Science.gov

Sample records for ray energy spectra

  1. Galactic cosmic ray composition and energy spectra

    NASA Technical Reports Server (NTRS)

    Mewaldt, R. A.

    1994-01-01

    Galactic cosmic ray nuclei represent a significant risk to long-duration spaceflight outside the magnetosphere. We review briefly existing measurements of the composition and energy spectra of heavy cosmic ray nuclei, pointing out which species and energy ranges are most critical to assessing cosmic ray risks for spaceflight. Key data sets are identified and a table of cosmic ray abundances is presented for elements from H to Ni (Z = 1 to 28). Because of the 22-year nature of the solar modulation cycle, data from the approaching 1998 solar minimum is especially important to reducing uncertainties in the cosmic ray radiation hazard. It is recommended that efforts to model this hazard take advantage of approaches that have been developed to model the astrophysical aspects of cosmic rays.

  2. Elemental composition and energy spectra of galactic cosmic rays

    NASA Technical Reports Server (NTRS)

    Mewaldt, R. A.

    1988-01-01

    A brief review is presented of the major features of the elemental composition and energy spectra of galactic cosmic rays. The requirements for phenomenological models of cosmic ray composition and energy spectra are discussed, and possible improvements to an existing model are suggested.

  3. ENERGY SPECTRA OF COSMIC-RAY NUCLEI AT HIGH ENERGIES

    SciTech Connect

    Ahn, H. S.; Ganel, O.; Han, J. H.; Kim, K. C.; Lee, M. H.; Malinine, A.; Allison, P.; Beatty, J. J.; Brandt, T. J.; Bagliesi, M. G.; Bigongiari, G.; Maestro, P.; Marrocchesi, P. S.; Barbier, L.; Childers, J. T.; DuVernois, M. A.; Conklin, N. B.; Coutu, S.; Jeon, J. A.; Minnick, S.

    2009-12-10

    We present new measurements of the energy spectra of cosmic-ray (CR) nuclei from the second flight of the balloon-borne experiment Cosmic-Ray Energetics And Mass (CREAM). The instrument included different particle detectors to provide redundant charge identification and measure the energy of CRs up to several hundred TeV. The measured individual energy spectra of C, O, Ne, Mg, Si, and Fe are presented up to approx10{sup 14} eV. The spectral shape looks nearly the same for these primary elements and it can be fitted to an E {sup -2.66} {sup +}- {sup 0.04} power law in energy. Moreover, a new measurement of the absolute intensity of nitrogen in the 100-800 GeV/n energy range with smaller errors than previous observations, clearly indicates a hardening of the spectrum at high energy. The relative abundance of N/O at the top of the atmosphere is measured to be 0.080 +- 0.025 (stat.)+-0.025 (sys.) at approx800 GeV/n, in good agreement with a recent result from the first CREAM flight.

  4. Energy spectra and composition of primary cosmic rays

    NASA Astrophysics Data System (ADS)

    Mueller, Dietrich; Swordy, Simon P.; Meyer, Peter; L'Heureux, Jacques; Grunsfeld, John M.

    1991-06-01

    New results are described on the energy spectra and relative abundances of primary cosmic ray nuclei from carbon to iron. The measurement was performed on the Spacelab-2 mission of the Space Shuttle Challenger in 1985, and extends to energies beyond 1 TeV per amu. The data indicate that the cosmic ray flux arriving near earth becomes enriched with heavier nuclei, most notably iron, as energy increases. Extrapolating to the source, with a simple leaky box model of galactic propagation with rigidity-dependent containment time, relative abundances of the elements are obtained that are quite similar to those reported at lower energy. In particular, the depletion of elements with high first ionization potential relative to the local galactic abundances, seems to persist in the cosmic ray source well up to TeV energies. A single power-law energy spectrum about E exp -2.1 provides a good description of the observed spectra of most elemental species.

  5. A BAYESIAN APPROACH TO COMPARING COSMIC RAY ENERGY SPECTRA

    SciTech Connect

    BenZvi, S. Y.; Pfendner, C. G.; Westerhoff, S.; Connolly, B. M.

    2011-09-01

    A common problem in ultra-high energy cosmic ray physics is the comparison of energy spectra. The question is whether the spectra from two experiments or two regions of the sky agree within their statistical and systematic uncertainties. We develop a method to directly compare energy spectra for ultra-high energy cosmic rays from two different regions of the sky in the same experiment without reliance on agreement with a theoretical model of the energy spectra. The consistency between the two spectra is expressed in terms of a Bayes factor, defined here as the ratio of the likelihood of the two-parent source hypothesis to the likelihood of the one-parent source hypothesis. Unlike other methods, for example {chi}{sup 2} tests, the Bayes factor allows for the calculation of the posterior odds ratio and correctly accounts for non-Gaussian uncertainties. The latter is particularly important at the highest energies, where the number of events is very small.

  6. On Measuring Cosmic Ray Energy Spectra with the Rapidity Distributions

    NASA Technical Reports Server (NTRS)

    Bashindzhagyan, G.; Adams, J.; Chilingarian, A.; Drury, L.; Egorov, N.; Golubkov, S.; Korotkova, N.; Panasyuk, M.; Podorozhnyi, D.; Procqureur, J.

    2000-01-01

    An important goal of cosmic ray research is to measure the elemental energy spectra of galactic cosmic rays up to 10(exp 16) eV. This goal cannot be achieved with an ionization calorimeter because the required instrument is too massive for space flight. An alternate method will be presented. This method is based on measuring the primary particle energy by determining the angular distribution of secondaries produced in a target layer. The proposed technique can be used over a wide range of energies (10 (exp 11) -10 (exp 16) eV) and gives an energy resolution of 60% or better. Based on this technique, a conceptual design for a new instrument (KLEM) will be presented. Due to its light weight, this instrument can have a large aperture enabling the direct measurement of cosmic rays to 1016 eV.

  7. Energy spectra and composition of primary cosmic rays

    SciTech Connect

    Mueller, D.; Swordy, S.P.; Meyer, P.; L'heureux, J.; Grunsfeld, J.M. )

    1991-06-01

    New results are described on the energy spectra and relative abundances of primary cosmic ray nuclei from carbon to iron. The measurement was performed on the Spacelab-2 mission of the Space Shuttle Challenger in 1985, and extends to energies beyond 1 TeV per amu. The data indicate that the cosmic ray flux arriving near earth becomes enriched with heavier nuclei, most notably iron, as energy increases. Extrapolating to the source, with a simple leaky box model of galactic propagation with rigidity-dependent containment time, relative abundances of the elements are obtained that are quite similar to those reported at lower energy. In particular, the depletion of elements with high first ionization potential relative to the local galactic abundances, seems to persist in the cosmic ray source well up to TeV energies. A single power-law energy spectrum about E exp {minus}2.1 provides a good description of the observed spectra of most elemental species. 33 refs.

  8. The low energy spectra of gamma-ray bursts

    NASA Technical Reports Server (NTRS)

    Bussard, R. W.; Lamb, F. K.

    1982-01-01

    The implications of observed gamma-ray burst spectra for the physical conditions and geometries of the sources are examined. It is noted that an explanation of the continua in terms of optically thin thermal bremsstrahlung requires a relatively large area but a fairly shallow depth. On the other hand, a spectrum similar to that observed could be produced by rapid flickering of sources with less extreme geometries if each flicker emits a Comptonized thermal spectrum. Either field inhomogeneities or plasma motions are required to interpret the low energy features as cyclotron extinction. An alternative explanation is photoelectric absorption by heavy atoms; this requires a field strength high enough to make one-photon electron positron annihilation possible. Observational tests of these possibilities are proposed

  9. Estimation of vertical sea level muon energy spectra from the latest primary cosmic ray elemental spectra

    NASA Astrophysics Data System (ADS)

    Mitra, M.; Molla, N. H.; Bhattacharyya, D. P.

    The directly measured elemental spectra of primary cosmic rays obtained from Webber et al., Seo et al., Menn et al., Ryan et al. and experiments like JACEE, CRN, SOKOL, RICH on P, He, CNO, Ne-S and Fe have been considered to estimate the vertical sea level muon energy spectra. The primary elemental energy spectra of P, He, CNO, Ne-S and Fe available from the different experimental data duly fitted by power law are given by Np(E)dE = 1.2216E-2.68 dE [cm2 .s.sr.GeV/n]-1 NHe(E)dE = 0.0424E-2.59 dE [cm2 .s.sr.GeV/n]-1 NCNO(E)dE = 0.0026E-2.57 dE[cm2 .s.sr.GeV/n]-1 NNe-S(E)dE = 0.00066E-2.57 dE [cm2 .s.sr.GeV/n]-1 NF e(E)dE = 0.0056E-2.55 dE [cm2 .s.sr.GeV/n]-1 Using the conventional superposition model the all nucleon primary cosmic ray spectrum has been derived which is of the form N(E)dE = 1.42E-2.66 dE [cm2 .s.sr.GeV/n]-1 We have considered all these spectra separately as parents of the secondary mesons and finallty the sea level muon fluxes at 00 from each species have been derived. To evaluate the meson spectra which are the initial air shower interaction products initiated by the primary nucleon air collisions, the hadronic energy moments have been calculated from the CERN LEBCEHS data for pp collisions and FNAL data for πp collisions. Pion production by secondary pions have been taken into account and the final total muon spectrum has been derived from pp rightarrowπ± x, pp → K± x, πp → π± x channels. The Z-factors have been corrected for p-air collisions. We have adopted the constant values of σp-air and σπ-air crosssections which are 273 mb and 213 mb, respectively. The adopted inelastic cross-sections for pp and πp interactions are 35 mb and 22 mb, respectively. The Q-G plasma correction of Z-factors have also been incorporated in the final form. The solution to the standard differential equation for mesons is considered for muon flux estimation from Ngenerations of the parent mesons. By this formulation vertical muon spectra from each element

  10. Use of thin ionization calorimeters for measurements of cosmic ray energy spectra

    NASA Technical Reports Server (NTRS)

    Jones, W. V.; Ormes, J. S.; Schmidt, W. K. H.

    1976-01-01

    The reliability of performing measurements of cosmic ray energy spectra with a thin ionization calorimeter was investigated. Monte Carlo simulations were used to determine whether energy response fluctuations would cause measured spectra to be different from the primary spectra. First, Gaussian distributions were assumed for the calorimeter energy resolutions. The second method employed a detailed Monte Carlo simulation of cascades from an isotropic flux of protons. The results show that as long as the energy resolution does not change significantly with energy, the spectral indices can be reliably determined even for sigma sub e/e = 50%. However, if the energy resolution is strongly energy dependent, the measured spectra do not reproduce the true spectra. Energy resolutions greatly improving with energy result in measured spectra that are too steep, while resolutions getting much worse with energy cause the measured spectra to be too flat.

  11. On the Energy Spectra of Individual Terrestrial Gamma ray Flashes

    NASA Astrophysics Data System (ADS)

    Mailyan, B. G.; Briggs, M. S.; Cramer, E. S.; Connaughton, V.; Dwyer, J. R.; Fitzpatrick, G.

    2015-12-01

    The Fermi Gamma-ray Burst Monitor (GBM) receives enough photons from some TGFs that spectral fitting of individual TGFs is possible. Previous TGF spectral fits relied upon summing the data from many TGFs. However, this spectral analysis of individual GBM TGFs is difficult because the number of photons is only adequate and because the extreme intensity of TGFs requires the analysis to correct for spectral distortions caused by pulse pileup. For each TGF in the sample, we compare Monte Carlo simulated TGF spectra to the observed detector counts. For each comparison, the best fit intensity is found, including correcting the predicted spectrum for pulse pileup. Using likelihood, we determine which of the simulations are consistent with each TGF, thus constraining the properties (e.g., altitude, beam width, etc.) of the TGF.

  12. CREAM: High Energy Frontier of Cosmic Ray Elemental Spectra

    NASA Astrophysics Data System (ADS)

    Seo, Eun-Suk

    The balloon-borne Cosmic Ray Energetics And Mass (CREAM) experiment was flown for 161 days in six flights over Antarctica. High energy cosmic-ray data were collected over a wide energy range from 10 (10) to 10 (15) eV at an average altitude of 38.5 km with 3.9 g/cm (2) atmospheric overburden. Cosmic-ray elements from protons (Z = 1) to iron nuclei (Z = 26) are separated with excellent charge resolution. Building on success of the balloon flights, the payload is being reconfigured for exposure on the International Space Station (ISS). This ISS-CREAM instrument is configured with the CREAM calorimeter for energy measurements, and four finely segmented Silicon Charge Detector layers for precise charge measurements. In addition, the Top and Bottom Counting Detectors (TCD and BCD) and Boronated Scintillator Detector (BSD) have been newly developed. The TCD and BCD are scintillator based segmented detectors to separate electrons from nuclei using the shower profile differences, while BSD distinguishes electrons from nuclei by detecting thermal neutrons that are dominant in nuclei induced showers. An order of magnitude increase in data collecting power is possible by utilizing the ISS to reach the highest energies practical with direct measurements. The project status including results from on-going analysis of existing data and future plans will be discussed.

  13. BATSE Observations of Gamma-Ray Burst Spectra. Part 3; Low-Energy Behavior of Time-Averaged Spectra

    NASA Technical Reports Server (NTRS)

    Preece, R. D.; Briggs, M. S.; Pendleton, G. N.; Paciesas, W. S.; Matteson, J. L.; Band, D. L.; Skelton, R. T.; Meegan, C. A.

    1996-01-01

    We analyze time-averaged spectra from 86 bright gamma-ray bursts from the first 5 years of the Burst And Transient Source Experiment (BATSE) on board the Compton Gamma Ray Observatory to determine whether the lowest energy data are consistent with a standard spectra form fit to the data at all energies. The BATSE Spectroscopy Detectors have the capability to observe photons as low as 5 keV. Using the gamma-ray burst locations obtained with the BATSE Large Area Detectors, the Spectroscopy Detectors' low-energy response can be modeled accurately. This, together with a postlaunch calibration of the lowest energy Spectroscopy Detector discriminator channel, which can lie in the range 5-20 keV, allows spectral deconvolution over a broad energy range, approx. 5 keV to 2 MeV. The additional coverage allows us to search for evidence of excess emission, or for a deficit, below 20 keV. While no burst has a significant (greater than or equal to 3 sigma) deficit relative to a standard spectra model, we find that 12 bursts have excess low-energy emission, ranging between 1.2 and 5.8 times the model flux, that exceeds 5 sigma in significance. This is evidence for an additional low-energy spectral component in at least some bursts, or for deviations from the power-law spectral form typically used to model gamma-ray bursts at energies below 100 keV.

  14. Quasar energy distributions. I - Soft X-ray spectra of quasars

    NASA Technical Reports Server (NTRS)

    Wilkes, Belinda J.; Elvis, Martin

    1987-01-01

    As the initial stage of a study of quasar energy distributions (QEDs), Einstein IPC spectra of 24 quasars are presented. These are combined with previously reported IPC spectra to form a sample of 33 quasars with well-determined soft X-ray slopes. A correlation analysis shows that radio loudness, rather than redshift or luminosity, is fundamentally related to the X-ray slope. This correlation is not followed by higher energy spectra of active galaxies. Two components are required to explain both sets of results. The best-fit column densities are systematically smaller than the Galactic values. The same effect is not present in a sample of BL Lac objects, implying that the effect is intrinsic to the quasars and is caused by a low-energy turnup in the quasar spectra.

  15. Photon interference effect in x-ray absorption spectra over a wide energy range

    NASA Astrophysics Data System (ADS)

    Nishino, Y.; Ishikawa, T.; Suzuki, M.; Kawamura, N.; Kappen, P.; Korecki, P.; Haack, N.; Materlik, G.

    2002-09-01

    We consider fundamental structures in x-ray absorption spectra over a wide energy range. We formulate the elastic scattering in addition to the photoelectric absorption in recently reported photon interference x-ray absorption fine structure (πXAFS). The simulations show excellent agreement with experimental x-ray absorption spectra for platinum and tungsten powders far above and below the L absorption edges. πXAFS can be as big as in the order of 10% of XAFS, and cannot be easily neglected in detailed analysis of XAFS and related phenomena.

  16. COMPARING THE ENERGY SPECTRA OF ULTRAHIGH ENERGY COSMIC RAYS MEASURED WITH EXTENSIVE AIR SHOWER ARRAYS

    SciTech Connect

    Ivanov, A. A.

    2010-03-20

    The energy spectra of ultrahigh energy cosmic rays (CRs) measured with giant extensive air shower (EAS) arrays exhibit discrepancies between the flux intensities and/or estimated CR energies exceeding experimental errors. The well-known intensity correction factor due to the dispersion of the measured quantity in the presence of a rapidly falling energy spectrum is insufficient to explain the divergence. Another source of systematic energy determination error is proposed concerning the charged particle density measured with the surface arrays, which arises due to simplifications (namely, the superposition approximation) in nucleus-nucleus interaction description applied to the shower modeling. Making use of the essential correction factors results in congruous CR energy spectra within experimental errors. Residual differences in the energy scales of giant arrays can be attributed to the actual overall accuracy of the EAS detection technique used. CR acceleration and propagation model simulations using the dip and ankle scenarios of the transition from galactic to extragalactic CR components are in agreement with the combined energy spectrum observed with EAS arrays.

  17. Energy spectra of cosmic-ray nuclei from 50 to 2000 GeV per amu

    NASA Technical Reports Server (NTRS)

    Grunsfeld, John M.; L'Heureux, Jacques; Meyer, Peter; Muller, Dietrich; Swordy, Simon P.

    1988-01-01

    A direct measurement of the elemental composition of cosmic rays up to energies of several TeV/amu was performed during the Spacelab 2 flight of the Space Shuttle. Results on the spectral shape for the elements C, O, Ne, Mg, Si, and Fe, obtained from this experiment, are presented. It was found that the C and O energy spectra retain a power-law spectrum in energy with an exponent Gamma of about 2.65. The Fe spectrum is flatter (Gamma of about 2.55) up to a particle energy of about 10 to the 14th eV, indicating a steady increase in the relative abundance of iron in cosmic rays up to this energy. The energy spectra of Ne, Mg, and Si are steeper than anticipated. This behavior is unexpected within current models of cosmic-ray acceleration.

  18. Filter-fluorescer measurement of low-voltage simulator x-ray energy spectra

    SciTech Connect

    Baldwin, G.T.; Craven, R.E.

    1986-01-01

    X-ray energy spectra of the Maxwell Laboratories MBS and Physics International Pulserad 737 were measured using an eight-channel filter-fluorescer array. The PHOSCAT computer code was used to calculate channel response functions, and the UFO code to unfold spectrum.

  19. X-ray ionization yields and energy spectra in liquid argon

    NASA Astrophysics Data System (ADS)

    Bondar, A.; Buzulutskov, A.; Dolgov, A.; Shekhtman, L.; Sokolov, A.

    2016-04-01

    The main purpose of this work is to provide reference data on X-ray ionization yields and energy spectra in liquid Ar to the studies in the field of Cryogenic Avalanche Detectors (CRADs) for rare-event and other experiments, based on liquid Ar detectors. We present the results of two related researches. First, the X-ray recombination coefficients in the energy range of 10-1000 keV and ionization yields at different electric fields, between 0.6 and 2.3 kV/cm, are determined in liquid Ar based on the results of a dedicated experiment. Second, the energy spectra of pulsed X-rays in liquid Ar in the energy range of 15-40 keV, obtained in given experiments including that with the two-phase CRAD, are interpreted and compared to those calculated using a computer program, to correctly determine the absorbed X-ray energy. The X-ray recombination coefficients and ionization yields have for the first time been presented for liquid Ar in systematic way.

  20. Calculation of neutron and gamma ray energy spectra for fusion reactor shield design: comparison with experiment

    SciTech Connect

    Santoro, R.T.; Alsmiller, R.G. Jr.; Barnes, J.M.; Chapman, G.T.

    1980-08-01

    Integral experiments that measure the transport of approx. 14 MeV D-T neutrons through laminated slabs of proposed fusion reactor shield materials have been carried out. Measured and calculated neutron and gamma ray energy spectra are compared as a function of the thickness and composition of stainless steel type 304, borated polyethylene, and Hevimet (a tungsten alloy), and as a function of detector position behind these materials. The measured data were obtained using a NE-213 liquid scintillator using pulse-shape discrimination methods to resolve neutron and gamma ray pulse height data and spectral unfolding methods to convert these data to energy spectra. The calculated data were obtained using two-dimensional discrete ordinates radiation transport methods in a complex calculational network that takes into account the energy-angle dependence of the D-T neutrons and the nonphysical anomalies of the S/sub n/ method.

  1. Which Epeak? The Characteristic Energy of Gamma-ray Burst Spectra

    NASA Astrophysics Data System (ADS)

    Preece, Robert; Goldstein, Adam; Bhat, Narayana; Stanbro, Matthew; Hakkila, Jon; Blalock, Dylan

    2016-04-01

    A characteristic energy of individual gamma-ray burst (GRB) spectra can in most cases be determined from the peak energy of the energy density spectra (ν {{ F }}ν ), called “{E}{{peak}}.” Distributions of {E}{{peak}} have been compiled for time-resolved spectra from bright GRBs, as well as time-averaged spectra and peak flux spectra for nearly every burst observed by the Compton Gamma Ray Observatory Burst And Transient Source Experiment and the Fermi Gamma-ray Burst Monitor (GBM). Even when determined by an instrument with a broad energy band, such as GBM (8 keV to 40 MeV), the distributions themselves peak at around 240 keV in the observer’s frame, with a spread of roughly a decade in energy. {E}{{peak}} can have considerable evolution (sometimes greater than one decade) within any given burst, as amply demonstrated by single pulses in GRB 110721A and GRB 130427A. Meanwhile, several luminosity or energy relations have been proposed to correlate with either the time-integrated or peak flux {E}{{peak}}. Thus, when discussing correlations with {E}{{peak}}, the question arises, “Which {E}{{peak}}?” A single burst may be characterized by any of a number of values for {E}{{peak}} that are associated with it. Using a single-pulse simulation model with spectral evolution as a proxy for the type of spectral evolution observed in many bursts, we investigate how the time-averaged {E}{{peak}} emerges from the spectral evolution within a single pulse, how this average naturally correlates with the peak flux derived {E}{{peak}} in a burst, and how the distribution in {E}{{peak}} values from many bursts derives its surprisingly narrow width.

  2. The Effects of Low- and High-Energy Cutoffs on Solar Flare Microwave and Hard X-Ray Spectra

    NASA Technical Reports Server (NTRS)

    Holman, G. D.; Oegerle, William (Technical Monitor)

    2002-01-01

    Microwave and hard x-ray spectra provide crucial information about energetic electrons and their environment in solar flares. These spectra are becoming better determined with the Owens Valley Solar Array (OVSA) and the recent launch of the Ramaty High Energy Solar Spectroscopic Imager (RHESSI). The proposed Frequency Agile Solar Radiotelescope (FASR) promises even greater advances in radio observations of solar flares. Both microwave and hard x-ray spectra are sensitive to cutoffs in the electron distribution function. The determination of the high-energy cutoff from these spectra establishes the highest electron energies produced by the acceleration mechanism, while determination of the low-energy cutoff is crucial to establishing the total energy in accelerated electrons. This paper will show computations of the effects of both high- and low-energy cutoffs on microwave and hard x-ray spectra. The optically thick portion of a microwave spectrum is enhanced and smoothed by a low-energy cutoff, while a hard x-ray spectrum is flattened below the cutoff energy. A high-energy cutoff steepens the microwave spectrum and increases the wavelength at which the spectrum peaks, while the hard x-ray spectrum begins to steepen at photon energies roughly an order of magnitude below the electron cutoff energy. This work discusses how flare microwave and hard x-ray spectra can be analyzed together to determine these electron cutoff energies. This work is supported in part by the NASA Sun-Earth Connection Program.

  3. Explanation of the local galactic cosmic ray energy spectra measured by Voyager 1. I. Protons

    SciTech Connect

    Schlickeiser, R.; Kempf, A.; Webber, W. R. E-mail: ank@tp4.rub.de

    2014-05-20

    Almost exactly 100 yr after the original discovery of cosmic rays, the V1 spacecraft has observed, for the first time, the local interstellar medium energy spectra of cosmic ray H, He, C/O nuclei at nonrelativistic kinetic energies, after leaving the heliosphere modulation region on 2012 August 25. We explain these observations by modeling the propagation of these particles in the local Galactic environment with an updated steady-state spatial diffusion model including all particle momentum losses with the local interstellar gas (Coulomb/ionization, pion production, adiabatic deceleration, and fragmentation interactions). Excellent agreement with the V1 cosmic ray H observations is obtained if the solar system resides within a spatially homogeneous layer of distributed cosmic ray sources injecting the same momentum power law ∝p {sup –s} with s = 2.24 ± 0.12. The best fit to the V1 H observations also provides an estimate of the characteristic break kinetic energy T{sub C} = 116 ± 27 MeV, representing the transition from ionization/Coulomb energy losses at low energies to pion production and adiabatic deceleration losses in a Galactic wind at high energies. As the determined value is substantially smaller than 217 MeV in the absence of adiabatic deceleration, our results prove the existence of a Galactic wind in the local Galactic environment.

  4. Explanation of the Local Galactic Cosmic Ray Energy Spectra Measured by Voyager 1. I. Protons

    NASA Astrophysics Data System (ADS)

    Schlickeiser, R.; Webber, W. R.; Kempf, A.

    2014-05-01

    Almost exactly 100 yr after the original discovery of cosmic rays, the V1 spacecraft has observed, for the first time, the local interstellar medium energy spectra of cosmic ray H, He, C/O nuclei at nonrelativistic kinetic energies, after leaving the heliosphere modulation region on 2012 August 25. We explain these observations by modeling the propagation of these particles in the local Galactic environment with an updated steady-state spatial diffusion model including all particle momentum losses with the local interstellar gas (Coulomb/ionization, pion production, adiabatic deceleration, and fragmentation interactions). Excellent agreement with the V1 cosmic ray H observations is obtained if the solar system resides within a spatially homogeneous layer of distributed cosmic ray sources injecting the same momentum power law vpropp -s with s = 2.24 ± 0.12. The best fit to the V1 H observations also provides an estimate of the characteristic break kinetic energy TC = 116 ± 27 MeV, representing the transition from ionization/Coulomb energy losses at low energies to pion production and adiabatic deceleration losses in a Galactic wind at high energies. As the determined value is substantially smaller than 217 MeV in the absence of adiabatic deceleration, our results prove the existence of a Galactic wind in the local Galactic environment.

  5. Ultra high energy cosmic rays: implications of Auger data for source spectra and chemical composition

    NASA Astrophysics Data System (ADS)

    Aloisio, R.; Berezinsky, V.; Blasi, P.

    2014-10-01

    We use a kinetic-equation approach to describe the propagation of ultra high energy cosmic ray protons and nuclei and calculate the expected spectra and mass composition at the Earth for different assumptions on the source injection spectra and chemical abundances. When compared with the spectrum, the elongation rate Xmax(E) and dispersion σ(Xmax) as observed with the Pierre Auger Observatory, several important consequences can be drawn: a) the injection spectra of nuclei must be very hard, ~ E-γ with γ~ 1- 1.6; b) the maximum energy of nuclei of charge Z in the sources must be ~ 5Z× 1018 eV, thereby not requiring acceleration to extremely high energies; c) the fit to the Auger spectrum can be obtained only at the price of adding an ad hoc light extragalactic component with a steep injection spectrum ~ E-2.7). In this sense, at the ankle EA≈ 5× 1018 eV) all the components are of extragalactic origin, thereby suggesting that the transition from Galactic to extragalactic cosmic rays occurs below the ankle. Interestingly, the additional light extragalactic component postulated above compares well, in terms of spectrum and normalization, with the one recently measured by KASCADE-Grande.

  6. Ultra high energy cosmic rays: implications of Auger data for source spectra and chemical composition

    SciTech Connect

    Aloisio, R.; Blasi, P.

    2014-10-01

    We use a kinetic-equation approach to describe the propagation of ultra high energy cosmic ray protons and nuclei and calculate the expected spectra and mass composition at the Earth for different assumptions on the source injection spectra and chemical abundances. When compared with the spectrum, the elongation rate X{sub max}(E) and dispersion σ(X{sub max}) as observed with the Pierre Auger Observatory, several important consequences can be drawn: a) the injection spectra of nuclei must be very hard, ∼ E{sup -γ} with γ∼ 1- 1.6; b) the maximum energy of nuclei of charge Z in the sources must be ∼ 5Z× 10{sup 18} eV, thereby not requiring acceleration to extremely high energies; c) the fit to the Auger spectrum can be obtained only at the price of adding an ad hoc light extragalactic component with a steep injection spectrum ∼ E{sup -2.7}). In this sense, at the ankle E{sub A}≈ 5× 10{sup 18} eV) all the components are of extragalactic origin, thereby suggesting that the transition from Galactic to extragalactic cosmic rays occurs below the ankle. Interestingly, the additional light extragalactic component postulated above compares well, in terms of spectrum and normalization, with the one recently measured by KASCADE-Grande.

  7. Impact of low-energy photons on the characteristics of prompt fission γ -ray spectra

    NASA Astrophysics Data System (ADS)

    Oberstedt, A.; Billnert, R.; Hambsch, F.-J.; Oberstedt, S.

    2015-07-01

    In this paper we report on a new study of prompt γ -rays from the spontaneous fission of 252Cf . Photons were measured in coincidence with fission fragments by employing four different lanthanide halide scintillation detectors. Together with results from a previous work of ours, we determined characteristic parameters with high precision, such as the average γ -ray multiplicity ν¯γ=(8.29 ±0.13 ), the average energy per photon ɛγ=(0.80 ±0.02 ) MeV, and the total γ -ray energy release per fission Eγ ,tot=(6.65 ±0.10 ) MeV. The excellent agreement between the individual results obtained in all six measurements proves the good repeatability of the applied experimental technique. The impact of low-energy photons, i.e., below 500 keV, on prompt fission γ -ray spectra characteristics has been investigated as well by comparing our results with those taken with the DANCE detector system, which appears to suffer from absorption effects in the low-energy region. Correction factors for this effect were estimated, giving results comparable to ours as well as to historical ones. From this we demonstrate that the different techniques of determining the average γ -ray multiplicity, either from a properly measured and normalized spectrum or a measured multiplicity distribution, give equivalent and consistent results.

  8. Galactic Cosmic-Ray Energy Spectra and Composition during the 2009-2010 Solar Minimum Period

    NASA Technical Reports Server (NTRS)

    Lave, K. A.; Wiedenbeck, Mark E.; Binns, W. R.; Christian, E. R.; Cummings, A. C.; Davis, A. J.; deNolfo, G. A.; Israel, M. H..; Leske, R. A.; Mewaldt, R. A.; Stone, E. C.; VonRosenvinge, T. T.

    2013-01-01

    We report new measurements of the elemental energy spectra and composition of galactic cosmic rays during the 2009-2010 solar minimum period using observations from the Cosmic Ray Isotope Spectrometer (CRIS) onboard the Advanced Composition Explorer. This period of time exhibited record-setting cosmic-ray intensities and very low levels of solar activity. Results are given for particles with nuclear charge 5 <= Z <= 28 in the energy range approx. 50-550 MeV / nucleon. Several recent improvements have been made to the earlier CRIS data analysis, and therefore updates of our previous observations for the 1997-1998 solar minimum and 2001-2003 solar maximum are also given here. For most species, the reported intensities changed by less than approx. 7%, and the relative abundances changed by less than approx. 4%. Compared with the 1997-1998 solar minimum relative abundances, the 2009-2010 abundances differ by less than 2sigma, with a trend of fewer secondary species observed in the more recent time period. The new 2009-2010 data are also compared with results of a simple "leaky-box" galactic transport model combined with a spherically symmetric solar modulation model. We demonstrate that this model is able to give reasonable fits to the energy spectra and the secondary-to-primary ratios B/C and (Sc+Ti+V)/Fe. These results are also shown to be comparable to a GALPROP numerical model that includes the effects of diffusive reacceleration in the interstellar medium.

  9. Energy Extraction from a Black Hole and Its Influence on X-Ray Spectra

    NASA Astrophysics Data System (ADS)

    Huang, Chang-Yin; Gong, Xiao-Long; Wang, Ding-Xiong

    2014-12-01

    Taking into account the energy and angular momentum transferred from a rotating black hole (BH) to the inner accretion disk by the magnetic connection (MC) process, we simulate the x-ray spectra from the disk-corona system with two different magnetic configurations using the Monte Carlo method. The results show that the MC process reduces the ratio of the power dissipated in the corona to the total and softens the spectrum. The influence of the MC process is stronger with a higher BH spin, a larger accretion rate, and a larger and more centralized magnetic flux threading the disk. The comparison of the model spectra with the observational data suggests that large-scale magnetic fields accumulating in the inner disk could be a candidate explanation for the hard-to-soft state evolutions in BH binaries.

  10. High energy X-ray spectra of cygnus XR-1 observed from OSO-8

    NASA Technical Reports Server (NTRS)

    Dolan, J. F.; Crannell, C. J.; Dennis, B. R.; Frost, K. J.; Orwig, L. E.

    1978-01-01

    X-ray spectra of Cygnus XR-1 were measured with the scintillation spectrometer on board the OSO-8 satellite during a period of one and one-half to three weeks in each of the years from 1975 to 1977. Observations were made when the source was both in a high state and in a low state. Typical spectra of the source between 15 and 250 keV are presented. The observed pivoting effect is consistent with two temperature accretion disk models of the X-ray emitting region. No significant break in the spectrum occurred at energies up to 150 keV. The high state as defined in the 3 to 6 keV bandwidth was found to be the higher luminosity state of the X-ray source. One transition from a low to a high state occurred during observations. The time of occurrence of this and other transitions is consistent with the hypothesis that all intensity transitions occur near periastron of the binary system, and that such transitions are caused by changes in the mass transfer rate between the primary and the accretion disk around the secondary.

  11. A model of galactic cosmic rays for use in calculating linear energy transfer spectra

    NASA Technical Reports Server (NTRS)

    Chen, J.; Chenette, D.; Clark, R.; Garcia-Munoz, M.; Guzik, T. G.; Pyle, K. R.; Sang, Y.; Wefel, J. P.

    1994-01-01

    The Galactic Cosmic Rays (GCR) contain fully stripped nuclei, from Hydrogen to beyond the Iron group, accelerated to high energies and are a major component of the background radiation encountered by satellites and interplanetary spacecraft. This paper presents a GCR model which is based upon our current understanding of the astrophysics of GCR transport through interstellar and interplanetary space. The model can be used to predict the energy spectra for all stable and long-lived radioactive species from H to Ni over an energy range from 50 to 50,000 MeV/nucleon as a function of a single parameter, the solar modulation level phi. The details of this model are summarized, phi is derived for the period 1974 to present, and results from this model during the 1990/1991 Combined Release and Radiation Effects Satellite (CRRES) mission are presented.

  12. GALACTIC COSMIC-RAY ENERGY SPECTRA AND COMPOSITION DURING THE 2009-2010 SOLAR MINIMUM PERIOD

    SciTech Connect

    Lave, K. A.; Binns, W. R.; Israel, M. H.; Wiedenbeck, M. E.; Christian, E. R.; De Nolfo, G. A.; Von Rosenvinge, T. T.; Cummings, A. C.; Davis, A. J.; Leske, R. A.; Mewaldt, R. A.; Stone, E. C.

    2013-06-20

    We report new measurements of the elemental energy spectra and composition of galactic cosmic rays during the 2009-2010 solar minimum period using observations from the Cosmic Ray Isotope Spectrometer (CRIS) onboard the Advanced Composition Explorer. This period of time exhibited record-setting cosmic-ray intensities and very low levels of solar activity. Results are given for particles with nuclear charge 5 {<=} Z {<=} 28 in the energy range {approx}50-550 MeV nucleon{sup -1}. Several recent improvements have been made to the earlier CRIS data analysis, and therefore updates of our previous observations for the 1997-1998 solar minimum and 2001-2003 solar maximum are also given here. For most species, the reported intensities changed by less than {approx}7%, and the relative abundances changed by less than {approx}4%. Compared with the 1997-1998 solar minimum relative abundances, the 2009-2010 abundances differ by less than 2{sigma}, with a trend of fewer secondary species observed in the more recent time period. The new 2009-2010 data are also compared with results of a simple ''leaky-box'' galactic transport model combined with a spherically symmetric solar modulation model. We demonstrate that this model is able to give reasonable fits to the energy spectra and the secondary-to-primary ratios B/C and (Sc+Ti+V)/Fe. These results are also shown to be comparable to a GALPROP numerical model that includes the effects of diffusive reacceleration in the interstellar medium.

  13. Energy Spectra of Cosmic Ray Nuclei to Above 100 Gev/nucleon. [measurement of energy spectra of cosmic ray nuclei boron to iron

    NASA Technical Reports Server (NTRS)

    Simon, M.; Spiegelhauer, H.; Schmidt, W. K. H.; Siohan, F.; Ormes, J. F.; Balasubrahmanyan, V. K.; Arens, J. F.

    1979-01-01

    The chemical composition cosmic rays as a function of energy in the range of a few GeV/nucleon to some hundreds of GeV/nucleon for boron through iron are presented. The experiment combined an ionization spectrometer and a gas Cherenkov counter, which was flown on a balloon, to perform two different and independent energy measurements. The experimental apparatus is described in detail. The energy dependence of the cosmic ray escape length for boron and iron is reported and predicted changes in the energy dependence of the ratios of primary nuclei 0/C and iron/C+0 are discussed.

  14. Energy spectra of elemental groups of cosmic rays: Update on the KASCADE unfolding analysis

    NASA Astrophysics Data System (ADS)

    Apel, W. D.; Arteaga, J. C.; Badea, A. F.; Bekk, K.; Blümer, J.; Bozdog, H.; Brancus, I. M.; Brüggemann, M.; Buchholz, P.; Cossavella, F.; Daumiller, K.; de Souza, V.; Doll, P.; Engel, R.; Engler, J.; Finger, M.; Fuhrmann, D.; Gils, H. J.; Glasstetter, R.; Grupen, C.; Haungs, A.; Heck, D.; Hörandel, J. R.; Huege, T.; Isar, P. G.; Kampert, K.-H.; Kang, D.; Kickelbick, D.; Klages, H. O.; Kolotaev, Y.; Łuczak, P.; Mathes, H. J.; Mayer, H. J.; Milke, J.; Mitrica, B.; Nehls, S.; Oehlschläger, J.; Ostapchenko, S.; Over, S.; Petcu, M.; Pierog, T.; Rebel, H.; Roth, M.; Schatz, G.; Schieler, H.; Schröder, F.; Sima, O.; Stümpert, M.; Toma, G.; Ulrich, H.; van Buren, J.; Walkowiak, W.; Weindl, A.; Wochele, J.; Wommer, M.; Zabierowski, J.

    2009-03-01

    The KASCADE experiment measures extensive air showers induced by cosmic rays in the energy range around the so-called knee. The data of KASCADE have been used in a composition analysis showing the knee at 3-5 PeV to be caused by a steepening in the light-element spectra [T. Antoni et al., (KASCADE Coll.), Astropart. Phys. 24 (2005) 1-25]. Since the applied unfolding analysis depends crucially on simulations of air showers, different high-energy hadronic interaction models (QGSJet and SIBYLL) were used. The results have shown a strong dependence of the relative abundance of the individual mass groups on the underlying model. In this update of the analysis we apply the unfolding method with a different low energy interaction model (FLUKA instead of GHEISHA) in the simulations. While the resulting individual mass group spectra do not change significantly, the overall description of the measured data improves by using the FLUKA model. In addition data in a larger range of zenith angle are analysed. The new results are completely consistent, i.e. there is no hint to any severe problem in applying the unfolding analysis method to KASCADE data.

  15. Low energy x-ray spectra measured with a mercuric iodide energy dispersive spectrometer in a scanning electron microscope

    SciTech Connect

    Iwanczyk, J.S.; Dabrowski, A.J.; Huth, G.C.; Bradley, J.G.; Conley, J.M.; Albee, A.L.

    1985-01-01

    A mercuric iodide energy dispersive x-ray spectrometer, with Peltier cooling provided for the detector and input field effect transistor, has been developed and tested in a scanning electron microscope. X-ray spectra were obtained with the 15 keV electron beam. An energy resolution of 225 eV (FWHM) for Mn-K/sub ..cap alpha../ at 5.9 keV and 195 eV (FWHM) for Mg-K line at 1.25 keV has been measured. Overall system noise level was 175 eV (FWHM). The detector system characterization with a carbon target demonstrated good energy sensitivity at low energies and lack of significant spectral artifacts at higher energies. 16 refs., 5 figs.

  16. Low energy X-ray spectra measured with a mercuric iodide energy dispersive spectrometer in a scanning electron microscope

    NASA Technical Reports Server (NTRS)

    Iwanczyk, J. S.; Dabrowski, A. J.; Huth, G. C.; Bradley, J. G.; Conley, J. M.

    1986-01-01

    A mercuric iodide energy dispersive X-ray spectrometer, with Peltier cooling provided for the detector and input field effect transistor, has been developed and tested in a scanning electron microscope. X-ray spectra were obtained with the 15 keV electron beam. An energy resolution of 225 eV (FWHM) for Mn-K(alpha) at 5.9 keV and 195 eV (FWHM) for the Mg-K line at 1.25 keV has been measured. Overall system noise level was 175 eV (FWHM). The detector system characterization with a carbon target demonstrated good energy sensitivity at low energies and lack of significant spectral artifacts at higher energies.

  17. Detailed parametrization of neutrino and gamma-ray energy spectra from high energy proton-proton interactions

    NASA Astrophysics Data System (ADS)

    Supanitsky, A. D.

    2016-02-01

    Gamma rays and neutrinos are produced as a result of proton-proton interactions that occur in different astrophysical contexts. The detection of these two types of messengers is of great importance for the study of different physical phenomena, related to nonthermal processes, taking place in different astrophysical scenarios. Therefore, the knowledge of the energy spectrum of these two types of particles, as a function of the incident proton energy, is essential for the interpretation of the observational data. In this paper, parametrizations of the energy spectra of gamma rays and neutrinos, originated in proton-proton collisions, are presented. The energy range of the incident protons considered extends from 102 to 108 GeV . The parametrizations are based on Monte Carlo simulations of proton-proton interactions performed with the hadronic interaction models QGSJET-II-04 and EPOS-LHC, which have recently been updated with the data taken by the Large Hadron Collider.

  18. High energy cosmic ray physics with underground muons in MACRO. II. Primary spectra and composition

    SciTech Connect

    Bellotti, R.; Cafagna, F.; Calicchio, M.; Castellano, M.; De Cataldo, G.; De Marzo, C.; Erriquez, O.; Favuzzi, C.; Fusco, P.; Giglietto, N.; Guarnaccia, P.; Mazziotta, M.N.; Montaruli, T.; Raino, A.; Spinelli, P.; Cecchini, S.; Dekhissi, H.; Fantini, R.; Giacomelli, G.; Mandrioli, G.; Margiotta-Neri, A.; Patrizii, L.; Popa, V.; Serra-Lugaresi, P.; Spurio, M.; Togo, V.; Hong, J.T.; Kearns, E.; Okada, C.; Orth, C.; Stone, J.L.; Sulak, L.R.; Barish, B.C.; Goretti, M.; Katsavounidis, E.; Kyriazopoulou, S.; Michael, D.G.; Nolty, R.; Peck, C.W.; Scholberg, K.; Walter, C.W.; Lane, C.; Steinberg, R.; Battistoni, G.; Bilokon, H.; Bloise, C.; Carboni, M.; Chiarella, V.; Forti, C.; Iarocci, E.; Marini, A.; Patera, V.; Ronga, F.; Satta, L.; Sciubba, A.; Spinetti, M.; Valente, V.; Antolini, R.; Bosio, T.; Di Credico, A.; Grillo, A.; Gustavino, C.; Mikheyev, S.; Parlati, S.; Reynoldson, J.; Scapparone, E.; Bower, C.; Habig, A.; Hawthorne, A.; Heinz, R.; Miller, L.; Mufson, S.; Musser, J.; De Mitri, I.; Monacelli, P.; Bernardini, P.; Mancarella, G.; Martello, D.; Palamara, O.; Petrera, S.; Pistilli, P.; Ricciardi, M.; Surdo, A.; Baker, R.; and others

    1997-08-01

    Multimuon data from the MACRO experiment at Gran Sasso have been analyzed using a new method, which allows one to estimate the primary cosmic ray fluxes. The estimated all-particle spectrum is higher and flatter than the one obtained from direct measurements but is consistent with EAS array measurements. The spectral indexes of the fitted energy spectrum are 2.56{plus_minus}0.05 for E{lt}500 TeV and 2.9{plus_minus}0.3 for E{gt}5000 TeV with a gradual change at intermediate energies. The average mass number shows little dependence on the primary energy below 1000 TeV, with a value of 10.1{plus_minus}2.5 at 100 TeV. At higher energies the best fit average mass shows a mild increase with energy, even though no definite conclusion can be reached taking into account errors. The fitted spectra cover a range from {approximately} 50 TeV up to several thousand TeV. {copyright} {ital 1997} {ital The American Physical Society}

  19. Reconciling the light component and all-particle cosmic ray energy spectra at the knee

    NASA Astrophysics Data System (ADS)

    Zhao, Yi; Jia, Huan-Yu; Zhu, Feng-Rong

    2015-12-01

    The knee phenomenon of the cosmic ray spectrum, which plays an important role in studying the acceleration mechanism of cosmic rays, is still an unsolved mystery. We try to reconcile the knee spectra measured by ARGO-YBJ and Tibet-III. A simple broken power-law model fails to explain the experimental data. Therefore a modified broken power-law model with non-linear acceleration effects is adopted, which can describe the sharp knee structure. This model predicts that heavy elements dominate at the knee. Supported by NSFC (11175147)

  20. Measurement of the high energy component of the x-ray spectra in the VENUS electron cyclotron resonance ion source

    SciTech Connect

    Leitner, D.; Benitez, J. Y.; Lyneis, C. M.; Todd, D. S.; Ropponen, T.; Ropponen, J.; Koivisto, H.; Gammino, S.

    2008-03-15

    High performance electron cyclotron resonance (ECR) ion sources, such as VENUS (Versatile ECR for NUclear Science), produce large amounts of x-rays. By studying their energy spectra, conclusions can be drawn about the electron heating process and the electron confinement. In addition, the bremsstrahlung from the plasma chamber is partly absorbed by the cold mass of the superconducting magnet, adding an extra heat load to the cryostat. Germanium or NaI detectors are generally used for x-ray measurements. Due to the high x-ray flux from the source, the experimental setup to measure bremsstrahlung spectra from ECR ion sources is somewhat different from that for the traditional nuclear physics measurements these detectors are generally used for. In particular, the collimation and background shielding can be problematic. In this paper, we will discuss the experimental setup for such a measurement, the energy calibration and background reduction, the shielding of the detector, and collimation of the x-ray flux. We will present x-ray energy spectra and cryostat heating rates depending on various ion source parameters, such as confinement fields, minimum B-field, rf power, and heating frequency.

  1. MEASUREMENT OF THE HIGH ENERGY COMPONENT OF THE X-RAY SPECTRA INTHE VENUS ECR ION SOURCE

    SciTech Connect

    Leitner, Daniela; Benitez, Janilee Y.; Lyneis, Claude M.; Todd,Damon S.; Ropponen,Tommi; Ropponen,Janne; Koivisto, Hannu; Gammino, Santo

    2007-11-15

    High performance electron cyclotron resonance (ECR) ion sources, such as VENUS (Versatile ECR for Nuclear Science), produce large amounts of x-rays. By studying their energy spectra, conclusions can be drawn about the electron heating process and the electron confinement. In addition, the bremsstrahlung from the plasma chamber is partly absorbed by the cold mass of the superconducting magnet adding an extra heat load to the cryostat. Germanium or NaI detectors are generally used for x-ray measurements. Due to the high x-ray flux from the source, the experimental set-up to measure bremsstrahlung spectra from ECR ion sources is somewhat different than for the traditional nuclear physics measurements these detectors are generally used for. In particular the collimation and background shielding can be problematic. In this paper we will discuss the experimental set-up for such a measurement, the energy calibration and background reduction, the correction for detector efficiency, the shielding of the detector and collimation of the x-ray flux. We will present x-ray energy spectra and cryostat heating rates in dependence of various ion source parameters such as confinement fields, minimum B-field, rf power and heating frequency.

  2. LOCALIZING INTEGRAL SOURCES WITH CHANDRA: X-RAY AND MULTI-WAVELENGTH IDENTIFICATIONS AND ENERGY SPECTRA

    SciTech Connect

    Tomsick, John A.; Bodaghee, Arash; Chaty, Sylvain; Rodriguez, Jerome; Halpern, Jules; Kalemci, Emrah; Oezbey Arabaci, Mehtap

    2012-08-01

    We report on Chandra observations of 18 hard X-ray (>20 keV) sources discovered with the INTEGRAL satellite near the Galactic plane. For 14 of the INTEGRAL sources, we have uncovered one or two potential Chandra counterparts per source. These provide soft X-ray (0.3-10 keV) spectra and subarcsecond localizations, which we use to identify counterparts at other wavelengths, providing information about the nature of each source. Despite the fact that all of the sources are within 5 Degree-Sign of the plane, four of the IGR sources are active galactic nuclei (AGNs; IGR J01545+6437, IGR J15391-5307, IGR J15415-5029, and IGR J21565+5948) and four others are likely AGNs (IGR J03103+5706, IGR J09189-4418, IGR J16413-4046, and IGR J16560-4958) based on each of them having a strong IR excess and/or extended optical or near-IR emission. We compare the X-ray and near-IR fluxes of this group of sources to those of AGNs selected by their 2-10 keV emission in previous studies and find that these IGR AGNs are in the range of typical values. There is evidence in favor of four of the sources being Galactic (IGR J12489-6243, IGR J15293-5609, IGR J16173-5023, and IGR J16206-5253), but only IGR J15293-5609 is confirmed as a Galactic source as it has a unique Chandra counterpart and a parallax measurement from previous optical observations that puts its distance at 1.56 {+-} 0.12 kpc. The 0.3-10 keV luminosity for this source is (1.4{sup +1.0}{sub -0.4}) Multiplication-Sign 10{sup 32} erg s{sup -1}, and its optical/IR spectral energy distribution is well described by a blackbody with a temperature of 4200-7000 K and a radius of 12.0-16.4 R{sub Sun }. These values suggest that IGR J15293-5609 is a symbiotic binary with an early K-type giant and a white dwarf accretor. We also obtained likely Chandra identifications for IGR J13402-6428 and IGR J15368-5102, but follow-up observations are required to constrain their source types.

  3. Measurements of cosmic-ray low-energy antiproton and proton spectra in a transient period of solar field reversal.

    PubMed

    Asaoka, Y; Shikaze, Y; Abe, K; Anraku, K; Fujikawa, M; Fuke, H; Haino, S; Imori, M; Izumi, K; Maeno, T; Makida, Y; Matsuda, S; Matsui, N; Matsukawa, T; Matsumoto, H; Matsunaga, H; Mitchell, J; Mitsui, T; Moiseev, A; Motoki, M; Nishimura, J; Nozaki, M; Orito, S; Ormes, J F; Saeki, T; Sanuki, T; Sasaki, M; Seo, E S; Sonoda, T; Streitmatter, R; Suzuki, J; Tanaka, K; Tanizaki, K; Ueda, I; Wang, J Z; Yajima, Y; Yamagami, Y; Yamamoto, A; Yamamoto, Y; Yamato, K; Yoshida, T; Yoshimura, K

    2002-02-01

    The energy spectra of cosmic-ray low-energy antiprotons ( *p's) and protons ( p's) have been measured by BESS in 1999 and 2000, during a period covering reversal at the solar magnetic field. Based on these measurements, a sudden increase of the *p/p flux ratio following the solar magnetic field reversal was observed, and it generally agrees with a drift model of the solar modulation. PMID:11863712

  4. The knee in the cosmic ray energy spectrum from the simultaneous EAS charged particles and muon density spectra

    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.

  5. Energy Spectra and Mass Composition of Cosmic Rays in the Fractal-Like Galactic Medium

    NASA Astrophysics Data System (ADS)

    Lagutin, A. A.; Tyumentsev, A. G.; Yushkov, A. V.

    We consider the problem of the cosmic ray spectrum formation assuming that cosmic rays are produced by galactic sources. The fractional diffusion equation proposed in our recent papers is used to describe the cosmic rays propagation in interstellar medium. We show that in the framework of this approach it is possible to explain the locally observed basic features of the cosmic rays in the energy region 1010 ÷ 1020 eV: difference between spectral exponents of protons and other nuclei, mass composition variation, "knee" problem, flattening of the primary spectrum for E ≥ 1018 ÷ 1019 eV.

  6. On the Energy Spectra of GeV/TeV Cosmic Ray Leptons

    SciTech Connect

    Stawarz, Lukasz; Petrosian, Vahe; Blandford, Roger D.; /KIPAC, Menlo Park

    2011-08-19

    Recent observations of cosmic ray electrons from several instruments have revealed various degrees of deviation in the measured electron energy distribution from a simple power-law, in a form of an excess around 0.1 to 1 TeV energies. An even more prominent deviation and excess has been observed in the fraction of cosmic ray positrons around 10 and 100 GeV energies. These observations have received considerable attention and many theoretical models have been proposed to explain them. The models rely on either dark matter annihilation/decay or specific nearby astrophysical sources, and involve several additional assumptions regarding the dark matter distribution or particle acceleration. In this paper we show that the observed excesses in the electron spectrum may be easily reproduced without invoking any unusual sources other than the general diffuse Galactic components of cosmic rays. The model presented here assumes a power-law injection of electrons (and protons) by supernova remnants, and evaluates their expected energy spectrum based on a simple kinetic equation describing the propagation of charged particles in the interstellar medium. The primary physical effect involved is the Klein-Nishina suppression of the electron cooling rate around TeV energies. With a very reasonable choice of the model parameters characterizing the local interstellar medium, we can reproduce the most recent observations by Fermi and HESS experiments. Interestingly, in our model the injection spectral index of cosmic ray electrons becomes comparable to, or even equal to that of cosmic ray protons. The Klein-Nishina effect may also affect the propagation of the secondary e{sup {+-}} pairs, and therefore modify the cosmic ray positron-to-electron ratio. We have explored this possibility by considering two mechanisms for production of e{sup {+-}} pairs within the Galaxy. The first is due to the decay of {pi}{sup {+-}}'s produced by interaction of cosmic ray nuclei with ambient protons

  7. High Energy Cosmic Ray Electron Spectra measured from the ATIC Balloon Experiment

    NASA Technical Reports Server (NTRS)

    Chang, J.; Schmidt, W. K. H.; Adams, J. H.; Ahn, H. S.; Bashindzhagyan, G.; Batkov, K. E.; Christl, M.; Fazely, A. R.; Ganel, O.; Gunasingha, R. M.

    2003-01-01

    The Advanced Thin Ionization Calorimeter Balloon Experiment (ATIC) is specifically designed for high energy cosmic ray ion detection. From simulation and a CERN beam test exposure we find that the design consisting of a graphite target and an energy detection device, a totally active calorimeter of BGO scintillator, gives us sufficient information to distinguish electrons from protons up to the TeV energy range. Balloon observations were successfully carried out over Antarctica in both 2000/2001 and 2002/2003 for a total of more than 35 days. This paper presents preliminary results on the spectrum of high energy electrons observed in the first ATIC flight.

  8. HEAO 1 A-2 low-energy detector X-ray spectra of the Lupus Loop and SN 1006

    SciTech Connect

    Leahy, D.A.; Nousek, J.; Hamilton, A.J.S. Pennsylvania State University, University Park Joint Institute for Laboratory Astrophysics, Boulder, CO )

    1991-06-01

    The Lupus Loop and SN 1006 were observed by the A-2 low-energy detector proportional counters on the HEAO 1 satellite as part of the all-sky survey. As a result of a major advance in understanding of detector response and background accurate analysis of the data has become possible. Soft X-ray spectra for both supernova remnants were constructed from the PHA data taken during the scanning observations. Single-temperature and two-temperature Raymond-Smith models were fitted to the observed spectra. In addition, power-law and power-law plus one-temperature models were fitted to the spectrum of SN 1006. Only two-component models provide an adequate description for both Lupus Loop and SN 1006 spectra. The temperatures, column densities, and emission measures are significantly more accurate than previous results. 29 refs.

  9. HEAO 1 A-2 low-energy detector X-ray spectra of the Lupus Loop and SN 1006

    NASA Technical Reports Server (NTRS)

    Leahy, D. A.; Nousek, J.; Hamilton, A. J. S.

    1991-01-01

    The Lupus Loop and SN 1006 were observed by the A-2 low-energy detector proportional counters on the HEAO 1 satellite as part of the all-sky survey. As a result of a major advance in understanding of detector response and background accurate analysis of the data has become possible. Soft X-ray spectra for both supernova remnants were constructed from the PHA data taken during the scanning observations. Single-temperature and two-temperature Raymond-Smith models were fitted to the observed spectra. In addition, power-law and power-law plus one-temperature models were fitted to the spectrum of SN 1006. Only two-component models provide an adequate description for both Lupus Loop and SN 1006 spectra. The temperatures, column densities, and emission measures are significantly more accurate than previous results.

  10. An Instrument to Measure Elemental Energy Spectra of Cosmic Ray Nuclei Up to 10(exp 16) eV

    NASA Technical Reports Server (NTRS)

    Adams, J.; Bashindzhagyan, G.; Chilingarian, A.; Drury, L.; Egorov, N.; Golubkov,S.; Korotkova, N.; Panasyuk, M.; Podorozhnyi, D.; Procqureur, J.

    2000-01-01

    A longstanding goal of cosmic ray research is to measure the elemental energy spectra of cosmic rays up to and through the "knee" (approx. equal to 3 x 10 (exp 15) eV. It is not currently feasible to achieve this goal with an ionization calorimeter because the mass required to be deployed in Earth orbit is very large (at least 50 tonnes). An alternative method will be presented. This is based on measuring the primary particle energy by determining the angular distribution of secondaries produced in a target layer using silicon microstrip detector technology. The proposed technique can be used over a wide range of energies (10 (exp 11)- 10 (exp 16) eV) and gives an energy resolution of 60% or better. Based on this technique, a design for a new lightweight instrument with a large aperture (KLEM) will be described.

  11. X-Ray Spectra of Young Pulsars and Their Wind Nebulae: Dependence on Spin-Down Energy Loss Rate

    NASA Technical Reports Server (NTRS)

    Gotthelf, E. V.

    2003-01-01

    An observational model is presented for the spectra of young rotation-powered pulsars and their nebulae based on a study of nine bright Crab-like pulsar systems observed with the Chandra X-ray observatory. A significant correlation is discovered between the X-ray spectra of these pulsars and that of their associated pulsar wind nebulae, both of which are observed to be a function of the spin-down energy loss rate, E. The 2-10 keV spectra of these objects are well characterized by an absorbed power-law model with photon indices, Gamma, in the range of 0.6 < Gamma (sub PSR) < 2.1 and 1.3 < Gamma(sub PWN) < 2.3, for the pulsars and their nebulae, respectively. A linear regression fit relating these two sets of indexes yields Gamma(sub PWN) = 0.91 +/- 0.18 + (0.66 +/- 0.11) Gamma (sub PSR), with a correlation coefficient of r = 0.97. The spectra of these pulsars are found to steepen as Gamma = Gamma(sub max) + alpha E (exp -1/2), with Gamma(sub max) providing an observational limit on the spectral slopes of young rotation-powered pulsars. These results reveal basic properties of young pulsar systems, allow new observational constraints on models of pulsar wind emission, and provide a means of predicting the energetics of pulsars lacking detected pulsations.

  12. ROLE OF LINE-OF-SIGHT COSMIC-RAY INTERACTIONS IN FORMING THE SPECTRA OF DISTANT BLAZARS IN TeV GAMMA RAYS AND HIGH-ENERGY NEUTRINOS

    SciTech Connect

    Essey, Warren; Kusenko, Alexander; Kalashev, Oleg; Beacom, John F.

    2011-04-10

    Active galactic nuclei (AGNs) can produce both gamma rays and cosmic rays. The observed high-energy gamma-ray signals from distant blazars may be dominated by secondary gamma rays produced along the line of sight by the interactions of cosmic-ray protons with background photons. This explains the surprisingly low attenuation observed for distant blazars, because the production of secondary gamma rays occurs, on average, much closer to Earth than the distance to the source. Thus, the observed spectrum in the TeV range does not depend on the intrinsic gamma-ray spectrum, while it depends on the output of the source in cosmic rays. We apply this hypothesis to a number of sources and, in every case, we obtain an excellent fit, strengthening the interpretation of the observed spectra as being due to secondary gamma rays. We explore the ramifications of this interpretation for limits on the extragalactic background light and for the production of cosmic rays in AGNs. We also make predictions for the neutrino signals, which can help probe the acceleration of cosmic rays in AGNs.

  13. Effects of the Electron Energy Distribution Function on Modeled X-ray Spectra

    SciTech Connect

    Shlyaptseva, A S; Hansen, S B

    2004-02-19

    This paper presents the results of a broad investigation into the effects of the electron energy distribution function on the predictions of non-LTE collisional-radiative atomic kinetics models. The effects of non-Maxwellian and suprathermal (''hot'') electron distributions on collisional rates (including three-body recombination) are studied. It is shown that most collisional rates are fairly insensitive to the functional form and characteristic energy of the electron distribution function as long as the characteristic energy is larger than the threshold energy for the collisional process. Collisional excitation and ionization rates, however, are highly sensitive to the fraction of hot electrons. This permits the development of robust spectroscopic diagnostics that can be used to characterize the electron density, bulk electron temperature, and hot electron fraction of plasmas with non-equilibrium electron distribution functions (EDFs). Hot electrons are shown to increase and spread out plasma charge state distributions, amplify the intensities of emission lines fed by direct collisional excitation and radiative cascades, and alter the structure of satellite features in both K- and L-shell spectra. The characteristic energy, functional form, and spatial properties of hot electron distributions in plasmas are open to characterization through their effects on high-energy continuum and line emission and on the polarization of spectral lines.

  14. Feynman scaling violation on baryon spectra in pp collisions at LHC and cosmic ray energies

    SciTech Connect

    Arakelyan, G. H.; Merino, C. Pajares, C.; Shabelski, Yu. M.

    2013-03-15

    A significant asymmetry in baryon/antibaryon yields in the central region of high energy collisions is observed when the initial state has nonzero baryon charge. This asymmetry is connected with the possibility of baryon charge diffusion in rapidity space. Such a diffusion should decrease the baryon charge in the fragmentation region and translate into the corresponding decrease of the multiplicity of leading baryons. As a result, a new mechanism for Feynman scaling violation in the fragmentation region is obtained. Another numerically more significant reason for the Feynman scaling violation comes from the fact that the average number of cut Pomerons increases with initial energy. We present the quantitative predictions of the Quark-Gluon String Model for the Feynman scaling violation at LHC energies and at even higher energies that can be important for cosmic ray physics.

  15. A new background subtraction method for energy dispersive X-ray fluorescence spectra using a cubic spline interpolation

    NASA Astrophysics Data System (ADS)

    Yi, Longtao; Liu, Zhiguo; Wang, Kai; Chen, Man; Peng, Shiqi; Zhao, Weigang; He, Jialin; Zhao, Guangcui

    2015-03-01

    A new method is presented to subtract the background from the energy dispersive X-ray fluorescence (EDXRF) spectrum using a cubic spline interpolation. To accurately obtain interpolation nodes, a smooth fitting and a set of discriminant formulations were adopted. From these interpolation nodes, the background is estimated by a calculated cubic spline function. The method has been tested on spectra measured from a coin and an oil painting using a confocal MXRF setup. In addition, the method has been tested on an existing sample spectrum. The result confirms that the method can properly subtract the background.

  16. SINGLE- AND TWO-COMPONENT GAMMA-RAY BURST SPECTRA IN THE FERMI GBM-LAT ENERGY RANGE

    SciTech Connect

    Veres, P.; Meszaros, P. E-mail: nnp@astro.psu.edu

    2012-08-10

    Most Fermi gamma-ray burst spectra appear as either a broken power law extending to GeV energies or as a broken power with a separate GeV power-law component. Here we show that such spectra can be understood in terms of magnetically dominated relativistic jets where a dissipative photosphere produces the prompt MeV emission, which is extended into the GeV range by inverse Compton scattering in the external shock, with possible contributions from a reverse shock as well. The bulk Lorentz factors required in these models are in the range of 300-600, and the MeV-GeV time delays arise naturally. In some cases an optical flash and a sub-dominant thermal component are also present.

  17. ENERGY-DEPENDENT LIGHT CURVES AND PHASE-RESOLVED SPECTRA OF HIGH-ENERGY GAMMA-RAYS FROM THE CRAB PULSAR

    SciTech Connect

    Li, X.; Zhang, L.

    2010-12-20

    Energy-dependent light curves and phase-resolved spectra of high-energy {gamma}-ray emission from the Crab pulsar have been detected recently by the Fermi Large Area Telescope (LAT). Within the framework of a two-pole, three-dimensional outer gap model, we calculate the energy-dependent light curves and phase-resolved spectra in the inertial observer's frame. Our results show that (1) the observed {gamma}-ray properties from both Fermi LAT and MAGIC can be reproduced well in this model; (2) the first peak of the light curves in the energy region less than {approx}10 GeV comes from the sum of emissions from both the north and south poles, and the second peak comes only from the emission from the south pole; however, the relative contribution of the two poles to the first peak changes with increasing {gamma}-ray energy, and the light curve in the energy region greater than {approx}20 GeV comes completely from the emission of the south pole; and (3) {gamma}-rays in the energy region greater than 100 MeV are produced through inverse Compton scattering from secondary pairs and the survival curvature photons, where the latter dominate over {gamma}-ray emission in the energy region greater than several GeV.

  18. ON THE ENERGY SPECTRA OF GeV/TeV COSMIC RAY LEPTONS

    SciTech Connect

    Stawarz, Lukasz; Petrosian, Vahe; Blandford, Roger D.

    2010-02-10

    Recent observations of cosmic ray (CR) electrons from several instruments have revealed various degrees of deviation in the measured electron energy distribution from a simple power law, in the form of an excess around 0.1-1 TeV energies. An even more prominent deviation and excess has been observed in the fraction of CR positrons around 10 and 100 GeV energies. These observations have received considerable attention and many theoretical models have been proposed to explain them. The models rely on either dark matter annihilation/decay or specific nearby astrophysical sources, and involve several additional assumptions regarding dark matter distribution or particle acceleration. In this paper, we show that the observed excesses in the electron spectrum may be easily re-produced without invoking any unusual sources other than the general diffuse Galactic components of CRs. The model presented here assumes a power-law injection of electrons (and protons) by supernova remnants (SNRs), and evaluates their expected energy spectrum based on a simple kinetic equation describing the propagation of charged particles in the interstellar medium (ISM). The primary physical effect involved is the Klein-Nishina suppression of the electron cooling rate around TeV energies. With a very reasonable choice of the model parameters characterizing the local ISM, we can reproduce the most recent observations by the Fermi and HESS experiments. Interestingly, in our model the injection spectral index of CR electrons becomes comparable to, or even equal to that of CR protons. The Klein-Nishina effect may also affect the propagation of the secondary e {sup +}- pairs, and therefore modify the CR positron-to-electron ratio. We have explored this possibility by considering two mechanisms for production of e {sup +}- pairs within the Galaxy. The first is due to the decay of pi{sup +}-'s produced by interaction of CR nuclei with ambient protons. The second source discussed here is due to the

  19. Composition and energy spectra of cosmic ray nuclei above 500 GeV/nucleon from the JACEE emulsion chambers

    NASA Astrophysics Data System (ADS)

    Burnett, T. H.; Dake, S.; Derrickson, J. H.; Fountain, W. F.; Fuki, M.; Gregory, J. C.; Hayashi, T.; Holynski, R.; Iwai, J.; Jones, W. V.

    1985-08-01

    The composition and energy spectra of charge groups (C - 0), (Ne - S), and (Z approximately 17) above 500 GeV/nucleon from the experiments of JACEE series balloonborne emulsion chambers are reported. Studies of cosmic ray elemental composition at higher energies provide information on propagation through interstellar space, acceleration mechanisms, and their sources. One of the present interests is the elemental composition at energies above 100 GeV/nucleon. Statistically sufficient data in this energy region can be decisive in judgment of propagation models from the ratios of SECONDARY/PRIMARY and source spectra (acceleration mechanism), as well as speculative contributions of different sources from the ratios of PRIMARY/PRIMARY. At much higher energies, i.e., around 10 to the 15th power eV, data from direct observation will give hints on the knee problem, as to whether they favor an escape effect possibly governed by magnetic rigidity above 10 to the 16th power eV.

  20. Composition and energy spectra of cosmic ray nuclei above 500 GeV/nucleon from the JACEE emulsion chambers

    NASA Technical Reports Server (NTRS)

    Burnett, T. H.; Dake, S.; Fountain, W. F.; Holynski, R.; Derrickson, J. H.; Fuki, M.; Gregory, J. C.; Hayashi, T.; Iwai, J.; Jones, W. V.

    1985-01-01

    The composition and energy spectra of charge groups (C - 0), (Ne - S), and (Z approximately 17) above 500 GeV/nucleon from the experiments of JACEE series balloonborne emulsion chambers are reported. Studies of cosmic ray elemental composition at higher energies provide information on propagation through interstellar space, acceleration mechanisms, and their sources. One of the present interests is the elemental composition at energies above 100 GeV/nucleon. Statistically sufficient data in this energy region can be decisive in judgment of propagation models from the ratios of SECONDARY/PRIMARY and source spectra (acceleration mechanism), as well as speculative contributions of different sources from the ratios of PRIMARY/PRIMARY. At much higher energies, i.e., around 10 to the 15th power eV, data from direct observation will give hints on the knee problem, as to whether they favor an escape effect possibly governed by magnetic rigidity above 10 to the 16th power eV.

  1. Reconsideration of the Iwasaki-Waggener iterative perturbation method for reconstructing high-energy X-ray spectra.

    PubMed

    Iwasaki, Akira; Kimura, Shigenobu; Sutoh, Kohji; Kamimura, Kazuo; Sasamori, Makoto; Seino, Morio; Komai, Fumio; Terashima, Singo; Kubota, Mamoru; Narita, Yuichiro; Hosokawa, Yoichiro; Miyazawa, Masanori

    2012-07-01

    We have reviewed applicable ranges for attenuating media and off-axis distances regarding the high-energy X-ray spectra reconstructed via the Iwasaki-Waggener iterative perturbation method for 4-20 MV X-ray beams. Sets of in-air relative transmission data used for reconstruction of spectra were calculated for low- and high-Z attenuators (acrylic and lead, respectively) by use of a functional spectral formula. More accurate sets of spectra could be reconstructed by dividing the off-axis distances of R = 0-20 cm into two series of R = 0-10 cm and R = 10-20 cm, and by taking into account the radiation attenuation and scatter in the buildup cap of the dosimeter. We also incorporated in the reconstructed spectra an adjustment factor (f (adjust) ≈ 1) that is determined by the attenuating medium, the acceleration voltage, and the set of off-axis distances. This resulted in calculated in-air relative transmission data to within ±2 % deviation for the low-Z attenuators water, acrylic, and aluminum (Al) with 0-50 cm thicknesses and R = 0-20 cm; data to within ±3 % deviation were obtained for high-Z attenuators such as iron (Fe), copper (Cu), silver (Ag), tungsten (W), platinum (Pt), gold (Au), lead (Pb), thorium (Th), and uranium (U) having thicknesses of 0-10 cm and R = 0-20 cm. By taking into account the radiation attenuation and scatter in the buildup cap, we could analyze the in-air chamber response along a line perpendicular to the isocenter axis. PMID:22696171

  2. ON THERMALIZATION IN GAMMA-RAY BURST JETS AND THE PEAK ENERGIES OF PHOTOSPHERIC SPECTRA

    SciTech Connect

    Vurm, Indrek; Piran, Tsvi; Lyubarsky, Yuri

    2013-02-20

    The low-energy spectral slopes of the prompt emission of most gamma-ray bursts (GRBs) are difficult to reconcile with radiatively efficient optically thin emission models irrespective of the radiation mechanism. An alternative is to ascribe the radiation around the spectral peak to a thermalization process occurring well inside the Thomson photosphere. This quasi-thermal spectrum can evolve into the observed non-thermal shape by additional energy release at moderate to small Thomson optical depths, which can readily give rise to the hard spectral tail. The position of the spectral peak is determined by the temperature and Lorentz factor of the flow in the thermalization zone, where the total number of photons carried by the jet is established. To reach thermalization, dissipation alone is not sufficient and photon generation requires an efficient emission/absorption process in addition to scattering. We perform a systematic study of all relevant photon production mechanisms searching for possible conditions in which thermalization can take place. We find that a significant fraction of the available energy should be dissipated at intermediate radii, {approx}10{sup 10} to a few Multiplication-Sign 10{sup 11} cm, and the flow there should be relatively slow: the bulk Lorentz factor could not exceed a few tens for all but the most luminous bursts with the highest E {sub pk} values. The least restrictive constraint for successful thermalization, {Gamma} {approx}< 20, is obtained if synchrotron emission acts as the photon source. This requires, however, a non-thermal acceleration deep below the Thomson photosphere transferring a significant fraction of the flow energy to relativistic electrons with Lorentz factors between 10 and 100. Other processes require bulk flow Lorentz factors of order of a few for typical bursts. We examine the implications of these results to different GRB photospheric emission models.

  3. Energy spectra of cosmic rays above 1 TeV per nucleon

    NASA Technical Reports Server (NTRS)

    Burnett, T. H.; Dake, S.; Derrickson, J. H.; Fountain, W. F.; Fuki, M.

    1990-01-01

    Direct measurements of cosmic-ray nuclei above 1 TeV/nucleon have been performed in a series of balloon-borne experiments with emulsion chambers. The observed all-particle spectrum above 20 TeV is consistent with the results of the Proton satellite and many air shower experiments. The proton spectrum is consistent with a power law having an index of 2.76 + or - 0.09 up to at least 100 TeV, but an overabundance of helium by a factor of 2 above 2 TeV per nucleon is found when compared with the extrapolation from the low energies. For heavy elements (C through Fe), the intensities around 1 TeV/nucleon are consistent, within the statistical errors, with the extrapolation from lower energy data using the Spacelab 2 spectral indices. An enhancement for the medium-heavy components (C through Ca) above 200 TeV is indicated. The mean mass above 50 TeV indicates slightly higher values than the results of the air shower experiments.

  4. A measurement of the absolute energy spectra of galactic cosmic rays during the 1976-77 solar minimum

    NASA Technical Reports Server (NTRS)

    Derrickson, J. H.; Parnell, T. A.; Austin, R. W.; Selig, W. J.; Gregory, J. C.

    1992-01-01

    An instrument designed to measure elemental cosmic ray abundances from boron to nickel in the energy region 0.5-2.0 GeV/nucl was flown on a high altitude balloon from Sioux Falls, South Dakota, on 30 September through 1 October 1976 at an average atmospheric depth of about 5 g/sq cm. Differential energy spectra of B, C, N, O, Ne, Mg, Si and Fe, extrapolated to the top of the atmosphere, were measured. The float altitude exposure of 17 h ended near Alpena, Michigan. The flight trajectory maintained a north easterly heading out of Sioux Falls traversing the upper midwest region between 84 and 97 deg west longitude while remaining between 43.5 and 45 deg north latitude. The maximum vertical cut-off for this flight path was 1.77 GV or 0.35 GeV/nucl.

  5. Relativistic X-ray reverberation modelling of the combined time-averaged and lag-energy spectra in AGN

    NASA Astrophysics Data System (ADS)

    Chainakun, P.; Young, A. J.; Kara, E.

    2016-08-01

    General relativistic ray tracing simulations of the time-averaged spectrum and energy-dependent time delays in AGN are presented. We model the lamp-post geometry in which the accreting gas is illuminated by an X-ray source located on the rotation axis of the black hole. The spectroscopic features imprinted in the reflection component are modelled using REFLIONX. The associated time delays after the direct continuum, known as reverberation lags, are computed including the full effects of dilution and ionization gradients on the disc. We perform, for the first time, simultaneous fitting of the time-averaged and lag-energy spectra in three AGN: Mrk 335, IRAS 13224-3809 and Ark 564 observed with XMM-Newton. The best fitting source height and central mass of each AGN partly agree with those previously reported. We find that including the ionization gradient in the model naturally explains lag-energy observations in which the 3 keV and 7-10 keV bands precede other bands. To obtain the clear 3 keV and 7-10 keV dips in the lag-energy profile, the model requires either a source height > 5$r_g$, or a disc that is highly ionized at small radii and is colder further out. We also show that fitting the lag or the mean spectra alone can lead to different results and interpretations. This is therefore important to combine the spectral and timing data in order to find the plausible but self-consistent fits which is achievable with our model.

  6. Relativistic X-ray reverberation modelling of the combined time-averaged and lag-energy spectra in AGN

    NASA Astrophysics Data System (ADS)

    Chainakun, P.; Young, A. J.; Kara, E.

    2016-08-01

    General relativistic ray tracing simulations of the time-averaged spectrum and energy-dependent time delays in active galactic nuclei (AGN) are presented. We model the lamp-post geometry in which the accreting gas is illuminated by an X-ray source located on the rotation axis of the black hole. The spectroscopic features imprinted in the reflection component are modelled using REFLIONX. The associated time delays after the direct continuum, known as reverberation lags, are computed including the full effects of dilution and ionization gradients on the disc. We perform, for the first time, simultaneous fitting of the time-averaged and lag-energy spectra in three AGN: Mrk 335, IRAS 13224-3809 and Ark 564 observed with XMM-Newton. The best-fitting source height and central mass of each AGN partly agree with those previously reported. We find that including the ionization gradient in the model naturally explains lag-energy observations in which the 3 keV and 7-10 keV bands precede other bands. To obtain the clear 3 keV and 7-10 keV dips in the lag-energy profile, the model requires either a source height >5 rg, or a disc that is highly ionized at small radii and is colder further out. We also show that fitting the lag or the mean spectra alone can lead to different results and interpretations. This is therefore important to combine the spectral and timing data in order to find the plausible but self-consistent fits which are achievable with our model.

  7. Bone densitometry using x-ray spectra

    NASA Astrophysics Data System (ADS)

    Krmar, M.; Shukla, S.; Ganezer, K.

    2010-10-01

    In contrast to the two distinct energy regions that are involved in dual-energy x-ray absorptiometry for bone densitometry, the complete spectrum of a beam transmitted through two layers of different materials is utilized in this study to calculate the areal density of each material. Test objects constructed from aluminum and Plexiglas were used to simulate cortical bone and soft tissue, respectively. Solid-state HPGe (high-purity germanium) detectors provided high-resolution x-ray spectra over an energy range of approximately 20-80 keV. Areal densities were obtained from spectra using two methods: a system of equations for two spectral regions and a nonlinear fit of the entire spectrum. Good agreement with the known areal densities of aluminum was obtained over a wide range of PMMA thicknesses. The spectral method presented here can be used to decrease beam hardening at a small number of bodily points selected for examination.

  8. RELATIVE COMPOSITION AND ENERGY SPECTRA OF LIGHT NUCLEI IN COSMIC RAYS: RESULTS FROM AMS-01

    SciTech Connect

    Aguilar, M.; Alcaraz, J.; Berdugo, J.; Allaby, J.; Alpat, B.; Ambrosi, G.; Azzarello, P.; Battiston, R.; Anderhub, H.; Ao, L.; Arefiev, A.; Arruda, L.; Barao, F.; Barreira, G.; Basile, M.; Bellagamba, L.; Bartoloni, A.; Becker, R.; Becker, U.; Bene, P.

    2010-11-20

    Measurement of the chemical and isotopic composition of cosmic rays is essential for the precise understanding of their propagation in the galaxy. While the model parameters are mainly determined using the B/C ratio, the study of extended sets of ratios can provide stronger constraints on the propagation models. In this paper, the relative abundances of light-nuclei lithium, beryllium, boron, and carbon are presented. The secondary-to-primary ratios Li/C, Be/C, and B/C have been measured in the kinetic energy range 0.35-45 GeV nucleon{sup -1}. The isotopic ratio {sup 7}Li/{sup 6}Li is also determined in the magnetic rigidity interval 2.5-6.3 GV. The secondary-to-secondary ratios Li/Be, Li/B, and Be/B are also reported. These measurements are based on the data collected by the Alpha Magnetic Spectrometer AMS-01 during the STS-91 space shuttle flight in 1998 June. Our experimental results are in substantial agreement with other measurements, where they exist. We describe our light-nuclei data with a diffusive-reacceleration model. A 10%-15% overproduction of Be is found in the model predictions and can be attributed to uncertainties in the production cross-section data.

  9. Interpretation of features in the cosmic ray proton and helium energy spectra in terms of a local source

    NASA Astrophysics Data System (ADS)

    Erlykin, A. D.; Wolfendale, A. W.

    2015-12-01

    Recent measurements using the AMS-02 cosmic ray (CR) spectrometer have shown structure in the spectra of protons and helium nuclei, structure that had been seen earlier but with lower precision. We interpret the measurements in terms of there having been an important contribution from a local supernova from which CRs have diffused to Earth. The characteristics of the source make it likely to be the same as that responsible for the structure in the positron and antiproton spectra.

  10. Gamma-ray Output Spectra from 239Pu Fission

    NASA Astrophysics Data System (ADS)

    Ullmann, John

    2015-05-01

    Gamma-ray multiplicities, individual gamma-ray energy spectra, and total gamma energy spectra following neutron-induced fission of 239Pu were measured using the DANCE detector at Los Alamos. Corrections for detector response were made using a forward-modeling technique based on propagating sets of gamma rays generated from a paramaterized model through a GEANT model of the DANCE array and adjusting the parameters for best fit to the measured spectra. The results for the gamma-ray spectrum and multiplicity are in general agreement with previous results, but the measured total gamma-ray energy is about 10% higher. A dependence of the gamma-ray spectrum on the gamma-ray multplicity was also observed. Global model calculations of the multiplicity and gamma energy distributions are in good agreement with the data, but predict a slightly softer total-energy distribution.

  11. X-ray spectra of Hercules X-1. 3: Pulse phase dependence in high energy continuum

    NASA Technical Reports Server (NTRS)

    Pravdo, S. H.; Bussard, R. W.; Becker, R. H.; Boldt, E. A.; Holt, S. S.; Serlemitsos, P. J.; Swank, J. H.

    1978-01-01

    Pulse phase-dependent spectral changes in the high energy (less than 20 keV) continuum of Hercules X-1 were observed. Cyclotron absorption of underlying continua can reproduce the observed angular dependence in the high energy cutoff. Implications of this model, which include the possibility of determining the angular separation between the line of sight and the neutron star magnetic field if the absorbing electron spectrum is known are discussed.

  12. Charge and energy spectra of cosmic rays with Z equal to or greater than 30.

    NASA Technical Reports Server (NTRS)

    Kobetich, E. J.; Price, P. B.; Shirk, E. K.; Eandi, R. D.; Osborne, W. Z.; Pinsky, L. S.; Rushing, R. B.

    1972-01-01

    A 2 g/sq cm stack (22 sq m in area) containing 41 plastic sheets, one G-5 emulsion, and one high-speed Cerenkov film detector was launched by balloon from Minneapolis on Sept. 4, 1970. The stack received an effective exposure of 48 hr at 2.8 mbar and a cutoff rigidity of about 1.8 GV. The abundance ratios relative to Fe are reported for various charges and charge groups from Z = 29 to 105 on the basis of 70 presently measured events as well as previously obtained results. Between Fe and the Pt peak, the cosmic ray abundances appear to be similar to solar system abundances; the heavier nuclei are strongly overabundant and appear to have originated about 10 m.y. ago in a rapid neutron capture process.

  13. Gamma-ray Output Spectra from 239 Pu Fission

    DOE PAGESBeta

    Ullmann, John

    2015-05-25

    Gamma-ray multiplicities, individual gamma-ray energy spectra, and total gamma energy spectra following neutron-induced fission of 239Pu were measured using the DANCE detector at Los Alamos. Corrections for detector response were made using a forward-modeling technique based on propagating sets of gamma rays generated from a paramaterized model through a GEANT model of the DANCE array and adjusting the parameters for best fit to the measured spectra. The results for the gamma-ray spectrum and multiplicity are in general agreement with previous results, but the measured total gamma-ray energy is about 10% higher. A dependence of the gamma-ray spectrum on the gamma-raymore » multplicity was also observed. Global model calculations of the multiplicity and gamma energy distributions are in good agreement with the data, but predict a slightly softer total-energy distribution.« less

  14. Resonant Compton scattering and gamma-ray burst continuum spectra

    NASA Technical Reports Server (NTRS)

    Baring, M. G.

    1995-01-01

    The Thomson limit of resonant inverse Compton scattering in the strong magnetic fields of neutron stars is considered as a mechanism for producing gamma-ray burst continuum spectra. Photon production spectra and electron cooling rates are presented using the full magnetic Thomson cross-section. Model emission spectra are obtained as self-consistent solutions of a set of photon and electron kinetic equations, displaying spectral breaks and other structure at gamma-ray energies.

  15. Energy levels and spectral lines in the X-ray spectra of highly charged W XLIV

    NASA Astrophysics Data System (ADS)

    Hao, Liang-Huan; Kang, Xiao-Ping

    2014-07-01

    The multi-configuration Dirac-Hartree-Fock method is employed to calculate the fine-structure energy levels, wavelengths, transition probabilities, and oscillator strengths for electric dipole allowed (E1) and forbidden (M1, E2, M2) lines for the 4 s 24 p and 4 s4 p 2 configurations of W XLIV. The valence-valence and core-valence correlation effects are accounted for in a systematic way. Breit interactions and quantum electrodynamics (QED) effects are estimated in subsequent relativistic configuration interaction (CI) calculations. The present results are in good agreement with other available theoretical and experimental values, and we predict new data for several levels where no other theoretical and/or experimental results are available, precise measurements are clearly needed here.

  16. Characterizing high energy spectra of NIF ignition Hohlraums using a differentially filtered high energy multipinhole x-ray imager.

    PubMed

    Park, Hye-Sook; Dewald, E D; Glenzer, S; Kalantar, D H; Kilkenny, J D; MacGowan, B J; Maddox, B R; Milovich, J L; Prasad, R R; Remington, B A; Robey, H F; Thomas, C A

    2010-10-01

    Understanding hot electron distributions generated inside Hohlraums is important to the national ignition campaign for controlling implosion symmetry and sources of preheat. While direct imaging of hot electrons is difficult, their spatial distribution and spectrum can be deduced by detecting high energy x-rays generated as they interact with target materials. We used an array of 18 pinholes with four independent filter combinations to image entire Hohlraums with a magnification of 0.87× during the Hohlraum energetics campaign on NIF. Comparing our results with Hohlraum simulations indicates that the characteristic 10-40 keV hot electrons are mainly generated from backscattered laser-plasma interactions rather than from Hohlraum hydrodynamics. PMID:21034047

  17. Characterizing high energy spectra of NIF ignition Hohlraums using a differentially filtered high energy multipinhole x-ray imager

    SciTech Connect

    Park, Hye-Sook; Dewald, E. D.; Glenzer, S.; Kalantar, D. H.; Kilkenny, J. D.; MacGowan, B. J.; Maddox, B. R.; Milovich, J. L.; Prasad, R. R.; Remington, B. A.; Robey, H. F.; Thomas, C. A.

    2010-10-15

    Understanding hot electron distributions generated inside Hohlraums is important to the national ignition campaign for controlling implosion symmetry and sources of preheat. While direct imaging of hot electrons is difficult, their spatial distribution and spectrum can be deduced by detecting high energy x-rays generated as they interact with target materials. We used an array of 18 pinholes with four independent filter combinations to image entire Hohlraums with a magnification of 0.87x during the Hohlraum energetics campaign on NIF. Comparing our results with Hohlraum simulations indicates that the characteristic 10-40 keV hot electrons are mainly generated from backscattered laser-plasma interactions rather than from Hohlraum hydrodynamics.

  18. Fine structure in cosmic ray spectra

    NASA Astrophysics Data System (ADS)

    Wolfendale, A. W.; Erlykin, A. D.

    2013-02-01

    The case is made for there being more 'structure' in the cosmic ray energy spectra than just the well-known knee at several PeV and the ankle at several EeV. Specifically, there seems to be a 'dip' or 'kink' at about 100 GeV/nucleon, a possible 'bump' at about 10 TeV, an 'iron peak' at 60 PeV and the possibility of further structure before the ankle is reached. The significance of the structures will be assessed.

  19. Pulsar gamma-rays: Spectra luminosities and efficiencies

    NASA Technical Reports Server (NTRS)

    Harding, A. K.

    1980-01-01

    The general characteristics of pulsar gamma ray spectra are presented for a model where the gamma rays are produced by curvature radiation from energetic particles above the polar cap and attenuated by pair production. The shape of the spectrum is found to depend on pulsar period, magnetic field strength, and primary particle energy. By a comparison of numerically calculated spectra with the observed spectra of the Crab and Vela pulsars, it is determined that primary particles must be accelerated to energies of about 3 x 10 to the 7th power mc sq. A genaral formula for pulsar gamma ray luminosity is determined and is found to depend on period and field strength.

  20. Measurement of the high energy component of the x-ray spectra in the VENUS electron cyclotron resonance ion source (abstract only)

    SciTech Connect

    Leitner, D.; Benitez, J. Y.; Lyneis, C. M.; Todd, D. S.; Ropponen, T.; Ropponen, J.; Koivisto, H.; Gammino, S.

    2008-02-15

    High performance electron cyclotron resonance (ECR) ion sources, such as VENUS (versatile ECR for nuclear science), produce large amounts of x rays. By studying their energy spectra, conclusions can be drawn about the electron heating process and the electron confinement. In addition, the bremsstrahlung from the plasma chamber is partly absorbed by the cold mass of the superconducting magnet adding an extra heat load to the cryostat. Germanium or NaI detectors are generally used for x-ray measurements. Due to the high x-ray flux from the source, the experimental setup to measure bremsstrahlung spectra from ECR ion sources is somewhat different than for the traditional nuclear physics measurements these detectors are generally used for. In particular, the collimation and background shielding can be problematic. In this paper we will discuss the experimental setup for such a measurement, the energy calibration and background reduction, the shielding of the detector, and collimation of the x-ray flux. We will present x-ray energy spectra and cryostat heating rates in dependence of various ion source parameters such as confinement fields, minimum B-field, rf power, and heating frequency.

  1. X-ray spectra of supernova remnants

    NASA Technical Reports Server (NTRS)

    Szymkowiak, A. E.

    1985-01-01

    X-ray spectra were obtained from fields in three supernova remnants with the solid state spectrometer of the HEAO 2 satellite. These spectra, which contain lines from K-shell transitions of several abundant elements with atomic numbers between 10 and 22, were compared with various models, including some of spectra that would be produced by adiabatic phase remnants when the time-dependence of the ionization is considered.

  2. Spectra of {gamma} rays feeding superdeformed bands

    SciTech Connect

    Lauritsen, T.; Khoo, T.L.; Henry, R.G.

    1995-08-01

    The spectrum of {gamma}rays coincident with SD transitions contains the transitions which populate the SD band. This spectrum can provide information on the feeding mechanism and on the properties (moment of inertia, collectivity) of excited SD states. We used a model we developed to explain the feeding of SD bands, to calculate the spectrum of feeding {gamma}rays. The Monte Carlo simulations take into account the trigger conditions present in our Eurogam experiment. Both experimental and theoretical spectra contain a statistical component and a broad E2 peak (from transitions occurring between excited states in the SD well). There is good resemblance between the measured and calculated spectra although the calculated multiplicity of an E2 bump is low by {approximately}30%. Work is continuing to improve the quality of the fits, which will result in a better understanding of excited SD states. In addition, a model for the last steps, which cool the {gamma} cascade into the SD yrast line, needs to be developed. A strong M1/E2 low-energy component, which we believe is responsible for this cooling, was observed.

  3. Derivation of a Relation for the Steepening of TeV Selected Blazar Gamma-Ray Spectra with Energy and Redshift

    NASA Technical Reports Server (NTRS)

    Stecker, F.

    2010-01-01

    We derive a relation for the steepening of blazar gamma-ray spectra between the multi-GeV Fermi energy range and the TeV energy range observed by atmospheric Cerenkov telescopes. The change in spectral index is produced by two effects: (1) an intrinsic steepening, independent of redshift, owing to the properties of emission and absorption in the source, and (2) a redshift-dependent steepening produced by intergalactic pair production interactions of blazar gamma-rays with low energy photons of the "intergalactic background light" (IBL). Given this relation, with good enough data on the mean gamma-ray SED of TeV Selected BL Lacs, the redshift evolution of the IBL can, in principle, be determined independently of stellar evolution models. We apply our relation to the results of new Fermi observations of TeV selected blazars.

  4. The difference in the energy spectra of galactic cosmic rays at the minima of the 19th and 20th solar activity cycles

    NASA Technical Reports Server (NTRS)

    Svirzhevskaya, A. K.; Stozhkov, Y. I.; Svirzhevsky, N. S.; Charakhchyan, T. N.

    1985-01-01

    The absorption curves of the cosmic ray charged component for solar minima in 1965 and 1975 to 1977 are analyzed on the basis of daily stratospheric measurements in Murmansk, Moscow, Alma-Ata and Mirny (Antarctic). Two distinct features in the energy spectra of galactic cosmic rays are revealed during these periods. At the 20th solar activity minimum there was the additional short range component of cosmic rays. Additional fluxes in the stratosphere at high latitudes caused by this component are probably protons and He nuclei with the energy 100 to 500 MeV/n. The fluxes are estimates as Approx. 300 sq m/s/sr. At the minimum in 1975 to 1977 the proton intensity in the energy range 1 to 15 GeV is 10 to 15% lower than that in the 1965 solar activity minimum.

  5. Measurement of backscattered x-ray spectra at the water surface in the energy range 60 kV to 120 kV.

    PubMed

    Aoki, Kiyoshi; Koyama, Masaki

    2002-04-01

    Backscattered x-ray spectra at the water surface have been measured by using a small silicon diode detector. The measurements have been made at tube voltages 60 kV to 120 kV (HVL 2.4-6.1 mm Al) and field sizes 5 x 5 cm2 to 30 x 30 cm2. The measured spectra are corrected for detector distortion and for the angular dependence of detector efficiency. The obtained backscattered spectrum has a lower mean energy and a narrower shape than the primary spectrum. The ratio of the mean energy of the backscattered spectrum to that of the primary spectrum is between 0.83 and 0.94. The ratio of the spectrum width at 10% of the continuous spectrum maximum is between 0.65 and 0.78. The change of spectral shape due to the field size is slight. In the high-voltage spectra, the peak due to the Compton scattering of tungsten Kalpha x-rays is observed. The backscatter factors (BSFs) calculated from the obtained spectra show a satisfactory agreement with other studies. The difference between the BSF defined as the ratio of air kerma and the BSF defined as the ratio of water kerma is also calculated; the maximum difference is 0.43%. The empirical equation showing the relation between the two BSFs is presented. PMID:11996064

  6. Experiment on the study of the nuclear component and energy spectra of solar cosmic rays on the Prognoz-9 satellite

    NASA Astrophysics Data System (ADS)

    Beliakov, S. A.; Gordeev, Iu. P.; Denisov, Iu. I.; Kolesov, G. Ia.; Podorolskii, A. N.

    1986-06-01

    The design of the semiconductor-telescope instrument on Prognoz-9 for measuring the characteristics of solar cosmic rays is described, and the factors determining its resolution are examined. Experimental data characterizing the operation of the instrument are presented. Hour-averaged and six-hour-averaged intensities are given for protons with energies of 6-19, 10-30, and 30-60 MeV, and for alpha particles with energies of 5-19 MeV/nucleon.

  7. A measurement of the energy spectra of cosmic rays from 20 to 1000 GeV per amu

    NASA Technical Reports Server (NTRS)

    Gregory, John C.; Takahashi, Y.; Hayashi, T.; Thoburn, C.; Parnell, T. A.; Watts, John W., Jr.; Fowler, P. H.; Masheder, M. R. W.; Derrickson, James H.

    1991-01-01

    A group collaboration was made in the development of the Bristol University Gas Spectrometer number 4 (BUGS 4). The BUGS 4 detector is designed to measure the charge spectrum for species between oxygen and the iron peak as a function of energy per nucleon, between 20 and 1000 GeV/amu. It is particularly concerned with energies above 50 GeV/amu. The high energy component is considerably less affected by propagation through the interstellar medium than the lower energy component and is expected to approach the original charge spectrum of the source more closely. This information allows one to unravel the effects of cosmic ray production, acceleration, and propagation. The detector is described in total detail. The method of estimating the charge and energy of a cosmic ray depends on the energy of the particle. Calculations and experiments lead to the expectation of a nearly constant charge resolution of about 0.2 charge units over the whole energy range except 4.5 less than gamma less than 20. In this band, the experiment is insensitive to energy. A balloon flight is planned in 1993.

  8. Monte Carlo based method for conversion of in-situ gamma ray spectra obtained with a portable Ge detector to an incident photon flux energy distribution.

    PubMed

    Clouvas, A; Xanthos, S; Antonopoulos-Domis, M; Silva, J

    1998-02-01

    A Monte Carlo based method for the conversion of an in-situ gamma-ray spectrum obtained with a portable Ge detector to photon flux energy distribution is proposed. The spectrum is first stripped of the partial absorption and cosmic-ray events leaving only the events corresponding to the full absorption of a gamma ray. Applying to the resulting spectrum the full absorption efficiency curve of the detector determined by calibrated point sources and Monte Carlo simulations, the photon flux energy distribution is deduced. The events corresponding to partial absorption in the detector are determined by Monte Carlo simulations for different incident photon energies and angles using the CERN's GEANT library. Using the detector's characteristics given by the manufacturer as input it is impossible to reproduce experimental spectra obtained with point sources. A transition zone of increasing charge collection efficiency has to be introduced in the simulation geometry, after the inactive Ge layer, in order to obtain good agreement between the simulated and experimental spectra. The functional form of the charge collection efficiency is deduced from a diffusion model. PMID:9450590

  9. Augmentation of ENDF/B fission product gamma-ray spectra by calculated spectra

    SciTech Connect

    Katakura, J. ); England, T.R. )

    1991-11-01

    Gamma-ray spectral data of the ENDF/B-V fission product decay data file have been augmented by calculated spectra. The calculations were performed with a model using beta strength functions and cascade gamma-ray transitions. The calculated spectra were applied to individual fission product nuclides. Comparisons with several hundred measured aggregate gamma spectra after fission were performed to confirm the applicability of the calculated spectra. The augmentation was extended to a preliminary ENDF/B-VI file, and to beta spectra. Appendix C provides information on the total decay energies for individual products and some comparisons of measured and aggregate values based on the preliminary ENDF/B-VI files. 15 refs., 411 figs.

  10. The width of gamma-ray burst spectra

    NASA Astrophysics Data System (ADS)

    Axelsson, Magnus; Borgonovo, Luis

    2015-03-01

    The emission processes active in the highly relativistic jets of gamma-ray bursts (GRBs) remain unknown. In this paper, we propose a new measure to describe spectra: the width of the EFE spectrum, a quantity dependent only on finding a good fit to the data. We apply this to the full sample of GRBs observed by Fermi/Gamma-ray Burst Monitor (GBM) and Compton Gamma-ray Observatory/Burst and Transient Source Experiment (BATSE). The results from the two instruments are fully consistent. We find that the median widths of spectra from long and short GRBs are significantly different (chance probability <10-6). The width does not correlate with either duration or hardness, and this is thus a new, independent distinction between the two classes. Comparing the measured spectra with widths of spectra from fundamental emission processes - synchrotron and blackbody radiation - the results indicate that a large fraction of GRB spectra are too narrow to be explained by synchrotron radiation from a distribution of electron energies: for example, 78 per cent of long GRBs and 85 per cent of short GRBs are incompatible with the minimum width of standard slow cooling synchrotron emission from a Maxwellian distribution of electrons, with fast cooling spectra predicting even wider spectra. Photospheric emission can explain the spectra if mechanisms are invoked to give a spectrum much broader than a blackbody.

  11. Correlations Between Variations in Solar EUV and Soft X-Ray Irradiance and Photoelectron Energy Spectra Observed on Mars and Earth

    NASA Technical Reports Server (NTRS)

    Peterson, W. K.; Brain, D. A.; Mitchell, D. L.; Bailey, S. M.; Chamberlin, P. C.

    2013-01-01

    Solar extreme ultraviolet (EUV; 10-120 nm) and soft X-ray (XUV; 0-10 nm) radiation are major heat sources for the Mars thermosphere as well as the primary source of ionization that creates the ionosphere. In investigations of Mars thermospheric chemistry and dynamics, solar irradiance models are used to account for variations in this radiation. Because of limited proxies, irradiance models do a poor job of tracking the significant variations in irradiance intensity in the EUV and XUV ranges over solar rotation time scales when the Mars-Sun-Earth angle is large. Recent results from Earth observations show that variations in photoelectron energy spectra are useful monitors of EUV and XUV irradiance variability. Here we investigate photoelectron energy spectra observed by the Mars Global Surveyor (MGS) Electron Reflectometer (ER) and the FAST satellite during the interval in 2005 when Earth, Mars, and the Sun were aligned. The Earth photoelectron data in selected bands correlate well with calculations based on 1 nm resolution observations above 27 nm supplemented by broadband observations and a solar model in the 0-27 nm range. At Mars, we find that instrumental and orbital limitations to the identifications of photoelectron energy spectra in MGS/ER data preclude their use as a monitor of solar EUV and XUV variability. However, observations with higher temporal and energy resolution obtained at lower altitudes on Mars might allow the separation of the solar wind and ionospheric components of electron energy spectra so that they could be used as reliable monitors of variations in solar EUV and XUV irradiance than the time shifted, Earth-based, F(10.7) index currently used.

  12. Correlations between variations in solar EUV and soft X-ray irradiance and photoelectron energy spectra observed on Mars and Earth

    NASA Astrophysics Data System (ADS)

    Peterson, W. K.; Brain, D. A.; Mitchell, D. L.; Bailey, S. M.; Chamberlin, P. C.

    2013-11-01

    extreme ultraviolet (EUV; 10-120 nm) and soft X-ray (XUV; 0-10 nm) radiation are major heat sources for the Mars thermosphere as well as the primary source of ionization that creates the ionosphere. In investigations of Mars thermospheric chemistry and dynamics, solar irradiance models are used to account for variations in this radiation. Because of limited proxies, irradiance models do a poor job of tracking the significant variations in irradiance intensity in the EUV and XUV ranges over solar rotation time scales when the Mars-Sun-Earth angle is large. Recent results from Earth observations show that variations in photoelectron energy spectra are useful monitors of EUV and XUV irradiance variability. Here we investigate photoelectron energy spectra observed by the Mars Global Surveyor (MGS) Electron Reflectometer (ER) and the FAST satellite during the interval in 2005 when Earth, Mars, and the Sun were aligned. The Earth photoelectron data in selected bands correlate well with calculations based on 1 nm resolution observations above 27 nm supplemented by broadband observations and a solar model in the 0-27 nm range. At Mars, we find that instrumental and orbital limitations to the identifications of photoelectron energy spectra in MGS/ER data preclude their use as a monitor of solar EUV and XUV variability. However, observations with higher temporal and energy resolution obtained at lower altitudes on Mars might allow the separation of the solar wind and ionospheric components of electron energy spectra so that they could be used as reliable monitors of variations in solar EUV and XUV irradiance than the time shifted, Earth-based, F10.7 index currently used.

  13. Evaluation of conversion coefficients relating air-kerma to H*(10) using primary and transmitted x-ray spectra in the diagnostic radiology energy range.

    PubMed

    Santos, J C; Mariano, L; Tomal, A; Costa, P R

    2016-03-01

    According to the International Commission on Radiation Units and Measurements (ICRU), the relationship between effective dose and incident air-kerma is complex and depends on the attenuation of x-rays in the body. Therefore, it is not practical to use this quantity for shielding design purposes. This correlation is adopted in practical situations by using conversion coefficients calculated using validated mathematical models by the ICRU. The ambient dose equivalent, H*(10), is a quantity adopted by the IAEA for monitoring external exposure. Dose constraint levels are established in terms of H*(10), while the radiation levels in radiometric surveys are calculated by means of the measurements of air-kerma with ion chambers. The resulting measurements are converted into ambient dose equivalents by conversion factors. In the present work, an experimental study of the relationship between the air-kerma and the operational quantity ambient dose equivalent was conducted using different experimental scenarios. This study was done by measuring the primary x-ray spectra and x-ray spectra transmitted through materials used in dedicated chest radiographic facilities, using a CdTe detector. The air-kerma to ambient dose equivalent conversion coefficients were calculated from these measured spectra. The resulting values of the quantity ambient dose equivalent using these conversion coefficients are more realistic than those available in the literature, because they consider the real energy distribution of primary and transmitted x-ray beams. The maximum difference between the obtained conversion coefficients and the constant value recommended in national and international radiation protection standards is 53.4%. The conclusion based on these results is that a constant coefficient may not be adequate for deriving the ambient dose equivalent. PMID:26835613

  14. A Measurement of the Energy Spectra of Cosmic Rays from 20 to 1000 GeV Per AMU

    NASA Astrophysics Data System (ADS)

    Gregory, J. C.; Thoburn, C.; Smith, A. E.; Petruzzo, J. J., III; Austin, R. W.; Derrickson, J. H.; Parnell, T. A.; Masheder, M. R. W.; Fowler, P. H.

    1997-11-01

    The design features and operational performance from the test flight of the fourth generation of spherical geometry cosmic ray detectors developed at Bristol University (Bristol University Gas Scintillator 4 - BUGS-4) are presented. The flight from Ft. Sumner (NM) in Sept. 1993 was the premier flight of a large (1m radius) spherical drift chamber which also gave gas scintillation and Cerenkov signals. The combinations of this chamber with one gas and two solid Cerenkov radiators lead to a large aperture factor (4.5 m2sr), but low (approximately 3.5 g/sq cm) instrument mass over the energy sensitive range 1 to several hundred GeV/a. Moreover, one simple timing measurement determined the impact parameter which provided a trajectory (path length) correction for all detector elements. This innovative and efficient design will be of interest to experimental groups engaged in studies of energetic charged particles. Although there were technical problems on the flight, which were compounded by the total destruction of BUGS-4 by fire while landing in Oklahoma, there was a period of stable operation during which the instrument was exposed at float altitude (approximately 125,000 ft.) to high energy cosmic rays. We present the performance of the instrument as determined from the analysis of these data and an appraisal of its novel design features. Suggestions for design improvements in a future instrument are made.

  15. A Measurement of the Energy Spectra of Cosmic Rays from 20 to 1000 GeV Per Amu

    NASA Technical Reports Server (NTRS)

    Gregory, J. C.; Thoburn, C.; Smith, A. E.; Petruzzo, J. J., III; Austin, R. W.; Derrickson, J. H.; Parnell, T. A.; Masheder, M. R. W.; Fowler, P. H.

    1997-01-01

    The design features and operational performance from the test flight of the fourth generation of spherical geometry cosmic ray detectors developed at Bristol University (Bristol University Gas Scintillator 4 - BUGS-4) are presented. The flight from Ft. Sumner (NM) in Sept. 1993 was the premier flight of a large (1m radius) spherical drift chamber which also gave gas scintillation and Cerenkov signals. The combinations of this chamber with one gas and two solid Cerenkov radiators lead to a large aperture factor (4.5 m2sr), but low (approximately 3.5 g/sq cm) instrument mass over the energy sensitive range 1 to several hundred GeV/a. Moreover, one simple timing measurement determined the impact parameter which provided a trajectory (path length) correction for all detector elements. This innovative and efficient design will be of interest to experimental groups engaged in studies of energetic charged particles. Although there were technical problems on the flight, which were compounded by the total destruction of BUGS-4 by fire while landing in Oklahoma, there was a period of stable operation during which the instrument was exposed at float altitude (approximately 125,000 ft.) to high energy cosmic rays. We present the performance of the instrument as determined from the analysis of these data and an appraisal of its novel design features. Suggestions for design improvements in a future instrument are made.

  16. Measuring Flash X-Ray Spectra with a Compton Spectrometer

    NASA Astrophysics Data System (ADS)

    Gehring, Amanda; Espy, Michelle; Haines, Todd; Hunter, James; King, Nick; Merrill, Frank; Sedillo, Robert; Urbaitis, Algis; Volegov, Petr

    2014-09-01

    The determination of the x-ray energy spectra of flash radiographic sources is difficult due to the short nature of the pulses (~50 ns). Recently, a Compton spectrometer has been refurbished and investigated as a potential device for conducting these measurements. The spectrometer was originally designed and characterized by Morgan et al.. The spectrometer consists of a 300 kg neodymium-iron magnet and measures spectra in the <1 MeV to 20 MeV energy range. In this apparatus, the incoming x-rays are collimated into a narrow beam before encountering a converter foil. Compton electrons are ejected and collimated so that the forward-directed electrons enter the magnetic field region of the device. The position of the electrons on the magnet focal plane is a function of their energy, allowing the x-ray spectrum to be reconstructed. Recent energy calibration measurements and the spectrum reconstruction of a Bremsstrahlung source will be presented. The determination of the x-ray energy spectra of flash radiographic sources is difficult due to the short nature of the pulses (~50 ns). Recently, a Compton spectrometer has been refurbished and investigated as a potential device for conducting these measurements. The spectrometer was originally designed and characterized by Morgan et al.. The spectrometer consists of a 300 kg neodymium-iron magnet and measures spectra in the <1 MeV to 20 MeV energy range. In this apparatus, the incoming x-rays are collimated into a narrow beam before encountering a converter foil. Compton electrons are ejected and collimated so that the forward-directed electrons enter the magnetic field region of the device. The position of the electrons on the magnet focal plane is a function of their energy, allowing the x-ray spectrum to be reconstructed. Recent energy calibration measurements and the spectrum reconstruction of a Bremsstrahlung source will be presented. LA-UR-14-23602.

  17. Optimal x-ray spectra for screen-film mammography.

    PubMed

    Jennings, R J; Eastgate, R J; Siedband, M P; Ergun, D L

    1981-01-01

    Theoretical and experimental techniques have been used to study optimal x-ray for screen-film mammography. A simple model of mammographic imaging predicts optimum x-ray energies which are significantly higher than the K-characteristic energies of Mo. A subjective comparison of x-ray spectra from Mo-anode and W-anode tubes indicates that spectra produced by a W-anode tube filtered with materials of atomic number just above that of Mo are more suitable for screen-film mammography than spectra produced by the Mo-anode/Mo-filter system. The imaging performance of K-edge filtered, W-anode tube spectra was compared to the performance of Mo-anode spectra using phantom measurements and mastectomy specimen radiography. It was shown that optimal W-anode spectra can produce equal contrast with an exposure reduction of a factor of two to three, a dose reduction of a factor of two, and equal or reducing tube loading, compared to Mo-anode spectra. A computer simulation was carried out to extend the initial, monoenergetic theory to the case of real, polychromatic sources. The effects of varying filter material and thickness, tube operating potential, and breast thickness were all studied. Since W-anode x-ray tubes are considered to be better for Xerox mammography than Mo-anode tubes, this study has shown that both Xerox and screen-film techniques can be performed optimally with a single, properly designed, W-anode x-ray tube. PMID:7290015

  18. Quasar X-Ray Spectra Revisited: Erratum

    NASA Astrophysics Data System (ADS)

    Shastri, P.; Wilkes, B. J.; Elvis, M.; McDowell, J.

    1994-08-01

    In the paper "Quasar X-Ray Spectra Revisited " by P. Shastri, B. J. Wilkes, M. Elvis, and J. McDowell (ApJ, 410,29 [1993]), there is an error in the flux density levels in Figures 4a and 4b. As a result of an error during rebinning of the optical spectrophotometry data, the flux density levels in those two figures are a factor of 5 lower then their actual value.

  19. Comparison of simulated and measured spectra from an X-ray tube for the energies between 20 and 35 keV

    NASA Astrophysics Data System (ADS)

    Yücel, M.; Emirhan, E.; Bayrak, A.; Ozben, C. S.; Yücel, E. Barlas

    2015-11-01

    Design and production of a simple and low cost X-ray imaging system that can be used for light industrial applications was targeted in the Nuclear Physics Laboratory of Istanbul Technical University. In this study, production, transmission and detection of X-rays were simulated for the proposed imaging device. OX/70-P dental tube was used and X-ray spectra simulated by Geant4 were validated by comparison with X-ray spectra measured between 20 and 35 keV. Relative detection efficiency of the detector was also determined to confirm the physics processes used in the simulations. Various time optimization tools were performed to reduce the simulation time.

  20. Quasar X-ray spectra revisited

    NASA Technical Reports Server (NTRS)

    Shastri, P.; Wilkes, B. J.; Elvis, M.; Mcdowell, J.

    1993-01-01

    A sample of 45 quasars observed by the IPC on the Einstein satellite is used to reexamine the relationship of the soft X-ray energy index with radio properties and the optical Fe II emission. The tendency for radio-loud quasars to have systematically flatter X-ray energy indices than radio-quiet quasars is confirmed with the soft X-ray excess having negligible effect. There is a tendency for the flatness of the X-ray slope to correlate with radio core dominance for radio-loud quasars, suggesting that a component of the X-ray emission is relativistically beamed. For the radio-quiet quasars, the soft X-ray energy indices with a mean of about 1.0 are consistent with the indices found at higher energies, although steeper than those observed for Seyfert 1 galaxies where the reflection model gives a good fit to the data. The correlation of Fe II emission line strength with X-ray energy index is confirmed for radio-quiet quasars using a subset of 18 objects. The radio-loud quasars show no evidence for a correlation. This relation suggests a connection between the ionizing continuum and line emission from the broad emission-line region (BELR) of radio-quiet quasars, but in the opposite sense to that predicted by current photoionization models. The correlations of X-ray slope with radio core dominance and Fe II equivalent width within the radio-loud and radio-quiet subclasses, respectively, imply that the observed wide range of X-ray energy indices is real rather than due to the large measuring uncertainties for individual objects.

  1. Differential energy spectra of low energy (less than 8.5 MeV per nucleon) heavy cosmic rays during solar quiet times. [from Explorer 47 satellite observation

    NASA Technical Reports Server (NTRS)

    Hovestadt, D.; Vollmer, O.; Gloeckler, G.; Fan, C. Y.

    1973-01-01

    Explorer 47 satellite observations of carbon, oxygen, and heavier nuclei differential energy spectra below 8.5 MeV/nucleon are presented for solar quiet time periods. A dE/dx vs E method for particle identification and energy determination was used. The instrumentation telescope included an isobutane proportional counter, a surface barrier Si detector, and a cylindrical plastic scintillator anticoincidence shield. The observations were performed outside the bow-shock and in the ecliptic plane. Results show an anisotropy of about 25% at 22 degrees west of the sun with a C/O ratio of 0.5 supporting a solar origin. The low energy portions of the C and O spectra have steep negative slopes, and the corresponding power law is given. Peculiarities in the O spectrum are discussed.

  2. X-Ray Energy Spectra of the Supersoft X-Ray Sources CAL 87 and RX J0925.7-4758 Observed with ASCA

    NASA Astrophysics Data System (ADS)

    Ebisawa, Ken; Mukai, Koji; Kotani, Taro; Asai, Kazumi; Dotani, Tadayasu; Nagase, Fumiaki; Hartmann, H. W.; Heise, J.; Kahabka, P.; van Teeseling, A.

    2001-04-01

    We report observation results of the supersoft X-ray sources CAL 87 and RX J0925.7-4758 with the X-ray CCD cameras (Solid-State Imaging Spectrometers [SISs]) on board ASCA. Because of the superior energy resolution of the SIS (ΔE/E~10% at 1 keV) relative to previous instruments, we could study detailed X-ray spectral structures of these sources for the first time. We have applied theoretical spectral models to CAL 87 and constrained the white dwarf mass and intrinsic luminosity as 0.8-1.2 Msolar and 4×1037-1.2×1038 ergs s-1, respectively. However, we have found the observed luminosity is an order of magnitude smaller than the theoretical estimate, which indicates that the white dwarf is permanently blocked by the accretion disk, and we are observing a scattering emission by a fully ionized accretion disk corona (ADC) whose column density is ~1.5×1023 cm-2. Through simulation we have shown that the orbital eclipse can be explained by the ADC model, such that a part of the extended X-ray emission from the ADC is blocked by the companion star filling its Roche lobe. We have found that very high surface gravity and temperature, ~1010 cm s-2 and ~100 eV, respectively, as well as a strong absorption edge at ~1.02 keV, are required to explain the X-ray energy spectrum of RX J0925.7-4758. These values are only possible for an extremely heavy white dwarf near the Chandrasekhar limit. Although the supersoft source luminosity should be ~1038 ergs s-1 at the Chandrasekhar limit, the observed luminosity of RX J0925.7-4758 is nearly 2 orders of magnitude smaller, even assuming an extreme distance of ~10 kpc. To explain the luminosity discrepancy, we propose a model in which very thick matter that was previously ejected from the system, as a form of jets, intervenes the line of sight and reduces the luminosity significantly because of Thomson scattering.

  3. Quasar x-ray spectra revisited

    NASA Technical Reports Server (NTRS)

    Shastri, P.; Wilkes, B. J.; Elvis, M.; Mcdowell, J.

    1992-01-01

    A sample of 45 quasars observed by the Imaging Proportional Counter (IPC) on the Einstein satellite is used to re-examine the relationship between the soft (0.2-3.5 keV) X-ray energy index and radio-loudness. We found the following: (1) the tendency for radio-loud quasars to have systematically flatter X-ray slopes than radio-quiet quasars (RQQ's) is confirmed with the soft X-ray excess having negligible effect; (2) there is a tendency for the flatness of the X-ray slope to correlate with radio core-dominance for radio-loud quasars, suggesting that a component of the X-ray emission is relativistically beamed; (3) for the RQQ's the soft X-ray slopes, with a mean of approximately 1.0, are consistent with the slopes found at higher energies (2-10 keV) although steeper than those observed for Seyfert 1 galaxies (also 2-10 keV) where the reflection model gives a good fit to the data; (4) the correlation of FeII emission line strength with X-ray energy index is confirmed for radio-quiet quasars using a subset of 18 quasars. The radio-loud quasars show no evidence for a correlation. This relation suggests a connection between the ionizing continuum and the line emission from the broad emission line region (BELR) of radio-quiet quasars, but in the opposite sense to that predicted by current photoionization models; and (5) the correlations of X-ray slope with radio core dominance and FeII equivalent width within the radio-loud and radio-quiet sub-classes respectively imply that the observed wide range of X-ray spectral slopes is real rather than due to the large measuring uncertainties for individual objects.

  4. The energy spectra of solar energetic particles

    NASA Technical Reports Server (NTRS)

    Mcguire, R. E.; Von Rosenvinge, T. T.

    1984-01-01

    A survey of recent results on the shapes and relative slopes of the spectra of various solar energetic particle populations is presented, with emphasis on the more extensive results currently available for protons, alphas and electrons. From previous work, it is found that proton spectra 0.8 to more than 400 MeV and alpha spectra 1.4 to 80 MeV/nucleon are best characterized, on average, by a functional form involving a Bessel function in momentum/nucleon. However, proton and alpha spectral slopes using this form are not equal, and there is significant variation from event to event. From other studies, electrons 0.02 to 20 MeV are also found to have curved spectra, but seem to be better fit with a double power law in energy. The spectral properties in both cases correlate with other measures of solar particle acceleration; e.g. gamma-ray line production, hard X-ray burst spectra and microwave fluxes.

  5. X-ray Spectra and Photoionized Plasmas

    NASA Astrophysics Data System (ADS)

    Kallman, Timothy R.

    2016-06-01

    Much of the emission from accreting compact objects (black holes and neutron stars) is in the X-ray band. Key diagnostic information about kinematics, gravitational potential, element abundances, and total energy output is contained in the emission and absorption features imprinted by reprocessing in gas which surrounds the accreting source. Observations of these features are a key goal of recent X-ray spectroscopy instruments. In this talk I will review the dominant physical processes in such plasmas, the likely spectral diagnostics, the science questions to be addressed, and examples from recent observations.

  6. The soft X-ray excess in Einstein quasar spectra

    NASA Technical Reports Server (NTRS)

    Masnou, J. L.; Wilkes, B. J.; Elvis, M.; Mcdowell, J. C.; Arnaud, K. A.

    1992-01-01

    An SNR-limited subsample of 14 quasars from the Wilkes and Elvis (1987) sample is presently investigated for low-energy excess above a high-energy power law in the X-ray spectra obtained by the Einstein Imaging Proportional Counter. A significant excess that is 1-6 times as strong as the high-energy component at 0.2 keV is noted in eight of the 14 objects. In the case of 3C273, multiple observations show the excess to be variable.

  7. FLUXEN portable equipment for direct X-ray spectra measurements

    NASA Astrophysics Data System (ADS)

    Aiello, S.; Bottigli, U.; Fauci, F.; Golosio, B.; Lo Presti, D.; Masala, G. L.; Oliva, P.; Raso, G.; Stumbo, S.; Tangaro, S.

    2004-02-01

    The proper use of imaging equipment in radiological units is based on an appropriate knowledge of the physical characteristics of the X-ray beam used. The FLUXEN PROJECT is working on a portable apparatus which, together with dedicated software, is able to perform an exact spectral reconstruction of the radiation produced in diagnostic X-ray tubes. The apparatus characterizes the energy spectrum of radiological tubes and also provides a measurement of the emitted flux. The acquisition system is based on a commercial CZT detector (3×3×2 mm 3), produced by AMPTEK, cooled by a Peltier cell, with a high efficiency in the diagnostic X-ray energy range and modified in the shaping electronics so as to obtain a faster response. The acquiring section lies on a NuDAQ I/O card with a sampling frequency of up to 20 MHz. The signal produced by the X-ray tube is wholly acquired and an off-line analysis is made so as to make possible an accurate recognition of pile-up events and a reconstruction of the emitted spectra. The reconstructed spectra of a General Electric Senographe DMR mammographic X-ray tube are shown.

  8. The sharpness of gamma-ray burst prompt emission spectra

    NASA Astrophysics Data System (ADS)

    Yu, Hoi-Fung; van Eerten, Hendrik J.; Greiner, Jochen; Sari, Re'em; Narayana Bhat, P.; von Kienlin, Andreas; Paciesas, William S.; Preece, Robert D.

    2015-11-01

    Context. We study the sharpness of the time-resolved prompt emission spectra of gamma-ray bursts (GRBs) observed by the Gamma-ray Burst Monitor (GBM) on board the Fermi Gamma-ray Space Telescope. Aims: We aim to obtain a measure of the curvature of time-resolved spectra that can be compared directly to theory. This tests the ability of models such as synchrotron emission to explain the peaks or breaks of GBM prompt emission spectra. Methods: We take the burst sample from the official Fermi GBM GRB time-resolved spectral catalog. We re-fit all spectra with a measured peak or break energy in the catalog best-fit models in various energy ranges, which cover the curvature around the spectral peak or break, resulting in a total of 1113 spectra being analyzed. We compute the sharpness angles under the peak or break of the triangle constructed under the model fit curves and compare them to the values obtained from various representative emission models: blackbody, single-electron synchrotron, synchrotron emission from a Maxwellian or power-law electron distribution. Results: We find that 35% of the time-resolved spectra are inconsistent with the single-electron synchrotron function, and 91% are inconsistent with the Maxwellian synchrotron function. The single temperature, single emission time, and location blackbody function is found to be sharper than all the spectra. No general evolutionary trend of the sharpness angle is observed, neither per burst nor for the whole population. It is found that the limiting case, a single temperature Maxwellian synchrotron function, can only contribute up to % of the peak flux. Conclusions: Our results show that even the sharpest but non-realistic case, the single-electron synchrotron function, cannot explain a large fraction of the observed GRB prompt spectra. Because any combination of physically possible synchrotron spectra added together will always further broaden the spectrum, emission mechanisms other than optically thin

  9. Energy spectra in bubbly turbulence

    NASA Astrophysics Data System (ADS)

    Luther, Stefan; van den Berg, Thomas H.; Rensen, Judith; Lohse, Detlef

    2004-11-01

    The energy spectrum of single phase turbulent flow - apart from intermittency corrections - has been known since Kolomogorov 1941, E(k) ∝ k-5/3. How do bubbles modify this spectrum? To answer this question, we inject micro bubbles (radius 100 μm) in fully turbulent flow (Re_λ=200) up to volume concentrations of 0.3 %. Energy spectra and velocity structure functions are measured with hot-film anemometry. Under our experimental conditions, we find an enhancement of energy on small scales confirming numerical predictions by Mazzitelli, Lohse, and Toschi [Phys. Fluids 15, L5 (2003)]. They propose a mechanism in which bubbles are clustering most likely in downflow regions. This clustering is a lift force effect suppressing large vortical structures, while enhancing energy input on small scales.

  10. Relativistic Effects on Reflection X-ray Spectra of AGN

    SciTech Connect

    Lee, Khee-Gan; Fuerst, Steven V.; Brandwardi-Raymond, Graziella; Wu, Kinwah; Crowley, Oliver; /University Coll. London

    2007-01-05

    We have calculated the reflection component of the X-ray spectra of active galactic nuclei (AGN) and shown that they can be significantly modified by the relativistic motion of the accretion flow and various gravitational effects of the central black hole. The absorption edges in the reflection spectra suffer severe energy shifts and smearing. The degree of distortion depends on the system parameters, and the dependence is stronger for some parameters such as the inner radius of the accretion disk and the disk viewing inclination angles. The relativistic effects are significant and are observable. Improper treatment of the reflection component of the X-ray continuum in spectral fittings will give rise to spurious line-like features, which will mimic the fluorescent emission lines and mask the relativistic signatures of the lines.

  11. Gamma-ray Output Spectra from 239 Pu Fission

    SciTech Connect

    Ullmann, John

    2015-05-25

    Gamma-ray multiplicities, individual gamma-ray energy spectra, and total gamma energy spectra following neutron-induced fission of 239Pu were measured using the DANCE detector at Los Alamos. Corrections for detector response were made using a forward-modeling technique based on propagating sets of gamma rays generated from a paramaterized model through a GEANT model of the DANCE array and adjusting the parameters for best fit to the measured spectra. The results for the gamma-ray spectrum and multiplicity are in general agreement with previous results, but the measured total gamma-ray energy is about 10% higher. A dependence of the gamma-ray spectrum on the gamma-ray multplicity was also observed. Global model calculations of the multiplicity and gamma energy distributions are in good agreement with the data, but predict a slightly softer total-energy distribution.

  12. A measurement of the energy spectra and relative abundance of the cosmic-ray H and He isotopes over a broad energy range

    NASA Technical Reports Server (NTRS)

    Webber, W. R.; Yushak, S. M.

    1983-01-01

    The measurements reported of these isotopes were made using two sets of detectors during the same minimum modulation period in 1977. One measurement was made with a balloon-borne telescope, the other with telescopes on the Voyager spacecraft. It is noted that together they provide the widest energy range yet available for studying these isotopes: 14-150 MeV per nucleon for H2 and 10-290 MeV per nucleon for He-3. The simultaneous helium isotope observations are used to give a mutually consistent picture of galactic propagation and solar modulation. The data define the form of the interstellar H-1 and He-4 spectra, an interstellar matter path length for both H-1 and He-4, and a total residual modulation for He-4. The H-2 observations suggest a picture that is very similar for the galactic propagation of H-1 and He-4.

  13. Size Effect on Nuclear Gamma-Ray Energy Spectra Acquired by Different Sized CeBr3, LaBr3:Ce, and NaI:Tl Gamma-Ray Detectors

    SciTech Connect

    Guss, Paul; Reed, Michael; Yuan, Ding; Beller, Denis; Cutler, Matthew; Contreras, Chris; Mukhopadhyay, Sanjoy; Wilde, Scott UNLV

    2014-03-01

    Gamma-ray energy spectra were acquired for different sizes of cerium tribromide (CeBr3), cerium-doped lanthanum tribromide (LaBr3:Ce), and thallium-doped sodium iodide (NaI:Tl) detectors. A comparison was conducted of the energy resolution and detection efficiency of these scintillator detectors for different sizes of detectors. The results of this study are consistent with the observation that for each size detector, LaBr3:Ce offers better resolution than either a CeBr3 or NaI:Tl detector of the same size. In addition, CeBr3 and LaBr3:Ce detectors could resolve some closely spaced peaks in the spectra of several radioisotopes that NaI:Tl could not. As the detector size increased, all three detector materials exhibited higher efficiency, albeit with slightly reduced resolution. Significantly, the very low intrinsic activity of CeBr3 is also demonstrated in this study, which, when combined with energy resolution characteristics for a range of detector sizes, could lead to an improved ability to detect special nuclear materials compared to the other detectors.

  14. Characterizing high energy spectra of NIF ignition hohlraums using a differentially filtered high energy multi-pinhole X-ray imager

    SciTech Connect

    Park, H; Dewald, E D; Glenzer, S; Kalantar, D H; Kilkenny, J D; MacGowan, B J; Maddox, B R; Milovich, J L; Prasad, R R; Remington, B A; Thomas, C A

    2010-05-11

    Understanding hot electron distributions generated inside hohlraums is important to the ignition campaign for controlling implosion symmetry and sources of preheat. While direct imaging of hot electrons is difficult, their spatial distribution and spectrum can be deduced by detecting high energy x-rays generated as they interact with the target materials. We used an array of 18 pinholes, with four independent filter combinations, to image entire hohlraums with a magnification of 0.87x during the hohlraum energetics campaign on NIF. Comparing our results with hohlraum simulations indicates that the characteristic 30 keV hot electrons are mainly generated from backscattered laser plasma interactions rather than from hohlraum hydrodynamics.

  15. DISCREPANT HARDENING OBSERVED IN COSMIC-RAY ELEMENTAL SPECTRA

    SciTech Connect

    Ahn, H. S.; Ganel, O.; Han, J. H.; Kim, K. C.; Lee, M. H.; Lutz, L.; Malinin, A.; Allison, P.; Beatty, J. J.; Bagliesi, M. G.; Bigongiari, G.; Maestro, P.; Marrocchesi, P. S.; Childers, J. T.; DuVernois, M. A.; Conklin, N. B.; Coutu, S.; Mognet, S. I.; Jeon, J. A.; Minnick, S.

    2010-05-01

    The balloon-borne Cosmic Ray Energetics And Mass experiment launched five times from Antarctica has achieved a cumulative flight duration of about 156 days above 99.5% of the atmosphere. The instrument is configured with complementary and redundant particle detectors designed to extend direct measurements of cosmic-ray composition to the highest energies practical with balloon flights. All elements from protons to iron nuclei are separated with excellent charge resolution. Here, we report results from the first two flights of {approx}70 days, which indicate hardening of the elemental spectra above {approx}200 GeV/nucleon and a spectral difference between the two most abundant species, protons and helium nuclei. These results challenge the view that cosmic-ray spectra are simple power laws below the so-called knee at {approx}10{sup 15} eV. This discrepant hardening may result from a relatively nearby source, or it could represent spectral concavity caused by interactions of cosmic rays with the accelerating shock. Other possible explanations should also be investigated.

  16. Measuring x-ray spectra of flash radiographic sources

    NASA Astrophysics Data System (ADS)

    Gehring, Amanda E.; Espy, Michelle A.; Haines, Todd J.; Mendez, Jacob; Moir, David C.; Sedillo, Robert; Shurter, Roger P.; Volegov, Petr; Webb, Timothy J.

    2015-08-01

    A Compton spectrometer has been re-commissioned for measurements of flash radiographic sources. The determination of the energy spectrum of these sources is difficult due to the high count rates and short nature of the pulses (~50 ns). The spectrometer is a 300 kg neodymium-iron magnet which measures spectra in the <1 MeV to 20 MeV energy range. Incoming x-rays are collimated into a narrow beam incident on a converter foil. The ejected Compton electrons are collimated so that the forward-directed electrons enter the magnetic field region of the spectrometer. The position of the electrons at the magnet's focal plane is a function of their momentum, allowing the x-ray spectrum to be reconstructed. Recent measurements of flash sources are presented.

  17. Measuring X-ray Spectra of Flash Radiographic Sources

    NASA Astrophysics Data System (ADS)

    Gehring, Amanda; Espy, Michelle; Haines, Todd; Mendez, Jacob; Moir, David; Sedillo, Robert; Volegov, Petr; Webb, Tim

    2015-10-01

    A Compton spectrometer has been re-commissioned for measurements of flash radiographic sources. The determination of the energy spectrum provides information about the x-ray production mechanisms of these sources (ie. reaction history of plasmas, electron-target interactions) and benefits the analysis of images obtained at radiographic facilities. However, the measurements of the spectra are difficult due to the high count rates and short nature of the pulses (~ 50 ns). The spectrometer is a 300 kg neodymium-iron magnet which measures spectra in the <1 MeV to 20 MeV energy range. Incoming x-rays are collimated into a narrow beam incident on a converter foil. The ejected Compton electrons are collimated so that the forward-directed electrons enter the magnetic field region of the spectrometer. The position of the electrons at the focal plane of the magnet is a function of their momentum, allowing the x-ray spectrum to be reconstructed. Recent measurements of both flash and continuous radiographic sources will be presented.

  18. Modeling Spectra of the North and South Jovian X-ray Auroras

    SciTech Connect

    Kharchenko, Vasili A; Bhardwaj, Anil; Dalgarno, A.; Schultz, David Robert; Stancil, Phillip C.

    2008-08-01

    Spectra of Jovian X-ray auroras observed from the North and South poles with the Chandra X-ray telescope are analyzed and compared with predicted spectra of the charge-exchange mechanism. To determine the theoretical spectra of Jovian X-ray auroras, we model numerically the collisionally induced evolution of energy and charge distributions of Oq+ and Sq+ ions, precipitating into the Jovian atmosphere. Monte Carlo simulations of the energy and charge relaxation of the precipitating ions are carried out with updated cross-sections of the ion stripping, electron capture, and gas-ionization collisions. X-ray and Extreme Ultraviolet (EUV) spectra of cascading radiation induced by individual energetic sulfur and oxygen ions are calculated, and relative intensities of X-ray emission lines are determined. Synthetic spectra of X-ray and EUV photons are computed at different initial kinetic energies and compositions of ion-precipitating fluxes. Theoretical spectra with adjustable initial energies and relative fraction of sulfur and oxygen ions are shown to be in good agreement with the spectra of X rays detected from the South and North polar regions. The abundances and initial energies of the precipitating ions are inferred by comparing synthetic and observed X-ray spectra. Comparisons are performed independently for the North and South pole emissions. Abundances of the precipitating sulfur ions are found to be four to five times smaller than those of oxygen ions, and averaged ion energies are determined to lie between 1 and 2 MeV/amu. Slightly different ion flux compositions are found to describe the observed spectra of X-ray emission from the North and South poles.

  19. The x-ray absorption spectra of water and ice

    NASA Astrophysics Data System (ADS)

    Kong, Lingzhu; Wu, Xifan; Car, Roberto

    2012-02-01

    We calculate the x-ray absorption spectra of liquid water at STP, hexagonal ice and amorphous low- and high-density ice at T=269K, using the static Coulomb-hole and screened exchange self energy approach ootnotetextW. Chen, X. Wu and R. Car, PRL 105, 017802 (2008) . We take the nuclear quantum effects into account by averaging over the Feynman path-integral replicas. We find that quantum disorder is particularly important in liquid water where it substantially improves the structure ootnotetextJ. Morrone and R. Car, PRL 101, 017801 (2008) Compared to Ref. 2, we use an improved screening model that includes the approximate local field correction ootnotetextM. Hybertsen and S. G. Louie, PRB 37, 2733 (1988). The resulting spectra are in significantly better agreement with experiments than in previous calculations.

  20. Galactic cosmic ray abundances and spectra behind defined shielding

    NASA Technical Reports Server (NTRS)

    Heinrich, W.; Benton, E. V.; Wiegel, B.; Zens, R.; Rusch, G.

    1994-01-01

    Linear Energy Transfer (LET) spectra have been measured for lunar missions and for several near Earth orbits ranging from 28 deg to 83 deg inclination. In some of the experiments the flux of Galactic Cosmic Rays (GCR) was determined separately from contributions caused by interactions in the detector material. Results of these experiments are compared to model calculations. The general agreement justifies the use of the model to calculate GCR fluxes. The magnitude of variations caused by solar modulation, geomagnetic shielding, and shielding by matter determined from calculated LET spectra is generally in agreement with experimental data. However, more detailed investigations show that there are some weak points in modeling solar modulation and shielding by material. These points are discussed in more detail.

  1. Energy spectra of high energy atmospheric neutrinos

    NASA Technical Reports Server (NTRS)

    Mitsui, K.; Minorikawa, Y.

    1985-01-01

    Focusing on high energy neutrinos ( or = 1 TeV), a new calculation of atmospheric neutrino intensities was carried out taking into account EMC effects observed in P-A collisions by accelerator, recent measurement of primary cosmic ray spectrum and results of cosmic ray muon spectrum and charge ratio. Other features of the present calculation are (1) taking into account kinematics of three body decays of kaons and charm particles in diffusion equations and (2) taking into account energy dependence of kaon production.

  2. Gamma-ray spectra from neutron capture on /sup 87/Sr

    SciTech Connect

    Sullivan, R.E.; Becker, J.A.; Stelts, M.L.

    1981-07-01

    The gamma-ray spectrum following neutron capture on /sup 87/Sr was measured at 3 neutron energies: E/sub n/ = thermal, 2 keV, and 24 keV. Gamma rays were detected in a three-crystal Ge(Li)-NaI-NaI pair spectrometer. Gamma-ray intensities deduced from these spectra by spectral unfolding are presented.

  3. Performance of the Tibet hybrid experiment (YAC-II + Tibet-III + MD) to measure the energy spectra of the light primary cosmic rays at energies 50-10,000 TeV

    NASA Astrophysics Data System (ADS)

    Huang, J.; Zhai, L. M.; Chen, D.; Shibata, M.; Katayose, Y.; Zhang, Ying; Liu, J. S.; Chen, Xu; Hu, X. B.; Zhang, X. Y.; Jia, H. Y.; Danzengluobu; Ohnishi, M.; Takita, M.

    2015-06-01

    A new hybrid detector system has been constructed by the Tibet ASγ collaboration at Tibet, China, since 2014 to measure the chemical composition of cosmic rays around the knee in the wide energy range. They consist of an air-shower-core detector-grid (YAC-II) to detect high energy electromagnetic component, the Tibet air-shower array (Tibet-III) and a large underground water-Cherenkov muon-detector array (MD). We have carried out a detailed air-shower Monte Carlo (MC) simulation to study the performance of the hybrid detectors by using CORSIKA (version 6.204), which includes QGSJET01c and SIBYLL2.1 hadronic interaction models. Assumed primary cosmic ray models are based on helium poor, helium rich and Gaisser's fit compositions around the knee. All detector responses are calculated using Geant4 (version 9.5) according to the real detector configurations and the MC events are reconstructed by the same procedure as the experimental data analysis. The energy determination is made by lateral density fitting (LDF) method using modified NKG function and the separation of the light components (proton, helium) is made by means of the artificial neural network (ANN) method and the random forest (RF) method. The systematic errors of the spectra of proton and helium caused by each steps of the analysis procedure are investigated including the dependence of the MC data on the hadronic interaction models and the primary composition models, and the algorithms for the primary mass identification. The systematic errors of the flux to be obtained by the new experiment are summarized as less than 30% in total. Our results show that the new hybrid experiment is powerful enough to study the chemical composition of the cosmic rays, in particular, to obtain the light-component spectra of the primary cosmic rays in 50-10,000 TeV energy range overlapping to the direct observation data at low energy side and ground-based indirect observations at high energy side. It is possible in this

  4. Decomposition of Wavelength Dispersive X-Ray Spectra

    PubMed Central

    Rémond, Guy; Myklebust, Robert; Fialin, Michel; Nockolds, Clive; Phillips, Matthew; Roques-Carmes, Claude

    2002-01-01

    Line shapes of atomic lines and soft x-ray emission bands measured with a wavelength dispersive spectrometer (WDS) with the Electron Probe Micro Analyzer (EPMA) are reviewed. Least square fitting to pseudo-Voigt profiles of the digitally measured spectra are used to account for the presence of non-diagram features (high and low energy satellites) and instrumental induced distortions. The effect of line width and relative intensities on the quality of fits is illustrated. Spectral distortions resulting from the presence of absorption edges within the analyzed wavelength region are illustrated for the case of FeLα,β emission bands for pure Fe and iron oxides. For quantitative analysis, an analytical approach is presented where the measured soft x-ray emission bands are corrected for self absorption before extracting the intensities from the experimental data. PMID:27446750

  5. Simulation and Experimental Verification of X-Ray Spectra

    NASA Astrophysics Data System (ADS)

    Deresch, A.; Jaenisch, G.-R.; Bellon, C.; Warrikhoff, A.

    2010-02-01

    A model is discussed which describes the generation of X-rays in conventional tubes using tabulated Bremsstrahlung energy spectra depending on three variables: the target atomic number, the incident electron kinetic energy, and the fraction of energy radiated. The constructed model includes technical tube parameters like kilovoltage, target material and target angle to also account for self-absorption in the target, as well as radiographic parameters like filtering. Additionally a parameter-free description of the characteristic radiation is included in the model. With the help of the simulation tool the influence of parameters can be separately studied. The validity of the proposed model is shown by measurements. This research is supported by the German Federal Ministry of Economics and Technology under contract MNPQ transfer II D 5-30/06.

  6. SIMULATION AND EXPERIMENTAL VERIFICATION OF X-RAY SPECTRA

    SciTech Connect

    Deresch, A.; Jaenisch, G.-R.; Bellon, C.; Warrikhoff, A.

    2010-02-22

    A model is discussed which describes the generation of X-rays in conventional tubes using tabulated Bremsstrahlung energy spectra depending on three variables: the target atomic number, the incident electron kinetic energy, and the fraction of energy radiated. The constructed model includes technical tube parameters like kilovoltage, target material and target angle to also account for self-absorption in the target, as well as radiographic parameters like filtering. Additionally a parameter-free description of the characteristic radiation is included in the model. With the help of the simulation tool the influence of parameters can be separately studied. The validity of the proposed model is shown by measurements. This research is supported by the German Federal Ministry of Economics and Technology under contract MNPQ transfer II D 5-30/06.

  7. Spectra of protons and nuclei in the energy range of 1010 ÷ 1020 eV in the framework of Galactic cosmic ray origin

    NASA Astrophysics Data System (ADS)

    Volkov, Nikolay; Lagutin, Anatoly; Tyumentsev, Alexander; Raikin, Roman

    2015-08-01

    We consider the problem of the cosmic ray spectrum formation assuming that cosmic rays are produced by Galactic sources. The anomalous diffusion equation proposed in our recent papers is used to describe cosmic ray propagation in the interstellar medium. We show that in the framework of this approach and with generation spectrum exponent γ = 2.85 it is possible to reproduce locally observed basic features of cosmic rays in the energy region of 1010 ÷ 1020 eV: difference between spectral exponents of protons and other nuclei, mass composition variation, “knee” problem, flattening of the primary spectrum at E ≥ 1018 ÷ 1019 eV. The crucial model predictions for the mass composition behaviour in the ultra-high energy region are discussed.

  8. A Simulation Study on the Flash X-Ray Spectra Spatial Distribution

    NASA Astrophysics Data System (ADS)

    Xu, Xiufeng; Li, Shiping; Cao, Hongrui; Xiao, Rui; Chen, Nan; Zhang, Linwen; Yin, Zejie

    2013-11-01

    Accurate measurement of flash X-ray energy spectra plays an important role in high-energy flash radiography. In this paper, by virtue of Geant4 toolkit, we simulated the generation and transport of X-ray photons resulting from the interaction of a high-energy electron beam with a solid thin target. We obtained the flash X-ray energy spectral distribution in the plane perpendicular to the electron beam incident direction. Our results indicate that the flash X-ray spectrum is almost uniform in the azimuthal direction but is quite different in the radius direction. Specifically, as the radius increases, the incident X-ray dose decreases significantly. Our work paves a theoretical basis for selecting appropriate structures and layout of the spectrometer and facilitates the measurements of flash X-ray energy spectra.

  9. The energy spectra of solar flare electrons

    NASA Technical Reports Server (NTRS)

    Evenson, P. A.; Hovestadt, D.; Meyer, P.; Moses, D.

    1985-01-01

    A survey of 50 electron energy spectra from .1 to 100 MeV originating from solar flares was made by the combination of data from two spectrometers onboard the International Sun Earth Explorer-3 spacecraft. The observed spectral shapes of flare events can be divided into two classes through the criteria of fit to an acceleration model. This standard two step acceleration model, which fits the spectral shape of the first class of flares, involves an impulsive step that accelerates particles up to 100 keV and a second step that further accelerates these particles up to 100 MeV by a single shock. This fit fails for the second class of flares that can be characterized as having excessively hard spectra above 1 MeV relative to the predictions of the model. Correlations with soft X-ray and meter radio observations imply that the acceleration of the high energy particles in the second class of flares is dominated by the impulsive phase of the flares.

  10. [Methods of detector response function establishment in X-ray fluorescence spectra analysis].

    PubMed

    Li, Zhe; Tuo, Xian-Guo; Yang, Jian-Bo; Liu, Ming-Zhe; Cheng, Yi; Wang, Lei; Zhou, Jian-Bin

    2012-11-01

    During the measurement and analysis process of X-ray fluorescence spectra, it is very helpful to improve the analyze speed, accuracy and automaticity of X-ray fluorescence spectra analysis by establishing detector response function(DRF), which represents the shape of full energy peak and can provide former basic data for subsequent X-ray analysis technique. For the theory and model of semiconductor DRF in X-ray energy spectrum measurements, methods of three typical detector response function model establishment, key parameters of full energy peak standard deviation and Fano factor calculation, etc. are discussed, and meanwhile, the summarization and contrast of existing studies are shown in this paper. Finally, the suggestion for modeling methods of DRF in X-ray fluorescence spectra measurements is provided. PMID:23387190

  11. Mammography X-Ray Spectra Simulated with Monte Carlo

    SciTech Connect

    Vega-Carrillo, H. R.; Gonzalez, J. Ramirez; Manzanares-Acuna, E.; Hernandez-Davila, V. M.; Villasana, R. Hernandez; Mercado, G. A.

    2008-08-11

    Monte Carlo calculations have been carried out to obtain the x-ray spectra of various target-filter combinations for a mammography unit. Mammography is widely used to diagnose breast cancer. Further to Mo target with Mo filter combination, Rh/Rh, Mo/Rh, Mo/Al, Rh/Al, and W/Rh are also utilized. In this work Monte Carlo calculations, using MCNP 4C code, were carried out to estimate the x-ray spectra produced when a beam of 28 keV electrons did collide with Mo, Rh and W targets. Resulting x-ray spectra show characteristic x-rays and continuous bremsstrahlung. Spectra were also calculated including filters.

  12. Preliminary spectra of the primary cosmic ray nuclei from the first year of the NUCLEON experiment exposure time

    NASA Astrophysics Data System (ADS)

    Panov, Alexander

    2016-07-01

    The NUCLEON cosmic ray observatory is designed to measure high energy cosmic ray composition and energy distribution. Methods of identification of charge and energy measurement for primary cosmic ray nuclei are considered. C, O, Ne, Mg, Si, Fe energy spectra are presented and discussed. The results are obtained from the first year of the planned exposure time.

  13. X-Ray Absorption Spectra of Uranium by Synchrotron Radiation

    NASA Astrophysics Data System (ADS)

    Adachi, Hirohiko; Fujima, Kazumi; Taniguchi, Kazuo; Miyake, Chie; Imoto, Shosuke

    1981-08-01

    The X-ray absorption spectra of U, UO2 and UCl4 near the U OIV and OV thresholds have been measured by use of synchrotron radiation. The absorption peaks at about 100 eV and 110 eV are observed for all of these materials. However, the detailed structure of the spectra depend on the chemical state.

  14. Measuring x-ray spectra of flash radiographic sources

    SciTech Connect

    Gehring, Amanda Elizabeth; Espy, Michelle A.; Haines, Todd Joseph; Mendez, Jacob; Moir, David C.; Sedillo, Robert; Shurter, Roger P.; Volegov, Petr Lvovich; Webb, Timothy J

    2015-11-02

    The x-ray spectra of flash radiographic sources is difficult to measure. The sources measured were Radiographic Integrated Test Stand-6 (370 rad at 1 m; 50 ns pulse) and Dual Axis Radiographic Hydrodynamic Test Facility (DARHT) (550 rad at 1 m; 50 ns pulse). Features of the Compton spectrometer are described, and spectra are shown. Additional slides present data on instrumental calibration.

  15. Energy rays tracking device

    SciTech Connect

    Monk, R.J.

    1981-05-12

    An energy rays tracking device includes a receiver for fixing a position relative to the direction of maximum energy rays, a prime mover for maintaining the alignment of the receiver and an energy rays user, an energy rays tracker for controlling the power to the prime mover in response to the receiver, a timed tracker for controlling the prime mover when the energy rays tracker is not functioning due to energy rays being too diffused, an energy sensitive element for detecting the presence or absence of energy rays, and a power controller responsive to the energy sensitive element for repositioning the receiver and the energy rays user for the following period of tracking is disclosed. The receiver includes an enclosure which only allows a selected pattern of direct rays to penetrate into the enclosure. A razor sharp edge at the opening of the enclosure maintains the outermost direct energy rays undiffused. A differential sensor sensitive to direct energy rays is installed inside the enclosure for determining the direction of the direct energy rays. In an application for tracking the sun, the time tracker uses a piecewise linear method of tracking. In the return cycle during the night, the return is interspersed with a wash cycle for cleaning the energy rays user.

  16. Spectra of cosmic x-ray sources

    SciTech Connect

    Holt, S.S.; Mccray, R.

    1982-02-01

    X-ray measurements provide the most direct probes of astrophysical environments with temperatures exceeding one million K. Progress in experimental research utilizing dispersive techniques (e.g., Bragg and grating spectroscopy) is considerably slower than that in areas utilizing photometric techniques, because of the relative inefficiency of the former for the weak X-ray signals from celestial sources. As a result, the term spectroscopy as applied to X-ray astronomy has traditionally satisfied a much less restrictive definition (in terms of resolving power) than it has in other wavebands. Until quite recently, resolving powers of order unity were perfectly respectable, and still provide (in most cases) the most useful spectroscopic data. In the broadest sense, X-ray photometric measurements are spectroscopic, insofar as they represent samples of the overall electromagnetic continua of celestial objects.

  17. Spectra of cosmic X-ray sources

    NASA Technical Reports Server (NTRS)

    Holt, S. S.; Mccray, R.

    1982-01-01

    X-ray measurements provide the most direct probes of astrophysical environments with temperatures exceeding one million K. Progress in experimental research utilizing dispersive techniques (e.g., Bragg and grating spectroscopy) is considerably slower than that in areas utilizing photometric techniques, because of the relative inefficiency of the former for the weak X-ray signals from celestial sources. As a result, the term "spectroscopy" as applied to X-ray astronomy has traditionally satisfied a much less restrictive definition (in terms of resolving power) than it has in other wavebands. Until quite recently, resolving powers of order unity were perfectly respectable, and still provide (in most cases) the most useful spectroscopic data. In the broadest sense, X-ray photometric measurements are spectroscopic, insofar as they represent samples of the overall electromagnetic continua of celestial objects.

  18. Soft X-Ray Spectra of AGN Discovered Via Their Hard X-Ray

    NASA Technical Reports Server (NTRS)

    Schwartz, Daniel

    1998-01-01

    This final report is a study of the Active Galactic Nuclei (AGN). Investigation of the soft x-ray spectra of AGN were performed by using their hard x-ray emission. ROSAT observations of AGN was also performed, which allowed for the study of these x-ray spectra and the structures of 7 clusters of galaxies.

  19. Covariance Analysis of Gamma Ray Spectra

    SciTech Connect

    Trainham, R.; Tinsley, J.

    2013-01-01

    The covariance method exploits fluctuations in signals to recover information encoded in correlations which are usually lost when signal averaging occurs. In nuclear spectroscopy it can be regarded as a generalization of the coincidence technique. The method can be used to extract signal from uncorrelated noise, to separate overlapping spectral peaks, to identify escape peaks, to reconstruct spectra from Compton continua, and to generate secondary spectral fingerprints. We discuss a few statistical considerations of the covariance method and present experimental examples of its use in gamma spectroscopy.

  20. Covariance analysis of gamma ray spectra

    SciTech Connect

    Trainham, R.; Tinsley, J.

    2013-01-15

    The covariance method exploits fluctuations in signals to recover information encoded in correlations which are usually lost when signal averaging occurs. In nuclear spectroscopy it can be regarded as a generalization of the coincidence technique. The method can be used to extract signal from uncorrelated noise, to separate overlapping spectral peaks, to identify escape peaks, to reconstruct spectra from Compton continua, and to generate secondary spectral fingerprints. We discuss a few statistical considerations of the covariance method and present experimental examples of its use in gamma spectroscopy.

  1. Energy spectra and LET spectra of protons behind shielding

    NASA Astrophysics Data System (ADS)

    Katz, Sari; Barak, Joseph

    2014-08-01

    With the advent of devices sensitive to SEU due to direct ionization by protons, it became important to know the flux and energies of protons behind aluminum shielding or within satellites. We present new analytically derived expressions for the energy distribution of incident protons, after passing the shielding, and of secondary protons emitted within the shielding. The results are compared with those of the MULASSIS code. In some cases, like a satellite in a GCR orbit, the contribution of the secondary protons to SEU might be the dominant one. Proton energy-distributions behind shielding are proportional, at low energy values, to inverse proton-LET in aluminum. Their calculated LET-spectra in silicon can be used for evaluating SEU-rate in space. The analytic expressions presented here can be useful in calculating the influence of shielding on other incident ions and secondary ions.

  2. Cometary Spectra Induced by Scattering and Florescence of Hard Solar X-Rays

    NASA Astrophysics Data System (ADS)

    Snios, B. T.; Lewkow, N.; Kharchenko, V. A.

    2013-12-01

    Accurate calculations of X-ray emissions from cometary atmospheres due to Scattering and Florescence (SF) of solar X-rays are carried out over the photon energy range 0.4-3.0 keV. Computations of the X-ray SF spectra are performed for different distributions of the cometary neutral gas, dust, and ice grains, including nano-size particles. The SF spectra of cometary X-rays above 1 keV are determined for different solar conditions, incorporating X-ray spectra induced by solar flares. Theoretical X-ray SF spectra are compared with the results of recent observations of several comets with the Chandra X-ray Observatory [1]. A correlation between the spectral shapes of the observed cometary and solar X-ray emissions above 1 keV has been found and analyzed. The strong similarity between the cometary SF spectra and the X-ray spectra observed from the Jupiter atmosphere with XMM-Newton [2] is analyzed in detail. Upper limits on the density of cometary nano-particles are determined through comparison of the theoretical and observational data. The X-ray SF spectra with photon energies above 1 keV are predicted for a model history of solar activity and compositions of cometary gas, dust, and ice particles, which could reflect evolutionary transformations of cometary environment. [1] Ewing, I., Christina, D. J., & Bodewits, D. et al. 2013, ApJ, 763, 66 [2] Branduardi-Raymont, G., Bhardwaj, A., & Elsner, R. F. et al. 2007, Planet. Space Sci., 55, 1126

  3. Cosmic-ray Spectra at Spherical Termination Shocks

    NASA Technical Reports Server (NTRS)

    Florinski, V.; Jokiph, J. R.

    2003-01-01

    We discuss the nature of the steady-state spectra of particles accelerated at stationary spherical shocks, such as the solar wind termination shock. In addition to the two well-know spectral regions characterized by a power-law momentum dependence and a high-energy cutoff, a new region can be identified. This consists of an enhancement of the cosmic-ray intensity (or a " bump") just below the cutoff. Similar features have been seen previously in multidimensional models and cosmic-ray modified shocks, where they were explained by acceleration and drift in the latitudinal direction along the shock face and decreasing effective shock compression ratio, respectively. We show that a similar bump may be obtained in a purely spherically symmetric geometry with no drifts, and that this effect may also have contributed to the previous results. We attribute this effect to increased shock acceleration efficiency at certain energies. We also demonstrate that a one-dimensional planar shock with a reflecting wall upstream can give a similar effect. We conclude that care is necessary in interpreting observed bumps in any given situation.

  4. A COMPARISON OF GADRAS SIMULATED AND MEASURED GAMMA RAY SPECTRA

    SciTech Connect

    Jeffcoat, R.; Salaymeh, S.

    2010-06-28

    Gamma-ray radiation detection systems are continuously being developed and improved for detecting the presence of radioactive material and for identifying isotopes present. Gamma-ray spectra, from many different isotopes and in different types and thicknesses of attenuation material and matrixes, are needed to evaluate the performance of these devices. Recently, a test and evaluation exercise was performed by the Savannah River National Laboratory that required a large number of gamma-ray spectra. Simulated spectra were used for a major portion of the testing in order to provide a pool of data large enough for the results to be statistically significant. The test data set was comprised of two types of data, measured and simulated. The measured data were acquired with a hand-held Radioisotope Identification Device (RIID) and simulated spectra were created using Gamma Detector Response and Analysis Software (GADRAS, Mitchell and Mattingly, Sandia National Laboratory). GADRAS uses a one-dimensional discrete ordinate calculation to simulate gamma-ray spectra. The measured and simulated spectra have been analyzed and compared. This paper will discuss the results of the comparison and offer explanations for spectral differences.

  5. Effective absorbing column density in the gamma-ray burst afterglow X-ray spectra

    NASA Astrophysics Data System (ADS)

    Campana, S.; Bernardini, M. G.; Braito, V.; Cusumano, G.; D'Avanzo, P.; D'Elia, V.; Ghirlanda, G.; Ghisellini, G.; Melandri, A.; Salvaterra, R.; Tagliaferri, G.; Vergani, S. D.

    2014-07-01

    We investigate the scaling relation between the observed amount of absorption in the X-ray spectra of gamma-ray burst afterglows and the absorber redshift. Through dedicated numerical simulations of an ideal instrument, we establish that this dependence has a power-law shape with index 2.4. However, for real instruments, this value depends on their low-energy cut-off, spectral resolution and on the detector spectral response in general. We thus provide appropriate scaling laws for specific instruments. Finally, we discuss the possibility to measure the absorber redshift from X-ray data alone. We find that 105-106 counts in the 0.3-10 keV band are needed to constrain the redshift with 10 per cent accuracy. As a test case, we discuss the XMM-Newton observation of GRB 090618 at z = 0.54. We are able to recover the correct redshift of this burst with the expected accuracy.

  6. Summarizing X-ray Stellar Spectra

    NASA Astrophysics Data System (ADS)

    Lee, Hyunsook; Kashyap, V.; XAtlas Collaboration

    2008-05-01

    XAtlas is a spectrum database made with the High Resolution Transmission Grating on the Chandra X-ray Observatory, after painstaking detailed emission measure analysis to extract quantified information. Here, we explore the possibility of summarizing this spectral information into relatively convenient measurable quantities via dimension reduction methods. Principal component analysis, simple component analysis, projection pursuit, independent component analysis, and parallel coordinates are employed to enhance any patterned structures embedded in the high dimensional space. We discuss pros and cons of each dimension reduction method as a part of developing clustering algorithms for XAtlas. The biggest challenge from analyzing XAtlas was handling missing values that pertain astrophysical importance. This research was supported by NASA/AISRP grant NNG06GF17G and NASA contract NAS8-39073.

  7. X-ray-binary spectra in the lamp post model

    NASA Astrophysics Data System (ADS)

    Vincent, F. H.; Różańska, A.; Zdziarski, A. A.; Madej, J.

    2016-05-01

    Context. The high-energy radiation from black-hole binaries may be due to the reprocessing of a lamp located on the black hole rotation axis and emitting X-rays. The observed spectrum is made of three major components: the direct spectrum traveling from the lamp directly to the observer; the thermal bump at the equilibrium temperature of the accretion disk heated by the lamp; and the reflected spectrum essentially made of the Compton hump and the iron-line complex. Aims: We aim to accurately compute the complete reprocessed spectrum (thermal bump + reflected) of black-hole binaries over the entire X-ray band. We also determine the strength of the direct component. Our choice of parameters is adapted to a source showing an important thermal component. We are particularly interested in investigating the possibility to use the iron-line complex as a probe to constrain the black hole spin. Methods: We computed in full general relativity the illumination of a thin accretion disk by a fixed X-ray lamp along the rotation axis. We used the ATM21 radiative transfer code to compute the local, energy-dependent spectrum emitted along the disk as a function of radius, emission angle and black hole spin. We then ray traced this local spectrum to determine the final reprocessed spectrum as received by a distant observer. We consider two extreme values of the black hole spin (a = 0 and a = 0.98) and discuss the dependence of the local and ray-traced spectra on the emission angle and black hole spin. Results: We show the importance of the angle dependence of the total disk specific intensity spectrum emitted by the illuminated atmosphere when the thermal disk emission is fully taken into account. The disk flux, together with the X-ray flux from the lamp, determines the temperature and ionization structure of the atmosphere. High black hole spin implies high temperature in the inner disk regions, therefore, the emitted thermal disk spectrum fully covers the iron-line complex. As a

  8. Model for Cumulative Solar Heavy Ion Energy and LET Spectra

    NASA Technical Reports Server (NTRS)

    Xapsos, Mike; Barth, Janet; Stauffer, Craig; Jordan, Tom; Mewaldt, Richard

    2007-01-01

    A probabilistic model of cumulative solar heavy ion energy and lineary energy transfer (LET) spectra is developed for spacecraft design applications. Spectra are given as a function of confidence level, mission time period during solar maximum and shielding thickness. It is shown that long-term solar heavy ion fluxes exceed galactic cosmic ray fluxes during solar maximum for shielding levels of interest. Cumulative solar heavy ion fluences should therefore be accounted for in single event effects rate calculations and in the planning of space missions.

  9. Cosmic Ray Spectra in Nambu-Goldstone Dark Matter Models

    SciTech Connect

    Ibe, Masahiro; Murayama, Hitoshi; Shirai, Satoshi; Yanagida, Tsutomu T.; ,

    2010-06-11

    We discuss the cosmic ray spectra in annihilating/decaying Nambu-Goldstone dark matter models. The recent observed positron/electron excesses at PAMELA and Fermi experiments are well fitted by the dark matter with a mass of 3TeV for the annihilating model, while with a mass of 6TeV for the decaying model. We also show that the Nambu-Goldstone dark matter models predict a distinctive gamma-ray spectrum in a certain parameter space.

  10. Energy spectra in microbubbly turbulence

    NASA Astrophysics Data System (ADS)

    van den Berg, Thomas H.; Luther, Stefan; Lohse, Detlef

    2006-03-01

    Microbubbles (R0=100μm) are injected in fully developed turbulence (Reλ=200) up to a volume concentration of 0.3%. An enhancement of the energy on small scales and a reduction on the large scales is observed, confirming theoretical prediction by I. Mazzitelli, D. Lohse, and F. Toschi [Phys. Fluids 15, L5 (2003)]. The result is a (nonuniversal) less steep slope than -5/3 in the power spectrum.

  11. Low-Energy Cosmic Rays

    NASA Astrophysics Data System (ADS)

    Wiedenbeck, M. E.; ACE/CRIS Collaboration

    2002-12-01

    Cosmic rays with energies below about 10 GeV/nucleon have been measured with high precision as a result of experiments on the HEAO, Ulysses, and ACE spacecrafts. The observations provide energy spectra, elemental abundances, and isotopic composition for elements up through Z=30. They include both stable and radioactive nuclides that are synthesized in stars or are produced by nuclear fragmentation during diffusion at high energies through interstellar medium. From these data one obtains a rather detailed picture of the origin of low-energy cosmic rays. For refractory species, the cosmic-ray source composition closely resembles that of the Sun, suggesting that cosmic rays are accelerated from a well-mixed sample of interstellar matter. A chemical fractionation process has depleted the abundances of volatile elements relative to refractories. Using various radioactive clock isotopes it has been shown that particle acceleration occurs at least 105 years after supernova nucleosynthesis and that the accelerated particles diffuse in the Galaxy for approximately 15 Myr after acceleration. Energy spectra and secondary-to-primary ratios are reasonably well accounted for by models in which particles gain the bulk of their energy in a single encounter with a strong shock. Among the large number of species that have been measured, 22Ne stands out as the only nuclide with an abundance that is clearly much different than solar. To test models proposed to account for this anomaly, the data are being analyzed for predicted smaller effects on abundances of other nuclides. In addition to providing a detailed understanding of the origin and acceleration of low-energy cosmic rays, these data are providing constraints on the chemical evolution of interstellar matter. This work was supported by NASA at Caltech (under grant NAG5-6912), JPL, NASA/GSFC, and Washington U.

  12. Preliminary cosmic ray proton and helium spectra from the first year of the NUCLEON experiment exposure time

    NASA Astrophysics Data System (ADS)

    Kovalev, Igor

    2016-07-01

    The NUCLEON cosmic ray observatory is designed to measure high energy cosmic ray composition and energy distribution. Methods of identification of charge and energy measurement are presented. Preliminary proton and helium spectra and proton to helium ratio are presented. The results are obtained from the first year of the planned exposure time.

  13. Energy spectra in elasto-inertial turbulence

    NASA Astrophysics Data System (ADS)

    Valente, P. C.; da Silva, C. B.; Pinho, F. T.

    2016-07-01

    Direct numerical simulations of statistically steady homogeneous isotropic turbulence in viscoelastic fluids described by the FENE-P model are presented. Emphasis is given to large polymer relaxation times compared to the eddy turnover time, which is a regime recently termed elasto-inertial turbulence. In this regime the polymers are ineffective in dissipating kinetic energy but they play a lead role in transferring kinetic energy to the small solvent scales which turns out to be concomitant with the depletion of the usual non-linear energy cascade. However, we show that the non-linear interactions are still highly active, but they lead to no net downscale energy transfer because the forward and reversed energy cascades are nearly balanced. Finally, we show that the tendency for a steeper elasto-inertial power-law spectra is reversed for large polymer relaxation times and the spectra tend towards the usual k-5/3 functional form.

  14. Experimental simulation of A-bomb gamma ray spectra: revisited.

    PubMed

    Pattison, John E; Payne, Lester C; Hugtenburg, Richard P; Beddoe, Alun H; Charles, Monty W

    2004-01-01

    It has been reported recently that the A-bomb gamma ray spectra received by the colon of the average Japanese survivor of Hiroshima and Nagasaki may be experimentally simulated using a hospital-based Philips SL15 linear accelerator. The simulated A-bomb gamma radiation may be used in radiobiology experiments to determine, amongst other things, the biological effectiveness of the A-bomb gamma radiation. However, in that study, the electron beams from the linear accelerator were poorly defined and photon contamination was ignored. In the study reported here, a Varian Clinac 2100C linear accelerator has been used for the same purpose but with photon contamination included in better defined output electron beams. It is found that the A-bomb gamma radiation can still be matched to an acceptable degree (<10%). The cause of the slightly poorer fit was due mainly to the different ranges of energies available from the linear accelerators used. The absorbed dose received by model breasts was also estimated in this study for the same situations as in the previous study. The ratio of the breast to colon doses was found to be only (3.9 +/- 4.0)% low compared with the expected values of 1.17 and 1.16 for Hiroshima and Nagasaki, respectively. These results provide further confirmation of the acceptability of the simple cylindrically symmetrical body models employed in these studies to represent the average Japanese survivor. PMID:15254320

  15. Features in the spectra of gamma-ray bursts

    NASA Technical Reports Server (NTRS)

    Stanek, Krzysztof Z.; Paczynski, Bohdan; Goodman, Jeremy

    1993-01-01

    Gravitational lensing of cosmological gamma-ray bursts by objects in the mass range about 10 exp 17 to 10 exp 20 g (femtolensing) may introduce complicated interference patterns that might be interpreted as absorption or emission lines in the bursts' spectra. This phenomenon, if detected, may be used as a unique probe of dark matter in the universe. The BATSE spectral data should allow one to detect such spectral features or to put significant upper limits on the cosmic density of a dark matter component that may be in the femtolensing range. Software to generate theoretical spectra has been developed, and it is accessible over the computer network with anonymous ftp.

  16. An optimal target-filter system for electron beam generated x-ray spectra

    SciTech Connect

    Hsu, Hsiao-Hua; Vasilik, D.G.; Chen, J.

    1994-04-01

    An electron beam generated x-ray spectrum consists of characteristic x rays of the target and continuous bremsstrahlung. The percentage of characteristic x rays over the entire energy spectrum depends on the beam energy and the filter thickness. To determine the optimal electron beam energy and filter thickness, one can either conduct many experimental measurements, or perform a series of Monte Carlo simulations. Monte Carlo simulations are shown to be an efficient tool for determining the optimal target-filter system for electron beam generated x-ray spectra. Three of the most commonly used low-energy x-ray metal targets (Cu, Zn and Mo) are chosen for this study to illustrate the power of Monte Carlo simulations.

  17. Reestimation of the production spectra of cosmic ray secondary positrons and electrons in the ISM

    NASA Technical Reports Server (NTRS)

    Wong, C. M.; Ng, L. K.

    1985-01-01

    A detailed calculation of the production spectra of charged hadrons produced by interactions of cosmic rays in the interstellar medium is presented along with a thorough treatment of pion and muon decays. Newly parameterized inclusive cross sections of hadrons were used and exact kinematic limitations were taken into account. Single parametrized expressions for the production spectra of both secondary positrons and electrons in the energy range .1 to 100 GeV are presented. The results are compared with other authors' predictions. Equilibrium spectra using various models are also presented.

  18. Spectra of X-ray and Gamma-ray Bursts Produced by Stepping Lightning Leaders

    NASA Astrophysics Data System (ADS)

    Celestin, Sebastien; Xu, Wei; Pasko, Victor

    2013-04-01

    Terrestrial gamma-ray flashes (TGFs) are bursts of high-energy photons originating from the Earth's atmosphere in association with thunderstorm activity. TGFs were serendipitously discovered by BATSE detector aboard the Compton Gamma-Ray Observatory originally launched to perform observations of celestial gamma-ray sources [Fishman et al., Science, 264, 1313, 1994]. These events have also been detected by the RHESSI satellite [Smith et al., Science, 307, 1085, 2005], the AGILE satellite [Marisaldi et al., JGR, 115, A00E13, 2010], and the Fermi Gamma-ray Space Telescope [Briggs et al., JGR, 115, A07323, 2010]. Moreover, measurements have correlated TGFs with initial development stages of normal polarity intra-cloud lightning that transports negative charge upward (+IC) [e.g, Lu et al., JGR, 116, A03316, 2011]. Photon spectra corresponding to well-established model of relativistic runaway electron avalanches (RREAs) usually provide a very good agreement with satellite observations [Dwyer and Smith, GRL, 32, L22804, 2005]. However, it has been suggested that high-potential +IC lightning leaders could produce a sufficient number of energetic electrons to explain TGFs [Celestin and Pasko, JGR, 116, A03315, 2011] and Xu et al. [GRL, 39, L08801, 2012] have shown that this mechanism could explain the TGF spectrum for lightning potentials higher than 100 MV. In addition to TGFs, X-ray bursts are produced by negative lightning leaders in association with stepping processes and are observed from the ground [Dwyer et al., GRL, 32, L01803, 2005]. However, the energy spectrum of X-ray bursts from lightning is still poorly known, mainly due to the low fluence detected from the ground. In this work, we use Monte Carlo models to study the acceleration of runaway electrons in the electric field produced around lightning leader tip and the associated bremsstrahlung photon spectra observed by low-orbit satellites in the case of high potential +IC discharges and from the ground in the

  19. Detector-Response Correction of Two-Dimensional γ -Ray Spectra from Neutron Capture

    DOE PAGESBeta

    Rusev, G.; Jandel, M.; Arnold, C. W.; Bredeweg, T. A.; Couture, A.; Mosby, S. M.; Ullmann, J. L.

    2015-05-28

    The neutron-capture reaction produces a large variety of γ-ray cascades with different γ-ray multiplicities. A measured spectral distribution of these cascades for each γ-ray multiplicity is of importance to applications and studies of γ-ray statistical properties. The DANCE array, a 4π ball of 160 BaF2 detectors, is an ideal tool for measurement of neutron-capture γ-rays. The high granularity of DANCE enables measurements of high-multiplicity γ-ray cascades. The measured two-dimensional spectra (γ-ray energy, γ-ray multiplicity) have to be corrected for the DANCE detector response in order to compare them with predictions of the statistical model or use them in applications. Themore » detector-response correction problem becomes more difficult for a 4π detection system than for a single detector. A trial and error approach and an iterative decomposition of γ-ray multiplets, have been successfully applied to the detector-response correction. Applications of the decomposition methods are discussed for two-dimensional γ-ray spectra measured at DANCE from γ-ray sources and from the 10B(n, γ) and 113Cd(n, γ) reactions.« less

  20. Detector-Response Correction of Two-Dimensional γ-Ray Spectra from Neutron Capture

    NASA Astrophysics Data System (ADS)

    Rusev, G.; Jandel, M.; Arnold, C. W.; Bredeweg, T. A.; Couture, A.; Mosby, S. M.; Ullmann, J. L.

    2015-05-01

    The neutron-capture reaction produces a large variety of γ-ray cascades with different γ-ray multiplicities. A measured spectral distribution of these cascades for each γ-ray multiplicity is of importance to applications and studies of γ-ray statistical properties. The DANCE array, a 4π ball of 160 BaF2 detectors, is an ideal tool for measurement of neutron-capture γ-rays. The high granularity of DANCE enables measurements of high-multiplicity γ-ray cascades. The measured two-dimensional spectra (γ-ray energy, γ-ray multiplicity) have to be corrected for the DANCE detector response in order to compare them with predictions of the statistical model or use them in applications. The detector-response correction problem becomes more difficult for a 4π detection system than for a single detector. A trial and error approach and an iterative decomposition of γ-ray multiplets, have been successfully applied to the detector-response correction. Applications of the decomposition methods are discussed for two-dimensional γ-ray spectra measured at DANCE from γ-ray sources and from the 10B(n, γ) and 113Cd(n, γ) reactions.

  1. Monte carlo simulation of x-ray spectra in diagnostic radiology and mammography using MCNP4C.

    PubMed

    Ay, M R; Shahriari, M; Sarkar, S; Adib, M; Zaidi, H

    2004-11-01

    The general purpose Monte Carlo N-particle radiation transport computer code (MCNP4C) was used for the simulation of x-ray spectra in diagnostic radiology and mammography. The electrons were transported until they slow down and stop in the target. Both bremsstrahlung and characteristic x-ray production were considered in this work. We focus on the simulation of various target/filter combinations to investigate the effect of tube voltage, target material and filter thickness on x-ray spectra in the diagnostic radiology and mammography energy ranges. The simulated x-ray spectra were compared with experimental measurements and spectra calculated by IPEM report number 78. In addition, the anode heel effect and off-axis x-ray spectra were assessed for different anode angles and target materials and the results were compared with EGS4-based Monte Carlo simulations and measured data. Quantitative evaluation of the differences between our Monte Carlo simulated and comparison spectra was performed using student's t-test statistical analysis. Generally, there is a good agreement between the simulated x-ray and comparison spectra, although there are systematic differences between the simulated and reference spectra especially in the K-characteristic x-rays intensity. Nevertheless, no statistically significant differences have been observed between IPEM spectra and the simulated spectra. It has been shown that the difference between MCNP simulated spectra and IPEM spectra in the low energy range is the result of the overestimation of characteristic photons following the normalization procedure. The transmission curves produced by MCNP4C have good agreement with the IPEM report especially for tube voltages of 50 kV and 80 kV. The systematic discrepancy for higher tube voltages is the result of systematic differences between the corresponding spectra. PMID:15584526

  2. Communication: On the difficulty of reproducibly measuring PbCl2 X-ray absorption spectra

    NASA Astrophysics Data System (ADS)

    Schwartz, Craig P.; Prendergast, David

    2015-09-01

    Previous measurements of the X-ray absorption spectra of PbCl2 at the chlorine K-edge have shown significant variation between different studies. Herein, using first principles simulations of X-ray absorption spectroscopy, we show that the observed spectral variations are due to the generation of Cl2 gas and depletion of chlorine from PbCl2, consistent with what is observed during ultraviolet absorption for the same compound. We note that Cl2 gas generation can also be initiated using higher resonant X-ray energies, including Pb X-ray absorption edges. While this casts doubt on previous interpretations of certain measurements, it does indicate a means of generating chlorine gas during in situ experiments by passing high energy x-rays through a hard x-ray transparent medium and onto PbCl2.

  3. Communication: On the difficulty of reproducibly measuring PbCl2 X-ray absorption spectra.

    PubMed

    Schwartz, Craig P; Prendergast, David

    2015-09-21

    Previous measurements of the X-ray absorption spectra of PbCl2 at the chlorine K-edge have shown significant variation between different studies. Herein, using first principles simulations of X-ray absorption spectroscopy, we show that the observed spectral variations are due to the generation of Cl2 gas and depletion of chlorine from PbCl2, consistent with what is observed during ultraviolet absorption for the same compound. We note that Cl2 gas generation can also be initiated using higher resonant X-ray energies, including Pb X-ray absorption edges. While this casts doubt on previous interpretations of certain measurements, it does indicate a means of generating chlorine gas during in situ experiments by passing high energy x-rays through a hard x-ray transparent medium and onto PbCl2. PMID:26395677

  4. Interatomic scattering in energy dependent photoelectron spectra of Ar clusters

    NASA Astrophysics Data System (ADS)

    Patanen, M.; Benkoula, S.; Nicolas, C.; Goel, A.; Antonsson, E.; Neville, J. J.; Miron, C.

    2015-09-01

    Soft X-ray photoelectron spectra of Ar 2p levels of atomic argon and argon clusters are recorded over an extended range of photon energies. The Ar 2p intensity ratios between atomic argon and clusters' surface and bulk components reveal oscillations similar to photoelectron extended X-ray absorption fine structure signal (PEXAFS). We demonstrate here that this technique allows us to analyze separately the PEXAFS signals from surface and bulk sites of free-standing, neutral clusters, revealing a bond contraction at the surface.

  5. Interatomic scattering in energy dependent photoelectron spectra of Ar clusters

    SciTech Connect

    Patanen, M.; Benkoula, S.; Nicolas, C.; Goel, A.; Antonsson, E.; Neville, J. J.; Miron, C.

    2015-09-28

    Soft X-ray photoelectron spectra of Ar 2p levels of atomic argon and argon clusters are recorded over an extended range of photon energies. The Ar 2p intensity ratios between atomic argon and clusters’ surface and bulk components reveal oscillations similar to photoelectron extended X-ray absorption fine structure signal (PEXAFS). We demonstrate here that this technique allows us to analyze separately the PEXAFS signals from surface and bulk sites of free-standing, neutral clusters, revealing a bond contraction at the surface.

  6. Prompt Fission Neutron Energy Spectra Induced by Fast Neutrons

    NASA Astrophysics Data System (ADS)

    Staples, Parrish Alan

    Prompt fission neutron energy spectra for ^{235}U and ^{239 }Pu have been measured for fission neutron energies greater than the energy of the incident neutrons inducing fission. The measurements were undertaken to investigate the shape dependence of the fission neutron spectra upon both the incident neutron energy and the mass of the nucleus undergoing fission. Measurements were made for both nuclides at the following incident neutron energies; 0.50 MeV, 1.50 MeV, 2.50 MeV and 3.50 MeV. The data are presented either as relative yields or as ratios of a measured spectrum to the ^{235}U spectrum at 0.50 MeV. Incident neutrons were produced by the ^7Li(p,n)^7Be reaction using a pulsed, bunched proton beam from the 5.5 MV Van de Graaff accelerator at the University of Massachusetts Lowell Pinanski Energy Center. The neutrons were detected by a thin liquid scintillator with good time resolution capabilities; time-of-flight techniques were used for neutron energy determination; in addition pulse-shape-discrimination was used to reduce gamma-ray background levels. The measurements are compared to calculations based on the Los Alamos Model of Madland and Nix to test its predictive capabilities. The data are fit by the Watt equation to determine the mean energy of the spectra, and to facilitate comparison of the results to previous measurements. The data are also compared directly to previous measurements.

  7. SPECTRA OF COSMIC-RAY PROTONS AND HELIUM PRODUCED IN SUPERNOVA REMNANTS

    SciTech Connect

    Ptuskin, Vladimir; Zirakashvili, Vladimir; Seo, Eun-Suk

    2013-01-20

    Data obtained in the Advanced Thin Ionization Calorimeter (ATIC-2), Cosmic Ray Energetics and Mass (CREAM), and Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA) experiments suggest that the elemental interstellar spectra of cosmic rays below the knee at a few times 10{sup 6} GeV are not simple power laws, but that they experience hardening at a magnetic rigidity of about 240 GV. Another essential feature is the difference between proton and helium energy spectra, such that the He/p ratio increases by more than 50% in the energy range from 10{sup 2} to 10{sup 4} GV. We consider the concavity of the particle spectrum resulting from the nonlinear nature of diffusive shock acceleration in supernova remnants (SNRs) as a possible reason for the observed spectrum hardening. The increase of the helium-to-proton ratio with energy can be interpreted as a consequence of cosmic-ray acceleration by forward and reverse shocks in SNRs. The contribution of particles accelerated by reverse shocks makes the concavity of the produced overall cosmic-ray spectrum more pronounced. The spectra of protons and helium nuclei accelerated in SNRs and released into the interstellar medium are calculated. The derived steady-state interstellar spectra are in reasonably good agreement with observations.

  8. MAGNETIC ENERGY SPECTRA IN SOLAR ACTIVE REGIONS

    SciTech Connect

    Abramenko, Valentyna; Yurchyshyn, Vasyl

    2010-09-01

    Line-of-sight magnetograms for 217 active regions (ARs) with different flare rates observed at the solar disk center from 1997 January until 2006 December are utilized to study the turbulence regime and its relationship to flare productivity. Data from the SOHO/MDI instrument recorded in the high-resolution mode and data from the BBSO magnetograph were used. The turbulence regime was probed via magnetic energy spectra and magnetic dissipation spectra. We found steeper energy spectra for ARs with higher flare productivity. We also report that both the power index, {alpha}, of the energy spectrum, E(k) {approx} k{sup -}{alpha}, and the total spectral energy, W = {integral}E(k)dk, are comparably correlated with the flare index, A, of an AR. The correlations are found to be stronger than those found between the flare index and the total unsigned flux. The flare index for an AR can be estimated based on measurements of {alpha} and W as A = 10{sup b}({alpha}W){sup c}, with b = -7.92 {+-} 0.58 and c = 1.85 {+-} 0.13. We found that the regime of the fully developed turbulence occurs in decaying ARs and in emerging ARs (at the very early stage of emergence). Well-developed ARs display underdeveloped turbulence with strong magnetic dissipation at all scales.

  9. TeV cosmic-ray proton and helium spectra in the myriad model

    NASA Astrophysics Data System (ADS)

    Bernard, G.; Delahaye, T.; Keum, Y.-Y.; Liu, W.; Salati, P.; Taillet, R.

    2013-07-01

    Context. Recent measurements of cosmic ray proton and helium spectra show a hardening above a few hundred GeV. This excess is hard to understand in the framework of the conventional models of Galactic cosmic ray production and propagation. Aims: We propose here to explain this anomaly by the presence of local sources (myriad model). Methods: Cosmic ray propagation is described as a diffusion process taking place inside a two-zone magnetic halo. We calculate the proton and helium fluxes at the Earth between 50 GeV and 100 TeV. As an improvement over a similar analysis, we consistently derive these fluxes by taking both local and remote sources for which a unique injection rate is assumed into account. Results: We find cosmic ray propagation parameters compatible with B/C measurements for which the proton and helium spectra agree remarkably with the PAMELA and CREAM measurements over four decades in energy.

  10. Effects of axion-photon mixing on gamma-ray spectra from magnetized astrophysical sources

    SciTech Connect

    Hochmuth, Kathrin A.; Sigl, Guenter

    2007-12-15

    Astrophysical {gamma}-ray sources come in a variety of sizes and magnetizations. We deduce general conditions under which {gamma}-ray spectra from such sources would be significantly affected by axion-photon mixing. We show that, depending on strength and coherence of the magnetic field, axion couplings down to {approx}(10{sup 13}GeV){sup -1} can give rise to significant axion-photon conversions in the environment of accreting massive black holes. Resonances can occur between the axion mass term and the plasma frequency term as well as between the plasma frequency term and the vacuum Cotton-Mouton shift. Both resonances and nonresonant transitions could induce detectable features or even strong suppressions in finite energy intervals of {gamma}-ray spectra from active galactic nuclei. Such effects can occur at keV to TeV energies for couplings that are currently allowed by all experimental constraints.

  11. Chandra X-ray grating spectra of V959 Mon

    NASA Astrophysics Data System (ADS)

    Orio, Marina; Zemko, Polina; Peretz, Uria; Behar, Ehud

    2016-07-01

    V959 Mon (Nova Mon 2012) was discovered in X-rays and gamma rays in the Summer of 2012, before it could be observed optically. It was observed twice with the Chandra gratings, by us in December of 2012 with the Low Energy Transmission Grating (LETG) and previously, in September of 2012, by another team with the Chandra High Energy Transmission Gratings. Although it seems very likely that only a small fraction of the ejecta emitted X-rays in small, dense clumps, the X-ray emission of the ejecta are very important for what the teach us about the kinematics, the chemical composition and nucleosynthesis of the nova. By December, the central source had shrunk almost to pre-outburst size and was visible in X-rays, revealing a massive, hot oxygen-neon white dwarf.

  12. On gamma-ray bursts spectra: A possible theoretical understanding

    NASA Astrophysics Data System (ADS)

    Chardonnet, Pascal; Filina, Anastasia; Popov, Mikhail; Chechetkin, Valery; Baranov, Andrey

    2015-12-01

    The study of spectra of gamma-ray burst is certainly a very promising part of the GRB studies. More and more data are available for GRBs and with time-sequence analysis it is possible also to propose a link with the other set of data represented by the light curves. Consequently, the explanation of the spectra requires both the local physical condition of the engine as well as the dynamic of the explosion process. In this view, we have analysed the GRB spectra with a specific model: black-body + thermal Bremsstrahlung. Our results show that this model is consistent with the observed GRB spectra. We can derive the temperature of the hot plasma needed to reproduce this spectrum consistent with the core of a very hot star ˜109 K. We have also found a correlation between the variation in time of this temperature and the variation of the spikes in luminosity of the light curves. This time profile each spike could be the correct fingerprint of the GRB physical process.Each spike, as a fingerprint, could keep the memory of the GRB physical process. If this model find a confirmation for other GRBs, this idea will ask us to open a new paradigm in GRB physics.

  13. Local environment of metal ions in phthalocyanines: K-edge X-ray absorption spectra.

    PubMed

    Rossi, G; d'Acapito, F; Amidani, L; Boscherini, F; Pedio, M

    2016-09-14

    We report a detailed study of the K-edge X-ray absorption spectra of four transition metal phthalocyanines (MPc, M = Fe, Co, Cu and Zn). We identify the important single and multiple scattering contributions to the spectra in the extended energy range and provide a robust treatment of thermal damping; thus, a generally applicable model for the interpretation of X-ray absorption fine structure spectra is proposed. Consistent variations of bond lengths and Debye Waller factors are found as a function of atomic number of the metal ion, indicating a variation of the metal-ligand bond strength which correlates with the spatial arrangement and occupation of molecular orbitals. We also provide an interpretation of the near edge spectral features in the framework of a full potential real space multiple scattering approach and provide a connection to the local electronic structure. PMID:27510989

  14. Cosmic ray mass and momentum spectra at mountain altitude

    NASA Technical Reports Server (NTRS)

    Barber, H. B.; Bowen, T.; Delise, D. A.; Jenkins, E. W.; Jones, J. J.; Kalbach, R. M.; Pifer, A. E.

    1975-01-01

    A cosmic ray mass spectrometer using a superconducting magnet, digitized wire spark chambers, and a scintillation counter time of flight system, has been operated at an altitude of 2750 meters. The apparatus is most sensitive to charged particles with momentum to mass ratios between 0.2 and 2.0. Results for the momentum spectra of protons and deuterons are presented, as well as upper limits for H-3 and He-3. The reaction nucleon + nucleon yields deuteron + pion accounts for part of the observed deuteron spectrum in the 0.9 to 3 GeV/c region.-

  15. Cyclotron scattering lines in gamma-ray burst spectra

    NASA Technical Reports Server (NTRS)

    Harding, Alice K.; Preece, Robert D.

    1989-01-01

    If cyclotron scattering, rather than absorption, is responsible for the line features observed recently in two gamma-ray burst spectra (Murakami et al., 1988), then the second and higher harmonics are due to resonant scattering events that excite the electron to Landau levels above the ground state. Here, relativistic Compton scattering cross sections are used to estimate the expected ratio of third to second harmonics in the presence of Doppler broadening. At the field strength (1.7 TG) required to give first and second harmonics at 19 keV and 38 keV, there should be no detectable third harmonic in the spectrum.

  16. X-ray spectra from convective photospheres of neutron stars

    SciTech Connect

    Zavlin, V.E.; Pavlov, G.G. |; Shibanov, Yu.A.; Rogers, F.J.; Iglesias, C.A.

    1996-01-17

    We present first results of modeling convective photospheres of neutron stars. We show that in photospheres composed of the light elements convection arises only at relatively low effective temperatures ({le}3 - 5 x 10{sup 4} K), whereas in the case of iron composition it arises at T{sub eff}{le} 3 x 10{sup 5}K. Convection changes the depth dependence of the photosphere temperature and the shapes of the emergent spectra. Thus, it should be taken into account for the proper interpretation of EUV/soft-X-ray observations of the thermal radiation from neutron stars.

  17. Spectra Transmitted by Mortar Barite in x-ray Qualities Applied in Diagnostic Radiology as Shielding

    NASA Astrophysics Data System (ADS)

    Almeida, A. T., Jr.; Araújo, F. G. S.; Nogueira, M. S.; Santos, M. A. P.

    2016-07-01

    Concrete which contains water, cement and aggregate, is widely used in building construction such as medical hospitals. The CdZnTe spectrometry system was used to acquire the transmitted spectra in the RQR qualities and the stripping procedure was performed by taking into account both the contributions of efficiency and x-ray escape fraction, experimentally determined. The samples were prepared in rectangular plate format with dimensions of (5 x 5) cm with thicknesses varying from 0.2cm to 2cm and exposed to x-ray beams generated. The HVL and the mean energy in this energy range was determined.

  18. High temperature matter and gamma ray spectra from microscopic black holes

    NASA Astrophysics Data System (ADS)

    Daghigh, Ramin; Kapusta, Joseph

    2002-03-01

    The relativistic viscous fluid equations describing the outflow of high temperature matter created via Hawking radiation from microscopic black holes are solved numerically for a realistic equation of state. We focus on black holes with initial temperatures greater than 100 GeV and lifetimes less than 6 days. The spectra of direct photons and photons from π0 decay are calculated for energies greater than 1 GeV. We calculate the diffuse gamma ray spectrum from black holes distributed in our galactic halo. However, the most promising route for their observation is to search for point sources emitting gamma rays of ever-increasing energy.

  19. Krypton K-Shell X-Ray Spectra Recorded by the HENEX Spectrometer

    SciTech Connect

    J. Seely; C. Back; C. Constantin, R. Lee; H. Chung; L. Hudson; C. Szabo; A. Henins; G. Holland; R. Atkin; L. Marlin

    2005-01-04

    High resolution x-ray spectra were recorded by the High Energy Electronic X-Ray (HENEX) spectrometer from a variety of targets irradiated by the Omega laser at the Laboratory for Laser Energetics. The HENEX spectrometer utilizes four reflection crystals covering the 1 keV to 20 keV energy range and one quartz(10-11) transmission crystal (Lau geometry) covering the 11 keV to 40 keV range. The time-integrated spectral images were recorded on five CMOS x-ray detectors. In the spectra recorded from krypton-filled gasbag and hohlraum targets, the helium-like K-shell transitions n=1-2, 1-3, and 1-4 appeared in the 13 keV to 17 keV energy range. A number of additional spectral features were observed at energies lower than the helium-like n=1-3 and n=1-4 transitions. Based on computational simulations of the spectra using the FLYCHK/FLYSPEC codes, which included opacity effects, these additional features are identified to be inner-shell transitions from the Li-like through N-like krypton charge states. The comparisons of the calculated and observed spectra indicate that these transitions are characteristic of the plasma conditions immediately after the laser pulse when the krypton density is 2x1018 cm-3 and the electron temperature is in the range 2.8 keV to 3.2 keV. These spectral features represent a new diagnostic for the charge state distribution, the density and electron temperature, and the plasma opacity. Laboratory experiments indicate that it is feasible to record K-shell spectra from gold and higher Z targets in the > 60 keV energy range using a Ge(220) transmission crystal.

  20. An MS-DOS-based program for analyzing plutonium gamma-ray spectra

    SciTech Connect

    Ruhter, W.D.; Buckley, W.M.

    1989-09-07

    A plutonium gamma-ray analysis system that operates on MS-DOS-based computers has been developed for the International Atomic Energy Agency (IAEA) to perform in-field analysis of plutonium gamma-ray spectra for plutonium isotopics. The program titled IAEAPU consists of three separate applications: a data-transfer application for transferring spectral data from a CICERO multichannel analyzer to a binary data file, a data-analysis application to analyze plutonium gamma-ray spectra, for plutonium isotopic ratios and weight percents of total plutonium, and a data-quality assurance application to check spectral data for proper data-acquisition setup and performance. Volume 3 contains the software listings for these applications.

  1. Portable computer to reduce gamma-ray spectra for plutonium isotopic ratios

    SciTech Connect

    Ruhter, W.D.; Camp, D.C.

    1981-05-15

    In response to Task A.63 of the International Safeguards Project Office (ISPO), to upgrade measurement technology used by the International Atomic Energy Agency (IAEA), a portable data-reduction microprocessor was designed and programmed which allows in-field reduction of gamma-ray spectra and interfaces with the IAEA's multichannel analyzers - the 1000 or 2000-channel memory Silena BS27/N. This report describes the components used in assembling the microprocessor unit: hardware, software used to control the unit, and the mathematical formulation used to obtain isotopic ratios from the gamma-ray data. A simple overview is presented of the unit's operation and the results of tests on gamma-ray spectra that sought to verify the unit's operating characteristics and to determine the precision and effectiveness of the software developed for data reduction.

  2. LET spectra of trapped anomalous cosmic rays in low-Earth orbit

    NASA Technical Reports Server (NTRS)

    Tylka, A. J.; Boberg, P. R.; Adams, J. H., Jr.

    1996-01-01

    Observations aboard Cosmos satelites discovered trapped anomalous cosmic rays (ACRs), tracked the variation in their intensity in 1986-1988, and measured their fluence, spectrum, and composition at solar minimum in the previous solar cycle. The MAST instrument aboard the SAMPEX satellite has observed trapped anomalous cosmic rays in the present solar cycle, confirmed the general features of the Cosmos data, and provided the first detailed observations of trapped ACRs. In this paper we apply theoretical modeling of trapped ACRs, which is shown to provide a reasonably good description of both the Cosmos and SAMPEX data, to calculate the integral linear-energy-transfer (LET) spectra due to trapped ACRs in typical low-Earth orbits. We compare these calculations with the LET spectra produced by galactic cosmic rays (GCRs) and non-trapped ACRs in order to assess the relative radiation hazard posed by trapped ACRs.

  3. Common origin of the high energy astronomical gamma rays, neutrinos and cosmic ray positrons?

    NASA Astrophysics Data System (ADS)

    Dado, Shlomo; Dar, Arnon

    2016-03-01

    We show that the observed fluxes, spectra and sky distributions of the high energy astronomical neutrinos, gamma rays and cosmic ray positrons satisfy the simple relations expected from their common production in hadronic collisions in/near source of high energy cosmic rays with diffuse matter.

  4. X-Ray and EUV Spectra of Comets

    NASA Astrophysics Data System (ADS)

    Krasnopolsky, V. A.

    2005-05-01

    Six comets have been observed using Chandra X-ray Observatory, and spectra of two comets, LINEAR S4 and McNaught-Hartley (MH), have been analyzed. A method was developed for processing, extraction, and analysis of the CXO/ACIS spectra of comets. This method differs from the standard CXO software and is based on a careful background correction (partially at the expense of the photon statistics) and extension of the spectrum down to 150 eV where the CXO/ACIS sensitivity is still significant. The x-ray luminosities of MH and prebreakup S4 are equal to 8.6 and 1.4× 1015 erg s-1 inside the apertures of 1.5 and 0.5× 104 km, respectively. (These boundaries are at 20% of the peak brightnesses.) Efficiencies of x-ray excitation corrected for the solar wind flow are similar and equal to 4.3× 1014 erg AU3/2, confirming the solar wind excitation of x-rays in comets. Spectra of MH and S4 consist of 10 and 8 emissions, respectively. Emissions at 380, 460, 560, 650, and 920 eV are present in both comets and identified as C+5, O+6, O+7, and Ne+8. These emissions and those at 780 and 850 eV in MH and 820 eV in S4 make it possible to determine some ion ratios in the solar wind: O+8/O+7 = 0.29 ± 0.04 and 0.14 ± 0.02, Ne+9/O+7 = (15± 6)× 10-3 and (19 ± 7)× 10-3 in MH and S4, respectively, and C+6/O+7 = 0.7 ± 0.2 in both comets. The observed Ne+8 emissions are the first data on Ne+9 in the solar wind. X-ray spectroscopy of comets may be used as a diagnostic tool to study the solar wind composition and its interaction with comets. Though the EUVE spectra of comet Hyakutake were measured with even better resolving power than the CXO spectra, their quantitative analysis is more difficult because of the great number of blended emissions. The most prominent lines are He+ 304 Å, O+4 215 Å, and C+4 249 Å. These lines were the first charge exchange emissions detected in comets. Although α-particles are much more abundant than heavy ions in the solar wind, the He+ emission

  5. Composition and spectra of primary cosmic-ray electrons and nuclei above 10 GeV

    NASA Technical Reports Server (NTRS)

    Meyer, P.

    1975-01-01

    Recent experiments have extended the knowledge of the flux and energy spectra of individual cosmic-ray components to much higher energies than had previously been accessible. Both electron and nuclear components show a behavior at high energy which is unexpected, and which carries information regarding the sources and the propagation of particles between sources and observer. Electromagnetic interactions which are suffered by the electrons in interstellar space should steepen their spectrum, a steepening that would reveal the average lifetime a cosmic-ray particle spends in the galaxy. Measurements up to 1000 GeV show no such steepening. It was discovered that the composition of the nuclear species which is now measured up to 100 GeV/nucleon changes with energy. This change indicates traversal of less interstellar matter by the high energy particles than by those of lower energy.-

  6. Comparison of hard and soft x-ray photoelectron spectra of silicon

    NASA Astrophysics Data System (ADS)

    Offi, F.; Werner, W. S. M.; Sacchi, M.; Torelli, P.; Cautero, M.; Cautero, G.; Fondacaro, A.; Huotari, S.; Monaco, G.; Paolicelli, G.; Smekal, W.; Stefani, G.; Panaccione, G.

    2007-08-01

    A detailed comparison of the surface sensitivity of x-ray photoemission spectroscopy for hard and soft x rays is presented and discussed. Electron scattering parameters and their energy dependence are given for Si and two Si spectra are analyzed: a MgKα (hν=1253.6eV) excited spectrum of the Si2p and 2s lines and a hard x-ray excited spectrum (hν=5925eV) of the Si1s line. The differential inelastic scattering characteristics for Si are extracted from reflection electron energy loss spectra taken at energies of 1500 and 4000eV . Using these scattering characteristics and electron mean free paths from the literature, simulated spectra are compared with experiment. The experimental spectra are deconvoluted to give the true intrinsic line shape corresponding to the theoretical collision statistics when interference effects between intrinsic and extrinsic scattering are neglected. The magnitude of interference effects cannot be assessed by our analysis. Within the (unknown) uncertainty introduced by neglecting interference effects, it is possible to determine the relative intensity of intrinsic and extrinsic excitations. In this way, it is found that in the case of the soft x-ray excited photoelectron spectrum of the shallower electronic shells ( 2p and 2s ), intrinsic plasmon creation is rather weak, and the apparent asymmetric line shape of the spectrum might be interpreted as the fact that electron-hole pair creation dominates the intrinsic loss spectrum, while an alternative explanation in terms of surface core level shifted components is also proposed. For the deeper core electronic shell, probed with hard x rays, the opposite situation is observed: while intrinsic electron-hole pair creation was not observed, a strong contribution of intrinsic plasmon losses of about 30% was seen.

  7. Intensities of high-energy cosmic rays at Mount Kanbala

    NASA Technical Reports Server (NTRS)

    Ren, J. R.; Kuang, H. H.; Huo, A. X.; Lu, S. L.; Su, S.; Wang, Y. X.; Xue, Y. G.; Wang, C. R.; He, M.; Zhang, N. J.

    1985-01-01

    The energy spectra of atmospheric cosmic rays at Mt. Kanbala (520 g/sq cm.) are measured with emulsion chambers. The power indexes of the spectra are values of about 2.0 for both gamma-rays and hadrons. Those fluxes are consistent with the ones expected from the model of primary cosmic rays with heavy nuclei of high content in the energy around 10 to the 15th power eV.

  8. Evaluation of the use of six diagnostic X-ray spectra computer codes.

    PubMed

    Meyer, P; Buffard, E; Mertz, L; Kennel, C; Constantinesco, A; Siffert, P

    2004-03-01

    A knowledge of photon energy spectra emitted from X-ray tubes in radiology is crucial for many research domains in the medical field. Since spectrometry is difficult because of high photon fluence rates, a convenient solution is to use computational models. This paper describes the use of six computer codes based on semiempirical or empirical models. The use of the codes was assessed, notably by comparing theoretical half value layers and air kerma with measurements on five different X-ray tubes used in a research hospital. It was found that three out of the six computer codes give relative spectra very close to those produced by X-ray units equipped with constant potential generators: the mean difference between measured and modelled half value layer was less than 3% with a standard deviation of 3.6% whatever the tube and the applied voltage. Absolute output is less accurate: for four computer codes, the mean difference between the measured and modelled air kerma was between 18% and 36%, with a standard deviation of 9% whatever the tube (except for the single phase generator) and the applied voltage. One of the codes gives a good output and beam quality for X-ray units equipped with 100% ripple voltage generators. The use of computational codes as described in this paper provides a means of modelling relative diagnostic X-ray spectra, the usefulness of the tube output data depending on the accuracy required by the end user. PMID:15020364

  9. Interactive Analysis of Gamm-ray Spectra from GE Semiconductor Detectors

    Energy Science and Technology Software Center (ESTSC)

    1997-09-25

    GAUSS IX is a tool to interactively analyze gamma-ray spectra from Ge Semicondutor detectors. The user has full control over the view of the spectrum being analyzed and the location of the peaks and peak regions. Analysis is performed at user request to the requested peak regions. The fit of a peak region can be previewed before archival or deletion. An iterative procedure is available for calibrating the energy and width equations.

  10. Gamma-ray spectra of individual components of decay series

    NASA Astrophysics Data System (ADS)

    Griffin, Henry

    2001-04-01

    In order to obtain high quality spectra to update the ``Heath Catalog" of spectra with Ge detectors, we (I and a group of Univ. of Michigan undergraduates*) have investigated the neutron activation and decay products related to natural thorium and natural uranium. We have used the UM Ford Nuclear Reactor for irradiations and the UM Phoenix Memorial Lab for the remaining work. Spectra have been obtained with a variety of detectors, some suitable for low energies (>5 keV) and others efficient (70%) for high energies. Sources have been obtained in a variety of forms, each of which has been characterized in comparison with a thin, point source. We will report on A=233 (Th, Pa, and U, and the Np-237 parent of Pa-233), A=234 (Th and the Pa isomers), and A=239 (U, Np, and the Am-243 parent of Np-239). *The 2000-01 undergrad research group consists of Jason Banker, Adam Berro, Adam Cole, Amelia Deschamps, Erik Epp, Ralph Pierre, and Emma Wong.

  11. Cosmic ray spectra measurements at the Yakutsk EAS array

    NASA Technical Reports Server (NTRS)

    Glushkov, A. V.; Egorov, T. A.; Efimov, N. N.; Pravdin, M. I.; Khristiansen, G. B.

    1985-01-01

    The extensive air showers (EAS) spectra on rho 600 obtained at the Yakutak array for 38000 operation hours in 1974 to 1982 are presented. The refined value of the conversion factor from rho 600 to E sub is given and based on it the primary energy spectrum is obtained. The Yakutsk EAS array classifies the showers on parameters which are well measured in real showers: in the central part - on Rho sub 300 and on the whole array - on Rho sub 600. The shower spectra are constructed first on these parameters, than - a single spectrum on Rho sub 600. The RHO sub 300 and Rho sub 600 values are determined on the particle lateral distribution function (LDF) obtained in Yakutsk and on approximation Rho approx. R sup/n using the experimental points closest to R* (300 and 600 m).

  12. Optimal binning of X-ray spectra and response matrix design

    NASA Astrophysics Data System (ADS)

    Kaastra, J. S.; Bleeker, J. A. M.

    2016-03-01

    Aims: A theoretical framework is developed to estimate the optimal binning of X-ray spectra. Methods: We derived expressions for the optimal bin size for model spectra as well as for observed data using different levels of sophistication. Results: It is shown that by taking into account both the number of photons in a given spectral model bin and their average energy over the bin size, the number of model energy bins and the size of the response matrix can be reduced by a factor of 10-100. The response matrix should then contain the response at the bin centre as well as its derivative with respect to the incoming photon energy. We provide practical guidelines for how to construct optimal energy grids as well as how to structure the response matrix. A few examples are presented to illustrate the present methods.

  13. Relativistic cosmic ray spectra in the full non-linear theory of shock acceleration

    NASA Technical Reports Server (NTRS)

    Eichler, D.; Ellison, D. C.

    1985-01-01

    The non-linear theory of shock acceleration was generalized to include wave dynamics. In the limit of rapid wave damping, it is found that a finite ave velocity tempers the acceleration of high Mach number shocks and limits the maximum compression ratio even when energy loss is important. For a given spectrum, the efficiency of relativistic particle production is essentially independent of v sub Ph. For the three families shown, the percentage of kinetic energy flux going into relativistic particles is (1) 72%, 2) 44%, and (3) 26% (this includes the energy loss at the upper energy cuttoff). Even small v sub ph, typical of the HISM, produce quasi-universal spectra that depend only weakly on the acoustic Mach number. These spectra should be close enough to e(-2) to satisfy cosmic ray source requirements.

  14. Determining x-ray spectra of radiographic sources with a Compton spectrometer

    NASA Astrophysics Data System (ADS)

    Gehring, Amanda E.; Espy, Michelle A.; Haines, Todd J.; Hunter, James F.; King, Nick S. P.; Manard, Manuel J.; Merrill, Frank E.; Morgan, George L.; Sedillo, Robert; Trainham, Rusty; Urbaitis, Algis V.; Volegov, Petr

    2014-09-01

    Flash radiography is a diagnostic with many physics applications, and the characterization of the energy spectra of such sources is of interest. A Compton spectrometer has been proposed to conduct these measurements. Our Compton spectrometer is a 300 kg neodymium-iron magnet constructed by Morgan et al1, and it is designed to measure spectra in the <1 MeV to 20 MeV range. In this device, the x-rays from a radiographic source are collimated into a narrow beam directed on a converter foil. The forward-selected Compton electrons that are ejected from the foil enter the magnetic field region of the spectrometer. The electrons are imaged on a focal plane, with their position determined as a function of their energy. The x-ray spectrum is then reconstructed. Challenges in obtaining these measurements include limited dose of x-rays and the short pulse duration (about 50 ns) for time-resolved measurements. Here we present energy calibration measurements of the spectrometer using a negative ion source. The resolution of the spectrometer was measured in previous calibration experiments to be the greater of 1% or 0.1 MeV/c1. The reconstruction of spectra from a bremsstrahlung source and Co-60 source are also presented.

  15. Characteristics of hard X-ray spectra of impulsive solar flares

    NASA Technical Reports Server (NTRS)

    Dulk, G. A.; Kiplinger, A. L.; Winglee, R. M.

    1992-01-01

    The typical characteristics of the hard X-ray emission of impulsive solar flares are examined. At times of hard X-ray peaks, spectra that break downward are the rule rather than the exception. The break energy is typically at about 100 keV and rarely exceed 150 keV. There is little or no dependence of spectral slopes or of the break energy on the hard X-ray fluxes. During the burst decay phases, there is a strong tendency for the spectra to evolve to either a single power law or to cross over to one that breaks upward. The break energy is usually lower after the crossover, but in about 30 percent of the cases it is higher. During the rise phase of many fast bursts, the rise in flux at high energies occurs later than that at lower energies. In most cases the high-energy flux catches up by the time of the burst peak and the lag is rarely or never observed in bursts whose rise time is more than about 10 s.

  16. Probing symmetry and symmetry breaking in resonant soft-x-ray fluorescence spectra of molecules

    SciTech Connect

    Glans, P.; Gunnelin, K.; Guo, J.

    1997-04-01

    Conventional non-resonant soft X-ray emission brings about information about electronic structure through its symmetry and polarization selectivity, the character of which is governed by simple dipole rules. For centro-symmetric molecules with the emitting atom at the inversion center these rules lead to selective emission through the required parity change. For the more common classes of molecules which have lower symmetry or for systems with degenerate core orbitals (delocalized over identical sites), it is merely the local symmetry selectivity that provides a probe of the local atomic orbital contribution to the molecular orbital. For instance, in X-ray spectra of first row species the intensities essentially map the p-density at each particular atomic site, and, in a molecular orbital picture, the contribution of the local p-type atomic orbitals in the LCAO description of the molecular orbitals. The situation is different for resonant X-ray fluorescence spectra. Here strict parity and symmetry selectivity gives rise to a strong frequency dependence for all molecules with an element of symmetry. In addition to symmetry selectivity the strong frequency dependence of resonant X-ray emission is caused by the interplay between the shape of a narrow X-ray excitation energy function and the lifetime and vibrational broadenings of the resonantly excited core states. This interplay leads to various observable effects, such as linear dispersion, resonance narrowing and emission line (Stokes) doubling. Also from the point of view of polarization selectivity, the resonantly excited X-ray spectra are much more informative than the corresponding non-resonant spectra. Examples are presented for nitrogen, oxygen, and carbon dioxide molecules.

  17. Primary γ-ray spectra in 44Ti of astrophysical interest

    NASA Astrophysics Data System (ADS)

    Larsen, A. C.; Goriely, S.; Bürger, A.; Guttormsen, M.; Görgen, A.; Harissopulos, S.; Kmiecik, M.; Konstantinopoulos, T.; Lagoyannis, A.; Lönnroth, T.; Mazurek, K.; Norrby, M.; Nyhus, H. T.; Perdikakis, G.; Schiller, A.; Siem, S.; Spyrou, A.; Syed, N. U. H.; Toft, H. K.; Tveten, G. M.; Voinov, A.

    2012-01-01

    Primary γ-ray spectra for a wide excitation-energy range have been extracted for 44Ti from particle-γ coincidence data of the 46Ti(p,tγ)44Ti reaction. These spectra reveal information on the γ-decay pattern of the nucleus and may be used to extract the level density and radiative strength function applying the Oslo method. Models of the level density and radiative strength function are used as input for cross-section calculations of the 40Ca(α,γ)44Ti reaction. Acceptable models should reproduce data on the 40Ca(α,γ)44Ti reaction cross section as well as the measured primary γ-ray spectra. This is only achieved when a coherent normalization of the slope of the level density and radiative strength function is performed. Thus, the overall shape of the experimental primary γ-ray spectra puts a constraint on the input models for the rate calculations.

  18. Influence of phantom materials on the energy dependence of LiF:Mg,Ti thermoluminescent dosimeters exposed to 20-300 kV narrow x-ray spectra, 137Cs and 60Co photons

    NASA Astrophysics Data System (ADS)

    Massillon-JL, G.; Cabrera-Santiago, A.; Minniti, R.; O'Brien, M.; Soares, C. G.

    2014-08-01

    LiF:Mg,Ti, are widely used to estimate absorbed-dose received by patients during diagnostic or medical treatment. Conveniently, measurements are usually made in plastic phantoms. However, experimental conditions vary from one group to another and consequently, a lack of consensus data exists for the energy dependence of thermoluminescent (TL) response. This work investigated the energy dependence of TLD-100 TL-response and the effect of irradiating the dosimeters in different phantom materials for a broad range of energy photons in an attempt to understand the parameters that affect the discrepancies reported by various research groups. TLD-100s were exposed to 20-300 kV narrow x-ray spectra, 137Cs and 60Co photons. Measurements were performed in air, PMMA, wt1, polystyrene and TLDS as surrounding material. Total air-kerma values delivered were between 50 and 150 mGy for x-rays and 50 mGy for 137Cs and 60Co beams; each dosimeter was irradiated individually. Relative response, R, defined as the TL-response per air-kerma and relative efficiency, RE, described as the TL-response per absorbed-dose (obtained through Monte Carlo (MC) and analytically) were used to describe the TL-response. Both R and RE are normalized to the responses in a 60Co beam. The results indicate that the use of different phantom materials affects the TL-response and this response varies with energy and material type. MC simulations reproduced qualitatively the experimental data: a) R increases, reaches a maximum at ~25 keV and decreases; b) RE decreases, down to a minimum at ~60 keV, increases to a maximum at ~150 keV and after decreases. Independent of the phantom materials, RE strongly depends on how the absorbed dose is evaluated and the discrepancies between RE evaluated analytically and by MC simulation are around 4% and 18%, dependent on the photon energy. The comparison between our results and that reported in the literature suggests that the discrepancy observed between

  19. Broadband turbulent spectra in gamma-ray burst light curves

    SciTech Connect

    Van Putten, Maurice H. P. M.; Guidorzi, Cristiano; Frontera, Filippo

    2014-05-10

    Broadband power density spectra offer a window to understanding turbulent behavior in the emission mechanism and, at the highest frequencies, in the putative inner engines powering long gamma-ray bursts (GRBs). We describe a chirp search method alongside Fourier analysis for signal detection in the Poisson noise-dominated, 2 kHz sampled, BeppoSAX light curves. An efficient numerical implementation is described in O(Nnlog n) operations, where N is the number of chirp templates and n is the length of the light-curve time series, suited for embarrassingly parallel processing. For the detection of individual chirps over a 1 s duration, the method is one order of magnitude more sensitive in signal-to-noise ratio than Fourier analysis. The Fourier-chirp spectra of GRB 010408 and GRB 970816 show a continuation of the spectral slope with up to 1 kHz of turbulence identified in low-frequency Fourier analysis. The same continuation is observed in an average spectrum of 42 bright, long GRBs. An outlook on a similar analysis of upcoming gravitational wave data is included.

  20. Numerical Study of the Generation of Linear Energy Transfer Spectra for Space Radiation Applications

    NASA Technical Reports Server (NTRS)

    Badavi, Francis F.; Wilson, John W.; Hunter, Abigail

    2005-01-01

    In analyzing charged particle spectra in space due to galactic cosmic rays (GCR) and solar particle events (SPE), the conversion of particle energy spectra into linear energy transfer (LET) distributions is a convenient guide in assessing biologically significant components of these spectra. The mapping of LET to energy is triple valued and can be defined only on open energy subintervals where the derivative of LET with respect to energy is not zero. Presented here is a well-defined numerical procedure which allows for the generation of LET spectra on the open energy subintervals that are integrable in spite of their singular nature. The efficiency and accuracy of the numerical procedures is demonstrated by providing examples of computed differential and integral LET spectra and their equilibrium components for historically large SPEs and 1977 solar minimum GCR environments. Due to the biological significance of tissue, all simulations are done with tissue as the target material.

  1. Simulation of gamma-ray spectra for a variety of user-specified detector designs

    NASA Technical Reports Server (NTRS)

    Rester, A. C., Jr.

    1994-01-01

    The gamma-ray spectrum simulation program BSIMUL was designed to allow the operator to follow the path of a gamma-ray through a detector, shield and collimator whose dimensions are entered by the operator. It can also be used to simulate spectra that would be generated by a detector. Several improvements have been made to the program within the last few months. The detector, shield and collimator dimensions can now be entered through an interactive menu whose options are discussed below. In addition, spectra containing more than one gamma-ray energy can now be generated with the menu - for isotopes listed in the program. Adding isotopes to the main routine is also quite easy. Subroutines have been added to enable the operator to specify the material and dimensions of a collimator. This report details the progress made in simulating gamma-ray spectra for a variety of user-specified detector designs. In addition, a short discussion of work done in the related areas of pulse shape analysis and the spectral analysis is included. The pulse shape analysis and spectral analysis work is being performed pursuant to the requirements of contract F-94-C-0006, for the Advanced Research Projects Agency and the U.S. Air Force.

  2. Characterization of neutron yield and x-ray spectra of a High Flux Neutron Generator (HFNG)

    NASA Astrophysics Data System (ADS)

    Nnamani, Nnaemeka; HFNG Collaboration

    2015-04-01

    The High Flux Neutron Generator (HFNG) is a DD plasma-based source, with a self-loading target intended for fundamental science and engineering applications, including 40 Ar/39 Ar geochronology, neutron cross section measurements, and radiation hardness testing of electronics. Our first estimate of the neutron yield, based on the population of the 4.486 hour 115 In isomer gave a neutron yield of the order 108 n/sec; optimization is ongoing to achieve the design target of 1011 n/sec. Preliminary x-ray spectra showed prominent energy peaks which are likely due to atomic line-emission from back-streaming electrons accelerated up to 100 keV impinging on various components of the HFNG chamber. Our x-ray and neutron diagnostics will aid us as we continue to evolve the design to suppress back-streaming electrons, necessary to achieve higher plasma beam currents, and thus higher neutron flux. This talk will focus on the characterization of the neutron yield and x-ray spectra during our tests. A collimation system is being installed near one of the chamber ports for improved observation of the x-ray spectra. This work is supported by NSF Grant No. EAR-0960138, U.S. DOE LBNL Contract No. DE-AC02-05CH11231, U.S. DOE LLNL Contract No. DE-AC52-07NA27344, and the UC Office of the President Award 12-LR-238745.

  3. On the Origin of X-Ray Spectra in Luminous Blazars

    NASA Astrophysics Data System (ADS)

    Sikora, Marek; Janiak, Mateusz; Nalewajko, Krzysztof; Madejski, Greg M.; Moderski, Rafał

    2013-12-01

    Gamma-ray luminosities of some quasar-associated blazars imply jet powers reaching values comparable to the accretion power even if assuming very strong Doppler boosting and very high efficiency of gamma-ray production. With much lower radiative efficiencies of protons than of electrons, and the recent reports of very strong coupling of electrons with shock-heated protons indicated by particle-in-cell simulations, the leptonic models seem to be strongly favored over the hadronic ones. However, the electron-proton coupling combined with the external-radiation-Compton (ERC) models of gamma-ray production in leptonic models predict extremely hard X-ray spectra, with energy indices α x ~ 0. This is inconsistent with the observed 2-10 keV slopes of blazars, which cluster around α x ~ 0.6. This problem can be resolved by assuming that electrons can be efficiently cooled down radiatively to non-relativistic energies, or that blazar spectra are entirely dominated by the synchrotron self-Compton (SSC) component up to at least 10 keV. Here, we show that the required cooling can be sufficiently efficient only at distances r < 0.03 pc. SSC spectra, on the other hand, can be produced roughly co-spatially with the observed synchrotron and ERC components, which are most likely located roughly at a parsec scale. We show that the dominant SSC component can also be produced much further than the dominant synchrotron and ERC components, at distances of >~ 10 pc. Hence, depending on the spatial distribution of the energy dissipation along the jet, one may expect to see γ-ray/optical events with either correlated or uncorrelated X-rays. In all cases the number of e+e- pairs per proton is predicted to be very low. The direct verification of the proposed SSC scenario, and particularly the question of the co-spatiality of the SSC component with other spectral components, requires sensitive observations in the hard X-ray band. This is now possible with the deployment of the Nu

  4. On the origin of X-ray spectra in luminous blazars

    SciTech Connect

    Sikora, Marek; Janiak, Mateusz; Moderski, Rafał; Nalewajko, Krzysztof; Madejski, Greg M. E-mail: mjaniak@camk.edu.pl

    2013-12-10

    Gamma-ray luminosities of some quasar-associated blazars imply jet powers reaching values comparable to the accretion power even if assuming very strong Doppler boosting and very high efficiency of gamma-ray production. With much lower radiative efficiencies of protons than of electrons, and the recent reports of very strong coupling of electrons with shock-heated protons indicated by particle-in-cell simulations, the leptonic models seem to be strongly favored over the hadronic ones. However, the electron-proton coupling combined with the external-radiation-Compton (ERC) models of gamma-ray production in leptonic models predict extremely hard X-ray spectra, with energy indices α {sub x} ∼ 0. This is inconsistent with the observed 2-10 keV slopes of blazars, which cluster around α {sub x} ∼ 0.6. This problem can be resolved by assuming that electrons can be efficiently cooled down radiatively to non-relativistic energies, or that blazar spectra are entirely dominated by the synchrotron self-Compton (SSC) component up to at least 10 keV. Here, we show that the required cooling can be sufficiently efficient only at distances r < 0.03 pc. SSC spectra, on the other hand, can be produced roughly co-spatially with the observed synchrotron and ERC components, which are most likely located roughly at a parsec scale. We show that the dominant SSC component can also be produced much further than the dominant synchrotron and ERC components, at distances of ≳ 10 pc. Hence, depending on the spatial distribution of the energy dissipation along the jet, one may expect to see γ-ray/optical events with either correlated or uncorrelated X-rays. In all cases the number of e{sup +}e{sup –} pairs per proton is predicted to be very low. The direct verification of the proposed SSC scenario, and particularly the question of the co-spatiality of the SSC component with other spectral components, requires sensitive observations in the hard X-ray band. This is now possible with the

  5. The hard X-ray emission spectra from accretion columns in intermediate polars

    NASA Technical Reports Server (NTRS)

    Yi, Insu; Vishniac, Ethan T.

    1994-01-01

    We consider the hard (greater than 2 keV) X-ray emission from accretion columns in an intermediate polar system, GK Per, using a simple settling solution. The rate of photon emission per logarithmic energy interval can be fitted with a power law, E(exp -gamma), with gamma approximately 2.0, in agreement with observations. This index is only weakly dependent on the mass accretion rate, dot-M, for dot-M in the range of a few times 10(exp 16-18) g/s. The peak energy of the photon spectra (after photoelectric absorption) is expected to be E(sub p) approximately (5 keV) gamma(exp -1/3) (N(sub H)/10(exp 23)/sq cm)(exp 1/3) where N(sub H) is the hydrogen column density along the line of sight. The observed spectra of GK Per and possibly of V1223 Sgr suggest N(sub H) approximately 10(exp 23)/sq cm. This large N(sub H) may be due to partially ionized preshock column material. Alternatively, we also consider absorption by the cool outer parts of an accretion disk. In this case the photoelectric absorption depth in the disk is a sensitive function of inclination. For GK Per the required inclination is approximately 83 deg. For mass accretion rates larger than a critical rate of approximately 10(exp 18) g/s, X-ray emission from the column accretion is significantly affected by radiation drag. Although the mass accretion rate increases dramatically during outbursts, the observed hard (greater than 2 keV) X-ray luminosity will not rise proportionately. The slope and peak energy of the outburst spectra are only weakly affected. We conclude that the observed X-ray spectra can be explained by this simple analytic solution and that the production of hard X-rays from the accretion shock at the magnetic poles in the intermediate polars is in general agreement with the observations. However, since the X-ray emission and absorption depend on the mass accretion rate in a complicated manner, observed hard X-ray luminosities (greater than 2 keV) are not a good indicator of the mass

  6. Assessment of different computational models for generation of x-ray spectra in diagnostic radiology and mammography.

    PubMed

    Ay, M R; Sarkar, S; Shahriari, M; Sardari, D; Zaidi, H

    2005-06-01

    Different computational methods based on empirical or semi-empirical models and sophisticated Monte Carlo calculations have been proposed for prediction of x-ray spectra both in diagnostic radiology and mammography. In this work, the x-ray spectra predicted by various computational models used in the diagnostic radiology and mammography energy range have been assessed by comparison with measured spectra and their effect on the calculation of absorbed dose and effective dose (ED) imparted to the adult ORNL hermaphroditic phantom quantified. This includes empirical models (TASMIP and MASMIP), semi-empirical models (X-rayb&m, X-raytbc, XCOMP, IPEM, Tucker et al., and Blough et al.), and Monte Carlo modeling (EGS4, ITS3.0, and MCNP4C). As part of the comparative assessment, the K x-ray yield, transmission curves, and half value layers (HVLs) have been calculated for the spectra generated with all computational models at different tube voltages. The measured x-ray spectra agreed well with the generated spectra when using X-raytbc and IPEM in diagnostic radiology and mammography energy ranges, respectively. Despite the systematic differences between the simulated and reference spectra for some models, the student's t-test statistical analysis showed there is no statistically significant difference between measured and generated spectra for all computational models investigated in this study. The MCNP4C-based Monte Carlo calculations showed there is no discernable discrepancy in the calculation of absorbed dose and ED in the adult ORNL hermaphroditic phantom when using different computational models for generating the x-ray spectra. Nevertheless, given the limited flexibility of the empirical and semi-empirical models, the spectra obtained through Monte Carlo modeling offer several advantages by providing detailed information about the interactions in the target and filters, which is relevant for the design of new target and filter combinations and optimization of

  7. Assessment of different computational models for generation of x-ray spectra in diagnostic radiology and mammography

    SciTech Connect

    Ay, M.R.; Sarkar, S.; Shahriari, M.; Sardari, D.; Zaidi, H.

    2005-06-15

    Different computational methods based on empirical or semi-empirical models and sophisticated Monte Carlo calculations have been proposed for prediction of x-ray spectra both in diagnostic radiology and mammography. In this work, the x-ray spectra predicted by various computational models used in the diagnostic radiology and mammography energy range have been assessed by comparison with measured spectra and their effect on the calculation of absorbed dose and effective dose (ED) imparted to the adult ORNL hermaphroditic phantom quantified. This includes empirical models (TASMIP and MASMIP), semi-empirical models (X-rayb and m, X-raytbc, XCOMP, IPEM, Tucker et al., and Blough et al.), and Monte Carlo modeling (EGS4, ITS3.0, and MCNP4C). As part of the comparative assessment, the K x-ray yield, transmission curves, and half value layers (HVLs) have been calculated for the spectra generated with all computational models at different tube voltages. The measured x-ray spectra agreed well with the generated spectra when using X-raytbc and IPEM in diagnostic radiology and mammography energy ranges, respectively. Despite the systematic differences between the simulated and reference spectra for some models, the student's t-test statistical analysis showed there is no statistically significant difference between measured and generated spectra for all computational models investigated in this study. The MCNP4C-based Monte Carlo calculations showed there is no discernable discrepancy in the calculation of absorbed dose and ED in the adult ORNL hermaphroditic phantom when using different computational models for generating the x-ray spectra. Nevertheless, given the limited flexibility of the empirical and semi-empirical models, the spectra obtained through Monte Carlo modeling offer several advantages by providing detailed information about the interactions in the target and filters, which is relevant for the design of new target and filter combinations and optimization of

  8. Polarization-dependent spectra of x-ray dielectronic satellite lines of Be-like Fe

    SciTech Connect

    Shlyaptseva, A.S.; Mancini, R.C.; Neill, P.; Beiersdorfer, P.; Crespo Lopez-Urrutia, J.R.; Widmann, K.

    1998-02-01

    We have studied the polarization properties of dielectronic satellite lines in Be-like Fe ions excited through resonant electron capture by an electron beam. Using the photon density-matrix formalism, we have calculated the degree of polarization and polarization-dependent spectra of dielectronic satellite lines, i.e., the spectral intensity distribution of lines associated with a given polarization state. Theoretical results have been compared with experiments performed at the Lawrence Livermore National Laboratory electron-beam ion trap where dielectronic satellite line emission from Fe ions produced at different energies of the electron beam was simultaneously recorded with two crystal spectrometers. These spectrometers had different polarization sensitivities. The experimental spectra recorded by the two spectrometers are reproduced by the theory. This ability to model the polarization dependence of x-ray line spectra is important for the diagnosis of electron beams in plasmas. {copyright} {ital 1998} {ital The American Physical Society}

  9. Possible use of pattern recognition for the analysis of Mars rover X-ray fluorescence spectra

    NASA Technical Reports Server (NTRS)

    Yin, Lo I; Trombka, Jacob I.; Seltzer, Stephen M.; Johnson, Robert G.; Philpotts, John A.

    1989-01-01

    On the Mars rover sample-return mission, the rover vehicle will collect and select samples from different locations on the Martian surface to be brought back to earth for laboratory studies. It is anticipated that an in situ energy-dispersive X-ray fluorescence (XRF) spectrometer will be on board the rover. On such a mission, sample selection is of higher priority than in situ quantitative chemical anlaysis. With this in mind, a pattern recognition technique is proposed as a simple, direct, and speedy alternative to detailed chemical analysis of the XRF spectra. The validity and efficacy of the pattern recognition technique are demonstrated by the analyses of laboratory XRF spectra obtained from a series of geological samples, in the form both of standardized pressed pellets and as unprepared rocks. It is found that pattern recognition techniques applied to the raw XRF spectra can provide for the same discrimination among samples as a knowledge of their actual chemical composition.

  10. Lifetime-vibrational interference effects in resonantly excited x-ray emission spectra of CO

    SciTech Connect

    Skytt, P.; Glans, P.; Gunnelin, K.

    1997-04-01

    The parity selection rule for resonant X-ray emission as demonstrated for O{sub 2} and N{sub 2} can be seen as an effect of interference between coherently excited degenerate localized core states. One system where the core state degeneracy is not exact but somewhat lifted was previously studied at ALS, namely the resonant X-ray emission of amino-substituted benzene (aniline). It was shown that the X-ray fluorescence spectrum resulting from excitation of the C1s at the site of the {open_quotes}aminocarbon{close_quotes} could be described in a picture separating the excitation and the emission processes, whereas the spectrum corresponding to the quasi-degenerate carbons could not. Thus, in this case it was necessary to take interference effects between the quasi-degenerate intermediate core excited states into account in order to obtain agreement between calculations and experiment. The different vibrational levels of core excited states in molecules have energy splittings which are of the same order of magnitude as the natural lifetime broadening of core excitations in the soft X-ray range. Therefore, lifetime-vibrational interference effects are likely to appear and influence the band shapes in resonant X-ray emission spectra. Lifetime-vibrational interference has been studied in non-resonant X-ray emission, and in Auger spectra. In this report the authors discuss results of selectively excited soft X-ray fluorescence spectra of molecules, where they focus on lifetime-interference effects appearing in the band shapes.

  11. The soft X ray excess in Einstein quasar spectra

    NASA Technical Reports Server (NTRS)

    Wilkes, Belinda J.; Masnou, Jean-Louis; Elvis, Martin; Mcdowell, Jonathan; Arnaud, Keith

    1989-01-01

    The soft X-ray excess component is studied for a signal to noise limited subsample of 14 quasars from the WE87 sample observed with the Einstein Imaging Proportional Counter (IPC). Detailed analysis of the IPC data, combined with Einstein Monitor Proportional Counter (MPC) data where possible, and use of accurate galactic N sub H values allows estimation of the strength of any excess and improvement of constraints on the spectral slope at higher X-ray energies. A significant excess in 9 of the 14 objects is found. It is confined in all but one case to below 0.6 keV and variable in the two cases where there are multiple observations. The relation of the soft excess to other continuum properties of the quasars is investigated.

  12. An iron absorption model of gamma-ray burst spectra

    NASA Technical Reports Server (NTRS)

    Liang, Edison P.; Kargatis, Vincent E.

    1994-01-01

    Most gamma-ray bursts (GRBs) exhibit deficits of X-rays below approximately 200 keV. Here we consider a spectral model in which the burst source is shielded by an optically thick layer of circumburster material (CBM) rich in iron-group elements whose photoelectric absorption opacity exceeds the Thomson opacity below approximately 120 keV. For power-law distributions of absorption depths along the lines of sight the absorbed spectrum can indeed mimic the typial GRB spectrum. This model predicts that (a) the spectrum should evolve monotonically from hard to soft during each energy release, which is observed in most bursts, especially in fast rise exponential decay bursts; (b) Fe spectral features near 7 keV may be present in some bursts; and (c) the ratio of burst distances to the CBM and to Earth should be approximately 10(exp -11) if the spectral evolution is purely due to Fe stripping by the photons.

  13. Unwrapping the X-ray spectra of active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Reynolds, C. S.

    2016-05-01

    Active galactic nuclei (AGN) are complex phenomena. At the heart of an AGN is a relativistic accretion disk around a spinning supermassive black hole (SMBH) with an X-ray emitting corona and, sometimes, a relativistic jet. On larger scales, the outer accretion disk and molecular torus act as the reservoirs of gas for the continuing AGN activity. And on all scales from the black hole outwards, powerful winds are seen that probably affect the evolution of the host galaxy as well as regulate the feeding of the AGN itself. In this review article, we discuss how X-ray spectroscopy can be used to study each of these components. We highlight how recent measurements of the high-energy cutoff in the X-ray continuum by NuSTAR are pushing us to conclude that X-ray coronae are radiatively-compact and have electron temperatures regulated by electron-positron pair production. We show that the predominance of rapidly-rotating objects in current surveys of SMBH spin is entirely unsurprising once one accounts for the observational selection bias resulting from the spin-dependence of the radiative efficiency. We review recent progress in our understanding of fast (v˜ (0.1-0.3)c, highly-ionized (mainly visible in Fe XXV and Fe XXVI lines), high-column density winds that may dominate quasar-mode galactic feedback. Finally, we end with a brief look forward to the promise of Astro-H and future X-ray spectropolarimeters.

  14. Multi-temperature analysis of hard X-ray spectra measured aboard the Prognoz 5 satellite

    NASA Astrophysics Data System (ADS)

    Sylwester, B.; Sylwester, J.; Jakimiec, J.; Valnicek, B.; Farnik, F.

    1983-01-01

    Following the method of multi-temperature analysis of hard X-ray spectra presented by B. Sylwester et al. (1981), in the present paper the authors analyse the hard X-ray radiation measured aboard the Prognoz 5 satellite by means of a Czechoslovak photometer. The analysis concerns the Feb. 11, 1977 flare event. Using the fluxes measured in 4 energy bands they have calculated the differential emission measure distributions for selected moments during the rise, maximum and decay phases of the flare development. The results of the analysis show that, in the case of the flare in question, the hard X-ray radiation from 6 to 60 keV could have been produced by purely thermal, multi-temperature plasma.

  15. Superluminal cascade spectra of TeV {gamma}-ray sources

    SciTech Connect

    Tomaschitz, Roman . E-mail: tom@geminga.org

    2007-03-15

    Astrophysical radiation sources are scrutinized in search of superluminal {gamma}-rays. The tachyonic spectral densities generated by ultra-relativistic electrons in uniform motion are fitted to the high-energy spectra of Galactic supernova remnants, such as RX J0852.0-4622 and the pulsar wind nebulae in G0.9+0.1 and MSH 15-52. The superluminal spectral maps of the unidentified TeV {gamma}-ray sources HESS J1303-631, TeV J2032+4130 and HESS J1825-137 are inferred from EGRET, HEGRA and HESS data. Tachyonic cascade spectra are quite capable of generating the spectral curvature seen in double-logarithmic plots, as well as the extended spectral plateaus defined by EGRET flux points in the GeV band. The curvature of the TeV spectra is intrinsic, caused by the Boltzmann factor in the source densities. The spectral averaging with thermal and exponentially cut power-law electron densities can be done in closed form, and systematic high- and low-temperature expansions of the superluminal spectral densities are derived. Estimates on the electron/proton populations generating the tachyon flux are obtained from the spectral fits, such as power-law indices, temperature and source counts. The cutoff temperatures of the source densities suggest ultra-high-energy protons in MSH 15-52, HESS J1825-137 and TeV J2032+4130.

  16. Very High Energy Gamma Ray Extension of GRO Observations

    NASA Technical Reports Server (NTRS)

    Weekes, Trevor C.

    1994-01-01

    The membership, progress, and invited talks, publications, and proceedings made by the Whipple Gamma Ray Collaboration is reported for june 1990 through May 1994. Progress was made in the following areas: the May 1994 Markarian Flare at Whipple and EGRET (Energetic Gamma Ray Experiment Telescope) energies; AGN's (Active Galactic Nuclei); bursts; supernova remnants; and simulations and energy spectra.

  17. PHASE-AVERAGED SPECTRA AND LUMINOSITIES OF GAMMA-RAY EMISSIONS FROM YOUNG ISOLATED PULSARS

    SciTech Connect

    Li, X.; Jiang, Z. J.; Zhang, L.

    2013-03-10

    We study the phase-averaged spectra and luminosities of {gamma}-ray emissions from young, isolated pulsars within a revised outer gap model. In the revised version of the outer gap, there are two possible cases for the outer gaps: the fractional size of the outer gap is estimated through the photon-photon pair process in the first case (Case I), and is limited by the critical field lines in the second case (Case II). The fractional size is described by Case I if the fractional size at the null charge surface in Case I is smaller than that in Case II, and vice versa. Such an outer gap can extend from the inner boundary, whose radial distance to the neutron star is less than that of the null charge surface to the light cylinder for a {gamma}-ray pulsar with a given magnetic inclination. When the shape of the outer gap is determined, assuming that high-energy emission at an averaged radius of the field line in the center of the outer gap, with a Gaussian distribution of the parallel electric field along the gap height, represents typical emission, the phase-averaged {gamma}-ray spectrum for a given pulsar can be estimated in the revised model with three model parameters. We apply the model to explain the phase-averaged spectra of the Vela (Case I) and Geminga (Case II) pulsars. We also use the model to fit the phase-averaged spectra of 54 young, isolated {gamma}-ray pulsars, and then calculate the {gamma}-ray luminosities and compare them with the observed data from Fermi-LAT.

  18. Measurement of cosmic-ray proton and helium spectra during the 1987 solar minimum

    NASA Technical Reports Server (NTRS)

    Seo, E. S.; Ormes, J. F.; Streitmatter, R. E.; Stochaj, S. J.; Jones, W. V.; Stephens, S. A.; Bowen, T.

    1991-01-01

    The differential cosmic-ray proton and helium spectra have been measured during the 1987 solar minimum using a balloon-borne superconducting magnetic spectrometer launched from Prince Albert, Canada. The changing geomagnetic cutoff along the balloon trajectory was observed in the low-energy proton data to be about 25 percent below the nominal calculated values. The absolute particle fluxes were approximately equal to the highest fluxes observed at the previous solar minimum in 1977. Above 10 GV the observed spectra are represented by a power law in rigidity with spectral indices of 2.74 + or - 0.02 for protons and 2.68 + or - 0.03 for helium. The measurements above 200 MeV per nucleon are consistent with rigidity power-law interstellar spectra modulated with the solar modulation parameter phi = 500 MV. The energy dependence of the proton-to-helium ratio is consistent with rigidity power-law injection spectra and rigidity-dependent propagation without reacceleration.

  19. Photon and neutrino spectra of time-dependent photospheric models of gamma-ray bursts

    SciTech Connect

    Asano, K.; Mészáros, P. E-mail: nnp@astro.psu.edu

    2013-09-01

    Thermal photons from the photosphere may be the primary source of the observed prompt emission of gamma-ray bursts (GRBs). In order to produce the observed non-thermal spectra, some kind of dissipation mechanism near the photosphere is required. In this paper we numerically simulate the evolution of the photon spectrum in a relativistically expanding shell with a time-dependent numerical code. We consider two basic models. One is a leptonic model, where a dissipation mechanism heats the thermal electrons maintaining their high temperature. The other model involves a cascade process induced by pp(pn)-collisions which produce high-energy electrons, modify the thermal spectrum, and emit neutrinos. The qualitative properties of the photon spectra are mainly determined by the optical depth at which the dissipation mechanism sets in. Too large optical depths lead to a broad and curved spectrum contradicting the observations, while for optical depths smaller than unity the spectral hardness becomes softer than observed. A significant shift of the spectral peak energy to higher energies due to a large energy injection can lead to an overly broad spectral shape. We show ideal parameter ranges for which these models are able to reproduce the observed spectra. For the pn-collision model, the neutrino fluence in the 10–100 GeV range is well above the atmospheric neutrino fluence, but its detection is challenging for presently available detectors.

  20. Measurement of Separate Cosmic-Ray Electron and Positron Spectra with the Fermi Large Area Telescope

    NASA Technical Reports Server (NTRS)

    Ferrara, E. C.; Harding, A. K.; McEnery, J. E.; Moiseev, A. A.; Ackemann, M.

    2012-01-01

    We measured separate cosmic-ray electron and positron spectra with the Fermi Large Area Telescope. Because the instrument does not have an onboard magnet, we distinguish the two species by exploiting Earth's shadow, which, is offset in opposite directions for opposite charges due to Earth's magnetic field. We estimate and subtract the cosmic-ray proton background using two different methods that produce consistent results. We report the electron-only spectrum, the positron-only spectrum, and the positron fraction between 20 and 200 Ge V. We confirm that the fraction rises with energy in the 20-100 Ge V range. The three new spectral points between 100 and 200 GeV are consistent with a fraction that is continuing to rise with energy.

  1. EVOLUTION OF X-RAY SPECTRA AND LIGHT CURVES OF V1494 AQUILAE

    SciTech Connect

    Rohrbach, J. G.; Ness, J.-U.; Starrfield, S. E-mail: Jan-Uwe.Ness@asu.edu E-mail: juness@sciops.esa.int

    2009-06-15

    We present six Chandra X-ray spectra and light curves obtained for the nova V1494 Aql (1999 No. 2) in outburst. The first three observations were taken with the Advanced CCD Imaging Spectrometer (ACIS-I) on days 134, 187, and 248 after outburst. The count rates were 1.00, 0.69, and 0.53 counts s{sup -1}, respectively. We found no significant periodicity in the ACIS light curves. The X-ray spectra show continuum emission and lines originating from N and O. We found acceptable spectral fits using isothermal APEC models with significantly increased elemental abundances of O and N for all observations. On day 248 after outburst a bright soft component appeared in addition to the fading emission lines. The Chandra observations on days 300, 304, and 727 were carried out with the High Resolution Camera/Low Energy Transmission Grating Spectrometer (LETGS). The spectra consist of continuum emission plus strong emission lines of O and N, implying a high abundance of these elements. On day 300, a flare occurred and periodic oscillations were detected in the light curves taken on days 300 and 304. This flare must have originated deep in the outflowing material since it was variable on short timescales. The spectra extracted immediately before and after the flare are remarkably similar, implying that the flare was an extremely isolated event. Our attempts to fit blackbody, cloudy, or APEC models to the LETGS spectra failed, owing to the difficulty in disentangling continuum and emission-line components. The spectrum extracted during the flare shows a significant increase in the strengths of many of the lines and the appearance of several previously undetected lines. In addition, some of the lines seen before and after the flare are not present during the flare. On day 727 only the count rate from the zeroth order could be derived, and the source was too faint for the extraction of a light curve or spectrum.

  2. Soft X-ray absorption spectra of aqueous salt solutions with highly charged cations in liquid microjets

    SciTech Connect

    Schwartz, Craig P.; Uejio, Janel S.; Duffin, Andrew M.; Drisdell, Walter S.; Smith, Jared D.; Saykally, Richard J.

    2010-03-11

    X-ray absorption spectra of 1M aqueous solutions of indium (III) chloride, yttrium (III) bromide, lanthanum (III) chloride, tin (IV) chloride and chromium (III) chloride have been measured at the oxygen K-edge. Relatively minor changes are observed in the spectra compared to that of pure water. SnCl{sub 4} and CrCl{sub 3} exhibit a new onset feature which is attributed to formation of hydroxide or other complex molecules in the solution. At higher energy, only relatively minor, but salt-specific changes in the spectra occur. The small magnitude of the observed spectral changes is ascribed to offsetting perturbations by the cations and anions.

  3. Ionization injection effects in x-ray spectra generated by betatron oscillations in a laser wakefield accelerator

    NASA Astrophysics Data System (ADS)

    Behm, K. T.; Zhao, T. Z.; Cole, J. M.; Maksimchuk, A.; Mangles, S. P. D.; Nees, J.; Wood, J. C.; Yanovsky, V.; Krushelnick, K.; Thomas, A. G. R.

    2016-05-01

    Single photon counting techniques were used with an x-ray CCD camera to measure features of synchrotron-like x-ray spectra generated by betatron oscillations of electrons in a laser wakefield accelerator (LWFA) with different injection techniques. Measurements were made using the Hercules laser system at the University of Michigan. With a single stage gas cell, we demonstrate that pure helium gas in our wakefield accelerator will produce spectra with higher critical energies than when helium mixed with nitrogen is used. This result was not evident when a two stage gas cell was used.

  4. BAYESIAN CONFIDENCE LIMITS OF ELECTRON SPECTRA OBTAINED THROUGH REGULARIZED INVERSION OF SOLAR HARD X-RAY SPECTRA

    SciTech Connect

    Emslie, A. Gordon; Massone, Anna Maria E-mail: annamaria.massone@cnr.it

    2012-11-10

    Many astrophysical observations are characterized by a single, non-repeatable measurement of a source brightness or intensity, from which we are to construct estimates for the true intensity and its uncertainty. For example, the hard X-ray count spectrum from transient events such as solar flares can be observed only once, and from this single spectrum one must determine the best estimate of the underlying source spectrum I({epsilon}), and hence the form of the responsible electron spectrum F(E). Including statistical uncertainties on the measured count spectrum yields a 'confidence strip' that delineates the boundaries of electron spectra that are consistent with the observed photon spectrum. In this short article, we point out that the expectation values of the source brightness and its variance in a given photon energy bin are in general not (as has been assumed in prior works) equal to n, the number of counts observed in that energy bin. Rather, they depend both on n and on prior knowledge of the overall photon spectrum. Using Bayesian statistics, we provide an explicit procedure and formulas for determining the 'confidence strip' (Bayesian credible region) for F(E), thus providing rigorous bounds on the intensity and shape of the accelerated electron spectrum.

  5. On the X-ray spectra of luminous, inhomogeneous accretion flows

    NASA Astrophysics Data System (ADS)

    Merloni, A.; Malzac, J.; Fabian, A. C.; Ross, R. R.

    2006-08-01

    We discuss the expected X-ray spectral and variability properties of black hole accretion discs at high luminosity, under the hypothesis that radiation-pressure-dominated discs are subject to violent clumping instabilities and, as a result, have a highly inhomogeneous two-phase structure. After deriving the full accretion disc solutions explicitly in terms of the parameters of the model, we study their radiative properties both with a simple two-zone model, treatable analytically, and with radiative transfer simulations which account simultaneously for energy balance and Comptonization in the hot phase, together with reflection, reprocessing, ionization and thermal balance in the cold phase. We show that, if not only the density, but also the heating rate within these flows is inhomogeneous, then complex reflection-dominated spectra can be obtained for a high enough covering fraction of the cold phase. In general, large reflection components in the observed X-ray spectra should be associated with strong soft excesses, resulting from the combined emission of ionized atomic emission lines. The variability properties of such systems are such that, even when contributing to a large fraction of the hard X-ray spectrum, the reflection component is less variable than the power-law-like emission originating from the hot Comptonizing phase, in agreement with what is observed in many Narrow Line Seyfert 1 galaxies and bright Seyfert 1. Our model falls within the family of those trying to explain the complex X-ray spectra of bright AGN with ionized reflection, but presents an alternative, specific, physically motivated, geometrical set-up for the complex multiphase structure of the inner regions of near-Eddington accretion flows.

  6. Detector-Response Correction of Two-Dimensional γ -Ray Spectra from Neutron Capture

    SciTech Connect

    Rusev, G.; Jandel, M.; Arnold, C. W.; Bredeweg, T. A.; Couture, A.; Mosby, S. M.; Ullmann, J. L.

    2015-05-28

    The neutron-capture reaction produces a large variety of γ-ray cascades with different γ-ray multiplicities. A measured spectral distribution of these cascades for each γ-ray multiplicity is of importance to applications and studies of γ-ray statistical properties. The DANCE array, a 4π ball of 160 BaF2 detectors, is an ideal tool for measurement of neutron-capture γ-rays. The high granularity of DANCE enables measurements of high-multiplicity γ-ray cascades. The measured two-dimensional spectra (γ-ray energy, γ-ray multiplicity) have to be corrected for the DANCE detector response in order to compare them with predictions of the statistical model or use them in applications. The detector-response correction problem becomes more difficult for a 4π detection system than for a single detector. A trial and error approach and an iterative decomposition of γ-ray multiplets, have been successfully applied to the detector-response correction. Applications of the decomposition methods are discussed for two-dimensional γ-ray spectra measured at DANCE from γ-ray sources and from the 10B(n, γ) and 113Cd(n, γ) reactions.

  7. Electron energy-loss spectra in molecular fluorine

    NASA Technical Reports Server (NTRS)

    Nishimura, H.; Cartwright, D. C.; Trajmar, S.

    1979-01-01

    Electron energy-loss spectra in molecular fluorine, for energy losses from 0 to 17.0 eV, have been taken at incident electron energies of 30, 50, and 90 eV and scattering angles from 5 to 140 deg. Features in the spectra above 11.5 eV energy loss agree well with the assignments recently made from optical spectroscopy. Excitations of many of the eleven repulsive valence excited electronic states are observed and their location correlates reasonably well with recent theoretical results. Several of these excitations have been observed for the first time and four features, for which there are no identifications, appear in the spectra.

  8. Study on Properties of Energy Spectra of the Molecular Crystals

    NASA Astrophysics Data System (ADS)

    Pang, Xiao-Feng; Chen, Xiang-Rong

    The energy-spectra of nonlinear vibration of molecular crystals such as acetanilide have been calculated by using discrete nonlinear Schrödinger equation appropriate to the systems, containing various interactions. The energy levels including higher excited states are basically consistent with experimental values obtained by infrared absorption and Raman scattering in acetanilide. We further give the features of distribution of the energy-spectra for the acetanilide. Using the energy spectra we also explained well experimental results obtained by Careri et al..

  9. Spatial power-spectra from Yohkoh soft X-ray images

    NASA Technical Reports Server (NTRS)

    Martens, Petrus C. H.; Gomez, Daniel O.

    1992-01-01

    We analyze three sequences of images from active regions, and a full disk image obtained by Yohkoh's Soft X-ray Telescope. Two sequences are from a region at center disk observed through different filters, and one sequence is from the limb. After Fourier-transforming the X-ray intensity of the images we find nearly isotropic power-spectra with an azimuthally integrated slope of -2.1 for the center disk, and -2.8 for the limb images. The full-disk picture yields a spectrum of -2.4. These results are different from the active region spectra obtained with the Normal Incidence X-ray Telescope which have a slope of the order of -3.0, and we ascribe this to the difference in temperature response between the instruments. However, both the SXT and NIXT results are consistent with coronal heating as the end result of a downward quasistatic cascade (in lengthscales) of free magnetic energy in the corona, driven by footpoint motions in the photosphere.

  10. Individual power density spectra of Swift gamma-ray bursts

    NASA Astrophysics Data System (ADS)

    Guidorzi, C.; Dichiara, S.; Amati, L.

    2016-05-01

    Context. Timing analysis can be a powerful tool with which to shed light on the still obscure emission physics and geometry of the prompt emission of gamma-ray bursts (GRBs). Fourier power density spectra (PDS) characterise time series as stochastic processes and can be used to search for coherent pulsations and, more in general, to investigate the dominant variability timescales in astrophysical sources. Because of the limited duration and of the statistical properties involved, modelling the PDS of individual GRBs is challenging, and only average PDS of large samples have been discussed in the literature thus far. Aims: We aim at characterising the individual PDS of GRBs to describe their variability in terms of a stochastic process, to explore their variety, and to carry out for the first time a systematic search for periodic signals and for a link between PDS properties and other GRB observables. Methods: We present a Bayesian procedure that uses a Markov chain Monte Carlo technique and apply it to study the individual PDS of 215 bright long GRBs detected with the Swift Burst Alert Telescope in the 15-150 keV band from January 2005 to May 2015. The PDS are modelled with a power-law either with or without a break. Results: Two classes of GRBs emerge: with or without a unique dominant timescale. A comparison with active galactic nuclei (AGNs) reveals similar distributions of PDS slopes. Unexpectedly, GRBs with subsecond-dominant timescales and duration longer than a few tens of seconds in the source frame appear to be either very rare or altogether absent. Three GRBs are found with possible evidence for a periodic signal at 3.0-3.2σ (Gaussian) significance, corresponding to a multi-trial chance probability of ~1%. Thus, we found no compelling evidence for periodic signal in GRBs. Conclusions: The analogy between the PDS of GRBs and of AGNs could tentatively indicate similar stochastic processes that rule BH accretion across different BH mass scales and objects

  11. Individual power density spectra of Swift gamma-ray bursts

    NASA Astrophysics Data System (ADS)

    Guidorzi, C.; Dichiara, S.; Amati, L.

    2016-04-01

    Context. Timing analysis can be a powerful tool with which to shed light on the still obscure emission physics and geometry of the prompt emission of gamma-ray bursts (GRBs). Fourier power density spectra (PDS) characterise time series as stochastic processes and can be used to search for coherent pulsations and, more in general, to investigate the dominant variability timescales in astrophysical sources. Because of the limited duration and of the statistical properties involved, modelling the PDS of individual GRBs is challenging, and only average PDS of large samples have been discussed in the literature thus far. Aims: We aim at characterising the individual PDS of GRBs to describe their variability in terms of a stochastic process, to explore their variety, and to carry out for the first time a systematic search for periodic signals and for a link between PDS properties and other GRB observables. Methods: We present a Bayesian procedure that uses a Markov chain Monte Carlo technique and apply it to study the individual PDS of 215 bright long GRBs detected with the Swift Burst Alert Telescope in the 15-150 keV band from January 2005 to May 2015. The PDS are modelled with a power-law either with or without a break. Results: Two classes of GRBs emerge: with or without a unique dominant timescale. A comparison with active galactic nuclei (AGNs) reveals similar distributions of PDS slopes. Unexpectedly, GRBs with subsecond-dominant timescales and duration longer than a few tens of seconds in the source frame appear to be either very rare or altogether absent. Three GRBs are found with possible evidence for a periodic signal at 3.0-3.2σ (Gaussian) significance, corresponding to a multi-trial chance probability of ~1%. Thus, we found no compelling evidence for periodic signal in GRBs. Conclusions: The analogy between the PDS of GRBs and of AGNs could tentatively indicate similar stochastic processes that rule BH accretion across different BH mass scales and objects

  12. Radial Distribution of Electron Spectra from High-Energy Ions

    NASA Technical Reports Server (NTRS)

    Cucinotta, Francis A.; Katz, Robert; Wilson, John W.

    1998-01-01

    The average track model describes the response of physical and biological systems using radial dose distribution as the key physical descriptor. We report on an extension of this model to describe the average distribution of electron spectra as a function of radial distance from an ion. We present calculations of these spectra for ions of identical linear energy transfer (LET), but dissimilar charge and velocity to evaluate the differences in electron spectra from these ions. To illustrate the usefulness of the radial electron spectra for describing effects that are not described by electron dose, we consider the evaluation of the indirect events in microdosimetric distributions for ions. We show that folding our average electron spectra model with experimentally determined frequency distributions for photons or electrons provides a good representation of radial event spectra from high-energy ions in 0.5-2 micrometer sites.

  13. The x ray variability of NGC6814: Power spectra

    NASA Technical Reports Server (NTRS)

    Done, C.; Madejski, G. M.; Mushotsky, R. F.; Turner, T. J.; Koyama, K.; Kunieda, H.

    1992-01-01

    Simulation techniques are used to obtain the X-ray variability power spectrum of unevenly sampled GINGA data from NGC6814. A simple power law is not an adequate description of the power spectrum, with the residuals showing excess power on timescales consistent with the periodicity seen in EXOSAT observations of this object. However the shape of the folded lightcurve is very different, with 3 main peaks, two of which are separated by an extremely sharp dip instead of the single peak and small harmonic structure observed by EXOSAT. Using the dip as a fiducial mark, a second GINGA observation of this source taken one year later is found to be consistent with being completely periodic and phase coherent with this first GINGA observation. Thus the period is consistent with being constant over a period of 6 years, but phase coherence is only maintained on timescales of approximately 1 year. Over 75 percent of the total source variability is due to the periodic component (r.m.s. amplitude of 36 percent). The residual variability can be described as the more usual 'flicker noise' f(exp -1.1) powerlaw. This shows no apparent high frequency break on timescales greater than 300 seconds. Subtle differences in the shape of the folded light curve with energy, and the very large amount of power in the periodic component suggest occultation as its origin, though amplification of variability from an X-ray emitting 'hot spot' at the disk inner radius through gravitational lensing is also possible. The former suffers from the very arbitrary nature of the periodic timescale, while the latter is unattractive as it cannot simply explain the lack of high frequency break in the residual power. That these models probably fail to provide an adequate explanation may be due to the added complexity of anisotropy of the X-ray emission, suggested by the discrepancy between the lack of soft photons implied by the flat spectrum and the copious source of soft photons available from reprocessing in

  14. Measurement of Separate Cosmic-Ray Electron and Positron Spectra with the Fermi Large Area Telescope

    NASA Technical Reports Server (NTRS)

    Ackermann, M.; Ajello, M.; Allafort, A.; Baldini, L.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Blandford, R. D.; Bloom, E. D.; Bonamente, E.; Brogland, A. W.; Bouvier, A.; Bregeon, J.; Brigida, M.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caraveo, P. A.; Ferrara, E. C.; Harding, A. K.; McEnery, J. E.

    2011-01-01

    We measured separate cosmic-ray electron and positron spectra with the Fermi Large Area Telescope. Because the instrument does not have an onboard magnet, we distinguish the two species by exploiting the Earth's shadow, which is offset in opposite directions for opposite charges due to the Earth's magnetic field. We estimate and subtract the cosmic-ray proton background using two different methods that produce consistent results. We report the electron-only spectrum, the positron-only spectrum, and the positron fraction between 20 GeV and 200 GeV, We confirm that the fraction rises with energy in the 20-100 GeV range and determine for the first time that it continues to rise between 100 and 200 GeV,

  15. X-ray spectra of a complete sample of extragalactic core-dominated radio sources

    NASA Technical Reports Server (NTRS)

    Brunner, H.; Lamer, G.; Worrall, D. M.; Staubert, R.

    1994-01-01

    We present ROSAT soft X-ray spectra for the members of a complete sample of 13 core-dominated, flat radio spectrum sources. The sample comprises all radio sources from a flux-limited radio catalog (S(sub 5GHz) greater than 1 Jy; Kuehr et al. 1981) which are north of delta = 70 deg, at galactic latitudes b greater than 10 deg, and have a flat radio spectrum between 1.4 and 5 GHz (alpha(sub r) less than 0.5; f approximately nu(sup -alpha)). The sources have already undergone much study at radio and optical wavelengths and are classified in broad terms as quasars (8 sources) and BL Lac objects (5 sources). We find mean X-ray power-law energy indices of alpha(sub x) = 0.59 +/- 0.19 for the quasars and 1.36 +/- 0.27 for the BL Lac objects (68% confidence range for two parameters of interest as determined by a maximum likelihood method), supporting earlier Einstein Observatory results for heterogeneous samples of sources (Worrall & Wilkes 1990). A non-zero dispersion on alpha(sub x) is found for both the quasars and the BL Lac objects. When we incorporate published radio, mm, and optical measurements and compare the X-ray and broad-band spectral indices alpha(sub x), alpha(sub rx), alpha(sub mm,x), and alpha(sub ox), the most obvious difference between the quasar and BL Lac subsamples lies within the X-ray band. We have fitted the multi-wavelength data to inhomogeneous synchotron-self-Compton models and find that, for the BL Lac objects with steep X-ray spectra, synchotron emission can account for the radio to soft X-ray measurements, whereas the BL Lac objects with hard X-ray spectra and the quasars require significant Compton emission to model the spectral flattening indicated by alpha(sub x) less than alpha(sub ox).

  16. Simulation of X-ray absorption spectra with orthogonality constrained density functional theory†

    PubMed Central

    Derricotte, Wallace D.; Evangelista, Francesco A.

    2015-01-01

    Orthogonality constrained density functional theory (OCDFT) is a variational time-independent approach for the computation of electronic excited states. In this work we extend OCDFT to compute core-excited states and generalize the original formalism to determine multiple excited states. Benchmark computations on a set of 13 small molecules and 40 excited states show that unshifted OCDFT/B3LYP excitation energies have a mean absolute error of 1.0 eV. Contrary to time-dependent DFT, OCDFT excitation energies for first- and second-row elements are computed with near-uniform accuracy. OCDFT core excitation energies are insensitive to the choice of the functional and the amount of Hartree–Fock exchange. We show that OCDFT is a powerful tool for the assignment of X-ray absorption spectra of large molecules by simulating the gas-phase near-edge spectrum of adenine and thymine. PMID:25690350

  17. PHASE-RESOLVED X-RAY SPECTRA OF MAGNETARS AND THE CORONAL OUTFLOW MODEL

    SciTech Connect

    Hascoët, Romain; Beloborodov, Andrei M.; Den Hartog, Peter R.

    2014-05-01

    We test a model recently proposed for the persistent hard X-ray emission from magnetars. In the model, hard X-rays are produced by a decelerating electron-positron flow in the closed magnetosphere. The flow decelerates as it radiates its energy away via resonant scattering of soft X-rays, then it reaches the top of the magnetic loop and annihilates there. We test the model against observations of three magnetars: 4U 0142+61, 1RXS J1708-4009, and 1E 1841-045. We find that the model successfully fits the observed phase-resolved spectra. We derive constraints on the angle between the rotational and magnetic axes of the neutron star, the object inclination to the line of sight, and the size of the active twisted region filled with the plasma flow. Using the fit of the hard X-ray component of the magnetar spectrum, we revisit the remaining soft X-ray component. We find that it can be explained by a modified two-temperature blackbody model. The hotter blackbody is consistent with a hot spot covering 1%-10% of the neutron star surface. Such a hot spot is expected at the base of the magnetospheric e {sup ±} outflow, as some particles created in the e {sup ±} discharge flow back and bombard the stellar surface.

  18. X-RAY SPECTRA FROM MAGNETOHYDRODYNAMIC SIMULATIONS OF ACCRETING BLACK HOLES

    SciTech Connect

    Schnittman, Jeremy D.; Krolik, Julian H.; Noble, Scott C. E-mail: jhk@pha.jhu.edu

    2013-06-01

    We present the results of a new global radiation transport code coupled to a general relativistic magnetohydrodynamic simulation of an accreting, non-rotating black hole. For the first time, we are able to explain from first principles in a self-consistent way all the components seen in the X-ray spectra of stellar-mass black holes, including a thermal peak and all the features associated with strong hard X-ray emission: a power law extending to high energies, a Compton reflection hump, and a broad iron line. Varying only the mass accretion rate, we are able to reproduce a wide range of X-ray states seen in most galactic black hole sources. The temperature in the corona is T{sub e} {approx} 10 keV in a boundary layer near the disk and rises smoothly to T{sub e} {approx}> 100 keV in low-density regions far above the disk. Even as the disk's reflection edge varies from the horizon out to Almost-Equal-To 6M as the accretion rate decreases, we find that the shape of the Fe K{alpha} line is remarkably constant. This is because photons emitted from the plunging region are strongly beamed into the horizon and never reach the observer. We have also carried out a basic timing analysis of the spectra and find that the fractional variability increases with photon energy and viewer inclination angle, consistent with the coronal hot spot model for X-ray fluctuations.

  19. Delayed Neutron Energy Spectra Following Fast Fission of Uranium

    NASA Astrophysics Data System (ADS)

    Villani, Marcel Franklin

    Delayed neutron energy spectra have been measured for six delay-time intervals following the fast fission of ^{238}U nuclei. The delay-time intervals span the range 0.17 to 10.2 seconds following initial fission while the measured spectra span neutron energies from 10 keV to 4 MeV. The experiment was performed utilizing the UMass/Lowell 5.5 MV Van de Graaff accelerator to produce fast neutrons for inducing fission in a ^{238} U lined fission chamber. The fission fragments were flushed via a helium jet stream to a well-shielded counting room where they were deposited onto a moving tape (magnetic audio tape) and transferred to a beta-neutron time-of-flight spectrometer. By adjusting the tape speed, composite delayed neutron time-of-flight spectra were measured for several different delay-time intervals. These measurements involved beta-neutron coincidences with ^6 Li-loaded glass scintillators for neutron energies from 10 keV to 450 keV and Bicron BC 501 liquid scintillators for the neutron energy range 200 keV-4 MeV. The measured composite delayed neutron energy spectra for ^{238}U are compared to the composite spectra for ^ {235}U and ^{239} Pu, and also to composite spectra derived for ^{238}U from the ENDF/B-VI database, which is based on summation calculations of individual precursor data supplemented by theoretical estimates. The composite spectra of ^{235}U and ^{239}Pu were obtained from previous measurements of delayed neutron spectra at this laboratory. The composite spectra are also decomposed into Keepin six-group spectra and compared with those for ^{239}Pu and ^{235}U. In addition, an equilibrium spectrum has been calculated from the measured composite spectra using several different analytical techniques and is also compared with the equilibrium spectrum of ^{238}U measured in an earlier study at this laboratory.

  20. Hints of the existence of axionlike particles from the gamma-ray spectra of cosmological sources

    SciTech Connect

    Sanchez-Conde, M. A.; Prada, F.; Paneque, D.; Bloom, E.; Dominguez, A.

    2009-06-15

    Axionlike particles (ALPs) are predicted to couple with photons in the presence of magnetic fields. This effect may lead to a significant change in the observed spectra of gamma-ray sources such as active galactic nuclei (AGNs). Here we carry out a detailed study that for the first time simultaneously considers in the same framework both the photon/axion mixing that takes place in the gamma-ray source and that one expected to occur in the intergalactic magnetic fields. An efficient photon/axion mixing in the source always means an attenuation in the photon flux, whereas the mixing in the intergalactic medium may result in a decrement and/or enhancement of the photon flux, depending on the distance of the source and the energy considered. Interestingly, we find that decreasing the value of the intergalactic magnetic field strength, which decreases the probability for photon/axion mixing, could result in an increase of the expected photon flux at Earth if the source is far enough. We also find a 30% attenuation in the intensity spectrum of distant sources, which occurs at an energy that only depends on the properties of the ALPs and the intensity of the intergalactic magnetic field, and thus independent of the AGN source being observed. Moreover, we show that this mechanism can easily explain recent puzzles in the spectra of distant gamma-ray sources, like the possible detection of TeV photons from 3C 66A (a source located at z=0.444) by MAGIC and VERITAS, which should not happen according to conventional models of photon propagation over cosmological distances. Another puzzle is the recent published lower limit to the extragalactic background light intensity at 3.6 {mu}m (which is almost twice larger as the previous one), which implies very hard spectra for some detected TeV gamma-ray sources located at z=0.1-0.2. The consequences that come from this work are testable with the current generation of gamma-ray instruments, namely Fermi (formerly known as GLAST) and

  1. Intergalactic Photon Spectra from the Far-IR to the UV Lyman Limit for 0 < z < 6 and the Optical Depth of the Universe to High-Energy Gamma Rays

    NASA Technical Reports Server (NTRS)

    Stecker, F. W.; Malkan, M. A.; Scully, S. T.

    2006-01-01

    We calculate the intergalactic photon density as a function of both energy and redshift for 0energies from.003 eV to the Lyman limit cutoff at 13.6 eV in a (Omega)CDM universe with (Omega)(Lambda)=0.7 and (Omega)m=0.3. The basic features of our backward-evolution model for galaxies were developed in earlier papers by Malkan & Stecker. With a few improvements, we find that this evolutionary model gives predictions of new deep number counts from Spitzer, as well as a calculation of the spectral energy distribution of the diffuse infrared background, which are in good agreement with the data. We then use our calculated intergalactic photon densities to extend previous work on the absorption of high-energy Gamma-rays in intergalactic space owing to interactions with low-energy photons and the 2.7 K cosmic microwave background radiation. We calculate the optical depth of the universe, Tau , for Gamma-rays having energies from 4 GeV to 100 TeV emitted by sources at redshifts from 0 to 5. We also give an analytic fit with numerical coefficients for approximating (E(Gamma), z). As an example of the application of our results, we calculate the absorbed spectrum of the blazar PKS 2155-304 at z=0.117 and compare it with the spectrum observed by the HESS air Cerenkov Gamma-ray telescope array.

  2. Spectra of Cosmic Ray Electrons and Diffuse Gamma Rays with the Constraints of AMS-02 and HESS Data

    NASA Astrophysics Data System (ADS)

    Chen, Ding; Huang, Jing; Jin, Hong-Bo

    2015-10-01

    Recently, AMS-02 reported their results of cosmic ray (CR) observations. In addition to the AMS-02 data, we add HESS data to estimate the spectra of CR electrons and the diffuse gamma rays above TeV. In the conventional diffusion model, a global analysis is performed on the spectral features of CR electrons and the diffuse gamma rays by the GALRPOP package. The results show that the spectrum structure of the primary component of CR electrons cannot be fully reproduced by a simple power law and that the relevant break is around 100 GeV. At the 99% confidence level (C.L.) the injection indices above the break decrease from 2.54 to 2.35, but the ones below the break are only in the range of 2.746-2.751. The spectrum of CR electrons does not need to add TeV cutoff to also match the features of the HESS data. Based on the difference between the fluxes of CR electrons and their primary components, the predicted excess of CR positrons is consistent with the interpretation that these positrons originate from a pulsar or dark matter. In the analysis of the Galactic diffuse gamma rays with the indirect constraint of AMS-02 and HESS data, it is found that the fluxes of Galactic diffuse gamma rays are consistent with the GeV data of the Fermi-Large Area Telescope (LAT) in the high-latitude regions. The results indicate that inverse Compton scattering is the dominant component in the range of hundreds of GeV to tens of TeV, respectively from the high-latitude regions to the low ones, and in all of the regions of the Galaxy the flux of diffuse gamma rays is less than that of CR electrons at the energy scale of 20 TeV.

  3. Bethe-Salpeter Equation Approach for Calculations of X-ray Spectra

    NASA Astrophysics Data System (ADS)

    Vinson, John

    X-ray spectroscopy is a powerful and widely used tool for the investigation of the electronic structure of a large variety of solid state materials, including crystals materials, liquids, amorphous solids, molecules, and extended states such as clusters or interfaces. The local nature of x-ray mediated electronic excitations, involving transitions to or from localized, atomic-like, core levels, makes them ideal probes of local electronic properties: bonding character, charge transfer, and local geometry. The interpretation of spectra relies on modeling the excitations accurately to provide a concrete connection between specific properties of a system and the resulting x-ray spectrum. As experimental techniques and facilities have improved, including third generation synchrotron sources and the advent of x-ray free electron lasers, measurements have been taken on wider ranges of systems, exploring the effects of temperature and pressure, and at higher resolutions than before, but theoretical techniques have lagged. Our goal is to develop a first-principles theoretical framework capable of achieving quantitative agreement with x-ray absorption near-edge structure (XANES) experiments. This thesis aims to develop the Bethe-Salpeter equation (BSE), a particle-hole Green's function method, for describing the excited electronic state produced in core-level x-ray absorption and related spectroscopies. Building upon density functional theory along with self-energy corrections, our approach provides connection to experiment with minimal adjustable parameters, to both aid in interpretation and highlight unaccounted for physical processes. While a fully parameter-free method for calculating x-ray spectroscopy remains elusive, our method presented here allows for quantitative comparison to experiment without system-dependent fits. This method has been implemented in the OCEAN software package, and results are presented for both insulating and metallic materials, including 3d

  4. Cosmic ray spectral deformation caused by energy determination errors

    NASA Astrophysics Data System (ADS)

    Carlson, Per; Wannemark, Conny

    2005-08-01

    Using simulation methods, distortion effects on energy spectra caused by errors in the energy determination have been investigated. For cosmic ray proton spectra falling steeply with kinetic energy E as E-2.7, significant effects appear. When magnetic spectrometers are used to determine the energy, the relative error increases linearly with the energy and distortions with a sinusoidal form appear starting at an energy that depends significantly on the error distribution but at an energy lower than that corresponding to the maximum detectable rigidity of the spectrometer. The effect should be taken into consideration when comparing data from different experiments, often having different error distributions.

  5. Signatures of a Two Million Year Old Supernova in the Spectra of Cosmic Ray Protons, Antiprotons, and Positrons.

    PubMed

    Kachelrieß, M; Neronov, A; Semikoz, D V

    2015-10-30

    The locally observed cosmic ray spectrum has several puzzling features, such as the excess of positrons and antiprotons above ~20  GeV and the discrepancy in the slopes of the spectra of cosmic ray protons and heavier nuclei in the TeV-PeV energy range. We show that these features are consistently explained by a nearby source which was active approximately two million years ago and has injected (2-3)×10^{50} erg in cosmic rays. The transient nature of the source and its overall energy budget point to the supernova origin of this local cosmic ray source. The age of the supernova suggests that the local cosmic ray injection was produced by the same supernova that has deposited ^{60}Fe isotopes in the deep ocean crust. PMID:26565453

  6. On the possibility of observing cosmic ray sources in high energy gamma rays

    NASA Technical Reports Server (NTRS)

    Ormes, J. F.

    1987-01-01

    If cosmic rays are accelerated by strong shocks, then cosmic ray sources should be characterized by spectra, dN/dE alpha E exp -(2.0-2.2), reflecting the strength of those shocks. This is expected from the 'standard leaky box' model of cosmic ray propagation in which the source spectra are harder than the observed spectra because higher energy particles have shorter residence times in the galactic magnetic fields. Furthermore, data on cosmic ray nucleons suggest that these sources might be surrounded by material. If the latter is true, such sources should be observable in gamma rays at energies beyond 1 GeV where the angular resolution of gamma-ray telescopes is optimized and the background is significantly reduced. For identified sources, the source location accuracy can be shown to improve with increasing energy in spite of the decreasing statistics, as long as the gamma-ray spectrum is harder than dN/dE alpha E exp -gamma. A Monte Carlo model is used to predict the photon spectra which would be expected from cosmic ray sources under varying assumptions about the strength of the shocks in the acceleration region.

  7. Cosmic ray LET spectra and doses on board Cosmos-2044 biosatellite

    NASA Technical Reports Server (NTRS)

    Watts, J. W., Jr.; Parnell, T. A.; Dudkin, V. E.; Kovalev, E. E.; Potapov, Yu. V.; Benton, E. V.; Frank, A. L.; Benton, E. R.; Beaujean, R.; Heilmann, C.

    1995-01-01

    Results of the experiments on board Cosmos-2044 (Biosatellite 9) are presented. Various nuclear track detectors (NTD) (dielectric, AgCl-based, nuclear emulsions) were used to obtain the Linear Energy Transfer (LET) spectra inside and outside the satellite. The spectra from the different NTDs have proved to be in general agreement. The results of LET spectra calculations using two different models are also presented. The resultant LET distributions are used to calculate the absorbed and equivalent doses and the orbit-averaged quality factors (QF) of the cosmic rays (CR). Absorbed dose rates inside (approximately 20 g cm (exp -2) shielding) and outside (1 g cm(exp -2) the spacecraft, omitting electrons, were found to be 4.8 and 8.6 mrad d (exp -1), respectively, while the corresponding equivalent doses were 8.8 and 19.7 mrem d(exp -1). The effects of the flight parameters on the total fluence of, and on the dose from the CR particles are analyzed. Integral dose distributions of the detected particles are also determined. The LET values which separate absorbed and equivalent doses into 50% intervals are estimated. The CR-39 dielectric NTD is shown to detect 20-30% of the absorbed dose and 60-70% of the equivalent dose in the Cosmos-2044 orbit. The influence of solar activity phase on the magnitude of CR flux is discussed.

  8. Examining molecular clouds in the Galactic Centre region using X-ray reflection spectra simulations.

    NASA Astrophysics Data System (ADS)

    Walls, M.; Chernyakova, M.; Terrier, R.; Goldwurm, A.

    2016-09-01

    In the centre of our galaxy lies a super-massive black hole, identified with the radio source Sagittarius A⋆. This black hole has an estimated mass of around 4 million solar masses. Although Sagittarius A⋆ is quite dim in terms of total radiated energy, having a luminosity that is a factor of 1010 lower than its Eddington luminosity, there is now compelling evidence that this source was far brighter in the past. Evidence derived from the detection of reflected X-ray emission from the giant molecular clouds in the galactic centre region. However, the interpretation of the reflected emission spectra cannot be done correctly without detailed modelling of the reflection process. Attempts to do so can lead to an incorrect interpretation of the data. In this paper we present the results of a Monte Carlo simulation code we developed in order to fully model the complex processes involved in the emerging reflection spectra. The simulated spectra can be compared to real data in order to derive model parameters and constrain the past activity of the black hole. In particular we apply our code to observations of Sgr B2, in order to constrain the position and density of the cloud and the incident luminosity of the central source. The results of the code have been adapted to be used in Xspec by a large community of astronomers.

  9. Electron spectra of xenon clusters irradiated with a laser-driven plasma soft-x-ray laser pulse

    SciTech Connect

    Namba, S.; Takiyama, K.; Hasegawa, N.; Kishimoto, M.; Nishikino, M.; Kawachi, T.

    2011-11-15

    Xenon clusters were irradiated with plasma soft-x-ray laser pulses (having a wavelength of 13.9 nm, time duration of 7 ps, and intensities of up to 10 GW/cm{sup 2}). The laser photon energy was high enough to photoionize 4d core electrons. The cross section is large due to a giant resonance. The interaction was investigated by measuring the electron energy spectra. The photoelectron spectra for small clusters indicate that the spectral width due to the 4d hole significantly broadens with increasing cluster size. For larger clusters, the electron energy spectra evolve into a Maxwell-Boltzmann distribution, as a strongly coupled cluster nanoplasma is generated.

  10. X-Ray Spectra from MHD Simulations of Accreting Black Holes

    NASA Technical Reports Server (NTRS)

    Schnittman, Jeremy D.; Krolik, Julian H.; Noble, Scott C.

    2012-01-01

    We present the results of a new global radiation transport code coupled to a general relativistic magneto-hydrodynamic simulation of an accreting, nonrotating black hole. For the first time, we are able to explain from first principles in a self-consistent way the X-ray spectra observed from stellar-mass black holes, including a thermal peak, Compton reflection hump, power-law tail, and broad iron line. Varying only the mass accretion rate, we are able to reproduce the low/hard, steep power-law, and thermal-dominant states seen in most galactic black hole sources. The temperature in the corona is T(sub e) 10 keV in a boundary layer near the disk and rises smoothly to T(sub e) greater than or approximately 100 keV in low-density regions far above the disk. Even as the disk's reflection edge varies from the horizon out to approximately equal to 6M as the accretion rate decreases, we find that the shape of the Fe Ka line is remarkably constant. This is because photons emitted from the plunging region are strongly beamed into the horizon and never reach the observer. We have also carried out a basic timing analysis of the spectra and find that the fractional variability increases with photon energy and viewer inclination angle, consistent with the coronal hot spot model for X-ray fluctuations.