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1

Hard x-ray spectra from laser-generated plasmas recorded by the HENEX spectrometer in the 1 keV40 keV energy range  

Microsoft Academic Search

Hard x-ray spectra were recorded by the High Energy Electronic X-Ray (HENEX) spectrometer from a variety of targets irradiated by the Omega laser at the Laboratory for Laser Energetics. The HENEX spectrometer utilizes four reflection crystals covering the 1 keV to 20 keV energy range and one quartz(10-11) transmission crystal (Laue geometry) covering the 11 keV to 40 keV range.

J. F. Seely; C. A. Back; C. Constantin; R. W. Lee; H.-K. Chung; L. T. Hudson; C. I. Szabo; A. Henins; G. E. Holland; R. Atkin

2005-01-01

2

Modeling the Chandra High Energy Transmission Gratings below 2 keV  

E-print Network

Modeling the Chandra High Energy Transmission Gratings below 2 keV K.A. Flanagana, T.H. Markerta, J The High Energy Transmission Grating Spectrometer of the Chandra X-Ray Observatory is a high spectral it below 2 keV to complete the coverage over the Chandra energy range. We investigate the carbon, nitrogen

3

Secondary ion emission from keV energy atomic and polyatomic projectile impacts on sodium iodate  

E-print Network

Secondary ion emission from keV energy atomic and polyatomic projectile impacts on sodium iodate M ion yield generated from keV energy polyatomic ion impacts on a sodium iodate surface is characteristic of ion emission expected from sodium iodide (i.e. (NaI)nI ), yet x-ray photoelectron spectroscopy

Goodman, Wayne

4

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

SciTech Connect

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.

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

5

Transmission crystal x-ray spectrometer covering the 6 keV-18 keV energy range with E??E = 1800 instrumental resolving power.  

PubMed

A high-resolution x-ray spectrometer utilizing a thin quartz transmission crystal and covering the 6 keV-18 keV energy range has been developed and tested. The spectrometer consists of a cylindrically bent crystal in a vacuum housing. The crystal position and the range of Bragg angles that are incident on the crystal can be adjusted to record an ?4 keV wide spectrum in the 6 keV-18 keV range. The spectrometer is of the Cauchois type and has a compact linear geometry that is convenient for deployment at laser-produced plasma, EBIT, and other x-ray sources. Test spectra of the W L and Mo K lines from laboratory sources have linewidths as small as 11 eV, approaching the natural widths, and instrumental resolving power as high as 1800. Techniques for enhancing the energy resolution are experimentally demonstrated. PMID:23126934

Seely, John; Feldman, Uri; Brown, Charles; Pereira, Nino; Hudson, Lawrence; Glover, Jack; Silver, Eric

2012-10-01

6

Energy loss and angular dispersion of 2-200 keV protons in amorphous silicon  

NASA Astrophysics Data System (ADS)

The energy loss of 2-200 keV protons in thin amorphous silicon foils has been measured for projectiles transmitted in the forward direction and as a function of the exit angle. At the lowest energies, differences of up to 30% with recently published values are observed. Angular effects in the energy loss, at low and high energies, have been investigated. The low-energy results are reproduced by model calculations and Monte Carlo simulations, which indicate that the inelastic energy loss does not show a dependence upon the impact parameter in the low energy region. A fitting formula for the present energy loss values is provided.

Famá, M.; Lantschner, G. H.; Eckardt, J. C.; Arista, N. R.; Gayone, J. E.; Sanchez, E.; Lovey, F.

2002-06-01

7

IBEX Heliospheric neutral atom energy spectra between 0.01 and 6 keV  

NASA Astrophysics Data System (ADS)

Since early 2009, 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 ~0.5 keV. For the globally distributed population, many neutrals in this energy range are produced by pick up (ionization) of interstellar neutrals in the heliosphere, convection across the termination shock, and a second charge exchange in the heliosheath. With more than 2 years of observations, enough low energy neutral atom measurements have been accumulated to extend IBEX observations down to energies below ~0.5 keV. At these energies, contributions from two additional populations of low energy neutral atoms from the heliosheath become significant. The first population is produced by charge exchange of interstellar neutrals in the heliosheath, beyond the termination shock, and a second charge exchange in the same region. The second population is produced by charge exchange between much slower solar wind ions in the heliosheath and interstellar neutrals. Using the energy overlap of the sensors and observations in different regions near the Earth to identify and remove backgrounds, energy spectra over the entire energy range of IBEX are produced. Compared to spectra at higher energies, neutral atom spectra at lower energies do not vary greatly from location to location in the sky, including in the direction of the IBEX ribbon. Implications for these observations on global heliospheric structure and interactions are discussed.

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

2011-12-01

8

Two zone plate interference contrast microscopy at 4 keV photon energy  

Microsoft Academic Search

The setup and first successful tests of an interference contrast microscope operating at a photon energy of 4 keV (? = 0.31 nm) is described. The interference contrast microscope is based on the full-field X-ray microscope operating at the ID21 beamline at the European Synchrotran Radiation Facility with the difference that two zone plates are used for the image generation

T. Wilhein; B. Kaulich; J. Susini

2001-01-01

9

Absolute detection efficiencies for keV energy atoms incident on a microchannel plate detector  

NASA Astrophysics Data System (ADS)

The absolute detection efficiencies of a microchannel plate detector (MCP) were determined experimentally for neutral hydrogen, carbon, and tungsten atoms with impact energies of 0.5-4.5 keV. We measured detection efficiencies using our recently developed method, which uses coincidence counting between neutralized incident ions and ionized target atoms in single-electron capture collisions. The obtained detection efficiencies showed similar impact-energy and mass dependence to those of rare gas atoms (Ne, Ar, Kr, and Xe), measured previously using our method. The detection efficiencies increased with increasing impact energy and converged to the open area ratio (?50%) of the MCP used. The efficiencies at fixed energies decreased as the mass of the incident atom increased. The absolute detection efficiencies obtained for H, C, W, Ne, Ar, Kr, and Xe atoms could be scaled according to the average electron emission yield estimated using the formulas for electronic and nuclear stopping powers.

Takahashi, N.; Adachi, Y.; Saito, M.; Haruyama, Y.

2013-11-01

10

Energy and position resolution of germanium microstrip detectors at x-ray energies from 15 to 100 keV  

SciTech Connect

In addition to their far greater X-ray detection efficiency, germanium strip detectors offer superior energy and position resolution as compared to those fabricated of silicon for energies in the range of 15 to 100 keV. The authors have characterized 200-[micro]m strip pitch detectors fabricated by two different processes. By scanning a 10-[micro]m-wide monochromatic synchrotron X-ray beam across these detectors, measurements were made on both spectral energy response and spatial resolution. X rays absorbed between neighboring diode strips suffer from charge diffusion splitting of their signals which seriously degrades the detector performance, but by reconstructing events using an energy-sum coincidence algorithm the authors succeeded in producing artifact-free spectra with energy resolution <2 keV, peak/valley ratios > 1000, and count uniformities across the detector surface <1.5% for energies below 60 keV. The experimentally measured energy spectra show remarkable agreement with those predicted by computer simulation, in which the EGS4 code for photon absorption is combined with a simple algorithm to account for charge diffusion.

Rossi, G.; Morse, J. (European Synchrotron Radiation Facility, Grenoble (France)); Protic, D. (Forschungszentrum Juelich GmbH (Germany). Inst. fuer Kernphysik)

1999-06-01

11

SURVIVAL DEPTH OF ORGANICS IN ICES UNDER LOW-ENERGY ELECTRON RADIATION ({<=}2 keV)  

SciTech Connect

Icy surfaces in our solar system are continually modified and sputtered with electrons, ions, and photons from solar wind, cosmic rays, and local magnetospheres in the cases of Jovian and Saturnian satellites. In addition to their prevalence, electrons specifically are expected to be a principal radiolytic agent on these satellites. Among energetic particles (electrons and ions), electrons penetrate by far the deepest into the ice and could cause damage to organic material of possible prebiotic and even biological importance. To determine if organic matter could survive and be detected through remote sensing or in situ explorations on these surfaces, such as water ice-rich Europa, it is important to obtain accurate data quantifying electron-induced chemistry and damage depths of organics at varying incident electron energies. Experiments reported here address the quantification issue at lower electron energies (100 eV-2 keV) through rigorous laboratory data analysis obtained using a novel methodology. A polycyclic aromatic hydrocarbon molecule, pyrene, embedded in amorphous water ice films of controlled thicknesses served as an organic probe. UV-VIS spectroscopic measurements enabled quantitative assessment of organic matter survival depths in water ice. Eight ices of various thicknesses were studied to determine damage depths more accurately. The electron damage depths were found to be linear, approximately 110 nm keV{sup -1}, in the tested range which is noticeably higher than predictions by Monte Carlo simulations by up to 100%. We conclude that computational simulations underestimate electron damage depths in the energy region {<=}2 keV. If this trend holds at higher electron energies as well, present models utilizing radiation-induced organic chemistry in icy solar system bodies need to be revisited. For interstellar ices of a few micron thicknesses, we conclude that low-energy electrons generated through photoionization processes in the interstellar medium could penetrate through ice grains significantly and trigger organic reactions several hundred nanometers deep-bulk chemistry thus competing with surface chemistry of astrophysical ice grains.

Barnett, Irene Li; Lignell, Antti; Gudipati, Murthy S., E-mail: gudipati@jpl.nasa.gov [Jet Propulsion Laboratory, California Institute of Technology, Mail Stop 183-301, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States)

2012-03-01

12

The Reuven Ramaty High Energy Solar Spectroscopic Imager observation of the 1809 keV line from Galactic 26Al  

E-print Network

Observations of the central radian of the Galaxy by the Reuven Ramaty High Energy Solar Spectroscopy Imager (RHESSI) have yielded a high-resolution measurement of the 1809 keV line from 26Al, detected at 11 sigma significance in nine months of data. The RHESSI result for the width of the cosmic line is 2.03 (+0.78, -1.21) keV FWHM. The best fit line width of 5.4 keV FWHM reported by Naya et al. (1996) using the Gamma-Ray Imaging Spectrometer (GRIS) balloon instrument is rejected with high confidence.

David M. Smith

2003-04-28

13

Low-energy electrons (5-50 keV) in the inner magnetosphere  

NASA Astrophysics Data System (ADS)

Transport and acceleration of the 5-50 keV electrons from the plasma sheet to geostationary orbit were investigated. These electrons constitute the low-energy part of the seed population for the high-energy MeV particles in the radiation belts and are responsible for surface charging. We modeled one nonstorm event on 24-30 November 2011, when the presence of isolated substorms was seen in the AE index. We used the Inner Magnetosphere Particle Transport and Acceleration Model (IMPTAM) with the boundary at 10 RE with moment values for the electrons in the plasma sheet. The output of the IMPTAM modeling was compared to the observed electron fluxes in 10 energy channels (from 5 to 50 keV) measured on board the AMC 12 geostationary spacecraft by the Compact Environmental Anomaly Sensor II with electrostatic analyzer instrument. The behavior of the fluxes depends on the electron energy. The IMPTAM model, driven by the observed parameters such as Interplanetary Magnetic Field (IMF) By and Bz, solar wind velocity, number density, dynamic pressure, and the Dst index, was not able to reproduce the observed peaks in the electron fluxes when no significant variations are present in those parameters. We launched several substorm-associated electromagnetic pulses at the substorm onsets during the modeled period. The observed increases in the fluxes can be captured by IMPTAM when substorm-associated electromagnetic fields are taken into account. Modifications of the pulse front velocity and arrival time are needed to exactly match the observed enhancements.

Ganushkina, N. Y.; Liemohn, M. W.; Amariutei, O. A.; Pitchford, D.

2014-01-01

14

Measurements of Neutron Capture Cross Sections for Gd Isotopes in the Energy Region from 10 keV to 90 keV  

NASA Astrophysics Data System (ADS)

The neutron capture cross sections of Gd isotopes (155Gd, 156Gd, 157Gd, and 158Gd) have been measured in the neutron energy range from 10 to 90 keV using the 3-MV Pelletron accelerator of the Research Laboratory for Nuclear Reactors at the Tokyo Institute of Technology. Pulsed keV neutrons were produced from the 7Li(p,n)7Be reaction by bombarding the lithium target with the 1.5-ns bunched proton beam from the Pelletron accelerator. The incident neutron spectrum on a capture sample was measured by means of a TOF method with a 6Li-glass detector. Capture ?-rays were detected with a large anti-Compton NaI(Tl) spectrometer, employing a TOF method. A pulse-height weighting technique was applied to observed capture ?-ray pulse-height spectra to derive capture yields. The capture cross sections were obtained by using the standard capture cross sections of 197Au. The present results were compared with the previous measurements and the evaluated values of ENDF/B-VI.

Kim, G. N.; Chung, W. C.; Ro, T. I.; Ohsaki, T.; Igashira, M.

2006-03-01

15

The development of a super-stable datum point for monitoring the energy scale of electron spectrometers in the energy range up to 20 keV  

Microsoft Academic Search

The long-term energy stability of the 7.5 keV and 17.8 keV conversion electrons of the 9.4 keV and 32 keV neutral transitions\\u000a respectively in 83mKr, emitted by solid 83Rb\\/83mKr sources, prepared by evaporation in a vacuum, is investigated using two different spectrometers. The results obtained indicate\\u000a the principal applicability of these 83Rb sources for monitoring the stability of the energy

D. Vénos; M. Zbo?il; J. Kašpar; O. Dragoun; J. Bonn; A. Kovalík; O. Lebeda; N. A. Lebedev; M. Ryšavý; K. Schlösser; A. Špalek; Ch. Weinheimer

2010-01-01

16

Monte Carlo calculations of energy deposition distributions of electrons below 20 keV in protein.  

PubMed

The distributions of energy depositions of electrons in semi-infinite bulk protein and the radial dose distributions of point-isotropic mono-energetic electron sources [i.e., the so-called dose point kernel (DPK)] in protein have been systematically calculated in the energy range below 20 keV, based on Monte Carlo methods. The ranges of electrons have been evaluated by extrapolating two calculated distributions, respectively, and the evaluated ranges of electrons are compared with the electron mean path length in protein which has been calculated by using electron inelastic cross sections described in this work in the continuous-slowing-down approximation. It has been found that for a given energy, the electron mean path length is smaller than the electron range evaluated from DPK, but it is large compared to the electron range obtained from the energy deposition distributions of electrons in semi-infinite bulk protein. The energy dependences of the extrapolated electron ranges based on the two investigated distributions are given, respectively, in a power-law form. In addition, the DPK in protein has also been compared with that in liquid water. An evident difference between the two DPKs is observed. The calculations presented in this work may be useful in studies of radiation effects on proteins. PMID:24519325

Tan, Zhenyu; Liu, Wei

2014-05-01

17

FHBS calculation of ionized electron angular and energy distribution following the p+H collision at 20 keV  

E-print Network

A Finite Hilbert Basis Set (FHBS) method to calculate the angular and energy distribution of ejected electrons in an ion-atom collision is presented. This method has been applied to the p + H collision at 20 keV impact energy. An interference effect...

Fu, Jun

2004-11-15

18

Dermatosis Papulosa Nigra and 10,600-nm CO2 laser, a good choice.  

PubMed

Dermatosis Papulosa Nigra (DPN) is a common skin condition observed in black people and considered a benign epithelial tumor, and more specifically, a particular topographic form of seborrheic keratosis. We treated five female patients affected by DPN with 10,600-nm CO2 laser. We propose the 10,600-nm CO2 laser as a valid therapeutic option in patients affected by DPN, since the treatment is well tolerated, causes no major side effects, and is effective and long lasting. PMID:24131098

Bruscino, Nicola; Conti, Rossana; Campolmi, Piero; Bonan, Paolo; Cannarozzo, Giovanni; Lazzeri, Linda; Moretti, Silvia

2014-06-01

19

Dicentric chromosomes in monolayers of human lymphocytes produced by monochromatized synchrotron radiation with photon energies from 1.83 keV to 17.4 keV  

Microsoft Academic Search

A systematic approach was used to examine the induction of dicentric chromosomes in human lymphocytes irradiated in vitro with monochromatized synchrotron radiation produced with photon energies in the range from 1.83 keV to 17.4 keV. To avoid potential confounding factors that could influence the outcome of the experiments, only blood from one individual was used. Since for the irradiation experiments with these

M. Krumrey; G. Ulm; E. Schmid

2004-01-01

20

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

NASA Astrophysics Data System (ADS)

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.

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

2014-08-01

21

Isotopic Mo Neutron Total Cross Section Measurements in the Energy Range 1 to 620 keV  

NASA Astrophysics Data System (ADS)

A series of new total cross section measurements for the stable molybdenum isotopes of 92,94,95,96,98,100Mo covering the energy range between 1 keV and 620 keV was performed at the Gaerttner LINAC Center at Rensselaer Polytechnic Institute. New high-accuracy resonance parameters were extracted from an analysis of the data using the multilevel R-matrix Bayesian code SAMMY. In the unresolved resonance region, average resonance parameters and fits to the total cross sections were obtained using the Bayesian Hauser-Feshbach statistical model code FITACS.

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

2014-05-01

22

The penetration of protons with energies of 300 to 500 keV through thin silicon crystals  

NASA Astrophysics Data System (ADS)

Angular distributions of protons ( E = 440 keV) behind a thin (1.3 to 2 ?m) <111> silicon single crystal have been measured for different angles of incidence. It is shown that for a target thickness of 2 ?m and for the angle of incidence ? equal to ? L the angular distributions are still anisotropic. The energy losses of protons for ? = 1.6 ?L and for different detection angles have been found. A reduction of energy losses for the direction parallel to the <111> axis has been revealed, which indicates the presence of a channeling fraction of the beam. For energies of 340, 440 and 550 keV, angular distribution of energy losses were measured for <111> Si. It is shown that their differences are due to different diffusion rates in the space of transverse energies. Results obtained for the proton beam directed in both channeling and random directions have been compared to existing experimental and theoretical data.

Kamyshan, A. S.; Komarov, F. F.; Kumakhov, M. A.; Liseenko, A. A.; Pozdeeva, T. V.

1992-04-01

23

Experimental study of ionization yield of liquid xenon for electron recoils in the energy range 2.8 - 80 keV  

E-print Network

We present the results of the first experimental study of ionization yield of electron recoils with energies below 100 keV produced in liquid xenon by the isotopes: 37Ar, 83mKr, 241Am, 129Xe, 131Xe. It is confirmed by a direct measurement with 37Ar isotope (2.82 keV) that the ionization yield is growing up with the energy decrease in the energy range below ~ 10 keV accordingly to the NEST predictions. Decay time of scintillation at 2.82 keV is measured to be 25 +/- 3 ns at the electric field of 3.75 kV/cm.

D. Yu. Akimov; V. V. Afanasyev; I. S. Alexandrov; V. A. Belov; A. I. Bolozdynya; A. A. Burenkov; Yu. V. Efremenko; D. A. Egorov; A. V. Etenko; M. A. Gulin; S. V. Ivakhin; V. A. Kaplin; A. K. Karelin; A. V. Khromov; M. A. Kirsanov; S. G. Klimanov; A. S. Kobyakin; A. M. Konovalov; A. G. Kovalenko; A. V. Kuchenkov; A. V. Kumpan; Yu. A. Melikyan; R. I. Nikolaev; D. G. Rudik; V. V. Sosnovtsev; V. N. Stekhanov

2014-08-08

24

Experimental study of ionization yield of liquid xenon for electron recoils in the energy range 2.8–80 keV  

NASA Astrophysics Data System (ADS)

We present the results of the first detailed experimental study of ionization yield of electron recoils with energies below 100 keV produced in liquid xenon by the isotopes 37Ar, 83mKr, 241Am, 129Xe, 131Xe. It is confirmed by a direct measurement with 37Ar isotope (2.82 keV) that the ionization yield increases with the energy decrease in the energy range below ~ 10 keV in accord with the NEST predictions. Decay time of scintillation at 2.82 keV is measured to be ? = 25 ± 3 ns at electric field 3.75 kV/cm.

Akimov, D. Yu.; Afanasyev, V. V.; Alexandrov, I. S.; Belov, V. A.; Bolozdynya, A. I.; Burenkov, A. A.; Efremenko, Yu. V.; Egorov, D. A.; Etenko, A. V.; Gulin, M. A.; Ivakhin, S. V.; Kaplin, V. A.; Karelin, A. K.; Khromov, A. V.; Kirsanov, M. A.; Klimanov, S. G.; Kobyakin, A. S.; Konovalov, A. M.; Kovalenko, A. G.; Kuchenkov, A. V.; Kumpan, A. V.; Melikyan, Yu. A.; Nikolaev, R. I.; Rudik, D. G.; Sosnovtsev, V. V.; Stekhanov, V. N.

2014-11-01

25

Experimental study of ionization yield of liquid xenon for electron recoils in the energy range 2.8 - 80 keV  

E-print Network

We present the results of the first experimental study of ionization yield of electron recoils with energies below 100 keV produced in liquid xenon by the isotopes: 37Ar, 83mKr, 241Am, 129Xe, 131Xe. It is confirmed by a direct measurement with 37Ar isotope (2.82 keV) that the ionization yield is growing up with the energy decrease in the energy range below ~ 10 keV accordingly to the NEST predictions. Decay time of scintillation at 2.82 keV is measured to be 25 +/- 3 ns at the electric field of 3.75 kV/cm.

Akimov, D Yu; Alexandrov, I S; Belov, V A; Bolozdynya, A I; Burenkov, A A; Efremenko, Yu V; Egorov, D A; Etenko, A V; Gulin, M A; Ivakhin, S V; Kaplin, V A; Karelin, A K; Khromov, A V; Kirsanov, M A; Klimanov, S G; Kobyakin, A S; Konovalov, A M; Kovalenko, A G; Kuchenkov, A V; Kumpan, A V; Melikyan, Yu A; Nikolaev, R I; Rudik, D G; Sosnovtsev, V V; Stekhanov, V N

2014-01-01

26

The prediction of thick target electron bremsstrahlung spectra in the 0.25–50 keV energy range  

Microsoft Academic Search

The importance of electron bremsstrahlung has continuously grown since its early discovery more than one century ago, increasingly being involved in different scientific areas. The present work deals with the prediction of thick-target bremsstrahlung spectrum in the frame of scanning electron microprobe analysis. X-ray energies considered range from 0.25 to 50 keV, whereas the models discussed involve electron incident energies up to

Jorge Trincavelli; Gustavo Castellano

2008-01-01

27

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

SciTech Connect

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 carbon samples together with the known experimental data from database EXFOR/CSISRS and ENDF libraries are presented.

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

2006-06-14

28

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

SciTech Connect

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 EBT3 film prototype with 7.5% Si shows a significant improvement in the energy response at very low energies compared to the commercial EBT3 films with 4% Cl. It shows under response of 15% ± 5% at about 20 keV to 2% ± 5% at about 40?keV. However, according to the manufacturer, the addition of 7.5% Si as SiO{sub 2} adversely affected the viscosity of the active fluid and therefore affected the potential use in commercial machine coating. The latest commercial EBT3 film model with 7% Al as Al{sub 2}O{sub 3} shows an overall improvement in S{sub AD,} {sub W}(Q) compared to previous commercial EBT3 films. It shows under response at all energies <100 keV, varying from 20% ± 4% at 20 keV to 6% ± 4% at 40?keV. Conclusions: The energy response of films in the energy range <100 keV can be improved by adjusting the active layer chemical composition. Removing bromine eliminated the over response at about 40?keV. The under response at energies ?30 keV is improved by adding 7% Al to the active layer in the latest commercial EBT3 film models.

Bekerat, H., E-mail: hamed.bekerat@mail.mcgill.ca; Devic, S.; DeBlois, F. [Medical Physics Unit, McGill University, Montréal, Québec H3G 1A4, Canada and Department of Radiation Oncology, Jewish General Hospital, Montréal, Québec H3T 1E2 (Canada)] [Medical Physics Unit, McGill University, Montréal, Québec H3G 1A4, Canada and Department of Radiation Oncology, Jewish General Hospital, Montréal, Québec H3T 1E2 (Canada); Singh, K.; Sarfehnia, A.; Seuntjens, J. [Medical Physics Unit, McGill University, Montréal, Québec H3G 1A4 (Canada)] [Medical Physics Unit, McGill University, Montréal, Québec H3G 1A4 (Canada); Shih, Shelley; Yu, Xiang; Lewis, D. [Ashland Specialty Ingredients, 1361 Alps Road, Wayne, New Jersey 07470 (United States)] [Ashland Specialty Ingredients, 1361 Alps Road, Wayne, New Jersey 07470 (United States)

2014-02-15

29

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)

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.

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

2013-04-01

30

Measurement of attenuation coefficients for bone, muscle, fat and water at 140, 364 and 662 keV ?-ray energies  

NASA Astrophysics Data System (ADS)

The half-value thicknesses, linear and mass attenuation coefficients of biological samples such as bone, muscle, fat and water have been measured at 140, 364 and 662 keV ?-ray energies by using the ATOMLABTM-930 medical spectrometer. The ?-rays were obtained from 99mTc, 131I and 137Cs ?-ray point sources. Also theoretical calculations have been performed in order to obtain the half-value thicknesses and, mass and linear attenuation coefficients at photon energies 0.001 keV 20 MeV for bone, muscle and water samples. The calculated value and the experimental results of this work and the other results in literature are found to be in good agreement.

Akar, A.; Balta?, H.; Çevik, U.; Korkmaz, F.; Okumu?o?lu, N. T.

2006-11-01

31

Parameterization of X-ray mass attenuation coefficients in the energy range of 1-150 keV  

Microsoft Academic Search

Knowledge of X-ray mass attenuation coefficients is necessary when the thick target PIXE method is applied for quantitative elemental analysis of materials. For this purpose, the X-ray mass attenuation coefficients of Veigele [Atom. Data Tables 5 (1973) 51] ave been parameterized in the photon energy range of 1-150 keV for all elements from hydrogen to plutonium (Z = 1-94), taking

J. Braziewicz; E. Braziewicz; M. Pajek

1993-01-01

32

Novel Method to Study Neutron Capture of U235 and U238 Simultaneously at keV Energies  

NASA Astrophysics Data System (ADS)

The neutron capture cross sections of the main uranium isotopes, U235 and U238, were measured simultaneously for keV energies, for the first time by combining activation technique and atom counting of the reaction products using accelerator mass spectrometry. New data, with a precision of 3%-5%, were obtained from mg-sized natural uranium samples for neutron energies with an equivalent Maxwell-Boltzmann distribution of kT ˜25 keV and for a broad energy distribution peaking at 426 keV. The cross-section ratio of U235(n ,?)/U238(n ,?) can be deduced in accelerator mass spectrometry directly from the atom ratio of the reaction products U236/U239, independent of any fluence normalization. Our results confirm the values at the lower band of existing data. They serve as important anchor points to resolve present discrepancies in nuclear data libraries as well as for the normalization of cross-section data used in the nuclear astrophysics community for s-process studies.

Wallner, A.; Belgya, T.; Bichler, M.; Buczak, K.; Dillmann, I.; Käppeler, F.; Lederer, C.; Mengoni, A.; Quinto, F.; Steier, P.; Szentmiklosi, L.

2014-05-01

33

Sub-second variations of high energy ( 300 keV) hard X-ray emission from solar flares  

NASA Technical Reports Server (NTRS)

Subsecond variations of hard X-ray emission from solar flares were first observed with a balloon-borne detector. With the launch of the Solar Maximum Mission (SMM), it is now well known that subsecond variations of hard X-ray emission occur quite frequently. Such rapid variations give constraints on the modeling of electron energization. Such rapid variations reported until now, however, were observed at relatively low energies. Fast mode data obtained by the Hard X-ray Burst Spectrometer (HXRBS) has time resolution of approximately 1 ms but has no energy resolution. Therefore, rapid fluctuations observed in the fast-mode HXRBS data are dominated by the low energy hard X-rays. It is of interest to know whether rapid fluctuations are observed in high-energy X-rays. The highest energy band at which subsecond variations were observed is 223 to 1057 keV. Subsecond variations observed with HXRBS at energies greater than 300 keV are reported, and the implications discussed.

Bai, Taeil

1986-01-01

34

Low-energy (< 10 keV) electron ionization and recombination model for a liquid argon detector  

NASA Astrophysics Data System (ADS)

Detailed understanding of the ionization process in noble liquid detectors is important for their use in applications such as the search for dark matter and coherent elastic neutrino-nucleus scattering. The response of noble liquid detectors to low-energy ionization events is poorly understood at this time. We describe a new simulation tool which predicts the ionization yield from electronic energy deposits (E < 10 keV) in liquid Ar, including the dependence of the yield on the applied electric drift field. The ionization signal produced in a liquid argon detector from 37Ar beta decay and 55Fe X-rays has been calculated using the new model.

Foxe, M.; Hagmann, C.; Jovanovic, I.; Bernstein, A.; Kazkaz, K.; Mozin, V.; Pereverzev, S. V.; Sangiorgio, S.; Sorensen, P.

2015-01-01

35

Resonance parameters of the reaction 12C(d,p?)13C in the vicinity of 1450 keV for accelerator energy calibration  

NASA Astrophysics Data System (ADS)

The observed resonance parameters of the 12C(d,p?)13C reaction in the vicinity of 1450 keV deuteron energy have been determined in a thorough procedure, fitting our recent experimental excitation curve, as well as earlier literature data with the Root Software Package. The resulting energy and width (FWHM) of resonance are 1445.8 ± 0.2 keV and 5.3 ± 0.4 keV, respectively. We propose the application of this resonance as a precise and simple method for accelerator energy calibration when performing DIGE analysis.

Csedreki, L.; Szíki, G. Á.; Szikszai, Z.; Kocsis, I.

2015-01-01

36

70 keV neutral hydrogen beam injector with energy recovery for application in thermonuclear fusion research  

NASA Astrophysics Data System (ADS)

A 70 keV 40 A hydrogen beam injector has been developed at Cadarache for a plasma diagnostic [motional Stark effect (MSE)] to provide a measurement of the plasma current distribution in the Tore-Supra tokamak. We present in this article the principle and the first experimental results of the injector, where a new type, and advantageous, energy recovery system, based on a magnetic neutralizer plasma confinement, has been developed. The hydrogen ion beam is accelerated to 70 keV with a three-grid multiaperture system (aperture diameter ?=11 mm) with an ion current density of ?160 mA/cm2. An ion source with a shape (height 1.2 m, width 80 mm) specifically adapted to the recovery system has been developed to meet the injector requirements: uniformity, high proton fraction (>80%), and high current density, ?160 mA/cm2 over the whole extraction surface (900 cm2). A neutral (H0) beam power of 500 kW has been achieved with a divergence of ?0.6° at 70 keV.

Simonin, A.; Armitano, A.; Brugnetti, R.; Cano, V.; Dougnac, H.; Fazilleau, P.

2002-08-01

37

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

SciTech Connect

{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.

Naqvi, A.A. [King Fahd Univ. of Petroleum and Minerals, Dhahran, (Saudi Arabia); Ayer, Z.; Ludwig, E. [King Fahd Univ. of Petroleum and Minerals, Dhahran (Saudi Arabia); [Duke Univ., Durham, NC (United States); [Univ. of North Carolina, Chappel Hill, NC (United States)

1994-12-31

38

Efficiency calibrations of cylindrically bent transmission crystals in the 20 to 80 keV x-ray energy range.  

PubMed

Two quartz (10-11) crystals were cylindrically bent to a 25.4 cm radius of curvature and were mounted in identical Cauchois-type transmission spectrometers, and the crystal diffraction efficiencies were measured to 5% absolute accuracy using narrow bandwidth x-ray source fluences in the 20 to 80 keV energy range. The measured integrated reflectivity values were compared to calculations performed using a computational model that accounts for the diffraction geometry of the bent transmission crystal. These crystal calibrations enable the accurate measurement of absolute hard x-ray emission levels from laser-produced plasmas and other laboratory sources. PMID:21499348

Szabo, Csilla I; Feldman, Uri; Seltzer, Stephen; Hudson, Lawrence T; O'Brien, Michelle; Park, Hye-Sook; Seely, John F

2011-04-15

39

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

NASA Astrophysics Data System (ADS)

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.

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

40

Understanding energy loss in large-angle scattering of keV electrons from Ar and Ne  

SciTech Connect

We present measurements of the spectra of electrons with energy between 0.6 and 2.25 keV elastically and inelastically scattered from Ar and Ne over large angles (from 3 deg. to 135 deg.). The intensity of the first loss feature [np{yields}(n+1)s], relative to that of the elastic peak, was determined and compared with the results of relativistic distorted-wave calculations (for the energy loss part) and a relativistic optical potential method (for the elastic peak). Good agreement was found. The distorted-wave calculations are compared with first Born calculations. At small angles, both theories coincide and estimates of the optical oscillator strength are obtained. However, at large angles, the first Born approximation predicts negligible intensity, in strong contrast to the distorted-wave theory and the experimental data. The implications of these results for the interpretation of measurements of the generalized oscillator strength are discussed.

Vos, M.; McEachran, R. P. [Atomic and Molecular Physics Laboratories, Research School of Physics and Engineering, Australian National University, Canberra ACT (Australia); Cooper, G.; Hitchcock, A. P. [Department of Chemistry and Chemical Biology, McMaster University, Hamilton, Ontario, L8S 4M1 (Canada)

2011-02-15

41

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

PubMed

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

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

2001-06-01

42

Thick target bremsstrahlung spectra produced by 204Tl beta particles in the photon energy region of 10 30 keV  

Microsoft Academic Search

Total bremsstrahlung (BS) spectra in thick targets of Al, Ti, Sn and Pb targets produced by complete absorption of 204Tl beta particles are studied at photon energy from 10 keV to 30 keV. The experimental BS spectra measured with X-PIPS Si(Li) detector are compared with the theoretical BS spectra obtained from Elwert corrected (non-relativistic) Bethe-Heitler theory and modified Elwert factor

Tajinder Singh; K. S. Kahlon; A. S. Dhaliwal

2008-01-01

43

Inelastic processes in K+-He collisions in energy range 0.7-10 keV  

NASA Astrophysics Data System (ADS)

Absolute cross sections for charge exchange, ionization, stripping, and excitation in K+-He collisions were measured in the ion energy range 0.7-10 keV. The experimental data and the schematic correlation diagrams are used to analyze and determine the mechanisms for these processes. The increase of the excitation probability of inelastic channels with the angle of scattering is revealed. An exceptionally highly excited state of He is observed and a peculiarity for the excitation function of the resonance line is explained. The intensity ratio for the excitation of the K II ?=60.1 nm and ?=61.2 nm lines is 5:1, which indicates the high probability for excitation of the singlet resonance level 1P1 compared to the triplet level 3P1. The similarity of the population of the 4p state of the potassium ion and atom as well as the anomalously small values of the excitation cross sections are explained.

Lomsadze, R. A.; Gochitashvili, M. R.; Kezerashvili, R. Ya.; Mosulishvili, N. O.; Phaneuf, R.

2013-04-01

44

12.6 keV Kr K-alpha X-ray Source For High Energy Density Physics Experiments  

SciTech Connect

A high contrast 12.6 keV Kr K{alpha} source has been demonstrated on the petawatt-class Titan laser facility. The contrast ratio (K{alpha} to continuum) is 65, with a competitive ultra short pulse laser to x-ray conversion efficiency of 10{sup -5}. Filtered shadowgraphy indicates that the Kr K{alpha} and K{beta} x-rays are emitted from a roughly 1 x 2 mm emission volume, making this source suitable for area backlighting and scattering. Spectral calculations indicate a typical bulk electron temperature of 50-70 eV (i.e. mean ionization state 13-16), based on the observed ratio of K{alpha} to K{beta}. Kr gas jets provide a debris-free high energy K{alpha} source for time-resolved diagnosis of dense matter.

Kugland, N; Constantin, C G; Niemann, C; Neumayer, P; Chung, H; Doppner, T; Kemp, A; Glenzer, S H; Girard, F

2008-04-22

45

Performance of LAPEX and its spectroscopic capabilities in the 20--300 keV energy band to observe SN1987a  

SciTech Connect

Recent observations of SN1987a both in the 1--10 keV and in the 10--350 keV energy range detected X-ray emission from the source with a very hard spectrum, a power law with ..cap alpha..approx.1.4, and a flux of approx.10 mCrab at 30 keV. We describe the performances of the LAPEX experiment for observation of SN1987a. In the 20--300 keV operative energy band of LAPEX, the following goals can be achieved: detection of emission lines due to Co/sup 57/ (122 keV) and Ti/sup 44/ (67.9 and 78.4 keV), elements that could be produced in the supernova explosion; measurement of the comptonized spectrum from the expanding ejecta; investigation on possible coherent pulsations due to a newly born pulsar down to timescales of approx.0.1 ms. In the following, a thorough description of the payload and of its performances will be given.

Frontera, F.; Basili, A.; Dal Fiume, D.; Franceschini, T.; Landini, G.; Morelli, E.; Pamini, M.; Poulsen, J.M.; SIlvestri, S.; Costa, E.; and others

1988-09-25

46

Rovibrational excitation in collisions of He on D2 at energies less than 2 keV  

NASA Astrophysics Data System (ADS)

This work presents a theoretical study of rovibrational excitation in electronically elastic collisions of He on either H2 or D2 in the collision energy range 100 eV<=Einc<=2 keV. Earlier classical trajectory collision calculations, which predicted the rovibrational excitation energy to follow a universal scaling law, are here generalized to (1) encompass vibrational excitation caused by a three-body force representing the He interacting with the H2 covalent bond, and (2) incorporate quantization of vibrational excitation by a semiquantal ansatz imposed on the otherwise classical calculations. Quantization of vibrational excitation is shown to cause a breakdown of the scaling law predicted by the fully classical theory. The collisional excitation calculations utilize straight-line trajectories in the framework of the impulsive approximation, and are based on an improved parametric fit to the ab initio interaction energy surface for the HeH2 triatomic molecular system. In addition to the usual two-body Bohr and Born-Mayer terms describing the He-H interactions, the new interaction potential incorporates a three-body term to describe the contribution arising from the He interacting with the H-H covalent bond. The three-body force gives rise to some vibrational excitation phenomena, which are here explored. Good agreement is obtained with experimental measurements on rovibrational excitation energies produced in quasielastic collisions of He on D2

Muchnick, Paul; Russek, Arnold

1994-03-01

47

First wave of cultivators spread to Cyprus at least 10,600 y ago  

PubMed Central

Early Neolithic sedentary villagers started cultivating wild cereals in the Near East 11,500 y ago [Pre-Pottery Neolithic A (PPNA)]. Recent discoveries indicated that Cyprus was frequented by Late PPNA people, but the earliest evidence until now for both the use of cereals and Neolithic villages on the island dates to 10,400 y ago. Here we present the recent archaeological excavation at Klimonas, which demonstrates that established villagers were living on Cyprus between 11,100 and 10,600 y ago. Villagers had stone artifacts and buildings (including a remarkable 10-m diameter communal building) that were similar to those found on Late PPNA sites on the mainland. Cereals were introduced from the Levant, and meat was obtained by hunting the only ungulate living on the island, a small indigenous Cypriot wild boar. Cats and small domestic dogs were brought from the mainland. This colonization suggests well-developed maritime capabilities by the PPNA period, but also that migration from the mainland may have occurred shortly after the beginning of agriculture. PMID:22566638

Vigne, Jean-Denis; Briois, François; Zazzo, Antoine; Willcox, George; Cucchi, Thomas; Thiébault, Stéphanie; Carrère, Isabelle; Franel, Yodrik; Touquet, Régis; Martin, Chloé; Moreau, Christophe; Comby, Clothilde; Guilaine, Jean

2012-01-01

48

Observation of particles with energy over 100 keV in z-pinch device  

NASA Astrophysics Data System (ADS)

The high energy particles were produced at the implosion of a tungsten wire array z-pinch onto a deuterated fiber at the S-300 device (4 MA, 700 kV, 100ns; RRC Kurchatov Institute, Moscow). The FWHM of the signal in spectral window 270 eV was 35-60 ns. The hard x-rays and neutrons with the FWHM (10-30) ns were produced during the soft x-ray maximum. The neutron yield from the D-D reaction reached 108 per shot. The mean energy of neutrons determined from time-of-flight analysis in the direction back to the anode, back to the cathode and side-on was in the range of (2.2-3.1) MeV and a time delay between neutron and hard x-rays maximum was in the range of (5-20)ns.

Kubes, Pavel; Klir, Daniel; Kravarik, Jozef; Bakshaev, Yuriy L.; Blinov, Peter I.; Chernenko, Andrey S.; Danko, Sergey A.; Hongchun, Cai; Ivanov, Michail I.; Korolev, Valery D.; Korelsky, Alexander V.; Kravchenko, Elena V.; Shaskov, Andrey Y.; Ustroev, Genady I.

2005-03-01

49

Imaging detectors for 20–100 keV x-ray backlighters in high-energy-density experimental science petawatt experiments  

Microsoft Academic Search

We are developing a petawatt laser for use as a high-energy backlighter source in the 20–100 keV range on the National Ignition Facility (NIF). High-energy x-ray backlighters will be essential for radiographing high-energy-density experimental science (HEDES) targets, especially to probe implosions and high areal density planar samples. For these high energy backlighter imaging experiments, we are developing two types of

J. E. Wickersham; H.-S. Park; P. M. Bell; J. A. Koch; O. L. Landen; J. D. Moody

2004-01-01

50

Imaging detectors for 20-100 keV x-ray backlighters in high-energy-density experimental science petawatt experiments  

Microsoft Academic Search

We are developing a petawatt laser for use as a high-energy backlighter source in the 20-100 keV range on the National Ignition Facility (NIF). High-energy x-ray backlighters will be essential for radiographing high-energy-density experimental science (HEDES) targets, especially to probe implosions and high areal density planar samples. For these high energy backlighter imaging experiments, we are developing two types of

J. E. Wickersham; H.-S. Park; P. M. Bell; J. A. Koch; O. L. Landen; J. D. Moody

2004-01-01

51

Calculations of mean free paths and stopping powers of low energy electrons (? 10 keV) in solids using a statistical model  

Microsoft Academic Search

A statistical model is described and employed to calculate inverse mean free paths and stopping powers for electrons of energies from a few eV to 10 keV above the Fermi level in Al, Si, Ni, Cu, Ag, and Au. Brief tables of mean free paths and stopping powers for these solids are presented. In some cases graphical displays of inverse

J. C. Ashley; C. J. Tungt; R. H. Ritchie; V. E. Anderson

1976-01-01

52

Non-proportional response between 0.1-100keV energy by means of highly monochromatic synchrotron X-rays  

E-print Network

Using highly monochromatic X-ray synchrotron irradiation ranging from 9 keV to 100 keV, accurate Lu2SiO5:Ce3+,Ca (LSO), Lu3Al5O12:Pr3+ (LuAG), Lu2Si2O7:Ce3+ (LPS) and Gd2SiO5:Ce3+ (GSO) non-proportional response curves were determined. By utilizing information from escape peaks in pulse height spectra the response curve can be extended down to several keV. A detailed study of the non-proportionality just above the K-edge is presented and from that a method, which we named K-dip spectroscopy, is obtained to reconstruct the electron response curve down to energies as low as 100 eV.

Ivan V. Khodyuk; Johan T. M. de Haas; Pieter Dorenbos

2011-01-24

53

Inelastic Neutron Scattering Studies of Uranium -238 and THORIUM-232 on States above 300 KEV for Incident Energies above 2.2 Mev.  

NASA Astrophysics Data System (ADS)

Differential cross sections have been measured at incident energies from 2.3 to 3.0 MeV for vibrational states between 600 and 1000 keV in ^{232 } Th and ^{238}U, as well as for the 307.4 keV level in uranium and the 333.2 keV level in thorium which are members of ground state rotational band. Excitation functions for these levels have been obtained over the incident energy range 2.3-3.0 MeV in 100-keV steps. Angular distributions for these states were measured at 2.4 and 2.8 MeV. The data were obtained via the neutron time-of-flight technique using the University of Lowell 5.5 MV pulsed Van-de-Graaff accelerator with Mobley bunching system. Neutrons were generated via the ^7Li(p,n) ^7 Be reaction in a metalic lithium target having a thickness of 15-25 keV. Overall resolution of 25-30 keV was maintained throughout the measurements. The bunched pulse durations were less than 1 ns. Pulse shape discrimination (PSD) was employed to suppress gamma-ray background. Data reduction included, background, tail and fission subtraction; corrections were made for multiple scattering and for finite sample size effects. Studies were developed, employing a user interactive code to generate scattered neutron group response functions from the shape of elastic and inelastic scattering peaks obtained from measurements on elemental iron. The results are compared with theoretical calculations and previous measurements.

Aliyar, Abobakr

54

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

NASA Astrophysics Data System (ADS)

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° 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.

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

2010-04-01

55

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

PubMed

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

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

2010-04-01

56

Absolute measurements of short-pulse, long-pulse, and capsule-implosion backlighter sources at x-ray energies greater than 10 keV  

Microsoft Academic Search

Laser-generated x-ray backlighters with x-ray energies > 10 keV are becoming essential diagnostic tools for many high energy density experiments. Examples include studies of high areal density cores for ignition designs, mid- to high-Z capsule implosion experiments, absolute equation of state experiments, dynamic diffraction under extreme pressures, and the study of material strength. Significant progress has been made recently using

Brian Maddox

2010-01-01

57

Thick target bremsstrahlung spectra produced by 204Tl beta particles in the photon energy region of 10 30 keV  

NASA Astrophysics Data System (ADS)

Total bremsstrahlung (BS) spectra in thick targets of Al, Ti, Sn and Pb targets produced by complete absorption of 204Tl beta particles are studied at photon energy from 10 keV to 30 keV. The experimental BS spectra measured with X-PIPS Si(Li) detector are compared with the theoretical BS spectra obtained from Elwert corrected (non-relativistic) Bethe-Heitler theory and modified Elwert factor (relativistic) Bethe-Heitler theories, with and without the contributions of polarization bremsstrahlung in a stripped atom approximation, described by Avdonina and Pratt (1999 J. Phys. B: At. Mol. Opt. Phys. 321 4261). It is observed that the experimental results show better agreement with the modified Elwert factor (relativistic) Bethe-Heitler theory having the contribution of polarization bremsstrahlung at photon energy from 10 keV to 30 keV. This indicates that the polarization bremsstrahlung must be taken into account while studying the spectral photon distributions produced by continuous beta particles in thick target materials.

Singh, Tajinder; Kahlon, K. S.; Dhaliwal, A. S.

2008-12-01

58

An improved long counter for neutron fluence measurement with a flat response over a wide energy range from 1 keV to 15 MeV  

NASA Astrophysics Data System (ADS)

A new long counter has been developed with a flat energy response over a wide range from 1 keV to 15 MeV. It consists of five 3He proportional counter tubes and a number of carefully designed polyethylene moderators. The structure of this detector was determined by careful Monte Carlo simulations. The calculated results show that the efficiency of this counter is uniform from 1 keV neutron energy to 15 MeV. Calibration was performed on an Am-Be source and the accelerator-produced monoenergetic D-D and D-T neutron sources. Fluctuation of the response curve is less than 10% over this energy range.

Hu, Q. Y.; Zhang, J. H.; Zhang, D.; Guo, H. S.; Yang, G. Z.; Li, B. J.; Ye, F.; Si, F. N.; Liu, J.; Fu, Y. C.; Ning, J. M.; Yang, J.; Yang, H. H.; Wang, W. C.

2014-12-01

59

Head-On Inverse Compton Scattering X-rays with Energy beyond 10 keV from Laser-Accelerated Quasi-Monoenergetic Electron Bunches  

NASA Astrophysics Data System (ADS)

Inverse Compton X-rays from laser-accelerated multiple electron bunches are observed. A Ti:sapphire laser (pulse energy: 500 mJ; pulse width: 150 fs) beam is divided into two beams. The main beam is focused onto an edge of a helium gas jet to accelerate electrons to energies of 14 and 23 MeV, which inversely scattered the head-on colliding secondary laser beam into 6 and 12 keV X-rays; this agrees well with that calculated from the electron spectra obtained. This demonstrates a first on-axis inverse Compton scattering X-ray energy detection beyond 10 keV induced by laser-accelerated electrons.

Mori, Yoshitaka; Kuwabara, Hajime; Ishii, Katsuhiro; Hanayama, Ryohei; Kawashima, Toshiyuki; Kitagawa, Yoneyoshi

2012-05-01

60

Measurements and assessment of 12C(d,p?)13C reaction cross sections in the deuteron energy range 740-2000 keV for analytical applications  

NASA Astrophysics Data System (ADS)

The total cross sections of the 12C(d,p?1)13C (E? = 3089 keV), 12C(d,p?2)13C (E? = 3684 keV) and 12C(d,p?3)13C (E? = 3854 keV) reactions, as well as differential cross sections for (d,po), (d,p1) reactions and (d,d0) elastic scattering were determined in the 740-2000 keV deuteron energy range using a self-supporting natural carbon foil and detecting the gamma-rays and particles simultaneously. In order to test the validity of the measured gamma-ray producing cross sections, benchmark experiments were performed using kapton foils with two different thicknesses. Both the obtained gamma- and particle production cross section results were compared with data existing in literature, and in the case of (d,po) the experimental differential cross section data were compared also with the theoretical evaluated values.

Csedreki, L.; Uzonyi, I.; Szíki, G. Á.; Szikszai, Z.; Gyürky, Gy.; Kiss, Á. Z.

2014-06-01

61

Effective atomic numbers of different types of materials for proton interaction in the energy region 1 keV-10 GeV  

NASA Astrophysics Data System (ADS)

The effective atomic numbers (Zeff) of different types of materials such as tissues, tissue equivalents, organic compounds, glasses and dosimetric materials have been calculated for total proton interactions in the energy region 1 keV-10 GeV. Also, effective atomic numbers relative to water (ZeffRW) have been presented in the entire energy region for the materials that show better water equivalent properties. Some human tissues such as adipose tissue, bone compact, muscle skeletal and muscle striated have been investigated in terms of tissue equivalency by comparing Zeff values and the better tissue equivalents have been determined for these tissues. With respect to the variation of Zeff with kinetic energy, it has been observed that Zeff seems to be more or less the same in the energy region 400 keV-10 GeV for the given materials except for the photographic emulsion, calcium fluoride, silicon dioxide, aluminum oxide and Teflon. The values of Zeff have found to be constant for photographic emulsion after 1 GeV, for calcium fluoride between 1 MeV and 1 GeV and for silicon dioxide, aluminum oxide and Teflon between 400 keV and 1 GeV. This constancy clearly shows the availability of using Zeff in estimating radiation response of the materials at first glance.

Kurudirek, Murat

2014-10-01

62

Measurements of the X-ray linear attenuation coefficient for low atomic number materials at energies 32-66 and 140 keV  

NASA Astrophysics Data System (ADS)

The X-ray linear attenuation coefficient was measured for materials containing elements hydrogen to calcium. Characteristic X-rays with energies 32- 66 keV were produced by X-ray fluorescence using a secondary target system, and 140 keV gamma rays were obtained from an unsealed 99 mTc source. The photon beams were highly collimated and recorded using energy dispersive detection. A high-purity germanium detector was utilised to distinguish between measurements with K ? and K ? characteristic X-rays, and the gamma ray measurements used a sodium iodide detector. Samples were selected on the basis of having known composition and mass densities were measured using a pycnometer. The samples comprised six plastics, seven crystalline materials, three tissue substitute materials, three liquids and six salt solutions. Our results have an uncertainty of less than 2% and are a few percent lower than values predicted by the tabulations.

Midgley, S. M.

2005-03-01

63

Dose distribution of a 125 keV mean energy microplanar x-ray beam for basic studies on microbeam radiotherapy  

SciTech Connect

A multislit collimator was designed and fabricated for basic studies on microbeam radiation therapy (MRT) with an x-ray energy of about 100 keV. It consists of 30 slits that are 25 {mu}m high, 30 mm wide, and 5 mm thick in the beam direction. The slits were made of 25 {mu}m-thick polyimide sheets that were separated by 175 {mu}m-thick tungsten sheets. The authors measured the dose distribution of a single microbeam with a mean energy of 125 keV by a scanning slit method using a phosphor coupled to a charge coupled device camera and found that the ratios of the dose at the center of a microbeam to that at midpositions to adjacent slits were 1050 and 760 for each side of the microbeam. This dose distribution was well reproduced by the Monte Carlo simulation code PHITS.

Ohno, Yumiko; Torikoshi, Masami; Suzuki, Masao; Umetani, Keiji; Imai, Yasuhiko; Uesugi, Kentaro; Yagi, Naoto [National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage, Chiba 263-8555 (Japan); Japan Synchrotron Radiation Research Institute, 1-1-1, Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan)

2008-07-15

64

Electron density of Rhizophora spp. wood using Compton scattering technique at 15.77, 17.48 and 22.16 keV XRF energies  

NASA Astrophysics Data System (ADS)

Compton (incoherently) scattered photons which are directly proportional to the electron density of the scatterer, have been employed in characterizing Rhizophora spp. as breast tissue equivalent. X-ray fluorescent scattered incoherently from Rhizophora spp. sample was measured using Si-PIN detector and three XRF energy values 15.77, 17.48 and 22.16 keV. This study is aimed at providing electron density information in support of the introduction of new tissue substitute materials for mammography phantoms.

Shakhreet, B. Z.; Bauk, S.; Shukri, A.

2015-02-01

65

Solar wind control of Earth's H+ and O+ outflow rates in the 15eV to 33keV energy range  

Microsoft Academic Search

Earth's high-latitude outflow of H+ and O+ ions has been examined with the Toroidal Imaging Mass-Angle Spectrograph instrument on the Polar satellite in the 15-eV to 33-keV energy range over an almost 3-year period near solar minimum (1996-1998). This outflow is compared with solar wind plasma and interplanetary magnetic field (IMF) data from the Wind spacecraft, the latter having been

O. W. Lennartsson; H. L. Collin; W. K. Peterson

2004-01-01

66

Solar wind control of Earth's H+ and O+ outflow rates in the 15eV to 33keV energy range  

Microsoft Academic Search

Earth's high-latitude outflow of H+ and O+ ions has been examined with the Toroidal Imaging Mass-Angle Spectrograph instrument on the Polar satellite in the 15-eV to 33-keV energy range over an almost 3-year period near solar minimum (1996–1998). This outflow is compared with solar wind plasma and interplanetary magnetic field (IMF) data from the Wind spacecraft, the latter having been

O. W. Lennartsson; H. L. Collin; W. K. Peterson

2004-01-01

67

Relativistic calculations of M-shell photoionization and X-ray production cross-sections for Hg at 5.96 keV excitation energy  

NASA Astrophysics Data System (ADS)

In this work we calculate photoionization and X-ray production cross-sections (XPCS) of M-shell vacancies in Hg at an incident photon energy of 5.96 keV (low energy X-rays of 55Fe radioactive source) using the Dirac-Fock method. Calculations are performed in single configuration approach with the Breit interaction and some vacuum polarization corrections included in the self-consistent method. Higher-order retardation corrections, self-energy and other vacuum polarization effects were also included as perturbations. Fluorescence and Coster-Kronig yields necessary to derive XPCS were obtained in a previous work using the exact same approach.

Sampaio, J. M.; Madeira, T. I.; Parente, F.; Indelicato, P.; Santos, J. P.; Marques, J. P.

2015-02-01

68

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

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.

Derrien, H

2005-12-05

69

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

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.

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

70

Development of a long-pulse (30-s), high-energy (120-keV) ion source for neutral-beam applications  

SciTech Connect

Multimegawatt neutral beams of hydrogen or deuterium atoms are needed for fusion machine applications such as MFTB-B, TFTR-U, DIII-U, and FED (INTOR or ETR). For these applications, a duoPIGatron ion source is being developed to produce high-brightness deuterium beams at a beam energy of approx. 120 keV for pulse lengths up to 30 s. A long-pulse plasma generator with active water cooling has been operated at an arc level of 1200 A with 30-s pulse durations. The plasma density and uniformity are sufficient for supplying a 60-A beam of hydrogen ions to a 13- by 43-cm accelerator. A 10- by 25-cm tetrode accelerator has been operated to form 120-keV hydrogen ion beams. Using the two-dimensional (2-D) ion extraction code developed at Oak Ridge National Laboratory (ORNL), a 13- by 43-cm tetrode accelerator has been designed and is being fabricated. The aperture shapes of accelerator grids are optimized for 120-keV beam energy.

Tsai, C.C.; Barber, G.C.; Blue, C.W.

1983-01-01

71

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

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.

Friedman, P.G.

1986-11-25

72

Moiré deflectometry using the Talbot-Lau interferometer as refraction diagnostic for High Energy Density plasmas at energies below 10 keV  

NASA Astrophysics Data System (ADS)

The highly localized density gradients expected in High Energy Density (HED) plasma experiments can be characterized by x-ray phase-contrast imaging in addition to conventional attenuation radiography. Moiré deflectometry using the Talbot-Lau grating interferometer setup is an attractive HED diagnostic due to its high sensitivity to refraction induced phase shifts. We report on the adaptation of such a system for operation in the sub-10 keV range by using a combination of free standing and ultrathin Talbot gratings. This new x-ray energy explored matches well the current x-ray backlighters used for HED experiments, while also enhancing phase effects at lower electron densities. We studied the performance of the high magnification, low energy Talbot-Lau interferometer, for single image phase retrieval using Moiré fringe deflectometry. Our laboratory and simulation studies indicate that such a device is able to retrieve object electron densities from phase shift measurements. Using laboratory x-ray sources from 7 to 15 ?m size we obtained accurate simultaneous measurements of refraction and attenuation for both sharp and mild electron density gradients.

Valdivia, M. P.; Stutman, D.; Finkenthal, M.

2014-07-01

73

Moiré deflectometry using the Talbot-Lau interferometer as refraction diagnostic for high energy density plasmas at energies below 10 keV.  

PubMed

The highly localized density gradients expected in High Energy Density (HED) plasma experiments can be characterized by x-ray phase-contrast imaging in addition to conventional attenuation radiography. Moiré deflectometry using the Talbot-Lau grating interferometer setup is an attractive HED diagnostic due to its high sensitivity to refraction induced phase shifts. We report on the adaptation of such a system for operation in the sub-10 keV range by using a combination of free standing and ultrathin Talbot gratings. This new x-ray energy explored matches well the current x-ray backlighters used for HED experiments, while also enhancing phase effects at lower electron densities. We studied the performance of the high magnification, low energy Talbot-Lau interferometer, for single image phase retrieval using Moiré fringe deflectometry. Our laboratory and simulation studies indicate that such a device is able to retrieve object electron densities from phase shift measurements. Using laboratory x-ray sources from 7 to 15 ?m size we obtained accurate simultaneous measurements of refraction and attenuation for both sharp and mild electron density gradients. PMID:25085141

Valdivia, M P; Stutman, D; Finkenthal, M

2014-07-01

74

Angular dependence of the electronic energy loss of 800-keV He ions along the Si{l_angle}100{r_angle} direction  

SciTech Connect

We present measurements of the stopping power of 800-keV {sup 4}He ions channeled along the Si{l_angle}100{r_angle} axis, as a function of the incidence angle. We compare the experimental results with theoretical calculations by using the impact-parameter-dependent energy loss obtained from the solution of the time-dependent Schr{umlt o}dinger equation through the coupled-channel method. This nonperturbative calculation provides reliable energy-loss results which are in good agreement with the experimental results. {copyright} {ital 1997} {ital The American Physical Society}

dos Santos, J.H.; Grande, P.L.; Behar, M.; Boudinov, H. [Instituto de Fisica da Universidade Federal do Rio Grande do Sul, Avenida Bento Goncalves 9500, 91501-970, Porto Alegre (Brazil)] [Instituto de Fisica da Universidade Federal do Rio Grande do Sul, Avenida Bento Goncalves 9500, 91501-970, Porto Alegre (Brazil); Schiwietz, G. [Bereich F, Hahn-Meitner-Institut Berlin, Glienicker Strasse 100, D-14109 Berlin (Germany)] [Bereich F, Hahn-Meitner-Institut Berlin, Glienicker Strasse 100, D-14109 Berlin (Germany)

1997-02-01

75

Experimental re-evaluation of the ?-ray energy and emission probability for the 159 keV transition in 238U following the ?-decay of 242Pu.  

PubMed

Because of the very low specific activity of (242)Pu, the non-destructive assay of this isotope by means of conventional high-resolution gamma-spectrometry (HRGS) is possible only for Pu samples highly rich in (242)Pu. For bulk samples suffering from the gamma self-attenuation and self-fluorescence effects, the only practical choice for the quantitative analysis of (242)Pu is the weak ?-line emitted in the 159 keV transition of its ?-decay daughter (238)U. A recent study revealed a significant disagreement between the (242)Pu mass values in a 99.72% enriched (242)PuO(2) sample as reported by HRGS and neutron coincidence counting. This fact motivated the present study on the experimental re-evaluation of the ?-emission probability for the 159 keV transition using a combination of ?-, ?- and mass-spectrometry techniques. The obtained new emission probability P(2)=(2.20±0.08)10(-6) turned out to be ?35% smaller than the currently adopted value. The study also suggested a new value E(2)=159.018±0.016 keV for the energy of the respective ?-ray. PMID:21144759

Berlizov, A N; van Belle, P; Zuleger, E; Ottmar, H

2011-02-01

76

Nonthermal X-rays from low-energy cosmic rays: application to the 6.4 keV line emission from the Arches cluster region  

NASA Astrophysics Data System (ADS)

Context. The iron K? line at 6.4 keV provides a valuable spectral diagnostic in several fields of X-ray astronomy. The line often results from the reprocessing of external hard X-rays by a neutral or low-ionized medium, but it can also be excited by impacts of low-energy cosmic rays. Aims: This paper aims to provide signatures allowing identification of radiation from low-energy cosmic rays in X-ray spectra showing the 6.4 keV Fe K? line. Methods: We study in detail the production of nonthermal line and continuum X-rays by interaction of accelerated electrons and ions with a neutral ambient gas. Corresponding models are then applied to XMM-Newton observations of the X-ray emission emanating from the Arches cluster region near the Galactic center. Results: Bright 6.4 keV Fe line structures are observed around the Arches cluster. This emission is very likely produced by cosmic rays. We find that it can result from the bombardment of molecular gas by energetic ions, but probably not by accelerated electrons. Using a model of X-ray production by cosmic-ray ions, we obtain a best-fit metallicity of the ambient medium of 1.7 ± 0.2 times the solar metallicity. A large flux of low-energy cosmic ray ions could be produced in the ongoing supersonic collision between the star cluster and an adjacent molecular cloud. We find that a particle acceleration efficiency in the resulting shock system of a few percent would give enough power in the cosmic rays to explain the luminosity of the nonthermal X-ray emission. Depending on the unknown shape of the kinetic energy distribution of the fast ions above ~1 GeV nucleon-1, the Arches cluster region may be a source of high-energy ?-rays detectable with the Fermi Gamma-ray Space Telescope. Conclusions: At present, the X-ray emission prominent in the 6.4 keV Fe line emanating from the Arches cluster region probably offers the best available signature for a source of low-energy hadronic cosmic rays in the Galaxy. Appendices are available in electronic form at http://www.aanda.org

Tatischeff, V.; Decourchelle, A.; Maurin, G.

2012-10-01

77

High energy observation of the Galactic center region 511 keV and Al-26 lines with HEXAGONE  

NASA Astrophysics Data System (ADS)

Results of the observation of the annihilation and Al-26 lines in the direction of the Galactic center during the HEXAGONE May 1989 balloon flight are presented. The observed profile and the intensity of the 511 keV line are compared with the theoretical models developed by Guessoum et al. (1991). On the assumption of a Gaussian profile with a constant step function, a flux of the annihilation line of (9.54 +/- 2.29) x 10 exp -4 ph/sq cm s is derived. It is shown that a warm medium (about 8000 K) is the best candidate to explain the annihilation of the positrons from the diffuse component of the 511 keV. In the case of Al-26, a model-dependent analysis is performed, taking into account the full response of the present detection system, together with distribution models proposed for the origin of the Al-26. Assuming a point source at the Galactic center, the flux is 1.9 x 10 exp -4 ph/sq cm s at 90 percent confidence level, and 4.6 x 10 exp -4 ph/sq cm s for a COS B-type distribution.

Durouchoux, Ph.; Wallyn, P.; Chapuis, C.; Matteson, J.; Bowman, B.; Pelling, M.; Peterson, L.; Vedrenne, G.; von Ballmoos, P.; Malet, I.; Niel, M.; Lin, R.; Feffer, P.; Smith, D.; Hurley, K.

1993-01-01

78

Energy loss of keV fluorine ions scattered off a missing-row reconstructed Au(110) surface under grazing incidence  

SciTech Connect

A joint experimental and theoretical study of energy loss is presented for 1-to-4-keV fluorine negative ions in grazing scattering on a missing-row reconstructed Au(110) surface. Measurements of energy losses for various azimuthal orientations of the crystal have been performed by means of a time-of-flight method with a pulsed beam. The dependence of the fraction of surviving negative ions on azimuthal angles, was determined. Our energy-loss data are discussed in light of trajectory and stopping-power calculations, where the explicit inclusion of the nonuniform electron density at the surface provides good agreement with the experimental data. The simulation allows us to delineate various trajectory classes that correspond to different contributions in the energy-loss spectra for various azimuthal orientations of the surface.

Chen, L. [Institut des Sciences Moleculaires (Unite Mixte de Recherche CNRS Universite, UMR 8214), bat 351, Universite de Paris Sud, Orsay F-91405 (France); School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000 (China); Shen, J.; Esaulov, V. A. [Institut des Sciences Moleculaires (Unite Mixte de Recherche CNRS Universite, UMR 8214), bat 351, Universite de Paris Sud, Orsay F-91405 (France); Valdes, J. E.; Vargas, P. [Department of Physics, Universidad Tecnica Federico Santa Maria, Valparaiso, Casilla 110-V (Chile)

2011-03-15

79

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

PubMed

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

Trunova, Valentina; Sidorina, Anna; Kriventsov, Vladimir

2014-10-17

80

Measurement of the mass energy-absorption coefficient of air for x-rays in the range from 3 to 60 keV.  

PubMed

For the first time the absolute photon mass energy-absorption coefficient of air in the energy range of 10 to 60 keV has been measured with relative standard uncertainties below 1%, considerably smaller than those of up to 2% assumed for calculated data. For monochromatized synchrotron radiation from the electron storage ring BESSY II both the radiant power and the fraction of power deposited in dry air were measured using a cryogenic electrical substitution radiometer and a free air ionization chamber, respectively. The measured absorption coefficients were compared with state-of-the art calculations and showed an average deviation of 2% from calculations by Seltzer. However, they agree within 1% with data calculated earlier by Hubbell. In the course of this work, an improvement of the data analysis of a previous experimental determination of the mass energy-absorption coefficient of air in the range of 3 to 10 keV was found to be possible and corrected values of this preceding study are given. PMID:23192280

Buhr, H; Büermann, L; Gerlach, M; Krumrey, M; Rabus, H

2012-12-21

81

950 keV X-Band Linac For Material Recognition Using Two-Fold Scintillator Detector As A Concept Of Dual-Energy X-Ray System  

SciTech Connect

One of the advantages of applying X-band linear accelerator (Linac) is the compact size of the whole system. That shows us the possibility of on-site system such as the custom inspection system in an airport. As X-ray source, we have developed X-band Linac and achieved maximum X-ray energy 950 keV using the low power magnetron (250 kW) in 2 {mu}s pulse length. The whole size of the Linac system is 1x1x1 m{sup 3}. That is realized by introducing X-band system. In addition, we have designed two-fold scintillator detector in dual energy X-ray concept. Monte carlo N-particle transport (MCNP) code was used to make up sensor part of the design with two scintillators, CsI and CdWO4. The custom inspection system is composed of two equipments: 950 keV X-band Linac and two-fold scintillator and they are operated simulating real situation such as baggage check in an airport. We will show you the results of experiment which was performed with metal samples: iron and lead as targets in several conditions.

Lee, Kiwoo; Natsui, Takuya; Hirai, Shunsuke; Uesaka, Mitsuru [University of Tokyo, 2-22 Tokai-mura, Ibaraki-ken 319-1188 (Japan); Hashimoto, Eiko [Japan atomic energy agency (JAEA), 4-49 Muramatsu Tokai-mura, Ibaraki-ken (Japan)

2011-06-01

82

Absolute measurements of short-pulse, long-pulse, and capsule-implosion backlighter sources at x-ray energies greater than 10 keV  

NASA Astrophysics Data System (ADS)

Laser-generated x-ray backlighters with x-ray energies > 10 keV are becoming essential diagnostic tools for many high energy density experiments. Examples include studies of high areal density cores for ignition designs, mid- to high-Z capsule implosion experiments, absolute equation of state experiments, dynamic diffraction under extreme pressures, and the study of material strength. Significant progress has been made recently using short pulse lasers, coupled to metal foil targets [1], and imploding capsules for producing high energy backlighters. Measuring the absolute x-ray flux and spectra from these sources is required for quantitative analysis of experimental data and for the design and planning of future experiments. We have performed an extensive series of experiments to measure the absolute x-ray flux and spectra on the Titan, Omega, Omega-EP, and NIF laser systems, employing single-photon-counting detectors, crystal spectrometers, and multichannel differential filtering (Ross-pair) and filter stack bremsstrahlung spectrometers. Calibrations were performed on these instruments [2] enabling absolute measurements of backlighter spectra to be made from 10 keV to 1 MeV. Various backlighter techniques that generate either quasi-monochromatic sources or broadband continuum sources will be presented and compared. For Molybdenum K? backlighters at x-ray energy of ˜17 keV we measure conversion efficiencies of 1.3x10-4 using 1 ?m wavelength short-pulse lasers at an intensity of ˜1x10^17 W/cm^2. This is a factor of ˜2 high than using 0.3 ?m wavelength long-pulse lasers at an intensity of ˜1x10^16 W/cm^2. Other types of backlighter targets include capsule implosion backlighters that can generate a very bright ``white-light'' continuum x-ray source and high-Z gas filled capsules that generate a quasi-line-source of x rays. We will present and compare the absolute laser energy to x-ray conversion efficiencies for these different backlighter techniques and give examples of the science experiments that they enable. Lawrence Livermore National Laboratory is operated by Lawrence Livermore National Security, LLC, for the U.S. Department of Energy, National Nuclear Security Administration under Contract DE-AC52-07NA27344. [4pt] [1] H-S. Park, PoP, 15, 072705 (2008). [0pt] [2] B. R. Maddox, RSI, submitted (2010).

Maddox, Brian

2010-11-01

83

Dose calculation for photon-emitting brachytherapy sources with average energy higher than 50 keV: Report of the AAPM and ESTRO  

SciTech Connect

Purpose: Recommendations of the American Association of Physicists in Medicine (AAPM) and the European Society for Radiotherapy and Oncology (ESTRO) on dose calculations for high-energy (average energy higher than 50 keV) photon-emitting brachytherapy sources are presented, including the physical characteristics of specific {sup 192}Ir, {sup 137}Cs, and {sup 60}Co source models. Methods: This report has been prepared by the High Energy Brachytherapy Source Dosimetry (HEBD) Working Group. This report includes considerations in the application of the TG-43U1 formalism to high-energy photon-emitting sources with particular attention to phantom size effects, interpolation accuracy dependence on dose calculation grid size, and dosimetry parameter dependence on source active length. Results: Consensus datasets for commercially available high-energy photon sources are provided, along with recommended methods for evaluating these datasets. Recommendations on dosimetry characterization methods, mainly using experimental procedures and Monte Carlo, are established and discussed. Also included are methodological recommendations on detector choice, detector energy response characterization and phantom materials, and measurement specification methodology. Uncertainty analyses are discussed and recommendations for high-energy sources without consensus datasets are given. Conclusions: Recommended consensus datasets for high-energy sources have been derived for sources that were commercially available as of January 2010. Data are presented according to the AAPM TG-43U1 formalism, with modified interpolation and extrapolation techniques of the AAPM TG-43U1S1 report for the 2D anisotropy function and radial dose function.

Perez-Calatayud, Jose; Ballester, Facundo; Das, Rupak K.; DeWerd, Larry A.; Ibbott, Geoffrey S.; Meigooni, Ali S.; Ouhib, Zoubir; Rivard, Mark J.; Sloboda, Ron S.; Williamson, Jeffrey F. [Radiotherapy Department, La Fe Polytechnic and University Hospital, Valencia 46026 (Spain); Department of Atomic, Molecular and Nuclear Physics, University of Valencia, Burjassot 46100 (Spain); Department of Human Oncology, University of Wisconsin, Madison, Wisconsin 53792 (United States); Department of Medical Physics and Accredited Dosimetry and Calibration Laboratory, University of Wisconsin, Madison, Wisconsin 53706 (United States); Department of Radiation Physics, University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030 (United States); Department of Radiation Oncology, Comprehensive Cancer Center of Nevada, Las Vegas, Nevada 89169 (United States); Radiation Oncology, Lynn Regional Cancer Center, 16313 South Military Trail, Delray Beach, Florida 33484 (United States); Department of Radiation Oncology, Tufts University School of Medicine, Boston, Massachusetts 02111 (United States); Department of Medical Physics, Cross Cancer Institute, Edmonton, Alberta T6G 1Z2 (Canada); Department of Radiation Oncology, Virginia Commonwealth University, Richmond, Virginia 23298 (United States)

2012-05-15

84

Remote Sensing of Icy Galilean Moon Surface and Atmospheric Composition Using Low Energy (1 eV-4 keV) Neutral Atom Imaging  

NASA Technical Reports Server (NTRS)

We describe a low energy neutral atom imager suitable for composition measurements Europa and other icy Galilean moons in the Jovian magnetosphere. This instrument employs conversion surface technology and is sensitive to either neutrals converted to negative ions, neutrals converted to positive ions and the positive ions themselves depending on the power supply. On a mission such as the Jupiter Icy Moons Orbiter (JIMO), two back-to-back sensors would be flown with separate power supplies fitted to the neutral atom and iodneutral atom sides. This will allow both remote imaging of 1 eV < E < 4 keV neutrals from icy moon surfaces and atmospheres, and in situ measurements of ions at similar energies in the moon ionospheres and Jovian magnetospheric plasma. The instrument provides composition measurements of the neutrals and ions that enter the spectrometer with a mass resolution dependent on the time-of-flight subsystem and capable of resolving molecules. The lower energy neutrals, up to tens of eV, arise from atoms and molecules sputtered off the moon surfaces and out of the moon atmospheres by impacts of more energetic (keV to MeV) ions from the magnetosphere. Direct Simulation Monte Carlo (DSMC) models are used to convert measured neutral abundances to compositional distributions of primary and trace species in the sputtered surfaces and atmospheres. The escaping neutrals can also be detected as ions after photo- or plasma-ionization and pickup. Higher energy, keV neutrals come from charge exchange of magnetospheric ions in the moon atmospheres and provide information on atmospheric structure. At the jovicentric orbits of the icy moons the presence of toroidal gas clouds, as detected at Europa's orbit, provide M e r opportunities to analyze both the composition of neutrals and ions originating from the moon surfaces, and the characteristics of magnetospheric ions interacting with neutral cloud material. Charge exchange of low energy ions near the moons, and directional distributions of the resultant neutrals, allow indirect global mapping of magnetic field structures around the moons. Temporal variation of the magnetic structures can be linked to induced magnetic fields associated with subsurface oceans.

Collier, M. R.; Sittler, E.; Chornay, D.; Cooper, J. F.; Coplan, M.; Johnson, R. E.

2004-01-01

85

Liquid helium cryostat with internal fluorescence detection for x-ray absorption studies in the 2-6 keV energy region.  

PubMed

X-ray absorption spectroscop (XAS) in the intermediate x-ray region (2-6 keV) for dilute biological samples has been limited because of detector/flux limitations and inadequate cryogenic instrumentation. We have designed and constructed a new tailpiece/sample chamber for a commercially available liquid helium cooled cryostat which overcomes difficulties related to low fluorescence signals by using thin window materials and incorporating an internal photodiode detector. With the apparatus, XAS data at the Cl, S, and Ca K edges have been collected on frozen solutions and biological samples at temperatures down to 60 K. A separate chamber has been incorporated for collecting room-temperature spectra of standard compounds (for energy calibration purposes) which prevents contamination of the cryostat chamber and allows the sample to remain undisturbed, both important concerns for studying dilute and radiation-sensitive samples. PMID:25057214

Holman, Karen L McFarlane; Latimer, Matthew J; Yachandra, Vittal K

2004-01-01

86

Liquid helium cryostat with internal fluorescence detection for x-ray absorption studies in the 2–6 keV energy region  

PubMed Central

X-ray absorption spectroscop (XAS) in the intermediate x-ray region (2–6 keV) for dilute biological samples has been limited because of detector/flux limitations and inadequate cryogenic instrumentation. We have designed and constructed a new tailpiece/sample chamber for a commercially available liquid helium cooled cryostat which overcomes difficulties related to low fluorescence signals by using thin window materials and incorporating an internal photodiode detector. With the apparatus, XAS data at the Cl, S, and Ca K edges have been collected on frozen solutions and biological samples at temperatures down to 60 K. A separate chamber has been incorporated for collecting room-temperature spectra of standard compounds (for energy calibration purposes) which prevents contamination of the cryostat chamber and allows the sample to remain undisturbed, both important concerns for studying dilute and radiation-sensitive samples. PMID:25057214

Holman, Karen L. McFarlane; Latimer, Matthew J.; Yachandra, Vittal K.

2014-01-01

87

Dependence of spectral shape of bremsstrahlung spectra on atomic number of target materials in the photon energy range of 5-30 keV  

NASA Astrophysics Data System (ADS)

Dependence of spectral shape of total bremsstrahlung spectra i.e. the sum of ordinary bremsstrahlung (OB) and polarization bremsstrahlung (PB), on the atomic number ( Z) of target materials (Al, Ti, Sn and Pb), produced by continuous beta particles of 90Sr and 204Tl, has been investigated in the photon energy region of 5-30 keV. It has been found that the spectral shape of total bremsstrahlung spectra, in terms of S ( k, Z) i.e. the number of photons of energy k per moc2 per beta disintegration, is not linearly dependent on the atomic number ( Z) of the target material and rather it is proportional to Zn. At lower photon energies, the index values ' n' of Z-dependence are much higher than unity, which is due to the larger contribution of PB into OB. The decrease in ' n' values with increase of photon energy is due to the decrease in contribution of PB into OB. It is clear that the index ' n' values obtained from the modified Elwert factor (relativistic) Bethe-Heitler theory, which include the contribution PB into OB, are in agreement with the experimentally measured results using X-PIPS Si(Li) detector. Hence the contribution of PB into the formation of a spectral shape of total bremsstrahlung spectra plays a vital role.

Singh, Tajinder; Kahlon, K. S.; Dhaliwal, A. S.

2012-02-01

88

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

SciTech Connect

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.

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

2011-02-08

89

Accurate transport simulation of electron tracks in the energy range 1 keV–4 MeV  

Microsoft Academic Search

Multipurpose electron transport simulation codes are widely used in the fields of radiation protection and dosimetry. Broadly based on multiple scattering theories and continuous energy loss stopping powers with some mechanism taking straggling into account, they give reliable answers to many problems. However they may be unsuitable in some specific situations. In fact, many of them are not able to

V. Cobut; L. Cirioni; J. P Patau

2004-01-01

90

Electron Capture Accompanied by Helium Ion Excitation in C^5+ + He Collisions at keV Energies  

Microsoft Academic Search

Cross sections for emission of He^+(2p-1s) radiation produced in single-electron-capture collisions of C^5+ ions with He atoms have been determined at energies in the range 4-8 keV\\/amu. High-resolution EUV collision spectroscopy measurements were facilitated by a glass-capillary-converter array, which increased the efficiency of the photon collection system by an order of magnitude. Cross sections for C^5+ + He collisions were

R. A. Phaneuf; V. Golovkina; V. Kantsyrev; A. Shlyaptseva; R. Bruch

1997-01-01

91

The X-ray behaviour of the high-energy peaked BL Lacertae source PKS 2155-304 in the 0.3-10 keV band  

NASA Astrophysics Data System (ADS)

We present the results of our monitoring of the high-energy peaked BL Lac object PKS 2155-304 by the Swift/X-Ray Telescope (XRT) during 2005-2012. Our timing study shows that the source was highly variable both on longer (weeks-to-months) and intra-day time-scales, up to a factor of 7 in flux, and 30 per cent in fractional variability amplitudes, with no periodic variations. The X-ray spectra are mainly curved with broad ranges of photon index, curvature parameter, and hardness ratio which exhibit significant variability with the flux on different time-scales. Our study of multi-wavelength cross-correlations has revealed that the one-zone SSC scenario seems to be valid for the most optical-to-gamma-ray flares observed during 2006-2012. An `orphan' X-ray flare with no counterpart in other spectral bands suggests the existence of different electron populations. Based on the absence of a correlation between photon index and curvature parameter (expected from the energy-dependent acceleration probability scenario), the observed distribution of curvature parameter from the XRT spectra peaking at b = 0.37, and the observed anti-correlation between the curvature parameter and the 0.3-10 keV flux (i.e. lower curvatures in flaring states), we conclude that the most likely mechanism responsible for producing X-ray emission during the flares is the stochastic acceleration of the electrons.

Kapanadze, B.; Romano, P.; Vercellone, S.; Kapanadze, S.

2014-10-01

92

Atom penetration from a thin film into the substrate during sputtering by polyenergetic Ar{sup +} ion beam with mean energy of 9.4 keV  

SciTech Connect

Penetration of alien atoms (Be, Ni) into Be, Al, Zr, Si and diamond was investigated under Ar{sup +} ion bombardment of samples having thermally evaporated films of 30--50 nm. Sputtering was carried out using a wide energy spectrum beam of Ar{sup +} ions of 9.4 keV to dose D = 1 {times} 10{sup 16}--10{sup 19} ion/cm{sup 2}. Implanted atom distribution in the targets was measured by Rutherford backscattering spectrometry (RBS) of H{sup +} and He{sup +} ions with energy of 1.6 MeV as well as secondary ion mass-spectrometry (SIMS). During the bombardment, the penetration depth of Ar atoms increases with dose linearly. This depth is more than 3--20 times deeper than the projected range of bombarding ions and recoil atoms. This is a deep action effect. The analysis shows that the experimental data for foreign atoms penetration depth are similar to the data calculated for atom migration through the interstitial site in a field of internal (lateral) compressive stresses created in the near-surface layer of the substrate as a result of implantation. Under these experimental conditions atom ratio r{sub i}/r{sub m} (r{sub i} -- radius of dopant, r{sub m} -- radius target of substrate) can play a principal determining role.

Kalin, B.A.; Gladkov, V.P.; Volkov, N.V.; Sabo, S.E. [Moscow Engineering Physics Inst. (Russian Federation)

1995-12-31

93

Developing a Compton Polarimeter to Measure Polarization of Hard X-Rays in the 50-300 keV Energy Range  

E-print Network

This paper discusses the latest progress in the development of GRAPE (Gamma-Ray Polarimeter Experiment), a hard X-ray Compton Polarimeter. The purpose of GRAPE is to measure the polarization of hard X-rays in the 50-300 keV energy range. We are particularly interested in X-rays that are emitted from solar flares and gamma-ray bursts (GRBs). Accurately measuring the polarization of the emitted radiation from these sources will lead, to a better understating of both the emission mechanisms and source geometries. The GRAPE design consists of an array of plastic scintillators surrounding a central high-Z crystal scintillator. We can monitor individual Compton scatters that occur in the plastics and determine whether the photon is photo absorbed by the high-Z crystal or not. A Compton scattered photon that is immediately photo absorbed by the high-Z crystal constitutes a valid event. These valid events provide us with the interaction locations of each incident photon and ultimately produces a modulation pattern for the Compton scattering of the polarized radiation. Comparing with Monte Carlo simulations of a 100% polarized beam, the level of polarization of the measured beam can then be determined. The complete array is mounted on a flat-panel multi-anode photomultiplier tube (MAPMT) that can measure the deposited energies resulting from the photon interactions. The design of the detector allows for a large field-of-view (>pi steradian), at the same time offering the ability to be close-packed with multiple modules in order to reduce deadspace. We plan to present in this paper the latest laboratory results obtained from GRAPE using partially polarized radiation sources.

J. S. Legere; P. Bloser; J. R. Macri; M. L. McConnell; T. Narita; J. M. Ryan

2005-08-14

94

Extension of self-seeding scheme with single crystal monochromator to lower energy < 5 keV as a way to generate multi-TW scale pulses at the European XFEL  

E-print Network

We propose a use of the self-seeding scheme with single crystal monochromator to produce high power, fully-coherent pulses for applications at a dedicated bio-imaging beamline at the European X-ray FEL in the photon energy range between 3.5 keV and 5 keV. We exploit the C(111) Bragg reflection (pi-polarization) in diamond crystals with a thickness of 0.1 mm, and we show that, by tapering the 40 cells of the SASE3 type undulator the FEL power can reach up to 2 TW in the entire photon energy range. The present design assumes the use of a nominal electron bunch with charge 0.1 nC at nominal electron beam energy 17.5 GeV. The main application of the scheme proposed in this work is for single shot imaging of individual protein molecules.

Geloni, Gianluca; Saldin, Evgeni

2012-01-01

95

On the 17-keV neutrino  

SciTech Connect

A brief review on the status of the 17-keV neutrino is presented. Several different experiments found spectral distortions which were consistently interpreted as evidence for a heavy neutrino admixture in [beta] decay. Recent experiments, however, rule out the existence of a 17-keV neutrino as well as escaping criticisms of earlier null results. Moreover, the majority of positive results have been reinterpreted in terms of instrumental effects, despite the need for a different explanation in each case. Anomalies persist in the low energy region of the tritium spectrum which deserve further investigation.

Hime, A.

1993-04-01

96

On the 17-keV neutrino  

SciTech Connect

A brief review on the status of the 17-keV neutrino is presented. Several different experiments found spectral distortions which were consistently interpreted as evidence for a heavy neutrino admixture in {beta} decay. Recent experiments, however, rule out the existence of a 17-keV neutrino as well as escaping criticisms of earlier null results. Moreover, the majority of positive results have been reinterpreted in terms of instrumental effects, despite the need for a different explanation in each case. Anomalies persist in the low energy region of the tritium spectrum which deserve further investigation.

Hime, A.

1993-04-01

97

Study of natMg(d,d0) reaction at detector angles between 90° and 170°, for the energy range Ed,lab=1660-1990 keV  

NASA Astrophysics Data System (ADS)

In the present work, the study of the natMg(d,d0) is presented for the energy range Ed,lab = 1660-1990 keV (in steps of 5 keV), for detector angles between 90° and 170°. Elastic scattering data for two forward angles (55° and 70°) were also obtained. In order to validate the obtained experimental results a thick Mg sample with Au evaporated on top was fabricated and benchmarking measurements were performed at various deuteron beam energies. The results of the present work are complementary to the recently published 24Mg(d,p0,1,2) reaction cross section data, thus facilitating the simultaneous depth profiling study of magnesium by both the d-NRA and EBS techniques.

Patronis, N.; Aslanoglou, X.; Axiotis, M.; Georgiadou, A.; Kokkoris, M.; Lagoyannis, A.; Misaelides, P.; Paneta, V.

2014-10-01

98

Implementation of low-energy surface-induced dissociation (eV SID) and high-energy collision-induced dissociation (keV CID)  

E-print Network

experiments, accomplished with a surface placed after the last reflectron electrode, the electrodes energy expression, E mv2 /2. As pointed out in the foreword to Cotter's book on TOF mass spectrometry [1

Wysocki, Vicki H.

99

Experimental response functions spanning the gamma-ray energy range of 123.6 keV to 11.67 MeV and response matrix generation for bismuth germanate scintillation detectors  

NASA Astrophysics Data System (ADS)

We report experimental response functions at 12 gamma-ray energies over the range of 123.6 keV to 11.67 MeV for a 2.54 cm diameter × 2.54 cm long and a 7.62 cm diameter × 7.62 cm long bismuth germanate scintillation detector. The measurements were made at, or corrected to correspond to, source-to-detector distances of 100 cm. The resolutions of the detectors at a gamma-ray energy of 661.6 keV are 11.6% for the small detector and 13.0% for the large detector. We also present an interpolation method for generating a response function at any gamma-ray energy in the range of 123.6 keV to 11.67 MeV for either scintillator using the experimental response functions. Additionally, this method is used in constructing response matrices for unfolding gamma-ray pulse-height distributions acquired with the detectors. A computer code written in FORTRAN-77 generates the response matrices.

Kiziah, Rex R.; Lowell, John R.

1991-07-01

100

Energy dependence of photon-induced K? and K? x-ray production cross-sections for some elements with 38?Z?51 in the energy range 20-50 keV  

NASA Astrophysics Data System (ADS)

The energy dependence of photon-induced K? and K? x-ray production (or x-ray fluorescence) cross-sections for Sr, Y, Mo, Ru, Pd, Ag, In and Sb elements has been studied in the energy range of 20-50 keV using Energy Dispersive X-Ray Fluorescence (EDXRF) Spectrometry. The photon energy dependence of K x-ray production cross-sections was measured with secondary excitation method. A radioisotope point source of 241Am was employed to excite the K x-rays of secondary exciter elements. The L x-ray yields from Th and U were measured to determine IoG (the intensity of exciter K x-rays falling on primary target). 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 K? and K? spectral peaks, as well as the net peak areas, have been determined by a fitting process. The measured K? and K? x-ray production cross-sections have been compared with calculated theoretical values in this energy regime. The present experimental results for all the elements were in general agreement with the theoretical values calculated using photoionization cross-sections, fractional rates (based on Hartree-Slater potentials) and fluorescence yields.

Seven, Sabriye

2012-05-01

101

Experimental and theoretical studies of the He(2+)-He system - Differential cross sections for direct, single-, and double-charge-transfer scattering at keV energies  

NASA Technical Reports Server (NTRS)

Measurements and calculations of differential cross sections for direct scattering, single-charge transfer, and double-charge transfer in collisions of 1.5-, 2.0-, 6.0-, and 10.0-keV (He-3)2+ with an He-4 target are reported. The measurements cover laboratory scattering angles below 1.5 deg with an angular resolution of about 0.03 deg. A quantum-mechanical molecular-state representation is employed in the calculations; in the case of single-charge transfer a two-state close-coupling calculation is carried out taking into account electron-translation effects. The theoretical calculations agree well with the experimental results for direct scattering and double-charge transfer. The present calculation identifies the origins of oscillatory structures observed in the differential cross sections.

Gao, R. S.; Dutta, C. M.; Lane, N. F.; Smith, K. A.; Stebbings, R. F.; Kimura, M.

1992-01-01

102

Accurate Monte Carlo calculations of the combined attenuation and build-up factors, for energies (20-1500 keV) and distances (0-10 cm) relevant in brachytherapy.  

PubMed

The combined build-up and attenuation factor, B exp (-mu r), of point isotropic photon sources in a water medium has been calculated using the Monte Carlo method, for energies (20-1500 keV) and distances (1-10 cm) relevant in brachytherapy. For the transport of photons and electrons, up-to-date and self-consistent total, partial and differential cross sections were used. The influence of coherent (Rayleigh) and incoherent (Compton) scattering, as well as the effects of the source and medium geometries on the calculations, were investigated in detail and it was found that these effects can lead to significant deviations from published data, especially at low energies and/or large distances from the sources. Our results can be used for any mono- or multi-energetic photon source in the energy range 20-1500 keV with uncertainties of the order of 2-3%, and they may influence treatment planning especially in the case of organs at risk which are usually near the edge of the body. PMID:1871210

Angelopoulos, A; Perris, A; Sakellariou, K; Sakelliou, L; Sarigiannis, K; Zarris, G

1991-06-01

103

Internal electron conversion of the isomeric {sup 57}Fe nucleus state with an energy of 14.4 keV excited by the radiation of the plasma of a high-power femtosecond laser pulse  

SciTech Connect

We recorded the spectrum of delayed secondary electrons ejected from the target, which was coated with a layer of iron enriched with the {sup 57}Fe isotope to 98%, under its irradiation by fluxes of broadband X-ray radiation and fast electrons from the plasma produced by a femtosecond laser pulse at an intensity of 10{sup 17} W cm{sup -2}. Maxima were identified at energies of 5.6, 7.2, and 13.6 keV in the spectrum obtained for a delay of 90 - 120 ns. The two last-listed maxima owe their origin to the internal electron conversion of the isomeric level with an energy of 14.4 keV and a lifetime of 98 ns to the K and L shells of atomic iron, respectively; the first-named level arises from a cascade K - L{sub 2}L{sub 3} Auger process. Photoexcitaion by the X-ray plasma radiation is shown to be the principal channel of the isomeric level excitation. (interaction of laser radiation with matter)

Golovin, G V; Savel'ev-Trofimov, Andrei B; Uryupina, D S; Volkov, Roman V [International Laser Center, M. V. Lomonosov Moscow State University, Moscow (Russian Federation)

2011-03-31

104

Response of a passivated implanted planar silicon (PIPS) detector for heavy ions with energies between 25 and 360 keV  

Microsoft Academic Search

Measurements of the energy response of a passivated implanted planar silicon (PIPS) detector for a variety of ions at low energies are presented. Such measurements are needed for the calibration of a PIPS detector used in a space borne time-of-flight mass spectrometer. Comparisons to similar measurements with state of the art silicon surface barrier (SSB) detectors show a weaker energy

Michael Oetliker

1993-01-01

105

Ultra-thin curved transmission crystals for high resolving power (up to E/?E = 6300) x-ray spectroscopy in the 6-13??keV energy range.  

PubMed

Ultra-thin curved transmission crystals operating in the Cauchois spectrometer geometry were evaluated for the purpose of achieving high spectral resolution in the 6-13 keV x-ray energy range. The crystals were silicon (111) and sapphire R-cut wafers, each 18 ?m thick, and a silicon (100) wafer of 50-?m thickness. The W L?1 spectral line at 8.398 keV from a laboratory source was used to evaluate the resolution. The highest crystal resolving power, E/?E=6300, was achieved by diffraction from the (33-1) planes of the Si(100) wafer that was cylindrically bent to a radius of curvature of 254 mm, where the (33-1) planes have an asymmetric angle of 13.26° from the normal of the crystal surface facing the x-ray source. This work demonstrates the ability to measure highly resolved line shapes of the K transitions of the elements Fe through Kr and the L transitions of the elements Gd through Th using a relatively compact spectrometer optical system and readily available thin commercial wafers. The intended application is as a diagnostic of laser-produced plasmas where the presence of multiple charged states and broadenings from high temperature and density requires high-resolution methods that are robust in a noisy source environment. PMID:25503010

Seely, John F; Hudson, Lawrence T; Glover, Jack L; Henins, Albert; Pereira, Nino

2014-12-15

106

Response of a passivated implanted planar silicon (PIPS) detector for heavy ions with energies between 25 and 360 keV  

NASA Astrophysics Data System (ADS)

Measurements of the energy response of a passivated implanted planar silicon (PIPS) detector for a variety of ions at low energies are presented. Such measurements are needed for the calibration of a PIPS detector used in a space borne time-of-flight mass spectrometer. Comparisons to similar measurements with state of the art silicon surface barrier (SSB) detectors show a weaker energy response and a much lower noise level of the PIPS detector. A dependence of the energy response on the incident angle of the ions was observed which is attributed to channeling of ions within the silicon crystal of the detector.

Oetliker, Michael

1993-12-01

107

The dissociation of 13CH and 12CH 2 molecules in He and N 2 at beam energies of 80-250 keV and possible implications for radiocarbon mass spectrometry  

NASA Astrophysics Data System (ADS)

Isotopic ratios of 14C at natural levels can be efficiently measured with accelerator mass spectrometry (AMS). In compact AMS systems, 13CH and 12CH 2 molecular interferences are destroyed in collisions with the stripper gas, a process which can be described by dissociation cross sections. These dissociation cross sections determine the gas areal density required for sufficient attenuation of the interfering molecular beams, and are therefore key parameters in the effort to further reduce the terminal voltage and thus the size of the AMS system. We measured the dissociation cross sections of 13CH and 12CH 2 in N 2 and He in the energy range of 80-250 keV. In N 2, cross sections were constant for energies above 100 keV with average values per molecule of (8.1 ± 0.4) × 10 -16 cm 2 for 13CH and (9.5 ± 0.5) × 10 -16 cm 2 for 12CH 2. In He, cross sections were constant over the full measured range of 80-150 keV with average values of (4.2 ± 0.3) × 10 - 16 cm 2 and (4.8 ± 0.4) × 10 -16 cm 2, respectively. A considerable reduction of the terminal voltage from the currently used 200 kV while using N 2 for 13CH and 12CH 2 molecule dissociation is not possible: the required N 2 areal densities of ˜1.4 ?g/cm 2, consequential angular straggling and a decreasing 1+ charge state fraction would reduce the ion beam transmission too much. This is not the case for He: sufficient molecule dissociation can be obtained with gas densities of ˜0.4 ?g/cm 2, for which angular straggling is relatively small. In addition, the 1+ charge state fraction still increases at lower stripping energies. Thus, the usage of He for stripping and molecule dissociation might allow the development of even smaller 14C-AMS systems than available today.

Schulze-König, T.; Seiler, M.; Suter, M.; Wacker, L.; Synal, H.-A.

2011-01-01

108

Beryllium and Graphite High-Accuracy Total Cross-Section Measurements in the Energy Range from 24 to 900 keV  

E-print Network

Beryllium and Graphite High-Accuracy Total Cross-Section Measurements in the Energy Range from 24 new measurements of the carbon and beryllium neutron total cross section in the energy range of 24. Measurements of three samples of different thicknesses of beryllium resulted in accurate total cross

Danon, Yaron

109

Nucl. Instr. Meth. Phys. Res. B., Accepted for publication (1995). Molecular dynamics simulation of ion ranges at keV energies  

E-print Network

Nucl. Instr. Meth. Phys. Res. B., Accepted for publication (1995). Molecular dynamics simulation In molecular dynamics simulations the time evolution of a system of atoms is calculated by solving molecular dynamics method for calculating ion ranges and deposited energies in the recoil energy region 100

Nordlund, Kai

110

Experimental study of interactions of highly charged ions with atoms at keV energies. Progress report, August 15, 1990--February 15, 1993  

SciTech Connect

This final progress report summarizes the work carried out during the 29 month period from August 15, 1990 to February 15, 1993 under grant DE-FG02-86ER13519. The following experiments were done. We measured the absolute total and one- and two- electron transfer cross sections for Ar{sup q+} (8{le} q {le} 16) on He and H{sub 2} at 2.3 qkeV, the angular distributions of the scattered projectiles in Ar{sup 8+,9+} collisions, with Ar and Kr at 2.3 qkeV, the electron emissions in low energy Ar{sup q+} on Ar collisions, the recoil ion charge state distributions in low energy Ar{sup q+} -Ar collisions, the absolute total and one-and two-electron transfer cross sections for Ar{sup 8+} on Ar at 2.3 qkeV, and the absolute total and one- and two-electron transfer cross sections for Ar{sup 8+} on Ar as a function of energy. We also used energy gain spectroscopy to study Ar{sup q+} on Ar collisions at 40 and 30 qeV, and time of flight spectroscopy to investigate ionization and dissociation of CO and N{sub 2} in collisions with low energy, highly charged argon ions. In addition, we applied the Goldberger and Watson transition theory to derive transition rates and cross sections for atomic radiative and/or non radiative processes, wrote a computer code TRANSIT which can calculate energies, wave functions and radiative and non radiative rates for atoms and ions. The code is highly modular and can easily be modified to calculate higher order processes. Finally, we have done an Ab-Initio molecular orbital electronic energy level calculation for the (ArAr){sup 8+} system as a function internuclear separation.

Kostroun, V.O.

1993-01-29

111

Crossed molecular beams study of inelastic non-adiabatic processes in gas phase collisions between sodium ions and ZnBr2 molecules in the 0.10-3.50 keV energy range.  

PubMed

Inelastic electronically non-adiabatic reactions between Na(+) ions and neutral ZnBr(2) molecules, both in their electronic ground state, have been studied using crossed beams techniques and measuring the decaying emission radiation of the excited species produced. The fluorescent emission corresponding to Na(3 (2)P) produced by a charge transfer reaction was observed, as well as that corresponding to the decay of Zn(4s 5s (3)S), generated by dissociation of the neutral target molecule, to Zn(4s 4p (3)P). The phosphorescent decaying emission of Zn*(4s 4p (3)P) to the zinc ground state was also observed. For each emission process, the cross section energy dependences have been measured in the 0.10-3.50 keV energy range in the laboratory system. The ground electronic state of the (NaZnBr(2))(+) collision system has been characterized by ab initio chemical structure calculations at the second order Möller-Plesset perturbation level of theory using pseudo-potentials. By performing restricted open shell Hartree-Fock calculations for C(2v) geometries, four singlet and four triplet potential energy surfaces of the system have been calculated and used to interpret qualitatively the observed reactions. A simple two-state dynamical model is presented that allows an estimation of the maximum values for measured cross sections at high collision energies to be made. PMID:23083158

de Andrés, J; Lucas, J M; Albertí, M; Bofill, J M; Belyaev, A; Aguilar, A

2012-10-21

112

Crossed molecular beams study of inelastic non-adiabatic processes in gas phase collisions between sodium ions and ZnBr2 molecules in the 0.10-3.50 keV energy range  

NASA Astrophysics Data System (ADS)

Inelastic electronically non-adiabatic reactions between Na+ ions and neutral ZnBr2 molecules, both in their electronic ground state, have been studied using crossed beams techniques and measuring the decaying emission radiation of the excited species produced. The fluorescent emission corresponding to Na(3 2P) produced by a charge transfer reaction was observed, as well as that corresponding to the decay of Zn(4s 5s 3S), generated by dissociation of the neutral target molecule, to Zn(4s 4p 3P). The phosphorescent decaying emission of Zn*(4s 4p 3P) to the zinc ground state was also observed. For each emission process, the cross section energy dependences have been measured in the 0.10-3.50 keV energy range in the laboratory system. The ground electronic state of the (NaZnBr2)+ collision system has been characterized by ab initio chemical structure calculations at the second order Möller-Plesset perturbation level of theory using pseudo-potentials. By performing restricted open shell Hartree-Fock calculations for C2v geometries, four singlet and four triplet potential energy surfaces of the system have been calculated and used to interpret qualitatively the observed reactions. A simple two-state dynamical model is presented that allows an estimation of the maximum values for measured cross sections at high collision energies to be made.

de Andrés, J.; Lucas, J. M.; Albertí, M.; Bofill, J. M.; Belyaev, A.; Aguilar, A.

2012-10-01

113

Energy Loss by keV Ions in Silicon H. O. Funsten, S. M. Ritzau,* R.W. Harper, and J. E. Borovsky  

E-print Network

prediction of ion-induced effects in silicon. We also observe a velocity threshold at 0.05 a.u. for the onset], secondary electron emission [10], and fullerene fragmentation [11], direct measure- ments of the partitioning of the energy loss between nuclear and electronic processes at velocities less than the Bohr

Johnson, Robert E.

114

Correlative multielectron processes in K-shell photoionization of Ca, Ti and V in the energy range of 8-35 keV  

Microsoft Academic Search

The Kalpha satellite spectra arising from the correlative multielectron processes accompanying K-shell photoionization of Ca, Ti and V were measured using a broad range crystal spectrometer. Multiconfiguration Dirac-Fock calculations were performed to interpret the observed x-ray energies and the spectral line shape. The calculations agree fairly well with the experimental results. The variation of the Kalpha L1 satellite and the

Masaki Oura; Hitoshi Yamaoka; Kiyoshi Kawatsura; Katsumi Takahiro; Naoki Takeshima; Yaming Zou; Roger Hutton; Shin Ito; Yohko Awaya; Mititaka Terasawa; Tsuguhisa Sekioka; Takeshi Mukoyama

2002-01-01

115

Analysis of temperature-dependent neutron transmission and self-indication measurements on tantalum at 2-keV neutron energy  

NASA Technical Reports Server (NTRS)

The method of pseudo-resonance cross sections is used to analyze published temperature-dependent neutron transmission and self-indication measurements on tantalum in the unresolved region. In the energy region analyzed, 1825.0 to 2017.0 eV, a direct application of the pseudo-resonance approach using a customary average strength function will not provide effective cross sections which fit the measured cross section behavior. Rather a local value of the strength function is required, and a set of resonances which model the measured behavior of the effective cross sections is derived. This derived set of resonance parameters adequately represents the observed resonance hehavior in this local energy region. Similar analyses for the measurements in other unresolved energy regions are necessary to obtain local resonance parameters for improved reactor calculations. This study suggests that Doppler coefficients calculated by sampling from grand average statistical distributions over the entire unresolved resonance region can be in error, since significant local variations in the statistical distributions are not taken into consideration.

Semler, T. T.

1973-01-01

116

Surface-morphology changes and damage in hot tungsten by impact of 80 eV - 12 keV He-ions and keV-energy self-atoms  

NASA Astrophysics Data System (ADS)

We report results of measurements on the evolution of the surface morphology of a hot tungsten surface due to impacting low-energy (80 - 12,000 eV) He ions, performed at the ORNL Multicharged Ion Research Facility (MIRF). Surface-morphology changes were investigated over a broad range of fluences, energies and temperatures for both virgin and pre-damaged W-targets. At low fluences, ordered coral-like and ridge-like surface structures are observed, with great grain-to-grain variability. At the largest fluences, individual grain characteristics disappear in FIB/SEM scans, and the entire surface is covered by a multitude of near-surface bubbles with a broad range of sizes, and disordered whisker growth, while in top-down SEM imaging the surface is virtually indistinguishable from the nanofuzz produced on linear plasma devices. These features are evident at progressively lower fluences as the He-ion energy is increased. In addition, simulations were carried out of damage caused by cumulative bombardment of 1 keV W self-atoms, using LAMMPS at the Kraken supercomputing facility of the University of Tennessee. The simulations show strong defect-recombination effects that lead to a saturation of the total defect number after a few hundred impacts, while sputtering and implantation lead to an imbalance of the vacancy and interstitial numbers.

Meyer, F. W.; Krstic, P. S.; Hijazi, H.; Bannister, M. E.; Dadras, J.; Parish, C. M.; Meyer, H. M., Iii

2014-04-01

117

Systematic survey of the dose enhancement in tissue-equivalent materials facing medium- and high-Z backscatterers exposed to X-rays with energies from 5 to 250 keV.  

PubMed

The present study has been inspired by the results of earlier dose measurements in tissue-equivalent materials adjacent to thin foils of aluminum, copper, tin, gold, and lead. Large dose enhancements have been observed in low-Z materials near the interface when this ensemble was irradiated with X-rays of qualities known from diagnostic radiology. The excess doses have been attributed to photo-, Compton, and Auger electrons released from the metal surfaces. Correspondingly, high enhancements of biological effects have been observed in single cell layers arranged close to gold surfaces. The objective of the present work is to systematically survey, by calculation, the values of the dose enhancement in low-Z media facing backscattering materials with a variety of atomic numbers and over a large range of photon energies. Further parameters to be varied are the distance of the point of interest from the interface and the kind of the low-Z material. The voluminous calculations have been performed using the PHOTCOEF algorithm, a proven set of interpolation functions fitted to long-established Monte Carlo results, for primary photon energies between 5 and 250 keV and for atomic numbers varying over the periodic system up to Z = 100. The calculated results correlate well with our previous experimental results. It is shown that the values of the dose enhancement (a) vary strongly in dependence upon Z and photon energy; (b) have maxima in the energy region from 40 to 60 keV, determined by the K and L edges of the backscattering materials; and (c) are valued up to about 130 for "International Commission on Radiological Protection (ICRP) soft tissue" (soft tissue composition recommended by the ICRP) as the adjacent low-Z material. Maximum dose enhancement associated with the L edge occurs for materials with atomic numbers between 50 and 60, e.g., barium (Z = 56) and iodine (Z = 53). Such materials typically serve as contrast media in medical X-ray diagnostics. The gradual reduction in the dose enhancement with increasing distance from the material interface, owed to the limited ranges of the emitted secondary electrons, has been documented in detail. The discussion is devoted to practical radiological aspects of the dose enhancement phenomenon. Cytogenetic effects in cell layers closely proximate to surfaces of medium-Z materials might vary over two orders of magnitude, because the dose enhancement is accompanied by the earlier observed about twofold increase in the low-dose RBEM at a tissue-to-gold interface. PMID:24633421

Seidenbusch, M; Harder, D; Regulla, D

2014-05-01

118

R-matrix analysis of {sup 235}U neutron transmission and cross sections in the energy range 0 to 2.25 keV  

SciTech Connect

This document describes a new R-matrix analysis of {sup 235}U cross section data in the energy range from 0 to 2,250 eV. The analysis was performed with the computer code SAMMY, that has recently been updated to permit, for the first time, inclusion of both differential and integral data within the analysis process. Fourteen differential data sets and six integral quantities were used in this evaluation: two measurements of fission plus capture, one of fission plus absorption, six of fission alone, two of transmission, and one of eta, plus standard values of thermal cross sections for fission, capture, and scattering, and of K1 and the Westcott g-factors for both fission and absorption. An excellent representation was obtained for the high-resolution transmission, fission, and capture cross-section data as well as for the integral quantities. The result is a single set of resonance parameters spanning the entire range up to 2,250 eV, a decided improvement over the present ENDF/VI evaluation, in which eleven discrete resonance parameter sets are required to cover that same energy range. This new evaluation is expected to greatly improve predictability of the criticality safety margins for nuclear systems in which {sup 235}U is present.

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

1997-11-01

119

Ion induced modification of polymers at energies between 100 keV and 1 GeV applied for optical waveguides and improved metal adhesion  

NASA Astrophysics Data System (ADS)

Polymers are a class of materials widely used for a broad field of applications. Ion irradiation ranging from several eV to GeV is a quite efficient tool to modify the properties of polymers like wettability, optical properties, adhesion between metal and polymer surfaces. In this paper ion induced chemical changes of polymers will be discussed in relation to the modified macroscopic properties. In the field of optical telecommunication, polymers are discussed as a new class of materials for the fabrication of passive optical devices. Ion irradiation is a promising method to generate structures with a modified index of refraction, which is necessary for the guidance of light with different wavelengths in optical devices. Modified optical properties of different polymers under ion irradiation will be discussed. Analytical investigations like infrared measurements and measurement of the outgassing reaction products during irradiation will be discussed to interpret the chemical changes of the polymers. Metallization of polymers is of interest in several fields of application like for multilayer systems in microtechnology or casings for radiation shielding for example. Ion beam mixing at low energies is a promising method to improve the metal/polymer adhesion. Also ion irradiation at high energies applied to a metal/polymer multilayer can improve the adhesion of a metal layer to a polymer surface, if not sufficient. Different metal/polymer systems will be presented as well as specific applications.

Rück, D. M.

2000-05-01

120

Observations of celestial X-ray sources above 20 keV with the high-energy scintillation spectrometer on board OSO 8  

NASA Technical Reports Server (NTRS)

High-energy X-ray spectra of the Crab Nebula, Cyg- XR-1, and Cen A were determined from observations with the scintillation spectrometer on board the OSO-8 satellite, launched in June, 1975. Each of these sources was observed over two periods of 8 days or more, enabling a search for day-to-day and year to year variations in the spectral and temporal characteristics of the X-ray emission. No variation in the light curve of the Crab pulsar was found from observations which span a 15-day period in March 1976, with demonstrable phase stability. Transitions associated with the binary phase of Cyg XR-1 and a large change in the emission from Con A are reported.

Crannell, C. J.; Dennis, B. R.; Dolan, J. H.; Frost, K. J.; Orwig, L. E.; Beall, J. H.; Maurer, G. S.

1977-01-01

121

Observations of celestial X-ray sources above 20 keV with the high-energy scintillation spectrometer on board OSO-8  

NASA Technical Reports Server (NTRS)

High-energy X-ray spectra of the Crab Nebula, Cyg XR-1, and Cen A were determined from observations with the scintillation spectrometer onboard the OSO-8 satellite, launched in June 1975. Each of these sources was observed over two periods of 8 days or more, allowing a search for day-to-day and year-to-year variations in the spectral and temporal characteristics of the X-ray emission. No variation in the light curve of the Crab pulsar was found from observations which span a 15-day period in March 1976, with demonstrable phase stability. Transitions associated with the binary phase of Cyg XR-1 and a large change in the emission from Cen A are reported.

Crannell, C. J.; Dennis, B. R.; Dolan, J. F.; Frost, K. J.; Orwig, L. E.; Beall, J. H.; Maurer, G. S.

1977-01-01

122

Calculation of proton total reaction cross sections for some target nuclei in incident energy range of 10-600 MeV  

SciTech Connect

In this study, proton total reaction cross sections have been investigated for some isotopes such as {sup 12}C, {sup 27}Al, {sup 9}Be, {sup 16}O, {sup 181}Ta, {sup 197}Au, {sup 6}Li, and {sup 14}N by a proton beam up to 600 MeV. Calculation of the proton total cross sections has been carried out by the analytic expression formulated by M.A. Alvi by using Coulomb-modified Glauber theory with the Helm model nuclear form factor. The obtained results have been discussed and compared with the available experimental data and found to be in agreement with each other.

Bueyuekuslu, H.; Kaplan, A., E-mail: kaplan@fef.sdu.edu.t [Sueleyman Demirel University, Faculty of Arts and Sciences, Department of Physics (Turkey); Aydin, A. [Kirikkale University, Faculty of Arts and Sciences, Department of Physics (Turkey); Tel, E. [Gazi University, Faculty of Arts and Sciences, Department of Physics (Turkey); Yildirim, G. [Abant Izzet Baysal University, Faculty of Arts and Sciences, Department of Physics (Turkey)

2010-10-15

123

A Monte Carlo track structure simulation code for the full-slowing-down carbon projectiles of energies 1 keV u-1-10 MeV u-1 in water  

NASA Astrophysics Data System (ADS)

The paper presents a new Monte Carlo track structure code (KURBUC_carbon) for simulations of full-slowing-down carbon projectiles C0-C6+ of energies 1 keV u-1-10 MeV u-1 in water vapour. The code facilitates investigation of the spatial resolution effect for scoring track parameters under the Bragg peak of a carbon ion beam. Interactions of carbon projectiles and secondary electrons were followed interaction-by-interaction down to a 1 keV u-1 cutoff for primary ions and down to 10 eV for electrons. Electronic interactions and nuclear elastic scattering were taken into account, including charge exchange reactions and double electronic interactions for the carbon projectiles. The reliability of the code was tested for radial dose, range and W-value. The calculated results were compared with the published experimental data and other model calculations. The results obtained showed good agreement in most cases where comparisons could be made. Depth dose profiles for 1-10 MeV u-1 C6+ were used to form a spread-out Bragg peak (SOBP) of 0.35 mm width in water. At all depths of the SOBP, the energy distributions of the carbon projectiles varied appreciably with the change in the scoring volume. The corresponding variation was nearly negligible for the track average linear energy transfer (LET), except at the distal end of the SOBP. By varying the scoring slab thickness from 1 to 100 µm, the maximum track average LET decreased by ˜30%. The Monte Carlo track structure simulation in the full-slowing-down mode is a powerful tool for investigation of the biophysical properties of radiation tracks under the Bragg peak and SOBP of a carbon ion beam. For estimation of radiation effectiveness under the Bragg peak the new Monte Carlo track structure code provides yet another accurate and effective dosimetry tool at a single cell level. This is because radiobiology within tissue elements can be understood better with dosimetry at cellular and subcellular level.

Liamsuwan, T.; Nikjoo, H.

2013-02-01

124

Grazing incidence imaging from 10 to 40 keV  

Microsoft Academic Search

The prospects for imaging X rays at energies from 10 to 40 keV with grazing incidence optics are explored. The scientific rationale and existing laboratory measurements are reviewed. Measurements of reflectivity using possible mirror materials are described. Iridium-coated float glass gives an improved performance over gold by the factor predicted by theory, but both had a lower absolute level. This

Martin Elvis; Daniel G. Fabricant; Paul Gorenstein

1988-01-01

125

Dynamics of fluxes of protons with energies 30-80 keV during geomagnetic storms on January 21-22, 2005, and December 14-15, 2006, according to data from low-orbit satellites  

NASA Astrophysics Data System (ADS)

We present the results of a comparative analysis of the dynamics of three populations of fluxes of protons with energy 30-80 keV as measured by NOAA solar-synchronous satellites ( POES 15, 16, 17) at low latitudes ( L < 2) and at latitudes lower and higher than the boundary of isotropic precipitation during the geomagnetic storms on January 21-22, 2005 and December 14-15, 2006. Based on a complex analysis of experimental data on particle fluxes at low orbits and on measurements of solar wind parameters performed by the ACE spacecraft, we have studied the dynamical peculiarities of the fluxes of particles and of their longitudinal distributions depending on the conditions in the interplanetary medium. It is shown that an increase of trapped particle fluxes and the development of the main phase of the geomagnetic storm on January 21-22, 2005 are associated with the magnetosphere's response to a prolonged action of an extremely powerful coronal mass ejection at a northern orientation of the IMF. On December 14, 2006 an insufficient amplitude and duration of the pressure impulse did not result in development of a disturbance similar to January 21-22, 2005. The development of the main phase of this storm is related to a southward turn of the IMF, which has occurred only seven hours after the SSC.

Vlasova, N. A.; Kalegaev, V. V.

2014-11-01

126

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

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(?1) 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

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

2012-04-01

127

FERMI OBSERVATIONS OF GRB 090510: A SHORT-HARD GAMMA-RAY BURST WITH AN ADDITIONAL, HARD POWER-LAW COMPONENT FROM 10 keV TO GeV ENERGIES  

SciTech Connect

We present detailed observations of the bright short-hard gamma-ray burst GRB 090510 made with the Gamma-ray Burst Monitor (GBM) and Large Area Telescope (LAT) on board the Fermi observatory. GRB 090510 is the first burst detected by the LAT that shows strong evidence for a deviation from a Band spectral fitting function during the prompt emission phase. The time-integrated spectrum is fit by the sum of a Band function with E{sub peak} = 3.9 {+-} 0.3 MeV, which is the highest yet measured, and a hard power-law component with photon index -1.62 {+-} 0.03 that dominates the emission below {approx}20 keV and above {approx}100 MeV. The onset of the high-energy spectral component appears to be delayed by {approx}0.1 s with respect to the onset of a component well fit with a single Band function. A faint GBM pulse and a LAT photon are detected 0.5 s before the main pulse. During the prompt phase, the LAT detected a photon with energy 30.5{sup +5.8}{sub -2.6} GeV, the highest ever measured from a short GRB. Observation of this photon sets a minimum bulk outflow Lorentz factor, {Gamma}{approx_gt} 1200, using simple {gamma}{gamma} opacity arguments for this GRB at redshift z = 0.903 and a variability timescale on the order of tens of ms for the {approx}100 keV-few MeV flux. Stricter high confidence estimates imply {Gamma} {approx_gt} 1000 and still require that the outflows powering short GRBs are at least as highly relativistic as those of long-duration GRBs. Implications of the temporal behavior and power-law shape of the additional component on synchrotron/synchrotron self-Compton, external-shock synchrotron, and hadronic models are considered.

Ackermann, M.; Bechtol, K.; Berenji, B.; Blandford, R. D.; Bloom, E. D.; Borgland, A. W.; Bouvier, A. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Asano, K. [Interactive Research Center of Science, Tokyo Institute of Technology, Meguro City, Tokyo 152-8551 (Japan); Atwood, W. B. [Santa Cruz Institute for Particle Physics, Department of Physics and Department of Astronomy and Astrophysics, University of California at Santa Cruz, Santa Cruz, CA 95064 (United States); Axelsson, M. [Department of Astronomy, Stockholm University, SE-106 91 Stockholm (Sweden); Baldini, L.; Bellazzini, R.; Bregeon, J. [Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa (Italy); Ballet, J. [Laboratoire AIM, CEA-IRFU/CNRS/Universite Paris Diderot, Service d'Astrophysique, CEA Saclay, 91191 Gif sur Yvette (France); Barbiellini, G. [Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste (Italy); Baring, M. G. [Department of Physics and Astronomy, Rice University, MS-108, P.O. Box 1892, Houston, TX 77251 (United States); Bastieri, D. [Istituto Nazionale di Fisica Nucleare, Sezione di Padova, I-35131 Padova (Italy); Bhat, P. N. [Center for Space Plasma and Aeronomic Research (CSPAR), University of Alabama in Huntsville, Huntsville, AL 35899 (United States); Bissaldi, E. [Max-Planck Institut fuer extraterrestrische Physik, 85748 Garching (Germany); Bonamente, E., E-mail: jchiang@slac.stanford.ed, E-mail: sylvain.guiriec@lpta.in2p3.f, E-mail: j.granot@herts.ac.u, E-mail: ohno@astro.isas.jaxa.j [Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, I-06123 Perugia (Italy)

2010-06-20

128

Neutron-capture gamma rays below 40 keV  

NASA Astrophysics Data System (ADS)

A review of neutron-capture gamma ray measurements below 40 keV is given and experimental methods are discussed. New experiments with a Si(Li) detector have been performed. Energies and absolute intensities of low energy (n, ?) transitions in 28Al, 40K, 52V, 128I, 134Cs, 160Tb, 166Ho, 170Tm, 176Lu, 182Ta, 192Ir, 198Au and 233Th are presented. These new results can serve calibration purposes and provide nuclear structure information.

Durner, P.; Von Egidy, T.; Hartmann, F. J.

1989-06-01

129

Stopping powers and extrapolated ranges for electrons (1-10 keV) in metals  

Microsoft Academic Search

A thin film quasiadiabatic calorimeter has been applied to the measurement of the stopping power for electrons, under conditions of small angle scattering, in Al, Ni, Cu, Ag and Au in the energy region 1 keV to 10 keV. Results are presented with an estimated precision of 15%. Corrections are included for the multiple scattering enhancement of the apparent path

K O Al-Ahmad; D E Watt

1983-01-01

130

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)

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.

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

1972-01-01

131

Backside-thinned CCDs for keV electron detection  

NASA Astrophysics Data System (ADS)

This paper presents preliminary results on the performance of n-channel, backside-thinned charge-coupled devices (CCDs) as electron-bombarded-semiconductor (EBS) imagers for the detection of 1-10 keV electrons. The devices exhibit average EBS gains ranging from approximately 50 at 1 keV to >1600 at 10 keV. Device radiation tolerance has been investigated by exposing normally-clocked devices to 6 keV electron doses up to 0.01 Coulombs/cm(superscript 2). Room temperature pre- and post-irradiation results are presented for these key device parameters: full well capacity, dark current, and charge transfer efficiency (CTE). At the maximum dose of 0.01 Coulombs/cm(superscript 2), full well capacity decreases 9% from an initial value of 680,000 e(superscript -), and dark current increases from energies other than 6 keV is estimated by measurement of the x-ray generation efficiency of silicon as a function of electron energy. Device stability after temperature cycling has been studied by subjecting packaged devices to vacuum bakes of 24 hours at 300 degree(s)C. Full well, CTE, EBS gain, and output amplifier performance are unchanged after the extended temperature cycle, while dark current decreases slightly by 15%. In summary, these initial results indicate that the CCD can function as both an efficient and robust electron imager.

Ravel, Mihir K.; Reinheimer, Alice L.

1991-07-01

132

Creation of 2-5 keV and 5-10 keV sky maps using XMM-Newton data  

NASA Astrophysics Data System (ADS)

Sky maps are powerful visualisation tools for quicklook analysis of extended sources. The latest sky map in soft X-rays (0.1-2.4 keV) has been created in the 1990's using ROSAT data. By analysing publically available data from XMM-Newton X-ray mission we constructed new sky maps in two energy bands - 2-5 keV and 5-10 keV, complementary to ROSAT data, covering approximately 1% of the sky, and included them in our web-based tool http://skyview.virgoua.org.

Savchenko, D. O.; Iakubovskyi, D. A.

2014-12-01

133

5 upgradable to 25Â keV free electron laser facility  

NASA Astrophysics Data System (ADS)

A free electron laser (FEL) facility utilizing a recirculated superconducting radio frequency (SRF) electron linear accelerator (linac) provides the opportunity to achieve about 5 times greater photon energy than an unrecirculated linac facility of similar cost. An electron linac configuration utilizing a 4 GeV unrecirculated, SRF linac could be used to drive a FEL producing 5 keV photons. However, for a similar cost, a recirculated SRF linac system can deliver the 4 GeV electrons for photon energies of 5 keV and provide an upgrade path to photon energies of 25 keV. Further support amounting to about a third of the initial investment would provide additional recirculated SRF linac and cryogenic capacity sufficient to deliver electron energies appropriate for 25 keV photons matching the European XFEL.

York, R. C.

2014-01-01

134

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

NASA Astrophysics Data System (ADS)

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.

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

2007-11-01

135

Results from Droxo. I. The variability of fluorescent Fe 6.4 keV emission in the young star Elias 29: High-energy electrons in the star's accretion tubes?  

E-print Network

AIMS. We study the variability of the Fe 6.4 KeV emission line from the Class I young stellar object Elias 29 in the Rho-Oph cloud. METHODS. We analysed the data from Elias 29 collected by XMM during a nine-day, nearly continuous observation of the Rho-Oph star-forming region (the Deep Rho-Oph X-ray Observation, named Droxo). The data were subdivided into six homogeneous time intervals, and the six resulting spectra were individually analysed. RESULTS. We detect significant variability in the equivalent width of the Fe 6.4 keV emission line from Elias 29. The 6.4 keV line is absent during the first time interval of observation and appears at its maximum strength during the second time interval (90 ks after Elias 29 undergoes a strong flare). The X-ray thermal emission is unchanged between the two observation segments, while line variability is present at a 99.9% confidence level. Given the significant line variability in the absence of variations in the X-ray ionising continuum and the weakness of the photoionising continuum from the star's thermal X-ray emission, we suggest that the fluorescence may be induced by collisional ionisation from an (unseen) population of non-thermal electrons. We speculate on the possibility that the electrons are accelerated in a reconnection event of a magnetically confined accretion loop, connecting the young star to its circumstellar disk.

G. Giardino; F. Favata; I. Pillitteri; E. Flaccomio; G. Micela; S. Sciortino

2007-10-10

136

Ultrafast 25 keV backlighting for experiments on Z.  

SciTech Connect

To extend the backlighting capabilities for Sandia's Z-Accelerator, Z-Petawatt, a laser which can provide laser pulses of 500 fs length and up to 120 J (100TW target area) or up to 450 J (Z/Petawatt target area) has been built over the last years. The main mission of this facility focuses on the generation of high energy X-rays, such as tin K{alpha} at 25 keV in ultra-short bursts. Achieving 25 keV radiographs with decent resolution and contrast required addressing multiple problems such as blocking of hot electrons, minimization of the source, development of suitable filters, and optimization of laser intensity. Due to the violent environment inside of Z, an additional very challenging task is finding massive debris and radiation protection measures without losing the functionality of the backlighting system. We will present the first experiments on 25 keV backlighting including an analysis of image quality and X-ray efficiency.

Headley, Daniel Ignacio; Rambo, Patrick K.; Geissel, Matthias; Schwarz, Jens; Sefkow, Adam B.; Atherton, Briggs W.; Kimmel, Mark W.; Pitts, Todd Alan; Robertson, Grafton Kincannon; Schollmeier, Marius; Speas, Christopher Shane

2010-10-01

137

Ultrafast 25 keV backlighting for experiments on Z.  

SciTech Connect

To extend the backlighting capabilities for Sandia's Z-Accelerator, Z-Petawatt, a laser which can provide laser pulses of 500 fs length and up to 120 J (100TW target area) or up to 450 J (Z / Petawatt target area) has been built over the last years. The main mission of this facility focuses on the generation of high energy X-rays, such as tin Ka at 25 keV in ultra-short bursts. Achieving 25 keV radiographs with decent resolution and contrast required addressing multiple problems such as blocking of hot electrons, minimization of the source, development of suitable filters, and optimization of laser intensity. Due to the violent environment inside of Z, an additional very challenging task is finding massive debris and radiation protection measures without losing the functionality of the backlighting system. We will present the first experiments on 25 keV backlighting including an analysis of image quality and X-ray efficiency.

Sefkow, Adam B.; Atherton, Briggs W.; Geissel, Matthias; Schollmeier, Marius; Pitts, Todd Alan; Rambo, Patrick K.; Schwarz, Jens; Kimmel, Mark W.

2010-11-01

138

Neutron Scattering Angular Distributions for ^159Tb at 570 keV and at 1000 keV  

NASA Astrophysics Data System (ADS)

Neutron elastic and inelastic scattering angular distributions for ^159Tb were measured via the time-of-flight (TOF) technique with incident neutron energies of 570 keV and 1000 keV. Measurements were made at 11 angles from 35^0 to 135^0 in 10-degree steps. Neutrons were generated by the^7Li(p,n)^7Be reaction at the UML Van de Graaff accelerator laboratory, with a pulsed proton beam, Mobley compressed to around 0.5 ns, irradiating a 15-keV thick metallic Li target. The time resolution of the accelerator was controlled by monitoring the width of the prompt target gamma-ray peak in a TOF spectrum with a fast scintillation detector. The terbium scatterer was disk shaped with a thickness of 0.6 cm and a diameter of 3.8 cm. Neutrons were detected by a 0.6-cm thick plastic scintillator. The relative efficiency of the detector was determined by comparison to a calibrated ^235U fission chamber. Measured cross sections are compared with previous work, ENDF/B-VI, JENDL, and JEF.

Seo, P.-N.; Egan, J. J.; Kegel, G. H. R.; Desimone, D. J.; Ko, Y. J.; McKittrick, T.; Ji, C.; Kim, D. S.

2000-10-01

139

Heliospheric Neutral Atom Spectra Between 0.01 and 6 keV fom IBEX  

NASA Technical Reports Server (NTRS)

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.

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

140

Heliospheric neutral atom spectra between 0.01 and 6 keV from IBEX  

NASA Astrophysics Data System (ADS)

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 ~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 ~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-1.

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.; Möbius, E.; Moore, T. E.; Petrinec, S. M.; Quinn, M.; Reisenfeld, D.; Saul, L. A.; Scheer, J. A.; Schwadron, N.; Trattner, K. J.; Vanderspek, R.; Wurz, P.

2012-07-01

141

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

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.

Rae, Nicholas A.; Chantler, Christopher T.; Barnea, Zwi; Jonge, Martin D. de; Tran, Chanh Q.; Hester, James R. [School of Physics, University of Melbourne, Victoria 3010 (Australia); Australian Synchrotron, Victoria 3168 (Australia); La Trobe University, Victoria 3086 (Australia); Australian Nuclear Science and Technology Organisation, New South Wales 2234 (Australia)

2010-02-15

142

30- to 100keV Protons Upstream From the Earth’s Bow Shock  

Microsoft Academic Search

Protons of 30 to 100 keV are found upstream from the bow shock whenever interplanetary magnetic fields connect the spacecraft and bow shock. Their energy spectrum is closely power law, d J\\/dE o: E- with v usually close to 3. The spectrum is sharply cut off above 100 keV. The protons do not appear upstream of a boundary determined by

R. P. Lin; C.-I. Meng; K. A. Anderson

1974-01-01

143

Energetic electrons, 50 keV 6 MeV, at geosynchronous orbit: their responses to solar wind variations  

E-print Network

1 Energetic electrons, 50 keV ­ 6 MeV, at geosynchronous orbit: their responses to solar wind of the upstream solar wind and of energetic electrons at geosynchronous orbit, we analyze the response of electrons over a wide energy range, 50 keV - 6 MeV, to solar wind variations. Enhancements of energetic

Li, Xinlin

144

Electron transfer in collisions of keV potassium ions with methane molecules  

NASA Astrophysics Data System (ADS)

Absolute total electron transfer cross sections have been measured for the K+-CH4 system, at impact energies 0.5-3.5 keV. The charge transfer cross sections show a monotonic increasing behaviour as a function of the incident energy. Semiempirical calculation is in good agreement with the present cross-section data.

Alarcón, F. B.; Martínez, H.

2013-03-01

145

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

DOEpatents

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.

Wang, Ching L. (Livermore, CA)

1983-01-01

146

The solar wind charge-transfer X-ray emission in the 1/4 keV energy range: inferences on Local Bubble hot gas at low Z  

E-print Network

We present calculations of the heliospheric SWCX emission spectra and their contributions in the ROSAT 1/4 keV band. We compare our results with the soft X-ray diffuse background (SXRB) emission detected in front of 378 identified shadowing regions during the ROSAT All-Sky Survey (Snowden et al. 2000). This foreground component is principally attributed to the hot gas of the so-called Local Bubble (LB), an irregularly shaped cavity of ~50-150 pc around the Sun, which is supposed to contain ~10^6 K plasma. Our results suggest that the SWCX emission from the heliosphere is bright enough to account for most of the foreground emission towards the majority of low galactic latitude directions, where the LB is the least extended. In a large part of directions with galactic latitude above 30deg the heliospheric SWCX intensity is significantly smaller than the measured one. However, the SWCX R2/R1 band ratio differs slightly from the data in the galactic center direction, and more significantly in the galactic anti-centre direction where the observed ratio is the smallest. Assuming that both SWCX and hot gas emission are present and their relative contributions vary with direction, we tested a series of thermal plasma spectra for temperatures ranging from 10^5 to 10^6.5 K and searched for a combination of SWCX spectra and thermal emission matching the observed intensities and band ratios, while simultaneously being compatible with O VI emission measurements. In the frame of collisional equilibrium models and for solar abundances, the range we derive for hot gas temperature and emission measure cannot reproduce the Wisconsin C/B band ratio. We emphasize the need for additional atomic data, describing consistently EUV and X-ray photon spectra of the charge-exchange emission of heavier solar wind ions.

D. Koutroumpa; R. Lallement; J. C. Raymond; V. Kharchenko

2008-12-19

147

Detection of interplanetary electrons from 18 keV to 1.8 MeV during solar quiet times.  

NASA Technical Reports Server (NTRS)

Observation of a quiet-time component of interplanetary electrons having energies above solar-wind energies and below those characterized as cosmic radiation. The energy spectrum of this component generally falls with energy from 18 keV to 1.8 MeV, but 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 that 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.

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

1972-01-01

148

Observations of gamma-ray burst spectra between 5 keV and 100 MeV  

NASA Astrophysics Data System (ADS)

The Franco-Soviet Lilas, Apex (Phobos mission), and Phebus (Granat satellite) experiments allow spectral observations of cosmic gamma-ray bursts over a very broad energy range from 5 keV up to 100 MeV. We present here typical results on continuum shapes, multiple absorption dips at low-energy (less than 100 keV), emission features around 500 keV, and spectral breaks at about 1 MeV. These observations are discussed in the framework of a highly-mgnetized emission source.

Barat, C.

1993-01-01

149

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

NASA Technical Reports Server (NTRS)

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.

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

2007-01-01

150

Gamma-ray burst spectra and time histories from 2 to 400keV  

NASA Astrophysics Data System (ADS)

The Gamma-Ray burst detector on Ginga consisted of a proportional counter to observe the x-rays and a scintillation counter to observe the gamma-rays. It was ideally suited to study the x-rays associated with gamma-ray bursts (GRBs). Ginga detected ~120 GRBs and 22 of them had sufficient statistics to determine spectra from 2 to 400keV. Although the Ginga and BATSE trigger criteria were very similar, the distribution of spectral parameters was different. Ginga observed bend energies in the spectra down to 2keV and had a larger fraction of bursts with low energy power law indexes greater than zero. The average ratio of energy in the x-ray band (2 to 10keV) compared to the gamma-ray band (50 to 300keV) was 24%. Some events had more energy in the x-ray band than in the gamma-ray band. One Ginga event had a period of time preceding the gamma rays that was effectively pure x-ray emission. This x-ray ``preactivity'' might be due to the penchant for the GRB time structure to be broader at lower energy rather than a different physical process. The x-rays tend to rise and fall slower than the gamma rays but they both tend to peak at about the same time. This argues against models involving the injection of relativistic electrons that cool by synchrotron radiation.

Fenimore, E. E.

1999-01-01

151

Response of liquid xenon to Compton electrons down to 1.5 keV  

NASA Astrophysics Data System (ADS)

The response of liquid xenon to low-energy electronic recoils is relevant in the search for dark-matter candidates which interact predominantly with atomic electrons in the medium, such as axions or axionlike particles, as opposed to weakly interacting massive particles which are predicted to scatter with atomic nuclei. Recently, liquid-xenon scintillation light has been observed from electronic recoils down to 2.1 keV, but without applied electric fields that are used in most xenon dark-matter searches. Applied electric fields can reduce the scintillation yield by hindering the electron-ion recombination process that produces most of the scintillation photons. We present new results of liquid xenon’s scintillation emission in response to electronic recoils as low as 1.5 keV, with and without an applied electric field. At zero field, a reduced scintillation output per unit deposited energy is observed below 10 keV, dropping to nearly 40% of its value at higher energies. With an applied electric field of 450V/cm, we observe a reduction of the scintillation output to about 75% relative to the value at zero field. We see no significant energy dependence of this value between 1.5 and 7.8 keV. With these results, we estimate the electronic-recoil energy thresholds of ZEPLIN-III, XENON10, XENON100, and XMASS to be 2.8, 2.5, 2.3, and 1.1 keV, respectively, validating their excellent sensitivity to low-energy electronic recoils.

Baudis, L.; Dujmovic, H.; Geis, C.; James, A.; Kish, A.; Manalaysay, A.; Marrodán Undagoitia, T.; Schumann, M.

2013-06-01

152

Tunable high-repetition-rate femtosecond few-hundred keV electron source  

NASA Astrophysics Data System (ADS)

Using three-dimensional particle-in-cell simulations, we demonstrate that femtosecond few-hundred keV electron pulses can be produced at a high repetition rate by tightly focusing few mJ few-cycle radially polarized laser pulses in a low density gas. In particular, we show that the laser pulse parameters and gas density can be optimized to cover the full 100–300 keV energy window that characterizes ultrafast electron diffraction imaging experiments. The active development of high-power laser sources promises routine operation at 1 kHz and above, allowing time-resolved electron diffraction on the femtosecond time scale.

Marceau, Vincent; Hogan-Lamarre, Pascal; Brabec, Thomas; Piché, Michel; Varin, Charles

2015-02-01

153

Scintillation efficiency and ionization yield of liquid xenon for mono-energetic nuclear recoils down to 4 keV  

E-print Network

Liquid Xenon (LXe) is an excellent material for experiments designed to detect dark matter in the form of Weakly Interacting Massive Particles (WIMPs). A low energy detection threshold is essential for a sensitive WIMP search. The understanding of the relative scintillation efficiency (Leff) and ionization yield of low energy nuclear recoils in LXe is limited for energies below 10 keV. In this paper, we present new measurements that extend the energy down to 4 keV, finding that Leff decreases with decreasing energy. We also measure the quenching of scintillation efficiency due to the electric field in LXe, finding no significant field dependence.

A. Manzur; A. Curioni; L. Kastens; D. N. McKinsey; K. Ni; T. Wongjirad

2009-09-05

154

Scintillation efficiency and ionization yield of liquid xenon for monoenergetic nuclear recoils down to 4 keV  

NASA Astrophysics Data System (ADS)

Liquid xenon (LXe) is an excellent material for experiments designed to detect dark matter in the form of weakly interacting massive particles (WIMPs). A low energy detection threshold is essential for a sensitive WIMP search. The understanding of the relative scintillation efficiency (Leff) and ionization yield of low energy nuclear recoils in LXe is limited for energies below 10 keV. In this article, we present new measurements that extend the energy down to 4 keV, finding that Leff decreases with decreasing energy. We also measure the quenching of scintillation efficiency caused by the electric field in LXe, finding no significant field dependence.

Manzur, A.; Curioni, A.; Kastens, L.; McKinsey, D. N.; Ni, K.; Wongjirad, T.

2010-02-01

155

Scintillation efficiency and ionization yield of liquid xenon for mono-energetic nuclear recoils down to 4 keV  

E-print Network

Liquid Xenon (LXe) is an excellent material for experiments designed to detect dark matter in the form of Weakly Interacting Massive Particles (WIMPs). A low energy detection threshold is essential for a sensitive WIMP search. The understanding of the relative scintillation efficiency (Leff) and ionization yield of low energy nuclear recoils in LXe is limited for energies below 10 keV. In this paper, we present new measurements that extend the energy down to 4 keV, finding that Leff decreases with decreasing energy. We also measure the quenching of scintillation efficiency due to the electric field in LXe, finding no significant field dependence.

Manzur, A; Kastens, L; McKinsey, D N; Ni, K; Wongjirad, T

2009-01-01

156

Scintillation efficiency and ionization yield of liquid xenon for monoenergetic nuclear recoils down to 4 keV  

SciTech Connect

Liquid xenon (LXe) is an excellent material for experiments designed to detect dark matter in the form of weakly interacting massive particles (WIMPs). A low energy detection threshold is essential for a sensitive WIMP search. The understanding of the relative scintillation efficiency (L{sub eff}) and ionization yield of low energy nuclear recoils in LXe is limited for energies below 10 keV. In this article, we present new measurements that extend the energy down to 4 keV, finding that L{sub eff} decreases with decreasing energy. We also measure the quenching of scintillation efficiency caused by the electric field in LXe, finding no significant field dependence.

Manzur, A.; Curioni, A.; Kastens, L.; McKinsey, D. N.; Ni, K.; Wongjirad, T. [Department of Physics, Yale University, New Haven, Connecticut 06520 (United States)

2010-02-15

157

A 25KeV, 30-milliamp hydrogen-ion injector for A 200MHz, 750KeV radiofrequency quadrupole  

Microsoft Academic Search

An injector development program is being pursued at Linac systems for satisfying linear accelerator input beam requirements. Proton beams with 25-keV beam energy and 30-mA current with variable duty factors are presently being produced. The two main injector ingredients are a microwave plasma source and a single - einzel lens for matching the proton beam into the radio frequency quadrupole

Donald Swenson; Frank Guy; Joel Starling; Carl Willis; Jim Potter; Joseph Sherman

2007-01-01

158

Neutron cross sections and average resonance parameters of 238 U for 55- and 144keV neutrons  

Microsoft Academic Search

In this connection, the total neutron cross section, the total and differential cross section for elastic scattering of neutrons by 2aaU for neutron energies of 55 and 144 keV, and also the total and differential cross sections for inelastic scattering of neutrons by 2aaU (with excitation of the 2 + level, E u = 45 keV) for E = 144

L. L. Litvinskii; V. P. Vertebnyi; V. A. Libman; A. V. Murzin

1987-01-01

159

Scintillation efficiency and ionization yield of liquid xenon for monoenergetic nuclear recoils down to 4 keV  

Microsoft Academic Search

Liquid xenon (LXe) is an excellent material for experiments designed to detect dark matter in the form of weakly interacting massive particles (WIMPs). A low energy detection threshold is essential for a sensitive WIMP search. The understanding of the relative scintillation efficiency (Leff) and ionization yield of low energy nuclear recoils in LXe is limited for energies below 10 keV.

A. Manzur; A. Curioni; L. Kastens; D. N. McKinsey; K. Ni; T. Wongjirad

2010-01-01

160

Xenon-neon gas proportional-scintillation counters for X rays below 2 keV: experimental results  

Microsoft Academic Search

The energy spectra of X-rays with energies below 2 keV measured with standard Xe filled gas proportional scintillation counters at atmospheric pressure exhibit a distorted tail towards the low energy region, due to the loss of electrons to the detector entrance window. In this framework, a Monte Carlo simulation study taking into account these losses has previously investigated the use

F. I. G. M. Borges; F. P. Santos; J. M. F. dos Santos; T. H. V. T. Dias; P. J. B. M. Rachinhas; C. A. N. Conde

2002-01-01

161

The double ionization of hydrogen by 5-25 keV He + ions  

NASA Astrophysics Data System (ADS)

The energy and angular distribution of fragment proton pairs produced in the dissociative ionisation of hydrogen by 5-25 keV ions has been investigated. The observed energy distributions show that two forms of Coulomb explosion occur. In addition to an energy group centred around 9.8 eV which is readily explained by a simple Franck-Condon transition to the H +H + repulsive state, an additional group centred around 5.5 eV is also observed. The mean energy of this latter group is independent of angle of detection and projectile energy and can be explained in terms of a two step excitation process.

Latimer, C. J.; Savage, O. G.

1995-10-01

162

The Solar Flare 4: 10 keV X-ray Spectrum  

NASA Technical Reports Server (NTRS)

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.

Phillips, K. J. H.

2004-01-01

163

Observations of the cosmic X-ray background below 4 keV  

SciTech Connect

The author reports the first measurement of the intensity and spectrum of the diffuse x-ray background in the 0.16 - 3.5 keV band which is free from contamination by sources with fluxes greater than {approximately}4 {times} 10{sup {minus}14} erg cm{sup {minus}2}s{sup {minus}1}. This result was made possible by the development of a number of techniques for removing cosmic-ray contamination and instrumental artifacts in the data collected by the Einstein Observatory Imaging Proportional Counter. The intensity is dependent on galactic longitude even when only high galactic latitude data are used, allowing a lower limit to be set on the galactic contribution to the emission in this band. The spectrum of the total background is consistent with a power law of slope {approximately}0.7 between 0.5 keV and 3.5 keV with a steep rise toward lower energies. A thorough reanalysis of the Einstein Observatory Deep Survey data is presented in order to determine the contribution of detected, discrete sources of x-ray emission to the cosmic x-ray background. Finally, all-sky maps are presented of diffuse x-ray emission in nine energy bands between 0.16 and 3.5 keV utilizing a complete data base of Einstein IPC observations.

Wu, Xiaoyi.

1990-01-01

164

A possible correlation between the 511 keV annihilation radiation and the 6.7 keV iron line emission in the Galactic plane  

NASA Astrophysics Data System (ADS)

The contributions of annihilation radiation from an interstellar component and a Galactic component are studied analytically. The models assume that extended sources are used to express the interstellar 511-keV emission so that the distribution of radiation is consistent with that of high-energy gamma rays or molecular CO gas. The diffuse line is assumed to follow the iron-line radiation along the Galactic longitude as a radiative product of supernova remnants. The analysis shows that two components could contribute the 511-keV annihilation radiation both from within the Galactic center and from interstellar annihilation sources. The results suggest an extended source with an intensity of 0.002 ph/sq cm/s/rad near the Galactic center, although the source is probably not variable and compact.

He, Z.; Durouchoux, Ph.; Chapuis, C.; Wallyn, P.

1991-08-01

165

Excimer Emission using 20keV Electron Beam Excitation  

NASA Astrophysics Data System (ADS)

A small, continuously emitting rare gas excimer light source has been developed. The gas is excited by a 20keV dc-electron beam. A 300nm thick, 1×1mm^2 SiNx foil sustaining a pressure difference up to 2bar, separates the target volume from the high vacuum part of the electron gun. Spectra of the rare gases Ar, Kr, and Xe have been studied. The monochromator detector system was intensity calibrated in the wavelength range from 115nm to 320nm. Electron beam currents of typically 1?A were used for excitation. When used as a VUV lamp on the second excimer continua, energy conversion efficiencies of 30% were obtained. Emissions originating from the so called left turning points have been clearly observed at 155, 173, and 222nm in Ar_2^*, Kr_2^*, and Xe_2^*, respectively. The so called third continua between 185nm and 240nm (Ar), 220nm and 250nm (Kr), and at 270nm (Xe) have been studied. A new continuum in Xe at 280nm was found. (Funded by the A.v.Humboldt Foundation and NSF (CTS 94-19440). The authors acknowledge support by H. Huggins, A. Liddle and W.L. Brown (Bell Laboratories, Lucent Technologies))

Wieser, J.; Ulrich, A.; Murnick, D. E.

1996-10-01

166

Secondary ion emission under keV carbon cluster bombardment  

E-print Network

Secondary ion mass spectrometry (SIMS) is a surface analysis technique capable of providing isotopic and molecular information. SIMS uses keV projectiles to impinge upon a sample resulting in secondary ion emission from nanometric dimensions...

Locklear, Jay Edward

2006-10-30

167

X-ray phase-contrast imaging at 100?keV on a conventional source  

PubMed Central

X-ray grating interferometry is a promising imaging technique sensitive to attenuation, refraction and scattering of the radiation. Applications of this technique in the energy range between 80 and 150?keV pose severe technical challenges, and are still mostly unexplored. Phase-contrast X-ray imaging at such high energies is of relevant scientific and industrial interest, in particular for the investigation of strongly absorbing or thick materials as well as for medical imaging. Here we show the successful implementation of a Talbot-Lau interferometer operated at 100?keV using a conventional X-ray tube and a compact geometry, with a total length of 54?cm. We present the edge-on illumination of the gratings in order to overcome the current fabrication limits. Finally, the curved structures match the beam divergence and allow a large field of view on a short and efficient setup. PMID:24903579

Thüring, T.; Abis, M.; Wang, Z.; David, C.; Stampanoni, M.

2014-01-01

168

X-ray phase-contrast imaging at 100 keV on a conventional source  

NASA Astrophysics Data System (ADS)

X-ray grating interferometry is a promising imaging technique sensitive to attenuation, refraction and scattering of the radiation. Applications of this technique in the energy range between 80 and 150 keV pose severe technical challenges, and are still mostly unexplored. Phase-contrast X-ray imaging at such high energies is of relevant scientific and industrial interest, in particular for the investigation of strongly absorbing or thick materials as well as for medical imaging. Here we show the successful implementation of a Talbot-Lau interferometer operated at 100 keV using a conventional X-ray tube and a compact geometry, with a total length of 54 cm. We present the edge-on illumination of the gratings in order to overcome the current fabrication limits. Finally, the curved structures match the beam divergence and allow a large field of view on a short and efficient setup.

Thüring, T.; Abis, M.; Wang, Z.; David, C.; Stampanoni, M.

2014-06-01

169

X-ray phase-contrast imaging at 100?keV on a conventional source.  

PubMed

X-ray grating interferometry is a promising imaging technique sensitive to attenuation, refraction and scattering of the radiation. Applications of this technique in the energy range between 80 and 150?keV pose severe technical challenges, and are still mostly unexplored. Phase-contrast X-ray imaging at such high energies is of relevant scientific and industrial interest, in particular for the investigation of strongly absorbing or thick materials as well as for medical imaging. Here we show the successful implementation of a Talbot-Lau interferometer operated at 100?keV using a conventional X-ray tube and a compact geometry, with a total length of 54?cm. We present the edge-on illumination of the gratings in order to overcome the current fabrication limits. Finally, the curved structures match the beam divergence and allow a large field of view on a short and efficient setup. PMID:24903579

Thüring, T; Abis, M; Wang, Z; David, C; Stampanoni, M

2014-01-01

170

Development of a Portable 950 keV X-band Linac for NDT  

SciTech Connect

We are developing a portable 950 keV X-band (9.4 GHz) linac X-ray source for on-site nondestructive testing of erosion of metal pipes at a petrochemical complex. To develop it, we adopted a compact X-band 9.4 GHz magnetron of 250 kW for RF generation device. The whole device, including power supply and cooling devices, were also downsized. The dose rate of X-ray converted in a tungsten target is designed to be 0.2 Gy/min at 1-m distance. We designed an accelerating tube that uses the {pi} mode for the lower energy part and the {pi}/2 mode cavity for the higher energy. We manufactured the accelerating tube and carried out beam acceleration tests, confirming that the electron beam was accelerated up to 950 keV.

Natsui, Takuya; Uesaka, Mitsuru; Yamamoto, Tomohiko; Sakamoto, Fumito; Hashimoto, Eiko; Kiwoo, Lee [Nuclear Professional School, the University of Tokyo, 2-22 Shirakata-Shirane, Tokai, Naka, Ibaraki 319-1188 (Japan); Nakamura, Naoki; Yamamoto, Masashi; Tanabe, Eiji [Accuthera Inc. 2-7-6, Kurigi, Asao, Kawasaki, Kanagawa 215-0033 (Japan); Yoshida, Mitsuhiro; Higo, Toshiyasu; Fukuda, Shigeki [High Energy Accelerator Research Organization, KEK 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan)

2009-03-10

171

Few arc-minute and keV resolutions with the TIGRE Compton telescope  

NASA Technical Reports Server (NTRS)

The tracking and imaging gamma ray experiment (TIGRE) Compton telescope concept can provide an angular resolution of a few arcmin, an energy resolution of a few keV and high sensitivity, while providing the wide field of view necessary for surveying and monitoring observations. Silicon and CdZnTe strip detectors are used to detect Compton pair events and determine their incident directions and energies. Above 400 keV, Compton recoil electrons are tracked through successive layers of thin silicon strip detectors. Compton scattered photons are detected with CdZnTe strip detectors. Pair electrons and positrons are tracked to provide high sensitivity observations in the 10 to 100 MeV range. Polarization studies are performed with large angle Compton scatter events. The TIGRE concept and development status are described.

Zych, A.; Bhattacharya, D.; Dixon, D.; ONeill, T.; Tuemer, T.; White, R. S.; Ryan, J.; McConnell, M.; Macri, J.; Oegelman, H.; Paulos, R.; Wheaton, W.; Akyuez, A.; Samimi, J.; Oezel, M.

1997-01-01

172

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

NASA Technical Reports Server (NTRS)

The discovery in XMM-Newton X-ray data of X-ray emission above 2 keY 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.

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

2007-01-01

173

A three-crystal spectrometer for 150 KeV synchrotron radiation  

SciTech Connect

A triple axis spectrometer for high energy ({ge}150 keV) synchrotron radiation has been constructed and characterized. The reciprocal space resolution function of this instrument has been measured using perfect silicon crystals as monochromator, sample, and analyzer. It was found to have dimensions of 1.0 {times} 10{sup {minus}5}{angstrom}{sup {minus}1} and 2.3 {times} 10{sup {minus}4}{angstrom}{sup {minus}1} in the directions perpendicular and parallel to the momentum transfer {rvec Q} respectively, comparable to those achievable using standard 8 keV triple axis instruments. The large penetration depths of high energy x-ray photons, combined with the high instrumental resolution, opens new possibilities in the study of truly bulk condensed matter systems. 7 refs., 5 figs.

Hastings, J.B.; Siddons, D.P.; Berman, L.E.; Schneider, J.R. (Brookhaven National Lab., Upton, NY (USA); Hahn-Meitner-Institut Berlin G.m.b.H. (Germany, F.R.))

1988-01-01

174

The diffuse X-ray spectrum from 14-200 keV as measured on OSO-5  

NASA Technical Reports Server (NTRS)

The measurement of energy spectrum of the diffuse component of cosmic X-ray flux made on the OSO-5 spacecraft is described. The contributions to the total counting rate of the actively shielded X-ray detector are considered in some detail and the techniques used to eliminate the non-cosmic components are described. Positive values for the cosmic flux are obtained in seven energy channels between 14 and 200 keV and two upper limits are obtained between 200 and 254 keV. The results can be fitted by a power law spectrum. A critical comparison is made with the OSO-3 results. Conclusions show that the reported break in the energy spectrum at 40 keV is probably produced by an erroneous correction for the radioactivity induced in the detector on each passage through the intense charged particle fluxes in the South Atlantic anomaly.

Dennis, B. R.; Suri, A. N.; Frost, K. J.

1973-01-01

175

Elemental content from 0 to 500 keV neutrons: Lunar Prospector results  

Microsoft Academic Search

Neutron spectroscopy is a new way to study planetary bodies that have sufficiently thin atmospheres. This technique was demonstrated for the first time with Lunar Prospector around the Moon. Here, we report results for moderated neutrons having energies from 0 to 500keV that were measured using the anti-coincidence shield (ACS) of the gamma-ray spectrometer. We describe the detection method, followed

I. Genetay; S. Maurice; W. C. Feldman; O. Gasnault; D. J. Lawrence; R. C. Elphic; C. d'Uston; A. B. Binder

2003-01-01

176

The Formulae for Parameters of the Secondary Electron Yield of Insulators from 10 keV to 30 keV  

NASA Astrophysics Data System (ADS)

Based on the formula for the average energy required to produce an internal secondary electron (?) in emitter, the energy band of insulator and the assumption that the maximum exit energy of secondary electron in insulator is reverse to the width of forbidden band, the formula for ? in insulator is deduced. On the basis of the formula for the number of internal secondary electrons produced in the direction of the velocity of primary electrons per unit path length, the energy band of insulator and the characteristic of secondary electron emission, the formula for the probability of secondary electrons passing over the surface barrier of insulator into the vacuum (B) is also deduced. According to some relationship between the parameters of secondary electron yield from insulator, the formula for the mean escape depth (1/?) is successfully deduced. The formulae for ? and 1/? are experimentally proven, respectively, and thereafter the formula for B is indirectly proven to be true by the experimental results. It is concluded that the formulae for ?, B and 1/? are universal to estimate ?, B and 1/? under the condition that primary electrons from 10 keV to 30 keV hit on an insulator, respectively.

Xie, Ai-Gen; Li, Qing-Fang; Chen, Yun-Yun; Wu, Hong-Yan

2013-12-01

177

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

NASA Astrophysics Data System (ADS)

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 ?m 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 ?m 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/XPS, and RHESSI, as well as the SphinX observations during the deep solar minimum of 2009. Using newly-developed computational methods, we analyze the differential emission measure (DEM) of the solar corona, and discuss the possible implications for X-ray-producing physical processes in the quiescent corona.

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

2013-12-01

178

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

NASA Astrophysics Data System (ADS)

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.

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

2005-07-01

179

Compact, maintainable 80-KeV neutral beam module  

DOEpatents

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.

Fink, Joel H. (Livermore, CA); Molvik, Arthur W. (Livermore, CA)

1980-01-01

180

A 24 keV liquid-metal-jet x-ray source for biomedical applications  

SciTech Connect

We present a high-brightness 24-keV electron-impact microfocus x-ray source based on continuous operation of a heated liquid-indium/gallium-jet anode. The 30-70 W electron beam is magnetically focused onto the jet, producing a circular 7-13 {mu}m full width half maximum x-ray spot. The measured spectral brightness at the 24.2 keV In K{sub {alpha}} line is 3 x 10{sup 9} photons/(s x mm{sup 2}x mrad{sup 2}x 0.1% BW) at 30 W electron-beam power. The high photon energy compared to existing liquid-metal-jet sources increases the penetration depth and allows imaging of thicker samples. The applicability of the source in the biomedical field is demonstrated by high-resolution imaging of a mammography phantom and a phase-contrast angiography phantom.

Larsson, D. H.; Takman, P. A. C.; Lundstroem, U.; Burvall, A.; Hertz, H. M. [Biomedical and X-Ray Physics, Department of Applied Physics, Royal Institute of Technology/Albanova, SE-10691 Stockholm (Sweden)

2011-12-15

181

The 511 keV emission from positron annihilation in the Galaxy  

SciTech Connect

The first {gamma}-ray line originating from outside the Solar System that was ever detected is the 511 keV emission from positron annihilation in the Galaxy. Despite 30 years of intense theoretical and observational investigation, the main sources of positrons have not been identified up to now. Observations in the 1990s with OSSE/CGRO (Oriented Scintillation Spectrometer Experiment on GRO satellite/Compton Gamma Ray Observatory) showed that the emission is strongly concentrated toward the Galactic bulge. In the 2000s, the spectrometer SPI aboard the European Space Agency's (ESA) International Gamma Ray Astrophysics Laboratory (INTEGRAL) allowed scientists to measure that emission across the entire Galaxy, revealing that the bulge-to-disk luminosity ratio is larger than observed at any other wavelength. This mapping prompted a number of novel explanations, including rather ''exotic'' ones (e.g., dark matter annihilation). However, conventional astrophysical sources, such as type Ia supernovae, microquasars, or x-ray binaries, are still plausible candidates for a large fraction of the observed total 511 keV emission of the bulge. A closer study of the subject reveals new layers of complexity, since positrons may propagate far away from their production sites, making it difficult to infer the underlying source distribution from the observed map of 511 keV emission. However, in contrast to the rather well-understood propagation of high-energy (>GeV) particles of Galactic cosmic rays, understanding the propagation of low-energy ({approx}MeV) positrons in the turbulent, magnetized interstellar medium still remains a formidable challenge. The spectral and imaging properties of the observed 511 keV emission are reviewed and candidate positron sources and models of positron propagation in the Galaxy are critically discussed.

Prantzos, N.; Boehm, C.; Bykov, A. M.; Diehl, R.; Ferriere, K.; Guessoum, N.; Jean, P.; Knoedlseder, J.; Marcowith, A.; Moskalenko, I. V.; Strong, A.; Weidenspointner, G. [CNRS, UMR7095, UMPC and Institut d'Astrophysique de Paris, F-75014, Paris (France) and LAPP, 9 Chemin de Bellevue, BP 110 F-74941 Annecy-le-Vieux (France); A. F. Ioffe Institute of Physics and Technology, Russian Academy of Sciences, 194021, St. Petersburg (Russian Federation); Max Planck Institut fuer Extraterrestrische Physik, D-85741 Garching (Germany); Laboratoire d'Astrophysique de Toulouse-Tarbes, Universite de Toulouse, CNRS, 14 avenue Edouard Belin, F-31400 Toulouse (France); American University of Sharjah, College of Arts and Sciences/Physics Department, P.O. Box 26666, Sharjah (United Arab Emirates); CESR, Universite de Toulouse, CNRS, 9, Avenue du Colonel Roche, Boite Postal 4346, F-31028 Toulouse Cedex 4 (France); L.U.P.M., Universite Montpellier II, CNRS, Place Eugene Bataillon, F-34095 Montpellier (France); Hansen Experimental Physics Laboratory and Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, Stanford, California 94305 (United States); Max Planck Institut fuer Extraterrestrische Physik, D-85741, Garching (Germany); Max Planck Institut fur Extraterrestrische Physik, Garching, D-85741 Germany, and MPI Halbleiterlabor, Otto-Hahn-Ring 6, D-81739 Muenchen (Germany)

2011-07-01

182

Study of avalanche photodiodes for soft X-ray detection below 20 keV  

NASA Astrophysics Data System (ADS)

The performance of the large area reach-through avalanche photodiode (APD), manufactured by Hamamatsu Photonics, K.K. as a high resolution X-ray detector is presented. The mentioned APD has an area of 3 mm ?, a fast time response for signal carrier collection and its thick depletion layer of 130 ?m shows a potential to be used as an effective X-ray absorber below 20 keV. Having a capacitance of ˜10 pF and a low dark current of 5 nA for a gain of 15, at room temperature, this APD had demonstrated one of the best energy resolutions within this kind of devices: 6.4% (FWHM) for 5.9 keV photons with a minimum detectable energy of 0.3 keV, measured at -20C. The experiments for the timing property were made in a synchrotron beam facility using an 8 keV X-ray beam; the reached count rate was above 108 counts/s, corresponding to a very short dead time of 4.5 ns/pulse. In order to test the radiation hardness of the APD, the device was irradiated at a Ring Cyclotron Facility with a 53.5 MeV proton beam. The total dose was of 11.3 krad and no fatal damage was found in the APD, although the dark current of the APD had shown an increase of one order of magnitude. Finally, the obtained results allow us to affirm that the reach-through APD has the potential to become an excellent X-ray detector, especially in the space mission application.

Yatsu, Y.; Kuramoto, Y.; Kataoka, J.; Kotoku, J.; Saito, T.; Ikagawa, T.; Sato, R.; Kawai, N.; Kishimoto, S.; Mori, K.; Kamae, T.; Ishikawa, Y.; Kawabata, N.

2006-08-01

183

Charge fraction measurements for 2.4-35 keV Arq+ (q=2-13) projectiles  

E-print Network

Charge fraction measurements for 2.4-35 keV Arq+ (q=2-13) projectiles backscattered from Au(110 We report on measurements of absolute scattered projectile charge fractions for Arq+ ions (q=2- 13 separation of all scattered charged states, including neutrals. At fixed projectile energy, the scattered ion

184

Compact 300 keV electron gun for radiation processing  

SciTech Connect

A new self-shielded system for surface radiation treatments has been developed, based on a 300 keV electron gun, able to irradiate a 100 mmx10 mm area. The compact and durable system described in this paper provides the required dose of treatment for several industrial or scientific research applications, with a good reproducibility of the parameters.

Auditore, L.; Barna, R.C.; De Pasquale, D.; Interdonato, S.; Italiano, A.; Trifiro, A.; Trimarchi, M. [INFN-Gruppo Collegato di Messina, I-98166 Messina (Italy); Dipartimento di Fisica dell'Universita di Messina, I-98166 Messina (Italy); Dipartimento di Fisica dell'Universita di Messina, I-98166 Messina (Italy); INFN-Gruppo Collegato di Messina, I-98166 Messina (Italy); INFN-Gruppo Collegato di Messina, I-98166 Messina (Italy); Dipartimento di Fisica dell'Universita di Messina, I-98166 Messina (Italy)

2005-12-15

185

KevJumba and the Adolescence of YouTube  

ERIC Educational Resources Information Center

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…

Saul, Roger

2010-01-01

186

Effective field theory and keV lines from dark matter  

NASA Astrophysics Data System (ADS)

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.

Krall, Rebecca; Reece, Matthew; Roxlo, Thomas

2014-09-01

187

Absorbed dose measurements and calculations in phantoms for 1.5 to 50 keV photons  

SciTech Connect

A Monte Carlo code EGS4 expanded for low energy photon transport was validated by measuring absorbed doses in a phantom for 30 and 10 keV monoenergetic photons from synchrotron radiation. Using the EGS4 code, depth doses at 0.07 mm, 0.02 to 0.1 mm, and 10 mm in the ICRU slab phantoms were calculated for 1.5 to 50 keV photons using the updated photon cross section data PHOTX. The results show that the doses at 0.02 to 0.1 mm below 10 keV are practical indices of effective dose as calculated by others. 19 refs., 7 figs., 7 tabs.

Nariyama, Nobuteru [Ship Research Institute, Tokyo (Japan); Tanaka, Shun-ichi; Nakane, Yoshihiro [Japan Atomic Energy Research Institute, Ibaraki (Japan)] [and others

1995-02-01

188

Absorbed dose measurements and calculations in phantoms for 1.5 to 50 keV photons.  

PubMed

A Monte Carlo code EGS4 expanded for low energy photon transport was validated by measuring absorbed doses in a phantom for 30 and 10 keV monoenergetic photons from synchrotron radiation. Using the EGS4 code, depth doses at 0.07 mm, 0.02 to 0.1 mm, and 10 mm in the ICRU slab phantoms were calculated for 1.5 to 50 keV photons using the updated photon cross section data PHOTX. The results show that the doses at 0.02 to 0.1 mm below 10 keV are practical indices of effective dose as calculated by others, based on the 1990 ICRP recommendations (1991). PMID:7814258

Nariyama, N; Tanaka, S; Nakane, Y; Namito, Y; Hirayama, H; Ban, S; Nakashima, H

1995-02-01

189

Measurement of the Ec.m. = 184 keV resonance strength in the 26gAl (p, gamma)27 Si reaction.  

PubMed

The strength of the Ec.m. = 184 keV resonance in the 26gAl(p, gamma)27 reaction has been measured in inverse kinematics using the DRAGON recoil separator at TRIUMF's ISAC facility. We measure a value of omega gamma = 35 +/- 7 microeV and a resonance energy of Ec.m. = 184 +/- 1 keV, consistent with p-wave proton capture into the 7652(3) keV state in 27Si, and discuss the implications of these values for 26GAl nucleosynthesis in typical oxygen-neon white-dwarf novae. PMID:16907298

Ruiz, C; Parikh, A; José, J; Buchmann, L; Caggiano, J A; Chen, A A; Clark, J A; Crawford, H; Davids, B; D'Auria, J M; Davis, C; Deibel, C; Erikson, L; Fogarty, L; Frekers, D; Greife, U; Hussein, A; Hutcheon, D A; Huyse, M; Jewett, C; Laird, A M; Lewis, R; Mumby-Croft, P; Olin, A; Ottewell, D F; Ouellet, C V; Parker, P; Pearson, J; Ruprecht, G; Trinczek, M; Vockenhuber, C; Wrede, C

2006-06-30

190

ENA (E>5 keV) Images from Cassini and Voyager ``ground truth'': Suprathermal Pressure in the Heliosheath  

NASA Astrophysics Data System (ADS)

Maps of energetic neutral atoms (ENA) of the heliosphere from Cassini [1] have been constructed spanning the energy range ~5<=E<=55 keV, and show a ``Belt'' in the sky of ~100° FWHM. Similarly, maps >6 keV have been obtained by the IBEX mission [2] and show a ``Ribbon'' that is narrower than the Belt and inclined to it in both ecliptic latitude (~25°) and longitude (~30°). The overlap in energy between Voyager ions [3] and Cassini ENA intensities (averaged over the ENA line of sight) enables us to deduce ion fluxes in the heliosheath, thus providing a continuous spectrum 5<=E<=4000 keV. These measurements are then used to estimate the local partial pressure over this energy range (~0.1 pPa), suggesting ?>25 [4] and the thickness of the heliosheath (~50 AU). Using a simulated PUI distribution [5], we estimate the E<6 keV contribution to be ~0.12 pPa. The balance of the non-thermal pickup ion (PUI) pressure against the stagnation pressure of the interstellar plasma and the local interstellar magnetic field (ISMF) at the nose of the heliopause implies an upper bound on the ISMF of ~0.64 nT.

Krimigis, S. M.; Mitchell, D. G.; Roelof, E. C.; Decker, R. B.

2010-12-01

191

Neutron transmission and capture measurements and analysis of /sup 60/Ni from 1 to 450 keV  

SciTech Connect

High-resolution transmission and capture measurements of /sup 60/Ni-enriched targets have been made at the Oak Ridge Electron Linear Accelerator (ORELA) from a few eV to 1800 keV in transmission and from 2.5 keV to 5 MeV in capture . The transmission data from 1 to 450 keV were analyzed with a multi-level R-matrix code which uses the Bayes' theorem for the fitting process. This code provides the energies and neutron widths of the resonances inside the 1- to 450-keV region as well as a possible parameterization for outside resonances to describe the smooth cross section in this region. The capture data were analyzed with a least-squares fitting code using the Breit-Wigner formula. From 2.5 to 450 keV, 166 resonances were seen in both sets of data. Correspondence between the energy scales shows a discontinuity around 300 keV which makes the matching of resonances at higher energies difficult. Eighty-nine resonances were seen in the capture data only. Average parameters for the 30 observed s-wave resonances were deduced. The average level spacing D/sub 0/ was found to be equal to 15.2 +- 1.5 keV, the strength function, S/sub 0/, equal to (2.2 +- 0.6) x 10/sup -4/ and the average radiation width, GAMMA/sub ..gamma../, equal to 1.30 +- 0.07 eV. The staircase plot of the reduced level widths and the plot of the Lorentz-weighted strength function averaged over various energy intervals show possible evidence for doorway states. The level densities calculated with the Fermi-gas model for l = 0 and for l > 0 resonances were compared with the cumulative number of observed resonances, but the analysis is not conclusive. The average capture cross section as a function of the neutron incident energy is compared to the tail of the giant electric dipole resonance prediction.

Perey, C.M.; Harvey, J.A.; Macklin, R.L.; Winters, R.R.; Perey, F.G.

1982-11-01

192

Proximity functions for electrons up to 10 keV  

SciTech Connect

Proximity functions for electrons up to 10 keV in water are computed from simulated particle tracks. Numerical results are given for the differential functions t(x) and the integral functions T(x). Basic characteristics of these functions and their connections to other microdosimetric quantities are considered. As an example of the applicability of the proximity functions, the quantity y/sub D/ for spheres is derived from t(x).

Chmelevsky, D. (Institut fuer Medizinische Strahlenkunde der Universitaet Wuerzburg, Germany); Kellerer, A.M.; Terrissol, M.; Patau, J.P.

1980-11-01

193

The average 0.5-200 keV spectrum of local active galactic nuclei and a new determination of the 2-10 keV luminosity function at z ? 0  

NASA Astrophysics Data System (ADS)

The broad-band X-ray spectra of active galactic nuclei (AGNs) contains information about the nuclear environment from Schwarzschild radii scales (where the primary power law is generated in a corona) to distances of ˜1 pc (where the distant reflector may be located). In addition, the average shape of the X-ray spectrum is an important input into X-ray background synthesis models. Here, local (z ? 0) AGN luminosity functions (LFs) in five energy bands are used as a low-resolution, luminosity-dependent X-ray spectrometer in order to constrain the average AGN X-ray spectrum between 0.5 and 200 keV. The 15-55 keV LF measured by Swift-BAT is assumed to be the best determination of the local LF, and then a spectral model is varied to determine the best fit to the 0.5-2 keV, 2-10 keV, 3-20 keV and 14-195 keV LFs. The spectral model consists of a Gaussian distribution of power laws with a mean photon-index and cutoff energy Ecut, as well as contributions from distant and disc reflection. The reflection strength is parametrized by varying the Fe abundance relative to solar, AFe, and requiring a specific Fe K? equivalent width (EW). In this way, the presence of the X-ray Baldwin effect can be tested. The spectral model that best fits the four LFs has = 1.85 ± 0.15, E_{cut}=270^{+170}_{-80} keV, A_{Fe}=0.3^{+0.3}_{-0.15}. The sub-solar AFe is unlikely to be a true measure of the gas-phase metallicity, but indicates the presence of strong reflection given the assumed Fe K? EW. Indeed, parametrizing the reflection strength with the R parameter gives R=1.7^{+1.7}_{-0.85}. There is moderate evidence for no X-ray Baldwin effect. Accretion disc reflection is included in the best-fitting model, but it is relatively weak (broad iron K? EW < 100 eV) and does not significantly affect any of the conclusions. A critical result of our procedure is that the shape of the local 2-10 keV LF measured by HEAO-1 and MAXI is incompatible with the LFs measured in the hard X-rays by Swift-BAT and RXTE. We therefore present a new determination of the local 2-10 keV LF that is consistent with all other energy bands, as well as the de-evolved 2-10 keV LF estimated from the XMM-Newton Hard Bright Survey. This new LF should be used to revise current measurements of the evolving AGN LF in the 2-10 keV band. Finally, the suggested absence of the X-ray Baldwin effect points to a possible origin for the distant reflector in dusty gas not associated with the AGN obscuring medium. This may be the same material that produces the compact 12 ?m source in local AGNs.

Ballantyne, D. R.

2014-01-01

194

Directivity of 100-500 keV solar flare hard X-ray emission  

NASA Technical Reports Server (NTRS)

We have identified 28 solar flares simultaneously observed by a SIGNE detector aboard the Venera 13 and Venera 14 spacecraft and the Hard X-Ray Burst Spectrometer (HXRBS) aboard the Solar Maximum Mission (SMM), over a wide range of observing angles. Fourteen of them were also observed by the Gamma Ray Spectrometer (GRS) on SMM and were included in a study of the directivity of solar X-radiation. The SIGNE and HXRBS energy coverages overlap in the 50-500 keV range, allowing a detailed comparison of energy spectra. Using this database, we have conducted stereoscopic studies of flare hard X-ray anisotropy. It is found that the 100-500 keV directivity is less than 3, both for the entire set of 28 flares and for the 14 flares which gave evidence for directivity in the SMM GRS study. We conclude that solar flare X-ray directivity can only be marginally present in our energy/observing angle range.

Li, P.; Hurley, K.; Barat, C.; Niel, M.; Talon, R.; Kurt, V.

1994-01-01

195

First limits on the 3-200 keV X-ray spectrum of the quiet Sun using RHESSI  

E-print Network

We present the first results using the Reuven Ramaty High-Energy Solar Spectroscopic Imager, RHESSI, to observe solar X-ray emission not associated with active regions, sunspots or flares (the quiet Sun). Using a newly developed chopping technique (fan-beam modulation) during seven periods of offpointing between June 2005 to October 2006, we obtained upper limits over 3-200 keV for the quietest times when the GOES12 1-8A flux fell below $10^{-8}$ Wm$^{-2}$. These values are smaller than previous limits in the 17-120 keV range and extend them to both lower and higher energies. The limit in 3-6 keV is consistent with a coronal temperature $\\leq 6$ MK. For quiet Sun periods when the GOES12 1-8A background flux was between $10^{-8}$ Wm$^{-2}$ and $10^{-7}$ Wm$^{-2}$, the RHESSI 3-6 keV flux correlates to this as a power-law, with an index of $1.08 \\pm 0.13$. The power-law correlation for microflares has a steeper index of $1.29 \\pm 0.06$. We also discuss the possibility of observing quiet Sun X-rays due to solar axions and use the RHESSI quiet Sun limits to estimate the axion-to-photon coupling constant for two different axion emission scenarios.

Iain G. Hannah; G. J Hurford; H. S. Hudson; R. P. Lin; K. van Bibber

2007-02-27

196

Cassini ENA (E > 5 keV) Heliosphere Belt and overlapping in-situ Voyager measurements: Pressure and ISMF implications  

NASA Astrophysics Data System (ADS)

Maps of energetic neutral atoms (ENA) of the heliosphere from Cassini (Krimigis et al, 2009) have been constructed spanning the energy range ~ 5 ? E ? 55 keV, and show a “Belt” in the sky of ~ 100° FWHM. ENA maps < 6 keV have been obtained by the IBEX mission (McComas et al, 2009) and show a “Ribbon” that is narrower than the Belt and inclined to it in both ecliptic latitude (~25°) and longitude (~30°). The overlap in energy between Voyager ions (Decker et al, 2009) and Cassini ENA intensities (averaged over the ENA line of sight) enables us to deduce ion fluxes in the heliosheath, thus providing a continuous spectrum 5 ? E ? 4000 keV. The Cassini ENAs provide a smooth transition spectrum between the accelerated pickup ions (PUI) and the well-established Voyager LECP j?E-1.5 tail at E > 28 keV, and lead to a thickness of the heliosheath of ~ 50 AU. These measurements are then used to estimate the local partial pressure over this energy range (~ 0.1 pPa), suggesting ? > 25 locally. Using a simulated PUI distribution (Giacalone and Decker, 2010) we estimate the E < 6 keV contribution to the pressure to be ~ 0.12 pPa. Assuming constant total pressure throughout the heliosheath, the balance of the non-thermal pickup ion (PUI) pressure against the stagnation pressure of the interstellar plasma and the hydrostatic pressure of the local interstellar magnetic field (ISMF) at the nose of the heliopause implies an upper bound on the ISMF of ~ 0.64 nT. Implications on the shape of the heliosphere are discussed.

Krimigis, S. M.; Mitchell, D. G.; Roelof, E. C.; Decker, R. B.

2010-12-01

197

Hydrogen-Atom Excitation and Ionization by Proton Impact in 50-Kev to 200-Kev Energy Region  

E-print Network

= ~, which is done by taking a pro- duct of matrices. At t= - the system starts out in some specific initial state. A U-matrix method was first used in Zimmerman's thesis for the pro- ton-hydrogen problem and has since been applied independently... and D. Dinwiddie,J. Chem. Phys. 57, 4919 (1972). 2J. F. Reading, A. L. Ford, and E. F. Fitchard, Phys. Hev. Lett. 36, 573 (1976); Phys. Aev. A 16, 133 (1977). 3I. M. Cheshire and E. C. Sullivan, Phys. Rev. 160, 4 (1967). E. H. Zimmerman, thesis...

Fitchard, E.; Ford, A. Lewis; Reading, John F.

1977-01-01

198

Fragmentation of singly charged adenine induced by neutral fluorine beam impact at 3 keV  

NASA Astrophysics Data System (ADS)

The fragmentation scheme of singly charged adenine molecule (H5C5N5+) has been studied via neutral fluorine impact at 3 keV. By analyzing in correlation the kinetic energy loss of the scattered projectile F- produced in single charge transfer process and the mass of the charged fragments, the excitation energy distribution of the parent adenine molecular ions has been determined for each of the main dissociation channels. Several fragmentation pathways unrevealed in standard mass spectra or in appearance energy measurements are investigated. Regarding the well-known hydrogen cyanide (HCN) loss sequence, we demonstrate that although the loss of a HCN is the dominant decay channel for the parent H5C5N5+ (m = 135), the decay of the first daughter ion H4C4N4+ (m = 108) involves not only the HNC (m = 27) loss but also the symmetric breakdown into two dimers of HCN.

Chen, L.; Brédy, R.; Bernard, J.; Montagne, G.; Allouche, A. R.; Martin, S.

2011-09-01

199

Differential Cross Sections for Ionization of Argon by 1 keV Positron and Electron Impact  

NASA Astrophysics Data System (ADS)

Differential information was generated by establishing coincidences and imposing conditions on data recorded for target ions, scattered projectiles, and ejected electrons, as a function of projectile energy loss and scattering angles; in order to describe the interaction between a positron (electron) 1 keV beam and a simple Ar jet. Single ionization triply differential cross section (TDCS) results exhibit two distinct regions (lobes) for which binary (events arising from 2-body interaction) and recoil (events which can only be produced by many-body interactions) interactions are associated. Results indicate that binary events are significantly larger for positron impact, in accordance with theoretical predictions. A similar feature is found for different energy losses and scattering angles. Intensity of the recoil lobe for both projectiles, positron and electron, is observed to depend on the energy loss and scattering angle. Also, it can be noticed that for positron impact the recoil interactions intensity is larger than that observed for electron impact.

Gavin, J.; DuBois, R. D.; de Lucio, O. G.

2014-04-01

200

A pulsed drift cavity to capture 30 keV ion bunches at ground potential  

NASA Astrophysics Data System (ADS)

To capture radioactive ion beams of tens of keV in an ion trap, the use of a pulsed drift cavity allows one to avoid placing the complete setup on a high voltage (HV) platform. By pulsing down the voltage on a long electrode while the ion bunch is inside it, the electric potential zero level can be shifted down over a range equal to the initial beam energy, thus allowing the ions to be captured in a trap at ground potential. The pulsed drift cavity of the WITCH setup, which is completely HV-platform free, is described here. It is demonstrated that bunched beams with energies of typically 30-60 keV, as will become available to all users at the ISOLDE facility after the installation of an RFQ buncher, can be transported over distances of tens of meters to the experiments and by means of a pulsed drift cavity directly be injected into a purification Penning trap. Simulation work showing the efficiency of such a system is discussed and tests showing the feasibility of such a system are presented. An estimate of the pulse down time is made from TOF spectra. An outlook on how the system can be improved is presented too.

Coeck, S.; Delauré, B.; Herbane, M.; Beck, M.; Golovko, V. V.; Kopecky, S.; Kozlov, V. Yu.; Kraev, I. S.; Lindroth, A.; Phalet, T.; Beck, D.; Delahaye, P.; Herlert, A.; Wenander, F.; Severijns, N.

2007-03-01

201

Hydroxyapatite-titanium interface reaction induced by keV electron irradiation  

NASA Astrophysics Data System (ADS)

Thin films of hydroxyapatite bioceramic, 5-50 Å in thickness, have been deposited on ion cleaned titanium surfaces to study the chemical-physical adhesion of metal-ceramic interfaces of biomedical devices (orthopaedic and dentistry prosthesis). Film deposition was performed in ultrahigh vacuum condition (10 -10 mbar) using 5 keV argon sputtering of hydroxyapatite matrix; the film thickness was measured in situ with Auger electron spectroscopy. The hydroxyapatite-titanium interface was irradiated with an electron beam of 0.5-5 keV energy and 0.2-2 A/cm 2 current density. During electron irradiation, Auger spectra show chemical shifts of phosphorus, titanium and oxygen peaks. The released electron energy induces modifications in the tetraedric phosphorus-oxygen groups with production of new chemical bonds between phosphorus, oxygen and titanium. Oxygen, for example, diffuses into the titanium interface forming titanium oxide. Chemical reactions induced by electron irradiation are driven by the metal-ceramic interface. Near the interface a strong and fast effect is observed while far from the interface a weak and slow effect occurs. Chemical reactions depend on the electron irradiation dose showing an inhibition threshold at about 10 19 e/cm 2 and, near the interface, a saturation condition at about 5 × 10 20 e/cm 2. Titanium-ceramic chemical reactions are inhibited if the substrate titanium surface is rich in oxide.

Torrisi, L.; Foti, G.

1992-03-01

202

Astrophysics and cosmology confront the 17 keV neutrino  

NASA Technical Reports Server (NTRS)

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.

Kolb, Edward W.; Turner, Michael S.

1991-01-01

203

Astrophysics and cosmology confront the 17-keV neutrino  

NASA Technical Reports Server (NTRS)

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.

Kolb, Edward W.; Turner, Michael S.

1991-01-01

204

Decaying vector dark matter as an explanation for the 3.5 keV line from galaxy clusters  

NASA Astrophysics Data System (ADS)

We present a Vector Dark Matter (VDM) model that explains the 3.5 keV line recently observed in the XMM-Newton observatory data from galaxy clusters. In this model, dark matter is composed of two vector bosons, V and V', which couple to the photon through an effective generalized Chern-Simons coupling, gV. V' is slightly heavier than V with a mass splitting mV' – mV simeq 3.5 keV. The decay of V' to V and a photon gives rise to the 3.5 keV line. The production of V and V' takes place in the early universe within the freeze-in framework through the effective gV coupling when mV' < T < ?, ? being the cut-off above which the effective gV coupling is not valid. We introduce a high energy model that gives rise to the gV coupling at low energies. To do this, V and V' are promoted to gauge bosons of spontaneously broken new U(1)V and U(1)V' gauge symmetries, respectively. The high energy sector includes milli-charged chiral fermions that lead to the gV coupling at low energy via triangle diagrams.

Farzan, Yasaman; Rezaei Akbarieh, Amin

2014-11-01

205

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

NASA Astrophysics Data System (ADS)

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 determined from RHESSI. We discuss the possible implications for X-ray-producing physical processes in the quiescent, active-region-free corona. The X123 spectrum could potentially serve as a reference for ~0.5-4 keV quiet Sun emission, to help improve solar spectral models such as CHIANTI and XPS Level 4. Our comparisons indicate that XPS Level 4 likely requires significant revisions in the SXR range, which may have downstream implications for the Earth ionosphere models that have used XPS Level 4 as their solar input.

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

2012-12-01

206

Electron nuclear dynamics of proton collisions with DNA/RNA bases at ELab = 80 keV: A contribution to proton cancer therapy research  

E-print Network

to proton cancer therapy research A.J. Privett, J.A. Morales Department of Chemistry and Biochemistry. Introduction Proton cancer therapy (PCT) utilizes high-energy H+ projectiles (from an initial energy of 200Electron nuclear dynamics of proton collisions with DNA/RNA bases at ELab = 80 keV: A contribution

Morales, Jorge Alberto

207

Detection of an Unexplained Emission Line at 3.56 keV  

NASA Astrophysics Data System (ADS)

We recently detected a weak unidentified emission line at ~3.56 keV in the stacked XMM spectra of 73 galaxy clusters spanning a redshift range 0.01 - 0.35. The line is seen at > 3? statistical significance in all three independent samples of XMM-Newton MOS and the full sample of the PN. The line is also detected at the same energy and consistent flux in the Chandra ACIS-S and ACIS-I spectra of the Perseus cluster, although it is not seen in the ACIS-I spectrum of Virgo. I will discuss why there should be no atomic transitions in thermal plasma at this energy, leaving the possibility that this line is a signature of decaying of sterile neutrinos.

Bulbul, Esra; Markevitch, Maxim L.; Foster, Adam; Smith, Randall K.; Loewenstein, Michael; Randall, Scott W.

2014-08-01

208

Active detection of shielded SNM with 60-keV neutrons  

SciTech Connect

Fissile materials, e.g. {sup 235}U and {sup 239}Pu, can be detected non-invasively by active neutron interrogation. A unique characteristic of fissile material exposed to neutrons is the prompt emission of high-energy (fast) fission neutrons. One promising mode of operation subjects the object to a beam of medium-energy (epithermal) neutrons, generated by a proton beam impinging on a Li target. The emergence of fast secondary neutrons then clearly indicates the presence of fissile material. Our interrogation system comprises a low-dose 60-keV neutron generator (5 x 10{sup 6}/s), and a 1 m{sup 2} array of scintillators for fast neutron detection. Preliminary experimental results demonstrate the detectability of small quantities (370 g) of HEU shielded by steel (200 g/cm{sup 2}) or plywood (30 g/cm{sup 2}), with a typical measurement time of 1 min.

Hagmann, C; Dietrich, D; Hall, J; Kerr, P; Nakae, L; Newby, R; Rowland, M; Snyderman, N; Stoeffl, W

2008-07-08

209

Au irradiation by 25-keV Au n ( n=1-65 600 ) clusters  

NASA Astrophysics Data System (ADS)

Although surface processes induced by single ionized atom irradiation are reasonably well understood, the use of atomic clusters as irradiation projectiles can give rise to nonlinear effects due to high deposited energy densities and the presence of many cluster atoms in a small surface region. A well known fact is that high energy density cascades at surfaces due to cluster bombardment can lead to enhanced sputtering yields. We use molecular dynamics simulations to study the irradiation of gold surfaces by 25-keV Au n ( n=1-65 600) clusters. We show that the sputtering yields by the clusters are, quite surprisingly, roughly constant for cluster sizes n=2-7600. This effect arises from the formation of surface heat spikes, resulting in violent microexplosions of the surface layers.

Salonen, E.; Nordlund, K.; Keinonen, J.

2003-12-01

210

Student research with 400keV beams: {sup 13}N radioisotope production target development  

SciTech Connect

The AN400 Van de Graaff accelerator at the Minnesota State University, Mankato, Applied Nuclear Science Lab has demonstrated utility as an accessible and versatile platform for student research. Despite the limits of low energy, the research team successfully developed projects with applications to the wider radioisotope production community. A target system has been developed for producing and extracting {sup 13}N by the {sup 12}C(d,n){sup 13}N reaction below 400keV. The system is both reusable and robust, with future applications to higher energy machines producing this important radioisotope for physiological imaging studies with Positron Emission Tomography. Up to 36({+-}1)% of the {sup 13}N was extracted from the graphite matrix when 35 A current was externally applied to the graphite target while simultaneously flushing the target chamber with CO{sub 2} gas.

Fru, L. Che; Clymer, J.; Compton, N.; Cotter, J.; Dam, H.; Lesko, Z.; Pautzke, J.; Prokop, C.; Swanson, L.; Roberts, A. D. [Department of Physics and Astronomy, Minnesota State University, Trafton Science Center N141, Mankato MN 56001 (United States)

2013-04-19

211

An extreme gravitationally redshifted iron line at 4.8 keV in Mrk 876  

E-print Network

X-ray spectral lines at unforeseen energies are important because they can shed light on the extreme physical conditions of the environment around the supermassive black holes of active galactic nuclei (AGN). Mrk 876 displays such a line at 4.8 keV rest-frame energy. A possible interpretation of its origin can be found in the hotspot scenario. In this scenario the primary radiation from a flare in the hot corona of an AGN illuminates a limited portion of the accretion disk that emits by fluorescence. In this context the line can represent an extreme gravitationally redshifted Fe line originating on the accretion disk below 6 gravitational radii from a rotating supermassive black hole. The correct estimate of the line significance requires a dedicated approach. Based on an existing rigorous approach, we have performed extensive Monte Carlo simulations. We determine that the line is a real feature at ~99 confidence level.

Bottacini, Eugenio; Greiner, Jochen; Ajello, Marco; Moskalenko, Igor; Persic, Massimo

2014-01-01

212

Observation of an ionospheric acceleration mechanism producing energetic (keV) ions primarily normal to the geomagnetic field direction  

Microsoft Academic Search

O\\/sup +\\/ ions with energies of approximately 1 keV have been observed flowing upward out of the ionosphere with a pitch angle distribution having a minimum along the magnetic field direction and maxima in about 130°⁻⁻¹⁴°sup 0\\/ range. The measurements were obtained with an energetic ion mass spectrometer experiment on the satellite 1976-65B at an altitude of about 7600 km

R. D. Sharp; R. G. Johnson; E. G. Shelley

1977-01-01

213

Measurements of 4–10 keV x-ray production with the Z-Beamlet laser  

Microsoft Academic Search

In order to characterize the current backlighting capability of Sandia’s Z-Beamlet laser (ZBL) over a range of high photon energies, we measured the x-ray conversion efficiency of the focused 527 nm ZBL beam into 4–10 keV x rays from He-like emission of the elements Sc through Ge (excluding Ga). The measurements approximated ZBL’s nominal backlighting geometry and laser performance at

L. E. Ruggles; J. L. Porter; P. K. Rambo; W. W. Simpson; M. F. Vargas; G. R. Bennett; I. C. Smith

2003-01-01

214

Measurements of 4-10 keV x-ray production with the Z-Beamlet laser  

Microsoft Academic Search

In order to characterize the current backlighting capability of Sandia's Z-Beamlet laser (ZBL) over a range of high photon energies, we measured the x-ray conversion efficiency of the focused 527 nm ZBL beam into 4-10 keV x rays from He-like emission of the elements Sc through Ge (excluding Ga). The measurements approximated ZBL's nominal backlighting geometry and laser performance at

L. E. Ruggles; J. L. Porter; P. K. Rambo; W. W. Simpson; M. F. Vargas; G. R. Bennett; I. C. Smith

2003-01-01

215

Observation of the 22.5keV Resonance in 149Sm by the Nuclear Lighthouse Effect  

Microsoft Academic Search

We have observed coherent nuclear resonant scattering of synchrotron radiation at the 22.5-keV resonance of 149Sm. High-speed rotational sample motion led to an angular deflection of the resonantly scattered radiation off the nonresonant primary beam. This allowed us to determine the resonance energy of the first excited nuclear level of 149Sm to be 22496(4) eV. Because of the angular deflection

R. Röhlsberger; K. W. Quast; T. S. Toellner; P. L. Lee; W. Sturhahn; E. E. Alp; E. Burkel

2001-01-01

216

Optima MDxt: A high throughput 335 keV mid-dose implanter  

SciTech Connect

The continuing demand for both energy purity and implant angle control along with high wafer throughput drove the development of the Axcelis Optima MDxt mid-dose ion implanter. The system utilizes electrostatic scanning, an electrostatic parallelizing lens and an electrostatic energy filter to produce energetically pure beams with high angular integrity. Based on field proven components, the Optima MDxt beamline architecture offers the high beam currents possible with singly charged species including arsenic at energies up to 335 keV as well as large currents from multiply charged species at energies extending over 1 MeV. Conversely, the excellent energy filtering capability allows high currents at low beam energies, since it is safe to utilize large deceleration ratios. This beamline is coupled with the >500 WPH capable endstation technology used on the Axcelis Optima XEx high energy ion implanter. The endstation includes in-situ angle measurements of the beam in order to maintain excellent beam-to-wafer implant angle control in both the horizontal and vertical directions. The Optima platform control system provides new generation dose control system that assures excellent dosimetry and charge control. This paper will describe the features and technologies that allow the Optima MDxt to provide superior process performance at the highest wafer throughput, and will provide examples of the process performance achievable.

Eisner, Edward; David, Jonathan; Justesen, Perry; Kamenitsa, Dennis; McIntyre, Edward; Rathmell, Robert; Ray, Andrew; Rzeszut, Richard [Axcelis Technologies, Inc., 108 Cherry Hill Drive, Beverly, MA 01915 (United States)

2012-11-06

217

Low noise scintillation detectors with a P-47 thin layer screen for electrons of several keV  

NASA Astrophysics Data System (ADS)

The applicability of a low-noise scintillation detector (ScD) for the registration of electrons of several keV energy has been studied employing photomultipliers (PM) of different types and sizes. With the application of a sedimented P-47 scintillation screen, the values of the low-energy sensitivity limit and those of the light conversion coefficient were determined as about 2.7-4.7 keV and 2.8-6.6 photoelectrons/keV, respectively, for the set of PM's (Philips-Valvo XP 2020, Philips-Valvo XP 2052, Philips-Valvo XP 2972, EMI 9124a) studied. It is concluded that such scintillation detectors might be used advantageously as electron counters in the range of E > 5 keV. Applications below this kinetic energy value are also feasible when applying a floating acceleration of several kV to the ScD — a voltage much lower than the values required for Everhart-Thornley detectors.

Kajcsos, Zs.; Meisel, W.; Griesbach, P.; Gütlich, P.; Sauer, Ch.; Kurz, R.; Hildebrand, K.; Albrecht, R.; Ligtenberg, M. A. C.

1994-09-01

218

Ionization and fragmentation of polycyclic aromatic hydrocarbon clusters in collisions with keV ions  

NASA Astrophysics Data System (ADS)

We report on an experimental study of the ionization and fragmentation of clusters of k polycyclic aromatic hydrocarbon (PAH) molecules using anthracene, C14H10, or coronene, C24H12. These PAH clusters are moderately charged and strongly heated in small impact parameter collisions with 22.5-keV He2+ ions, after which they mostly decay in long monomer evaporation sequences with singly charged and comparatively cold monomers as dominating end products. We describe a simple cluster evaporation model and estimate the number of PAH molecules in the clusters that have to be hit by He2+ projectiles for such complete cluster evaporations to occur. Highly charged and initially cold clusters are efficiently formed in collisions with 360-keV Xe20+ ions, leading to cluster Coulomb explosions and several hot charged fragments, which again predominantly yield singly charged, but much hotter, monomer ions than the He2+ collisions. We present a simple formula, based on density-functional-theory calculations, for the ionization energy sequences as functions of coronene cluster size, rationalized in terms of the classic electrostatic expression for the ionization of a charged conducting object. Our analysis indicates that multiple electron removal by highly charged ions from a cluster of PAH molecules rapidly may become more important than single ionization as the cluster size k increases and that this is the main reason for the unexpectedly strong heating in these types of collisions.

Johansson, H. A. B.; Zettergren, H.; Holm, A. I. S.; Seitz, F.; Schmidt, H. T.; Rousseau, P.; ?awicki, A.; Capron, M.; Domaracka, A.; Lattouf, E.; Maclot, S.; Maisonny, R.; Manil, B.; Chesnel, J.-Y.; Adoui, L.; Huber, B. A.; Cederquist, H.

2011-10-01

219

Sterilization of foods with low-energy electrons (``soft-electrons'')  

NASA Astrophysics Data System (ADS)

Electrons with an energy of 300 keV or lower were defined as "Soft-electrons", which showed several advantages over conventional irradiation with gamma-rays or high-energy electrons in decontamination of grains and spices. Energies of electrons necessary to reduce microbial loads to levels lower than 10 CFU/g were 60 keV for brown rice, 75 keV for wheat, 100 keV for white pepper, coriander and basil, 130 keV for buckwheat, 160 keV for rough rice, and 210 keV for black pepper. Electrons with such energies did not significantly influence the quality.

Hayashi, Toru; Takahashi, Yoko; Todoriki, Setsuko

1998-06-01

220

Absolute measurement of the unresolved cosmic X-ray background in the 0.5-8 keV band with Chandra  

E-print Network

We present the absolute measurement of the unresolved 0.5-8 keV cosmic X-ray background (CXB) in the Chandra Deep Fields (CDFs) North and South, the longest observations with Chandra (2 Ms and 1 Ms, respectively). We measure the unresolved CXB intensity by extracting spectra of the sky, removing all point and extended sources detected in the CDF. To model and subtract the instrumental background, we use observations obtained with ACIS in stowed position, not exposed to the sky. The unresolved signal in the 0.5-1 keV band is dominated by diffuse Galactic and local thermal-like emission. In the 1-8 keV band, the unresolved spectrum is adequately described by a power law with a photon index 1.5. We find unresolved CXB intensities of (1.04+/-0.14)x10^-12 ergs cm^-2 s^-1 deg^-2 for the 1-2 keV band and (3.4+/-1.7)x10^-12 ergs cm^-2 s^-1 deg^-2 for the 2-8 keV band. Our detected unresolved intensities in these bands significantly exceed the expected flux from sources below the CDF detection limits, if one extrapolates the logN/logS curve to zero flux. Thus these background intensities imply either a genuine diffuse component, or a steepening of the logN/logS curve at low fluxes, most significantly for energies <2 keV. Adding the unresolved intensity to the total contribution from sources detected in these fields and wider-field surveys, we obtain a total intensity of the extragalactic CXB of (4.6+/-0.3)x10^-12 ergs cm^-2 s^-1 deg^-2 for 1-2 keV and (1.7+/-0.2)x10^-11 ergs cm^-2 s^-1 deg^-2 for 2-8 keV. These totals correspond to a CXB power law normalization (for photon index 1.4) of 10.9 photons cm^-2 s^-1 keV^-1 sr^-1 at 1 keV. This corresponds to resolved fracations of 77+/-3% and 80+/-8% for 1-2 and 2-8 keV, respectively.

Ryan C. Hickox; Maxim Markevitch

2006-03-24

221

Recoils, flows and explosions: surface damage mechanisms in metals and semiconductors during 50 eV-50 keV ion bombardment  

NASA Astrophysics Data System (ADS)

We review some recent simulation results on mechanisms of damage production close to a surface during ion irradiation. The simulation work encompasses studies of several metals and semiconductors at irradiation energies ranging from a few tens of eVs to 50 keV. The results show that in dense metals the presence of a surface can dramatically enhance the damage production upto energies of at least 50 keV. The added damage is mostly in the form of vacancy clusters, which can extend quite deep, ˜10 nm, in the sample. In semiconductors, by contrast, the surface in general has little effect on the damage production in bulk.

Nordlund, K.; Keinonen, J.; Ghaly, M.; Averback, R. S.

1999-01-01

222

High-resolution spectra of 20-300 keV hard X-rays from electron precipitation over Antarctica  

SciTech Connect

In December 1990, a set of liquid-nitrogen-cooled germanium hard X-ray and gamma-ray spectrometers was flown aboard a high-altitude balloon from McMurdo, Antarctica, for solar, astrophysical, and terrestrial observations. This flight was the first circumnavigation ({approximately}9-day duration) of the Antarctic continent by a large (800,000-cubic-meter) balloon. Bremsstrahlung hard X-ray emission extending up to {approximately}300 keV, from the precipitation of high-energy electrons, was observed on six separate occasions over the auroral zone, all during low geomagnetic activity (K{sub p}{le} 2+). All events were consistent with emission at the trapping boundary; observation over the polar cap showed no precipitation. The authors present the first high-resolution ({Delta}E {approximately}2 keV) full width at half maximum (FWHM) spectra of this hard X-ray emission in the energy range 20-300 keV. The observed count spectra are deconvolved by model-independent techniques to photon spectra and then to the precipitating electron spectra. The spectral hardness shows all inverse relation with L as expected. This result suggests that high-resolution spectroscopy could be extremely effective in characterizing electron precipitation if coupled with imaging capability. 26 refs., 9 figs., 1 tab.

Smith, D.M. [Univ. of Maryland, College Park, MD (United States)] [Univ. of Maryland, College Park, MD (United States); Lin, R.P. [Univ. of California, Berkeley, CA (United States)] [Univ. of California, Berkeley, CA (United States); Hurley, A.K. [Univ. of California, Berkeley, CA (United States)] [and others] [Univ. of California, Berkeley, CA (United States); and others

1995-10-01

223

Contrasting physics in wire array z pinch sources of 1-20 keV emission on the Z facilitya)  

NASA Astrophysics Data System (ADS)

Imploding wire arrays on the 20 MA Z generator have recently provided some of the most powerful and energetic laboratory sources of multi-keV photons, including ˜375 kJ of Al K-shell emission (h? ˜ 1-2 keV), ˜80 kJ of stainless steel K-shell emission (h? ˜ 5-9 keV) and a kJ-level of Mo K-shell emission (h? ˜ 17 keV). While the global implosion dynamics of these different wire arrays are very similar, the physical process that dominates the emission from these x-ray sources fall into three broad categories. Al wire arrays produce a column of plasma with densities up to ˜3 × 1021 ions/cm3, where opacity inhibits the escape of K-shell photons. Significant structure from instabilities can reduce the density and increase the surface area, therefore increase the K-shell emission. In contrast, stainless steel wire arrays operate in a regime where achieving a high pinch temperature (achieved by thermalizing a high implosion kinetic energy) is critical and, while opacity is present, it has less impact on the pinch emissivity. At higher photon energies, line emission associated with inner shell ionization due to energetic electrons becomes important.

Ampleford, D. J.; Jones, B.; Jennings, C. A.; Hansen, S. B.; Cuneo, M. E.; Harvey-Thompson, A. J.; Rochau, G. A.; Coverdale, C. A.; Laspe, A. R.; Flanagan, T. M.; Moore, N. W.; Sinars, D. B.; Lamppa, D. C.; Harding, E. C.; Thornhill, J. W.; Giuliani, J. L.; Chong, Y.-K.; Apruzese, J. P.; Velikovich, A. L.; Dasgupta, A.; Ouart, N.; Sygar, W. A.; Savage, M. E.; Moore, J. K.; Focia, R.; Wagoner, T. C.; Killebrew, K. L.; Edens, A. D.; Dunham, G. S.; Jones, M. C.; Lake, P. W.; Nielsen, D. S.; Wu, M.; Carlson, A. L.; Kernahan, M. D.; Ball, C. R.; Scharberg, R. D.; Mulville, T. D.; Breden, E. W.; Speas, C. S.; Olivas, G.; Sullivan, M. A.; York, A. J.; Justus, D. W.; Cisneros, J. C.; Strizic, T.; Reneker, J.; Cleveland, M.; Vigil, M. P.; Robertson, G.; Sandoval, D.; Cox, C.; Maurer, A. J.; Graham, D. A.; Huynh, N. B.; Toledo, S.; Molina, L. P.; Lopez, M. R.; Long, F. W.; McKee, G. R.; Porter, J. L.; Herrmann, M. C.

2014-05-01

224

Contrasting physics in wire array z pinch sources of 1-20?keV emission on the Z facility  

SciTech Connect

Imploding wire arrays on the 20 MA Z generator have recently provided some of the most powerful and energetic laboratory sources of multi-keV photons, including ?375?kJ of Al K-shell emission (h????1–2?keV), ?80?kJ of stainless steel K-shell emission (h????5–9?keV) and a kJ-level of Mo K-shell emission (h????17?keV). While the global implosion dynamics of these different wire arrays are very similar, the physical process that dominates the emission from these x-ray sources fall into three broad categories. Al wire arrays produce a column of plasma with densities up to ?3?×?10{sup 21} ions/cm{sup 3}, where opacity inhibits the escape of K-shell photons. Significant structure from instabilities can reduce the density and increase the surface area, therefore increase the K-shell emission. In contrast, stainless steel wire arrays operate in a regime where achieving a high pinch temperature (achieved by thermalizing a high implosion kinetic energy) is critical and, while opacity is present, it has less impact on the pinch emissivity. At higher photon energies, line emission associated with inner shell ionization due to energetic electrons becomes important.

Ampleford, D. J., E-mail: damplef@sandia.gov; Jones, B.; Jennings, C. A.; Hansen, S. B.; Cuneo, M. E.; Harvey-Thompson, A. J.; Rochau, G. A.; Coverdale, C. A.; Laspe, A. R.; Flanagan, T. M.; Moore, N. W.; Sinars, D. B.; Lamppa, D. C.; Harding, E. C.; Sygar, W. A.; Savage, M. E.; Moore, J. K.; Focia, R.; Wagoner, T. C.; Killebrew, K. L. [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States); and others

2014-05-15

225

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

NASA Astrophysics Data System (ADS)

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.

Carlson, Eric; Jeltema, Tesla; Profumo, Stefano

2015-02-01

226

SMM observations of gamma-ray transients. 2: A search for gamma-ray lines between 400 and 600 keV from the Crab Nebula  

NASA Technical Reports Server (NTRS)

We have search spectra obtained by the Solar Maximum Mission Gamma-Ray Spectrometer during 1981-1988 for evidence of transient gamma-ray lines from the Crab Nebula which have been reported by previous experiments at energies 400-460 keV and 539 keV. We find no evidence for significant emission in any of these lines on time scales between aproximately 1 day and approximately 1 yr. Our 3 sigma upper limits on the transient flux during 1 d intervals are approximately equal to 2.2 x 10(exp -3) photons/sq cm/s for narrow lines at any energy, and approximately equal to 2.9 x 10(exp -3) photons/sq cm/s for the 539 keV line if it is as broad as 42 keV Full Width at Half Maximum (FWHM). We also searched our data during the approximately 5 hr period on 1981 June 6 during which Owens, Myers, & Thompson (1985) reported a strong line at 405 keV. We detected no line down to a 3 upper sigma limit of 3.3 x 10(exp -3) photons/sq cm/s in disagreement with the flux 7.2 +/- 2.1 x 10(exp -3) photos/sq cm/s measured by Owens et al.

Harris, Michael J.; Share, Gerald H.; Leising, Mark D.

1994-01-01

227

Excess Astrophysical Photons from a 0.1-1 keV Cosmic Axion Background  

NASA Astrophysics Data System (ADS)

Primordial decays of string theory moduli at z˜1012 naturally generate a dark radiation cosmic axion background with 0.1-1 keV energies. This cosmic axion background can be detected through axion-photon conversion in astrophysical magnetic fields to give quasithermal excesses in the extreme ultraviolet and soft x-ray bands. Substantial and observable luminosities may be generated even for axion-photon couplings ?10-11GeV-1. We propose that axion-photon conversion may explain the observed excess emission of soft x rays from galaxy clusters, and may also contribute to the diffuse unresolved cosmic x-ray background. We list a number of correlated predictions of the scenario.

Conlon, Joseph P.; Marsh, M. C. David

2013-10-01

228

Interatomic potentials from rainbow scattering of keV noble gas atoms under axial surface channeling  

NASA Astrophysics Data System (ADS)

For grazing scattering of keV Ne and Ar atoms from a Ag(1 1 1) and a Cu(1 1 1) surface under axial surface channeling conditions we observe well defined peaks in the angular distributions for scattered projectiles. These peaks can be attributed to "rainbow-scattering" and are closely related to the geometry of potential energy surfaces which can be approximated by the superposition of continuum potentials along strings of atoms in the surface plane. The dependence of rainbow angles on the scattering geometry provides stringent tests on the scattering potentials. From classical trajectory calculations based on universal (ZBL), adjusted Moliere (O'Connor and Biersack), and individual interatomic potentials we obtain corresponding rainbow angles for comparison with the experimental data. We find good overall agreement with the experiments for a description of trajectories based on adjusted Moliere and individual potentials, whereas the agreement is poorer for potentials with ZBL screening.

Schüller, A.; Wethekam, S.; Mertens, A.; Maass, K.; Winter, H.; Gärtner, K.

2005-04-01

229

Excess astrophysical photons from a 0.1-1 keV cosmic axion background.  

PubMed

Primordial decays of string theory moduli at z~10(12) naturally generate a dark radiation cosmic axion background with 0.1-1 keV energies. This cosmic axion background can be detected through axion-photon conversion in astrophysical magnetic fields to give quasithermal excesses in the extreme ultraviolet and soft x-ray bands. Substantial and observable luminosities may be generated even for axion-photon couplings <10(-11) GeV(-1). We propose that axion-photon conversion may explain the observed excess emission of soft x rays from galaxy clusters, and may also contribute to the diffuse unresolved cosmic x-ray background. We list a number of correlated predictions of the scenario. PMID:24160588

Conlon, Joseph P; Marsh, M C David

2013-10-11

230

Calculations of stopping powers of 100 eV-30 keV electrons in 31 elemental solids  

NASA Astrophysics Data System (ADS)

We present calculated electron stopping powers (SPs) for 31 elemental solids (Li, Be, glassy C, graphite, diamond, Na, Mg, K, Sc, Ti, V, Fe, Y, Zr, Nb, Mo, Ru, Rh, In, Sn, Cs, Gd, Tb, Dy, Hf, Ta, W, Re, Os, Ir, and Bi). These SPs were determined with an algorithm previously used for the calculation of electron inelastic mean free paths and from energy-loss functions (ELFs) derived from experimental optical data. The SP calculations were made for electron energies between 100eV and 30keV and supplement our earlier SP calculations for ten additional solids (Al, Si, Cr, Ni, Cu, Ge, Pd, Ag, Pt, and Au). Plots of SP versus atomic number for the group of 41 solids show clear trends. Multiple peaks and shoulders are seen that result from the contributions of valence-electron and various inner-shell excitations. Satisfactory agreement was found between the calculated SPs and values from the relativistic Bethe SP equation with recommended values of the mean excitation energy (MEE) for energies above 10keV. We determined effective MEEs versus maximum excitation energy from the ELFs for each solid. Plots of effective MEE versus atomic number showed the relative contributions of valence-electron and different core-electron excitations to the MEE. For a maximum excitation energy of 30keV, our effective MEEs agreed well for Be, graphite, Na, Al, and Si with recommended MEEs; a difference for Li was attributed to sample oxidation in the SP measurements for the recommended MEE. Substantially different effective MEEs were found for the three carbon allotropes (graphite, diamond, and glassy C).

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

2008-03-01

231

SOME CHARACTERISTICS OF THE SPECTRA OF RESONANCE ABSORPTION OF 23.8 kev $gamma$-RAYS BY Sn¹¹⁹ NUCLEI  

Microsoft Academic Search

The probabilities for absorption of 23.8 kev gamma quanta by Sn\\/sup ; 119\\/ without recoil energy losses are measured for 14 tin-containing compounds at ; 77 and 300 deg K temperature. A very weak temperature dependence of this ; probability was observed for some of the compounds. The main regularities ; pertaining to the magnitude of the chemical isomer shifts

V. A. Brukhanov; N. N. Delyagin; A. A. Opalenko; V. S. Shpinel

1962-01-01

232

20-150 keV proton impact induced ionization of uracil: fragmentation ratios and branching ratios for electron capture and direct ionization  

E-print Network

of relevance to cancer therapy techniques in which beams of accelerated ions are used to deliver localized doses of energy to kill cells within tumors (proton and hadron therapies) [Moretto-Capelle and Le1 20-150 keV proton impact induced ionization of uracil: fragmentation ratios and branching ratios

Paris-Sud XI, Université de

233

Inelastic scattering of 1060-keV neutrons by /sup 238/U  

SciTech Connect

The possibility is substantiated of determining the cross sections for inelastic scattering of neutrons from analysis of the ..gamma..-ray spectra produced in inelastic scattering. The experimental apparatus is described and the sources of error are discussed. The cross sections are determined for inelastic scattering of neutrons with E/sub n/=1060 keV for the following levels of the /sup 238/U nucleus: 680, 732, and 930 keV, and also the cross section for inelastic scattering of neutrons with E/sub n/=850 keV for the 680-keV level of /sup 238/U.

Kozulin, E.M.; Lebedev, L.S.; Nemilov, Y.A.; Pobedonostsev, L.A.; Tutin, T.A.; Filatenkov, A.A.; Trofimov, Y.N.

1979-03-01

234

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

NASA Technical Reports Server (NTRS)

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.

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

1996-01-01

235

CAN THE EXCESS IN THE Fe XXVI Ly{gamma} LINE FROM THE GALACTIC CENTER PROVIDE EVIDENCE FOR 17 keV STERILE NEUTRINOS?  

SciTech Connect

Sterile neutrinos (or right-handed neutrinos) are a plausible warm dark matter candidate. We find that the excess of the intensity in the 8.7 keV line (at the energy of the Fe XXVI Ly{gamma} line) in the spectrum of the Galactic center observed by Suzaku cannot be explained by standard ionization and recombination processes. We suggest that the origin of this excess is via decays of sterile neutrinos with a mass of 17.4 keV. The estimated value of the mixing angle sin{sup 2}(2{theta}) = (4.4 {+-} 2.2) x 10{sup -12} lies in the allowed region of the mixing angle for a dark matter sterile neutrino with a mass of 17-18 keV.

Prokhorov, Dmitry [Korea Astronomy and Space Science Institute, Hwaam-dong, Yuseong-gu, Daejeon 305-348 (Korea, Republic of); Silk, Joseph, E-mail: prokhorov@kasi.re.k [Astrophysics, Department of Physics, University of Oxford, Keble Road Ox1 3RH, Oxford (United Kingdom)

2010-12-20

236

3.5-keV X-ray line from nearly-degenerate WIMP dark matter decays  

E-print Network

The unidentified emission line at the energy of $\\sim$3.5~keV observed in X-rays from galaxy clusters may originate from a process involving a dark matter particle. On the other hand, a weakly interacting massive particle (WIMP) has been an attractive dark matter candidate, due to its well-understood thermal production mechanism and its connection to physics at the TeV scale. In this paper, we pursue the possibility that the 3.5-keV X-ray arises from a late time decay of a WIMP dark matter into another WIMP dark matter, both of which have the mass of $O(100)$~GeV and whose mass splitting is about 3.5~keV. We focus on the simplest case where there are two Majorana dark matter particles and two charged scalars that couple with a standard model matter particle. By assuming a hierarchical structure in the couplings of the two dark matter particles and two charged scalars, it is possible to explain the 3.5-keV line and realize the WIMP dark matter scenario at the same time. Since the effective coupling of the two different Majorana dark matter particles and one photon violates CP symmetry, the model always contains a new source of CP violation, so the model's connection to the physics of electric dipole moments is discussed. The model's peculiar signatures at the LHC are also studied. We show the prospect of detecting the charged scalars through a detailed collider simulation.

Cheng-Wei Chiang; Toshifumi Yamada

2014-07-28

237

Study of keV radiation properties of Mo and Ti X-pinch plasma sources using a pinhole transmission grating spectrometer  

SciTech Connect

The properties of keV x-ray radiations from Mo and Ti X-pinch plasma sources at the current of 800 kA were investigated by a pinhole transmission grating spectrometer. The spectrometer was characterized by a high linear dispersion rate (2.9 A/mm), and from its time-integrated diffraction images, rich information about the X-pinch sources (e.g., source number, source size, and absolute spectra) could be obtained. Multiple hot spots were produced in all the Mo tests with loads made of two or four 25 mum wires with or without a shunt wire, and obvious increases both in the radiation intensity and in the source size around the spectral region of 2.6 keV were observed. In Ti X-pinch tests, a single keV x-ray burst with a source size of approx200 mum and a time duration of approx200 ps in full width at half maximum was obtained using a load made of two 50 mum wires plus a shunt wire. The intensity of x-rays decreased sharply from approx10{sup 11} photon eV{sup -1} sr{sup -1} at 1 keV to approx10{sup 8} photon eV{sup -1} sr{sup -1} at 4 keV. The energy-dependent source size in the band of 1-4 keV is less than 100 mum and seemed to shrink quickly as x-ray energy increases.

Li Jing [Institute of Fluid Physics, CAEP, Mianyang 621900 (China); Department of Engineering Physics, Tsinghua University, Beijing 100084 (China); Deng Jianjun; Xie Weiping; Huang Xianbin; Yang Libing; Zhou Shaotong; Duan Shuchao; Zhang Siqun; Dan Jiakun [Institute of Fluid Physics, CAEP, Mianyang 621900 (China); Zhu Xiaoli [Key Laboratory of Nano-Fabrication and Novel Devices Integrated Technology, Institute of Microelectronics, CAS, Beijing 100029 (China)

2010-07-15

238

Study of 1–8 keV K-? x-ray emission from high intensity femtosecond laser produced plasma  

SciTech Connect

We report an experimental study on the optimization of a laser plasma based x-ray source of ultra-short duration K-? line radiation. The interaction of pulses from a CPA based Ti:sapphire laser (10 TW, 45 fs, 10 Hz) system with magnesium, titanium, iron and copper solid target generates bright 1-8 keV K-? x-ray radiation. The x-ray yield was optimized with the laser pulse duration (at fixed fluence) which is varied in the range of 45 fs to 1.4 ps. It showed a maximum at laser pulse duration of ?740 fs, 420 fs, 350 and 250 fs for Mg (1.3 keV), Ti (4.5 keV), Fe (6.4 keV) and Cu (8.05 keV) respectively. The x-ray yield is observed to be independent of the sign of the chirp. The scaling of the K-? yield (I{sub x} ? I{sub L}{sup ?}) for 45 fs and optimized pulse duration were measured for laser intensities in the region of 3 × 10{sup 14} – 8 × 10{sup 17}. The x-ray yield shows a much faster scaling exponent ? = 1.5, 2.1, 2.4 and 2.6 for Mg, Ti, Fe and Cu respectively at optimized pulse duration compared to scaling exponent of 0.65, 1.3, 1.5, and 1.7 obtained for 45 fs duration laser pulses. The laser to x-ray energy conversion efficiencies obtained for different target materials are ?{sub Mg} = 1.2 × 10{sup ?5}, ?{sub Ti} = 3.1 × 10{sup ?5}, ?{sub Fe} = 2.7 × 10{sup ?5}, ?{sub Cu} = 1.9 × 10{sup ?5}. The results have been explained from the efficient generation of optimal energy hot electrons at longer laser pulse duration. The faster scaling observed at optimal pulse duration indicates that the x-ray source is generated at the target surface and saturation of x-ray emission would appear at larger laser fluence. An example of utilization of the source for measurement of shock-wave profiles in a silicon crystal by time resolved x-ray diffraction is also presented.

Arora, V., E-mail: arora@rrcat.gov.in; Naik, P. A.; Chakera, J. A.; Bagchi, S.; Tayyab, M.; Gupta, P. D. [Laser Plasma Division, Raja Rammana Centre for Advanced Technology, Indore 452 013 (India)] [Laser Plasma Division, Raja Rammana Centre for Advanced Technology, Indore 452 013 (India)

2014-04-15

239

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)

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.

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

2014-10-01

240

Molecular dynamics simulation of radiation damage in CaCd6 quasicrystal cubic approximant up to 10 keV.  

PubMed

Due to the peculiar nature of the atomic order in quasicrystals, examining phase transitions in this class of materials is of particular interest. Energetic particle irradiation can provide a way to modify the structure locally in a quasicrystal. To examine irradiation-induced phase transitions in quasicrystals on the atomic scale, we have carried out molecular dynamics simulations of collision cascades in CaCd6 quasicrystal cubic approximant with energies up to 10 keV at 0 and 300 K. The results show that the threshold energies depend surprisingly strongly on the local coordination environments. The energy dependence of stable defect formation exhibits a power-law dependence on cascade energy, and surviving defects are dominated by Cd interstitials and vacancies. Only a modest effect of temperature is observed on defect survival, while irradiation temperature increases lead to a slight increase in the average size of both vacancy clusters and interstitial clusters. PMID:23802969

Chen, P H; Avchachov, K; Nordlund, K; Pussi, K

2013-06-21

241

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)

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.

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

1997-01-01

242

Radiation transmission of concrete including boron waste for 59.54 and 80.99 keV gamma rays  

NASA Astrophysics Data System (ADS)

Accurate measurement have been made to determine radiation transmission of boron compounds by using an extremely narrow collimated beam transmission method for 59.54 and 80.99 keV gamma energy with a Si(Li) detector. Appreciable variations were observed in the transmission factors of the concrete samples including different boron wastes (borogypsum and colemanite concentrator waste). Additionally, mass attenuation coefficients were also calculated. It is seen that ?/ ? is increased with increasing boron concentration in the concrete and the both kind of boron waste have nearly the same property in the radiation transmission.

Demir, Demet; Kele?, Gürbüz

2006-04-01

243

One-dimensional x-ray imaging using a spherically bent mica crystal at 4.75 keV  

SciTech Connect

One-dimensional x-ray imaging of static gold bars using a spherically bent mica crystal is presented for the first time at an x-ray energy of 4.75 keV. X rays are produced using 1-ns-square pulses on the TRIDENT laser facility driving the He-like resonance transition in solid titanium disks. Time-integrated images of square profile parallel gold bars are recorded on direct exposure film with a magnification of {approx}10. Rising edge measurements of the bars demonstrate resolutions of about 6--7 {mu}m over a 400 {mu}m field of view.

Workman, J.; Evans, S.; Kyrala, G. A.

2001-01-01

244

LUCIA — a new 1-7 keV ?-XAS Beamline  

NASA Astrophysics Data System (ADS)

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 × 1 ?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.

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

2004-05-01

245

Classical dynamics simulations of 4 keV Ar sputtering of Ca(1 0 0)  

NASA Astrophysics Data System (ADS)

Classical dynamics computer simulations were used to study the sputtering of Ca(1 0 0) crystallites by 4 keV Ar projectiles. The short range Ar-Ca and Ca-Ca interactions were represented by Ziegler-Biersack-Littmark (ZBL) screened Coulomb potentials. The attractive long range Ca-Ca interactions were represented either by a Morse pair potential, or by a Finnis-Sinclair (FS) many-body potential, both of which were obtained by fitting to the structural and physical properties of Ca. The simulations compared the predicted sputtering behaviour of the crystallites for normal and random directions of projectile incidence. The sputtering characteristics predicted by the Morse and FS potentials were broadly similar, although small systematic differences were noted in the yields and angular distributions of sputtered atoms. The predicted sputter yields for Ca atoms and Ca2 clusters were found to be generally higher (by a factor of ?2) than the experimental yields reported for polycrystalline Ca targets [C.S. Hansen et al., Surf. Sci. 398 (1998) 211-220]. The predicted energy distributions for Ca atoms were found to decline less rapidly with energy (?E-1.6) than the experimental distribution for polycrystalline Ca (?E-2).

Karolewski, M. A.

1999-10-01

246

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

SciTech Connect

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.

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

247

Monochromatic 8.05-keV Flash Radiography of Imploded Cone-in-Shell Targets  

NASA Astrophysics Data System (ADS)

Fast ignition has the potential of high fusion gains through the ignition of massive DT fuel assemblies. The cone-in-shell target concept might be one way of achieving this goal. Integrated experiments on OMEGA have demonstrated ˜4% coupling efficiency of short-pulse laser energy into the compressed target.footnotetextW. Theobald et al., Phys. Plasmas 18, 056305 (2011). An improved target design has been developed with a low-Z cone tip. The goal was to validate 2-D radiation--hydrodynamic modeling predictions of the new target design. The technique used was flash radiography from a monochromatic 8.05-keV x-ray source.footnotetext J. A. King et al., Appl. Phys. Lett. 86, 191501 (2005). Cu foils were irradiated by the 1.5-kJ, 10-ps OMEGA EP short-pulse laser to generate a bright Cu K? area backlighter source, which was used in combination with monochromatic imaging with a spherical Bragg crystal to backlight the cone-in-shell implosions at various times around peak compression. Flash radiography provides high-quality images of the fuel assembly with ˜10-ps time resolution and ˜10-?m spatial resolution. This work was supported by the U.S. Department of Energy under Cooperative Agreement Nos. DE-FC52-08NA28302 and DE-FC02-04ER54789.

Theobald, W.; Solodov, A. A.; Stoeckl, C.; Glebov, V. Yu.; Ivancic, S.; Marshall, F. J.; McKiernan, G.; Mileham, C.; Sangster, T. C.; Beg, F. N.; Jarrott, C.; Giraldez, E.; Stephens, R. B.; Wei, M. S.; Key, M. H.; McLean, H.; Santos, J.

2012-10-01

248

Measurement of the ionization yield of nuclear recoils in liquid argon at 80 and 233 keV  

NASA Astrophysics Data System (ADS)

The energy calibration of nuclear recoil detectors is of primary importance to rare-event experiments such as those of direct dark matter search and coherent neutrino-nucleus scattering. In particular, such a calibration is performed by measuring the ionization yield of nuclear recoils in liquid Ar and Xe detection media, using neutron elastic scattering off nuclei. In the present work, the ionization yield for nuclear recoils in liquid Ar has for the first time been measured in the higher energy range, at 80 and 233 keV, using a two-phase Cryogenic Avalanche Detector (CRAD) and DD neutron generator. The ionization yield in liquid Ar at an electric field of 2.3 kV/cm amounted to 7.8+/-1.1 and 9.7+/-1.3 \\text{e}^-/\\text{keV} at 80 and 233 keV, respectively. The Jaffe model for nuclear recoil-induced ionization, in contrast to that of Thomas-Imel, can probably consistently describe the energy dependence of the ionization yield.

Bondar, A.; Buzulutskov, A.; Dolgov, A.; Grishnyaev, E.; Polosatkin, S.; Shekhtman, L.; Shemyakina, E.; Sokolov, A.

2014-10-01

249

Measurement of the ionization yield of nuclear recoils in liquid argon at 80 and 233 keV  

E-print Network

The energy calibration of nuclear recoil detectors is of primary importance to rare-event experiments such as those of direct dark matter search and coherent neutrino-nucleus scattering. In particular, such a calibration is performed by measuring the ionization yield of nuclear recoils in liquid Ar and Xe detection media, using neutron elastic scattering off nuclei. In the present work, the ionization yield for nuclear recoils in liquid Ar has for the first time been measured in the higher energy range, at 80 and 233 keV, using a two-phase Cryogenic Avalanche Detector (CRAD) and DD neutron generator. The ionization yield in liquid Ar at an electric field of 2.3 kV/cm amounted to 7.8+/-1.1 and 9.7+/-1.3 e-/keV at 80 and 233 keV respectively. The Jaffe model for nuclear recoil-induced ionization, in contrast to that Thomas-Imel, can probably consistently describe the energy dependence of the ionization yield.

A. Bondar; A. Buzulutskov; A. Dolgov; E. Grishnyaev; S. Polosatkin; L. Shekhtman; E. Shemyakina; A. Sokolov

2014-09-23

250

On the origin of the 6.4 keV line in the Galactic Center region  

NASA Astrophysics Data System (ADS)

We analyse the 6.4 keV iron line component produced in the Galactic Center (GC) region by cosmic rays in dense molecular clouds (MCs) and in the diffuse molecular gas. We showed that this component, in principle, can be seen in several years in the direction of the cloud Srg B2. If this emission is produced by low energy CRs which ionize the interstellar molecular gas the intensity of the line is quite small, <1%. However, we cannot exclude that local sources of CRs or X-ray photons nearby the cloud may provide much higher intensity of the line from there. Production of the line emission from molecular clouds depends strongly on processes of CR penetration into them. We show that turbulent motions of neutral gas may generate strong magnetic fluctuations in the clouds which prevent free penetration of CRs into the clouds from outside. We provide a special analysis of the line production by high energy electrons. We concluded that these electrons hardly provide the diffuse 6.4 keV line emission from the GC because their density is depleted by ionization losses. We do not exclude that local sources of electrons may provide an excesses of the 6.4 keV line emission in some molecular clouds and even reproduce a relatively short time variations of the iron line emission. However, we doubt whether a single electron source provides the simultaneous short time variability of the iron line emission from clouds which are distant from each other on hundred pc as observed for the GC clouds. An alternative speculation is that local electron sources could also provide the necessary effect of the line variations in different clouds that are seen simultaneously by chance that seems, however, very unlikely.

Dogiel, V. A.; Chernyshov, D. O.; Kiselev, A. M.; Cheng, K.-S.

2014-02-01

251

Calculations of stopping powers and inelastic mean free paths for 20 eV-20 keV electrons in 11 types of human tissue.  

PubMed

Systematic calculations are performed for determining the stopping powers (SP) and inelastic mean free paths (IMFP) for 20 eV-20 keV electrons in 11 types of human tissue. The calculations are based on a dielectric model, including the Born-Ochkur exchange correction. The optical energy loss functions (OELF) are empirically evaluated, because of the lack of available experimental optical data for the 11 tissues under consideration. The evaluated OELFs are examined by the f-sum rule expected from the dielectric response theory, and by calculation of the mean excitation energy. The calculated SPs are compared with those for PMMA (polymethylmethacrylate, a tissue equivalent material) and liquid water. The SP and IMFP data presented here are the results for the 11 human tissues over the energy range of 20 eV-20 keV, and are of importance in radiotherapy planning and for studies of various radiation effects on human tissues. PMID:24144616

Tan, Zhenyu; Liu, Wei

2013-12-01

252

Multipole mixing ratios of the 198 and 177 keV ?-ray transitions in 169Tm  

NASA Astrophysics Data System (ADS)

The multipole mixing ratios for the 198 and 177 keV ?-ray transitions in 169Tm are determined as ?(198)=-6.1+0.4-0.6 and ?(177)=-0.20+0.04-0.03 from new measurements of angular correlation of the 63-198 and 63-177 keV cascades in addition to measurements on the cascades passing through the 118 and 139 keV levels. The present value of ?(198) indicates an almost pure E2 character for the 198 keV ? ray while from earlier measurements an admixture of only 9% E2 was reported for this ? ray. For both the 198 and 177 keV transitions the results do not agree with the conversion electron measurements and indicate that the conversion processes in these transitions are not normal. From time-differential measurement on the 63-198 keV cascade, the relaxation constant ?2=(0.31+/-0.21)×107 sec-1 is obtained using the source in acetic acid solution. The integral attenuation coefficients for the 316 keV level are found to be G2=0.19+/-0.04 in liquid chloride source and G2=0.57+/-0.06 in liquid acetate source.

Dey, C. C.; Sinha, B. K.

1994-01-01

253

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

NASA Astrophysics Data System (ADS)

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 d?/d?, 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.

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

2006-05-01

254

Digging gold: keV He(+) ion interaction with Au.  

PubMed

Helium ion microscopy (HIM) was used to investigate the interaction of a focused He(+) ion beam with energies of several tens of kiloelectronvolts with metals. HIM is usually applied for the visualization of materials with extreme surface sensitivity and resolution. However, the use of high ion fluences can lead to significant sample modifications. We have characterized the changes caused by a focused He(+) ion beam at normal incidence to the Au{111} surface as a function of ion fluence and energy. Under the influence of the beam a periodic surface nanopattern develops. The periodicity of the pattern shows a power-law dependence on the ion fluence. Simultaneously, helium implantation occurs. Depending on the fluence and primary energy, porous nanostructures or large blisters form on the sample surface. The growth of the helium bubbles responsible for this effect is discussed. PMID:23946914

Veligura, Vasilisa; Hlawacek, Gregor; Berkelaar, Robin P; van Gastel, Raoul; Zandvliet, Harold J W; Poelsema, Bene

2013-01-01

255

Measurement of the 10 keV resonance in the B10(p,?0)Be7 reaction via the Trojan Horse method  

NASA Astrophysics Data System (ADS)

The B10(p ,?0)Be7 bare nucleus astrophysical S (E) factor has been measured for the first time at energies from about 100 keV down to about 5 keV by means of the Trojan Horse method (THM). In this energy region, the S (E) factor is strongly dominated by the 8.699 MeV C11 level (J?=52+), producing an s-wave resonance centered at about 10 keV in the entrance channel. Up to now, only the high-energy tail of this resonance has been measured, while the low-energy trend is extrapolated from the available direct data. The THM has been applied to the quasifree H2(B10,?0 Be7)n reaction induced at a boron-beam energy of 24.5 MeV. An accurate analysis leads to the determination of the B10(p ,?0)Be7 S (E) factor and of the corresponding electron screening potential Ue, thus giving for the first time an independent evaluation of it.

Spitaleri, C.; Lamia, L.; Puglia, S. M. R.; Romano, S.; La Cognata, M.; Crucillà, V.; Pizzone, R. G.; Rapisarda, G. G.; Sergi, M. L.; Del Santo, M. Gimenez; Carlin, N.; Munhoz, M. G.; Souza, F. A.; Szanto de Toledo, A.; Tumino, A.; Irgaziev, B.; Mukhamedzhanov, A.; Tabacaru, G.; Burjan, V.; Kroha, V.; Hons, Z.; Mrazek, J.; Zhou, Shu-Hua; Li, Chengbo; Wen, Qungang; Wakabayashi, Y.; Yamaguchi, H.; Somorjai, E.

2014-09-01

256

Stopping powers and inelastic mean free path of 200eV-50keV electrons in polymer PMMA, PE, and PVC.  

PubMed

The stopping power (SP) and inelastic mean free path (IMFP) of three polymers: polymethyl methacrylate (PMMA), polyethylene (PE), and polyvinyl chloride (PVC) for electron energies from 200eV to 50keV have been determined based on dielectric models. The energy loss function (ELF) is the main input in the calculation of the SP and IMFP for the dielectric models. ELF in this study was determined from a previously published quantitative analysis of reflection electron energy loss spectroscopy (REELS) spectra. The SP of PMMA, PE and PVC decreases and the IMFP increases with increasing electron energies up to 50keV. For comparison, data from the National Institute of Standards and Technology (NIST) database for electron energies from 10 to 50keV were used and show that SP in this study is lowered by 10-15%. The obtained IMFP for PE was compared with those calculated using the TPP2M predictive equations and shows that a reasonable agreement with a root-mean-square (rms) is 7.01Å. The present approach has high potential for the experimental determination of SP and IMFP from the REELS spectra. PMID:25464178

Tahir, Dahlang; Suarga; Sari, Nur Harmila; Yulianti

2014-10-14

257

Os-187(n, n') inelastic cross section at 34 keV  

NASA Astrophysics Data System (ADS)

A measurement of the Os-187 inelastic neutron cross section to the 3/2(-) 9.75 keV excited state with 34 + or - 2 keV incident neutrons gives 1.5 + or - 0.2 barns. Pulsed neutron time of flight and a short anisotropic iron-aluminum filter allowed separation of the inelastic yield from the 1/2(-) ground-state elastic yield at 24 keV. The influence of the result on r-process galactic age calculations via the Re-Os decay chronometer is discussed, and the need for further theoretical calculations is emphasized.

Macklin, R. L.; Hill, N. W.; Harvey, J. A.; Winters, R. R.

1983-11-01

258

The gyromagnetic ratio of the 589 keV 3\\/2 ? state of 117 In  

Microsoft Academic Search

Theg-factor of the 589 keV state of117In has been determined by a measurement of the rotation of the 1,303–273 keV? —? directional correlation in an external magnetic field of 9.55(1) T. The result,g3\\/2(589 keV)=+0.068(39), contradicts the usual interpretation of the state as the 2p3\\/2 single proton hole configuration for which the Schmidt value isg3\\/2-(Schmidt)=+2.53. It favours the interpretation as the

A. Alzner; E. Bodenstedt; B. Gemünden; H. Reif

1985-01-01

259

First measurement of a p(n, gamma)d reaction cross section between 10 and 80 keV  

NASA Astrophysics Data System (ADS)

For the first time we have successfully measured the important cross section of the p(n, gamma)d reaction at astrophysically relevant energies between 10 and 80 keV, where the difference in the cross section between old and new calculations is quite large. In the measurement we used a prompt gamma-ray detection method, combined with a pulsed neutron beam, which is crucial for determining the cross section accurately by discriminating small true signals from huge background signals; we also used a recently developed Monte Carlo code for correcting neutron multiple-scattering effects in a sample. The cross sections derived in the present experiment were 318 (25) microbarn 203 (19) microbarn and 151 (7) microbarn at neutron energies of 20, 40, and 64 keV, respectively. They do not follow a simple l/nu law and are in good agreement with new calculations. Regarding the primordial abundances of light elements, the present result supports a recent calculation by Smith et al. However, the discrepancy in the deuteron photodisintegration cross sections between the experimental values and a newly calculated one by Ohtsubo et al. remains to be explained.

Suzuki, T. S.; Nagai, Y.; Shima, T.; Kikuchi, T.; Sato, H.; Kii, T.; Igashira, M.

1995-02-01

260

An Einstein survey of the 1 keV soft X-ray background in the Galactic plane  

NASA Technical Reports Server (NTRS)

We have analyzed 56 Einstein Observatory Imaging Proportional Counter (IPC) observations within +/- 3 deg of the Galactic plane in order to determine the low-latitude soft X-ray background flux in the 0.56-1.73 keV band. Any detected X-ray point source which fell within our regions of study was removed from the image, enabling us to present maps of the background flux as a function of Galactic latitude along 18 meridians. These maps reveal considerable structure to the background in the Galactic plane on an angular scale of approximately 1 deg. Our results are compared with those of an earlier study of the 1 keV X-ray background along l = 25 deg by Kahn & Caillault. The double-peaked structure they found is not discernible in our results, possibly because of the presence of solar backscattered flux in their data. A model which takes into account contributions to the background by extragalactic and stellar sources, the distribution of both atomic and molecular absorbing material with the Galaxy, the energy dependence of the cross section for absorption of X-rays, and the energy dependence of the detector has been constructed and fitted to these new data to derive constraints on the scale height, temperature, and volume emissivity of the unaccounted-for X-ray-emitting material. The results of this model along l = 25 deg are roughly similar to those of the model of Kahn & Caillault along the same meridian.

Stanford, John M.; Caillault, Jean-Pierre

1994-01-01

261

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

NASA Astrophysics Data System (ADS)

Simple analytical expressions for the electron backscattering coefficient, ?, 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 ? with a decrease in energy E° for high-Z elements and the reverse behavior for low-Z elements. The proposed expressions for ? (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 ?-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.

Cazaux, J.

2012-10-01

262

The Swift/Fermi GRB 080928 from 1 eV to 150 keV  

NASA Technical Reports Server (NTRS)

We present the results of a comprehensive study of the Gamma-Ray Burst 080928 and of its afterglow. GRB 08092 was a long burst detected by Swift/BAT and Fermi/GBM, It is one of the exceptional cases where optical emission was already detected when the GRB itself was still radiating in the gamma-ray band. for nearly 100 seconds simultaneous optical X-ray and gamma-ray data provide a coverage of the spectral energy distribution of the transient source from about 1 eV to 150 keV. Here we analyze the prompt emission, constrain its spectral propertIes. and set lower limits on the initial Lorentz factor of the relativistic outflow, In particular. we show that the SED during the main prompt emission phase is in agreement with synchrotron radiation. We construct the optical/near-infrared light curve and the spectral energy distribution based on Swift/UVOT. ROTSE-Illa (Australia) and GROND (La Silla) data and compare it to the X-ray light curve retrieved from the Swift/XRT repository. We show that its bumpy shape can be modeled by multiple energy injections into the forward shock. Furthermore, we provide evidence that the temporal and spectral evolution of the first strong flare seen in the early X-ray light curve can be explained by large-angle emission. Finally, we report on the results of our search for the GRB host galaxy, for which only a deep upper limit can be provided.

Sonbas, Eda; Rossi, A.; Schulze, S.; Klose, S.; Kann, D. A.; Ferrero, P.; NicuesaGuelbenzu, A.; Rau, A.; Kruehler, T.; Greiner, J.; Schady, P.; Afonso, P. M. J.; Clemens, C.; Filgas, R.; KuepcuYoldas, A.; McBreen, S.; Olivares, F.; Szokoly, G.; Yoldas, A.; Krimm, H. A.; Johannesson, G.; Panaitescu, A.; Yuan, F.; Pandey, S. B.; Akerlof, C. W.

2010-01-01

263

A DATABASE OF >20 keV ELECTRON GREEN'S FUNCTIONS OF INTERPLANETARY TRANSPORT AT 1 AU  

SciTech Connect

We use interplanetary transport simulations to compute a database of electron Green's functions, i.e., differential intensities resulting at the spacecraft position from an impulsive injection of energetic (>20 keV) electrons close to the Sun, for a large number of values of two standard interplanetary transport parameters: the scattering mean free path and the solar wind speed. The nominal energy channels of the ACE, STEREO, and Wind spacecraft have been used in the interplanetary transport simulations to conceive a unique tool for the study of near-relativistic electron events observed at 1 AU. In this paper, we quantify the characteristic times of the Green's functions (onset and peak time, rise and decay phase duration) as a function of the interplanetary transport conditions. We use the database to calculate the FWHM of the pitch-angle distributions at different times of the event and under different scattering conditions. This allows us to provide a first quantitative result that can be compared with observations, and to assess the validity of the frequently used term beam-like pitch-angle distribution.

Agueda, N.; Sanahuja, B. [Departament d'Astronomia i Meteorologia, Institut de Ciencies del Cosmos, Universitat de Barcelona, Barcelona (Spain); Vainio, R. [Department of Physics, University of Helsinki, Helsinki (Finland)

2012-10-15

264

A fresh look at keV sterile neutrino dark matter from frozen-in scalars  

NASA Astrophysics Data System (ADS)

Sterile neutrinos with a mass of a few keV can serve as cosmological warm dark matter. We study the production of keV sterile neutrinos in the early universe from the decay of a frozen-in scalar. Previous studies focused on heavy frozen-in scalars with masses above the Higgs mass leading to a hot spectrum for sterile neutrinos with masses below 8 - 10 keV. Motivated by the recent hints for an X-ray line at 3.55 keV, we extend the analysis to lighter frozen-in scalars, which allow for a cooler spectrum. Below the electroweak phase transition, several qualitatively new channels start contributing. The most important ones are annihilation into electroweak vector bosons, particularly W -bosons as well as Higgs decay into pairs of frozen-in scalars when kinematically allowed.

Adulpravitchai, Adisorn; Schmidt, Michael A.

2015-01-01

265

THE ORIGIN OF THE 6.4 keV LINE EMISSION AND H{sub 2} IONIZATION IN THE DIFFUSE MOLECULAR GAS OF THE GALACTIC CENTER REGION  

SciTech Connect

We investigate the origin of the diffuse 6.4 keV line emission recently detected by Suzaku and the source of H{sub 2} ionization in the diffuse molecular gas of the Galactic center (GC) region. We show that Fe atoms and H{sub 2} molecules in the diffuse interstellar medium of the GC are not ionized by the same particles. The Fe atoms are most likely ionized by X-ray photons emitted by Sgr A* during a previous period of flaring activity of the supermassive black hole. The measured longitudinal intensity distribution of the diffuse 6.4 keV line emission is best explained if the past activity of Sgr A* lasted at least several hundred years and released a mean 2-100 keV luminosity {approx}> 10{sup 38} erg s{sup -1}. The H{sub 2} molecules of the diffuse gas cannot be ionized by photons from Sgr A*, because soft photons are strongly absorbed in the interstellar gas around the central black hole. The molecular hydrogen in the GC region is most likely ionized by low-energy cosmic rays, probably protons rather than electrons, whose contribution into the diffuse 6.4 keV line emission is negligible.

Dogiel, V. A.; Chernyshov, D. O. [I. E. Tamm Theoretical Physics Division of P. N. Lebedev Institute of Physics, Leninskii pr. 53, 119991 Moscow (Russian Federation); Tatischeff, V. [Centre de Spectrometrie Nucleaire et de Spectrometrie de Masse, IN2P3/CNRS and Univ Paris-Sud, F-91405 Orsay Campus (France); Cheng, K.-S. [Department of Physics, University of Hong Kong, Pokfulam Road, Hong Kong (Hong Kong); Terrier, R. [Astroparticule et Cosmologie, Universite Paris7/CNRS/CEA, Batiment Condorcet, F-75013 Paris (France)

2013-07-10

266

Development of a 9 keV x-ray backlighter for the Z accelerator  

Microsoft Academic Search

Development of a 9 keV point projection backlighter using the Z-Beamlet laser system in Sandia's 20-MA Z accelerator is currently underway. This effort seeks to develop a more sensitive detector capable of distinguishing the backlighting x-rays from the x-ray background noise of the Z accelerator. Characterization of the Z x-ray background is in progress. Additionally, 9 keV x-ray conversion efficiency

M. R. Lopez; J. L. Porter; G. R. Bennett; L. E. Ruggles; W. W. Simpson; D. F. Wenger; I. C. Smith; K. V. Cone

2004-01-01

267

Development of an 18 keV X-Ray Thomson Scattering Source for the Characterization of Dense States of Matter  

NASA Astrophysics Data System (ADS)

The accurate characterization of material properties under extreme conditions is an important issue for the understanding of high energy density states of matter, from planetary interiors to capsule implosions relevant to inertial confinement fusion. High energy x-ray Thomson Scattering at 18 keV will make it possible to characterize very dense states of matter such as 50x compressed beryllium, ICF-like ablator materials, aluminum compressed up to 4x by a single shock, and isochorically heated mid-Z elements (such as Ti). Here we present results from a backscattering experiment carried out at the Omega Laser Facility, performed on aluminum, the highest-Z material probed to this date. We will also demonstrate the viability of molybdenum He-alpha (18 keV) as a suitable backlighter probe source.

Ma, Tammy; Lee, Haeja; Doeppner, Tilo; Falcone, Roger; Fortmann, Carsten; Kritcher, Andrea; Landen, Otto; Glenzer, Siegfried

2010-11-01

268

Nuclear resonant forward scattering of synchrotron radiation from 121 Sb at 37.13 keV.  

SciTech Connect

We report on the observation of nuclear resonant forward scattering of synchrotron radiation from {sup 121}Sb nuclei. A temperature stabilized {alpha}Al{sub 2}O{sub 3} crystal Bragg backscattering high-resolution monochromator with a relative energy resolution of 2 x 10{sup -7} was introduced. As first spectroscopic applications the hyperfine parameters in Sb{sub 2}O{sub 3}, USb and DySb were determined. The energy of the nuclear transition in {sup 121}Sb was measured to be 37.1298(2)keV, 40 times more precisely than reported before. The results open the field of nuclear resonance spectroscopy on antimony compounds taking advantage of the outstanding features of 3rd-generation synchrotron sources. Nuclear resonance scattering on Sb compounds at these sources allows element-specific dynamical studies on thermoelectric materials as well as studies on magnetism in micro- and nanometer dimensional systems like spintronic devices.

Wille, H. C.; Shvydko, Y. V.; Alp, E. E.; Ruter, H. D.; Leupold, O.; Sergueev, I.; Ruffer, R.; Barla, A.; Sanchez, J. P.; X-Ray Science Division; European Synchrotron Radiation Facility; Univ. of Hamburg; Hamburder Synchrotronstrahlungslabor

2006-02-22

269

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

PubMed

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. PMID:25430181

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

2014-11-01

270

INTEGRAL Observations of the Galactic 511 keV Emission and MeV Gamma-ray Astrophysics  

NASA Technical Reports Server (NTRS)

Although there are a number of interesting phenomena, such as Nucleosynthesis in stars, in the MeV energy region, the observations have been difficult due to a small signal to noise (background) ratio (less than 1%). While NASA's Compton Gamma-ray Observatory (CGRO) enabled us to explore the Gamma-ray universe, ESA's INTEGRAL mission, launched in 2002, is providing us more detailed information with its superior energy and angular resolution. We will briefly discuss some of the current issues in MeV Gamma-ray Astrophysics. Then, we will focus on the Galactic 511 keV emission with the latest INTEGRAL observations, and talk about challenges we currently have.

Watanabe, Ken

2005-01-01

271

Investigation of X-rays ~5-30keV from a 3kJ Dense Plasma Focus using Silicon Detectors  

Microsoft Academic Search

We describe the selection of silicon photodiodes to measure the medium energy (5-30keV) x-rays from the NX2 plasma focus device for H, N, Ar and Ne filling gas. The dense plasma focus is a device that focuses a gas into a column of hot dense plasma using a m agnetic field. The high temperature in the pl asma means that

J. Y. Tan; S. Kanesan; A. C. Patran; R. S. Rawat; P. Lee

272

X pinch X-ray radiation above 8 keV for application to high-resolution radiography of biological specimens  

Microsoft Academic Search

The X pinch is a dense plasma X-ray source that is known to emit sub-ns bursts of X-rays in the 2.5 - 8 keV energy range from a very small (?1 ?m) source commonly referred to as a micropinch. As such, it has been successfully used as a point source for X-ray radiographic imaging of small biological samples with spatial

ByungMoo Song; T. A. Shelkovenko; S. A. Pikuz; M. A. Mitchell; K. M. Chandler; D. A. Hammer

2003-01-01

273

X pinch X-ray radiation above 8 keV for application to high-resolution radiography of biological specimens  

Microsoft Academic Search

The X pinch is a dense plasma X-ray source that is known to emit subnanosecond bursts of X-rays in the 2.5-8 keV energy range from a very small (?1 ?m) source commonly referred to as a micropinch. As such, it has been successfully used as a point source for X-ray radiographic imaging of small biological samples with spatial resolution as

Byung Moo Song; T. A. Shelkovenko; S. A. Pikuz; M. A. Mitchell; K. M. Chandler; D. A. Hammer

2004-01-01

274

Bragg diffraction using a 100 ps 17.5 keV x-ray backlighter and the Bragg diffraction imager  

Microsoft Academic Search

A new diagnostic for measuring Bragg diffraction of petawatt-generated high-energy x rays off a laser-compressed crystal was designed and tested successfully at the Omega EP laser facility on static Mo and Ta (111) oriented single crystal samples using a 17.5 keV Mo Kalpha backlighter. The Bragg diffraction imager consists of a heavily shielded enclosure and a precisely positioned beam block

B. R. Maddox; H.-S. Park; J. Hawreliak; A. Elsholz; R. van Maren; B. A. Remington; A. Comley; J. S. Wark

2010-01-01

275

Electron collisional detachment processes for a 250 keV D/sup -/ ion beam in a partially ionized hydrogen target  

SciTech Connect

Neutral atom beams with energies above 200 keV may be required for various purposes in magnetic fusion devices following TFTR, JET and MFTF-B. These beams can be produced much more efficiently by electron detachment from negative ion beams than by electron capture by positive ions. We have investigated the efficiency with which such neutral atoms can be produced by electron detachment in partially ionized hydrogen plasma neutralizers.

Savas, S.E.

1980-09-01

276

Laser streaking of free electrons at 25 keV  

NASA Astrophysics Data System (ADS)

Recording electronic motion in atomic systems requires attosecond and picometre resolutions. Current attosecond technology provides photon pulses up to an energy range of 100 eV, with wavelengths far too long to access structures on the atomic scale. In contrast, ultrashort free-electron pulses with sub-Ångstrom de Broglie wavelengths offer the potential to resolve sub-atomic structures. Here, we demonstrate an optical-field-driven streak camera for their temporal characterization. Our concept is to have an electron beam and a laser beam intersect at an ultrathin metal mirror, and potentially offers attosecond resolution. The technique will be instrumental in advancing ultrafast electron diffraction towards ever higher temporal resolution in the pursuit of the long-term goal of sub-atomic four-dimensional imaging. As a first application, we study the influence of electron-electron interactions on the characteristics of few-electron pulses.

Kirchner, F. O.; Gliserin, A.; Krausz, F.; Baum, P.

2014-01-01

277

Angular scattering of 1–50 keV ions through graphene and thin carbon foils: Potential applications for space plasma instrumentation  

SciTech Connect

We present experimental results for the angular scattering of ?1–50 keV H, He, C, O, N, Ne, and Ar ions transiting through graphene foils and compare them with scattering through nominal ?0.5 ?g?cm{sup ?2} carbon foils. Thin carbon foils play a critical role in time-of-flight ion mass spectrometers and energetic neutral atom sensors in space. These instruments take advantage of the charge exchange and secondary electron emission produced as ions or neutral atoms transit these foils. This interaction also produces angular scattering and energy straggling for the incident ion or neutral atom that acts to decrease the performance of a given instrument. Our results show that the angular scattering of ions through graphene is less pronounced than through the state-of-the-art 0.5 ?g?cm{sup ?2} carbon foils used in space-based particle detectors. At energies less than 50 keV, the scattering angle half width at half maximum, ?{sub 1/2}, for ?3–5 atoms thick graphene is up to a factor of 3.5 smaller than for 0.5 ?g?cm{sup ?2} (?20 atoms thick) carbon foils. Thus, graphene foils have the potential to improve the performance of space-based plasma instruments for energies below ?50 keV.

Ebert, Robert W., E-mail: rebert@swri.edu [Southwest Research Institute, P. O. Drawer 28510, San Antonio, Texas 78228-0510 (United States); Allegrini, Frédéric; Fuselier, Stephen A.; Nicolaou, Georgios [Southwest Research Institute, P. O. Drawer 28510, San Antonio, Texas 78228-0510 (United States) [Southwest Research Institute, P. O. Drawer 28510, San Antonio, Texas 78228-0510 (United States); Physics and Astronomy Department, University of Texas at San Antonio, One UTSA Circle, San Antonio, Texas 78249 (United States); Bedworth, Peter; Sinton, Steve [Lockheed Martin Advanced Technology Center, 3251 Hanover Street, Palo Alto, California 94304 (United States)] [Lockheed Martin Advanced Technology Center, 3251 Hanover Street, Palo Alto, California 94304 (United States); Trattner, Karlheinz J. [Lockheed Martin Advanced Technology Center, 3251 Hanover Street, Palo Alto, California 94304 (United States) [Lockheed Martin Advanced Technology Center, 3251 Hanover Street, Palo Alto, California 94304 (United States); Laboratory for Atmospheric and Space Physics, University of Colorado, 1234 Innovation Drive, Boulder, Colorado 80303 (United States)

2014-03-15

278

Angular scattering of 1-50 keV ions through graphene and thin carbon foils: Potential applications for space plasma instrumentation  

NASA Astrophysics Data System (ADS)

We present experimental results for the angular scattering of ˜1-50 keV H, He, C, O, N, Ne, and Ar ions transiting through graphene foils and compare them with scattering through nominal ˜0.5 ?g cm-2 carbon foils. Thin carbon foils play a critical role in time-of-flight ion mass spectrometers and energetic neutral atom sensors in space. These instruments take advantage of the charge exchange and secondary electron emission produced as ions or neutral atoms transit these foils. This interaction also produces angular scattering and energy straggling for the incident ion or neutral atom that acts to decrease the performance of a given instrument. Our results show that the angular scattering of ions through graphene is less pronounced than through the state-of-the-art 0.5 ?g cm-2 carbon foils used in space-based particle detectors. At energies less than 50 keV, the scattering angle half width at half maximum, ?1/2, for ˜3-5 atoms thick graphene is up to a factor of 3.5 smaller than for 0.5 ?g cm-2 (˜20 atoms thick) carbon foils. Thus, graphene foils have the potential to improve the performance of space-based plasma instruments for energies below ˜50 keV.

Ebert, Robert W.; Allegrini, Frédéric; Fuselier, Stephen A.; Nicolaou, Georgios; Bedworth, Peter; Sinton, Steve; Trattner, Karlheinz J.

2014-03-01

279

Generalized spectra model for 1-100 keV X-ray emission from Cygnus X-3 based on EXOSAT data  

NASA Astrophysics Data System (ADS)

The X-ray spectrum of the highly variable X-ray source, Cyg X-3, has so far defied a consistent explanation based on simple emission models. We have extracted two of the best data sets from the EXOSAT archives and performed a detailed spectral analysis for its 'high' and 'low' states. The analysis of the less frequently occurring 'low' state is presented for the first time for the EXOSAT data. Combining data from the medium-energy argon and xenon detectors and the gas scintillation proportional counter, with a better energy resolution, and carrying out a simultaneous fit, we find that the X-ray continuum in both the 'high' and 'low' state can be explained as a sum of a blackbody emission and emission from a Comptonized plasma cloud with a common absorption. The Comptonization model is sufficient as well as preferable to many other models, in explaining the observed X-ray emission up to 100 keV. In addition, we find an emission-line feature due to ionized iron (Fe XX-Fe XXVI) and absorption features due to cold iron (Fe I) as well as highly ionized iron (Fe XXV-Fe XXXVI). The presence of absorption due to Fe I has been shown for the first time here. This is the simplest and the most generalized spectral model for the 1-100 keV X-ray emission from Cyg X-3, to date. We find that the blackbody temperature derived in the 'high ' state (1.47 keV) is much lower than that derived for the 'low' state (2.40 keV) and is associated with an increase in the blackbodly radius in the 'high' state. The ratio of blackbody flux to the total flux is approximately 0.61 in the 'high' state and approximately 0.44 in the 'low' state. The Fe line energy is significantly higher in the 'high' state (approximately 6.95 keV) compared to the 'low' state (approximately 6.56 keV). The Comptonization parameter changes from 2 to approximately 15 in going from the 'high' to the 'low' state implying a highly saturated Comptonization in the 'low' state. The Comptonized region has high electron temperature and low opacity in the 'high' state and vice versa in the 'low' state. The orbital light curve is mostly explained by variations in the intensities of the continuum components. We discuss the likely origin of different emission regions, continuum and line, and interpret them in terms of an accretion disk corona.

Rajeev, M. R.; Chitnis, V. R.; Rao, A. R.; Singh, K. P.

1994-03-01

280

The INTEGRAL View Of The 511 keV Annihilation Line In Our Galaxy  

NASA Astrophysics Data System (ADS)

It is well know from theory and laboratory practice that an electron-positron pair can annihilate into a couple of 511 keV (the electron rest mass) gamma ray photons. The first detection of 511 keV photons from the Galactic center region dates back to early seventies. Soon after, a continuum gamma ray emission due to 3 gamma ortho-positronium decay was also measured. A 511 keV line in the Galactic gamma ray emission gives a unique proof that a large number of positrons are injected in the astrophysical environments, but nowadays we still do not know where these particles are generated. Positrons can be generated by a number of processes, in particular beta+ decays of unstable isotopes produced by stars and supernovae and energetic outflows from compact objects, but the few claimed detections of a 511 keV line from compact galactic sources are quite controversial. This fact could be explained by propagation of positrons in the intergalactic medium before they annihilate away from the birth place. The measure made with the spectrometer SPI aboard INTernational Gamma RAy Laboratory (INTEGRAL), launched on October 17 2002, confirms that about 10E43 positrons per second annihilate in the bulge of our Galaxy. Moreover, there is some evidence of an asymmetry of the 511 keV emission along the Galactic longitude, possibly correlated with the spacial distribution of the hard X (E > 20 keV) Low Mass X-ray Binaries detected by the imager IBIS aboard INTEGRAL. With IBIS, using about 5 years of observations, we find no evidence of 511 keV point sources. With an exposure of 10 Ms, in the center of the Galaxy we estimate a 1.6 x 10E-04 ph/cm2/s flux 2 sigma upper limit; a similar limit is given in a wide area in the Galactic center region with similar exposures.

De Cesare, G.

2011-09-01

281

The BeppoSAX 0.1-18 keV spectrum of the bright atoll source GX 9+1: an indication of the source distance  

NASA Astrophysics Data System (ADS)

We report the results of a long, 350 ks, BeppoSAX observation of the bright atoll source GX 9+1 in the 0.12-18 keV energy range. During this observation GX 9+1 showed a large count rate variability in its lightcurve. From its color-color diagram we selected six zones and extracted the source energy spectrum from each zone. We find that the model, composed of a blackbody plus a Comptonized component absorbed by an equivalent hydrogen column of ~1.4 × 1022 cm-2, fits the spectra in the energy range 1-18 keV well; however, below 1 keV a soft excess is present. We find that the spectrum of GX 9+1, in the 0.12-18 keV energy range, is well fitted by the model above, if we use an equivalent hydrogen column of ~0.8 × 1022 cm-2, together with several absorption edges from ionized matter (O VII, O VIII, Ne IX, Ar XVII, and Ca XX) and an absorption line from Si XIV. From the study of these features we deduce that the electron density of the plasma and the equivalent hydrogen column density associated with the ionized matter is ~1012 cm-3 and ~1023 cm-2, respectively, at a distance from the central object of r ˜ 1011 cm, while at larger distances the equivalent hydrogen column density associated to the ionized matter decreases down to ~1022 cm-2. The value of the equivalent hydrogen column of ~0.8 × 1022 cm-2 associated to the interstellar matter implies that GX 9+1 is at a distance of 5 kpc, and not 8.5-10 kpc as usually assumed. This result implies that the atoll source GX 9+1 does not emit at the Eddington limit, as supposed until now, but has a luminosity of 6 × 1037 erg/s in the 0.1-18 keV energy range, typical of LMXBs belonging to the bright atoll class.

Iaria, R.; di Salvo, T.; Robba, N. R.; Lavagetto, G.; Burderi, L.; Stella, L.; van der Klis, M.

2005-08-01

282

Suprathermal (E greater than 5 keV) ENA images of the Heliosphere from Cassini and in situ Voyager measurements: Is there pressure balance?  

NASA Astrophysics Data System (ADS)

The Ion and Neutral Camera (INCA), part of the Magnetospheric Imaging Instrument(MIMI) sensor suite on the Cassini orbiter at Saturn, is an ENA imager designed to obtain measurements of magnetospheric phenomena, and has done so for more than five years. When not pointing at the planet, INCA can sense ENA from other sources, notably those traversing the interplanetary medium from all directions. Maps of such emissions (Krimigis et al, 2009) have now been constructed spanning the energy range 5 < E < 55 keV, and show a "Belt" in the sky of about 100° FWHM. Similarly, maps < 6 keV have been obtained by the IBEX mission (McComas et al, 2009) and show a "Ribbon" that is narrower than the Belt and inclined to it in both ecliptic latitude (25° ) and longitude (30° ). Measurements of energetic ions by Voyagers 1, 2 in the heliosheath (Decker et al, 2009) show pressures 28 keV about 0.2 pdynes/cm2 vs 0.04 pdynes/cm2 for the local B about 0.1nT (Burlaga et al, 2009), i.e. ? > 5. The overlap in energy between Voyager ions and Cassini ENA intensities (averaged over the ENA line of sight) enables us to deduce ion fluxes in the heliosheath, thus providing a continuous spectrum 5 < E < 4000 keV. These measurements are then used to estimate the thickness of the heliosheath (about 50 AU) and the local pressure ( 1.3 pdynes/cm2 ), suggesting ? > 33. The pressure at < 6 keV is more difficult to estimate because appropriate Voyager normalization between the IBEX ENA and in situ heliosheath ions is currently unavailable. Nevertheless, pick up ions (PUI) dominate the heliosheath at > 5 keV, at least at the location of the two Voyagers. Based on the symmetrical distribution of ENA intensities in galactic coordinates, it is hypothesized that the local interstellar magnetic field plays an important role in determining the shape of the heliospheric cavity and it must have a central role in global pressure balance of heliosheath plasma and the local interstellar flow. >>

Krimigis, Stamatios; Krimigis, Stamatios M.; Mitchell, Donald; Roelof, Edmond; Decker, Robert

283

Molecular dynamics simulations of sputtering of Langmuir-Blodgett multilayers by keV C(60) projectiles.  

PubMed

Coarse-grained molecular dynamics computer simulations are applied to investigate fundamental processes induced by an impact of keV C(60) projectile at an organic overlayer composed of long, well-organized linear molecules. The energy transfer pathways, sputtering yields, and the damage induced in the irradiated system, represented by a Langmuir-Blodgett (LB) multilayers composed from molecules of bariated arachidic acid, are investigated as a function of the kinetic energy and impact angle of the projectile and the thickness of the organic system. In particular, the unique challenges of depth profiling through a LB film vs. a more isotropic solid are discussed.The results indicate that the trajectories of projectile fragments and, consequently, the primary energy can be channeled by the geometrical structure of the overlayer. Although, a similar process is known from sputtering of single crystals by atomic projectiles, it has not been anticipated to occur during C(60) bombardment due to the large size of the projectile. An open and ordered molecular structure of LB films is responsible for such behavior. Both the extent of damage and the efficiency of sputtering depend on the kinetic energy, the impact angle, and the layer thickness. The results indicate that the best depth profiling conditions can be achieved with low-energy cluster projectiles irradiating the organic overlayer at large off-normal angles. PMID:20174461

Paruch, R; Rzeznik, L; Czerwinski, B; Garrison, B J; Winograd, N; Postawa, Z

2009-04-01

284

keV Sterile Neutrino Dark Matter and Low Scale Leptogenesis  

E-print Network

We consider a simple extension of the Standard Model to consistently explain the observation of a peak in the galactic X-ray spectrum at 3.55 keV and the light neutrino masses along with the baryon asymmetry of the universe. The baryon asymmetry is generated through leptogenesis, the lepton asymmetry being generated by the decay of a heavy neutrino with TeV mass scale. The extra singlet fermion introduced in the model can be identified as a warm dark matter candidate of mass 7.1 keV. It decays with a lifetime much larger than the age of the universe, producing a final state photon. The Yukawa interactions between the extra singlet neutrino and a heavier right-handed neutrino play a crucial role in simultaneously achieving low scale leptogenesis and relic density of the keV dark matter candidate.

Kang, Sin Kyu

2014-01-01

285

CUBIC: Measuring the X-ray background from 0.2 - 10 keV  

NASA Astrophysics Data System (ADS)

The CUBIC (Cosmic X-ray Background Instrument using CCDs) will be launched later this year to begin a three-year mission to measure the spectrum of the Diffuse X-ray Background. The instrument incorporates two CCDs for moderate non-dispersive spectral resolution in the bandpass 0.2 - 10.0 keV. The field of view is 5 x 5 degrees below 1 keV and 10 x 10 degrees above 3 keV. Observations will consist of 50,000 - 100,000 second integrations. The instrument was built at Penn State and has been integrated into the Argentine/US SAC-B satellite, which is now awaiting launch on a Pegasus XL vehicle. We describe the instrument design and performance specifications and present pre-flight calibration data.

Burrows, D. N.; Skinner, M. A.; Nousek, J. A.; Garmire, G. P.

1996-05-01

286

Inelastic X-ray scattering with 0.75?meV resolution at 25.7?keV using a temperature-gradient analyzer.  

PubMed

The use of temperature-gradient analyzers for non-resonant high-resolution inelastic X-ray scattering is investigated. The gradient compensates for geometrical broadening of the energy resolution by adjusting the lattice spacing of the analyzer crystal. Applying a ?12?mK temperature gradient across a 9.5?cm analyzer, resolutions of 0.75?(2)?meV FWHM at 25.7?keV for Si(13?13?13) and 1.25?(2)?meV at 21.7?keV for Si(11?11?11) were measured, while retaining large (250?mm) clearance between the sample position and detector, and reasonable (9.3?mrad × 8.8?mrad) analyzer acceptance. The temperature control and stability are discussed. PMID:25537581

Ishikawa, Daisuke; Ellis, David S; Uchiyama, Hiroshi; Baron, Alfred Q R

2015-01-01

287

A 9 month long soft X-ray survey of the Large Magellanic Cloud. I - X-ray map at 1/4 keV  

NASA Technical Reports Server (NTRS)

Data from the HEAO 1 low energy detector was used to map the diffuse 1/4 keV X-ray background around the LMC. Data was collected over 9 mos in 1977-1978 using detectors sensitive in the range 0.18-2.8 keV. Diffuse emission, rather than absorption, was observed from the LMC, as were two large emission (2 million K) regions with very low surface brightness. The regions coincided with the Shapley III supergiant shell of optical nebulosity and the LMC bar. Higher spatial resolution imagery is required if the emission features are to be confirmed as the same type of phenomena as the X-ray superbubble in Cygnus.

Singh, K. P.; Nousek, J. A.; Burrows, D. N.; Garmire, G. P.

1987-01-01

288

The {sup 14}C(n,{gamma}) cross section between 10 keV and 1 MeV  

SciTech Connect

The neutron capture cross section of {sup 14}C is of relevance for several nucleosynthesis scenarios such as inhomogeneous Big Bang models, neutron induced CNO cycles, and neutrino driven wind models for the r process. The {sup 14}C(n,{gamma}) reaction is also important for the validation of the Coulomb dissociation method, where the (n,{gamma}) cross section can be indirectly obtained via the time-reversed process. So far, the example of {sup 14}C is the only case with neutrons where both, direct measurement and indirect Coulomb dissociation, have been applied. Unfortunately, the interpretation is obscured by discrepancies between several experiments and theory. Therefore, we report on new direct measurements of the {sup 14}C(n,{gamma}) reaction with neutron energies ranging from 20 to 800 keV.

Reifarth, R.; Couture, A.; Haight, R. C.; Rundberg, R. S.; Wilhelmy, J. B. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Heil, M.; Dababneh, S.; Kaeppeler, F.; Plag, R. [Forschungszentrum Karlsruhe, Institut fuer Kernphysik, P. O. Box 3640, D-76021 Karlsruhe (Germany); Forssen, C. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Fundamental Physics, Chalmers University of Technology, S-412 96 Goeteborg (Sweden); Besserer, U.; Doerr, L. [Forschungszentrum Karlsruhe, Tritiumlabor, P. O. Box 3640, D-76021 Karlsruhe (Germany); Goerres, J.; O'Brien, S.; Wiescher, M. [University of Notre Dame, Physics Department, Notre Dame, Indiana 46556 (United States); Mengoni, A. [CERN, CH-1211 Geneva 23 (Switzerland); Patronis, N. [Nuclear Physics Laboratory, Department of Physics, The University of Ioannina, GR-45110 Ioannina (Greece)

2008-01-15

289

Chemistry and structure of beta silicon carbide implanted with high-dose aluminum. [168 keV  

SciTech Connect

Single-crystal [beta]-SiC was implanted with aluminum to 3.90 x 10[sup 17] ions/cm[sup 2] at 168 keV at 773 K. The resultant compositional and structural characteristics were studied by Rutherford backscattering spectrometry. Auger electron spectroscopy, X-ray photoelectron spectroscopy, and cross-sectional transmission electron microscopy. No aluminum redistribution was observed during implantation. The Si-to-C ratio exhibited a negative deviation from unity in the implanted region. The shift in the photoelectron binding energies indicated the formation of aluminum carbide. The studies by electron microscopy showed that the implanted region consists of slightly misoriented [beta]-SiC crystals and textured crystalline aluminum carbide precipitates.

Du, Honghua; Yang, Zunde; Libera, M. (Stevens Inst. of Tech., Hoboken, NJ (United States). Dept. of Materials Science and Engineering); Jacobson, D.C. (AT and T Bell Laboratories, Murray Hill, NJ (United States)); Wang, Yu C.; Davis, R.F. (North Carolina State Univ., Raleigh, NC (United States). Dept. of Materials Science and Engineering)

1993-02-01

290

Thermoluminescence of ion-implanted LiF crystals using 100 keV rare gas ions  

NASA Astrophysics Data System (ADS)

We report the thermoluminescence of pure LiF crystals following implantation with Ne, Ar, Kr and Xe ions of 100 keV energy. Fluences were in the range 1 × 10 13 to 3 × 10 17 ions cm -2. Glow curves produced by different ions have similar structure with peaks near 230°C, 280°C, 295°C, 312°C and 335°C. Relative peak heights vary slightly from sample to sample depending on the type and fluence of the implanted ions but the overall intensity of the glow curves is essentially independent of fluence over a wide range. Other factors investigated include the effect on the glow curves of dose rate and the presence of magnesium dopant in the target crystal. A comparison is made with gamma-irradiated crystals.

Davidson, A. T.; Kozakiewicz, A. G.; Wilkinson, D. J.; Comins, J. D.; Derry, T. E.

1998-05-01

291

The colouration of CaF2 crystals by keV and GeV ions  

NASA Astrophysics Data System (ADS)

CaF2 crystals have been implanted with a variety of ions of widely different energies and mass. Effects have been monitored using optical absorption in the range 120-750 nm. This includes the vacuum UV region. For 100 keV ions (Al, Mg, Kr) we observe extrinsic colloid bands in the case of implanted metal ions at high fluences (10(17) ions cm(2) ) but no colour centres (F, F-2 etc). For GeV ions (U, Ni) we observe prominent absorption bands in the visible region at fluences of 10(12) ions cm(-2) attributed to extrinsic calcium colloids. New optical features are discussed including an absorption band near 185 nm in the VUV and bands at 604 nm and 672 nm in the visible region.

Davidson, A. T.; Kozakiewicz, A. G.; Comins, J. D.; Derry, T. E.; Schwartz, K.; Trautmann, C.

292

VUV optical absorption in sapphire crystals following implantation with 100 keV O +, Al + and Cr + Ions  

NASA Astrophysics Data System (ADS)

We report optical absorption (OA) measurements in Al 2O 3 crystals following implantation with O +, Al + and Cr + ions of 100 keV energy. Fluences were between 4×10 15 and 1×10 17 ions/cm 2 and the wavelength range was 150-350 nm. The vacuum ultraviolet region is included in our investigation. In addition to the F band near 204 nm (6.08 eV) we observe ion specific effects at shorter wavelengths. This is attributed to a different ability of the projectile ions to form stable F and F + centres when implanted near ambient temperature. Implantation at a higher temperature of 200 °C results in enhanced and similar OA at 200 nm in the case of Al + and Cr + ions.

Kozakiewicz, A. G.; Davidson, A. T.; Derry, T. E.

2002-05-01

293

Laser characterization of the depth profile of complex refractive index of PMMA implanted with 50 keV silicon ions  

NASA Astrophysics Data System (ADS)

The depth profile of the complex refractive index of silicon ion (Si+) implanted polymethylmethacrylate (PMMA) is studied, in particular PMMA implanted with Si+ ions accelerated to a relatively low energy of 50 keV and at a fluence of 3.2 × 1015 cm-2. The ion-modified material with nano-clustered structure formed in the near(sub)surface layer of a thickness of about 100 nm is optically characterized by simulation based on reflection ellipsometry measurements at a wavelength of 632.8 nm (He-Ne laser). Being of importance for applications of ion-implanted PMMA in integrated optics, optoelectronics and optical communications, the effect of the index depth profile of Si+-implanted PMMA on the profile of the reflected laser beam due to laser-induced thermo-lensing in reflection is also analyzed upon illumination with a low power cw laser (wavelength 532 nm, optical power 10 - 50 mW).

Stefanov, Ivan L.; Stoyanov, Hristiyan Y.; Petrova, Elitza; Russev, Stoyan C.; Tsutsumanova, Gichka G.; Hadjichristov, Georgi B.

2013-03-01

294

Determination of K Shell Fluorescence Yields of Hf Compounds at 123.6 keV  

SciTech Connect

The aim of this study was to determine of K shell fluorescence yields ({omega}K) of Hf compounds. The targets were irradiated with {gamma}-photons at 123.6 keV from 57Co annular source. The K X-rays from different targets were dedected using a (Ultra-LEGe) semiconductor dedector with a resolution of 150 eV at 5.9 keV. The measured K shell fluorescence yields results compare with the literature semi-emprical prediction that taken from Krause.

Aylikci, Volkan; Apaydin, Goekhan; Kaya, Necati; Cengiz, Erhan; Tirasoglu, Engin [Department of Physics, Faculty of Arts and Sciences, Karadeniz Technical University, 61080 Trabzon (Turkey)

2007-04-23

295

Influence of organic ions on DNA damage induced by 1 eV to 60 keV electrons  

PubMed Central

We report the results of a study on the influence of organic salts on the induction of single strand breaks (SSBs) and double strand breaks (DSBs) in DNA by electrons of 1 eV to 60 keV. Plasmid DNA films are prepared with two different concentrations of organic salts, by varying the amount of the TE buffer (Tris-HCl and EDTA) in the films with ratio of 1:1 and 6:1 Tris ions to DNA nucleotide. The films are bombarded with electrons of 1, 10, 100, and 60 000 eV under vacuum. The damage to the 3197 base-pair plasmid is analyzed ex vacuo by agarose gel electrophoresis. The highest yields are reached at 100 eV and the lowest ones at 60 keV. The ratios of SSB to DSB are surprisingly low at 10 eV (~4.3) at both salt concentrations, and comparable to the ratios measured with 100 eV electrons. At all characteristic electron energies, the yields of SSB and DSB are found to be higher for the DNA having the lowest salt concentration. However, the organic salts are more efficient at protecting DNA against the damage induced by 1 and 10 eV electrons. DNA damage and protection by organic ions are discussed in terms of mechanisms operative at each electron energy. It is suggested that these ions create additional electric fields within the groove of DNA, which modify the resonance parameter of 1 and 10 eV electrons, namely, by reducing the electron capture cross-section of basic DNA units and the lifetime of corresponding transient anions. An interstrand electron transfer mechanism is proposed to explain the low ratios for the yields of SSB to those of DSB produced by 10 eV electrons. PMID:20969428

Zheng, Yi; Sanche, Léon

2011-01-01

296

On energetic electrons (>38 keV) in the central plasma sheet: Data analysis and modeling  

E-print Network

On energetic electrons (>38 keV) in the central plasma sheet: Data analysis and modeling Bingxian on the magnetopause result in higher (lower) energetic electron fluxes in the CPS with a time delay of about 1 hour, while the influence of solar wind ion density on the energetic electrons fluxes is insignificant

Li, Xinlin

297

Heliospheric Energetic Particle Reservoirs: Ulysses and ACE 175-315 keV Electron Observations  

E-print Network

Heliospheric Energetic Particle Reservoirs: Ulysses and ACE 175-315 keV Electron Observations D-3) that evolve similarly in time. We use near-relativistic electron observations from both the ACE and Ulysses 2000 and November 2001 when Ulysses was at high (>70 deg) latitudes and at heliocentric radial

Sanahuja, Blai

298

17 keV neutrino and large magnetic moment solution of the solar neutrino puzzle  

E-print Network

Zee-type models with Majorons naturally incorporate the 17 keV neutrino but in their minimal version fail to simultaneously solve the solar neutrino puzzle. If there is a sterile neutrino state, we find a particularly simple solution to the solar neutrino problem, which besides $\

Eugeni Akhmedov; Zurab Berezhiani; Goran Senjanovic; Zhijian Tao

1992-09-02

299

Performance assessment of a slat gamma camera collimator for 511 keV imaging  

NASA Astrophysics Data System (ADS)

The physical performance of a prototype slat collimator is described for gamma camera planar imaging at 511 keV. Measurements were made of sensitivity, spatial resolution and a septal penetration index at 511 keV. These measurements were repeated with a commercial parallel hole collimator designed for 511 keV imaging. The slat collimator sensitivity was 22.9 times that of the parallel hole collimator with 10 cm tissue equivalent scatter material, and 16.8 times the parallel hole collimator sensitivity in air. Spatial resolution was also better for the slat collimator than the parallel hole collimator (FWHM at 10 cm in air 17.9 mm and 21.2 mm respectively). Septal penetration was compared by a single value for the counts at 120 mm from the point source profile peak, expressed as a percentage of the peak counts, showing less penetration for the slat collimator than the parallel hole collimator (1.9% versus 3.6% respectively). In conclusion, these results show that the slat collimator may have advantages over the parallel hole collimator for 511 keV imaging, though the greater complexity of operation of the slat collimator and potential sources of artefact in slat collimator imaging are recognized.

Britten, Alan J.; Klie, Robert

1999-07-01

300

Tables and graphs of photon-interaction cross sections from 0. 1 keV to 100 MeV derived from the LLL evaluated-nuclear-data library  

SciTech Connect

Energy-dependent evaluated photon interaction cross sections and related parameters are presented for elements H through Cf(Z = 1 to 98). Data are given over the energy range from 0.1 keV to 100 MeV. The related parameters include form factors and average energy deposits per collision (with and without fluorescence). Fluorescence information is given for all atomic shells that can emit a photon with a kinetic energy of 0.1 keV or more. In addition, the following macroscopic properties are given: total mean free path and energy deposit per centimeter. This information is derived from the Livermore Evaluated-Nuclear-Data Library (ENDL) as of October 1978.

Plechaty, E.F.; Cullen, D.E.; Howerton, R.J.

1981-11-11

301

Theoretical Approach Of The Reduction Of Chromatic And Spherical Aberrations In An Acceleration Lens System For Hundreds Of keV Gaseous Ion Nanobeam  

SciTech Connect

The focused gaseous ion beam (gas-FIB) system composed of a series of electrostatic lenses, called ''acceleration lens system'', has been developed to form nanobeams using gaseous ions generated from a plasma ion source. Ion beams are accelerated and focused simultaneously by a pair of electrodes. A new all-in-one compact acceleration system including an acceleration tube is now under development to form 300 keV ion nanobeam. Chromatic and spherical aberrations are, however, hindrance to form nanobeams with their smaller sizes in diameter. A deceleration lens, which performs like a defocusing lens, was theoretically introduced to downstream of the present acceleration lens system to reduce the aberrations. Ion beam optics simulations were carried out to show that this aberration reduction technique is effective to reduce chromatic and spherical aberrations. As a result, we reduced the chromatic aberration coefficient by 26%, the spherical aberration coefficient by 17% and a beam diameter by 17%, with the deceleration energy of 15 keV. In case of using an electrostatic acceleration tube with 100 mm length, the final beam diameter of 103 nm at 300 keV is obtained by the all-in-one acceleration lens system with the total acceleration length of only 650 mm.

Ohkubo, Takeru; Ishii, Yasuyuki; Kamiya, Tomihiro [Takasaki Advanced Radiation Research Institute, Japan Atomic Energy Agency (JAEA), 1233 Watanuki-machi, Takasaki, Gunma, 370-1292 (Japan)

2011-06-01

302

Total L-shell X-ray production cross sections by 400-700 keV proton impact for elements with 34 < or = Z < or = 53.  

PubMed

Total L-shell X-ray production cross sections induced by protons with energies between 400 and 700 keV were measured for elements with atomic number Z between 34 and 53. The ECPSSR theory describes appropriately the results. This model modifies the plane wave born approximation by considering projectile energy loss (E), Coulomb deflection of the incoming ion (C), polarization and change in electron binding energies through a perturbed stationary states method (PSS) and relativistic values of target electron mass (R). A comparison is given with previously published data for proton energies below 1 MeV and 26 < or = Z < or = 53, based on a scaling obtained from a reduced velocity parameter zeta(L)R. The results show that the scaling for these atomic numbers and energy ranges is adequate and a semi-empirical expression to calculate those cross sections is proposed. PMID:11214881

Miranda, J; Ledesma, R; de Lucio, O G

2001-03-01

303

A new grating X-ray spectrometer for 2-4 keV enabling a separate observation of In-L? and Sn-L? emissions of indium tin oxide.  

PubMed

A new multilayer-coated varied line-spaced grating, JS4000, was fabricated and tested for extending the upper limit of a grating X-ray spectrometer for electron microscopy. This grating was designed for 2-3.8 keV at a grazing incidence angle of 1.35°. It was revealed that this new multilayer structure enables us to take soft-X-ray emission spectra continuously from 1.5 to 4.3 keV at the same optical setting. The full-width at half maximum of Te-L(?1,2) (3.8 keV) emission peak was 27 eV. This spectrometer was applied to indium tin oxide particles and clearly resolved Sn-L(?) (3444 eV) and In-L(?1) (3487 eV) peaks, which could not be resolved by a widely used energy-dispersive X-ray spectrometer. PMID:23307948

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

2013-06-01

304

The 0.3–30 keV spectra of Powerful Starburst Galaxies: NuSTAR and Chandra observations ofNGC 3256 and NGC 3310  

NASA Astrophysics Data System (ADS)

We present nearly simultaneous Chandra and NuSTAR observations of two actively star-forming galaxies: NGC 3256 and NGC 3310. The NuSTAR galaxy-wide spectra of both galaxies follow steep power law distributions, similar to the spectra of bright individual ultra-luminous X-ray sources (ULXs) that have been studied by NuSTAR. The X-ray emission from both galaxies is spatially resolved by Chandra, which indicates that hot gas dominates the E < 1 – 3 keV emission, while ULXs make up a majority of the emission at E > 1-3 keV. Using new and archival Chandra data we found that both galaxies have candidate AGNs coincident with nuclear regions. However, the steep NuSTAR spectra of both galaxies restricts these candidates to be low luminosity AGN, and a non-AGN nature cannot be ruled out. We find the average 0.3 –30 keV SFR-normalized spectra of NGC 3256 and NGC 3310, combined with equivalent measurements for M83 and NGC 253, show sharpening power-law slopes at energies above 3 – 6 keV due to ULX populations. Our observations therefore constrain the average spectral shape of an unbiased population of ULXs to be similar to the super-Eddington accreting ULXs that have been studied by NuSTAR. We also find that for NGC 3310, there is a factor of 5 times excess X-ray emission, due to an overabundance of ULXs in the galaxy compared to typical galaxies. We argue that the excess is due to the relatively low metallicity of the young stellar population in the galaxy.

NuSTAR Starburst Team

2015-01-01

305

The 0.3–30 keV spectra of Powerful Starburst Galaxies: NuSTAR and Chandra observations ofNGC 3256 and NGC 3310  

NASA Astrophysics Data System (ADS)

We present nearly simultaneous Chandra and NuSTAR observations of two actively star-forming galaxies: NGC 3256 and NGC 3310. The NuSTAR galaxy-wide spectra of both galaxies follow steep power law distributions, similar to the spectra of bright individual ultra-luminous X-ray sources (ULXs) that have been studied by NuSTAR. The X-ray emission from both galaxies is spatially resolved by Chandra, which indicates that hot gas dominates the E < 1 - 3 keV emission, while ULXs make up a majority of the emission at E > 1-3 keV. Using new and archival Chandra data we found that both galaxies have candidate AGNs coincident with nuclear regions. However, the steep NuSTAR spectra of both galaxies restricts these candidates to be low luminosity AGN, and a non-AGN nature cannot be ruled out. We find the average 0.3 -30 keV SFR-normalized spectra of NGC 3256 and NGC 3310, combined with equivalent measurements for M83 and NGC 253, show sharpening power-law slopes at energies above 3 - 6 keV due to ULX populations. Our observations therefore constrain the average spectral shape of an unbiased population of ULXs to be similar to the super-Eddington accreting ULXs that have been studied by NuSTAR. We also find that for NGC 3310, there is a factor of 5 times excess X-ray emission, due to an overabundance of ULXs in the galaxy compared to typical galaxies. We argue that the excess is due to the relatively low metallicity of the young stellar population in the galaxy.

Tyler, Joshua; Lehmer, Bret; Hornschemeier, Ann E.; Yukita, Mihoko; Wik, Daniel R.; Ptak, Andrew; Stern, Daniel; Harrison, Fiona; Maccarone, Tom; Zezas, Andreas; Antoniou, Vallia; NuSTAR Starburst Team

2015-01-01

306

Measurement of the -3 keV resonance in the reaction 13C(?,n)16O of importance in the s-process.  

PubMed

The (13)C(?,n)(16)O reaction is the neutron source for the main component of the s-process, responsible for the production of most nuclei in the mass range 90energy interval where the (13)C(?,n)(16)O is effective from 140 to 230 keV. In this region, the astrophysical S(E)-factor is dominated by the -3 keV subthreshold resonance due to the 6.356 MeV level in (17)O, giving rise to a steep increase of the S(E)-factor. Notwithstanding that it plays a crucial role in astrophysics, no direct measurements exist inside the s-process energy window. The magnitude of its contribution is still controversial as extrapolations, e.g., through the R matrix and indirect techniques, such as the asymptotic normalization coefficient (ANC), yield inconsistent results. The discrepancy amounts to a factor of 3 or more right at astrophysical energies. Therefore, we have applied the Trojan horse method to the (13)C((6)Li,n(16)O)d quasifree reaction to achieve an experimental estimate of such contribution. For the first time, the ANC for the 6.356 MeV level has been deduced through the Trojan horse method as well as the n-partial width, allowing to attain an unprecedented accuracy in the (13)C(?,n)(16)O study. Though a larger ANC for the 6.356 MeV level is measured, our experimental S(E)-factor agrees with the most recent extrapolation in the literature in the 140-230 keV energy interval, the accuracy being greatly enhanced thanks to this innovative approach. PMID:23368189

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

2012-12-01

307

Accretion Properties of a Sample of Hard X-Ray (<60 keV) Selected Seyfert 1 Galaxies  

NASA Astrophysics Data System (ADS)

We examine the accretion properties in a sample of 42 hard (3-60 keV) X-ray selected nearby broad-line active galactic nuclei (AGNs). The energy range in the sample is harder than that usually used in similar previous studies. These AGNs are mainly complied from the RXTE All Sky Survey, and complemented by the released INTEGRAL AGN catalog. The black hole masses, bolometric luminosities of AGN, and Eddington ratios are derived from their optical spectra in terms of the broad H? emission line. The tight correlation between the hard X-ray (3-20 keV) and bolometric/line luminosity is well identified in our sample. Also identified is a strong inverse Baldwin relationship of the H? emission line. In addition, all of these hard X-ray AGNs are biased toward luminous objects with a high Eddington ratio (mostly between 0.01 and 0.1) and a low column density (<1022 cm-2), which is most likely due to the selection effect of the surveys. The hard X-ray luminosity is consequently found to be strongly correlated with the black hole mass. We believe the sample completeness will be improved in the next few years by the ongoing Swift and the International Gamma-Ray Astrophysics Laboratory missions, and by the next advanced missions, such as NuSTAR, Simbol-X, and NeXT. Finally, the correlation between RFe (= optical Fe II/H?) and disk temperature as assessed by T vprop (L/L Edd)M -1 BH leads us to suggest that the strength of the Fe II emission is mainly determined by the shape of the ionizing spectrum.

Wang, J.; Mao, Y. F.; Wei, J. Y.

2009-02-01

308

Accretion Properties of A Sample of Hard X-ray (<60keV) Selected Seyfert 1 Galaxies  

E-print Network

We examine the accretion properties in a sample of 42 hard (3-60keV) X-ray selected nearby broad-line AGNs. The energy range in the sample is harder than that usually used in the similar previous studies. These AGNs are mainly complied from the RXTE All Sky Survey (XSS), and complemented by the released INTEGRAL AGN catalog. The black hole masses, bolometric luminosities of AGN, and Eddington ratios are derived from their optical spectra in terms of the broad H$\\beta$ emission line. The tight correlation between the hard X-ray (3-20keV) and bolometric/line luminosity is well identified in our sample. Also identified is a strong inverse Baldwin relationship of the H$\\beta$ emission line. In addition, all these hard X-ray AGNs are biased toward luminous objects with high Eddington ratio (mostly between 0.01 to 0.1) and low column density ($<10^{22} \\mathrm{cm^{-2}}$), which is most likely due to the selection effect of the surveys. The hard X-ray luminosity is consequently found to be strongly correlated with the black hole mass. We believe the sample completeness will be improved in the next few years by the ongoing Swift and INTEGRAL missions, and by the next advanced missions, such as NuSTAR, Simbol-X, and NeXT. Finally, the correlation between RFe (=optical FeII/H$\\beta$) and disk temperature as assessed by $T\\propto (L/L_{\\mathrm{Edd}})M_{\\mathrm{BH}}^{-1}$ leads us to suggest that the strength of the FeII emission is mainly determined by the shape of the ionizing spectrum.

J. Wang; Y. F. Mao; J. Y. Wei

2008-11-20

309

Production and Performance of the InFOCmicronS 20-40 keV Graded Multilayer Mirror  

NASA Technical Reports Server (NTRS)

The International Focusing Optics Collaboration for micron Crab Sensitivity (InFOC micronS) balloon-borne hard x-ray incorporates graded multilayer technology to obtain significant effective area at energies previously inaccessible to x-ray optics. The telescope mirror consists of 2040 segmented thin aluminum foils coated with replicated Pt/C multilayers. A sample of these foils was scanned using a pencil-beam reflectometer to determine, multilayer quality. The results of the reflectometer measurements demonstrate our capability to produce large quantity of foils while maintaining high-quality multilayers with a mean Nevot-Croce interface roughness of 0.5nm. We characterize the performance of the complete InFOC micronS telescope with a pencil beam raster scan to determine the effective area and encircled energy function of the telescope. The effective area of the complete telescope is 78, 42 and 22 square centimeters at 20 30 and 40 keV. respectively. The measured encircled energy fraction of the mirror has a half-power diameter of 2.0 plus or minus 0.5 arcmin (90% confidence). The mirror successfully obtained an image of the accreting black hole Cygnus X-1 during a balloon flight in July, 2001. The successful completion and flight test of this telescope demonstrates that graded-multilayer telescopes can be manufactured with high reliability for future x-ray telescope missions such as Constellation-X.

Berendse, F.; Owens, S. M.; Serlemitsos, P. J.; Tueller, J.; Chan, K.-W.; Soong, Y.; Krimm, H.; Baumgartner, W. H.; Tamura, K.; Okajima, T.; Tawara, Y.; White, Nicholas E. (Technical Monitor)

2002-01-01

310

Enhanced room temperature oxidation in silicon and porous silicon under 10 keV x-ray irradiation  

E-print Network

Enhanced room temperature oxidation in silicon and porous silicon under 10 keV x-ray irradiation been suggested that gamma irradiation accelerates oxidation of porous silicon.5 Irradiation silicon samples that occurs over three decades of 10 keV x-ray irradiation. II. SAMPLE PREPARATION Silicon

Weiss, Sharon

311

New XAFS spectroscopic investigations in the 1-2 keV region. Final report on LDRD program  

SciTech Connect

Until recently x-ray absorption fine structure (XAFS) measurements in the 1-2 keV region remained a challenging experimental task. This was primarily due to the lack of an adequate monochromator crystal that possessed both the required x-ray properties (large d-spacing, high resolution and reflectivity) and materials properties (ultra-high vacuum (UHV) capability, damage resistance in a synchrotron radiation beam, absence of constituent element absorption edges and stability, both thermal and mechanical). Traditionally, XAFS spectra in this photon energy range have been measured in a piece-wise fashion using a combination of monochromator crystals. Very recently, we have an experimental breakthrough in XAFS spectroscopy in this soft x-ray region. This energy region is of great importance for materials and basic research since the K-edges of Na (1070 eV), Mg (1303 eV), Al (1557 eV) and Si (1839 eV), the L-edges of some 4p elements from Ga to Sr and the M-edges of the rare-earth elements fall within this energy window of the electromagnetic spectrum. YB{sub 66}, a complex binary semiconducting yttrium boride having a cubic crystal structure with a lattice constant of 23.44 {angstrom} has been singled out as a candidate monochromator material for synchrotron radiation in the 1-2 keV region. There is no intrinsic absorption by the constituent elements in this region, which can adequately be dispersed by the (400) reflection having a 2d value of 11.76 {angstrom}. In terms of vacuum compatibility, resistance to radiation damage, thermal and mechanical stability, YB{sub 66} satisfies all the material requirements for use as a monochromator in a synchrotron beam. In the past few years, LLNL in collaboration with a number of other research institutes has pioneered the development of this unique man-made crystal for use as soft x-ray monochromator with synchrotron light sources for materials science studies. 23 refs., 4 figs.

Wong, J.; Froba, M.; Tamura, E.

1996-03-01

312

Molecular dynamics simulation of radiation damage in CaCd{sub 6} quasicrystal cubic approximant up to 10 keV  

SciTech Connect

Due to the peculiar nature of the atomic order in quasicrystals, examining phase transitions in this class of materials is of particular interest. Energetic particle irradiation can provide a way to modify the structure locally in a quasicrystal. To examine irradiation-induced phase transitions in quasicrystals on the atomic scale, we have carried out molecular dynamics simulations of collision cascades in CaCd{sub 6} quasicrystal cubic approximant with energies up to 10 keV at 0 and 300 K. The results show that the threshold energies depend surprisingly strongly on the local coordination environments. The energy dependence of stable defect formation exhibits a power-law dependence on cascade energy, and surviving defects are dominated by Cd interstitials and vacancies. Only a modest effect of temperature is observed on defect survival, while irradiation temperature increases lead to a slight increase in the average size of both vacancy clusters and interstitial clusters.

Chen, P. H. [Accelerator Laboratory, University of Helsinki, P.O. Box 43, 00014 Helsinki (Finland); Science and Technology on Surface Physics and Chemistry Laboratory, P.O. Box 718-35, 621907 Mianyang (China); Avchachov, K.; Nordlund, K. [Accelerator Laboratory, University of Helsinki, P.O. Box 43, 00014 Helsinki (Finland); Pussi, K. [Department of Mathematics and Physics, Lappeenranta University of Technology, P.O. Box 20, FIN-53851 Lappeenranta (Finland)

2013-06-21

313

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)

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.

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

2012-01-01

314

7 keV sterile neutrino dark matter in U(1) R -lepton number model  

NASA Astrophysics Data System (ADS)

We study the phenomenology of a keV sterile neutrino in a supersymmetric model with U(1) R -lepton number in the light of a very recent observation of an X-ray line signal at around 3.5 keV, detected in the X-ray spectra of Andromeda galaxy and various galaxy clusters including the Perseus galaxy cluster. This model not only provides a small tree level mass to one of the active neutrinos but also renders a suitable warm dark matter candidate in the form of a sterile neutrino with negligible active-sterile mixing. Light neutrino masses and mixing can be explained once one-loop radiative corrections are taken into account. The scalar sector of this model can accommodate a Higgs boson with a mass of ˜125 GeV. In this model gravitino is the lightest supersymmetric particle (LSP) and we also study the cosmological implications of this light gravitino with mass.

Chakraborty, Sabyasachi; Ghosh, Dilip Kumar; Roy, Sourov

2014-10-01

315

Experimental results of a dual-beam ion source for 200 keV ion implanter  

SciTech Connect

A dual beam ion source for 200 keV ion implanter aimed to produce 200 keV H{sub 2}{sup +} and He{sup +} beams simultaneously has been developed. Not suitable to use the analyzing magnet, the purity of beam extracted from the source becomes important to the performance of implanter. The performance of ion source was measured. The results of experiments show that the materials of inlet tube of ion source, the time of arc ionization in ion source, and the amount of gas flow have significant influence on the purity of beam. The measures by using copper as inlet tube material, long time of arc ionization, and increasing the inlet of gas flow could effectively reduce the impurity of beam. And the method using the gas mass flow controller to adjust the proportion of H{sub 2}{sup +} and He{sup +} is feasible.

Chen, L. H., E-mail: lihuachen@ciae.ac.cn; Cui, B. Q.; Ma, R. G.; Ma, Y. J.; Tang, B.; Huang, Q. H.; Jiang, W. S.; Zheng, Y. N. [Department of Nuclear Physics, China Institute of Atomic Energy, Beijing 102413 (China)] [Department of Nuclear Physics, China Institute of Atomic Energy, Beijing 102413 (China)

2014-02-15

316

Experimental results of a dual-beam ion source for 200 keV ion implanter  

NASA Astrophysics Data System (ADS)

A dual beam ion source for 200 keV ion implanter aimed to produce 200 keV H2+ and He+ beams simultaneously has been developed. Not suitable to use the analyzing magnet, the purity of beam extracted from the source becomes important to the performance of implanter. The performance of ion source was measured. The results of experiments show that the materials of inlet tube of ion source, the time of arc ionization in ion source, and the amount of gas flow have significant influence on the purity of beam. The measures by using copper as inlet tube material, long time of arc ionization, and increasing the inlet of gas flow could effectively reduce the impurity of beam. And the method using the gas mass flow controller to adjust the proportion of H2+ and He+ is feasible.

Chen, L. H.; Cui, B. Q.; Ma, R. G.; Ma, Y. J.; Tang, B.; Huang, Q. H.; Jiang, W. S.; Zheng, Y. N.

2014-02-01

317

Range profiles of 600-1200 keV Xe(+) implanted in KTiOPO4  

NASA Astrophysics Data System (ADS)

600-1200 keV Xe(+) were implanted into KTiOPO4 (potassium titany phosphate) in increments of 100 keV. The depth distributions of implanted Xe(+) in KTiOPO4 were measured by Rutherford backscattering. The effects of chanelling, temperature, and dose on the depth distribution were briefly investigated. All range distributions were nearly Gaussian. The mean projected range and range straggling obtained were compared with the TRIM'91 code, projected range algorithm (PRAL) and Wang and Shi's (WS) calculation procedure based on Biersack's angular diffusion model. The results show that TRIM's 91 systematically underestimates the projected range by approximately 25%, PRAL underestimates the range by approximately 28%, and WS underestimates the range by approximately 7%. All calculate the underestimated range straggling by approximately a factor of two.

Wang, Ke-Ming; Ding, Pei-Jun; Wang, Wei; Lanford, W. A.; Shi, Bo-Rong; Yu, Zheng-Gang; Lu, Qing-Ming

1994-08-01

318

SMM detection of diffuse Galactic 511 keV annihilation radiation  

NASA Technical Reports Server (NTRS)

Observations of the 511 keV annihilation line from the vicinity of the Galactic center from October to February for 1980/1981, 1981/1982, 1982/1983, 1984/1985, and 1985/1986 are presented. The measurements were made with the gamma-ray spectrometer on the SMM. The design of the instrument and some of its properties used in the analysis are described, and the methods used for accumulating, fitting, and analyzing the data are outlined. It is shown how the Galactic 511 keV line was separated from the intense and variable background observed in orbit. The SMM observations are compared with previous measurements of annihilation radiation from the Galactic center region, and the astrophysical implications are discussed. It is argued that most of the measurements made to date suggest the presence of an extended Galactic source of annihilation radiation.

Share, G. H.; Kinzer, R. L.; Kurfess, J. D.; Messina, D. C.; Purcell, W. R.

1988-01-01

319

Limits on a variable source of 511 keV annihilation radiation near the Galactic center  

NASA Technical Reports Server (NTRS)

The Gamma Ray Spectrometer (GRS) on the Solar Maximum Mission satellite (SMM) has observed a strong Galactic source of 511 keV annihilation radiation from its launch in 1980 to its reentry in 1989. These observations are consistent with an extended source having an intensity of about 0.002 gamma/sq cm/s averaged over the central radian of Galactic longitude. These data are searched for evidence of the variable Galactic center source of 511 keV line radiation which was reported to have reappeared in 1988 by Leventhal et al. The SMM data are consistent with, but do not require, a compact source emitting a time-averaged flux of about 0.0004 gamma/sq cm/s during about 3 month transits in 1987 and 1988; they are inconsistent with a compact source flux in excess of 0.0008 gamma/sq cm/s for each year.

Share, Gerald H.; Leising, Mark D.; Messina, Daniel C.; Purcell, William R.

1990-01-01

320

30 nm resolution x-ray imaging at 8 keV using third order diffraction of a zone plate lens objective in a transmission microscope  

SciTech Connect

A hard x-ray transmission microscope with 30 nm spatial resolution has been developed employing the third diffraction order of a zone plate objective. The microscope utilizes a capillary type condenser with suitable surface figure to generate a hollow cone illumination which is matched in illumination range to the numerical aperture of the third order diffraction of a zone plate with an outmost zone width of 50 nm. Using a test sample of a 150 nm thick gold spoke pattern with finest half-pitch of 30 nm, the authors obtained x-ray images with 30 nm resolution at 8 keV x-ray energy.

Yin, G.-C.; Song, Y.-F.; Tang, M.-T.; Chen, F.-R.; Liang, Keng S.; Duewer, Frederick W.; Feser, Michael; Yun Wenbing; Shieh, H.-P.D. [National Synchrotron Radiation Research Center, 101 Hsin-Ann Road, Hsinchu 30076, Taiwan (China) and Department of Photonics, National Chiao Tung University, Hsinchu 300, Taiwan; and Display Institute, National Chiao Tung University, Hsinchu 300, Taiwan (China); National Synchrotron Radiation Research Center, 101 Hsin-Ann Road, Hsinchu 30076, Taiwan (China); Xradia Inc., 5052 Commercial Circle, Concord, California 94520 (United States); Department of Photonics, National Chiao Tung University, Hsinchu 300, Taiwan and Display Institute, National Chiao Tung University, Hsinchu 300, Taiwan (China)

2006-11-27

321

Measurement of the 20 and 90 keV resonances in the 18O(p,alpha)15N reaction via the Trojan horse method.  

PubMed

The 18O(p,alpha)15N reaction is of primary importance in several astrophysical scenarios, including fluorine nucleosynthesis inside asymptotic giant branch stars as well as oxygen and nitrogen isotopic ratios in meteorite grains. Thus the indirect measurement of the low energy region of the 18O(p,alpha)15N reaction has been performed to reduce the nuclear uncertainty on theoretical predictions. In particular the strength of the 20 and 90 keV resonances has been deduced and the change in the reaction rate evaluated. PMID:18999593

La Cognata, M; Spitaleri, C; Mukhamedzhanov, A M; Irgaziev, B; Tribble, R E; Banu, A; Cherubini, S; Coc, A; Crucillà, V; Goldberg, V Z; Gulino, M; Kiss, G G; Lamia, L; Mrazek, J; Pizzone, R G; Puglia, S M R; Rapisarda, G G; Romano, S; Sergi, M L; Tabacaru, G; Trache, L; Trzaska, W; Tumino, A

2008-10-10

322

Earth X-ray albedo for cosmic X-ray background radiation in the 1--1000 keV band  

E-print Network

We present calculations of the reflection of the cosmic X-ray background (CXB) by the Earth's atmosphere in the 1--1000 keV energy range. The calculations include Compton scattering and X-ray fluorescent emission and are based on a realistic chemical composition of the atmosphere. Such calculations are relevant for CXB studies using the Earth as an obscuring screen (as was recently done by INTEGRAL). The Earth's reflectivity is further compared with that of the Sun and the Moon -- the two other objects in the Solar system subtending a large solid angle on the sky, as needed for CXB studies.

E. Churazov; S. Sazonov; R. Sunyaev; M. Revnivtsev

2006-08-11

323

Picosecond x-ray measurements from 100 eV to 30 keV  

SciTech Connect

Picosecond x-ray measurements relevant to the Livermore Laser Fusion Program are reviewed. Resolved to 15 picoseconds, streak camera detection capabilities extend from 100 eV to higher than 30 keV, with synchronous capabilities in the visible, near infrared, and ultraviolet. Capabilities include automated data retrieval using charge coupled devices (CCD's), absolute x-ray intensity levels, novel cathodes, x-ray mirror/reflector combinations, and a variety of x-ray imaging devices.

Attwood, D.T.; Kauffman, R.L.; Stradling, G.L.

1980-10-15

324

Origin of the Galactic Disk 6.7 kev Line Emission  

NASA Technical Reports Server (NTRS)

The goal of this program was to determine if the extended FeXXV 6.7 kev line emission might possibly be produced and confined by the hot wind-shocked bubbles to accompany UC HII regions. The main result of this study are: (1) FeXXV is detected in the W3 complex, but at a level that could only explain a small fraction of the galactic disk emission if all UC HII regions emit at about the same intensity as the W3 complex; (2) Two X-ray sources are detected in W3. W3-X 1 coincides with the radio image of this region, but W3-X2 has no radio, optical, or infrared counterpart; (3) There is no evidence for variability of W3-X1 during the period of observations (approx, 40,000 sec); (4) The X-ray spectrum of W3-X1 has no emission shortward of 1 kev, it peaks at approx. 2 kev and show significant emission out to approx. 6 kev. No individual lines are resolved. There is currently no generally accepted theory for extended hard X-ray emission in HII regions. Perhaps the most significant discovery of this program has been the detection of extended hard X-rays and the realization that some entirely new processes must be invoked to understand this; and (5)A minimum (chi)(sup 2) fit of the spectrum implies a H absorbing column of N(sub H) approx, equals to 2.1 x 10(exp 22)/ cm, a temperature of the emitting plasma of 7 x 10(exp 7) K, and a luminosity of approx. equal to 10(33)erg/s.

Churchwell, Ed

1997-01-01

325

The quiet time structure of energetic (35--560 keV) radiation belt electrons  

Microsoft Academic Search

In this paper we present detailed Explorer 45 observations of the equatorial radial profiles and pitch angle distributions of energetic (35-560 keV) radiation belt electrons obtained during extended periods of relatively quiet geomagnetic activity. There were no magnetic storms during these quiet periods, and the 3-hour-range Kp index remained at values of <4+. Sufficient observations of the two-zone radial distribution

L. R. Lyons; D. J. Williams

1975-01-01

326

Performance characteristics of HBC stripper foils irradiated by 650 keV H- and high intensity DC ion beams  

NASA Astrophysics Data System (ADS)

Newly developed Hybrid type Boron mixed Carbon (HBC) stripper foils are extensively used not only for the RCS of J-PARC and PSR of LANL, but also for other low energy, high intensity proton accelerators in medical applications. We had before tested HBC stripper foils with 3.2 MeV Ne+ and DC heavy ion beams. In order to further understand characteristics of HBC stripper foils, we measured the following parameters using the KEK-650 keV H- and light ion Cockcroft Walton DC accelerator: foil lifetime, thickness reduction, uniformity before and after beam irradiation, and foil deformation. Energy deposition in the present experiment was adjusted to a similar level to that of the HBC foil used in the RCS of J-PARC’. In addition, to understand the reason why the HBC stripper foils have high durability against high intensity beam irradiation, we investigated various physical properties, and compared them between the HBC foils and other tested carbon stripper foils. The sizes of the carbon particles in the HBC foil were found to play a vital role in the lifetime.

Sugai, I.; Takagi, A.; Takeda, Y.; Irie, Y.; Oyaizu, M.; Kawakami, H.

2014-06-01

327

A large scale height galactic component of the diffuse 2-60 keV background  

NASA Technical Reports Server (NTRS)

The diffuse 2-60 keV X-ray background has a galactic component clearly detectable by its strong variation with both galactic latitude and longitude. This galactic component is typically 10 percent of the extragalactic background toward the galactic center, half that strong toward the anticenter, and extrapolated to a few percent of the extragalactic background toward the galactic poles. It is acceptably modeled by a finite radius emission disk with a scale height of several kiloparsecs. The averaged galactic spectrum is best fitted by a thermal spectrum of kT about 9 keV, a spectrum much softer than the about 40 keV spectrum of the extragalactic component. The most likely source of this emission is low luminosity stars with large scale heights such as subdwarfs. Inverse Compton emission from GeV electrons on the microwave background contributes only a fraction of the galactic component unless the local cosmic ray electron spectrum and intensity are atypical.

Iwan, D.; Marshall, F. E.; Boldt, E. A.; Mushotzky, R.; Shafer, R. A.; Stottlemyer, A.

1982-01-01

328

Investigation on gamma-ray position sensitivity at 662 keV in a spectroscopic 3' x 3' LaBr3:Ce scintillator  

NASA Astrophysics Data System (ADS)

The position sensitivity of a thick, cylindrical and continuous 3' x 3' (7.62 cm x 7.62 cm) LaBr3:Ce crystal was studied using a 1 mm collimated beam of 662 keV gamma rays from a 400 MBq intense 137Cs source and a spectroscopic photomultiplier (PMT) (HAMAMATSU R6233-100SEL). The PMT entrance window was covered by black absorber except for a small window 1 cm x 1 cm wide. A complete scan of the detector over a 0.5 cm step grid was performed for three positions of the 1 cm x 1 cm window. For each configuration the energy spectrum was measured and the peak centroid, the FWHM, the area and peak asymmetry of the 662 keV gamma transition were analyzed. The data show that, even in a 3' thick LaBr3:Ce crystal with diffusive surfaces the position of the full energy peak centroid depends on the source position. We verified that, on average, the position of the full energy peak centroids measured in the three 1 cm x 1 cm window configurations is sufficient for the correct identification of the collimated gamma source position.

Giaz, A.; Camera, F.; Birocchi, F.; Blasi, N.; Boiano, C.; Brambilla, S.; Coelli, S.; Fiorini, C.; Marone, A.; Million, B.; Riboldi, S.; Wieland, O.

2015-02-01

329

Theoretical Investigation of Transmission-Type Phase Shifter Made with Muscovite Mica Crystal for 1-keV Region  

NASA Astrophysics Data System (ADS)

In a soft x-ray region from 0.7 keV to 1.1 keV, the performance of transmission-type phase shifter was investigated theoretically based on the dynamical theory. As the result it was found that natural muscovite, KAl2(AlSi3O10)(OH)2, could be used as phase shifters in both symmetric Bragg and Laue geometries. In particular, the muscovite(002) having 5 ?m thickness in Laue geometry showed a phase retardation of ˜±90° and a transmittance of ˜0.02% at 0.88 keV.

Imazono, Takashi; Koike, Masato

2007-01-01

330

A New Method for Selecting Compton Thick AGN Above 10 keV with NuSTAR and Swift BAT  

NASA Astrophysics Data System (ADS)

We present NuSTAR observations of a new sample of heavily obscured AGN identified based on their Swift BAT spectra above 10 keV. We use the 70 month Swift Bat all-sky maps with a scheme optimized to detect nearby, heavily obscured, Compton-thick AGN using the Compton curvature which have excesses between 24-50 keV and decrements in the 14-20 keV band. We demonstrate that these targets are among the brightest examples of reflection-dominated AGN available across the sky, providing a detailed study of nearby Compton-thick AGN.

Koss, Michael; NuSTAR

2015-01-01

331

Comparative Dosimetric Estimates of a 25 keV Electron Micro-beam with three Monte Carlo Codes  

SciTech Connect

The calculations presented compare the different performances of the three Monte Carlo codes PENELOPE-1999, MCNP-4C and PITS, for the evaluation of Dose profiles from a 25 keV electron micro-beam traversing individual cells. The overall model of a cell is a water cylinder equivalent for the three codes but with a different internal scoring geometry: hollow cylinders for PENELOPE and MCNP, whereas spheres are used for the PITS code. A cylindrical cell geometry with scoring volumes with the shape of hollow cylinders was initially selected for PENELOPE and MCNP because of its superior simulation of the actual shape and dimensions of a cell and for its improved computer-time efficiency if compared to spherical internal volumes. Some of the transfer points and energy transfer that constitute a radiation track may actually fall in the space between spheres, that would be outside the spherical scoring volume. This internal geometry, along with the PENELOPE algorithm, drastically reduced the computer time when using this code if comparing with event-by-event Monte Carlo codes like PITS. This preliminary work has been important to address dosimetric estimates at low electron energies. It demonstrates that codes like PENELOPE can be used for Dose evaluation, even with such small geometries and energies involved, which are far below the normal use for which the code was created. Further work (initiated in Summer 2002) is still needed however, to create a user-code for PENELOPE that allows uniform comparison of exact cell geometries, integral volumes and also microdosimetric scoring quantities, a field where track-structure codes like PITS, written for this purpose, are believed to be superior.

Mainardi, Enrico; Donahue, Richard J.; Blakely, Eleanor A.

2002-09-11

332

NuSTAR AND CHANDRA INSIGHT INTO THE NATURE OF THE 3-40 keV NUCLEAR EMISSION IN NGC 253  

SciTech Connect

We present results from three nearly simultaneous Nuclear Spectroscopic Telescope Array (NuSTAR) and Chandra monitoring observations between 2012 September 2 and 2012 November 16 of the local star-forming galaxy NGC 253. The 3-40 keV intensity of the inner {approx}20 arcsec ({approx}400 pc) nuclear region, as measured by NuSTAR, varied by a factor of {approx}2 across the three monitoring observations. The Chandra data reveal that the nuclear region contains three bright X-ray sources, including a luminous (L{sub 2-10{sub keV}} {approx} few Multiplication-Sign 10{sup 39} erg s{sup -1}) point source located {approx}1 arcsec from the dynamical center of the galaxy (within the 3{sigma} positional uncertainty of the dynamical center); this source drives the overall variability of the nuclear region at energies {approx}>3 keV. We make use of the variability to measure the spectra of this single hard X-ray source when it was in bright states. The spectra are well described by an absorbed (N{sub H} Almost-Equal-To 1.6 Multiplication-Sign 10{sup 23} cm{sup -2}) broken power-law model with spectral slopes and break energies that are typical of ultraluminous X-ray sources (ULXs), but not active galactic nuclei (AGNs). A previous Chandra observation in 2003 showed a hard X-ray point source of similar luminosity to the 2012 source that was also near the dynamical center ({theta} Almost-Equal-To 0.4 arcsec); however, this source was offset from the 2012 source position by Almost-Equal-To 1 arcsec. We show that the probability of the 2003 and 2012 hard X-ray sources being unrelated is >>99.99% based on the Chandra spatial localizations. Interestingly, the Chandra spectrum of the 2003 source (3-8 keV) is shallower in slope than that of the 2012 hard X-ray source. Its proximity to the dynamical center and harder Chandra spectrum indicate that the 2003 source is a better AGN candidate than any of the sources detected in our 2012 campaign; however, we were unable to rule out a ULX nature for this source. Future NuSTAR and Chandra monitoring would be well equipped to break the degeneracy between the AGN and ULX nature of the 2003 source, if again caught in a high state.

Lehmer, B. D. [Johns Hopkins University, Homewood Campus, Baltimore, MD 21218 (United States); Wik, D. R.; Hornschemeier, A. E.; Ptak, A.; Leyder, J.-C.; Venters, T.; Zhang, W. W. [NASA Goddard Space Flight Center, Code 662, Greenbelt, MD 20771 (United States); Antoniou, V. [Department of Physics and Astronomy, Iowa State University, 12 Physics Hall, Ames, IA 50011 (United States); Argo, M. K. [ASTRON, the Netherlands Institute for Radio Astronomy, Postbus 2, 7990 AA, Dwingeloo (Netherlands); Bechtol, K. [Kavli Institute for Cosmological Physics, Chicago, IL 60637 (United States); Boggs, S.; Craig, W. W.; Krivonos, R. [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States); Christensen, F. E. [DTU Space-National Space Institute, Technical University of Denmark, Elektrovej 327, DK-2800 Lyngby (Denmark); Hailey, C. J. [Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States); Harrison, F. A. [Caltech Division of Physics, Mathematics and Astronomy, Pasadena, CA 91125 (United States); Maccarone, T. J. [School of Physics and Astronomy, University of Southampton, Highfield SO17 IBJ (United Kingdom); Stern, D. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Zezas, A. [Physics Department, University of Crete, Heraklion (Greece)

2013-07-10

333

Cross-field Diffusion of Energetic (100 keV to 2 MeV) Protons in Interplanetary Space  

NASA Astrophysics Data System (ADS)

Magnetic field magnitude decreases (MDs) are observed in several regions of the interplanetary medium. In this paper, we characterize MDs observed by the Ulysses spacecraft instrumentation over the solar south pole by using magnetic field data to obtain the empirical size, magnetic field MD, and frequency of occurrence distribution functions. The interaction of energetic (100 keV to 2 MeV) protons with these MDs is investigated. Charged particle and MD interactions can be described by a geometrical model allowing the calculation of the guiding center shift after each interaction. Using the distribution functions for the MD characteristics, Monte Carlo simulations are used to obtain the cross-field diffusion coefficients as a function of particle kinetic energy. It is found that the protons under consideration cross-field diffuse at a rate of up to ?11% of the Bohm rate. The same method used in this paper can be applied to other space regions where MDs are observed, once their local features are well known.

da Costa, Edio, Jr.; Tsurutani, Bruce T.; Virgínia Alves, Maria; Echer, Ezequiel; Lakhina, Gurbax S.

2013-12-01

334

Sputtering of Al nanoclusters by 1-13 keV monatomic or polyatomic ions studied by Molecular Dynamics simulations  

NASA Astrophysics Data System (ADS)

Molecular Dynamics (MD) simulations were employed to study sputtering of freestanding and supported spherical Al nanoclusters with 2-10 nm diameters under bombardment by Al1 and Al13 projectiles with energies of 1-13 keV at normal and oblique incidence. Both monatomic and clustered yields of secondary emission are found to be larger than those for (1 1 1) flat surface of the bulk Al (at equal irradiation conditions). In some events, target nanocluster receives a backward momentum and therefore its major part (more than 1/2 of the mass) is ejected due to produced secondary emission mainly towards the substrate direction. This “recoil effect” is found more pronounced under the impact of cluster projectiles and its probability decreases with increase of the target cluster size. A restricted number of MD simulations were performed to verify whether this “recoil effect” is strong enough to desorb a 4 nm Al nanocluster off an Al (1 1 1) substrate. Desorption was observed under oblique Al13 impact within the impact parameter range of 0.6-0.9.

Zhurkin, Evgeny E.; Grigorev, Petr Yu.

2013-05-01

335

60 keV Ar+-ion induced modification of microstructural, compositional, and vibrational properties of InSb  

NASA Astrophysics Data System (ADS)

Room temperature irradiation of InSb(111) by 60 keV Ar+-ions at normal (0°) and oblique (60°) angles of incidence led to the formation of nanoporous structure in the high fluence regime of 1 × 1017 to 3 × 1018 ions cm-2. While a porous layer comprising of a network of interconnected nanofibers was generated by normal ion incidence, evolution of plate-like structures was observed for obliquely incident ions. Systematic studies of composition and structure using energy dispersive x-ray spectroscopy, Raman spectroscopy, x-ray photoelectron spectroscopy, Raman mapping, grazing incidence x-ray diffraction, and cross-sectional transmission electron microscopy revealed a high degree of oxidation of the ion-induced microstructures with the presence of In2O3 and Sb2O3 phases and presence of nanocrystallites within the nanoporous structures. The observed structural evolution was understood in terms of processes driven by ion-induced defect accumulation within InSb.

Datta, D. P.; Garg, S. K.; Satpati, B.; Sahoo, P. K.; Kanjilal, A.; Dhara, S.; Kanjilal, D.; Som, T.

2014-10-01

336

Subsurface and interface channeling of keV ions in graphene/SiC  

NASA Astrophysics Data System (ADS)

Using molecular-dynamics simulation, we study the impact of 3 keV Ar and Xe ions on a ?-SiC (1 1 1) surface covered by a single graphene layer. At glancing ion incidence angles, we observe the ions to undergo interface channeling between the graphene and the first SiC surface layer. This behavior is particularly pronounced for Xe ions, where at incidence angles of 70-75° more than 50% of the ions are channeled. This process is accompanied by abundant damage production and sputtering in the graphene layer. Similarities and differences to subsurface channeling in elemental materials are discussed.

Rosandi, Yudi; Urbassek, Herbert M.

2014-12-01

337

Microchannel plate pinhole camera for 20 to 100 keV x-ray imaging  

SciTech Connect

We present the design and construction of a sensitive pinhole camera for imaging suprathermal x-rays. Our device is a pinhole camera consisting of four filtered pinholes and microchannel plate electron multiplier for x-ray detection and signal amplification. We report successful imaging of 20, 45, 70, and 100 keV x-ray emissions from the fusion targets at our Novette laser facility. Such imaging reveals features of the transport of hot electrons and provides views deep inside the target.

Wang, C.L.; Leipelt, G.R.; Nilson, D.G.

1984-10-03

338

Ion and photon emission from keV cluster impacts on surfaces  

E-print Network

ION AND PHOTON EMISSION FROM KEV CLUSTER IMPACTS ON SURFACES A Thesis by ALICE YAU-LIC YAU Submined to the Office of Graduate Studies of Texas A8cM University in panial fulfillment of the requirements for the degree of MASTER OF SCIENCE May... 1992 Major Subject: Chemistry ION AND PHOTON EMISSION FROM KEY CLUSTER IMPACTS ON SURFACES A Thesis by ALICE YAU-LIC YAU Approved as to style and content by: Emile A. Schweikert (Chair of Committee) David H. Russell (Member) Kevin L. Wolf...

Yau, Alice Yau-Lic

2012-06-07

339

3.55 keV line in Minimal Decaying Dark Matter scenarios  

E-print Network

We investigate the possibility of reproducing the recently reported $3.55\\,\\mbox{keV}$ 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.

Arcadi, Giorgio; Dradi, Federico

2014-01-01

340

Electronic sputtering of solid oxygen and ozone by 100 keV protons  

NASA Astrophysics Data System (ADS)

Sputtering of condensed gases by fast ions occurs by electronic excitations which couple into atomic motion through pathways that are usually unknown. As a model system for molecular solids, we studied solid oxygen irradiated by 100 keV protons. We measured sputtering with a quartz-crystal microbalance and a differentially-pumped mass spectrometer, and studied changes in the sample using optical absorption. We found a dependence of the sputtering yield of oxygen with ion dose, which we attribute to ozone formation and accumulation in the solid films. By controlled warming of the films we can vary the ozone concentration. We found an unusually large sputtering yield for solid ozone.

Teolis, Ben; Fama, Marcelo; Baragiola, Raul

2002-03-01

341

Differential cross sections for single ionization of H2 by 75keV proton impact  

NASA Astrophysics Data System (ADS)

We have calculated Triply differential cross sections (TDCS) and doubly differential cross sections (DDCS) for single ionization of H2 by 75 keV proton impact using the molecular 3 body distorted wave Eikonal initial state (M3DW-EIS) approach. Previously published measured DDCS-P (differential in the projectile scattering angle and integrated over the ejected electron angles) found pronounced structures at relatively large angles which were interpreted as an interference resulting from the two-centered potential of the molecule.

Chowdhury, U.; Schulz, M.; Madison, D. H.

2012-11-01

342

17 keV photon induced damage of Bi-2212 whiskers by synchrotron ?-beam exposure  

NASA Astrophysics Data System (ADS)

Experimental data show that the normal state resistivity of superconducting Bi2Sr2CaCu2O8 + ? (Bi-2212) whiskers increases after a 6 h irradiation by a synchrotron ?-beam with 17 keV photons. We analyse this result on the basis of previously reported effects in Bi-2212 whiskers due to ageing or heating processes. A finite element model of the experimental setup clarifies that the heat load induced by the microbeam has to be excluded as a possible cause for the material changes. The knock on the interstitial, loosely bound, O species by secondary electrons is discussed as the most likely mechanism responsible for this effect.

Aldica, G.; Cagliero, S.; Agostino, A.; Lamberti, C.; Truccato, M.

2011-03-01

343

Dark Matter Search Using Chandra Observations of Willman 1, and a Spectral Feature Consistent with a Decay Line of a 5 keV Sterile Neutrino  

E-print Network

We report the results of a search for an emission line from radiatively decaying dark matter in the Chandra X-ray Observatory spectrum of the ultra-faint dwarf spheroidal galaxy Willman 1. 99% confidence line flux upper limits over the 0.4-7 keV Chandra bandpass are derived and mapped to an allowed region in the sterile neutrino mass-mixing angle plane that is consistent with recent constraints from Suzaku X-ray Observatory and Chandra observations of the Ursa Minor and Draco dwarf spheroidals. A significant excess to the continuum, detected by fitting the particle-background-subtracted source spectrum, indicates the presence of a narrow emission feature with energy 2.51 +/- 0.07 (0.11) keV and flux [3.53 +/- 1.95 (2.77)] X 10^(-6) photons/cm^2/s at 68% (90%) confidence. Interpreting this as an emission line from sterile neutrino radiative decay, we derive the corresponding allowed range of sterile neutrino mass and mixing angle using two approaches. The first assumes that dark matter is solely composed of sterile neutrinos, and the second relaxes that requirement. The feature is consistent with the sterile neutrino mass of 5.0 +/- 0.2 keV and a mixing angle in a narrow range for which neutrino oscillations can produce all of the dark matter and for which sterile neutrino emission from the cooling neutron stars can explain pulsar kicks, thus bolstering both the statistical and physical significance of our measurement.

Michael Loewenstein; Alexander Kusenko

2009-12-03

344

Improving accuracy and reliability of 186-keV measurements for unattended enrichment monitoring  

SciTech Connect

Improving the quality of safeguards measurements at Gas Centrifuge Enrichment Plants (GCEPs), whilst reducing the inspection effort, is an important objective given the number of existing and new plants that need to be safeguarded. A useful tool in many safeguards approaches is the on-line monitoring of enrichment in process pipes. One aspect of this measurement is a simple, reliable and precise passive measurement of the 186-keV line from {sup 235}U. (The other information required is the amount of gas in the pipe. This can be obtained by transmission measurements or pressure measurements). In this paper we describe our research efforts towards such a passive measurement system. The system includes redundant measurements of the 186-keV line from the gas and separately from the wall deposits. The design also includes measures to reduce the effect of the potentially important background. Such an approach would practically eliminate false alarms and can maintain the operation of the system even with a hardware malfunction in one of the channels. The work involves Monte Carlo modeling and the construction of a proof-of-principle prototype. We will carry out experimental tests with UF{sub 6} gas in pipes with and without deposits in order to demonstrate the deposit correction.

Ianakiev, Kiril D [Los Alamos National Laboratory; Boyer, Brian D [Los Alamos National Laboratory; Swinhoe, Martyn T [Los Alamos National Laboratory; Moss, Cal E [Los Alamos National Laboratory; Goda, Joetta M [Los Alamos National Laboratory; Favalli, Andrea [Los Alamos National Laboratory; Lombardi, Marcie [Los Alamos National Laboratory; Paffet, Mark T [Los Alamos National Laboratory; Hill, Thomas R [Los Alamos National Laboratory; Mac Arthur, Duncan W [Los Alamos National Laboratory; Smith, Morag K [Los Alamos National Laboratory

2010-01-01

345

EMISSION LINES BETWEEN 1 AND 2 keV IN COMETARY X-RAY SPECTRA  

SciTech Connect

We present the detection of new cometary X-ray emission lines in the 1.0-2.0 keV range using a sample of comets observed with the Chandra X-Ray Observatory and ACIS spectrometer. We have selected five comets from the Chandra sample with good signal-to-noise spectra. The surveyed comets are C/1999 S4 (LINEAR), C/1999 T1 (McNaught-Hartley), 153P/2002 (Ikeya-Zhang), 2P/2003 (Encke), and C/2008 8P (Tuttle). We modeled the spectra with an extended version of our solar wind charge exchange (SWCX) emission model. Above 1 keV, we find Ikeya-Zhang to have strong emission lines at 1340 and 1850 eV which we identify as being created by SWCX lines of Mg XI and Si XIII, respectively, and weaker emission lines at 1470, 1600, and 1950 eV formed by SWCX of Mg XII, Mg XI, and Si XIV, respectively. The Mg XI and XII and Si XIII and XIV lines are detected at a significant level for the other comets in our sample (LS4, MH, Encke, 8P), and these lines promise additional diagnostics to be included in SWCX models. The silicon lines in the 1700-2000 eV range are detected for all comets, but with the rising background and decreasing cometary emission, we caution that these detections need further confirmation with higher resolution instruments.

Ewing, Ian; Christian, Damian J. [Department of Physics and Astronomy, California State University, 18111 Nordhoff Street, Northridge, CA 91330 (United States)] [Department of Physics and Astronomy, California State University, 18111 Nordhoff Street, Northridge, CA 91330 (United States); Bodewits, Dennis [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States)] [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States); Dennerl, Konrad [Max-Planck-Institut fuer extraterrestrische Physik, Postfach 1312, D-85741 Garching Germany (Germany)] [Max-Planck-Institut fuer extraterrestrische Physik, Postfach 1312, D-85741 Garching Germany (Germany); Lisse, Carey M. [Planetary Exploration Group, Space Department, Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Rd, Laurel, MD 20723 (United States)] [Planetary Exploration Group, Space Department, Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Rd, Laurel, MD 20723 (United States); Wolk, Scott J., E-mail: ian.ewing.794@my.csun.edu, E-mail: daman.christian@csun.edu [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

2013-01-20

346

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

NASA Astrophysics Data System (ADS)

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 ?A cm -2 to 64 ?A 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.

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

1981-05-01

347

Radiation blistering in inconel-625 due to 100 keV helium ion irradiation  

NASA Astrophysics Data System (ADS)

The objective of this study was to determine whether the change of angle of incidence of an ion beam impinging on surface blisters during their growth phase (before exfoliation) could influence the blister skin thickness and the blister crater depth. Polished, polycrystalline Inconel-625 samples were irradiated at room temperature and at normal incidence to the major sample surface with 100 keV helium ions to a total dose of 6.24 × 10 18 ions/cm 2. The results revealed that many exfoliated blisters leave craters which have two or three concentric pits. The blister skin thickness near the center of the blister was found to agree well with the calculated projected range of 100 keV He ions in nickel. However, the blister skin thickness of some exfoliated blisters along the edge of the fracture surface showed different thicknesses. A model is proposed to explain the observed blister crater/blister skin fracture features in terms of a change of angle of incidence of the incident ions to the surface during the growth phase of surface blisters.

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

1988-05-01

348

The origin of the “local” ¼ keV X-ray flux  

NASA Astrophysics Data System (ADS)

The Solar Wind interacts with interstellar neutrals via charge exchange producing a spatially and temporally varying x-ray flux difficult to separate from other diffuse sources. The Diffuse X-rays from the Local Galaxy (DXL) mission measured the spatial signature of Solar Wind Charge eXchange (SWCX) emission using 2 large-area proportional counters. DXL was able to separate the SWCX contribution from the more dominant flux originating in the Local Hot Bubble. The data from the mission provide a robust estimate of the SWCX contribution to the RASS data in the ¼ keV band, showing that the total SWCX contribution is 40%±5% (stat) ±5% (sys) of the minimal ¼ keV flux in the Galactic plane. This result implies that the measured fluxes are dominated by interstellar emission, strengthening the idea of a hot bubble filling the cavity in the local interstellar medium extending ~50-150 pc from the Sun. Combined with recent three-dimensional maps of the local interstellar medium and Voyager measurements of the magnetic field outside the heliosphere, it also leads to a consistent picture of the local interstellar environment.

Uprety, Youaraj; Chiao, Meng; Collier, Michael; Cravens, Thomas; Galeazzi, Massimiliano; Koutroumpa, Dimitra; Kuntz, K. D.; Lallement, Rosine; Lepri, Susan T.; Liu, Wenhao; McCammon, Dan; Morgan, Kelsey; Porter, Frederick Scott; Puspitarini, Lucky; Robertson, Ina; Snowden, Steven L.; Thomas, Nicholas Evan; Ursino, Eugenio; Walsh, Brian R.

2014-08-01

349

The 16 August 1997 Novaya Zemlya seismic event as viewed from GSN stations KEV and KBS  

SciTech Connect

Using current and historic seismic records from Global Seismic Network stations KEV and KBS, the authors find that S minus P arrival time comparisons between nuclear explosions and the 16 August 1997 seismic event (m{sub b} {approx} 3.6) from near Novaya Zemlya clearly indicate that (relative to KEV) the 16 August event occurred at least 80 km east of the Russian test site. Including S minus P arrival times from KBS constrains the location to beneath the Kara Sea and in good agreement with previously reported locations, over 100 km southeast of the test site. From an analysis of P{sub n}/S{sub n} waveform ratios at frequencies above 4 Hz, they find that the 16 August event falls within the population of regional earthquakes and is distinctly separated from Novaya Zemlya and other northern Eurasian nuclear explosion populations. Thus, given its location and waveform characteristics, they conclude the 16 August event was an earthquake. The 16 August event was not detected at teleseismic distances, and thus, this event provides a good example of the regional detection, location, and identification efforts that will be required to monitor the Comprehensive Test Ban Treaty below m{sub b} {approx} 4.

Hartse, H.E.

1997-11-01

350

Observations of energetic electrons /E no less than about 200 keV/ in the earth's magnetotail - Plasma sheet and fireball observations  

NASA Technical Reports Server (NTRS)

An earlier paper by the authors (1976) has reported on energetic electron anisotropies observed in conjunction with the acceleration regions identified by Frank et al., (1976). The present paper gives more detailed analyses of observations in the distant plasma sheet, including specific features of intensities, energy spectra, and pitch angle distributions of the very energetic electrons associated with intense plasma particle events, with energies ranging between 50 eV and 45 keV, detected with an electron/isotope spectrometer aboard the earth-orbiting spacecraft Imp 8. Two domains are considered: the plasma sheet and the regions near and within the localized magnetotail acceleration regions known as the fireball regions. The instrumentation used offered a number of observational advantages over many previous studies, including inherently low background, large geometric factors, excellent species identification, good angular distribution measurement capability, and availability of high resolution of differential intensities.

Baker, D. N.; Stone, E. C.

1977-01-01

351

Close-packed Arrays of Transition-edge X-ray Microcalorimeters with High Spectral Resolution at 5.9 keV  

NASA Technical Reports Server (NTRS)

We present measurements of high fill-factor arrays of superconducting transition-edge x-ray microcalorimeters designed to provide rapid thermalization of the x-ray energy. We designed an x-ray absorber that is cantilevered over the sensitive part of the thermometer itself, making contact only at normal metal-features. With absorbers made of electroplated gold, we have demonstrated an energy resolution between 2.4 and 3.1 eV at 5.9 keV on 13 separate pixels. We have determined the thermal and electrical parameters of the devices throughout the superconducting transition, and, using these parameters, have modeled all aspects of the detector performance.

Iyomoto, N.; Bandler, S. R.; Brekosky, R. P.; Brown, A.-D.; Chervenak, J. A.; Finkbeiner, F. M.; Kelley, R. L.; Kilbourne, C. A.; Porter, F. S.; Sadleir, J. E.; Smith, S. J.; Figueroa-Feliciano, E.

2007-01-01

352

Measurement of L x-ray emission from elements in 64 <= Z <= 73 interval stimulated by 59.54 keV photons  

NASA Astrophysics Data System (ADS)

Accurate measurements (mostly within 5%) of L?, L? and L? x-ray emission cross sections were carried out on thick foils of elements lying in 64 <= Z <= 73 interval, stimulated by 59.54 keV photons. They can be of help as an overall reference to compare the theoretical and semi-empirical approaches by which the atomic parameters included in the expressions of L emission cross sections are evaluated. An appropriate extension of the expression linking the cross section to the counting rate measured in reflection geometry on thick targets makes it possible to overcome the difficulties arising from the width in energy of the L? and L? groups and from the jump present in the attenuation coefficients of the target elements within the energy interval of their L? emission lines.

Baraldi, C.; Casnati, E.; Tartari, A.; Singh, B.

2005-08-01

353

Measurement of the {sup 13}C(?,n){sup 16}O reaction with the Trojan horse method: Focus on the sub threshold resonance at ?3 keV  

SciTech Connect

The {sup 13}C(?,n){sup 16}O reaction is the neutron source of the main component of the s-process. The astrophysical S(E)-factor is dominated by the ?3 keV sub-threshold resonance due to the 6.356 MeV level in {sup 17}O. Its contribution is still controversial as extrapolations, e.g., through R-matrix calculations, and indirect techniques, such as the asymptotic normalization coefficient (ANC), yield inconsistent results. Therefore, we have applied the Trojan Horse Method (THM) to the {sup 13}C({sup 6}Li,n{sup 16}O)d reaction to measure its contribution. For the first time, the ANC for the 6.356 MeV level has been deduced through the THM, allowing to attain an unprecedented accuracy. Though a larger ANC for the 6.356 MeV level is measured, our experimental S(E) factor agrees with the most recent extrapolation in the literature in the 140-230 keV energy interval, the accuracy being greatly enhanced thanks to this innovative approach, merging together two well establish indirect techniques, namely, the THM and the ANC.

La Cognata, M. [Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali del Sud, Catania (Italy); Spitaleri, C.; Guardo, G. L.; Puglia, S. M. R.; Romano, S.; Spartà, R. [Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali del Sud, Catania and Dipartimento di Fisica e Astronomia, Università di Catania, Catania (Italy); Trippella, O. [Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali del Sud, Catania and Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, and Dipartimento di Fisica, Università di Perugia, Perugia (Italy); Kiss, G. G. [Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali del Sud, Catania and Institute of Nuclear Research (ATOMKI), Debrecen (Hungary); Rogachev, G. V.; Avila, M.; Koshchiy, E.; Kuchera, A.; Santiago, D. [Department of Physics, Florida State University, Tallahassee, Florida (United States); Mukhamedzhanov, A. M. [Cyclotron Institute, Texas A and M University, College Station, Texas (United States); Lamia, L. [Dipartimento di Fisica e Astronomia, Università di Catania, Catania (Italy)

2014-05-02

354

Scintillation response of liquid xenon to low energy nuclear recoils  

Microsoft Academic Search

Liquid Xenon (LXe) is expected to be an excellent target and detection medium to search for dark matter in the form of Weakly Interacting Massive Particles (WIMPs). We have measured the scintillation efficiency of nuclear recoils with kinetic energy between 10.4 and 56.5 keV relative to that of 122 keV gamma rays from C57o. The scintillation yield of 56.5 keV

E. Aprile; K. L. Giboni; P. Majewski; K. Ni; M. Yamashita; R. Hasty; A. Manzur; D. N. McKinsey

2005-01-01

355

Dynamic transmission of intermediate energy proton through polycarbonate nanocapillary  

NASA Astrophysics Data System (ADS)

Dynamic transmission of 10~120keV proton through polycarbonate nanocapillary were observed. 10keV proton is guided along the capillary and the charge purity is about 80%. But protons with energies near 100keV show remarkable differences. The charge purity of them is also high, but the transmitted particles move along the direction of incident beam, while not along the capillary axis.

Shao, J. X.; Wang, G. Y.; Ma, X.; Cui, Y.; Zhou, W.; Song, Q.; Chen, X. M.

2014-04-01

356

Sputtering of parent-like ions from large organic adsorbates on metals under keV ion bombardment  

NASA Astrophysics Data System (ADS)

Thin films of hydrocarbon molecules, unsaturated fatty acid and low molecular weight polystyrene deposited on different metal substrates (silver, copper and gold) were bombarded by 15 keV Ga ions and the secondary ions were mass- and energy-analysed by means of a time-of-flight secondary ion mass spectrometer. The samples were studied in order to evidence the effects of different substrates and coverages on the emission of the parent and cationised molecular ions, and to gain a better understanding of the large molecular ion emission processes. Ion beam degradation studies were realised for fundamental purposes too. In general, the kinetic energy distributions of metal-cationised molecules are broad in comparison with those of the parent ions, and of the smaller polystyrene fingerprint ions. In addition, the velocity distributions of the parent ions and of the metal-cationised molecules are similar. Parent ions of aromatic molecules are, on average, more energetic than those of aliphatic molecules. In the case of metal-cationised molecules, the three hypotheses of emission of a preformed complex, recombination in the selvedge and metastable decay of larger aggregates are critically reviewed in comparison with the experimental data. The recombination hypothesis cannot account for the whole set of observations. On the other hand, the very different evolutions of the parent ions and of the metal-cationised molecules in the degradation experiments cannot be explained solely in the frame of metastable decay reactions, although the kinetic energy measurements show that a significant fraction of the parent-like ions are produced in the vacuum. The augmentation of the secondary ion kinetic energy with increasing molecule size for triacontane monomers and dimers, and for silver-cationised polystyrene oligomers, is in disagreement with the sputtering by a single cascade atom, too. Finally, the discussion outlines the conditions that must be satisfied to model the experimental observations and proposes a view of the sputtering of these large molecular cations based on multiple collision processes and possible subsequent dissociation in the vacuum.

Delcorte, A.; Bertrand, P.

1998-09-01

357

Tip-based source of femtosecond electron pulses at 30?keV  

SciTech Connect

We present a nano-scale photoelectron source, optimized for ultrashort pulse durations and well-suited for time-resolved diffraction and advanced laser acceleration experiments. A tungsten tip of several-ten-nanometers diameter mounted in a suppressor-extractor electrode configuration allows the generation of 30?keV electron pulses with an estimated pulse duration of 9?fs (standard deviation; 21?fs full width at half maximum) at the gun exit. We infer the pulse duration from particle tracking simulations, which are in excellent agreement with experimental measurements of the electron-optical properties of the source in the spatial domain. We also demonstrate femtosecond-laser triggered operation of the apparatus. The temporal broadening of the pulse upon propagation to a diffraction sample can be greatly reduced by collimating the beam. Besides the short electron pulse duration, a tip-based source is expected to feature a large transverse coherence and a nanometric emittance.

Hoffrogge, Johannes; Paul Stein, Jan [Max Planck Institute of Quantum Optics, Hans-Kopfermann-Str. 1, 85748 Garching (Germany); Krüger, Michael; Förster, Michael; Hammer, Jakob; Ehberger, Dominik; Hommelhoff, Peter, E-mail: peter.hommelhoff@fau.de [Max Planck Institute of Quantum Optics, Hans-Kopfermann-Str. 1, 85748 Garching (Germany); Department für Physik, Friedrich-Alexander-Universität Erlangen-Nürnberg, Staudtstr. 1, 91058 Erlangen (Germany); Baum, Peter [Max Planck Institute of Quantum Optics, Hans-Kopfermann-Str. 1, 85748 Garching (Germany); Ludwig-Maximilians-Universität München, Am Coulombwall 1, 85748 Garching (Germany)

2014-03-07

358

X-ray lines from R-parity violating decays of keV sparticles  

NASA Astrophysics Data System (ADS)

If R parity is only mildly violated, then the lightest supersymmetric particle (LSP) can be stable over cosmologically time scales and still account for the dark matter relic density. We examine the possibility of generating detectable x-ray lines from R-parity violating decays of keV-scale LSP dark matter to neutrino-photon pairs. Specifically, we consider scenarios in which the LSP is a light gravitino, bino, or hidden sector photino. Potential signals are discussed in the context of recent claims of an unidentified 3.5 keV x-ray line in studies of stacked galaxy clusters. We comment on the difficulties in obtaining the observed relic density for keV-scale bino or hidden photino dark matter and some possible resolutions.

Kolda, Christopher; Unwin, James

2014-07-01

359

Sputtering yields exceeding 1000 by 80 keV Xe irradiation of Au nanorods  

NASA Astrophysics Data System (ADS)

Using experiments and computer simulations, we find that 80 keV Xe ion irradiation of Au nanorods can produce sputtering yields exceeding 1000, which to our knowledge are the highest yields reported for sputtering by single ions in the nuclear collision regime. This value is enhanced by more than an order of magnitude compared to the same irradiation of flat Au surfaces. Using MD simulations, we show that the very high yield can be understood as a combination of enhanced yields due to low incoming angles at the sides of the nanowire, as well as the high surface-to-volume ratio causing enhanced explosive sputtering from heat spikes. We also find, both in experiments and simulations, that channeling has a strong effect on the sputtering yield: if the incoming beam happens to be aligned with a crystal axis of the nanorod, the yield can decrease to about 100.

Ilinov, A.; Kuronen, A.; Nordlund, K.; Greaves, G.; Hinks, J. A.; Busby, P.; Mellors, N. J.; Donnelly, S. E.

2014-12-01

360

Stopping of 5-100 keV helium in molybdenum, chromium, copper and nickel  

NASA Astrophysics Data System (ADS)

The stopping power of Mo, Cr, Cu and Ni for He ions at velocities below the Bohr velocity has been studied. The stopping power values were deduced by comparing ranges of 5-100 keV He(+) -ions determined with the elastic-recoil-detection-analysis (ERDA) method with those obtained in molecular dynamics simulations. The nuclear slowing down was treated through the use of molecular dynamics calculations and a potential obtained from density-functional theory calculations. The comparisons of the range profiles showed that the electronic stopping powers given by J.F. Ziegler, J.P. Biersack and U. Littmark (The Stopping Powers and Ranges of Ions in Matter, vol. 1, Pergamon press, New York, 1985) had to be multiplied with a factor of 1.20 ± 0.07 for Mo and Cr and 1.00 ± 0.06 for Cu and Ni.

Sillanpää, J.; Vainonen-Ahlgren, E.; Haussalo, P.; Keinonen, J.

1998-06-01

361

Positron production scenarios and the angular profile of the galactic center 511-keV line  

E-print Network

The observed angular profile of the 511-keV photon excess from the Milky Way galactic center can allow us to select among combinations of various dark matter and other positron production mechanisms with various models for the dark matter distribution. We find that a relic decay scenario gives too flat an angular distribution for any dark matter distribution in our survey, but that a dark matter-dark matter collisional scenario, or a scenario that involves particles emitted from a localized central source producing positrons some distance out, can match the observed galactic center angular profile if the dark matter distribution is neither too flat nor too cuspy. Additionally, positron migration or diffusion before annihilation broadens the angular profile to an extent that an average migration of more than half a kiloparsec is not viable with most dark matter distributions. The observed angular profile is also consistent with the occurrence of transient events in the past, followed by isotropic positron diff...

Abidin, Zainul; Carlson, Carl E

2010-01-01

362

Positron production scenarios and the angular profile of the galactic center 511-keV line  

E-print Network

The observed angular profile of the 511-keV photon excess from the Milky Way galactic center can allow us to select among combinations of various dark matter and other positron production mechanisms with various models for the dark matter distribution. We find that a relic decay scenario gives too flat an angular distribution for any dark matter distribution in our survey, but that a dark matter-dark matter collisional scenario, or a scenario that involves particles emitted from a localized central source producing positrons some distance out, can match the observed galactic center angular profile if the dark matter distribution is neither too flat nor too cuspy. Additionally, positron migration or diffusion before annihilation broadens the angular profile to an extent that an average migration of more than half a kiloparsec is not viable with most dark matter distributions. The observed angular profile is also consistent with the occurrence of transient events in the past, followed by isotropic positron diffusion.

Zainul Abidin; Andrei Afanasev; Carl E. Carlson

2010-06-28

363

Silicon-carbon bond inversions driven by 60-keV electrons in graphene.  

PubMed

We demonstrate that 60-keV electron irradiation drives the diffusion of threefold-coordinated Si dopants in graphene by one lattice site at a time. First principles simulations reveal that each step is caused by an electron impact on a C atom next to the dopant. Although the atomic motion happens below our experimental time resolution, stochastic analysis of 38 such lattice jumps reveals a probability for their occurrence in a good agreement with the simulations. Conversions from three- to fourfold coordinated dopant structures and the subsequent reverse process are significantly less likely than the direct bond inversion. Our results thus provide a model of nondestructive and atomically precise structural modification and detection for two-dimensional materials. PMID:25259987

Susi, Toma; Kotakoski, Jani; Kepaptsoglou, Demie; Mangler, Clemens; Lovejoy, Tracy C; Krivanek, Ondrej L; Zan, Recep; Bangert, Ursel; Ayala, Paola; Meyer, Jannik C; Ramasse, Quentin

2014-09-12

364

A search for the 478 keV line from the decay of nucleosynthetic Be-7  

NASA Technical Reports Server (NTRS)

Unstable Be-7 (half-life 53.28 days) is expected to be present in the ejecta of classical novae. If the frequency of novae in the central Galaxy is high enough, a nearly steady state abundance of Be-7 will be present there. Data accumulated during transits of the Galactic center across the aperture of the Solar Maximum Mission Gamma Ray Spectrometer have been searched for evidence of the 478 keV gamma-ray line resulting from Be-7 decay. A 3-sigma upper limit of 0.00016 gamma/sq cm s has been placed on the emission in this line from the central radian of the Galactic plane. Less stringent limits have been set on the production of Be-7 in Nova Aquilae 1982, Nova Vulpeculae 1984 No. 2, and Nova Centauri 1986 from observations with the same instrument.

Harris, Michael J.; Leising, Mark D.; Share, Gerald H.

1991-01-01

365

Differential cross sections for single ionization of H2 by 75-keV proton impact  

NASA Astrophysics Data System (ADS)

We have calculated triply differential cross sections (TDCS) and doubly differential cross sections (DDCS) for single ionization of H2 by 75-keV proton impact using the molecular three-body distorted-wave-eikonal initial-state (M3DW-EIS) approach. Previously published measured DDCS (differential in the projectile scattering angle and integrated over the ejected electron angles) found pronounced structures at relatively large angles that were interpreted as an interference resulting from the two-centered potential of the molecule. Theory treating H2 as atomic H multiplied by a molecular interference factor only predicts the observed structure when assumptions are made about the molecular orientation. Here we apply the M3DW-EIS method, which does not rely on such an ad hoc approach, but rather treats the interference from first principles.

Chowdhury, U.; Schulz, M.; Madison, D. H.

2011-03-01

366

Differential cross sections for single ionization of H2 by 75keV proton impact  

NASA Astrophysics Data System (ADS)

We have calculated Triply differential cross sections (TDCS) and doubly differential cross sections (DDCS) for single ionization of by 75 KeV proton impact using the molecular 3 body distorted wave Eikonal initial state (M3DW-EIS) approach. Previously published measured DDCS (differential in the projectile scattering angle and integrated over the ejected electron angles) found pronounced structures at relatively large angles which were interpreted as an interference resulting from the two-centered potential of the molecule. Theory treating H2 as atomic H multiplied by a molecular interference factor only predict the observed structure when assumptions are made about the molecular orientation. Here we apply the M3DW-EIS method, which does not rely on such an ad hoc approach, but rather treats the interference from first principles and we find the same structure without assuming any preferential orientations.

Chowdhury, Uttam; Schulz, Michael; Madison, Don

2011-06-01

367

Silicon-Carbon Bond Inversions Driven by 60-keV Electrons in Graphene  

NASA Astrophysics Data System (ADS)

We demonstrate that 60-keV electron irradiation drives the diffusion of threefold-coordinated Si dopants in graphene by one lattice site at a time. First principles simulations reveal that each step is caused by an electron impact on a C atom next to the dopant. Although the atomic motion happens below our experimental time resolution, stochastic analysis of 38 such lattice jumps reveals a probability for their occurrence in a good agreement with the simulations. Conversions from three- to fourfold coordinated dopant structures and the subsequent reverse process are significantly less likely than the direct bond inversion. Our results thus provide a model of nondestructive and atomically precise structural modification and detection for two-dimensional materials.

Susi, Toma; Kotakoski, Jani; Kepaptsoglou, Demie; Mangler, Clemens; Lovejoy, Tracy C.; Krivanek, Ondrej L.; Zan, Recep; Bangert, Ursel; Ayala, Paola; Meyer, Jannik C.; Ramasse, Quentin

2014-09-01

368

350 keV accelerator based PGNAA setup to detect nitrogen in bulk samples  

NASA Astrophysics Data System (ADS)

Nitrogen concentration was measured in explosive and narcotics proxy material, e.g. anthranilic acid, caffeine, melamine, and urea samples, bulk samples through thermal neutron capture reaction using 350 keV accelerator based prompt gamma ray neutron activation (PGNAA) setup. Intensity of 2.52, 3.53-3.68, 4.51, 5.27-5.30 and 10.38 MeV prompt gamma rays of nitrogen from the bulk samples was measured using a cylindrical 100 mm×100 mm (diameter×height ) BGO detector. Inspite of interference of nitrogen gamma rays from bulk samples with capture prompt gamma rays from BGO detector material, an excellent agreement between the experimental and calculated yields of nitrogen gamma rays has been obtained. This is an indication of the excellent performance of the PGNAA setup for detection of nitrogen in bulk samples.

Naqvi, A. A.; Al-Matouq, Faris A.; Khiari, F. Z.; Gondal, M. A.; Rehman, Khateeb-ur; Isab, A. A.; Raashid, M.; Dastageer, M. A.

2013-11-01

369

Microstructural investigation of alumina implanted with 30 keV nitrogen ions  

NASA Astrophysics Data System (ADS)

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.

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

370

511 keV line from millisecond pulsars in the Galactic center  

E-print Network

Observations of a strong and extended positron-electron annihilation line emission in the Galactic center (GC) region by the SPI/INTEGRAL are challenging to the existing models of positron sources in the Galaxy. In this paper, we study the possibility that pulsar winds from a millisecond pulsar population in the GC produce the 511 keV line. Our preliminary estimations predict that the e+/- annihilation rate in the GC is around 5 x 10E+42 sE-1, which is consistent with the present observational constraints. Therefore, the e+/- pairs from pulsar winds can contribute significantly to the positron sources in the Galactic center region. Furthermore, since the diffusion length of positrons is short in the magnetic field, we predict that the intensity distribution of the annihilation line should follow the distribution of millisecond pulsars, which should then correlate to the mass distribution in the GC.

Wei Wang

2006-12-21

371

Mechanisms of O2 Sputtering from Water Ice by keV Ions  

NASA Technical Reports Server (NTRS)

We have conducted experiments on the sputtering of water ice by 100 keV Ar(+) between 20 and 150 K. Our findings indicate that the temperature dependence of the total sputtering yield is heavily influenced by the thermal and irradiation history of the ice, showing a complex dependence on irradiation fluence that is correlated to the ejection of O2 molecules. The results suggest that O2 produced by the ions inside the ice diffuses to the surface where it is trapped and then ejected via sputtering or thermal desorption. A high concentration of O2 can trap in a subsurface layer during bombardment at 130 K, which we relate to the formation of hydrogen and its escape from that region. A simple model allows us to determine the depth profile of the absolute concentration of O2 trapped in the ice.

Teolis, B. D.; Vidal, R. A.; Shi, J.; Baragiola, R. A.

2005-01-01

372

Wavefront analysis and beam profiling from 40 eV up to 40 keV  

NASA Astrophysics Data System (ADS)

A wavefront sensing and beam monitoring system applicable to various kinds of X-ray and EUV sources like synchrotron radiation from undulators, X-ray lasers and laser induced plasma sources in the spectral range from 40 eV up to 40 keV is presented. One of the main applications will be the feedback for adaptive optical elements, e.g. deformable mirrors, for X-rays above 10 keV. It also provides the possibility to estimate the source dimension and distance. The wavefront sensor is based on a modified Hartmann setup; the beam is sampled by a rectangular grid and generates a distorted image on the detector. Comparison of this image with a known reference yields the wavefront's local slope at an extensive number of points. However, the Hartmann pattern is not directly imaged but is converted to the visible spectral range by a scintillator. This offers the possibility to use off the shelf cameras for image acquisition. First measurements, performed at the VUV-FEL (DESY, Hamburg) and at ELETTRA (Trieste), show the feasibility of this approach. The Hartmann principle offers the advantage to measure both, intensity and phase, thus allowing to reconstruct not only the wavefront but also the beam profile. Wavefront resolution of up to ?/100 (? = 1 nm) can be achieved. The intensity profile and the beam shape can be measured with a spatial resolution better than 10 ?m. With the current setup it is also possible to analyze the temporal and spatial stability of the source.

Nisius, Thomas; Schäfer, David; Früke, Rolf; Wilhein, Thomas

2006-08-01

373

The Extragalactic X-ray Background in the 0.2 - 2 keV Range  

NASA Technical Reports Server (NTRS)

We made the first measurement of the extragalactic 0.7 keV background. We detected the X-ray shadow of a neutral gas cloud in the Magellanic Bridge. We further constrained the point-like source contribution based on the mean spectrum of detected sources and on our early autocorrelation function analysis of the background. We find that our measurement extragalactic background intensity is significantly greater than the total point-like source contribution expected if sources are responsible for all the observed background intensity in the 1-2 keV range. For a further confirmation of the theoretical prediction of the hot intergalactic medium, we have conducted a pilot project to search for enhanced X-ray-emitting features near rich clusters of galaxies. We have reported the discovery of an elongated complex of extended X-ray-emitting objects in and around the galaxy cluster A2125, based on an archival deep ROSAT/PSPC observation. Using multicolor optical imaging of galaxies in the field, we find that this complex represents a hierarchical superstructure spanning approx. 11 Mpc at the redshift approx. 0.247. The multiple peak X-ray morphology and large blue galaxy fraction of A2125 indicate that the cluster is undergoing a coalescence of subunits. The superstructure contains two additional clusters, projected at distances of only 3 and 4.3 Mpc from A2125. The most interesting feature is, however, the low-surface-brightness X-ray emission from a moderate galaxy concentration away from individual clusters. The emission likely arises in a hot (approx. 10(exp 7) K) intergalactic medium, as predicted in N-body/hydro simulations of structure formation. These results demonstrate the potential of X-ray observations as a powerful tool to study the large-scale structure of the universe.

Wang, Q. Daniel

1997-01-01

374

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

SciTech Connect

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.

Wang, Linghua [Department of Geophysics, Peking University, 100871 Beijing (China); Lin, Robert P.; Salem, Chadi; Pulupa, Marc; Larson, Davin E.; Luhmann, Janet G. [Space Sciences Laboratory, University of California, Berkeley, CA 94720-7450 (United States); Yoon, Peter H., E-mail: wanglhwang@gmail.com [School of Space Research, Kyung Hee University, Yongin, Gyeonggi (Korea, Republic of)

2012-07-01

375

Design and fabrication of a surface conversion negative ion source and an 80 keV pre-accelerator  

SciTech Connect

The design and fabrication of a surface conversion negative ion source and an 80 keV pre-accelerator intended for use as a proof-of-principle demonstration leading to a radiation-hardened 400 keV TFF based beamline for the next generation mirror or tokamak reactor will be described in this paper. Experience gained in a previous source and accelerator module was utilized to redefine the overall design and construction for this second generation CW device. The source will provide 1 to 2 amps of H/sup -/ for acceleration by a 3 electrode 80 keV preaccelerator. Particular attention was placed on the mounting of the source to the primary high-voltage insulator, the insulator itself, magnet installation, converter shape and construction, cesium injector and exit aperture design, and accelerator construction, with an overall emphasis on serviceability.

Matuk, C.A.; Anderson, O.A.; Biagi, L.A.; Berkner, K.H.; Cooper, W.S.; Ehlers, K.W.; Kwan, J.; Leung, K.N.; Lietzke, A.F.; Maruyama, Y.

1983-12-01

376

Measurements of L shell X-ray yields of thick Ag target by 6-29 keV electron impact  

NASA Astrophysics Data System (ADS)

In this paper, the L shell X-ray yields for a thick Ag target have been measured at incident electron energies of 6-29 keV. The experimental values are compared with the Monte Carlo simulation results that are obtained by using the PENELOPE code, in which the inner-shell ionization cross sections by electron impact calculated in the theoretical frame of distorted wave Born approximation are used. The experimental and simulation values are in agreement with ~10% difference. Meanwhile, the L shell X-ray production cross sections are also obtained based on the measured L shell X-ray yields for a thick Ag target in this paper, and are compared with other experimental Ag L shell X-ray production cross section data by electron and positron impact measured previously and some theoretical models. Some factors that could affect these comparisons are also discussed in this paper.

Zhao, J. L.; Tian, L. X.; Li, X. L.; An, Z.; Zhu, J. J.; Liu, M. T.

2015-02-01

377

A comparative study of defects in LiF implanted with 100 KeV Al, Mg and Ar by slow Positron Annihilation Spectroscopy  

NASA Astrophysics Data System (ADS)

The fluence-dependent evolution of defects in LiF implanted at room temperature with Al+, Mg+, Ar+ ions is measured using the slow positron beam technique. Samples were implanted with 100 KeV ions to doses of 1015 and 1016 cm-2. Doppler broadened spectra of positron annihilation as a function of positron incident energy are measured and are analyzed by the computer program VEPFIT. The depth profiles of the defect distribution are presented and discussed as a function of dose and nature of the implanted ions. The Positron Annihilation Spectroscopy (PAS) results are correlated with optical absorption measurements on the crystals, and are shown to provide important information about the spatial extent of defects in ion-implanted samples.

Sendezera, E. J.; Davidson, A. T.; Kozakiewicz, A. G.; Anwand, W.; Brauer, G.; Nicht, E. H.

378

Analysis of auroras caused by precipitation of high energy electrons  

NASA Astrophysics Data System (ADS)

It has been regarded that keV electrons precipitating into the upper atmosphere are the main source of auroral emissions. Hence, extensive efforts have been made to relate observed auroral intensity to the precipitating energy flux of these electrons while the role of the electrons above ~ 20 keV was not examined well. Our previous study showed the intensity of the long LBH (1600 Å - 1715 Å) was enhanced very much compared to that of the short LBH (1400 Å - 1500 Å) when the characteristic energy of the precipitating electrons increased from 1 keV to >7 keV, in accordance with the theoretical models. In this paper, we would like to present the results of our study for even higher energy electrons. Measurement of electrons for the energy above ~ 20 keV is technically difficult and in fact, we were unable to find any previous observations for this high energy range except the one made on STSAT-1 for the electrons of 170 ~ 360 keV. Thus, we selected the events in which the fluxes both in the low energy (100 eV ~ 20 keV) and in the high energy (170 ~ 360 keV) were enhanced, and examined the auroral spectra for these events observed simultaneously by the imaging spectrograph on the same spacecraft. While the accurate characteristic energy could not be determined because of the gap in the energy range, our result showed the intensity ratio of the long LBH to the short LBH ranged from 1.2 to 2.0 in these events, in contrast to 1.0 or smaller for the events in which the highest enhancement was seen only in the low energy. Our study suggests that intense auroras might be accompanied by high energy electrons above 20 keV.

Lee, C.; Lee, J.; Min, K.; Parks, G. K.; Fillingim, M. O.; Cho, K.; Kim, K.; Han, W.; Edelstein, J.

2009-12-01

379

Energy dependence of Fricke-xylenol orange gel and gel based on Turnbull blue for low-energy photons  

NASA Astrophysics Data System (ADS)

The paper describes the energy dependence of two types of radiochromic gels, a Fricke-xylenol orange gel (FX gel) and a gel based on Turnbull blue (TB gel), on low energy photons between 14 and 145 keV. Gel samples were irradiated at reference photon fields at the Czech Metrology Institute and evaluated by two independent optical methods. Measurements revealed that the response of the TB gel is independent on photon energy down to at least 14 keV photons, while the FX gel is energy dependent for photons below roughly 50 keV.

Šolc, Jaroslav; Sochor, Vladimír; Kozubíková, Petra

2015-01-01

380

Analysis of auroras caused by precipitation of high energy electrons  

Microsoft Academic Search

It has been regarded that keV electrons precipitating into the upper atmosphere are the main source of auroral emissions. Hence, extensive efforts have been made to relate observed auroral intensity to the precipitating energy flux of these electrons while the role of the electrons above ~ 20 keV was not examined well. Our previous study showed the intensity of the

C. Lee; J. Lee; K. Min; G. K. Parks; M. O. Fillingim; K. Cho; K. Kim; W. Han; J. Edelstein

2009-01-01

381

The production and sputtering of S2 by keV ion bombardment  

NASA Technical Reports Server (NTRS)

The ion bombardment of S-containing molecules in comets is simulated experimentally. Mass-analyzed 30-keV beams of Ar(+) and He(+) are directed at solid S, H2S, and CS2 targets at temperatures 15 K, and the neutral molecular species produced are ionized and analyzed using a quadrupole mass spectrometer. The dominant species detected are S1 and S2 for the S target, H2S and S2 for the H2S target, and S, CS, S2, and CS2 for the CS2 target. In the latter case, it is found that after about 10 to the 14th He(+) ions/sq cm have struck the target, further sputtering is prevented by formation of a dark brown deposit which is stable at room temperature; the residue forms more slowly when Ar(+) ions are used. These results, indicating relatively efficient S2 production by ion bombardment, are applied to theoretical models of S2 production and/or ejection by solar-wind, solar-flare, or cosmic-ray ions striking comets. It is found that direct solar-wind production of S2 by sputtering is unlikely at realistic bombardment rates, but that H2S-S2 conversion by energetic ions could be significant, with less stringent ice-temperature and irradiation-flux constraints than in the case of S2 production by photons.

Boring, J. W.; Chrisey, D. B.; Oshaughnessy, D. J.; Phipps, J. A.; Zhao, N.

1986-01-01

382

On the keV sterile neutrino search in electron capture  

NASA Astrophysics Data System (ADS)

A joint effort of cryogenic microcalorimetry (CM) and high-precision Penning-trap mass spectrometry (PT-MS) in investigating atomic orbital electron capture (EC) can shed light on the possible existence of heavy sterile neutrinos with masses from 0.5 to 100 keV. Sterile neutrinos are expected to perturb the shape of the atomic de-excitation spectrum measured by CM after a capture of the atomic orbital electrons by a nucleus. This effect should be observable in the ratios of the capture probabilities from different orbits. The sensitivity of the ratio values to the contribution of sterile neutrinos strongly depends on how accurately the mass difference between the parent and the daughter nuclides of EC transitions can be measured by, for example, PT-MS. A comparison of such probability ratios in different isotopes of a certain chemical element allows one to exclude many systematic uncertainties, and thus could make feasible a determination of the contribution of sterile neutrinos on a level below 1%. Several electron capture transitions suitable for such measurements are discussed.

Filianin, P. E.; Blaum, K.; Eliseev, S. A.; Gastaldo, L.; Novikov, Yu N.; Shabaev, V. M.; Tupitsyn, I. I.; Vergados, J.

2014-09-01

383

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

NASA Astrophysics Data System (ADS)

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 ?A/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.

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

2001-04-01

384

The Poker Face of the Majoron Dark Matter Model: LUX to keV Line  

E-print Network

We study the viability of pseudo Nambu-Goldstone bosons (Majorons) arising in see-saw models as dark matter candidates. Interestingly the stability of the Majoron as dark matter is related to the scale that sets the see-saw and leptogenesis mechanisms, while its annihilation and scattering cross section off nuclei can be set through the Higgs portal. For $\\mathcal{O}(GeV) - \\mathcal{O}(TeV)$ Majorons, we compute observables such as the abundance, scattering cross section, Higgs invisible decay width, and emission lines and compare with current data in order to outline the excluded versus still viable parameter space regions. We conclude that the simplest Majoron dark matter models coupling through the Higgs portal, except at the Higgs resonance, are excluded by current direct detection data for Majorons lighter than $225$~GeV and future runnings are expected to rule out decisively the 1GeV-1TeV window. Lastly, we point out that light keV-scale Majorons whose relic density is set by thermal freeze-in from sterile neutrinos can account for the keV line observed by XMM-Newton observatory in the spectrum of 73 galaxy clusters, within a see-saw model with a triplet Higgs.

Farinaldo S. Queiroz; Kuver Sinha

2014-04-04

385

Teflon impregnated anatase TiO2 nanoparticles irradiated by 80 keV Xe+ ions  

NASA Astrophysics Data System (ADS)

We report the effect of 80 keV Xe+ ion irradiation on the morphological and optical responses of TiO2 nanoparticles spread over commercially available polytetrafluoroethylene (PTFE, Teflon). These nanoparticles were synthesized via a convenient, sol-gel approach with titanium isopropoxide as the main precursor. From X-ray diffraction (XRD) studies we found that, the nanoparticles crystallize in anatase phase and with a preferential orientation of crystallites along (1 0 1) plane. Upon irradiation at a fluence of 1.25 × 1017 ions/cm2, the nanoparticle dimension was found to increase from a value of ˜9 nm to ˜20-30 nm. Essentially, particle growth is predicted as a consequence of swelling behavior accompanied by the formation of Xe van der Waal crystals in isolated regions of nano-titania. Evidence of nanoripples was also witnessed on the surface of the irradiated nano-titania. The morphological evolution was assessed both by atomic force and transmission electron microscopies (AFM and TEM) independently. From the UV-Vis optical absorption studies, the estimated optical band gap was found to drop with increasing fluence, while refractive index exhibited a remarkable improvement. Photoluminescence (PL) studies have revealed that, the band edge emission and those due to the self trapped excitons (STE) and other oxygen vacancy related ones were manifested considerably as a result of Xe ion irradiation.

Khanam, Rizwin; Paul, Nibedita; Kumar, P.; Kanjilal, D.; Ahmed, Gazi A.; Mohanta, Dambarudhar

2014-10-01

386

In situ observation of microstructure evolution in tungsten under 400 keV Kr+ irradiation  

NASA Astrophysics Data System (ADS)

Tungsten was irradiated with 400 keV Kr+ ions using the IVEM-Tandem Facility at Argonne National Laboratory. The evolution of microstructure and gas bubbles during the irradiation was observed by in situ transmission electron microscopy. Under irradiation, dislocation loops were created and grew into an increased density of network dislocations with increasing Kr+ ion fluence. The irradiation induced final microstructure consists of dislocation cells ?50 nm in diameter separated by dislocation walls. The irradiation also induced formation of Kr gas bubbles with an average diameter of 1.4 nm after 3.0 × 1016 ions/cm2 at 525 K. The gas bubbles were observed to grow to 2.6 nm diameter after additional Kr-irradiation of 5.0 × 1016 ions/cm2 at 815 K. The relationship between bubble size and irradiation time was obtained from experimental data obtained at 815 K and an empirical formula for calculating Kr bubble size was developed by fitting bubble growth equations with experiment data. The growth mechanisms of Kr gas bubbles in tungsten are discussed.

Ran, Guang; Huang, Shilin; Huang, Zijing; Yan, Qingzhi; Xu, Jiangkun; Li, Ning; Wang, Lumin

2014-12-01

387

7 keV Dark Matter as X-ray Line Signal in Radiative Neutrino Model  

E-print Network

We study a light dark matter in a radiative neutrino model to explain the X-ray line signal at about $3.5$ keV recently reported by XMN-Newton X-ray observatory using data of various galaxy clusters and Andromeda galaxy. The signal requires very tiny mixing between the dark matter and an active neutrino; $\\sin^2 2\\theta\\approx 10^{-10}$. It could suggest that such a light dark matter cannot contribute to the observed neutrino masses if we use the seesaw mechanism. In other words, neutrino masses might come a structure different from the dark matter. We propose a model in which Dirac type active neutrino masses are induced at one-loop level. On the other hand the mixing between active neutrino and dark matter are generated at two-loop level. As a result we can explain both the observed neutrino masses and the X-ray line signal from the dark matter decay with rather mild hierarchy of parameters in TeV scale.

Seungwon Baek; Hiroshi Okada

2014-03-20

388

100 keV electron backscattered range and coefficient for silicon.  

SciTech Connect

The authors have measured the range and intensity of backscattered electrons in silicon from a 100 keV source using a process independent method. Backscattered electrons contributed to the total dose of features written in a negative tone electron beam resist. Instead of measuring the height of the resist and using a contrast curve to convert the resist height to dose, the heights of the features were made equal by adjusting the backscattered contribution through dose assignments. Creating features of equal height eliminated the need to use a contrast curve to convert from resist height to total dose. Also, it allowed for measurements of the backscattered contribution from larger distances. Using a circularly symmetric torus pattern, the three-dimensional backscatter problem was reduced to a 1-dimensional Gaussian form. The authors measured the range of the backscattered electrons, {beta}, to be 31.08 {+-} 0.06 {micro}m. By varying the writing dose of the pattern, we determined the backscatter coefficient, {eta}, to be 0.63 {+-} 0.03.

Czaplewski, D.A.; Ocola, L.E. (Center for Nanoscale Materials)

2012-01-01

389

Energy.  

ERIC Educational Resources Information Center

This issue focuses on the theme of "Energy," and describes several educational resources (Web sites, CD-ROMs and software, videos, books, activities, and other resources). Sidebars offer features on alternative energy, animal energy, internal combustion engines, and energy from food. Subthemes include harnessing energy, human energy, and natural…

Online-Offline, 1998

1998-01-01

390

The determination of shadow cone dimensions for 0.5-5 keV Ar, Kr and Xe projectiles  

NASA Astrophysics Data System (ADS)

The shadow cones of 0.5-5.0 keV Ar, Kr and Xe projectiles scattered from a range of target atoms between C and Cs have been calculated by classical scattering theory using the Ziegler-Biersack-Littmark potential. The results are compared with existing literature algorithms, and the concept of a universal shadow cone curve is examined.

Tan, Hean Seng; Karolewski, M. A.

1993-02-01

391

The attenuation coefficient of ammonium chloride for 662 keV gamma radiation, measured for dilute solutions  

NASA Astrophysics Data System (ADS)

The technique developed for the direct measurement of linear attenuation and mass attenuation (or absorption) coefficients of dilute solutions of salts has been applied to the attenuation of 662 keV gamma rays from 137Cs in dilute NH 4Cl solution.

Teli, M. T.; Chaudhari, L. M.

1996-04-01

392

A Catalog of Soft X-Ray Shadows, and More Contemplation of the 1/4 KeV Background  

NASA Technical Reports Server (NTRS)

This paper presents a catalog of shadows in the 1/4 keV soft X-ray diffuse background 4 (SXRB) that were identified by a comparison between ROSAT All-Sky Survey maps and DIRB&corrected IRAS 100 micron maps. These "shadows" are the negative correlations between the surface brightness of the SXRB and the column density of the Galactic interstellar medium (ISIM) over limited angular regions (a few degrees in extent). We have compiled an extensive but not exhaustive set of 378 shadows in the polar regions of the Galaxy (Absolute value (beta) > and approximately equal 20 deg.), and determined their foreground and background X-ray intensities (relative to the absorbing features), and the respective hardness ratios of that emission. The portion of the sky that was examined to find these shadows was restricted in general to regions where the minimum column density is less than and approximately equal to 4 x 10(exp 20) H/square cm, i.e., relatively high Galactic latitudes, and to regions away from distinct extended features in the SXRB such as supernova remnants and superbubbles. The results for the foreground intensities agree well with the recent results of a general analysis of the local 1/4 KeV emission while the background intensities show additional. but not unexpected scatter. The results also confirm the existence of a gradient in the hardness of the local 1/4 keV emission along a Galactic center/ anticenter axis with a temperature that varies from 10(exp 6.13) K to 10(exp 6.02) K, respectively. The average temperature of the foreground component from this analysis is 10(exp 6.08) K, compared to 10(exp 6.06) K in the previous analysis. Likewise, the average temperature for the distant component for the current and previous analyses are 10(exp 6.06) K and 10(exp 6.02) K, respectively. Finally, the results for the 1/4 keV halo emission are compared to the observed fluxes at 3/4 keV, where the lack of correlation suggests that the Galactic halo's 1/4 keV and 3/4 keV fluxes are likely produced by separate emission regions.

Snowden, S. L.; Freyberg, M. J.; Kuntz, K. D.; Sanders, W. T.

1999-01-01

393

2-20 ns interframe time 2-frame 6.151 keV x-ray imaging on the recently upgraded Z Accelerator: A progress report  

SciTech Connect

When used for the production of an x-ray imaging backlighter source on Sandia National Laboratories' recently upgraded 26 MA Z Accelerator, the terawatt-class, multikilojoule, 526.57 nm Z-Beamlet laser (ZBL) [P. K. Rambo et al., Appl. Opt. 44, 2421 (2005)], in conjunction with the 6.151 keV (1s{sup 2}-1s2p triplet line of He-like Mn) curved-crystal imager [D. B. Sinars et al., Rev. Sci. Instrum. 75, 3672 (2004); G. R. Bennett et al., Rev. Sci. Instrum. 77, 10E322 (2006)], is capable of providing a high quality x radiograph per Z shot for inertial confinement fusion (ICF), complex hydrodynamics, and other high-energy-density physics experiments. For example, this diagnostic has recently afforded microgram-scale mass perturbation measurements on an imploding ignition-scale 1 mg ICF capsule [G. R. Bennett et al., Phys. Rev. Lett. 99, 205003 (2007)], where the perturbation was initiated by a surrogate deuterium-tritium (DT) fuel fill tube. Using an angle-time multiplexing technique, ZBL now has the capability to provide two spatially and temporally separated foci in the Z chamber, allowing 'two-frame' imaging to be performed, with an interframe time range of 2-20 ns. This multiplexing technique allows the full area of the four-pass amplifiers to be used for the two pulses, rather than split the amplifiers effectively into two rectangular sections, with one leg delayed with respect to the other, which would otherwise double the power imposed onto the various optics thereby halving the damage threshold, for the same irradiance on target. The 6.151 keV two frame technique has recently been used to image imploding wire arrays, using a 7.3 ns interframe time. The diagnostic will soon be converted to operate with p-rather than s-polarized laser light for enhanced laser absorption in the Mn foil, plus other changes (e.g., operation at the possibly brighter 6.181 keV Mn 1s{sup 2}-1s2p singlet line), to increase x-ray yields. Also, a highly sensitive inline multiframe ultrafast (1 ns gate time) digital x-ray camera is being developed [G. R. Bennett et al., Rev. Sci. Instrum. 77, 10E322 (2006)] to extend the system to 'four-frame' and markedly improve the signal-to-noise ratio. [At present, time-integrating Fuji BAS-TR2025 image plate (scanned with a Fuji BAS-5000 device) forms the time-integrated image-plane detector.].

Bennett, G. R.; Smith, I. C.; Shores, J. E.; Sinars, D. B.; Robertson, G.; Atherton, B. W.; Jones, M. C.; Porter, J. L. [Sandia National Laboratories, P.O. Box 5800, Albuquerque, New Mexico 87185-1193 (United States)

2008-10-15

394

NaI(Tl) electron energy resolution  

NASA Astrophysics Data System (ADS)

NaI(Tl) electron energy resolution ?e was measured using the Modified Compton Coincidence Technique (MCCT). The MCCT allowed detection of nearly monoenergetic internal electrons resulting from the scattering of incident 662 keV gamma rays within a primary NaI(Tl) detector. Scattered gamma rays were detected using a secondary HPGe detector in a coincidence mode. Measurements were carried out for electron energies ranging from 16 to 438 keV, by varying the scattering angle. Measured HPGe coincidence spectra were deconvolved to determine the scattered energy spectra from the NaI(Tl) detector. Subsequently, the NaI(Tl) electron energy spectra were determined by subtracting the energy of scattered spectra from the incident source energy (662 keV). Using chi-squared minimization, iterative deconvolution of the internal electron energy spectra from the measured NaI(Tl) spectra was then used to determine ?e at the electron energy of interest. ?e values determined using this technique represent variations in light production from monoenergetic electrons, light collection at the photomultiplier tube (PMT) photocathode, photoelectron production, photoelectron collection at the first dynode, and PMT gain, as well as noise from the accompanying electronics. It has been found that the electron energy resolution varies from 24.8% at 16 keV to 6.7% at 438 keV. Results from this study can be used to verify the significance of the different contributions to intrinsic energy resolution.

Mengesha, W.; Valentine, J. D.

2002-06-01

395

The 2-79 keV X-Ray Spectrum of the Circinus Galaxy with NuSTAR, XMM-Newton, and Chandra: A Fully Compton-thick Active Galactic Nucleus  

NASA Astrophysics Data System (ADS)

The Circinus galaxy is one of the closest obscured active galactic nuclei (AGNs), making it an ideal target for detailed study. Combining archival Chandra and XMM-Newton data with new NuSTAR observations, we model the 2-79 keV spectrum to constrain the primary AGN continuum and to derive physical parameters for the obscuring material. Chandra's high angular resolution allows a separation of nuclear and off-nuclear galactic emission. In the off-nuclear diffuse emission, we find signatures of strong cold reflection, including high equivalent-width neutral Fe lines. This Compton-scattered off-nuclear emission amounts to 18% of the nuclear flux in the Fe line region, but becomes comparable to the nuclear emission above 30 keV. The new analysis no longer supports a prominent transmitted AGN component in the observed band. We find that the nuclear spectrum is consistent with Compton scattering by an optically thick torus, where the intrinsic spectrum is a power law of photon index ? = 2.2-2.4, the torus has an equatorial column density of N H = (6-10) × 1024 cm-2, and the intrinsic AGN 2-10 keV luminosity is (2.3-5.1) × 1042 erg s-1. These values place Circinus along the same relations as unobscured AGNs in accretion rate versus ? and LX versus L IR phase space. NuSTAR's high sensitivity and low background allow us to study the short timescale variability of Circinus at X-ray energies above 10 keV for the first time. The lack of detected variability favors a Compton-thick absorber, in line with the spectral fitting results.

Arévalo, P.; Bauer, F. E.; Puccetti, S.; Walton, D. J.; Koss, M.; Boggs, S. E.; Brandt, W. N.; Brightman, M.; Christensen, F. E.; Comastri, A.; Craig, W. W.; Fuerst, F.; Gandhi, P.; Grefenstette, B. W.; Hailey, C. J.; Harrison, F. A.; Luo, B.; Madejski, G.; Madsen, K. K.; Marinucci, A.; Matt, G.; Saez, C.; Stern, D.; Stuhlinger, M.; Treister, E.; Urry, C. M.; Zhang, W. W.

2014-08-01

396

The 3.5 keV X-ray line signature from annihilating and decaying dark matter in Weinberg model  

E-print Network

Recently two groups independently observed unidentified X-ray line signal at the energy 3.55 keV from the galaxy clusters and Andromeda galaxy. We show that this anomalous signal can be explained in annihilating dark matter model, for example, fermionic dark matter model in hidden sector with global $U(1)_X$ symmetry proposed by Weinberg. There are two scenarios for the production of the annihilating dark matters. In the first scenario the dark matters with mass 3.55 keV decouple from the interaction with Goldstone bosons and go out of thermal equilibrium at high temperature ($>$ 1 TeV) when they are still relativistic, their number density per comoving volume being essentially fixed to be the current value. The correct relic abundance of this warm dark matter is obtained by assuming that about ${\\cal O}(10^3)$ relativistic degrees of freedom were present at the decoupling temperature or alternatively large entropy production occurred at high temperature. In the other scenario, the dark matters were absent at high temperature, and as the universe cools down, the SM particles annihilate or decay to produce the dark matters non-thermally as in `freeze-in' scenario. It turns out that the DM production from Higgs decay is the dominant one. In the model we considered, only the first scenario can explain both X-ray signal and relic abundance. The X-ray signal arises through $p$-wave annihilation of dark matter pair into two photons through the scalar resonance without violating the constraints from big bang nucleosynthesis, cosmic microwave background, and astrophysical objects such as red giants or white dwarfs. We also discuss the possibility that the signal may result from a decaying dark matter in a simple extension of Weinberg model.

Seungwon Baek; P. Ko; Wan-Il Park

2014-05-15

397

Energy!  

NSDL National Science Digital Library

Students will be introduced to energy, what it is and the different forms of energy. Energy - the ability to do work! Energy is necessary to our everyday lives and is found all around us all the time. We can not do anything without using energy. For the purposes of this class it is important that we understand there are ...

Larsen, Mr.

2009-09-24

398

Cross sections of K-shell ionization by electron impact, measured from threshold to 100 keV, for Au and Bi  

NASA Astrophysics Data System (ADS)

We have measured cross sections for the ionization of the K shell by electrons with energies from the respective thresholds up to 100 keV, for Au and Bi. The experimental values are obtained by dividing the number of counts in the K? peak by the number of counts in an energy interval near the tip of the bremsstrahlung continuum, and multiplying this ratio by the theoretical estimate of bremsstrahlung emission towards the detector in this energy interval. Although such a procedure has already been described in the literature, here it is implemented avoiding some of the simplifications made in earlier works. Our experimental cross sections, which are the first ones to be reported for atoms with Z>47 close to the threshold, are in reasonable agreement with the theoretical predictions of the semirelativistic distorted-wave Born approximation. Hippler's plane-wave Born approximation with corrections for Coulomb and exchange effects yields cross sections that are closer to the experimental data than those evaluated from the relativistic binary-encounter-Bethe model.

Fernández-Varea, J. M.; Jahnke, V.; Maidana, N. L.; Malafronte, A. A.; Vanin, V. R.

2014-08-01

399

Experimental evidence for the curve crossing mechanism for collisional excitation in keV N2+*/He collisions by emission spectroscopy.  

PubMed

Collision-induced emission (CIE) experiments were carried out by coupling a spectrograph and charge-coupled device detector (CCD) to a commercial analytical mass spectrometer. An Einzel lens and a deceleration-reacceleration lens assembly as described in the current article were installed in the mass spectrometer to allow for the deceleration of the ions before collision. Collision-induced emission spectra of N2+*/He collisions at lab frame collision energies from 2 to 8 keV were obtained from 190-1020 nm. The emissions were assigned to the Deltav=+2, +1, 0, -1, -2 vibrational transition progression in the N2+* B 2Sigmau+-->X 2Sigmag+ electronic transition as well as some atomic lines from the fragments N+, N* and the target gas He. N2+* A 2u-->X 2Sigmag+ emission was also observed but was very weak due to the long lifetime of the A 2u state. The relative intensities of the N2+*, N, and N+ emissions are independent of the ion translational energy within the studied energy range. This observation supports the curve-crossing mechanism for collisional excitation, suggesting that a complicated sequence of curve-crossings takes place upon collisional activation. PMID:17266217

Poon, Clement; Mayer, Paul M

2007-02-01

400

Measurement of the F19(p,?)Ne20 reaction and interference terms from Ec.m.=200-760 keV  

NASA Astrophysics Data System (ADS)

The F19(p,?)Ne20 reaction represents the only breakout path for the carbon-nitrogen-oxygen cycle operating at temperatures below T=0.1 GK, an energy regime important for main-sequence hydrogen burning as well as hydrogen burning in asymptotic giant branch stars. Large experimental uncertainties exist due to unknown low energy direct and resonant reaction contributions that have been difficult to study because of the high ?-ray background from the F19(p,?2?) reaction. A new detection technique has been developed at the University of Notre Dame to measure the F19(p,?) and F19(p,?i?) reactions over an energy range of Ec.m.=200-760 keV. The analysis was carried out in a Breit-Wigner framework. This allowed a new determination of the resonance parameters as well as a first measurement of the signs of the interference terms. Partial widths and resonance strengths are reported for the resonances in this region.

Couture, A.; Beard, M.; Couder, M.; Görres, J.; Lamm, L.; Leblanc, P. J.; Lee, H. Y.; O'Brien, S.; Palumbo, A.; Stech, E.; Strandberg, E.; Tan, W.; Uberseder, E.; Ugalde, C.; Wiescher, M.; Azuma, R.

2008-01-01

401

Structural and optical properties of 70-keV carbon ion beam synthesized carbon nanoclusters in thermally grown silicon dioxide  

NASA Astrophysics Data System (ADS)

The structural and optical properties of carbon nanoclusters formed in thermally grown silicon dioxide film via the ion beam synthesis process have been investigated. A low-energy (70 keV) carbon ion beam (C-) at a fluence of 3 × 1017 atoms/cm2 was used for implantation into a thermally grown silicon dioxide layer (500 nm thick) on a Si (100) wafer. Several parts of the implanted samples were subsequently annealed in a gas mixture (4 % H2 + 96 % Ar) at 900 °C for different time periods. The as-implanted and annealed samples were characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy, Raman spectroscopy, transmission electron microscopy (TEM), and photoluminescence spectroscopy (PL). The carbon ion implantation depth profile was simulated using a widely used Monte Carlo-based simulation code SRIM-2012. Additionally, the elemental depth profile of the implanted carbon along with host elements of silicon and oxygen were simulated using a dynamic ion-solid interaction code T-DYN, which incorporates the effects of the surface sputtering and gradual change in the elemental composition in the implanted layers due to high-fluence ion implantation. The elemental depth profile obtained from the XPS measurements matches closely to the T-DYN predictions. Raman measurements indicate the formation of graphitic phases in the annealed samples. The graphitic peak (G-peak) was found to be increased with the annealing time duration. In the sample annealed for 10 min, the sizes of the carbon nanoclusters were found to be 1-4 nm in diameter using TEM. The PL measurements at room temperature using a 325-nm laser show broad-band emissions in the ultraviolet to visible range in the as-implanted sample. Intense narrow bands along with the broad bands were observed in the annealed samples. The defects present in the as-grown samples along with carbon ion-induced defect centers in the as-implanted samples are the main contributors to the observed broad-band luminescence centered around 2.4 and 2.9 eV. The intense narrow peaks observed in the PL spectra centered on ~2.67 and 2.8 eV with full width at half maxima ? 150 meV are believed to be mainly due to the quantum size effects of the carbon nanoclusters formed in the annealed samples. The relative intensities of the narrow peaks are seen to be changing with the annealing time interval. This may be due to the change in the size distribution of the carbon nanoclusters.

Poudel, P. R.; Poudel, P. P.; Paramo, J. A.; Strzhemechny, Y. M.; Rout, B.; McDaniel, F. D.

2015-02-01

402

Structural and optical properties of 70-keV carbon ion beam synthesized carbon nanoclusters in thermally grown silicon dioxide  

NASA Astrophysics Data System (ADS)

The structural and optical properties of carbon nanoclusters formed in thermally grown silicon dioxide film via the ion beam synthesis process have been investigated. A low-energy (70 keV) carbon ion beam (C-) at a fluence of 3 × 1017 atoms/cm2 was used for implantation into a thermally grown silicon dioxide layer (500 nm thick) on a Si (100) wafer. Several parts of the implanted samples were subsequently annealed in a gas mixture (4 % H2 + 96 % Ar) at 900 °C for different time periods. The as-implanted and annealed samples were characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy, Raman spectroscopy, transmission electron microscopy (TEM), and photoluminescence spectroscopy (PL). The carbon ion implantation depth profile was simulated using a widely used Monte Carlo-based simulation code SRIM-2012. Additionally, the elemental depth profile of the implanted carbon along with host elements of silicon and oxygen were simulated using a dynamic ion-solid interaction code T-DYN, which incorporates the effects of the surface sputtering and gradual change in the elemental composition in the implanted layers due to high-fluence ion implantation. The elemental depth profile obtained from the XPS measurements matches closely to the T-DYN predictions. Raman measurements indicate the formation of graphitic phases in the annealed samples. The graphitic peak (G-peak) was found to be increased with the annealing time duration. In the sample annealed for 10 min, the sizes of the carbon nanoclusters were found to be 1-4 nm in diameter using TEM. The PL measurements at room temperature using a 325-nm laser show broad-band emissions in the ultraviolet to visible range in the as-implanted sample. Intense narrow bands along with the broad bands were observed in the annealed samples. The defects present in the as-grown samples along with carbon ion-induced defect centers in the as-implanted samples are the main contributors to the observed broad-band luminescence centered around 2.4 and 2.9 eV. The intense narrow peaks observed in the PL spectra centered on ~2.67 and 2.8 eV with full width at half maxima ? 150 meV are believed to be mainly due to the quantum size effects of the carbon nanoclusters formed in the annealed samples. The relative intensities of the narrow peaks are seen to be changing with the annealing time interval. This may be due to the change in the size distribution of the carbon nanoclusters.

Poudel, P. R.; Poudel, P. P.; Paramo, J. A.; Strzhemechny, Y. M.; Rout, B.; McDaniel, F. D.

2014-09-01

403

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

SciTech Connect

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.

Mio, A. M.; D'Arrigo, G.; Rimini, E.; Spinella, C. [IMM-CNR, Strada VIII 5, Zona Industriale, I-95121 Catania (Italy); Milazzo, R. G. [IMM-CNR, Strada VIII 5, Zona Industriale, I-95121 Catania (Italy); Dipartimento di Fisica e Astronomia, Universita di Catania, Via S. Sofia 64, I-95123 Catania (Italy); Peto, L.; Nadzeyka, A.; Bauerdick, S. [Raith GmbH, Konrad-Adenauer-Allee 8, 44263 Dortmund (Germany)

2013-01-28

404

The INTEGRAL/SPI 511 keV Signal from Hidden Valleys  

SciTech Connect

We examine under what circumstances the INTEGRAL/SPI 511 keV signal can originate from decays of MeV-scale composite states produced by: (A) thermonuclear (type Ia) or (B) core collapse supernovae (SNe). The requisite dynamical properties that would account for the observed data are quite distinct, for cases (A) and (B). We determine these requirements in simple hidden valley models, where the escape fraction problem is naturally addressed, due to the long lifetime of the new composite states. A novel feature of scenario (A) is that the dynamics of type Ia SNe, standard candles for cosmological measurements, might be affected by our mechanism. In case (A), the mass of the state mediating between the hidden sector and the SM e{sup +}e{sup -} could be a few hundred GeV and within the reach of a 500GeV e{sup +}e{sup -} linear collider. We also note that kinetic mixing of the photon with a light vector state may provide an interesting alternate mediation mechanism in this case. Scenarios based on case (B) are challenged by the need for a mechanism to transport some of the produced positrons toward the Galactic bulge, due to the inferred distribution of core collapse sources. The mass of the mediator in case (B) is typically hundreds of TeV, leading to long-lived particles that could, under certain circumstances, include a viable dark matter candidate. The appearance of long-lived particles in typical models leads to cosmological constraints and we address how a consistent cosmic history may be achieved.

Davoudiasl, H.; Perez, G.

2009-12-01

405

Energy  

NSDL National Science Digital Library

The Energy SciPack explores the many forms of energy and the concept that energy can change from one form to another. The focus is on Standards and Benchmarks related to energy, energy transfer, and the conservation of energy. Work and simple machines are used throughout the SciPack to explain energy transformations.In addition to comprehensive inquiry-based learning materials tied to Science Education Standards and Benchmarks, the SciPack includes the following additional components:? Pedagogical Implications section addressing common misconceptions, teaching resources and strand maps linking grade band appropriate content to standards. ? Access to one-on-one support via e-mail to content "Wizards".? Final Assessment which can be used to certify mastery of the concepts.Learning Outcomes:Energy: Different Kinds of Energy? Recognize that energy can be associated with non-living objects.? Reject the notion that energy is some physical entity or casual agent.? Recognize some common forms of energy, such as chemical, thermal, etc.? Classify different forms of energy as being either kinetic or potential energy (or both).Energy: Energy Transformations? Recognize that there are ways to measure the amount of different kinds of energy that allow us to track how much of one form is changed into another.? Recognize that energy is conserved, meaning it is not "used up" and does not appear out of nowhere.? Give examples of transformation of energy, including recognizing the forms of energy involved.? Construct an argument against an example that claims to be a perpetual motion machine.Energy: Thermal Energy, Heat, and Temperature? Distinguish between thermal energy and heat.? Explain thermal energy as the random motion of particles.? Cite examples of thermal energy being transferred and explain it as conduction, radiation, or convection.Energy: Useful and Not So Useful Energy? Explain why an energy transformation always appears to be less than 100% efficient.? Explain the apparent "loss" of energy in a transformation.? Relate the "spreading out" of thermal energy to the decrease in the usefulness of energy.

National Science Teachers Association (NSTA)

2007-03-21

406

Measurement of the Scintillation Yield of Low-Energy Electrons in Liquid Xenon  

E-print Network

We have measured the energy dependence of the liquid xenon (LXe) scintillation yield of electrons with energy between 2.1 and 120.2keV, using the Compton coincidence technique. A LXe scintillation detector with a very high light detection efficiency was irradiated with 137Cs {\\gamma} rays and the energy of the Compton-scattered {\\gamma} rays was measured with a high-purity germanium (HPGe) detector placed at different scattering angles. The excellent energy resolution of the HPGe detector allows the selection of events with Compton electrons of known energy in the LXe detector. We find that the scintillation yield initially increases as the electron energy decreases from 120 keV to about 60keV but then decreases by about 30% from 60keV to 2keV. The measured scintillation yield was also measured with conversion electrons from the 32.1 keV and 9.4 keV transitions of the 83mKr isomer, used as an internal calibration source. We find that the scintillation yield of the 32.1 keV transition is compatible with that o...

Aprile, E; Choi, B; Contreras, H A; Giboni, K -L; Goetzke, L W; Koglin, J E; Lang, R F; Lim, K E; Fernandez, A J Melgarejo; Persiani, R; Plante, G; Rizzo, A

2012-01-01

407

Angular distribution of Au and U L x-rays induced by 22.6-keV photons  

SciTech Connect

The angular distribution of the L x-ray fluorescent lines from Au and U induced by 22.6-keV x rays from a {sup 109}Cd has been measured. A Si(Li) detector having a resolution of 160 eV at 5.90 keV was used to detect these L lines over the angular range of 70 degree sign -150 degree sign . No strong anisotropy was observed as mentioned by some groups. In the case of Au, a maximum anisotropy of 5% was observed while for U it was within experimental errors (2%). From the angular distribution of the L1 line of Au, the alignment parameter was obtained and its value was found to be 0.10{+-}0.14.

Santra, S.; Mitra, D.; Sarkar, M.; Bhattacharya, D. [Saha Institute of Nuclear Physics, 1/AF, Bidhannagar, Kolkata 700064 (India)

2007-02-15

408

SMM observation of a cosmic gamma-ray burst from 20 keV to 100 MeV  

NASA Technical Reports Server (NTRS)

The Solar Maximum Mission gamma-ray spectrometer has detected an intense gamma-ray burst that occurred on August 5, 1984. The burst originated from a source in the constellation Hydra and lasted about 45 s. Its integral fluence at 20 keV was 0.003 erg/sq cm. Spectral evolution similar to other bursts detected by SMM was observed. The overall shape of the spectrum from 20 keV to 100 MeV, on timescales as short as 2 s, is relatively constant. This shape can be fitted by the sum of an exponential-type function and a power law. There is no evidence for narrow or broadened emission lines.

Share, G. H.; Matz, S. M.; Messina, D. C.; Nolan, P. L.; Chupp, E. L.

1986-01-01

409

High-Energy Photoemission at HASYLAB  

SciTech Connect

An instrument for high-energy X-ray photoelectron spectroscopy is operated at the BW2 wiggler beamline of HASYLAB. The photon energy ranges from 2.3 to 10 keV, the electron energy reaches up to 7.5 keV (including an optional 2.5 keV sample bias, the current electron analyzer limit is 5 keV). Using a Si(311) double crystal monochromator, the total energy resolution is 0.37 eV at 4.3 keV as determined from the Si 2p photoemission. For Si(111) typical values are 0.45 eV at 3 keV. The photon flux typically amounts to 5x1012 1/s for Si(111). Focusing is achieved by the combination of a sagittally bent monochromator crystal and a tangentially bent mirror in the monochromatic beam. The focus size (FWHM) at the sample is 0.25 mm (vertical) x 2 mm (horizontal) which is well matching the acceptance of the SCIENTA SES-200 electron analyzer. Selected results are shown to demonstrate the instrument performance.

Drube, W.; Eickhoff, Th.; Schulte-Schrepping, H.; Heuer, J. [Hamburger Synchrotronstrahlungslabor HASYLAB at Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, 22603 Hamburg (Germany)

2004-05-12

410

Differential cross sections for scattering of 0.5-, 1.5-, and 5.0-keV hydrogen atoms by He, H2, N2, and O2  

NASA Technical Reports Server (NTRS)

This paper reports measurements of absolute cross sections, differential in angle, for scattering of 0.5-, 1.5-, and 5.0-keV hydrogen atoms by He, H2, N2, and O2 at laboratory scattering angles between 0.1 and 5 deg. The measured cross sections are the sums of those for elastic and inelastic collisions having a fast H atom product and are needed for calculating energy transfer to the upper atmosphere from precipitating ring current particles.

Newman, J. H.; Chen, Y. S.; Smith, K. A.; Stebbings, R. F.

1986-01-01

411

Experimental evidence for Young's interference effects in autoionization following 30 keV He2++H2 collision  

NASA Astrophysics Data System (ADS)

The emission of electrons from autoionizing He** outgoing projectiles formed in a double capture 30 keV He2+ +H2 collision has been analysed at detection angles ranging from 90° up to 162°. The autoionization cross section differential in the angle is found to oscillate. This result is attributed to a Young interference mechanism produced by the postcollisional interaction of the emitted electron with the two-centre exploding H+ + H+ residual target.

J-Ychesnel; Hajaji, A.; Barrachina, R. O.; Frémont, F.

2007-03-01

412

TIME-RESOLVED 1-10 keV CRYSTAL SPECTROMETER FOR THE Z MACHINE AT SANDIA NATIONAL LABORATORIES  

SciTech Connect

We have designed, fabricated, calibrated, and fielded a fast, time-resolved 1-10 keV crystal spectrometer to observe the evolution of wire pinch spectra at the Z machine at Sandia National Laboratories. The instrument has two convex cylindrical crystals (PET and KAP). Both crystals Bragg reflect x-rays into an array of ten silicon diodes, providing continuous spectral coverage in twenty channels from 1.0 to 10 keV. The spectral response of the instrument has been calibrated from 1.0 to 6.3 keV at beamline X8A at the National Synchrotron Light Source. The time response of the 1-mm2 silicon detectors was measured with the Pulsed X-ray Source at Bechtel Nevada's Los Alamos Operations, where 2-nanosecond full-width half-maximum (FWHM) waveforms with 700-picosecond rise times typically were observed. The spectrometer has been fielded recently on several experimental runs at the Z Machine. In this paper, we present the time-resolved spectra resulting from the implosions of double-nested tungsten wire arrays onto 5-mm diameter foam cylinders. We also show the results obtained for a double-nested stainless steel wire array with no target cylinder. The spectrometer was located at the end of a 7.1-meter beamline on line-of sight (LOS)21/22, at an angle 12{sup o} above the equatorial plane, and was protected from the debris field by a customized dual-slit fast valve. The soft detector channels below 2.0 keV recorded large signals at pinch time coinciding with signals recorded on vacuum x-ray diodes (XRDs). On experiment Z993, the spectrometer channels recorded a second pulse with a hard x-ray emission spectrum several nanoseconds after pinch time.

D. V. Morgan; S. Gardner; R. Liljestrand; M. Madlener; S. Slavin; M. Wu

2003-06-01

413

Time-resolved 1-10 keV crystal spectrometer for the Z machine at Sandia national laboratories  

Microsoft Academic Search

We have designed, fabricated, calibrated, and fielded a fast, time-resolved 1-10 keV crystal spectrometer to observe the evolution of wire pinch spectra at the Z machine at Sandia national laboratories. The instrument has two convex cylindrical crystals (PET and KAP). Both crystals Bragg reflect X-rays into an array of ten silicon diodes, providing continuous spectral coverage in twenty channels from

D. V. Morgan; S. Gardner; R. Lijiestrand; M. Madlener; S. Slavin; M. Wu; T. J. Nash; V. L. Kantsyrev; D. A. Fedin

2003-01-01

414

Chemistry and structure of beta silicon carbide implanted with high-dose aluminum. [168 keV  

Microsoft Academic Search

Single-crystal [beta]-SiC was implanted with aluminum to 3.90 x 10[sup 17] ions\\/cm[sup 2] at 168 keV at 773 K. The resultant compositional and structural characteristics were studied by Rutherford backscattering spectrometry. Auger electron spectroscopy, X-ray photoelectron spectroscopy, and cross-sectional transmission electron microscopy. No aluminum redistribution was observed during implantation. The Si-to-C ratio exhibited a negative deviation from unity in the

Honghua Du; Zunde Yang; Matthew Libera; Dale C. Jacobson; Yu C. Wang; Robert F. Davis

1993-01-01

415

X-ray backlighting sources of 4 to 10 keV for laser-fusion targets  

Microsoft Academic Search

High-intensity, short-duration x-ray pulses are necessary to diagnose the compression of laser film targets. Present target designs are such that backlighting sources ranging from a few thousand electron volts to 100 keV will be necessary. The desired source durations range from a few tens of picoseconds for flash radiography to several nanoseconds for streaked backlighting, and the source occurrence must

V. C. Rupert; D. L. Matthews; L. N. Koppel

1981-01-01

416

Response of diamond particle detector using x-ray injection @ NSLS-X15A (19 keV)  

E-print Network

Response of diamond particle detector using x-ray injection @ NSLS-X15A (19 keV) T. Tsang BNL Nov-ray beam size: 0.2 x 0.2 mm2 Measured results Transmittance of Au pad: 0.92 Absorption of diamond: 0.0672 Typical photocurrent (ave): ~nA Diamond responsivity: 0.00464 A/W detector response map x-ray injection

McDonald, Kirk

417

ENA Images of the Heliosheath (5-55 keV) from Cassini/INCA: Updated with data 2010-2012  

NASA Astrophysics Data System (ADS)

We have published energetic neutral atom (ENA) images of the heliosheath from cumulative observations (2003 through 2009) of the Cassini/INCA ENA imager in orbit around Saturn. We have now augmented the data set to include observations during 2010-2012. All-sky maps are made in four energy channels (5-55 keV). The spatial coverage for a given year period depends upon the INCA viewing directions, which vary considerably from year to year due to the evolution of the Cassini orbit. Contamination due to the Sun (which moves 12deg/yr along the ecliptic) and to Saturn's magnetosphere must be carefully removed, but fortunately the obscurations due the Sun and Saturn move across the sky. Consequently, some regions of the sky are sampled in a half-year by the 90degx120deg INCA field of view with sufficient (6° x 6°) pixel statistics to allow quantitative interpretation of spatial structure and energy spectral dependence in these individual regions. The most recent data (2010-2012) contains some of the best ENA samplings of regions so far. Of particular interest are the regions associated with the pixels containing Voyager 1 and Voyager 2. We will report on this work in progress. See also the poster by Dialynas et al. (this Conference).

Roelof, E.; Krimigis, S.; Mitchell, D.; Decker, R.; Dialynas, K.

2012-04-01

418

Shifting of the electron-capture-to-the-continuum peak in proton-helium collisions at 10 and 20 keV  

SciTech Connect

A refined theoretical approach has been developed to study the double-differential cross sections (DDCS's) in proton-helium collisions as a function of the ratio of ionized electron velocity to the incident proton velocity. The refinement is done in the present coupled-channel calculation by introducing a continuum distorted wave in the final state coupled with discrete states including direct as well as charge transfer channels. It is confirmed that the electron-capture-to-the-continuum (ECC) peak is slightly shifted to a lower electron velocity than the equivelocity position. Comparing measurements and classical trajectory Monte Carlo (CTMC) calculations at 10 and 20 keV proton energies, excellent agreement of the ECC peak heights is achieved at both energies. However, a minor disagreement in the peak positions between the present calculation and the CTMC results is noted. A smooth behavior of the DDCS is found in the present calculation on both sides of the peak whereas the CTMC results show some oscillatory behavior particularly to the left of the peak, associated with the statistical nature of CTMC calculations.

Bhattacharya, S. [Department of Physics, Surendranath College, Kolkata 700 009 (India); Deb, N.C.; Roy, K. [Department of Theoretical Physics, Indian Association for the Cultivation of Science, Jadavpur, Calcutta 700 032 (India); Sahoo, S.; Crothers, D.S.F. [Department of Applied Mathematics and Theoretical Physics, Queen's University Belfast, Belfast BT7 1NN, Northern Ireland (United Kingdom)

2005-01-01

419

Observation of 511 keV peak high count rate in studying (n,x) and (g,x) reactions on terbium  

E-print Network

Experimental investigation of (n, x) and (g, x) reactions on Tb-159 with activation technique was carried out. Tb specimens of natural composition were irradiated with (d-d) and (d-t) neutrons using NG-300 neutron generator. Additionally the series of experiments were performed with application of M-30 microtrone as a source of electrons for bremsstrahlung spectra production with end point energies 7.5, 9.5, 11, 11.5, 12, 12.5, 16.5, and 18.5 MeV. Instrumental spectra of Tb specimens were measured with HPGe and Ge(Li) spectrometers. Within the main scope of nuclear reactions research and accurate {\\gamma}-spectrometry of Tb specimens a high count rate in 511 keV {\\gamma}-line peak was observed. The first-priority analysis of Tb specimen impurities was done with further attempts to explain a result of observations with reference to the specific nuclear properties of Tb which could appear due to complex GDR structure. The energy threshold of the process detected was determined around 12.2 MeV. The lower estimate of cross section value for this process was assumed and calculated.

I. Kadenko; N. Dzysiuk

2011-01-26

420

Observation of 511 keV peak high count rate in studying (n,x) and (g,x) reactions on terbium  

E-print Network

Experimental investigation of (n, x) and (g, x) reactions on Tb-159 with activation technique was carried out. Tb specimens of natural composition were irradiated with (d-d) and (d-t) neutrons using NG-300 neutron generator. Additionally the series of experiments were performed with application of M-30 microtrone as a source of electrons for bremsstrahlung spectra production with end point energies 7.5, 9.5, 11, 11.5, 12, 12.5, 16.5, and 18.5 MeV. Instrumental spectra of Tb specimens were measured with HPGe and Ge(Li) spectrometers. Within the main scope of nuclear reactions research and accurate {\\gamma}-spectrometry of Tb specimens a high count rate in 511 keV {\\gamma}-line peak was observed. The first-priority analysis of Tb specimen impurities was done with further attempts to explain a result of observations with reference to the specific nuclear properties of Tb which could appear due to complex GDR structure. The energy threshold of the process detected was determined around 12.2 MeV. The lower estimat...

Kadenko, I

2011-01-01

421

Constraints on 3.55 keV line emission from stacked observations of dwarf spheroidal galaxies  

E-print Network

Several recent works have reported the detection of an unidentified X-ray line at 3.55 keV, which could possibly be attributed to the decay of dark matter (DM) particles in the halos of galaxy clusters and in the M31 galaxy. We analyze all publicly-available XMM-Newton data of dwarf spheroidal galaxies to test the possible DM origin of the line. Dwarf spheroidal galaxies have high mass-to-light ratios and their interstellar medium is not a source of diffuse X-ray emission, thus they are expected to provide the cleanest DM decay line signal. Our analysis shows no evidence for the presence of the line in the stacked spectra of the dwarf galaxies. It excludes the sterile neutrino DM decay origin of the 3.5 keV line reported by Bulbul et al. (2014) at the level of 4.6 sigma under standard assumptions about the Galactic DM column density in the direction of selected dwarf galaxies and at the level of 3.3 sigma assuming minimal Galactic DM column density. As a by-product of our analysis, we provide updated upper limits to the mixing angle of sterile neutrino DM in the mass range between 2 and 20 keV.

D. Malyshev; A. Neronov; D. Eckert

2014-08-15

422

Astronomical Publications "The energy spectrum of the Crab nebula in the range 15 keV to 60  

E-print Network

chopper for use in infrared photometry". Observatory, 92, 140­141, 1972. 9. I.S. Glass and M.W. Feast, "An infrared object probably associated with OH 338.5+0.1". Ap Letts, 13, 81­83, 1973. 10. M.W. Feast and I with PKS radio sources". MNRAS, 162, 35­37p, 1973. 12. I.S. Glass and M.W. Feast, "Infrared photometry

Glass, Ian S.

423

New elastic electron scattering factors for the elements for incident energies of 10, 40, 60, and 90 keV  

SciTech Connect

An improved set of scattering factors for all neutral elements has bee completed for inclusion in the new edition of the International Tables of X-ray Crystallography . These calculations are compared with the former electron scattering factors and the deviations between the two are discussed.(AIP)

Ross, A.W.; Fink, M.

1986-12-01

424

Dependence of Cell Survival on Iododeoxyuridine Concentration in 35-keV Photon-Activated Auger Electron Radiotherapy  

SciTech Connect

Purpose: To measure and compare Chinese hamster ovary cell survival curves using monochromatic 35-keV photons and 4-MV x-rays as a function of concentration of the radiosensitizer iododeoxyuridine (IUdR). Methods and Materials: IUdR was incorporated into Chinese hamster ovary cell DNA at 16.6 {+-} 1.9%, 12.0 {+-} 1.4%, and 9.2 {+-} 1.3% thymidine replacement. Cells were irradiated from 1 to 8 Gy with 35-keV synchrotron-generated photons and conventional radiotherapy 4-MV x-rays. The effects of the radiation were measured via clonogenic survival assays. Surviving fraction was plotted vs. dose and fit to a linear quadratic model. Sensitization enhancement ratios (SER{sub 10}) were calculated as the ratio of doses required to achieve 10% surviving fraction for cells without and with DNA-incorporated IUdR. Results: At 4 MV, SER{sub 10} values were 2.6 {+-} 0.1, 2.2 {+-} 0.1, and 1.5 {+-} 0.1 for 16.6%, 12.0%, and 9.2% thymidine replacement, respectively. At 35 keV, SER{sub 10} values were 4.1 {+-} 0.2, 3.0 {+-} 0.1, and 2.0 {+-} 0.1, respectively, which yielded SER{sub 10} ratios (35 keV:4 MV) of 1.6 {+-} 0.1, 1.4 {+-} 0.1, and 1.3 {+-} 0.1, respectively. Conclusions: SER{sub 10} increases monotonically with percent thymidine replacement by IUdR for both modalities. As compared to 4-MV x-rays, 35-keV photons produce enhanced SER{sub 10} values whose ratios are linear with percent thymidine replacement and assumed to be due to Auger electrons contributing to enhanced dose to DNA. Although this Auger effectiveness factor is less than the radiosensitization factor of IUdR, both could be important for the clinical efficacy of IUdR radiotherapy.

Dugas, Joseph P., E-mail: joseph.dugas@utsouthwestern.ed [Department of Physics and Astronomy, Louisiana State University and Agricultural and Mechanical College, Baton Rouge, LA (United States); Varnes, Marie E. [Department of Physics and Astronomy, Louisiana State University and Agricultural and Mechanical College, Baton Rouge, LA (United States); Mary Bird Perkins Cancer Center, Baton Rouge, LA (United States); Sajo, Erno; Welch, Christopher E. [Department of Physics and Astronomy, Louisiana State University and Agricultural and Mechanical College, Baton Rouge, LA (United States); Ham, Kyungmin [Center for Advanced Microstructures and Devices, Louisiana State University and Agricultural and Mechanical College, Baton Rouge, LA (United States); Hogstrom, Kenneth R. [Department of Physics and Astronomy, Louisiana State University and Agricultural and Mechanical College, Baton Rouge, LA (United States); Mary Bird Perkins Cancer Center, Baton Rouge, LA (United States)

2011-01-01

425

Observation of gamma-ray bursts from 10 keV to 9 MeV  

NASA Technical Reports Server (NTRS)

Time histories and count-rate spectra of some of the gamma-ray bursts detected by the spectrometer on the Solar Maximum Mission between Feb. 20, 1980, and May 1981 are presented. Individual peaks observed in some of the bursts are found to differ significantly in hardness from one another. The similarity in the time profiles in the different energy bands is seen as suggesting that photons spanning two decades in energy are produced by the same mechanism. It is noted that all of the bursts are detected to energies greater than approximately 1 MeV. Two of the spectra presented are seen as being well fit by single power laws; the indices, however, are strikingly different. The other two sepctra require either two power laws or an exponential function. No clear evidence is found for the existence of narrow line features in any of the bursts.

Share, G. H.; Kurfess, J. D.; Dee, S.; Chupp, E. L.; Ryan, J. M.; Forrest, D. J.; Lanigan, J.; Rieger, E.; Kanbach, G.; Reppin, C.

1982-01-01

426

Monte Carlo simulation of 1-10-KeV electron scattering in a gold target  

NASA Astrophysics Data System (ADS)

A new Monte Carlo simulation of electron scattering has been achieved for extension to the low-energy region and to heavy elements such as Au. The Kanaya-Okayama equation, which includes adjustable parameters, is used for the calculation of energy loss instead of the Bethe equation. Further, the Mott equation, which is obtained from a more exact treatment for elastic scattering, is used instead of the screened Rutherford equation for angular scattering. The calculated results are compared with various kinds of experimental results such as the electron range, the backscattering coefficient, and the depth distribution of energy dissipation. The theoretical results are found to be in satisfactory agreement with the experimental results.

Kotera, Masatoshi; Murata, Kenji; Nagami, Koichi

1981-02-01

427

Analyzing power formula and application to low energy nuclear reactions  

Microsoft Academic Search

General formulas of analyzing powers in nuclear reactions are derived in a model-independent way, decomposing the analyzing powers by the rank of tensors in the spin space by the invariant-amplitude method. The validity of the formulas is examined in low energy reactions, the 3He(d-->,p)4He reaction at the 430-keV resonance and 1H(d-->,gamma)3He reactions at energies below 80 keV, for which the

M. Tanifuji; H. Kameyama

1999-01-01

428

Low-spin states and the non-observation of a proposed 2202-keV, 0+ isomer in 68Ni  

NASA Astrophysics Data System (ADS)

The low-spin level scheme of 68Ni was investigated with the Gammasphere array following reactions between a 70Zn beam and 238U, 208Pb, and 197Au targets. Spin assignments for some states have been verified through ?-ray angular correlations, including the 0+ assignment for the 2511-keV level. Two previously unknown states at 3302 and 3405 keV have been identified. No evidence was found for a recently reported 216-ns, 0+ isomer at 2202 keV that was attributed to a proton two-particle, two-hole intruder configuration, despite experimental conditions similar to those used in the measurement reporting its discovery.

Chiara, C. J.; Broda, R.; Walters, W. B.; Janssens, R. V. F.; Albers, M.; Alcorta, M.; Bertone, P. F.; Carpenter, M. P.; Hoffman, C. R.; Lauritsen, T.; Rogers, A. M.; Seweryniak, D.; Zhu, S.; Kondev, F. G.; Fornal, B.; Królas, W.; Wrzesi?ski, J.; Larson, N.; Liddick, S. N.; Prokop, C.; Suchyta, S.; David, H. M.; Doherty, D. T.

2012-10-01

429

IonCCD detector for miniature sector-field mass spectrometer: investigation of peak shape and detector surface artifacts induced by keV ion detection.  

PubMed

A recently described ion charge coupled device detector IonCCD (Sinha and Wadsworth, Rev. Sci. Instrum. 76(2), 2005; Hadjar, J. Am. Soc. Mass Spectrom. 22(4), 612-624, 2011) is implemented in a miniature mass spectrometer of sector-field instrument type and Mattauch-Herzog (MH)-geometry (Rev. Sci. Instrum. 62(11), 2618-2620, 1991; Burgoyne, Hieftje and Hites J. Am. Soc. Mass Spectrom. 8(4), 307-318, 1997; Nishiguchi, Eur. J. Mass Spectrom. 14(1), 7-15, 2008) for simultaneous ion detection. In this article, we present first experimental evidence for the signature of energy loss the detected ion experiences in the detector material. The two energy loss processes involved at keV ion kinetic energies are electronic and nuclear stopping. Nuclear stopping is related to surface modification and thus damage of the IonCCD detector material. By application of the surface characterization techniques atomic force microscopy (AFM) and X-ray photoelectrons spectroscopy (XPS), we could show that the detector performance remains unaffected by ion impact for the parameter range observed in this study. Secondary electron emission from the (detector) surface is a feature typically related to electronic stopping. We show experimentally that the properties of the MH-mass spectrometer used in the experiments, in combination with the IonCCD, are ideally suited for observation of these stopping related secondary electrons, which manifest in reproducible artifacts in the mass spectra. The magnitude of the artifacts is found to increase linearly as a function of detected ion velocity. The experimental findings are in agreement with detailed modeling of the ion trajectories in the mass spectrometer. By comparison of experiment and simulation, we show that a detector bias retarding the ions or an increase of the B-field of the IonCCD can efficiently suppress the artifact, which is necessary for quantitative mass spectrometry. PMID:21952900

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

2011-10-01

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