Anisotropy and the knee of the energy spectrum
NASA Technical Reports Server (NTRS)
Clay, R. W.
1985-01-01
The measured cosmic ray energy spectrum exhibits clear structure (the knee) at approx 3 x 10 to the 15th power eV (sea level shower size approx 3 x 10 to the 5th power particles). Additionally, at energies in this general region, there occur apparent changes in shower development such that the observed characteristics of showers at this energy appear different to those characteristics observed at somewhat higher energies. At energies just below this region, the cosmic ray anisotropy amplitude apparently begins a progressive increase with energy. The latter effect does not clearly fit with the first two since there appears to be no significant change exactly at the knee. However, the phase of the first harmonic of the anisotropy appears to show a substantial change just where the energy spectrum shows structure and in the middle of the shower development changes. The first harmonic phase appears to change from approx. 18 hours R.A. to approx. 5 hours R.A. as the energy of observation moves through the knee. In this paper the latter change is examined in some detail by taking into account information contained in the second harmonic of the anisotropy.
Spectrum and anisotropy of cosmic rays at TeV-PeV-energies and contribution of nearby sources
NASA Astrophysics Data System (ADS)
Sveshnikova, L. G.; Strelnikova, O. N.; Ptuskin, V. S.
2013-12-01
The role of nearby galactic sources, the supernova remnants, in formation of observed energy spectrum and large-scale anisotropy of high-energy cosmic rays is studied. The list of these sources is made up based on radio, X-ray and gamma-ray catalogues. The distant sources are treated statistically as ensemble of sources with random positions and ages. The source spectra are defined based on the modern theory of cosmic ray acceleration in supernova remnants while the propagation of cosmic rays in the interstellar medium is described in the frameworks of galactic diffusion model. Calculations of dipole component of anisotropy are made to reproduce the experimental procedure of "two-dimensional" anisotropy measurements. The energy dependence of particle escape time in the process of acceleration in supernova remnants and the arm structure of sources defining the significant features of anisotropy are also taken into account. The essential new trait of the model is a decreasing number of core collapse SNRs being able to accelerate cosmic rays up to the given energy, that leads to steeper total cosmic ray source spectrum in comparison with the individual source spectrum. We explained simultaneously the new cosmic ray data on the fine structure of all particle spectrum around the knee and the amplitude and direction of the dipole component of anisotropy in the wide energy range 1 TeV-1 EeV. Suggested assumptions do not look exotic, and they confirm the modern understanding of cosmic ray origin.
A model for the proton spectrum and cosmic ray anisotropy
NASA Technical Reports Server (NTRS)
Xu, C.
1985-01-01
The problem of the origin of the cosmic rays is still uncertain. As a theory, it should explain the support of particles and energy, the mechanism of acceleration and propagation as well as some important features obtained directly from cosmic ray experiments, such as the power spectrum and the knee. There are two kinds of models for interpreting the knee of the cosmic ray spectrum. One is the leaky box model. Another model suggests that the cut-off rigidity of the main sources causes the knee. The present paper studies the spectrum and the anisotropy of cosmic rays in an isotropic diffuse model with explosive discrete sources in an infinite galaxy.
Glushkov, A.V.; Pravdin, M.I.
2005-07-01
Data from the Yakutsk extensive air shower array for the period 1974-2004 are used to analyze the energy spectrum and anisotropy of primary cosmic rays (PCRs) with energy E{sub 0} {>=} 10{sup 17} eV. The spectra from different regions of the sky are shown to differ in shape. Enhanced and reduced particle fluxes come from the disks of the Galaxy and the Supergalaxy (the Local Supercluster of galaxies) at E{sub 0} {>=} 5 x 10{sup 18} eV and E{sub 0} {<=} (2-3) x 10{sup 18} eV, respectively. This is interpreted as a manifestation of the possible interaction between extragalactic PCRs and the matter of these spatial structures.
NASA Astrophysics Data System (ADS)
Soheyli, Saeed; Khanlari, Marzieh Varasteh
2016-04-01
Effects of the various neutron emission energy spectra, as well as the influence of the angular momentum of pre-scission neutrons on theoretical predictions of fission fragment angular anisotropies for several heavy-ion induced fission systems are considered. Although theoretical calculations of angular anisotropy are very sensitive to neutron emission correction, the effects of the different values of kinetic energy of emitted neutrons derived from the various neutron emission energy spectra before reaching to the saddle point on the prediction of fission fragment angular distribution by the model are not significant and can be neglected, since these effects on angular anisotropies of fission fragments for a wide range of fissility parameters and excitation energies of compound nuclei are not more than 10%. Furthermore, the theoretical prediction of fission fragment angular anisotropy is not sensitive to the angular momentum of emitted neutrons.
Effects of anisotropy on the frequency spectrum of gravity waves observed by MST radar
NASA Technical Reports Server (NTRS)
Liu, C. H.
1986-01-01
In the investigation of gravity waves using mesosphere-stratosphere-troposphere radar data, model gravity-wave spectra have been used. In these model spectra, one usually assumes azimuthal symmetry. The effect of spectral anisotropy on the observed spectrum is studied here. It is shown that for a general Garrett-Munk-type spectrum, the anisotropy does not affect the frequency spectrum observed by the vertically beamed radar. For the oblique beam, however, the observed frequency spectrum is changed. A general gravity wave spectrum including azimuthal anisotropy is considered.
Cosmic ray transport and anisotropies to high energies
NASA Astrophysics Data System (ADS)
Biermann, P. L.; Caramete, L. I.; Meli, A.; Nath, B. N.; Seo, E.-S.; de Souza, V.; Becker Tjus, J.
2015-10-01
A model is introduced, in which the irregularity spectrum of the Galactic magnetic field beyond the dissipation length scale is first a Kolmogorov spectrum k-5/3 at small scales λ = 2 π/k with k the wave-number, then a saturation spectrum k-1, and finally a shock-dominated spectrum k-2 mostly in the halo/wind outside the Cosmic Ray disk. In an isotropic approximation such a model is consistent with the Interstellar Medium (ISM) data. With this model we discuss the Galactic Cosmic Ray (GCR) spectrum, as well as the extragalactic Ultra High Energy Cosmic Rays (UHECRs), their chemical abundances and anisotropies. UHECRs may include a proton component from many radio galaxies integrated over vast distances, visible already below 3 EeV.
Full - sky search for ultrahigh - energy cosmic ray anisotropies
Luis A. Anchordoqui et al.
2003-07-02
Using data from the SUGAR and the AGASA experiments taken during a 10 yr period with nearly uniform exposure to the entire sky, we search for anisotropy patterns in the arrival directions of cosmic rays with energies > 10{sup 19.6} eV. We determine the angular power spectrum from an expansion in spherical harmonics for modes out to {ell} = 5. Based on available statistics, we find no significant deviation from isotropy. We compare the rather modest results which can be extracted from existing data samples with the results that should be forthcoming as new full-sky observatories begin operation.
Anisotropy of plasmon spectrum due to joint Rashba and Dresselhaus spin-orbit interaction
NASA Astrophysics Data System (ADS)
Badalyan, Samvel; Matos-Abiague, Alex; Vignale, Giovanni; Fabian, Jaroslav
2008-03-01
We have investigated the combined effect of Rashba and Dresselhaus spin-orbit interaction (SOI) on the many-body polarization function of a two-dimensional electron system (2DES). The dielectric function of a 2DES is calculated within the random phase approximation and the plasmon energy spectrum as a function of the momentum magnitude for its different orientations is obtained. Our calculations show the peaked behavior of dynamical structure factor as a function of the polar angle of momentum. This strong peak corresponds to the plasmon, which is damped due to SOI. Thus, we have clearly demonstrated that due to the anisotropy of the spin-orbit interaction, the plasmons with the definite values of energy and momentum can be excited only in the certain direction.
CMB anisotropy power spectrum using linear combinations of WMAP maps
Saha, Rajib; Prunet, Simon; Jain, Pankaj; Souradeep, Tarun
2008-07-15
In recent years the goal of estimating different cosmological parameters precisely has set new challenges in the effort to accurately measure the angular power spectrum of the CMB. This has required removal of foreground contamination as well as detector noise bias with reliability and precision. Recently, a novel, model-independent method for the estimation of the CMB angular power spectrum solely from multifrequency observations has been proposed and implemented on the first year WMAP data by Saha et al. 2006. All previous estimates of the power spectrum of the CMB are based upon foreground templates using data sets from different experiments. However, our methodology demonstrates that the CMB angular spectrum can be reliably estimated with precision from a self-contained analysis of the WMAP data. In this work we provide a detailed description of this method. We also study and identify the biases present in our power spectrum estimate. We apply our methodology to extract the power spectrum from the WMAP data.
Cosmic ray anisotropies at high energies
NASA Technical Reports Server (NTRS)
Martinic, N. J.; Alarcon, A.; Teran, F.
1986-01-01
The directional anisotropies of the energetic cosmic ray gas due to the relative motion between the observers frame and the one where the relativistic gas can be assumed isotropic is analyzed. The radiation fluxes formula in the former frame must follow as the Lorentz invariance of dp/E, where p, E are the 4-vector momentum-energy components; dp is the 3-volume element in the momentum space. The anisotropic flux shows in such a case an amplitude, in a rotating earth, smaller than the experimental measurements from say, EAS-arrays for primary particle energies larger than 1.E(14) eV. Further, it is shown that two consecutive Lorentz transformations among three inertial frames exhibit the violation of dp/E invariance between the first and the third systems of reference, due to the Wigner rotation. A discussion of this result in the context of the experimental anisotropic fluxes and its current interpretation is given.
Anisotropy Enhancement of Thermal Energy Transport in Supported Black Phosphorene.
Chen, Jige; Chen, Shunda; Gao, Yi
2016-07-01
Thermal anisotropy along the basal plane of materials possesses both theoretical importance and application value in thermal transport and thermoelectricity. Though common two-dimensional materials may exhibit in-plane thermal anisotropy when suspended, thermal anisotropy would often disappear when supported on a substrate. In this Letter, we find a strong anisotropy enhancement of thermal energy transport in supported black phosphorene. The chiral preference of energy transport in the zigzag rather than the armchair direction is greatly enhanced by coupling to the substrate, up to a factor of approximately 2-fold compared to the suspended one. The enhancement originates from its puckered lattice structure, where the nonplanar armchair energy transport relies on the out-of-plane corrugation and thus would be hindered by the flexural suppression due to the substrate, while the planar zigzag energy transport is not. As a result, thermal conductivity of supported black phosphorene shows a consistent anisotropy enhancement under different temperatures and substrate coupling strengths. PMID:27320775
On the anisotropies of interplanetary low-energy proton intensities
NASA Technical Reports Server (NTRS)
Pesses, M. E.; Sarris, E. T.
1975-01-01
Explorer 35 proton anisotropic flux data (proton energies between 0.3 and 6.3 MeV) and simultaneous magnetic field measurements were used to supply more information on the propagation characteristics of low-energy protons in the interplanetary medium. During the rising portions of the proton events, large field-aligned anisotropies were observed. During the decaying part of the proton events, either radial anisotropy or near-isotropy was noticed. In addition, certain observations made during the decaying part of the proton events revealed anisotropies deviating significantly from the radial direction.
The Cosmic Microwave Background Anisotropy Power Spectrum from the BEAST Experiment
NASA Astrophysics Data System (ADS)
O'Dwyer, Ian J.; Bersanelli, Marco; Childers, Jeffrey; Figueiredo, Newton; Halevi, Doron; Huey, Greg; Lubin, Philip M.; Maino, Davide; Mandolesi, Nazzareno; Marvil, Joshua; Meinhold, Peter R.; Mejía, Jorge; Natoli, Paolo; O'Neill, Hugh; Pina, Agenor; Seiffert, Michael D.; Stebor, Nathan C.; Tello, Camilo; Villela, Thyrso; Wandelt, Benjamin D.; Williams, Brian; Wuensche, Carlos Alexandre
2005-05-01
The Background Emission Anisotropy Scanning Telescope (BEAST) is a 2.2 m off-axis telescope with an eight-element mixed Q-band (38-45 GHz) and Ka-band (26-36 GHz) focal plane, designed for balloon-borne and ground-based studies of the cosmic microwave background (CMB). Here we present the CMB angular power spectrum calculated from 682 hr of data observed with the BEAST instrument. We use a binned pseudo-Cl estimator (the MASTER method). We find results that are consistent with other determinations of the CMB anisotropy for angular wavenumbers l between 100 and 600. We also perform cosmological parameter estimation. The BEAST data alone produce a good constraint on Ωk≡1-Ωtot=-0.074+/-0.070, consistent with a flat universe. A joint parameter estimation analysis with a number of previous CMB experiments produces results consistent with previous determinations.
First Year Wilkinson Microwave Anisotropy Probe(WMAP)Observations: The Angular Power Spectrum
NASA Technical Reports Server (NTRS)
Hinshaw, G.; Spergel, D. N.; Verde, L.; Hill, R. S.; Meyer, S. S.; Barnes, C.; Bennett, C. L.; Halpern, M.; Jarosik, N.; Kogut, A.
2003-01-01
We present the angular power spectrum derived from the first-year Wilkinson Microwave Anisotropy Probe (WMAP) sky maps. We study a variety of power spectrum estimation methods and data combinations and demonstrate that the results are robust. The data are modestly contaminated by diffuse Galactic foreground emission, but we show that a simple Galactic template model is sufficient to remove the signal. Point sources produce a modest contamination in the low frequency data. After masking approximately 700 known bright sources from the maps, we estimate residual sources contribute approximately 3500 mu sq Kappa at 41 GHz, and approximately 130 mu sq Kappa at 94 GHz, to the power spectrum [iota(iota + 1)C(sub iota)/2pi] at iota = 1000. Systematic errors are negligible compared to the (modest) level of foreground emission. Our best estimate of the power spectrum is derived from 28 cross-power spectra of statistically independent channels. The final spectrum is essentially independent of the noise properties of an individual radiometer. The resulting spectrum provides a definitive measurement of the CMB power spectrum, with uncertainties limited by cosmic variance, up to iota approximately 350. The spectrum clearly exhibits a first acoustic peak at iota = 220 and a second acoustic peak at iota approximately 540, and it provides strong support for adiabatic initial conditions. Researchers have analyzed the CT(sup Epsilon) power spectrum, and present evidence for a relatively high optical depth, and an early period of cosmic reionization. Among other things, this implies that the temperature power spectrum has been suppressed by approximately 30% on degree angular scales, due to secondary scattering.
Kim, Jaiseung; Naselsky, Pavel
2010-05-10
We have investigated non-Gaussianity of our early universe by comparing the parity asymmetry of the Wilkinson Microwave Anisotropy Probe (WMAP) power spectrum with simulations. We find that odd-parity preference of the WMAP data (2 {<=} l {<=} 18) is anomalous at 4-in-1000 level. We find it likely that low quadrupole power is part of this parity asymmetry rather than an isolated anomaly. Further investigation is required to find out whether the origin of this anomaly is a cosmological or a systematic effect. The data from Planck Surveyor, which has systematics distinct from WMAP, will help us to resolve the origin of the anomalous odd-parity preference.
RESIDUAL ENERGY SPECTRUM OF SOLAR WIND TURBULENCE
Chen, C. H. K.; Bale, S. D.; Salem, C. S.; Maruca, B. A.
2013-06-20
It has long been known that the energy in velocity and magnetic field fluctuations in the solar wind is not in equipartition. In this paper, we present an analysis of 5 yr of Wind data at 1 AU to investigate the reason for this. The residual energy (difference between energy in velocity and magnetic field fluctuations) was calculated using both the standard magnetohydrodynamic (MHD) normalization for the magnetic field and a kinetic version, which includes temperature anisotropies and drifts between particle species. It was found that with the kinetic normalization, the fluctuations are closer to equipartition, with a mean normalized residual energy of {sigma}{sub r} = -0.19 and mean Alfven ratio of r{sub A} = 0.71. The spectrum of residual energy, in the kinetic normalization, was found to be steeper than both the velocity and magnetic field spectra, consistent with some recent MHD turbulence predictions and numerical simulations, having a spectral index close to -1.9. The local properties of residual energy and cross helicity were also investigated, showing that globally balanced intervals with small residual energy contain local patches of larger imbalance and larger residual energy at all scales, as expected for nonlinear turbulent interactions.
Non-Gaussianities in the cosmological perturbation spectrum due to primordial anisotropy II
Dey, Anindya; Kovetz, Ely; Paban, Sonia E-mail: elykovetz@gmail.com
2012-10-01
We continue to investigate possible signatures of a pre-inflationary anisotropic phase in two-point and three point correlation functions of the curvature perturbation for high-momentum modes which exit the horizon well after isotropization. The late time dynamics of these modes is characterized by a non-Bunch Davies vacuum state which encodes all the information about initial anisotropy in the background space-time. We observe that, unlike the non-planar momenta, there exist regimes of planar momenta for which scale invariance of the power spectrum is strongly broken. This regime of planar momenta gives rise to enhanced non-Gaussianity in certain squeezed triangle configurations, although the enhancement of the f{sub NL} parameter is limited by the breakdown of linear perturbation theory at ''exact planarity{sup .} Finally, we demonstrate that for the range of planar modes for which scale invariance of the power spectrum is preserved, non-Gaussianity in the curvature perturbation spectrum is naturally constrained to be extremely small.
Anisotropy vs chemical composition at ultra-high energies
Lemoine, Martin; Waxman, Eli E-mail: eli.waxman@weizmann.ac.il
2009-11-01
This paper proposes and discusses a test of the chemical composition of ultra-high energy cosmic rays that relies on the anisotropy patterns measured as a function of energy. In particular, we show that if one records an anisotropy signal produced by heavy nuclei of charge Z above an energy E{sub thr}, one should record an even stronger (possibly much stronger) anisotropy at energies >E{sub thr}/Z due to the proton component that is expected to be associated with the sources of the heavy nuclei. This conclusion remains robust with respect to the parameters characterizing the sources and it does not depend at all on the modelling of astrophysical magnetic fields. As a concrete example, we apply this test to the most recent data of the Pierre Auger Observatory. Assuming that the anisotropy reported above 55 EeV is not a statistical accident, and that no significant anisotropy has been observed at energies ∼<10 EeV, we show that the apparent clustering toward Cen A cannot be attributed to heavy nuclei. Similar conclusions are drawn regarding the apparent excess correlation with nearby active galactic nuclei. We then discuss a robust lower bound to the magnetic luminosity that a source must possess in order to be able to accelerate particles of charge Z up to 100 EeV, L{sub B} ∼> 10{sup 45} Z{sup −2} erg/s. Using this bound in conjunction with the above conclusions, we argue that the current PAO data does not support the model of cosmic ray origin in active radio-quiet or even radio-loud galaxies. Finally, we demonstrate that the apparent clustering in the direction of Cen A can be explained by the contribution of the last few gamma-ray bursts or magnetars in the host galaxy thanks to the scattering of the cosmic rays on the magnetized lobes.
Chiang, Lung-Yih; Chen, Fei-Fan
2012-05-20
The angular power spectrum of the cosmic microwave background temperature anisotropies is one of the most important characteristics in cosmology that can shed light on the properties of the universe such as its geometry and total density. Using flat sky approximation and Fourier analysis, we estimate the angular power spectrum from an ensemble of the least foreground-contaminated square patches from the Wilkinson Microwave Anisotropy Probe W and V frequency band map. This method circumvents the issue of foreground cleaning and that of breaking orthogonality in spherical harmonic analysis because we are able to mask out the bright Galactic plane region, thereby rendering a direct measurement of the angular power spectrum. We test and confirm the Gaussian statistical characteristic of the selected patches, from which the first and second acoustic peaks of the power spectrum are reproduced, and the third peak is clearly visible, albeit with some noise residual at the tail.
Energy distribution in the quantum spectrum
NASA Astrophysics Data System (ADS)
Bi, Siwen
2015-11-01
At first this paper summarizes the current situation and historical development of the spectrum research, the difficulties and demand background. Then it introduces the research status of quantum spectrum and research ideas of energy distribution in quantum spectrum. We explain the concept of quantum spectrum, the difference between quantum spectrum and spectrum. We elaborate energy distribution in quantum spectrum from three aspects, which are representation, feature and mechanism of quantum spectrum energy distribution. Finally we describe the application of monochrome quantum spectrum about imaging and detection aspects and give an overview of the quantum spectrum. Based on above research results we continue to study and achieve the detection of multi-spectral imaging, which provide the technical basis for the application. We try access to an advanced stage of quantum spectrum study as soon as possible.
Energy spectrum of sputtered uranium
NASA Technical Reports Server (NTRS)
Weller, R. A.; Tombrello, T. A.
1977-01-01
The fission track technique for detecting uranium 235 was used in conjunction with a mechanical time-of-flight spectrometer to measure the energy spectrum in the region 1 eV to 1 keV of material sputtered from a 93% enriched U-235 foil by 80 keV Ar-40(+) ions. The spectrum was found to exhibit a peak in the region 2-4 eV and to decrease approximately as E to the -1.77 power for E is approximately greater than 100 eV. The design, construction and resolution of the mechanical spectrometer are discussed and comparisons are made between the data and the predictions of the ramdom collision cascade model of sputtering.
NASA Technical Reports Server (NTRS)
Wright, E. L.; Smoot, G. F.; Bennett, C. L.; Lubin, P. M.
1994-01-01
The angular power spectrum estimator developed by Peebles (1973) and Hauser & Peebles (1973) has been modified and applied to the 2 yr maps produced by the Cosmic Background Explorer Satellite Differential Microwave Radiometer (COBE DMR)). The power spectrum of the real sky has been compared to the power spectra of a large number of simulated random skies produced with noise equal to the observed noise and primordial density fluctuation power spectra of power-law form, with P(k) proportional to k(exp n). Within the limited range of spatial scales covered by the COBE DMR, corresponding to spherical harmonic indices 3 less than or = l is less than or approximately = 30, the best-fitting value of the spectral index is n = 1.25(sup +0.39 sub -0.44) with the Harrisson-Zel'dovich value n = 1 approximately 0.5 sigma below the best fit. For 3 less than or = l less than or approximately = 19, the best fit is n = 1.46(sup +0.39 sub -0.44). Comparing the COBE DMR delta-T/T at small l to the delta-T/T at l approximately = 50 from degree scale anisotropy experiments gives a smaller range of acceptable spectral indices which includes n = 1.
Anisotropies at Ultra High Energies and the Galactic Halo
NASA Astrophysics Data System (ADS)
Wolfendale, Arnold
1999-08-01
A measure of consistency is appearing in measurements of the anisotropy of arrival directions above 1017 eV and these show a Galactic Plane Enhancement and a S-N excess, to about 3.1018 eV. The implication is that Galactic particles predominate here. At higher energies, where an Extragalactic origin is preferred, a contender for the `sources' is exotic dark matter particles. However, an analysis of the anisotropy at the highest energies, or, rather, the lack of it, makes this interpretation highly unlikely. Instead, `bottom-up' acceleration, in galaxy-systems is preferred; the likely mass mixture of the primaries, above 1018 eV, helps to explain why strong clustering of arrival is not observed.
Limiting energy spectrum of a saturated radiation belt
NASA Technical Reports Server (NTRS)
Schulz, Michael; Davidson, Gerald T.
1988-01-01
The condition for magnetospheric wave growth in the presence of anisotropic charged particle distributions is used to extend the Kennel-Petschek theory that traditionally imposes an upper bound on the integral flux of charged particles at energies above a certain threshold to provide a limit on the differential flux at any energy above this threshold. A closed-form expression is derived for the limiting energy spectrum consistent with marginal occurrence of a magnetospheric maser at all wave frequencies below a certain fraction of the electron or proton gyrofrequency. The bounded integral can be recast in such a way that repeated differentiations with respect to v(parallel) actually generate a closed expression for the limiting form of the velocity space distribution, and thus for the limiting energy spectrum of the corresponding particles, whenever the anisotropy parameter is an integer.
Spectrum and Anisotropy of Turbulence from Multi-frequency Measurement of Synchrotron Polarization
NASA Astrophysics Data System (ADS)
Lazarian, A.; Pogosyan, D.
2016-02-01
We consider turbulent synchrotron-emitting media that also exhibit Faraday rotation and provide a statistical description of synchrotron polarization fluctuations. In particular, we consider these fluctuations as a function of the spatial separation of the direction of the measurements and as a function of wavelength for the same line of sight. On the basis of our general analytical approach, we introduce several measures that can be used to obtain the spectral slopes and correlation scales of both the underlying magnetic turbulence responsible for emission and the spectrum of the Faraday rotation fluctuations. We show the synergetic nature of these measures and discuss how the study can be performed using sparsely sampled interferometric data. We also discuss how additional characteristics of turbulence can be obtained, including the turbulence anisotropy and the three-dimensional direction of the mean magnetic field. In addition, we consider the cases when the synchrotron emission and Faraday rotation regions are spatially separated. Appealing to our earlier study, we explain that our new results are applicable to a wide range of spectral indexes of relativistic electrons responsible for synchrotron emission. We expect wide application of our techniques, both with existing synchrotron data sets and with big forthcoming data sets from LOFAR and SKA.
NASA Astrophysics Data System (ADS)
Alsop, David Charles
The results of two experiments to study the diffuse background at millimeter and submillimeter wavelengths are reported. The first experiment was a rocket-borne photometer designed to measure the spectrum of the background. The background was observed in six bands centered at 7, 13, 20, 30, 40, and 50 cm-1. After the flight, a systematic error was detected in the flight data. A model for the error was developed and an attempt at correction was made, but indications that the correction was not complete were found. The second experiment was a search for anisotropy in the Cosmic Microwave Background at one degree angular scales. The search employed a multiband, bolometric receiver mounted on a balloon-borne telescope. The search achieved the highest statistical sensitivity at this angular scale, which is of crucial importance for constraining theories of structure formation in the universe. Signals in excess of random were detected but concern over possible systematic error sources prevents the interpretation of the signals as uniquely cosmological in origin.
Chiang, Lung-Yih; Chen, Fei-Fan
2011-09-10
The cross-power spectrum is a quadratic estimator between two maps that can provide unbiased estimate of the underlying power spectrum of the correlated signals, which is therefore used for extracting the power spectrum in the Wilkinson Microwave Anisotropy Probe (WMAP) data. In this paper, we discuss the limit of the cross-power spectrum and derive the residual from the uncorrelated signal, which is the source of error in power spectrum extraction. We employ the estimator to extract window functions by crossing pairs of extragalactic point sources. We demonstrate its usefulness in WMAP difference assembly maps where the window functions are measured via Jupiter and then extract the window functions of the five WMAP frequency band maps.
Anisotropy expectations for ultra-high-energy cosmic rays with future high-statistics experiments
NASA Astrophysics Data System (ADS)
Rouillé d'Orfeuil, B.; Allard, D.; Lachaud, C.; Parizot, E.; Blaksley, C.; Nagataki, S.
2014-07-01
Context. Ultra-high-energy cosmic rays (UHECRs) have attracted a lot of attention in astroparticle physics and high-energy astrophysics, due to their challengingly high energies, and to their ability to constrain the physical processes and astrophysical parameters in the most energetic sources of the universe. Despite their very large acceptance, current detectors have failed to detect significant anisotropies in their arrival directions, which had been expected to lead to the long-sought identification of their sources. Some indications about the composition of the UHECRs, which may become heavier at the highest energies, have even called into question the possibility that such a goal could be achieved in the foreseeable future. Aims: We investigate the potential value of a new-generation detector, with an exposure increased by one order of magnitude, to overcome the current situation and make notable progress in detecting anisotropies and thus in the study of UHECRs. We take as an example the expected performances of the JEM-EUSO detector, assuming a uniform full-sky coverage with a total exposure of 300 000 km2 sr yr. Methods: We simulated realistic UHECR sky maps for a wide range of possible astrophysical scenarios allowed by the current constraints, taking the energy losses and photo-dissociation of the UHE protons and nuclei into account, as well as their deflections by intervening magnetic fields. These sky maps, built for both the expected statistics of JEM-EUSO and the current Pierre Auger Observatory statistics, as a reference, were analysed from the point of view of their intrinsic anisotropies, using the two-point correlation function. A statistical study of the resulting anisotropies was performed for each astrophysical scenario, varying the UHECR source composition and spectrum and the source density and exploring a set of five hundred independent realizations for each choice of a parameter set. Results: We find that significant anisotropies are
NASA Astrophysics Data System (ADS)
Donzelli, S.; Maino, D.; Bersanelli, M.; Childers, J.; Figueiredo, N.; Lubin, P. M.; Meinhold, P. R.; O'Dwyer, I. J.; Seiffert, M. D.; Villela, T.; Wandelt, B. D.; Wuensche, C. A.
2006-06-01
We present the angular power spectrum of the cosmic microwave background (CMB) component extracted with FASTICA from the Background Emission Anisotropy Scanning Telescope (BEAST) data. BEAST is a 2.2-m off-axis telescope with a focal plane comprising eight elements at Q (38-45 GHz) and Ka (26-36 GHz) bands. It operates from the UC (University of California) White Mountain Research Station at an altitude of 3800 m. The BEAST CMB angular power spectrum has already been calculated by O'Dwyer et al. using only the Q-band data. With two input channels, FASTICA returns two possible independent components. We found that one of these two has an unphysical spectral behaviour, while the other is a reasonable CMB component. After a detailed calibration procedure based on Monte Carlo (MC) simulations, we extracted the angular power spectrum for the identified CMB component and found a very good agreement with the already published BEAST CMB angular power spectrum and with the Wilkinson Microwave Anisotropy Probe (WMAP) data.
NREL Spectrum of Clean Energy Innovation (Brochure)
Not Available
2011-09-01
This brochure describes the NREL Spectrum of Clean Energy Innovation, which includes analysis and decision support, fundamental science, market relevant research, systems integration, testing and validation, commercialization and deployment. Through deep technical expertise and an unmatched breadth of capabilities, the National Renewable Energy Laboratory (NREL) leads an integrated approach across the spectrum of renewable energy innovation. From scientific discovery to accelerating market deployment, NREL works in partnership with private industry to drive the transformation of our nation's energy systems. NREL integrates the entire spectrum of innovation, including fundamental science, market relevant research, systems integration, testing and validation, commercialization, and deployment. Our world-class analysis and decision support informs every point on the spectrum. The innovation process at NREL is inter-dependent and iterative. Many scientific breakthroughs begin in our own laboratories, but new ideas and technologies may come to NREL at any point along the innovation spectrum to be validated and refined for commercial use.
Dixneuf, Sophie; Rachet, Florent; Chrysos, Michael
2015-02-28
Owing in part to the p orbitals of its filled L shell, neon has repeatedly come on stage for its peculiar properties. In the context of collision-induced Raman spectroscopy, in particular, we have shown, in a brief report published a few years ago [M. Chrysos et al., Phys. Rev. A 80, 054701 (2009)], that the room-temperature anisotropic Raman lineshape of Ne-Ne exhibits, in the far wing of the spectrum, a peculiar structure with an aspect other than a smooth wing (on a logarithmic plot) which contrasts with any of the existing studies, and whose explanation lies in the distinct way in which overlap and exchange interactions interfere with the classical electrostatic ones in making the polarizability anisotropy, α∥ - α⊥. Here, we delve deeper into that study by reporting data for that spectrum up to 450 cm(-1) and for even- and odd-order spectral moments up to M6, as well as quantum lineshapes, generated from SCF, CCSD, and CCSD(T) models for α∥ - α⊥, which are critically compared with the experiment. On account of the knowledge of the spectrum over the augmented frequency domain, we show how the inverse scattering problem can be tackled both effectively and economically, and we report an analytic function for the anisotropy whose quantum lineshape faithfully reproduces our observations. PMID:25725726
Dixneuf, Sophie; Rachet, Florent; Chrysos, Michael
2015-02-28
Owing in part to the p orbitals of its filled L shell, neon has repeatedly come on stage for its peculiar properties. In the context of collision-induced Raman spectroscopy, in particular, we have shown, in a brief report published a few years ago [M. Chrysos et al., Phys. Rev. A 80, 054701 (2009)], that the room-temperature anisotropic Raman lineshape of Ne–Ne exhibits, in the far wing of the spectrum, a peculiar structure with an aspect other than a smooth wing (on a logarithmic plot) which contrasts with any of the existing studies, and whose explanation lies in the distinct way in which overlap and exchange interactions interfere with the classical electrostatic ones in making the polarizability anisotropy, α{sub ∥} − α{sub ⊥}. Here, we delve deeper into that study by reporting data for that spectrum up to 450 cm{sup −1} and for even- and odd-order spectral moments up to M{sub 6}, as well as quantum lineshapes, generated from SCF, CCSD, and CCSD(T) models for α{sub ∥} − α{sub ⊥}, which are critically compared with the experiment. On account of the knowledge of the spectrum over the augmented frequency domain, we show how the inverse scattering problem can be tackled both effectively and economically, and we report an analytic function for the anisotropy whose quantum lineshape faithfully reproduces our observations.
Energy spectrum of C60 fullerene
NASA Astrophysics Data System (ADS)
Mironov, G. I.; Murzashev, A. I.
2011-11-01
The energy spectrum of the C60 fullerene has been calculated in terms of the Shubin-Vonsovskii-Hubbard model using an approximation of static fluctuations. Based on the spectrum, the optical absorption bands at 4.84, 5.88, and 6.30 eV observed experimentally have been successfully explained. It has been concluded that the model used is applicable for the calculation of the energy spectrum and the energy properties of other nanosystems, such as fullerenes of higher orders, carbon nanotubes, and grafen planes.
The energy spectrum in a barotropic atmosphere
NASA Astrophysics Data System (ADS)
Kurgansky, M. V.
2008-03-01
In a forced-dissipative barotropic model of the atmosphere on a spherical planet, by following mathematical techniques in (Thompson, P. D.: The equilibrium energy spectrum of randomly forced two-dimensional turbulence, Journal of the Atmospheric Sciences, 30, 1593-1598, 1973) but applying them in a novel context of the discrete spectrum on a rotating sphere, the "minus 2" energy spectrum for wavenumbers much greater than a characteristic wavenumber of the baroclinic forcing has been obtained if the forcing is taken in the simplest and most fundamental form. Some observation-based atmospheric kinetic energy spectra, with their slopes lying between "minus 2" and "minus 3" laws, are discussed from the perspective of the deduced "minus 2" energy spectrum.
NASA Astrophysics Data System (ADS)
Ghosh, Bahniman; Pramanik, Tanmoy; Dey, Rik; Roy, Urmimala; Register, Leonard; Banerjee, Sanjay
2015-03-01
We propose and demonstrate, through simulation, an ultra low energy memory device on a topological insulator thin film. The device consists of a thin layer of Fe deposited on the surface of a topological insulator, Bi2Se3. The top surface of Fe is covered with MgO so that the ferromagnetic layer has perpendicular anisotropy. Current is passed on the surface of the topological insulator which switches the magnetization of the Fe ferromagnet through strong exchange interaction, between electrons contributing to the surface current on the Bi2Se3 and the d electrons in the ferromagnet, and spin transfer torque due to shunting of current through the ferromagnet. Voltage controlled magnetic anisotropy enables ultra low energy switching. Our micromagnetic simulations, predict switching time of the order of 2.4 ns and switching energy of the order of 0.16 fJ for a ferromagnetic bit with thermal stability of 90 kBT. The proposed structure combines the advantages of both large spin torque from topological insulators and those of perpendicular anisotropy materials. This work is supported by NRI SWAN and NSF NASCENT Center.
Aghamousa, Amir; Arjunwadkar, Mihir; Souradeep, Tarun E-mail: mihir@ncra.tifr.res.in
2012-02-01
Using a nonparametric function estimation methodology, we present a comparative analysis of the Wilkinson Microwave Anisotropy Probe (WMAP) 1-, 3-, 5-, and 7-year data releases for the cosmic microwave background (CMB) angular power spectrum with respect to the following key questions. (1) How well is the power spectrum determined by the data alone? (2) How well is the {Lambda}CDM model supported by a model-independent, data-driven analysis? (3) What are the realistic uncertainties on peak/dip locations and heights? Our results show that the height of the power spectrum is well determined by data alone for multipole l approximately less than 546 (1-year), 667 (3-year), 804 (5-year), and 842 (7-year data). We show that parametric fits based on the {Lambda}CDM model are remarkably close to our nonparametric fits in l-regions where data are sufficiently precise. In contrast, the power spectrum for an H{Lambda}CDM model is progressively pushed away from our nonparametric fit as data quality improves with successive data realizations, suggesting incompatibility of this particular cosmological model with respect to the WMAP data sets. We present uncertainties on peak/dip locations and heights at the 95% (2{sigma}) level of confidence and show how these uncertainties translate into hyperbolic 'bands' on the acoustic scale (l{sub A} ) and peak shift ({phi}{sub m}) parameters. Based on the confidence set for the 7-year data, we argue that the low-l upturn in the CMB power spectrum cannot be ruled out at any confidence level in excess of about 10% ( Almost-Equal-To 0.12{sigma}). Additional outcomes of this work are a numerical formulation for minimization of a noise-weighted risk function subject to monotonicity constraints, a prescription for obtaining nonparametric fits that are closer to cosmological expectations on smoothness, and a method for sampling cosmologically meaningful power spectrum variations from the confidence set of a nonparametric fit.
Liu, Ruo-Yu; Wang, Xiang-Yu; Taylor, Andrew M.; Lemoine, Martin; Waxman, Eli
2013-10-20
The joint analysis of anisotropy signals and chemical composition of ultra-high-energy cosmic rays offers strong potential for shedding light on the sources of these particles. Following up on an earlier idea, this paper studies the anisotropies produced by protons of energy >E/Z, assuming that anisotropies at energy >E have been produced by nuclei of charge Z, which share the same magnetic rigidity. We calculate the number of secondary protons produced through photodisintegration of the primary heavy nuclei. Making the extreme assumption that the source does not inject any proton, we find that the source(s) responsible for anisotropies such as reported by the Pierre Auger Observatory should lie closer than ∼20-30, 80-100, and 180-200 Mpc if the anisotropy signal is mainly composed of oxygen, silicon, and iron nuclei, respectively. A violation of this constraint would otherwise result in the secondary protons forming a more significant anisotropy signal at lower energies. Even if the source were located closer than this distance, it would require an extraordinary metallicity ∼> 120, 1600, and 1100 times solar metallicity in the acceleration zone of the source, for oxygen, silicon, and iron, respectively, to ensure that the concomitantly injected protons do not produce a more significant low-energy anisotropy. This offers interesting prospects for constraining the nature and the source of ultra-high-energy cosmic rays with the increase in statistics expected from next-generation detectors.
Surface anisotropy broadening of the energy barrier distribution in magnetic nanoparticles.
Pérez, N; Guardia, P; Roca, A G; Morales, M P; Serna, C J; Iglesias, O; Bartolomé, F; García, L M; Batlle, X; Labarta, A
2008-11-26
The effect of surface anisotropy on the distribution of energy barriers in magnetic fine particles of nanometer size is discussed within the framework of the Tln(t/τ(0)) scaling approach. The comparison between the distributions of the anisotropy energy of the particle cores, calculated by multiplying the volume distribution by the core anisotropy, and of the total anisotropy energy, deduced by deriving the master curve of the magnetic relaxation with respect to the scaling variable Tln(t/τ(0)), enables the determination of the surface anisotropy as a function of the particle size. We show that the contribution of the particle surface to the total anisotropy energy can be well described by a size-independent value of the surface energy per unit area which permits the superimposition of the distributions corresponding to the particle core and effective anisotropy energies. The method is applied to a ferrofluid composed of non-interacting Fe(3-x)O(4) particles of 4.9 nm average size and x about 0.07. Even though the size distribution is quite narrow in this system, a relatively small value of the effective surface anisotropy constant K(s) = 2.9 × 10(-2) erg cm(-2) gives rise to a dramatic broadening of the total energy distribution. The reliability of the average value of the effective anisotropy constant, deduced from magnetic relaxation data, is verified by comparing it to that obtained from the analysis of the shift of the ac susceptibility peaks as a function of the frequency. PMID:21836285
New calorimetric all-particle energy spectrum
NASA Technical Reports Server (NTRS)
Linsley, J.
1985-01-01
Both the maximum size N sub m and the sea level muon size N sub mu have been used separately to find the all-particle energy spectrum in the air shower domain. However the conversion required, whether from N sub m to E or from N sub mu to E, has customarily been carried out by means of calculations based on an assumed cascase model. It is shown here that by combining present data on N sub m and N sub mu spectra with data on: (1); the energy spectrum of air shower muons and (2) the average width of the electron profile, one can obtain empirical values of the N sub m to E and N sub mu to E conversion factors, and an empirical calorimetric all-particle spectrum, in the energy range 2 x 10 to the 6th power E 2 x 10 to the 9th power GeV.
Energy spectrum control for modulated proton beams.
Hsi, Wen C; Moyers, Michael F; Nichiporov, Dmitri; Anferov, Vladimir; Wolanski, Mark; Allgower, Chris E; Farr, Jonathan B; Mascia, Anthony E; Schreuder, Andries N
2009-06-01
In proton therapy delivered with range modulated beams, the energy spectrum of protons entering the delivery nozzle can affect the dose uniformity within the target region and the dose gradient around its periphery. For a cyclotron with a fixed extraction energy, a rangeshifter is used to change the energy but this produces increasing energy spreads for decreasing energies. This study investigated the magnitude of the effects of different energy spreads on dose uniformity and distal edge dose gradient and determined the limits for controlling the incident spectrum. A multilayer Faraday cup (MLFC) was calibrated against depth dose curves measured in water for nonmodulated beams with various incident spectra. Depth dose curves were measured in a water phantom and in a multilayer ionization chamber detector for modulated beams using different incident energy spreads. Some nozzle entrance energy spectra can produce unacceptable dose nonuniformities of up to +/-21% over the modulated region. For modulated beams and small beam ranges, the width of the distal penumbra can vary by a factor of 2.5. When the energy spread was controlled within the defined limits, the dose nonuniformity was less than +/-3%. To facilitate understanding of the results, the data were compared to the measured and Monte Carlo calculated data from a variable extraction energy synchrotron which has a narrow spectrum for all energies. Dose uniformity is only maintained within prescription limits when the energy spread is controlled. At low energies, a large spread can be beneficial for extending the energy range at which a single range modulator device can be used. An MLFC can be used as part of a feedback to provide specified energy spreads for different energies. PMID:19610318
Energy spectrum control for modulated proton beams
Hsi, Wen C.; Moyers, Michael F.; Nichiporov, Dmitri; Anferov, Vladimir; Wolanski, Mark; Allgower, Chris E.; Farr, Jonathan B.; Mascia, Anthony E.; Schreuder, Andries N.
2009-06-15
In proton therapy delivered with range modulated beams, the energy spectrum of protons entering the delivery nozzle can affect the dose uniformity within the target region and the dose gradient around its periphery. For a cyclotron with a fixed extraction energy, a rangeshifter is used to change the energy but this produces increasing energy spreads for decreasing energies. This study investigated the magnitude of the effects of different energy spreads on dose uniformity and distal edge dose gradient and determined the limits for controlling the incident spectrum. A multilayer Faraday cup (MLFC) was calibrated against depth dose curves measured in water for nonmodulated beams with various incident spectra. Depth dose curves were measured in a water phantom and in a multilayer ionization chamber detector for modulated beams using different incident energy spreads. Some nozzle entrance energy spectra can produce unacceptable dose nonuniformities of up to {+-}21% over the modulated region. For modulated beams and small beam ranges, the width of the distal penumbra can vary by a factor of 2.5. When the energy spread was controlled within the defined limits, the dose nonuniformity was less than {+-}3%. To facilitate understanding of the results, the data were compared to the measured and Monte Carlo calculated data from a variable extraction energy synchrotron which has a narrow spectrum for all energies. Dose uniformity is only maintained within prescription limits when the energy spread is controlled. At low energies, a large spread can be beneficial for extending the energy range at which a single range modulator device can be used. An MLFC can be used as part of a feedback to provide specified energy spreads for different energies.
Bisnovatyi-Kogan, Gennady S.
2009-09-20
We construct numerical models of spherically symmetric Newtonian stellar clusters with anisotropic distribution functions. These models generalize solutions obtained earlier for isotropic Maxwellian distribution functions with an energy cutoff and take into account distributions with different levels of anisotropy.
Energy spectrum of buoyancy-driven turbulence.
Kumar, Abhishek; Chatterjee, Anando G; Verma, Mahendra K
2014-08-01
Using high-resolution direct numerical simulation and arguments based on the kinetic energy flux Π(u), we demonstrate that, for stably stratified flows, the kinetic energy spectrum E(u)(k)∼k(-11/5), the potential energy spectrum E(θ)(k)∼k(-7/5), and Π(u)(k)∼k(-4/5) are consistent with the Bolgiano-Obukhov scaling. This scaling arises due to the conversion of kinetic energy to the potential energy by buoyancy. For weaker buoyancy, this conversion is weak, hence E(u)(k) follows Kolmogorov's spectrum with a constant energy flux. For Rayleigh-Bénard convection, we show that the energy supply rate by buoyancy is positive, which leads to an increasing Π(u)(k) with k, thus ruling out Bolgiano-Obukhov scaling for the convective turbulence. Our numerical results show that convective turbulence for unit Prandt number exhibits a constant Π(u)(k) and E(u)(k)∼k(-5/3) for a narrow band of wave numbers. PMID:25215829
Energy spectrum of buoyancy-driven turbulence
NASA Astrophysics Data System (ADS)
Kumar, Abhishek; Chatterjee, Anando G.; Verma, Mahendra K.
2014-08-01
Using high-resolution direct numerical simulation and arguments based on the kinetic energy flux Πu, we demonstrate that, for stably stratified flows, the kinetic energy spectrum Eu(k)˜k-11/5, the potential energy spectrum Eθ(k)˜k-7/5, and Πu(k)˜k-4/5 are consistent with the Bolgiano-Obukhov scaling. This scaling arises due to the conversion of kinetic energy to the potential energy by buoyancy. For weaker buoyancy, this conversion is weak, hence Eu(k) follows Kolmogorov's spectrum with a constant energy flux. For Rayleigh-Bénard convection, we show that the energy supply rate by buoyancy is positive, which leads to an increasing Πu(k) with k, thus ruling out Bolgiano-Obukhov scaling for the convective turbulence. Our numerical results show that convective turbulence for unit Prandt number exhibits a constant Πu(k) and Eu(k)˜k-5/3 for a narrow band of wave numbers.
Adaptive, full-spectrum solar energy system
Muhs, Jeffrey D.; Earl, Dennis D.
2003-08-05
An adaptive full spectrum solar energy system having at least one hybrid solar concentrator, at least one hybrid luminaire, at least one hybrid photobioreactor, and a light distribution system operably connected to each hybrid solar concentrator, each hybrid luminaire, and each hybrid photobioreactor. A lighting control system operates each component.
Search for ultra high energy cosmic ray anisotropy with Auger
NASA Astrophysics Data System (ADS)
Boghrat, Pedram
2008-09-01
isotropic. In fact, no events out of 10 events in an independent data set are found to correlate. Therefore, this hypothesis is also disfavored. The region 17° around Cen A is shown to have an excess of UHECR with energies larger than 57EeV with a confidence of 2.3x10 -3 . However, Cen A is not shown to be the source unambiguously. Despite this, Cen A is the closest radiogalaxy, at 3.4 Mpc, whose radio lobes extend over about 10° of the sky and is themost likely source of this anisotropy.
NASA Astrophysics Data System (ADS)
Sandratskii, L. M.
2015-10-01
We report the first-principles study of the correlated behavior of the magnetic anisotropy energy (MAE) and orbital moment anisotropy (OMA) as the functions of the thickness N of the Fe film. The work is motivated by recent experimental studies combining photoemission, x-ray magnetic circular dichroism, and magnetic anisotropy measurements. In agreement with experiment, the correlated oscillations of MAE (N ) and OMA (N ) are obtained that have their origin in the formation of the 3d quantum well states (QWS) confined in the films. The main contribution to the oscillation amplitude comes from the surface layer. This is an interesting feature of the phenomenon consisting in the peculiar dependence of the physical quantities on the thickness of the film. We demonstrate that the band structure of the bulk Fe does not reflect adequately the properties of the 3d QWS in thin films and, therefore, does not provide the basis for understanding the oscillations of MAE (N ) and OMA (N ) . A detailed point-by-point analysis in the two-dimensional (2D) Brillouin zone (BZ) of the film shows that the contribution of the Γ point, contrary to a rather common expectation, does not play an important role in the formation of the oscillations. Instead, the most important contributions come from a broad region of the 2D BZ distant from the center of the BZ. Combining symmetry arguments and direct calculations we show that orbital moments of the electronic states possess nonzero transverse components orthogonal to the direction of the spin magnetization. The account for this feature is crucial in the point-by-point analysis of the OMA. On the basis of the calculations for noncollinear spin configurations we suggest interpretations of two interesting experimental findings: fast temperature decay of the oscillation amplitude in MAE (N ) and unexpectedly strong spin mixing of the initial states of the photoemission process.
On the Site-Decomposition of Magnetocrystalline Anisotropy Energy Using Ome-Electron Eigenstates
Aberg, Daniel; Sadigh, Babak; Benedict, Lorin X.
2015-10-26
We discuss two di erent schemes for decomposing the magnetocrystalline anisotropy energy into atomic site-speci c contributions, and show that one of these, which uses projected single-particle states, is inherently ill-de ned in practical applications. We therefore argue that the other decomposition scheme, involving ground state matrix elements of the spin-orbit operator, is preferable for the numerical prediction of one-site contributions to the anisotropy.
NASA Astrophysics Data System (ADS)
Sauls, James; Wu, Hao; Chung, Suk Bum
2015-06-01
Recent theories of Sr2RuO4 based on the interplay of strong interactions, spin-orbit coupling and multi-band anisotropy predict chiral or helical ground states with strong anisotropy of the pairing states, with deep minima in the excitation gap, as well as strong phase anisotropy for the chiral ground state. We develop time-dependent mean field theory to calculate the Bosonic spectrum for the class of 2D chiral superconductors spanning 3He-A to chiral superconductors with strong anisotropy. Chiral superconductors support a pair of massive Bosonic excitations of the time-reversed pairs labeled by their parity under charge conjugation. These modes are degenerate for 2D 3He-A. Crystal field anisotropy lifts the degeneracy. Strong anisotropy also leads to low-lying Fermions, and thus to channels for the decay of the Bosonic modes. Selection rules and phase space considerations lead to large asymmetries in the lifetimes and hybridization of the Bosonic modes with the continuum of un-bound Fermion pairs. We also highlight results for the excitation of the Bosonic modes by microwave radiation that provide clear signatures of the Bosonic modes of an anisotropic chiral ground state.
Anisotropies of ultrahigh energy cosmic ray nuclei diffusing from extragalactic sources
NASA Astrophysics Data System (ADS)
Harari, Diego; Mollerach, Silvia; Roulet, Esteban
2015-09-01
We obtain the dipolar anisotropies in the arrival directions of ultrahigh energy cosmic ray nuclei diffusing from nearby extragalactic sources. We consider mixed-composition scenarios in which different cosmic ray nuclei are accelerated up to the same maximum rigidity, so that E
Universal energy spectrum from point sources
NASA Technical Reports Server (NTRS)
Tomozawa, Yukio
1992-01-01
The suggestion is made that the energy spectrum from point sources such as galactic black hole candidates (GBHC) and active galactic nuclei (AGN) is universal on the average, irrespective of the species of the emitted particles, photons, nucleons, or others. The similarity between the observed energy spectra of cosmic rays, gamma-rays, and X-rays is discussed. In other words, the existing data for gamma-rays and X-rays seem to support the prediction. The expected data from the Gamma Ray Observatory are to provide a further test.
MAGNETIC FIELDS AND COSMIC-RAY ANISOTROPIES AT TeV ENERGIES
Battaner, Eduardo; Castellano, Joaquín; Masip, Manuel E-mail: jcastellano@correo.ugr.es
2015-02-01
Several cosmic-ray (CR) observatories have provided high-accuracy maps of the sky at TeV-PeV energies. The data reveal an O(0.1%) deficit from north galactic directions that peaks at 10 TeV and then evolves with the energy, together with other anisotropies at smaller angular scales. Using the Boltzmann equation, we derive expressions for the CR flux that fit these features. The anisotropies depend on the local interstellar magnetic field B{sub IS}, on the average galactic field B{sub R} in our vicinity, and on correlations between fluctuating quantities. We show that the initial dipole anisotropy along B{sub IS} can be modulated by changes in the global CR flow, and that a variation in the dipole direction would imply a given radius of coherence for the local B{sub IS}. We also show that small- and medium-scale anisotropies may appear when the full-sky anisotropy finds a field configuration acting as a magnetic lens.
ADAPTIVE FULL-SPECTRUM SOLOR ENERGY SYSTEMS
Byard D. Wood
2004-04-01
This RD&D project is a three year team effort to develop a hybrid solar lighting (HSL) system that transports solar light from a paraboloidal dish concentrator to a luminaire via a large core polymer fiber optic. The luminaire can be a device to distribute sunlight into a space for the production of algae or it can be a device that is a combination of solar lighting and electric lighting. A benchmark prototype system has been developed to evaluate the HSL system. Sunlight is collected using a one-meter paraboloidal concentrator dish with two-axis tracking. A secondary mirror consisting of eight planar-segmented mirrors directs the visible part of the spectrum to eight fibers (receiver) and subsequently to eight luminaires. This results in about 8,200 lumens incident at each fiber tip. Each fiber can illuminate about 16.7 m{sup 2} (180 ft{sup 2}) of office space. The IR spectrum is directed to a thermophotovoltaic (TPV) array to produce electricity. During this reporting period, the project team made advancements in the design of the second generation (Alpha) system. For the Alpha system, the eight individual 12 mm fibers have been replaced with a centralized bundle of 3 mm fibers. The TRNSYS Full-Spectrum Solar Energy System model has been updated and new components have been added. The TPV array and nonimaging device have been tested and progress has been made in the fiber transmission models. A test plan was developed for both the high-lumen tests and the study to determine the non-energy benefits of daylighting. The photobioreactor team also made major advancements in the testing of model scale and bench top lab-scale systems.
The fractal energy measurement and the singularity energy spectrum analysis
NASA Astrophysics Data System (ADS)
Xiong, Gang; Zhang, Shuning; Yang, Xiaoniu
2012-12-01
The singularity exponent (SE) is the characteristic parameter of fractal and multifractal signals. Based on SE, the fractal dimension reflecting the global self-similar character, the instantaneous SE reflecting the local self-similar character, the multifractal spectrum (MFS) reflecting the distribution of SE, and the time-varying MFS reflecting pointwise multifractal spectrum were proposed. However, all the studies were based on the depiction of spatial or differentiability characters of fractal signals. Taking the SE as the independent dimension, this paper investigates the fractal energy measurement (FEM) and the singularity energy spectrum (SES) theory. Firstly, we study the energy measurement and the energy spectrum of a fractal signal in the singularity domain, propose the conception of FEM and SES of multifractal signals, and investigate the Hausdorff measure and the local direction angle of the fractal energy element. Then, we prove the compatibility between FEM and traditional energy, and point out that SES can be measured in the fractal space. Finally, we study the algorithm of SES under the condition of a continuous signal and a discrete signal, and give the approximation algorithm of the latter, and the estimations of FEM and SES of the Gaussian white noise, Fractal Brownian motion and the multifractal Brownian motion show the theoretical significance and application value of FEM and SES.
Shick, A B; Hong, S C; Maca, F; Lichtenstein, A I
2014-11-26
The electronic structure, magnetic moments, effective exchange interaction parameter and the magnetic anisotropy energy of [monolayer Co]/Ir(1 1 1) and Co intercalated graphene on Ir(1 1 1) are studied making use of the first-principles density functional theory calculations. A large positive magnetic anisotropy of 1.24 meV/Co is found for [monolayer Co]/Ir(1 1 1), and a high Curie temperature of 1190 K is estimated. These findings show the Co/Ir(1 1 1) system is a promising candidate for perpendicular ultra-high density magnetic recording applications. The magnetic moments, exchange interactions and the magnetic anisotropy are strongly affected by graphene. Reduction of the magnetic anisotropy and the Curie temperature are found for graphene/[monolayer Co]/Ir(1 1 1). It is shown that for graphene placed in the hollow-hexagonal positions over the monolayer Co, the magnetic anisotropy remains positive, while for the placements with one of the C atoms on the top of Co it becomes negative. These findings may be important for assessing the use of graphene for magnetic recording and magnetoelectronic applications. PMID:25351898
Study of the high energy Cosmic Rays large scale anisotropies with the ANTARES neutrino telescope
NASA Astrophysics Data System (ADS)
Illuminati, Giulia
2016-02-01
We present the analysis method used to search for an anisotropy in the high energy Cosmic Rays arrival distribution using data collected by the ANTARES telescope. ANTARES is a neutrino detector, where the collected data are dominated by a large background of cosmic ray muons. Therefore, the background data are suitable for high-statistics studies of cosmic rays in the Northern sky. The main challenge for this analysis is accounting for those effects which can mimic an apparent anisotropy in the muon arrival direction: the detector exposure asymmetries, non-uniform time coverage, diurnal and seasonal variation of the atmospheric temperature. Once all these effects have been corrected, a study of the anisotropy profiles along the right ascension can be performed.
Gradients and anisotropies of high energy cosmic rays in the outer heliosphere
NASA Technical Reports Server (NTRS)
Fillius, W.; Roelof, E. C.; Smith, E. J.; Wood, D.; Ip, W. H.
1985-01-01
Previous studies at lower energies have shown that the cosmic ray density gradients vary in space and time, and many authors currently are suggesting that the radial gradient associated with solar cycle modulation is supported largely by narrow barriers which encircle the Sun and propagate outward with the solar wind. If so, the anisotropy is a desirable way to detect spatial gradients, because it can be associated with the local solar wind and magnetic field conditions. With this in mind, the anisotropy measurements made by the UCSD Cerenkov detectors on Pioneers 10 and 11 are studied. It is shown that the local anisotropy varies greatly, but that the long term average is consistent with the global radial gradient measured between two spacecraft over a baseline of many AU.
SLC energy spectrum monitor using synchrotron radiation
Seeman, J.; Brunk, W.; Early, R.; Ross, M.; Tillmann, E.; Walz, D.
1986-04-01
The SLAC Linac is being upgraded for the use in the SLAC Linear Collider (SLC). The improved Linac must accelerate electron and positron bunches from 1.2 GeV to 50 GeV while producing output energy spectra of about 0.2%. The energy spectra must be maintained during operation to provide for good beam transmission and to minimize chromatic effects in the SLC ARCs and Final Focus. the energy spectra of these beams are determined by the bunch length and intensity, the RF phase and waveform and the intra-bunch longitudinal wakefields. A non-destructive energy spectrum monitor has been designed using a vertical wiggler magnet located downstream of the horizontal beam splitter at the end of the SLC Linac. It produces synchrotron radiation which is viewed in an off-axis x-ray position sensitive detector. The expected resolution is 0.08%. The design considerations of this monitor are presented in this paper. A pair of these monitors is under construction with an installation date set for late summer 1986. 5 refs., 6 figs.
The matter power spectrum of dark energy models and the Harrison-Zel'dovich prescription
Duran, Ivan; Pavón, Diego; Atrio-Barandela, Fernando E-mail: atrio@usal.es
2012-04-01
According to the Harrison-Zel'dovich prescription, the amplitude of matter density perturbations at horizon crossing is the same at all scales. Based on this prescription, we show how to construct the matter power spectrum of generic dark energy models from the power spectrum of a ΛCDM model without the need of solving in full the dynamical equations describing the evolution of all energy density perturbations. Our approach allows to make model predictions of observables that can be expressed in terms of the matter power spectrum alone, such as the amplitude of matter fluctuations, peculiar velocities, cosmic microwave background temperature anisotropies on large angular scales or the weak lensing convergence spectrum. Then, models that have been tested only at the background level using the rate of the expansion of the Universe can now be tested using data on gravitational clustering and on large scale structure. This method can save a lot of effort in checking the validity of dark energy models. As an example of the accurateness of the approximation used, we compute the power spectrum of different dark energy models with constant equation of state parameter (w{sub DE} = −0.1, -0.5 and -0.8, ruled out by observations but easy to compare to numerical solutions) using our methodology and discuss the constraints imposed by the low multipoles of the cosmic microwave background.
Cosmological anisotropy from non-comoving dark matter and dark energy
Harko, Tiberiu; Lobo, Francisco S. N. E-mail: flobo@cii.fc.ul.pt
2013-07-01
We consider a cosmological model in which the two major fluid components of the Universe, dark energy and dark matter, flow with distinct four-velocities. This cosmological configuration is equivalent to a single anisotropic fluid, expanding with a four-velocity that is an appropriate combination of the two fluid four-velocities. The energy density of the single cosmological fluid is larger than the sum of the energy densities of the two perfect fluids, i.e., dark energy and dark matter, respectively, and contains a correction term due to the anisotropy generated by the differences in the four-velocities. Furthermore, the gravitational field equations of the two-fluid anisotropic cosmological model are obtained for a Bianchi type I geometry. By assuming that the non-comoving motion of the dark energy and dark matter induces small perturbations in the homogeneous and isotropic Friedmann-Lemaitre-Robertson-Walker type cosmological background, and that the anisotropy parameter is small, the equations of the cosmological perturbations due to the non-comoving nature of the two major components are obtained. The time evolution of the metric perturbations is explicitly obtained for the cases of the exponential and power law background cosmological expansion. The imprints of a non-comoving dark energy - dark matter on the Cosmic Microwave Background and on the luminosity distance are briefly discussed, and the temperature anisotropies and the quadrupole are explicitly obtained in terms of the metric perturbations of the flat background metric. Therefore, if there is a slight difference between the four-velocities of the dark energy and dark matter, the Universe would acquire some anisotropic characteristics, and its geometry will deviate from the standard FLRW one. In fact, the recent Planck results show that the presence of an intrinsic large scale anisotropy in the Universe cannot be excluded a priori, so that the model presented in this work can be considered as a
Energy Dependence of Electron Anisotropy and Agyrotropy from PIC Simulations of Tail Reconnection
NASA Astrophysics Data System (ADS)
Newman, D. L.; Goldman, M. V.; Lapenta, G.; Eastwood, J. P.
2015-12-01
MMS is capable of measuring particle distributions with unprecedented temporal resolution. These distributions will aid in the identification of key regions of the reconnecting plasma, such as the electron diffusion region and dipolarization fronts (DFs) in Earth's magnetotail. Electron anisotropy and agyrotropy are particularly useful diagnostics for this purpose. Normally, anisotropy and agyrotropy are defined as properties of the total pressure tensor. However, such global velocity-space measures of the electron distribution can hide detailed energy-dependent variations. Using electron distributions from 2D and 3D PIC simulations of tail reconnection, we employ a combination of 3D velocity-space visualization techniques and energy-dependent anisotropy and agyrotropy measures to analyze the distributions from regions in the vicinity of the reconnection x-line, the magnetic separatricies, and DFs. For example, regions of the reconnection exhaust near a DF can exhibit a nearly isotropic pressure tensor due to the competing influences of low-energy electrons, which contribute disproportionately to the parallel pressure, and high-energy electron, which contribute disproportionately to the perpendicular pressure.
Angular anisotropy of photofission of even-even nuclei at above-barrier energies
Rudnikov, V.E.; Smirenkin, G.N.; Soldatov, A.S.; Juhasz, S.
1988-09-01
Results of measurements are presented for angular distributions of photofission fragments of /sup 232/Th and /sup 234//sup ,//sup 236//sup ,//sup 238/U by bremsstrahlung ..gamma.. rays in the maximum energy range of E/sub max/ = 6--10 MeV. The observed angular anisotropy of photofission is discussed as a function of E/sub max/ and the nucleon composition of the nucleus.
Effect of photon energy spectrum on dosimetric parameters of brachytherapy sources
Ghorbani, Mahdi; Davenport, David
2016-01-01
Abstract Aim The aim of this study is to quantify the influence of the photon energy spectrum of brachytherapy sources on task group No. 43 (TG-43) dosimetric parameters. Background Different photon spectra are used for a specific radionuclide in Monte Carlo simulations of brachytherapy sources. Materials and methods MCNPX code was used to simulate 125I, 103Pd, 169Yb, and 192Ir brachytherapy sources. Air kerma strength per activity, dose rate constant, radial dose function, and two dimensional (2D) anisotropy functions were calculated and isodose curves were plotted for three different photon energy spectra. The references for photon energy spectra were: published papers, Lawrence Berkeley National Laboratory (LBNL), and National Nuclear Data Center (NNDC). The data calculated by these photon energy spectra were compared. Results Dose rate constant values showed a maximum difference of 24.07% for 103Pd source with different photon energy spectra. Radial dose function values based on different spectra were relatively the same. 2D anisotropy function values showed minor differences in most of distances and angles. There was not any detectable difference between the isodose contours. Conclusions Dosimetric parameters obtained with different photon spectra were relatively the same, however it is suggested that more accurate and updated photon energy spectra be used in Monte Carlo simulations. This would allow for calculation of reliable dosimetric data for source modeling and calculation in brachytherapy treatment planning systems. PMID:27247558
Turner, Michael J; Thomas, Sajesh P; Shi, Ming W; Jayatilaka, Dylan; Spackman, Mark A
2015-03-01
We present an approach to understanding crystal packing via 'energy frameworks', that combines efficient calculation of accurate intermolecular interaction energies with a novel graphical representation of their magnitude. In this manner intriguing questions, such as why some crystals bend with an applied force while others break, and why one polymorph of a drug exhibits exceptional tabletability compared to others, can be addressed in terms of the anisotropy of the topology of pairwise intermolecular interaction energies. This approach is applied to a sample of organic molecular crystals with known bending, shearing and brittle behaviour, to illustrate its use in rationalising their mechanical behaviour at a molecular level. PMID:25525647
On muon energy spectrum in muon groups underground
NASA Technical Reports Server (NTRS)
Bakatanov, V. N.; Chudakov, A. E.; Novoseltsev, Y. F.; Novoseltseva, M. V.; Stenkin, Y. V.
1985-01-01
A method is described which was used to measure muon energy spectrum characteristics in muon groups underground using mu-e decays recording. The Baksan Telescope's experimental data on mu-e decays intensity in muon groups of various multiplicities are analyzed. The experimental data indicating very flat spectrum does not however represent the total spectrum in muon groups. Obviously the muon energy spectrum depends strongly on a distance from the group axis. The core attraction effect makes a significant distortion, making the spectrum flatter. After taking this into account and making corrections for this effect the integral total spectrum index in groups has a very small depencence on muon multiplicity and agrees well with expected one: beta=beta (sub expected) = 1.75.
NASA Technical Reports Server (NTRS)
Fichtel, C. E.; Simpson, G. A.; Thompson, D. J.
1978-01-01
Results are reported for an investigation of the intensity, energy spectrum, and spatial distribution of the diffuse gamma radiation detected by SAS 2 away from the galactic plane in the energy range above 35 MeV. The gamma-ray data are compared with relevant data obtained at other wavelengths, including 21-cm emission, radio continuum radiation, and the limited UV and radio information on local molecular hydrogen. It is found that there are two quite distinct components to the diffuse radiation, one of which shows a good correlation with the galactic matter distribution and continuum radiation, while the other has a much steeper energy spectrum and appears to be isotropic at least on a coarse scale. The galactic component is interpreted in terms of its implications for both local and more distant regions of the Galaxy. The apparently isotropic radiation is discussed partly with regard to the constraints placed on possible models by the steep energy spectrum, the observed intensity, and an upper limit on the anisotropy.
Ion Anisotropy and High-Energy Variability of Large Solar Particle Events: A Comparative Study
NASA Technical Reports Server (NTRS)
Tan, Lun C.; Reames, Donald V.; Ng, Chee K.
2008-01-01
We have made comparative studies of ion anisotropy and high-energy variability of solar energetic particle (SEP) events previously examined by the Solar, Heliospheric, and Interplanetary Environment (SHINE) Workshop campaign. We have found distinctly different characteristics of SEPs between two large "gradual" events having very similar solar progenitors (the 2002 April 21 and August 24 events). Since the scattering centers of SEPs are approximately frozen in the solar wind, we emphasize work in the solar-wind frame where SEPs tend to be isotropized, and small anisotropies are easier to detect. While in the August event no streaming reversal occurred, in the April event the field-aligned anisotropy of all heavy ions showed sign of streaming reversal. The difference in streaming reversal was consistent with the difference in the presence of the outer reflecting boundary. In the April event the magnetic mirror, which was located behind the interplanetary shock driven by the preceding coronal mass ejection (CME), could block the stream of SEPs, while in the August event SEPs escaped freely because of the absence of nearby boundary. The magnetic mirror was formed at the bottleneck of magnetic field lines draped around a flank of the preceding CME. In the previous SHINE event analysis the contrasting event durations and Fe/O ratios of the both events were explained as the interplay between shock geometry and seed population. Our new findings, however, indicate that event duration and time as well as spectral variation are also affected by the presence of a nearby reflecting boundary.
Gradients and anisotropies of high energy cosmic rays in the outer heliosphere
NASA Technical Reports Server (NTRS)
Fillius, W.; Roelof, E. C.; Smith, E. J.; Wood, D.; Ip, W. H.
1985-01-01
Two cosmic rays which pass through the same point going in opposite directions will, in the absence of scattering and inhomogeneities in the magnetic field, trace helices about adjacent flux tubes, whose centerlines are separated by one gyrodiameter. A directional anisotropy at the point suggests a difference in the number of cosmic rays loading the two flux tubes; that is, a density gradient over the baseline of a gyrodiameter. Previous studies at lower energies have shown that the cosmic ray density gradients vary in time and space. It is suggested that the radial gradient associated with solar cycle modulation is supported largely by narrow barriers which encircle the sun and propagate outward with the solar wind. If so, the anisotropy is a desirable way to detect spatial gradients, because it can be associated with the local solar wind and magnetic field conditions. Anisotropic measurements made by Cerenkov detectors on Pioneers 10 and 11 were studied. It was found that local anisotropy varies greatly, but that the long term average is consistent with the global radial gradient measured between two spacecraft over a baseline of many AU.
Energy spectrum of stably-stratified and convective turbulent flows
NASA Astrophysics Data System (ADS)
Verma, Mahendra; Kumar, Abhishek
2015-11-01
In the inertial range of fluid turbulence, the energy flux is constant, while the energy spectrum scales as k - 5 / 3 (k=wavenumber). The buoyancy however could change the phenomenology dramatically. Bolgiano and Obukhov (1959) had conjectured that stably stratified flows (as in atmosphere) exhibits a decrease in the energy flux as k - 4 / 5 due to the conversion of kinetic energy to the potential energy, consequently, the energy spectrum scales as k - 11 / 5. We show using detailed numerical analysis that the stably stratified flows indeed exhibit k - 11 / 5 energy spectrum for Froude numbers Fr near unity. The flow becomes anisotropic for small Froude numbers. For weaker buoyancy (large Fr), the kinetic energy follows Kolmogorov's spectrum with a constant energy flux. However, in convective turbulence, the energy flux is a nondecreasing function of wavenumber since the buoyancy feeds positively into the kinetic energy. Hence, the kinetic energy spectrum is Kolmogorov-like (k - 5 / 3) or shallower. We also demonstrate the above scaling using a shell model of buoyancy-driven turbulence.
Turbulent diffusion phase transition is due to singular energy spectrum.
Wallstrom, T C
1995-01-01
The phase transition for turbulent diffusion, reported by Avellaneda and Majda [Avellaneda, M. & Majda, A. J. (1994) Philos. Trans. R. Soc. London A 346, 205-233, and several earlier papers], is traced to a modeling assumption in which the energy spectrum of the turbulent fluid is singularly dependent on the viscosity in the inertial range. Phenomenological models of turbulence and intermittency, by contrast, require that the energy spectrum be independent of the viscosity in the inertial range. When the energy spectrum is assumed to be consistent with the phenomenological models, there is no phase transition for turbulent diffusion. Images Fig. 2 PMID:11607590
One particularity of energy-angular secondary electrons spectrum
NASA Astrophysics Data System (ADS)
Borisov, S. S.; Zaitsev, S. I.
2006-05-01
In this work we discuss the problems of the energy-angular spectrum of backscattered and true secondary electrons simulation using the discrete (DLA) and the continuous (CLA) loss approximations. The presence of an angular spectrum artefact - the deviation from the sinusoidal distribution over the range of 177-18O° from the beam direction is shown.
Spectrum and energy transfer in steady Burgers turbulence
NASA Technical Reports Server (NTRS)
Girimaji, Sharath S.; Zhou, YE
1995-01-01
The spectrum, energy transfer, and spectral interactions in steady Burgers turbulence are studied using numerically generated data. The velocity field is initially random and the turbulence is maintained steady by forcing the amplitude of a band of low wavenumbers to be invariant in time, while permitting the phase to change as dictated by the equation. The spectrum, as expected, is very different from that of Navier-Stokes turbulence. It is demonstrated that the far range of the spectrum scales as predicted by Burgers. Despite the difference in their spectra, in matters of the spectral energy transfer and triadic interactions Burgers turbulence is similar to Navier-Stokes turbulence.
Electromagnetic Weibel Instability in Intense Charged Particle Beams with Large Energy Anisotropy
Edward A. Startsev; Ronald C. Davidson
2003-10-20
In plasmas with strongly anisotropic distribution functions, collective instabilities may develop if there is sufficient coupling between the transverse and longitudinal degrees of freedom. Our previous numerical and theoretical studies of intense charged particle beams with large temperature anisotropy [E. A. Startsev, R. C. Davidson and H. Qin, PRSTAB, 6, 084401 (2003); Phys. Plasmas 9, 3138 (2002)] demonstrated that a fast, electrostatic, Harris-like instability develops, and saturates nonlinearly, for sufficiently large temperature anisotropy (T{sub {perpendicular}b}/T{sub {parallel}b} >> 1). The total distribution function after saturation, however, is still far from equipartitioned. In this paper the linearized Vlasov-Maxwell equations are used to investigate detailed properties of the transverse electromagnetic Weibel-type instability for a long charge bunch propagating through a cylindrical pipe of radius r{sub w}. The kinetic stability analysis is carried out for azimuthally symmetric perturbations about a two-temperature thermal equilibrium distribution in the smooth-focusing approximation. The most unstable modes are identified, and their eigenfrequencies, radial mode structure and instability thresholds are determined. The stability analysis shows that, although there is free energy available to drive the electromagnetic Weibel instability, the finite transverse geometry of the charged particle beam introduces a large threshold value for the temperature anisotropy ((T{sub {perpendicular}b}/T{sub {parallel}b}){sup Weibel} >> (T{sub {perpendicular}b}/T{sub {parallel}b}){sup Harris}) below which the instability is absent. Hence, unlike the case of an electrically neutral plasma, the Weibel instability is not expected to play as significant a role in the process of energy isotropization of intense unneutralized charged particle beams as the electrostatic Harris-type instability.
Electromagnetic Weibel instability in intense charged particle beams with large energy anisotropy
NASA Astrophysics Data System (ADS)
Startsev, Edward A.; Davidson, Ronald C.
2003-12-01
In plasmas with strongly anisotropic distribution functions, collective instabilities may develop if there is sufficient coupling between the transverse and longitudinal degrees of freedom. Our previous numerical and theoretical studies of intense charged particle beams with large temperature anisotropy [E. A. Startsev, R. C. Davidson, and H. Qin, Phys. Rev. ST Accel. Beams 6, 084401 (2003); Phys. Plasmas 9, 3138 (2002)] demonstrated that a fast, electrostatic, Harris-type instability develops, and saturates nonlinearly, for sufficiently large temperature anisotropy (T⊥b/T∥b≫1). The total distribution function after saturation, however, is still far from equipartitioned. In this paper the linearized Vlasov-Maxwell equations are used to investigate detailed properties of the transverse electromagnetic Weibel-type instability for a long charge bunch propagating through a cylindrical pipe of radius rw. The kinetic stability analysis is carried out for azimuthally symmetric perturbations about a two-temperature thermal equilibrium distribution in the smooth-focusing approximation. The most unstable modes are identified, and their eigenfrequencies, radial mode structure and instability thresholds are determined. The stability analysis shows that, although there is free energy available to drive the electromagnetic Weibel instability, the finite transverse geometry of the charged particle beam introduces a large threshold value for the temperature anisotropy [(T⊥b/T∥b)Weibel≫(T⊥b/T∥b)Harris] below which the instability is absent. Hence, unlike the case of an electrically neutral plasma, the Weibel instability is not expected to play as significant a role in the process of energy isotropization of intense unneutralized charged particle beams as the electrostatic Harris-type instability.
The High Energy Spectrum of NGC 4151
NASA Technical Reports Server (NTRS)
Beckmann, V.; Gehrels, N.; Shrader, C.; Soldi, S.; Lubinski, P.; Zdziarski, A. A.; Petrucci, P.-O.; Malzac, J.
2005-01-01
We present first INTEGRAL observations of the type 1.5 Seyfert galaxy NGC 4151. Combining several INTEGRAL observations performed during 2003, totaling approximately 400 ksec of exposure time, allow us to study the spectrum in the 3 - 300 keV range. The measurements presented here reveal an overall spectrum from X-rays up to the soft gamma-rays that can be described by an absorbed (N(sub H) approximately equal to 5 x 10(exp 22) per square centimeter) and non-variable thermal component, plus a Fe Kalpha line, and an exponential cutoff occurs at 110 keV, consistent with earlier claims. The Galactic hydrogen column density in the line of sight is N(sub H), Gal approximately equal to 2.1 x 10 (exp 20) per square centimeter. The time resolved analysis shows little variation of the spectral parameters. The comparison with CGRO/OSSE data shows that the same spectral model can be applied over a time span of 15 years, while the flux varied by a factor of 2. Applying a Compton reflection component improves the model fit to the INTEGRAL data. Nonetheless the data available to date cannot significantly confirm or exclude the existence of reflection, nor is a high iron overabundance in the absorber, as had been previously suggested, clearly detectable.
Abreu, P
2011-06-17
The Pierre Auger Collaboration has reported evidence for anisotropy in the distribution of arrival directions of the cosmic rays with energies E > Eth = 5.5 x 1019 eV. These show a correlation with the distribution of nearby extragalactic objects, including an apparent excess around the direction of Centaurus A. If the particles responsible for these excesses at E > Eth are heavy nuclei with charge Z, the proton component of the sources should lead to excesses in the same regions at energies E/Z. We here report the lack of anisotropies in these directions at energies above Eth/Z (for illustrativemore » values of Z = 6,13,26). If the anisotropies above Eth are due to nuclei with charge Z, and under reasonable assumptions about the acceleration process, these observations imply stringent constraints on the allowed proton fraction at the lower energies.« less
De Bernardis, Francesco; Pagano, Luca; Melchiorri, Alessandro; Serra, Paolo; Cooray, Asantha E-mail: luca.pagano@roma1.infn.it E-mail: alessandro.melchiorri@roma1.infn.it
2008-06-15
We search for the presence of cosmological neutrino background (CNB) anisotropies in recent Wilkinson Microwave Anisotropy Probe (WMAP) five-year data using their signature imprinted on modifications to the cosmic microwave background (CMB) anisotropy power spectrum. By parameterizing the neutrino background anisotropies with the speed viscosity parameter c{sub vis}, we find that the WMAP five-year data alone provide only a weak indication for CNB anisotropies with c{sub vis}{sup 2}>0.06 at the 95% confidence level. When we combine CMB anisotropy data with measurements of galaxy clustering, the SN-Ia Hubble diagram, and other cosmological information, the detection increases to c{sub vis}{sup 2}>0.16 at the same 95% confidence level. Future data from Planck, combined with a weak lensing survey such as the one expected with DUNE from space, will be able to measure the CNB anisotropy parameter at about 10% accuracy. We discuss the degeneracy between neutrino background anisotropies and other cosmological parameters such as the number of effective neutrinos species and the dark energy equation of state.
On the Linearly-Balanced Kinetic Energy Spectrum
NASA Technical Reports Server (NTRS)
Lu, Huei,-Iin; Robertson, F. R.
1999-01-01
It is well known that the earth's atmospheric motion can generally be characterized by the two dimensional quasi-geostrophic approximation, in which the constraints on global integrals of kinetic energy, entrophy and potential vorticity play very important roles in redistributing the wave energy among different scales of motion. Assuming the hypothesis of Kolmogrov's local isotropy, derived a -3 power law of the equilibrium two-dimensional kinetic energy spectrum that entails constant vorticity and zero energy flows from the energy-containing wave number up to the viscous cutoff. In his three dimensional quasi-geostrophic theory, showed that the spectrum function of the vertical scale turbulence - expressible in terms of the available potential energy - possesses the same power law as the two dimensional kinetic energy spectrum. As the slope of kinetic energy spectrum in the inertial range is theoretically related to the predictability of the synoptic scales (Lorenz, 1969), many general circulation models includes a horizontal diffusion to provide reasonable kinetic energy spectra, although the actual power law exhibited in the atmospheric general circulation is controversial. Note that in either the atmospheric modeling or the observational analyses, the proper choice of wave number Index to represent the turbulence scale Is the degree of the Legendre polynomial.
Ion beam energy spectrum calculation via dosimetry data deconvolution.
Harper-Slaboszewicz, Victor Jozef; Sharp, Andrew Clinton
2010-10-01
The energy spectrum of a H{sup +} beam generated within the HERMES III accelerator is calculated from dosimetry data to refine future experiments. Multiple layers of radiochromic film are exposed to the beam. A graphic user interface was written in MATLAB to align the film images and calculate the beam's dose depth profile. Singular value regularization is used to stabilize the unfolding and provide the H{sup +} beam's energy spectrum. The beam was found to have major contributions from 1 MeV and 8.5 MeV protons. The HERMES III accelerator is typically used as a pulsed photon source to experimentally obtain photon impulse response of systems due to high energy photons. A series of experiments were performed to explore the use of Hermes III to generate an intense pulsed proton beam. Knowing the beam energy spectrum allows for greater precision in experiment predictions and beam model verification.
NASA Technical Reports Server (NTRS)
Marsden, R. G.; Sanderson, T. R.; Wenzel, K. P.; Smith, E. J.
1985-01-01
It is known that the interplanetary medium in the period approaching solar maximum is characterized by an enhancement in the occurrence of transient solar wind streams and shocks and that such systems are often associated with looplike magnetic structures or clouds. There is observational evidence that bidirectional, field aligned flows of low energy particles could be a signature of such looplike structures, although detailed models for the magnetic field configuration and injection mechanisms do not exist at the current time. Preliminary results of a survey of low energy proton bidirectional anisotropies measured on ISEE-3 in the interplanetary medium between August 1978 and May 1982, together with magnetic field data from the same spacecraft are presented.
NREL Spectrum of Clean Energy Innovation: Issue 3 (Book)
Not Available
2012-11-01
This quarterly magazine is dedicated to stepping beyond the technical journals to reveal NREL's vital work in a real-world context for our stakeholders. Continuum provides insights into the latest and most impactful clean energy innovations, while spotlighting those talented researchers and unique facilities that make it all happen. This edition focuses on the NREL Spectrum of Clean Energy Innovation.
Hadron intensity and energy spectrum at 4380 m above level
NASA Technical Reports Server (NTRS)
Cananov, S. D.; Chadranyan, E. K.; Khizanishvili, L. A.; Ladaria, N. K.; Roinishvili, N. N.
1985-01-01
The flux value of hadrons with E (sup gamma) h or = 5 TeV, where E (sup gamma) h or = is the energy transferred into electromagnetic component is presented. It is shown that the energy spectrum slope beta of hadrons with E h or = 20 TeV is equal to 1.9.
Ge, Gui-Xian; Li, Ying-Bin; Wang, Guang-Hou; Wan, Jian-Guo
2016-04-20
To solve the fundamental dilemma in data storage applications, it is crucial to manipulate the magnetic anisotropy energy (MAE). Herein, using first-principles calculations, we predict that the system of double-vacancy graphene decorated by iridium atoms possesses high stability, giant MAE, perpendicular-anisotropy and long-range ferromagnetic coupling. More importantly, the amplitude of MAE can be manipulated by electric fields. This is due to the change in the occupation number of Ir-5d orbitals. The present hybrid system could be a high-performance nanoscale information storage device with ultralow energy consumption. PMID:27063394
Spectrum tailoring of the neutron energy spectrum in the context of delayed neutron detection
Koehler, William E; Tobin, Steve J; Sandoval, Nathan P; Fensin, Mike L
2010-01-01
For the purpose of measuring plutonium mass in spent fuel, a delayed neutron instrument is of particular interest since, if properly designed, the delayed neutron signal from {sup 235}U is significantly stronger than the signature from {sup 239}Pu or {sup 241}Pu. A key factor in properly designing a delayed neutron instrument is to minimize the fission of {sup 238}U. This minimization is achieved by keeping the interrogating neutron spectrum below {approx} 1 MeV. In the context of spent fuel measurements it is desirable to use a 14 MeV (deuterium and tritium) neutron generator for economic reasons. Spectrum tailoring is the term used to describe the inclusion of material between the 14 MeV neutrons and the interrogated object that lower the neutron energy through nuclear reactions and moderation. This report quantifies the utility of different material combination for spectrum tailoring.
Parameterizations of Pion Energy Spectrum in Nucleon-Nucleon Collisions
NASA Technical Reports Server (NTRS)
Cucinotta, Franics A.; Wilson, John W.; Norbury, John W.
1998-01-01
The effects of pion (PI) production are expected to play an important role in radiation exposures in the upper atmosphere or on the Martian surface. Nuclear databases for describing pion production are developed for radiation transport codes to support these studies. We analyze the secondary energy spectrum of pions produced in nucleon-nucleon (NN) collisions in the relativistic one-pion exchange model. Parametric formulas of the isospin cross sections for one-pion production channels are discussed and are used to renormalize the model spectrum. Energy spectra for the deuteron related channels (NN yields dPi) are also described.
Energy Spectrum in the Dissipation Range of Fluid Turbulence
NASA Technical Reports Server (NTRS)
Martinez, D. O.; Chen, S.; Doolen, G. D.; Kraichnan, R. H.; Wang, L.-P.; Zhou, Y.
1996-01-01
High resolution, direct numerical simulations of the three-dimensional incompressible Navier-Stokes equations are carried out to study the energy spectrum in the dissipation range. An energy spectrum of the form A(k/k( sub d))(sup alpha) exp[- betak/k(sub d) is confirmed. The possible values of the parameters alpha and beta, as well as their dependence on Revnolds numbers and length scales, are investigated, showing good agreement with recent theoretical predictions. A "bottleneck'-type effect is reported at k/k(sub d) approximately 4, exhibiting a possible transition from near-dissipation to far- dissipation.
Anisotropy studies around the galactic centre at EeV energies with the Auger Observatory
NASA Astrophysics Data System (ADS)
Abraham, J.; Aglietta, M.; Aguirre, C.; Allard, D.; Allekotte, I.; Allison, P.; Alvarez, C.; Alvarez-Muñiz, J.; Ambrosio, M.; Anchordoqui, L.; Anjos, J. C.; Aramo, C.; Arisaka, K.; Armengaud, E.; Arneodo, F.; Arqueros, F.; Asch, T.; Asorey, H.; Atulugama, B. S.; Aublin, J.; Ave, M.; Avila, G.; Bacelar, J.; Bäcker, T.; Badagnani, D.; Barbosa, A. F.; Barbosa, H. M. J.; Barkhausen, M.; Barnhill, D.; Barroso, S. L. C.; Bauleo, P.; Beatty, J.; Beau, T.; Becker, B. R.; Becker, K. H.; Bellido, J. A.; Benzvi, S.; Berat, C.; Bergmann, T.; Bernardini, P.; Bertou, X.; Biermann, P. L.; Billoir, P.; Blanch-Bigas, O.; Blanco, F.; Blasi, P.; Bleve, C.; Blümer, H.; Boghrat, P.; Boháčová, M.; Bonifazi, C.; Bonino, R.; Boratav, M.; Brack, J.; Brunet, J. M.; Buchholz, P.; Busca, N. G.; Caballero-Mora, K. S.; Cai, B.; Camin, D. V.; Capdevielle, J. N.; Caruso, R.; Castellina, A.; Cataldi, G.; Cazón, L.; Cester, R.; Chauvin, J.; Chiavassa, A.; Chinellato, J. A.; Chou, A.; Chye, J.; Claes, D.; Clark, P. D. J.; Clay, R. W.; Clay, S. B.; Connolly, B.; Cordier, A.; Cotti, U.; Coutu, S.; Covault, C. E.; Cronin, J.; Dagoret-Campagne, S.; Quang, T. Dang; Darriulat, P.; Daumiller, K.; Dawson, B. R.; de Almeida, R. M.; de Carvalho, L. A.; de Donato, C.; de Jong, S. J.; de Mello, W. J. M.; de Mello Neto, J. R. T.; de Mitri, I.; de Oliveira, M. A. L.; de Souza, V.; Del Peral, L.; Deligny, O.; Della Selva, A.; Delle Fratte, C.; Dembinski, H.; di Giulio, C.; Diaz, J. C.; Dobrigkeit, C.; D'Olivo, J. C.; Dornic, D.; Dorofeev, A.; Dova, M. T.; D'Urso, D.; Duvernois, M. A.; Engel, R.; Epele, L.; Erdmann, M.; Escobar, C. O.; Etchegoyen, A.; Ewers, A.; Facal San Luis, P.; Falcke, H.; Fauth, A. C.; Fazio, D.; Fazzini, N.; Fernández, A.; Ferrer, F.; Ferry, S.; Fick, B.; Filevich, A.; Filipčič, A.; Fleck, I.; Fokitis, E.; Fonte, R.; Fuhrmann, D.; Fulgione, W.; García, B.; Garcia-Pinto, D.; Garrard, L.; Garrido, X.; Geenen, H.; Gelmini, G.; Gemmeke, H.; Geranios, A.; Ghia, P. L.; Giller, M.; Gitto, J.; Glass, H.; Gobbi, F.; Gold, M. S.; Gomez Albarracin, F.; Gómez Berisso, M.; Gómez Herrero, R.; Gonçalves Do Amaral, M.; Gongora, J. P.; Gonzalez, D.; Gonzalez, J. G.; González, M.; Góra, D.; Gorgi, A.; Gouffon, P.; Grassi, V.; Grillo, A.; Grunfeld, C.; Grupen, C.; Guarino, F.; Guedes, G. P.; Gutiérrez, J.; Hague, J. D.; Hamilton, J. C.; Harakeh, M. N.; Harari, D.; Harmsma, S.; Hartmann, S.; Harton, J. L.; Haungs, A.; Healy, M. D.; Hebbeker, T.; Heck, D.; Hojvat, C.; Homola, P.; Hörandel, J.; Horneffer, A.; Horvat, M.; Hrabovský, M.; Huege, T.; Iarlori, M.; Insolia, A.; Kaducak, M.; Kalashev, O.; Kampert, K. H.; Keilhauer, B.; Kemp, E.; Klages, H. O.; Kleifges, M.; Kleinfeller, J.; Knapik, R.; Knapp, J.; Koang, D.-H.; Kolotaev, Y.; Kopmann, A.; Krömer, O.; Kuhlman, S.; Kuijpers, J.; Kunka, N.; Kusenko, A.; Lachaud, C.; Lago, B. L.; Lebrun, D.; Lebrun, P.; Lee, J.; Letessier-Selvon, A.; Leuthold, M.; Lhenry-Yvon, I.; Longo, G.; López, R.; Lopez Agüera, A.; Lucero, A.; Maldera, S.; Malek, M.; Maltezos, S.; Mancarella, G.; Manceñido, M. E.; Mandat, D.; Mantsch, P.; Mariazzi, A. G.; Maris, I. C.; Martello, D.; Martinez, N.; Martínez, J.; Martínez, O.; Mathes, H. J.; Matthews, J.; Matthews, J. A. J.; Matthiae, G.; Maurin, G.; Maurizio, D.; Mazur, P. O.; McCauley, T.; McEwen, M.; McNeil, R. R.; Medina, G.; Medina, M. C.; Medina Tanco, G.; Meli, A.; Melo, D.; Menichetti, E.; Menshikov, A.; Meurer, Chr.; Meyhandan, R.; Micheletti, M. I.; Miele, G.; Miller, W.; Mollerach, S.; Monasor, M.; Monnier Ragaigne, D.; Montanet, F.; Morales, B.; Morello, C.; Moreno, E.; Morris, C.; Mostafá, M.; Muller, M. A.; Mussa, R.; Navarra, G.; Nellen, L.; Newman-Holmes, C.; Newton, D.; Thi, T. Nguyen; Nichol, R.; Nierstenhöfer, N.; Nitz, D.; Nogima, H.; Nosek, D.; Nožka, L.; Oehlschläger, J.; Ohnuki, T.; Olinto, A.; Oliveira, L. F. A.; Olmos-Gilbaja, V. M.; Ortiz, M.; Ostapchenko, S.; Otero, L.; Palatka, M.; Pallotta, J.; Parente, G.; Parizot, E.; Parlati, S.; Patel, M.; Paul, T.; Payet, K.; Pech, M.; PeĶala, J.; Pelayo, R.; Pepe, I. M.; Perrone, L.; Petrera, S.; Petrinca, P.; Petrov, Y.; Pham Ngoc, D.; Pham Thi, T. N.; Piegaia, R.; Pierog, T.; Pisanti, O.; Porter, T. A.; Pouryamout, J.; Prado, L.; Privitera, P.; Prouza, M.; Quel, E. J.; Rautenberg, J.; Reis, H. C.; Reucroft, S.; Revenu, B.; Řídký, J.; Risi, A.; Risse, M.; Rivière, C.; Rizi, V.; Robbins, S.; Roberts, M.; Robledo, C.; Rodriguez, G.; Rodríguez Frías, D.; Rodriguez Martino, J.; Rodriguez Rojo, J.; Ros, G.; Rosado, J.; Roth, M.; Roucelle, C.; Rouillé-D'Orfeuil, B.; Roulet, E.; Rovero, A. C.; Salamida, F.; Salazar, H.; Salina, G.; Sánchez, F.; Santander, M.; Santos, E. M.; Sarkar, S.; Sato, R.; Scherini, V.; Schieler, H.; Schmidt, T.; Scholten, O.; Schovánek, P.; Schüssler, F.; Sciutto, S. J.; Scuderi, M.; Semikoz, D.; Sequeiros, G.; Shellard, R. C.; Siffert, B. B.; Sigl, G.; Skelton, P.; Slater, W.; de Grande, N. Smetniansky; Smiałkowski, A.; Šmída, R.; Smith, B. E.; Snow, G. R.; Sokolsky, P.; Sommers, P.; Sorokin, J.; Spinka, H.; Strazzeri, E.; Stutz, A.; Suarez, F.; Suomijärvi, T.; Supanitsky, A. D.; Swain, J.; Szadkowski, Z.; Tamashiro, A.; Tamburro, A.; Tascau, O.; Ticona, R.; Timmermans, C.; Tkaczyk, W.; Todero Peixoto, C. J.; Tonachini, A.; Torresi, D.; Travnicek, P.; Tripathi, A.; Tristram, G.; Tscherniakhovski, D.; Tueros, M.; Tunnicliffe, V.; Ulrich, R.; Unger, M.; Urban, M.; Valdés Galicia, J. F.; Valiño, I.; Valore, L.; van den Berg, A. M.; van Elewyck, V.; Vazquez, R. A.; Veberič, D.; Veiga, A.; Velarde, A.; Venters, T.; Verzi, V.; Videla, M.; Villaseñor, L.; Vo van, T.; Vorobiov, S.; Voyvodic, L.; Wahlberg, H.; Wainberg, O.; Waldenmaier, T.; Walker, P.; Warner, D.; Watson, A. A.; Westerhoff, S.; Wiebusch, C.; Wieczorek, G.; Wiencke, L.; Wilczyńska, B.; Wilczyński, H.; Wileman, C.; Winnick, M. G.; Xu, J.; Yamamoto, T.; Younk, P.; Zas, E.; Zavrtanik, D.; Zavrtanik, M.; Zech, A.; Zepeda, A.; Zha, M.; Ziolkowski, M.; Pierre Auger Collaboration
2007-04-01
Data from the Pierre Auger Observatory are analyzed to search for anisotropies near the direction of the Galactic Centre at EeV energies. The exposure of the surface array in this part of the sky is already significantly larger than that of the fore-runner experiments. Our results do not support previous findings of localized excesses in the AGASA and SUGAR data. We set an upper bound on a point-like flux of cosmic rays arriving from the Galactic Centre which excludes several scenarios predicting sources of EeV neutrons from Sagittarius A. Also the events detected simultaneously by the surface and fluorescence detectors (the ‘hybrid’ data set), which have better pointing accuracy but are less numerous than those of the surface array alone, do not show any significant localized excess from this direction.
NASA Astrophysics Data System (ADS)
Lee, Wei-Li; Startsev, Edward A.; Davidson, Ronald C.
2004-11-01
In intense charged particle beams with large temperature anisotropy free energy is available to drive a transverse electromagnetic Weibel-type instability. The finite transverse geometry of the confined beam makes a detailed theoretical investigation difficult. In this paper the newly developed bEASt (beam eigenmode and spectra) code which solves the linearized Vlasov-Maxwell equations is used to investigate the detailed properties of the Weibel instability for a long charge bunch propagating through a cylindrical pipe of radius r_w. The stability analysis is carried out for azimuthally symmetric perturbations about a two-temperature thermal equilibrium distribution in the smooth-focusing approximation. To study the nonlinear stage of the instability, the Darwin model is being developed and incorporated into the Beam Equilibrium Stability and Transport(BEST) code.
Anisotropy studies around the Galactic Centre at EeV energies with the Auger Observatory
Aglietta, M.; Aguirre, C.; Allard, D.; Allekotte, I.; Allison, P.; Alvarez, C.; Alvarez-Muniz, J.; Ambrosio, M.; Anchordoqui, L.; Anjos, J.C.; Aramo, C.; /Centro Atomico Bariloche /Buenos Aires, IAFE /Buenos Aires, CONICET /Pierre Auger Observ. /La Plata U. /Natl. Tech. U., San Rafael /Adelaide U. /Catholic U. of Bolivia, La Paz /Bolivia U. /Rio de Janeiro, CBPF /Sao Paulo U.
2006-07-01
Data from the Pierre Auger Observatory are analyzed to search for anisotropies near the direction of the Galactic Centre at EeV energies. The exposure of the surface array in this part of the sky is already significantly larger than that of the fore-runner experiments. Our results do not support previous findings of localized excesses in the AGASA and SUGAR data. We set an upper bound on a point-like flux of cosmic rays arriving from the Galactic Centre which excludes several scenarios predicting sources of EeV neutrons from Sagittarius A. Also the events detected simultaneously by the surface and fluorescence detectors (the ''hybrid'' data set), which have better pointing accuracy but are less numerous than those of the surface array alone, do not show any significant localized excess from this direction.
Density functional theory calculations of magnetocrystalline anisotropy energies for (Fe1-xCox)2B
Daene, Markus; Kim, Soo Kyung; Surh, Michael P.; Aberg, Daniel; Benedict, Lorin X.
2015-06-15
We present and discuss density functional theory calculations of magnetic properties of the family of ferromagnetic compounds, (Fe1-xCox)2B, focusing specifically on the magnetocrystalline anisotropy energy (MAE). Using periodic supercells of various sizes (up to 96 atoms), it is shown that the general qualitative features of the composition dependence of the MAE is in agreement with experimental findings, while our predicted magnitudes are larger than those of experiment. We find that the use of small supercells (6 and 12-atom) favors larger MAE values relative to a statistical sample of configurations constructed with 96-atom supercells. As a result, the effect of latticemore » relaxations is shown to be small. Calculations of the Curie temperature for this alloy are also presented.« less
High Energy Atmospheric Neutrino Fluxes From a Realistic Primary Spectrum
NASA Astrophysics Data System (ADS)
Campos Penha, Felipe; Dembinski, Hans; Gaisser, Thomas K.; Tilav, Serap
2016-03-01
Atmospheric neutrino fluxes depend on the energy spectrum of primary nucleons entering the top of the atmosphere. Before the advent of AMANDA and the IceCube Neutrino Observatory, measurements of the neutrino fluxes were generally below ~ 1TeV , a regime in which a simple energy power law sufficed to describe the primary spectrum. Now, IceCube's muon neutrino data extends beyond 1PeV , including a combination of neutrinos from astrophysical sources with background from atmospheric neutrinos. At such high energies, the steepening at the knee of the primary spectrum must be accounted for. Here, we describe a semi-analytical approach for calculating the atmospheric differential neutrino fluxes at high energies. The input is a realistic primary spectrum consisting of 4 populations with distinct energy cutoffs, each with up to 7 representative nuclei, where the parameters were extracted from a global fit. We show the effect of each component on the atmospheric neutrino spectra, above 10TeV . The resulting features follow directly from recent air shower measurements included in the fit. Felipe Campos Penha gratefully acknowledges financial support from CAPES (Processo BEX 5348/14-5), CNPq (Processo 142180/2012-2), and the Bartol Research Institute.
High energy primary electron spectrum observed by the emulsion chamber
NASA Technical Reports Server (NTRS)
Nishimura, J.; Fujii, M.; Aizu, H.; Hiraiwa, N.; Taira, T.; Kobayashi, T.; Niu, K.; Koss, T. A.; Lord, J. J.; Golden, R. L.
1978-01-01
A detector of the emulsion chamber type is used to measure the energy spectrum of cosmic-ray electrons. Two large emulsion chambers, each having an area of 40 by 50 sq cm, are exposed for about 25.5 hr at an average pressure altitude of 3.9 mbar. About 500 high-energy cascades (no less than about 600 GeV) are detected by searching for dark spots on the X-ray films. A power-law energy dependence formula is derived for the spectrum of primary cosmic-ray electrons in the energy region over 100 GeV. The results are in good agreement with the transition curves obtained previously by theoretical and Monte Carlo calculations.
NASA Astrophysics Data System (ADS)
Gordon, J. M.; Gartstein, Yu N.
2013-10-01
A common problem of nonradiative energy transfer (NRET) from a small energy donor into a neighbouring energy acceptor layer is addressed with the emphasis on the layer thickness dependence. Two complementary approaches are employed to study dielectric polarization effects on NRET into thin films: a macroscopic analysis treating the acceptor layer as a continuum characterized by a frequency-dependent dielectric function, and a direct modelling utilizing discrete acceptor lattices, each of the acceptors being a polarizable point dipole. Explicit illustrations are provided of an interesting phenomenon, when NRET into thinner films can counter-intuitively be more efficient than NRET into thicker films. We show that this phenomenon may take place for a broad range of the acceptor polarization responses, including metallic-like and insulating behaviour as well as responses with weak and strong dissipation. The spectral vicinity of a strong dielectric resonance in the acceptor layer is studied as a specific example. The role of geometry-derived and intrinsic anisotropy of the acceptor response is clarified in the illustrations. Our results suggest that NRET optimization might be possible in the design of hybrid nanostructures, where the geometry of the structures is better matched with spectral properties of donor and acceptor subsystems.
Linear energy transfer spectrum measurement experiment (P0006)
NASA Technical Reports Server (NTRS)
Benton, E. V.; Parnell, T. A.
1984-01-01
The linear energy transfer (LET) is the energy deposited per unit path length of charged particle traversing matter. For estimating the rate of damage from single-hit phenomena, the quantity that best combines the radiation environment, orbital situation, and spacecraft shielding is the linear energy transfer (LET) spectrum at the device location. This experiment will measure the LET spectrum behind different shielding configurations for approximately 1 year. The shielding will be increased in increments of approximately 1 G/sq cm up to a maximum shieldng of 16 G/sq cm. In addition to providing critical information to future spacecraft designers, these measurements will also provide data that will be extremely valuable to other experiments on LDEF.
Linear energy transfer spectrum measurement experiment (P0006)
Benton, E.V.; Parnell, T.A.
1984-02-01
The linear energy transfer (LET) is the energy deposited per unit path length of charged particle traversing matter. For estimating the rate of damage from single-hit phenomena, the quantity that best combines the radiation environment, orbital situation, and spacecraft shielding is the linear energy transfer (LET) spectrum at the device location. This experiment will measure the LET spectrum behind different shielding configurations for approxmately 1 year. The shielding will be increased in increments of approximately 1 G/sq cm up to a maximum shieldng of 16 G/sq cm. In addition to providing critical information to future spacecraft designers, these measurements will also provide data that will be extremely valuable to other experiments on LDEF.
Liu Ruoyu; Wang Xiangyu
2012-02-10
It has been suggested that hypernova remnants, with a substantial amount of energy in semi-relativistic ejecta, can accelerate intermediate mass or heavy nuclei to ultrahigh energies and provide a sufficient amount of energy in cosmic rays to account for the observed flux. We here calculate the expected energy spectrum and chemical composition of ultrahigh energy cosmic rays from such semi-relativistic hypernovae. With a chemical composition equal to that of the hypernova ejecta and a flat or hard spectrum for cosmic rays at the sources, the spectrum and composition of the propagated cosmic rays observed at the Earth can be compatible with the measurements by the Pierre Auger Observatory.
Energy landscape and dynamics of an HP lattice model of proteins —The role of anisotropy
NASA Astrophysics Data System (ADS)
Cieplak, Marek; Banavar, Jayanth R.
2013-12-01
We present the results of exact numerical studies of the energy landscape and the dynamics of a 12-monomer chain comprised of two types of amino acids called the HP model. We benchmark our findings against the corresponding results of previous studies of a Go model, which encodes the native state conformation. We also show how the energy landscape gets modified dramatically and improves the folding properties on incorporating the inherent anisotropy of a chain, albeit in a simplified manner.
Foundations of observing dark energy dynamics with the Wilkinson Microwave Anisotropy Probe
Corasaniti, P.S.; Kunz, M.; Parkinson, D.; Copeland, E.J.; Bassett, B.A.
2004-10-15
Detecting dark energy dynamics is the main quest of current dark energy research. Addressing the issue demands a fully consistent analysis of cosmic microwave background, large-scale structure and SN-Ia data with multiparameter freedom valid for all redshifts. Here we undertake a ten parameter analysis of general dark energy confronted with the first year Wilkinson Microwave Anisotropy Probe, 2dF galaxy survey and latest SN-Ia data. Despite the huge freedom in dark energy dynamics there are no new degeneracies with standard cosmic parameters apart from a mild degeneracy between reionization and the redshift of acceleration, both of which effectively suppress small scale power. Breaking this degeneracy will help significantly in detecting dynamics, if it exists. Our best-fit model to the data has significant late-time evolution at z<1.5. Phantom models are also considered and we find that the best-fit crosses w=-1 which, if confirmed, would be a clear signal for radically new physics. Treatment of such rapidly varying models requires careful integration of the dark energy density usually not implemented in standard codes, leading to crucial errors of up to 5%. Nevertheless cosmic variance means that standard {lambda} cold dark matter models are still a very good fit to the data and evidence for dynamics is currently very weak. Independent tests of reionization or the epoch of acceleration (e.g., integrated Sachs-Wolfe-large scale structure correlations) or reduction of cosmic variance at large scales (e.g., cluster polarization at high redshift) may prove key in the hunt for dynamics.
Surface-Energy-Anisotropy-Induced Orientation Effects on RayleighInstabilities in Sapphire
Santala, Melissa; Glaeser, Andreas M.
2006-01-01
Arrays of controlled-geometry, semi-infinite pore channels of systematically varied crystallographic orientation were introduced into undoped m-plane (10{bar 1}0) sapphire substrates using microfabrication techniques and ion-beam etching and subsequently internalized by solid-state diffusion bonding. A series of anneals at 1700 C caused the breakup of these channels into discrete pores via Rayleigh instabilities. In all cases, channels broke up with a characteristic wavelength larger than that expected for a material with isotropic surface energy, reflecting stabilization effects due to surface-energy anisotropy. The breakup wavelength and the time required for complete breakup varied significantly with channel orientation. For most orientations, the instability wavelength for channels of radius R was in the range of 13.2R-25R, and complete breakup occurred within 2-10 h. To first order, the anneal times for complete breakup scale with the square of the breakup wavelength. Channels oriented along a <11{bar 2}0> direction had a wavelength of {approx} 139R, and required 468 h for complete breakup. Cross-sectional analysis of channels oriented along a <11{bar 2}0> direction showed the channel to be completely bounded by stable c(0001), r{l_brace}{bar 1}012{r_brace}, and s{l_brace}10{bar 1}1{r_brace} facets.
The energy spectrum of Jovian electrons in interplanetary space
NASA Technical Reports Server (NTRS)
Christon, S. P.; Cummings, A. C.; Stone, E. C.; Webber, W. R.
1985-01-01
The energy spectrum of electrons with energies approximately 10 to approximately 180 MeV measured with the electron telescope on the Voyager 1 and 2 spacecraft in interplanetary space from 1978 to 1983 is reported. The kinetic energy of electrons is determined by double dE/dx measurements from the first two detectors (D1,D2) of a stack of eight solid state detectors and by the range of particle penetration into the remaining six detectors (D3 to D8) which are interleaved with tungsten absorbers.
The energy spectrum of Jovian electrons in interplanetary space
NASA Astrophysics Data System (ADS)
Christon, S. P.; Cummings, A. C.; Stone, E. C.; Webber, W. R.
1985-08-01
The energy spectrum of electrons with energies approx 10 to approx 180 MeV measured with the electron telescope on the Voyager 1 and 2 spacecraft in interplanetary space from 1978 to 1983 is studied. The kinetic energy of electrons is determined by double dE/dx measurements from the first two detectors (D1, D2) of a stack of eight solid state detectors and by the range of particle penetration into the remaining six detectors (D3 to D8) which are interleaved with tungsten absorbers. From 1978 to 1983 (radial range approx 2 to approx 12 AU) electrons of Jovian origin were clearly observable for electrons stopping in D3(e or MeV) and in D4 (E or = 8 MeV). . For electrons stopping in D5 (E or = 12 MeV), the jovian flux dominated the galactic electron flux for a period of approximately one year near the encounter with Jupiter. Jovian electrons were also observed in D6(E or = 21 Mev) 1 MeV but not in D7(E 28 MeV). A detailed interpretation of the electron variations in all energy channels depends on an accurate subtraction of background induced by energetic protons of a few 100 MeV. This substraction is facilitated by laboratory calibration results at several energies. Further results on the differential energy spectrum of Jovian electrons and limits on the maximum detected energies will be reported.
Measurement of the magnetic anisotropy energy constants for magneto-optical recording media
NASA Technical Reports Server (NTRS)
Hajjar, R. A.; Wu, T. H.; Mansuripur, M.
1992-01-01
Measurement of the magneto-optical polar Kerr effect is performed on rare earth-transition metal (RE-TM) amorphous films using in-plane fields. From this measurement and the measurement of the saturation magnetization using a vibrating sample magnetometer (VSM), the magnetic anisotropy constants are determined. The temperature dependence is presented of the magnetic anisotropy in the range of -175 to 175 C. The results show a dip in the anisotropy near magnetic compensation. This anomaly is explained based on the finite exchange coupling between the rare earth and transition metal subnetworks.
Energy Spectrum of Cosmic-Ray Electrons at TeV Energies
Aharonian, F.; Akhperjanian, A. G.; Sahakian, V.; Barres de Almeida, U.; Chadwick, P. M.; Cheesebrough, A.; Dickinson, H. J.; Hadjichristidis, C.; Keogh, D.; McComb, T. J. L.; Nolan, S. J.; Orford, K. J.; Osborne, J. L.; Rayner, S. M.; Rulten, C. B.; Spangler, D.; Ward, M.; Bazer-Bachi, A. R.; Borrel, V.; Olive, J-F.
2008-12-31
The very large collection area of ground-based {gamma}-ray telescopes gives them a substantial advantage over balloon or satellite based instruments in the detection of very-high-energy (>600 GeV) cosmic-ray electrons. Here we present the electron spectrum derived from data taken with the High Energy Stereoscopic System (H.E.S.S.) of imaging atmospheric Cherenkov telescopes. In this measurement, the first of this type, we are able to extend the measurement of the electron spectrum beyond the range accessible to direct measurements. We find evidence for a substantial steepening in the energy spectrum above 600 GeV compared to lower energies.
Abreu, P.
2012-01-01
Observations of cosmic ray arrival directions made with the Pierre Auger Observatory have previously provided evidence of anisotropy at the 99% CL using the correlation of ultra high energy cosmic rays (UHECRs) with objects drawn from the Veron-Cetty Veron catalog. In this paper we report on the use of three catalog independent methods to search for anisotropy. The 2pt-L, 2pt+ and 3pt methods, each giving a different measure of self-clustering in arrival directions, were tested on mock cosmic ray data sets to study the impacts of sample size and magnetic smearing on their results, accounting for both angular and energy resolutions. If the sources of UHECRs follow the same large scale structure as ordinary galaxies in the local Universe and if UHECRs are deflected no more than a few degrees, a study of mock maps suggests that these three methods can efficiently respond to the resulting anisotropy with a P-value = 1.0% or smaller with data sets as few as 100 events. Using data taken from January 1, 2004 to July 31, 2010 we examined the 20, 30, ..., 110 highest energy events with a corresponding minimum energy threshold of about 51 EeV. The minimum P-values found were 13.5% using the 2pt-L method, 1.0% using the 2pt+ method and 1.1% using the 3pt method for the highest 100 energy events. In view of the multiple (correlated) scans performed on the data set, these catalog-independent methods do not yield strong evidence of anisotropy in the highest energy cosmic rays.
LOCAL ANISOTROPY, HIGHER ORDER STATISTICS, AND TURBULENCE SPECTRA
Matthaeus, W. H.; Wan, M.; Osman, K. T.; Servidio, S.; Carbone, V.; Dmitruk, P.; Oughton, S.
2012-05-10
Correlation anisotropy emerges dynamically in magnetohydrodynamics (MHD), producing stronger gradients across the large-scale mean magnetic field than along it. This occurs both globally and locally, and has significant implications in space and astrophysical plasmas, including particle scattering and transport, and theories of turbulence. Properties of local correlation anisotropy are further documented here by showing through numerical experiments that the effect is intensified in more localized estimates of the mean field. The mathematical formulation of this property shows that local anisotropy mixes second-order with higher order correlations. Sensitivity of local statistical estimates to higher order correlations can be understood in connection with the stochastic coordinate system inherent in such formulations. We demonstrate this in specific cases, and illustrate the connection to higher order statistics by showing the sensitivity of local anisotropy to phase randomization, after which the global measure of anisotropy is recovered at all scales of averaging. This establishes that anisotropy of the local structure function is not a measure of anisotropy of the energy spectrum. Evidently, the local enhancement of correlation anisotropy is of substantial fundamental interest and must be understood in terms of higher order correlations, specifically fourth-order and above.
Estimation of magnetic moment and anisotropy energy of magnetic markers for biosensing application
NASA Astrophysics Data System (ADS)
Enpuku, K.; Sasayama, T.; Yoshida, T.
2016-05-01
We present a method to evaluate the magnetic moment (m) and the anisotropy energy (E) of magnetic markers, which are the key parameters employed in biosensing applications. The distributions of the m and E values in the marker are evaluated by analyzing the static magnetization (M-H) curve of the suspended markers and the frequency dependence of the AC susceptibility of the immobilized markers, respectively. Then, we obtain the relationship between m and E. In the experiment, four markers made of multicore and single core nanoparticles are examined. We obtain distributions of the m and E values, which show the particular characteristics of each marker. Although the m and E values are widely distributed in the marker, a clear relationship is obtained between the values. Therefore, the obtained m-E curve, as well as the distribution of the m and E values, provides a framework to discuss the dynamic behavior of the immobilized markers. The difference in the estimated m-E curves between the markers is also discussed.
Silant’ev, A. V.
2015-10-15
Anticommutator Green’s functions and the energy spectrum of C{sub 60} fullerene are calculated in the approximation of static fluctuations within the Hubbard model. On the basis of this spectrum, an interpretation is proposed for the experimentally observed optical absorption bands of C{sub 60} fullerene. The parameters of C{sub 60} fullerene that characterize it within the Hubbard model are calculated by the optical absorption spectrum.
Fast energy and energy spectrum feedback in the SLC Linac
Abrams, G.S.; Soderstrom, E.; Seeman, J.T.; Campisi, I.E.; Herrmannsfeldt, W.; Lee, M.; Petersen, A.; Phinney, N.; Ross, M.; Thompson, K.
1987-01-01
The energies and energy spectra of the positron and electron beams emerging from the SLC Linac must be carefully maintained so that the beams can be transported through the Arcs to the Final Focus without phase space dilution and also to specify the collision energy. A fastback system has been designed and constructed to control these parameters. The energies and energy spectra are measured nondestructively using position monitors and synchrotron radiation width monitors. The controls consist of rf phases in the Damping Rings, SLED timing, and rf amplitude. Theoretical aspects of the feedback process, algorithms, and operational experience are discussed.
Abreu, P
2011-06-17
The Pierre Auger Collaboration has reported evidence for anisotropy in the distribution of arrival directions of the cosmic rays with energies E > E_{th} = 5.5 x 10^{19} eV. These show a correlation with the distribution of nearby extragalactic objects, including an apparent excess around the direction of Centaurus A. If the particles responsible for these excesses at E > E_{th} are heavy nuclei with charge Z, the proton component of the sources should lead to excesses in the same regions at energies E/Z. We here report the lack of anisotropies in these directions at energies above E_{th}/Z (for illustrative values of Z = 6,13,26). If the anisotropies above E_{th} are due to nuclei with charge Z, and under reasonable assumptions about the acceleration process, these observations imply stringent constraints on the allowed proton fraction at the lower energies.
Exact energy spectrum for models with equally spaced point potentials
NASA Astrophysics Data System (ADS)
Caudrelier, V.; Crampé, N.
2006-03-01
We describe a non-perturbative method for computing the energy band structures of one-dimensional models with general point potentials sitting at equally spaced sites. This is done thanks to a Bethe ansatz approach and the method is applicable even when periodicity is broken, that is when Bloch's theorem is not valid any more. We derive the general equation governing the energy spectrum and illustrate its use in various situations. In particular, we get exact results for boundary effects. We also study non-perturbatively the effects of impurities in such systems. Finally, we discuss the possibility of including interactions between the particles of these systems.
Rustwick, Bryce A.
2005-08-01
Both academia and industry alike have paid close attention to the mechanisms of microstructural selection during the solidification process. The forces that give rise to and the principles which rule the natural selection of particular morphologies are important to understanding and controlling new microstructures. Interfacial properties play a very crucial role to the selection of such microstructure formation. In the solidification of a metallic alloy, the solid-liquid interface is highly mobile and responds to very minute changes in the local conditions. At this interface, the driving force must be large enough to drive solute diffusion, maintain local curvature, and overcome the kinetic barrier to move the interface. Therefore, the anisotropy of interfacial free energy with respect to crystallographic orientation is has a significant influence on the solidification of metallic systems. Although it is generally accepted that the solid-liquid interfacial free energy and its associated anisotropy are highly important to the overall selection of morphology, the confident measurement of these particular quantities remains a challenge, and reported values are scarce. Methods for measurement of the interfacial free energy include nucleation experiments and grain boundary groove experiments. The predominant method used to determine anisotropy of interfacial energy has been equilibrium shape measurement. There have been numerous investigations involving grain boundaries at a solid-liquid interface. These studies indicated the GBG could be used to describe various interfacial energy values, which affect solidification. Early studies allowed for an estimate of interfacial energy with respect to the GBG energy, and finally absolute interfacial energy in a constant thermal gradient. These studies however, did not account for the anisotropic nature of the material at the GBG. Since interfacial energy is normally dependent on orientation of the crystallographic plane of the
Shikama, T. Hasuo, M.; Kitaoka, H.
2014-07-15
Anisotropy in the electron energy distribution function (EEDF) in an electron cyclotron resonance plasma with magnetized electrons and weakly magnetized ions is experimentally investigated using a directional Langmuir probe. Under an assumption of independent EEDFs in the directions parallel and perpendicular to the magnetic field, the directional variation of the EEDF is evaluated. In the measured EEDFs, a significantly large population density of electrons with energies larger than 30 eV is found in one of the cross-field directions depending on the magnetic field direction. With the aid of an electron trajectory calculation, it is suggested that the observed anisotropic electrons originate from the EEDF anisotropy and the cross-field electron drift.
XTE Proposal #20102--"SS 433's High Energy Spectrum"
NASA Technical Reports Server (NTRS)
Band, David L.; Blanco, P.; Rothschild, R.; Kawai, N.; Kotani, T.; Oka, T.; Wagner, R. M.; Hjellming, R.; Rupen, M.; Brinkmann, W.
1999-01-01
We observed the jet-producing compact binary system SS 433 with RXTE during three multiwavelength campaigns, the first in conjunction with ASCA observations, the second simultaneous with a VLA-VLBA-MERLIN campaign, and the third associated with a Nobeyama millimeter-band campaign. All these campaigns included optical observations. Occurring at different jet precession and binary phases, the observations also monitored the system during a radio flare. The data provide SS 433's X-ray spectrum over more than an energy decade, and track the spectral variations as the X-ray source was partially eclipsed. The continuum can be modeled as a power law with an exponential cutoff, which can be detected to approximately 50 keV. Strong line emission is evident in the 5-10 keV range which can be modeled as a broad line whose energy is precession independent and a narrow line whose energy does vary with jet precession phase; this line model is clearly an over simplification since the PCA does not have sufficient energy resolution to detect the lines ASCA observed. The eclipses are deeper at high energy and at jet precession phases when the jets are more inclined towards and away from us. A large radio flare occurred between two sets of X-ray monitoring observations; an X-ray observation at the peak of the flare found a softer spectrum with a flux approximately 1/3 that of the quiescent level.
Energy spectrum of sputtered uranium - A new technique
NASA Technical Reports Server (NTRS)
Weller, R. A.; Tombrello, T. A.
1978-01-01
The fission track technique for detecting U-235 has been used in conjunction with a mechanical time-of-flight spectrometer in order to measure the energy spectrum in the region 1 eV to 1 keV of material sputtered from a 93% enriched U-235 foil by 80 keV Ar-40(+) ions. The spectrum was found to exhibit a peak in the region 2-4 eV and to decrease approximately as E exp -1.77 for E not less than 100 eV. The design, construction and resolution of the mechanical spectrometer are discussed and comparisons are made between the data and the predictions of the random collision cascade model of sputtering.
Sharp knee phenomenon of primary cosmic ray energy spectrum
NASA Astrophysics Data System (ADS)
Ter-Antonyan, Samvel
2014-06-01
Primary energy spectral models are tested in the energy range of 1-200 PeV using standardized extensive air shower responses from BASJE-MAS, Tibet, GAMMA and KASCADE scintillation shower arrays. Results point toward the two-component origin of observed cosmic ray energy spectra in the knee region consisting of a pulsar component superimposed upon rigidity-dependent power law diffuse Galactic flux. The two-component energy spectral model accounts for both the sharp knee shower spectral phenomenon and observed irregularity of all-particle energy spectrum in the region of 50-100 PeV. Alternatively, tested multipopulation primary energy spectra predicted by nonlinear diffusive shock acceleration models describe observed shower spectra in the knee region provided that the cutoff magnetic rigidities of accelerating particles are 6±0.3 and 45±2 PV for the first two populations, respectively. Both tested spectral models confirm the predominant H-He primary nuclei origin of observed shower spectral knee. The parameters of tested energy spectra are evaluated using solutions of the inverse problem on the basis of the corresponding parameterizations of energy spectra for primary H, He, O-like and Fe-like nuclei, standardized shower size spectral responses in the 550-1085 g/cm2 atmospheric slant depth range and near vertical muon truncated size spectra detected by the GAMMA array.
Universal Raising and Lowering Operators for a Discrete Energy Spectrum
NASA Astrophysics Data System (ADS)
Torres-Vega, Gabino
2016-06-01
We consider the first-order finite-difference expression of the commutator between d / dx and x. This is the appropriate setting in which to propose commutators and time operators for a quantum system with an arbitrary potential function and a discrete energy spectrum. The resulting commutators are identified as universal lowering and raising operators. We also find time operators which are finite-difference derivations with respect to the energy. The matrix elements of the commutator in the energy representation are analyzed, and we find consistency with the equality [hat{T},hat{H}]=ihbar . We apply the theory to the particle in an infinite well and for the Harmonic oscillator as examples.
Universal Raising and Lowering Operators for a Discrete Energy Spectrum
NASA Astrophysics Data System (ADS)
Torres-Vega, Gabino
2016-03-01
We consider the first-order finite-difference expression of the commutator between d / dx and x. This is the appropriate setting in which to propose commutators and time operators for a quantum system with an arbitrary potential function and a discrete energy spectrum. The resulting commutators are identified as universal lowering and raising operators. We also find time operators which are finite-difference derivations with respect to the energy. The matrix elements of the commutator in the energy representation are analyzed, and we find consistency with the equality [hat{T},hat{H}]=ihbar . We apply the theory to the particle in an infinite well and for the Harmonic oscillator as examples.
Rondinone, A.J.; Samia, A.C.S.; Zhang, Z.J.
1999-08-19
Superparamagnetism is a unique feature of magnetic nanoparticles. Spinel ferrite nanoparticles provide great opportunities for studying the mechanism of superparamagnetic properties. CoFe{sub 2}O{sub 4} nanocrystallites have been synthesized with a microemulsion method. The neutron diffraction studies and the temperature-dependent decay of magnetization show the superparamagnetic relaxation occurring in these nanoparticles. The neutron diffraction shows a high degree of inversion with the 78% tetrahedral sites occupied by Fe{sup 3+} cations. The nanoparticles with a 12 nm diameter have a blocking temperature around 320 K. The field-cooled and zero-field-cooled magnetization measurements display a divergence below the blocking temperature. The energy barrier distribution of magnetic anisotropy is derived from the temperature-dependent decay of magnetization. The magnetic anisotropy is clearly the origin of the divergence in the field-cooled and zero-field-cooled magnetization measurements. The energy barrier distribution function is used in a computer simulation of the zero-field-cooled magnetization, and the calculated magnetization has a great consistency with experimentally measured values. These studies on the magnetic anisotropy distribution elucidate the mechanism of superparamagnetic relaxation and facilitate the design and control of superparamagnetic properties in nanoparticles.
NASA Astrophysics Data System (ADS)
Jugdutt, Bernadine A.; Ofori-Opoku, Nana; Provatas, Nikolas
2015-10-01
This work uses Ginzburg-Landau theory derived from a recent structural phase-field-crystal model of binary alloys developed by the authors to study the roles of concentration, temperature, and pressure on the interfacial energy anisotropy of a solid-liquid front. It is found that the main contribution to the change in anisotropy with concentration arises from a change in preferred crystallographic orientation controlled by solute-dependent changes in the two-point density correlation function of a binary alloy, a mechanism that leads to such phenomena as solute-induced elastic strain and dislocation-assisted solute clustering. Our results are consistent with experimental observations in recent studies by Rappaz et al. [J. Fife, P. Di Napoli, and M. Rappaz, Metall. Mater. Trans. A 44, 5522 (2013), 10.1007/s11661-013-1912-7]. This is the first PFC work, to our knowledge, to incorporate temperature, pressure, and density into the thermodynamic description of alloys.
Jugdutt, Bernadine A; Ofori-Opoku, Nana; Provatas, Nikolas
2015-10-01
This work uses Ginzburg-Landau theory derived from a recent structural phase-field-crystal model of binary alloys developed by the authors to study the roles of concentration, temperature, and pressure on the interfacial energy anisotropy of a solid-liquid front. It is found that the main contribution to the change in anisotropy with concentration arises from a change in preferred crystallographic orientation controlled by solute-dependent changes in the two-point density correlation function of a binary alloy, a mechanism that leads to such phenomena as solute-induced elastic strain and dislocation-assisted solute clustering. Our results are consistent with experimental observations in recent studies by Rappaz et al. [J. Fife, P. Di Napoli, and M. Rappaz, Metall. Mater. Trans. A 44, 5522 (2013)]. This is the first PFC work, to our knowledge, to incorporate temperature, pressure, and density into the thermodynamic description of alloys. PMID:26565255
Dose rate constant and energy spectrum of interstitial brachytherapy sources.
Chen, Z; Nath, R
2001-01-01
In the past two years, several new manufacturers have begun to market low-energy interstitial brachytherapy seeds containing 125I and 103Pd. Parallel to this development, the National Institute of Standards and Technology (NIST) has implemented a modification to the air-kerma strength (S(K)) standard for 125I seeds and has also established an S(K) standard for 103Pd seeds. These events have generated a considerable number of investigations on the determination of the dose rate constants (inverted V) of interstitial brachytherapy seeds. The aim of this work is to study the general properties underlying the determination of dose rate constant and to develop a simple method for a quick and accurate estimation of dose rate constant. As the dose rate constant of clinical seeds is defined at a fixed reference point, we postulated that dose rate constant may be calculated by treating the seed as an effective point source when the seed's source strength is specified in S(K) and its source characteristics are specified by the photon energy spectrum measured in air at the reference point. Using a semi-analytic approach, an analytic expression for dose rate constant was derived for point sources with known photon energy spectra. This approach enabled a systematic study of dose rate constant as a function of energy. Using the measured energy spectra, the calculated dose rate constant for 125I model 6711 and 6702 seeds and for 192Ir seed agreed with the AAPM recommended values within +/-1%. For the 103Pd model 200 seed, the agreement was 5% with a recently measured value (within the +/-7% experimental uncertainty) and was within 1% with the Monte Carlo simulations. The analytic expression for dose rate constant proposed here can be evaluated using a programmable calculator or a simple spreadsheet and it provides an efficient method for checking the measured dose rate constant for any interstitial brachytherapy seed once the energy spectrum of the seed is known. PMID:11213926
Spectrum and energy levels of kryptonlike ion Nb VI
Reader, J.; Ekberg, J.O.
1993-05-01
The spectrum of five-times ionized niobium, Nb, VI, was observed from 238 to 2700 {angstrom} with sliding spark discharges on 10.7-m normal- and grazing-incidence spectrographs. Experimental energies were determined for all levels of the 4s{sup 2}4p{sup 6}, 4s{sup 2}4p{sup 6}, 4s{sup 2}4p{sup 5}4d, 4f, 5s, 5p, 5g, 6s, and 4s4p{sup 6}4d configurations as well as some levels of 4p{sup 5}6g. A total of 291 lines were classified as transitions between 88 observed levels. A previous analysis of this spectrum was found to be totally erroneous. Large hyperfine splittings were found for several levels of the 4p{sup 5}5s and 5p configurations. The observed configurations were theoretically interpreted by means of Hartree-Fock calculations and least squares fits of the energy parameters to the observed levels. A revised value of the ionization energy was obtained from the 4p{sup 5}5g and 6g configurations.
Search for the end of the cosmic ray energy spectrum
Linsley, John
1998-06-15
The title I was asked to speak about expresses an idea that occurred rather recently in the history of cosmic ray studies. I argue that the idea of a possible end of the cosmic ray energy spectrum came into being after a sequence of three rapid advances in knowledge which I describe, calling them 'breakthroughs'. I suggest that the present workshop be regarded as a step toward a fourth breakthrough. I argue that this may occur through application of the Space Airwatch concept--the earth atmosphere as target and signal generator--as embodied in the NASA OWL project.
MAXIMA: Observations of CMB anisotropy
NASA Astrophysics Data System (ADS)
Rabii, Bahman
This document describes the Millimeter Anisotropy eXperiment IMaging Array (MAXIMA), a balloon-borne experiment measuring the temperature anisotropy of the Cosmic Microwave Background (CMB) on angular scales of 10 ' to 5°. MAXIMA data are used to discriminate between cosmological models and to determine cosmological parameters. MAXIMA maps the CMB using 16 bolometric detectors observing in spectral bands centered at 150 GHz, 230 GHz, and 410 GHz, with 10 ' resolution at all frequencies. The combined receiver sensitivity to CMB anisotropy is ˜40 μK
NASA Astrophysics Data System (ADS)
Wang, Shihong; Liu, Zhiliang; Pang, Chongguang
2015-07-01
The geographic character of the inverse cascade is analyzed based on the spectral kinetic energy flux calculated in the global ocean, using sea surface height (SSH) data from satellites, reanalysis data, and model outputs. It is shown that the strongest inverse cascade occurs mostly in high-energy eastward-flowing currents, such as the Antarctic Circumpolar Current (ACC), the Kuroshio Extension, and the Gulf Stream, which matches the global distribution pattern of the eddy kinetic energy (EKE). Hence, the eddy scales predicted by the local linear baroclinic instability Lbci and from the altimeter observation Leddy are mapped out and compared with the energy injection scale Linj and the arrest-start scale Larrest-start of the inverse cascade, respectively. Generally, Lbci agrees well with Linj in the midlatitude and high-latitude oceans, especially in the Northern Hemisphere. Leddy falls within the arrest ranges of the inverse cascade and is quite close to Larrest-start. Finally, the depth dependence and the anisotropy of the inverse kinetic energy cascade are also diagnosed in the global ocean. We have found that the strength of the inverse cascades decreases with increasing depth, but the global pattern of the strength is nearly invariable. Meanwhile, the variations in depth hardly affect the Linj and Larrest-start. After considering the anisotropy in the spectral flux calculation, a possible inertial range for the zonal spectral kinetic energy flux is expected, where the cascade magnitude will keep a nearly constant negative value associated with the oceanic zonal jets.
Understanding the Energy Spectrum from the Second Run of CDMSlite
NASA Astrophysics Data System (ADS)
Pepin, Mark; SuperCDMS Collaboration
2015-04-01
The first run of the CDMSlite experiment demonstrated the use of Neganov-Luke phonon amplification in a single SuperCDMS detector to achieve lower energy thresholds for the direct detection of dark matter. A longer physics run with improved noise rejection has been recorded with a larger voltage bias of -70 V applied across the same detector, yielding an amplification factor of 15 (for electron recoils) and reducing the statistical uncertainty of the measured background rate. In order to extract optimal dark-matter sensitivity with these data it is important to understand the shape and composition of the background spectrum at the lowest energies. The dominant backgrounds in this high-voltage mode are from Compton scatters, internal activation lines (primarily from 71 Ge decays), and microphonic noise. This presentation will consider the contributions from these sources and how the electric field geometry in the detector can distort the spectra. Prospects for new results will also be discussed.
Monocular measurement of the ultra-high energy cosmic ray spectrum
NASA Astrophysics Data System (ADS)
Shah, Priti Dhanesh
The Telescope Array Project was designed to observe cosmic rays with energies greater than 1018 eV. Its goals are to study the physics of cosmic rays by measuring their anisotropy, composition, and energy spectrum. This work makes a monocular measurement of the ultra high energy cosmic ray spectrum and analyzes the physics produced from that spectrum. The flux of cosmic rays observed on Earth follows a power law over 12 decades in energy and 32 decades in flux. At the highest energies, the spectrum has detailed structure. Studying these features can tell us about the astrophysics of the production and propagation of cosmic rays. First, it can tell us about the sources of cosmic rays such as they capable of producing a power law spectrum and the maximum energy of cosmic rays that they can produce. Second, the acceleration mechanisms that can boost cosmic rays to ultra high energies can be studied. Third, the spectral features themselves can tell us about their possible cause for formation. For example, the ankle feature in the ultra high energy regime can tell us if it is the galactic-extragalactic transition or if it is due to e+e- pair production. Fourth, the energy losses that cosmic rays incur can tell us about their physical interactions during propagation. Studying the physics of the cosmic ray spectrum in the ultra high energy regime with data from the Telescope Array Project is the goal of this analysis. The Telescope Array Project consists of three fluorescence detectors overlooking an array of 507 scintillation surface detectors. Due to their extremely low flux at these energies, cosmic rays can only be observed indirectly via an extensive air shower produced when they collide with the nucleus of an atom in the Earth's atmosphere. These charged secondary particles produce fluorescence light. The array of surface detectors observes the lateral footprint of the extensive air shower when it reaches the ground. The fluorescence detectors observe the
Energy spectrum of the optical polaron at finite total momentum
NASA Astrophysics Data System (ADS)
Gerlach, B.; Kalina, F.
1999-10-01
In the following discussion we are concerned with the standard Fröhlich model for an optical polaron. We clarify the qualitative properties of the energy spectrum for arbitrary total momentum Q. Concerning the ground-state energy, we establish an effective lower bound. Until now, we have to assume that the electron-phonon coupling parameter α does not exceed a specified positive value. Using this bound, we demonstrate that the ground-state energy coincides with the continuum edge for \\|Q\\|>=\\|QC\\|, QC being finite. Consequently, it is only for \\|Q\\|<\\|QC\\| that an isolated ground state exists at all. This behavior is strikingly different from that of the corresponding system in lower dimensions, which has been analyzed previously by other authors, the discussion of the three-dimensional case remaining incomplete. Concerning the overall behavior of the ground-state energy as a function of Q and α, we find an increase (strict decrease) with increasing \\|Q\\|(α). In addition, we present an approach to the excited states. Interestingly enough, this can be based entirely on the knowledge of the ground-state energy and ground-state wave function.
Low energy photon mimic of the tritium beta decay energy spectrum
NASA Astrophysics Data System (ADS)
Malabre-O'Sullivan, Neville
Tritium is a radioactive hydrogen isotope that is typically produced via neutron interaction with heavy water (D2O), producing tritiated water (DTO). As a result of this, tritium accounts for roughly a third of all occupational exposures at a CANDU type nuclear power plant. This identifies a need to study the biological effects associated with tritium (and low energy electrons in general). However, there are complications regarding the dosimetry of tritium, as well as difficulties in handling and using tritium for the purposes of biophysics experiments. To avoid these difficulties, an experiment has been proposed using photons to mimic the beta decay energy spectrum of tritium. This would allow simulation of the radiation properties of tritium, so that a surrogate photon source can be used for biophysics experiments. Through experimental and computational means, this work has explored the use of characteristic x-rays of various materials to modify the output spectrum of an x-ray source, such that it mimics the tritium beta decay spectrum. Additionally, the resultant primary electron spectrum generated in water from an x-ray source was simulated. The results from this research have indicated that the use of characteristic x-rays is not a viable method for simulating a tritium source. Also, the primary electron spectrum generated in water shows some promise for simulating tritium exposure, however further work must be done to investigate the slowing down electron spectrum. Keywords: Tritium, MCNP, low energy electrons, biophysics, characteristic x-rays.
Anisotropies in the interplanetary intensity of solar protons with energies greater than 0.3 MeV.
NASA Technical Reports Server (NTRS)
Innanen, W. G.; Van Allen, J. A.
1973-01-01
By using Explorer 35 interplanetary observations of solar protons with energies greater than 0.3 MeV during ten selected solar events (1967-1970) the tine dependence of intensity and of the angular distribution of intensity has been studied for the first time in the sub-MeV range of energy. The respective contributions of diffusive and convective transport are resolved. Results are qualitatively similar to those of McCracken et al. (1968, 1971) in the energy range from 7.5to 45 MeV; but, as was expected, convective transport is found to be relatively more important at the lower energies. The convective component of the anisotropy vector yields values of the solar wind velocity in good agreement with directly measured values.
Uber, R.E.; Mansuripur, M.
1988-11-01
Optical investigation of magneto-optical films is complementary to conventional torque and VSM magnetometry. In the authors' laboratory, they are now measuring anisotropy energy constants of RE-TM thin films at temperatures from ambient to 150/sup 0/C. An in-plane magnetic field (up to 16.5 KOe) is applied to a saturated sample with perpendicular magnetization. The movement away from the perpendicular direction is monitored using the polar Kerr effect. At the HeNe wavelength, the Kerr effect is principally due to the top 500 angstroms of the transition metal subnetwork in the films.
NASA Astrophysics Data System (ADS)
Kim, Nam-Hui; Jung, Jinyong; Cho, Jaehun; Han, Dong-Soo; Yin, Yuxiang; Kim, June-Seo; Swagten, Henk J. M.; You, Chun-Yeol
2016-04-01
The interfacial Dzyaloshinskii-Moriya interaction (iDMI), surface anisotropy energy, and spin pumping at the Ir/Co interface are experimentally investigated by performing Brillouin light scattering. Contrary to previous reports, we suggest that the sign of the iDMI at the Ir/Co interface is the same as in the case of the Pt/Co interface. We also find that the magnitude of the iDMI energy density is relatively smaller than in the case of the Pt/Co interface, despite the large strong spin-orbit coupling (SOC) of Ir. The saturation magnetization and the perpendicular magnetic anisotropy (PMA) energy are significantly improved due to a strong SOC. Our findings suggest that an SOC in an Ir/Co system behaves in different ways for iDMI and PMA. Finally, we determine the spin pumping effect at the Ir/Co interface, and it increases the Gilbert damping constant from 0.012 to 0.024 for 1.5 nm-thick Co.
Spectrum of Quantized Energy for a Lengthening Pendulum
Choi, Jeong Ryeol; Song, Ji Nny; Hong, Seong Ju
2010-09-30
We considered a quantum system of simple pendulum whose length of string is increasing at a steady rate. Since the string length is represented as a time function, this system is described by a time-dependent Hamiltonian. The invariant operator method is very useful in solving the quantum solutions of time-dependent Hamiltonian systems like this. The invariant operator of the system is represented in terms of the lowering operator a(t) and the raising operator a{sup {dagger}}(t). The Schroedinger solutions {psi}{sub n}({theta}, t) whose spectrum is discrete are obtained by means of the invariant operator. The expectation value of the Hamiltonian in the {psi}{sub n}({theta}, t) state is the same as the quantum energy. At first, we considered only {theta}{sup 2} term in the Hamiltonian in order to evaluate the quantized energy. The numerical study for quantum energy correction is also made by considering the angle variable not only up to {theta}{sup 4} term but also up to {theta}{sup 6} term in the Hamiltonian, using the perturbation theory.
Determination of neutron energy spectrum at KAMINI shielding experiment location.
Sen, Sujoy; Bagchi, Subhrojit; Prasad, R R; Venkatasubramanian, D; Mohanakrishnan, P; Keshavamurty, R S; Haridas, Adish; Arul, A John; Puthiyavinayagam, P
2016-09-01
The neutron spectrum at KAMINI reactor south beam tube end has been determined using multifoil activation method. This beam tube is being used for characterizing neutron attenuation of novel shield materials. Starting from a computed guess spectrum, the spectrum adjustment/unfolding procedure makes use of minimization of a modified constraint function representing (a) least squared deviations between the measured and calculated reaction rates, (b) a measure of sharp fluctuations in the adjusted spectrum and (c) the square of the deviation of adjusted spectrum from the guess spectrum. The adjusted/unfolded spectrum predicts the reaction rates accurately. The results of this new procedure are compared with those of widely used SAND-II code. PMID:27389881
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Anisotropy of the semiclassical gluon field of a large nucleus at high energy
NASA Astrophysics Data System (ADS)
Dumitru, Adrian; Skokov, Vladimir
2015-04-01
The McLerran-Venugopalan model describes a highly boosted hadron/nucleus as a sheet of random color charges which source soft classical Weizsäcker-Williams gluon fields. We show that due to fluctuations, individual configurations are azimuthally anisotropic. We present initial evidence that impact parameter dependent small-x Jalilian-Marian, Iancu, McLerran, Weigert, Leonidov and Kovner (JIMWLK) resummation preserves such anisotropies over several units of rapidity. Finally, we compute the first four azimuthal Fourier amplitudes of the S-matrix of a fundamental dipole in such background fields.
NASA Technical Reports Server (NTRS)
Venters, T. M.; Pavlidou, V.
2012-01-01
The intergalactic magnetic field (IGMF) may leave an imprint on the anisotropy properties of the extragalactic gamma-ray background, through its effect on electromagnetic cascades triggered by interactions between very high energy photons and the extragalactic background light. A strong IGMF will deflect secondary particles produced in these cascades and will thus tend to isotropize lower energy cascade photons, thus inducing a modulation in the anisotropy energy spectrum of the gamma-ray background. Here we present a simple, proof-of-concept calculation of the magnitude of this effect and demonstrate that the two extreme cases (zero IGMF and IGMF strong enough to completely isotropize cascade photons) would be separable by ten years of Fermi observations and reasonable model parameters for the gamma-ray background. The anisotropy energy spectrum of the Fermi gamma-ray background could thus be used as a probe of the IGMF strength.
NASA Technical Reports Server (NTRS)
Venters, T. M.; Pavlidou, V.
2013-01-01
The intergalactic magnetic field (IGMF) may leave an imprint on the angular anisotropy of the extragalactic gamma-ray background through its effect on electromagnetic cascades triggered by interactions between very high energy photons and the extragalactic background light. A strong IGMF will deflect secondary particles produced in these cascades and will thus tend to isotropize lower energy cascade photons, thereby inducing a modulation in the anisotropy energy spectrum of the gamma-ray background. Here we present a simple, proof-of-concept calculation of the magnitude of this effect and demonstrate that current Fermi data already seem to prefer nonnegligible IGMF values. The anisotropy energy spectrum of the Fermi gamma-ray background could thus be used as a probe of the IGMF strength.
Colossal anisotropy of the magnetic properties of doped lithium nitrodometalates
NASA Astrophysics Data System (ADS)
Antropov, V. P.; Antonov, V. N.
2014-09-01
We present a first-principles investigation of the electronic structure and physical properties of doped lithium nitridometalates Li2(Li1-xMx)N (LiMN) with M = Cr, Mn, Fe, Co, and Ni. The diverse properties include the equilibrium magnetic moments, magneto-crystalline anisotropy, magneto-optical Kerr spectra, and x-ray magnetic circular dichroism. We explain the colossal magnetic anisotropy in LiFeN by its unique electronic structure which ultimately leads to a series of unusual physical properties. The most unique property is a complete suppression of relativistic effects and freezing of orbital moments for in-plane orientation of the magnetization. This leads to the colossal spatial anisotropy of many magnetic properties including energy, Kerr, and dichroism effects. LiFeN is identified as an ultimate single-ion anisotropy system where a nearly insulating state can be produced by a spin orbital coupling alone. A very nontrivial strongly fluctuating and sign changing character of the magnetic anisotropy with electronic 3d-atomic doping is predicted theoretically. A large and highly anisotropic Kerr effect due to the interband transitions between atomic-like Fe 3d bands is found for LiFeN. A giant anisotropy of the x-ray magnetic circular dichroism for the Fe K spectrum and a very weak one for the Fe L2,3 spectra in LiFeN are also predicted.
Ion Temperature Anisotropies in Helicon Plasmas
NASA Astrophysics Data System (ADS)
Balkey, Matthew M.; Boiven, Robert; Keiter, Paul; Kline, John; Scime, Earl; Spangler, Robert
1999-11-01
Laser induced fluorescence measurements of the ion temperature in an argon helicon plasma indicate a substantial ion temperature anisotropy (perpendicular over parallel). The perpendicular ion temperature scales linearly with the applied magnetic field strength and also depends on the RF driving frequency and amplitude. We will present measurements of the ion temperature as a function of magnetic field, RF amplitude, and RF frequency. We will also present measurements of the electromagnetic fluctuation spectrum in the source. Preliminary measurements suggest that the RF driving wave may parametrically decay into waves that can couple to the ions, thus providing a path for RF energy directly into the ions.
NASA Astrophysics Data System (ADS)
Tournus, F.; Bonet, E.
2011-05-01
We study a model system made of non-interacting monodomain ferromagnetic nanoparticles, considered as macrospins, with a randomly oriented uniaxial magnetic anisotropy. We derive a simple differential equation governing the magnetic moment evolution in an experimental magnetic susceptibility measurement, at low field and as a function of temperature, following the well-known Zero-Field Cooled/Field Cooled (ZFC/FC) protocol. Exact and approximate analytical solutions are obtained, together for the ZFC curve and the FC curve. The notion of blocking temperature is discussed and the influence of various parameters on the curves is investigated. A crossover temperature is defined and a comparison is made between our progressive crossover model (PCM) and the crude "two states" or abrupt transition model (ATM), where the particles are assumed to be either fully blocked or purely superparamagnetic. We consider here the case of a single magnetic anisotropy energy (MAE), which is a prerequisite before considering the more realistic and experimentally relevant case of an assembly of particles with a MAE distribution (cf. part II that follows).
Multibunch energy and spectrum control in the SLC High Energy Linac
Seeman, J.T.; Decker, F.J.; Jobe, R.K.; Hsu, I.
1991-05-01
Three intense bunches (two electron and one positron) are accelerated on each rf pulse in the SLC Linac. Careful control of the energy and energy spectrum of each bunch is needed to provide acceptable beams at the collision point and the positron productive target. The required rf amplitude, timing, and phase adjustments can be calculated and adjusted in real time to correct for changing conditions. BNS damping and energy feedback systems reduce the available reserve energy, which is limited. Observations and stability of actual beams are reviewed. Implications for a future collider are discussed. 10 refs., 3 figs., 1 tab.
Aab, Alexander
2015-05-01
We analyze the distribution of arrival directions of ultra-high-energy cosmic rays recorded at the Pierre Auger Observatory in 10 years of operation. The data set, about three times larger than that used in earlier studies, includes arrival directions with zenith angles up to 80°, thus covering from -90° to +45° in declination. After updating the fraction of events correlating with the active galactic nuclei (AGNs) in the Véron-Cetty and Véron catalog, we subject the arrival directions of the data with energies in excess of 40 EeV to different tests for anisotropy. We search for localized excess fluxes, self-clustering of event directions at angular scales up to 30°, and different threshold energies between 40 and 80 EeV. We then look for correlations of cosmic rays with celestial structures both in the Galaxy (the Galactic Center and Galactic Plane) and in the local universe (the Super-Galactic Plane). We also examine their correlation with different populations of nearby extragalactic objects: galaxies in the 2MRS catalog, AGNs detected by Swift-BAT, radio galaxies with jets, and the Centaurus A (Cen A) galaxy. None of the tests show statistically significant evidence of anisotropy. As a result, the strongest departures from isotropy (post-trial probabilitymore » $$\\sim 1.4$$%) are obtained for cosmic rays with $$E\\gt 58$$ EeV in rather large windows around Swift AGNs closer than 130 Mpc and brighter than 1044 erg s-1 (18° radius), and around the direction of Cen A (15° radius).« less
Aab, Alexander
2015-05-01
We analyze the distribution of arrival directions of ultra-high-energy cosmic rays recorded at the Pierre Auger Observatory in 10 years of operation. The data set, about three times larger than that used in earlier studies, includes arrival directions with zenith angles up to 80°, thus covering from -90° to +45° in declination. After updating the fraction of events correlating with the active galactic nuclei (AGNs) in the Véron-Cetty and Véron catalog, we subject the arrival directions of the data with energies in excess of 40 EeV to different tests for anisotropy. We search for localized excess fluxes, self-clustering of event directions at angular scales up to 30°, and different threshold energies between 40 and 80 EeV. We then look for correlations of cosmic rays with celestial structures both in the Galaxy (the Galactic Center and Galactic Plane) and in the local universe (the Super-Galactic Plane). We also examine their correlation with different populations of nearby extragalactic objects: galaxies in the 2MRS catalog, AGNs detected by Swift-BAT, radio galaxies with jets, and the Centaurus A (Cen A) galaxy. None of the tests show statistically significant evidence of anisotropy. As a result, the strongest departures from isotropy (post-trial probability $\\sim 1.4$%) are obtained for cosmic rays with $E\\gt 58$ EeV in rather large windows around Swift AGNs closer than 130 Mpc and brighter than 10^{44} erg s^{-1} (18° radius), and around the direction of Cen A (15° radius).
NASA Astrophysics Data System (ADS)
Aab, A.; Abreu, P.; Aglietta, M.; Ahn, E. J.; Samarai, I. Al; Albuquerque, I. F. M.; Allekotte, I.; Allen, J.; Allison, P.; Almela, A.; Alvarez Castillo, J.; Alvarez-Muñiz, J.; Alves Batista, R.; Ambrosio, M.; Aminaei, A.; Anchordoqui, L.; Andringa, S.; Aramo, C.; Aranda, V. M.; Arqueros, F.; Asorey, H.; Assis, P.; Aublin, J.; Ave, M.; Avenier, M.; Avila, G.; Awal, N.; Badescu, A. M.; Barber, K. B.; Bäuml, J.; Baus, C.; Beatty, J. J.; Becker, K. H.; Bellido, J. A.; Berat, C.; Bertaina, M. E.; Bertou, X.; Biermann, P. L.; Billoir, P.; Blaess, S. G.; Blanco, M.; Bleve, C.; Blümer, H.; Boháčová, M.; Boncioli, D.; Bonifazi, C.; Bonino, R.; Borodai, N.; Brack, J.; Brancus, I.; Bridgeman, A.; Brogueira, P.; Brown, W. C.; Buchholz, P.; Bueno, A.; Buitink, S.; Buscemi, M.; Caballero-Mora, K. S.; Caccianiga, B.; Caccianiga, L.; Candusso, M.; Caramete, L.; Caruso, R.; Castellina, A.; Cataldi, G.; Cazon, L.; Cester, R.; Chavez, A. G.; Chiavassa, A.; Chinellato, J. A.; Chudoba, J.; Cilmo, M.; Clay, R. W.; Cocciolo, G.; Colalillo, R.; Coleman, A.; Collica, L.; Coluccia, M. R.; Conceição, R.; Contreras, F.; Cooper, M. J.; Cordier, A.; Coutu, S.; Covault, C. E.; Cronin, J.; Curutiu, A.; Dallier, R.; Daniel, B.; Dasso, S.; Daumiller, K.; Dawson, B. R.; de Almeida, R. M.; De Domenico, M.; de Jong, S. J.; de Mello Neto, J. R. T.; De Mitri, I.; de Oliveira, J.; de Souza, V.; del Peral, L.; Deligny, O.; Dembinski, H.; Dhital, N.; Di Giulio, C.; Di Matteo, A.; Diaz, J. C.; Díaz Castro, M. L.; Diogo, F.; Dobrigkeit, C.; Docters, W.; D'Olivo, J. C.; Dorofeev, A.; Dorosti Hasankiadeh, Q.; Dova, M. T.; Ebr, J.; Engel, R.; Erdmann, M.; Erfani, M.; Escobar, C. O.; Espadanal, J.; Etchegoyen, A.; Facal San Luis, P.; Falcke, H.; Fang, K.; Farrar, G.; Fauth, A. C.; Fazzini, N.; Ferguson, A. P.; Fernandes, M.; Fick, B.; Figueira, J. M.; Filevich, A.; Filipčič, A.; Fox, B. D.; Fratu, O.; Freire, M. M.; Fröhlich, U.; Fuchs, B.; Fujii, T.; Gaior, R.; García, B.; Garcia-Gamez, D.; Garcia-Pinto, D.; Garilli, G.; Gascon Bravo, A.; Gate, F.; Gemmeke, H.; Ghia, P. L.; Giaccari, U.; Giammarchi, M.; Giller, M.; Glaser, C.; Glass, H.; Gómez Berisso, M.; Gómez Vitale, P. F.; Gonçalves, P.; Gonzalez, J. G.; González, N.; Gookin, B.; Gordon, J.; Gorgi, A.; Gorham, P.; Gouffon, P.; Grebe, S.; Griffith, N.; Grillo, A. F.; Grubb, T. D.; Guarino, F.; Guedes, G. P.; Hampel, M. R.; Hansen, P.; Harari, D.; Harrison, T. A.; Hartmann, S.; Harton, J. L.; Haungs, A.; Hebbeker, T.; Heck, D.; Heimann, P.; Herve, A. E.; Hill, G. C.; Hojvat, C.; Hollon, N.; Holt, E.; Homola, P.; Hörandel, J. R.; Horvath, P.; Hrabovský, M.; Huber, D.; Huege, T.; Insolia, A.; Isar, P. G.; Jandt, I.; Jansen, S.; Jarne, C.; Josebachuili, M.; Kääpä, A.; Kambeitz, O.; Kampert, K. H.; Kasper, P.; Katkov, I.; Kégl, B.; Keilhauer, B.; Keivani, A.; Kemp, E.; Kieckhafer, R. M.; Klages, H. O.; Kleifges, M.; Kleinfeller, J.; Krause, R.; Krohm, N.; Krömer, O.; Kruppke-Hansen, D.; Kuempel, D.; Kunka, N.; LaHurd, D.; Latronico, L.; Lauer, R.; Lauscher, M.; Lautridou, P.; Le Coz, S.; Leão, M. S. A. B.; Lebrun, D.; Lebrun, P.; Leigui de Oliveira, M. A.; Letessier-Selvon, A.; Lhenry-Yvon, I.; Link, K.; López, R.; Louedec, K.; Lozano Bahilo, J.; Lu, L.; Lucero, A.; Ludwig, M.; Malacari, M.; Maldera, S.; Mallamaci, M.; Maller, J.; Mandat, D.; Mantsch, P.; Mariazzi, A. G.; Marin, V.; Mariş, I. C.; Marsella, G.; Martello, D.; Martin, L.; Martinez, H.; Martínez Bravo, O.; Martraire, D.; Masías Meza, J. J.; Mathes, H. J.; Mathys, S.; Matthews, J.; Matthews, J. A. J.; Matthiae, G.; Maurel, D.; Maurizio, D.; Mayotte, E.; Mazur, P. O.; Medina, C.; Medina-Tanco, G.; Meissner, R.; Melissas, M.; Melo, D.; Menshikov, A.; Messina, S.; Meyhandan, R.; Mićanović, S.; Micheletti, M. I.; Middendorf, L.; Minaya, I. A.; Miramonti, L.; Mitrica, B.; Molina-Bueno, L.; Mollerach, S.; Monasor, M.; Monnier Ragaigne, D.; Montanet, F.; Morello, C.; Mostafá, M.; Moura, C. A.; Muller, M. A.; Müller, G.; Müller, S.; Münchmeyer, M.; Mussa, R.; Navarra, G.; Navas, S.; Necesal, P.; Nellen, L.; Nelles, A.; Neuser, J.; Nguyen, P. H.; Niechciol, M.; Niemietz, L.; Niggemann, T.; Nitz, D.; Nosek, D.; Novotny, V.; Nožka, L.; Ochilo, L.; Oikonomou, F.; Olinto, A.; Oliveira, M.; Pacheco, N.; Pakk Selmi-Dei, D.; Palatka, M.; Pallotta, J.; Palmieri, N.; Papenbreer, P.; Parente, G.; Parra, A.; Paul, T.; Pech, M.; Pȩkala, J.; Pelayo, R.; Pepe, I. M.; Perrone, L.; Petermann, E.; Peters, C.; Petrera, S.; Petrov, Y.; Phuntsok, J.; Piegaia, R.; Pierog, T.; Pieroni, P.; Pimenta, M.; Pirronello, V.; Platino, M.; Plum, M.; Porcelli, A.; Porowski, C.; Prado, R. R.; Privitera, P.; Prouza, M.; Purrello, V.; Quel, E. J.; Querchfeld, S.; Quinn, S.; Rautenberg, J.; Ravel, O.; Ravignani, D.; Revenu, B.; Ridky, J.; Riggi, S.; Risse, M.; Ristori, P.; Rizi, V.; Rodrigues de Carvalho, W.; Rodriguez Fernandez, G.; Rodriguez Rojo, J.; Rodríguez-Frías, M. D.; Rogozin, D.; Ros, G.; Rosado, J.; Rossler, T.; Roth, M.; Roulet, E.; Rovero, A. C.; Saffi, S. J.; Saftoiu, A.; Salamida, F.; Salazar, H.; Saleh, A.; Salesa Greus, F.; Salina, G.; Sánchez, F.; Sanchez-Lucas, P.; Santo, C. E.; Santos, E.; Santos, E. M.; Sarazin, F.; Sarkar, B.; Sarmento, R.; Sato, R.; Scharf, N.; Scherini, V.; Schieler, H.; Schiffer, P.; Schmidt, D.; Scholten, O.; Schoorlemmer, H.; Schovánek, P.; Schröder, F. G.; Schulz, A.; Schulz, J.; Schumacher, J.; Sciutto, S. J.; Segreto, A.; Settimo, M.; Shadkam, A.; Shellard, R. C.; Sidelnik, I.; Sigl, G.; Sima, O.; Śmiałkowski, A.; Šmída, R.; Snow, G. R.; Sommers, P.; Sorokin, J.; Squartini, R.; Srivastava, Y. N.; Stanič, S.; Stapleton, J.; Stasielak, J.; Stephan, M.; Stutz, A.; Suarez, F.; Suomijärvi, T.; Supanitsky, A. D.; Sutherland, M. S.; Swain, J.; Szadkowski, Z.; Szuba, M.; Taborda, O. A.; Tapia, A.; Tepe, A.; Theodoro, V. M.; Timmermans, C.; Todero Peixoto, C. J.; Toma, G.; Tomankova, L.; Tomé, B.; Tonachini, A.; Torralba Elipe, G.; Torres Machado, D.; Travnicek, P.; Trovato, E.; Ulrich, R.; Unger, M.; Urban, M.; Valdés Galicia, J. F.; Valiño, I.; Valore, L.; van Aar, G.; van Bodegom, P.; van den Berg, A. M.; van Velzen, S.; van Vliet, A.; Varela, E.; Vargas Cárdenas, B.; Varner, G.; Vázquez, J. R.; Vázquez, R. A.; Veberič, D.; Verzi, V.; Vicha, J.; Videla, M.; Villase ñor, L.; Vlcek, B.; Vorobiov, S.; Wahlberg, H.; Wainberg, O.; Walz, D.; Watson, A. A.; Weber, M.; Weidenhaupt, K.; Weindl, A.; Werner, F.; Widom, A.; Wiencke, L.; Wilczyńska, B.; Wilczyński, H.; Williams, C.; Winchen, T.; Wittkowski, D.; Wundheiler, B.; Wykes, S.; Yamamoto, T.; Yapici, T.; Yuan, G.; Yushkov, A.; Zamorano, B.; Zas, E.; Zavrtanik, D.; Zavrtanik, M.; Zepeda, A.; Zhou, J.; Zhu, Y.; Zimbres Silva, M.; Ziolkowski, M.; Zuccarello, F.; Pierre Auger Collaboration
2015-05-01
We analyze the distribution of arrival directions of ultra-high-energy cosmic rays recorded at the Pierre Auger Observatory in 10 years of operation. The data set, about three times larger than that used in earlier studies, includes arrival directions with zenith angles up to 80°, thus covering from -90{}^\\circ to +45{}^\\circ in declination. After updating the fraction of events correlating with the active galactic nuclei (AGNs) in the Véron-Cetty and Véron catalog, we subject the arrival directions of the data with energies in excess of 40 EeV to different tests for anisotropy. We search for localized excess fluxes, self-clustering of event directions at angular scales up to 30°, and different threshold energies between 40 and 80 EeV. We then look for correlations of cosmic rays with celestial structures both in the Galaxy (the Galactic Center and Galactic Plane) and in the local universe (the Super-Galactic Plane). We also examine their correlation with different populations of nearby extragalactic objects: galaxies in the 2MRS catalog, AGNs detected by Swift-BAT, radio galaxies with jets, and the Centaurus A (Cen A) galaxy. None of the tests show statistically significant evidence of anisotropy. The strongest departures from isotropy (post-trial probability ˜ 1.4%) are obtained for cosmic rays with E\\gt 58 EeV in rather large windows around Swift AGNs closer than 130 Mpc and brighter than 1044 erg s-1 (18° radius), and around the direction of Cen A (15° radius).
Cosmic ray anisotropy in fractional differential models of anomalous diffusion
Uchaikin, V. V.
2013-06-15
The problem of galactic cosmic ray anisotropy is considered in two versions of the fractional differential model for anomalous diffusion. The simplest problem of cosmic ray propagation from a point instantaneous source in an unbounded medium is used as an example to show that the transition from the standard diffusion model to the Lagutin-Uchaikin fractional differential model (with characteristic exponent {alpha} = 3/5 and a finite velocity of free particle motion), which gives rise to a knee in the energy spectrum at 10{sup 6} GeV, increases the anisotropy coefficient only by 20%, while the anisotropy coefficient in the Lagutin-Tyumentsev model (with exponents {alpha} = 0.3 and {beta} = 0.8, a long stay of particles in traps, and an infinite velocity of their jumps) is close to one. This is because the parameters of the Lagutin-Tyumentsev model have been chosen improperly.
NASA Astrophysics Data System (ADS)
Baberschke, Klaus
The enormous research on magnetic properties of ultrathin films and nanostructures produces also new activities in the fundamental understanding of the magnetic anisotropy energy (MAE) and the anisotropy of the orbital magnetic momentapprox 0.05\\ Å. This small change in structure and symmetry increa ses the MAE by several orders of magnitude and lifts the quenching of the orbital moment. Increases of 20-30 % of the orbital moment mu _{L} are observed. This experimental finding is confirmed by full relativistic ab initio calculations. Various experiments deliver the full temperature dependence of all MAE contributions. The temperature dependence remains a challenge for the theory in itine rant magnetism.
NASA Astrophysics Data System (ADS)
Shin, Sang Chul; Kim, Sanghoon; Han, Jungjin; Hong, Jongill; Kang, Shinill
2011-11-01
Magnetic stripes were achieved from hydrogen-ion-irradiated areas separated by the nonirradiated areas masked by UV-imprinted polymeric patterns. A perpendicular magnetic anistropy with a squareness of 0.96 and a coercivity of 2 kOe in (CoOx/Pd)10 multilayer films was induced via deoxidization, which heavily depended on the acceleration energy of hydrogen ion irradiation in the range of 400 eV. These phenomena were demonstrated via deoxidization of cobalt oxide to pure cobalt as observed by X-ray diffraction, accompanying the formation of a CoPd(111) phase indicating perpendicular magnetic anisotropy due to the preferential removal or reduction of oxygen atoms in multilayer films.
ANALYSIS OF LARGE-SCALE ANISOTROPY OF ULTRA-HIGH ENERGY COSMIC RAYS IN HiRes DATA
Abbasi, R. U.; Abu-Zayyad, T.; Allen, M.; Archbold, G.; Belov, K.; Belz, J. W.; Bergman, D. R.; Blake, S. A.; Brusova, O. A.; Burt, G. W.; Cannon, C.; Cao, Z.; Deng, W.; Fedorova, Y.; Findlay, J.; Gray, R. C.; Hanlon, W. F.; Amann, J. F.; Hoffman, C. M.; Finley, C. B.
2010-04-10
Stereo data collected by the HiRes experiment over a six-year period are examined for large-scale anisotropy related to the inhomogeneous distribution of matter in the nearby universe. We consider the generic case of small cosmic-ray deflections and a large number of sources tracing the matter distribution. In this matter tracer model the expected cosmic-ray flux depends essentially on a single free parameter, the typical deflection angle {theta} {sub s}. We find that the HiRes data with threshold energies of 40 EeV and 57 EeV are incompatible with the matter tracer model at a 95% confidence level unless {theta} {sub s} > 10 deg. and are compatible with an isotropic flux. The data set above 10 EeV is compatible with both the matter tracer model and an isotropic flux.
Ultra high energy events in ECHOS series and primary energy spectrum
NASA Technical Reports Server (NTRS)
Capdevielle, J. N.; Iwai, J.; Ogata, T.
1985-01-01
The compilation of ultra high energy jets suggests at present the existence of a bump in primary energy spectrum (with the standard concept of high energy collisions). The pseudo-rapidity distribution exhibits some typical anomalies, more than the (P sub t) behavior, which are (may be) the fingerprints of quark gluon plasma transition. The next results of Emulsion Chamber on Supersonic (ECHOS) will be in both cases determinant to confirm those tendancies, as well as an important effort of the cosmic ray community to develop in that sense a flying emulsion chamber experiment.
NASA Astrophysics Data System (ADS)
Aleksandrov, V. V.; Volkov, G. S.; Grabovski, E. V.; Gritsuk, A. N.; Lakhtyushko, N. I.; Medovshchikov, S. F.; Oleinik, G. M.; Svetlov, E. V.
2014-02-01
Results are presented from measurements of the anisotropy of energy losses in high-current Z-pinches produced by the implosion of wire arrays at the ANGARA-5-1 facility at load currents of up to 4MA. The energy losses were measured in the radial direction and along the pinch axis from the anode side. The main diagnostics were time-integrated thermocouple calorimeters, nanosecond X-ray diodes (XRDs) with different filters, and a foil radiation calorimeter with a time resolution of 2 μs. The azimuthal anisotropy of energy losses was measured for different wire array configurations and different shapes of the high-voltage electrode. The presence of strong initial azimuthal inhomogeneity of the wire mass distribution (sectioned arrays), as well as the use of conical electrodes instead of plane ones, does not increase the azimuthal inhomogeneity of the total energy losses. For cylindrical wire arrays, energy losses in the radial direction are compared with those along the pinch axis. According to XRD and calorimetric measurements, the radiation yield per unit solid angle along the pinch axis is two to three times lower than that in the radial direction. In the axial direction, the energy flux density of the expanding plasma is two to three times lower than the radiation intensity. The measured radiation yield across the pinch is 2.5-5 kJ/sr, while that along the pinch axis is 1-2 kJ/sr. The results obtained by means of XRDs agree to within measurement errors with those obtained using the radiation calorimeter. It is found that the energy per unit solid angle carried by the expanding plasma in the radial direction does not exceed 10% of the soft X-ray yield. Analysis of the structure of time-integrated pinhole images and signals from the radial and axial XRDs shows that radiation emitted in the radial direction from the hot central region of the pinch is partially screened by the less dense surrounding plasma halo, whereas radiation emitted in the axial direction is a
NASA Astrophysics Data System (ADS)
Guo, Yi-Qing; Tian, Zhen; Jin, Chao
2016-03-01
Recent precise measurements of cosmic ray spectra revealed an anomalous hardening at ∼200 GV, observed by the ATIC, CREAM, PAMELA, and AMS02 experiments. Particularly, the latest observation of the \\bar{p}/p ratio by AMS02 demonstrated a flat distribution, which further validated the spectral anomalies of secondary particles. All those new phenomena indicated that the conventional propagation model of cosmic rays meets a challenge. In this work, the spatial-dependent diffusion coefficient D(r,z,p) is employed by tracing the source distribution under the physical picture of the two-halo model in the DRAGON package. Under such a scenario, the model calculation will result in two-component spectra for primary nuclei. Due to the smaller rigidity dependence of D(r,z,p) in the galactic disk, the ratios secondary-to-primary will inevitably be flatter and the expected anisotropy of cosmic rays will be much more attenuated than in the conventional model. As a result, we can reproduce the spectral hardening of protons, the flat ratios of \\bar{p}/p and B/C, and consistent anisotropy from ∼100 GeV to ∼100 TeV by only adopting one set of spatial-dependent diffusion coefficients D(r,z,p) in a galactic disk.
Energy dependence of the spin excitation anisotropy in uniaxial-strained BaFe1.9Ni0.1As2
Song, Yu; Lu, Xingye; Abernathy, Douglas L.; Tam, David W.; Niedziela, Jennifer L.; Tian, Wei; Si, Qimiao; Dai, Pengcheng; Luo, Huiqian
2015-11-06
In this study, we use inelastic neutron scattering to study the temperature and energy dependence of the spin excitation anisotropy in uniaxial-strained electron-doped iron pnictide BaFe1.9Ni0.1As2 near optimal superconductivity (Tc = 20K). Our work has been motivated by the observation of in-plane resistivity anisotropy in the paramagnetic tetragonal phase of electron-underdoped iron pnictides under uniaxial pressure, which has been attributed to a spin-driven Ising-nematic state or orbital ordering. Here we show that the spin excitation anisotropy, a signature of the spin-driven Ising-nematic phase, exists for energies below 60 meV in uniaxial-strained BaFe1.9Ni0.1As2. Since this energy scale is considerably larger thanmore » the energy splitting of the dxz and dyz bands of uniaxial-strained Ba(Fe1–xCox)2As2 near optimal superconductivity, spin Ising-nematic correlations are likely the driving force for the resistivity anisotropy and associated electronic nematic correlations.« less
Energy dependence of the spin excitation anisotropy in uniaxial-strained BaFe1.9Ni0.1As2
NASA Astrophysics Data System (ADS)
Song, Yu; Lu, Xingye; Abernathy, D. L.; Tam, David W.; Niedziela, J. L.; Tian, Wei; Luo, Huiqian; Si, Qimiao; Dai, Pengcheng
2015-11-01
We use inelastic neutron scattering to study the temperature and energy dependence of the spin excitation anisotropy in uniaxial-strained electron-doped iron pnictide BaFe1.9Ni0.1As2 near optimal superconductivity (Tc=20 K ). Our work has been motivated by the observation of in-plane resistivity anisotropy in the paramagnetic tetragonal phase of electron-underdoped iron pnictides under uniaxial pressure, which has been attributed to a spin-driven Ising-nematic state or orbital ordering. Here we show that the spin excitation anisotropy, a signature of the spin-driven Ising-nematic phase, exists for energies below ˜60 meV in uniaxial-strained BaFe1.9Ni0.1As2 . Since this energy scale is considerably larger than the energy splitting of the dx z and dy z bands of uniaxial-strained Ba (Fe1-xCox) 2As2 near optimal superconductivity, spin Ising-nematic correlations are likely the driving force for the resistivity anisotropy and associated electronic nematic correlations.
Hu, Bo; He, Wei; Ye, Jun; Tang, Jin; Zhang, Yong-Sheng; Ahmad, Syed Sheraz; Zhang, Xiang-Qun; Cheng, Zhao-Hua
2015-01-01
It is challenging to determine domain wall pinning energy and magnetic anisotropy since both coherent rotation and domain wall displacement coexist during magnetization switching process. Here, angular dependence anisotropic magnetoresistance (AMR) measurements at different magnetic fields were employed to determine magnetic anisotropy constants and domain wall pinning energy of Fe/MgO(001) ultrathin film. The AMR curves at magnetic fields which are high enough to ensure the coherent rotation of magnetization indicate a smooth behavior without hysteresis between clockwise (CW) and counter-clockwise (CCW) rotations. By analyzing magnetic torque, the magnetic anisotropy constants can be obtained. On the other hand, the AMR curves at low fields show abrupt transitions with hysteresis between CW and CCW rotations, suggesting the presence of multi-domain structures. The domain wall pinning energy can be obtained by analyzing different behaviors of AMR. Our work suggests that AMR measurements can be employed to figure out precisely the contributions of magnetic anisotropy and domain wall pinning energy, which is still a critical issue for spintronics. PMID:26369572
NASA Technical Reports Server (NTRS)
Van Staden, M. L.; Potgieter, M. S.
1991-01-01
A drift with a simulated wavy neutral sheet have been used to study the effects of the reversal of the solar magnetic field every 11 years and the changes in the waviness of the heliospheric neutral sheet, corresponding to changes in solar activity, on the diurnal anisotropy at an energy of 20 GeV. The results indicate that the long-term behavior of the diurnal anisotropy, especially the phase shift from one solar minimum period to another, which seems to depend on the polarity of the IMF, has a theoretical explanation in the drift picture of the modulation of cosmic rays in the heliosphere.
NASA Astrophysics Data System (ADS)
Li, Dongzhe; Smogunov, Alexander; Barreteau, Cyrille; Ducastelle, François; Spanjaard, Daniel
2013-12-01
We report tight-binding (TB) calculations of magnetocrystalline anisotropy energy (MAE) of iron slabs and nanoclusters with a particular focus on local analysis. After clarifying various concepts and formulations for the determination of MAE, we apply our realistic TB model to the analysis of the magnetic anisotropy of Fe (001), Fe (110) slabs and of two large Fe clusters with (001) and (110) facets only: a truncated pyramid and a truncated bipyramid containing 620 and 1096 atoms, respectively. It is shown that the MAE of slabs originates mainly from outer layers; a small contribution from the subsurface gives rise, however, to an oscillatory behavior for large thicknesses. Interestingly, the MAE of the nanoclusters considered is almost solely due to (001) facets and the base perimeter of the pyramid. We believe that this fact could be used to efficiently control the anisotropy of iron nanoparticles and could also have consequences on their spin dynamics.
Characteristics of high energy cosmic ray diurnal anisotropy on day-to-day basis
NASA Astrophysics Data System (ADS)
Tiwari, C. M.; Tiwari, D. P.
2008-10-01
Diurnal variation of cosmic ray intensity for the period of 1989 to 2000 at Kiel, Haleakakla, Rome, Hermanus, Calgary, and Goose Bay neutron monitors has been studied. Frequency histograms are generated for each year by using the daily values of amplitudes and phases. In the present analysis we have derived the yearly mean amplitude and phase of the diurnal variation of cosmic ray intensity. It has been concluded from the analysis that the diurnal amplitude is mostly concentrated in between the amplitude values of 0.1% and 0.4%, whereas the phase of diurnal anisotropy is concentrated in the belt of 100 to 225 degrees. As such, the various characteristics of long-term diurnal variation of cosmic ray intensity for the maxima of solar activity cycle 22 to the next maxima of solar activity cycle 23 have been studied. The minimum amplitudes are apparent for the minimum solar activity periods starting from 1995 and up to 1997 at Kiel, Haleakakla, Rome, Hermanus, Calgary and Goose Bay stations. The diurnal amplitude has been found to have almost recovered to its values observed during 1989 to 1990. It is also seen that the diurnal amplitudes are much larger by a factor of two at high/middle latitude stations as compared to that for low latitude stations, where the amplitudes are even ˜01% or less during 1996. The phase is significantly earlier during 1996 and 1997 with some significant change starting in 1995. As such, competitive is a continuous decreasing trend in the diurnal phase with smaller change at high/middle latitude and significantly much larger change at low latitudes.
Energy spectrum of cascades generated by muons in Baksan underground scintillation telescope
NASA Technical Reports Server (NTRS)
Bakatanov, V. N.; Chudakov, A. E.; Novoseltsev, Y. F.; Novoseltseva, M. V.; Achkasov, V. M.; Semenov, A. M.; Stenkin, Y. V.
1985-01-01
Spectrum of cascades generated by cosmic ray muons underground is presented. The mean zenith angle of the muon arrival is theta=35 deg the depth approx. 1000 hg/sq cm. In cascades energy range 700 GeV the measured spectrum is in agreement with the sea-level integral muon spectrum index gamma=3.0. Some decrease of this exponent has been found in the range 4000 Gev.
Wirawan, Rahadi; Waris, Abdul; Djamal, Mitra; Handayani, Gunawan
2015-04-16
The spectrum of gamma energy absorption in the NaI crystal (scintillation detector) is the interaction result of gamma photon with NaI crystal, and it’s associated with the photon gamma energy incoming to the detector. Through a simulation approach, we can perform an early observation of gamma energy absorption spectrum in a scintillator crystal detector (NaI) before the experiment conducted. In this paper, we present a simulation model result of gamma energy absorption spectrum for energy 100-700 keV (i.e. 297 keV, 400 keV and 662 keV). This simulation developed based on the concept of photon beam point source distribution and photon cross section interaction with the Monte Carlo method. Our computational code has been successfully predicting the multiple energy peaks absorption spectrum, which derived from multiple photon energy sources.
Anisotropy in MHD turbulence due to a mean magnetic field
NASA Technical Reports Server (NTRS)
Shebalin, J. V.; Matthaeus, W. H.; Montgomery, D.
1982-01-01
The development of anisotropy in an initially isotropic spectrum is studied numerically for two-dimensional magnetohydrodynamic turbulence. The anisotropy develops due to the combined effects of an externally imposed dc magnetic field and viscous and resistive dissipation at high wave numbers. The effect is most pronounced at high mechanical and magnetic Reynolds numbers. The anisotropy is greater at the higher wave numbers.
Large angular scale CMB anisotropy from an excited initial mode
NASA Astrophysics Data System (ADS)
Sojasi, A.; Mohsenzadeh, M.; Yusofi, E.
2016-07-01
According to inflationary cosmology, the CMB anisotropy gives an opportunity to test predictions of new physics hypotheses. The initial state of quantum fluctuations is one of the important options at high energy scale, as it can affect observables such as the CMB power spectrum. In this study a quasi-de Sitter inflationary background with approximate de Sitter mode function built over the Bunch-Davies mode is applied to investigate the scale-dependency of the CMB anisotropy. The recent Planck constraint on spectral index motivated us to examine the effect of a new excited mode function (instead of pure de Sitter mode) on the CMB anisotropy at large angular scales. In so doing, it is found that the angular scale-invariance in the CMB temperature fluctuations is broken and in the limit ℓ < 200 a tiny deviation appears. Also, it is shown that the power spectrum of CMB anisotropy is dependent on a free parameter with mass dimension H << M * < M p and on the slow-roll parameter ɛ. Supported by the Islamic Azad University, Rasht Branch, Rasht, Iran
The high energy X-ray spectrum of the Crab Nebula observed from OSO 8
NASA Technical Reports Server (NTRS)
Dolan, J. F.; Crannell, L. J.; Dennis, B. R.; Orwig, L. E.; Maurer, G. S.; Frost, K. J.
1977-01-01
The X-ray spectrum of the Crab Nebula was measured with the scintillation spectrometer on board the OSO-8 satellite. The total emission of the X-ray source shows no long term variability. The spectrum itself can be described by a single power law out to energies of at least 500 keV.
Primordial anisotropies in gauged hybrid inflation
NASA Astrophysics Data System (ADS)
Akbar Abolhasani, Ali; Emami, Razieh; Firouzjahi, Hassan
2014-05-01
We study primordial anisotropies generated in the model of gauged hybrid inflation in which the complex waterfall field is charged under a U(1)gauge field. Primordial anisotropies are generated either actively during inflation or from inhomogeneities modulating the surface of end of inflation during waterfall transition. We present a consistent δN mechanism to calculate the anisotropic power spectrum and bispectrum. We show that the primordial anisotropies generated at the surface of end of inflation do not depend on the number of e-folds and therefore do not produce dangerously large anisotropies associated with the IR modes. Furthermore, one can find the parameter space that the anisotropies generated from the surface of end of inflation cancel the anisotropies generated during inflation, therefore relaxing the constrains on model parameters imposed from IR anisotropies. We also show that the gauge field fluctuations induce a red-tilted power spectrum so the averaged power spectrum from the gauge field can change the total power spectrum from blue to red. Therefore, hybrid inflation, once gauged under a U(1) field, can be consistent with the cosmological observations.
Energy spectrum of the recurrent cosmic rays variation during the solar minimum 23/24
NASA Astrophysics Data System (ADS)
Gil, Agnieszka; Alania, Michael
2016-07-01
We study temporal changes of the power-law energy/ rigidity spectrum of the first three harmonics of the recurrent variation of the galactic cosmic rays (GCR) intensity during the unusual solar minimum 23/24 and compare with four previous minima. We show that the energy spectrum of the amplitudes of the recurrent variation is soft in the minimum 23/24. Moreover, while the energy spectrum of the amplitudes of the first harmonic of the recurrent variation of the GCR intensity practically behaves as during earlier four minima, the energy spectrum of the amplitudes of the second and the third harmonics demonstrate a valuable softening. We attribute this phenomenon to the decrease of an extension of heliosphere caused by the drop of the solar wind dynamic pressure during the solar minimum 23/24.
Energy spectrum analysis of blast waves based on an improved Hilbert-Huang transform
NASA Astrophysics Data System (ADS)
Li, L.; Wang, F.; Shang, F.; Jia, Y.; Zhao, C.; Kong, D.
2016-07-01
Using the improved Hilbert-Huang transform (HHT), this paper investigates the problems of analysis and interpretation of the energy spectrum of a blast wave. It has been previously established that the energy spectrum is an effective feature by which to characterize a blast wave. In fact, the higher the energy spectra in a frequency band of a blast wave, the greater the damage to a target in the same frequency band. However, most current research focuses on analyzing wave signals in the time domain or frequency domain rather than considering the energy spectrum. We propose here an improved HHT method combined with a wavelet packet to extract the energy spectrum feature of a blast wave. When applying the HHT, the signal is first roughly decomposed into a series of intrinsic mode functions (IMFs) by empirical mode decomposition. The wavelet packet method is then performed on each IMF to eliminate noise on the energy spectrum. Second, a coefficient is introduced to remove unrelated IMFs. The energy of each instantaneous frequency can be derived through the Hilbert transform. The energy spectrum can then be obtained by adding up all the components after the wavelet packet filters and screens them through a coefficient to obtain the effective IMFs. The effectiveness of the proposed method is demonstrated by 12 groups of experimental data, and an energy attenuation model is established based on the experimental data. The improved HHT is a precise method for blast wave signal analysis. For other shock wave signals from blasting experiments, an energy frequency time distribution and energy spectrum can also be obtained through this method, allowing for more practical applications.
Anisotropy of low energy direct photons in relativistic heavy ion collisions
NASA Astrophysics Data System (ADS)
Koide, T.; Kodama, T.
2016-09-01
Using the Wigner function approach for electromagnetic radiation fields, we investigate the behavior of low energy photons radiated by the deceleration processes of two colliding nuclei in relativistic heavy ion collisions. The angular distribution reveals information of the initial geometric configurations, which is reflected in the anisotropic parameter v 2, with an increasing v 2 as energy decreases. This behavior is qualitatively different to the v 2 from the hadrons produced in the collisions.
Energy spectrum and transport in narrow HgTe quantum wells
Germanenko, A. V.; Minkov, G. M.; Rut, O. E.; Sherstobitov, A. A.; Dvoretsky, S. A.; Mikhailov, N. N.
2015-01-15
The results of an experimental study of the transport phenomena and the hole energy spectrum of two-dimensional systems in the quantum well of HgTe zero-gap semiconductor with normal arrangement of quantum-confinement subbands are presented. An analysis of the experimental data allows us to reconstruct the carrier energy spectrum near the hole subband extrema. The results are interpreted using the standard kP model.
Extragalactic radiation and the ultra-high-energy cosmic-ray spectrum
NASA Technical Reports Server (NTRS)
Stecker, F. W.
1989-01-01
The effect of extragalactic microwave and submillimeter-radiation fields on the ultrahigh-energy cosmic-ray spectrum is reexamined. It is found that the general characteristics of the spectrum can be derived from fairly simple analytical arguments. It is shown that the various spectral features obtained by numerical calculations can be explored by simpler and more general means. This approach is illustrated using a newly derived lifetime-energy relation based on the new submillimeter observations.
Enhancement of high-energy cosmic-ray spectrum by type-II supernovae
NASA Technical Reports Server (NTRS)
Takahashi, Y.; Miyaji, S.; Parnell, T. A.; Weisskopf, M. C.; Hayashi, T.
1986-01-01
The cosmic-ray spectrum has an intensity enhancement in the energy range 10 to the 14th to 10 to the 16th eV per nucleus. Recent observations of heavy cosmic rays in this energy range indicate that the Ca/Fe ratio may be as large as 10 times the solar value. It is suggested that pulsars in type-II supernova remnants are the origin of this component of the cosmic-ray spectrum.
Evolution of the ultra high energy cosmic ray spectrum by transport equation
Hill, C.T.; Schramm, D.N.
1983-04-01
Ultra-high energy proton primaries interacting with the 3/sup 0/K photon background are treated as a transport phenomenon. Baryon number is explicitly conserved and the evolved spectrum develops a bump at a scale of order 5x10/sup 19/ eV, below the cutoff, due to the pile-up of energy degraded protons. This may correspond in part to the observed ankle structure in the CR spectrum.
Phenomenological Rashba model for calculating the electron energy spectrum on a cylinder
NASA Astrophysics Data System (ADS)
Savinskiĭ, S. S.; Belosludtsev, A. V.
2007-05-01
The energy spectrum of an electron on the surface of a cylinder is calculated using the Pauli equation with an additional term that takes into account the spin-orbit interaction. This term is taken in the approximation of a phenomenological Rashba model, which provides exact expressions for the wave functions and the electron energy spectrum on the cylinder surface in a static magnetic field.
Revisiting the hardening of the cosmic ray energy spectrum at TeV energies
NASA Astrophysics Data System (ADS)
Thoudam, Satyendra; Hörandel, Jörg R.
2013-11-01
Measurements of cosmic rays by experiments such as ATIC, CREAM and PAMELA indicate a hardening of the cosmic ray energy spectrum at TeV energies. In our recent work, we showed that the hardening can be due to the effect of nearby supernova remnants. We showed it for the case of protons and helium nuclei. In this paper, we present an improved and more detailed version of our previous work, and extend our study to heavier cosmic ray species such as boron, carbon, oxygen and iron nuclei. Unlike our previous study, the present work involves a detailed calculation of the background cosmic rays and follows a consistent treatment of cosmic ray source parameters between the background and the nearby components. Moreover, we also present a detailed comparison of our results on the secondary-to-primary ratios, secondary spectra and the diffuse gamma-ray spectrum with the results expected from other existing models, which can be checked by future measurements at high energies.
Chluba, Jens; Erickcek, Adrienne L.; Ben-Dayan, Ido
2012-10-20
In the early universe, energy stored in small-scale density perturbations is quickly dissipated by Silk damping, a process that inevitably generates {mu}- and y-type spectral distortions of the cosmic microwave background (CMB). These spectral distortions depend on the shape and amplitude of the primordial power spectrum at wavenumbers k {approx}< 10{sup 4} Mpc{sup -1}. Here, we study constraints on the primordial power spectrum derived from COBE/FIRAS and forecasted for PIXIE. We show that measurements of {mu} and y impose strong bounds on the integrated small-scale power, and we demonstrate how to compute these constraints using k-space window functions that account for the effects of thermalization and dissipation physics. We show that COBE/FIRAS places a robust upper limit on the amplitude of the small-scale power spectrum. This limit is about three orders of magnitude stronger than the one derived from primordial black holes in the same scale range. Furthermore, this limit could be improved by another three orders of magnitude with PIXIE, potentially opening up a new window to early universe physics. To illustrate the power of these constraints, we consider several generic models for the small-scale power spectrum predicted by different inflation scenarios, including running-mass inflation models and inflation scenarios with episodes of particle production. PIXIE could place very tight constraints on these scenarios, potentially even ruling out running-mass inflation models if no distortion is detected. We also show that inflation models with sub-Planckian field excursion that generate detectable tensor perturbations should simultaneously produce a large CMB spectral distortion, a link that could potentially be established with PIXIE.
Anisotropy analysis of the thermal stresses and strain energies in BCC metal films
NASA Astrophysics Data System (ADS)
Zhang, Jian-Min; Zhang, Yan; Xu, Ke-Wei
2005-11-01
A thin polycrystalline film tightly bonded to a thick substrate of different thermal expansion coefficients will experience thermal stresses when the temperature is changed in applications. Calculations of these stresses and the corresponding strain energies for grains having various crystallographic orientations (hkl) relative to the film surface were made for a polycrystalline film composed of the BCC metal Cr, Fe, K, Li, Mo, Na, Nb, Ta, V and W, respectively. Neglecting W, which is isotropic, the stresses and strain energy densities are not grain orientation (hkl) dependence. The remaining BCC metals may be grouped into two classes. In the first group (Cr, Mo, Nb and V), the (1 0 0)-oriented grains have the highest stresses and strain energy densities and (1 1 1)-oriented grains the lowest, the stresses σ1 and σ2 in the film surface and strain energy densities in other (hkl)-oriented grains decrease linearly with increasing angle between (hkl) and (1 0 0), and have σ1<σ2 excepting in (1 0 0)- and (1 1 1)-oriented grains. The contrary conclusions are obtained for the second group (Fe, K, Li, Na and Ta).
Energy spectrum transfer equations of solar wind turbulence
NASA Technical Reports Server (NTRS)
Tu, C.-Y.
1995-01-01
The recent studies of transfer equations for solar wind magnetohydrodynamic (MHD) turbulence are reviewed with emphasis on the comparison with the statistical observational results. Helios and Voyager missions provide an opportunity to study the the radial evolution of the power spectrum. the cross-helicity the Alfven ratio and the minimum variance direction. Spectrum transfer equations are considered as a tool to explore the nature of this radial evolution of the fluctuations. The transfer equations are derived from incompressible MHD equations. Generally one needs to make assumptions about the nature of the fluctuations and the nature of the turbulent non-linear interactions to obtain numerical results which can be compared with the observations. Some special model results for several simple cases SUCH as for structures or strong mixing. for Alfven waves with weak turbulent interactions. and for a superposition of structures and Alfven waves. are discussed. The difference between the various approaches to derive and handle the transfer equations are also addressed. Finally some theoretical description of the compressible fluctuations are also briefly reviewed.
NASA Astrophysics Data System (ADS)
Smart, D. F.; Shea, M. A.; Friedberg, W.; Copeland, K.; Sauer, H. H.
2005-12-01
The radiation dose to aircrews and passengers is a phenomenon of societal interest. There is a requirement to provide alerts whenever the radiation dose exceeds 20 micro-sieverts per hour at flight altitudes. The possibility that this might occur during a large high-energy solar cosmic ray event has resulted in much speculation. During the 20 January 2005 ground-level event the FAA Solar Radiation Alert System would have issued such an alert for aircraft at high latitudes for flight altitudes above 40,000 feet. Analysis of the GOES high-energy proton data results in a predicted dose rate of 23 micro Sv per hour at 60,000 feet for the first hour of the event. We also predict that the maximum peak dose rate would have been higher at the geographical position corresponding to the peak anisotropic flux intensity and would be correspondingly lower at geographical positions receiving a lower high energy solar cosmic ray flux. The solar high-energy flux anisotropy is extremely variable among the observed solar cosmic ray ground-level events. The 20 January 2005 event had one of the most extreme anisotropies yet observed by ground-level cosmic ray neutron monitors. We discuss the effects of this anisotropy with respect to aircraft radiation dose.
Segmentation-free x-ray energy spectrum estimation for computed tomography
NASA Astrophysics Data System (ADS)
Zhao, Wei; Zhang, Qiude; Niu, Tianye
2016-03-01
X-ray energy spectrum plays an essential role in imaging and related tasks. Due to the high photon flux of clinical CT scanners, most of the spectrum estimation methods are indirect and are usually suffered from various limitations. The recently proposed indirect transmission measurement-based method requires at least the segmentation of one material, which is insufficient for CT images of highly noisy and with artifacts. To combat for the bottleneck of spectrum estimation using segmented CT images, in this study, we develop a segmentation-free indirect transmission measurement based energy spectrum estimation method using dual-energy material decomposition. The general principle of the method is to compare polychromatic forward projection with raw projection to calibrate a set of unknown weights which are used to express the unknown spectrum together with a set of model spectra. After applying dual-energy material decomposition using high-and low-energy raw projection data, polychromatic forward projection is conducted on material-specific images. The unknown weights are then iteratively updated to minimize the difference between the raw projection and estimated projection. Both numerical simulations and experimental head phantom are used to evaluate the proposed method. The results indicate that the method provides accurate estimate of the spectrum and it may be attractive for dose calculations, artifacts correction and other clinical applications.
EFTEM spectrum imaging at high-energy resolution.
Schaffer, Bernhard; Kothleitner, Gerald; Grogger, Werner
2006-01-01
This paper deals with the application of high-energy resolution EFTEM image series and the corrections needed for reliable data interpretation. The detail of spectral information gained from an image series is largely determined by the intrinsic energy resolution. In this work we show that energy resolution values of as low as 0.8 eV in spectra extracted from EFTEM image series can be obtained with a small energy-selecting slit. At this resolution level aberrations of the energy filter, in particular the non-isochromaticity, can no longer be neglected. We show that the four most prominent factors for EFTEM image series data correction--spatial drift, non-isochromaticity, energy drift and image distortion--must not be treated independently but have to be corrected in unison. We present an efficient algorithm for this correction, and demonstrate the applied correction for the case of a GaN/AlN multilayer sample. PMID:16872748
Influence of the Richtmyer-Meshkov instability on the kinetic energy spectrum.
Weber, Christopher R.
2010-09-01
The fluctuating kinetic energy spectrum in the region near the Richtmyer-Meshkov instability (RMI) is experimentally investigated using particle image velocimetry (PIV). The velocity field is measured at a high spatial resolution in the light gas to observe the effects of turbulence production and dissipation. It is found that the RMI acts as a source of turbulence production near the unstable interface, where energy is transferred from the scales of the perturbation to smaller scales until dissipation. The interface also has an effect on the kinetic energy spectrum farther away by means of the distorted reflected shock wave. The energy spectrum far from the interface initially has a higher energy content than that of similar experiments with a flat interface. These differences are quick to disappear as dissipation dominates the flow far from the interface.
The Large Scale Structure of the Galactic Magnetic Field and High Energy Cosmic Ray Anisotropy
NASA Astrophysics Data System (ADS)
Alvarez-Muñiz, Jaime; Stanev, Todor
2006-10-01
Measurements of the magnetic field in our Galaxy are complex and usually difficult to interpret. A spiral regular field in the disk is favored by observations, however the number of field reversals is still under debate. Measurements of the parity of the field across the Galactic plane are also very difficult due to the presence of the disk field itself. In this work we demonstrate that cosmic ray protons in the energy range 1018 to 1019eV, if accelerated near the center of the Galaxy, are sensitive to the large scale structure of the Galactic Magnetic Field (GMF). In particular if the field is of even parity, and the spiral field is bi-symmetric (BSS), ultra high energy protons will predominantly come from the Southern Galactic hemisphere, and predominantly from the Northern Galactic hemisphere if the field is of even parity and axi-symmetric (ASS). There is no sensitivity to the BSS or ASS configurations if the field is of odd parity.
NASA Astrophysics Data System (ADS)
Alimi, J.-M.; Füzfa, A.; Boucher, V.; Rasera, Y.; Courtin, J.; Corasaniti, P.-S.
2010-01-01
Quintessence has been proposed to account for dark energy (DE) in the Universe. This component causes a typical modification of the background cosmic expansion, which, in addition to its clustering properties, can leave a potentially distinctive signature on large-scale structures. Many previous studies have investigated this topic, particularly in relation to the non-linear regime of structure formation. However, no careful pre-selection of viable quintessence models with high precision cosmological data was performed. Here we show that this has led to a misinterpretation (and underestimation) of the imprint of quintessence on the distribution of large-scale structures. To this purpose, we perform a likelihood analysis of the combined Supernova Ia UNION data set and Wilkinson Microwave Anisotropy Probe 5-yr data to identify realistic quintessence models. These are specified by different model parameter values, but still statistically indistinguishable from the vanilla Λ cold dark matter (ΛCDM). Differences are especially manifest in the predicted amplitude and shape of the linear matter power spectrum though these remain within the uncertainties of the Sloan Digital Sky Survey data. We use these models as a benchmark for studying the clustering properties of dark matter haloes by performing a series of high-resolution N-body simulations. In this first paper, we specifically focus on the non-linear matter power spectrum. We find that realistic quintessence models allow for relevant differences of the dark matter distribution with respect to the ΛCDM scenario well into the non-linear regime, with deviations of up to 40 per cent in the non-linear power spectrum. Such differences are shown to depend on the nature of DE, as well as the scale and epoch considered. At small scales (k ~ 1-5hMpc-1, depending on the redshift), the structure formation process is about 20 per cent more efficient than in ΛCDM. We show that these imprints are a specific record of the cosmic
Is the Smagorinsky coefficient sensitive to uncertainty in the form of the energy spectrum?
NASA Astrophysics Data System (ADS)
Meldi, M.; Lucor, D.; Sagaut, P.
2011-12-01
We investigate the influence of uncertainties in the shape of the energy spectrum over the Smagorinsky ["General circulation experiments with the primitive equations. I: The basic experiment," Mon. Weather Rev. 91(3), 99 (1963)] subgrid scale model constant CS: the analysis is carried out by a stochastic approach based on generalized polynomial chaos. The free parameters in the considered energy spectrum functional forms are modeled as random variables over bounded supports: two models of the energy spectrum are investigated, namely, the functional form proposed by Pope [Turbulent Flows (Cambridge University Press, Cambridge, 2000)] and by Meyers and Meneveau ["A functional form for the energy spectrum parametrizing bottleneck and intermittency effects," Phys. Fluids 20(6), 065109 (2008)]. The Smagorinsky model coefficient, computed from the algebraic relation presented in a recent work by Meyers and Sagaut ["On the model coefficients for the standard and the variational multi-scale Smagorinsky model," J. Fluid Mech. 569, 287 (2006)], is considered as a stochastic process and is described by numerical tools streaming from the probability theory. The uncertainties are introduced in the free parameters shaping the energy spectrum in correspondence to the large and the small scales, respectively. The predicted model constant is weakly sensitive to the shape of the energy spectrum when large scales uncertainty is considered: if the large-eddy simulation (LES) filter cut is performed in the inertial range, a significant probability to recover values lower in magnitude than the asymptotic Lilly-Smagorinsky model constant is recovered. Furthermore, the predicted model constant occurrences cluster in a compact range of values: the correspondent probability density function rapidly drops to zero approaching the extremes values of the range, which show a significant sensitivity to the LES filter width. The sensitivity of the model constant to uncertainties propagated in the
The microwave background anisotropies: observations.
Wilkinson, D
1998-01-01
Most cosmologists now believe that we live in an evolving universe that has been expanding and cooling since its origin about 15 billion years ago. Strong evidence for this standard cosmological model comes from studies of the cosmic microwave background radiation (CMBR), the remnant heat from the initial fireball. The CMBR spectrum is blackbody, as predicted from the hot Big Bang model before the discovery of the remnant radiation in 1964. In 1992 the cosmic background explorer (COBE) satellite finally detected the anisotropy of the radiation-fingerprints left by tiny temperature fluctuations in the initial bang. Careful design of the COBE satellite, and a bit of luck, allowed the 30 microK fluctuations in the CMBR temperature (2.73 K) to be pulled out of instrument noise and spurious foreground emissions. Further advances in detector technology and experiment design are allowing current CMBR experiments to search for predicted features in the anisotropy power spectrum at angular scales of 1 degrees and smaller. If they exist, these features were formed at an important epoch in the evolution of the universe--the decoupling of matter and radiation at a temperature of about 4,000 K and a time about 300,000 years after the bang. CMBR anisotropy measurements probe directly some detailed physics of the early universe. Also, parameters of the cosmological model can be measured because the anisotropy power spectrum depends on constituent densities and the horizon scale at a known cosmological epoch. As sophisticated experiments on the ground and on balloons pursue these measurements, two CMBR anisotropy satellite missions are being prepared for launch early in the next century. PMID:9419320
Dual-Energy CT: Spectrum of Thoracic Abnormalities.
Otrakji, Alexi; Digumarthy, Subba R; Lo Gullo, Roberto; Flores, Efren J; Shepard, Jo-Anne O; Kalra, Mannudeep K
2016-01-01
Recent studies have demonstrated that dual-energy computed tomography (CT) can provide useful information in several chest-related clinical indications. Compared with single-energy CT, dual-energy CT of the chest is feasible with the use of a radiation-dose-neutral scanning protocol. This article highlights the different types of images that can be generated by using dual-energy CT protocols such as virtual monochromatic, virtual unenhanced (ie, water), and pulmonary blood volume (ie, iodine) images. The physical basis of dual-energy CT and material decomposition are explained. The advantages of the use of virtual low-monochromatic images include reduced volume of intravenous contrast material and improved contrast resolution of images. The use of virtual high-monochromatic images can reduce beam hardening and contrast streak artifacts. The pulmonary blood volume images can help differentiate various parenchymal abnormalities, such as infarcts, atelectasis, and pneumonias, as well as airway abnormalities. The pulmonary blood volume images allow quantitative and qualitative assessment of iodine distribution. The estimation of iodine concentration (quantitative assessment) provides objective analysis of enhancement. The advantages of virtual unenhanced images include differentiation of calcifications, talc, and enhanced thoracic structures. Dual-energy CT has applications in oncologic imaging, including diagnosis of thoracic masses, treatment planning, and assessment of response to treatment. Understanding the concept of dual-energy CT and its clinical application in the chest are the goals of this article. PMID:26761530
Particle Energy Spectrum, Revisited from a Counting Statistics Perspective
2012-07-28
In nuclear science, gamma and neutron spectra are counted energy by energy, and then particle by particle. Until recently, few studies have been performed on how exactly those energy spectra are counted, or how those counts are correlated. Because of lack of investigation, cross section covariance and correlation matrices are usually estimated using perturbation method. We will discuss a statistical counting scheme that shall mimic the gamma and neutron counting process used in nuclear science. From this counting scheme, the cross section covariance and correlation can be statistically derived.
Excitation energy dependent Raman spectrum of MoSe2
Nam, Dahyun; Lee, Jae-Ung; Cheong, Hyeonsik
2015-01-01
Raman investigation of MoSe2 was carried out with eight different excitation energies. Seven peaks, including E1g, A1g, E2g1, and A2u2 peaks are observed in the range of 100–400 cm−1. The phonon modes are assigned by comparing the peak positions with theoretical calculations. The intensities of the peaks are enhanced at different excitation energies through resonance with different optical transitions. The A1g mode is enhanced at 1.58 and 3.82 eV, which are near the A exciton energy and the band-to-band transition between higher energy bands, respectively. The E2g1 mode is strongly enhanced with respect to the A1g mode for the 2.71- and 2.81-eV excitations, which are close to the C exciton energy. The different enhancements of the A1g and E2g1 modes are explained in terms of the symmetries of the exciton states and the exciton-phonon coupling. Other smaller peaks including E1g and A2u2 are forbidden but appear due to the resonance effect near optical transition energies. PMID:26601614
Observation of energy spectrum of electron albedo in low latitude region at Hyderabad, India
NASA Technical Reports Server (NTRS)
Verma, S. D.; Bhatnagar, S. P.
1985-01-01
The preliminary results are presented of the measurement of the energy spectrum of low energy (5-24 MeV) albedo electrons, moving upward as well as downwards, at about 37 km (-4 mb) altitude, over Hyderabad, India, in low latitude region. The flux and energy spectrum was observed by a bi-directional, multidetector charged particle telescope which was flown in a high altitude balloon on 8th December 1984. Results based on a quick look data acquisition and analysis system are presented here.
Li, Min; Zhou, Tong; Song, Yanan
2016-07-01
A grain size characterization method based on energy attenuation coefficient spectrum and support vector regression (SVR) is proposed. First, the spectra of the first and second back-wall echoes are cut into several frequency bands to calculate the energy attenuation coefficient spectrum. Second, the frequency band that is sensitive to grain size variation is determined. Finally, a statistical model between the energy attenuation coefficient in the sensitive frequency band and average grain size is established through SVR. Experimental verification is conducted on austenitic stainless steel. The average relative error of the predicted grain size is 5.65%, which is better than that of conventional methods. PMID:26995732
Primary CR energy spectrum and mass composition by the data of Tunka-133 array
NASA Astrophysics Data System (ADS)
Prosin, V. V.; Berezhnev, S. F.; Budnev, N. M.; Chiavassa, A.; Chvalaev, O. A.; Dyachok, A. V.; Epimakhov, S. N.; Gress, O. A.; Gress, T. I.; Kalmykov, N. N.; Karpov, N. I.; Konstantinov, E. N.; Korobchenko, A. V.; Korosteleva, E. E.; Kozhin, V. A.; Kuzmichev, L. A.; Lubsandorzhiev, B. K.; Lubsandorzhiev, N. B.; Mirgazov, R. R.; Monkhoev, R. D.; Osipova, E. A.; Pakhorukov, A. L.; Panasyuk, M. I.; Pankov, L. V.; Popova, E. G.; Ptuskin, V. S.; Semeney, Y. A.; Silaev, A. A.; Silaev, A. A., Jr.; Skurikhin, A. V.; Spiering, C.; Sveshnikova, L. G.; Zagorodnikov, A. V.
2015-08-01
The Cherenkov light array for the registration of extensive air showers (EAS) Tunka-133 collected data during 5 winter seasons from 2009 to 2014.-The differential energy spectrum of all particles and the dependence of the average maximum depth on the energy in the range of 6 ṡ 1015-1018 eV measured for 1540 hours of observation are presented.
Energy spectrum, dissipation, and spatial structures in reduced Hall magnetohydrodynamic
Martin, L. N.; Dmitruk, P.; Gomez, D. O.
2012-05-15
We analyze the effect of the Hall term in the magnetohydrodynamic turbulence under a strong externally supported magnetic field, seeing how this changes the energy cascade, the characteristic scales of the flow, and the dynamics of global magnitudes, with particular interest in the dissipation. Numerical simulations of freely evolving three-dimensional reduced magnetohydrodynamics are performed, for different values of the Hall parameter (the ratio of the ion skin depth to the macroscopic scale of the turbulence) controlling the impact of the Hall term. The Hall effect modifies the transfer of energy across scales, slowing down the transfer of energy from the large scales up to the Hall scale (ion skin depth) and carrying faster the energy from the Hall scale to smaller scales. The final outcome is an effective shift of the dissipation scale to larger scales but also a development of smaller scales. Current sheets (fundamental structures for energy dissipation) are affected in two ways by increasing the Hall effect, with a widening but at the same time generating an internal structure within them. In the case where the Hall term is sufficiently intense, the current sheet is fully delocalized. The effect appears to reduce impulsive effects in the flow, making it less intermittent.
Expected spectrum of high-energy photons from ball lightning
NASA Astrophysics Data System (ADS)
Shmatov, M. L.
2006-04-01
Two methods for identifying the flux of high-energy photons as emitted by ball lightning are proposed. It is assumed that ball lightning has a core consisting of oscillating clouds of electrons and totally ionized ions. A search for tooth enamel changes due to the influence of high-energy photons from ball lightning to reveal the influence of such photons on human beings is also proposed. This diagnostic measure should be taken if after observation of ball lightning symptoms similar to those of radiation sickness arise or ball lightning causes heavy burns.
Magnetic anisotropy control in Ga1-x Mnx As magnetic semiconductors
NASA Astrophysics Data System (ADS)
Stagraczyński, S.; Jasiukiewicz, C.; Dugaev, V. K.; Berakdar, J.
2016-08-01
Using the six-band Kane model of the electron energy spectrum in the valence band of GaMnAs magnetic semiconductor we investigate the dependence of the crystalline magnetic anisotropy on the magnitude of magnetization and on the doping with holes. Our main focus is on the difference between two possible models related to the constraint on the total hole number or on the chemical potential. Our results show that the theoretical results for magnetic anisotropy can change dramatically with the use of different constraints.
Electron energy spectrum in circularly polarized laser irradiated overdense plasma
Liu, C. S.; Tripathi, V. K.; Shao, Xi; Kumar, Pawan
2014-10-15
A circularly polarized laser normally impinged on an overdense plasma thin foil target is shown to accelerate the electrons in the skin layer towards the rear, converting the quiver energy into streaming energy exactly if one ignores the space charge field. The energy distribution of electrons is close to Maxwellian with an upper cutoff ε{sub max}=mc{sup 2}[(1+a{sub 0}{sup 2}){sup 1/2}−1], where a{sub 0}{sup 2}=(1+(2ω{sup 2}/ω{sub p}{sup 2})|a{sub in}|{sup 2}){sup 2}−1, |a{sub in}| is the normalized amplitude of the incident laser of frequency ω, and ω{sub p} is the plasma frequency. The energetic electrons create an electrostatic sheath at the rear and cause target normal sheath acceleration of protons. The energy gain by the accelerated ions is of the order of ε{sub max}.
Energy spectrum of neutrals formed in an ion accelerator
Fink, J.H.
1982-03-15
This work presents an estimate of the energy distribution of the neutrals formed in the ion beam accelerator. However it does not determine the fraction of those neutrals which leave the neutral beam injector and go on into the reactor. To do that, more details of the beam line performance are needed.
Energy spectrum and wavefunction of electrons in hybrid superconducting nanowires
NASA Astrophysics Data System (ADS)
Kruchinin, S. P.
2016-03-01
Recent experiments have fabricated structured arrays. We study hybrid nanowires, in which normal and superconducting regions are in close proximity, by using the Bogoliubov-de Gennes equations for superconductivity in a cylindrical nanowire. We succeed to obtain the quantum energy levels and wavefunctions of a superconducting nanowire. The obtained spectra of electrons remind Hofstadter’s butterfly.
NASA Astrophysics Data System (ADS)
Zhukova, Victoria
The azimuthal anisotropy of charged particles is an important feature of the hot and dense medium produced in heavy ion collisions. In non-central nucleus-nucleus collisions, the maximum particle density defines an event plane which is an approximation to the participant plane. The participant plane reflects the direction of the maximum of the pressure gradient set up by the participating nucleons. The initial nuclear overlap region is spatially asymmetric with an “almond-like” shape. This spatial asymmetry is reflected in the momentum distribution of the particles with respect to the event plane. The anisotropy is quantified in terms of a Fourier expansion of the observed particle yields relative to the event-by-event orientation of the participant plane. The second coefficient of the expansion, υ 2, often referred to as “elliptic flow”, carries information on the early collision dynamics when measured in the low-pT domain. A similar signal of a different origin is observed in the high- pT regime and is associated with parton energy loss in the presence of the medium. In this work the azimuthal anisotropy of charged hadrons is determined over an extended transverse momentum (p t) range up to approximately 60 GeV/c in PbPb collisions at sNN = 2.76 TeV, covering both the low-pt region associated with hydrodynamic flow phenomena and the high-pt region, pt > 12 GeV/c, where the anisotropies reflect the path-length dependence of parton energy loss in the created medium.
ON THE VERY HIGH ENERGY SPECTRUM OF THE CRAB PULSAR
Chkheidze, N.; Machabeli, G.; Osmanov, Z.
2011-04-01
In the present paper, we construct a self-consistent theory interpreting the observations from the MAGIC Cherenkov Telescope of the very high energy (VHE) pulsed emission from the Crab pulsar. In particular, on the basis of Vlasov's kinetic equation, we study the process of quasi-linear diffusion (QLD) developed by means of the cyclotron instability. This mechanism provides simultaneous generation of low (radio) and VHE (0.01-25 GeV) emission on light cylinder scales in one location of the pulsar magnetosphere. A different approach to the synchrotron emission is considered, giving the spectral index of the VHE emission ({beta} = 2) and the exponential cutoff energy (23 GeV) in good agreement with the observational data.
On the groundstate energy spectrum of magnetic knots and links
NASA Astrophysics Data System (ADS)
Ricca, Renzo L.; Maggioni, Francesca
2014-05-01
By using analytical results for the constrained minimum energy of magnetic knots we determine the influence of internal twist on the minimum magnetic energy levels of knots and links, and by using ropelength data from the RIDGERUNNER tightening algorithm (Ashton et al 2011 Exp. Math. 20 57-90) we obtain the groundstate energy spectra of the first 250 prime knots and 130 prime links. The two spectra are found to follow an almost identical logarithmic law. By assuming that the number of knot types grows exponentially with the topological crossing number, we show that this generic behavior can be justified by a general relationship between ropelength and crossing number, which is in good agreement with former analytical estimates (Buck and Simon 1999 Topol. Appl. 91 245-57, Diao 2003 J. Knot Theory Ramifications 12 1-16). Moreover, by considering the ropelength averaged over a given knot family, we establish a new connection between the averaged ropelength and the topological crossing number of magnetic knots.
A New Method of Prompt Fission Neutron Energy Spectrum Unfolding
Zeynalova, O. V.; Zeynalov, Sh.; Hambsch, F.-J.; Oberstedt, S.
2010-11-25
The prompt neutron emission in spontaneous fission of {sup 252}Cf has been investigated applying digital signal electronics along with associated digital signal processing algorithms. The goal was to find out the reasons of a long time existing discrepancy between theoretical calculations and the measurements of prompt fission neutron (PFN) emission dependence on the total kinetic energy (TKE) of fission fragments (FF). On the one hand the {sup 252}Cf(sf) reaction is one of the main references for nuclear data, on the other hand the understanding of PFN emission mechanism is very important for nuclear fission theory. Using a twin Frisch-grid ionization chamber for fission fragment (FF) detection and a NE213-equivalent neutron detector in total about 10{sup 7} fission fragment-neutron coincidences have been registered. Fission fragment kinetic energy, mass and angular distribution, neutron time-of-flight and pulse shape have been investigated using a 12 bit waveform digitizer. The signal waveforms have been analyzed using digital signal processing algorithms. For the first time the dependence of the number of emitted neutrons as a function of total kinetic energy (TKE) of the fragments is in very good agreement with theoretical calculations in the range of TKE from 140-220 MeV.
A New Method of Prompt Fission Neutron Energy Spectrum Unfolding
NASA Astrophysics Data System (ADS)
Zeynalova, O. V.; Zeynalov, Sh.; Hambsch, F.-J.; Oberstedt, S.
2010-11-01
The prompt neutron emission in spontaneous fission of 252Cf has been investigated applying digital signal electronics along with associated digital signal processing algorithms. The goal was to find out the reasons of a long time existing discrepancy between theoretical calculations and the measurements of prompt fission neutron (PFN) emission dependence on the total kinetic energy (TKE) of fission fragments (FF). On the one hand the 252Cf (sf) reaction is one of the main references for nuclear data, on the other hand the understanding of PFN emission mechanism is very important for nuclear fission theory. Using a twin Frisch-grid ionization chamber for fission fragment (FF) detection and a NE213-equivalent neutron detector in total about 107 fission fragment-neutron coincidences have been registered. Fission fragment kinetic energy, mass and angular distribution, neutron time-of-flight and pulse shape have been investigated using a 12 bit waveform digitizer. The signal waveforms have been analyzed using digital signal processing algorithms. For the first time the dependence of the number of emitted neutrons as a function of total kinetic energy (TKE) of the fragments is in very good agreement with theoretical calculations in the range of TKE from 140-220 MeV.
Nassan, L; Abdallah, B; Omar, H; Sarheel, A; Alsomel, N; Ghazi, N
2016-01-01
The focus of this article was on the experimental estimation of the neutron energy spectrum in the inner irradiation site of the miniature neutron source reactor (MNSR), using, for the first time, a selected set of deposited metal films on Teflon (DMFTs) neutron detectors. Gold, copper, zinc, titanium, aluminum, nickel, silver, and chromium were selected because of the dependence of their neutron cross-sections on neutron energy. Emphasis was placed on the usability of this new type of neutron detectors in the total neutron energy spectrum adjustment. The measured saturation activities per target nucleus values of the DMFTs, and the calculated neutron spectrum in the inner irradiation site using the MCNP-4C code were used as an input for the STAY'SL computer code during the adjustment procedure. The agreement between the numerically calculated and experimentally adjusted spectra results was discussed. PMID:26562448
The spectrum of flare protons in the low-energy range
NASA Astrophysics Data System (ADS)
Daibog, E. I.; Kurt, V. G.; Stolpovskii, V. G.
1981-09-01
An analysis is presented of the spectra of flare protons in the 0.08-150 MeV energy range, measured at about 1 AE on the Prognoz-6 satellite. The spectral data are compared with the energy dependence of the observation time of the maximum flux of flare protons. It is shown that changes in the slope in the spectrum and in the energy dependence of maximum times occur at approximately the same energy. Energy losses of protons in the interplanetary medium due to adiabatic cooling are determined. This effect is significant for protons with energies less than 1 MeV, and, in the case of flares of low importance, plays a decisive role in the formation of the spectrum of the observed flare protons.
Energy spectrum of argon ions emitted from Filippov type Sahand plasma focus
Mohammadnejad, M.; Pestehe, S. J.; Mohammadi, M. A.
2013-07-15
The energy and flux of the argon ions produced in Sahand plasma focus have been measured by employing a well-designed Faraday cup. The secondary electron emission effects on the ion signals are simulated and the dimensions of Faraday cup are optimized to minimize these effects. The measured ion energy spectrum is corrected for the ion energy loss and charge exchange in the background gas. The effects of the capacitor bank voltage and working gas pressure on the ion energy spectrum are also investigated. It has been shown that the emitted ion number per energy increases as the capacitor bank voltage increases. Decreasing the working gas pressure leads to the increase in the number of emitted ion per energy.
NASA Astrophysics Data System (ADS)
Abu-Zayyad, T.; Aida, R.; Allen, M.; Anderson, R.; Azuma, R.; Barcikowski, E.; Belz, J. W.; Bergman, D. R.; Blake, S. A.; Cady, R.; Cheon, B. G.; Chiba, J.; Chikawa, M.; Cho, E. J.; Cho, W. R.; Fujii, H.; Fujii, T.; Fukuda, T.; Fukushima, M.; Hanlon, W.; Hayashi, K.; Hayashi, Y.; Hayashida, N.; Hibino, K.; Hiyama, K.; Honda, K.; Iguchi, T.; Ikeda, D.; Ikuta, K.; Inoue, N.; Ishii, T.; Ishimori, R.; Ito, H.; Ivanov, D.; Iwamoto, S.; Jui, C. C. H.; Kadota, K.; Kakimoto, F.; Kalashev, O.; Kanbe, T.; Kasahara, K.; Kawai, H.; Kawakami, S.; Kawana, S.; Kido, E.; Kim, H. B.; Kim, H. K.; Kim, J. H.; Kim, J. H.; Kitamoto, K.; Kitamura, S.; Kitamura, Y.; Kobayashi, K.; Kobayashi, Y.; Kondo, Y.; Kuramoto, K.; Kuzmin, V.; Kwon, Y. J.; Lan, J.; Lim, S. I.; Lundquist, J. P.; Machida, S.; Martens, K.; Matsuda, T.; Matsuura, T.; Matsuyama, T.; Matthews, J. N.; Minamino, M.; Miyata, K.; Murano, Y.; Myers, I.; Nagasawa, K.; Nagataki, S.; Nakamura, T.; Nam, S. W.; Nonaka, T.; Ogio, S.; Ohnishi, M.; Ohoka, H.; Oki, K.; Oku, D.; Okuda, T.; Ono, M.; Oshima, A.; Ozawa, S.; Park, I. H.; Pshirkov, M. S.; Rodriguez, D. C.; Roh, S. Y.; Rubtsov, G.; Ryu, D.; Sagawa, H.; Sakurai, N.; Sampson, A. L.; Scott, L. M.; Shah, P. D.; Shibata, F.; Shibata, T.; Shimodaira, H.; Shin, B. K.; Shin, J. I.; Shirahama, T.; Smith, J. D.; Sokolsky, P.; Springer, R. W.; Stokes, B. T.; Stratton, S. R.; Stroman, T.; Suzuki, S.; Takahashi, Y.; Takeda, M.; Taketa, A.; Takita, M.; Tameda, Y.; Tanaka, H.; Tanaka, K.; Tanaka, M.; Thomas, S. B.; Thomson, G. B.; Tinyakov, P.; Tkachev, I.; Tokuno, H.; Tomida, T.; Troitsky, S.; Tsunesada, Y.; Tsutsumi, K.; Tsuyuguchi, Y.; Uchihori, Y.; Udo, S.; Ukai, H.; Urban, F.; Vasiloff, G.; Wada, Y.; Wong, T.; Yamakawa, Y.; Yamane, R.; Yamaoka, H.; Yamazaki, K.; Yang, J.; Yoneda, Y.; Yoshida, S.; Yoshii, H.; Zhou, X.; Zollinger, R.; Zundel, Z.
2015-02-01
We measure the spectrum of cosmic rays with energies greater than 1018.2 eV with the fluorescence detectors (FDs) and the surface detectors (SDs) of the Telescope Array Experiment using the data taken in our first 2.3-year observation from May 27, 2008 to September 7, 2010. A hybrid air shower reconstruction technique is employed to improve accuracies in determination of arrival directions and primary energies of cosmic rays using both FD and SD data. The energy spectrum presented here is in agreement with our previously published spectra and the HiRes results.
Energy spectrum of cosmic-ray iron nucleus observed with emulsion chamber
NASA Technical Reports Server (NTRS)
Ohta, I.; Tasaka, S.; Sato, Y.; Shimada, E.; Tanaka, S.; Sugimoto, H.; Taira, K.; Tateyama, N.
1985-01-01
Energy spectrum of cosmic-ray Fe-nucleus has been measured from 4 GeV per nucleon to beyond 100 GeV per nucleon. The data were obtained using emulsion chambers on a balloon from Sanriku, Japan. The energies were estimated by the opening angle method after calibrated using 1.88 GeV per nucleon Fe collisions. The spectrum of Fe is approximately E-2.5 in the range from 10 to 200 GeV per nucleon. This result is in good agreement with those of other experiments.
Backscatter, anisotropy, and polarization of solar hard X-rays
NASA Technical Reports Server (NTRS)
Bai, T.; Ramaty, R.
1978-01-01
The problems of anisotropy, polarization, center-to-limb variation of the X-ray spectrum, and Compton backscatter are investigated in a study of solar hard X-rays. Effect of backscatter are found particularly important for anisotropic sources which emit hard X-rays predominantly toward the photosphere; for such anisotropic primary X-ray sources, the observed X-ray flux near 30 keV does not depend significantly on the position of the flare. In addition, the degree of polarization of the sum of the primary and reflected X-rays with energies in the 15 to 30 keV range may be as high as 30%. Determination of the height and anisotropy of the primary X-ray sources from study of the albedo patch is also discussed.
NASA Astrophysics Data System (ADS)
Vorndran, Shelby D.; Wu, Yuechen; Ayala, Silvana; Kostuk, Raymond K.
2015-09-01
Concentrating and spectrum splitting photovoltaic (PV) modules have a limited acceptance angle and thus suffer from optical loss under off-axis illumination. This loss manifests itself as a substantial reduction in energy yield in locations where a significant portion of insulation is diffuse. In this work, a spectrum splitting PV system is designed to efficiently collect and convert light in a range of illumination conditions. The system uses a holographic lens to concentrate shortwavelength light onto a smaller, more expensive indium gallium phosphide (InGaP) PV cell. The high efficiency PV cell near the axis is surrounded with silicon (Si), a less expensive material that collects a broader portion of the solar spectrum. Under direct illumination, the device achieves increased conversion efficiency from spectrum splitting. Under diffuse illumination, the device collects light with efficiency comparable to a flat-panel Si module. Design of the holographic lens is discussed. Optical efficiency and power output of the module under a range of illumination conditions from direct to diffuse are simulated with non-sequential raytracing software. Using direct and diffuse Typical Metrological Year (TMY3) irradiance measurements, annual energy yield of the module is calculated for several installation sites. Energy yield of the spectrum splitting module is compared to that of a full flat-panel Si reference module.
All-Particle Cosmic Ray Energy Spectrum Measured with 26 Icetop Stations
NASA Technical Reports Server (NTRS)
Abbasi, R.; Abdou, Y.; Abu-Zayyad, T.; Ackermann, M.; Adams, J.; Aguilar, J. A.; Ahlers, M.; Altmann, D.; Andeen, K.; Auffenberg, J.; Bai, X.; Baker, M.; Barwick, S. W.; Baum, V.; Bay, R.; Bazo Alba, J. L.; Beattie, K.; Beatty, J. J.; Bechet, S.; Becker, J. K.; Becker, K.-H; Bell, M.; Benabderrahmane, M. L.; BenZvi, S.; Stamatikos, M.
2013-01-01
We report on a measurement of the cosmic ray energy spectrum with the IceTop air shower array, thesurface component of the IceCube Neutrino Observatory at the South Pole. The data used in this analysiswere taken between June and October, 2007, with 26 surface stations operational at that time, corresponding to about one third of the final array. The fiducial area used in this analysis was 0.122 square kilometers.The analysis investigated the energy spectrum from 1 to 100 PeV measured for three different zenithangle ranges between 0 and 46. Because of the isotropy of cosmic rays in this energy range the spectrafrom all zenith angle intervals have to agree. The cosmic-ray energy spectrum was determined under differentassumptions on the primary mass composition. Good agreement of spectra in the three zenithangle ranges was found for the assumption of pure proton and a simple two-component model. Forzenith angles theta less than 30 deg., where the mass dependence is smallest, the knee in the cosmic ray energy spectrumwas observed at about 4 PeV, with a spectral index above the knee of about -3.1. Moreover, an indicationof a flattening of the spectrum above 22 PeV was observed.
Introducing the concept of anisotropy at different scales for modeling optical turbulence.
Toselli, Italo
2014-08-01
In this paper, the concept of anisotropy at different atmospheric turbulence scales is introduced. A power spectrum and its associated structure function with inner and outer scale effects and anisotropy are also shown. The power spectrum includes an effective anisotropic parameter ζ(eff) to describe anisotropy, which is useful for modeling optical turbulence when a non-Kolmogorov power law and anisotropy along the direction of propagation are present. PMID:25121545
Scaling-law for the energy dependence of anatomic power spectrum in dedicated breast CT
Vedantham, Srinivasan; Shi, Linxi; Glick, Stephen J.; Karellas, Andrew
2013-01-15
Purpose: To determine the x-ray photon energy dependence of the anatomic power spectrum of the breast when imaged with dedicated breast computed tomography (CT). Methods: A theoretical framework for scaling the empirically determined anatomic power spectrum at one x-ray photon energy to that at any given x-ray photon energy when imaged with dedicated breast CT was developed. Theory predicted that when the anatomic power spectrum is fitted with a power curve of the form k f{sup -{beta}}, where k and {beta} are fit coefficients and f is spatial frequency, the exponent {beta} would be independent of x-ray photon energy (E), and the amplitude k scales with the square of the difference in energy-dependent linear attenuation coefficients of fibroglandular and adipose tissues. Twenty mastectomy specimens based numerical phantoms that were previously imaged with a benchtop flat-panel cone-beam CT system were converted to 3D distribution of glandular weight fraction (f{sub g}) and were used to verify the theoretical findings. The 3D power spectrum was computed in terms of f{sub g} and after converting to linear attenuation coefficients at monoenergetic x-ray photon energies of 20-80 keV in 5 keV intervals. The 1D power spectra along the axes were extracted and fitted with a power curve of the form k f{sup -{beta}}. The energy dependence of k and {beta} were analyzed. Results: For the 20 mastectomy specimen based numerical phantoms used in the study, the exponent {beta} was found to be in the range of 2.34-2.42, depending on the axis of measurement. Numerical simulations agreed with the theoretical predictions that for a power-law anatomic spectrum of the form k f{sup -{beta}}, {beta} was independent of E and k(E) =k{sub 1}[{mu}{sub g}(E) -{mu}{sub a}(E)]{sup 2}, where k{sub 1} is a constant, and {mu}{sub g}(E) and {mu}{sub a}(E) represent the energy-dependent linear attenuation coefficients of fibroglandular and adipose tissues, respectively. Conclusions: Numerical
An Energy-Efficient Game-Theory-Based Spectrum Decision Scheme for Cognitive Radio Sensor Networks
Salim, Shelly; Moh, Sangman
2016-01-01
A cognitive radio sensor network (CRSN) is a wireless sensor network in which sensor nodes are equipped with cognitive radio. In this paper, we propose an energy-efficient game-theory-based spectrum decision (EGSD) scheme for CRSNs to prolong the network lifetime. Note that energy efficiency is the most important design consideration in CRSNs because it determines the network lifetime. The central part of the EGSD scheme consists of two spectrum selection algorithms: random selection and game-theory-based selection. The EGSD scheme also includes a clustering algorithm, spectrum characterization with a Markov chain, and cluster member coordination. Our performance study shows that EGSD outperforms the existing popular framework in terms of network lifetime and coordination overhead. PMID:27376290
A new neutron energy spectrum unfolding code using a two steps genetic algorithm
NASA Astrophysics Data System (ADS)
Shahabinejad, H.; Hosseini, S. A.; Sohrabpour, M.
2016-03-01
A new neutron spectrum unfolding code TGASU (Two-steps Genetic Algorithm Spectrum Unfolding) has been developed to unfold the neutron spectrum from a pulse height distribution which was calculated using the MCNPX-ESUT computational Monte Carlo code. To perform the unfolding process, the response matrices were generated using the MCNPX-ESUT computational code. Both one step (common GA) and two steps GAs have been implemented to unfold the neutron spectra. According to the obtained results, the new two steps GA code results has shown closer match in all energy regions and particularly in the high energy regions. The results of the TGASU code have been compared with those of the standard spectra, LSQR method and GAMCD code. The results of the TGASU code have been demonstrated to be more accurate than that of the existing computational codes for both under-determined and over-determined problems.
An Energy-Efficient Game-Theory-Based Spectrum Decision Scheme for Cognitive Radio Sensor Networks.
Salim, Shelly; Moh, Sangman
2016-01-01
A cognitive radio sensor network (CRSN) is a wireless sensor network in which sensor nodes are equipped with cognitive radio. In this paper, we propose an energy-efficient game-theory-based spectrum decision (EGSD) scheme for CRSNs to prolong the network lifetime. Note that energy efficiency is the most important design consideration in CRSNs because it determines the network lifetime. The central part of the EGSD scheme consists of two spectrum selection algorithms: random selection and game-theory-based selection. The EGSD scheme also includes a clustering algorithm, spectrum characterization with a Markov chain, and cluster member coordination. Our performance study shows that EGSD outperforms the existing popular framework in terms of network lifetime and coordination overhead. PMID:27376290
Long-term differential energy spectrum for solar-flare iron-group particles
NASA Technical Reports Server (NTRS)
Blanford, G. E.; Fruland, R. M.; Morrison, D. A.
1975-01-01
A long-term solar-flare differential energy spectrum for iron-group nuclei from approximately 0.1 to approximately 600 MeV/amu is derived from track density profile measurements in sample 64455 and sample 68815. Measurements from uneroded surfaces were obtained from quench crystals of plagioclase in 64455, and a Kr-81/Kr method indicates that the exposure age of this sample is 2,010,000 yrs. The power laws which best fit the normalized track density data are reported; the energy spectrum consists of two power law curves smoothly joined together which in turn are smoothly connected to a modulated galactic cosmic-ray spectrum. Standard track production versus depth profiles can be used to determine solar-flare track exposure ages and erosion rates for lunar samples.
Neutron energy spectrum characterization on TMR-1 at the Indiana University neutron source
NASA Astrophysics Data System (ADS)
Halstead, Matthew R.; Lee, Sangjin; Petrosky, James; Bickley, Abigail; Sokol, Paul
The energy spectrum of the Neutron Radiation Effects Program (NREP) beam line, Target-Moderator-Reflector-1 (TMR-1), at Indiana University has not been previously characterized. The facility has a unique proton source with variable pulse length (15-600 ms) and energy (13 MeV). Thus, it can produce a unique and tailored neutron beam when incident on a beryllium target. Through a combination of MCNP-X particle simulations, neutron activation experiments, and application of a spectrum unfolding code (SAND-II), the neutron source is characterized. Eight activation foils and wires were irradiated in the target area and the gamma activity measured. This information was used in an unfolding code, SAND-II, to deconvolve the spectrum, using the MCNP simulations as a basis for the spectral fitting.
A two-stage spectrum sensing scheme based on energy detection and a novel multitaper method
NASA Astrophysics Data System (ADS)
Qi, Pei-Han; Li, Zan; Si, Jiang-Bo; Xiong, Tian-Yi
2015-04-01
Wideband spectrum sensing has drawn much attention in recent years since it provides more opportunities to the secondary users. However, wideband spectrum sensing requires a long time and a complex mechanism at the sensing terminal. A two-stage wideband spectrum sensing scheme is considered to proceed spectrum sensing with low time consumption and high performance to tackle this predicament. In this scheme, a novel multitaper spectrum sensing (MSS) method is proposed to mitigate the poor performance of energy detection (ED) in the low signal-to-noise ratio (SNR) region. The closed-form expression of the decision threshold is derived based on the Neyman-Pearson criterion and the probability of detection in the Rayleigh fading channel is analyzed. An optimization problem is formulated to maximize the probability of detection of the proposed two-stage scheme and the average sensing time of the two-stage scheme is analyzed. Numerical results validate the efficiency of MSS and show that the two-stage spectrum sensing scheme enjoys higher performance in the low SNR region and lower time cost in the high SNR region than the single-stage scheme. Project supported by the National Natural Science Foundation of China (Grant No. 61301179), the China Postdoctoral Science Foundation (Grant No. 2014M550479), and the Doctorial Programs Foundation of the Ministry of Education, China (Grant No. 20110203110011).
The energy spectrum of electrons and cosmic-ray confinement A new measurement and its interpretation
NASA Technical Reports Server (NTRS)
Tang, K.-K.
1984-01-01
Measurements of the cosmic ray flux and electron energy spectrum from 5 GeV to 300 GeV, with an absolute uncertainty in the flux level of + or - 10 percent at low energies and + or - 30 percent at 100 GeV, are described. The measured spectrum appears to represent the competing processes of radiative energy loss in the interstellar medium and leakage out of the Galaxy. In the framework of the leaky box model and diffusion models, the result is most consistent with the picture of cosmic ray electrons spending an average of 10 million years in the Galaxy independent of electron energy, probably propagating in a halo as well as in the galactic disk.
Study of La-binding energies by analysis of its photodetachment spectrum
NASA Astrophysics Data System (ADS)
Pan, Lin; Beck, Donald
2016-05-01
In this study, relativistic configuration interaction (RCI) is employed to investigate the electron affinity and binding energies of the negative ion of lanthanum, by reinterpreting an earlier experimental photoelectron kinetic energy spectrum of La-. For the electron affinity of lanthanum, our study revises the original experimental interpretation of 0.47 +/- 0.02 eV and agrees well with the earlier RCI value of 0.545 eV. The calculation yields also the binding energies for thirteen excited states of La-. These energies are compared to results of recent experimental studies on La-. The details of the calculation, identities of main features in the experimental spectrum will be presented in our poster. National Science Foundation, Grant No. PHY-0968205
Semiclassical analysis of the Efimov energy spectrum in the unitary limit
Bhaduri, Rajat K.; Brack, Matthias; Murthy, M. V. N.
2011-06-15
We demonstrate that the (s-wave) geometric spectrum of the Efimov energy levels in the unitary limit is generated by the radial motion of a primitive periodic orbit (and its harmonics) of the corresponding classical system. The action of the primitive orbit depends logarithmically on the energy. It is shown to be consistent with an inverse-squared radial potential with a lower cutoff radius. The lowest-order WKB quantization, including the Langer correction, is shown to reproduce the geometric scaling of the energy spectrum. The (WKB) mean-squared radii of the Efimov states scale geometrically like the inverse of their energies. The WKB wave functions, regularized near the classical turning point by Langer's generalized connection formula, are practically indistinguishable from the exact wave functions even for the lowest (n=0) state, apart from a tiny shift of its zeros that remains constant for large n.
Semiclassical analysis of the Efimov energy spectrum in the unitary limit
NASA Astrophysics Data System (ADS)
Bhaduri, Rajat K.; Brack, Matthias; Murthy, M. V. N.
2011-06-01
We demonstrate that the (s-wave) geometric spectrum of the Efimov energy levels in the unitary limit is generated by the radial motion of a primitive periodic orbit (and its harmonics) of the corresponding classical system. The action of the primitive orbit depends logarithmically on the energy. It is shown to be consistent with an inverse-squared radial potential with a lower cutoff radius. The lowest-order WKB quantization, including the Langer correction, is shown to reproduce the geometric scaling of the energy spectrum. The (WKB) mean-squared radii of the Efimov states scale geometrically like the inverse of their energies. The WKB wave functions, regularized near the classical turning point by Langer’s generalized connection formula, are practically indistinguishable from the exact wave functions even for the lowest (n=0) state, apart from a tiny shift of its zeros that remains constant for large n.
Balloon measurements of the energy spectrum of cosmic electrons between 1 and 25 GeV.
NASA Technical Reports Server (NTRS)
Earl, J. A.; Neely, D. E.; Rygg, T. A.
1972-01-01
During three balloon flights made in 1966 and 1967, cosmic electrons were investigated with the aid of a hodoscope detector that provided extensive and detailed information on each cosmic-ray event triggering the apparatus. Similar information obtained during calibration exposures to protons and pions as well as to electrons was used to provide identification of cosmic electrons and to determine their energies. Differential primary electron intensities measured in the range from 1 to 25 GeV were substantially larger than some earlier measurements. In conjunction with existing measurements at energies above 100 GeV, this finding indicates that the energy spectrum of cosmic electrons is steeper than that of cosmic-ray nuclei and consequently suggests that Compton/synchrotron energy loss plays a significant role in shaping the electron spectrum.
Power Versus Spectrum 2-D Sensing in Energy Harvesting Cognitive Radio Networks
NASA Astrophysics Data System (ADS)
Zhang, Yanyan; Han, Weijia; Li, Di; Zhang, Ping; Cui, Shuguang
2015-12-01
Energy harvester based cognitive radio is a promising solution to address the shortage of both spectrum and energy. Since the spectrum access and power consumption patterns are interdependent, and the power value harvested from certain environmental sources are spatially correlated, the new power dimension could provide additional information to enhance the spectrum sensing accuracy. In this paper, the Markovian behavior of the primary users is considered, based on which we adopt a hidden input Markov model to specify the primary vs. secondary dynamics in the system. Accordingly, we propose a 2-D spectrum and power (harvested) sensing scheme to improve the primary user detection performance, which is also capable of estimating the primary transmit power level. Theoretical and simulated results demonstrate the effectiveness of the proposed scheme, in term of the performance gain achieved by considering the new power dimension. To the best of our knowledge, this is the first work to jointly consider the spectrum and power dimensions for the cognitive primary user detection problem.
Magnetic properties and anisotropy in magnetic thin films and superlattices
NASA Astrophysics Data System (ADS)
Guo, Wenli
A systematic study of the magnetic properties and anisotropy in magnetic thin films as well as superlattices is presented in this thesis. The main objective is to investigate by means of the Green function technique the order-disorder phase transition and reorientation transition in a non-perturbative microscopic theory valid in the whole temperature range of interest. We consider the magnetic systems that may consist of an arbitrary number of layers with any spin. We start with a discussion of general properties and origins of anisotropies of the magnetic systems, and a list of questions that we are trying to answer. A comparison between different theoretical approaches follows. The Green function method is used to derive analytical expressions for various anisotropies. The energy spectrum and the spontaneous magnetization are obtained as well. Based on these results, the transition temperature and the Curie temperature are calculated as functions of the Fe film thickness. It is shown that the condition for the reorientation transition is equivalent to that for the zero energy gap at the bottom of the spin-wave spectrum. Special features under the influence of normal external field, anisotropic exchange couplings and next-nearest-neighbor couplings on the magnetization reorientation of magnetic thin films are then investigated in detail. It is demonstrated that the nature of perpendicular remanent (PR) depends primarily on the surface anisotropy and film thickness. The magnetic properties of Tb/Fe superlattices are also studied. It shows ferrimagnetic properties and normal uniaxial anisotropy. An approximation is proposed to treat magnetic Ni films of arbitrary thickness and arbitrary lattice structure for general spin. It is a much simpler way of calculation, in which one does not have to solve the determinant equation, especially the one with off-diagonal elements. The temperature and thickness dependence of various anisotropies are then investigated. There
The effect of stochastic re-acceleration on the energy spectrum of shock-accelerated protons
Afanasiev, Alexandr; Vainio, Rami; Kocharov, Leon
2014-07-20
The energy spectra of particles in gradual solar energetic particle (SEP) events do not always have a power-law form attributed to the diffusive shock acceleration mechanism. In particular, the observed spectra in major SEP events can take the form of a broken (double) power law. In this paper, we study the effect of a process that can modify the power-law spectral form produced by the diffusive shock acceleration: the stochastic re-acceleration of energetic protons by enhanced Alfvénic turbulence in the downstream region of a shock wave. There are arguments suggesting that this process can be important when the shock propagates in the corona. We consider a coronal magnetic loop traversed by a shock and perform Monte Carlo simulations of interactions of shock-accelerated protons with Alfvén waves in the loop. The wave-particle interactions are treated self-consistently, so the finiteness of the available turbulent energy is taken into account. The initial energy spectrum of particles is taken to be a power law. The simulations reveal that the stochastic re-acceleration leads either to the formation of a spectrum that is described in a wide energy range by a power law (although the resulting power-law index is different from the initial one) or to a broken power-law spectrum. The resulting spectral form is determined by the ratio of the energy density of shock-accelerated protons to the wave energy density in the shock's downstream region.
Testing oscillating primordial spectrum and oscillating dark energy with astronomical observations
Liu, Jie; Li, Hong; Zhang, Xinmin; Xia, Jun-Qing E-mail: hongli@ihep.ac.cn E-mail: xmzhang@ihep.ac.cn
2009-07-01
In this paper we revisit the issue of determining the oscillating primordial scalar power spectrum and oscillating equation of state of dark energy from the astronomical observations. By performing a global analysis with the Markov Chain Monte Carlo method, we find that the current observations from five-year WMAP and SDSS-LRG matter power spectrum, as well as the ''union'' supernovae sample, constrain the oscillating index of primordial spectrum and oscillating equation of state of dark energy with the amplitude less than |n{sub amp}| < 0.116 and |w{sub amp}| < 0.232 at 95% confidence level, respectively. This result shows that the oscillatory structures on the primordial scalar spectrum and the equation of state of dark energy are still allowed by the current data. Furthermore, we point out that these kinds of modulation effects will be detectable (or gotten a stronger constraint) in the near future astronomical observations, such as the PLANCK satellite, LAMOST telescope and the currently ongoing supernovae projects SNLS.
Lorentz Invariance Violation and the Observed Spectrum of Ultrahigh Energy Cosmic Rays
NASA Technical Reports Server (NTRS)
Scully, S. T.; Stecker, F. W.
2009-01-01
There has been much interest in possible violations of Lorentz invariance, particularly motivated by quantum gravity theories. It has been suggested that a small amount of Lorentz invariance violation (LIV) could turn of photomeson interactions of ultrahigh energy cosmic rays (UHECRs) with photons of the cosmic background radiation and thereby eliminate the resulting sharp steepening in the spectrum of the highest energy CRs predicted by Greisen Zatsepin and Kuzmin (GZK). Recent measurements of the UHECR spectrum reported by the HiRes and Auger collaborations, however, indicate the presence of the GZK effect. We present the results of a detailed calculation of the modification of the UHECR spectrum caused by LIV using the formalism of Coleman and Glashow. We then compare these results with the experimental UHECR data from Auger and HiRes. Based on these data, we find a best fit amount of LIV of 4.5+1:5 ..4:5 x 10(exp -23),consistent with an upper limit of 6 x 10(exp -23). This possible amount of LIV can lead to a recovery of the cosmic ray spectrum at higher energies than presently observed. Such an LIV recovery effect can be tested observationally using future detectors.
Ferromagnetism and strong magnetic anisotropy of the PbMnBO4 orthoborate single crystals
NASA Astrophysics Data System (ADS)
Pankrats, A.; Sablina, K.; Eremin, M.; Balaev, A.; Kolkov, M.; Tugarinov, V.; Bovina, A.
2016-09-01
The PbMnBO4 orthoborate single crystals were first grown and their magnetic properties and ferromagnetic resonance were studied. It was found that the ferromagnetic state below the Curie temperature TC=31 K is characterized by the strong magnetic anisotropy. The significant effective anisotropy fields of PbMnBO4 determine the energy gap in the FMR spectrum, which is extraordinary large for ferromagnets (112 GHz at T=4.2 K). It was shown that the static Jahn-Teller effect characteristic of the Mn3+ ion leads to both the ferromagnetic ordering and the strong magnetic anisotropy in the crystal. In the strong external magnetic field the induced ferromagnetic ordering is retained in the crystal above the Curie temperature up to the temperatures multiply higher than TC. A weak anomaly of the dielectric permittivity was observed in PbMnBO4 at the Curie temperature at which the long-range ferromagnetic order is established.
The Temperature Dependence of the Magnetisation and Anisotropy of Ultrathin Ferromagnetic Films
NASA Astrophysics Data System (ADS)
Kaplan, Bengü
1997-01-01
The problem of the thermal stability of the magnetisation has attracted renewed interest since recent investigations of ultrathin epitaxial films establish the existence of long range magnetic order in plane [1,2]. We have used spin-wave theory [3] which can be expected to provide an adequate description of the excitation spectrum where the magnetisation is close to saturation, i.e., at temperatures significantly smaller than the Curie temperature. We take into account the effects of the dipole interaction, exchange interaction, ~Zeeman enegy and the magnetocrystalline anisotropy without restriction to the uniaxial case. The exchange gap for these spin waves is determined by a combination of the various anisotropy constants. We show that the temperature dependence of the magnetisation deviation is given in terms of the energy gap alone for a two dimensional magnetic film, and also the small in-plane anisotropies cannot be neglected for monolayer films.
Formation of Magnetic Anisotropy by Lithography.
Kim, Si Nyeon; Nam, Yoon Jae; Kim, Yang Doo; Choi, Jun Woo; Lee, Heon; Lim, Sang Ho
2016-01-01
Artificial interface anisotropy is demonstrated in alternating Co/Pt and Co/Pd stripe patterns, providing a means of forming magnetic anisotropy using lithography. In-plane hysteresis loops measured along two principal directions are explained in depth by two competing shape and interface anisotropies, thus confirming the formation of interface anisotropy at the Co/Pt and Co/Pd interfaces of the stripe patterns. The measured interface anisotropy energies, which are in the range of 0.2-0.3 erg/cm(2) for both stripes, are smaller than those observed in conventional multilayers, indicating a decrease in smoothness of the interfaces when formed by lithography. The demonstration of interface anisotropy in the Co/Pt and Co/Pd stripe patterns is of significant practical importance, because this setup makes it possible to form anisotropy using lithography and to modulate its strength by controlling the pattern width. Furthermore, this makes it possible to form more complex interface anisotropy by fabricating two-dimensional patterns. These artificial anisotropies are expected to open up new device applications such as multilevel bits using in-plane magnetoresistive thin-film structures. PMID:27216420
Formation of Magnetic Anisotropy by Lithography
Kim, Si Nyeon; Nam, Yoon Jae; Kim, Yang Doo; Choi, Jun Woo; Lee, Heon; Lim, Sang Ho
2016-01-01
Artificial interface anisotropy is demonstrated in alternating Co/Pt and Co/Pd stripe patterns, providing a means of forming magnetic anisotropy using lithography. In-plane hysteresis loops measured along two principal directions are explained in depth by two competing shape and interface anisotropies, thus confirming the formation of interface anisotropy at the Co/Pt and Co/Pd interfaces of the stripe patterns. The measured interface anisotropy energies, which are in the range of 0.2–0.3 erg/cm2 for both stripes, are smaller than those observed in conventional multilayers, indicating a decrease in smoothness of the interfaces when formed by lithography. The demonstration of interface anisotropy in the Co/Pt and Co/Pd stripe patterns is of significant practical importance, because this setup makes it possible to form anisotropy using lithography and to modulate its strength by controlling the pattern width. Furthermore, this makes it possible to form more complex interface anisotropy by fabricating two-dimensional patterns. These artificial anisotropies are expected to open up new device applications such as multilevel bits using in-plane magnetoresistive thin-film structures. PMID:27216420
Abreu, P.; Aglietta, M.; Ahn, E.J.; Albuquerque, I.F.M.; Allard, D.; Allekotte, I.; Allen, J.; Allison, P.; Alvarez Castillo, J.; Alvarez-Muniz, J.; Ambrosio, M.; /Naples U. /INFN, Naples /Nijmegen U., IMAPP
2011-11-01
We present a comprehensive study of the influence of the geomagnetic field on the energy estimation of extensive air showers with a zenith angle smaller than 60{sup o}, detected at the Pierre Auger Observatory. The geomagnetic field induces an azimuthal modulation of the estimated energy of cosmic rays up to the {approx} 2% level at large zenith angles. We present a method to account for this modulation of the reconstructed energy. We analyse the effect of the modulation on large scale anisotropy searches in the arrival direction distributions of cosmic rays. At a given energy, the geomagnetic effect is shown to induce a pseudo-dipolar pattern at the percent level in the declination distribution that needs to be accounted for. In this work, we have identified and quantified a systematic uncertainty affecting the energy determination of cosmic rays detected by the surface detector array of the Pierre Auger Observatory. This systematic uncertainty, induced by the influence of the geomagnetic field on the shower development, has a strength which depends on both the zenith and the azimuthal angles. Consequently, we have shown that it induces distortions of the estimated cosmic ray event rate at a given energy at the percent level in both the azimuthal and the declination distributions, the latter of which mimics an almost dipolar pattern. We have also shown that the induced distortions are already at the level of the statistical uncertainties for a number of events N {approx_equal} 32 000 (we note that the full Auger surface detector array collects about 6500 events per year with energies above 3 EeV). Accounting for these effects is thus essential with regard to the correct interpretation of large scale anisotropy measurements taking explicitly profit from the declination distribution.
Zhuang, Tao-Tao; Liu, Yan; Li, Yi; Zhao, Yuan; Wu, Liang; Jiang, Jun; Yu, Shu-Hong
2016-05-23
The full harvest of solar energy by semiconductors requires a material that simultaneously absorbs across the whole solar spectrum and collects photogenerated electrons and holes separately. The stepwise integration of three semiconducting sulfides, namely ZnS, CdS, and Cu2-x S, into a single nanocrystal, led to a unique ternary multi-node sheath ZnS-CdS-Cu2-x S heteronanorod for full-spectrum solar energy absorption. Localized surface plasmon resonance (LSPR) in the nonstoichiometric copper sulfide nanostructures enables effective NIR absorption. More significantly, the construction of pn heterojunctions between Cu2-x S and CdS leads to staggered gaps, as confirmed by first-principles simulations. This band alignment causes effective electron-hole separation in the ternary system and hence enables efficient solar energy conversion. PMID:27062543
Measurements of the spectrum and energy dependence of X-ray transition radiation
NASA Technical Reports Server (NTRS)
Cherry, M. L.
1978-01-01
The results of experiments designed to test the theory of X-ray transition radiation and to verify the predicted dependence of the characteristic features of the radiation on the radiator dimensions are presented. The X-ray frequency spectrum produced by 5- to 9-GeV electrons over the range 4 to 30 keV was measured with a calibrated single-crystal Bragg spectrometer, and at frequencies up to 100 keV with an NaI scintillator. The interference pattern in the spectrum and the hardening of the radiation with increasing foil thickness are clearly observed. The energy dependence of the total transition-radiation intensity was studied using a radiator with large dimensions designed to yield energy-dependent signals at very high particle energies, up to E/mc-squared approximately equal to 100,000. The results are in good agreement with the theoretical predictions.
Mars Energy Spectrum studies from Assimilated MCS data using the UK MGCM
NASA Astrophysics Data System (ADS)
Valeanu, Alexandru; Read, Peter; Wang, Yixiong; Lewis, Stephen; Montabone, Luca; Tabataba-Vakili, Fachreddin
2015-04-01
Introduction The energy spectrum (ES) analysis is a renowned tool for understanding the driving mechanisms behind atmospheric turbulence (Lindborg, 1998). We aim to investigate whether energy and enstrophy inertial ranges exist in the kinetic energy spectrum (KES), and to quantify the corresponding cascades (with their ranges), and relationship with the atmospheric forcing and energy dissipation scales. The calculation of the ES from observational data is known to be highly non-trivial due to the lack of global coverage in space and time. Gage and Nastrom (1984) were the first to overcome this problem for Earth but this has not so far been attempted for Mars. Our approach is to take the sparse observational data and assimilate it using a global numerical model. We present preliminary results using the Mars Climate Sounder (MCS) retrievals and the LMD-UK Mars GCM (MGCM). This was pioneered by Lewis and Read (1999). Methodology The equations we used to calculate the Eddy and Zonal Mean kinetic energies are derived from total KES formula presented in Lindborg and Augier (2013). Hence, adding the two spectra together, we obtain the full KES spectrum as presented in their paper. For the Available Potential Energy Spectrum (APES), we have used a preliminary simplified version of the approach presented in Lindborg and Augier (2013). The Energy Spectra To date we have assimilated the MCS data at the resolution of T31 (triangular truncation), hence the ES only spans up to total wavenumber 31. This encompasses a portion of the energy inertial range, which might be expected to manifest the -3 exponential law by analogy with the Earth (Gage & Nastrom, 1984). Features: - velocities and corresponding KEs are higher with increasing height compared to Earth, - "-3" slope is restricted to ~30 km altitude, suggesting an early departure from the enstrophy inertial range, - boundary layer velocities are similar to Earth References 1. Gage and Nastrom, A Climatology of Atmospheric
Measuring the neutron energy spectrum of laser-fusion targets with CR-39
Lane, S.M.
1983-09-01
We are developing a detector capable of measuring the neutron energy spectrum from a laser fusion target containing DT fuel. From such a spectrum the compressed areal density of the DT can be inferred by observing the fraction of 14.1 MeV neutrons down-shifted in energy by elastic scattering. The detector consists of a 0.1 cm thick Ta x-ray and debris shield backed by a 50 to 200 ..mu..m polyethylene radiator followed by layers of CR-39. The energy of each neutron producing a knock-on proton in the radiatior, that in turn creates a damage track in the CR-39, can be derived from the resultant track diameter, location, and orientation. We have analyzed the proton sensitivity and sample readability of 5 types of CR-39 in the energy range 3 to 11 MeV and have found a type fabricated by American Acrylics from a monomer made by a French company, Allymer, to be the most acceptable. Calibration curves were obtained for this plastic at energies of 3 to 15 MeV and dip angles ranging from 75 to 90/sup 0/. These curves were subsequently used to unfold a 14.7 MeV spectrum generated at the Livermore Rotating Target Neutron Source.
Spectrum and energy levels of five-times ionized zirconium (Zr VI)
NASA Astrophysics Data System (ADS)
Reader, Joseph; Lindsay, Mark D.
2016-02-01
We carried out a new analysis of the spectrum of five-times-ionized zirconium Zr VI. For this we used sliding-spark discharges together with normal- and grazing-incidence spectrographs to observe the spectrum from 160 to 2000 Å. These observations showed that the analysis of this spectrum by Khan et al (1985 Phys. Scr. 31 837) contained a significant number of incorrect energy levels. We have now classified ˜420 lines as transitions between 23 even-parity levels 73 odd-parity levels. The 4s24p5, 4s4p6, 4s24p44d, 5s, 5d, 6s configurations are now complete, although a few levels of 4s24p45d are tentative. We determined Ritz-type wavelengths for ˜135 lines from the optimized energy levels. The uncertainties range from 0.0003 to 0.0020 Å. Hartree-Fock calculations and least-squares fits of the energy parameters to the observed levels were used to interpret the observed configurations. Oscillator strengths for all classified lines were calculated with the fitted parameters. The results are compared with values for the level energies, percentage compositions, and transition probabilities from recent ab initio theoretical calculations. The ionization energy was revised to 777 380 ± 300 cm-1 (96.38 ± 0.04 eV).
Wavelet Spatial Energy Spectrums Studies on Drag Reduction by Micro-bubble Injection
Ling Zhen; Yassin Hassan
2006-07-01
In this study, continuous wavelet transforms and spatial correlation techniques are employed to determine the space-localized wavenumber energy spectrum of the velocity signals in turbulent channel flow. The flow conditions correspond to single phase flow and micro-bubbles injected two phase flow. The wavelet energy spectrums demonstrate that the wavenumber (eddy size) content of the velocity signals is not only space-dependent but also micro-bubbles can impact the eddy size content. Visual observations of the wavelet energy spectrum spatial distribution was realized by using Particle Image Velocimetry (PIV) measurement technique. The two phase flow condition corresponds to a drag reduction of 38.4% with void fraction of 4.9%. The present results provide evidence that micro-bubbles in the boundary layer of a turbulent channel flow can help adjust the eddy size distributions near the wall. This can assist in explaining that micro-bubbles are performing as buffers to keep the energy of fluid particles going in stream-wise direction and reducing the energy of fluid particles going in normal direction. (authors)
The puzzle of the ankle in the Ultrahigh Energy Cosmic Ray Spectrum, and composition indicators
NASA Astrophysics Data System (ADS)
Farrar, Glennys
2015-08-01
The sharp change in slope of the ultra-high energy cosmic ray spectrum around 10^18.6 eV (the ankle), combined with evidence of a light but extragalactic component near and below the ankle and intermediate composition above, has proved exceedingly challenging to understand theoretically. In this talk I discuss two possible solutions to the puzzle and how they can be (in)validated.First, I present a new mechanism whereby photo-disintegration of ultra-high energy nuclei in the region surrounding a UHECR accelerator naturally accounts for the observed spectrum and inferred composition (using LHC-tuned models extrapolated to UHE) at Earth. We discuss the conditions required to reproduce the spectrum above 10^17.5 eV and the composition, which -- in our model -- consists below the ankle of extragalactic protons and the high energy tail of Galactic Cosmic Rays, and above the ankle of surviving nuclei from the extended source. Predictions for the spectrum and flavors of neutrinos resulting from this process will be presented, and also implications for candidate sources.The other possible explanation is that in actuality UHECRs are entirely or almost entirely protons, and the cross-section for p-Air scattering increases more rapidly above center-of-mass energy of 70 TeV (10 times the current LHC cm energy) than predicted in conventional models. This gives an equally good fit to the depth-of-shower maximum behavior obverved by Auger, while being an intriguing sign of new state in QCD at extremely high energy density.
NASA Astrophysics Data System (ADS)
Bijay, Biplab; Banik, Prabir; Bhadra, Arunava
2016-09-01
In this work we examine with the help of Monte Carlo simulation whether a consistent primary energy spectrum of cosmic rays emerges from both the experimentally observed total charged particles and muon size spectra of cosmic ray extensive air showers considering primary composition may or may not change beyond the knee of the energy spectrum. It is found that EAS-TOP observations consistently infer a knee in the primary energy spectrum provided the primary is pure unchanging iron whereas no consistent primary spectrum emerges from simultaneous use of the KASCADE observed total charged particle and muon spectra. However, it is also found that when primary composition changes across the knee the estimation of spectral index of total charged particle spectrum is quite tricky, depends on the choice of selection of points near the knee in the size spectrum.
The Cosmic Ray Energy Spectrum and Related Measurements with the Pierre Auger Observatory
Abraham, : J.; Abreu, P.; Aglietta, M.; Aguirre, C.; Ahn, E.J.; Allard, D.; Allekotte, I.; Allen, J.; Alvarez-Muniz, J.; Ambrosio, M.; Anchordoqui, L.
2009-06-01
These are presentations to be presented at the 31st International Cosmic Ray Conference, in Lodz, Poland during July 2009. It consists of the following presentations: (1) Measurement of the cosmic ray energy spectrum above 10{sup 18} eV with the Pierre Auger Observatory; (2) The cosmic ray flux observed at zenith angles larger than 60 degrees with the Pierre Auger Observatory; (3) Energy calibration of data recorded with the surface detectors of the Pierre Auger Observatory; (4) Exposure of the Hybrid Detector of The Pierre Auger Observatory; and (5) Energy scale derived from Fluorescence Telescopes using Cherenkov Light and Shower Universality.
Fukuda, Makoto; Kiran Kumar, N. A. P.; Koyanagi, Takaaki; Garrison, Lauren M.; Snead, Lance L.; Katoh, Yutai; Hasegawa, Akira
2016-07-02
We performed a neutron irradiation to single crystal pure tungsten in the mixed spectrum High Flux Isotope Reactor (HFIR). In order to investigate the influences of neutron energy spectrum, the microstructure and irradiation hardening were compared with previous data obtained from the irradiation campaigns in the mixed spectrum Japan Material Testing Reactor (JMTR) and the sodium-cooled fast reactor Joyo. The irradiation temperatures were in the range of ~90–~800 °C and fast neutron fluences were 0.02–9.00 × 1025 n/m2 (E > 0.1 MeV). Post irradiation evaluation included Vickers hardness measurements and transmission electron microscopy. Moreover, the hardness and microstructure changes exhibitedmore » a clear dependence on the neutron energy spectrum. The hardness appeared to increase with increasing thermal neutron flux when fast fluence exceeds 1 × 1025 n/m2 (E > 0.1 MeV). Finally, irradiation induced precipitates considered to be χ- and σ-phases were observed in samples irradiated to >1 × 1025 n/m2 (E > 0.1 MeV), which were pronounced at high dose and due to the very high thermal neutron flux of HFIR. Although the irradiation hardening mainly caused by defects clusters in a low dose regime, the transmutation-induced precipitation appeared to impose additional significant hardening of the tungsten.« less
Relativistic and thermal effects on the magnon spectrum of a ferromagnetic monolayer.
Rózsa, L; Udvardi, L; Szunyogh, L
2013-12-18
A spin model including magnetic anisotropy terms and Dzyaloshinsky-Moriya interactions is studied for the case of a ferromagnetic monolayer with C2v symmetry like Fe/W(110). Using the quasiclassical stochastic Landau-Lifshitz-Gilbert equations, the magnon spectrum of the system is derived using linear response theory. The Dzyaloshinsky-Moriya interaction leads to asymmetry in the spectrum, while the anisotropy terms induce a gap. It is shown that, in the presence of lattice defects, both the Dzyaloshinsky-Moriya interactions and the two-site anisotropy lead to a softening of the magnon energies. Two methods are developed to investigate the magnon spectrum at finite temperatures. The theoretical results are compared to atomistic spin dynamics simulations and good agreement is found between them. PMID:24275952
Contribution from individual nearby sources to the spectrum of high-energy cosmic-ray electrons
NASA Astrophysics Data System (ADS)
Sedrati, R.; Attallah, R.
2014-04-01
In the last few years, very important data on high-energy cosmic-ray electrons and positrons from high-precision space-born and ground-based experiments have attracted a great deal of interest. These particles represent a unique probe for studying local comic-ray accelerators because they lose energy very rapidly. These energy losses reduce the lifetime so drastically that high-energy cosmic-ray electrons can attain the Earth only from rather local astrophysical sources. This work aims at calculating, by means of Monte Carlo simulation, the contribution from some known nearby astrophysical sources to the cosmic-ray electron/positron spectra at high energy (≥ 10 GeV). The background to the electron energy spectrum from distant sources is determined with the help of the GALPROP code. The obtained numerical results are compared with a set of experimental data.
Fermi-LAT γ-ray anisotropy and intensity explained by unresolved radio-loud active galactic nuclei
Mauro, Mattia Di; Cuoco, Alessandro; Donato, Fiorenza; Siegal-Gaskins, Jennifer M. E-mail: alessandro.cuoco@to.infn.it E-mail: jsg@tapir.caltech.edu
2014-11-01
Radio-loud active galactic nuclei (AGN) are expected to contribute substantially to both the intensity and anisotropy of the isotropic γ-ray background (IGRB). In turn, the measured properties of the IGRB can be used to constrain the characteristics of proposed contributing source classes. We consider individual subclasses of radio-loud AGN, including low-, intermediate-, and high-synchrotron-peaked BL Lacertae objects, flat-spectrum radio quasars, and misaligned AGN. Using updated models of the γ-ray luminosity functions of these populations, we evaluate the energy-dependent contribution of each source class to the intensity and anisotropy of the IGRB. We find that collectively radio-loud AGN can account for the entirety of the IGRB intensity and anisotropy as measured by the Fermi Large Area Telescope (LAT). Misaligned AGN provide the bulk of the measured intensity but a negligible contribution to the anisotropy, while high-synchrotron-peaked BL Lacertae objects provide the dominant contribution to the anisotropy. In anticipation of upcoming measurements with the Fermi-LAT and the forthcoming Cherenkov Telescope Array, we predict the anisotropy in the broader energy range that will be accessible to future observations.
Cosmic ray energy spectrum around the knee obtained by the Tibet Experiment and future prospects
NASA Astrophysics Data System (ADS)
Katayose, Yusaku
The measurement of the energy spectrum and the chemical composition of cosmic rays at the 'Knee' energy region have been made in the Tibet-AS experiment since 1990. The 1st phase of the Tibet hybrid experiment(1996-1999) consisted of Tibet II air-shower array(AS), Emulsion Chamber(EC) and burst detector(BD). The EC was used to detect high energy-gamma-families of the energy greater than 20 TeV at the core of ASs of which more than 80% are induced by light nuclei like protons or helium. Due to the high spatial resolution of the EC, proton and helium events were separated from others and we obtained the energy spectrum of each of them using 177 family events. We also obtained all-particle energy spectrum of primary cosmic rays in a wide range from 1014 eV to 1017 eV by the Tibet-III air-shower array. The size spectrum exhibits a sharp knee at a corresponding primary energy around 4 PeV. These results strongly indicated that the fraction of the light component to the all particle spectrum is decreasing around the knee.The observation of the AS core has been continued with upgraded Tibet III array and burst detectors without using X-ray films, which still works as the selector for the air showers induced by light component (pHe). This second phase experiment shows that the dominance of the heavy elements at the knee reported by the first phase experiment is confirmed with higher statistics by one order.Our results suggest that the main component at the knee is heavy elements (heavier than helium) because of the low intensities of observed proton and helium fluxes, whose summed flux are less than 30% of all particles. A new air-shower-core detector(YAC) will be added to the Tibet AS array to explicitly measure the heavy elements around the knee and beyond. In this paper, the results of composition study with the Tibet experiment are summarized and the prospects for the next phase experiment are described.
NASA Astrophysics Data System (ADS)
Nedzinskas, R.; Karpus, V.; Čechavičius, B.; Kavaliauskas, J.; Valušis, G.
2015-06-01
A simple analytical method for electron energy spectrum calculations of cylindrical quantum dots (QDs) and quantum rods (QRs) is presented. The method is based on a replacement of an actual QD or QR hamiltonian with an approximate one, which allows for a separation of variables. Though this approach is known in the literature, it is essentially expanded in the present paper by taking into account a discontinuity of the effective mass, which is of importance in actual semiconductor heterostructures, e.g., InGaAs QDs or QRs embedded in GaAs matrix. Several examples of InGaAs QDs and QRs are considered—their energy spectrum calculations show that the suggested method yields reliable results both for the ground and excited states. The proposed analytical model is verified by numerical calculations, results of which coincide with an accuracy of ∼1 meV.
The energy spectrum and geometrical structure of Galactic turbulent magnetic field
NASA Astrophysics Data System (ADS)
Sun, Xiaohui; Gaensler, Bryan; Mcclure-Griffiths, Naomi; Purcell, Cormac; Hill, Alex; Burkhart, Blakesley; Lazarian, Alex
2012-04-01
The energy spectrum and geometrical structure of the turbulent magnetic field can offer a solid test of different theoretical models on the generation and evolution of Galactic magnetic fields. They are also pivotal to understanding the propagation of cosmic-ray particles. However, the energy spectrum has been difficult to determine and the geometrical structure has never been obtained so far, due to lack of proper methods and observations. We aim to infer these quantities by applying our newly developed techniques to polarisation images. These images are required to be observed with high angular resolution and broadband multi-channel polarimetry, which is possible only recently using the ATCA. As a pilot study, we plan to map the 2X2 degree high-latitude field centred at l=255.5 degree and b=-38 degree at 1.1-3.1 GHz in total intensity and polarisation.
The energy spectrum and geometrical structure of Galactic turbulent magnetic field
NASA Astrophysics Data System (ADS)
Sun, Xiaohui; Gaensler, Bryan; Mcclure-Griffiths, Naomi; Purcell, Cormac; Hill, Alex; Burkhart, Blakesley; Lazarian, Alex
2012-10-01
The energy spectrum and geometrical structure of the turbulent magnetic field can offer a solid test of different theoretical models on the generation and evolution of Galactic magnetic fields. They are also pivotal to understanding the propagation of cosmic-ray particles. However, the energy spectrum has been difficult to determine and the geometrical structure has never been obtained so far, due to lack of proper methods and observations. We aim to infer these quantities by applying our newly developed techniques to polarisation images. These images are required to be observed with high angular resolution and broadband multi-channel polarimetry, which is possible only recently using the ATCA. As a pilot study, we plan to map the 2X2 degree high-latitude field centred at l=255.5 degree and b=-38 degree at 1.1-3.1 GHz in total intensity and polarisation.