. PMID:25708955

  18. Resonantly enhanced electron-positron pair production in ultra-intense laser-matter interaction

    NASA Astrophysics Data System (ADS)

    Fillion-Gourdeai, Francois; Lorin, Emmanuel; Bandrauk, Andre

    2013-05-01

    A new mechanism for pair production from the interaction of a laser with two nuclei is presented. The latter takes advantage of the Stark effect in diatomic molecules and the presence of molecular resonances in the negative and positive energy continua. Both move in the complex energy plane as the interatomic distance and the electric field strength are varied. We demonstrate that there is an enhancement of pair production at the crossing of these resonances. This mechanism is studied in a very simple one-dimensional model where the nuclei are modelled by delta function potential wells and the laser by a constant electric field. The position of resonances is evaluated by using the Weyl-Titchmarch-Kodaira theory, which allows to treat singular boundary value problems and to compute the spectral density. The rate of producing pairs is also computed. It is shown that this process yields a positron production rate which is approximately an order of magnitude higher than in the single nucleus case and a few orders of magnitudes higher than Schwinger's tunnelling result in a static field.

  19. Plasma mediated off-resonance plasmonic enhanced ultrafast laser-induced nanocavitation.

    PubMed

    Boulais, Etienne; Lachaine, Rémi; Meunier, Michel

    2012-09-12

    The generation of nanobubbles around plasmonic nanostructures is an efficient approach for imaging and therapy, especially in the field of cancer research. We show a novel method using infrared femtosecond laser that generates ≈800 nm bubbles around off-resonance gold nanospheres using 200 mJ/cm(2) 45 fs pulses. We present experimental and theoretical work that demonstrate that the nanobubble formation results from the generation of a nanoscale plasma around the particle due to the enhanced near-field rather than from the heating of the particle. Energy absorbed in the nanoplasma is indeed more than 11 times the energy absorbed in the particle. When compared to the usual approach that uses nanosecond laser to induce the extreme heating of in-resonance nanoparticles to initiate bubble formation, our off-resonance femtosecond technique is shown to bring many advantages, including avoiding the particles fragmentation, working in the optical window of biological material and using the deposited energy more efficiently. PMID:22845691

  20. Constraints on the neutron skin and symmetry energy from the anti-analog giant dipole resonance in 208Pb

    NASA Astrophysics Data System (ADS)

    Cao, Li-Gang; Roca-Maza, X.; Colò, G.; Sagawa, H.

    2015-09-01

    We investigate the impact of the neutron skin thickness, Δ Rn p , on the energy difference between the anti-analog giant dipole resonance (AGDR), EAGDR, and the isobaric analog state (IAS), EIAS, in a heavy nucleus such as 208Pb. For guidance, we first develop a simple and analytic, yet physical, approach based on the droplet model that linearly connects the energy difference EAGDR-EIAS with Δ Rn p . To test this correlation on more fundamental grounds, we employ a family of systematically varied Skyrme energy density functionals where variations on the value of the symmetry energy at saturation density J are explored. The calculations have been performed within the fully self-consistent Hartree-Fock (HF) plus charge-exchange random phase approximation (RPA) framework. We confirm the linear correlation within our microscopic approach and we can compare our results with available experimental data in 208Pb in order to extract a preferred value for Δ Rn p and, in turn, for the symmetry energy parameters. Averaging the results from two available experimental data, our analysis gives Δ Rn p = 0.236 ±0.018 fm, J = 33.2 ±1.0 MeV, and a slope parameter of the symmetry energy at saturation L = 97.3 ±11.2 MeV. The errors include the experimental uncertainties and a lower-limit estimate of model uncertainties. These results are consistent with those extracted from different experimental data albeit L and Δ Rn p are somewhat large when compared to previous estimations based on giant resonance studies. Possible hints whether model dependence can explain this difference are provided.

  1. The role of plasmonic resonance in enhancement of interaction of light and silver nanostructures in fluorescence

    NASA Astrophysics Data System (ADS)

    Guo, Shy-Haugh

    Plasmonic resonant coupling in noble metallic nanostructures to incident radiation and the related subject of localized behavior of electromagnetic waves are currently of great interest due to their potential application to biosensing, chemical sensing, optical transmission, and nanophotonic devices. In this thesis we present the results of experimental investigations and numerical calculations on nanometer-sized metallic structure enhanced fluorescence (nMEF). These investigations are carried out with silver nanostructures fabricated by two different methods: e-beam lithography (top down) and spray pyrolysis (bottom up). By fabrication of arrays of nanoparticles with varying shape, size, and inter-particle spacing, we determine the dependence of fluorescence enhancement on these critical dimensions and locate the optimum configuration for fluorescence enhancement for a given molecule and excitation wavelength. For practical applications, especially for rapid sensor fabrication, we then repeat the nMEF measurement with size-selected Ag nanoparticles produced with a spray pyrolysis instrument equipped with differential mobility analyzer (DMA), basing our choice of particle size and average spacing (˜coverage(-0.5) on the findings from our results on electron-beam lithographically patterned structures. To explore the role of particle plasmons in fluorescence enhancement quantitatively we compared the plasmon resonance frequencies for rod-shaped nanoparticles vs. width-to-length aspect ratios, with the shape which produces the optimum enhancement for a particular excitation/fluorescent-emission-peak frequency/polarization combination. In further experiments we measured fluorescence from two dimensional metallic stripes, with systematically-varying widths and spacings, both with and without an underlying noble metallic film. Finally, to probe the effect of the substrate, we compared fluorescence measurements in the absence of metal nanoparticles over oxide

  2. A new model for Overhauser enhanced nuclear magnetic resonance using nitroxide radicals

    NASA Astrophysics Data System (ADS)

    Armstrong, Brandon D.; Han, Songi

    2007-09-01

    Nitroxide free radicals are the most commonly used source for dynamic nuclear polarization (DNP) enhanced nuclear magnetic resonance (NMR) experiments and are also exclusively employed as spin labels for electron spin resonance (ESR) spectroscopy of diamagnetic molecules and materials. Nitroxide free radicals have been shown to have strong dipolar coupling to H1 in water, and thus result in large DNP enhancement of H1 NMR signal via the well known Overhauser effect. The fundamental parameter in a DNP experiment is the coupling factor, since it ultimately determines the maximum NMR signal enhancements which can be achieved. Despite their widespread use, measurements of the coupling factor of nitroxide free radicals have been inconsistent, and current models have failed to successfully explain our experimental data. We found that the inconsistency in determining the coupling factor arises from not taking into account the characteristics of the ESR transitions, which are split into three (or two) lines due to the hyperfine coupling of the electron to the N14 nuclei (or N15) of the nitric oxide radical. Both intermolecular Heisenberg spin exchange interactions as well as intramolecular nitrogen nuclear spin relaxation mix the three (or two) ESR transitions. However, neither effect has been taken into account in any experimental studies on utilizing or quantifying the Overhauser driven DNP effects. The expected effect of Heisenberg spin exchange on Overhauser enhancements has already been theoretically predicted and observed by Bates and Drozdoski [J. Chem. Phys. 67, 4038 (1977)]. Here, we present a new model for quantifying Overhauser enhancements through nitroxide free radicals that includes both effects on mixing the ESR hyperfine states. This model predicts the maximum saturation factor to be considerably higher by the effect of nitrogen nuclear spin relaxation. Because intramolecular nitrogen spin relaxation is independent of the nitroxide concentration, this

  3. Enhancing the sensitivity of localized surface plasmon resonance (LSPR) biosensors using nanorods and DNA aptamers

    NASA Astrophysics Data System (ADS)

    Chuang, Po-Chun; Liao, Pei-Chen; Chen, Yih-Fan

    2015-03-01

    Localized surface plasmon resonance (LSPR) biosensors have drawn much attention for their promising application in point-of-care diagnostics. While surface plasmon resonance (SPR) biosensing systems have been well developed, LSPR systems have the advantages of simpler and more compact setups. The LSPR peak shifts caused by the binding of molecules to the LSPR substrates, however, are usually smaller than 1 nm if no signal amplification mechanism is used. When using nanoparticles to enhance the sensitivity of LSPR biosensors, because of the short field penetration depth, the nanoparticles should be very close to the LSPR substrate to induce significant shifts in the LSPR peak position. In this study, we used DNA aptamers and gold nanorods to significantly increase the change in the LSPR peak position with the concentration of the target molecules. We have successfully used the proposed mechanism to detect 0.1 nM interferongamma (IFN-γ), a biomarker related to the diagnosis of latent tuberculosis infection. The calibration curves obtained in pure buffers and serum-containing buffers show that accurate detection can be achieved even when the sample is from complex biological fluids such as serum. Because of the enhancement in the sensitivity by the proposed sensing scheme, it is possible to use a low-cost spectrometer to build a LSPR biosensing system.

  4. Dispersion curve-based sensitivity engineering for enhanced surface plasmon resonance detection

    NASA Astrophysics Data System (ADS)

    El-Gohary, Sherif H.; Eom, Seyoung; Lee, Soo Yeol; Byun, Kyung Min

    2016-07-01

    Manipulation of dispersion curve for enhancing surface plasmon resonance (SPR) detection is proposed. Based on strong correlation between slope of dispersion curve and SPR angle shift, it is confirmed that dispersion curve characteristics can be employed as an analysis tool to evaluate SPR sensor performance and to predict anomalous plasmonic behaviors. Complicated resonance shift in SPR angle, especially in the presence of metallic nanograting, such as negative shift, can be controlled reliably by engineering the dispersion curve. As it has a dependence on geometrical parameters of metallic films and gratings, dispersion relation engineering is also useful in optimizing the sensor sensitivity. For a wavelength of λ=630 nm, introduction of a gold nanograting shows a significant improvement in sensitivity by more than 5 times, compared to a traditional thin-film-based SPR structure. In addition, we find that use of a longer wavelength in near-infrared region can be advantageous for avoiding a negative SPR shift and obtaining a narrow and deep SPR curve. Our approach is expected to extend the applicability of dispersion-based sensitivity engineering technique to a variety of SPR platforms for highly enhanced SPR detection.

  5. Modulating the Morphology of Gold Graphitic Nanocapsules for Plasmon Resonance-Enhanced Multimodal Imaging.

    PubMed

    Lai, Xiao-Fang; Zou, Yu-Xiu; Wang, Shan-Shan; Zheng, Meng-Jie; Hu, Xiao-Xiao; Liang, Hao; Xu, Yi-Ting; Wang, Xue-Wei; Ding, Ding; Chen, Long; Chen, Zhuo; Tan, Weihong

    2016-05-17

    With their unique optical properties and distinct Raman signatures, graphitic nanomaterials can serve as substrates for surface-enhanced Raman spectroscopy (SERS) or provide signal amplification for bioanalysis and detection. However, a relatively weak Raman signal has limited further biomedical applications. This has been addressed by encapsulating gold nanorods (AuNRs) in a thin graphitic shell to form gold graphitic nanocapsules. This step improves plasmon resonance, which enhances Raman intensity, and has the potential for integrating two-photon luminescence (TPL) imaging capability. However, changing the morphology of gold graphitic nanocapsules such that high quality and stability are achieved remains a challenge. To address this task, we herein report a confinement chemical vapor deposition (CVD) method to prepare the construction of AuNR-encapsulated graphitic nanocapsules with these properties. Specifically, through morphological modulation, we (1) achieved higher plasmon resonance with near-IR incident light, thus achieving greater Raman intensity, and (2) successfully integrated two-photon luminescence dual-modal (Raman/TPL) bioimaging capabilities. Cancer-cell-specific aptamers were further modified on the AuNR@G graphitic surface through simple, but strong, π-π interactions to achieve imaging selectivity through differential cancer cell recognition. PMID:27089383

  6. Resonantly enhanced method for generation of tunable, coherent vacuum-ultraviolet radiation

    DOEpatents

    Glownia, J.H.; Sander, R.K.

    1982-06-29

    Carbon Monoxide vapor is used to generate coherent, tunable vacuum ultraviolet radiation by third-harmonic generation using a single tunable dye laser. The presence of a nearby electronic level resonantly enhances the nonlinear susceptibility of this molecule allowing efficient generation of the vuv light at modest pump laser intensities, thereby reducing the importance of a six-photon multiple-photon ionization process which is also resonantly enhanced by the same electronic level but no higher order. By choosing the pump radiation wavelength to be of shorter wavelength than individual vibronic levels used to extend tunability stepwise from 154.4 to 124.6 nm, and the intensity to be low enough, multiple-photon ionization can be eliminated. Excitation spectra of the third-harmonic emission output exhibit shifts to shorter wavelength and broadening with increasing CO pressure due to phase matching effects. Increasing the carbon monoxide pressure, therefore, allows the substantial filling in of gaps arising from the stepwise tuning thereby providing almost continuous tunability over the quoted range of wavelength emitted.

  7. Enhanced antibody recognition with a magneto-optic surface plasmon resonance (MO-SPR) sensor.

    PubMed

    Manera, Maria Grazia; Ferreiro-Vila, Elías; Garcia-Martin, José Miguel; Garcia-Martin, Antonio; Rella, Roberto

    2014-08-15

    A comparison between sensing performance of traditional SPR (Surface Plasmon Resonance) and magneto-optic SPR (MOSPR) transducing techniques is presented in this work. MOSPR comes from an evolution of traditional SPR platform aiming at modulating Surface Plasmon wave by the application of an external magnetic field in transverse configuration. Previous work demonstrated that, when the Plasmon resonance is excited in these structures, the external magnetic field induces a modification of the coupling of the incident light with the Surface Plasmon Polaritons (SPP). Besides, these structures can lead to an enhancement in the magneto-optical (MO) activity when the SPP is excited. This phenomenon is exploited in this work to demonstrate the possibility to use the enhanced MO signal as proper transducer signal for investigating biomolecular interactions in liquid phase. To this purpose, the transducer surface was functionalized by thiol chemistry and used for recording the binding between Bovine Serum Albumin molecules immobilized onto the surface and its complementary target. Higher sensing performance in terms of sensitivity and lower limit of detection of the MOSPR biosensor with respect to traditional SPR sensors is demonstrated. PMID:24632137

  8. Enhancement of second-harmonic generation in nonlinear nanolaminate metamaterials by nanophotonic resonances.

    PubMed

    Hsiao, Hui-Hsin; Abass, Aimi; Fischer, Johannes; Alaee, Rasoul; Wickberg, Andreas; Wegener, Martin; Rockstuhl, Carsten

    2016-05-01

    Nanolaminate metamaterials recently attracted a lot of attention as a novel second-order nonlinear material that can be used in integrated photonic circuits. Here, we explore theoretically and numerically the opportunity to enhance the nonlinear response from such nanolaminates by exploiting Fano resonances supported in grating-coupled waveguides. The enhancement factor of the radiated second harmonic signal compared to a flat nanolaminate can reach values as large as 35 for gold gratings and even 7000 for MgF2 gratings. For the MgF2 grating, extremely high-Q Fano resonances are excited in such all-dielectric system that result in strong local fields in the nonlinear waveguide layer to boost the nonlinear conversion. A significant portion of the nonlinear signal is also strongly coupled to a dark waveguide mode, which remains guided in the nanolaminate. The strong excitation of a dark mode at the second harmonic frequency provides a viable method for utilizing second-order nonlinearities for light generation and manipulation in integrated photonic circuits. PMID:27137578

  9. Dynamic contrast-enhanced magnetic resonance imaging of the sarcopenic muscle

    PubMed Central

    Nicolato, Elena; Farace, Paolo; Asperio, Roberto M; Marzola, Pasquina; Lunati, Ernesto; Sbarbati, Andrea; Osculati, Francesco

    2002-01-01

    Background Studies about capillarity of the aged muscle provided conflicting results and no data are currently available about the magnetic resonance imaging (MRI) in vivo characteristics of the microvascular bed in aged rats. We have studied age-related modifications of the skeletal muscle by in vivo T2-relaxometry and dynamic contrast-enhanced magnetic resonance imaging (CE-MRI) at high field intensity (4.7 T). The aim of the work was to test the hypothesis that the ageing process involves microvessels in skeletal muscle. Methods The study was performed in 4-month-old (n = 6) and 20-month-old (n = 6) rats. Results At MRI examination, the relaxation time T2 of the gastrocnemius muscle showed no significant difference between these two groups. The kinetic of contrast penetration in the tissue showed that in 4-month-old rats the enhancement values of the signal intensity at different time-points were significantly higher than those found in senescent rats. Conclusion The reported finding suggests that there is a modification of the microcirculatory function in skeletal muscle of aged rats. This work also demonstrates that CE-MRI allows for an in vivo quantification of the multiple biological processes involving the skeletal muscle during aging. Therefore, CE-MRI could represent a further tool for the follow up of tissue modification and therapeutic intervention both in patients with sarcopenia and in experimental models of this pathology. PMID:12049675

  10. Mapping prefrontal circuits in vivo with manganese-enhanced magnetic resonance imaging in monkeys.

    PubMed

    Simmons, Janine M; Saad, Ziad S; Lizak, Martin J; Ortiz, Michael; Koretsky, Alan P; Richmond, Barry J

    2008-07-23

    Manganese-enhanced magnetic resonance imaging (MEMRI) provides a powerful tool to study multisynaptic circuits in vivo and thereby to link information about neural structure and function within individual subjects. Making the best use of MEMRI in monkeys requires minimizing manganese-associated neurotoxicity, maintaining sensitivity to manganese-dependent signal changes and mapping transport throughout the brain without a priori anatomical hypotheses. Here, we performed intracortical injections of isotonic MnCl(2), comparisons of preinjection and postinjection scans, and voxelwise statistical mapping. Isotonic MnCl(2) did not cause cell death at the injection site, damage to downstream targets of manganese transport, behavioral deficits, or changes in neuronal responsiveness. We detected and mapped manganese transport throughout cortical-subcortical circuits by using voxelwise statistical comparisons of at least 10 preinjection and two postinjection scans. We were able to differentiate between focal and diffuse projection fields and to distinguish between the topography of striatal projections from orbitofrontal and anterior cingulate cortex in a single animal. This MEMRI approach provides a basis for combining circuit-based anatomical analyses with simultaneous single-unit recordings and/or functional magnetic resonance imaging in individual monkeys. Such studies will enhance our interpretations of functional data and our understanding of how neuronal activity is transformed as it propagates through a circuit. PMID:18650340

  11. Resonantly enhanced method for generation of tunable, coherent vacuum ultraviolet radiation

    DOEpatents

    Glownia, James H.; Sander, Robert K.

    1985-01-01

    Carbon Monoxide vapor is used to generate coherent, tunable vacuum ultraviolet radiation by third-harmonic generation using a single tunable dye laser. The presence of a nearby electronic level resonantly enhances the nonlinear susceptibility of this molecule allowing efficient generation of the vuv light at modest pump laser intensities, thereby reducing the importance of a six-photon multiple-photon ionization process which is also resonantly enhanced by the same electronic level but to higher order. By choosing the pump radiation wavelength to be of shorter wavelength than individual vibronic levels used to extend tunability stepwise from 154.4 to 124.6 nm, and the intensity to be low enough, multiple-photon ionization can be eliminated. Excitation spectra of the third-harmonic emission output exhibit shifts to shorter wavelength and broadening with increasing CO pressure due to phase matching effects. Increasing the carbon monoxide pressure, therefore, allows the substantial filling in of gaps arising from the stepwise tuning thereby providing almost continuous tunability over the quoted range of wavelength emitted.

  12. Ultrafast dynamics of near-field enhancements at an off-resonance nano-dimer via femtosecond laser excitations

    NASA Astrophysics Data System (ADS)

    Du, GuangQing; Yang, Qing; Chen, Feng; Bian, Hao; Wu, Yanmin; Lu, Yu; Farooq, Umar; Hou, Xun

    2015-04-01

    Giant electric-field enhancements localized on nano-antennas are important for the optical near-field applications in fields such as super-resolution imaging, near-field optical tweezers, and photothermal therapy. Physically, the field enhancement requires plasmon resonance with respect to structure matching. We report a tunable near-field effect, including localized electric-field enhancement and resistive heating at an off-resonance Au nano-sphere dimer via femtosecond laser irradiation. The near field was strongly modified (up to 81 times) with respect to time evolution at a laser fluence of 0.1 \\text{J/cm}2 . The results are explained as thermal dynamics manipulation of the Au nano-sphere dimer plasmon resonances. This study provides a new alternative route to tailoring the near-field enhancement for wide applications in nano-antennas.

  13. K{sub S} Lambda Photoproduction On The Neutron Within The Resonance Region

    SciTech Connect

    Taylor, Charles E.; Cole, Philip L.

    2014-01-01

    We report some preliminary differential cross section results for the gammad --> K{sub S} Lambda(p) reaction using a circularly-polarized photon beam and an unpolarized LD{sub 2} target. The data was collected at the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab. For this study the photon energy ranged from 1.3 to 2.53 GeV, which covers from the reaction threshold through the nucleon resonance regimes. The acceptance- and flux-corrected yields show peaks at the center-of mass energies W = 1.7 and W = 1.9 GeV. These first-time results will aid in unraveling the spectrum of non-strange excited baryons.

  14. Overall picture of the cascade gamma decay of neutron resonances within a modified practical model

    NASA Astrophysics Data System (ADS)

    Sukhovoj, A. M.; Mitsyna, L. V.; Jovancevic, N.

    2016-05-01

    The intensities of two-step cascades in 43 nuclei of mass number in the range of 28 ≤ A ≤ 200 were approximated to a high degree of precision within a modified version of the practical cascade-gammadecay model introduced earlier. In this version, the rate of the decrease in the model-dependent density of vibrational levels has the same value for any Cooper pair undergoing breakdown. The most probable values of radiative strength functions both for E1 and for M1 transitions are determined by using one or two peaks against a smooth model dependence on the gamma-transition energy. The statement that the thresholds for the breaking of Cooper pairs are higher for spherical than for deformed nuclei is a basic result of the respective analysis. The parameters of the cascade-decay process are now determined to a precision that makes it possible to observe the systematic distinctions between them for nuclei characterized by different parities of neutrons and protons.

  15. Localized surface plasmon resonances in nanostructures to enhance nonlinear vibrational spectroscopies: towards an astonishing molecular sensitivity

    PubMed Central

    2014-01-01

    Summary Vibrational transitions contain some of the richest fingerprints of molecules and materials, providing considerable physicochemical information. Vibrational transitions can be characterized by different spectroscopies, and alternatively by several imaging techniques enabling to reach sub-microscopic spatial resolution. In a quest to always push forward the detection limit and to lower the number of needed vibrational oscillators to get a reliable signal or imaging contrast, surface plasmon resonances (SPR) are extensively used to increase the local field close to the oscillators. Another approach is based on maximizing the collective response of the excited vibrational oscillators through molecular coherence. Both features are often naturally combined in vibrational nonlinear optical techniques. In this frame, this paper reviews the main achievements of the two most common vibrational nonlinear optical spectroscopies, namely surface-enhanced sum-frequency generation (SE-SFG) and surface-enhanced coherent anti-Stokes Raman scattering (SE-CARS). They can be considered as the nonlinear counterpart and/or combination of the linear surface-enhanced infrared absorption (SEIRA) and surface-enhanced Raman scattering (SERS) techniques, respectively, which are themselves a branching of the conventional IR and spontaneous Raman spectroscopies. Compared to their linear equivalent, those nonlinear vibrational spectroscopies have proved to reach higher sensitivity down to the single molecule level, opening the way to astonishing perspectives for molecular analysis. PMID:25551056

  16. MnDPDP enhanced magnetic resonance imaging of focal liver lesions.

    PubMed

    King, L J; Burkill, G J C; Scurr, E D; Vlavianos, P; Murray-Lyons, I; Healy, J C

    2002-12-01

    Mangafodipir trisodium (MnDPDP) is a contrast agent for use in magnetic resonance imaging (MRI) of the liver. The agent is taken up by normal hepatocytes resulting in increased signal on T1-weighted imaging, and is excreted in the biliary system. Hepatocyte-containing liver neoplasms such as hepatomas or focal nodular hyperplasia (FNH), take up MnDPDP and demonstrate varying degrees of enhancement. Metastatic liver deposits and primary liver tumours of non-hepatocyte origin do not typically enhance with MnDPDP thus increasing their conspicuity compared with pre-contrast T1-weighted images. Metastases may demonstrate rim enhancement particularly on delayed imaging at 24 h, which can increase their conspicuity, thus allowing better visualization of small lesions. Functional biliary obstruction due to liver metastases can also result in wedge shaped areas of parenchymal enhancement. The MRI features of various focal liver after continuance with lesions following MnDPDP are discussed and illustrated including primary lesions such as hepatoma and secondary metastases. PMID:12475527

  17. Late gadolinium enhanced cardiovascular magnetic resonance of lamin A/C gene mutation related dilated cardiomyopathy

    PubMed Central

    2011-01-01

    Background The purpose of this study was to identify early features of lamin A/C gene mutation related dilated cardiomyopathy (DCM) with cardiovascular magnetic resonance (CMR). We characterise myocardial and functional findings in carriers of lamin A/C mutation to facilitate the recognition of these patients using this method. We also investigated the connection between myocardial fibrosis and conduction abnormalities. Methods Seventeen lamin A/C mutation carriers underwent CMR. Late gadolinium enhancement (LGE) and cine images were performed to evaluate myocardial fibrosis, regional wall motion, longitudinal myocardial function, global function and volumetry of both ventricles. The location, pattern and extent of enhancement in the left ventricle (LV) myocardium were visually estimated. Results Patients had LV myocardial fibrosis in 88% of cases. Segmental wall motion abnormalities correlated strongly with the degree of enhancement. Myocardial enhancement was associated with conduction abnormalities. Sixty-nine percent of our asymptomatic or mildly symptomatic patients showed mild ventricular dilatation, systolic failure or both in global ventricular analysis. Decreased longitudinal systolic LV function was observed in 53% of patients. Conclusions Cardiac conduction abnormalities, mildly dilated LV and depressed systolic dysfunction are common in DCM caused by a lamin A/C gene mutation. However, other cardiac diseases may produce similar symptoms. CMR is an accurate tool to determine the typical cardiac involvement in lamin A/C cardiomyopathy and may help to initiate early treatment in this malignant familiar form of DCM. PMID:21689390

  18. Liver metastases: Contrast-enhanced ultrasound compared with computed tomography and magnetic resonance.

    PubMed

    Cantisani, Vito; Grazhdani, Hektor; Fioravanti, Cristina; Rosignuolo, Maria; Calliada, Fabrizio; Messineo, Daniela; Bernieri, Maria Giulia; Redler, Adriano; Catalano, Carlo; D'Ambrosio, Ferdinando

    2014-08-01

    The development of ultrasound contrast agents with excellent tolerance and safety profiles has notably improved liver evaluation with ultrasound (US) for several applications, especially for the detection of metastases. In particular, contrast enhanced ultrasonography (CEUS) allows the display of the parenchymal microvasculature, enabling the study and visualization of the enhancement patterns of liver lesions in real time and in a continuous manner in all vascular phases, which is similar to contrast-enhanced computed tomography (CT) and contrast-enhanced magnetic resonance imaging. Clinical studies have reported that the use of a contrast agent enables the visualization of more metastases with significantly improved sensitivity and specificity compared to baseline-US. Furthermore, studies have shown that CEUS yields sensitivities comparable to CT. In this review, we describe the state of the art of CEUS for detecting colorectal liver metastases, the imaging features, the literature reports of metastases in CEUS as well as its technique, its clinical role and its potential applications. Additionally, the updated international consensus panel guidelines are reported in this review with the inherent limitations of this technique and best practice experiences. PMID:25110428

  19. Contrast-Enhanced Magnetic Resonance Imaging in Pediatric Patients: Review and Recommendations for Current Practice

    PubMed Central

    Bhargava, Ravi; Hahn, Gabriele; Hirsch, Wolfgang; Kim, Myung-Joon; Mentzel, Hans-Joachim; Olsen, Øystein E.; Stokland, Eira; Triulzi, Fabio; Vazquez, Elida

    2013-01-01

    Magnetic resonance imaging (MRI), frequently with contrast enhancement, is the preferred imaging modality for many indications in children. Practice varies widely between centers, reflecting the rapid pace of change and the need for further research. Guide-line changes, for example on contrast-medium choice, require continued practice reappraisal. This article reviews recent developments in pediatric contrast-enhanced MRI and offers recommendations on current best practice. Nine leading pediatric radiologists from internationally recognized radiology centers convened at a consensus meeting in Bordeaux, France, to discuss applications of contrast-enhanced MRI across a range of indications in children. Review of the literature indicated that few published data provide guidance on best practice in pediatric MRI. Discussion among the experts concluded that MRI is preferred over ionizing-radiation modalities for many indications, with advantages in safety and efficacy. Awareness of age-specific adaptations in MRI technique can optimize image quality. Gadolinium-based contrast media are recommended for enhancing imaging quality. The choice of most appropriate contrast medium should be based on criteria of safety, tolerability, and efficacy, characterized in age-specific clinical trials and personal experience. PMID:25114547

  20. Highly enhanced green emission from InGaN quantum wells due to surface plasmon resonance on aluminum films

    SciTech Connect

    Tateishi, Kazutaka; Okamoto, Koichi Tamada, Kaoru; Funato, Mitsuru; Kawakami, Yoichi

    2015-03-23

    Photoluminescence (PL) from InGaN/GaN quantum wells was highly enhanced by the surface plasmon (SP) resonance on aluminum thin films. The enhancement ratio of green emission reached 80, which was much larger than the previously reported enhancements on silver films. The resulting large enhancement should be attributed to an ∼20-fold enhancement of the excitation efficiency and ∼4-fold enhancement of the emission efficiency by the excitation and emission spectra. The temperature dependence of the PL intensities and the time-resolved PL measurements were also performed to understand the detailed mechanism. We concluded that the resonance between the excitation light and the SP on the Al surface should improve the excitation efficiency, i.e., the light absorption efficiency. This result suggests that the Al films have an extraordinary photon confinement effect, which are unique properties of plasmonics with Al and should be useful for new and wider applications.

  1. Neutron Resonance Transmission Analysis (NRTA): A Nondestructive Assay Technique for the Next Generation Safeguards Initiative’s Plutonium Assay Challenge

    SciTech Connect

    J. W. Sterbentz; D. L. Chichester

    2010-12-01

    This is an end-of-year report for a project funded by the National Nuclear Security Administration's Office of Nuclear Safeguards (NA-241). The goal of this project is to investigate the feasibility of using Neutron Resonance Transmission Analysis (NRTA) to assay plutonium in commercial light-water-reactor spent fuel. This project is part of a larger research effort within the Next-Generation Safeguards Initiative (NGSI) to evaluate methods for assaying plutonium in spent fuel, the Plutonium Assay Challenge. The first-year goals for this project were modest and included: 1) developing a zero-order MCNP model for the NRTA technique, simulating data results presented in the literature, 2) completing a preliminary set of studies investigating important design and performance characteristics for the NRTA measurement technique, and 3) documentation of this work in an end of the year report (this report). Research teams at Los Alamos National Laboratory (LANL), Lawrence Berkeley National Laboratory (LBNL), Pacific Northwest National Laboratory (PNNL), and at several universities are also working to investigate plutonium assay methods for spent-fuel safeguards. While the NRTA technique is well proven in the scientific literature for assaying individual spent fuel pins, it is a newcomer to the current NGSI efforts studying Pu assay method techniques having just started in March 2010; several analytical techniques have been under investigation within this program for two to three years or more. This report summarizes a nine month period of work.

  2. Enhanced detection of rolling element bearing fault based on stochastic resonance

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaofei; Hu, Niaoqing; Cheng, Zhe; Hu, Lei

    2012-11-01

    Early bearing faults can generate a series of weak impacts. All the influence factors in measurement may degrade the vibration signal. Currently, bearing fault enhanced detection method based on stochastic resonance(SR) is implemented by expensive computation and demands high sampling rate, which requires high quality software and hardware for fault diagnosis. In order to extract bearing characteristic frequencies component, SR normalized scale transform procedures are presented and a circuit module is designed based on parameter-tuning bistable SR. In the simulation test, discrete and analog sinusoidal signals under heavy noise are enhanced by SR normalized scale transform and circuit module respectively. Two bearing fault enhanced detection strategies are proposed. One is realized by pure computation with normalized scale transform for sampled vibration signal, and the other is carried out by designed SR hardware with circuit module for analog vibration signal directly. The first strategy is flexible for discrete signal processing, and the second strategy demands much lower sampling frequency and less computational cost. The application results of the two strategies on bearing inner race fault detection of a test rig show that the local signal to noise ratio of the characteristic components obtained by the proposed methods are enhanced by about 50% compared with the band pass envelope analysis for the bearing with weaker fault. In addition, helicopter transmission bearing fault detection validates the effectiveness of the enhanced detection strategy with hardware. The combination of SR normalized scale transform and circuit module can meet the need of different application fields or conditions, thus providing a practical scheme for enhanced detection of bearing fault.

  3. FUNDAMENTAL AREAS OF PHENOMENOLOGY (INCLUDING APPLICATIONS): Theoretical Investigation of Coherent Enhancement for Resonant Two-Photon Transitions

    NASA Astrophysics Data System (ADS)

    Zhang, Shi-An; Wang, Zu-Geng; Sun, Zhen-Rong

    2008-06-01

    We theoretically investigate the coherent enhancement of resonant two-photon transitions (TPT) in a three-level atomic system. The TPT can be coherently enhanced by modulating spectral amplitude due to eliminating the destructive interference, though partial laser energy losses. Maximal enhancement of TPT can be achieved by modulating spectral phase due to establishing completely constructive interference. Our research provides a theoretical basis for experimental investigation and appears to have potential application on coherent control in the complicated quantum system.

  4. Hollow Au/Ag nanostars displaying broad plasmonic resonance and high surface-enhanced Raman sensitivity

    NASA Astrophysics Data System (ADS)

    Garcia-Leis, Adianez; Torreggiani, Armida; Garcia-Ramos, Jose Vicente; Sanchez-Cortes, Santiago

    2015-08-01

    Bimetallic Au/Ag hollow nanostar (HNS) nanoparticles with different morphologies were prepared in this work. These nanoplatforms were obtained by changing the experimental conditions (concentration of silver and chemical reductors, hydroxylamine and citrate) and by using Ag nanostars as template nanoparticles (NPs) through galvanic replacement. The goal of this research was to create bimetallic Au/Ag star-shaped nanoparticles with advanced properties displaying a broader plasmonic resonance, a cleaner exposed surface, and a high concentration of electromagnetic hot spots on the surface provided by the special morphology of nanostars. The size, shape, and composition of Ag as well as their optical properties were studied by extinction spectroscopy, hyperspectral dark field microscopy, transmission and scanning electron microscopy (TEM and SEM), and energy dispersive X-ray spectroscopy (EDX). Finally, the surface-enhanced Raman scattering (SERS) activity of these HNS was investigated by using thioflavin T, a biomarker of the β-amyloid fibril formation, responsible for Alzheimer's disease. Lucigenin, a molecule displaying different SERS activities on Au and Ag, was also used to explore the presence of these metals on the NP surface. Thus, a relationship between the morphology, plasmon resonance and SERS activity of these new NPs was made.Bimetallic Au/Ag hollow nanostar (HNS) nanoparticles with different morphologies were prepared in this work. These nanoplatforms were obtained by changing the experimental conditions (concentration of silver and chemical reductors, hydroxylamine and citrate) and by using Ag nanostars as template nanoparticles (NPs) through galvanic replacement. The goal of this research was to create bimetallic Au/Ag star-shaped nanoparticles with advanced properties displaying a broader plasmonic resonance, a cleaner exposed surface, and a high concentration of electromagnetic hot spots on the surface provided by the special morphology of nanostars

  5. Measurement of nitric oxide concentrations in flames by using electronic-resonance-enhanced coherent anti-Stokes Raman scattering.

    PubMed

    Kulatilaka, Waruna D; Chai, Ning; Naik, Sameer V; Laurendeau, Normand M; Lucht, Robert P; Kuehner, Joel P; Roy, Sukesh; Gord, James R

    2006-11-15

    We have measured nitric oxide (NO) concentrations in flames by using electronic-resonance-enhanced coherent anti-Stokes Raman spectroscopy (ERE-CARS). Visible pump and Stokes beams were tuned to a Q-branch vibrational Raman resonance of NO. A UV probe beam was tuned into resonance with specific rotational transitions in the (v"=1,v'=0) vibrational band in the A(2)Sigma(+)-X(2)Pi electronic transition, thus providing a substantial electronic-resonance enhancement of the resulting CARS signal. NO concentrations were measured at levels down to 50 parts in 10(6) in H(2)/air flames at atmospheric pressure. NO was also detected in heavily sooting C(2)H(2)/air flames at atmospheric pressure with minimal background interference. PMID:17072422

  6. Resonant Pedestal Pressure Reduction Induced by a Thermal Transport Enhancement due to Stochastic Magnetic Boundary Layers in High Temperature Plasmas

    SciTech Connect

    Schmitz, O.; Evans, T.E.; Fenstermacher, M. E.; Unterberg, E. A.; Austin, M. E.; Bray, B. D.; Brooks, N. H.; Frerichs, H.; Groth, M.; Jakubowski, M. W.; Lasnier, C. J.; Lehnen, M.; Leonard, A. W.; Mordijck, S.; Moyer, R.A.; Osborne, T. H.; Reiter, D.; Samm, U.; Schaffer, M. J.; Unterberg, B.; West, W. P.

    2009-01-01

    Good alignment of the magnetic field line pitch angle with the mode structure of an external resonant magnetic perturbation (RMP) field is shown to induce modulation of the pedestal electron pressure p(e) in high confinement high rotation plasmas at the DIII-D tokamak with a shape similar to ITER, the next step tokamak experiment. This is caused by an edge safety factor q(95) resonant enhancement of the thermal transport, while in contrast, the RMP induced particle pump out does not show a significant resonance. The measured p(e) reduction correlates to an increase in the modeled stochastic layer width during pitch angle variations matching results from resistive low rotation plasmas at the TEXTOR tokamak. These findings suggest a field line pitch angle resonant formation of a stochastic magnetic edge layer as an explanation for the q(95) resonant character of type-I edge localized mode suppression by RMPs.

  7. Resonant Pedestal Pressure Reduction Induced by a Thermal Transport Enhancement due to Stochastic Magnetic Boundary Layers in High Temperature Plasmas

    SciTech Connect

    Schmitz, O.; Frerichs, H.; Lehnen, M.; Reiter, D.; Samm, U.; Unterberg, B.; Evans, T. E.; Austin, M. E.; Bray, B. D.; Brooks, N. H.; Leonard, A. W.; Osborne, T. H.; Schaffer, M. J.; West, W. P.; Fenstermacher, M. E.; Groth, M.; Lasnier, C. J.; Unterberg, E. A.; Jakubowski, M. W.; Mordijck, S.

    2009-10-16

    Good alignment of the magnetic field line pitch angle with the mode structure of an external resonant magnetic perturbation (RMP) field is shown to induce modulation of the pedestal electron pressure p{sub e} in high confinement high rotation plasmas at the DIII-D tokamak with a shape similar to ITER, the next step tokamak experiment. This is caused by an edge safety factor q{sub 95} resonant enhancement of the thermal transport, while in contrast, the RMP induced particle pump out does not show a significant resonance. The measured p{sub e} reduction correlates to an increase in the modeled stochastic layer width during pitch angle variations matching results from resistive low rotation plasmas at the TEXTOR tokamak. These findings suggest a field line pitch angle resonant formation of a stochastic magnetic edge layer as an explanation for the q{sub 95} resonant character of type-I edge localized mode suppression by RMPs.

  8. Measurement of sub threshold resonance contributions to fusion reactions: the case of the 13C(α, n)16O astrophysical neutron source

    NASA Astrophysics Data System (ADS)

    La Cognata, M.; Spitaleri, C.; Trippella, O.; Kiss, G. G.; Rogachev, G. V.; Mukhamedzhanov, A. M.; Avila, M.; Guardo, G. L.; Koshchiy, E.; Kuchera, A.; Lamia, L.; Puglia, S. M. R.; Romano, S.; Santiago, D.; Spartà, R.

    2015-01-01

    The 13C(α, n)16O reaction is the neutron source for the main component of the s-process. It is is active inside the helium-burning shell of asymptotic giant branch stars, at temperatures ≲ 108 K. In this temperature region, corresponding to an energy interval of 140 - 230 keV, the 13C(α, n)16O cross section is dominated by the -3 keV sub-threshold resonance due to the 6.356 MeV level in 17O. Direct measurements could not establish its contribution owing to the Coulomb barrier between interacting nuclei, strongly reducing the cross section at astrophysical energies. Similarly, indirect measurements and extrapolations yielded inconsistent results, calling for further investigations. The Trojan Horse Method was applied to the 13C(6Li, n16O)d quasi-free reaction to access the low as well as the negative energy region of the 13C(α, n)16O reaction. By using the generalized R-matrix approach, the asymptotic normalization coefficient (C˜17O(1/2+)α13C)2 of the 6.356 MeV level was deduced. For the first time, the Trojan Horse Method and the asymptotic normalization coefficient were used in synergy. Our indirect approach lead to (C˜17O(1/2+)α13C)2 = 7.7-1.5+1.6 fm-1, slightly larger than the values in the literature, determining a 13C(α, n)16O reaction rate slightly larger than the one in the literature at temperatures lower than 108 K, with enhanced accuracy.

  9. Impact of a low-energy enhancement in the gamma-ray strength function on the neutron-capture cross section

    SciTech Connect

    Larsen, A. C.; Goriely, S.

    2010-07-15

    A low-energy enhancement of the gamma-ray strength function in several light and medium-mass nuclei has been observed recently in {sup 3}He-induced reactions. The effect of this enhancement on (n,gamma) cross sections is investigated for stable and unstable neutron-rich Fe, Mo, and Cd isotopes. Our results indicate that the radiative neutron capture cross sections may increase considerably due to the low-energy enhancement when approaching the neutron drip line. This could have non-negligible consequences on r-process nucleosynthesis calculations.

  10. Impact of the plasmonic near- and far-field resonance-energy shift on the enhancement of infrared vibrational signals.

    PubMed

    Vogt, Jochen; Huck, Christian; Neubrech, Frank; Toma, Andrea; Gerbert, David; Pucci, Annemarie

    2015-09-01

    We report on the impact of the differing spectral near- and far-field properties of resonantly excited gold nanoantennas on the vibrational signal enhancement in surface-enhanced infrared absorption (SEIRA). The knowledge on both spectral characteristics is of considerable importance for the optimization of plasmonic nanostructures for surface-enhanced spectroscopy techniques. From infrared micro-spectroscopic measurements, we simultaneously obtain spectral information on the plasmonic far-field response and, via SEIRA spectroscopy of a test molecule, on the near-field enhancement. The molecular test layer of 4,4'-bis(N-carbazolyl)-1,1'-biphenyl (CBP) was deposited on the surface of gold nanoantennas with different lengths and thus different far-field resonance energies. We carefully studied the Fano-type vibrational lines in a broad spectral window, in particular, how the various vibrational signals are enhanced in relation to the ratio of the far-field plasmonic resonance and the molecular vibrational frequencies. As a detailed experimental proof of former simulation studies, we show the clearly red-shifted maximum SEIRA enhancement compared to the far-field resonance. PMID:25516198

  11. Distinguishing S-plus-minus and S-plus-plus electron pairing symmetries by neutron spin resonances in superconducting Sodium-Iron-Cobalt-Arsenic (transitional temperature = 18 Kelvin)

    SciTech Connect

    Das, Tanmoy; Balatsky, Alexander V.; Zhang, Chenglin; Li, Haifeng; Su, Yiki; Nethertom, Tucker; Redding, Caleb; Carr, Scott; Schneidewind, Astrid; Faulhaber, Enrico; Li, Shiliang; Yao, Daoxin; Bruckel, Thomas; Dai, Pengchen; Sobolev, Oleg

    2012-06-05

    A determination of the superconducting (SC) electron pairing symmetry forms the basis for establishing a microscopic mechansim for superconductivity. For iron pnictide superconductors, the s{sup {+-}}-pairing symmetry theory predicts the presence of a sharp neutron spin resonance at an energy below the sum of hole and electron SC gap energies (E {le} 2{Delta}). Although the resonances have been observed for various iron pnictide superconductors, they are broad in energy and can also be interpreted as arising from the s{sup ++}-pairing symmetry with E {ge} 2{Delta}. Here we use inelastic neutron scattering to reveal a sharp resonance at E = 7 meV in the SC NaFe{sub 0.935}Co{sub 0.045}As (T{sub c} = 18 K). By comparing our experiments with calculated spin-excitations spectra within the s{sup {+-}} and s{sup ++}-pairing symmetries, we conclude that the resonance in NaFe{sub 0.935}Co{sub 0.045}As is consistent with the s{sup {+-}}-pairing symmetry, thus eliminating s{sup ++}-pairing symmetry as a candidate for superconductivity.

  12. Digital neutron image enhancement based on total variation-based ℓ0 minimization

    NASA Astrophysics Data System (ADS)

    Qiao, Shuang; Bai, Guanying; Sun, Jianing

    2016-01-01

    For the digital neutron radiography applications, low contrast is inevitable due to the neutron and photon statistics limited or high transmission (and low attenuation) in the sample. In this paper, we introduce a total variation-based ℓ0 minimization model and solve it by an alternating minimization approach. The proposed model is applied to base & detail decomposition for the dynamic range modification and detail magnification. Experimental results on several real neutron images are presented to demonstrate the effectiveness of the proposed method.

  13. Enhanced surface plasmon resonance on a smooth silver film with a seed growth layer.

    PubMed

    Liu, Hong; Wang, Bing; Leong, Eunice S P; Yang, Ping; Zong, Yun; Si, Guangyuan; Teng, Jinghua; Maier, Stefan A

    2010-06-22

    This paper reports an effective method to enhance the surface plasmon resonance (SPR) on Ag films by using a thin Ni seed layer assisted deposition. Ag films with a thickness of about 50 nm were deposited by electron beam evaporation above an ultrathin Ni seed layer of approximately 2 nm on both silicon and quartz substrates. The root-mean-square (rms) surface roughness and the correlation length have been reduced from >4 nm and 28 nm for a pure Ag film to approximately 1.3 and 19 nm for Ag/Ni films, respectively. Both experimental and simulation results show that the Ag/Ni films exhibit an enhanced SPR over the pure Ag film with a narrower full width at half-maximum. Ag films with a Ge seed layer have also been prepared under the same conditions. The surface roughness can be reduced to less than 0.7 nm, but narrowing of the SPR curve is not observed due to increased absorptive damping in the Ge seed layer. Our results show that Ni acts as a roughness-diminishing growth layer for the Ag film while at the same time maintaining and enhancing the plasmonic properties of the combined structures. This points toward its use for low-loss plasmonic devices and optical metamaterials applications. PMID:20515054

  14. Label-Enhanced Surface Plasmon Resonance: A New Concept for Improved Performance in Optical Biosensor Analysis

    PubMed Central

    Granqvist, Niko; Hanning, Anders; Eng, Lars; Tuppurainen, Jussi; Viitala, Tapani

    2013-01-01

    Surface plasmon resonance (SPR) is a well-established optical biosensor technology with many proven applications in the study of molecular interactions as well as in surface and material science. SPR is usually applied in the label-free mode which may be advantageous in cases where the presence of a label may potentially interfere with the studied interactions per se. However, the fundamental challenges of label-free SPR in terms of limited sensitivity and specificity are well known. Here we present a new concept called label-enhanced SPR, which is based on utilizing strongly absorbing dye molecules in combination with the evaluation of the full shape of the SPR curve, whereby the sensitivity as well as the specificity of SPR is significantly improved. The performance of the new label-enhanced SPR method was demonstrated by two simple model assays: a small molecule assay and a DNA hybridization assay. The small molecule assay was used to demonstrate the sensitivity enhancement of the method, and how competitive assays can be used for relative affinity determination. The DNA assay was used to demonstrate the selectivity of the assay, and the capabilities in eliminating noise from bulk liquid composition variations. PMID:24217357

  15. Wavelength-selective emitters with pyramid nanogratings enhanced by multiple resonance modes

    NASA Astrophysics Data System (ADS)

    Nguyen-Huu, Nghia; Pištora, Jaromír; Cada, Michael

    2016-04-01

    Binary gratings with high or low metal filling ratios in a grating region have been demonstrated as successful candidates in enhancing the emittance of emitters for thermophotovoltaics since they could support surface plasmons (SPs), the Rayleigh-Wood anomaly (RWA), or cavity resonance (CR) within their geometries. This work shows that combining a tungsten binary grating with a low and high filling ratio to form a pyramid grating can significantly increase the emittance, which is nearly perfect in the wavelength region from 0.6 to 1.72 μm, while being 0.1 at wavelengths longer than 2.5 μm. Moreover, the emittance spectrum of the hybrid tungsten grating is insensitive to the angle of incidence. The enhancement demonstrated by magnetic field and Poynting vector patterns is due to the interplay between SPs and RWA modes at short wavelengths, and CR at long wavelengths. Furthermore, a combined grating made of nickel is also proposed providing enhanced emittance in a wide angle of incidence.

  16. Wavelength-selective emitters with pyramid nanogratings enhanced by multiple resonance modes.

    PubMed

    Nguyen-Huu, Nghia; Pištora, Jaromír; Cada, Michael

    2016-04-15

    Binary gratings with high or low metal filling ratios in a grating region have been demonstrated as successful candidates in enhancing the emittance of emitters for thermophotovoltaics since they could support surface plasmons (SPs), the Rayleigh-Wood anomaly (RWA), or cavity resonance (CR) within their geometries. This work shows that combining a tungsten binary grating with a low and high filling ratio to form a pyramid grating can significantly increase the emittance, which is nearly perfect in the wavelength region from 0.6 to 1.72 μm, while being 0.1 at wavelengths longer than 2.5 μm. Moreover, the emittance spectrum of the hybrid tungsten grating is insensitive to the angle of incidence. The enhancement demonstrated by magnetic field and Poynting vector patterns is due to the interplay between SPs and RWA modes at short wavelengths, and CR at long wavelengths. Furthermore, a combined grating made of nickel is also proposed providing enhanced emittance in a wide angle of incidence. PMID:26938942

  17. Resonant-Like Enhancement of the High-Energy Plateau in ATD

    NASA Astrophysics Data System (ADS)

    Krajewska, Katarzyna; Fabrikant, Ilya I.; Starace, Anthony F.

    2006-05-01

    We calculate the intensity variation of above-threshold detachment (ATD) rates for H^- and F^- in the high-energy plateau region, by solving the time-dependent Schr"odinger equation within the Sturmian-Floquet approach [1]. We find pronounced enhancement of the ATD spectra as the laser-field intensity induces ATD channel closings. We confirm previous results on negative ions with an active s-electron [2], and extend them to the case of p-symmetry of the initial state. Depending on the symmetry of the initial state, we show that the enhancement is most pronounced for even- or odd-channel closures. Similar resonant-like enhancements have been observed experimentally in above-threshold ionization spectra for rare gases [3], calculations for which are in progress. [1] R. M. Potvliege, Comp. Phys. Comm. 114, 42 (1998); [2] B. Borca et al., Phys. Rev. Lett. 88, 193001 (2002); [3] See, e.g., F. Grasbon et al., Phys. Rev. Lett. 91, 173003 (2003).

  18. Accelerating Nuclear Magnetic Resonance (NMR) Analysis of Soil Organic Matter with Dynamic Nuclear Polarization (DNP) Enhancement

    NASA Astrophysics Data System (ADS)

    Normand, A. E.; Smith, A. N.; Long, J. R.; Reddy, K. R.

    2014-12-01

    13C magic angle spinning (MAS) solid state Nuclear Magnetic Resonance (ssNMR) has become an essential tool for discerning the chemical composition of soil organic matter (SOM). However, the technique is limited due to the inherent insensitivity of NMR resulting in long acquisition times, especially for low carbon (C) soil. The pursuits of higher magnetic fields or concentrating C with hydrofluoric acid are limited solutions for signal improvement. Recent advances in dynamic nuclear polarization (DNP) have addressed the insensitivity of NMR. DNP utilizes the greater polarization of an unpaired electron in a given magnetic field and transfers that polarization to an NMR active nucleus of interest via microwave irradiation. Signal enhancements of up to a few orders of magnitude have been achieved for various DNP experiments. In this novel study, we conduct DNP 13C cross-polarization (CP) MAS ssNMR experiments of SOM varying in soil C content and chemical composition. DNP signal enhancements reduce the experiment run time allowing samples with low C to be analyzed in hours rather than days. We compare 13C CP MAS ssNMR of SOM with multiple magnetic field strengths, hydrofluoric acid treatment, and novel DNP approaches. We also explore DNP surface enhanced NMR Spectroscopy (SENP) to determine the surface chemistry of SOM. The presented results and future DNP MAS ssNMR advances will lead to further understanding of the nature and processes of SOM.

  19. Competition of Resonant and Nonresonant Paths in Resonance-Enhanced Two-Photon Single Ionization of He by an Ultrashort Extreme-Ultraviolet Pulse

    NASA Astrophysics Data System (ADS)

    Ishikawa, Kenichi L.; Ueda, Kiyoshi

    2012-01-01

    We theoretically study the pulse-width dependence of the photoelectron angular distribution (PAD) from the resonance-enhanced two-photon single ionization of He by femtosecond (≲20fs) extreme-ultraviolet pulses, based on the time-dependent perturbation theory and simulations with the full time-dependent Schrödinger equation. In particular, we focus on the competition between resonant and nonresonant ionization paths, which leads to the relative phase δ between the S and D wave packets distinct from the corresponding scattering phase shift difference. When the spectrally broadened pulse is resonant with an excited level, the competition varies with pulse width, and, therefore, δ and the PAD also change with it. On the other hand, when the Rydberg manifold is excited, δ and the PAD do not much vary with the pulse width, except for the very short-pulse regime.

  20. Implementation of propeller, spiral, and variable density spiral methods for dynamic contrast enhanced magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    Ahunbay, Ergun Emin

    2001-09-01

    Previous studies showed that dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) is a valuable tool for the prognosis and diagnosis of cancer, however it requires a tradeoff between temporal and spatial resolution. The ultimate goal of this dissertation is to compare the temporal performance of three methods (spiral, propeller and variable density spiral), given a certain spatial resolution requirement, for the DCE-MRI. These methods show distinction from the conventional MRI methods in their k-space coverage. Propeller and Variable Density Spiral methods use an approach of oversampling the center of k-space, updating the central 13-20% of the radial k-space more frequently than the peripheries. The reason for this is that most of the image data resides in the central part of k-space. Spiral method, on the other hand approaches the problem by updating the overall k-space as fast as possible, faster than the conventional methods. Comparison is performed mainly by computer simulations, where ground truth is known. In addition to computer simulations, these three methods are compared in- vivo, by tracking the DCE-MRI signal amplitude variation with time for each method on a healthy volunteer's liver. One limitation of the spiral and variable density spiral imaging methods is the effect of off-resonance frequencies on image quality. For these spiral based methods, long readout times are desired to have short overall imaging times and high temporal resolution. However, for long readout times, off resonance frequencies blur the images and reduce the spatial resolution. In this dissertation a new method is proposed which is less complicated than most other methods, and reaches an acceptable level of accuracy with less amount of CPU time compared to previously effective methods.

  1. Surface-enhanced resonance Raman scattering of hemoproteins and those in complicated biological systems.

    PubMed

    Kitahama, Yasutaka; Ozaki, Yukihiro

    2016-08-15

    In this review article, we discuss surface-enhanced resonance Raman scattering (SERRS) studies of hemeproteins such as myoglobin, hemoglobin, and cytochrome on various metal substrates; for example, colloidal silver nanoparticles coated with and without self-assembled monolayers (SAM), a roughened silver electrode protected with and without SAM, a sharp silver tip, and colloidal gold nanoparticles coated with and without SAM. Moreover, we classify the studies in terms of an excitation wavelength; namely, excitation at the B- (Soret) band, Q- (α and β) band, and in the near infrared (NIR) range. In the SERRS studies with B band excitation, it has been shown that the hemeprotein on a silver surface takes a non-native form through detachment from the heme pocket in the protein. With Q band excitation, on the other hand, the change in SERRS has been explained by the orientation of the hemeprotein on the surface. Even by excitation in the NIR range, the peak positions are consistent with the assignment of the major vibrational modes of heme despite there being no resonance Raman effect. Thus, the SERRS of hemeproteins is influenced by a resonance Raman effect, LSPR, and interactions with the metal surface such as structural changes, orientation, and selective adsorption. Moreover, we discuss how SERRS has been applied to complicated biological systems such as living cells containing hemeprotein. For mitochondria, a change of the oxidation-state was observed by the electron transport chain in the cell and at different positions. As an example of a biomedical application of SERRS, the sensitive detection of malaria is presented. PMID:27381192

  2. Enhanced Absorption in 2D Materials Via Fano- Resonant Photonic Crystals

    SciTech Connect

    Wang, Wenyi; Klotz, Andrey; Yang, Yuanmu; Li, Wei; Kravchenko, Ivan I.; Briggs, Dayrl P.; Bolotin, Kirill; Valentine, Jason

    2015-05-01

    The use of two-dimensional (2D) materials in optoelectronics has attracted much attention due to their fascinating optical and electrical properties. For instance, graphenebased devices have been employed for applications such as ultrafast and broadband photodetectors and modulators while transition metal dichalcogenide (TMDC) based photodetectors can be used for ultrasensitive photodetection. However, the low optical absorption of 2D materials arising from their atomic thickness limits the maximum attainable external quantum efficiency. For example, in the visible and NIR regimes monolayer MoS2 and graphene absorb only ~10% and 2.3% of incoming light, respectively. Here, we experimentally demonstrate the use of Fano-resonant photonic crystals to significantly boost absorption in atomically thin materials. Using graphene as a test bed, we demonstrate that absorption in the monolayer thick material can be enhanced to 77% within the telecommunications band, the highest value reported to date. We also show that the absorption in the Fano-resonant structure is non-local, with light propagating up to 16 μm within the structure. This property is particularly beneficial in harvesting light from large areas in field-effect-transistor based graphene photodetectors in which separation of photo-generated carriers only occurs ~0.2 μm adjacent to the graphene/electrode interface.

  3. Resonant enhancement of macroscopic quantum tunneling in Josephson junctions: Influence of coherent two-level systems

    NASA Astrophysics Data System (ADS)

    Fistul, M. V.

    2015-07-01

    We report a theoretical study of the macroscopic quantum tunneling (MQT) in small Josephson junctions containing randomly distributed two-level systems. We focus on a Josephson phase escape for switching from the superconducting (the zero-voltage) state to a resistive one. Above the crossover temperature Tc r the thermal fluctuations of the Josephson phase induce such a switching, and as T resonant enhancement of the MQT. This phenomenon manifests itself by a narrow peak in the dependence of Tc r(Φ ) occurring in the intermediate range of Φ , i.e., 0 <Φ <ϕ0 (ϕ0 is the magnetic flux quantum). We explain this effect quantitatively by a strong resonant suppression of the potential barrier for the Josephson phase escape that is due to the coherent quantum Rabi oscillations in two-level systems present in the junction.

  4. Noise-enhanced stability and double stochastic resonance of active Brownian motion

    NASA Astrophysics Data System (ADS)

    Zeng, Chunhua; Zhang, Chun; Zeng, Jiakui; Liu, Ruifen; Wang, Hua

    2015-08-01

    In this paper, we study the transient and resonant properties of active Brownian particles (ABPs) in the Rayleigh-Helmholtz (RH) and Schweitzer-Ebeling-Tilch (SET) models, which is driven by the simultaneous action of multiplicative and additive noise and periodic forcing. It is shown that the cross-correlation between two noises (λ) can break the symmetry of the potential to generate motion of the ABPs. In case of no correlation between two noises, the mean first passage time (MFPT) is a monotonic decrease depending on the multiplicative noise, however in case of correlation between two noises, the MFPT exhibits a maximum, depending on the multiplicative noise for both models, this maximum for MFPT identifies the noise-enhanced stability (NES) effect of the ABPs. By comparing with case of no correlation (λ =0.0 ), we find two maxima in the signal-to-noise ratio (SNR) depending on the cross-correlation intensity, i.e. the double stochastic resonance is shown in both models. For the RH model, the SNR exhibits two maxima depending on the multiplicative noise for small cross-correlation intensity, while in the SET model, it exhibits only a maximum depending on the multiplicative noise. Whether λ =0.0 or not, the MFPT is a monotonic decrease, and the SNR exhibits a maximum, depending on the additive noise in both models.

  5. Enhancement of Rydberg-mediated single-photon nonlinearities by electrically tuned Förster resonances

    PubMed Central

    Gorniaczyk, H.; Tresp, C.; Bienias, P.; Paris-Mandoki, A.; Li, W.; Mirgorodskiy, I.; Büchler, H. P.; Lesanovsky, I.; Hofferberth, S.

    2016-01-01

    Mapping the strong interaction between Rydberg atoms onto single photons via electromagnetically induced transparency enables manipulation of light at the single-photon level and few-photon devices such as all-optical switches and transistors operated by individual photons. Here we demonstrate experimentally that Stark-tuned Förster resonances can substantially increase this effective interaction between individual photons. This technique boosts the gain of a single-photon transistor to over 100, enhances the non-destructive detection of single Rydberg atoms to a fidelity beyond 0.8, and enables high-precision spectroscopy on Rydberg pair states. On top, we achieve a gain larger than 2 with gate photon read-out after the transistor operation. Theory models for Rydberg polariton propagation on Förster resonance and for the projection of the stored spin-wave yield excellent agreement to our data and successfully identify the main decoherence mechanism of the Rydberg transistor, paving the way towards photonic quantum gates. PMID:27515278

  6. Plasmon resonances and the plasmon-induced field enhancement in nanoring dimers

    NASA Astrophysics Data System (ADS)

    Yin, Haifeng; Zhang, Hong; Cheng, Xin-Lu

    2013-03-01

    Plasmon resonances and the plasmon-induced field enhancement (FE) in sodium nanoring dimers are investigated by time-dependent density functional theory. For larger separations, the optical absorption, the induced charge response and the frequency dependent current demonstrate that there are two capacitive coupling plasmon modes. One feature of FE is that, in the surface region of the nanoring, it has a very large maximum. Another feature of FE is that, along the perpendicular bisector of the line segment joining the two nanoring center points in the middle region of the nanoring dimers, it has maxima. With the decrease of the gap distance, because of the electrons tunneling across the dimer junction and screening, collective excitation modes are changed, and the charge transfer plasmon modes emerge in the nanoring dimers. FE induced by any plasmon modes decreases in the gap region. Moreover, corresponding to different gap distances, the high-energy plasmon resonance peak almost does not shift, because this plasmon mode is mainly the collective excitation as a result of interactions among degenerate individual electronic states.

  7. Plasmon resonance enhanced temperature-dependent photoluminescence of Si-V centers in diamond

    NASA Astrophysics Data System (ADS)

    Cheng, Shaoheng; Song, Jie; Wang, Qiliang; Liu, Junsong; Li, Hongdong; Zhang, Baolin

    2015-11-01

    Temperature dependent optical property of diamond has been considered as a very important factor for realizing high performance diamond-based optoelectronic devices. The photoluminescence feature of the zero phonon line of silicon-vacancy (Si-V) centers in Si-doped chemical vapor deposited single crystal diamond (SCD) with localized surface plasmon resonance (LSPR) induced by gold nanoparticles has been studied at temperatures ranging from liquid nitrogen temperature to 473 K, as compared with that of the SCD counterpart in absence of the LSPR. It is found that with LSPR the emission intensities of Si-V centers are significantly enhanced by factors of tens and the magnitudes of the redshift (width) of the emissions become smaller (narrower), in comparison with those of normal emissions without plasmon resonance. More interestingly, these strong Si-V emissions appear remarkably at temperatures up to 473 K, while the spectral feature was not reported in previous studies on the intrinsic Si-doped diamonds when temperatures are higher than room temperature. These findings would lead to reaching high performance diamond-based devices, such as single photon emitter, quantum cryptography, biomarker, and so forth, working under high temperature conditions.

  8. Signal enhancement in cantilever magnetometry based on a co-resonantly coupled sensor.

    PubMed

    Körner, Julia; Reiche, Christopher F; Gemming, Thomas; Büchner, Bernd; Gerlach, Gerald; Mühl, Thomas

    2016-01-01

    Cantilever magnetometry is a measurement technique used to study magnetic nanoparticles. With decreasing sample size, the signal strength is significantly reduced, requiring advances of the technique. Ultrathin and slender cantilevers can address this challenge but lead to increased complexity of detection. We present an approach based on the co-resonant coupling of a micro- and a nanometer-sized cantilever. Via matching of the resonance frequencies of the two subsystems we induce a strong interplay between the oscillations of the two cantilevers, allowing for a detection of interactions between the sensitive nanocantilever and external influences in the amplitude response curve of the microcantilever. In our magnetometry experiment we used an iron-filled carbon nanotube acting simultaneously as nanocantilever and magnetic sample. Measurements revealed an enhancement of the commonly used frequency shift signal by five orders of magnitude compared to conventional cantilever magnetometry experiments with similar nanomagnets. With this experiment we do not only demonstrate the functionality of our sensor design but also its potential for very sensitive magnetometry measurements while maintaining a facile oscillation detection with a conventional microcantilever setup. PMID:27547621

  9. Signal enhancement in cantilever magnetometry based on a co-resonantly coupled sensor

    PubMed Central

    Körner, Julia; Reiche, Christopher F; Gemming, Thomas; Büchner, Bernd; Gerlach, Gerald

    2016-01-01

    Summary Cantilever magnetometry is a measurement technique used to study magnetic nanoparticles. With decreasing sample size, the signal strength is significantly reduced, requiring advances of the technique. Ultrathin and slender cantilevers can address this challenge but lead to increased complexity of detection. We present an approach based on the co-resonant coupling of a micro- and a nanometer-sized cantilever. Via matching of the resonance frequencies of the two subsystems we induce a strong interplay between the oscillations of the two cantilevers, allowing for a detection of interactions between the sensitive nanocantilever and external influences in the amplitude response curve of the microcantilever. In our magnetometry experiment we used an iron-filled carbon nanotube acting simultaneously as nanocantilever and magnetic sample. Measurements revealed an enhancement of the commonly used frequency shift signal by five orders of magnitude compared to conventional cantilever magnetometry experiments with similar nanomagnets. With this experiment we do not only demonstrate the functionality of our sensor design but also its potential for very sensitive magnetometry measurements while maintaining a facile oscillation detection with a conventional microcantilever setup. PMID:27547621

  10. Metabolic properties in stroked rats revealed by relaxation-enhanced magnetic resonance spectroscopy at ultrahigh fields.

    PubMed

    Shemesh, Noam; Rosenberg, Jens T; Dumez, Jean-Nicolas; Muniz, Jose A; Grant, Samuel C; Frydman, Lucio

    2014-01-01

    (1)H magnetic resonance spectroscopy (MRS) yields site-specific signatures that directly report metabolic concentrations, biochemistry and kinetics-provided spectral sensitivity and quality are sufficient. Here, an enabling relaxation-enhanced (RE) MRS approach is demonstrated that by combining highly selective spectral excitations with operation at very high magnetic fields, delivers spectra exhibiting signal-to-noise ratios >50:1 in under 6 s for ~5 × 5 × 5 (mm)(3) voxels, with flat baselines and no interference from water. With this spectral quality, MRS was used to interrogate a number of metabolic properties in stroked rat models. Metabolic confinements imposed by randomly oriented micro-architectures were detected and found to change upon ischaemia; intensities of downfield resonances were found to be selectively altered in stroked hemispheres; and longitudinal relaxation time of lactic acid was found to increase by over 50% its control value as early as 3-h post ischaemia, paralleling the onset of cytotoxic oedema. These results demonstrate potential of (1)H MRS at ultrahigh fields. PMID:25229942

  11. Plasmon resonance enhanced temperature-dependent photoluminescence of Si-V centers in diamond

    SciTech Connect

    Cheng, Shaoheng; Song, Jie; Wang, Qiliang; Liu, Junsong; Li, Hongdong; Zhang, Baolin

    2015-11-23

    Temperature dependent optical property of diamond has been considered as a very important factor for realizing high performance diamond-based optoelectronic devices. The photoluminescence feature of the zero phonon line of silicon-vacancy (Si-V) centers in Si-doped chemical vapor deposited single crystal diamond (SCD) with localized surface plasmon resonance (LSPR) induced by gold nanoparticles has been studied at temperatures ranging from liquid nitrogen temperature to 473 K, as compared with that of the SCD counterpart in absence of the LSPR. It is found that with LSPR the emission intensities of Si-V centers are significantly enhanced by factors of tens and the magnitudes of the redshift (width) of the emissions become smaller (narrower), in comparison with those of normal emissions without plasmon resonance. More interestingly, these strong Si-V emissions appear remarkably at temperatures up to 473 K, while the spectral feature was not reported in previous studies on the intrinsic Si-doped diamonds when temperatures are higher than room temperature. These findings would lead to reaching high performance diamond-based devices, such as single photon emitter, quantum cryptography, biomarker, and so forth, working under high temperature conditions.

  12. Enhanced absorption in two-dimensional materials via Fano-resonant photonic crystals

    SciTech Connect

    Wang, Wenyi; Klots, Andrey; Bolotin, Kirill I.; Yang, Yuanmu; Li, Wei; Valentine, Jason; Kravchenko, Ivan I.; Briggs, Dayrl P.

    2015-05-04

    The use of two-dimensional (2D) materials in optoelectronics has attracted much attention due to their fascinating optical and electrical properties. However, the low optical absorption of 2D materials arising from their atomic thickness limits the maximum attainable external quantum efficiency. For example, in the visible and near-infrared regimes monolayer MoS{sub 2} and graphene absorb only ∼10% and 2.3% of incoming light, respectively. Here, we experimentally demonstrate the use of Fano-resonant photonic crystals to significantly boost absorption in atomically thin materials. Using graphene as a test bed, we demonstrate that absorption in the monolayer thick material can be enhanced to 77% within the telecommunications band, the highest value reported to date. We also show that the absorption in the Fano-resonant structure is non-local, with light propagating up to 16 μm within the structure. This property is particularly beneficial in harvesting light from large areas in field-effect-transistor based graphene photodetectors in which separation of photo-generated carriers only occurs ∼0.2 μm adjacent to the graphene/electrode interface.

  13. Resonant enhancement of the zero-phonon emission from a colour centre in a diamond cavity

    NASA Astrophysics Data System (ADS)

    Faraon, Andrei; Barclay, Paul E.; Santori, Charles; Fu, Kai-Mei C.; Beausoleil, Raymond G.

    2011-05-01

    Integrated quantum photonic technologies are key for future applications in quantum information, ultralow-power opto-electronics and sensing. As individual quantum bits, nitrogen-vacancy centres in diamond are among the most promising solid-state systems identified to date, because of their long-lived electron and nuclear spin coherence, and capability for individual optical initialization, readout and information storage. The major outstanding hurdle lies in interconnecting many nitrogen vacancies for large-scale computation. One of the most promising approaches in this regard is to couple them to optical resonators, which can be further interconnected in a photonic network. Here, we demonstrate coupling of the zero-phonon line of individual nitrogen vacancies to the modes of microring resonators fabricated in single-crystal diamond. Zero-phonon line enhancement by more than a factor of 10 is estimated from lifetime measurements. The devices are fabricated using standard semiconductor techniques and off-the-shelf materials, thus enabling integrated diamond photonics.

  14. Enhanced Absorption in 2D Materials Via Fano- Resonant Photonic Crystals

    DOE PAGESBeta

    Wang, Wenyi; Klotz, Andrey; Yang, Yuanmu; Li, Wei; Kravchenko, Ivan I.; Briggs, Dayrl P.; Bolotin, Kirill; Valentine, Jason

    2015-05-01

    The use of two-dimensional (2D) materials in optoelectronics has attracted much attention due to their fascinating optical and electrical properties. For instance, graphenebased devices have been employed for applications such as ultrafast and broadband photodetectors and modulators while transition metal dichalcogenide (TMDC) based photodetectors can be used for ultrasensitive photodetection. However, the low optical absorption of 2D materials arising from their atomic thickness limits the maximum attainable external quantum efficiency. For example, in the visible and NIR regimes monolayer MoS2 and graphene absorb only ~10% and 2.3% of incoming light, respectively. Here, we experimentally demonstrate the use of Fano-resonant photonicmore » crystals to significantly boost absorption in atomically thin materials. Using graphene as a test bed, we demonstrate that absorption in the monolayer thick material can be enhanced to 77% within the telecommunications band, the highest value reported to date. We also show that the absorption in the Fano-resonant structure is non-local, with light propagating up to 16 μm within the structure. This property is particularly beneficial in harvesting light from large areas in field-effect-transistor based graphene photodetectors in which separation of photo-generated carriers only occurs ~0.2 μm adjacent to the graphene/electrode interface.« less

  15. Enhancement of Rydberg-mediated single-photon nonlinearities by electrically tuned Förster resonances.

    PubMed

    Gorniaczyk, H; Tresp, C; Bienias, P; Paris-Mandoki, A; Li, W; Mirgorodskiy, I; Büchler, H P; Lesanovsky, I; Hofferberth, S

    2016-01-01

    Mapping the strong interaction between Rydberg atoms onto single photons via electromagnetically induced transparency enables manipulation of light at the single-photon level and few-photon devices such as all-optical switches and transistors operated by individual photons. Here we demonstrate experimentally that Stark-tuned Förster resonances can substantially increase this effective interaction between individual photons. This technique boosts the gain of a single-photon transistor to over 100, enhances the non-destructive detection of single Rydberg atoms to a fidelity beyond 0.8, and enables high-precision spectroscopy on Rydberg pair states. On top, we achieve a gain larger than 2 with gate photon read-out after the transistor operation. Theory models for Rydberg polariton propagation on Förster resonance and for the projection of the stored spin-wave yield excellent agreement to our data and successfully identify the main decoherence mechanism of the Rydberg transistor, paving the way towards photonic quantum gates. PMID:27515278

  16. Extremely narrow resonances, giant sensitivity and field enhancement in low-loss waveguide sensors

    NASA Astrophysics Data System (ADS)

    Nesterenko, D. V.; Hayashi, S.; Sekkat, Z.

    2016-06-01

    Low-loss waveguides (WGs), which support excitation of waveguide modes (WMs), are based on a dielectric WG separated from an absorptive film by a low-index dielectric spacer layer. We perform numerical and analytical study of the impact of the losses imposed to the WG in a planar sensing structure in the Kretschmann configuration on the resonance properties of the excitation. We demonstrate that the loss degree of the WMs can be controlled by the thickness of the spacer layer for both s and p polarizations. Extremely narrow resonances are discovered in the reflectivity spectra due to excitation of the low-loss WMs, and the maximum of the estimated sensitivity by intensity is found to be of 105-fold higher as compared to the conventional surface plasmon and WG-coupled surface plasmon sensors. We reveal the giant field intensity enhancement of 107-fold on the surface of the sensing structure in aqueous sensing media that can provide stronger fluorescence intensity at lower sample volumes for fluorescent labeling sensing.

  17. Evidence for enhanced optical properties through plasmon resonance energy transfer in silver silica nanocomposites

    NASA Astrophysics Data System (ADS)

    Mol, Beena; Joy, Lija K.; Thomas, Hysen; Thomas, Vinoy; Joseph, Cyriac; Narayanan, T. N.; Al-Harthi, Salim; Unnikrishnan, N. V.; Anantharaman, M. R.

    2016-02-01

    Silver nanoparticles were dispersed in the pores of monolithic mesoporous silica prepared by a modified sol-gel method. Structural and microstructural analyses were carried out by Fourier transform infrared spectroscopy and transmission electron microscopy. X-ray photoelectron spectroscopy was employed to determine the chemical states of silver in the silica matrix. Optical absorption studies show the evolution absorption band around 300 nm for silver (Ag) in a silica matrix and it was found to be redshifted to 422 nm on annealing. Photoluminescence studies indicate the presence of various luminescent emitting centers corresponding to silver ions and silver dimers in the SiO2 matrix. The enhancement of absorption and photoluminescence properties is attributed to plasmon resonance energy transfer from Ag nanoparticles to luminescent species in the matrix.

  18. Enhancing dominant modes in nonstationary time series by means of the symbolic resonance analysis.

    PubMed

    beim Graben, Peter; Drenhaus, Heiner; Brehm, Eva; Rhode, Bela; Saddy, Douglas; Frisch, Stefan

    2007-12-01

    We present the symbolic resonance analysis (SRA) as a viable method for addressing the problem of enhancing a weakly dominant mode in a mixture of impulse responses obtained from a nonlinear dynamical system. We demonstrate this using results from a numerical simulation with Duffing oscillators in different domains of their parameter space, and by analyzing event-related brain potentials (ERPs) from a language processing experiment in German as a representative application. In this paradigm, the averaged ERPs exhibit an N400 followed by a sentence final negativity. Contemporary sentence processing models predict a late positivity (P600) as well. We show that the SRA is able to unveil the P600 evoked by the critical stimuli as a weakly dominant mode from the covering sentence final negativity. PMID:18163770

  19. Resonance-induced absorption enhancement in colloidal quantum dot solar cells using nanostructured electrodes.

    PubMed

    Mahpeykar, Seyed Milad; Xiong, Qiuyang; Wang, Xihua

    2014-10-20

    The application of nanostructured indium-doped tin oxide (ITO) electrodes as diffraction gratings for light absorption enhancement in colloidal quantum dot solar cells is numerically investigated using finite-difference time-domain (FDTD) simulation. Resonant coupling of the incident diffracted light with supported waveguide modes in light absorbing layer at particular wavelengths predicted by grating far-field projection analysis is shown to provide superior near-infrared light trapping for nanostructured devices as compared to the planar structure. Among various technologically feasible nanostructures, the two-dimensional nano-branch array is demonstrated as the most promising polarization-independent structure and proved to be able to maintain its performance despite structural imperfections common in fabrication. PMID:25607315

  20. Enhanced visibility of two-mode thermal squeezed states via degenerate parametric amplification and resonance

    NASA Astrophysics Data System (ADS)

    Mahboob, I.; Okamoto, H.; Yamaguchi, H.

    2016-08-01

    Two-mode squeezed states, generated via non-degenerate parametric down-conversion, are invariably revealed via their entangled vacuum or correlated thermal fluctuations. Here, two-mode thermal squeezed states, generated in an electromechanical system, are made bright by means of degenerate parametric amplification of their constituent modes to the point where they are almost perfect, even when seeded from low intensity non-degenerate parametric down-conversion. More dramatically, activating the degenerate parametric resonances of the underlying modes yields perfect correlations which can be resolved via the coordinated switching of their phase bi-stable vibrations, without recourse to monitoring their thermal fluctuations. This ability to enhance the two-mode squeezed states and to decipher them without needing to observe their intrinsic noise is supported by both analytical and numerical modelling and it suggests that the technical constraints to making this phenomenon more widely available can be dramatically relaxed.