Science.gov

Sample records for kev range

  1. Mutagenic effect of a keV range N + beam on mammalian cells

    NASA Astrophysics Data System (ADS)

    Feng, Huiyun; Wu, Lijun; Yu, Lixiang; Han, Wei; Liu, Xuelan; Yu, Zengliang

    2005-07-01

    The radiobiological effects of a keV (5-20 keV) range nitrogen ion (N +) beam on mammalian cells were studied, particularly with regard to the induction of mutation in the cell genome. The experiment demonstrated that the 20 keV N + beam, which resulted in cell death to a certain extent, induced a 2-3 fold increase in the mutation rates at the CD59 gene locus of the mammalian A L cells as compared to the control. Within certain fluence ranges (0-6 × 10 14 N +/cm 2), the cell survival displayed a down-up-down pattern which is similar to the phenomenon known as 'hyper-radiosensitivity' manifested under low-dose irradiation; the CD59 mutation rate firstly showed a gradual rise up to a 3-fold increment above the background level as the ion fluence went up to 4 × 10 14 N +/cm 2, after this peak point however, a downtrend appeared though the ion fluence increased further. It was also observed that the fraction of CD59 mutation bears no proportional relation to ion energy in further experiments of mutation induction by N + beams with the incident energies of 5, 10, 15 and 20 keV at the same fluence of 3 × 10 14 N +/cm 2. Analyses of the deletion patterns of chromosome 11 in CD59- mutants induced by 5-20 keV N + beams showed that these ions did not result in large-size chromosome deletions in this mammalian cell system. A preliminary discussion, suggesting that the mutagenic effect of such low-energy ion influx on mammalian cells could result from multiple processes involving direct collision of particles with cellular DNA, and cascade atomic and molecular reactions due to plentiful primary and secondary particles, was also presented. The study provided the first glimpse into the roles low-energy ions may play in inducing mutagenesis in mammalian cells, and results will be of much value in helping people to understand the contribution of low-energy ions to radiological effects of various ionising radiations.

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

    SciTech Connect

    Derrien, H.

    2002-09-30

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

  3. Calibration of semiconductor detectors in the 200-8500 keV range at VNIIM.

    PubMed

    Tereshchenko, Evgeny E; Moiseev, Nikolay

    2012-09-01

    At the ionising radiation department of the D.I. Mendeleyev Institute for Metrology, a semiconductor detector was calibrated in the energy range 200-8500 keV using (n,2γ) and (n,γ) reactions. Separate cylindrical targets (77 mm diameter and 10mm height) were made from mercuric sulphate, sodium chloride and metallic titanium. A (252)Cf spontaneous fission neutron source, placed in 150 mm diameter polyethylene ball, was used to generate thermal neutrons. The optimal target dimensions were determined taking into account the thermal neutron cross-sections and gamma-radiation attenuations in the target materials. The influence of the background radiation induced by neutrons from the walls, floors and ceilings was also taken into account. The shapes of the efficiency curves for point and volume sources in the 200-8500 keV range have been investigated. The experimental results are in good agreement with Monte-Carlo calculations. The emission rate of the 6.13 MeV photons from a (238)Pu-(13)C source was determined with an expanded uncertainty, U(c), of 10% (k=2). PMID:22512978

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

    PubMed

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

    2005-01-01

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

  5. Attosecond quantum entanglement in neutron Compton scattering from water in the keV range

    NASA Astrophysics Data System (ADS)

    Chatzidimitriou-Dreismann, C. A.

    2006-11-01

    Scattering of neutrons in the 24- 150 keV incident energy range from H2O relative to that of D2O and H2O- D2O mixtures was reported very recently. Studying time-of-flight integrated intensities, the applied experimental procedure appears to be transparent and may open up a novel class of neutron experiments regarding the “anomalous” scattering from protons, firstly observed in our experiment at ISIS in the 5- 100 eV range. The keV-results were analyzed within standard theory, also including (1) multiple scattering and (2) the strong incident-energy dependence of the neutron-proton cross-section σH(E0) in this energy range. The analysis reveals a striking anomalous ratio of scattering intensity of H2O relative to that of D2O of about 20%, thus being in surprisingly good agreement with the earlier results of the original experiment at ISIS.

  6. Calibration of SIOM-5FW film in the range of 0.1-4 keV

    NASA Astrophysics Data System (ADS)

    Chenais-Popovics, C.; Reverdin, C.; Ioannou, I.

    2006-06-01

    The SIOM-5FW film produced for the sub-keV x-ray detection range was calibrated here in a wide energy range (0.1-4keV). A single set of parameters valid in the whole measured energy range was determined for the calibration of the Shangai 5F (SIOM-5FW) film from a parametric fit of the data. The sensitivity of the SIOM-5FW film was measured to be four times lower than that of the Kodak DEF film at 2.5keV photon energy. Modeling of the DEF and SIOM-5FW films provides a good comparison of their sensitivity in the 0.1-10keV range.

  7. Calibration of SIOM-5FW film in the range of 0.1-4 keV

    SciTech Connect

    Chenais-Popovics, C.; Reverdin, C.; Ioannou, I.

    2006-06-15

    The SIOM-5FW film produced for the sub-keV x-ray detection range was calibrated here in a wide energy range (0.1-4 keV). A single set of parameters valid in the whole measured energy range was determined for the calibration of the Shangai 5F (SIOM-5FW) film from a parametric fit of the data. The sensitivity of the SIOM-5FW film was measured to be four times lower than that of the Kodak DEF film at 2.5 keV photon energy. Modeling of the DEF and SIOM-5FW films provides a good comparison of their sensitivity in the 0.1-10 keV range.

  8. Characterisation of a counting imaging detector for electron detection in the energy range 10-20 keV

    NASA Astrophysics Data System (ADS)

    Moldovan, G.; Sikharulidze, I.; Matheson, J.; Derbyshire, G.; Kirkland, A. I.; Abrahams, J. P.

    2012-07-01

    As part of a feasibility study into the use of novel electron detector for X-ray photoelectron emission microscopes (XPEEM) and related methods, we have characterised the imaging performance of a counting Medipix 2 readout chip bump bonded to a Silicon diode array sensor and directly exposed to electrons in the energy range 10-20 keV. Detective Quantum Efficiency (DQE), Modulation Transfer Function (MTF) and Noise Power Spectra (NPS) are presented, demonstrating very good performance for the case of electrons with an energy of 20 keV. Significant reductions in DQE are observed for electrons with energy of 15 keV and less, down to levels of 20% for electrons of 10 keV.

  9. Neutron Total Cross Sections of {sup 235}U From Transmission Measurements in the Energy Range 2 keV to 300 keV and Statistical Model Analysis of the Data

    SciTech Connect

    Derrien, H.; Harvey, J.A.; Larson, N.M.; Leal, L.C.; Wright, R.Q.

    2000-05-01

    The average {sup 235}U neutron total cross sections were obtained in the energy range 2 keV to 330 keV from high-resolution transmission measurements of a 0.033 atom/b sample.1 The experimental data were corrected for the contribution of isotope impurities and for resonance self-shielding effects in the sample. The results are in very good agreement with the experimental data of Poenitz et al.4 in the energy range 40 keV to 330 keV and are the only available accurate experimental data in the energy range 2 keV to 40 keV. ENDF/B-VI evaluated data are 1.7% larger. The SAMMY/FITACS code 2 was used for a statistical model analysis of the total cross section, selected fission cross sections and data in the energy range 2 keV to 200 keV. SAMMY/FITACS is an extended version of SAMMY which allows consistent analysis of the experimental data in the resolved and unresolved resonance region. The Reich-Moore resonance parameters were obtained 3 from a SAMMY Bayesian fits of high resolution experimental neutron transmission and partial cross section data below 2.25 keV, and the corresponding average parameters and covariance data were used in the present work as input for the statistical model analysis of the high energy range of the experimental data. The result of the analysis shows that the average resonance parameters obtained from the analysis of the unresolved resonance region are consistent with those obtained in the resolved energy region. Another important result is that ENDF/B-VI capture cross section could be too small by more than 10% in the energy range 10 keV to 200 keV.

  10. NEUTRON TOTAL CROSS SECTIONS OF 235U FROM TRANSMISSION MEASUREMENTS IN THE ENERGY RANGE 2 keV to 300 keV AND STATISTICAL MODEL ANALYSIS OF THE DATA

    SciTech Connect

    Derrien, H.

    2000-05-22

    The average {sup 235}U neutron total cross sections were obtained in the energy range 2 keV to 330 keV from high-resolution transmission measurements of a 0.033 atom/b sample. The experimental data were corrected for the contribution of isotope impurities and for resonance self-shielding effects in the sample. The results are in very good agreement with the experimental data of Poenitz et al. in the energy range 40 keV to 330 keV and are the only available accurate experimental data in the energy range 2 keV to 40 keV. ENDF/B-VI evaluated data are 1.7% larger. The SAMMY/FITACS code was used for a statistical model analysis of the total cross section, selected fission cross sections and {alpha} data in the energy range 2 keV to 200 keV. SAMMY/FITACS is an extended version of SAMMY which allows consistent analysis of the experimental data in the resolved and unresolved resonance region. The Reich-Moore resonance parameters were obtained from a SAMMY Bayesian fits of high resolution experimental neutron transmission and partial cross section data below 2.25 keV, and the corresponding average parameters and covariance data were used in the present work as input for the statistical model analysis of the high energy range of the experimental data. The result of the analysis shows that the average resonance parameters obtained from the analysis of the unresolved resonance region are consistent with those obtained in the resolved energy region. Another important result is that ENDF/B-VI capture cross section could be too small by more than 10% in the energy range 10 keV to 200 keV.

  11. Neutron Scattering Cross Sections for Natural Carbon in the Energy Range 2-133 keV

    SciTech Connect

    Gritzay, O; Gnidak, M; Kolotyi, V; Korol, O; Razbudey, V; Venedyktov, V; Richardson, J H; Sale, K

    2006-06-14

    Natural carbon is well known as reactor structure material and at the same time as one of the most important neutron scattering standards, especially at energies less than 2 MeV, where the neutron total and neutron scattering cross sections are essentially identical. The best neutron total cross section experimental data for natural carbon in the range 1-500 keV have uncertainties of 1-4%. However, the difference between these data and those based on R-matrix analysis and used in the ENDF libraries is evident, especially in the energy range 1-60 keV. Experimental data for total scattering neutron cross sections for this element in the energy range 1-200 keV are scanty. The use of the technique of neutron filtered beams developed at the Kyiv Research Reactor makes it possible to reduce the uncertainty of the experimental data and to measure the neutron scattering cross sections on natural carbon in the energy range 2-149 keV with accuracies of 3-6%. Investigations of the neutron scattering cross section on carbon were carried out using 5 filters with energies 2, 3.5, 24, 54 and 133 keV. The neutron scattering cross sections were measured using a detector system covering nearly 2{pi}. The detector consisting of {sup 3}He counters (58 units), was located just above the carbon samples. The {sup 3}He counters (CHM-37, 7 atm, diameter =18 mm, L=50 cm) are placed in five layers (12 or 11 in each layer). To determine the neutron scattering cross section on carbon the relative method of measurement was used. The isotope {sup 208}Pb was used as the standard. The normalization factor, which is a function of detector efficiency, thickness of the carbon samples, thickness of the {sup 208}Pb sample, geometry, etc., for each sample and for each filter energy has been obtained through Monte Carlo calculations by means of the MCNP4C code. The results of measurements of the neutron scattering cross sections at reactor neutron filtered beams with energies in the range 2-133 keV on

  12. Optical constants for hard x-ray multilayers over the energy range E = 35 - 180 keV

    NASA Astrophysics Data System (ADS)

    Windt, David L.; Donguy, Soizik; Hailey, Charles J.; Koglin, Jason E.; Honkimaki, Veijo; Ziegler, Eric; Christensen, Finn E.; Harrison, Fiona A.

    2004-02-01

    We have determined experimentally optical constants for eight thin film materials that can be used in hard X-ray multilayer coatings. Thin film samples of Ni.97V.03, Mo, W, Pt, C, B4C, Si and SiC were deposited by magnetron sputtering onto superpolished optical flats. Optical constants were determined from fits to reflectance-vs-incidence angle measurements made using synchrotron radiation over the energy range E=35 180 keV. We have also measured the X-ray reflectance of a prototype W/SiC multilayer coating over the energy range E=35 100 keV, and we compare the measured reflectance with a calculation using the newly derived optical constants.

  13. Analysis of experimental data on neutron-proton scattering in the energy range between 0 and 150 keV

    SciTech Connect

    Babenko, V. A. Petrov, N. M.

    2009-04-15

    Experimental data on neutron-proton scattering in the energy range between 0 and 150 keV are analyzed by using various sets of effective-range parameters. It is shown that, in contrast to the parameters corresponding to the phase shifts of a Nijmegen group, the parameters corresponding to the experimental phase shifts reported by a group from George Washington University (GWU group) lead to very good agreement between the calculated cross sections and their experimental counterparts in the energy region under consideration. On the basis of the experimental value of the cross section for neutron-proton scattering at an energy of 2 keV, the total cross section for neutron-proton scattering at zero energy was found to be {sigma}{sub 0} = 20.428(16) b, which is in very good agreement with a value of {sigma}{sub 0} = 20.423(9) b, which was obtained as the weighted mean of the cross sections presented by Houke and Hurst. It is shown that, in the energy region around several tens of keV units, the effective-range parameters matched with Dilg's cross-section value of {sigma}{sub 0} = 20.491(14) b lead to calculated cross sections whose values are in excess of their experimental counterparts.

  14. Analysis of experimental data on neutron-proton scattering in the energy range between 0 and 150 keV

    NASA Astrophysics Data System (ADS)

    Babenko, V. A.; Petrov, N. M.

    2009-04-01

    Experimental data on neutron-proton scattering in the energy range between 0 and 150 keV are analyzed by using various sets of effective-range parameters. It is shown that, in contrast to the parameters corresponding to the phase shifts of a Nijmegen group, the parameters corresponding to the experimental phase shifts reported by a group from George Washington University (GWU group) lead to very good agreement between the calculated cross sections and their experimental counterparts in the energy region under consideration. On the basis of the experimental value of the cross section for neutron—proton scattering at an energy of 2 keV, the total cross section for neutron-proton scattering at zero energy was found to be σ 0 = 20.428(16) b, which is in very good agreement with a value of σ 0 = 20.423(9) b, which was obtained as the weighted mean of the cross sections presented by Houke and Hurst. It is shown that, in the energy region around several tens of keV units, the effective-range parameters matched with Dilg’s cross-section value of σ 0 = 20.491(14) b lead to calculated cross sections whose values are in excess of their experimental counterparts.

  15. Ranges of Channelled keV B Ions in Si Crystals with Impact Parameter Dependent Stopping Power

    NASA Astrophysics Data System (ADS)

    Kabadayi, Önder

    In this study we calculated channelled ion ranges of boron ions by using an impact parameter dependent stopping power model. Impact parameter dependent stopping powers for boron ions penetrating into Si <100> are investigated first for energies from 10 to 150 keV. We assumed that impact parameter dependent stopping powers can be expressed by a modified Oen-Robinson formula [1] (Oen et al. Nucl. Instr. Meth. B132, 647 (1976)). The model is implemented by developing a computer code to solve a differential equation numerically for which mean ion ranges can be obtained. The results are compared with experimental data as well as Crystal-TRIM, SRIM and similar procedures calculating ion ranges in solids. We have found an agreement between our results and literature.

  16. Ionization at the Noble Gases Ion-Atom Collisions in the 1-7 KeV Energy Range

    NASA Astrophysics Data System (ADS)

    Kikiani, Boris; Chitaladze, Marika; Japaridze, Josif; Kavlashvili, Nana

    2002-10-01

    The absolute total cross sections for production of free electrons, all positive show target gas ions and partial cross sections for production of double charged slow target gas ions at these collisions have been measured. The measurements were carried out by improved transfers electric field ("condenser") and magnetic mass-analyzer methods[1]. It was shown that in the investigated energy range practically there are now slow ions with charged state more than two. Control experiments have been shown that process of electron's liberation from fast particles ("stripping" process) is unlikely in the investigated energy range. Therefore, one can to suppose that total cross sections for productions of free electrons are equal to the total cross sections of ionization of the target gas atoms. For symmetrical pairs of colliding particles (He+ _ He, Ne+ _ Ne , etc) and for pairs He+ _ Ne, Ar+ _ Kr and Kr+ _ Xe values of partial cross-sections are negligible. In the cases of He+ _ Kr and He+ _ Xe pairs value of these partial cross sections increases with colliding energy and reaches about three percent at the energy 4kev. However, in the cases of He+ _ Ar, Na+ _ Ar, Kr, Xe the values of relative portion of the double charged ions in the total amount of slow positive ions are significant (for example in He+ _ Ar collision at the energy of 4kev this portion is about 20-25 percent). Analyzes of the correlation diagrams of the diabetics terms of colliding particles system (MS) [2] show that the electron capture processes are accompanying by simultaneous excitation of auto- ionization states of target gas ions. The decay of these states are responsible for realize of double ionization process of the target gas atoms. 1. B. Kikiani, R.Lomsadze, N. Mosulishvili, Proceedings of Tbilisi State University, Physics, 34, 114, 1999; 2 M. Barat, W.Lichten, Phys. Rev, A6, 211, 1972.

  17. Experimental investigation of the multiple scatter peak of gamma rays in portland cement in the energy range 279-1332 keV

    NASA Astrophysics Data System (ADS)

    Singh, Tejbir; Singh, Parjit S.

    2011-12-01

    The pulse height spectra for different thicknesses of portland cement in the reflected geometry has been recorded with the help of a NaI(Tl) scintillator detector and 2 K MCA card using different gamma-ray sources such as Hg203 (279 keV), Cs137 (662 keV) and Co60 (1173 and 1332 keV). It has been observed that the multiple scatter peak for portland cement appears at 110 (±7) keV in all the spectra irrespective of different incident photon energies in the range 279-1332 keV from different gamma-ray sources. Further, the variation in the intensity of the multiple scatter peak with the thickness of portland cement in the backward semi-cylinders has been investigated.

  18. Mass attenuation coefficients of Martian meteorites and Earth composition in the energy range 1 keV-100 GeV

    NASA Astrophysics Data System (ADS)

    Ün, M.; Han, E. Narmanli; Ün, A.

    2016-04-01

    Mass attenuation coefficients for 24 Martian meteorites have been determined in the energy range from 1 keV to 100 GeV. The values of mass attenuation coefficients (µ/ρ) of the samples were calculated the WINXCOM program. The obtained results for Martian meteorites have been compared with the results for Earth composition and similarities or differences also evaluated.

  19. High-resolution integrated germanium Compton polarimeter for the γ-ray energy range 80 keV-1 MeV

    NASA Astrophysics Data System (ADS)

    Sareen, R. A.; Urban, W.; Barnett, A. R.; Varley, B. J.

    1995-06-01

    Parameters which govern the choice of a detection system to measure the linear polarization of γ rays at low energies are discussed. An integrated polarimeter is described which is constructed from a single crystal of germanium. It is a compact planar device with the sectors defined electrically, and which gives an energy resolution in the add-back mode of 1 keV at 300 keV. Its performance is demonstrated in a series of calibration measurements using both unpolarized radiation from radioactive sources and polarized γ rays from the 168Er(α,2n)170Yb reaction at Eα=25 MeV. Polarization measurements at energies as low as 84 keV have been achieved, where the sensitivity was 0.32±0.09. The sensitivity, efficiency, and energy resolution are reported. Our results indicate that energy resolution should be included in the definition of the figure of merit and we relate the new definition to earlier work. The comparisons show the advantages of the present design in the energy range below 300 keV and its competitiveness up to 1500 keV.

  20. A balloon-borne instrument for high-resolution astrophysical spectroscopy in the 20-8000 keV energy range

    NASA Technical Reports Server (NTRS)

    Paciesas, W. S.; Baker, R.; Boclet, D.; Brown, S.; Cline, T.; Costlow, H.; Durouchoux, P.; Ehrmann, C.; Gehrels, N.; Hameury, J. M.

    1983-01-01

    The Low Energy Gamma ray Spectrometer (LEGS) is designed to perform fine energy resolution measurements of astrophysical sources. The instrument is configured for a particular balloon flight with either of two sets of high purity germanium detectors. In one configuration, the instrument uses an array of three coaxial detectors (effective volume equal to or approximately 230 cubic cm) inside an NaI (T1) shield and collimator (field of view equal to or approximately 16 deg FWHM) and operates in the 80 to 8000 keV energy range. In the other configuration, three planar detectors (effective area equal to or approximately square cm) surrounded by a combination of passive Fe and active NaI for shielding and collimation (field of view equal to or approximately 5 deg x 10 deg FWHM) are optimized for the 20 to 200 keV energy range. In a typical one day balloon flight, LEGS sensitivity limit (3 sigma) for narrow line features is less than or approximately .0008 ph/cm/s square (coaxial array: 80 to 2000 keV) and less than or approximately .0003 ph/square cm/s (planar array: 50 to 150 keV).

  1. Effective atomic numbers and electron densities of bacteriorhodopsin and its comprising amino acids in the energy range 1 keV-100 GeV

    NASA Astrophysics Data System (ADS)

    Ahmadi, Morteza; Lunscher, Nolan; Yeow, John T. W.

    2013-04-01

    Recently, there has been an interest in fabrication of X-ray sensors based on bacteriorhodopsin, a proton pump protein in cell membrane of Halobacterium salinarium. Therefore, a better understanding of interaction of X-ray photons with bacteriorhodopsin is required. We use WinXCom program to calculate the mass attenuation coefficient of bacteriorhodopsin and its comprising amino acids for photon energies from 1 keV to 100 GeV. These amino acids include alanine, arginine, asparagine, aspartic acid, glutamine, glutamic acid, glycine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine, valine, Asx1, Asx2, Glx1 and Glx2. We then use that data to calculate effective atomic number and electron densities for the same range of energy. We also emphasize on two ranges of energies (10-200 keV and 1-20 MeV) in which X-ray imaging and radiotherapy machines work.

  2. Comparison of Martian meteorites with earth composition: Study of effective atomic numbers in the energy range 1 keV-100 GeV

    NASA Astrophysics Data System (ADS)

    Ün, Adem; Han, Ibrahim; Ün, Mümine

    2016-04-01

    Effective atomic (Zeff) and electron numbers (Neff) for 24 Martian meteorites have been determined in the energy range from 1 keV to 100 GeV and also for sixteen significant energies of commonly used radioactive sources. The values of Zeff and Neff for all sample were obtained from the DirectZeff program. The obtained results for Martian meteorites have been compared with the results for Earth composition and similarities or differences also evaluated.

  3. Development of a soft x-ray diffractometer for a wideband multilayer grating with a novel layer structure in the 2-4 keV range

    SciTech Connect

    Imazono, Takashi; Koike, Masato; Kawachi, Tetsuya; Hasegawa, Noboru; Koeda, Masaru; Nagano, Tetsuya; Sasai, Hiroyuki; Oue, Yuki; Yonezawa, Zeno; Kuramoto, Satoshi; Terauchi, Masami; Takahashi, Hideyuki; Handa, Nobuo; Murano, Takanori

    2012-07-11

    We have been developing a wavelength-dispersive soft x-ray spectrograph covering an energy region of 50-4000 eV to attach to a conventional electron microscope. Observation of soft x-ray emission in the 2-4 keV range needs a multilayer coated grating. In order to evaluate the performance of the optical component in the energy region, a goniometric apparatus has been newly developed and the preliminary performance has been tested using synchrotron radiation.

  4. Attenuation coefficients of soils and some building materials of Bangladesh in the energy range 276-1332 keV.

    PubMed

    Alam, M N; Miah, M M; Chowdhury, M I; Kamal, M; Ghose, S; Rahman, R

    2001-06-01

    The linear and mass attenuation coefficients of different types of soil, sand, building materials and heavy beach mineral samples from the Chittagong and Cox's Bazar area of Bangladesh were measured using a high-resolution HPGe detector and the gamma-ray energies 276.1, 302.8, 356.0, 383.8, 661.6 and 1173.2 and 1332.5 keV emitted from point sources of 133Ba, 137Cs and 60Co, respectively. The linear attenuation coefficients show a linear relationship with the corresponding densities of the samples studied. The variations of the mass attenuation coefficient with gamma-ray energy were exponential in nature. The measured mass attenuation coefficient values were compared with measurements made in other countries for similar kinds of materials. The values are in good agreement with each other in most cases. PMID:11300413

  5. Measurement of the x-ray mass attenuation coefficient and determination of the imaginary component of the atomic form-factor of tin over the energy range of 29 keV-60 keV.

    SciTech Connect

    de Jonge, M. D.; Tran, C. Q.; Chantler, C. T.; Barnea, Z.; Dhal, B. P.; Paterson, D.; Kanter, E. P.; Southworth, S. H.; Young, L.; Beno, M. A.; Linton, J. A.; Jennings, G.; Univ. of Melbourne; Australian Synchrotron Project

    2007-01-01

    We use the x-ray extended-range technique (XERT) [C. T. Chantler et al., Phys. Rev. A 64, 062506 (2001)] to measure the mass attenuation coefficients of tin in the x-ray energy range of 29-60 keV to 0.04-3 % accuracy, and typically in the range 0.1-0.2 %. Measurements made over an extended range of the measurement parameter space are critically examined to identify, quantify, and correct a number of potential experimental systematic errors. These results represent the most extensive experimental data set for tin and include absolute mass attenuation coefficients in the regions of x-ray absorption fine structure, extended x-ray absorption fine structure, and x-ray absorption near-edge structure. The imaginary component of the atomic form factor f{sub 2} is derived from the photoelectric absorption after subtracting calculated Rayleigh and Compton scattering cross sections from the total attenuation. Comparison of the result with tabulations of calculated photoelectric absorption coefficients indicates that differences of 1-2 % persist between calculated and observed values.

  6. Absolute calibration of Kodak Biomax-MS film response to x rays in the 1.5- to 8-keV energy range

    NASA Astrophysics Data System (ADS)

    Marshall, F. J.; Knauer, J. P.; Anderson, D.; Schmitt, B. L.

    2006-10-01

    The absolute response of Kodak Biomax-MS film to x rays in the range from 1.5- to 8-keV has been measured using a laboratory electron-beam generated x-ray source. The measurements were taken at specific line energies by using Bragg diffraction to produce monochromatic beams of x rays. Multiple exposures were taken on Biomax MS film up to levels exceeding optical densities of 2 as measured by a microdensitometer. The absolute beam intensity for each exposure was measured with a Si (Li) detector. Additional response measurements were taken with Kodak direct exposure film (DEF) so as to compare the results of this technique to previously published calibrations. The Biomax-MS results have been fitted to a semiempirical mathematical model (Knauer et al., these proceedings). Users of the model can infer absolute fluences from observed exposure levels at either interpolated or extrapolated energies. To summarize the results: Biomax MS has comparable sensitivity to DEF film below 3keV but has reduced sensitivity above 3keV (˜50%). The lower exposure results from thinner emulsion layers, designed for use with phosphor screens. The ease with which Biomax-MS can be used in place of DEF (same format film, same developing process, and comparable sensitivity) makes it a good replacement.

  7. Absolute calibration of Kodak Biomax-MS film response to x rays in the 1.5- to 8-keV energy range

    SciTech Connect

    Marshall, F. J.; Knauer, J. P.; Anderson, D.; Schmitt, B. L

    2006-10-15

    The absolute response of Kodak Biomax-MS film to x rays in the range from 1.5- to 8-keV has been measured using a laboratory electron-beam generated x-ray source. The measurements were taken at specific line energies by using Bragg diffraction to produce monochromatic beams of x rays. Multiple exposures were taken on Biomax MS film up to levels exceeding optical densities of 2 as measured by a microdensitometer. The absolute beam intensity for each exposure was measured with a Si(Li) detector. Additional response measurements were taken with Kodak direct exposure film (DEF) so as to compare the results of this technique to previously published calibrations. The Biomax-MS results have been fitted to a semiempirical mathematical model (Knauer et al., these proceedings). Users of the model can infer absolute fluences from observed exposure levels at either interpolated or extrapolated energies. To summarize the results: Biomax MS has comparable sensitivity to DEF film below 3 keV but has reduced sensitivity above 3 keV ({approx}50%). The lower exposure results from thinner emulsion layers, designed for use with phosphor screens. The ease with which Biomax-MS can be used in place of DEF (same format film, same developing process, and comparable sensitivity) makes it a good replacement.

  8. Energy response of GR-200A thermoluminescence dosemeters to 60Co and to monoenergetic synchrotron radiation in the energy range 28-40 keV.

    PubMed

    Emiro, F; Di Lillo, F; Mettivier, G; Fedon, C; Longo, R; Tromba, G; Russo, P

    2016-01-01

    The response of LiF:Mg,Cu,P thermoluminescence dosemeters (type GR-200A) to monoenergetic radiation of energy 28, 35, 38 and 40 keV was evaluated with respect to irradiation with a calibrated (60)Co gamma-ray source. High-precision measurements of the relative air kerma response performed at the SYRMEP beamline of the ELETTRA synchrotron radiation facility (Trieste, Italy) showed a significant deviation of the average response to low-energy X-rays from that to (60)Co, with an over-response from 6 % (at 28 keV) to 22 % (at 40 keV). These data are not consistent with literature data for these dosemeters, where model predictions gave deviation from unity of the relative air kerma response of about 10 %. The authors conclude for the need of additional determinations of the low-energy relative response of GR-200A dosemeters, covering a wider range of monoenergetic energies sampled at a fine energy step, as planned in future experiments by their group at the ELETTRA facility. PMID:25737582

  9. Reference neutron fields of the KIGAM for the neutron energy range between 144 keV and 2.5 MeV

    NASA Astrophysics Data System (ADS)

    Kim, G. D.; Woo, H. J.; Choi, H. W.; Park, J. W.; Trinh, T. A.

    2012-08-01

    The Korea Institute of Geoscience and Mineral Resources (KIGAM) is constructing a reference neutron field facility as a national project. Neutron fields consist of mono-energetic sources of 144 keV, 250 keV, 565 keV, and 2.5 MeV have a fluence range from 102 neutrons/cm2/sec to 103 neutrons/cm2/sec. The systems for the reference neutron fields, such as a duo-plasmatron ion source, a 4-MHz beam bunching system, a neutron chamber, an irradiation room, a neutron time-of-flight (n-TOF) system, a long-counter, and a sample moving system, were designed and fabricated. The neutron energies of the reference neutron fields and their spreads were observed by using the n-TOF system. The neutron fluence was measured by using a long-counter for energies below 1 MeV and a proton-recoil counter for 2.5 MeV. The long-counter efficiency was calibrated by the Japan Atomic Energy Agency (JAEA) which had a traceability of mono-energetic neutron sources to both Japanese and international standards. The efficiency of the proton-recoil counter was obtained by using a calculation with detailed construction information.

  10. 6 x 6-cm fully depleted pn-junction CCD for high-resolution spectroscopy in the 0.1- to 15-keV photon energy range

    NASA Astrophysics Data System (ADS)

    von Zanthier, Christoph; Holl, Peter; Kemmer, Josef; Lechner, Peter; Maier, B.; Soltau, Heike; Stoetter, R.; Braeuninger, Heinrich W.; Dennerl, Konrad; Haberl, Frank; Hartmann, R.; Hartner, Gisela D.; Hippmann, H.; Kastelic, E.; Kink, W.; Krause, N.; Meidinger, Norbert; Metzner, G.; Pfeffermann, Elmar; Popp, M.; Reppin, Claus; Stoetter, Diana; Strueder, Lothar; Truemper, Joachim; Weber, U.; Carathanassis, D.; Engelhard, S.; Gebhart, Th.; Hauff, D.; Lutz, G.; Richter, R. H.; Seitz, H.; Solc, P.; Bihler, Edgar; Boettcher, H.; Kendziorra, Eckhard; Kraemer, J.; Pflueger, Bernhard; Staubert, Ruediger

    1998-04-01

    The concept and performance of the fully depleted pn- junction CCD system, developed for the European XMM- and the German ABRIXAS-satellite missions for soft x-ray imaging and spectroscopy in the 0.1 keV to 15 keV photon range, is presented. The 58 mm X 60 mm large pn-CCD array uses pn- junctions for registers and for the backside instead of MOS registers. This concept naturally allows to fully deplete the detector volume to make it an efficient detector to photons with energies up to 15 keV. For high detection efficiency in the soft x-ray region down to 100 eV, an ultrathin pn-CCD backside deadlayer has been realized. Each pn-CCD-channel is equipped with an on-chip JFET amplifier which, in combination with the CAMEX-amplifier and multiplexing chip, facilitates parallel readout with a pixel read rate of 3 MHz and an electronic noise floor of ENC < e-. With the complete parallel readout, very fast pn-CCD readout modi can be implemented in the system which allow for high resolution photon spectroscopy of even the brightest x-ray sources in the sky.

  11. Reduction in the intensity of solar X-ray emission in the 2- to 15-keV photon energy range and heating of the solar corona

    SciTech Connect

    Mirzoeva, I. K.

    2013-04-15

    The time profiles of the energy spectra of low-intensity flares and the structure of the thermal background of the soft X-ray component of solar corona emission over the period of January-February, 2003, are investigated using the data of the RHESSI project. A reduction in the intensity of X-ray emission of the solar flares and the corona thermal background in the 2- to 15-keV photon energy range is revealed. The RHESSI data are compared with the data from the Interball-Geotail project. A new mechanism of solar corona heating is proposed on the basis of the results obtained.

  12. A low background-rate detector for ions in the 5 to 50 keV energy range to be used for radioisotope dating with a small cyclotron

    SciTech Connect

    Friedman, P.G.

    1986-11-25

    Accelerator mass spectrometry in tandem Van de Graaff accelerators has proven successful for radioisotope dating small samples. We are developing a 20 cm diameter 30 to 40 keV cyclotron dedicated to high-sensitivity radioisotope dating, initially for /sup 14/C. At this energy, range and dE/dx methods of particle identification are impossible. Thus arises the difficult problem of reliably detecting 30 to 40 keV /sup 14/C at 10/sup -2/ counts/sec in the high background environment of the cyclotron, where lower energy ions, electrons, and photons bombard the detector at much higher rates. We have developed and tested an inexpensive, generally useful ion detector that allows dark-count rates below 10/sup -4/ counts/sec and excellent background suppression. With the cyclotron tuned near the /sup 13/CH background peak, to the frequency for /sup 14/C, the detector suppresses the background to 6 x 10/sup -4/ counts/sec. For each /sup 14/C ion the detectors grazing-incidence Al/sub 2/O/sub 3/ conversion dynode emits about 20 secondary electrons, which are independently multiplied in separate pores of a microchannel plate. The output signal is proportional to the number of secondary electrons, allowing pulse-height discrimination of background. We have successfully tested the detector with positive /sup 12/C, /sup 23/Na, /sup 39/K, /sup 41/K, /sup 85/Rb, /sup 87/Rb, and /sup 133/Cs at 5 to 40 keV, and with 36 keV negative /sup 12/C and /sup 13/CH. It should detect ions and neutrals of all species, at energies above 5 keV, with good efficiency and excellent background discrimination. Counting efficiency and background discrimination improve with higher ion energy. The detector can be operated at least up to 2 x 10/sup -7/ Torr and be repeatedly exposed to air. The maximum rate is 10/sup 6.4/ ions/sec in pulse counting mode and 10/sup 9.7/ ions/sec in current integrating mode.

  13. Neutron Resonance Parameters of 238U and the Calculated Cross Sections from the Reich-Moore Analysis of Experimental Data in the Neutron Energy Range from 0 keV to 20 keV

    SciTech Connect

    Derrien, H

    2005-12-05

    The neutron resonance parameters of {sup 238}U were obtained from a SAMMY analysis of high-resolution neutron transmission measurements and high-resolution capture cross section measurements performed at the Oak Ridge Electron Linear Accelerator (ORELA) in the years 1970-1990, and from more recent transmission and capture cross section measurements performed at the Geel Linear Accelerator (GELINA). Compared with previous evaluations, the energy range for this resonance analysis was extended from 10 to 20 keV, taking advantage of the high resolution of the most recent ORELA transmission measurements. The experimental database and the method of analysis are described in this report. The neutron transmissions and the capture cross sections calculated with the resonance parameters are compared with the experimental data. A description is given of the statistical properties of the resonance parameters and of the recommended values of the average parameters. The new evaluation results in a slight decrease of the effective capture resonance integral and improves the prediction of integral thermal benchmarks by 70 pcm to 200 pcm.

  14. Absolute calibration of a photodiode array with the use of the synchrotron radiation in the range of 1-10 keV

    NASA Astrophysics Data System (ADS)

    Beck, L.; Bizeuil, C.; Soullie, G.

    1995-02-01

    The silicon photodiode array Hamamatsu S3901 series (1024, 25 μm pixel) were primarily developed for the visible-UV spectral range, mainly for photon wavelengths between 200 and 1100 nm. By utilizing it without a quartz window, it is demonstrated that this sensor can be used for x rays, especially in the 1-10 keV range. Experimental measurements of the absolute detection efficiency of the photodiode array between 1.5 and 12 keV are presented. The experiments were performed on an x-ray tube-excited secondary targets and on the SB3 beamline at the Super ACO storage ring (LURE-Orsay). The measured spectral efficiency is compared with the results of a simple model calculation based on the data given in the Hamamatsu note. The simulation is in good agreement with the experimental data for a silicon active depth of 6 μm and a silicon dioxide passivation layer of 5 μm. The linearity is better than 1% and the spatial resolution is estimated to be 120 μm.

  15. A novel flat-response x-ray detector in the photon energy range of 0.1-4 keV

    NASA Astrophysics Data System (ADS)

    Li, Zhichao; Jiang, Xiaohua; Liu, Shenye; Huang, Tianxuan; Zheng, Jian; Yang, Jiamin; Li, Sanwei; Guo, Liang; Zhao, Xuefeng; Du, Huabin; Song, Tianming; Yi, Rongqing; Liu, Yonggang; Jiang, Shaoen; Ding, Yongkun

    2010-07-01

    A novel flat-response x-ray detector has been developed for the measurement of radiation flux from a hohlraum. In order to obtain a flat response in the photon energy range of 0.1-4 keV, it is found that both the cathode and the filter of the detector can be made of gold. A further improvement on the compound filter can then largely relax the requirement of the calibration x-ray beam. The calibration of the detector, which is carried out on Beijing Synchrotron Radiation Facility at Institute of High Energy Physics, shows that the detector has a desired flat response in the photon energy range of 0.1-4 keV, with a response flatness smaller than 13%. The detector has been successfully applied in the hohlraum experiment on Shenguang-III prototype laser facility. The radiation temperatures inferred from the detector agree well with those from the diagnostic instrument Dante installed at the same azimuth angle from the hohlraum axis, demonstrating the feasibility of the detector.

  16. A novel flat-response x-ray detector in the photon energy range of 0.1-4 keV

    SciTech Connect

    Li Zhichao; Guo Liang; Jiang Xiaohua; Liu Shenye; Huang Tianxuan; Yang Jiamin; Li Sanwei; Zhao Xuefeng; Du Huabin; Song Tianming; Yi Rongqing; Liu Yonggang; Jiang Shaoen; Ding Yongkun; Zheng Jian

    2010-07-15

    A novel flat-response x-ray detector has been developed for the measurement of radiation flux from a hohlraum. In order to obtain a flat response in the photon energy range of 0.1-4 keV, it is found that both the cathode and the filter of the detector can be made of gold. A further improvement on the compound filter can then largely relax the requirement of the calibration x-ray beam. The calibration of the detector, which is carried out on Beijing Synchrotron Radiation Facility at Institute of High Energy Physics, shows that the detector has a desired flat response in the photon energy range of 0.1-4 keV, with a response flatness smaller than 13%. The detector has been successfully applied in the hohlraum experiment on Shenguang-III prototype laser facility. The radiation temperatures inferred from the detector agree well with those from the diagnostic instrument Dante installed at the same azimuth angle from the hohlraum axis, demonstrating the feasibility of the detector.

  17. A novel flat-response x-ray detector in the photon energy range of 0.1-4 keV.

    PubMed

    Li, Zhichao; Jiang, Xiaohua; Liu, Shenye; Huang, Tianxuan; Zheng, Jian; Yang, Jiamin; Li, Sanwei; Guo, Liang; Zhao, Xuefeng; Du, Huabin; Song, Tianming; Yi, Rongqing; Liu, Yonggang; Jiang, Shaoen; Ding, Yongkun

    2010-07-01

    A novel flat-response x-ray detector has been developed for the measurement of radiation flux from a hohlraum. In order to obtain a flat response in the photon energy range of 0.1-4 keV, it is found that both the cathode and the filter of the detector can be made of gold. A further improvement on the compound filter can then largely relax the requirement of the calibration x-ray beam. The calibration of the detector, which is carried out on Beijing Synchrotron Radiation Facility at Institute of High Energy Physics, shows that the detector has a desired flat response in the photon energy range of 0.1-4 keV, with a response flatness smaller than 13%. The detector has been successfully applied in the hohlraum experiment on Shenguang-III prototype laser facility. The radiation temperatures inferred from the detector agree well with those from the diagnostic instrument Dante installed at the same azimuth angle from the hohlraum axis, demonstrating the feasibility of the detector. PMID:20687719

  18. A direct comparison of Ge and Si(Li) detectors in the 2--20 keV range

    SciTech Connect

    Rossington, C.S.; Giauque, R.D.; Jaklevic, J.M.

    1991-10-01

    The spectral response of high purity Ge (HPGe) and lithium-drifted Si (Si(Li)) surface barrier detectors of similar geometry has been measured over a range of x-ray energies under identical experimental conditions. Detector characteristics such as spectral background, escape peak intensity, entrance window absorption, and energy resolution are presented and compared. Although these characteristic have been discussed in the literature previously, this paper represents an attempt to consolidate the information by making comparisons under equivalent experimental conditions for the two types of detectors. A primary goal of the study is a comparison of the two types of detectors for use in x-ray fluorescence applications.

  19. Measurement of the x-ray mass attenuation coefficients of gold in the 38-50-keV energy range

    SciTech Connect

    Islam, M T; Rae, N A; Glover, J L; Barnea, Z; de Jonge, M D; Tran, C Q; Wang, J; Chantler, C T

    2010-11-12

    We used synchrotron x rays to measure the x-ray mass attenuation coefficients of gold at nine energies from 38 to 50 keV with accuracies of 0.1%. Our results are much more accurate than previous measurements in this energy range. A comparison of our measurements with calculated mass attenuation coefficients shows that our measurements fall almost exactly midway between the XCOM and FFAST calculated theoretical values, which differ from one another in this energy region by about 4%, even though the range includes no absorption edge. The consistency and accuracy of these measurements open the way to investigations of the x-ray attenuation in the region of the L absorption edge of gold.

  20. Inelastic processes in Na+-Ne, Na+-Ar, Ne+-Na, and Ar+-Na collisions in the energy range 0.5-14 keV

    NASA Astrophysics Data System (ADS)

    Lomsadze, R. A.; Gochitashvili, M. R.; Kezerashvili, R. Ya.

    2015-12-01

    Absolute cross sections for charge-exchange, ionization, and excitation in Na+-Ne and Na+-Ar collisions were measured in the ion energy range 0.5 -10 keV using a refined version of a capacitor method and collision and optical spectroscopy methods simultaneously in the same experimental setup. Ionization cross sections for Ne+-Na and Ar+-Na collisions are measured at energies of 2 -14 keV using a crossed-beam spectroscopy method. The experimental data and the schematic correlation diagrams are used to analyze and determine the mechanisms for these processes. For the charge-exchange process in Na+-Ar collisions two nonadiabatic regions are revealed and mechanisms responsible for these regions are explained. Structural peculiarity on the excitation function for the resonance lines of argon atoms in Na+-Ar collisions are observed and the possible mechanisms of this phenomenon are explored. The measured ionization cross sections for Na+-Ne and Ne+-Na collisions in conjunction with the Landau-Zener formula are used to determine the coupling matrix element and transition probability in a region of pseudocrossing of the potential curves.

  1. Low-background-rate detector for ions in the 5- to 50-keV energy range to be used for radioisotope dating with a small cyclotron

    SciTech Connect

    Friedman, P.G.

    1986-01-01

    Accelerator mass spectrometry in tandem Van de Graaff accelerators has proven successful for radioisotope dating small samples. Small, inexpensive cyclotrons serving this purpose would make the technique accessible to more researchers and inexpensive enough to compare many small samples. To this end, VC Berkeley is developing a 20-cm-diameter, 30- to 40-keV cyclotron dedicated to high-sensitivity radioisotope dating, initially for /sup 14/C. At this energy, range and dE/dx methods of particle identification are impossible. Thus arises the difficult problem of reliably detecting 30- to 40-keV /sup 14/C at 10/sup -1/ counts/sec in the high-background environment of the cyclotron, where lower energy ions, electrons, and photons bombard the detector at much higher rates. To meet this challenge, an inexpensive, generally useful ion detector was developed that allows dark-count rates below 10/sup -4/ counts/sec and excellent background suppression. With the cyclotron tuned near the /sup 13/CH background peak, to the frequency for /sup 14/C, the detector suppresses the background to 6 x 10/sup -4/ counts/sec. For each /sup 14/C ion, the detector's grazing-incidence Al/sub 2/O/sub 3/ conversion dynode emits about 20 secondary electrons, which are independently multiplied in separate pores of a microchannel plate. The output signal is proportional to the number of secondary electrons, allowing pulse-height discrimination of background.

  2. Absolute Calibration of Kodak Biomax-MS Film Response to X Rays in the 1.5- to 8-keV Energy Range

    SciTech Connect

    Marshall, F.J.; Knauer, J.P.; Anderson, D.; Schmitt, B.L.

    2006-09-28

    The absolute response of Kodak Biomax-MS film to x rays in the range from 1.5- to 8-keV has been measured using a laboratory e-beam generated x-ray source. The measurements were taken at specific line energies by using Bragg diffraction to produce monochromatic beams of x rays. Multiple exposures were taken on Biomax MS film up to levels exceeding optical densities of 2 as measured by a microdensitometer. The absolute beam intensity for each exposure was measured with a Si(Li) detector. Additional response measurements were taken with Kodak direct exposure film (DEF) so as to compare the results of this technique to previously published calibrations.

  3. Neutron-induced fission cross section of Np237 in the keV to MeV range at the CERN n_TOF facility

    DOE PAGESBeta

    Diakaki, M.; Karadimos, D.; Vlastou, R.; Kokkoris, M.; Demetriou, P.; Skordis, E.; Tsinganis, A.; Abbondanno, U.; Aerts, G.; Álvarez, H.; et al

    2016-03-17

    We experimentally determined the neutron-induced fission cross section of Np-237 at the high-resolution and high-intensity facility n_TOF, at CERN, in the energy range 100 keV to 9 MeV, using the U-235(n, f) and U-238(n, f) cross section standards below and above 2 MeV, respectively. Moreover, a fast ionization chamber was used in order to detect the fission fragments from the reactions and the targets were characterized as far as their mass and homogeneity are concerned by means of a spectroscopy and Rutherford backscattering spectroscopy respectively. Finally, theoretical calculations within the Hauser-Feshbach formalism have been performed, employing the EMPIRE code, andmore » the model parameters were tuned in order to successfully reproduce the experimental fission cross-sectional data and simultaneously all the competing reaction channels.« less

  4. Wide-Band KB Optics for Spectro-Microscopy Imaging Applications in the 6-13 keV X-ray Energy Range

    SciTech Connect

    Ziegler, E.; De Panfilis, S.; Peverini, L.; Vaerenbergh, P. van; Rocca, F.

    2007-01-19

    We present a Kirkpatrick-Baez optics (KB) system specially optimized to operate in the 6-13 keV X-ray range, where valuable characteristic lines are present. The mirrors are coated with aperiodic laterally graded (Ru/B4C)35 multilayers to define a 15% energy bandpass and to gain flux as compared to total reflection mirrors. For any X-ray energy selected the shape of each mirror can be optimized with a dynamical bending system so as to concentrate the X-ray beam into a micrometer-size spot. Once the KB mirrors are aligned at the X-ray energy corresponding to the barycenter of the XAS spectrum to be performed they remain in a steady state during the micro-XAS scans to minimize beam displacements. Results regarding the performance of the wideband KB optics and of the spectro-microscopy setup are presented, including beam stability issues.

  5. Investigation of Methanol Formation Mechanisms in H2O+CH4 Ices Subjected to 5 keV Electrons at a 10-100 K Temperature Range

    NASA Astrophysics Data System (ADS)

    Stelmach, K. B.; Cooper, P. D.

    2014-12-01

    Methane (CH4) and water are one of the most common molecules in both planetary bodies and interstellar dust grains. Another common molecule, methanol (CH3OH), is thought to form in CH4+H2O ices. However, the exact formation mechanisms of methanol from cosmic rays are not well known, especially in the temperatures of interest. Experiments were performed using high energy electrons (5 keV) to irradiate mixtures of 1:10, 1:5, and 1:3 CH4+H2O ices under a temperature range of 10-100 Kelvin with Fourier Transform Infrared (FTIR) spectroscopy being used to identify the products. Isotopologues of the two molecules (D2O and CD4) were used to probe for the mechanisms. Other products were formed as well and their potential mechanisms are identified. The implications of the mechanisms for planetary and interstellar chemistry are discussed.

  6. Neutron-induced fission cross section of 237Np in the keV to MeV range at the CERN n_TOF facility

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

    The neutron-induced fission cross section of 237Np was experimentally determined at the high-resolution and high-intensity facility n_TOF, at CERN, in the energy range 100 keV to 9 MeV, using the 235U(n ,f ) and 238U(n ,f ) cross section standards below and above 2 MeV, respectively. A fast ionization chamber was used in order to detect the fission fragments from the reactions and the targets were characterized as far as their mass and homogeneity are concerned by means of α spectroscopy and Rutherford backscattering spectroscopy respectively. Theoretical calculations within the Hauser-Feshbach formalism have been performed, employing the empire code, and the model parameters were tuned in order to successfully reproduce the experimental fission cross-sectional data and simultaneously all the competing reaction channels.

  7. Absolute detection efficiency of a microchannel plate detector to X rays in the 1-100 KeV energy range

    NASA Astrophysics Data System (ADS)

    Burginyon, Gary A.; Jacoby, Barry A.; Wobser, James K.; Ernst, Richard; Ancheta, Dione S.; Tirsell, Kenneth G.

    1993-02-01

    There is little information in the literature on the performance of working micro-channel plate (MCP) detectors at high x-ray energies. We have measured the absolute efficiency of a microchannel-plate-intensified, subnanosecond, one dimensional imaging x-ray detector developed at LLNL in the 1 to 100 keV range and at 1.25 MeV. The detector consists of a gold photocathode deposited on the front surface of the MCP (optimized for Ni K(subscript (alpha) ) x rays) to convert x rays to electrons, an MCP to amplify the electrons, and a fast In:CdS phosphor that converts the electron's kinetic energy to light. The phosphor is coated on a fiber-optic faceplate to transmit the light out of the vacuum system. Electrostatic focusing electrodes compress the electron current out of the MCP in one dimension while preserving spatial resolution in the other. The calibration geometry, dictated by a recent experiment, required grazing incidence x rays (15.6 degree(s)) onto the MCP detector in order to maximize deliverable current. The experiment also used a second detector made up of 0.071 in. thick BC422 plastic scintillator material from the Bicron Corporation. We compare the absolute efficiencies of these two detectors in units of optical W/cm(superscript 2) into 4 (pi) per x ray W/cm(superscript 2) incident. At 7.47 keV and 900 volts MCP bias, the MCP detector delivers approximately 1400 times more light than the scintillator detector.

  8. Learning to Apply Metrology Principles to the Measurement of X-ray Intensities in the 500 eV to 110 keV Energy Range

    SciTech Connect

    Haugh, M. J.; Pond, T.; Silbernagel, C.; Torres, P.; Marlett, K.; Goldin, F.; Cyr, S.

    2011-02-08

    National Security Technologies, LLC (NSTec), Livermore Operations, has two optical radiation calibration laboratories accredited by “the National Voluntary Laboratories Accreditation Program (NVLAP) which is the accrediting body of” the National Institute of Standards and Technology (NIST), and is now working towards accreditation for its X-ray laboratories. NSTec operates several laboratories with X-ray sources that generate X-rays in the energy range from 50 eV to 115 keV. These X-ray sources are used to characterize and calibrate diagnostics and diagnostic components used by the various national laboratories, particularly for plasma analysis on the Lawrence Livermore National Laboratory (LLNL) National Ignition Facility (NIF). Because X-ray photon flux measurement methods that can be accredited, i.e., traceable to NIST, have not been developed for sources operating in these energy ranges, NSTec, NIST, and the National Voluntary Accreditation Program (NVLAP) together have defined a path toward the development and validation of accredited metrology methods for X-ray energies. The methodology developed for the high energy X-ray (HEX) Laboratory was NSTec’s starting point for X-ray metrology accreditation and will be the basis for the accredited processes in the other X-ray laboratories. This paper will serve as a teaching tool, by way of this example using the NSTec X-ray sources, for the process and methods used in developing an accredited traceable metrology.

  9. Angular distribution of bremsstrahlung produced by electrons with initial energies in the range from 10 to 20 keV incident on thick Ag

    NASA Astrophysics Data System (ADS)

    Gonzales, Daniel; Cavness, Brandon; Williams, Scott

    2012-03-01

    Experimental results are presented comparing the intensities of the thick-target bremsstrahlung produced by electrons with initial energies ranging from 10 to 20 keV incident on Ag, measured at forward angles in the range of 0 to 55 degrees. When the data are corrected for attenuation due to photon absorption within the target, the results indicate that the detected radiation is distributed anisotropically only at photon energies k that are approximately equal to the initial energy of the incident electrons E0. The results of our experiments suggest that, as k/E0->0, the detected radiation essentially becomes isotropic due primarily to the scattering of electrons within the target. Comparison to the theory of Kissel et al. [At. Data Nucl. Data Tables 28, 381 (1983)] suggests that the angular distribution of bremsstrahlung emitted by electrons incident on thick targets is similar to the angular distribution of bremsstrahlung emitted by electrons incident on free-atom targets only when k/E0 1. The experimental data also are in approximate agreement with the angular distribution predictions of the Monte Carlo program PENELOPE.

  10. High accuracy experimental determination of copper and zinc mass attenuation coefficients in the 100 eV to 30 keV photon energy range

    NASA Astrophysics Data System (ADS)

    Ménesguen, Y.; Gerlach, M.; Pollakowski, B.; Unterumsberger, R.; Haschke, M.; Beckhoff, B.; Lépy, M.-C.

    2016-02-01

    The knowledge of atomic fundamental parameters such as mass attenuation coefficients with low uncertainties, is of decisive importance in elemental quantification using x-ray fluorescence analysis techniques. Several databases are accessible and frequently used within a large community of users. These compilations are most often in good agreement for photon energies in the hard x-ray ranges. However, they significantly differ for low photon energies and around the absorption edges of any element. In a joint cooperation of the metrology institutes of France and Germany, mass attenuation coefficients of copper and zinc were determined experimentally in the photon energy range from 100 eV to 30 keV by independent approaches using monochromatized synchrotron radiation at SOLEIL (France) and BESSY II (Germany), respectively. The application of high-accuracy experimental techniques resulted in mass attenuation coefficient datasets determined with low uncertainties that are directly compared to existing databases. The novel datasets are expected to enhance the reliability of mass attenuation coefficients.

  11. An in-vacuum x-ray diffraction microscope for use in the 0.7-2.9 keV range

    SciTech Connect

    Vine, D. J.; Williams, G. J.; Clark, J. N.; Putkunz, C. T.; Abbey, B.; Nugent, K. A.; Pfeifer, M. A.; Legnini, D.; Roehrig, C.; Wrobel, E.; McNulty, I.; Huwald, E.; Riessen, G. van; Peele, A. G.; Beetz, T.; Irwin, J.; Feser, M.; Hornberger, B.

    2012-03-15

    A dedicated in-vacuum coherent x-ray diffraction microscope was installed at the 2-ID-B beamline of the Advanced Photon Source for use with 0.7-2.9 keV x-rays. The instrument can accommodate three common implementations of diffractive imaging; plane wave illumination; defocused-probe (Fresnel diffractive imaging) and scanning (ptychography) using either a pinhole, focused or defocused probe. The microscope design includes active feedback to limit motion of the optics with respect to the sample. Upper bounds on the relative optics-to-sample displacement have been measured to be 5.8 nm(v) and 4.4 nm(h) rms/h using capacitance micrometry and 27 nm/h using x-ray point projection imaging. The stability of the measurement platform and in-vacuum operation allows for long exposure times, high signal-to-noise and large dynamic range two-dimensional intensity measurements to be acquired. Finally, we illustrate the microscope's stability with a recent experimental result.

  12. Neutron capture and fission cross section of /sup 243/Am in the energy range from 5 to 250 keV

    SciTech Connect

    Wisshak, K.; Kappeler, F.

    1983-11-01

    The neutron capture and subthreshold fission cross section of /sup 243/Am was measured in the energy range from 5 to 250 keV using /sup 197/Au and /sup 235/U as the respective standards. Neutrons were produced via the /sup 7/Li(p,n) and the T(p,n) reaction with the Karlsruhe 3-MV pulsed Van de Graaff accelerator. Capture events were detected by two Moxon-Rae detectors with graphite and bismuth graphite converters, respectively. Fission events were registered by an Ne-213 liquid scintillator with pulse-shape discriminator equipment. Flight paths as short as 50 to 70 mm were used to obtain an optimum signal-to-background ratio. After correction for the different efficiency of the individual converter materials, the capture cross section could be determined with a total uncertainty of 3 to 6%. The respective values for the fission cross section are 8 to 12%. The results are compared to predictions of recent evaluations, which in some cases are severely discrepant.

  13. Time-resolved analysis of the X-ray emission of femtosecond-laser-produced plasmas in the 1.5-keV range

    NASA Astrophysics Data System (ADS)

    Bastiani-Ceccotti, S.; Audebert, P.; Nagels-Silvert, V.; Geindre, J. P.; Gauthier, J. C.; Adam, J. C.; Héron, A.; Chenais-Popovics, C.

    Recent experimental results on ion beams produced in high-intensity laser-solid interactions indicate the presence of very intense electric fields in the target. This suggests the possibility of efficiently heating a solid material by means of the fast electrons created during the laser-solid interactions and trapped in the target, rather than by the laser photons themselves. We tested this mechanism by irradiating very small cubic aluminum targets with the LULI 100-TW, 300-fs laser at 1.06-μm wavelength. X-ray spectra were measured with an ultra-fast streak camera, coupled to a conical Bragg crystal, providing spectra in the 1.5-keV range with high temporal and spectral resolution. The results indicate the creation of a hot plasma, but a very low coupling between the rapid electrons and the solid. A tentative explanation, in agreement with other experimental results and with preliminary particle-in-cell (PIC) simulations, points out the fatal role of the laser prepulse.

  14. Determination of the effective atomic numbers and electron densities for YBaCuO superconductor in the range 59.5 136 keV

    NASA Astrophysics Data System (ADS)

    Baltaş, H.; Çevik, U.

    2008-04-01

    The effective atomic numbers and electron densities of YBa 2Cu 3O 7-δ superconductor at 59.5, 65.2, 77.1, 94.6, 122 and 136 keV were calculated by using the measured mass attenuation coefficients. Measurements were made by performing transmission experiments in a well-collimated narrow beam geometry set-up by employing Si(Li) detector with a resolution of 0.16 keV at 5.9 keV. These values are found to be in good agreement with theoretical values calculated based on XCOM data. The observed crystal structure of YBa 2Cu 3O 7-δ superconductor is close to the theoretical structure. Zeff and Nel experimental values showed good agreement with the theoretical values for calcined and sintered YBa 2Cu 3O 7-δ.

  15. Studies on effective atomic numbers for photon energy absorption and electron density of some narcotic drugs in the energy range 1 keV-20 MeV

    NASA Astrophysics Data System (ADS)

    Gounhalli, Shivraj G.; Shantappa, Anil; Hanagodimath, S. M.

    2013-04-01

    Effective atomic numbers for photon energy absorption ZPEA,eff, photon interaction ZPI,eff and for electron density Nel, have been calculated by a direct method in the photon-energy region from 1 keV to 20 MeV for narcotic drugs, such as Heroin (H), Cocaine (CO), Caffeine (CA), Tetrahydrocannabinol (THC), Cannabinol (CBD), Tetrahydrocannabivarin (THCV). The ZPEA,eff, ZPI,eff and Nel values have been found to change with energy and composition of the narcotic drugs. The energy dependence ZPEA,eff, ZPI,eff and Nel is shown graphically. The maximum difference between the values of ZPEA,eff, and ZPI,eff occurs at 30 keV and the significant difference of 2 to 33% for the energy region 5-100 keV for all drugs. The reason for these differences is discussed.

  16. First INTEGRAL Observations of V404 Cygni during the 2015 Outburst: Spectral Behavior in the 20-650 keV Energy Range

    NASA Astrophysics Data System (ADS)

    Roques, Jean-Pierre; Jourdain, Elisabeth; Bazzano, Angela; Fiocchi, Mariateresa; Natalucci, Lorenzo; Ubertini, Pietro

    2015-11-01

    In 2015 June, the source V404 Cygni (= GS2023+38) underwent an extraordinary outburst. We present the results obtained during the first revolution dedicated to this target by the INTEGRAL mission and focus on the spectral behavior in the hard X-ray domain, using both SPI and IBIS instruments. The source exhibits extreme variability and reaches fluxes of several tens of Crab. However, the emission between 20 and 650 keV can be understood in terms of two main components, varying on all the observable timescales, similar to what is observed in the persistent black hole system Cyg X-1. The low-energy component (up to ˜200 keV) presents a rather unusual shape, probably due to the intrinsic source variability. Nonetheless, a satisfactory description is obtained with a Comptonization model, if an unusually hot population of seed photons (kT0 ˜ 7 keV) is introduced. Above this first component, a clear excess extending up to 400-600 keV leads us to investigate a scenario where an additional (cutoff) power law could correspond to the contribution of the jet synchrotron emission, as proposed in Cyg X-1. A search for an annihilation feature did not provide any firm detection, with an upper limit of 2 × 10-4 ph cm-2 s-1 (2σ) for a narrow line centered at 511 keV, on the averaged obtained spectrum. Based on observations with INTEGRAL, an ESA project with instruments and science data center funded by ESA member states (especially the PI countries: Denmark, France, Germany, Italy, Spain, and Switzerland), Czech Republic, and Poland with the participation of Russia and USA.

  17. First INTEGRAL Observations of V404 Cygni during the 2015 Outburst: Spectral Behavior in the 20–650 keV Energy Range

    NASA Astrophysics Data System (ADS)

    Roques, Jean-Pierre; Jourdain, Elisabeth; Bazzano, Angela; Fiocchi, Mariateresa; Natalucci, Lorenzo; Ubertini, Pietro

    2015-11-01

    In 2015 June, the source V404 Cygni (= GS2023+38) underwent an extraordinary outburst. We present the results obtained during the first revolution dedicated to this target by the INTEGRAL mission and focus on the spectral behavior in the hard X-ray domain, using both SPI and IBIS instruments. The source exhibits extreme variability and reaches fluxes of several tens of Crab. However, the emission between 20 and 650 keV can be understood in terms of two main components, varying on all the observable timescales, similar to what is observed in the persistent black hole system Cyg X-1. The low-energy component (up to ∼200 keV) presents a rather unusual shape, probably due to the intrinsic source variability. Nonetheless, a satisfactory description is obtained with a Comptonization model, if an unusually hot population of seed photons (kT0 ∼ 7 keV) is introduced. Above this first component, a clear excess extending up to 400–600 keV leads us to investigate a scenario where an additional (cutoff) power law could correspond to the contribution of the jet synchrotron emission, as proposed in Cyg X-1. A search for an annihilation feature did not provide any firm detection, with an upper limit of 2 × 10‑4 ph cm‑2 s‑1 (2σ) for a narrow line centered at 511 keV, on the averaged obtained spectrum. Based on observations with INTEGRAL, an ESA project with instruments and science data center funded by ESA member states (especially the PI countries: Denmark, France, Germany, Italy, Spain, and Switzerland), Czech Republic, and Poland with the participation of Russia and USA.

  18. Ionic Liquids as a Reference Material Candidate for the Quick Performance Check of Energy Dispersive X-ray Spectrometers for the Low Energy Range below 1 keV

    PubMed Central

    2016-01-01

    Ionic liquids (ILs) are proposed as simple and efficient test materials to evaluate the performance of energy dispersive X-ray spectrometers (EDS) in the low energy range below 1 keV. By only one measurement, C Kα, N Kα, O Kα, and F Kα X-ray lines can be excited. Additionally, the S Kα line at 2.3 keV and, particularly, the S L series at 149 eV complete the picture with X-ray lines offered by the selected ILs. The well-known (certifiable) elemental composition of the ILs selected in the present study can be used to check the accuracy of results produced with the available EDS quantification routines in the low energy range, simultaneously, for several low atomic number elements. A comparison with other reference materials in use for testing the performance of EDS in the low energy range is included. PMID:27336962

  19. Measurement of X-ray mass attenuation coefficients in biological and geological samples in the energy range of 7-12keV.

    PubMed

    Trunova, Valentina; Sidorina, Anna; Kriventsov, Vladimir

    2014-10-17

    Information about X-ray mass attenuation coefficients in different materials is necessary for accurate X-ray fluorescent analysis. The X-ray mass attenuation coefficients for energy of 7-12keV were measured in biological (Mussel and Oyster tissues, blood, hair, liver, and Cabbage leaves) and geological (Baikal sludge, soil, and Alaskite granite) samples. The measurements were carried out at the EXAFS Station of Siberian Synchrotron Radiation Center (VEPP-3). Obtained experimental mass attenuation coefficients were compared with theoretical values calculated for some samples. PMID:25464176

  20. Calculations of electron stopping powers for 41 elemental solids over the 50 eV to 30 keV range with the full Penn algorithm

    NASA Astrophysics Data System (ADS)

    Shinotsuka, H.; Tanuma, S.; Powell, C. J.; Penn, D. R.

    2012-01-01

    We present mass collision electron stopping powers (SPs) for 41 elemental solids (Li, Be, graphite, diamond, glassy C, Na, Mg, Al, Si, K, Sc, Ti, V, Cr, Fe, Co, Ni, Cu, Ge, Y, Nb, Mo, Ru, Rh, Pd, Ag, In, Sn, Cs, Gd, Tb, Dy, Hf, Ta, W, Re, Os, Ir, Pt, Au, and Bi) that were calculated from experimental energy-loss-function data with the full Penn algorithm for electron energies between 50 eV and 30 keV. Improved sets of energy-loss functions were used for 19 solids. Comparisons were made of these SPs with SPs calculated with the single-pole approximation, previous SP calculations, and experimental SPs. Generally satisfactory agreement was found with SPs from the single-pole approximation for energies above 100 eV, with other calculated SPs, and with measured SPs.

  1. Mass attenuation coefficient of binderless, pre-treated and tannin-based Rhizophora spp. particleboards using 16.59 - 25.26 keV photon energy range

    NASA Astrophysics Data System (ADS)

    Mohd Yusof, Mohd Fahmi; Hamid, Puteri Nor Khatijah Abdul; Bauk, Sabar; Hashim, Rokiah; Tajuddin, Abdul Aziz

    2015-04-01

    The Rhizophora spp. particleboards were fabricated using ≤ 104 µm particle size at three different fabrication methods; binderless, steam pre-treated and tannin-added. The mass attenuation coefficient of Rhizophora spp. particleboards were measured using x-ray fluorescent (XRF) photon from niobium, molybdenum, palladium, silver and tin metal plates that provided photon energy between 16.59 to 25.26 keV. The results were compared to theoretical values for water calculated using photon cross-section database (XCOM).The results showed that all Rhizophora spp. particleboards having mass attenuation coefficient close to calculated XCOM for water. Tannin-added Rizophora spp. particleboard was nearest to calculated XCOM for water with χ2 value of 13.008 followed by binderless Rizophora spp. (25.859) and pre-treated Rizophora spp. (91.941).

  2. Neutron capture cross sections of natural Yb, /sup 170/Yb, /sup 175/Lu, and /sup 184/W in the energy range from 5 to 200 keV for the /sup 176/Lu-chronometer

    SciTech Connect

    Beer, H.; Wisshak, K.; Kaeppeler, F.

    1980-09-01

    The neutron capture cross sections of natural Yb, /sup 170/Yb, /sup 175/Lu and /sup 184/W have been measured in the keV neutron energy range with a pulsed Van de Graaff accelerator using the kinematically collimated neutron beam from the /sup 7/Li(p,n) and the T(p,n) reaction. Prompt capture gamma rays were registered by a Moxon-Rae detector. All measurements were performed in a single run relative to the /sup 197/Au cross section as a standard. The cross sections of /sup 175/Lu and /sup 170/Yb were used to investigate the /sup 176/Lu-cosmic clock.

  3. Experimental and MC determination of HPGe detector efficiency in the 40-2754 keV energy range for measuring point source geometry with the source-to-detector distance of 25 cm.

    PubMed

    Dryak, Pavel; Kovar, Petr

    2006-01-01

    A precise model of a 40% relative efficiency p-type HPGe detector was created for photon detection efficiency calculation using the MCNP code. All detector parameters were determined by different experiments. No experimental calibration points were used for the modification of detector parameters. The model was validated by comparing calculated and experimental full energy peak efficiencies in the 40-2754 keV energy range, for point-source geometry with the source-to-detector distance of 25 cm. PMID:16564693

  4. Measurement of the x-ray mass attenuation coefficient and determination of the imaginary component of the atomic form factor of molybdenum over the 13.5-41.5-keV energy range

    NASA Astrophysics Data System (ADS)

    de Jonge, Martin D.; Tran, Chanh Q.; Chantler, Christopher T.; Barnea, Zwi; Dhal, Bipin B.; Cookson, David J.; Lee, Wah-Keat; Mashayekhi, Ali

    2005-03-01

    We use the x-ray extended-range technique (XERT) [Chantler , Phys. Rev. A 64, 062506 (2001)] to measure the mass attenuation coefficients of molybdenum in the x-ray energy range of 13.5-41.5keV to 0.02-0.15 % accuracy. Measurements made over an extended range of the measurement parameter space are critically examined to identify, quantify, and correct where necessary a number of experimental systematic errors. These results represent the most extensive experimental data set for molybdenum and include absolute mass attenuation coefficients in the regions of the x-ray absorption fine structure (XAFS) and x-ray-absorption near-edge structure (XANES). The imaginary component of the atomic form-factor f2 is derived from the photoelectric absorption after subtracting calculated Rayleigh and Compton scattering cross sections from the total attenuation. Comparison of the result with tabulations of calculated photoelectric absorption coefficients indicates that differences of 1-15 % persist between the calculated and observed values.

  5. Combined ion (Ar+, 20 keV) and light irradiation of the quenched Fe-8.25 at % Mn alloy. Separation between thermal and radiation induced long-range effects

    NASA Astrophysics Data System (ADS)

    Ovchinnikov, V. V.; Gushchina, N. V.; Bedin, S. A.

    2016-02-01

    Mössbauer and X-ray diffraction investigations of the radiation-induced α → γ phase transformation and short-range-order formation processes in the quenched Fe-8.25 at % Mn alloy under combined exposure (simultaneous visible light and Ar+ 20-keV ion beam irradiation) are carried out. Combined exposure made it possible to fix the target stationary temperature, and hence, the intensity of thermally-stimulated processes; an energy and ion current density could independently be varied in a wide range. As a result, an important contribution of a non-thermal constituent of ion beam exposure to the structural state of alloy was proved. Only in the presence of ion beam, an α → γ (bcc → fcc) phase transformation and accelerated intraphase processes preparing this transformation are observed in the deep layers of the target (about 103 Rp). With allowance for the relatively low level of thermally and radiation-stimulated processes, radiation-dynamic effects associated with propagation of intense post-cascade solitary waves, which can rearrange metastable matters, are considered as the cause of the observed transformations.

  6. Measurement of mass attenuation coefficients of Rhizophora spp. binderless particleboards in the 16.59-25.26 keV photon energy range and their density profile using x-ray computed tomography.

    PubMed

    Marashdeh, M W; Bauk, S; Tajuddin, A A; Hashim, R

    2012-04-01

    The mass attenuation coefficients of Rhizophora spp. binderless particleboard with four different particle sizes (samples A, B, C and D) and natural raw Rhizophora spp. wood (sample E) were determined using single-beam photon transmission in the energy range between 16.59 and 25.26 keV. This was done by determining the attenuation of K(α1) X-ray fluorescent (XRF) photons from niobium, molybdenum, palladium, silver and tin targets. The results were compared with theoretical values of young-age breast (Breast 1) and water calculated using a XCOM computer program. It was found that the mass attenuation coefficient of Rhizophora spp. binderless particleboards to be close to the calculated XCOM values in water than natural Rhizophora spp. wood. Computed tomography (CT) scans were then used to determine the density profile of the samples. The CT scan results showed that the Rhizophora spp. binderless particleboard has uniform density compared to natural Rhizophora spp. wood. In general, the differences in the variability of the profile density decrease as the particle size of the pellet samples decreases. PMID:22304963

  7. Energy dependence of photon-induced Kα and Kβ x-ray production cross-sections for some elements with 42≤Z≤68 in the energy range 38-80 keV

    NASA Astrophysics Data System (ADS)

    Seven, Sabriye; Erdoğan, Hasan

    2015-12-01

    The energy dependence of photon-induced Kα and Kβ x-ray production cross-sections for Mo, Ru, Pd, In, Sb, Cs, La, Pr, Sm, Tb and Er elements has been studied in the energy range of 38-80 keV with secondary excitation method. K x-ray intensities were measured using Energy Dispersive X-Ray Fluorescence (EDXRF) Spectrometry. The measurements have been made by observing the x-ray emissions, with the help of HPGe detector coupled with a multichannel analyzer. The areas of the Kα and Kβ spectral peaks, as well as the net peak areas, have been determined by a fitting process. The measured Kα and Kβ x-ray production cross-sections have been compared with calculated theoretical values in this energy regime. The results have been plotted versus excitation energy. The present experimental Kα and Kβ x-ray production cross-section values for all the elements were in general agreement with the theoretical values calculated using photoionization cross-sections, fluorescence yields and fractional rates based on Hartree-Slater potentials.

  8. High angular resolution cosmic X-ray astronomy observations in the energy range 0.15-2 keV and XUV observations of nearby stars from an attitude controlled rocket

    NASA Technical Reports Server (NTRS)

    Garmire, G. P.

    1974-01-01

    The construction of a two dimensional focusing Wolter Type I mirror system for X-ray and XUV astronomical observations from an Astrobee F sounding rocket is described. The mirror design goal will have a one degree field, a 20-arc seconds resolution, an effective area of about 50 sq cm at 1 keV and 10 sq cm at 0.25 keV on axis. A star camera provides aspect data to about 15-arc seconds. Two detectors are placed at the focus with an interchange mechanism to allow a detector change during flight. The following specific developments are reported: (1) position sensitive proportional counter development; (2) channel plate multiplier development; (3) telescope mirror development and payload structure; (4) Australian rocket flight results; (5) Comet Kohoutek He I observation; and (6) Vela, Puppis A, and Gem-Mon bright patch observations.

  9. Energy dependent response of the Fricke gel dosimeter prepared with 270 Bloom gelatine for photons in the energy range 13.93 keV-6 MeV

    NASA Astrophysics Data System (ADS)

    Cavinato, C. C.; Campos, L. L.

    2010-07-01

    The spectrophotometric energy dependent response to photons with effective energies between 13.93 keV and 6 MeV of the Fricke xylenol gel (FXG) dosimeter developed at IPEN, prepared using 270 Bloom gelatine, was evaluated in order to verify the possible dosimeter application in other medicine areas in addition to radiosurgery, for example, breast radiotherapy and blood bags radiosterilization. Other dosimetric characteristics were also evaluated. The obtained results indicate that the FXG dosimeter can contribute to dosimetry in different medical application areas including magnetic resonance imaging (MRI) evaluation technique that permits three-dimensional (3D) dose distribution evaluation.

  10. X-ray mass attenuation coefficients and imaginary components of the atomic form factor of zinc over the energy range of 7.2-15.2 keV

    SciTech Connect

    Rae, Nicholas A.; Chantler, Christopher T.; Barnea, Zwi; Jonge, Martin D. de; Tran, Chanh Q.; Hester, James R.

    2010-02-15

    The x-ray mass attenuation coefficients of zinc are measured in a high-accuracy experiment between 7.2 and 15.2 keV with an absolute accuracy of 0.044% and 0.197%. This is the most accurate determination of any attenuation coefficient on a bending-magnet beamline and reduces the absolute uncertainty by a factor of 3 compared to earlier work by advances in integrated column density determination and the full-foil mapping technique described herein. We define a relative accuracy of 0.006%, which is not the same as either the precision or the absolute accuracy. Relative accuracy is the appropriate parameter for standard implementation of analysis of near-edge spectra. Values of the imaginary components f'' of the x-ray form factor of zinc are derived. Observed differences between the measured mass attenuation coefficients and various theoretical calculations reach a maximum of about 5% at the absorption edge and up to 2% further than 1 keV away from the edge. The measurements invite improvements in the theoretical calculations of mass attenuation coefficients of zinc.

  11. Mass attenuation coefficient of binderless, pre-treated and tannin-based Rhizophora spp. particleboards using 16.59 – 25.26 keV photon energy range

    SciTech Connect

    Mohd Yusof, Mohd Fahmi Hamid, Puteri Nor Khatijah Abdul; Tajuddin, Abdul Aziz; Bauk, Sabar; Hashim, Rokiah

    2015-04-29

    The Rhizophora spp. particleboards were fabricated using ≤ 104 µm particle size at three different fabrication methods; binderless, steam pre-treated and tannin-added. The mass attenuation coefficient of Rhizophora spp. particleboards were measured using x-ray fluorescent (XRF) photon from niobium, molybdenum, palladium, silver and tin metal plates that provided photon energy between 16.59 to 25.26 keV. The results were compared to theoretical values for water calculated using photon cross-section database (XCOM).The results showed that all Rhizophora spp. particleboards having mass attenuation coefficient close to calculated XCOM for water. Tannin-added Rizophora spp. particleboard was nearest to calculated XCOM for water with χ2 value of 13.008 followed by binderless Rizophora spp. (25.859) and pre-treated Rizophora spp. (91.941)

  12. Electron Flux Models at GEO: 30 keV - 600 keV

    NASA Astrophysics Data System (ADS)

    Boynton, R.; Balikhin, M. A.; Sibeck, D. G.; Walker, S. N.; Ganushkina, N. Y.

    2015-12-01

    Forecast models are developed for the electron fluxes measured by the Magnetospheric Electron Detector (MagED) onboard the Geostationary Operational Environmental Satellite (GOES) 13. The models employ solar wind and geomagnetic indices as inputs to produce a forecast of the electron flux at Geostationary Earth Orbit (GEO) for five energy ranges from 30 keV - 600 keV. All of these models will be implemented in real time to forecast the electron fluxes on the PROGRESS project website (https://ssg.group.shef.ac.uk/progress2/html/index.phtml).

  13. Preparation for B4C/Mo2C multilayer deposition of alternate multilayer gratings with high efficiency in the 0.5-2.5 keV energy range

    NASA Astrophysics Data System (ADS)

    Choueikani, Fadi; Delmotte, Franck; Bridou, Françoise; Lagarde, Bruno; Mercere, Pascal; Otero, Edwige; Ohresser, Philippe; Polack, François

    2013-03-01

    This paper presents a study of B4C/Mo2C multilayers mirrors with the aim of using it in the achievement of Alternate MultiLayer (AML) grating. Such component allows a high efficiency in the 500-2500 eV energy range for the DEIMOS beamline. Multilayers were deposited on silicon substrate. They are characterized by reflectometry under grazing incidence. Numerical adjustments were performed with a model of two layers in the period without any interfacial. A prototype of AML grating was fabricated and characterized. The efficiency of the first order of diffraction was worth 15% at 1700 eV.

  14. Calculation of electron-impact rotationally elastic total cross sections for NH{sub 3}, H{sub 2}S, and PH{sub 3} over the energy range from 0.01 eV to 2 keV

    SciTech Connect

    Limbachiya, Chetan; Vinodkumar, Minaxi; Mason, Nigel

    2011-04-15

    This paper report results of calculation of the total cross section Q{sub T} for electron impact on NH{sub 3}, H{sub 2}S, and PH{sub 3} over a wide range of incident energies from 0.01 eV to 2 keV. Total cross sections Q{sub T} (elastic plus electronic excitation) for incident energies below the ionization threshold of the target were calculated using the UK molecular R-matrix code through the Quantemol-N software package and cross sections at higher energies were derived using the spherical complex optical potential formalism. The two methods are found to give self-consistent values where they overlap. The present results are, in general, found to be in good agreement with previous experimental and theoretical results.

  15. Measurement of photon mass attenuation coefficients of plutonium from 60 to 2615 keV

    NASA Astrophysics Data System (ADS)

    Rettschlag, M.; Berndt, R.; Mortreau, P.

    2007-11-01

    Measurements have been made to determine plutonium photon mass attenuation coefficients by using a collimated-beam transmission method in the energy range from 60 to 2615 keV. These experimental results were compared with previous experimental and theoretical data. Good agreements are observed in the 240-800 keV energy range, whereas differences up to maximum 10% are observed out of these limits.

  16. One 17-keV Majorana neutrino?

    NASA Astrophysics Data System (ADS)

    Carlson, Eric; Randall, Lisa

    1991-06-01

    A model is presented accommodating a 17-keV neutrino with 1 percent mixing with the electron neutrino and bounds on the electron-neutrino mass and neutrinoless double-beta decay. However, in contrast to previous models, there is only a single state with mass 17 keV. This model is consistent with cosmological and supernova-cooling constraints, and incorporates the Mikheyev-Smirnov-Wolfenstein explanation of the low solar-neutrino counts. Possible signatures of this model include an excess of muon neutrinos from a supernova explosion, spread over a period of 10-1000 sec, and a Higgs-boson decay signature of leptons plus missing energy.

  17. Characterization of the PILATUS photon-counting pixel detector for X-ray energies from 1.75 keV to 60 keV

    NASA Astrophysics Data System (ADS)

    Donath, T.; Brandstetter, S.; Cibik, L.; Commichau, S.; Hofer, P.; Krumrey, M.; Lüthi, B.; Marggraf, S.; Müller, P.; Schneebeli, M.; Schulze-Briese, C.; Wernecke, J.

    2013-03-01

    The PILATUS detector module was characterized in the PTB laboratory at BESSY II comparing modules with 320 μm thick and newly developed 450 μm and 1000 μm thick silicon sensors. Measurements were carried out over a wide energy range, in-vacuum from 1.75 keV to 8.8 keV and in air from 8 keV to 60 keV. The quantum efficiency (QE) was measured as a function of energy and the spatial resolution was measured at several photon energies both in terms of the modulation transfer function (MTF) from edge profile measurements and by directly measuring the point spread function (PSF) of a single pixel in a raster scan with a pinhole beam. Independent of the sensor thickness, the measured MTF and PSF come close to those for an ideal pixel detector with the pixel size of the PILATUS detector (172 × 172 μm2). The measured QE follows the values predicted by calculation. Thicker sensors significantly enhance the QE of the PILATUS detectors for energies above 10 keV without impairing the spatial resolution and noise-free detection. In-vacuum operation of the PILATUS detector is possible at energies as low as 1.75 keV.

  18. Stacked depth graded multilayer for hard X-rays measured up to 130 keV

    NASA Astrophysics Data System (ADS)

    Jensen, C. P.; Christensen, F. E.; Romaine, S.; Bruni, R.; Zhong, Z.

    2007-09-01

    Depth graded multilayer designs for hard x-ray telescopes in the 10 keV to 70-80 keV energy range have had either W or Pt as the heavy element. These materials have been chosen because of reasonable optical constants, the possibility to grow smooth interfaces with the spacer material, and the stability over time. On the flip side both W and Pt have an absorption edge -- 69.5 keV (W) and 78.4 keV (Pt) -- which is very close to the two 44Ti lines at 67.9 keV and 78.4 keV that are produced in the envelope of a super nova explosion. Other materials have better optical constants and no absorption edges in this energy range, for example Ni 0.93V 0.07, but are not used because of high interface roughness. By using a WC/SiC multilayer for the bottom and a Ni 0.93V 0.07/SiC multilayer for the thicker top layers of a depth graded multilayer we have made a reflector that doesn't have a clear absorption edge. This reflector has been measured at energies between 8 keV and 130 keV. At a graze angle of 0.11 degree there is still nearly the same reflectivity below the W absorption edge as for a traditional W based coating, and above the W absorption edge there is still 48% reflection at 80 keV.

  19. Detection of interplanetary electrons from 18 keV to 1.8 MeV during solar quiet times, 1. On the origin of 200 KeV interplanetary electrons, 2.

    NASA Technical Reports Server (NTRS)

    Lin, R. P.; Anderson, K. A.; Cline, T. L.; Ramaty, R.; Fisk, L. A.

    1972-01-01

    A quiet time component of interplanetary electrons having energies above solar wind energies and below those characterized as cosmic radiation was observed. Its energy spectrum falls with energy from 18 keV to 1.8 MeV, but it shows a feature in the 100 to 300 keV range. The observed temporal variations of the intensity suggest that the 18 to 100 keV portion is solar and the 0.3 to 1.8 MeV portion is galactic in origin. Solar and terrestrial neutron decay electrons appear inadequate to explain the 100 to 300 keV feature.

  20. Measurement of the mass attenuation coefficient from 81 keV to 1333 keV for elemental materials Al, Cu and Pb

    NASA Astrophysics Data System (ADS)

    Gjorgieva, Slavica; Barandovski, Lambe

    2016-03-01

    The mass attenuation coefficients (μ/ρ) for 3 high purity elemental materials Al, Cu and Pb were measured in the γ-ray energy range from 81 keV up to 1333 keV using 22Na, 60Co 133Ba and 133Cs as sources of gamma radiation. Well shielded detector (NaI (Tl) semiconductor detector) was used to measure the intensity of the transmitted beam. The measurements were made under condition of good geometry, assuring that any photon absorbed or deflected appreciably does not reach the detector. The measured values are compared with the theoretical ones obtained by Seltzer (1993).

  1. Measurement of mass attenuation coefficients for four mixtures using X-rays from 13 keV up to 40 keV

    NASA Astrophysics Data System (ADS)

    Angelone, M.; Esposito, A.; Chiti, M.; Gentile, A.

    2001-06-01

    The total absorption coefficients for some selected organic compounds relevant to health physics, Triaflol BN (C 3H 4O 2) n, Triaflol TN (C 12H 18O 7) n, Kapton (C 44H 20O 10) n, and Melinex (C 10H 8N 4O 4) n were measured in the X-ray energy range from 13 keV up to about 40 keV using a collimator, high purity germanium detector with thin Be window and variable energy X-ray source. The measured values are compared with the theoretical ones obtained using the XCOM code. The agreement is generally good within a few percent.

  2. Experimental Determination of the HPGe Spectrometer Efficiency Calibration Curves for Various Sample Geometry for Gamma Energy from 50 keV to 2000 keV

    NASA Astrophysics Data System (ADS)

    Saat, Ahmad; Hamzah, Zaini; Yusop, Mohammad Fariz; Zainal, Muhd Amiruddin

    2010-07-01

    Detection efficiency of a gamma-ray spectrometry system is dependent upon among others, energy, sample and detector geometry, volume and density of the samples. In the present study the efficiency calibration curves of newly acquired (August 2008) HPGe gamma-ray spectrometry system was carried out for four sample container geometries, namely Marinelli beaker, disc, cylindrical beaker and vial, normally used for activity determination of gamma-ray from environmental samples. Calibration standards were prepared by using known amount of analytical grade uranium trioxide ore, homogenized in plain flour into the respective containers. The ore produces gamma-rays of energy ranging from 53 keV to 1001 keV. Analytical grade potassium chloride were prepared to determine detection efficiency of 1460 keV gamma-ray emitted by potassium isotope K-40. Plots of detection efficiency against gamma-ray energy for the four sample geometries were found to fit smoothly to a general form of ɛ = AΕa+BΕb, where ɛ is efficiency, Ε is energy in keV, A, B, a and b are constants that are dependent on the sample geometries. All calibration curves showed the presence of a "knee" at about 180 keV. Comparison between the four geometries showed that the efficiency of Marinelli beaker is higher than cylindrical beaker and vial, while cylindrical disk showed the lowest.

  3. Experimental Determination of the HPGe Spectrometer Efficiency Calibration Curves for Various Sample Geometry for Gamma Energy from 50 keV to 2000 keV

    SciTech Connect

    Saat, Ahmad; Hamzah, Zaini; Yusop, Mohammad Fariz; Zainal, Muhd Amiruddin

    2010-07-07

    Detection efficiency of a gamma-ray spectrometry system is dependent upon among others, energy, sample and detector geometry, volume and density of the samples. In the present study the efficiency calibration curves of newly acquired (August 2008) HPGe gamma-ray spectrometry system was carried out for four sample container geometries, namely Marinelli beaker, disc, cylindrical beaker and vial, normally used for activity determination of gamma-ray from environmental samples. Calibration standards were prepared by using known amount of analytical grade uranium trioxide ore, homogenized in plain flour into the respective containers. The ore produces gamma-rays of energy ranging from 53 keV to 1001 keV. Analytical grade potassium chloride were prepared to determine detection efficiency of 1460 keV gamma-ray emitted by potassium isotope K-40. Plots of detection efficiency against gamma-ray energy for the four sample geometries were found to fit smoothly to a general form of {epsilon} = A{Epsilon}{sup a}+B{Epsilon}{sup b}, where {epsilon} is efficiency, {Epsilon} is energy in keV, A, B, a and b are constants that are dependent on the sample geometries. All calibration curves showed the presence of a ''knee'' at about 180 keV. Comparison between the four geometries showed that the efficiency of Marinelli beaker is higher than cylindrical beaker and vial, while cylindrical disk showed the lowest.

  4. 2-165 keV observations of active galaxies and the diffuse background

    NASA Technical Reports Server (NTRS)

    Rothschild, R. E.; Baity, W. A.; Gruber, D. E.; Matteson, J. L.; Peterson, L. E.; Mushotzky, R. F.

    1983-01-01

    HEAO 1 spectral observations of 12 active galaxies in the 12-165 keV and 2-50 keV ranges are reported. The spectra of these galaxies in the 2-165 keV range are well represented by a single power law model; within experimental uncertainties a narrow dispersion in power law index attributable to the individual galaxies is observed, while the 2-165 keV luminosities of these galaxies ranged from 3 x 10 to the 43rd to 3 x 10 to the 45th ergs/s. An apparent universality of the spectral form is found which can be interpreted as due to a common electron distribution with a temperature of tens of keV in the Compton scattering region or as a common nonthermal power-law distribution generating the observed flux through synchrotron-Compton processes. The data indicate that relativistic particles are likely to be responsible for the X-rays from cores of active galaxies through synchroton-Compton processes. In addition, it is noted that only weak number evolution, if any at all, is present in active galaxies.

  5. Width of the 511 keV line from the bulge of the galaxy

    SciTech Connect

    Zhitnitsky, Ariel

    2007-11-15

    In this paper I present the detail estimations for the width of the 511 keV line produced by a mechanism when dark matter is represented by macroscopically large dense nuggets. I argue that the width of 511 keV emission in this mechanism is very narrow (in a few keV range) in agreement with all observations. The dominant mechanism of the annihilation in this case is the positronium formation e{sup +}e{sup -}{yields}{sup 1}S{sub 0}{yields}2{gamma} rather than a direct e{sup +}e{sup -}{yields}2{gamma} annihilation. I also discuss some generic features of the {gamma} rays spectrum (in few MeV range) resulting from this mechanism.

  6. Interstellar photoelectric absorption cross sections, 0.03-10 keV

    NASA Technical Reports Server (NTRS)

    Morrison, R.; Mccammon, D.

    1983-01-01

    An effective absorption cross section per hydrogen atom has been calculated as a function of energy in the 0.03-10 keV range using the most recent atomic cross section and cosmic abundance data. Coefficients of a piecewise polynomial fit to the numerical results are given to allow convenient application in automated calculations.

  7. The Average 0.5-200 keV Spectrum of AGNs at 0

    NASA Astrophysics Data System (ADS)

    Ballantyne, David R.

    2013-04-01

    The X-ray spectra of AGNs span nearly three decades in energy and are comprised of many separate components: a power-law with a high energy cutoff, reflection from the accretion disk as well as distant material, and, in many cases, a soft excess. Aside from a small number of bright sources observed with BeppoSAX, the full energy range of AGN spectra has only been studied in piecemeal by a fleet of X-ray observatories that can only focus on a small part of the entire spectrum. Therefore, while catalogues of the spectral properties of hundreds of AGNs have been published in different energy bands, these results are isolated from one another and a clear picture of the broadband spectral properties of typical AGNs remains elusive. In this work, we make use of the 0 X-ray luminosity functions of AGNs in the 0.5-2 keV, 2-10 keV, 3-20 keV, 15-55 keV and 14-195 keV bands to construct the spectral model of an average AGN that can simultaneously account for all 5 luminosity functions. Enhanced iron abundances, disk reflection, and the presence or absence of the X-ray Baldwin Effect are considered, along with the traditional parameters of photon index and cutoff energy. Applications to X-ray background modelling and AGN physics are discussed.

  8. Spatial distribution of upstream magnetospheric geq50 keV ions

    NASA Astrophysics Data System (ADS)

    Anagnostopoulos, G. C.; Argyropoulos, G.; Kaliabetsos, G.

    2000-01-01

    We present for the first time a statistical study of geq50 keV ion events of a magnetospheric origin upstream from Earth's bow shock. The statistical analysis of the 50-220 keV ion events observed by the IMP-8 spacecraft shows: (1) a dawn-dusk asymmetry in ion distributions, with most events and lower intensities upstream from the quasi-parallel pre-dawn side (4 LT-6 LT) of the bow shock, (2) highest ion fluxes upstream from the nose/dusk side of the bow shock under an almost radial interplanetary magnetic field (IMF) configuration, and (3) a positive correlation of the ion intensities with the solar wind speed and the index of geomagnetic index Kp, with an average solar wind speed as high as 620 km s-1 and values of the index Kp > 2. The statistical results are consistent with (1) preferential leakage of sim50 keV magnetospheric ions from the dusk magnetopause, (2) nearly scatter free motion of sim50 keV ions within the magnetosheath, and (3) final escape of magnetospheric ions from the quasi-parallel dawn side of the bow shock. An additional statistical analysis of higher energy (290-500 keV) upstream ion events also shows a dawn-dusk asymmetry in the occurrence frequency of these events, with the occurrence frequency ranging between sim16%-sim34% in the upstream region.

  9. Ion-chain interaction in keV ion-beam-irradiated polystyrene

    SciTech Connect

    Calcagno, L.; Foti, G.; Licciardello, A.; Puglisi, O.

    1987-09-21

    Molecular weight distribution has been measured in monodisperse polystyrene film (MW = 9 000 amu) after ion bombardment, in the ion fluence range 10/sup 11/--10/sup 13/ ions/cm/sup 2/. The chosen beams are 100 keV He, 200 keV Ne, and 400 keV Ar. The experimental data have been interpreted in terms of a simple statistical model for cross-links. The chemical yield is found to be very high and equal to 0.30, about a factor of 10 higher than the values given in the literature for gamma irradiation (M. Dole, in The Radiation Chemistry of Macromolecules (Academic, New York, 1973), Vol. 2, Chap. 5, p. 57).

  10. Heliospheric Neutral Atom Spectra Between 0.01 and 6 keV fom IBEX

    NASA Technical Reports Server (NTRS)

    Fuselier, S. A.; Allegrini, F.; Bzowski, M.; Funsten, H. O.; Ghielmetti, A. G.; Gloeckler, G.; Heirtzler, D.; Janzen, P.; Kubiak, M.; Kucharek, H.; McComas, D. J.; Moebius, E.; Moore, T. E.; Petrinec, S. M.; Quinn, M.; Reisenfeld, D.; Saul, L. A.; Scheer, J. A.; Schwardron, N.; Trattner, K. J.; Vanderspek, R.; Wurz, P.

    2012-01-01

    Since 2008 December, the Interstellar Boundary Explorer (IBEX) has been making detailed observations of neutrals from the boundaries of the heliosphere using two neutral atom cameras with overlapping energy ranges. The unexpected, yet defining feature discovered by IBEX is a Ribbon that extends over the energy range from about 0.2 to 6 keV. This Ribbon is superposed on a more uniform, globally distributed heliospheric neutral population. With some important exceptions, the focus of early IBEX studies has been on neutral atoms with energies greater than approx. 0.5 keV. With nearly three years of science observations, enough low-energy neutral atom measurements have been accumulated to extend IBEX observations to energies less than approx. 0.5 keV. Using the energy overlap of the sensors to identify and remove backgrounds, energy spectra over the entire IBEX energy range are produced. However, contributions by interstellar neutrals to the energy spectrum below 0.2 keV may not be completely removed. Compared with spectra at higher energies, neutral atom spectra at lower energies do not vary much from location to location in the sky, including in the direction of the IBEX Ribbon. Neutral fluxes are used to show that low energy ions contribute approximately the same thermal pressure as higher energy ions in the heliosheath. However, contributions to the dynamic pressure are very high unless there is, for example, turbulence in the heliosheath with fluctuations of the order of 50-100 km/s.

  11. Estimates of the Compton backscattering feature at approximately 150 keV in the Crab Nebula pulsar

    NASA Astrophysics Data System (ADS)

    Bednarek, W.; Cremonesi, O.; Treves, A.

    1994-04-01

    The Compton backscattering feature at approximately 150 keV from the Crab Nebula pulsar is evaluated in a picture where the 440 keV emission is interpreted as due to positron annihilation in the pulsar crust. Monte Carlo simulations indicate a broad feature the intensity of which is expected in the range 10-5 - 10-4 ph/sq cm/s. The possibility of detection of the feature is discussed.

  12. Ion yields and erosion rates for Si{sub 1-x}Ge{sub x}(0<=x<=1) ultralow energy O{sub 2}{sup +} secondary ion mass spectrometry in the energy range of 0.25-1 keV

    SciTech Connect

    Morris, R. J. H.; Dowsett, M. G.

    2009-06-01

    We report the SIMS parameters required for the quantitative analysis of Si{sub 1-x}Ge{sub x} across the range of 0<=x<=1 when using low energy O{sub 2}{sup +} primary ions at normal incidence. These include the silicon and germanium secondary ion yield [i.e., the measured ion signal (ions/s)] and erosion rate [i.e., the speed at which the material sputters (nm/min)] as a function of x. We show that the ratio R{sub x} of erosion rates, Si{sub 1-x}Ge{sub x}/Si, at a given x is almost independent of beam energy, implying that the properties of the altered layer are dominated by the interaction of oxygen with silicon. R{sub x} shows an exponential dependence on x. Unsurprisingly, the silicon and germanium secondary ion yields are found to depart somewhat from proportionality to (1-x) and x, respectively, although an approximate linear relationship could be used for quantification across around 30% of the range of x (i.e., a reference material containing Ge fraction x would give reasonably accurate quantification across the range of +-0.15x). Direct comparison of the useful (ion) yields [i.e., the ratio of ion yield to the total number of atoms sputtered for a particular species (ions/atom)] and the sputter yields [i.e., the total number of atoms sputtered per incident primary ion (atoms/ions)] reveals a moderate matrix effect where the former decrease monotonically with increasing x except at the lowest beam energy investigated (250 eV). Here, the useful yield of Ge is found to be invariant with x. At 250 eV, the germanium ion and sputter yields are proportional to x for all x.

  13. Steady State Sputtering Yields and Surface Compositions of Depleted Uranium and Uranium Carbide bombarded by 30 keV Gallium or 16 keV Cesium Ions.

    SciTech Connect

    Siekhaus, W. J.; Teslich, N. E.; Weber, P. K.

    2014-10-23

    Depleted uranium that included carbide inclusions was sputtered with 30-keV gallium ions or 16-kev cesium ions to depths much greater than the ions’ range, i.e. using steady-state sputtering. The recession of both the uranium’s and uranium carbide’s surfaces and the ion corresponding fluences were used to determine the steady-state target sputtering yields of both uranium and uranium carbide, i.e. 6.3 atoms of uranium and 2.4 units of uranium carbide eroded per gallium ion, and 9.9 uranium atoms and 3.65 units of uranium carbide eroded by cesium ions. The steady state surface composition resulting from the simultaneous gallium or cesium implantation and sputter-erosion of uranium and uranium carbide were calculated to be U₈₆Ga₁₄, (UC)₇₀Ga₃₀ and U₈₁Cs₉, (UC)₇₉Cs₂₁, respectively.

  14. Physics of a 17 keV neutrino.

    NASA Astrophysics Data System (ADS)

    Kayser, B.

    The possible 17 keV neutrino, if real, cannot be νμ but could be essentially ντ. Relic 17 keV neutrinos from the big bang must have disappeared, through a non-Standard-Model decay or annihilation process, before the present epoch. If one assumes that the 17 keV neutrino is not a Dirac neutrino of the conventional kind, then one is led to picture it as a Dirac neutrino of the unconventional Zeldovich-Konopinski-Mahmoud kind. It is then an amalgam of ντ and ν¯μ.

  15. Evaluation of 238U Resonance Parameters from 0 to 20 keV

    NASA Astrophysics Data System (ADS)

    Derrien, H.; Courcelle, A.; Leal, L. C.; Larson, N.; Santamarina, A.

    2005-05-01

    The neutron resonance parameters of 238U were obtained in the energy range 0 to 20 keV from a sequential SAMMY analysis of the most recent high-resolution neutron transmission and neutron capture cross-section measurements. Special care was taken in the analysis of the lowest s-wave resonances leading to resonance parameters slightly different from those of ENDF/B-VI (Moxon-Sowerby resonance parameters). The resolved-resonance range was extended to 20 keV, taking advantage of the high-resolution neutron transmission data of Harvey and neutron capture data of Macklin et al. Preliminary integral tests were performed with the new resonance parameters; thermal low-enriched benchmark calculations show an improvement of the keff prediction, mainly due to a 1.5% decrease of the capture cross section at 0.0253 eV and about a 0.4% decrease of the effective shielded resonance capture integral.

  16. Evaluation of 238U Resonance Parameters from 0 to 20 keV

    SciTech Connect

    Derrien, H.; Leal, L.C.; Larson, N.; Courcelle, A.; Santamarina, A.

    2005-05-24

    The neutron resonance parameters of 238U were obtained in the energy range 0 to 20 keV from a sequential SAMMY analysis of the most recent high-resolution neutron transmission and neutron capture cross-section measurements. Special care was taken in the analysis of the lowest s-wave resonances leading to resonance parameters slightly different from those of ENDF/B-VI (Moxon-Sowerby resonance parameters). The resolved-resonance range was extended to 20 keV, taking advantage of the high-resolution neutron transmission data of Harvey and neutron capture data of Macklin et al. Preliminary integral tests were performed with the new resonance parameters; thermal low-enriched benchmark calculations show an improvement of the keff prediction, mainly due to a 1.5% decrease of the capture cross section at 0.0253 eV and about a 0.4% decrease of the effective shielded resonance capture integral.

  17. Study of photon attenuation coefficients of some multielement materials. [123-1250 keV

    SciTech Connect

    Bhandal, G.S. ); Singh, K. . Dept. of Physics)

    1994-03-01

    Total photon mass attenuation of six multielement shielding materials (concrete, plaster of paris, quick lime, black cement, white cement, and silica) is measured in the 123- to 1,250-keV energy range. The experimental results are analyzed in terms of cross sections, effective atomic numbers, and electron densities. Considerable sensitivity of the total mass attenuation coefficients and effective atomic numbers to variations in oxygen content are found in these multielement materials.

  18. Compton polarimeter for 10–30 keV x rays

    SciTech Connect

    Weber, S.; Beilmann, C.; Shah, C.; Tashenov, S.

    2015-09-15

    We present a simple and versatile polarimeter for x rays in the energy range of 10–30 keV. It uses Compton scattering in low-Z materials such as beryllium or boron carbide. The azimuthal distribution of the scattered x rays is sampled by an array of 12 silicon PIN diodes operated at room temperature. We evaluated the polarimetry performance using Monte-Carlo simulations and show experimental results.

  19. Compton polarimeter for 10-30 keV x rays.

    PubMed

    Weber, S; Beilmann, C; Shah, C; Tashenov, S

    2015-09-01

    We present a simple and versatile polarimeter for x rays in the energy range of 10-30 keV. It uses Compton scattering in low-Z materials such as beryllium or boron carbide. The azimuthal distribution of the scattered x rays is sampled by an array of 12 silicon PIN diodes operated at room temperature. We evaluated the polarimetry performance using Monte-Carlo simulations and show experimental results. PMID:26429432

  20. Precise Determination of the Intensity of 226Ra Alpha Decay to the 186 keV Excited State

    SciTech Connect

    S.P. LaMont; R.J. Gehrke; S.E. Glover; R.H. Filby

    2001-04-01

    There is a significant discrepancy in the reported values for the emission probability of the 186 keV gamma-ray resulting from the alpha decay of 226 Ra to 186 keV excited state of 222 Rn. Published values fall in the range of 3.28 to 3.59 gamma-rays per 100 alpha-decays. An interesting observation is that the lower value, 3.28, is based on measuring the 186 keV gamma-ray intensity relative to the 226 Ra alpha-branch to the 186 keV level. The higher values, which are close to 3.59, are based on measuring the gamma-ray intensity from mass standards of 226 Ra that are traceable to the mass standards prepared by HÓNIGSCHMID in the early 1930''s. This discrepancy was resolved in this work by carefully measuring the 226 Ra alpha-branch intensities, then applying the theoretical E2 multipolarity internal conversion coefficient of 0.692±0.007 to calculate the 186 keV gamma-ray emission probability. The measured value for the alpha branch to the 186 keV excited state was (6.16±0.03)%, which gives a 186 keV gamma-ray emission probability of (3.64±0.04)%. This value is in excellent agreement with the most recently reported 186 keV gamma-ray emission probabilities determined using 226 Ra mass standards.

  1. Parameter estimation of magnetospheric particle distributions in the energy range 20 to 500 keV

    NASA Astrophysics Data System (ADS)

    Torkar, K. M.

    1982-04-01

    A computer program which analyzes the energy spectra of energetic magnetospheric particles is described. The instrument characteristics and experimental design of the geostationary satellite GEOS-2 which provided the raw data are indicated. The program is designed to run on a UNIVAC 1100/81 computer and requires a plotter and a terminal with basic display enhancement features. Three dimensional charts showing the spectral distribution of energetic electrons are included.

  2. The dynamic range of LZ

    NASA Astrophysics Data System (ADS)

    Yin, J.

    2016-02-01

    The electronics of the LZ experiment, the 7-tonne dark matter detector to be installed at the Sanford Underground Research Facility (SURF), is designed to permit studies of physics where the energies deposited range from 1 keV of nuclear-recoil energy up to 3,000 keV of electron-recoil energy. The system is designed to provide a 70% efficiency for events that produce three photoelectrons in the photomultiplier tubes (PMTs). This corresponds approximately to the lowest energy threshold achievable in multi-tonne time-projection chambers, and drives the noise specifications for the front end. The upper limit of the LZ dynamic range is defined to accommodate the electroluminescence (S2) signals. The low-energy channels of the LZ amplifiers provide the dynamic range required for the tritium and krypton calibrations. The high-energy channels provide the dynamic range required to measure the activated Xe lines.

  3. Secondary ion emission from V and Al surfaces under keV light ion on bombardment

    NASA Astrophysics Data System (ADS)

    Blauner, Patricia G.; Weller, Martha R.; Kaurin, Michael G.; Weller, Robert A.

    1986-03-01

    Positive secondary ion mass spectra have been measured for oxidized polycrystalline V and Al targets bombarded by H +, H 2+, He + and Ar + ions with beam energies ranging from 25 keV to 275 keV. An enhancement in the relative yield of positive ions of electronegative surface constituents, in particular O + is observed under light ion bombardment. Metallic ion intensities were found to decrease with increasing primary beam energy in proportion to the estimated total sputtering yields for these targets and beams. In contrast, the O + secondary ion intensities were independent of primary beam energy. This behavior is similar to that observed previously with heavy ions of comparable velocities. In addition, for the projectiles and targets used in these measurements, no energy thresholds or collective effects were observed in the emission of any positive ion. Published data on secondary ion emission resulting from electron, photon, and heavy ion bombardment are compared with these results.

  4. Seeded quantum FEL at 478 keV

    SciTech Connect

    Guenther, M. M.; Jentschel, M.; Thirolf, P. G.; Seggebrock, T.; Habs, D.

    2012-07-09

    We present for the first time the concept of a seeded {gamma} quantum Free-Electron-Laser (QFEL) at 478 keV, which has very different properties compared to a classical. The basic concept is to produce a highly brilliant {gamma} beam via SASE. To produce highly intense and coherent {gamma} beam, we intend to use a seeded FEL scheme. Important for the production of such a {gamma} beam are novel refractive {gamma}-lenses for focusing and an efficient monochromator, allowing to generate a very intense and coherent seed beam. The energy of the {gamma} beam is 478 keV, corresponding to a wavelength in the sub-Angstrom regime (1/38 A). To realize a coherent {gamma} beam at 478 keV, it is necessary to use a quantum FEL design. At such high radiation energies a classical description of the {gamma}-FEL becomes wrong.

  5. Compact, maintainable 80-KeV neutral beam module

    DOEpatents

    Fink, Joel H.; Molvik, Arthur W.

    1980-01-01

    A compact, maintainable 80-keV arc chamber, extractor module for a neutral beam system immersed in a vacuum of <10.sup.-2 Torr, incorporating a nested 60-keV gradient shield located midway between the high voltage ion source and surrounding grounded frame. The shield reduces breakdown or arcing path length without increasing the voltage gradient, tends to keep electric fields normal to conducting surfaces rather than skewed and reduces the peak electric field around irregularities on the 80-keV electrodes. The arc chamber or ion source is mounted separately from the extractor or ion accelerator to reduce misalignment of the accelerator and to permit separate maintenance to be performed on these systems. The separate mounting of the ion source provides for maintaining same without removing the ion accelerator.

  6. The effect of 1 to 5 keV electrons on the reproductive integrity of microorganisms

    NASA Technical Reports Server (NTRS)

    Barengoltz, J. B.; Brady, J.

    1977-01-01

    Microorganisms were exposed to simulated space environment in order to assess the effect of electrons in the energy range 1 to 5 keV on their colony-forming ability. The test system consisted of an electron gun and power supply, a dosimetry subsystem, and a vacuum subsystem. The system was capable of current densities ranging from 0.1 nA/sq cm to 5 micro A/sq cm on a 25 sq on target and an ultimate vacuum of 0.0006 N/sq m (0.000004 torr). The results of the experimental program show a significant reduction in microbial reproductive integrity.

  7. New Observations of Soft X-ray (0.5-5 keV) Solar Spectra

    NASA Astrophysics Data System (ADS)

    Caspi, A.; Woods, T. N.; Mason, J. P.; Jones, A. R.; Warren, H. P.

    2013-12-01

    The solar corona is the brightest source of X-rays in the solar system, and the X-ray emission is highly variable on many time scales. However, the actual solar soft X-ray (SXR) (0.5-5 keV) spectrum is not well known, particularly during solar quiet periods, as, with few exceptions, this energy range has not been systematically studied in many years. Previous observations include high-resolution but very narrow-band spectra from crystal spectrometers (e.g., Yohkoh/BCS), or integrated broadband irradiances from photometers (e.g., GOES/XRS, TIMED/XPS, etc.) that lack detailed spectral information. In recent years, broadband measurements with moderate energy resolution (~0.5-0.7 keV FWHM) were made by SphinX on CORONAS-Photon and SAX on MESSENGER, although they did not extend to energies below ~1 keV. We present observations of solar SXR emission obtained using new instrumentation flown on recent SDO/EVE calibration rocket underflights. The photon-counting spectrometer, a commercial Amptek X123 with a silicon drift detector and an 8 μm Be window, measures the solar disk-integrated SXR emission from ~0.5 to >10 keV with ~0.15 keV FWHM resolution and 1 s cadence. A novel imager, a pinhole X-ray camera using a cooled frame-transfer CCD (15 μm pixel pitch), Ti/Al/C filter, and 5000 line/mm Au transmission grating, images the full Sun in multiple spectral orders from ~0.1 to ~5 nm with ~10 arcsec/pixel and ~0.01 nm/pixel spatial and spectral detector scales, respectively, and 10 s cadence. These instruments are prototypes for future CubeSat missions currently being developed. We present new results of solar observations on 04 October 2013 (NASA sounding rocket 36.290). We compare with previous results from 23 June 2012 (NASA sounding rocket 36.286), during which solar activity was low and no signal was observed above ~4 keV. We compare our spectral and imaging measurements with spectra and broadband irradiances from other instruments, including SDO/EVE, GOES/XRS, TIMED

  8. Observations of solar flare photon energy spectra from 20 keV to 7 MeV

    NASA Technical Reports Server (NTRS)

    Yoshimori, M.; Watanabe, H.; Nitta, N.

    1985-01-01

    Solar flare photon energy spectra in the 20 keV to 7 MeV range are derived from the Apr. 1, Apr. 4, apr. 27 and May 13, 1981 flares. The flares were observed with a hard X-ray and a gamma-ray spectrometers on board the Hinotori satellite. The results show that the spectral shape varies from flare to flare and the spectra harden in energies above about 400 keV. Effects of nuclear line emission on the continuum and of higher energy electron bremsstrahlung are considered to explain the spectral hardening.

  9. Cross section for induced L X-ray emission by protons of energy <400 keV

    NASA Astrophysics Data System (ADS)

    Mohan, Harsh; Jain, Arvind Kumar; Kaur, Mandeep; Singh, Parjit S.; Sharma, Sunita

    2014-08-01

    In performing ion beam analysis, cross section for induced L X-ray emission plays a crucial role. There are different approaches by which these can be found experimentally or can be calculated theoretically based on various models. L X-ray production cross sections for Bi with protons in the energy range 260-400 keV at the interval of 20 keV are measured. These are compared with calculations obtained on the basis of current prevailing theories ECPSSR and ECPSSR-UA. Their importance in understanding this phenomenon and existing arguments in this regard will be highlighted.

  10. KevJumba and the Adolescence of YouTube

    ERIC Educational Resources Information Center

    Saul, Roger

    2010-01-01

    This article considers the significance of YouTube as a pedagogical space from which young people can play participatory roles as theorists in their own constructions as popular cultural subjects. Drawing upon the public profile of "KevJumba," a teenager who makes videos of himself on YouTube, the article suggests that representational practices…

  11. Effective field theory and keV lines from dark matter

    SciTech Connect

    Krall, Rebecca; Reece, Matthew; Roxlo, Thomas E-mail: mreece@physics.harvard.edu

    2014-09-01

    We survey operators that can lead to a keV photon line from dark matter decay or annihilation. We are motivated in part by recent claims of an unexplained 3.5 keV line in galaxy clusters and in Andromeda, but our results could apply to any hypothetical line observed in this energy range. We find that given the amount of flux that is observable, explanations in terms of decay are more plausible than annihilation, at least if the annihilation is directly to Standard Model states rather than intermediate particles. The decay case can be explained by a scalar or pseudoscalar field coupling to photons suppressed by a scale not far below the reduced Planck mass, which can be taken as a tantalizing hint of high-scale physics. The scalar case is particularly interesting from the effective field theory viewpoint, and we discuss it at some length. Because of a quartically divergent mass correction, naturalness strongly suggests the theory should be cut off at or below the 1000 TeV scale. The most plausible such natural UV completion would involve supersymmetry. These bottom-up arguments reproduce expectations from top-down considerations of the physics of moduli. A keV line could also arise from the decay of a sterile neutrino, in which case a renormalizable UV completion exists and no direct inference about high-scale physics is possible.

  12. A study of 2-20 KeV X-rays from the Cygnus region

    NASA Technical Reports Server (NTRS)

    Bleach, R. D.

    1972-01-01

    Two rocket-borne proportional counters, each with 650 sq c, met area and 1.8 x 7.1 deg FWHM rectangular mechanical collimation, surveyed the Cygnus region in the 2 to 20 keV energy range on two occasions. X-ray spectral data gathered on 21 September 1970 from discrete sources in Cygnus are presented. The data from Cyg X-1, Cyg X-2, and Cyg X-3 have sufficient statistical significance to indicate mutually exclusive spectral forms for the three. Upper limits are presented for X-ray intensities above 2 keV for Cyg X-4 and Cyg X-5 (Cygnus loop). A search was made on 9 August 1971 for a diffuse component of X-rays 1.5 keV associated with an interarm region of the galaxy at galactic longitudes in the vicinity of 60 degrees. A statistically significant excess associated with a narrow disk component was detected. Several possible emission models are discussed, with the most likely candidate being a population of unresolvable low luminosity discrete sources.

  13. Low-energy x-ray dosimetry studies (6 to 16 keV) at SSRL beamline 1-5

    NASA Astrophysics Data System (ADS)

    Ipe, N. E.; Chatterji, S.; Fassò, A.; Kase, K. R.; Seefred, R.; Olko, P.; Bilski, P.; Soares, C.

    1997-07-01

    Synchrotron radiation facilities provide a unique opportunity for low-energy x-ray dosimetry studies because of the availability of monochromatic x-ray beams. Results of such studies performed at the Stanford Synchrotron Radiation Laboratory (SSRL) are described. Polish lithium fluoride thermoluminescent dosemeters (TLDs), MTS-N(LiF:Mg, Ti- 0.4 mm thick), MCP-N (LiF:Mg, Cu, P - 0.4 mm thick) were exposed free in air to monochromatic x-rays (6-16 keV). These exposures were monitored with an SSRL ionization chamber. The responses (counts/Gy) of MTS-N and MCP-N were generally found to increase with increasing energy. The response at 16 keV is about 3 and 4 times higher than the response at 6 keV for MTS-N and MCP-N, respectively. Irradiation at 6 keV indicates a fairly linear dose response for both type of TLDs over a dose range of 0.01 to 0.4 Gy. In addition there appears to be no significant difference in responses between irradiating the TLDs from the front and the back sides. The energy response of the PTW ionization chamber type 23342 relative to the SSRL ionization chamber is within ±4.5% between 6 and 16 keV. Both the TLDs and the PTW ionization chamber can also be used for beam dosimetry.

  14. Sub-arcsecond X-ray Telescope for Imaging the Solar Corona at 1 keV

    NASA Astrophysics Data System (ADS)

    Gallagher, D.; Cash, W.; Jelsma, S.

    1996-05-01

    Over the past several years at the University of Colorado we have been developing an X-ray telescope that uses a new technique for focusing X-rays with grazing incidence optics The telescope uses spherical optics for all its components, thus utilizing the high quality surfaces obtainable when polishing spherical optics as compared to that of aspherical optics. A prototype engineering X-ray telescope has been fabricated and tested using the 300 meter vacuum pipe at White Sands Missile Range, NM. The telescope uses approximately 2 degree graze angles with tungsten coatings which gives a bandpass of 0.25-1.5 keV and a peak effective area of 0.08 cm(2) at 0.83 keV. Results from X-ray testing at energies of 0.25 keV and 0.93 keV (C-K and Cu-L) will be presented which verify 0.5 arcseconds performance at 0.93 keV. Results from modeling the X-ray telescope's response to the sun show that the current optics design would be capable of recording on the order of 10 images of a solar active region during a 300 second NASA sounding rocket flight at resolution of 0.5 arcsecond.

  15. DWBA analysis of {sup 12}C(d,p){sup 13}C cross section data below 300 keV deuteron energy

    SciTech Connect

    Naqvi, A.A.; Ayer, Z.; Ludwig, E. ||

    1994-12-31

    {sup 12}C(d,p){sup 13}T differential cross section data at 200, 220, 250, 280 and 300 keV deuteron energies has been analyzed using finite range DWBA codes PTOLEMY and TWOFNR. It was observed that shape and magnitude of the cross section data at 300, 280 keV energies can be fitted well but the shape of 250, 220 and 200 keV data cannot be fitted. However 250, 220 and 200 keV data shape can be fitted by changing the optical model parameters at each energy. This indicates a very strong energy dependence of the optical model parameters data of the entrance channel over such a small energy range which is not observed in the presently available elastic scattering data of the entrance channel.

  16. Rise time in 20-32 keV impulsive X-radiation

    NASA Technical Reports Server (NTRS)

    Vorpahl, J. A.; Takakura, T.

    1974-01-01

    A new property of the X-ray impulsive component observed in solar flares is discussed, giving attention to the relation between the slope of the electron power spectrum and the rise time in the 20-32 keV X-ray spike. This particular energy range was chosen because it offered the greatest number of impulsive events while being sufficiently high to avoid contamination by soft X radiation. It is found for the thin-target model that the electron spectrum tends to be softer when the acceleration rate is smaller.

  17. Photon, Electron and Secondary Ion Emission from Single C60 keV Impacts

    PubMed Central

    Fernandez-Lima, F. A.; Eller, M. J.; Verkhoturov, S. V.; Della-Negra, S.; Schweikert, E. A.

    2010-01-01

    This paper presents the first observation of coincidental emission of photons, electrons and secondary ions from individual C60 keV impacts. An increase in photon, electron and secondary ion yields is observed as a function of C60 projectile energy. The effect of target structure/composition on photon and electron emissions at the nanometer level is shown for a CsI target. The time-resolved photon emission may be characterized by a fast component emission in the UV-Vis range with a short decay time, while the electron and secondary ion emission follow a Poisson distribution. PMID:21218166

  18. 40-keV electron durable trapping electron

    SciTech Connect

    Feynman, J.; Hardy, D.A.; Mullen, E.G.

    1984-03-01

    The positron and extent of the region in which electrons with energies less than 40-keV are durably trapped in the nightside magnetosphere is found for both normal and disturbed geomagnetic conditions by using data from the P78-2 (SCATHA) satellite. The region of the magnetosphere from 5.3 to 7.9 R/sub E/ was studied. In this region neither solar-magnetic nor geocentric-solar magnetospheric coordinates order the data satisfactorily. A new coordinate systems called composite coordinates is introduced. It takes account of the fact that this region of the magnetosphere is strongly influenced by both the earth's ddipole field and the direction of the solar wind. In composite coordinates when Kp< or =4+, 40-keV electron fluxes were almost continuously present in a region centered on the equatorial palne and 1.2 R/sub E/ in half width. At larger composite coordinate latitudes there is another region more than 1 R/sub E/ thick within which 40-keV electron fluxes routinely appear and disappear on time scales of one hour as the trapping boundary actively moves over the satellite. We have no evidence that SCATHA over entered the tail lobes where no particles are trapped. When Kp> or =6- the region in which 40-keV electron fluxes were always present moved earthward and/or thinned but remained ordered in composite coordinates. We suggest that the new coordinate system will be useful for ordering other data sets taken in this region of the magnetosphere.

  19. A neutron spectrometer for neutron energies between 1 eV and 10 keV

    SciTech Connect

    Wang, C.K.; Blue, T.E.

    1988-01-01

    In boron neutron capture therapy (BNCT), it is the consensus that epithermal neutron beams have advantages over thermal beams in treating deep-seated brain tumors, and large neutron fields have advantages over narrow beams, since whole-brain irradiations are thought to be necessary in many cases. Epithermal neutron sources for BNCT, which include filtered reactor neutron beams and moderated reactor neutron fields, are currently being developed at many institutions around the world. Neutrons with energies between 1 eV and 10 keV are most suitable for treating brain tumors. However, techniques for measuring neutron spectra in a vacuum in this energy range are not well developed. This paper describes a new type of neutron spectrometer that has a set of response functions that peak at equally spaced intervals on a logarithmic energy scale ranging from 1 eV to 10 keV; therefore, neutron spectra (or histograms) in this energy range can be obtained by properly applying spectrum unfolding techniques to the measured data. The spectrometer is applicable for measurements in a vacuum for both narrow neutron beams and wide neutron fields.

  20. Attenuation of photons at 3 to 14 keV energies in helium

    SciTech Connect

    Azuma, Y.; Berry, H.G.; Gemmell, D.S.

    1995-08-01

    Using X-ray photons at the X24A, X23B and X23A2 beam lines at NSLS, we measured the total photo-attenuation cross section of helium for photons in the energy range of 3 to 14 keV. In this range the photoionization cross section decreases rapidly with energy, so that Compton scattering is significant at 4 keV and dominates at the highest energies. The apparatus consisted of a 1.4-m long helium-absorption tube, 5 cm in diameter, with 75-{mu} thick, 7-mm diameter, kapton end windows. The tube could be filled with helium up to a pressure of 10{sup 6} Pa. We attained a precision of 1-2% in the attenuation cross section. The measurements verify the dominance of Compton scattering in this energy range and its importance in recent measurements of the ratio of double-to-single photoionization of helium. The measured cross sections are close to the combined calculated cross sections for Compton scattering and photoionization, and we are able to distinguish the contributions of the two effects.

  1. The Hard X-ray 20-40 keV AGN Luminosity Function

    NASA Technical Reports Server (NTRS)

    Beckmann, V.; Soldi, S.; Shrader, C. R.; Gehrels, N.; Produit, N.

    2006-01-01

    We have compiled a complete, significance limited extragalactic sample based on approximately 25,000 deg(sup 2) to a limiting flux of 3 x 10(exp -11) ergs per square centimeter per second. (approximately 7,000 deg(sup 2)) to a flux limit of 10(exp -11) ergs per square centimeter per second)) in the 20 - 40 keV band with INTEGRAL. We have constructed a detailed exposure map to compensate for effects of non-uniform exposure. The flux-number relation is best described by a power-law with a slope of alpha = 1.66 plus or minus 0.11. The integration of the cumulative flux per unit area leads to f(sub 20-40 keV) = 2.6 x 10(exp -10) ergs per square centimeter per second per sr(sup -1) which is about 1% of the known 20-40 keV X-ray background. We present the first luminosity function of AGN in the 20-40 keV energy range, based on 68 extragalactic objects detected by the imager IBIS/ISGRI on-board INTEGRAL. The luminosity function shows a smoothly connected two power-law form, with an index of gamma (sub 1) = 0.9 below, and gamma (sub 2) = 2.2 above the turn-over luminosity of L(sub *), = 4.6 x 10(sup 43) ergs per second. The emissivity of all INTEGRAL AGNs per unit volume is W(sub 20-40keV)(greater than 10(sup 41) ergs per second) = 2.8 x 10(sup 38) ergs per second h(sup 3)(sub 70) Mpc(sup -3). These results are consistent with those derived in the 2-20keV energy band and do not show a significant contribution by Compton-thick objects. Because the sample used in this study is truly local (z(raised bar) = 0.022)), only limited conclusions can be drawn for the evolution of AGNs in this energy band. But the objects explaining the peak in the cosmic X-ray background are likely to be either low luminosity AGN (L(sub x) less than 10(sup 41) ergs per second) or of other type, such as intermediate mass black holes, clusters, and star forming regions.

  2. Observational consistency and future predictions for a 3.5 keV ALP to photon line

    SciTech Connect

    Alvarez, Pedro D.; Conlon, Joseph P.; Day, Francesca V.; Marsh, M.C. David; Rummel, Markus

    2015-04-09

    Motivated by the possibility of explaining the 3.5 keV line through dark matter decaying to axion-like particles that subsequently convert to photons, we study ALP-photon conversion for sightlines passing within 50 pc of the galactic centre. Conversion depends on the galactic centre magnetic field which is highly uncertain. For fields at low or mid-range of observational estimates (10–100 μG), no observable signal is possible. For fields at the high range of observational estimates (a pervasive poloidal mG field over the central 150 pc) it is possible to generate sufficient signal to explain recent observations of a 3.5 keV line in the galactic centre. In this scenario, the galactic centre line signal comes predominantly from the region with z>20pc, reconciling the results from the Chandra and XMM-Newton X-ray telescopes. The dark matter to ALP to photon scenario also naturally predicts the non-observation of the 3.5 keV line in stacked galaxy spectra. We further explore predictions for the line flux in galaxies and suggest a set of galaxies that is optimised for observing the 3.5 keV line in this model.

  3. Charge state distributions and charge exchange cross sections of carbon in helium at 30-258 keV

    NASA Astrophysics Data System (ADS)

    Maxeiner, Sascha; Seiler, Martin; Suter, Martin; Synal, Hans-Arno

    2015-10-01

    With the introduction of helium stripping in radiocarbon (14C) accelerator mass spectrometry (AMS), higher +1 charge state yields in the 200 keV region and fewer beam losses are observed compared to nitrogen or argon stripping. To investigate the feasibility of even lower beam energies for 14C analyses the stripping characteristics of carbon in helium need to be further studied. Using two different AMS systems at ETH Zurich (myCADAS and MICADAS), ion beam transmissions of carbon ions for the charge states -1, +1, +2 and +3 were measured in the range of 258 keV down to 30 keV. The correction for beam losses and the extraction of charge state yields and charge exchange cross sections will be presented. An increase in population of the +1 charge state towards the lowest measured energies up to 75% was found as well as agreement with previous data from literature. The findings suggest that more compact radiocarbon AMS systems are possible and could provide even higher efficiency than current systems operating in the 200 keV range.

  4. Relative dissociation fractions of SF6 under impact of 15-keV to 30-keV H- and C- negative ions

    NASA Astrophysics Data System (ADS)

    Zhao, Zilong; Li, Junqin; Zhang, Xuemei

    2013-10-01

    The relative dissociation fractions for the production of fragment ions and ion pairs of SF6 are studied for H- and C- impact in the energy range from 15 to 30 keV. Recoil ions (SF4+, SF3+, SF2+, SF+, S+, F+, SF42+, SF22+) and ion pairs (SF3++F+,SF2++F+,SF++F+,S++F+, F++F+) are detected and identified in coincidence with scattered projectiles in two charge states (q=0 and q=+1) by using a time-of-flight spectrometer. The relative dissociation fractions are energy dependent for both single-electron-loss (SL) channel and double-electron-loss (DL) channel processes for certain negative ions. It is also found that the relative dissociation fractions for DL are larger than those for SL. In addition, the degree of fragmentation will become greater with a larger mass number of the projectiles at the same impact energy for the same electron-loss channel. A comparison of the time-of-flight spectra is made between that under negative-ion impact and that under electron impact, and it is found that the probability of production of SFn+ ions with n odd is higher than that of similar ions with n even, and the probability of production of SFn2+ ions with n even is higher than that of similar ions withn odd under H-, C-, positive-ion, and electron impact. We analyze this interesting phenomenon from the bond-dissociation energies of SFn+ and SFn2+. We also analyze the coincident time-of-flight spectra of two fragment ions resulting from double ionization of SF6 by H- and C- impact and describe the major dissociation pathways of SF62+ for H- and C- impact in the energy range from 15 to 30 keV.

  5. Extreme energetic electron fluxes in low Earth orbit: Analysis of POES E > 30, E > 100, and E > 300 keV electrons

    NASA Astrophysics Data System (ADS)

    Meredith, Nigel P.; Horne, Richard B.; Isles, John D.; Green, Janet C.

    2016-02-01

    Energetic electrons are an important space weather hazard. Electrons with energies less than about 100 keV cause surface charging, while higher-energy electrons can penetrate materials and cause internal charging. In this study we conduct an extreme value analysis of the maximum 3-hourly flux of E > 30 keV, E > 100 keV, and E > 300 keV electrons in low Earth orbit as a function of L∗, for geomagnetic field lines that map to the outer radiation belt, using data from the National Oceanic and Atmospheric Administration Polar Operational Environmental Satellites (POES) from July 1998 to June 2014. The 1 in 10 year flux of E > 30 keV electrons shows a general increasing trend with distance ranging from 1.8 × 107 cm-2 s-1 sr-1 at L∗=3.0 to 6.6 × 107 cm-2 s-1 sr-1 at L∗=8.0. The 1 in 10 year flux of E > 100 keV electrons peaks at L∗=4.5-5.0 at 1.9 × 107 cm-2 s-1 sr-1 decreasing to minima of 7.1 × 106 and 8.7 × 106 cm-2 s-1 sr-1 at L∗=3.0 and 8.0, respectively. In contrast to the E > 30 keV electrons, the 1 in 10 year flux of E > 300 keV electrons shows a general decreasing trend with distance, ranging from 2.4 × 106 cm-2 s-1 sr-1 at L∗=3.0 to 1.2 × 105 cm-2 s-1 sr-1 at L∗=8.0. Our analysis suggests that there is a limit to the E > 30 keV electrons with an upper bound in the range 5.1 × 107 to 8.8 × 107 cm-2 s-1 sr-1. However, the results suggest that there is no upper bound for the E > 100 keV and E > 300 keV electrons.

  6. Simulations of Microchannel Plate Sensitivity to <20 keV X-rays as a Function of Energy and Incident Angle

    SciTech Connect

    Kruschwitz, Craig; Wu, M.; Rochau, G. A.

    2013-06-13

    We present results of Monte Carlo simulations of microchannel plate (MCP) response to x-rays in the 250 eV to 20 keV energy range as a function of both x-ray energy and impact angle. The model is based on the model presented in Rochau et al. (2006). However, while the Rochau et al. (2006) model was two-dimensional, and their results only went to 5 keV, our results have been expanded to 20 keV, and our model has been incorporated into a three-dimensional Monte Carlo MCP model that we have developed over the past several years (Kruschwitz et al. 2011). X-ray penetration through multiple MCP pore walls is increasingly important above 5 keV. The effect of x-ray penetration through multiple pores on MCP performance was studied and is presented.

  7. Suppression of repetitive surface exfoliation of Inconel 625 implanted sequentially with helium ions of different energies (20 100 keV)

    NASA Astrophysics Data System (ADS)

    Rao, A. S.; Whitton, J. L.; Kaminsky, M.

    Studies were conducted to explore if the surface exfoliation of Inconel 625, typical for 100 keV 4He + irradiations can be reduced by pre-irradiating the surfaces with helium ions sequentially over the energy range 20 to 50 keV. Polished, polycrystalline Inconel 625 samples were irradiated at 298K and 573K with 4He + at six different energies in the range from 20 to 50 keV in an order of decreasing energies. For each energy the dose was 0.13 C/cm 2, resulting in a total dose of 0.89 C/cm 2. Subsequently, these samples were implanted with 100 keV 4He + to a dose of 1.0 C/cm 2 or 2.0 C/cm 2. The results reveal that the low energy 4He + implants prior to the 100 keV 4He + implant reduce significantly the erosion yield typical for 100-keV 4He + irradiations alone. For 573K these reduced yields are still about one order of magnitude greater than physical sputtering yields.

  8. The Context for IMAP: Voyager and INCA Observations of the Heliosheath at E > 5 keV

    NASA Astrophysics Data System (ADS)

    Krimigis, Stamatios M.

    2016-04-01

    The basic premise of the proposed Interstellar Mapping and Acceleration Probe (IMAP) is detailed scientific understanding of the Heliosheath (HS) and beyond, a region of space explored in situ by Voyager 1 (V1) since 2004, Voyager 2 (V2) since 2007, and remotely via energetic neutral atoms (ENA) by the Cassini/INCA (Ion and Neutral CAmera) since 2003 and IBEX since 2009. The IMAP instrumentation proposed for this purpose combines and extends the IBEX and INCA ENA energy ranges (0.3- 20 keV and 3-200 keV, for low and high energy, respectively). All three missions-Voyagers, Cassini/INCA, and IBEX- have made discovery-class measurements in the HS, the Voyagers providing in situ ion intensities at E > 30 keV, while INCA images ENA in the range 5 < E < 55 keV, and IBEX 0.3 < E < 6 keV. The partial overlap in energy coverage between Voyager ions and INCA ENA allows for the possibility of observing the intensity and time evolution of ions in the HS, thought to give rise to the ENAs via charge-exchange, and the resultant ENA images in the inner heliosphere and their spatial and/or temporal variability. Unfortunately, no such "ground truth" ion measurements are possible at Voyager in the ENA energy range imaged by IBEX. Some of the key findings from the Voyager and Cassini/INCA measurements are as follows: (1) The HS contains a hot plasma population that carries a substantial part (30-50 %) of the total pressure at E > 5 keV, the rest residing below that range, resulting in a beta (particle/magnetic pressure) always > 1, typically >10. (2) The width of the HS in the direction of V1 is ~ 30 AU, but is thought to be larger (40-70 AU) in the southern ecliptic where V2 currently travels.. (3) The ENA intensities at E > 5 keV exhibit a correlation with the solar cycle (SC) over the period 2003 to 2015, with minimum intensities in the anti-nose direction observed ~ 1.5 yrs after solar minimum followed by a recovery thereafter. (4) The in situ ion measurements at V2 within the HS

  9. Model-independent analysis of dark matter points to a particle mass at the keV scale

    NASA Astrophysics Data System (ADS)

    de Vega, H. J.; Sanchez, N. G.

    2010-05-01

    We present a model-independent analysis of dark matter (DM) decoupling both ultrarelativistically (UR) and non-relativistically (NR) based on the DM phase-space density . We derive explicit formulae for the DM particle mass m and for the number of ultrarelativistic degrees of freedom gd at decoupling. We find that for DM particles decoupling UR both at local thermal equilibrium (LTE) and out of LTE, m turns out to be in the keV scale. For example, for DM Majorana fermions decoupling at LTE the resulting mass is m ~= 0.85 keV. For DM particles decoupling NR, results in the keV scale (Td is the decoupling temperature) and the value of m is consistent with the keV scale. In all cases, DM turns out to be cold DM (CDM). In addition, lower and upper bounds on the DM annihilation cross-section for NR decoupling are derived. We evaluate the free-streaming (Jeans) wavelength and Jeans mass: they are independent of the type of DM except for the DM self-gravity dynamics. The free-streaming wavelength today turns to be in the kpc range. These results are based on our theoretical analysis, on astronomical observations of dwarf spheroidal satellite galaxies in the Milky Way and on N-body numerical simulations. We analyse and discuss the results for from analytic approximate formulae for both linear fluctuations and the (non-linear) spherical model and from N-body simulations results. In this way we obtain upper bounds for the DM particle mass, which are all below the 100-keV range.

  10. Astrophysics and cosmology confront the 17-keV neutrino

    NASA Technical Reports Server (NTRS)

    Kolb, Edward W.; Turner, Michael S.

    1991-01-01

    A host of astrophysical and cosmological arguments severely constrain the properties of a 17 keV Dirac neutrino. Such a neutrino must have interactions beyond those of the standard electroweak theory to reduce its cosmic abundance (through decay or annihilation) by a factor of two hundred. A predicament arises because the additional helicity states of the neutrino necessary to construct a Dirac mass must have interactions strong enough to evade the astrophysical bound from SN 1987A, but weak enough to avoid violating the bound from primordial nucleosynthesis.

  11. Astrophysics and cosmology confront the 17 keV neutrino

    NASA Technical Reports Server (NTRS)

    Kolb, Edward W.; Turner, Michael S.

    1991-01-01

    A host of astrophysical and cosmological arguments severely constrain the properties of a 17 keV Dirac neutrino. Such a neutrino must have interactions beyond those of the standard electroweak theory to reduce its cosmic abundance (through decay or annihilation) by a factor of two hundred. A predicament arises because the additional helicity states of the neutrino necessary to construct a Dirac mass must have interactions strong enough to evade the astrophysical bound from SN 1987A, but weak enough to avoid violating the bound from primordial nucleosynthesis.

  12. Gel behavior of keV ion irradiated polystyrene

    SciTech Connect

    Calcagno, L.; Foti, G.; Licciardello, A.; Puglisi, O.

    1988-10-17

    Among the chemical and physical modifications induced by ion bombardment of polymers, the solubility changes are very important because of technological application for lithography in microelectronic devices. Solubility changes due to the occurrence of crosslinkings have been followed on monodisperse and polydisperse polystyrene after ion irradiations (10/sup 11/--10/sup 14/ ions/cm/sup 2/, keV energy). By using the Inokuty gel theory (M. Inokuti J. Appl. Phys. 38, 2999 (1963)), the chemical yield (crosslinking/eV) has been determined for different molecular weights and molecular weight distributions.

  13. 511 keV photons from superconducting cosmic strings.

    PubMed

    Ferrer, Francesc; Vachaspati, Tanmay

    2005-12-31

    We show that a tangle of light superconducting strings in the Milky Way could be the source of the observed 511 keV emission from electron-positron annihilation in the Galactic bulge. The scenario predicts a flux that is in agreement with observations if the strings are at the approximately 1 TeV scale, making the particle physics within reach of planned accelerator experiments. The emission is directly proportional to the galactic magnetic field, and future observations should be able to differentiate the superconducting string scenario from other proposals. PMID:16486335

  14. Neutron total cross section measurements in the energy region from 47 keV to 20 MeV

    SciTech Connect

    Poenitz, W.P.; Whalen, J.F.

    1983-05-01

    Neutron total cross sections were measured for 26 elements. Data were obtained in the energy range from 47 keV to 20 MeV for 11 elements in the range of light-mass fission products. Previously reported measurements for eight heavy and actinide isotopes were extended to 20 MeV. Data were also obtained for Cu (47 keV to 1.4 MeV) and for Sc, Zn, Nd, Hf, and Pt (1.8 to 20 MeV). The present work is part of a continuing effort to provide accurate neutron total cross sections for evaluations and for optical-model parameteriztions. The latter are required for the derivation of other nuclear-data information of importance to applied programs. 37 references.

  15. Evolution of nanodot morphology on polycarbonate (PC) surfaces by 40 keV Ar+

    NASA Astrophysics Data System (ADS)

    Goyal, Meetika; Chawla, Mahak; Gupta, Divya; Shekhawat, Nidhi; Sharma, Annu; Aggarwal, Sanjeev

    2016-05-01

    In the present paper we have discussed the effect of 40 keV Ar+ ions irradiation on nanoscale surface morphology of Polycarbonate (PC) substrate. Specimens were sputtered at off normal incidences of 30°, 40° and 50° with the fluence of 1 × 1016 Ar+cm-2. The topographical behaviour of specimens was studied by using Atomic Force Microscopy (AFM) technique. AFM study demonstrates the evolution of nano dot morphology on PC specimens on irradiating with 1 × 1016 Ar+cm-2. Average size of dots varied from 37-95 nm in this specified range of incidence while density of dots varied from 0.17-3.0 × 107 dotscm-2. Such variations in morphological features have been supported by estimation of ion range and sputtering yield through SRIM simulations.

  16. The Electron Excitation Function of H Lyman-(alpha) from Threshold to 1.8 keV

    NASA Technical Reports Server (NTRS)

    James, G. K.; Slevin, J. A.; Shemansky, D. E.; McConkey, J. W.; Dziczek, D.; Kanik, I.; Ajello, J. M.

    1996-01-01

    The excitation function of prompt Lyman-(alpha) radiation, produced by electron impact excitation of atomic hydrogen, has been measured for the first time over an extended energy range from threshold to 1.8 keV. Measurments were obtained in a crossed-beams experiment using both magnetically confined and electrostatically focused electrons in collision with atomic hydrogen produced by an intense discharge source.

  17. A New Observation of the Quiet Sun Soft X-ray (0.5-5 keV) Spectrum

    NASA Astrophysics Data System (ADS)

    Caspi, A.; Woods, T. N.; Stone, J.

    2012-12-01

    The solar corona is the brightest source of X-rays in the solar system, and the X-ray emission is highly variable with solar activity. While this is particularly true during solar flares, when emission can be enhanced by many orders of magnitude up to gamma-ray energies, even the so-called "quiet Sun" is bright in soft X-rays (SXRs), as the ~1-2 MK ambient plasma of the corona emits significant thermal bremsstrahlung up to ~5 keV. However, the actual solar SXR (0.5-5 keV) spectrum is not well known, particularly during quiet periods, as, with few exceptions, this energy range has not been systematically studied in many years. Previous observations include ultra-high-resolution but very narrow-band spectra from crystral spectrometers (e.g. Yohkoh/BCS), or integrated broadband irradiances from photometers (e.g. GOES/XRS, TIMED/XPS, etc.) that lack detailed spectral information. In recent years, broadband measurements with fair energy resolution (~0.5-0.7 keV FWHM) were made by SphinX on CORONAS-Photon and XRS on MESSENGER, although they did not extend below ~1 keV. We present observations of the quiet Sun SXR emission obtained using a new SXR spectrometer flown on the third SDO/EVE underflight calibration rocket (NASA 36.286). The commercial off-the-shelf Amptek X123 silicon drift detector, with an 8-micron Be window and custom aperture, measured the solar SXR emission from ~0.5 to >10 keV with ~0.15 keV FWHM resolution (though, due to hardware limitations, with only ~0.12 keV binning) and 2-sec cadence over ~5 minutes on 23 June 2012. Despite the rising solar cycle, activity on 23 June 2012 was abnormally low, with no visible active regions and GOES XRS emission near 2010 levels; we measured no solar counts above ~4 keV during the observation period. We compare our X123 measurements with spectra and broadband irradiances from other instruments, including the SphinX observations during the deep solar minimum of 2009, and with upper limits of >3 keV quiet Sun emission

  18. Contribution of the 6.7 keV Emission line from Stellar Flares to the Galactic Ridge X-ray Emission

    NASA Astrophysics Data System (ADS)

    Nwachukwu Eze, Romanus; Eze, Ambrose; Nwafor, Jude; Esaenwi, Sudum; Okeke, Pius; Ebisawa, Ken; Smith, Randall

    2015-08-01

    Stellar flares create sudden bursts of hot plasma that contain a wide range of temperatures, and are capable of generating 6.7 keV Fe XXV emission line via electronic collisional excitation. Using the measured 6.7 keV fluxes from a collection of Suzaku-observed stellar flares as a baseline, we estimate their contribution to the 6.7 keV emission line from the Galactic Ridge X-ray emission (GRXE). We modeled the extracted stellar flares’ spectra from our sources with an absorbed Bremstrahlung. We found strong 6.7 keV emission line from the extracted stellar flares’ spectra which is similar to the observed 6.7 keV emission line from the GRXE, while the 6.4 and 7.0 keV lines appear to be faint. The present result supports the earlier result that stellar flares contribute significantly to the total luminosity of the GRXE and that the GRXE luminosity could be primarily explained via hard X-ray emitting symbiotic stars (hSSs), and magnetic cataclysmic variables (mCVs), along with other white dwarf binary systems and stellar flares.

  19. 7.1 keV sterile neutrino constraints from X-ray observations of 33 clusters of galaxies with Chandra ACIS

    NASA Astrophysics Data System (ADS)

    Hofmann, F.; Sanders, J. S.; Nandra, K.; Clerc, N.; Gaspari, M.

    2016-08-01

    Context. Recently an unidentified emission line at 3.55 keV has been detected in X-ray spectra of clusters of galaxies. The line has been discussed as a possible decay signature of 7.1 keV sterile neutrinos, which have been proposed as a dark matter (DM) candidate. Aims: We aim to put constraints on the proposed line emission in a large sample of Chandra-observed clusters and obtain limits on the mixing angle in a 7.1 keV sterile neutrino DM scenario. Methods: For a sample of 33 high-mass clusters of galaxies, we merge all observations from the Chandra data archive. Each cluster has more than 100 ks of combined exposure. The resulting high signal-to-noise spectra are used to constrain the flux of an unidentified line emission at 3.55 keV in the individual spectra and a merged spectrum of all clusters. Results: We obtained very detailed spectra around the 3.55 keV range and limits on an unidentified emission line. Assuming all DM were made of 7.1 keV sterile neutrinos, the upper limits on the mixing angle are sin2(2Θ) < 10.1×10-11 from ACIS-I and < 40.3×10-11 from ACIS-S data at 99.7 per cent confidence level. Conclusions: We do not find evidence for an unidentified emission line at 3.55 keV. The sample extends the list of objects searched for an emission line at 3.55 keV and will help to identify the best targets for future studies of the potential DM decay line with upcoming X-ray observatories like Hitomi (Astro-H), eROSITA, and Athena.

  20. The repetitive flaking of inconel 625 by 100 keV helium ion bombardment

    NASA Astrophysics Data System (ADS)

    Whitton, J. L.; Chen, Hao Ming; Littmark, U.; Emmoth, B.

    1981-05-01

    Repetitive flaking of Inconel 625 occurs with ion bombardment doses of than 10 18 100 keV helium ions cm -2, with up to 39 exfoliations being observed after bombardment with 3 × 10 19 ions cm -2. The thickness of the flakes, measured by scanning electron microscopy, is some 30% greater than when measured by Rutherford backscattering (RBS) of 1.8 MeV helium ions. These RBS measurements compare well with the thickness of the remaining layers in the resultant craters and to the most probable range of the 100 keV helium. The area of the flakes is dictated by the grain boundaries, and when one flake is ejected, the adjacent grains are prevented from doing so since there now exists an escape route for the injected helium. A strong dose rate dependence is observed; decreasing the beam current from 640 μA cm -2 to 64 μA cm -2 results in a factor 20 fewer flakes being exfoliated (for the same total dose of 3 × 10 19 ions cm -2). Successive flakes decrease in area, suggesting that eventually a cratered, but stable, surface will result with the only erosion being by the much less effective mechanism of sputtering.

  1. Magnetic moment of the 2083 keV level of 140Ce

    NASA Astrophysics Data System (ADS)

    Ohkubo, Y.; Taniguchi, A.; Xu, Q.; Tanigaki, M.; Shimizu, N.; Otsuka, T.

    2013-04-01

    For the magnetic moment of the 2083 keV level of 140Ce, there are four published data, all obtained by applying an external magnetic field of less than 5 T to a liquid sample containing 140La using the time-differential perturbed angular correlation (TDPAC) technique. Although these four values are consistent within two times their uncertainties (2σ), the range of values in 2σ extends from μ=+3.0 to +5.2 (in units of nuclear magneton, μN). This time, the TDPAC technique was successfully applied to the 2083 keV level of 140Ce implanted in an Fe foil. The magnetic moment of this level was determined to be μ=+4.00(20)μN, employing the known hyperfine field at 141Ce in Fe, -41(2) T, which agrees very well with one of the values, μ=+4.06(15)μN. The present value is compared with two shell-model calculations.

  2. Metastable dark matter mechanisms for INTEGRAL 511 keV γ rays and DAMA/CoGeNT events

    NASA Astrophysics Data System (ADS)

    Cline, James M.; Frey, Andrew R.; Chen, Fang

    2011-04-01

    We explore dark matter mechanisms that can simultaneously explain the galactic 511 keV gamma rays observed by INTEGRAL/SPI, the DAMA/LIBRA annual modulation, and the excess of low-recoil dark matter candidates observed by CoGeNT. It requires three nearly degenerate states of dark matter in the 4-7 GeV mass range, with splittings, respectively, of order MeV and a few keV. The top two states have the small mass gap and transitions between them, either exothermic or endothermic, and can account for direct detections. Decays from one of the top states to the ground state produce low-energy positrons in the Galaxy whose associated 511 keV gamma rays are seen by INTEGRAL. This decay can happen spontaneously, if the excited state is metastable (longer lived than the age of the Universe), or it can be triggered by inelastic scattering of the metastable states into the shorter-lived ones. We focus on a simple model where the dark matter is a triplet of an SU(2) hidden sector gauge symmetry, broken at the scale of a few GeV, giving masses of order ≲1GeV to the dark gauge bosons, which mix kinetically with the standard model hypercharge. The purely decaying scenario can give the observed angular dependence of the 511 keV signal with no positron diffusion, while the inelastic scattering mechanism requires transport of the positrons over distances ˜1kpc before annihilating. We note that an x-ray line of several keV in energy, due to single-photon decays involving the top dark matter states, could provide an additional component to the diffuse x-ray background. The model is testable by proposed low-energy fixed-target experiments.

  3. Metastable dark matter mechanisms for INTEGRAL 511 keV {gamma} rays and DAMA/CoGeNT events

    SciTech Connect

    Cline, James M.; Frey, Andrew R.; Chen, Fang

    2011-04-15

    We explore dark matter mechanisms that can simultaneously explain the galactic 511 keV gamma rays observed by INTEGRAL/SPI, the DAMA/LIBRA annual modulation, and the excess of low-recoil dark matter candidates observed by CoGeNT. It requires three nearly degenerate states of dark matter in the 4-7 GeV mass range, with splittings, respectively, of order MeV and a few keV. The top two states have the small mass gap and transitions between them, either exothermic or endothermic, and can account for direct detections. Decays from one of the top states to the ground state produce low-energy positrons in the Galaxy whose associated 511 keV gamma rays are seen by INTEGRAL. This decay can happen spontaneously, if the excited state is metastable (longer lived than the age of the Universe), or it can be triggered by inelastic scattering of the metastable states into the shorter-lived ones. We focus on a simple model where the dark matter is a triplet of an SU(2) hidden sector gauge symmetry, broken at the scale of a few GeV, giving masses of order < or approx. 1 GeV to the dark gauge bosons, which mix kinetically with the standard model hypercharge. The purely decaying scenario can give the observed angular dependence of the 511 keV signal with no positron diffusion, while the inelastic scattering mechanism requires transport of the positrons over distances {approx}1 kpc before annihilating. We note that an x-ray line of several keV in energy, due to single-photon decays involving the top dark matter states, could provide an additional component to the diffuse x-ray background. The model is testable by proposed low-energy fixed-target experiments.

  4. High resolution 17 keV to 75 keV backlighters for High Energy Density experiments

    SciTech Connect

    Park, H; Maddox, B R; Giraldez, E; Hatchett, S P; Hudson, L; Izumi, N; Key, M H; Pape, S L; MacKinnon, A J; MacPhee, A G; Patel, P K; Phillips, T W; Remington, B A; Seely, J F; Tommasini, R; Town, R; Workman, J

    2008-02-25

    We have developed 17 keV to 75 keV 1-dimensional and 2-dimensional high-resolution (< 10 {micro}m) radiography using high-intensity short pulse lasers. High energy K-{alpha} sources are created by fluorescence from hot electrons interacting in the target material after irradiation by lasers with intensity I{sub L} > 10{sup 17} W/cm{sup 2}. We have achieved high resolution point projection 1-dimensional and 2-dimensional radiography using micro-foil and micro-wire targets attached to low-Z substrate materials. The micro-wire size was 10 {micro}m x 10 {micro}m x 300 {micro}m on a 300 {micro}m x 300 {micro}m x 5 {micro}m CH substrate. The radiography performance was demonstrated using the Titan laser at LLNL. We observed that the resolution is dominated by the micro-wire target size and there is very little degradation from the plasma plume, implying that the high energy x-ray photons are generated mostly within the micro-wire volume. We also observe that there are enough K{alpha} photons created with a 300 J, 1-{omega}, 40 ps pulse laser from these small volume targets, and that the signal-to-noise ratio is sufficiently high, for single shot radiography experiments. This unique technique will be used on future high energy density (HED) experiments at the new Omega-EP, ZR and NIF facilities.

  5. Angular differential cross sections for excitation of atomic hydrogen to its N = 2 level by impact of 15-100 keV He/sup +/ ions

    SciTech Connect

    Aldag, J.E.

    1980-01-01

    Differential cross section for excitation of atomic hydrogen to its n = 2 level by 15-100 keV He/sup +/ ions have been determned for c.m. angles from 0 to 8 mrad. The cross sections were obtained from an analysis of the angular distribution of the scattered ions which had lost an energy corresponding to the excitation of the target to its n = 2 level. The shape of the differential cross section changes rapidly with increasing incident energy. At 15 keV, the cross section changes rapidly with increasing incident energy. At 15 keV, the cross section falls off by a factor of 5 in 6 mrad. At 100 keV, the cross section decreases by nearly six orders or magnitude in the same angular range. The middle and high energy results are in good agreement with a recent Glauber approximation calculation for the scattering. Comparison of the present reduced cross section results with those at lower energy (0.75 to 1.5 keV) indicates that the collision mechanism is not the same. Excitation to n greater than or equal to 3 levels was clearly present in the energy-loss spectra for the process in contradiction to the molecular orbital description of the mechanism. Total cross section results are given for the same scattering process in the 15-200 keV range and are also in good agreement with the Glauber and VPSA theory results. The experimental and Glauber differential results, however, are clearly different at 25 keV.

  6. Measurement of high-energy (10–60 keV) x-ray spectral line widths with eV accuracy

    SciTech Connect

    Seely, J. F. Feldman, U.; Glover, J. L.; Hudson, L. T.; Ralchenko, Y.; Henins, Albert; Pereira, N.; Di Stefano, C. A.; Kuranz, C. C.; Drake, R. P.; Chen, Hui; Williams, G. J.; Park, J.

    2014-11-15

    A high resolution crystal spectrometer utilizing a crystal in transmission geometry has been developed and experimentally optimized to measure the widths of emission lines in the 10–60 keV energy range with eV accuracy. The spectrometer achieves high spectral resolution by utilizing crystal planes with small lattice spacings (down to 2d = 0.099 nm), a large crystal bending radius and Rowland circle diameter (965 mm), and an image plate detector with high spatial resolution (60 μm in the case of the Fuji TR image plate). High resolution W L-shell and K-shell laboratory test spectra in the 10–60 keV range and Ho K-shell spectra near 47 keV recorded at the LLNL Titan laser facility are presented. The Ho K-shell spectra are the highest resolution hard x-ray spectra recorded from a solid target irradiated by a high-intensity laser.

  7. Anomalous scattering of keV neutrons from H2O and D2O : I. Single scattering events

    NASA Astrophysics Data System (ADS)

    Chatzidimitriou-Dreismann, C. A.; Krzystyniak, M.

    2006-05-01

    Scattering of neutrons in the 24-150 keV incident energy range from H2O relative to that of D2O and H2O-D2O mixtures was reported recently by Moreh et al. This work is related to neutron Compton scattering experiments regarding the 'anomalous' scattering from protons, observed earlier at ISIS by Chatzidimitriou-Dreismann et al in the 5-100 eV range. Here we provide the complete data reduction scheme of time-of-flight integrated intensities measured at keV energy transfers, within the impulse approximation of standard theory and for single scattering events. Current investigations of multiple scattering events and the associated preliminary results are mentioned. Direct application of the theoretical results to the new keV scattering data reveals an anomalous ratio of scattering intensity of H2O relative to that of D2O of about 20%, thus being in good agreement with the earlier results of the original experiment at ISIS.

  8. The energy spectrum of 20 keV-20 MeV electrons accelerated in large solar flares

    NASA Technical Reports Server (NTRS)

    Lin, R. P.; Mewaldt, R. A.; Van Hollebeke, M. A. I.

    1982-01-01

    IMP 6, 7, and 8 measurements of the energy spectrum of 20 keV to 20 MeV electrons observed from large solar flares are presented. To minimize propagation effects, only events from flares at W30 deg to W90 deg solar longitude are considered. The energy spectra are constructed using the maximum flux observed at each energy. It is shown that these spectra are representative of the spectra of the electrons escaping from the sun over this range of energies. It is found that every event shows the same spectral shape: a double power law with a smooth transition around 100-200 keV and power law exponents of 0.6-2.0 below and 2.4-4.3 above. The more intense the event, the harder the observed spectrum; in certain cases, the spectra are observed to steepen above 3 MeV.

  9. Auroral electrons of energy less than 1 keV observed at rocket altitudes.

    NASA Technical Reports Server (NTRS)

    Arnoldy, R. L.; Choy, L. W.

    1973-01-01

    Measurements of electrons of energy less than 1 keV in the auroral precipitation with detectors aboard three rocket flights are discussed. Detectors simultaneously measured the flux of electrons moving up and down the magnetic field lines. Electrons of energy less than a few hundred electron volts show directional intensities ranging from isotropic over the upper hemisphere, to field aligned into the atmosphere, to a net streaming out of the atmosphere. Cases of reflection coefficients greater than 1 for the few hundred electron volts and lower-energy electrons occur when measurements were made north of auroral forms. These electrons might represent the high-energy tail of the return Birkeland currents. The origin of the low-energy electrons is itself in question.

  10. A microwave beam waveguide undulator for a brilliant above 100 keV photon source.

    SciTech Connect

    Kang, Y. W.

    1999-04-19

    For generation of photons above 100-keV with a magnetic field strength in the range 0.2-0.5 Tesla, an undulator wavelength {lambda}{sub u} shorter than 5 mm may be needed with beam in the Advanced Photon Source (APS) storage ring. A microwave beam waveguide undulator system has been investigated for generation of such light. The waveguide structure consists of two parallel reflector surfaces that can be derived from an elliptically cylindrical waveguide. The structure can support deflecting TE{sub m0} modes with very low microwave loss. A microwave ring resonator circuit employing the beam waveguide is considered to construct an undulator with the above requirement. Microwave properties of the beam waveguide structure have been investigated, and the design criteria for a microwave undulator are discussed.

  11. Microstructural investigation of alumina implanted with 30 keV nitrogen ions

    NASA Astrophysics Data System (ADS)

    Shikha, Deep; Jha, Usha; Sinha, S. K.; Barhai, P. K.; Sarkhel, G.; Nair, K. G. M.; Dash, S.; Tyagi, A. K.; Kothari, D. C.

    2007-11-01

    Among ceramics, alumina is being widely used as biomaterials now these days. It is being used as hip joints, tooth roots etc. Ion implantation has been employed to modify its surface without changing it bulk properties. 30 keV nitrogen with varying ion dose ranging from 5 × 10 15 ions/cm 2 to 5 × 10 17 ions/cm 2 is implanted in alumina. Surface morphology has been studied with optical microscope and atomic force microscope (AFM). Improvement in brittleness has been observed with the increase in ion dose. Compound formation and changes in grain size have been studied using X-Ray diffraction (XRD). AlN compound formation is also observed by Fourier transform infrared spectroscopy (FTIR). The change in the grain size is related with the nanohardness and Hall-Petch relationship is verified.

  12. 511 keV line and diffuse gamma rays from moduli

    SciTech Connect

    Kasuya, Shinta; Kawasaki, Masahiro

    2006-03-15

    We obtain the spectrum of gamma-ray emissions from the moduli whose decay into e{sup +}e{sup -} accounts for the 511 keV line observed by SPI/INTERGRAL. The moduli emit gamma rays through internal bremsstrahlung, and also decay directly into two gammas via tree and/or one-loop diagrams. We show that the internal bremsstahlung constrains the mass of the moduli below {approx}40 MeV model-independently. On the other hand, the flux of two gammas directly decayed from the moduli through one-loop diagrams will exceed the observed galactic diffuse gamma-ray background if the moduli mass exceeds {approx}20 MeV in the typical situation. Moreover, forthcoming analysis of SPI data in the range of 1-8 MeV may detect the line emisson with the energy half the moduli mass in the near future, which confirms the decaying moduli scenario.

  13. Effect of 200 keV argon ion implantation on refractive index of polyethylene terepthlate (PET)

    NASA Astrophysics Data System (ADS)

    Kumar, Rajiv; Chawla, Mahak; Rubi, Sharma, Annu; Aggarwal, Sanjeev; Kumar, Praveen; Kanjilal, D.

    2012-06-01

    In the present work, the effect of argon ion implantation has been studied on the refractive index of PET. The specimens were implanted at 200 keV with argon ions in the fluence range of 1×1015 to 1×1017 ions cm-2. The refractive indices have been found to increase with implantation dose and wavelength (in visible region) obtained by using UV-visible spectroscopy. Also a drastic decrease in optical band gap (from 3.63 eV to 1.48eV) and increase in Urbach energy (from 0.29 eV to 3.70 eV) with increase in implantation dose has been observed. The possible correlation between the changes observed in the refractive indices and the Urbachenergyhave been discussed.

  14. Range Ecosystems

    Technology Transfer Automated Retrieval System (TEKTRAN)

    After more than two hundred years, grazing remains California’s most extensive land use. The ‘Range Ecosystems’ chapter in the ‘Ecosystems of California’ sourcebook provides an integrated picture of the biophysical, social, and economic aspects of lands grazed by livestock in the state. Grazing mana...

  15. Anisotropic pitch angle distribution of ~100 keV microburst electrons in the loss cone: measurements from STSAT-1

    NASA Astrophysics Data System (ADS)

    Lee, J. J.; Parks, G. K.; Lee, E.; Tsurutani, B. T.; Hwang, J.; Cho, K. S.; Kim, K.-H.; Park, Y. D.; Min, K. W.; McCarthy, M. P.

    2012-11-01

    Electron microburst energy spectra in the range of 170 keV to 360 keV have been measured using two solid-state detectors onboard the low-altitude (680 km), polar-orbiting Korean STSAT-1 (Science and Technology SATellite-1). Applying a unique capability of the spacecraft attitude control system, microburst energy spectra have been accurately resolved into two components: perpendicular to and parallel to the geomagnetic field direction. The former measures trapped electrons and the latter those electrons with pitch angles in the loss cone and precipitating into atmosphere. It is found that the perpendicular component energy spectra are harder than the parallel component and the loss cone is not completely filled by the electrons in the energy range of 170 keV to 360 keV. These results have been modeled assuming a wave-particle cyclotron resonance mechanism, where higher energy electrons travelling within a magnetic flux tube interact with whistler mode waves at higher latitudes (lower altitudes). Our results suggest that because higher energy (relativistic) microbursts do not fill the loss cone completely, only a small portion of electrons is able to reach low altitude (~100 km) atmosphere. Thus assuming that low energy microbursts and relativistic microbursts are created by cyclotron resonance with chorus elements (but at different locations), the low energy portion of the microburst spectrum will dominate at low altitudes. This explains why relativistic microbursts have not been observed by balloon experiments, which typically float at altitudes of ~30 km and measure only X-ray flux produced by collisions between neutral atmospheric particles and precipitating electrons.

  16. QUIET-TIME INTERPLANETARY {approx}2-20 keV SUPERHALO ELECTRONS AT SOLAR MINIMUM

    SciTech Connect

    Wang, Linghua; Lin, Robert P.; Salem, Chadi; Pulupa, Marc; Larson, Davin E.; Luhmann, Janet G.; Yoon, Peter H.

    2012-07-01

    We present a statistical survey of {approx}2-20 keV superhalo electrons in the solar wind measured by the SupraThermal Electron instrument on board the two STEREO spacecraft during quiet-time periods from 2007 March through 2009 March at solar minimum. The observed superhalo electrons have a nearly isotropic angular distribution and a power-law spectrum, f{proportional_to}v{sup -{gamma}}, with {gamma} ranging from 5 to 8.7, with nearly half between 6.5 and 7.5, and an average index of 6.69 {+-} 0.90. The observed power-law spectrum varies significantly on a spatial scale of {approx}>0.1 AU and a temporal scale of {approx}>several days. The integrated density of quiet-time superhalo electrons at 2-20 keV ranges from {approx}10{sup -8} cm{sup -3} to 10{sup -6} cm{sup -3}, about 10{sup -9}-10{sup -6} of the solar wind density, and, as well as the power-law spectrum, shows no correlation with solar wind proton density, velocity, or temperature. The density of superhalo electrons appears to show a solar-cycle variation at solar minimum, while the power-law spectral index {gamma} has no solar-cycle variation. These quiet-time superhalo electrons are present even in the absence of any solar activity-e.g., active regions, flares or microflares, type III radio bursts, etc.-suggesting that they may be accelerated by processes such as resonant wave-particle interactions in the interplanetary medium, or possibly by nonthermal processes related to the acceleration of the solar wind such as nanoflares, or by acceleration at the CIR forward shocks.

  17. On the Spectral Hardening at gsim300 keV in Solar Flares

    NASA Astrophysics Data System (ADS)

    Li, G.; Kong, X.; Zank, G.; Chen, Y.

    2013-05-01

    It has long been noted that the spectra of observed continuum emissions in many solar flares are consistent with double power laws with a hardening at energies gsim300 keV. It is now widely believed that at least in electron-dominated events, the hardening in the photon spectrum reflects an intrinsic hardening in the source electron spectrum. In this paper, we point out that a power-law spectrum of electrons with a hardening at high energies can be explained by the diffusive shock acceleration of electrons at a termination shock with a finite width. Our suggestion is based on an early analytical work by Drury et al., where the steady-state transport equation at a shock with a tanh profile was solved for a p-independent diffusion coefficient. Numerical simulations with a p-dependent diffusion coefficient show hardenings in the accelerated electron spectrum that are comparable with observations. One necessary condition for our proposed scenario to work is that high-energy electrons resonate with the inertial range of the MHD turbulence and low-energy electrons resonate with the dissipation range of the MHD turbulence at the acceleration site, and the spectrum of the dissipation range ~k -2.7. A ~k -2.7 dissipation range spectrum is consistent with recent solar wind observations.

  18. ON THE SPECTRAL HARDENING AT {approx}>300 keV IN SOLAR FLARES

    SciTech Connect

    Li, G.; Kong, X.; Zank, G.; Chen, Y.

    2013-05-20

    It has long been noted that the spectra of observed continuum emissions in many solar flares are consistent with double power laws with a hardening at energies {approx}>300 keV. It is now widely believed that at least in electron-dominated events, the hardening in the photon spectrum reflects an intrinsic hardening in the source electron spectrum. In this paper, we point out that a power-law spectrum of electrons with a hardening at high energies can be explained by the diffusive shock acceleration of electrons at a termination shock with a finite width. Our suggestion is based on an early analytical work by Drury et al., where the steady-state transport equation at a shock with a tanh profile was solved for a p-independent diffusion coefficient. Numerical simulations with a p-dependent diffusion coefficient show hardenings in the accelerated electron spectrum that are comparable with observations. One necessary condition for our proposed scenario to work is that high-energy electrons resonate with the inertial range of the MHD turbulence and low-energy electrons resonate with the dissipation range of the MHD turbulence at the acceleration site, and the spectrum of the dissipation range {approx}k {sup -2.7}. A {approx}k {sup -2.7} dissipation range spectrum is consistent with recent solar wind observations.

  19. Measurements of total atomic attenuation cross sections of Tm, Yb, Lu, Hf, Ta, W, Re and Os Elements at 122keV and 136keV

    SciTech Connect

    Kaya, N.; Tirasoglu, E.; Apaydin, G.; Kobya, A. I.

    2007-04-23

    The aim of this study was to measure the total atomic attenuation cross sections ({sigma}t) in eighth elements (69{<=}Z{<=}76) at 122 keV and 136 keV. The experimental values of the cross sections were determined using the transmission geometry. Measurements have been performed using an annular source (Co-57) and Ultra-LEGe solid state detector with a resolution of 150 eV at 5.9 keV. Experimental results have been compared with theoretically calculated values and other available experimental results. Good agreement was observed among the experimental, theoretical and other experimental values.

  20. Wide range magnetic electron spectrograph

    NASA Technical Reports Server (NTRS)

    Coplan, M. A.; Wang, L.-J.; Moore, J. H.; Hoffman, R. A.

    1989-01-01

    An electron spectrogrpah is described that covers electron energies from 400 eV to 200 keV with an energy resolution of 10 percent. This overlaps the range of electrostatic deflection devices at low energy and solid state detectors at high energy. The spectrograph uses magnetic deflection of the electrons to achieve energy separation and images the full range of energies on a single plane. The magnetic circuit uses the fringing field of two axially located magnets to attain the large energy range. Six separate electron beams can be dispersed in the field, each entering the circuit from a different angle. This is a particular advantage when measuring plasma electron three-dimensional velocity distributions. The angular response of the instrument is particularly favorable and the stray magnetic field is sufficiently low to meet spacecraft requirements.

  1. SPECTRAL PROPERTIES OF {approx}0.5-6 keV ENERGETIC NEUTRAL ATOMS MEASURED BY THE INTERSTELLAR BOUNDARY EXPLORER (IBEX) ALONG THE LINES OF SIGHT OF VOYAGER

    SciTech Connect

    Desai, M. I.; Allegrini, F. A.; Dayeh, M. A.; McComas, D. J.; Schwadron, N. A.; De Majistre, B.; Funsten, H.; Heerikhuisen, J.; Pogorelov, N.; Zank, G. P.

    2012-04-20

    Energetic neutral atoms (ENAs) observed by the Interstellar Boundary Explorer (IBEX) provide powerful diagnostics about the origin of the progenitor ion populations and the physical mechanisms responsible for their production. Here we survey the fluxes, energy spectra, and energy dependence of the spectral indices of {approx}0.5-6 keV ENAs measured by IBEX-Hi along the lines of sight of Voyager 1 and 2. We compare the ENA spectra observed at IBEX with predictions of Zank et al. who modeled the microphysics of the heliospheric termination shock to predict the shape and relative contributions of three distinct heliosheath ion populations. We show that (1) the ENA spectral indices exhibit similar energy dependence along V1 and V2 directions-the spectrum hardens to {gamma} {approx} 1 between {approx}1 and 2 keV and softens to {gamma} {approx} 2 below {approx}1 keV and above {approx}2 keV, (2) the observed ENA fluxes agree to within {approx}50% of the Zank et al. predictions and are unlikely to be produced by core solar wind (SW) ions, and (3) the ENA spectra do not exhibit sharp cutoffs at {approx}twice the SW speed as is typically observed for shell-like pickup ion (PUI) distributions in the heliosphere. We conclude that ENAs at IBEX are generated by at least two types of ion populations whose relative contributions depend on the ENA energy: transmitted PUIs in the {approx}0.5-5 keV energy range and reflected PUIs above {approx}5 keV energy. The {approx}0.5-5 keV PUI distribution is probably a superposition of Maxwellian or kappa distributions and partially filled shell distributions in velocity space.

  2. Checking the potassium origin of the new emission line at 3.5 keV using the K XIX line complex at 3.7 keV

    NASA Astrophysics Data System (ADS)

    Iakubovskyi, Dmytro

    2015-11-01

    It is currently unclear whether the new line at ˜3.5 keV, recently detected in various samples of galaxy clusters, the Andromeda galaxy and the central part of our Galaxy, is caused by potassium emission lines. By using the latest astrophysical atomic emission line data base, AtomDB v. 3.0.2, we show that the most promising method to check its potassium origin directly will be the study of the K XIX emission line complex at ˜3.7 keV using forthcoming X-ray imaging spectrometers such as the Soft X-ray spectometer onboard the Astro-H mission or the microcalorimeter onboard the Micro-X sounding rocket experiment. In order to further reduce the remaining (factor of ˜3-5) uncertainty of the 3.7/3.5 keV ratio, more precise modelling should be performed, including the removal of significant spatial inhomogeneities, a detailed treatment of background components, and the extension of the modelled energy range.

  3. Variable Gap Undulator for 1.5-48 Kev Free Electron Laser at Linac Coherent Light Source

    SciTech Connect

    Pellegrini, C.; Wu, J.; /SLAC

    2011-08-17

    We study the feasibility of generating femtosecond duration Free-Electron Laser with a variable photon energy from 1.5 to 48 keV, using an electron bunch with the same characteristics of the LINAC Coherent Light Source (LCLS) bunch, and a planar undulator with additional focusing. We assume that the electron bunch energy can be changed, and the undulator has a variable gap, allowing a variable undulator parameter. It is assumed to be operated in an ultra-low charge and ultra-short pulse regime. We study the feasibility of a tunable, short pulse, X-ray FEL with photon energy from 1.5 to 48 keV, using an electron beam like the one in the LCLS and a 2:5 cm period, variable gap, planar undulator. The beam energy changes from 4.6 to 13.8 GeV, the electorn charge is kept at 10 pC, and the undulator parameter varies from 1 to 3. The undulator length needed to saturate the 48 keV FEL is about 55 m, with a peak power around 5 GW. At longer wavelength the saturation length is as short as 15 m, and the peak power around 20 GW. The results from the analytical models and the GENESIS simulations show that the system is feasible. The large wavelength range, full tunability and short, few femtosecond pulses, together with the large peak power, would provide a powerful research tool.

  4. Sub-arcsec X-Ray Telescope for Imaging The Solar Corona In the 0.25 - 1.2 keV Band

    NASA Technical Reports Server (NTRS)

    Gallagher, Dennis; Cash, Webster; Jelsma, Schuyler; Farmer, Jason

    1996-01-01

    We have developed an X-ray telescope that uses a new technique for focusing X-rays with grazing incidence optics. The telescope was built with spherical optics for all of its components, utilizing the high quality surfaces obtainable when polishing spherical (as opposed to aspherical) optics. We tested the prototype X-ray telescope in the 300 meter vacuum pipe at White Sands Missile Range, NM. The telescope features 2 degee graze angles with tungsten coatings, yielding a bandpass of 0.25-1.5 keV with a peak effective area of 0.8 sq cm at 0.83 keV. Results from X-ray testing at energies of 0.25 keV and 0.93 keV (C-K and Cu-L) verify 0.5 arcsecond performance at 0.93 keV. Results from modeling the X-ray telescope's response to the Sun show that the current design would be capable of recording 10 half arcsecond images of a solar active region during a 300 second NASA sounding rocket flight.

  5. Where do the 3.5 keV photons come from? A morphological study of the Galactic Center and of Perseus

    SciTech Connect

    Carlson, Eric; Jeltema, Tesla; Profumo, Stefano E-mail: tesla@ucsc.edu

    2015-02-01

    We test the origin of the 3.5 keV line photons by analyzing the morphology of the emission at that energy from the Galactic Center and from the Perseus cluster of galaxies. We employ a variety of different templates to model the continuum emission and analyze the resulting radial and azimuthal distribution of the residual emission. We then perform a pixel-by-pixel binned likelihood analysis including line emission templates and dark matter templates and assess the correlation of the 3.5 keV emission with these templates. We conclude that the radial and azimuthal distribution of the residual emission is incompatible with a dark matter origin for both the Galactic center and Perseus; the Galactic center 3.5 keV line photons trace the morphology of lines at comparable energy, while the Perseus 3.5 keV photons are highly correlated with the cluster's cool core, and exhibit a morphology incompatible with dark matter decay. The template analysis additionally allows us to set the most stringent constraints to date on lines in the 3.5 keV range from dark matter decay.

  6. Subarcsecond x-ray telescope for imaging the solar corona in the 0.25- to 1.2-keV band

    NASA Astrophysics Data System (ADS)

    Gallagher, Dennis J.; Cash, Webster C.; Jelsma, Schuyler; Farmer, Jason

    1996-07-01

    We have developed an x-ray telescope that uses a new technique for focusing x-rays with grazing incidence optics. The telescope was built with spherical optics for all of its components, utilizing the high quality surfaces obtainable when polishing spherical (as opposed to aspherical) optics. We tested the prototype x-ray telescope in the 300 meter vacuum pipe at White Sands Missile Range, NM. The telescope features 2 degree graze angles with tungsten coatings, yielding a bandpass of 0.25-1.5 keV with a peak effective area of 0.8 cm(superscript 2) at 0.83 keV. Results from x-ray testing at energies of 0.25 keV and 0.93 keV (C-K and Cu-L) verify 0.5 arcsecond performance at 0.93 keV. Results from modeling the x-ray telescope's response to the SUn show that the current design would be capable of recording 10 half arcsecond images of a solar active region during a 300 second NASA sounding rocket flight.

  7. Direct and indirect signal detection of 122 keV photons with a novel detector combining a pnCCD and a CsI(Tl) scintillator

    NASA Astrophysics Data System (ADS)

    Schlosser, D. M.; Huth, M.; Hartmann, R.; Abboud, A.; Send, S.; Conka-Nurdan, T.; Shokr, M.; Pietsch, U.; Strüder, L.

    2016-01-01

    By combining a low noise fully depleted pnCCD detector with a CsI(Tl) scintillator, an energy-dispersive area detector can be realized with a high quantum efficiency (QE) in the range from below 1 keV to above 100 keV. In direct detection mode the pnCCD exhibits a relative energy resolution of 1% at 122 keV and spatial resolution of less than 75 μm, the pixel size of the pnCCD. In the indirect detection mode, i.e. conversion of the incoming X-rays in the scintillator, the measured energy resolution was about 9-13% at 122 keV, depending on the depth of interaction in the scintillator, while the position resolution, extracted with the help of simulations, was 30 μm only. We show simulated data for incident photons of 122 keV and compare the various interaction processes and relevant physical parameters to experimental results obtained with a radioactive 57Co source.

  8. Deep XMM observations of Draco rule out at the 99 per cent confidence level a dark matter decay origin for the 3.5 keV line

    NASA Astrophysics Data System (ADS)

    Jeltema, Tesla; Profumo, Stefano

    2016-06-01

    We searched for an X-ray line at energies around 3.5 keV in deep, ˜1.6 Ms XMM-Newton observations of the dwarf spheroidal galaxy Draco. No line was found in either the Metal Oxide Semi-conductor (MOS) or the p-type/n-type semiconductor (PN) detectors. The data in this energy range are completely consistent with a single, unfolded power-law modelling the particle background, which dominates at these energies, plus instrumental lines; the addition of a ˜3.5 keV line feature gives no improvement to the fit. The corresponding upper limit on the line flux rules out a dark matter decay origin for the 3.5 keV line found in observations of clusters of galaxies and in the Galactic Centre at greater than 99 per cent confidence level.

  9. Oxygen incorporation in polyethylene implanted with 150 keV Sb+ ions

    NASA Astrophysics Data System (ADS)

    Hnatowicz, V.; Kvítek, J.; Švorčík, V.; Rybka, V.; Popok, V.

    1994-06-01

    Samples of polyethylene (PE) loaded with carbon black up to 8 wt.% and implanted with 150 keV Sb+ ions to the doses from 2×1013-2×1015 cm-2 were studied using standard Rutherford Back Scattering (RBS) technique. On the PE samples implanted to the doses above 2×1014 cm-2, a considerable surface carbonization is observed. The measured parameters of the Sb depth profile are compared with theoretical TRIM estimations. The projected range is by 25% lower than the theoretical one and the range straggling is about twice of that predicted. The differences are explained by stepwise polymer degradation during the ion bombardment. Strong oxidation of the ion implanted polymers is also observed. The oxygen depth profiles from the sample surface up to the depth comparable with Sb+ ion range evolve from nearly uniform one for low ion doses to highly non-uniform one for doses above 1×1015 cm-2. The total oxygen content in the sample surface layer 300 nm thick reaches a maximum for the doses of (1-2)×1014 cm-2.

  10. HEXIT-SAT: a mission concept for x-ray grazing incidence telescopes from 0.5 to 70 keV

    NASA Astrophysics Data System (ADS)

    Fiore, Fabrizio; Perola, Giuseppe C.; Pareschi, Giovanni; Citterio, Oberto; Anselmi, Alberto; Comastri, Andrea

    2004-10-01

    While the energy density of the Cosmic X-ray Background (CXB) provides a statistical estimate of the super massive black hole (SMBH) growth and mass density in the Universe, the lack, so far, of focusing instrument in the 20-60 keV (where the CXB energy density peaks), frustrates our effort to obtain a comprehensive picture of the SMBH evolutionary properties. HEXIT-SAT (High Energy X-ray Imaging Telescope SATellite) is a mission concept capable of exploring the hard X-ray sky with focusing/imaging instrumentation, to obtain an unbiased census of accreting SMBH up to the redshifts where galaxy formation peaks, and on extremely wide luminosity ranges. This will represent a leap forward comparable to that achieved in the soft X-rays by the Einstein Observatory in the late 70'. In addition to accreting SMBH, and very much like the Einstein Observatory, this mission would also have the capabilities of investigating almost any type of the celestial X-ray sources. HEXIT-SAT is based on high throughput (>400 cm2 @ 30 keV; >1200 cm2 @ 1 keV), high quality (15 arcsec Half Power Diameter) multi-layer optics, coupled with focal plane detectors with high efficiency in the full 0.5-70keV range. Building on the BeppoSAX experience, a low-Earth, equatorial orbit, will assure a low and stable particle background, and thus an extremely good sensitivity for faint hard X-ray sources. At the flux limits of 1/10 microCrab (10-30 keV) and 1/3 microCrab (20-40 keV) (reachable in one Msec observation) we should detect ~100 and ~40 sources in the 15 arcmin FWHM Field of View respectively, thus resolving >80% and ~65% of the CXB where its energy density peaks.

  11. Investigation of pulsed X-ray radiation of a plasma focus in a broad energy range

    SciTech Connect

    Savelov, A. S. Salakhutdinov, G. Kh.; Koltunov, M. V.; Lemeshko, B. D.; Yurkov, D. I.; Sidorov, P. P.

    2011-12-15

    The results of the experimental investigations of the spectral composition of plasma focus X-ray radiation in the photon energy range of 1.5 keV-400 keV are presented. Three regions in the radiation spectrum where the latter is of a quasi-thermal nature with a corresponding effective temperature are distinguished.

  12. Range and range rate system

    NASA Technical Reports Server (NTRS)

    Graham, Olin L. (Inventor); Russell, Jim K. (Inventor); Epperly, Walter L. (Inventor)

    1988-01-01

    A video controlled solid state range finding system which requires no radar, high power laser, or sophisticated laser target is disclosed. The effective range of the system is from 1 to about 200 ft. The system includes an opto-electric camera such as a lens CCD array device. A helium neon laser produces a source beam of coherent light which is applied to a beam splitter. The beam splitter applies a reference beam to the camera and produces an outgoing beam applied to a first angularly variable reflector which directs the outgoing beam to the distant object. An incoming beam is reflected from the object to a second angularly variable reflector which reflects the incoming beam to the opto-electric camera via the beam splitter. The first reflector and the second reflector are configured so that the distance travelled by the outgoing beam from the beam splitter and the first reflector is the same as the distance travelled by the incoming beam from the second reflector to the beam splitter. The reference beam produces a reference signal in the geometric center of the camera. The incoming beam produces an object signal at the camera.

  13. Weak Solar Flares in 3 -31.5 keV X-rays Detected in the Coronas-F Experiment

    NASA Astrophysics Data System (ADS)

    Gusev, Anatoly; Pugacheva, Galina; Martin, Inácio M.; Spjeldvik, Walther

    The RPS-1 spectrometer on the board of the Coronas-F satellite detecting solar X-rays in the range of 3-31.5 keV using a CdTe detector is described and some results of the observation of weak solar flares are presented. The detector has a high detection efficiency and radiation damage resistance necessary for long time space experiments. It has an active area of 46 mm2, a thickness of 1.4 mm, an operation voltage of 100 V, an energy resolution of 0.88 keV (13.87 keV Am241), a power consumption of 8.5 W, and a mass of 1.8 kg. The width of the first 12 channels (3-9 keV) is 0.5 keV, the width of the next 12 channels is 1 keV, and the width of the last 8 channels (21-31.5 keV) is 1.3 keV. The spectrum accumulation time in 32 channels is 16 s. The spectrometer provides vast experimental data on the spectra of soft X-ray emission of solar flares. The high spectral resolution of the instrument allows an investigation of the dynamics of the temperature in the source using the direct comparison of the spectrum shape with some models, for example, with the CHIANTI 5.2 model. It was noted that hardness of the spectrum in the flare maximum increases with the flare class and solar activity level. The magnetic heating of the corona was confirmed by the spectra of the background solar X ray radiation for various numbers of sunspots: the more sunspots, the harder the spectrum of the X-ray background radiation was registered and, respectively, the stronger was the impact on the Earth's atmosphere. Near the solar activity maximum, the background radiation intensity increased by more than an order of magnitude and the maximum energy increased from 6 to 20 keV. (To the memory of Drs. V.M. Pankov and V.L. Prokhin, colleagues and coworkers in the Coronas-F mission.)

  14. Atomic, Molecular, and Optical Physics: Optical Excitation Function of H(1s-2p) Produced by electron Impact from Threshold to 1.8 keV

    NASA Technical Reports Server (NTRS)

    James, G. K.; Slevin, J. A.; Shemansky, D. E.; McConkey, J. W.; Bray, I.; Dziczek, D.; Kanik, I.; Ajello, J. M.

    1997-01-01

    The optical excitation function of prompt Lyman-Alpha radiation, produced by electron impact on atomic hydrogen, has been measured over the extended energy range from threshold to 1.8 keV. Measurements were obtained in a crossed-beams experiment using both magnetically confined and electrostatically focused electrons in collision with atomic hydrogen produced by an intense discharge source. A vacuum-ultraviolet mono- chromator system was used to measure the emitted Lyman-Alpha radiation. The absolute H(1s-2p) electron impact excitation cross section was obtained from the experimental optical excitation function by normalizing to the accepted optical oscillator strength, with corrections for polarization and cascade. Statistical and known systematic uncertainties in our data range from +/- 4% near threshold to +/- 2% at 1.8 keV. Multistate coupling affecting the shape of the excitation function up to 1 keV impact energy is apparent in both the present experimental data and present theoretical results obtained with convergent close- coupling (CCC) theory. This shape function effect leads to an uncertainty in absolute cross sections at the 10% level in the analysis of the experimental data. The derived optimized absolute cross sections are within 7% of the CCC calculations over the 14 eV-1.8 keV range. The present CCC calculations converge on the Bethe- Fano profile for H(1s-2p) excitation at high energy. For this reason agreement with the CCC values to within 3% is achieved in a nonoptimal normalization of the experimental data to the Bethe-Fano profile. The fundamental H(1s-2p) electron impact cross section is thereby determined to an unprecedented accuracy over the 14 eV - 1.8 keV energy range.

  15. HEAO 1 observations of the Perseus cluster above 10 keV

    NASA Technical Reports Server (NTRS)

    Primini, F. A.; Howe, S. K.; Lang, F.; Levine, A. M.; Lewin, W. H. G.; Rothschild, R.; Baity, W. A.; Gruber, D. E.; Knight, F. K.; Basinska, E.

    1981-01-01

    Results are presented of HEAO 1 observations of the Perseus cluster from 10 to 150 keV in 1977 August and 1978 February and August. The spectrum exhibits a previously unknown hard (greater than 25 keV) component in addition to the previously known thermal bremsstrahlung emission. The data presented show no significant evidence of variability from 10.5 keV to 93.5 keV, and a comparison of our results with earlier results indicates no strong evidence for variability above 25 keV over a time scale of 4 yr. If the hard-component excess is due to NGC 1275, the data imply a 2-6 keV X-ray luminosity of 1 x 10 to the 44th ergs/s for the galaxy, or about 15% of the total cluster emission from 2 to 6 keV and a 25-40 keV luminosity of 8 x 10 to the 43rd ergs/s.

  16. Planned investigation of energetic particle populations (approximately 20-500 keV) in the close Martian environment

    NASA Astrophysics Data System (ADS)

    McKenna-Lawlor, S.; Rusznyak, P.; Gringauz, K.; Klimenko, I.; Lutsenko, V.; Verigin, M.; Korth, A.; Richter, A.; Fischer, S.; Polasek, C.

    1995-04-01

    Energetic particle observations made by the Irish SLED instrument on the Phobos 2 spacecraft in 1989 have revealed the presence, within the overall energy range less than 30 keV - greater than 3.2 MeV, of variously located energetic particle populations in the close Marian environment. The signatures of characteristic boundaries have also been recorded for the first time in energetic particles in the distant Martian magnetotail. The new SLED-II instrument on the Mars-94 Mission is designed to study in detail, with 4 pi measurement capability, these and other energetic particle phenomena at Mars, while operating, over an extended period, at low altitudes above the planet.

  17. Electron back-scattering coefficient below 5 keV: Analytical expressions and surface-barrier effects

    NASA Astrophysics Data System (ADS)

    Cazaux, J.

    2012-10-01

    Simple analytical expressions for the electron backscattering coefficient, η, are established from published data obtained in the ˜0.4-5 keV range for 21 elements ranging from Be to Au. They take into account the decline in η with a decrease in energy E° for high-Z elements and the reverse behavior for low-Z elements. The proposed expressions for η (E°) lead to crossing energies situated in the 0.4-1 keV range and they may be reasonably extended to any of the other elements—via an interpolation procedure—to metallic alloys and probably to compounds. The influence of the surface barrier on the escape probability of the back-scattered electrons is next evaluated. This evaluation provides a theoretical basis to explain the observed deviation between various published data as a consequence of surface contamination or oxidation. Various practical applications and strategies are deduced for the η-measurements in dedicated instruments as well for the image interpretation in low voltage scanning electron microscopy based on the backscattered electron detection. In this microscopy, the present investigation allows to generalize the scarce contrast changes and contrast reversals previously observed on multi elemental samples and it suggests the possibility of a new type of contrast: the work function contrast.

  18. Observations of the scatter-free solar-flare electrons in the energy range 20-1000 keV

    NASA Technical Reports Server (NTRS)

    Wang, J. R.; Fisk, L. A.; Lin, R. P.

    1971-01-01

    Observations of the scatter-free electron events from solar active region McMath No. 8905 are presented. The measurements were made on Explorer 33 satellite. The data show that more than 80% of the electrons from these events undergo no or little scattering and that these electrons travel only approximately 1.5 a.u. between the sun and the earth. The duration of these events cannot be accounted fully by velocity dispersion alone. It is suggested that these electrons could be continuously injected into interplanetary medium for a time interval of approximately 2 to 3 minutes. Energy spectra of these electrons are discussed.

  19. Stability of Extraterrestrial Glycine under Energetic Particle Radiation Estimated from 2 keV Electron Bombardment Experiments

    NASA Astrophysics Data System (ADS)

    Maté, B.; Tanarro, I.; Escribano, R.; Moreno, M. A.; Herrero, V. J.

    2015-06-01

    The destruction of solid glycine under irradiation with 2 keV electrons has been investigated by means of IR spectroscopy. Destruction cross sections, radiolysis yields, and half-life doses were determined for samples at 20, 40, 90, and 300 K. The thickness of the irradiated samples was kept below the estimated penetration depth of the electrons. No significant differences were obtained in the experiments below 90 K, but the destruction cross section at 300 K was larger by a factor of 2. The radiolysis yields and half-life doses are in good accordance with recent MeV proton experiments, which confirms that electrons in the keV range can be used to simulate the effects of cosmic rays if the whole sample is effectively irradiated. In the low temperature experiments, electron irradiation leads to the formation of residues. IR absorptions of these residues are assigned to the presence CO2, CO, OCN-, and CN- and possibly to amide bands I to III. The protection of glycine by water ice is also studied. A water ice film of ˜150 nm is found to provide efficient shielding against the bombardment of 2 keV electrons. The results of this study show also that current Monte Carlo predictions provide a good global description of electron penetration depths. The lifetimes estimated in this work for various environments ranging from the diffuse interstellar medium to the inner solar system, show that the survival of hypothetical primeval glycine from the solar nebula in present solar system bodies is not very likely.

  20. K+ charge transfer in H2 at low keV collisions

    NASA Astrophysics Data System (ADS)

    Alarcón, F. B.; Martinez, H.; Fuentes, B. E.; Yousif, F. B.

    2013-08-01

    Absolute electron capture cross sections for the K+-H2 pair, employing beam collision spectroscopy for 0.4-4 keV energy were measured. The capture cross section increased with the increase in collision energy. The results below 2 keV overlap with previously measured data of other investigators and extend down in energy to 400 eV, where no previous data have been reported. Experimental data were compared with calculations employing the Olson model, which were found to agree in behavior as well as with an absolute value above 100 keV.

  1. Neutron cross sections of 122Te, 123Te, and 124Te between 1 and 60 keV

    NASA Astrophysics Data System (ADS)

    Xia, Y.; Gerstenhöfer, Th. W.; Jaag, S.; Käppeler, F.; Wisshak, K.

    1992-05-01

    The currently favored s process scenario of helium shell burning in low mass stars involves a range of thermal energies from kT=12 to 25 keV with most of the neutron exposure taking place at low temperatures. Therefore, differential cross sections are required down to the region of resolved resonances for the reliable determination of the Maxwellian-averaged cross sections typical of the stellar plasma. This work deals with the neutron capture cross sections of the important s only isotopes 122Te, 123Te, and 124Te, which were measured between 1 and 60 keV neutron energy with a setup of Moxon-Rae detectors. The systematic uncertainties achieved in this experiment are ~5%, but statistical uncertainties are smaller than 2%. In addition to the Moxon-Rae detectors, the setup includes a 6Li glass detector which could be used to determine the total neutron cross sections simultaneously. These results represent the first set of experimental data in this energy range.

  2. Mass attenuation coefficients of soil and sediment samples using gamma energies from 46.5 to 1332 keV.

    PubMed

    Al-Masri, M S; Hasan, M; Al-Hamwi, A; Amin, Y; Doubal, A W

    2013-02-01

    Mass attenuation coefficients of various soil and sediment samples (density range between 1.0 and 1.7 g cm(-3)) collected from 60 sites distributed in Syrian land have been determined for gamma lines of 46.5, 59.5, 88, 122, 165, 392, 661, 1173, and 1332 keV using gamma spectrometry and simulation software program X-com. The average mass attenuation coefficients for the studied samples were found to be 0.513, 0.316, 0.195, 0.155, 0.134, 0.096, 0.077, 0.058, and 0.055 cm(2) g(-1) at previous energies, respectively. The results have shown that Ca and Fe contents of the samples have strong effect on the mass attenuation coefficient at lower energies. In addition, self-attenuation correction factors determined using mass attenuation coefficient was in good agreement with addition spiked reference material method provided that the sample thickness is 2.7 cm. However, mass attenuation coefficients determined in this study can be used for determination of gamma emitters at energy ranges from 46.5 to 1332 keV in any soil and sediment samples having density of 1.0-1.7 g cm(-3). PMID:23103572

  3. Is keV ion-induced pattern formation on Si(001) caused by metal impurities?

    PubMed

    Macko, Sven; Frost, Frank; Ziberi, Bashkim; Förster, Daniel F; Michely, Thomas

    2010-02-26

    We present ion beam erosion experiments performed in ultrahigh vacuum using a differentially pumped ion source and taking care that the ion beam hits the Si(001) sample only. Under these conditions no ion beam patterns form on Si for angles theta < or = 45 degrees with respect to the global surface normal using 2 keV Kr+ and fluences of approximately 2 x 10(22) ions m(-2). In fact, the ion beam induces a smoothening of preformed patterns. Simultaneous sputter deposition of stainless steel in this angular range creates a variety of patterns, similar to those previously ascribed to clean ion-beam-induced destabilization of the surface profile. Only for grazing incidence with 60 degrees < or = theta < or = 83 degrees do pronounced ion beam patterns form. It appears that the angular-dependent stability of Si(001) against pattern formation under clean ion beam erosion conditions is related to the angular dependence of the sputtering yield, and not primarily to a curvature-dependent yield as invoked frequently in continuum theory models. PMID:20097973

  4. Is keV ion-induced pattern formation on Si(001) caused by metal impurities?

    NASA Astrophysics Data System (ADS)

    Macko, Sven; Frost, Frank; Ziberi, Bashkim; Förster, Daniel F.; Michely, Thomas

    2010-02-01

    We present ion beam erosion experiments performed in ultrahigh vacuum using a differentially pumped ion source and taking care that the ion beam hits the Si(001) sample only. Under these conditions no ion beam patterns form on Si for angles thetav<=45° with respect to the global surface normal using 2 keV Kr+ and fluences of ≈ 2 × 1022 ions m-2. In fact, the ion beam induces a smoothening of preformed patterns. Simultaneous sputter deposition of stainless steel in this angular range creates a variety of patterns, similar to those previously ascribed to clean ion-beam-induced destabilization of the surface profile. Only for grazing incidence with 60°<=thetav<=83° do pronounced ion beam patterns form. It appears that the angular-dependent stability of Si(001) against pattern formation under clean ion beam erosion conditions is related to the angular dependence of the sputtering yield, and not primarily to a curvature-dependent yield as invoked frequently in continuum theory models.

  5. Ion-induced photon emission of magnesium aluminate spinel during 60 keV Cu - implantation

    NASA Astrophysics Data System (ADS)

    Bandourko, V.; Lay, T. T.; Takeda, Y.; Lee, C. G.; Kishimoto, N.

    2001-04-01

    The beam-solid interaction during high flux heavy-ion implantation has been studied by the in situ detection of photon emission. A spinel of MgO· n(Al 2O 3) with n=2.4 was irradiated with 60 keV Cu - at dose rates of 10, 50 or 100 μA/cm 2 to a dose of 1.5×10 17 ions/cm2. Under the implantation, photon emission ranging from 1.4 to 6.2 eV was detected by a time-resolved optical device based on a fast-response CCD (Princeton Instruments: IMAX-512). Emission lines of sputtered Mg, Al and Cu atoms were observed. A comparison of the dose and dose rate dependence of the Cu I line intensity from MgO· n(Al 2O 3) with those obtained for amorphous (a-)SiO 2 substrate revealed the good correlation of Cu I line intensity with nanoparticle formation detected by optical absorbance measurement.

  6. MULTI-KEV X-RAY YIELDS FROM HIGH-Z GAS TARGETS FIELDED AT OMEGA

    SciTech Connect

    Kane, J O; Fournier, K B; May, M J; Colvin, J D; Thomas, C A; Marrs, R E; Compton, S M; Moody, J D; Bond, E J; Davis, J F

    2010-11-04

    The authors report on modeling of x-ray yield from gas-filled targets shot at the OMEGA laser facility. The OMEGA targets were 1.8 mm long, 1.95 mm in diameter Be cans filled with either a 50:50 Ar:Xe mixture, pure Ar, pure Kr or pure Xe at {approx} 1 atm. The OMEGA experiments heated the gas with 20 kJ of 3{omega} ({approx} 350 nm) laser energy delivered in a 1 ns square pulse. the emitted x-ray flux was monitored with the x-ray diode based DANTE instruments in the sub-keV range. Two-dimensional x-ray images (for energies 3-5 keV) of the targets were recorded with gated x-ray detectors. The x-ray spectra were recorded with the HENWAY crystal spectrometer at OMEGA. Predictions are 2D r-z cylindrical with DCA NLTE atomic physics. Models generally: (1) underpredict the Xe L-shell yields; (2) overpredict the Ar K-shell yields; (3) correctly predict the Xe thermal yields; and (4) greatly underpredict the Ar thermal yields. However, there are spreads within the data, e.g. the DMX Ar K-shell yields are correctly predicted. The predicted thermal yields show strong angular dependence.

  7. LUCIA - a new 1-7 keV {mu}-XAS Beamline

    SciTech Connect

    Janousch, M.; Schmidt, Th.; Wetter, R.; Grolimund, G.; Scheidegger, A.M.; Flank, A.-M.; Lagarde, P.; Cauchon, G.; Bac, S.; Dubuisson, J.M.

    2004-05-12

    LURE-SOLEIL (France) and the Swiss Light Source (SLS) are building together a new micro focused beamline for micro x-ray absorption spectroscopy and micro imaging. This line is designed to deliver a photon flux of the order of 1012 ph/sec on a 1 x 1 {mu}m spot within the energy domain of 0.8 to 7 keV. This beam line is being installed on the X07M straight section of SLS. The source is an APPLE II undulator with a period of 54 mm. The main advantage of this device lies in the delivery of any degree of polarization, linear or circular, over the whole energy range, without the need of a sample-position change. The monochromator will be a fixed exit double crystal equipped with 5 sets of crystals, thanks to the very narrow photon beam from the undulator ( Beryl, KTP, YB66, InSb(111), Si(111) ). The optics includes a first horizontal focusing mirror (spherical), which produces an intermediate source for the horizontal mirror of a Kirkpatrick-Baez (KB) system. The vertical mirror of the KB directly images the source. Finally, a low-pass double mirror filter insures a proper harmonic rejection.

  8. Effects of combined irradiation of 500 keV protons and atomic oxygen on polyimide films

    NASA Astrophysics Data System (ADS)

    Novikov, Lev; Chernik, Vladimir; Zhilyakov, Lev; Voronina, Ekaterina; Chirskaia, Natalia

    2016-07-01

    Polyimide films are widely used on the spacecraft surface as thermal control coating, films in different constuctions, etc. However, the space ionizing radiation of different types can alter the mechanical, optical and electrical properties of polyimide films. For example, it is well known that 20-100 keV proton irradiation causes breaking of chemical bonds and destruction of the surface layer in polyimide, deterioration of its optical properties, etc. In low-Earth orbits serious danger for polymeric materials is atomic oxygen of the upper atmosphere of the Earth, which is the main component in the range of heights of 200-800 km. Due to the orbital spacecraft velocity, the collision energy of oxygen atoms with the surface ( 5 eV) enhances their reactivity and opens additional pathways of their reaction with near-surface layers of materials. Hyperthermal oxygen atom flow causes erosion of the polyimide surface by breaking chemical bonds and forming of volatiles products (primarily, CO and CO _{2}), which leads to mass losses and degradation of material properties. Combined effect of protons and oxygen plasma is expected to give rise to synergistic effects enhancing the destruction of polyimide surface layers. This paper describes experimental investigation of polyimide films sequential irradiation with protons and oxygen plasma. The samples were irradiated by 500 keV protons at fluences of 10 ^{14}-10 ^{16} cm ^{-2} produced with SINP cascade generator KG-500 and 5-20 eV neutral oxygen atoms at fluence of 10 ^{20} cm ^{-2} generated by SINP magnetoplasmodynamics accelerator. The proton bombardment causes the decrease in optical transmission coefficient of samples, but their transmittance recovers partially after the exposure to oxygen plasma. The results of the comparative analysis of polyimide optical transmission spectra, Raman and XPS spectra obtained at different stages of the irradiation of samples, data on mass loss of samples due to erosion of the surface are

  9. Precision Measurements of the 278 keV {sup 14}N(p,{gamma}) and the 151 keV {sup 18}O(p,{alpha}) Resonance Parameters

    SciTech Connect

    Borowski, M.; Lieb, K. P.; Uhrmacher, M.; Bolse, W.

    2009-01-28

    In thin film technology, analytical methods for monitoring the deposition of oxide and nitride coatings and the effects of corrosive, laser and ion-beam treatments have attracted considerable attention. For depth-profiling the concentrations of light isotopes, resonant nuclear reaction analysis is an excellent non-destructive ion-beam analytical tool. We report here on precision measurements of the 278 keV {sup 14}N(p,{gamma}) and the 151 keV {sup 18}O(p,{alpha}) resonances using the high-resolution proton beam of the Goettingen IONAS accelerator. The deduced resonance energies E{sub R} and total widths {gamma}(in the laboratory system) are E{sub R} = 277.60(27) keV and {gamma} = 1115(33) eV for the {sup 14}N(p,{gamma}) resonance, and E{sub R} = 150.97(26) keV and {gamma} = 178(35) eV for the {sup 18}O(p,{alpha}) resonance. These values are significantly more precise than the ones quoted in the literature.

  10. Possible low energy (E less than keV) nonthermal X-ray events. [analysis of proportional counter detector data from OGO-5

    NASA Technical Reports Server (NTRS)

    Kahler, S. W.

    1973-01-01

    A search of the 3- to 30-keV data from the NRL proportional counter detector on the Orbiting Geophysical Observatory-5 (OGO-5) satellite has yielded several events which may be nearly completely nonthermal in the e greater than 3 and less than 10 keV range. In each case an impulsive hard X-ray burst accompained by an impulsive microwave burst was associated with a low energy X-ray burst whose profile was a simple rise and fall. The lack of a two component nature in the low energy range argues that the low energy X-ray flux is due to a single physical mechanism, in this case nonthermal bremsstrahlung from accelerated electrons. However, the spectra and time profiles are quite consistent with a thermal interpretation. Polarization measurements are probably necessary to resolve the physical origin of such bursts.

  11. Absolute Calibration of Image Plate for electrons at energy between 100 keV and 4 MeV

    SciTech Connect

    Chen, H; Back, N L; Eder, D C; Ping, Y; Song, P M; Throop, A

    2007-12-10

    The authors measured the absolute response of image plate (Fuji BAS SR2040) for electrons at energies between 100 keV to 4 MeV using an electron spectrometer. The electron source was produced from a short pulse laser irradiated on the solid density targets. This paper presents the calibration results of image plate Photon Stimulated Luminescence PSL per electrons at this energy range. The Monte Carlo radiation transport code MCNPX results are also presented for three representative incident angles onto the image plates and corresponding electron energies depositions at these angles. These provide a complete set of tools that allows extraction of the absolute calibration to other spectrometer setting at this electron energy range.

  12. Compact focusing spectrometer: Visible (1 eV) to hard x-rays (200 keV)

    NASA Astrophysics Data System (ADS)

    Baronova, E. O.; Stepanenko, A. M.; Pereira, N. R.

    2014-11-01

    A low-cost spectrometer that covers a wide range of photon energies can be useful to teach spectroscopy, and for simple, rapid measurements of the photon spectrum produced by small plasma devices. The spectrometer here achieves its wide range, nominally from 1 eV to 200 keV, with a series of spherically and cylindrically bent gratings or crystals that all have the same shape and the same radius of curvature; they are complemented by matching apertures and diagnostics on the Rowland circle that serves as the circular part of the spectrometer's vacuum vessel. Spectral lines are easily identified with software that finds their positions from the dispersion of each diffractive element and the known energies of the lines.

  13. Fragmentation of H2O by 1 -- 5 keV He^2+ ions: Experiment and Theory

    NASA Astrophysics Data System (ADS)

    Stolterfoht, N.; Hellhammer, R.; Sobocinski, P.; Cabrera-Trujillo, R.; Ohrn, Y.; Deumens, E.; Sabin, J.

    2006-05-01

    Fragmentation of H2O molecules induced by ^3He^2+ impact was investigated experimentally as a function of the energy in the range from 1-5 keV. Collisions at large impact parameters are found to produce fragment protons with energies centered around peaks at 6 eV and 15 eV. The H^+ fragments were detected in the angular range from 25 to 135 with respect to the incident beam direction. Absolute fragmentation cross sections dσ/dφ, differential in the emission angle are found to be anisotropic, with protons preferentially emitted at angles near 90 . In addition to the experiments, we performed quantum-mechanical calculations to understand the fragmentation mechanisms producing protons at preferred energies and angles. The theoretical results are obtained using the Electron-Nuclear Dynamics formalism (END), which solves the time-dependent Schr"odinger equation.

  14. Differential cross sections for scattering of 0.5-, 1.5-, and 5.0 keV oxygen atoms by He, N2, and O2

    NASA Technical Reports Server (NTRS)

    Schafer, D. A.; Newman, J. H.; Smith, K. A.; Stebbings, R. F.

    1987-01-01

    This paper reports measurements of absolute scattering cross sections, differential in angle, for collisions of ground-state oxygen atoms with He, N2, and O2. Data are presented for scattering of 0.5-, 1.5-, and 5.0-keV oxygen-atom projectiles in the range of laboratory frame angles between 0.06 and 5 deg. These measurements provide information relevant to calculations of the aeronomic consequences of O(+) precipitation in the earth's upper atmosphere.

  15. The 5-10 keV AGN luminosity function at 0.01 < z < 4.0

    NASA Astrophysics Data System (ADS)

    Fotopoulou, S.; Buchner, J.; Georgantopoulos, I.; Hasinger, G.; Salvato, M.; Georgakakis, A.; Cappelluti, N.; Ranalli, P.; Hsu, L. T.; Brusa, M.; Comastri, A.; Miyaji, T.; Nandra, K.; Aird, J.; Paltani, S.

    2016-03-01

    The active galactic nuclei (AGN) X-ray luminosity function traces actively accreting supermassive black holes and is essential for the study of the properties of the AGN population, black hole evolution, and galaxy-black hole coevolution. Up to now, the AGN luminosity function has been estimated several times in soft (0.5-2 keV) and hard X-rays (2-10 keV). AGN selection in these energy ranges often suffers from identification and redshift incompleteness and, at the same time, photoelectric absorption can obscure a significant amount of the X-ray radiation. We estimate the evolution of the luminosity function in the 5-10 keV band, where we effectively avoid the absorbed part of the spectrum, rendering absorption corrections unnecessary up to NH ~ 1023 cm-2. Our dataset is a compilation of six wide, and deep fields: MAXI, HBSS, XMM-COSMOS, Lockman Hole, XMM-CDFS, AEGIS-XD, Chandra-COSMOS, and Chandra-CDFS. This extensive sample of ~1110 AGN (0.01 < z < 4.0, 41 < log Lx < 46) is 98% redshift complete with 68% spectroscopic redshifts. For sources lacking a spectroscopic redshift estimation we use the probability distribution function of photometric redshift estimation specifically tuned for AGN, and a flat probability distribution function for sources with no redshift information. We use Bayesian analysis to select the best parametric model from simple pure luminosity and pure density evolution to more complicated luminosity and density evolution and luminosity-dependent density evolution (LDDE). We estimate the model parameters that describe best our dataset separately for each survey and for the combined sample. We show that, according to Bayesian model selection, the preferred model for our dataset is the LDDE. Our estimation of the AGN luminosity function does not require any assumption on the AGN absorption and is in good agreement with previous works in the 2-10 keV energy band based on X-ray hardness ratios to model the absorption in AGN up to redshift three

  16. Effect of 200 keV Ar{sup +} implantation on optical and electrical properties of polyethyleneterepthalate (PET)

    SciTech Connect

    Kumar, Rajiv Goyal, Meetika Sharma, Ambika; Aggarwal, Sanjeev; Sharma, Annu; Kanjilal, D.

    2015-05-15

    In the present paper we have discussed the effect of 200 keV Ar{sup +} ions on the electrical and optical properties of PET samples. PET samples were implanted with 200 keV Ar{sup +} ions to various doses ranging from 1×10{sup 15} to 1×10{sup 17} Ar{sup +} cm{sup 2}. The changes in the electrical and optical properties of pristine and implanted PET specimens have been studied by using Keithley electrometer and UV-Visible absorption spectroscopy. The electrical conductivity has found to be increased with increasing ion dose. The optical studies have revealed the drastic alterations in optical band gap from 3.63 eV to 1.48 eV and also increase in number of carbon atoms per cluster from 215 to 537. Further, the change in the electrical conductivity and optical band gap has also been correlated with the formation of conductive islands in the implanted layers of PET.

  17. Attosecond keV x-ray pulses driven by Thomson scattering in a tight focus regime

    NASA Astrophysics Data System (ADS)

    Kim, D.; Lee, H.; Chung, S.; Lee, K.

    2009-06-01

    The radiation of a relativistic electron interacting with a co-propagating tightly focused high-power laser is investigated. High-order fields (HOFs) existing in a tight focus (a few micrometers or so) affect the dynamics of electrons rather significantly so as to enhance radiation intensity by several orders of magnitude. In the case of a co-propagating interaction geometry, the second-order field plays an important role in radiation enhancement. It is demonstrated that when HOFs are included, the radiation efficiency is increased by a factor of up to 100 000 for w0 = 2 and 5 μm, with a laser intensity of 2.2×1020 W cm-2, compared with that when HOFs are not included. The enhancement is larger for smaller electron energies and laser beam waists. It has also been shown that when an electron bunch interacts with a high-intensity tightly-focused femtosecond laser pulse in a co-propagation geometry, attosecond (~300 as) x-ray pulses can be produced. The photon energy can reach about 40 keV for an electron energy of 2 GeV. The physical scheme investigated in this work can be used for an ultrafast (attosecond or femtosecond) x-ray source in the range of 10-100 keV.

  18. Laser-driven 6-16 keV x-ray imaging and backlighting with spherical crystals

    NASA Astrophysics Data System (ADS)

    Schollmeier, M.; Rambo, P. K.; Schwarz, J.; Smith, I. C.; Porter, J. L.

    2014-10-01

    Laser-driven x-ray self-emission imaging or backlighting of High Energy Density Physics experiments requires brilliant sources with keV energies and x-ray crystal imagers with high spatial resolution of about 10 μ m. Spherically curved crystals provide the required resolution when operated at near-normal incidence, which minimizes image aberrations due to astigmatism. However, this restriction dramatically limits the range of suitable crystal and spectral line combinations. We present a survey of crystals and spectral lines for x-ray backlighting and self-emission imaging with energies between 6 and 16 keV. Ray-tracing simulations including crystal rocking curves have been performed to predict image brightness and spatial resolution. Results have been benchmarked to experimental data using both Sandia's 4 kJ, ns Z-Beamlet and 200 J, ps Z-Petawatt laser systems. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. SAND NO. 2014-15552A.

  19. Efficient focusing of 8 keV X-rays with multilayer Fresnel zone plates fabricated by atomic layer deposition and focused ion beam milling.

    PubMed

    Mayer, Marcel; Keskinbora, Kahraman; Grévent, Corinne; Szeghalmi, Adriana; Knez, Mato; Weigand, Markus; Snigirev, Anatoly; Snigireva, Irina; Schütz, Gisela

    2013-05-01

    Fresnel zone plates (FZPs) recently showed significant improvement by focusing soft X-rays down to ~10 nm. In contrast to soft X-rays, generally a very high aspect ratio FZP is needed for efficient focusing of hard X-rays. Therefore, FZPs had limited success in the hard X-ray range owing to difficulties of manufacturing high-aspect-ratio zone plates using conventional techniques. Here, employing a method of fabrication based on atomic layer deposition (ALD) and focused ion beam (FIB) milling, FZPs with very high aspect ratios were prepared. Such multilayer FZPs with outermost zone widths of 10 and 35 nm and aspect ratios of up to 243 were tested for their focusing properties at 8 keV and shown to focus hard X-rays efficiently. This success was enabled by the outstanding layer quality thanks to ALD. Via the use of FIB for slicing the multilayer structures, desired aspect ratios could be obtained by precisely controlling the thickness. Experimental diffraction efficiencies of multilayer FZPs fabricated via this combination reached up to 15.58% at 8 keV. In addition, scanning transmission X-ray microscopy experiments at 1.5 keV were carried out using one of the multilayer FZPs and resolved a 60 nm feature size. Finally, the prospective of different material combinations with various outermost zone widths at 8 and 17 keV is discussed in the light of the coupled wave theory and the thin-grating approximation. Al2O3/Ir is outlined as a promising future material candidate for extremely high resolution with a theoretical efficiency of more than 20% for as small an outermost zone width as 10 nm at 17 keV. PMID:23592622

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

    SciTech Connect

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

    1990-12-01

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

  1. Influence of ~7 keV sterile neutrino dark matter on the process of reionization

    NASA Astrophysics Data System (ADS)

    Rudakovskyi, Anton; Iakubovskyi, Dmytro

    2016-06-01

    Recent reports of a weak unidentified emission line at ~3.5 keV found in spectra of several matter-dominated objects may give a clue to resolve the long-standing problem of dark matter. One of the best physically motivated particle candidate able to produce such an extra line is sterile neutrino with the mass of ~7 keV . Previous works show that sterile neutrino dark matter with parameters consistent with the new line measurement modestly affects structure formation compared to conventional cold dark matter scenario. In this work, we concentrate for the first time on contribution of the sterile neutrino dark matter able to produce the observed line at ~3.5 keV, to the process of reionization. By incorporating dark matter power spectra for ~7 keV sterile neutrinos into extended semi-analytical `bubble' model of reionization we obtain that such sterile neutrino dark matter would produce significantly sharper reionization compared to widely used cold dark matter models, impossible to `imitate' within the cold dark matter scenario under any reasonable choice of our model parameters, and would have a clear tendency of lowering both the redshift of reionization and the electron scattering optical depth (although the difference is still below the existing model uncertainties). Further dedicated studies of reionization (such as 21 cm measurements or studies of kinetic Sunyaev-Zeldovich effect) will thus be essential for reconstruction of particle candidate responsible the ~3.5 keV line.

  2. HEAO 3 upper limits to the expected 1634 KeV line from SS 483

    NASA Technical Reports Server (NTRS)

    Wheaton, W. A.; Ling, J. C.; Mahoney, W. A.; Jacobson, A. S.

    1985-01-01

    A model based on 24 Mg(1369) was developed as the source of the lines in which refractory grains in the jets, containing Mg and 0, are bombarded, by ambient protons in the local ISM. The narrowness of the features results because the recoil Mg nucleus is stopped in the grain before the 1369 keV excited state decays. A consequence of the 24 Mg interpretation is the expected appearance of other emission lines, due to 20 Ne and 20 Na, which are produced by proton bombardment of 24 Mg at the 33 MeV/nucleon energy corresponding to the velocity of the jets. These lines appear at rest energies of 1634 keV and 1636 keV, respectively, and should have essentially the same total flux as that emited at 1369 keV. The HEAO 3 data are examined to search for the 1634 keV (rest) emission. The observation and analysis, the results, and the implications for the understanding of SS 433 are discussed.

  3. Maskless implants of 20 keV Ga{sup +} in thin crystalline silicon on insulator

    SciTech Connect

    Mio, A. M.; D'Arrigo, G.; Rimini, E.; Spinella, C.; Milazzo, R. G.; Peto, L.; Nadzeyka, A.; Bauerdick, S.

    2013-01-28

    A nano-sized ion beam apparatus has been used as maskless lithography to implant 20 keV Ga{sup +} ions into a 26 nm thick silicon crystalline film on insulator. The ion beam, with about 5 nm standard deviation, delivered few hundred ions during a single shot. Circular areas with nominal diameter of 20 or 50 nm were irradiated to a fluence of 5 Multiplication-Sign 10{sup 14}/cm{sup 2}. Transmission electron microscopy evidenced that the damaged regions are characterized by an irregular contour with many disordered filaments. Damage extends across the layer thickness and fast Fourier transform analysis indicates that implantation causes the amorphization of a region which extends beyond the nominal diameter. In situ annealing experiments demonstrated that the disordered filamentary regions disappear in the 250-450 Degree-Sign C temperature range and the interfaces with the surrounding crystalline regions sharpen. A temperature as high as 600 Degree-Sign C is required to fully re-crystallize the amorphous core of the implanted dots. Reordering occurs by multi-orientation lateral solid-phase epitaxial growth and the breaking of (111) and (101) interfaces, due to the formation of twins, triggers a fast crystallization kinetics. Rapid thermal annealing (890 Degree-Sign C-10 s) completely crystallizes the amorphous regions, twins are absent and small cluster of defects remains instead. Preliminary scanning capacitance measurements indicate that the implanted atoms, after crystallization, are electrically active. The implant method is then a viable processing step for the doping of non-bulk fully depleted ultra-thin-body MOSFET.

  4. Improving the energy response of external beam therapy (EBT) GafChromic{sup TM} dosimetry films at low energies (≤100 keV)

    SciTech Connect

    Bekerat, H. Devic, S.; DeBlois, F.; Singh, K.; Sarfehnia, A.; Seuntjens, J.; Shih, Shelley; Yu, Xiang; Lewis, D.

    2014-02-15

    Purpose: Purpose of this work is to investigate the effects of varying the active layer composition of external beam therapy (EBT) GafChromic{sup TM} films on the energy dependence of the film, as well as try to develop a new prototype with more uniform energy response at low photon energies (⩽100 keV). Methods: First, the overall energy response (S{sub AD,} {sub W}(Q)) of different commercial EBT type film models that represent the three different generations produced to date, i.e., EBT, EBT2, and EBT3, was investigated. Pieces of each film model were irradiated to a fixed dose of 2 Gy to water for a wide range of beam qualities and the corresponding S{sub AD,} {sub W}(Q) was measured using a flatbed document scanner. Furthermore, the DOSRZnrc Monte Carlo code was used to determine the absorbed dose to water energy dependence of the film, f(Q). Moreover, the intrinsic energy dependence, k{sub bq}(Q), for each film model was evaluated using the corresponding S{sub AD,} {sub W}(Q) and f(Q). In the second part of this study, the authors investigated the effects of changing the chemical composition of the active layer on S{sub AD,} {sub W}(Q). Finally, based on these results, the film manufacturer fabricated several film prototypes and the authors evaluated their S{sub AD,} {sub W}(Q). Results: The commercial EBT film model shows an under response at all energies below 100 keV reaching 39% ± 4% at about 20 keV. The commercial EBT2 and EBT3 film models show an under response of about 27% ± 4% at 20 keV and an over response of about 16% ± 4% at 40 keV.S{sub AD,} {sub W}(Q) of the three commercial film models at low energies show strong correlation with the corresponding f{sup −1}(Q) curves. The commercial EBT3 model with 4% Cl in the active layer shows under response of 22% ± 4% at 20 keV and 6% ± 4% at about 40 keV. However, increasing the mass percent of chlorine makes the film more hygroscopic which may affect the stability of the film's readout. The

  5. Dwarf galaxy γ-excess and 3.55 keV X-ray line in a nonthermal Dark Matter model

    NASA Astrophysics Data System (ADS)

    Biswas, Anirban; Majumdar, Debasish; Roy, Probir

    2016-01-01

    Recent data from Reticulum II (RetII) require the energy range of the FermiLAT γ-excess to be ∼2\\text-10 \\text{GeV} . We adjust our unified nonthermal Dark Matter (DM) model to accommodate this. We have two extra scalars beyond the Standard Model to also explain the 3.55 keV X-ray line. Now the mass of the heavier of them has to be increased to lie around 250 GeV, while that of the lighter one remains at 7.1 keV. This requires a new seed mechanism for the γ-excess and new Boltzmann equations for the generation of the DM relic density. All concerned data for RetII and the X-ray line can now be fitted well and consistency with other indirect limits attained.

  6. Sputtering and surface structure modification of gold thin films deposited onto silicon substrates under the impact of 20-160 keV Ar+ ions

    NASA Astrophysics Data System (ADS)

    Mammeri, S.; Ouichaoui, S.; Ammi, H.; Dib, A.

    2014-10-01

    The induced sputtering and surface state modification of Au thin films bombarded by swift Ar+ ions under normal incident angle have been studied over an energy range of (20-160) keV using three complementary techniques: Rutherford backscattering spectroscopy (RBS), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The sputtering yields determined by RBS measurements using a 2 MeV 4He+ ion beam were found to be consistent with previous data measured within the Ar+ ion energy region E ⩽ 50 keV, which are thus extended to higher bombarding energies. Besides, the SEM and XRD measurements clearly point out that the irradiated Au film surfaces undergo drastic modifications with increasing the Ar+ ion energy, giving rise to the formation of increasingly sized grains of preferred (1 1 1) crystalline orientations. The relevance of different sputtering yield models for describing experimental data is discussed with invoking the observed surface effects induced by the Ar+ ion irradiation.

  7. The response of a fast phosphor screen scintillator (ZnO:Ga) to low energy ions (0-60 keV)

    SciTech Connect

    Jimenez-Rey, D.; Rodriguez-Barquero, L.

    2010-10-15

    ZnO:Ga is a promising, high time resolution candidate for use as a fast-ion-loss detector in TJ-II. We compare its ionoluminescence with that of the standard fast-ion-loss detector material, SrGa{sub 2}S{sub 4}:Eu (also known as TG-Green), when irradiated by H{sup +} ions with a range of energies E{<=}60 keV using a dedicated laboratory setup. It is found that ZnO:Ga is a reasonably good candidate for detecting low energy (E<60 keV) ions as it has excellent time resolution; however, its sensitivity is about 100 times lower than TG-Green, potentially limiting it to applications with high energy ion loss signals.

  8. Angular dependence of L X-rays emission for Ag by 10 keV electron-impact

    NASA Astrophysics Data System (ADS)

    Wang, Xing; Xu, Zhongfeng; Zhang, Ying; Ma, Chao; Zhu, Chengwei

    2016-08-01

    The characteristic X-ray intensities of Ag-Lα, Lβ1, Lβ2 and Lγ1 are measured in electron-impact ionization at energy of 10 keV. The emission angle in this work ranges from 0° to 20° at interval of 5°. The angular dependence of L X-ray intensity ratios has been investigated for Lα / Lβ1, Lβ2 / Lβ1 and Lγ1 / Lβ1. It is found from the experimental results that the emissions of Lβ1, Lβ2 and Lγ1 X-rays are spatially isotropic, while the Lα X-rays exhibit anisotropic emission. Consequently, the alignment behavior of vacancy states is discussed with thorough analysis of vacancy transfer process.

  9. One-sided imaging of large, dense objects using the 511 keV photons from induced pair production

    SciTech Connect

    Tavora, L.M.; Gilboy, W.B.; Morton, E.J.; Morgado, R.E.; Estep, R.J.; Rawool-Sullivan, M.

    1998-03-01

    The use of annihilation photons from photon-induced electron-positron pair production as a means of inspecting objects when only one side is accessible is described. The Z2 dependence of the pair production cross section and the high penetration of 511 keV photons suggest that this method should be capable of localizing high Z materials in lower Z matrices. The experimental results for the dependence of the back streaming photon yield on Z indicate that dynamic ranges of the order of 20 may be obtained for materials with 4 < Z < 82. Results for point to point images obtained in line scans of representative geometries are also shown. Simulation studies based on the EGS4 Monte Carlo code were also performed and their results show an agreement with experimental data of the order of 5%.

  10. 20-100 keV K(alpha) X-Ray Source Generation by Short Pulse High Intensity Lasers

    SciTech Connect

    Park, H-S; Koch, J A; Landen, O L; Phillips, T W; Goldsack, T

    2003-08-22

    We are studying the feasibility of utilizing K{alpha} x-ray sources in the range of 20 to 100 keV as a backlighters for imaging various stages of implosions and high areal density planar samples driven by the NIF laser facility. The hard x-ray K{alpha} sources are created by relativistic electron plasma interactions in the target material after a radiation by short pulse high intensity lasers. In order to understand K{alpha} source characteristics such as production efficiency and brightness as a function of laser parameters, we have performed experiments using the 10 J, 100 fs JanUSP laser. We utilized single-photon counting spectroscopy and x-ray imaging diagnostics to characterize the K{alpha} source. We find that the K{alpha} conversion efficiency from the laser energy is {approx} 3 x 10{sup -4}.

  11. Structural and magnetic properties of zinc ferrite thin films irradiated by 90 keV neon ions

    NASA Astrophysics Data System (ADS)

    Gafton, E. V.; Bulai, G.; Caltun, O. F.; Cervera, S.; Macé, S.; Trassinelli, M.; Steydli, S.; Vernhet, D.

    2016-08-01

    The effects of 90 keV neon beam irradiation on the structure and magnetic properties of zinc ferrite thin films have been investigated through several methods, namely, X-ray diffraction technique, Vibrating Sample and SQUID magnetometers. Beforehand, the pristine have also been characterized using profilometry and microscopy techniques. In particular single-phase formation of the thin films deposited on monocrystalline Si (111) substrate by pulsed laser deposition technique was confirmed. Crystal lattice, coercivity, saturation magnetization have been studied for the first time, as a function of ion penetration depth and irradiation fluence. The chemical composition and the crystallinity of the films are not affected with the ion impact acting as a mechanical stress relief. On the contrary, both magnetization and coercivity are sensitive to Neq+ ion irradiation and exhibit different behaviours depending on the ion fluence range.

  12. Cross sections for ionization of tetrahydrofuran by protons at energies between 300 and 3000 keV

    NASA Astrophysics Data System (ADS)

    Wang, Mingjie; Rudek, Benedikt; Bennett, Daniel; de Vera, Pablo; Bug, Marion; Buhr, Ticia; Baek, Woon Yong; Hilgers, Gerhard; Rabus, Hans

    2016-05-01

    Double-differential cross sections for ionization of tetrahydrofuran by protons with energies from 300 to 3000 keV were measured at the Physikalisch-Technische Bundesanstalt ion accelerator facility. The electrons emitted at angles between 15∘ and 150∘ relative to the ion-beam direction were detected with an electrostatic hemispherical electron spectrometer. Single-differential and total ionization cross sections have been derived by integration. The experimental results are compared to the semiempirical Hansen-Kocbach-Stolterfoht model as well as to the recently reported method based on the dielectric formalism. The comparison to the latter showed good agreement with experimental data in a broad range of emission angles and energies of secondary electrons. The scaling property of ionization cross sections for tetrahydrofuran was also investigated. Compared to molecules of different size, the ionization cross sections of tetrahydrofuran were found to scale with the number of valence electrons at large impact parameters.

  13. Imager of low energy neutral atoms (ILENA) - Imaging neutrals from the magnetosphere at energies below 20 keV

    NASA Technical Reports Server (NTRS)

    Herrero, Federico A.; Smith, Mark F.

    1992-01-01

    We describe a new imager suitable for measurements of magnetospheric neutrals with energies from about 100 eV to about 10 keV; an energy range adequate for imaging the plasmasheet neutral atoms out to about 10 R(E). The instrument, an outgrowth of a study of atom-surface collisions in support of satellite drag calculations, separates incident photons from neutral atoms by surface scattering and conversion of the neutrals to ions. Subsequently, the ions formed on the first surface are accelerated through a light rejection section which also disperses the ions according to energy. The dispersed ion beam is then allowed to impact a second surface where a start pulse is generated to obtain ion velocity and energy/charge. The second surface is chosen to give large secondary electron emission without regard to charge state of the particles reflected from it. The data supporting the proposed ILENA design is presented in the first part of the paper.

  14. Guidelines for using a 10-keV x-ray source for hardness assurance

    SciTech Connect

    Fleetwood, D.M.

    1986-01-01

    In this paper, work done at Sandia is summarized that demonstrates that it is possible to use a 10-keV x-ray source for hardness assurance. Transistor data is presented that shows that a 10-keV x-ray source can be used as a reliable process monitor, in the sense that Co-60 part response can be predicted easily and reliably from x-ray part response. Further, test structure and functional part data is presented that illustrates how an x-ray source may be employed for wafer lot acceptance for silicon-gate CMOS devices that either employ quardbands or hardened field oxides for device isolation. Finally, a few words are said about the use of high-Z gate metallizations. These results should provide guidelines for implementation of lot acceptance testing with a 10-keV x-ray source.

  15. Evaluation of the 1077 keV γ-ray emission probability from 68Ga decay

    NASA Astrophysics Data System (ADS)

    Huang, Xiao-Long; Jiang, Li-Yang; Chen, Xiong-Jun; Chen, Guo-Chang

    2014-04-01

    68Ga decays to the excited states of 68Zn through the electron capture decay mode. New recommended values for the emission probability of 1077 keV γ-ray given by the ENSDF and DDEP databases all use data from absolute measurements. In 2011, JIANG Li-Yang deduced a new value for 1077 keV γ-ray emission probability by measuring the 69Ga(n,2n) 68Ga reaction cross section. The new value is about 20% lower than values obtained from previous absolute measurements and evaluations. In this paper, the discrepancies among the measurements and evaluations are analyzed carefully and the new values are re-recommended. Our recommended value for the emission probability of 1077 keV γ-ray is (2.72±0.16)%.

  16. The Morphology of the X-ray Emission above 2 keV from Jupiter's Aurorae

    NASA Technical Reports Server (NTRS)

    Elsner, R.; Branduardi-Raymont, G.; Galand, M.; Grodent, D.; Waite, J. H.; Cravens, T.; Ford, P.

    2007-01-01

    The discovery in XMM-Newton X-ray data of X-ray emission above 2 keV from Jupiter's aurorae has led us to reexamine the Chandra ACIS-S observations taken in Feb 2003. Chandra's superior spatial resolution has revealed that the auroral X-rays with E > 2 keV are emitted from the periphery of the region emitting those with E < 1 keV. We are presently exploring the relationship of this morphology to that of the FUV emission from the main auroral oval and the polar cap. The low energy emission has previously been established as due to charge exchange between energetic precipitating ions of oxygen and either sulfur or carbon. It seems likely to us that the higher energy emission is due to precipitation of energetic electrons, possibly the same population of electrons responsible for the FUV emission. We discuss our analysis and interpretation.

  17. Hydrogenation kinetics in oxidized boron-doped silicon irradiated by keV electrons

    NASA Astrophysics Data System (ADS)

    Lin, Wallace Wan-Li; Sah, Chih-Tang

    1988-08-01

    Hydrogenation kinetics of boron acceptors in oxidized silicon during and after repeated 8-keV electron irradiation (225-2700-μC/cm2 stresses and 10-168-h interirradiation anneals) at room temperature are reported. Hydrogenation proceeds rapidly during irradiation but continues for many hours after the 8-keV electron beam is removed. Postoxidation process dependencies show that postoxidation and postmetallization annealing processes reduce the hydrogenation effect during the 8-keV electron irradiation, while exposure of the oxide to water prior to aluminum electrode deposition enhances it. The data can be interpreted by our two-reaction model consisting of the hydrogen capture reaction by the boron acceptor and the hydrogen recombination reaction to form hydrogen molecule.

  18. Hyper-filter-fluorescer spectrometer for x-rays above 120 keV

    DOEpatents

    Wang, Ching L.

    1983-01-01

    An apparatus utilizing filter-fluorescer combinations is provided to measure short bursts of high fluence x-rays above 120 keV energy, where there are no practical absorption edges available for conventional filter-fluorescer techniques. The absorption edge of the prefilter is chosen to be less than that of the fluorescer, i.e., E.sub.PRF E.sub.F. In this way, the response function is virtually zero between E.sub.PRF and E.sub.F and well defined and enhanced in an energy band of less than 1000 keV above the 120 keV energy.

  19. An overview of energetic particles (from 55 keV to > 30 MeV) recorded in the close Martian environment, and their energization in local and external processes

    NASA Astrophysics Data System (ADS)

    McKenna-Lawlor, S.; Afonin, V. V.; Kirsch, E.; Schwingenschuh, K.; Slavin, J. A.; Trotignon, J. G.

    1998-01-01

    Observations made by the SLED particle detector on Phobos-2 in the close Martian environment from 29 January to 27 March, 1989 during the early rising phase of Solar Cycle 22, show the frequent presence close to the planet, under reasonably "quiet" interplanetary conditions, of particles with energies ( E) in the range from several tens of, to several hundred, keV. Under disturbed interplanetary circumstances, particles reaching energies of several tens of MeV were recorded close to Mars. Those particles in the keV range were observed at well-defined locations, i.e. at the Terminator Shocks ( E up to ≈600 keV); just inside the subsolar Planetopause ( E up to ≈225 keV), and travelling down the Tail, E≥55 keV. These three populations are herein suggested, instancing various candidate mechanisms, to have been energized by processes local to the planet. Since the seed particles for ions accelerated at the Terminator Shocks may comprise ambient, pre-accelerated, solar particles, the energies of ions detected by SLED during Bow Shock transits was observed (during two months) to vary between ≈50 keV and ≈600 keV. Particles with energies up to several tens of MeV which were found to suffuse the close planetary environment over extended periods, are interpreted to have been produced in association with solar processes external to Mars (Co-rotating Interaction Regions; Gradual and Impulsive Solar Events). Particle enhancements in the keV range recorded by SLED (under favourable magnetic conditions) during Bow Shock traversals, provide topographical information concerning the location of the Martian subsolar and distant shock surfaces. These observations constitute a new data set, complementary to those determinations of key boundaries derived from plasma and magnetic field measurements made aboard various American and Russian spacecraft at Mars which, for more than thirty years now, have been generally used in modelling the Solar Wind interaction with the planet

  20. Charge dynamics of MgO single crystals subjected to KeV electron irradiation

    NASA Astrophysics Data System (ADS)

    Boughariou, A.; Blaise, G.; Braga, D.; Kallel, A.

    2004-04-01

    A scanning electron microscope has been equipped to study the fundamental aspects of charge trapping in insulating materials, by measuring the secondary electron emission (SEE) yield σ with a high precision (a few percent), as a function of energy, electron current density, and dose. The intrinsic secondary electron emission yield σ0 of uncharged MgO single crystals annealed at 1000 °C, 2 h, has been studied at four energies 1.1, 5, 15, and 30 keV on three different crystal orientations (100), (110), and (111). At low energies (1.1 and 5 keV) σ0 depends on the crystalline orientation wheras at high energies (30 keV) no differentiation occurs. It is shown that the value of the second crossover energy E2, for which the intrinsic SEE yield σ0=1, is extremely delicate to measure with precision. It is about 15 keV±500 eV for the (100) orientation, 13.5 keV±500 eV for the (110), and 18.5 keV±500 eV for the (111) one. At low current density J⩽105 pA/cm2, the variation of σ with the injected dose makes possible the observation of a self-regulated regime characterized by a steady value of the SEE yield σst=1. At low energies 1.1 and 5 keV, there is no current density effects in MgO, but at high energies ≈30 keV, apparent current density effects come from a bad collect of secondary electrons, due to very high negative surface potential. At 30 keV energy, an intense erratic electron exoemission was observed on the MgO (110) orientation annealed at 1500 °C. This phenomenon is the result of a disruptive process similar to flashover, which takes place at the surface of the material.

  1. Discovery of a 3.5 keV line in the Galactic Centre and a critical look at the origin of the line across astronomical targets

    NASA Astrophysics Data System (ADS)

    Jeltema, Tesla; Profumo, Stefano

    2015-06-01

    We examine the claimed excess X-ray line emission near 3.5 keV including both a new analysis of XMM-Newton observations of the Milky Way centre and a reanalysis of the data on M 31 and clusters. In no case do we find conclusive evidence for an excess. In the case of the Galactic Centre, we show that known plasma lines, including in particular K XVIII lines at 3.48 and 3.52 keV, provide a satisfactory fit to the XMM data. We estimate the expected flux of the K XVIII lines and find that the measured line flux falls squarely within the predicted range based on the brightness of other well-measured lines in the energy range of interest and on detailed multitemperature plasma models. We then re-assess the evidence for excess emission from clusters of galaxies, allowing for systematic uncertainty in the expected flux from known plasma lines and additional uncertainty due to potential variation in the abundances of different elements. We find that no conclusive excess line emission can be advocated when considering systematic uncertainties in Perseus or in other clusters. We also reanalyse the XMM data for M 31 and find no statistically significant line emission near 3.5 keV to a level greater than 1σ. Finally, we analyse the Tycho supernova remnant, which shows similar plasma features to the sources above, but does not host any significant dark matter. We detect a 3.55 keV line from Tycho, which points to possible systematic effects in the flux determination of weak lines, or to relative elemental abundances vastly different from theoretical expectations.

  2. Optical excitation function of H(1s-2p) produced by electron impact from threshold to 1.8 keV

    SciTech Connect

    James, G.K.; Slevin, J.A.; Shemansky, D.E.; McConkey, J.W.; Bray, I.; Dziczek, D.; Kanik, I.; Ajello, J.M.

    1997-02-01

    The optical excitation function of prompt Lyman-{alpha} radiation, produced by electron impact on atomic hydrogen, has been measured over the extended energy range from threshold to 1.8 keV. Measurements were obtained in a crossed-beams experiment using both magnetically confined and electrostatically focused electrons in collision with atomic hydrogen produced by an intense discharge source. A vacuum-ultraviolet monochromator system was used to measure the emitted Lyman-{alpha} radiation. The absolute H(1s-2p) electron impact excitation cross section was obtained from the experimental optical excitation function by normalizing to the accepted optical oscillator strength, with corrections for polarization and cascade. Our data are significantly different from the earlier experimental results and which are limited to energies below 200 eV. Statistical and known systematic uncertainties in our data range from {plus_minus}4{percent} near threshold to {plus_minus}2{percent} at 1.8 keV. Multistate coupling affecting the shape of the excitation function up to 1 keV impact energy is apparent in both the present experimental data and present theoretical results obtained with convergent close-coupling (CCC) theory. This shape function effect leads to an uncertainty in absolute cross sections at the 10{percent} level in the analysis of the experimental data. The derived optimized absolute cross sections are within 7{percent} of the CCC calculations over the 14 eV{endash}1.8 keV range. The present CCC calculations converge on the Bethe-Fano profile for H(1s-2p) excitation at high energy. For this reason agreement with the CCC values to within 3{percent} is achieved in a nonoptimal normalization of the experimental data to the Bethe-Fano profile. The fundamental H(1s-2p) electron impact cross section is thereby determined to an unprecedented accuracy over the 14 eV {endash} 1.8 keV energy range. (Abstract Truncated)

  3. Observations of 12-200 keV X-rays from GX 339-4

    NASA Technical Reports Server (NTRS)

    Nolan, P. L.; Gruber, D. E.; Knight, F. K.; Matteson, J. L.; Peterson, L. E.; Levine, A. M.; Lewin, W. H. G.; Primini, F. A.

    1982-01-01

    X-ray spectra of GX 339-4 measured on three occasions in 1977 and 1978 are presented. These are the first reported measurements above 10 keV. The spectra can be described as the superposition of a soft component, which is dominant below about 20 keV, and a hard component at higher energy. Simultaneous measurements at lower energy show that the soft component vanished during the observation in early 1978. The behavior of these two components is similar to that of the spectrum of Cygnus X-1; this reinforces the previously noted resemblance in rapid X-ray variability.

  4. Tomographic scanning microscope for 1-4 KeV x-rays

    SciTech Connect

    McNulty, I.; Feng, Y.P.; Hadda, W.S.; Trebes, J.E.

    1995-12-31

    X-ray microtomography enables three-dimensional imaging at submicron resolution with elemental and chemical state contrast. The 1-4 KeV energy region is promising for microtomography of biological, microelectronics, and materials sciences specimens. To capitalize on this potential, we are constructing a tomographic scanning x-ray microscope for 1-4 KeV x-ray on a spherical grating monochromator beamline at the Advance Photon Source. The microscope, which uses zone plate optics, has an anticipated spatial resolution of 100 nm and an energy resolution of better than 1 eV.

  5. 3.55 keV line in minimal decaying dark matter scenarios

    SciTech Connect

    Arcadi, Giorgio; Covi, Laura; Dradi, Federico

    2015-07-20

    We investigate the possibility of reproducing the recently reported 3.55 keV line in some simple decaying dark matter scenarios. In all cases a keV scale decaying DM is coupled with a scalar field charged under SM gauge interactions and thus capable of pair production at the LHC. We will investigate how the demand of a DM lifetime compatible with the observed signal, combined with the requirement of the correct DM relic density through the freeze-in mechanism, impacts the prospects of observation at the LHC of the decays of the scalar field.

  6. Realistic Sterile Neutrino Dark Matter with KeV Mass does not Contradict Cosmological Bounds

    SciTech Connect

    Boyarsky, Alexey; Lesgourgues, Julien; Ruchayskiy, Oleg

    2009-05-22

    Previous fits of sterile neutrino dark matter (DM) models to cosmological data ruled out masses smaller than {approx}8 keV, assuming a production mechanism that is not the best motivated from a particle physics point of view. Here we focus on a realistic extension of the standard model with three sterile neutrinos, consistent with neutrino oscillation data and baryogenesis, with the lightest sterile neutrino being the DM particle. We show that for each mass {>=}2 keV there exists at least one model accounting for 100% of DM and consistent with Lyman-{alpha} and other cosmological, astrophysical, and particle physics data.

  7. 511 keV line from Q balls in the galactic center

    SciTech Connect

    Kasuya, Shinta; Takahashi, Fuminobu

    2005-10-15

    The 511 keV photons from the galactic center can be explained by positrons produced through Q-ball decay. In the scheme of gauge-mediated supersymmetry breaking, large Q balls with lepton charge are necessarily long-lived. In particular, the lifetime can be as long as (or even longer than) the age of the Universe. If kinematically allowed, such large Q balls decay into positrons, which eventually annihilate with electrons into 511 keV photons. Our scenario is realized within the minimal supersymmetric standard model in the inflationary universe, which is very plausible.

  8. A multilayer grating with a novel layer structure for a flat-field spectrograph attached to transmission electron microscopes in energy region of 2-4 keV

    SciTech Connect

    Imazono, T.; Koike, M.; Koeda, M.; Nagano, T.; Sasai, H.; Oue, Y.; Yonezawa, Z.; Kuramoto, S.; Terauchi, M.; Takahashi, H.; Handa, N.; Murano, T.

    2012-05-17

    A multilayer mirror with a novel layer structure to uniformly enhance the reflectivity in a few keV energy range at a fixed angle of incidence is invented and applied to a multilayer grating for use in a flat-field spectrograph attached to a conventional electron microscope. The diffraction efficiency of the fabricated multilayer grating having the new layer structure is evaluated at the angle of incidence of 88.65 deg. in the energy region of 2.1-4.0 keV. It is shown that the multilayer grating is effective to uniformly enhance the diffraction efficiency and able to be practically used in this energy region.

  9. Dynamical framework for KeV Dirac neutrino warm dark matter

    NASA Astrophysics Data System (ADS)

    Robinson, Dean J.; Tsai, Yuhsin

    2014-08-01

    If the source of the reported 3.5 keV x-ray line is a sterile neutrino, comprising an O(1) fraction of the dark matter (DM), then it exhibits the property that its mass times mixing angle is ˜ few×10-2 eV, a plausible mass scale for the active neutrinos. This property is a common feature of Dirac neutrino mixing. We present a framework that dynamically produces light active and keV sterile Dirac neutrinos, with appropriate mixing angles to be the x-ray line source. The central idea is that the right-handed active neutrino is a composite state, while elementary sterile neutrinos gain keV masses similarly to the quarks in extended technicolor. The entire framework is fixed by just two dynamical scales and may automatically exhibit a warm dark matter (WDM) production mechanism—dilution of thermal relics from late decays of a heavy composite neutrino—such that the keV neutrinos may comprise an O(1) fraction of the DM. In this framework, the WDM is typically quite cool and within structure formation bounds, with temperature ˜ few×10-2Tν and free-streaming length ˜ few kpc. A toy model that exhibits the central features of the framework is also presented.

  10. Using a 10-keV x-ray source for hardness assurance

    SciTech Connect

    Fleetwood, D.M.; Beegle, R.W.; Sexton, F.W.; Winokur, P.S.; Miller, S.L.; Schwank, J.R.; Jones, R.V.; McWhorter, P.J.

    1986-01-01

    It is shown that a 10 keV x-ray source can be used to predict the responses of microelectronic circuits to Co-60 irradiation. Guidelines for using an x-ray tester in a hardness assurance program for VLSI CMOS circuits are suggested. 5 refs., 2 figs., 1 tbl.

  11. Constraining models for keV sterile neutrinos by quasidegenerate active neutrinos

    NASA Astrophysics Data System (ADS)

    Merle, Alexander

    2012-12-01

    We present a no-go theorem for keV sterile neutrino dark matter: if sterile neutrinos at the keV scale play the role of dark matter, they are typically unstable and their decay produces an astrophysical monoenergetic x-ray line. It turns out that the observational bound on this line is so strong that it contradicts the existence of a quasidegenerate spectrum of active neutrinos in a seesaw type I framework where the Casas-Ibarra matrix R is real. This is the case in particular for models without CP violation. We give a general proof of this theorem. While the theorem (like every no-go theorem) relies on certain assumptions, the situation under which it applies is still sufficiently general to lead to interesting consequences for keV neutrino model building. In fact, depending on the outcome of the next generation experiments, one might be able to rule out whole classes of models for keV sterile neutrinos.

  12. Field aligned currents and the auroral spectrum below 1 keV

    NASA Technical Reports Server (NTRS)

    Arnoldy, R. L.

    1973-01-01

    Measurements during auroral events were conducted with the aid of detectors flown aboard three Nike-Tomahawk rocket flights. The detectors used to measure the auroral spectrum below 1 keV consisted of electrostatic analyzers positioned in the rocket to measure particles moving up and down the magnetic field lines. The analyzers measured electrons and protons simultaneously during a given sweep.

  13. 20-keV undulators for a 6-GeV storage ring

    SciTech Connect

    Kim, S.H.; Cho, Y.

    1985-10-01

    The main goal of the future 6-GeV electron storage ring is to provide 20-keV fundamental harmonic radiations from insertion devices. Parameter restrictions of REC-vanadium permendur hybrid undulators have been examined. The critical factor is the achieveable minimum gap of the undulator. Variations of the spectral brilliance for different beam parameters are also shown.

  14. The 20 keV undulators for a 6-GeV storage ring

    NASA Astrophysics Data System (ADS)

    Kim, S. H.; Cho, Y.

    The main goal of the future 6-GeV electron storage ring is to provide 20-keV fundamental harmonic radiations from insertion devices. Parameter restrictions of REC-Vanadium permendur hybrid undulators were examined. The critical factor is the achievable minimum gap of the undulator. Variations of the spectral brilliance for different beam parameters are also shown.

  15. The Solar Flare 4: 10 keV X-ray Spectrum

    NASA Technical Reports Server (NTRS)

    Phillips, K. J. H.

    2004-01-01

    The 4-10 keV solar flare spectrum includes highly excited lines of stripped Ca, Fe, and Ni ions as well as a continuum steeply falling with energy. Groups of lines at approximately 7 keV and approximately 8 keV, observed during flares by the broad-band RHESSI spectrometer and called here the Fe-line and Fe/Ni-line features, are formed mostly of Fe lines but with Ni lines contributing to the approximately 8 keV feature. Possible temperature indicators of these line features are discussed - the peak or centroid energies of the Fe-line feature, the line ratio of the Fe-line to the Fe/Ni-line features, and the equivalent width of the Fe-line feature. The equivalent width is by far the most sensitive to temperature. However, results will be confused if, as is commonly believed, the abundance of Fe varies from flare to flare, even during the course of a single flare. With temperature determined from the thermal continuum, the Fe-line feature becomes a diagnostic of the Fe abundance in flare plasmas. These results are of interest for other hot plasmas in coronal ionization equilibrium such as stellar flare plasmas, hot gas in galaxies, and older supernova remnants.

  16. Energetic electron fluxes (E180 KeV) observed by the Giotto experiment EPA during encounter with Comet Halley

    NASA Astrophysics Data System (ADS)

    Kirsch, E.; McKenna-Lawlor, S.; Thompson, A.; Osullivan, D.; Neubauer, F. M.

    1986-12-01

    The Energetic Particle Detector system EPA/EPONA onboard Giotto detects ions and electrons with energies greater than 20 keV in various energy channels. In this paper, electron fluxes are presented together with data from the Giotto Magnetometer Experiment. Electrons >180 keV were recorded from the transit of the foreshock, inbound, until the last observation outbound at approximately 03:00 UT on 15 March 1986. Energy spectra for the inbound pass are shown. One flux enhancement in the >300 keV channel and several in the >180 keV channel were recorded outbound. Possible acceleration mechanisms for the energetic electrons are considered.

  17. Improvements of the standardization of (134)Cs by the critical window setting for 605keV photopeak.

    PubMed

    Yunoki, Akira; Kawada, Yasushi; Hino, Yoshio

    2016-03-01

    In the standardization of (134)Cs by the 4πβ-γ coincidence method with a γ-window at 605keV, the satellite components of 563keV and 569keV overlapping the 605keV peak cause a steep slope and non-linearity of the efficiency extrapolation function. By shifting the lower threshold of a γ-window higher, the satellite components are eliminated, and the slope tends to horizontal. Nearly flat efficiency curves were obtained by using a CeBr3 scintillator for detecting γ-photons, as well as a NaI(Tl) scintillator. PMID:26702547

  18. Elastic and inelastic processes in H{sup +}+C{sub 2}H{sub 6} collisions below the 10-keV regime

    SciTech Connect

    Suzuki, Reiko; Rai, Sachchida N.; Liebermann, Heinz-Peter; Buenker, Robert J.; Pichl, Lukas; Kimura, Mineo

    2005-11-15

    Charge-transfer processes in collisions of H{sup +} ions with C{sub 2}H{sub 6} molecules are investigated theoretically below 10-keV collision energies within a molecular representation. Converged total as well as differential cross sections are obtained in this energy range within a discrete basis of electronic states computed by ab inito methods. The present collision system suggests that the combination of the Demkov-type and Landau-Zener-type mechanisms primarily governs the scattering dynamics for the flux exit from the initial channel. The present charge-transfer cross sections determined are found to agree very well with all available experimental data below a few keV, but begin to deviate above 3 keV, in which the present results slowly decrease, while measurements stay nearly constant. From the study of the electronic state calculation, we provide some information on fragmented species, which should help shed some light on the fragmentation mechanism and process of C{sub 2}H{sub 6}{sup +} ions produced after charge transfer. In addition, the vibrational effect of the initial target to charge transfer is examined.

  19. KEY COMPARISON: International key comparison of 24 keV neutron fluence measurements (1993-2009): CCRI(III)-K1

    NASA Astrophysics Data System (ADS)

    Thomas, D. J.; Lewis, V. E.; Klein, H.; Allisy-Roberts, P. J.

    2010-01-01

    A comparison of 24.5 keV neutron fluence standards was organized by Section III (Neutron Measurements) of the Comité Consultatif des Rayonnements Ionisants, (CCRI). The exercise involved the circulation of a set of three different-diameter Bonner spheres for calibration in fields with energies around 24.5 keV. The fields were produced using four different methods of neutron production. The responses (counts per unit neutron fluence) of the individual spheres were initially determined for the neutron energy of the production method, or methods, employed. To derive the 24.5 keV responses, it was necessary to make corrections for spectral effects, and these were achieved by using response functions for the spheres calculated using the code MCNP. The results demonstrate good consistency within the estimated uncertainties (ranging from about 5% to 10% at the 95% confidence level) between the results reported by all the participants. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCRI Section III, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

  20. High Voltage-Cylinder Sector Analyzer 300/15: a cylindrical sector analyzer for electron kinetic energies up to 15 keV.

    PubMed

    Rubio-Zuazo, J; Escher, M; Merkel, M; Castro, G R

    2010-04-01

    We have developed an energy analyzer, High Voltage-Cylinder Sector Analyzer 300/15, for electron kinetic energies up to 15 keV. It is especially suited for hard x-ray photoelectron spectroscopy, but also for ultraviolet and soft x-ray photoelectron spectroscopy (ultraviolet photoemission spectroscopy, x-ray photoemission spectroscopy), Auger electron spectroscopy, and reflection high energy electron spectroscopy. The analyzer is based on a cylinder sector with 90 degrees deflection, 300 mm slit-to-slit distance, and a four-element pre-retarding lens system with 50 mm sample-to-lens distance. The result is a very compact design of the analyzer that is easily integrated into a multipurpose experiment with different techniques. A low noise/low drift electronics is capable of continuous energy scans from 0 to 15 keV using nonlinear lens curves. The first analyzer is allocated at the Spanish CRG SpLine beamline at the ESRF at an end station where simultaneous surface x-ray diffraction is possible. The analyzer is operated routinely since 2006 up to 15 keV electron kinetic energy, expanding the achievable electron kinetic energy range compared to other commercial analyzers. In this work we present a detailed description of the developed electron analyzer. The analyzer capabilities, in terms of energy resolution and transmission, are shown by using an electron gun, an ultraviolet-discharge lamp, and hard x-ray synchrotron radiation as excitation sources. PMID:20441333

  1. Soft x-ray (0.2keV) imager for z-pinch plasma radiation sources

    SciTech Connect

    Failor, B.H.; Qi, N.; Levine, J.S.; Sze, H.; Gullickson, E.M.

    2004-10-01

    Z-pinches can produce intense fluxes of argon K-shell (3 keV) radiation, but typically only a fraction of the load mass near the axis of the pinch radiates in this spectral range. The majority of the mass does not get hot or dense enough to radiate efficiently in the K-shell. We have designed, built, and tested an instrument to image pinch emission, specifically the radial emission profile, at energies below the K-shell in order to track the location of the cooler mass. A gold mirror provides a high-energy cut-off at 2 keV while a transmission grating disperses the incoming radiation and provides a low-energy cutoff at 0.1 keV. A vertical slit images the pinch radiation in the radial direction and the emission profile is recorded with either an extreme ultraviolet-sensitive charge-coupled device camera (time-integrated) or a linear photodiode array ({approx}1 ns time resolution). We present results for the mirror, grating, and system characterization obtained at the Advanced Light Source synchrotron located at Lawrence Berkeley National Laboratory (Berkeley, CA)

  2. Spectral Analysis on Solar Flares with an Emission > 300 keV

    NASA Astrophysics Data System (ADS)

    Vargas, R.; Connaughton, V.

    2013-12-01

    The continuum gamma-ray emission from solar flares is caused when a population of electrons is accelerated to relativistic speeds and interacts with the solar plasma. However, it has been theorized that the gamma-ray emission from some brighter flares comes from two populations of electrons. Using the Gamma-Ray Burst Monitor (GBM), we studied the gamma-ray emission spectra of solar flares and paid special attention to the solar flares that showed emission above 300 keV. We found that the emission above 300 keV was better fit with a broken power-law than a single power-law, evidence that the gamma-ray emission from certain solar flares involved two populations of electrons. Specifically, our best model involved a broken power law that had a steeper slope before the break in energy than after. We studied the spectral parameters as a function of time during the period of the high-energy emission. We also found that solar flares with emission above 300 keV form a small subset (~4%) of flares that trigger GBM above 20 keV. One of the flares with an emission greater than 300 keV was fitted with a Broken Power Law model. Only data from the BGO detector was used in making the plots. Various parameters of the fit have been plotted vs. time with the top two graphs representing the light curves of the flare from different detectors (BGO-0 and NaI-4). A spectral fit for bn100612038 for the time interval of [45s-50s] using only the BGO (0) detector file. Data from this fit was used in creating the other plots.

  3. Uranium enrichment measurements using the intensity ratios of self-fluorescence X-rays to 92* keV gamma ray in UXK alpha spectral region.

    PubMed

    Yücel, H; Dikmen, H

    2009-04-30

    In this paper, the known multigroup gamma-ray analysis method for uranium (MGAU) as one of the non-destructive gamma-ray spectrometry methods has been applied to certified reference nuclear materials (depleted, natural and enriched uranium) containing (235)U isotope in the range of 0.32-4.51% atom (235)U. Its analysis gives incorrect results for the low component (235)U in depleted and natural uranium samples where the build-up of the decay products begins to interfere with the analysis. The results reveal that the build-up of decay products seems to be significant and thus the algorithms for the presence of decay products should be improved to resulting in the correct enrichment value. For instance, for the case of (235)U analysis in depleted uranium or natural ore samples, self-induced X-rays such as 94.6 keV and 98.4 keV lying in UXK(alpha) spectral region used by MGAU can be excluded from the calculation. Because the significant increases have been observed in the intensities of uranium self-induced X-rays due to gamma-ray emissions with above 100 keV energy arising from decay products of (238)U and (235)U and these parents. Instead, the use of calibration curve to be made between the intensity ratios of self-fluorescence X-rays to 92(*)keV gamma-ray and the certified (235)U abundances is suggested for the determination of (235)U when higher amounts of decay products are detected in the gamma-ray spectrum acquired for the MGAU analysis. PMID:19203602

  4. Performance of a 6 mm thick CdTe detector for 166 keV gamma rays

    NASA Astrophysics Data System (ADS)

    McKee, B. T. A.; Goetz, T.; Hazlett, T.; Forkert, L.

    1988-11-01

    In order to extend the utility of CdTe detectors to higher gamma ray energies, yet avoid increasing the charge collection problems of thick detectors, a 6 mm thick detector configuration has been developed consisting of three crystals 2 mm thick and of 16 mm diameter. The active volume is over 1.0 cm 3. The performance of this detector has been evaluated for gamma rays of 166 keV energy by measuring the pulse height spectra and determining the intrinsic peak and total efficiencies over a range of bias voltages and amplifier time constants. A maximum peak and total efficiency of 41% and 80% were obtained with 200 V bias and 2 μs amplifier time constant, although under these conditions the noise width was almost 40 keV FWHM. A Monte Carlo model was used to simulate the gamma ray and electron interaction in this 6 mm detector. Charge collection, including trapping effects, was incorporated into the model. The model pulse height spectra could be approximately matched to the measured data using hole and electron effective mobility values of 60 and 600 cm 2/V s, and hole and electron mean trapping times of 25 and 15 μs. Our findings indicate that detectors such as this will not be useful for high resolution spectroscopic applications, but the high gamma ray stopping power will be of interest for applications where the noise width is acceptable. Results from the modelling imply that in this detector shallow trapping sites (reducing the effective mobility) are more important than deep trapping sites in contributing to incomplete charge collection.

  5. A Deep 0.3-10 keV Spectrum of the H2O Maser Galaxy IC 2560

    NASA Astrophysics Data System (ADS)

    Tilak, Avanti; Greenhill, Lincoln J.; Done, Chris; Madejski, Grzegorz

    2008-05-01

    We present a new XMM-Newton spectrum of the Seyfert 2 nucleus of IC 2560, which hosts H2O maser emission from an inclined Keplerian accretion disk. The X-ray spectrum shows soft excess due to multitemperature ionized plasma, a hard continuum, and strong emission features, from Mg, Si, S, Ca, Fe, and Ni, mainly due to fluorescence. It is consistent with reflection of the continuum from a mostly neutral medium and obscuration due to a high column density, >1024 cm-2. The amplitude of the reflected component may exceed 10% of the central unobscured luminosity. This is higher than the reflected fraction of a few percent observed in other Seyfert 2 sources such as NGC 4945. We observe an emission line at 6.7 keV, possibly due to Fe XXV, undetected in previous Chandra observations. The absorption column density associated with this line is less than 1023 cm-2, which is lower than the obscuration of the central source. We hypothesize that this highly ionized Fe line emission originates in warm gas, which is also responsible for a scattered component of continuum emission that may dominate the spectrum between 1 and 3 keV. We compare X-ray and maser emission characteristics of IC 2560 and other AGNs that exhibit water maser emission originating in disk structures around central engines. The temperature for the region of the disk associated with maser action is consistent with the expected 400-1000 K range. The clumpiness of disk structures (inferred from the maser distribution) may depend on the unobscured luminosities of the central engines.

  6. Effect of 800 keV argon ions pre-damage on the helium blister formation of tungsten exposed to 60 keV helium ions

    NASA Astrophysics Data System (ADS)

    Chen, Zhe; Han, Wenjia; Yu, Jiangang; Zhu, Kaigui

    2016-04-01

    This study aims to investigate the effect of Ar8+ ions pre-damage on the following He2+ irradiation behavior of polycrystalline tungsten. We compared the irradiation resistance performance against 60 keV He2+ ions of undamaged tungsten samples with that of pre-damaged samples which were preliminarily exposed to 800 keV Ar8+ ions at a fluence of 4 × 1019 ions m-2. The experimental results indicate that the helium blistering of tungsten could be effectively relieved by the Ar8+ ions pre-damage, while the retention of helium around low energy desorption sites in the pre-damaged tungsten was larger than that of the undamaged samples. A strong orientation dependence of blistering had been observed, with the blister occurred preferentially on the surface of grains with normal direction close to <111>. The Ar8+ ions irradiation-induced damage altered the morphology of helium bubbles in tungsten exposed to the following He2+ irradiation significantly. The intensity of helium release peaks at relatively low temperatures (<600 K) was enhanced due to Ar8+ ions pre-damage.

  7. Efficient laser-induced 6-8 keV x-ray production from iron oxide aerogel and foil-lined cavity targets

    SciTech Connect

    Perez, F.; Kay, J. J.; Patterson, J. R.; Kane, J.; May, M.; Emig, J.; Colvin, J.; Gammon, S.; Satcher, J. H. Jr.; Fournier, K. B.; Villette, B.; Girard, F.; Reverdin, C.; Sorce, C.; Jaquez, J.

    2012-08-15

    The performance of new iron-based laser-driven x-ray sources has been tested at the OMEGA laser facility for production of x rays in the 6.5-8.5 keV range. Two types of targets were experimentally investigated: low-density iron oxide aerogels (density 6-16 mg/cm{sup 3}) and stainless steel foil-lined cavity targets (steel thickness 1-5 {mu}m). The targets were irradiated by 40 beams of the OMEGA laser (500 J/beam, 1 ns pulse, wavelength 351 nm). All targets showed good coupling with the laser, with <5% of the incident laser light backscattered by the resulting plasma in all cases (typically <2.5%). The aerogel targets produced T{sub e}=2 to 3 keV, n{sub e}=0.12-0.2 critical density plasmas yielding a 40%-60% laser-to-x-ray total conversion efficiency (CE) (1.2%-3% in the Fe K-shell range). The foil cavity targets produced T{sub e}{approx} 2 keV, n{sub e}{approx} 0.15 critical density plasmas yielding a 60%-75% conversion efficiency (1.6%-2.2% in the Fe K-shell range). Time-resolved images illustrate that the volumetric heating of low-density aerogels allow them to emit a higher K-shell x-ray yield even though they contain fewer Fe atoms. However, their challenging fabrication process leads to a larger shot-to-shot variation than cavity targets.

  8. The low energy particle detector sled (~30 keV-3.2 MeV) and its performance on the phobos mission to mars and its moons

    NASA Astrophysics Data System (ADS)

    McKenna-Lawlor, S.; Afonin, V. V.; Gringauz, K. I.; Keppler, E.; Kirsch, E.; Richter, A.; Witte, M.; O'Sullivan, D.; Thompson, A.; Somogyi, A. J.; Szabo, L.; Varga, A.

    1990-05-01

    A low energy particle detector system (SLED) is described which was designed to measure the flux densities of electrons and ions in the energy range from ~30 keV to a few MeV in (a) the varying solar aspect angles and temperatures pertaining during the Cruise Phase of the Phobos Mission and (b) in the low temperature environment (reaching -25° C) pertaining during Mars Encounter. Representative data illustrating the excellent functioning of SLED during both phases of the mission are presented.

  9. Fission cross section measurements of Cm-247, Cf-250 and Es-254 from 0. 1 eV to 80 keV

    SciTech Connect

    Danon, Y.; Slovacek, R.E.; Block, R.C. . Dept. of Nuclear Engineering and Engineering Physics); Lougheed, R.W.; Hoff, R.W. ); Moore, M.S. )

    1990-01-01

    Fission cross section measurements were made with the RINS system over the neutron energy range from approximately 0.1 eV to 80 keV upon samples of Cm-247, Cf-250 and Es-254. The Cm-247 measurement was undertaken to complete the RINS fission cross section measurement sequence of the curium isotopes, Es-254 was measured because it is a very heavy odd-odd nucleus which might show interesting nuclear structure effects in its fission cross section, and Cf-250 was measured to account for its buildup as a daughter product from the 276-day halflife Es-254. 6 refs., 3 figs.

  10. One-ampere, 80-keV, long pulse H - source and accelerator

    NASA Astrophysics Data System (ADS)

    Kwan, J. W.; Ackerman, G. D.; Anderson, O. A.; Chan, C. F.; Cooper, W. S.; deVries, G. J.; Lietzke, A. F.; Soroka, L.; Steele, W. F.

    1986-05-01

    The design and operation of the surface-conversion H- ion source and the 80-keV preaccelerator are discussed. Both the source and the preaccelerator, together with the transverse field focusing (TFF) matching and pumping beam transport section (presently being tested), will be parts of a negative-ion-based neutral beam line. Results from testing the source and preaccelerator have shown that the system can accelerate more than 1 A of H- ions at 80 keV continuously; the preaccelerator operates at an optimum perveance which matches the one predicted by WOLF code computer simulation. Deconditioning of the preaccelerator due to cesium contamination is a critical problem. A method has been developed to cope with this problem.