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1

19 CFR 10.600 - Accessories, spare parts, or tools.  

Code of Federal Regulations, 2010 CFR

...DEPARTMENT OF THE TREASURY ARTICLES CONDITIONALLY FREE, SUBJECT TO A REDUCED RATE, ETC. Dominican Republic-Central America-United States Free Trade Agreement Rules of Origin § 10.600 Accessories, spare parts, or tools. (a)...

2010-04-01

2

19 CFR 10.600 - Accessories, spare parts, or tools.  

Code of Federal Regulations, 2013 CFR

...CUSTOMS AND BORDER PROTECTION, DEPARTMENT OF HOMELAND SECURITY; DEPARTMENT OF THE TREASURY ARTICLES CONDITIONALLY...ETC. Dominican Republic-Central America-United States Free Trade Agreement Rules of Origin § 10.600...

2013-04-01

3

19 CFR 10.600 - Accessories, spare parts, or tools.  

Code of Federal Regulations, 2011 CFR

...CUSTOMS AND BORDER PROTECTION, DEPARTMENT OF HOMELAND SECURITY; DEPARTMENT OF THE TREASURY ARTICLES CONDITIONALLY...ETC. Dominican Republic-Central America-United States Free Trade Agreement Rules of Origin § 10.600...

2011-04-01

4

19 CFR 10.600 - Accessories, spare parts, or tools.  

Code of Federal Regulations, 2014 CFR

...CUSTOMS AND BORDER PROTECTION, DEPARTMENT OF HOMELAND SECURITY; DEPARTMENT OF THE TREASURY ARTICLES CONDITIONALLY...ETC. Dominican Republic-Central America-United States Free Trade Agreement Rules of Origin § 10.600...

2014-04-01

5

Complete polarization analysis in the 1keV to 2keV energy range using a high-precision polarimeter  

NASA Astrophysics Data System (ADS)

The Beryl and YB66 crystals are proved to be suitable as analyzers in the energy range from 1.0keV to 2.0keV. The s-component reflectivity (Rs) of Beryl crystal reaches up to 10% with polarizing power Rs/Rp over 1000 at 1.1keV. The free-standing W/B4C multilayer has the phase shift over 5° with moderate transmission up to 1.7keV. The Bragg resonance width of the Beryl crystal is only 350 microradians at 1.1keV, and the incidence angle of the beam onto the crystal needs to be constant within 50 microradians or better. A high-precision polarimeter was used for the polarimetry experiment, and the complete polarization analysis of the APPLE II undulator at 1.1 keV and 1.56keV will be presented.

Wang, Hongchang; Dhesi, Sarnjeet; Bencok, Peter; Steadman, Paul; Maccherozzi, Francesco; Sawhney, Kawal

2013-03-01

6

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

E-print Network

PH YSICAL RE VIE% A VOLUME 16, N UMBER 8 SEPTEMBER 1977 Hydrogen-atom excitation and ionization by proton impact in the 50- to 200-keV energy region E. Fitchard, A. L. Ford, and J. F. Reading Cyclotron Institute and Department of Physics, Texas A...&M University, College Station, Texas 77843 (Received 28 December 1976) We report results for n = 2 and n = 3 excitation and ionization in proton-hydrogen collisions. The calculations use a single-center {target) basis with s, p, and d angular momentum states...

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

1977-01-01

7

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

8

Gamma Ray Attenuation Coefficient Measurement in Energies 1172 keV and 1332 keV for Neutron Absorbent Saturated Solutions  

Microsoft Academic Search

The compounds, NaBO, HBO, CdCl and NaCl and their solutions, attenuate gamma rays in addition to neutron absorption. These compounds are widely used in shielding of neutron sources, reactor control and neutron converters. Mass attenuation coefficients of gamma related to saturated solutions of the above four compounds, in energies 1172 keV and 1332 keV have been measured by NaI detector

Jalali; Majid

2006-01-01

9

What Happened to the High-Energy (> 100 keV) Particles at Mercury?  

NASA Astrophysics Data System (ADS)

After the first Mariner 10 flyby of Mercury in 1974, when high-energy (> 100 keV) particles were observed along with sudden changes in the magnetic field, it was expected that Mercury's magnetosphere would be flooded with energetic particles. However, after more than two years in orbit around Mercury, measurements made by the Energetic Particle Spectrometer (EPS) aboard the MESSENGER spacecraft have revealed that high-energy (> 100 keV) particles are the exception rather than the rule. Typically, the observed bulk particle energies in Mercury's magnetosphere are on the order of 1-10 keV, with observations of electrons at low intensities up to ~100 keV. What makes this relative lack of high-energy particles perhaps even more surprising is that magnetic reconnection is observed by the MESSENGER Magnetometer (MAG) to occur at Mercury with great regularity on both the dayside and nightside. To help understand these observations, global-scale three-dimensional kinetic simulations of Mercury's magnetosphere have been carried out with different solar wind forcing conditions. The results show that because of the relatively small dimensions of the magnetotail, the cross-tail convection electric potential typically achieves maximum values of 10-20 kV. Coupled with a downstream magnetotail reconnection location of at most ~ 4RM (where RM is Mercury's radius), reconnection and betatron acceleration result in plasma bulk energies in the inner magnetosphere that are typically < 20 keV, consistent with the observations. The results also indicate that plasma wave activity, commonly observed near Mercury's geomagnetic equator, is not effective in energizing plasma to energies > 100 keV, although the waves could be responsible for energization of up to several keV, as well as cause strong pitch-angle scattering. When compared with observations and simulations of Earth's magnetosphere, the results found for Mercury's relatively small magnetosphere can be used to understand global-scale transport and acceleration processes more generally in planetary magnetospheres.

Schriver, D.; Travnicek, P. M.; Anderson, B. J.; Ashour-Abdalla, M.; Baker, D. N.; Benna, M.; Boardsen, S. A.; Hellinger, P.; Ho, G. C.; Korth, H.; Krimigis, S. M.; McNutt, R. L., Jr.; Raines, J. M.; Richard, R. L.; Slavin, J. A.; Solomon, S. C.; Starr, R. D.; Zurbuchen, T.

2013-12-01

10

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

SciTech Connect

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

Saat, Ahmad [Institute of Science, Universiti Teknologi MARA, 40450 Shah Alam (Malaysia); Hamzah, Zaini; Yusop, Mohammad Fariz; Zainal, Muhd Amiruddin [Faculty of Applied Sciences, Universiti Teknologi MARA, 40450 Shah Alam (Malaysia)

2010-07-07

11

Charge-coupled-device response to electron beam energies of less than 1 keV up to 20 keV  

NASA Technical Reports Server (NTRS)

Recent developments of backside treatment for the backside-illuminated scientifc CCD imagers have shown near-theoretical efficiency even at the short wavelength region of the spectrum. By using SEM performance comparisons of backside-treated and untreated CCDs to an electron flux varying from 1 to 100 pA and beam energy ranging from less than 1 keV up to 20 keV are obtained. The theoretical analysis, the SEM testing procedure, and the quantum efficiency measurement results are presented. It is shown, for example, that the average quantum efficiency increases from less than 1 percent for an untreated CCD to nearly 40 percent for a backside-treated CCD at a beam energy of 1 kev.

Daud, Taher; Janesick, James R.; Evans, Kenneth; Elliott, Tom

1987-01-01

12

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

13

Towards Advanced-fuel Fusion Electron, Ion Energy >100 keV in a Dense Plasma  

E-print Network

Controlled fusion with advanced fuels requires average electron and ion energies above 100 keV (equivalent to 1.1 billion K) in a dense plasma. We have met this requirement and demonstrated electron and ion energies over 100 keV in a compact and inexpensive dense plasma focus device. We have achieved this in plasma "hot spots" or plasmoids that, in our best results, had a density-confinement-time-energy product of 5.0 x1015 keVsec/cm3, a record for any fusion experiment. We measured the electron energies with an X-ray detector instrument that demonstrated conclusively that the hard X-rays were generated by the hot spots.

Lerner, E J; Oona, H; Luginbill, A D; Boydston, J C; Ferguson, J M; Lindeburg, B A; Lerner, Eric J.; Freeman, Bruce L.; Oona, Hank; Luginbill, Alvin D.; Boydston, John C.; Ferguson, Jim M.; Lindeburg, Brent A.

2002-01-01

14

183W Resonance Parameter Evaluation in the Neutron Energy Range Up to 5 keV  

SciTech Connect

We generated a preliminary set of resonance parameters for {sup 183}W in the neutron energy range of thermal up to 5 keV. In the analyzed energy range, this work represents a significant improvement over the current resonance evaluation in the ENDF/B-VII.1 library limited up to 2.2 keV. The evaluation methodology uses the Reich-Moore approximation to fit, with the R-matrix code SAMMY, the high-resolution measurements performed in 2007 at the GEel LINear Accelerator (GELINA) facility. The transmission data and the capture cross sections calculated with the set of resonance parameters are compared with the experimental values, and the average properties of the resonance parameters are discussed.

Pigni, Marco T [ORNL] [ORNL; Dunn, Michael E [ORNL] [ORNL; Guber, Klaus H [ORNL] [ORNL

2012-01-01

15

The 93Zr(n,?) reaction up to 8 keV neutron energy  

NASA Astrophysics Data System (ADS)

The (n,?) reaction of the radioactive isotope 93Zr has been measured at the n_TOF high-resolution time-of-flight facility at CERN. Resonance parameters have been extracted in the neutron energy range up to 8 keV, yielding capture widths smaller (14%) than reported in an earlier experiment. These results are important for detailed nucleosynthesis calculations and for refined studies of waste transmutation concepts.

Tagliente, G.; Milazzo, P. M.; Fujii, K.; Abbondanno, U.; Aerts, G.; Álvarez, H.; Alvarez-Velarde, F.; Andriamonje, S.; Andrzejewski, J.; Audouin, L.; Badurek, G.; Baumann, P.; Be?vá?, F.; Belloni, F.; Berthoumieux, E.; Calviño, F.; Calviani, M.; Cano-Ott, D.; Capote, R.; Carrapiço, C.; Cennini, P.; Chepel, V.; Chiaveri, E.; Colonna, N.; Cortes, G.; Couture, A.; Dahlfors, M.; David, S.; Dillmann, I.; Domingo-Pardo, C.; Dridi, W.; Duran, I.; Eleftheriadis, C.; Embid-Segura, M.; Ferrari, A.; Ferreira-Marques, R.; Furman, W.; Goncalves, I.; Gonzalez-Romero, E.; Gramegna, F.; Guerrero, C.; Gunsing, F.; Haas, B.; Haight, R.; Heil, M.; Herrera-Martinez, A.; Jericha, E.; Käppeler, F.; Kadi, Y.; Karadimos, D.; Karamanis, D.; Kerveno, M.; Kossionides, E.; Krti?ka, M.; Lamboudis, C.; Leeb, H.; Lindote, A.; Lopes, I.; Lukic, S.; Marganiec, J.; Marrone, S.; Martínez, T.; Massimi, C.; Mastinu, P.; Mengoni, A.; Moreau, C.; Mosconi, M.; Neves, F.; Oberhummer, H.; O'Brien, S.; Papachristodoulou, C.; Papadopoulos, C.; Paradela, C.; Patronis, N.; Pavlik, A.; Pavlopoulos, P.; Perrot, L.; Pigni, M. T.; Plag, R.; Plompen, A.; Plukis, A.; Poch, A.; Praena, J.; Pretel, C.; Quesada, J.; Reifarth, R.; Rosetti, M.; Rubbia, C.; Rudolf, G.; Rullhusen, P.; Salgado, J.; Santos, C.; Sarchiapone, L.; Savvidis, I.; Stephan, C.; Tain, J. L.; Tassan-Got, L.; Tavora, L.; Terlizzi, R.; Vannini, G.; Vaz, P.; Ventura, A.; Villamarin, D.; Vincente, M. C.; Vlachoudis, V.; Vlastou, R.; Voss, F.; Walter, S.; Wiescher, M.; Wisshak, K.

2013-01-01

16

Self-attenuation correction factors for bioindicators measured by ? spectrometry for energies <100 keV  

NASA Astrophysics Data System (ADS)

The mass attenuation coefficients for a number of marine and terrestrial bioindicators were measured using ? spectrometry for energies between 22 and 80 keV. These values were then used to find the correction factor k for the apparent radioactivity. The experimental results were compared with a Monte Carlo simulation performed using PENELOPE in order to evaluate the reliability of the simplified calculation and to determine the correction factors.

Manduci, L.; Tenailleau, L.; Trolet, J. L.; De Vismes, A.; Lopez, G.; Piccione, M.

2010-01-01

17

Kinoform lens focusing of high-energy x-rays (50 - 100 keV)  

NASA Astrophysics Data System (ADS)

High-energy x-rays from a synchrotron source are well suited for numerous applications, such as studies of materials structure and stress in bulk or extreme environments. Some of these methods require high spatial resolution. Planar kinoforms are shown to focus monochromatized undulator radiation in the 50-100 keV range down to 0.2-1.5 ?m beam sizes at 0.25-2 m focal distances. These lenses were fabricated by reactive ion etching of silicon. At such high x-ray energies, these optics can offer substantial transmission and lens aperture.

Shastri, S. D.; Evans-Lutterodt, K.; Sheffield, R. L.; Stein, A.; Metzler, M.; Kenesei, P.

2014-09-01

18

High order reflectivity of graphite (HOPG) crystals for x ray energies up to 22 keV  

SciTech Connect

We used Kr K{alpha} (12.6 keV) and Ag K{alpha} (22.1 keV) x-rays, produced by petawatt class laser pulses interacting with a Kr gas jet and a silver foil, to measure the integrated crystal reflectivity of flat Highly Oriented Pyrolytic Graphite (HOPG) up to fifth order. The reflectivity in fourth order is lower by a factor of 50 when compared to first order diffraction. In second order the integrated reflectivity decreases from 1.3 mrad at 12.6 keV to 0.5 mrad at 22.1 keV. The current study indicates that HOPG crystals are suitable for measuring scattering signals from high energy x ray sources (E {ge} 20 keV). These energies are required to penetrate through the high density plasma conditions encountered in inertial confinement fusion capsule implosions on the National Ignition Facility.

Doeppner, T; Neumayer, P; Girard, F; Kugland, N L; Landen, O L; Niemann, C; Glenzer, S H

2008-04-30

19

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

20

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

SciTech Connect

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

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

2000-05-01

21

Electron Transfer in p-Ar Collisions at keV Energies  

SciTech Connect

Absolute differential and total cross sections for single electron capture of H{sup +} ions impinging on Ar atoms in the energy range of 0.5-5.0 keV and scattering angles from -5.0 deg. to 5.0 deg. are reported. The absolute differential cross (DCS) sections for all acceleration energies shows a decreasing behavior with increasing angle, showing an overall decrease of six orders of magnitude. The total cross section is found to be between the range of 4.9 and 15 A{sup 2}. The total cross sections display an increasing behavior as a function of the incident energy. The absolute differential and total cross section are compared with other available measurements and a recent theoretical approach.

Alarcon, F. B. [Facultad de Ciencias, Universidad Nacional Autonoma de Mexico, Apdo. Postal 70542, 04510 Coyoacan, Mexico, D.F. (Mexico); Martinez, H. [Instituto de Ciencias Fisicas, Universidad Nacional Autonoma de Mexico, Apartado postal 48-3, 62210, Cuernavaca, Morelos (Mexico); Castillo, F. [Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico (Mexico)

2009-03-10

22

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

NASA Astrophysics Data System (ADS)

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

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

2012-07-01

23

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

24

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

25

Mechanical engineering of a 75-keV proton injector for the Low Energy Demonstration Accelerator  

SciTech Connect

A dc injector capable of 75-keV, 110-mA proton beam operation is under development for the Low Energy Demonstration Accelerator (LEDA) project at Los Alamos. The injector uses a dc microwave proton source which has demonstrated 98% beam availability while operating at design parameters. A high-voltage isolation transformer is avoided by locating all ion source power supplies and controls at ground potential. The low-energy beam transport system (LEBT) uses two solenoid focusing and two steering magnets for beam matching and centroid control at the RFQ matchpoint. This paper will discuss proton source microwave window design, H{sub 2} gas flow control, vacuum considerations, LEBT design, and an iris for beam current control.

Hansborough, L.D.; Hodgkins, D.J.; Meyer, E.A.; Schneider, J.D.; Sherman, J.D.; Stevens, R.R. Jr.; Zaugg, T.J.

1997-10-01

26

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

27

X-ray-refractive-index measurements at photon energies above 100 keV with a grating interferometer  

NASA Astrophysics Data System (ADS)

The knowledge of the x-ray index of refraction of materials is important for the interpretation or simulation of many x-ray physics phenomena. But its precise and accurate experimental determination is challenging, particularly in the hard x-ray energy range above 100 keV. In this article we present and discuss experimental measurements of the real and imaginary part of the index of refraction for different materials based on x-ray grating interferometry at energies above 130 keV.

Ruiz-Yaniz, M.; Zanette, I.; Rack, A.; Weitkamp, T.; Meyer, P.; Mohr, J.; Pfeiffer, F.

2015-03-01

28

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

29

Highly ionized Fe X-ray lines at energies 7.7-8.6 keV  

E-print Network

Fe XXV lines at 1.85 A (6.70 keV) and nearby Fe XXIV satellites have been widely used for determining the temperature of the hottest parts of solar flare and tokamak plasmas, though the spectral region is crowded and the lines are blended during flare impulsive stages. The aim of this work is to show that similarly excited Fe lines in the 7.7--8.6 keV (1.44--1.61 A) region have the same diagnostic capability with the advantage of not being so crowded. Spectra in the 7.7--8.6 keV range are synthesized using the CHIANTI spectral package for conditions (temperature, turbulent velocities) appropriate to solar flares. The calculated spectra show that the Fe lines in the 7.7--8.6 keV are well separated even when turbulent velocities are present, and Fe XXIV/Fe XXV line ratios should therefore provide valuable tools for diagnosing flares and tokamak plasmas. It is concluded that Fe lines in the 7.7--8.6 keV range are ideal for the measurement of flare temperature and for detecting the presence of low-energy nonthermal electrons present at flare impulsive stages. An indication of what type of instruments to observe this region is given.

K. J. H. Phillips

2008-09-09

30

A Monte Carlo method for calculating the energy response of plastic scintillators to polarized photons below 100 keV  

Microsoft Academic Search

The energy response of plastic scintillators (Eljen Technology EJ-204) to polarized soft gamma-ray photons below 100keV has been studied, primarily for the balloon-borne polarimeter, PoGOLite. The response calculation includes quenching effects due to low-energy recoil electrons and the position dependence of the light collection efficiency in a 20cm long scintillator rod. The broadening of the pulse-height spectrum, presumably caused by

T. Mizuno; Y. Kanai; J. Kataoka; M. Kiss; K. Kurita; M. Pearce; H. Tajima; H. Takahashi; T. Tanaka; M. Ueno; Y. Umeki; H. Yoshida; M. Arimoto; M. Axelsson; C. Marini Bettolo; G. Bogaert; P. Chen; W. Craig; Y. Fukazawa; S. Gunji; T. Kamae; J. Katsuta; N. Kawai; S. Kishimoto; W. Klamra; S. Larsson; G. Madejski; J. S. T. Ng; F. Ryde; S. Rydström; T. Takahashi; T. S. Thurston; G. Varner

2009-01-01

31

Charged particle innershell ionization in K-shell excitation for target binding energies less than 1 keV  

Microsoft Academic Search

The first Born and ECPSSR theories are tested by comparison with experimental K-shell X-ray production cross sections for X-ray energies less than 1 keV. These data are reported here for incident hydrogen, helium, and lithium ions in the energy range 0.5 to 5 MeV with use of a windowless Si(Li) X-ray detector. It was found that the first Born theory

Y. C. Yu

1993-01-01

32

Mass energy-transfer and mass energy-absorption coefficients, including in-flight positron annihilation for photon energies 1 keV to 100 MeV  

Microsoft Academic Search

Mass energy transfer (Mu sub u Rho) and mass energy absorption coefficients (Mu sub en Rho) are tabulated in units of sq. cm\\/g for photon energies between 1 keV and 100 MeV for 29 elements (Z = 1-92), and 14 mixtures and compounds of general dosimetric interest. Cross sections for photo-effect, incoherent scattering, and pair and triplet production are those

P. D. Higgins; F. H. Attix; J. H. Hubbell; S. M. Seltzer; M. J. Berger

1991-01-01

33

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

34

Excitation energy distributions and statistical dissociation of C702+ prepared in collisions with F+ ions at 3 keV  

NASA Astrophysics Data System (ADS)

The statistical dissociation of C702+ has been studied as a function of the internal energy using collision induced dissociation under energy control (CIDEC). Doubly charged ions C702+ were prepared in F+ (3 keV) + C70 ? F- + C702+ collisions. Up to seven successive evaporation of C2 have been observed in a time range of 1.7 ?s. The dissociation energies of C70-2m2+ (m=1-7) were determined using a statistical cascade model to reproduce the excitation energy distribution of C702+ parent ions for each dissociation channel. Results are in good agreement with previous theoretical calculations.

Brédy, R.; Ortéga, C.; Ji, M.; Chen, L.; Bernard, J.; Montagne, G.; Qian, D.; Li, B.; Ma, X.; Martin, S.

2014-04-01

35

YAP imager and its application with high-energy X-ray beams up to 150 keV  

NASA Astrophysics Data System (ADS)

An X-ray imaging detector called YAP imager has been developed for high-energy X-ray region at the SPring-8 facility. It possesses a [128×128] matrix of YAlO 3:Ce crystals, each element having a volume of 1×1×6 mm 3. A NIM logic module using programmable logic device chip was also developed as a position encoder. The YAP imager has been applied for some applications with a thermal barrier coating material and multi-layer metal sheets targets in the incident X-ray energy region of 70-150 keV. Direct X-ray beam profile at 100 keV was also measured.

Hirota, K.; Toyokawa, H.; Suzuki, M.; Kudo, T.; Nomachi, M.; Sugaya, Y.; Yosoi, M.; Gorin, A.; Manuilov, I.; Riazantsev, A.; Kuroda, K.

2003-09-01

36

Observation of A0535 + 26 at energies above 150 keV with the FIGARO II experiment  

NASA Astrophysics Data System (ADS)

The transient pulsating X-ray source A0535 + 26 was observed by the FIGARO II gamma-ray experiment on 1990 July 9. The periodogram of about 6 hr of data shows only one significant signal (3.5 sigma) at the period of 103.2 s, very close to the expected one. The folded light curve is characterized by a double-peak structure and a narrow dip; it is similar to that at lower energies. The pulsed flux is (8.6 +/- 2.3) x 10 exp -6 photons/sq cm/s/keV in the 148-260 keV band. We also find evidence of a low-energy cutoff below 167 keV.

Cusumano, G.; Mineo, T.; Sacco, B.; Scarsi, L.; Gerardi, G.; Agrinier, B.; Barouch, E.; Comte, R.; Parlier, B.; Masnou, J. L.; Massaro, E.; Matt, G.; Costa, E.; Salvati, M.; Mandrou, P.; Niel, M.; Olive, J. F.

1992-10-01

37

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

38

Novel method to study neutron capture of 235U and 238U simultaneously at keV energies.  

PubMed

The neutron capture cross sections of the main uranium isotopes, (235)U and (238)U, 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 (235)U(n,?)/(238)U(n,?) can be deduced in accelerator mass spectrometry directly from the atom ratio of the reaction products (236)U/(239)U, 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. PMID:24877933

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

2014-05-16

39

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

40

Mass energy-transfer and mass energy-absorption coefficients, including in-flight positron annihilation for photon energies 1 keV to 100 MeV  

SciTech Connect

Mass energy-transfer (Mu(sub u)/Rho) and mass energy-absorption coefficients (Mu(sub en)/Rho) are tabulated in units of (sqcm/g) for photon energies between 1 keV and 100 MeV for 29 elements (Z = 1-92), and 14 mixtures and compounds of general dosimetric interest. Cross sections for photo-effect, incoherent scattering, pair and triplet production are those compiled or generated by the National Institute of Standards and Technology (NIST) (formerly the National Bureau of Standards). Corrections are included for in-flight positron annihilation, previously not applied in NIST calculations for energies above 10 MeV.

Higgins, P.D.; Attix, F.H.; Hubbell, J.H.; Seltzer, S.M.; Berger, M.J.

1991-11-01

41

Dissociative ionization cross sections of CO2 at electron impact energy of 5 keV  

NASA Astrophysics Data System (ADS)

The dissociative ionization of CO2 induced by 5 keV electrons in two-body and three-body dissociative channels of CO22+ and CO23+ is identified by the ion—ion coincidence- method using a momentum imaging spectrometer. The partial ionization cross sections (PICSs) of different ionic fragments are measured and the results generally agree with the calculations made by a semi-empirical approach. Furthermore, the PICSs of the dissociative channels are also obtained by carefully considering the detection efficiency of the micro-channel plates and the total transmission efficiency of the time of flight system.

Wang, En-Liang; Shen, Zhen-Jie; Yang, Hong-Jiang; Tang, Ya-Guo; Shan, Xu; Chen, Xiang-Jun

2014-11-01

42

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

43

Low-energy x-ray dosimetry studies (7 to 17.5 keV) with synchroton radiation  

SciTech Connect

Unique properties of synchrotron radiation (SR), such as its high intensity, brightness, polarization, and broad spectral distribution (extending from x-ray to infra-red wavelengths) make it an attractive light source for numerous experiments. As SR facilities are rapidly being built all over the world, they introduce the need for low-energy x-ray dosemeters because of the potential radiation exposure to experimenters. However, they also provide a unique opportunity for low-energy x-ray dosimetry studies because of the availability of monochromatic x-ray beams. Results of such studies performed at the Stanford Synchrotron Radiation Laboratory are described. Lithium fluoride TLDs (TLD-100) of varying thicknesses (0.015 to 0.08 cm) were exposed free in air to monochromatic x-rays (7 to 17.5 keV). These exposures were monitored with ionization chambers. The response (nC/Gy) was found to increase with increasing TLD thickness and with increasing beam energy. A steeper increase in response with increasing energy was observed with the thicker TLDs. The responses at 7 and 17.5 keV were within a factor of 2.3 and 5.2 for the 0.015 and 0.08 cm-thick TLDs, respectively. The effects of narrow (beam size smaller than the dosemeter) and broad (beam size larger than the dosemeter) beams on the response of the TLDs are also reported.

Ipe, N.E.; Bellamy, H.; Flood, J.R. [and others

1995-06-01

44

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

SciTech Connect

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

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

2007-12-10

45

Angular Anisotropy of the 3H(d, ?) n Reaction at Deuteron Energies Below 200 keV  

NASA Astrophysics Data System (ADS)

The angular distributions of particles emitted from the reaction were measured at 7.5 intervals from 60 to for incoming deuteron energies of 100, 150, and 200 keV using 50 and 80 g/cm thick TiT targets. The overall uncertainty of 0.16% of the data made it possible to determine Legendre-polynomial coefficients up to . The results are compared with an -matrix parameterization. The measured angular anisotropies present the first experimental evidence of -wave contributions to the cross section in the vicinity of the -wave resonance in He.

Bém, P.; Kroha, V.; Mareš, J.; Šime?ková, E.; Trgi?ová, M.; Ver?imák, P.

46

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

Microsoft Academic Search

The X-ray linear attenuation coefficient was measured for materials containing elements hydrogen to calcium. Characteristic X-rays with energies 32–66keV were produced by X-ray fluorescence using a secondary target system, and 140keV gamma rays were obtained from an unsealed 99mTc source. The photon beams were highly collimated and recorded using energy dispersive detection. A high-purity germanium detector was utilised to distinguish

S. M. Midgley

2005-01-01

47

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

Microsoft Academic Search

The X-ray linear attenuation coefficient was measured for materials containing elements hydrogen to calcium. Characteristic X-rays with energies 32-66keV were produced by X-ray fluorescence using a secondary target system, and 140keV gamma rays were obtained from an unsealed 99mTc source. The photon beams were highly collimated and recorded using energy dispersive detection. A high-purity germanium detector was utilised to distinguish

S. M. Midgley

2005-01-01

48

Nuclear and electronic energy loss by 1 keV to 60 keV ions in silicon : comparison of measurement to SRIM  

SciTech Connect

Comparison of TRIM simulations with measurements of the energy lost to electronic and nuclear stopping processes using 1 00% internal carrier collection efficiency silicon photodiodes shows a large, systematic overestimation by TRIM of electronic energy loss.

Funsten, H. O. (Herbert O.); Harper, R. W. (Ronnie W.); Ritzau, S. M. (Stephen M.); Korde, R. (Raj)

2003-01-01

49

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

SciTech Connect

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

Kruschwitz, Craig [NSTec; Wu, M. [SNL; Rochau, G. A. [SNL

2013-06-13

50

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

51

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

52

Dosimetric properties of high energy current (HEC) detector in keV x-ray beams  

NASA Astrophysics Data System (ADS)

We introduce a new x-ray radiation detector. The detector employs high-energy current (HEC) formed by secondary electrons consisting predominantly of photoelectrons and Auger electrons, to directly convert x-ray energy to detector signal without externally applied power and without amplification. The HEC detector is a multilayer structure composed of thin conducting layers separated by dielectric layers with an overall thickness of less than a millimeter. It can be cut to any size and shape, formed into curvilinear surfaces, and thus can be designed for a variety of QA applications. We present basic dosimetric properties of the detector as function of x-ray energy, depth in the medium, area and aspect ratio of the detector, as well as other parameters. The prototype detectors show similar dosimetric properties to those of a thimble ionization chamber, which operates at high voltage. The initial results obtained for kilovoltage x-rays merit further research and development towards specific medical applications.

Zygmanski, Piotr; Shrestha, Suman; Elshahat, Bassem; Karellas, Andrew; Sajo, Erno

2015-04-01

53

An Algorithm for Determining Energy Deposition Profiles in Elemental Slabs by Low ( keV) Energy Electrons: An Internal Charging Application  

Microsoft Academic Search

Internal charging\\/discharging is an important concern for today's spacecraft. An important tool for tracking charge buildup in slabs of material that includes a self-consistent solution of the electric fields in the material is the NUMIT code. To date, one of limitations on use of that code has been determining the effects for particles with energy less than 100 keV. To

Wousik Kim; Insoo Jun; Henry B. Garrett

2008-01-01

54

Investigation of the projectile atomic number influence to the total sputtering yield in the keV energy region  

NASA Astrophysics Data System (ADS)

The non-monotonous dependence of the total sputtering yield on the projectile atomic number, which is unexpected in the frame of the Sigmund linear cascade theory, is investigated using Monte Carlo simulations (program SRIM 2003). This effect is studied on the example of aluminum sputtering by six different projectiles (N, Ne, Al, Ar, Kr and Xe) at normal incidence. The incident projectile energy is 2 keV. Investigation consists of the analyses of ASI distributions of sputtered atoms as well as of nuclear energy loss depth distributions of projectiles with fixed number of ejected atoms. The results show that the non-monotonous behavior of Y( Z) is due to the ability of projectiles somewhat lighter than aluminum to efficiently eject large number of atoms by formation of collision cascades in the subsurface region which are directed towards the surface. On the other hand, ions that are heavier or significantly lighter than aluminum cannot form this type of cascades - the heavier ions cannot transfer a lot of energy to recoils in a primary knock-on collision that will move towards the surface, while significantly lighter ions transfer the energy too deep into the target.

Bundaleski, N.

2008-01-01

55

Optimum condition of efficiency functions for HPGe ?-ray detectors in the 121-1408 keV energy range  

NASA Astrophysics Data System (ADS)

The optimum condition of three commonly used functions in the Genie 2000 ? spectra analysis software have been studied in the 121-1408 keV energy range. The three functions are applied for fitting the full-energy peak efficiency of the HPGe gamma-ray detector. A detailed procedure to obtain the optimum condition is described. The HPGe detector is calibrated at 11 cm by three radioactive sources of point form (152Eu, 137Cs, 60Co) providing 11 energy peaks. After data processing, results shows that the three functions used in the Genie 2000 gamma spectra analysis software fit best at orders 3-5. Lastly the standard radioactive source 133Ba is chosen to validate the results. Differences between the standard activity of 133Ba and the result obtained from the fitting functions are below 1.5%. Therefore the optimum orders of the three functions used in the Genie 2000 ? spectra analysis software are 3-5 with the 11 energy peaks.

Chen, Zhi-Lin; Song, Guo-Yang; Mu, Long; Wang, He-Yi; Xing, Shi-Xiong; Guo, Hong-Bo; Liao, Zhen-Xing; Chen, Ping; Hua, Sheng

2010-05-01

56

Low Energy Neutrino and Dark Matter Physics with Sub-Kev Germanium Detector  

NASA Astrophysics Data System (ADS)

The research program of TEXONO Collaboration is on low energy neutrino and dark matter physics. The current goals are on the development of germanium detectors with sub-keV sensitivities to realize experiments on neutrino magnetic moments, neutrino-nucleus coherent scattering, as well as dark natter searches. The compatible sensitivities on low mass WIMP-nucleus for spin-independent and spin-dependent has been achieved with a four-channel ultra-low-energy germanium prototype detector with 4X5 g at the Kuo-Sheng Neutrino Laboratory (KSNL). Data are being taken with point-contact germanium detector at KSNL is demonstrated. The dark matter program has evolved into a dedicated experiment at China Jin-Ping Laboratory (CJPL), where is world's deepest underground laboratory. Recent status and plans would be discussed.

Lin, Shin-Ted

2013-11-01

57

Dosimetric properties of high energy current (HEC) detector in keV x-ray beams.  

PubMed

We introduce a new x-ray radiation detector. The detector employs high-energy current (HEC) formed by secondary electrons consisting predominantly of photoelectrons and Auger electrons, to directly convert x-ray energy to detector signal without externally applied power and without amplification. The HEC detector is a multilayer structure composed of thin conducting layers separated by dielectric layers with an overall thickness of less than a millimeter. It can be cut to any size and shape, formed into curvilinear surfaces, and thus can be designed for a variety of QA applications. We present basic dosimetric properties of the detector as function of x-ray energy, depth in the medium, area and aspect ratio of the detector, as well as other parameters. The prototype detectors show similar dosimetric properties to those of a thimble ionization chamber, which operates at high voltage. The initial results obtained for kilovoltage x-rays merit further research and development towards specific medical applications. PMID:25789488

Zygmanski, Piotr; Shrestha, Suman; Elshahat, Bassem; Karellas, Andrew; Sajo, Erno

2015-04-01

58

Calculated response of intrinsic germanium detectors to narrow beams of photons with energies up to ˜300 keV  

NASA Astrophysics Data System (ADS)

The response of small intrinsic Ge detectors has been calculated for photons incident with energies up to ˜300 keV. The results include the effects of scattering and escape from the detector of the photons and of Ge characteristic X-rays produced in photoelectric absorption. Included also are the effects of the backscattering of photons from material behind the detector. The results, based on Monte Carlo calculations for various photon energies and detector sizes, have been generalized on the basis of a single-scatter model and are given as a set of formulae that can be evaluated for any photon energy and detector size in the range of interest. The predictions obtained with the formulae are shown to agree well with available data from measurements and from Monte Carlo calculations made by other authors. The formulae are used to tabulate photopeak efficiencies for a large number of commercially available detectors, and to generate response functions for unfolding measured pulse-height distributions obtained for continuous incident spectra.

Seltzer, Stephen M.

59

Simbol-X: A Formation Flight Mission with an Unprecedented Imaging Capability in the 0.5-80 Kev Energy Band  

E-print Network

The discovery of X-ray emission from cosmic sources in the 1960s has opened a new powerful observing window on the Universe. In fact, the exploration of the X-ray sky during the 70s-90s has established X-ray astronomy as a fundamental field of astrophysics. Today, the emission from astrophysical sources is by large best known at energies below 10 keV. The main reason for this situation is purely technical since grazing incidence reflection has so far been limited to the soft X-ray band. Above 10 keV all the observations have been obtained with collimated detectors or coded mask instruments. To make a leap step forward in X-ray astronomy above 10 keV it is necessary to extend the principle of focusing X ray optics to higher energies, up to 80 keV and beyond. To this end, ASI and CNES are presently studying the implementation of a X-ray mission called Simbol-X. Taking advantage of emerging technology in mirror manufacturing and spacecraft formation flying, Simbol-X will push grazing incidence imaging up to 80 keV and beyond, providing a strong improvement both in sensitivity and angular resolution compared to all instruments that have operated so far above 10 keV. This technological breakthrough will open a new high-energy window in astrophysics and cosmology. Here we will address the problematic of the development for such a distributed and deformable instrument. We will focus on the main performances of the telescope, like angular resolution, sensitivity and source localization. We will also describe the specificity of the calibration aspects of the payload distributed over two satellites and therefore in a not "frozen" configuration.

Gianpiero Tagliaferri; Philippe Ferrando; Jean-Michel Le Duigou; Giovanni Pareschi; Philippe Laurent; Giuseppe Malaguti; Rodolphe Cledassou; Mauro Piermaria; Olivier La Marle; Fabrizio Fiore; Paolo Giommi

2008-10-20

60

Energy and angular distribution of electrons ejected from argon by 5keV to 1.5MeV protons  

Microsoft Academic Search

Cross sections, differential in emission energy and angle, have been measured for the ejection of electrons in collisions of H+ with argon gas targets. Incident-proton energies studied were from 5 keV to 1.5 MeV and electron emission angles ranged from 10° to 160°. Integration of the double-differential cross sections over emission angle and energy yield results in good agreement with

T. L. Criswell; L. H. Toburen; M. E. Rudd

1977-01-01

61

Energy and angular distribution of electrons ejected from argon by 5keV to 1. 5MeV protons  

Microsoft Academic Search

Cross sections, differential in emission energy and angle, have been measured for the ejection of electrons in collisions of H\\/sup +\\/ with argon gas targets. Incident-proton energies studied were from 5 keV to 1.5 MeV and electron emission angles ranged from 10degree to 160degree. Integration of the double-differential cross sections over emission angle and energy yield results in good agreement

T. L. Criswell; L. H. Toburen; M. E. Rudd

1977-01-01

62

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

NASA Technical Reports Server (NTRS)

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

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

1983-01-01

63

Measurement of high-energy (10-60 keV) x-ray spectral line widths with eV accuracya)  

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

64

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

SciTech Connect

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

Seely, J. F., E-mail: seelyjf@gmail.com; Feldman, U. [Artep Inc., 2922 Excelsior Springs Court, Ellicott City, Maryland 21042 (United States); Glover, J. L.; Hudson, L. T.; Ralchenko, Y.; Henins, Albert [National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); Pereira, N. [Ecopulse Inc., P. O. Box 528, Springfield, Virginia 22152 (United States); Di Stefano, C. A.; Kuranz, C. C.; Drake, R. P. [University of Michigan, Ann Arbor, Michigan 48109 (United States); Chen, Hui; Williams, G. J.; Park, J. [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States)

2014-11-15

65

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

PubMed

A high resolution crystal spectrometer utilizing a crystal in transmission geometry has been developed and experimentally optimized to measure the widths of emission lines in the 10-60 keV energy range with eV accuracy. The spectrometer achieves high spectral resolution by utilizing crystal planes with small lattice spacings (down to 2d = 0.099 nm), a large crystal bending radius and Rowland circle diameter (965 mm), and an image plate detector with high spatial resolution (60 ?m in the case of the Fuji TR image plate). High resolution W L-shell and K-shell laboratory test spectra in the 10-60 keV range and Ho K-shell spectra near 47 keV recorded at the LLNL Titan laser facility are presented. The Ho K-shell spectra are the highest resolution hard x-ray spectra recorded from a solid target irradiated by a high-intensity laser. PMID:25430194

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

2014-11-01

66

Variation in the Calibrated Response of LiF, Al2O3, and Silicon Dosimeters When Used for In-Phantom Measurements of Source Photons With Energies Between 30 KeV AND 300 KeV.  

PubMed

The MCNP5 radiation transport code was used to quantify changes in the absorbed dose conversion factor for LiF, Al2O3, and silicon-based electronic dosimeters calibrated in-air using standard techniques and summarily used to measure absorbed dose to water when placed in a water phantom. A mono-energetic photon source was modeled at energies between 30 keV and 300 keV for a point-source placed at the center of a water phantom, a point-source placed at the surface of the phantom, and for a 10-cm radial field geometry. Dosimetric calculations were obtained for water, LiF, Al2O3, and silicon at depths of 0.2 cm and 10 cm from the source. These results were achieved using the MCNP5 *FMESH photon energy-fluence tally, which was coupled with the appropriate DE/DF card for each dosimetric material studied to convert energy-fluence into the absorbed dose. The dosimeter's absorbed dose conversion factor was calculated as a ratio of the absorbed dose to water to that of the dosimeter measured at a specified phantom depth. The dosimeter's calibration value also was obtained. Based on these results, the absorbed dose conversion factor for a LiF dosimeter was found to deviate from its calibration value by up to 9%, an Al2O3 dosimeter by 43%, and a silicon dosimeter by 61%. These data therefore can be used to obtain LiF, Al2O3, and silicon dosimeter correction factors for mono-energetic and poly-energetic sources at measurement depths up to 10 cm under the irradiation geometries investigated herein. PMID:25706137

Poudel, Sashi; Currier, Blake; Medich, David C

2015-04-01

67

Collision-theory calculations of rate constants for some atmospheric radical reactions over the temperature range 10-600 K  

Microsoft Academic Search

Rate constants have been calculated for a number of bimolecular reactions of HOâ, OH, H, ClO, BrO, SO, O(³P), O(¹D), NO, and NOâ, over the temperature range 10-600 K. For half of the reactions studied so far, calculated capture rates agree with listed experimental rate constants at 300 K to within the stated uncertainties, and calculated temperature coefficients are also

L. F. Phillips

1990-01-01

68

Measurement of the internal bremsstrahlung spectrum of a (89)Sr beta emitter in the 1-100keV photon energy regime.  

PubMed

The internal bremsstrahlung (IB) spectrum of (89)Sr, which is a unique first forbidden beta emitter, is studied in the 1-100keV photon energy regime. The IB spectrum is experimentally measured using a Si(Li) detector, which is efficient in this photon energy regime, and is compared with the IB distributions that are predicted by the Knipp, Uhlenbeck and Bloch (KUB), Nilsson, and Lewis and Ford theories. In the soft energy regime up to 15keV, the measured results are in agreement with all the aforementioned theories. However, from 16-30keV, the experimental results are in agreement with the Lewis and Ford theory, which applies to forbidden transitions, and at higher photon energies, the Nilsson theory best describes the measured results. The differences among the different theories also increase with the photon energy. The effect of the electrostatic Coulomb field on the IB process for beta emitters with different end-point energies is investigated by comparing the ratio of the IB probabilities predicted using the KUB and Nilsson theories for (35)S and (89)Sr, i.e., soft and hard beta emitters, respectively. The Coulomb effect is shown to be significant in the high photon energy regime and for beta emitters with low end-point energies. PMID:25675900

Singh, Amrit; Dhaliwal, A S

2015-04-01

69

Studies on effective atomic numbers and electron densities of essential amino acids in the energy range 1 keV–100 GeV  

Microsoft Academic Search

The effective atomic numbers and electron densities of essential amino acids histidine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine have been calculated for total and partial photon interactions by the direct method in the wide energy range of 1keV–100GeV using WinXCOM. The values of these parameters have been found to change with energy and composition of the amino acids.

S. R. Manohara; S. M. Hanagodimath

2007-01-01

70

Interferometric phase-contrast X-ray CT imaging of VX2 rabbit cancer at 35keV X-ray energy  

NASA Astrophysics Data System (ADS)

Imaging of large objects at 17.7-keV low x-ray energy causes huge x-ray exposure to the objects even using interferometric phase-contrast x-ray CT (PCCT). Thus, we tried to obtain PCCT images at high x-ray energy of 35keV and examined the image quality using a formalin-fixed VX2 rabbit cancer specimen with 15-mm in diameter. The PCCT system consisted of an asymmetrically cut silicon (220) crystal, a monolithic x-ray interferometer, a phase-shifter, an object cell and an x-ray CCD camera. The PCCT at 35 keV clearly visualized various inner structures of VX2 rabbit cancer such as necrosis, cancer, the surrounding tumor vessels, and normal liver tissue. Besides, image-contrast was not degraded significantly. These results suggest that the PCCT at 35 KeV is sufficient to clearly depict the histopathological morphology of VX2 rabbit cancer specimen.

Takeda, Tohoru; Wu, Jin; Tsuchiya, Yoshinori; Yoneyama, Akio; Lwin, Thet-Thet; Hyodo, Kazuyuki; Itai, Yuji

2004-05-01

71

Interferometric phase-contrast X-ray CT imaging of VX2 rabbit cancer at 35keV X-ray energy  

SciTech Connect

Imaging of large objects at 17.7-keV low x-ray energy causes huge x-ray exposure to the objects even using interferometric phase-contrast x-ray CT (PCCT). Thus, we tried to obtain PCCT images at high x-ray energy of 35keV and examined the image quality using a formalin-fixed VX2 rabbit cancer specimen with 15-mm in diameter. The PCCT system consisted of an asymmetrically cut silicon (220) crystal, a monolithic x-ray interferometer, a phase-shifter, an object cell and an x-ray CCD camera. The PCCT at 35 keV clearly visualized various inner structures of VX2 rabbit cancer such as necrosis, cancer, the surrounding tumor vessels, and normal liver tissue. Besides, image-contrast was not degraded significantly. These results suggest that the PCCT at 35 KeV is sufficient to clearly depict the histopathological morphology of VX2 rabbit cancer specimen.

Takeda, Tohoru; Wu Jin; Tsuchiya, Yoshinori; Lwin, Thet-Thet; Itai, Yuji [Institute of Clinical Medicine, University of Tsukuba, Tsukuba-shi, Ibaraki 305-8575 (Japan); Yoneyama, Akio [Advanced Research Laboratory, Hitachi, Ltd., Hatoyama, Saitama, 350-0395 (Japan); Hyodo, Kazuyuki [Material Structure Science, High Energy Accelerator Research Organization, Tsukuba 305-0801 (Japan)

2004-05-12

72

The pulse profile of the Crab pulsar in the energy range 45 keV-1.2 MeV  

NASA Technical Reports Server (NTRS)

The Crab Nebula pulsar (PSR 0531+21) is the best studied and most intense of the nontransient X-ray pulsars. However, since its spectrum drops rapidly with energy, a well-resolved pulse profile has not previously been obtained above 200 keV. In the hard X-ray and low-energy gamma-ray region, an accurate pulse profile can be obtained with a balloon-borne detector of sufficient area during a single transit of the source. A new measurement of the pulse profile of PSR 0531+21 in the energy range above 45 keV obtained with a large-area scintillation detector array is reported. The detector array was flown on a balloon launched from Palestine, Texas on 1980 October 6, reaching a float altitude 4.5 g/sq cm at 0230 UTC October 7. The primary objective of the experiment was to detect and study weak gamma-ray bursts.

Wilson, R. B.; Fishman, G. J.

1983-01-01

73

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

74

Energy and fluence calibration of the neutron spectrometer ROSPEC at the IRSN AMANDE facility between 70 keV and 4.5 MeV.  

PubMed

The ROSPEC device is a multi-detector system, which has been designed by Bubble Technologies Industries (BTI at Chalk River, ON, Canada) to assess neutron spectra, and hence neutron dose quantities, at workplace fields. It is made up of six gaseous proportional counters that detect neutrons via the elastic (n,p) scattering (four hydrogenous counters) and with the (3)He(n,p)T reaction (two (3)He-filled counters). Results of the calibration of a similar rotating spectrometer (ROSPEC) have been described by Rosenstock et al.((1)). For energy and fluence calibration purposes, measurements were performed with the accelerator for metrology and neutron applications in external dosimetry (AMANDE) facility at the Laboratory of Neutron Metrology and Dosimetry (Institute of Radiation Protection and Nuclear Safety, IRSN, France). This facility provides monoenergetic neutron radiation fields from 2 keV to 20 MeV. Two kinds of experiments were carried out. First, the ROSPEC was used in its rotational mode for the ISO energies. Then, each detector was irradiated with all the available neutron energies, in a well defined position with the rotation of the device stopped. The energy values of the neutron beam were calculated using the TARGET code. A BC501-A liquid scintillation spectrometer provided the fluence values for energies beyond 1.2 MeV, a methane-filled SP2 counter from 800 keV to 1.4 MeV and an H(2)-filled SP2 counter from 144 to 800 keV. Reference data for 70 keV monoenergetic neutrons were obtained using the IRSN Long Counter. Results showed that the ROSPEC device was in agreement with the absolute neutron fluences within 10%. Moreover, the new energy calibration factors are in good agreement with those derived by BTI. PMID:19509004

Benmosbah, M; Asselineau, B

2009-07-01

75

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

76

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

77

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

Microsoft Academic Search

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 gamma-ray energies by using the ATOMLABTM-930 medical spectrometer. The gamma-rays were obtained from 99mTc, 131I and 137Cs gamma-ray point sources. Also theoretical calculations have been performed in order to obtain the half-value thicknesses

A. Akar; H. Baltas; U. Çevik; F. Korkmaz; N. T. Okumusoglu

2006-01-01

78

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

79

Measurement of total M shell photoionization cross sections for Au, Pb, Th and U in the energy region 6 12 keV  

Microsoft Academic Search

The total M shell relative photoionization cross-sections for Au, Pb, Th and U have been measured in the energy region 6 12 keV. External conversion K X-rays of suitable elements has been employed as incident photons to photo ionize the total M shell of elements under investigation. The method provides relative cross-sections therefore does not make use of theoretically calculated

K. S. Mann; K. S. Kahlon; N. Singh; K. L. Allawadhi

2007-01-01

80

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

81

Kirkpatrick-Baez microscope with spherical multilayer mirrors around 2.5keV photon energy  

NASA Astrophysics Data System (ADS)

A Kirkpatrick-Baez (KB) x-ray microscope has been developed for the diagnostics of inertial confinement fusion (ICF). The KB microscope system works around 2.5keV with the magnification of 20. It consists of two spherical multilayer mirrors. The grazing angle is 3.575° at 2.5keV. The influence of the slope error of optical components and the alignment errors is simulated by SHADOW software. The mechanical structure which can perform fine tuning is designed. Experiment result with Manson x-ray source shows that the spatial resolution of the system is about 3-4?m over a field of view of 200?m.

An, Ning; Du, Xuewei; Wang, Qiuping; Cao, Zhurong; Jiang, Shaoen; Ding, Yongkun

2014-09-01

82

An innovative experimental setup for the measurement of sputtering yield induced by keV energy ions  

SciTech Connect

An innovative experimental equipment allowing to study the sputtering induced by ion beam irradiation is presented. The sputtered particles are collected on a catcher which is analyzed in situ by Auger electron spectroscopy without breaking the ultra high vacuum (less than 10{sup ?9} mbar), avoiding thus any problem linked to possible contamination. This method allows to measure the angular distribution of sputtering yield. It is now possible to study the sputtering of many elements such as carbon based materials. Preliminary results are presented in the case of highly oriented pyrolytic graphite and tungsten irradiated by an Ar{sup +} beam at 2.8 keV and 7 keV, respectively.

Salou, P.; Lebius, H.; Benyagoub, A.; Langlinay, T.; Lelièvre, D.; Ban-d’Etat, B. [CIMAP (CEA-CNRS-ENSICAEN-UCBN), Boulevard Henri Becquerel, BP 5133, 14070 Caen Cedex 5 (France)] [CIMAP (CEA-CNRS-ENSICAEN-UCBN), Boulevard Henri Becquerel, BP 5133, 14070 Caen Cedex 5 (France)

2013-09-15

83

An innovative experimental setup for the measurement of sputtering yield induced by keV energy ions.  

PubMed

An innovative experimental equipment allowing to study the sputtering induced by ion beam irradiation is presented. The sputtered particles are collected on a catcher which is analyzed in situ by Auger electron spectroscopy without breaking the ultra high vacuum (less than 10(-9) mbar), avoiding thus any problem linked to possible contamination. This method allows to measure the angular distribution of sputtering yield. It is now possible to study the sputtering of many elements such as carbon based materials. Preliminary results are presented in the case of highly oriented pyrolytic graphite and tungsten irradiated by an Ar(+) beam at 2.8 keV and 7 keV, respectively. PMID:24089874

Salou, P; Lebius, H; Benyagoub, A; Langlinay, T; Lelièvre, D; Ban-d'Etat, B

2013-09-01

84

Mass energy-transfer and mass energy-absorption coefficients, including in-flight positron annihilation for photon energies 1 keV to 100 MeV, 1992  

Microsoft Academic Search

Mass energy-transfer and mass energy-absorption coefficients are tabulated in units of sq cm\\/g for photon energies between 1 keV and 100 MeV for 29 elements (Z = 1-92), and 14 mixtures and compounds of general desimetric interest. Cross sections for photo-effects, incoherent scattering, and pair and triplet production are those compiled or generated by the National Institute of Standards and

P. D. Higgins; F. H. Attix; J. H. Hubbell; S. M. Seltzer; M. J. Berger

1992-01-01

85

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

86

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

87

He/sup 0/ on D/sub 2/ collisions at keV energies and the HeH/sub 2/ energy surface  

SciTech Connect

An experimental and theoretical study of He/sup 0/ on D/sub 2/ collisions at energies 1.0, 1.5, and 2.0 keV has been carried out to probe and to understand the energy surface of the ground electronic state of the HeH/sub 2/ triatomic molecule and of the intersections of this surface with those of low-lying electronically excited states. At each collision energy, doubly differential energy-loss spectra have been obtained and the results have been analyzed in terms of a parametric fit to an ab initio calculated ground-state energy surface. The scaled energy loss for quasielastic collisions (electronically elastic collisions with vibrational-rotational excitation) are shown to constitute a sensitive probe of the region of the ground-state energy surface in which the proximity of the He projectile breaks the H/sub 2/ (or D/sub 2/) bond. Sigmund scaling has been experimentally demonstrated to hold for the quasielastic channel in He on D/sub 2/ collisions despite the strong presence of electronically inelastic processes, a finding of particular significance, since the scaling law was derived under the assumption that there are no accessible electronically inelastic channels in the collision system. The theoretical study confirms this behavior for collisions in which electronic excitation is velocity independent and occurs in well-defined surface intersection regions. Cross sections differential in angle but integrated over all vibrotational-rotational inelastic energy losses have been both calculated and experimentally measured for the quasielastic channel, and the two are found to be in good agreement.

Jakacky J. Jr.; Pollack, E.; Snyder, R.; Russek, A.

1985-04-01

88

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

89

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

SciTech Connect

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

Mirzoeva, I. K., E-mail: colombo2006@mail.ru [Russian Academy of Sciences, Space Research Institute (Russian Federation)

2013-04-15

90

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

91

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

SciTech Connect

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. [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218 (United States)

2014-07-15

92

Monte Carlo study of correction factors for Spencer-Attix cavity theory at photon energies at or above 100 keV.  

PubMed

To develop a primary standard for 192Ir sources, the basic science on which this standard is based, i.e., Spencer-Attix cavity theory, must be established. In the present study Monte Carlo techniques are used to investigate the accuracy of this cavity theory for photons in the energy range from 20 to 1300 keV, since it is usually not applied at energies below that of 137Cs. Ma and Nahum [Phys. Med. Biol. 36, 413-428 (1991)] found that in low-energy photon beams the contribution from electrons caused by photons interacting in the cavity is substantial. For the average energy of the 192Ir spectrum they found a departure from Bragg-Gray conditions of up to 3% caused by photon interactions in the cavity. When Monte Carlo is used to calculate the response of a graphite ion chamber to an encapsulated 192Ir source it is found that it differs by less than 0.3% from the value predicted by Spencer-Attix cavity theory. Based on these Monte Carlo calculations, for cavities in graphite it is concluded that the Spencer-Attix cavity theory with delta = 10 keV is applicable within 0.5% for photon energies at 300 keV or above despite the breakdown of the assumption that there is no interaction of photons within the cavity. This means that it is possible to use a graphite ion chamber and Spencer-Attix cavity theory to calibrate an 192Ir source. It is also found that the use of delta related to the mean chord length instead of delta = 10 keV improves the agreement with Spencer-Attix cavity theory at 60Co from 0.2% to within 0.1% of unity. This is at the level of accuracy of which the Monte Carlo code EGSnrc calculates ion chamber responses. In addition, it is shown that the effects of other materials, e.g., insulators and holders, have a substantial effect on the ion chamber response and should be included in the correction factors for a primary standard of air kerma. PMID:10984227

Borg, J; Kawrakow, I; Rogers, D W; Seuntjens, J P

2000-08-01

93

Sputtering yields, range and range straggling in Al following Kr + ions bombardment in the energy range (20-160) keV  

NASA Astrophysics Data System (ADS)

The sputtering of Al metallic films by 84Kr + ions has been studied over the energy range (20-160) keV. Sputtering yield data have been extracted by means of the Rutherford backscattering technique (RBS) using a 2 MeV beam of 4He + ions. They have been compared to values derived by Sigmund's linear cascade theory, Yamamura's semi-empirical formula or by Monte Carlo computer simulation using the TRIM code. A fair agreement was observed between the measured sputtering yields and the predicted ones. The depth profiles of the implanted Kr + ions into Al have also been measured, and then fitted assuming Gaussian shape distributions, which allowed us to extract the projected range, Rp, and the associated range straggling, ? Rp. For the former stopping parameter, a very good agreement is obtained between experiment and the LSS theory predictions while the MC simulation also accounts satisfactorily for the measured data over the whole explored energy range, reflecting an adequate description of the projectile-target interaction by the universal potential of the Thomas-Fermi type assumed in the LSS formalism. In contrast, the ? Rp measured data show to be consistent with the predicted values only at E ? 60 keV but lie to ˜30% above them at lower energies. This discrepancy not caused by the sputtering effect relates to an incomplete evaluation of the range straggling by theory at low bombarding energies.

Mammeri, S.; Ouichaoui, S.; Zemih, R.; Ammi, H.; Abdesselam, M.; Chami, A. C.

2005-10-01

94

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

95

Measurement of total M shell photoionization cross sections for Au, Pb, Th and U in the energy region 6–12 keV  

Microsoft Academic Search

.  The total M shell relative photoionization \\u000a cross-sections for Au, Pb, Th and U have been measured in the energy region \\u000a 6–12 keV. External conversion K X-rays of suitable elements has been employed \\u000a as incident photons to photo ionize the total M shell of elements under \\u000a investigation. The method provides relative cross-sections therefore does \\u000a not make use of theoretically calculated average M

K. S. Mann; K. S. Kahlon; N. Singh; K. L. Allawadhi

2007-01-01

96

Measurement of mass attenuation coefficients of some boron compounds and the trommel sieve waste in the energy range 15.746– 40.930 keV  

Microsoft Academic Search

Mass attenuation coefficients of some boron compounds (H3BO3,Na2B4O7 and B3Al2O3) and the trommel sieve waste (TSW) have been measured by using an extremely narrow collimated-beam transmission method in the energy range 15.746–40.930keV. The characteristic K? and K? X-rays of Zr, Mo, Ag, In, Sb, Ba and Pr passed through H3BO3,Na2B4O7, B3Al2O3 and TSW were detected with a high-resolution Si(Li) detector.

Orhan ?çelli; Salih Erzeneo?lu; Recep Boncukçuo?lu

2003-01-01

97

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

SciTech Connect

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

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

2010-11-12

98

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

99

Mass energy-transfer and mass energy-absorption coefficients, including in-flight positron annihilation for photon energies 1 keV to 100 MeV, 1992  

SciTech Connect

Mass energy-transfer and mass energy-absorption coefficients are tabulated in units of sq cm/g for photon energies between 1 keV and 100 MeV for 29 elements (Z = 1-92), and 14 mixtures and compounds of general dosimetric interest. Cross sections for photo-effect, incoherent scattering, pair and triplet production are those compiled or generated by the National Institute of Standards and Technology (NIST) (formerly the National Bureau of Standards). Corrections are included for in-flight positron annihilation, previously not applied in NIST calculations for energies above 10 MeV. Agreement with recently published data is good for energies above 1 MeV, but the authors find differences in mass energy-absorption coefficients in the low energy region of as much as 4% compared with the last NIST compilation, and as much as 9% when compared with other recent compilations.

Higgins, P.D.; Attix, F.H.; Hubbell, J.H.; Seltzer, S.M.; Berger, M.J.

1992-03-01

100

Array-compatible transition-edge sensor microcalorimeter {gamma}-ray detector with 42 eV energy resolution at 103 keV  

SciTech Connect

The authors describe a microcalorimeter {gamma}-ray detector with measured energy resolution of 42 eV full width at half maximum for 103 keV photons. This detector consists of a thermally isolated superconducting transition-edge thermometer and a superconducting bulk tin photon absorber. The absorber is attached with a technique compatible with producing arrays of high-resolution {gamma}-ray detectors. The results of a detailed characterization of the detector, which includes measurements of the complex impedance, detector noise, and time-domain pulse response, suggest that a deeper understanding and optimization of the thermal transport between the absorber and thermometer could significantly improve the energy resolution of future detectors.

Zink, B. L.; Ullom, J. N.; Beall, J. A.; Irwin, K. D.; Doriese, W. B.; Duncan, W. D.; Ferreira, L.; Hilton, G. C.; Horansky, R. D.; Reintsema, C. D.; Vale, L. R. [National Institute of Standards and Technology, 325 Broadway MC 817.03, Boulder, Colorado 80305 (United States)

2006-09-18

101

{sup 241}Am(n,{gamma}) cross section in the neutron energy region between 0.02 eV and 300 keV  

SciTech Connect

The Detector for Advanced Neutron Capture Experiments (DANCE) at Los Alamos National Laboratory (LANL) was used for a neutron capture cross section measurement on {sup 241}Am. The high granularity of the DANCE array (160 BaF2 detectors in a 4{pi} geometry) enables an efficient detection of prompt gamma rays following neutron capture. The preliminary results on the {sup 241}Am(n,{gamma}) cross section are presented from 0.02 eV to 300 keV. The cross section at thermal energy E{sub n} = 0.0253 eV was determined to be 665{+-}33 barns. Resonance parameters were obtained using the SAMMY7 fit to the measured cross section in the resonance region. Significant discrepancies were found between our results and data evaluations for the first three lowest lying resonances. The cross section for neutrons with E{sub n}>l keV agrees well with the ENDF/B-VII.0 and JENDL-3.3 evaluations.

Jandel, M.; Bredeweg, T. A.; Bond, E. M.; Chadwick, M. B.; Clement, R. R.; Couture, A.; O' Donnell, J. M.; Haight, R. C.; Reifarth, R.; Rundberg, R. S.; Ullmann, J. L.; Vieira, D. J.; Wilhelmy, J. B.; Wouters, J. M. [Los Alamos National Laboratory, Los Alamos, NM, 87545 (United States); Macri, R. A.; Wu, C. Y.; Becker, J. A. [Lawrence Livermore National Laboratory, Livermore, CA, 94550 (United States)

2008-04-17

102

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

E-print Network

. . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 E. Results of Angular and Energy Distributions from TCE . . . . . 67 V CONCLUSIONS : : : : : : : : : : : : : : : : : : : : : : : : : : : 71 REFERENCES : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 73 APPENDIX A... interaction between the projectile proton and the target electron at a lower impact energy. What we need is a pro- 3 jectile continuum channel to effectively simulate the electron ionization. This brought us to use the Two-Centered Expansion (TCE) method...

Fu, Jun

2004-11-15

103

YIELDS OF IONS AND EXCITED STATES IN NONPOLAR LIQUIDS EXPOSED TO X-RAYS OF 1 TO 30 KEV ENERGY  

SciTech Connect

When x-rays from a synchrotron source are absorbed in a liquid, the x-ray energy (E{sub x}) is converted by the photoelectric effect into the kinetic energy of the electrons released. For hydrocarbons, absorption by the K-electrons of carbon dominates. Thus the energy of the photoelectron (E{sub pe}) is E{sub x}-E{sub b}, where E{sub b} is the K-shell binding energy of carbon. Additional electrons with energy equal to E{sub b} is released in the Auger process that fills the hole in the K-shell. These energetic electrons will produce many ionizations, excitations and products. The consequences of the high density of ionizations and excitations along the track of the photoelectron and special effects near the K-edge are examined here.

HOLROYD,R.A.

1999-08-18

104

A semi-empirical approach to analyze the activities of cylindrical radioactive samples using gamma energies from 185 to 1764 keV.  

PubMed

This work suggests a method for determining the activities of cylindrical radioactive samples. The self-attenuation factor was applied for providing the self-absorption correction of gamma rays in the sample material. The experimental measurement of a (238)U reference sample and the calculation using the MCNP5 code allow obtaining the semi-empirical formulae of detecting efficiencies for the gamma energies ranged from 185 to 1764keV. These formulae were used to determine the activities of the (238)U, (226)Ra, (232)Th, (137)Cs and (40)K nuclides in the IAEA RGU-1, IAEA-434, IAEA RGTh-1, IAEA-152 and IAEA RGK-1 radioactive standards. The coincidence summing corrections for gamma rays in the (238)U and (232)Th series were applied. The activities obtained in this work were in good agreement with the reference values. PMID:25113537

Huy, Ngo Quang; Binh, Do Quang

2014-12-01

105

Calibration of X-ray detectors in the 8 to 115 keV energy range and their application to diagnostics on the National Ignition Facility  

SciTech Connect

The calibration of X-ray diagnostics is of paramount importance to the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory (LLNL). National Security Technologies LLC (NSTec) fills this need by providing a wide variety of calibration and diagnostic development services in support of the ongoing research efforts at NIF. The X-ray source in the High Energy X-ray lab utilizes induced fluorescence in a variety of metal foils to produce a beam of characteristic X rays ranging from 8 to 111 keV. Presented are the methods used for calibrating a High Purity Germanium detector, which has been absolutely calibrated using radioactive check sources, compared against a silicon photodiode calibrated at Physikalisch Technische Bundesanstalt (PTB). Also included is a limited presentation of results from the recent calibration of the upgraded Filter Fluorescer X ray Spectrometer.

J. J. Lee, M. J. Haugh, G. LaCaille, and P. Torres

2012-10-01

106

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

107

High-precision measurement of the light response of BC-418 plastic scintillator to protons with energies from 100 keV to 10 MeV  

NASA Astrophysics Data System (ADS)

The determination of the light response of many organic scintillators to various types of radiation has been a subject of numerous experimental as well as theoretical studies in the past. But while the data on light response to particles with energies above 1 MeV are precise and abundant, the information on light response to very low energy particles (i.e. below 1 MeV) is scarce or completely missing. In this study we measured the light response of a BC-418 scintillator to protons with energies from 100 keV to 10 MeV. The experiment was performed at Weapons Neutron Research Facility at LANSCE, Los Alamos. The neutron beam from a spallation source is used to irradiate the active target made from BC-418 plastic scintillator. The recoiled protons detected in the active target are measured in coincidence with elastically scattered incident neutrons detected by and adjacent liquid scintillator. Time of flight of the incident neutron and the knowledge of scattering geometry allow for a kinematically complete and high-precision measurement of the light response as a function of the proton energy.

Henzl, Vladimir; Daub, Brian; French, Jennifer; Matthews, June; Kovash, Michael; Wender, Stephen; Famiano, Michael; Koehler, Katrina; Yuly, Mark

2010-11-01

108

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

NASA Astrophysics Data System (ADS)

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

Gonzales, Daniel; Cavness, Brandon; Williams, Scott

2012-03-01

109

Angular distribution of thick-target bremsstrahlung produced by electrons with initial energies ranging from 10 to 20 keV incident on Ag  

NASA Astrophysics Data System (ADS)

Experimental results are presented comparing the intensities of the bremsstrahlung produced by electrons with initial energies ranging from 10 to 20 keV incident on a thick Ag target, measured at forward angles in the range of 0° to 55°. When the data are corrected for attenuation due to photon absorption within the target, the results indicate that the detected radiation is distributed anisotropically only at photon energies k that are approximately equal to the initial energy of the incident electrons E0. The results of our experiments suggest that, as k/E0 ? 0, the detected radiation essentially becomes isotropic due primarily to the scattering of electrons within the target. A comparison to the theory of Kissel [At. Data Nucl. Data TablesADNDAT0092-640X10.1016/0092-640X(83)90001-3 28, 381 (1983)] suggests that the angular distribution of bremsstrahlung emitted by electrons incident on thick targets is similar to the angular distribution of bremsstrahlung emitted by electrons incident on free-atom targets only when k/E0 ? 1. The experimental data also are in approximate agreement with the angular distribution predictions of the Monte Carlo program penelope.

Gonzales, D.; Cavness, B.; Williams, S.

2011-11-01

110

Ion Beam Materials Analysis and Modifications at keV to MeV Energies at the University of North Texas  

NASA Astrophysics Data System (ADS)

The University of North Texas (UNT) Ion Beam Modification and Analysis Laboratory (IBMAL) has four particle accelerators including a National Electrostatics Corporation (NEC) 9SDH-2 3 MV tandem Pelletron, a NEC 9SH 3 MV single-ended Pelletron, and a 200 kV Cockcroft-Walton. A fourth HVEC AK 2.5 MV Van de Graaff accelerator is presently being refurbished as an educational training facility. These accelerators can produce and accelerate almost any ion in the periodic table at energies from a few keV to tens of MeV. They are used to modify materials by ion implantation and to analyze materials by numerous atomic and nuclear physics techniques. The NEC 9SH accelerator was recently installed in the IBMAL and subsequently upgraded with the addition of a capacitive-liner and terminal potential stabilization system to reduce ion energy spread and therefore improve spatial resolution of the probing ion beam to hundreds of nanometers. Research involves materials modification and synthesis by ion implantation for photonic, electronic, and magnetic applications, micro-fabrication by high energy (MeV) ion beam lithography, microanalysis of biomedical and semiconductor materials, development of highenergy ion nanoprobe focusing systems, and educational and outreach activities. An overview of the IBMAL facilities and some of the current research projects are discussed.

Rout, Bibhudutta; Dhoubhadel, Mangal S.; Poudel, Prakash R.; Kummari, Venkata C.; Lakshantha, Wickramaarachchige J.; Manuel, Jack E.; Bohara, Gyanendra; Szilasi, Szabolcs Z.; Glass, Gary A.; McDaniel, Floyd D.

2014-02-01

111

Measurement of the 13C(?, n)16O reaction at astrophysical energies using the Trojan Horse Method. Focus on the -3 keV sub-threshold resonance  

NASA Astrophysics Data System (ADS)

Most of the nuclei in the mass range 90 ? A ? 208 are produced through the so-called s-process, namely through a series of neutron capture reactions on seed nuclei followed by ?-decays. The 13C(?, n)16O reaction is the neutron source for the main component of the s-process. It is active inside the helium-burning shell of asymptotic giant branch stars, at temperatures ? 108 K, corresponding to an energy interval of 140 - 230 keV. In this region, the astrophysical S(E)-factor is dominated by the -3 keV sub-threshold resonance due to the 6.356 MeV level in 17O. Direct measurements could not soundly establish its contribution owing to the cross section suppression at astrophysical energies determined by the Coulomb barrier between interacting nuclei. Indirect measurements and extrapolations yielded inconsistent results, calling for further investigations. The Trojan Horse Method turns out to be very suited for the study of the 13C(?, n)16O reaction as it allows us to access the low as well as the negative energy re- gion, in particular in the case of resonance reactions. We have applied the Trojan HorseMethod to the 13C(6Li, n16O)d quasi-free reaction. By using the modified R-matrix approach, the asymptotic normalization coefficient {( {tilde C{? 13{{C}}}17{{O(1/}{{{2}}{ + }}{{)}}}} )^2} of the 6.356 MeV level has been deduced as well as the n-partial width, allowing to attain an unprecedented accuracy for the 13C(?, n)16O astrophysical factor. A preliminary analysis of a partial data set has lead to {( {tilde C{? 13{{C}}}17{{O(1/}{{{2}}{ + }}{{)}}}} )^2} = 6.7 - 0.6 + 0.9 {{f}}{{{m}} - 1}, slightly larger than the values in the literature, determining a 13C(?, n)16O reaction rate in agreement with the most results in the literature at ˜ 108 K, with enhanced accuracy thanks to this innovative approach.

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.

2014-03-01

112

Focusing x-ray monochromator for EXAFS studies in the energy range 4-30 keV  

SciTech Connect

The design and operating principles of a focusing x-ray monochromator are described. Consistent with extended x-ray absorption fine structure (EXAFS) applications it allows rapid tuning while maintaining high energy resolution and a fixed focus at the sample. The basic instrument consists of two opposing two crystal monochromators with the second and third crystals operating as a dispersive monochromator. This provides the intrinsic resolution of the crystals independent of silt settings or source size effects. Focusing is achieved by a sagittally bent fourth crystal. To maintain a fixed focus two options are available. In the first, the second crystal pair is translated while the radius of the fourth crystal is held fixed. Thus, the focus remains at the sample even though the angle of incidence on the bent crystal is changing. In the second option the radius of the bent crystal is changed dynamically as the scan is carried out. These techniques are compared and a crystal bender designed for rapid tuning is described.

Heald, S.M.

1983-01-01

113

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

114

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

115

Technical Note: Influence of the phantom material on the absorbed-dose energy dependence of the EBT3 radiochromic film for photons in the energy range 3 keV–18 MeV  

SciTech Connect

Purpose: Water is the reference medium for radiation therapy dosimetry, but for film dosimetry it is more practical to use a solid phantom. As the composition of solid phantoms differs from that of water, the energy dependence of film exposed within solid phantoms may also differ. The energy dependence of a radiochromic film for a given beam quality Q (energy for monoenergetic beams) has two components: the intrinsic energy dependence and the absorbed-dose energy dependence f(Q), the latter of which can be calculated through a Monte Carlo simulation of radiation transport. The authors used Monte Carlo simulations to study the influence of the phantom material on the f(Q) of the EBT3 radiochromic film (Ashland Specialty Ingredients, Wayne, NJ) for photon beams with energies between 3 keV and 18 MeV. Methods: All simulations were carried out with the general-purpose Monte Carlo code PENELOPE 2011. The geometrical model consisted of a cylindrical phantom, with the film positioned at different depths depending on the initial photon energy. The authors simulated monoenergetic parallel photon beams and x-ray beams from a superficial therapy system. To validate their choice of simulation parameters, they also calculated f(Q) for older film models, EBT and EBT2, comparing with published results. In addition to water, they calculated f(Q) of the EBT3 film for solid phantom materials commonly used for film dosimetry: RW1 and RW3 (PTW-Freiburg, Freiburg, Germany), Solid Water (Gammex-RMI, Madison, WI), and PMMA. Finally, they combined their calculated f(Q) with published overall energy response data to obtain the intrinsic energy dependence of the EBT3 film in water. Results: The calculated f(Q) for EBT and EBT2 films was statistically compatible with previously published data. Between 10 keV and 18 MeV, the variation found in f(Q) of the EBT3 film for water was within 2.3%, with a standard statistical uncertainty less than 1%. If the quantity dose-to-water in the phantom is considered, which is the common practice in radiation dosimetry, the maximum difference of energy dependence for the solid phantoms with respect to water is about 6%, at an energy of 50 keV. Conclusions: The EBT3 film shows a reasonably constant absorbed-dose energy dependence when irradiated in water. If the dose-to-water in the phantom is considered, the maximum difference of EBT3 film energy dependence with the solid phantoms studied with respect to water is about 6% (at an energy of 50 keV). The reported overall energy dependence of the EBT3 film in water at energies below 100 keV is mainly due to the intrinsic energy dependence.

Hermida-López, M., E-mail: mhermida@vhebron.net [NCTeam, Strahlenklinik, Universitätsklinikum Essen, Hufelandstraße 55, Essen D-45122, Germany and Servei de Física i Protecció Radiològica, Hospital Universitari Vall d’Hebron, Pg. Vall d’Hebron 119-129, Barcelona 08035 (Spain); Lüdemann, L.; Flühs, A. [Medical Physics, Strahlenklinik, Universitätsklinikum Essen, Hufelandstraße 55, Essen D-45122 (Germany); Brualla, L. [NCTeam, Strahlenklinik, Universitätsklinikum Essen, Hufelandstraße 55, Essen D-45122 (Germany)

2014-11-01

116

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

NASA Astrophysics Data System (ADS)

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

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

2010-07-01

117

Saturated ablation in metal hydrides and acceleration of protons and deuterons to keV energies with a soft-x-ray laser  

SciTech Connect

Studies of materials under extreme conditions have relevance to a broad area of research, including planetary physics, fusion research, materials science, and structural biology with x-ray lasers. We study such extreme conditions and experimentally probe the interaction between ultrashort soft x-ray pulses and solid targets (metals and their deuterides) at the FLASH free-electron laser where power densities exceeding 10{sup 17} W/cm{sup 2} were reached. Time-of-flight ion spectrometry and crater analysis were used to characterize the interaction. The results show the onset of saturation in the ablation process at power densities above 10{sup 16} W/cm{sup 2}. This effect can be linked to a transiently induced x-ray transparency in the solid by the femtosecond x-ray pulse at high power densities. The measured kinetic energies of protons and deuterons ejected from the surface reach several keV and concur with predictions from plasma-expansion models. Simulations of the interactions were performed with a nonlocal thermodynamic equilibrium code with radiation transfer. These calculations return critical depths similar to the observed crater depths and capture the transient surface transparency at higher power densities.

Andreasson, J.; Iwan, B.; Abreu, E.; Seibert, M. M.; Hajdu, J.; Timneanu, N. [Department of Cell and Molecular Biology, Uppsala University, Box 596, SE-75124 Uppsala (Sweden); Andrejczuk, A. [Faculty of Physics, University of Bialystok, Lipowa Str. 41, PL-15424 Bialystok (Poland); Bergh, M. [Swedish Defence Research Agency, SE-16490 Stockholm (Sweden); Caleman, C. [Physik Department E17, Technische Universitaet Muenchen, James-Franck-Strasse, DE-85748 Garching (Germany); Nelson, A. J. [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550 (United States); Bajt, S.; Faeustlin, R. R.; Singer, W.; Toleikis, S.; Tschentscher, T. [Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, DE-22603 Hamburg (Germany); Chalupsky, J.; Hajkova, V.; Juha, L. [Institute of Physics ASCR, Na Slovance 2, CZ-18221 Prague 8 (Czech Republic); Chapman, H. N. [Center for Free-Electron Laser Science, DESY, Notkestrasse 85, DE-22607 Hamburg (Germany); Department of Physics, University of Hamburg, Luruper Chaussee 149, DE-22761 Hamburg (Germany); Heimann, P. A. [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, California 94720 (United States)

2011-01-15

118

Saturated ablation in metal hydrides and acceleration of protons and deuterons to keV energies with a soft-x-ray laser  

NASA Astrophysics Data System (ADS)

Studies of materials under extreme conditions have relevance to a broad area of research, including planetary physics, fusion research, materials science, and structural biology with x-ray lasers. We study such extreme conditions and experimentally probe the interaction between ultrashort soft x-ray pulses and solid targets (metals and their deuterides) at the FLASH free-electron laser where power densities exceeding 1017 W/cm2 were reached. Time-of-flight ion spectrometry and crater analysis were used to characterize the interaction. The results show the onset of saturation in the ablation process at power densities above 1016 W/cm2. This effect can be linked to a transiently induced x-ray transparency in the solid by the femtosecond x-ray pulse at high power densities. The measured kinetic energies of protons and deuterons ejected from the surface reach several keV and concur with predictions from plasma-expansion models. Simulations of the interactions were performed with a nonlocal thermodynamic equilibrium code with radiation transfer. These calculations return critical depths similar to the observed crater depths and capture the transient surface transparency at higher power densities.

Andreasson, J.; Iwan, B.; Andrejczuk, A.; Abreu, E.; Bergh, M.; Caleman, C.; Nelson, A. J.; Bajt, S.; Chalupsky, J.; Chapman, H. N.; Fäustlin, R. R.; Hajkova, V.; Heimann, P. A.; Hjörvarsson, B.; Juha, L.; Klinger, D.; Krzywinski, J.; Nagler, B.; Pálsson, G. K.; Singer, W.; Seibert, M. M.; Sobierajski, R.; Toleikis, S.; Tschentscher, T.; Vinko, S. M.; Lee, R. W.; Hajdu, J.; Tîmneanu, N.

2011-01-01

119

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

NASA Astrophysics Data System (ADS)

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 time shifted to the subsolar magnetopause and averaged for 15 min prior to each sampling of Earth's magnetic field-aligned ion flow densities. When the flow data are arranged according to the polarity of the IMF Bz (in GSM coordinates) and limited to times with Bz > 3 nT or Bz < -3 nT, the total rate of ion outflow is seen to be significantly enhanced with negative Bz, typically by factors of 2.5-3 for the O+ and 1.5-2 for the H+, more than previously reported from similar but less extensive comparisons. With either IMF Bz polarity the rate of ion outflow is well correlated with the solar wind energy flow density, especially well with the density of kinetic energy flow. The rate of ion outflow within the instrument's energy range is a strong function of the Polar satellite altitude, increasing almost threefold from perigee (R ˜ 2 RE) toward apogee (R ˜ 4-9 RE) for O+ ions, i.e., up to 1026 ions s-1 or more per hemisphere. The apogee enhancement may be still larger for the H+, but it is obscured by mantle flow of cusp origin solar H+. Ion mean energy also increases with altitude, leading to about a twentyfold increase in the O+ energy flow rate from Polar perigee to apogee altitude, reaching values of 20 GW or more per hemisphere. While the perigee outflow of H+ has little or no seasonal modulation, in terms of ions s-1 the O+ outflow rates at both altitudes do increase during local summer and so does the rate of cusp origin H+ flow near apogee. The latter rate, in fact, has very similar seasonal modulation as the O+ rates, suggesting that it has a significant influence on the O+ outflow.

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

2004-12-01

120

Tables of X-ray mass attenuation coefficients and mass energy-absorption coefficients 1 keV to 20 MeV for elements Z=1 to 92 and 48 additional substances of dosimetric interest  

Microsoft Academic Search

Tables and graphs of the photon mass attenuation coefficient mu\\/rho and the mass energy-absorption coefficient mu(en)\\/rho are presented for all of the elements Z=1 to 92, and for 48 compounds and mixtures of radiological interest. The tables cover energies of the photon (x ray, gamma ray, bremsstrahlung) from 1 keV to 20 MeV. The mu\\/rho values are taken from the

J. H. Hubbell; Stephen M Seltzer

1995-01-01

121

Generation of L sub-shell photo-ionization cross-sections for elements 18? Z?92 at energies .320–115.606 keV (A computer program ‘LSPICS’)  

Microsoft Academic Search

L sub-shell photo-ionization cross-sections, ?Li, for elements 18?Z?92 at energies .320–115.606keV have been generated from an empirical relation fitted to Scofield's L sub-shell photo-ionization cross-section values. The excitation energy E for an element is constrained by the condition that only L and higher shell vacancies are produced in the elements. The closeness of generated and existing values of Scofield's L

Ajay Sharma; Raj Mittal

2005-01-01

122

Electron impact calculations of total elastic cross sections over a wide energy range - 0.01 eV to 2 keV for CH4, SiH4 and H2O  

Microsoft Academic Search

In this paper we report the results of a new theoretical methodology for determining the total elastic electron scattering cross section, Q el , over a wide range of incident energies between 0.01 eV and 2 keV. We have combined results from the UK molecular R-matrix code using Quantemol-N software to determine Q el for incident energies between 0.01 eV

M. Vinodkumar; C. G. Limbachiya; K. N. Joshipura; N. J. Mason

2011-01-01

123

Calculation of electron-impact rotationally elastic total cross sections for NHâ, HâS, and PHâ over the energy range from 0.01 eV to 2 keV  

Microsoft Academic Search

This paper report results of calculation of the total cross section Q{sub T} for electron impact on NHâ, HâS, and PHâ over a wide range of incident energies from 0.01 eV to 2 keV. Total cross sections Q{sub T} (elastic plus electronic excitation) for incident energies below the ionization threshold of the target were calculated using the UK molecular R-matrix

Chetan Limbachiya; Minaxi Vinodkumar; Nigel Mason

2011-01-01

124

Calculation of electron-impact rotationally elastic total cross sections for NH3, H2S, and PH3 over the energy range from 0.01 eV to 2 keV  

Microsoft Academic Search

This paper report results of calculation of the total cross section QT for electron impact on NH3, H2S, and PH3 over a wide range of incident energies from 0.01 eV to 2 keV. Total cross sections QT (elastic plus electronic excitation) for incident energies below the ionization threshold of the target were calculated using the UK molecular R-matrix code through

Chetan Limbachiya; Minaxi Vinodkumar; Nigel Mason

2011-01-01

125

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

126

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

127

Demonstration of direct energy recovery of full energy ions at 40 keV on a PLT\\/ISX beam system  

Microsoft Academic Search

The desire for multisecond beams in the 80 keV\\/nucleon energy range at 10 MW\\/module emphasized the need for technological advances in several areas. At such beam energies, as much as 75 percent of the initial beam energy is retained in the unneutralized ion components. As a result, two questions immediately come to mind: how can one dispose of this energy;

W. L. Stirling; G. C. Barber; W. K. Dagenhart; R. R. Feezell; W. L. Gardner; H. H. Haselton; J. Kim; M. Menon; N. S. Ponte; C. C. Tsai

1980-01-01

128

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

129

Cross Sections and Swarm Coefficients for Nitrogen Ions and Neutrals in N2 and Argon Ions and Neutrals in Ar for Energies from 0.1 eV to 10 keV  

Microsoft Academic Search

Graphical and tabulated data and the associated bibliography are presented for cross sections for elastic, excitation, and ionization collisions of N+, N+2, N, and N2 with N2 and for Ar+ and Ar with Ar for laboratory energies from 0.1 eV to 10 keV. Where appropriate, drift velocities and reaction or excitation coefficients are calculated from the cross sections and recommended

A. V. Phelps

1991-01-01

130

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 29-60 keV  

Microsoft Academic Search

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

Martin D. de Jonge; Chanh Q. Tran; Christopher T. Chantler; Zwi Barnea; Bipin B. Dhal; David Paterson; Elliot P. Kanter; Stephen H. Southworth; Linda Young; Mark A. Beno; Jennifer A. Linton; Guy Jennings

2007-01-01

131

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 29-60keV  

Microsoft Academic Search

We use the x-ray extended-range technique (XERT) [C. T. Chantler , Phys. Rev. A 64, 062506 (2001)] to measure the mass attenuation coefficients of tin in the x-ray energy range of 29-60keV 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

Martin D. de Jonge; Chanh Q. Tran; Christopher T. Chantler; Zwi Barnea; Bipin B. Dhal; David Paterson; Elliot P. Kanter; Stephen H. Southworth; Linda Young; Mark A. Beno; Jennifer A. Linton; Guy Jennings

2007-01-01

132

Demonstration of Direct Energy Recovery of Full Energy Ions at 40 keV on a PLT\\/ISX Beam System  

Microsoft Academic Search

Neutral beam injection systems that employ positive ion sources presently operate at energies of about 40 to 50 keV\\/nucleon at 60 A (Princeton Large Torus (PLT)) or 100 A (Princeton Divertor Experiment (PDX) or the Oak Ridge National Laboratory (ORNL) Impurities Study Experiment (ISX)) with about 60% conversion efficiency. However, the desire for multisecond beams in the 80-keV\\/nucleon energy range

W. L. Stirling; G. C. Barber; W. K. Dagenhart; R. R. Feezell; W. L. Gardner; H. H. Haselton; J. Kim; M. Menon; N. S. Ponte; C. C. Tsai; J. H. Whealton

1981-01-01

133

Energy dependence of the total cross section for electron scattering by N 2 and CO molecules at energies above 1 keV  

Microsoft Academic Search

Recently, an analytical formula to reproduce total cross section data for electron scattering by diatomic molecules has been published by Liu and Sun (Phys. Lett. A 222 (1996) 233). This formula was derived by fitting available experimental data for intermediate and high energy to a one-parameter expression that the authors state to be based on the Born approximation. However, as

G. García; F. Blanco

2001-01-01

134

Energy distributions of hydrocarbon secondary ions from thin organic films under keV ion bombardment: Correlation between kinetic and formation energy of ions sputtered from tricosenoic acid  

NASA Astrophysics Data System (ADS)

The kinetic energy distributions (KED) of secondary ions sputtered from tricosenoic acid films under Ga + bombardment have been presented recently [1]. Below mass 100, the positive ion spectrum of tricosenoic acid is mainly constituted by the series of C xH y+ peaks. Within each C iH y+ series, the KED of these ions broadens when the number y of hydrogen atoms decreases. In this paper, we propose a phenomenological model accounting for the characteristic behavior of these ions. It is based on an initial transfer of momentum leading to the emission of an original fragment, reflecting the chemical structure of the target, and followed by a fast reorganization when its internal energy is in excess. Consequently, the ions emitted as a result of a violent collision, carrying a large excess of internal energy, will exhibit both a broad KED and a high degree of reorganization with respect to the structure of the original fragment. This interpretation highlights the effect of the chemical and molecular structure of the organic target on the emission process of the secondary molecular ions. Indeed, this structure determines the nature of the original fragments which have proved their utility for analytical purpose. These fragments lead to intense peaks in the mass spectra, allowing the recognition of the original chemical structure of the samples (fingerprint). In addition, such secondary ions resulting from a direct emission pathway, as suggested by their very narrow KED, turn out to be the best candidates for quantification.

Delcorte, A.; Bertrand, P.

1996-09-01

135

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

PubMed

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

Dryak, Pavel; Kovar, Petr

2006-01-01

136

Schwinger variational approach for a direct excitation of hydrogen-like (Li2+ (1s)) target to the level n=3 by proton impact energies from 9 keV to 3 MeV  

NASA Astrophysics Data System (ADS)

The excitation cross sections for hydrogen-like (Li2+(1s)) to the 3s, 3p and 3d states by proton impact have been calculated in a wide energy range from 9 keV to 3 MeV, using the Schwinger's variational principle within the impact parameter formalism. These cross sections are relevant to controlled nuclear fusion studies [1]. The behaviors of the computed cross sections are in excellent agreement with available theoretical results, obtained by close-coupling method which is those of TCAO of Ermolaev et al [1] and SCE of Hall et al [2].

Khelfaoui, Friha; Lasri, Boumediene; Abbes, Oukacha

2012-06-01

137

The 1 keV to 200 keV X-ray Spectrum of NGC 2992 and NGC 3081  

E-print Network

The Seyfert 2 galaxies NGC 2992 and NGC 3081 have been observed by INTEGRAL and Swift. We report about the results and the comparison of the spectrum above 10 keV based on INTEGRAL IBIS/ISGRI, Swift/BAT, and BeppoSAX/PDS. A spectrum can be extracted in the X-ray energy band ranging from 1 keV up to 200 keV. Although NGC 2992 shows a complex spectrum below 10 keV, the hard tail observed by various missions exhibits a slope with photon index = 2, independent on the flux level during the observation. No cut-off is detectable up to the detection limit around 200 keV. In addition, NGC 3081 is detected in the INTEGRAL and Swift observation and also shows an unbroken Gamma = 1.8 spectrum up to 150 keV. These two Seyfert galaxies give further evidence that a high-energy cut-off in the hard X-ray spectra is often located at energies E_C >> 100 keV. In NGC 2992 a constant spectral shape is observed over a hard X-ray luminosity variation by a factor of 11. This might indicate that the physical conditions of the emitting hot plasma are constant, while the amount of plasma varies, due to long-term flaring activity.

Volker Beckmann; Neil Gehrels; Jack Tueller

2007-04-20

138

(Temperature coefficient of U-235 fueled thermal reactors and nuclear data on eta at thermal neutron energies and 239-Pu fission cross sections between 1 and 100 keV)  

SciTech Connect

The Evaluation Cooperation Subgroup, Actinide Data in the Thermal Energy Range,'' met primarily to discuss problems related to the temperature coefficient of U-235 fueled thermal reactors and nuclear data on eta at thermal neutron energies, the number of neutrons emitted per neutron absorbed. The preliminary results of the eta measurements done by M. Moxon of Harwell at Oak Ridge were presented and preliminary results by H. Weigman of Geel with a new method were presented. All three measurements from Geel show a pronounced down-slope of eta with decreasing neutron energy and both measurements by Moxon show only a very slight down slope. Acceptance of the Geel results would solve about one-third of the problem in the calculated reactor temperature coefficient. The Evaluation Cooperation Subgroup, 239-Pu Fission Cross Sections between 1 and 100 keV,'' met to discuss the 4% lower than the previously evaluated fission cross sections between 20 eV and 100 keV as evaluated from the fission data of the Weston and Todd and transmission data of J. A. Harvey (all of ORNL). These lower fission cross sections are discrepant with integral measurements, however, it is conceivable that there could be compensating effects, perhaps in the U-238 cross sections. A general meeting and a benchmark testing session of the JEF were attended as a representative of CSEWG JEF-2.2 is scheduled for general release after about another year of testing. Cooperation in evaluation of nuclear data between Europe, Japan, and the US has increased dramatically in the last few years because of manpower limitations.

Weston, L.W.

1990-12-21

139

The INTEGRAL – HESS\\/MAGIC connection: A new class of cosmic high energy accelerators from keV to TeV  

Microsoft Academic Search

The recent completion and operation of the High Energy Stereoscopic System [1], an array of ground based imaging Cherenkov telescopes, has provided a survey with unprecedented sensitivity of the inner part of the Galaxy and revealed a new population of very high energy gamma-rays sources emitting at E > 100 GeV. Most of them were reported to have no known

Pietro Ubertini

2005-01-01

140

The INTEGRAL — HESS\\/MAGIC connection: A new class of cosmic high energy accelerators from keV to TeV  

Microsoft Academic Search

The recent completion and operation of the High Energy Stereoscopic System [1], an array of ground based imaging Cherenkov telescopes, has provided a survey with unprecedented sensitivity of the inner\\u000a part of the Galaxy and revealed a new population of very high energy gamma-rays sources emitting at E > 100 GeV. Most of them\\u000a were reported to have no known

P. Ubertini

141

X-ray attenuation coefficient measurements for photon energies 4.508–13.375 keV in Cu, Cr and their compounds and the validity of the mixture rule  

Microsoft Academic Search

To investigate the validity of the mixture rule which is used to compute the mass attenuation coefficients in compounds, the total mass attenuation coefficients for Cu, Cr elements and Cu2O, CuC2O4, CuCl2·2H2O, Cu(C2H3O2)2·H2O, Cr2O3, Cr(NO3)3, Cr2(SO4)3·H2O, Cr3(CH3CO7)(OH)2 compounds were measured at photon energies between 4.508 and 13.375keV by using the secondary excitation method. Ti, Mn, Fe, Ni, Zn, Ge, As,

Ü Turgut; Ö ?im?ek; E Büyükkasap; M Ertu?rul

2004-01-01

142

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

143

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

144

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

145

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

146

Collision spectroscopy of the He/sup 0/ + D/sub 2/ system in the 1 to 2 keV energy range  

SciTech Connect

Direct scattering of He/sup 0/ on D/sub 2/ is studied, both theoretically and experimentally, with particular emphasis on quasi-elastic scattering. Sigmund scaling is demonstrated, despite the presence of inelastic channels. This is significant, because one of the requirements in Sigmund's derivation is that no inelastic channels be open. In addition, cross sections for the quasi-elastic processes as well as the one and two electron excitation processes are studied. Some of the lowest lying excited state surfaces of the HeH/sub 2/ system are calculated, as well as the portion of the ground state surface in which the He projectile is in close proximity to the H/sub 2/ target. Agreement between theory and experiment for the scaling and for the cross sections indicate that some understanding of the ground state energy surface was attained. In addition, classical scattering calculations were carried out to better understand this surface and to understand the breakdown of the scaling due to velocity effects.

Jakacky, J.M. Jr.

1984-01-01

147

Energy-loss scaling in 0. 5--3. 5-keV Ne/sup +/ and Ne collisions with H/sub 2/ and D/sub 2/  

SciTech Connect

Enery losses are measured in Ne/sup +/+D/sub 2/, Ne/sup +/+H/sub 2/, and Ne+D/sub 2/ collisions for beam energies 0.5< or =E< or =3.5 keV and scattering angles theta< or =5 /sup 0/. Rotational and vibrational excitation of the target molecule is found, but the probability of direct electronic excitation is seen to be extremely small. The results indicate that the most probable laboratory energy loss T/sub 0/ for a projectile with mass M/sub p/ scattered by a homonuclear binary molecule with atomic masses M scales so that the quantity f=T/sub 0/M/(M/sub p/Etheta/sup 2/) is a function of the reduced scattering angle tau=Etheta only, as recently predicted theoretically by Sigmund. The function f (tau) is found to be the same for the Ne/sup +/+D/sub 2/ and Ne/sup +/+H/sub 2/ systems, but is strongly dependent on the charge state of the projectile.

Andersen, N.; Vedder, M.; Russek, A.; Pollack, E.

1980-03-01

148

X-ray M-shell spectra of multiply-charged tungsten ions produced at the energy of the electron beam of 3.9 keV at the LLNL EBIT  

NASA Astrophysics Data System (ADS)

X-ray M-shell spectra of multiply-charged tungsten ions are spectroscopically studied. These spectra were collected at the LLNL EBIT-I at the energy of the electron beam of 3.9 keV and recorded by a broad-band x-ray microcalorimeter spectrometer (XRS). The XRS covered the spectral region from 3.5 to 8 å, which represented several distinct groups of lines due to 3-4, 3-5, and 3-6 transitions. The development of spectroscopic modeling of M-shell tungsten spectra is presented. Modeling indicates that Ni-like lines dominate at this electron energy and include not only the allowed E1 transitions but also the forbidden M1 and E2 transitions. The advantage of using LLNL EBIT data for the development of M-shell diagnostics of plasmas is shown. Work was supported by DOE-NNSA/NV Cooperative Agreement DE-FC52-01NV14050. Work at LLNL was performed under the auspices of the DOE by UC-LLNL under contract W-7405-Eng-48.

Hoppe, Travis; Harris, Cliff; Beiersdorfer, Peter; Boyce, Kevin R.

2005-05-01

149

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 29-60 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.

Jonge, Martin D. de; Tran, Chanh Q.; Chantler, Christopher T.; Barnea, Zwi; Dhal, Bipin B.; Paterson, David; Kanter, Elliot P.; Southworth, Stephen H.; Young, Linda; Beno, Mark A.; Linton, Jennifer A.; Jennings, Guy [X-Ray Operations and Research, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439 (United States); School of Physics, University of Melbourne, Victoria 3010 (Australia); Australian Synchrotron Project, Major Projects Victoria, 800 Blackburn Road, Clayton, Victoria 3168 (Australia); Chemistry Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439 (United States); BESSRC-CAT, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439 (United States)

2007-03-15

150

Linear attenuation coefficients of tissues from 1 keV to 150 keV  

NASA Astrophysics Data System (ADS)

The linear attenuation coefficients and three interaction processes have been computed for liver, kidney, muscle, fat and for a range of x-ray energies from 1 keV to 150 keV. Molecular photoelectric absorption cross sections were calculated from atomic cross section data. Total coherent (Rayleigh) and incoherent (Compton) scattering cross sections were obtained by numerical integration over combinations of F2m(x) with the Thomson formula and Sm(x) with the Klein-Nishina formula, respectively. For the coherent (Rayleigh) scattering cross section calculations, molecular form factors were obtained from recent experimental data in the literature for values of x<1 Å-1 and from the relativistic modified atomic form factors for values of x?1 Å-1. With the inclusion of molecular interference effects in the coherent (Rayleigh) scattering, more accurate knowledge of the scatter from these tissues will be provided. The number of elements involved in tissue composition is 5 for liver, 47 for kidney, 44 for muscle and 3 for fat. The results are compared with previously published experimental and theoretical linear attenuation coefficients. In general, good agreement is obtained. The molecular form factors and scattering functions and cross sections are incorporated into a Monte Carlo program. The energy distributions of x-ray photons scattered from tissues have been simulated and the results are presented.

Böke, Aysun

2014-09-01

151

Fermi Observations of GRB 090510: A Short-Hard Gamma-ray Burst with an Additional, Hard Power-law Component from 10 keV TO GeV Energies  

NASA Astrophysics Data System (ADS)

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 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 ?20 keV and above ?100 MeV. The onset of the high-energy spectral component appears to be delayed by ~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+5.8 -2.6 GeV, the highest ever measured from a short GRB. Observation of this photon sets a minimum bulk outflow Lorentz factor, ?gsim 1200, using simple ?? opacity arguments for this GRB at redshift z = 0.903 and a variability timescale on the order of tens of ms for the ?100 keV-few MeV flux. Stricter high confidence estimates imply ? >~ 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.; Asano, K.; Atwood, W. B.; Axelsson, M.; Baldini, L.; Ballet, J.; Barbiellini, G.; Baring, M. G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Bhat, P. N.; Bissaldi, E.; Blandford, R. D.; Bloom, E. D.; Bonamente, E.; Borgland, A. W.; Bouvier, A.; Bregeon, J.; Brez, A.; Briggs, M. S.; Brigida, M.; Bruel, P.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caraveo, P. A.; Carrigan, S.; Casandjian, J. M.; Cecchi, C.; Çelik, Ö.; Charles, E.; Chiang, J.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Connaughton, V.; Conrad, J.; Dermer, C. D.; de Palma, F.; Dingus, B. L.; Silva, E. do Couto e.; Drell, P. S.; Dubois, R.; Dumora, D.; Farnier, C.; Favuzzi, C.; Fegan, S. J.; Finke, J.; Focke, W. B.; Frailis, M.; Fukazawa, Y.; Fusco, P.; Gargano, F.; Gasparrini, D.; Gehrels, N.; Germani, S.; Giglietto, N.; Giordano, F.; Glanzman, T.; Godfrey, G.; Granot, J.; Grenier, I. A.; Grondin, M.-H.; Grove, J. E.; Guiriec, S.; Hadasch, D.; Harding, A. K.; Hays, E.; Horan, D.; Hughes, R. E.; Jóhannesson, G.; Johnson, W. N.; Kamae, T.; Katagiri, H.; Kataoka, J.; Kawai, N.; Kippen, R. M.; Knödlseder, J.; Kocevski, D.; Kouveliotou, C.; Kuss, M.; Lande, J.; Latronico, L.; Lemoine-Goumard, M.; Llena Garde, M.; Longo, F.; Loparco, F.; Lott, B.; Lovellette, M. N.; Lubrano, P.; Makeev, A.; Mazziotta, M. N.; McEnery, J. E.; McGlynn, S.; Meegan, C.; Mészáros, P.; Michelson, P. F.; Mitthumsiri, W.; Mizuno, T.; Moiseev, A. A.; Monte, C.; Monzani, M. E.; Moretti, E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nakajima, H.; Nakamori, T.; Nolan, P. L.; Norris, J. P.; Nuss, E.; Ohno, M.; Ohsugi, T.; Omodei, N.; Orlando, E.; Ormes, J. F.; Ozaki, M.; Paciesas, W. S.; Paneque, D.; Panetta, J. H.; Parent, D.; Pelassa, V.; Pepe, M.; Pesce-Rollins, M.; Piron, F.; Preece, R.; Rainò, S.; Rando, R.; Razzano, M.; Razzaque, S.; Reimer, A.; Ritz, S.; Rodriguez, A. Y.; Roth, M.; Ryde, F.; Sadrozinski, H. F.-W.; Sander, A.; Scargle, J. D.; Schalk, T. L.; Sgrò, C.; Siskind, E. J.; Smith, P. D.; Spandre, G.; Spinelli, P.; Stamatikos, M.; Stecker, F. W.; Strickman, M. S.; Suson, D. J.; Tajima, H.; Takahashi, H.; Takahashi, T.; Tanaka, T.; Thayer, J. B.; Thayer, J. G.; Thompson, D. J.; Tibaldo, L.; Toma, K.; Torres, D. F.; Tosti, G.; Tramacere, A.; Uchiyama, Y.; Uehara, T.; Usher, T. L.; van der Horst, A. J.; Vasileiou, V.; Vilchez, N.; Vitale, V.; von Kienlin, A.; Waite, A. P.; Wang, P.; Wilson-Hodge, C.; Winer, B. L.; Wu, X. F.; Yamazaki, R.; Yang, Z.; Ylinen, T.; Ziegler, M.

2010-06-01

152

Grazing incidence imaging from 10 to 40 keV.  

PubMed

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 may be due to a lower density of the thin metal layer caused by the deposition method. The reflectivity of a sample of iridium-coated float glass was measured at small grazing angles (25-5 min of arc) at energies of 8, 17, and 26 keV. High reflectivity (>50%) was seen out to angles of 33, 16, and 11 min of arc, respectively. These are close to the theoretical values. A design for a high energy imaging telescope of the Explorer class is described. PMID:20531601

Elvis, M; Fabricant, D G; Gorenstein, P

1988-04-15

153

Search For Anomalous n-p Scattering At 60 eV-140 keV  

NASA Astrophysics Data System (ADS)

A search for an anomalous n-p scattering from a polyethylene sample (CH2) at 8 final energies between 64 eV and 2.5 keV was carried out. The scattering intensities were compared to that from a graphite (C) sample. The results were found to confirm our previous n-p results on H2O at a final energy of 24.3 keV where no n-p scattering anomaly was observed. The present results refute all proposed models attempting to explain the occurrence of any n-p scattering anomaly at keV neutron energies.

Moreh, R.; Block, R. C.; Danon, Y.

2009-01-01

154

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

Microsoft Academic Search

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 2615keV. These experimental results were compared with previous experimental and theoretical data. Good agreements are observed in the 240–800keV energy range, whereas differences up to maximum 10% are observed out of these limits.

M. Rettschlag; R. Berndt; P. Mortreau

2007-01-01

155

The Solar Wind Charge-Transfer X-Ray Emission in the 1\\/4 keV Energy Range: Inferences on Local Bubble Hot Gas at Low Z  

Microsoft Academic Search

We present calculations of the heliospheric solar wind charge-exchange (SWCX) emission spectra and the resulting contributions of this diffuse background in the ROSAT 1\\/4 keV bands. We compare our results with the soft X-ray background (SXRB) emission detected in front of 378 identified shadowing regions during the ROSAT All-Sky Survey. This foreground component is principally attributed to the hot gas

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

2009-01-01

156

Effects of 50 keV and 100 keV Proton Irradiation on GaInP/GaAs/Ge Triple-Junction Solar Cells  

NASA Astrophysics Data System (ADS)

GaInP/GaAs/Ge triple-junction solar cells were irradiated with 50 keV and 100 keV protons at fluences of 5 × 1010 cm-2, 1 × 1011 cm-2, 1 × 1012 cm-2, and 1 × 1013 cm-2. Their performance degradation is analyzed using current-voltage characteristics and spectral response measurements, and then the changes in Isc, Voc, Pmax and the spectral response of the cells are observed as functions of proton irradiation fluence and energy. The results show that the spectral response of the top cell degrades more significantly than that of the middle cell, and 100 keV proton-induced degradation rates of Isc, Voc and Pmax are larger compared with 50 keV proton irradiation.

Wang, Rong; Feng, Zhao; Liu, Yunhong; Lu, Ming

2012-07-01

157

A keV string axion from high scale supersymmetry  

NASA Astrophysics Data System (ADS)

Various theoretical and experimental considerations motivate models with high-scale supersymmetry breaking. While such models may be difficult to test in colliders, we propose looking for signatures at much lower energies. We show that a keV line in the x-ray spectrum of galaxy clusters (such as the recently disputed 3.5-keV observation) can have its origin in a universal string axion coupled to a hidden supersymmetry breaking sector. A linear combination of the string axion and an additional axion in the hidden sector remains light, obtaining a mass of order 10 keV through supersymmetry breaking dynamics. In order to explain the x-ray line, the scale of supersymmetry breaking must be about 1 011 - 12 GeV . This motivates high-scale supersymmetry as in pure gravity mediation or minimal split supersymmetry and is consistent with all current limits. Since the axion mass is controlled by a dynamical mass scale, this mass can be much higher during inflation, avoiding isocurvature (and domain wall) problems associated with high-scale inflation. In an appendix, we present a mechanism for dilaton stabilization that additionally leads to O (1 ) modifications of the gaugino mass from anomaly mediation.

Henning, Brian; Kehayias, John; Murayama, Hitoshi; Pinner, David; Yanagida, Tsutomu T.

2015-02-01

158

The X-ray Emissivity of the Universe: 2-200 Kev  

NASA Technical Reports Server (NTRS)

Observational results on the diffuse X-ray background between 2 and 200 keV are reported. Data are presented as a function of the volume emissivity function B (E) (ergs/sec cu Mpc keV emitted at energy E). The prescription for this is first to establish the spectral intensity I (E) (ergs/sec sq cm ster keV) measured at the earth, second to subtract the contribution due to known, discrete sources, and third to unfold the integral equation which relates the measured intensity to the emissivity.

Schwartz, D.; Gursky, H.

1973-01-01

159

The 17-keV neutrino  

NASA Astrophysics Data System (ADS)

The experimental evidence of a distortion in the ?-spectra of 3H, 35S, 63Ni, 14C and IBEC-spectrum of 71Ge is reviewed. The distortions seen in the five nuclei are consistent with their interpretation as the signal of the emission of a neutrino of 17-keV mass and mixing angle of 0.1. Some of the implications of this discovery are reviewed.

Simpson, John J.

1992-07-01

160

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

161

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

162

Search for a 17 keV neutrino  

NASA Astrophysics Data System (ADS)

We performed an experiment designed to search for evidence of a heavy neutrino of mass 17 keV in the beta decay of 63Ni. We used an iron-free double focusing magnetic spectrometer to measure the 63Ni spectrum in a narrow energy range around the expected threshold. We obtained the response function by measuring the internal conversion spectrum of 109Cd and extrapolating the shape. We measured an upper limit on the mixing of 0.30% at 95% confidence level. We discuss this result in the context of subsequent experiments and the reanalysis of the most precise positive experiment.

Wilson, Scott Roland

2000-10-01

163

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

164

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

SciTech Connect

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

Limbachiya, Chetan [P. S. Science College, Kadi 382 715, Gujarat (India); Vinodkumar, Minaxi [V. P. and R. P. T. P. Science College, Vallabh Vidyanagar 388 120, Gujarat (India); Mason, Nigel [Department of Physics and Astronomy, Open University, Milton Keynes, MK7 6AA (United Kingdom)

2011-04-15

165

Compton backscattered 511 keV annihilation line emission and the 170 keV line from the Galactic center direction  

NASA Technical Reports Server (NTRS)

It is shown that Compton scattering of 511 keV electron-positron annihilation radiation produces a linelike reflection feature at 170 keV from backscattered photons. Assuming simple models of clouds and accretion disks around a compact source, the paper explores the spectrum of Compton-scattered annihilation line emission for a range of geometries, opacities, and observing angles, and finds that the linelike feature is produced under a wide variety of conditions. It is further shown that such Compton backscattering of slightly redshifted annihilation line emission from the inner edge of an accretion disk could account for the 170 keV line emission and higher energy continuum observed together with the 511 keV annihilation radiation from the direction of the Galactic center. Identification of the observed 170 keV line as a slightly redshifted annihilation line reflection feature provides strong new evidence that the source of this emission is a compact object surrounded by a disk of presumably accreting matter.

Lingenfelter, Richard E.; Hua, Xin-Min

1991-01-01

166

Gamma ray attenuation coefficient measurements at 1115, 1173, and 1332 keV  

Microsoft Academic Search

Gamma ray attenuation coefficients in C, Al, Cu, Zr, Sn and Pb were measured for gamma ray energies 1115, 1173 and 1330 keV using the technique employed earlier by the authors for similar measurements at lower energies. The results will be presented here and discussed.

S. Gopal; B. Sanjeevaiah

1977-01-01

167

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

168

Tomographic scanning microscope for 1-4 KeV x-rays  

SciTech Connect

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

McNulty, I.; Feng, Y.P. [Argonne National Lab., IL (United States); Hadda, W.S.; Trebes, J.E. [Lawrence Livermore National Lab., CA (United States)

1995-12-31

169

5 (Upgradable to 25 keV) Free Electron Laser (FEL) Facility  

E-print Network

A Free Electron Laser (FEL) facility utilizing a recirculated Superconducting Radio Frequency (SRF) linear accelerator (linac) provides the opportunity to achieve about five times greater photon energy than an unrecirculated linac of similar cost. > A 4 GeV SRF, cw, electron linac can be used to drive an FEL producing 5 keV photons. The SLAC National Accelerator Laboratory, a Department of Energy (DOE) Basic Energy Sciences (BES) laboratory, proposes to utilize a 4 GeV unrecirculated, SRF, linac in a segment of existing linac tunnel. > For an initial investment similar to that of the proposed SLAC strategy, a recirculated SRF linac system could 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 upgrade funds for additional SRF linac and cryogenic capacity sufficient to provide electron energies appropriate for 25 keV photons matching the European XFEL.

York, R C

2013-01-01

170

No 17 keV neutrino: Admixture <0.073% (95% C.L.)  

NASA Astrophysics Data System (ADS)

To solve the controversial issue concerning the possible existence of a 17 keV neutrino with a 1% admixture in nuclear ? decay, we searched directly for any evidence of a production-threshold effect. The 63Ni ? spectrum was measured with a magnetic spectrometer, with very high statistics along with a fine energy scan over a narrow energy region around the expected threshold. The obtained mixing strength was ||U||2=[-0.011+/-0.033(stat)+/-0.030(syst)]%, very consistent with zero, and decisively excluding the existence of a 17 keV neutrino admixing at the 1% level with the electron neutrino. The corresponding upper limit was set at ||U||2<0.073% (95% C.L.). A new limit was also obtained for a wider mass range: ||U||2<0.15% (95% C.L.) for 10.5 to 25.0 keV neutrinos.

Ohshima, T.; Sakamoto, H.; Sato, T.; Shirai, J.; Tsukamoto, T.; Sugaya, Y.; Takahashi, K.; Suzuki, T.; Rosenfeld, C.; Wilson, S.; Ueno, K.; Yonezawa, Y.; Kawakami, H.; Kato, S.; Shibata, S.; Ukai, K.

1993-06-01

171

keV ion irradiation assisted prebiotic synthesis of oligopeptide in the solar system  

NASA Astrophysics Data System (ADS)

In this paper, keV ion assisted peptide formation from amino acid monomers is studied. To investigate the possible role of low energy ion irradiation in prebiotic synthesis of oligopeptides, we applied keV Ar + and N + ion beams to solid state phenylalanine. After ion irradiation, it was found that phenylalanine dipeptide was formed and the optimal pH value for peptide formation was 8-9. A radical mechanism was also deduced for our observations. In view of the ubiquitous existence of keV ions in early space and on the early Earth, we suggest that low energy charged particles might have played a role in chemical evolution in the solar system.

Wang, W.; Yuan, H.; Wang, X.; Yu, Z.

172

Spectral Constraints on SEYFERT-2 Galaxies as Major Contributors to the Hard 3-100-KEV X-Ray Background  

NASA Astrophysics Data System (ADS)

It has been suggested that the flat spectrum of the X-ray background (XRB) above 3 keV and below ~15 keV could be explained by the superposition of absorbed sources at different redshifts. To explain the steepening of the XRB spectrum above ~15 keV, the intrinsic source spectrum should cut off at ~50-100 keV, as observed in NGC 4151 and galactic black hole candidates. Here, assuming that Seyfert 2 galaxies are Seyfert 1 galaxies obscured by intervening matter in the line of sight, as postulated by the unified model, and that they provide the major contribution to the XRB in the 3-100 keV energy range, we derive some constraints on their spectrum and evolution, and indicate, in view of future ASCA measurements, the use of iron spectral features as a test of the model.

Matt, G.; Fabian, A. C.

1994-03-01

173

SHEEP the ASCA 5-10 keV survey  

E-print Network

We present the first results of the hard (5-10 keV) ASCA GIS survey SHEEP (Search for the High Energy Extragalactic Population). We have analysed 149 fields covering an area of 39 sq. deg detecting 69 sources. Several of these appear to be associated with QSOs and Seyfert-1 galaxies but with hard X-ray spectra, probably due to high absorption. Indeed, the hardness ratio analysis shows that the spectra of the majority of our sources can be represented with a ``scatterer'' model similar to obscured Seyfert galaxies locally. According to this model, our sources present high intrinsic absorption (logN_H~23) but also significant amounts of soft X-ray emission coming from scattered light.

Georgantopoulos, I; Ptak, A

2001-01-01

174

The {sup 10}B(n,{alpha}{sub 1}{gamma}){sup 7}Li cross section from 10 keV to 1 MeV  

SciTech Connect

This work is an extension of the shape measurement of the {sup 10}B(n,{alpha}{sub 1}{gamma}){sup 7}Li reaction from 200 keV to 4 MeV reported previously. To obtain absolute values that measurement was normalized to the ENDF/B-VI evaluation in the 200 keV to 1 MeV neutron energy region. This experiment was undertaken to extend the neutron energy range to lower energies and thus enable the relative cross section to be normalized to ENDF/B-VI at 10 keV where the cross section is better known. The results of this experiment show a deviation from the shape of the cross section as given in the ENDF/B-VI evaluation by 5% in the region from 100 keV to 300 keV but good agreement with ENDF/B-VI from 200 keV to 1 MeV.

Schrack, R.A.; Wasson, O.A. [National Institute of Standards and Technology, Gaithersburg, MD (United States); Larson, D.C.; Dickens, J.K.; Todd, J.H. [Oak Ridge National Lab., TN (United States)

1994-12-31

175

A Compton camera for spectroscopic imaging from 100keV to 1MeV  

NASA Astrophysics Data System (ADS)

The objective of this work is to investigate Compton camera technology for spectroscopic imaging of gamma rays in the 100keV to 1MeV range. An efficient, specific purpose Monte Carlo code was developed to investigate the image formation process in Compton cameras. The code is based on a pathway sampling technique with extensive use of variance reduction techniques. The code includes detailed Compton scattering physics, including incoherent scattering functions, Doppler broadening, and multiple scattering. Experiments were performed with two different camera configurations for a scene containing a 75Se source and a 137Cs source. The first camera was based on a fixed silicon detector in the front plane and a CdZnTe detector mounted in the stage. The second camera configuration was based on two CdZnTe detectors. Both systems were able to reconstruct images of 75Se, using the 265keV line, and 137Cs, using the 662keV line. Only the silicon-CdZnTe camera was able to resolve the low intensity 400keV line of 75Se. Neither camera was able to reconstruct the 75Se source location using the 136keV line. The energy resolution of the silicon-CdZnTe camera system was 4% at 662keV. This camera reproduced the location of the 137Cs source by event circle image reconstruction with angular resolutions of 10° for a source on the camera axis and 14° for a source 30° off axis. Typical detector pair efficiencies were measured as 3 x 10-11 at 662keV. The dual CdZnTe camera had an energy resolution of 3.2% at 662keV. This camera reproduced the location of the 137Cs source by event circle image reconstruction with angular resolutions of 8° for a source on the camera axis and 12° for a source 20° off axis. Typical detector pair efficiencies were measured as 7 x 10-11 at 662keV. Of the two prototype camera configurations tested, the silicon-CdZnTe configuration had superior imaging characteristics. This configuration is less sensitive to effects caused by source decay cascades and random coincident events. An implementation of the expectation maximum-maximum likelihood reconstruction technique improved the angular resolution to 6° and reduced the background in all the images. The measured counting rates were a factor of two low for the silicon-CdZnTe camera, and up to a factor of four high for the dual CdZnTe camera compared to simulation. (Abstract shortened by UMI.)

Earnhart, Jonathan Raby Dewitt

176

0-350 KEV GAMMA RAYS FROM THERMAL NEUTRON CAPTURE IN S, Sc, AND I  

Microsoft Academic Search

The level schemes of odd-odd nuclei were determined by using the energy ; and intensity measurements of gamma rays emitted after neutron capture. Gamma ; spectra from Sc⁴⁶ and I¹²⁸ and from S in natural isotopic mixture ; were recorded by a scintillation spectrometer in the region from 0 to 350 kev. ; The apparatus and methods used are described.

M. Cristu; D. Dorcioman; V. Cojocaru; D. Dragomirescu

1961-01-01

177

Interstellar photoelectric absorption cross sections, 0.03-10 keV  

NASA Technical Reports Server (NTRS)

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

Morrison, R.; Mccammon, D.

1983-01-01

178

Radiative n11B capture accounting 21 and 430 keV resonances  

E-print Network

In the framework of the modified potential cluster model the possibility of describing the available experimental data for the total cross sections for n11B radiative capture at thermal and astrophysical energies were considered with taking into account the 21 and 430 keV resonances.

S. B. Dubovichenko; N. A. Burkova

2014-03-13

179

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

180

A possible line feature at 73 keV from the Crab Nebula  

NASA Technical Reports Server (NTRS)

Evidence is reported for a possible line feature at 73 keV from the Crab Nebula. The experiment was conducted with a balloon-borne high-resolution gamma-ray spectrometer on June 10, 1974, over Palestine, Texas. The intensity and the width of the line derived from the fitting of these data are approximately 0.0038 photon per (sq cm-sec) and less than 4.9 keV FWHM, respectively. The line is superposed on a power-law continuum of 11.2 E to the -2.16 photons per (sq cm-keV) in the energy range from 53 to 300 keV, which is consistent with other measurements of the Crab Nebula spectrum.

Ling, J. C.; Mahoney, W. A.; Willett, J. B.; Jacobson, A. S.

1979-01-01

181

primary emission energy was set to 140 Kev which corresponds to 99mTc. The parameters of the Monte Carlo program were set so that the voxel size was 1.5 x  

E-print Network

of the phantom, water was assumed to be the uniform attenuating medium. The collimator was modeled to correspond to a Low Energy All Purpose (LEAP) collimator with an acceptance angle of 1.5 de­ grees FWHM. Given, the range of pixels sampled was 0 to 350 and a standard deviation of 10 was chosen. No attenuation

Duncan, James S.

182

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

2010-01-18

183

Electron capture in collisions of O{sup 2+}({sup 3}{ital P}) ions with He atoms at energies below 10 keV: The effect of metastable O{sup 2+}({sup 1}{ital D}) ions  

SciTech Connect

Electron capture in O{sup 2+}({sup 3}{ital P},{sup 1}{ital D})+He collisions is studied theoretically by using a semiclassical molecular representation with six molecular channels at collision energies above 50 eV and by using a fully quantum-mechanical molecular representation with three {Pi} channels below these energies. The {ital ab} {ital initio} potential curves and nonadiabatic coupling matrix elements for the HeO{sup 2+} system are obtained from multireference single- and double-excitation configuration-interaction calculations employing a relatively large basis set. The present total cross sections for electron capture by the ground-state O{sup 2+} ions are found to be in reasonable accord with those calculated by Gargaud, Bacchus-Montabonel, and McCarroll [J. Chem. Phys. {bold 99}, 4495 (1993)] below 30 eV/u but are slightly larger above this energy. Partial cross sections for the {ital l} distribution are also slightly different. Cross sections for electron capture by the metastable O{sup 2+} ions decrease much more sharply than those for the ground-state ion as the energy is lowered, reaching a difference between them approximately as large as one to two orders of magnitude below 100 eV. The present rate coefficient for the reaction is approximately 10{sup {minus}9} cm{sup 3}/s above 10000 K, suggesting that the small rate coefficient of about 10{sup {minus}12} cm{sup 3}/s at 20000 K observed by Kwang and Fang [Phys. Rev. Lett. {bold 71}, 4127 (1993)] for electron capture by the ground-state ion might be caused, in part, by a mixture of ground and metastable ions in their experiment. {copyright} {ital 1996 The American Physical Society.}

Kimura, M. [Department of Allied Health Science, Yamaguchi University, Ube 755 (Japan)] [Department of Allied Health Science, Yamaguchi University, Ube 755 (Japan); [Department of Physics, Rice University, Houston, Texas 77251 (United States); Gu, J.P.; Hirsch, G.; Buenker, R.J. [Theoretische Chemie, Bergische Universitaet-Gesamthochschule Wuppertal, D-42097 Wuppertal (Germany)] [Theoretische Chemie, Bergische Universitaet-Gesamthochschule Wuppertal, D-42097 Wuppertal (Germany)

1996-06-01

184

High sensitivity search for a 17 keV neutrino. Negative indication with an upper limit of 0.095%  

NASA Astrophysics Data System (ADS)

We have performed a search for a 17 keV neutrino by looking for a kink in the 63Ni ?-spectrum near the expected energy threshold. Using a large number of events (2.4 × 10 9) accumulated in a narrow energy region with the INS iron-free ??2 ?-spectrometer, we obtain a mixing strength of [1.8±3.3(stat.)±3.3(syst.)]×10 -4, and no indication of the presence of a 17 keV neutrino with the order of 1% mixing. We set an upper limit of 0.095% for the admixture of a neutrino with a mass of 17 keV and of 0.1% with a mass range of 10-24 keV, at the 95% confidence level.

Kawakami, H.; Kato, S.; Oshima, T.; Rosenfeld, C.; Sakamoto, H.; Sato, T.; Shibata, S.; Shirai, J.; Sugaya, Y.; Suzuki, T.; Takahashi, K.; Tsukamoto, T.; Ueno, K.; Ukai, K.; Wilson, S.; Yonezawa, Y.

1992-08-01

185

New Measurement of the Relative Scintillation Efficiency of Xenon Nuclear Recoils Below 10 keV  

E-print Network

Liquid xenon is an important detection medium in direct dark matter experiments, which search for low-energy nuclear recoils produced by the elastic scattering of WIMPs with quarks. The two existing measurements of the relative scintillation efficiency of nuclear recoils below 20 keV lead to inconsistent extrapolations at lower energies. This results in a different energy scale and thus sensitivity reach of liquid xenon dark matter detectors. We report a new measurement of the relative scintillation efficiency below 10 keV performed with a liquid xenon scintillation detector, optimized for maximum light collection. Greater than 95% of the interior surface of this detector was instrumented with photomultiplier tubes, giving a scintillation yield of 19.6 photoelectrons/keV electron equivalent for 122 keV gamma rays. We find that the relative scintillation efficiency for nuclear recoils of 5 keV is 0.14, staying constant around this value up to 10 keV. For higher energy recoils we measure a value around 20%, consistent with previously reported data. In light of this new measurement, the XENON10 experiment's results on spin-independent WIMP-nucleon cross section, which were calculated assuming a constant 0.19 relative scintillation efficiency, change from $8.8\\times10^{-44}$ cm$^2$ to $9.9\\times10^{-44}$ cm$^2$ for WIMPs of mass 100 GeV/c$^2$, and from $4.4\\times10^{-44}$ cm$^2$ to $5.6\\times10^{-44}$ cm$^2$ for WIMPs of mass 30 GeV/c$^2$.

E. Aprile; L. Baudis; B. Choi; K. L. Giboni; K. E. Lim; A. Manalaysay; M. E. Monzani; G. Plante; R. Santorelli; M. Yamashita

2010-05-16

186

Towards measurement of recoils below 4 keV with the ?ROSEBUD? experiment  

Microsoft Academic Search

An experiment to look for light WIMPs with sapphire bolometers is to be installed in the Canfranc Underground Laboratory (at 2450 m.w.e) in the Spanish Pyrenees. In the first stage two small 25g bolometers with NTD-Ge sensors, operating at 25mK, with an energy threshold of 300eV and FWHM energy resolution of 120eV at 1.5keV will perform a background test experiment.

C. Bobin; N. Coron; G. Dambier; E. García; C. Goldbach; D. González; J. Leblanc; P. de Marcillac; A. Morales; J. Morales; G. Nollez; A. Ortiz de Solórzano; J. Puimedón; A. Salinas; M. L. Sarsa; S. Scopel; J. A. Villar

1999-01-01

187

Towards measurements of recoils below 4 keV with the ROSEBUD experiment  

Microsoft Academic Search

An experiment to look for light WIMPs with sapphire bolometers is to be installed in the Canfranc Underground Laboratory (at 2450 m.w.e) in the Spanish Pyrenees. In the first stage two small 25 g bolometers with NTD-Ge sensors, operating at 25 mK, with an energy threshold of 300 eV and FWHM energy resolution of 120 eV at 1.5 keV will

C. Bobin; N. Coron; G. Dambier; E. Garcia; C. Goldbach; D. Gonzalez; J. Leblanc; P. de Marcillac; A. Morales; J. Morales; G. Nollez; A. Ortiz de Solorzano; J. Puimedon; A. Salinas; M. L. Sarsa; S. Scopel; J. A. Villar

1999-01-01

188

Observations of proton spectra (1.0 less than or equal to proton energy less than or equal to 300 keV) and pitch angle distributions at the plasmapause  

NASA Technical Reports Server (NTRS)

Detailed proton spectral and pitch angle distribution observations were obtained from two proton detectors and a fluxgate magnetometer flown on Small Scientific Satellite A (Explorer 45). The data of interest are from orbit 99 in-bound occurring on 17 December 1971, some 8 hours prior to the sudden commencement of a magnetic storm. The data are consistent with the initiation of ion cyclotron instability when certain requirements are met. These criteria are met initially at the altitude at which the sudden intensity decrease occurs. However, after the initiation of the instability, the linear theory is unable to explain the further evolution of intensities, pitch angle distributions, and energy spectra of the ring current particles.

Williams, D. J.; Fritz, T. A.; Konradi, A.

1972-01-01

189

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

190

Implications of a 17 keV neutrino for baryogenesis  

NASA Astrophysics Data System (ADS)

There is some experimental evidence for a 17 keV component of the electron neutrino, in the form of the recent observations of kinks in the beta-decay spectra of tritium, 14C, 35S and 63Ni. In this paper I show that most particle-physics models consistent with the 17 keV neutrino require a baryogenesis scale below ~ 106 GeV. Furthermore, models with a 17 keV neutrino typically contain new sources of CP violation, and the cosmological baryon asymmetry could be generated by anomalous electroweak interactions during a first-order weak phase transition.

Nelson, Ann E.

1992-08-01

191

The MPE X-ray test facility PANTER: Calibration of hard X-ray (15-50 kev) optics  

NASA Astrophysics Data System (ADS)

The Max-Planck-Institut für extraterrestrische Physik (MPE) in Garching, Germany, uses its large X-ray beam line facility PANTER for testing X-ray astronomical instrumentation. A number of telescopes, gratings, filters, and detectors, e.g. for astronomical satellite missions like Exosat, ROSAT, Chandra (LETG), BeppoSAX, SOHO (CDS), XMM-Newton, ABRIXAS, Swift (XRT), have been successfully calibrated in the soft X-ray energy range (< 15keV). Moreover, measurements with mirror test samples for new missions like ROSITA and XEUS have been carried out at PANTER. Here we report on an extension of the energy range, enabling calibrations of hard X-ray optics over the energy range 15-50 keV. Several future X-ray astronomy missions (e.g., Simbol-X, Constellation-X, XEUS) have been proposed, which make use of hard X-ray optics based on multilayer coatings. Such optics are currently being developed by the Osservatorio Astronomico di Brera (OAB), Milano, Italy, and the Harvard-Smithsonian Center for Astrophysics (CfA), Cambridge, MA, USA. These optics have been tested at the PANTER facility with a broad energy band beam (up to 50 keV) using the XMM-Newton EPIC-pn flight spare CCD camera with its good intrinsic energy resolution, and also with monochromatic X-rays between C-K (0.277 keV) and Cu-K? (8.04 keV).

Freyberg, M. J.; Bräuninger, H.; Burkert, W.; Hartner, G. D.; Citterio, O.; Mazzoleni, F.; Pareschi, G.; Spiga, D.; Romaine, S.; Gorenstein, P.; Ramsey, B. D.

2005-12-01

192

Neutron scattering cross sections for {sup 239}Pu at 700 keV  

SciTech Connect

Neutron elastic and inelastic scattering angular distributions for {sup 239}Pu have been measured via the time-of-flight technique at an incident neutron energy of 700 keV. Neutrons were generated at the University of Massachusetts Lowell Type CN Van de Graaff accelerator laboratory, with a pulsed proton beam, Mobley compressed to < 0.5 ns, irradiating a 10 keV thick metallic Li target. The angle integrated cross sections were obtained as 5060.0 {+-} 120 mb for the ground + 7.9 keV states and 518.9 {+-} 17.5 mb for the 57 + 76 keV states of {sup 239}Pu. These results are compared with the measurements by Haouat et al. and show good agreement. In this work, a single plastic scintillation detector was used to obtain the neutron scattering time-of-flight spectra with a flight path of 175 cm. These results are also compared with calculations by Young et al. as listed in ENDF/B-VI. They are in good agreement.

Yue, G.; O`Connor, M.; Egan, J.J.; Kegel, G.H.R. [Univ. of Massachusetts, Lowell, MA (United States)

1994-12-31

193

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

194

X-pinch source characteristics for x-rays above 10 keV  

NASA Astrophysics Data System (ADS)

X pinch radiation produced by electron beams accelerated in the X pinch minidiode ranging in energy from 10 to 100 keV has been studied and used to image a variety of different objects. The experiments have been carried out using the XP pulser (470 kA, 100 ns) at Cornell University and the BIN pulser (280 kA, 120 ns) at the P.N. Lebedev Physical Institute. This electron-beam-generated x-ray source's geometric, temporal and spectral properties have been studied over different energy ranges between 10 and 100 keV. The imaging was carried out in a low magnification scheme, and spatial resolution of a few tens of ?m was demonstrated.

Shelkovenko, Tatyana A.; Pikuz, Sergei A.; Romanova, Vera M.; Ivanenkov, Georgii V.; Song, ByungMoo; Chandler, Katherine M.; Mitchell, Marc D.; Hammer, David A.

2004-01-01

195

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

196

A HAXPES measurement system up to 15 keV developed at BL46XU of SPring-8  

NASA Astrophysics Data System (ADS)

In order to achieve much larger probing depth than the conventional HAXPES system of BL46XU, a HAXPES measurement system equipped with a cylindrical sector analyzer, Focus HV-CSA 300/15 has been developed, by which photoelectrons with the kinetic energy up to 15 keV can be analyzed. The Si 1s peak which comes from the buried Si wafer underneath the 60 nm SiO2 thin films can be clearly identified in the spectra excited by the photon energy of 14 keV, indicating the much larger probing depth than the conventional HAXPES measurement with 8 keV X-ray. The total energy resolution estimated from the Au Fermi edge spectra was ~0.5 eV, which is sufficient for the chemical state analysis of materials.

Oji, H.; Cui, Y.-T.; Koganezawa, T.; Isomura, N.; Dohmae, K.; Son, J.-Y.

2014-04-01

197

20 keV Minimum Gap Undulator at 6 GeV Argonne National Laboratory  

E-print Network

of the fundamental wavelength is shown in Fig, 4 as a function of the undulator gap. To achieve the photon energy20 keV Minimum Gap Undulator at 6 GeV s. H. Kim Argonne National Laboratory 1. Introduction LS-7 S period, and g = undulator gap. Typically M = 4, h/A = 1/4 and Br = 0.9 ~ 0.9ST are used for the design u

Kemner, Ken

198

Thin Film Growth and Surface Modification by keV Ion Beam  

Microsoft Academic Search

High-quality ZnO film and highly wettable polymethylmethacrylate (PMMA) are obtained by using a keV ion beam. ZnO films are grown on glass substrates by ion beam sputter deposition, changing the oxygen\\/argon gas ratio, ion beam energy, and substrate temperature. Physical properties of ZnO films were investigated by X-ray diffraction, Rutherford backscattering spectroscopy, and the Van der Pauw method. All the

Sung-Chang Choi; Yong-Wook Park; Won-Kook Choi; Ki-Hwan Kim; Jun-Sik Cho; Sung Han; Jung Cho; Sun Jung; Young-Gun Han; Byong-Kook Yoo; Hyung-Jin Jung; Seok-Keun Koh

1998-01-01

199

INTEGRAL 11-year hard X-ray survey above 100 keV  

NASA Astrophysics Data System (ADS)

We present the results of an all-sky survey, performed with data acquired by the Imager on-Board the INTEGRAL Satellite (IBIS) telescope on board the INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) observatory over 11 years of operation, at energies above 100 keV. The catalogue of detected sources includes 132 objects. The statistical sample detected on the time-averaged 100-150 keV map at a significance above 5? contains 88 sources: 28 active galactic nuclei (AGNs), 38 low-mass X-ray binaries (LMXBs), 10 high-mass X-ray binaries (HMXBs) and 12 rotation-powered young X-ray pulsars. The catalogue also includes 15 persistent sources, which were registered at significance 4? ? S/N < 5?, where S/N is the signal-to-noise ratio, but at the same time were firmly detected (?12?) in the lower 17-60 keV energy band. All registered sources are known X-ray emitters, which means that the catalogue has 100 per cent purity in this respect. Additionally, 29 catalogued sources were detected significantly in different time slices of the survey. In the context of the survey, we present a hardness ratio for Galactic and extragalactic sources, an LMXB longitudinal asymmetry and a number-flux relation for non-blazar AGNs. At higher energies, in the 150-300 keV energy band, 25 sources have been detected with S/N ? 5?, including seven AGNs, 13 LMXBs, three HMXBs and two rotation-powered pulsars. Among LMXBs and HMXBs, we identified 12 black hole candidates (BHCs) and four neutron star (NS) binaries.

Krivonos, R.; Tsygankov, S.; Lutovinov, A.; Revnivtsev, M.; Churazov, E.; Sunyaev, R.

2015-04-01

200

The emission and propagation of ? 40keV solar flare electrons  

Microsoft Academic Search

Observations of prompt ~ 40 keV solar flare electron events by the IMP series of satellites in the period August, 1966 to December, 1967 are tabulated along with prompt energetic solar proton events in the period 1964–1967. The interrelationship of the various types of energetic particle emission by the sun, including relativistic energy electrons reported by Cline and McDonald (1968)

R. P. Lin

1970-01-01

201

Spectral sensitivity of the Y?-4 photographic film in the 0.27–3keV range  

Microsoft Academic Search

The sensitometric characteristics of a Y?-4 photographic film were measured in the 0.27–3 keV spectral region. It was ascertained\\u000a that, as the photon energy decreased from 3.2 to 1.2 keV, the Y?-4 photographic-film sensitivity remained virtually constant\\u000a and the abruptly fell. Comparison of the Y?-4, Y?-2T and Y?-P films showed that their sensitivities are functions of the photon\\u000a energy.

A. V. Bessarab; S. A. Pospelova; V. A. Tokarev; A. V. Chukalovskii

2000-01-01

202

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

203

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

204

Energy risk in Latin America:Energy risk in Latin America: the growing challengesthe growing challenges  

E-print Network

challenges Universidad Católica de Chile Department of Electrical Engineering Hugh Rudnick IEE International resources -economic reforms opened space for private investment in energy -development of an infrastructure 73.000 MW 90%H;10%T COLOMBIA 13.100 MW 64%H;36%T CHILE 10.600 MW 40%H;60%T MEXICO 42.500 MW 23%H;67%T

Dixon, Juan

205

PITCH-ANGLE DISTRIBUTIONS AND TEMPORAL VARIATIONS OF 0.3-300 keV SOLAR IMPULSIVE ELECTRON EVENTS  

SciTech Connect

We investigate the propagation of {approx}0.3-300 keV electrons in five solar impulsive electron events, observed by the WIND three-dimensional Plasma and Energetic Particle instrument, that have rapid-rise and rapid-decay temporal profiles. In two events, the temporal profiles above 25 keV show a second peak of inward-traveling electrons tens of minutes after the first peak, followed by a third peak due to outward-traveling electrons minutes later-likely due to reflection/scattering first at {approx}0.7-1.7 AU past the Earth, and then in the inner heliosphere inside 1 AU. In the five events, below a transition energy E{sub 0} ({approx}10-40 keV), the pitch-angle distributions are highly anisotropic with a pitch-angle width at half-maximum (PAHM) of <15{sup 0} (unresolved) through the time of the peak; the ratio {Lambda} of the peak flux of scattered (22.{sup 0}5-90{sup 0} relative to the outward direction) to field-aligned scatter-free (0{sup 0}-22.{sup 0}5) electrons is {approx}<0.1. Above E{sub 0}, the PAHM at the flux peak increases with energy up to 85{sup 0} at 300 keV, and {Lambda} also increases with energy up to {approx}0.8 at 300 keV. Thus, low-energy electrons propagated essentially scatter-free through the interplanetary medium, while high-energy electrons experienced pitch-angle scattering, with scattering strength increasing with energy. The transition energy E{sub 0} between the two populations is always such that the electron gyroradius ({rho}{sub e}) is approximately equal to the local thermal proton gyroradius ({rho}{sub Tp}), suggesting that the higher energy electrons were scattered by resonance with turbulent fluctuations at scale {approx}>{rho}{sub Tp} in the solar wind.

Wang, L.; Lin, R. P.; Krucker, Saem, E-mail: wanglh@berkeley.edu [Space Sciences Laboratory, University of California, Berkeley, CA 94720-7450 (United States)

2011-02-01

206

Origin of 200-keV interplanetary electrons.  

NASA Technical Reports Server (NTRS)

The suggestion by Lin et al. (1972) that a distinct spectral feature exists at about 200 keV, which could be due to a neutron-decay electron component of either solar or galactic origin, is examined. Alternative sources models, including production by nearby galactic objects or acceleration at the outer boundary of the solar system, are also considered.

Ramaty, R.; Cline, T. L.; Fisk, L. A.

1972-01-01

207

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

208

The Complex 0.1-100 keV X-Ray Spectrum of PKS2155-304  

E-print Network

A long ($>100,000$ seconds) observation of the bright BL Lac object PKS 2155-304 has been carried out with the Narrow Field Instruments of the BeppoSAX satellite as part of the Science Verification Phase. The source was detected between 0.1 and about 100 keV at an intermediate intensity level compared to previous observations. The unique spectral coverage of BeppoSAX has allowed us to detect a number of spectral features. Between 0.1 and 10 keV the spectrum can be well described by a convex spectrum with (energy) slope gradually steepening from 1.1 to 1.6. At higher energies evidence for a sharp spectral hardening is found, while in the soft X-rays (0.1-1.0 keV) some evidence for an absorption feature was found. Indication for an emission line at 6.4 keV in the source rest frame is present. Repeated variability of $\\approx 20-30%$ around the mean flux is clearly detected on time scales of a few hours. From the symmetry and timescale of the observed variations we derive limits on the magnetic field and on the maximum energy of the emitting particles, implying that PKS 2155-304 should not be bright at TeV energies.

P. Giommi et al

1998-03-11

209

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

NASA Technical Reports Server (NTRS)

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

Bleach, R. D.

1972-01-01

210

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

211

Feasibility study for DEXA using synchrotron CT at 20-35 keV  

NASA Astrophysics Data System (ADS)

A nonlinear model for the x-ray linear attenuation coefficient ? is employed for dual energy x-ray analysis (DEXA). Nonlinear simultaneous equations formed by ? and energy dependent model parameters are solved for the electron density Ne and fourth compositional ratio R4 which has the same ‘units’ as the atomic number. Computed tomography data was acquired at 20-35 keV using bending magnet synchrotron radiation, a double crystal monochromator, a rotation stage and an area detector. Test objects contained liquid samples as mixtures of ethanol, water and salt solutions with known density and composition. Various noise sources are identified and give ? uncertainties of 1-2%. A fan beam geometry allowed the detection of forward scattered radiation with measured ? being 6% lower than expectations for a narrow beam. Energy dependent model parameters were obtained by solving linear simultaneous equations formed by ? and material parameters based upon Ne and R4. DEXA accuracy was studied as a function of photon energy and sample composition. Propagation of errors analysis identifies the importance of the fractional compositional cross-products whose difference at the two beam energies should exceed 0.1, requiring 10 keV or more separation. For a reasonable approximation for the adjustable model parameters, the mean difference between the DEXA solution and true values (?Ne, ?R4) are (1.0%, 0.5%) for soft tissue and (1.5%, 0.8%) for bone like samples.

Midgley, S. M.

2013-02-01

212

Feasibility study for DEXA using synchrotron CT at 20-35 keV.  

PubMed

A nonlinear model for the x-ray linear attenuation coefficient ? is employed for dual energy x-ray analysis (DEXA). Nonlinear simultaneous equations formed by ? and energy dependent model parameters are solved for the electron density N(e) and fourth compositional ratio R(4) which has the same 'units' as the atomic number. Computed tomography data was acquired at 20-35 keV using bending magnet synchrotron radiation, a double crystal monochromator, a rotation stage and an area detector. Test objects contained liquid samples as mixtures of ethanol, water and salt solutions with known density and composition. Various noise sources are identified and give ? uncertainties of 1-2%. A fan beam geometry allowed the detection of forward scattered radiation with measured ? being 6% lower than expectations for a narrow beam. Energy dependent model parameters were obtained by solving linear simultaneous equations formed by ? and material parameters based upon N(e) and R(4). DEXA accuracy was studied as a function of photon energy and sample composition. Propagation of errors analysis identifies the importance of the fractional compositional cross-products whose difference at the two beam energies should exceed 0.1, requiring 10 keV or more separation. For a reasonable approximation for the adjustable model parameters, the mean difference between the DEXA solution and true values (?N(e), ?R(4)) are (1.0%, 0.5%) for soft tissue and (1.5%, 0.8%) for bone like samples. PMID:23369847

Midgley, S M

2013-02-21

213

PET attenuation coefficients from CT images: experimental evaluation of the transformation of CT into PET 511keV attenuation coefficients  

Microsoft Academic Search

The CT data acquired in combined PET\\/CT studies provide a fast and essentially noiseless source for the correction of photon attenuation in PET emission data. To this end, the CT values relating to attenuation of photons in the range of 40-140 keV must be transformed into linear attenuation coefficients at the PET energy of 511 keV. As attenuation depends on

C. Burger; G. Goerres; S. Schoenes; A. Buck; A. Lonn; G. von Schulthess

2002-01-01

214

L-shell x-ray-production cross sections in lead by proton bombardment (240--440 keV)  

SciTech Connect

The L-shell x-ray-production process in lead (Pb) by proton impact over the energy range 240--440 keV has been studied. The x rays emitted from a thin (44.4 +- 3.9 ..mu..g/cm/sup 2/) Pb target were detected using a high-purity Ge low-energy photon spectroscopy detector. The total x-ray cross sections and the x-ray cross sections for the Ll, L..cap alpha../sub 1,2/, L..beta..'s, L..gamma../sub 1/, and L..gamma../sub 2,3/ components were determined at 20-keV intervals over the bombarding energy range. The experimental x-ray cross sections were found to be in reasonable agreement with those predicted by perturbed stationary-state (PSS) theory with relativistic (R), energy-loss (E), and Coulomb-deflection (C) corrections (ECPSSR).

Moheb, H.; Bigaouette, R.; Inman, F.W.

1985-12-01

215

Microvariability of 0.3-10 keV Flux in HBL Source Mrk 421  

NASA Astrophysics Data System (ADS)

Mrk 421 was observed more than 550 times by Swift-XRT through the 0.3-10 keV energy band which revealed a strong flaring activity in the source. The most violent event was recorded during 2013 April 11-20 observations when the flux varied with a factor of 4-5 and attained its highest value of ~200 cts s-1. Intraday flux variations, sometimes with timescales as short as <1 ks, were also evident. Flux variability was accompanied with significant spectral changes.

Kapanadze, Bidzina

2014-12-01

216

Emission of secondary ions after grazing impact of keV ions on solid surfaces  

NASA Astrophysics Data System (ADS)

We have scattered He+ and Ar+ ions with energies of 10 and 20 keV from solid surfaces and investigated by means of a quadrupole mass spectrometer the emission of secondary ions. Compared to the established method of secondary ion mass spectroscopy (SIMS), the impact of ions proceeds under a grazing angle of incidence of about 2°. In experiments with a Cu(1 0 0) target covered with an ultrathin Fe3O4 film as well as ZnO and ZnMgO surfaces we have explored some basic features of this variant of SIMS concerning the potential application as surface analytical tool.

Nakajima, K.; Lienemann, J.; Eberlein, P.; Kimura, K.; Maass, K.; Winter, H.

2014-12-01

217

Cusp electron production in 75--300 keV He{sup +} + Ar collisions  

SciTech Connect

Cusp-electron production has been investigated in collisions of 75--300 keV He{sup +} with Ar. The relative contributions from electron capture to the continuum (ECC), transfer ionization (TI), and electron loss to the continuum (ELC) to the total cusp electron production were measured. Over the energy range investigated, ECC was found to decrease from about 86% to 80%, TI decreased from about 12% to 1%, and ELC increased from about 2% to 20%. The present results are consistent with earlier work for He{sup +} and O{sup q+} projectiles.

Plano, V.L. [Michigan State Univ., East Lansing, MI (US); Sarkadi, L.; Zavodszky, P.; Berenyi, D.; Palinkas, J.; Gulyas, L.; Takacs, E.; Toth, L. [Inst. of Nuclear Research, Debrecen (HU); Tanis, J.A. [Western Michigan Univ., Kalamazoo, MI (US)

1992-12-31

218

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

NASA Technical Reports Server (NTRS)

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

Barengoltz, J. B.; Brady, J.

1977-01-01

219

Asymmetric 511 keV Positron Annihilation Line Emission from the Inner Galactic Disk  

NASA Technical Reports Server (NTRS)

A recently reported asymmetry in the 511 keV gamma-ray line emission from the inner galactic disk is unexpected and mimics an equally unexpected one in the distribution of LMXBs seen at hard X-ray energies. A possible conclusion is that LMXBs are an important source of the positrons whose annihilation gives rise to the line. We will discuss these results, their statistical significance and that of any link between the two. The implication of any association between LMXBs and positrons for the strong annihilation radiation from the galactic bulge will be reviewed.

Skinner, Gerry; Weidenspointner, Georg; Jean, Pierre; Knodlseder, Jurgen; Ballmoos, Perer von; Bignami, Giovanni; Diehl, Roland; Strong, Andrew; Cordier, Bertrand; Schanne, Stephane; Winkler, Christoph

2008-01-01

220

Optimization of phosphor screens for charge coupled device based detectors and 7{endash}34 keV x-rays  

SciTech Connect

Phosphor screens convert x-ray images to visible light images in two-dimensional charge coupled device (CCD) based detector systems used for x-ray diffraction. Some experimental and theoretical aspects of phosphor screen performance are described in this article. The efficiencies of x-ray-to-light conversion were measured using a CCD camera for transmission phosphor screens fabricated from two different phosphor powders, Y{sub 2}O{sub 2}S:Eu (P22R) and Gd{sub 2}O{sub 2}S:Tb (P43), for screen mass thicknesses of 3{endash}50 mg/cm{sup 2} and for x-ray energies of 7{endash}34 keV. A model was developed and evaluated for the dependence of the emitted light brightness on screen thickness and x-ray energy. Inputs to the model are x-ray absorption coefficients and light attenuation versus thickness data, which were determined experimentally for the phosphors and found to be dominated by scattering rather than absorption. The angular distribution of emitted light, was found to be nearly Lambertian. Broadening of image features in the x-ray-to-visible-light conversion by phosphors for 19.6 keV x-rays was found to increase approximately linearly with phosphor screen thicknesses in the range of 30{endash}160 {mu}m, but with a minimum width of 110 {mu}m for P22R phosphor and 70 {mu}m for P43 phosphor. In the range of 7{endash}15 keV, maximum brightness was obtained for P43 phosphor screens of about 10 mg/cm{sup 2} mass thickness (60 {mu}m). For P22R screens, the thickness for maximum brightness increased from about 8 mg/cm{sup 2} (50 {mu}m) for 7 keV to more than 46 mg/cm{sup 2} (210 {mu}m) for 15 keV. For 7 keV the maximum brightnesses for P22R and P43 phosphors were about the same. For 10 keV the maximum brightness for P43 phosphor was about 60{percent} greater than the maximum brightness for P22R phosphor samples tested. For 15 keV the maximum brightness for P43 phosphor was again about 60{percent} greater than that for the P22R samples tested. (Abstract Truncated)

Wang, P.; Cargill, G.S. III [Department of Chemical Engineering, Materials Science and Mining Engineering, Columbia University, New York, New York 10027 (United States)] [Department of Chemical Engineering, Materials Science and Mining Engineering, Columbia University, New York, New York 10027 (United States)

1997-02-01

221

Optimization of phosphor screens for charge coupled device based detectors and 7-34 keV x-rays  

NASA Astrophysics Data System (ADS)

Phosphor screens which convert x-ray images to visible light images are key components in two-dimensional charge coupled device (CCD) based detector systems used for x-ray diffraction. Some experimental and theoretical aspects of phosphor screen performance are described in this article. The efficiencies of x-ray-to-light conversion were measured using a CCD camera for transmission phosphor screens fabricated from two different phosphor powders, Y2O2S:Eu (P22R) and Gd2O2S:Tb (P43), for screen mass thicknesses of 3-50 mg/cm2 and for x-ray energies of 7-34 keV. A model was developed and evaluated for the dependence of the emitted light brightness on screen thickness and x-ray energy. Inputs to the model are x-ray absorption coefficients available from published compilations, and light attenuation versus thickness data, which were determined experimentally for the phosphors and found to be dominated by scattering rather than absorption. The angular distribution of emitted light, measured for one of the phosphor screens, was found to be nearly Lambertian. Broadening of image features in the x-ray-to-visible-light conversion by phosphors for 19.6 keV x-rays was found to increase approximately linearly with phosphor screen thicknesses in the range of 30-160 ?m, but with a minimum width of 110 ?m for P22R phosphor and 70 ?m for P43 phosphor. In the range of 7-15 keV, maximum brightness was obtained for P43 phosphor screens of about 10 mg/cm2 mass thickness (60 ?m). For P22R screens, the thickness for maximum brightness increased from about 8 mg/cm2 (50 ?m) for 7 keV to more than 46 mg/cm2 (210 ?m) for 15 keV. For 7 keV the maximum brightnesses for P22R and P43 phosphors were about the same. For 10 keV the maximum brightness for P43 phosphor was about 60% greater than the maximum brightness for P22R phosphor samples tested. For 15 keV the maximum brightness for P43 phosphor was again about 60% greater than that for the P22R samples tested. In the range of 20-34 keV, maximum brightness would occur for thicknesses greater than 46 mg/cm2 (210 ?m) for P22R phosphor and greater than 40 mg/cm2 (160 ?m) for P43 phosphor. Comparing the brightness for 90 ?m thickness for the two phosphors, P43 was about 30% brighter for 20 keV, 20% brighter for 24 keV, and 10% brighter for both 29 and 34 keV.

Wang, P.-C.; Cargill, G. S., III

1997-02-01

222

Space-charge neutralization measurement of a 75keV, 130mA hydrogen-ion beam  

Microsoft Academic Search

A 75-keV, 130-mA dc mode proton injector is being developed at Los Alamos. The two-solenoid focusing system used in this injector relies on effective beam space-charge (s.c.) neutralization by beam ionization of the residual gas. The degree of s.c. neutralization is determined by measurement of the energy distribution of slow ions created in the beam region. A non-interceptive gridded-energy analyzer

Robin Ferdinand; Joseph Sherman; R. R. Stevens Jr.; Thomas Zaugg

1997-01-01

223

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

224

Sputtering of thin benzene and polystyrene overlayers by keV Ga and C 60 bombardment  

NASA Astrophysics Data System (ADS)

The mechanisms of ion-stimulated desorption of thin organic overlayers deposited on metal substrates by mono- and polyatomic projectiles are examined using molecular dynamics (MD) computer simulations. A monolayer of polystyrene tetramers (PS4) physisorbed on Ag{1 1 1} is irradiated by 15 keV Ga and C 60 projectiles at normal incidence. The results are compared with the data obtained for a benzene overlayer to investigate the differences in sputtering mechanisms of weakly and strongly bound organic molecules. The results indicate that the sputtering yield decreases with the increase of the binding energy and the average kinetic energy of parent molecules is shifted toward higher kinetic energy. Although the total sputtering yield of organic material is larger for 15 keV C 60, the impact of this projectile leads to a significant fragmentation of ejected species. As a result, the yield of the intact molecules is comparable for C 60 and Ga projectiles. Our data indicate that chemical analysis of the very thin organic films performed by detection of sputtered neutrals will not benefit from the use of C 60 projectiles.

Czerwi?ski, B.; Delcorte, A.; Garrison, B. J.; Samson, R.; Winograd, N.; Postawa, Z.

2006-07-01

225

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

226

Fragmentation of multicharged C70q+ prepared in collisions with F+ ions at 3 keV  

NASA Astrophysics Data System (ADS)

Ionization and successive evaporation of C70r+ is studied as a function of the internal energy using collision induced dissociation under energy control. Multicharged ions C70r+ are prepared in F+ (3 keV) + C70 ? F? + C70r+ + ne collisions. Up to seven successive evaporation of C2 are observed in an excitation energy range from 40 to 100eV. The dissociation energies of C70-2m2+ (m=1-7) are determined using a statistical cascade model to reproduce the excitation energy distribution of C702+ parent ions for each dissociation channel. Results are in good agreement with previous theoretical calculations.

Martin, S.; Brédy, R.; Ortéga, C.; Ji, M.; Chen, L.; Bernard, J.; Montagne, G.; Zhu, X.; Qian, D.; Ma, X.

2015-01-01

227

Origin of energetic electron precipitation >30 keV into the atmosphere  

NASA Astrophysics Data System (ADS)

Energetic electrons are deposited into the atmosphere from Earth's inner magnetosphere, resulting in the production of odd nitrogen (NOx). During polar night, NOx can be transported to low altitudes, where it can destroy ozone, affecting the atmospheric radiation balance. Since the flux of energetic electrons trapped in the magnetosphere is related to solar activity, the precipitation of these electrons into Earth's atmosphere provides a link between solar variability and changes in atmospheric chemistry which may affect Earth's climate. To determine the global distribution of the precipitating flux, we have built a statistical model binned by auroral electrojet (AE) index, magnetic local time (MLT), and L shell of E > 30 keV precipitating electrons from the Medium Energy Proton and Electron Detector (MEPED) on board the NOAA Polar Orbiting Environmental Satellites (POES) low-altitude satellites NOAA-15, NOAA-16, NOAA-17, and NOAA-18. We show that the precipitating flux increases with geomagnetic activity, suggesting that the flux is related to substorm activity. The precipitating fluxes maximize during active conditions where they are primarily seen outside of the plasmapause on the dawnside. The global distribution of the precipitating flux of E > 30 keV electrons is well-correlated with the global distribution of lower-band chorus waves as observed by the plasma wave experiment onboard the Combined Release and Radiation Effects Satellite (CRRES) satellite. In addition, the electron precipitation occurs where the pitch angle diffusion coefficient due to resonant interaction between electrons and whistler mode chorus waves is high, as calculated using the pitch angle and energy diffusion of ions and electrons (PADIE) code. Our results suggest that lower-band chorus is very important for scattering >30 keV electrons from Earth's inner magnetosphere into the atmosphere.

Lam, Mai Mai; Horne, Richard B.; Meredith, Nigel P.; Glauert, Sarah A.; Moffat-Griffin, Tracy; Green, Janet C.

2010-04-01

228

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

SciTech Connect

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

Cline, James M.; Frey, Andrew R.; Chen, Fang [Physics Department, McGill University, 3600 University Street, Montreal, Quebec, H3A 2T8 (Canada)

2011-04-15

229

Resolving the 10-40 keV cosmic X-ray background with constellation-X  

NASA Astrophysics Data System (ADS)

The energy density of the Cosmic X-ray background (XRB) peaks around 30 keV (see Figure 1), an energy not yet probed by focussing imaging instruments. The first hard X-ray telescope due to fly on a space mission will be that on board Constellation-X. The imaging capability, besides providing an improvement of several orders of magnitude in sensitivity over current passively collimated detectors, will permit for the first time to resolve a fraction of the XRB at this most crucial energy. Synthesis models of the XRB based on obscured AGN predict that at least 40% of the 10-40 keV XRB will be resolved by Constellation-X. .

Matt, Giorgio; Pompilio, Fulvio; La Franca, Fabio

2001-12-01

230

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

231

Do scattering effects resolve the 17-keV conundrum?  

NASA Astrophysics Data System (ADS)

The anomalies observed in ß-decay measurements at Oxford can be reinterpreted after account is made for a more complete electron response function. Specifically, a reanalysis including intermediate scattering effects places an upper limit (90% CL) on the mixing probability for a 17-keV neutrino of 0.35% and 0.53%, using the 35S and 63Ni data respectively. Despite the different geometries employed, scattering effects can play an important role in the 35S experiments at Guelph, although a rigorous treatment is difficult. Missing links remains, and thoughts are provided on how the situation can be clarified with additional ß-dacay measurements.

Hime, A.

1993-01-01

232

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

233

Status report on a dc 130 mA, 75 keV proton injector (invited)  

SciTech Connect

A 110 mA, 75 keV dc proton injector is being developed at Los Alamos. A microwave proton source is coupled to a two solenoid, space-charge neutralized, low-energy beam transport (LEBT) system. The ion source produces 110 mA proton current at 75 keV using 600{endash}800 W of 2.45 GHz discharge power. Typical proton fraction is 85{percent}{endash}90{percent} of the total extracted ion current, and the rms normalized beam emittance after transport through a prototype 2.1 m LEBT is 0.20 ({pi}mmmrad). Beam space-charge neutralization is measured to be {gt}98{percent} which enables the solenoid magnetic transport to successfully match the injector beam into a radio-frequency quadrupole. Beam simulations indicate small emittance growth in the proposed 2.8 m low-energy demonstration accelerator LEBT. The LEBT also contains beam diagnostics, steering, and a beam deflector for variable duty factor and accelerator fast protect functions. The injector beam availability status is also discussed. {copyright} {ital 1998 American Institute of Physics.}

Sherman, J.; Arvin, A.; Hansborough, L.; Hodgkins, D.; Meyer, E.; Schneider, J.D.; Smith, H.V. Jr.; Stettler, M.; Stevens, R.R. Jr.; Thuot, M.; Zaugg, T. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Ferdinand, R. [CEA-Saclay, LNS, 91191 Gif-sur-Yvette Cedex (France)] [CEA-Saclay, LNS, 91191 Gif-sur-Yvette Cedex (France)

1998-02-01

234

Investigations of ripple pattern formation on Germanium surfaces using 100-keV Ar+ ions  

NASA Astrophysics Data System (ADS)

We have investigated the formation of nanoripples on the surface of germanium, Ge(100), due to the effect of 100-keV Ar + ion irradiation. The irradiation was carried out at different incidence angles from 0° to 75° in steps of 15° with respect to the surface normal with a fixed ion fluence of approximately 3 × 1017 ions/cm2. Atomic force micrographs show an increase in surface roughness from 0.5 to 4.3 nm for the pristine sample and the sample irradiated at 60° incidence angle due to cos-1( ?) dependence on sputtering yield. With increase in angle of incidence, there is transition observed from nanodots to aligned nanodots perpendicular to the direction of the beam. There is an increase in size of the nanostructures observed from 44 to 103 nm with angle of incidence. The formation of nanoripples initiates at an angle of ? ~ 45°. Ripple pattern formation has taken place on the Ge surface in the energy regime of 100 keV as compared to the other reports which had been carried out using very low energy ions. Raman spectra reveal that the near surface of crystalline Ge samples becomes amorphous due to interaction of Ar+ ions due to creation of defects through collision cascades.

Sulania, Indra; Agarwal, Dinesh; Husain, Mushahid; Avasthi, Devesh Kumar

2015-02-01

235

Status report on a dc 130-mA, 75-keV proton injector  

SciTech Connect

A 110-mA, 75-keV dc proton injector is being developed at Los Alamos. We use a microwave proton source coupled to a two solenoid, space-charge neutralized, low-energy beam transport (LEBT) system. The ion source produces 110-mA proton current at 75 keV using 600 - 800 W of 2.45 GHz input discharge power. Typical proton fraction is 85-90% of the total extracted ion current, and the rms normalized beam emittance after transport through a prototype 2.1 m LEBT is 0.20 ({pi}mm-mrad). Beam space-charge neutralization is measured to be > 98% which enables the solenoid magnetic transport to successfully match the injector beam into a radio-frequency quadrupole (RFQ). Beam simulations indicate small emittance growth in the proposed 2.8 m low-energy demonstration accelerator (LEDA) LEBT. The LEBT also contains beam diagnostics, steering, and a beam deflector for variable duty factor and accelerator fast protect functions. The injector computer controls and reliability status are also discussed.

Sherman, J.; Arvin, A.; Hodgkins, D. [and others

1997-10-01

236

Investigations of ripple pattern formation on Germanium surfaces using 100-keV Ar(+) ions.  

PubMed

We have investigated the formation of nanoripples on the surface of germanium, Ge(100), due to the effect of 100-keV Ar (+) ion irradiation. The irradiation was carried out at different incidence angles from 0° to 75° in steps of 15° with respect to the surface normal with a fixed ion fluence of approximately 3?×?10(17) ions/cm(2). Atomic force micrographs show an increase in surface roughness from 0.5 to 4.3 nm for the pristine sample and the sample irradiated at 60° incidence angle due to cos(-1)(?) dependence on sputtering yield. With increase in angle of incidence, there is transition observed from nanodots to aligned nanodots perpendicular to the direction of the beam. There is an increase in size of the nanostructures observed from 44 to 103 nm with angle of incidence. The formation of nanoripples initiates at an angle of ??~?45°. Ripple pattern formation has taken place on the Ge surface in the energy regime of 100 keV as compared to the other reports which had been carried out using very low energy ions. Raman spectra reveal that the near surface of crystalline Ge samples becomes amorphous due to interaction of Ar(+) ions due to creation of defects through collision cascades. PMID:25852384

Sulania, Indra; Agarwal, Dinesh; Husain, Mushahid; Avasthi, Devesh Kumar

2015-01-01

237

keV Photon Emission from Light Nonthermal Dark Matter  

E-print Network

We propose a possible explanation for the recent claim of an excess at 3.5 keV in the X-ray spectrum within a minimal extension of the standard model that explains dark matter and baryon abundance of the universe. The dark matter mass in this model is ${\\cal O}({\\rm GeV})$ and its relic density has a non-thermal origin. The model includes two colored scalars of ${\\cal O}({\\rm TeV})$ mass ($X_{1,2}$), and two singlet fermions that are almost degenerate in mass with the proton ($N_{1,2}$). The heavier fermion $N_2$ undergoes radiative decay to the lighter one $N_1$ that is absolutely stable. Radiative decay with a life time $\\sim 10^{23}$ seconds can account for the claimed 3.5 keV line, which requires couplings $\\sim 10^{-3}-10^{-1}$ between $X_{1,2}, ~ N_{1,2}$ and the up-type quarks. The model also gives rise to potentially detectable monojet, dijet, and monotop signals at the LHC.

Rouzbeh Allahverdi; Bhaskar Dutta; Yu Gao

2014-03-23

238

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

SciTech Connect

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

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

2011-08-17

239

Decaying Vector Dark Matter as an Explanation for the 3.5 keV Line from Galaxy Clusters  

E-print Network

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 $V^\\prime$, which couple to the photon through an effective generalized Chern-Simons coupling, $g_V$. $V^\\prime$ is slightly heavier than $V$ with a mass splitting $m_{V^\\prime}-m_V\\simeq 3.5$~keV. The decay of $V^\\prime$ to $V$ and a photon gives rise to the 3.5~keV line. The production of $V$ and $V^\\prime$ takes place in the early universe within the freeze-in framework through the effective $g_V$ coupling when $m_{V^\\prime}energy model that gives rise to the $g_V$ coupling at low energies. To do this, $V$ and $V^\\prime$ are promoted to gauge bosons of spontaneously broken new $U(1)_V$ and $U(1)_{V^\\prime}$ gauge symmetries, respectively. The high energy sector includes milli-charged chiral fermions that lead to the $g_V$ coupling at low energy via triangle diagrams.

Yasaman Farzan; Amin Rezaei Akbarieh

2014-11-21

240

Two-plane focusing of 30 keV undulator radiation.  

PubMed

An imaging experiment using a two-plane focusing refractive lens made of aluminium and operated in the hard X-ray range is described. The lens is made of a series of 1 and 0.8 mm-diameter lenses drilled through a 2 mm aluminium plate. It is exposed to the white beam from an undulator with total power as high as 1.7 kW and normal-incidence power density of 100 W mm(-2). The measured r.m.s, size of the image is 0.12 x 0.06 mm at a photon energy of 30 keV. Theoretical estimates for the transmission, aperture and tolerance of alignment of such lenses are made. It is found that the aperture of the lens is dominated by photoelectric absorption (Compton scattering) in the low (high) energy range of the spectrum. Beryllium is the most promising material. PMID:16687793

Elleaume, P

1998-01-01

241

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

NASA Astrophysics Data System (ADS)

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 13N by the 12C(d,n)13N 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 13N was extracted from the graphite matrix when 35 A current was externally applied to the graphite target while simultaneously flushing the target chamber with CO2 gas.

Fru, L. Che; Clymer, J.; Compton, N.; Cotter, J.; Dam, H.; Lesko, Z.; Pautzke, J.; Prokop, C.; Swanson, L.; Roberts, A. D.

2013-04-01

242

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

243

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

244

Point Defect Cluster Formation in Iron Displacement Cascades Up to 50 keV  

SciTech Connect

The results of molecular dynamics displacement cascade simulations in iron at energies up to 50 keV and temperatures of 100, 600, and 900K are summarized, with a focus on the characterization of interstitial and vacancy clusters that are formed directly within the cascade. The fraction of the surviving point defects contained in clusters, and the size distributions of these in-cascade clusters have been determined. Although the formation of true vacancy clusters appears to be inhibited in iron, a significant degree of vacancy site correlation was observed. These well correlated arrangements of vacancies can be considered nascent clusters, and they have been observed to coalesce during longer term Monte Carlo simulations which permit short range vacancy diffusion. Extensive interstitial clustering was observed. The temperature and cascade energy dependence of the cluster size distributions are discussed in terms of their relevance to microstructural evolution and mechanical property changes in irradiated iron-based alloys.

Stoller, R.E.

1998-11-30

245

L x-ray production cross sections from 50-300 keV proton impact on selected 4d transition elements  

NASA Astrophysics Data System (ADS)

L x-rays were measured from the impact on thick targets of protons in the 50-300 keV energy range. The derived L sub-shell cross sections were compared with the ECPSSR theory and with measurements by others. It was found that ECPSSR over-predicts the measurements as the impact energy decreases.

Cipolla, Sam J.

2009-11-01

246

Influence of 250 keV Ge ions fluence on electrical and optical properties of SiC  

Microsoft Academic Search

Commercially graded SiC samples were implanted with 250keV germanium ions (Ge+) at room temperature. For Ge+ ions source, laser-induced plasma (LIP) technique was used. Ge+ implantation was confirmed by energy dispersive X-ray (EDX) analysis. Change in FWHM and lattice constant of SiC samples has been observed after the Ge implantation, calculated by Bragg's law from XRD analysis. A comparison of

M. S. Rafique; N. Tahir

2007-01-01

247

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

248

Operation and Development of the 500-keV Negative-Ion-Based Neutral Beam Injection System for JT-60U  

SciTech Connect

The 500-keV negative-ion based neutral beam injector for JT-60U started operation in 1996. The beam power has been increased gradually through optimizing operation parameters of the ion sources and conquering many troubles in the ion source and power supplies caused by a high voltage break-down in the accelerator. However, some issues remain to be solved concerning the ion source for increasing further the beam power and the beam energy. The most serious issue of them is non-uniformity of source plasma in the arc chamber. Various countermeasures have been implemented to improve the non-uniformity. Some of those countermeasures have been found to be partially effective in reducing the non-uniformity of the source plasma, and as the result the ion source, so far, has accelerated negative-ion beams of 17.4A at 403keV with deuterium and 20A at 360keV with hydrogen against the goal of 22A at 500keV. The neutral beam injection power into the plasma has reached 5.8MW at 400keV with deuterium. Further efforts to reach the target of 10MW at 500keV have been continued.

Kuriyama, M.; Akino, N.; Ebisawa, N.; Grisham, L.; Honda, A.; Itoh, T.; Kawai, M.; Kazawa, M.; Mogaki, K.; Ohara, Y.; Ohga, T.; Okumura, Y.; Oohara, H.; Umeda, N.; Usui, K.; Watanabe, K.; Yamamoto, M.; Yamamoto, T. [Japan Atomic Energy Research Institute (Japan)

2002-09-15

249

Erosion of thin carbon foils by 20 keV and 40 keV Ar{sup +} irradiation  

SciTech Connect

Nominal 2 {mu}g/cm{sup 2} C foils were irradiated with 20 and 40 keV Ar{sup +} ions at fluences up to 1.1x10{sup 16} Ar{sup +}/cm{sup 2}. Foil erosion (determined by measuring changes in angular scatter distribution of 2-keV protons transiting the foil) is observed to reach a constant rate of 3.5 C atoms removed per incident Ar{sup +}. The independence of the sputter yield on foil thickness indicates that interactions leading to sputtering occur within a depth of 0.5 {mu}g/cm{sup 2} of the sputter surface. Using theoretical and TRIM estimates for the backwater sputtering yield, the transmission sputtering yield is a factor of 3-16 times larger than the backward sputtering yield. The fraction of holes created in the foil by Ar{sup +} irradiation linearly increases with fluence above a fluence of 4x10{sup 15} Ar{sup +}/cm{sup 2}, and the foil lifetime is 8.7x10{sup 15} Ar{sup +}/cm{sup 2}.

Funsten, H.O.; Shappirio, M.

1996-10-01

250

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

NASA Astrophysics Data System (ADS)

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

2012-11-01

251

Magnetospheric plasma modeling (0-100 keV)  

SciTech Connect

Spacecraft surface charging, which is primarily a current balance phenomenon, is in general a function of the dominant currents to and from the vehicle's surface. Within the near-earth magnetosphere the dominant currents to the surface are the ambient space plasma fluxes between approximately 0 and 100 keV. A major effort to understand the near-earth environment was initiated when spacecraft charging became a major issue. The present paper has the objective to summarize the basic features of the models which have resulted from this effort. A description is given of four categories of models, based primarily on the degree of empirical and theoretical input. Types of quantitative models are discussed, taking into account definitions, statistical models, analytic models, static models, and time-dependent models. Engineering models are also considered, giving attention to baseline models and worst-case models. 90 references.

Garrett, H.B.; Spitale, G.C.

1985-06-01

252

Phase-contrast imaging and tomography at 60 keV using a conventional x-ray tube source  

SciTech Connect

Phase-contrast imaging at laboratory-based x-ray sources using grating interferometers has been developed over the last few years for x-ray energies of up to 28 keV. Here, we show first phase-contrast projection and tomographic images recorded at significantly higher x-ray energies, produced by an x-ray tube source operated at 100 kV acceleration voltage. We find our measured tomographic phase images in good agreement with tabulated data. The extension of phase-contrast imaging to this significantly higher x-ray energy opens up many applications of the technique in medicine and industrial nondestructive testing.

Donath, Tilman; Bunk, Oliver; Groot, Waldemar; Bednarzik, Martin; Gruenzweig, Christian; David, Christian [Paul Scherrer Institut, 5232 Villigen PSI (Switzerland); Pfeiffer, Franz [Paul Scherrer Institut, 5232 Villigen PSI (Switzerland); Ecole Polytechnique Federale de Lausanne, 1015 Lausanne (Switzerland); Hempel, Eckhard; Popescu, Stefan; Hoheisel, Martin [Siemens AG, Healthcare Sector, 91301 Forchheim (Germany)

2009-05-15

253

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

254

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

255

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

256

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

257

Development of a 110-m-mA, 75-keV proton injector for high-current, CW linacs  

SciTech Connect

A dc proton injector is being developed for a 6.7 MeV CW RFQ at Los Alamos. The RFQ input beam requirements are 75 keV energy, 110 mA dc proton current, and 0.20 {pi}mm-mrad rms normalized emittance. The injector has now produced a 75-keV, 117-mA dc proton beam (130 mA total current) with the required emittance. The emittance has been measured after a 2.1 m long two-solenoid beam transport system. The measured emittance can be explained in terms of the ion source emittance and beam transport through the focusing elements. Measured proton fractions are 90-92% of the beam current. Engineering of the accelerating column high-voltage design is being improved to increase the injector reliability. Injector design details and status are presented.

Sherman, J.D.; Bolme, G.O.; Hansborough, L.D. [and others

1996-09-01

258

Strength of the Ec.m.=1113 keV resonance in 20Ne(p,?)21Na  

NASA Astrophysics Data System (ADS)

The 20Ne(p,?)21Na reaction is the starting point of the NeNa cycle, which is an important process for the production of intermediate mass elements. The Ec.m.=1113 keV resonance plays an important role in the determination of stellar rates for this reaction since it is used to normalize experimental direct capture yields at lower energies. The commonly accepted strength of this resonance, ??=1.13±0.07 eV, has been misinterpreted as the strength in the center-of-mass frame when it is actually the strength in the laboratory frame. This has motivated a new measurement of the Ec.m.=1113 keV resonance strength in 20Ne(p,?)21Na using the DRAGON recoil mass spectrometer. The DRAGON result, 0.972±0.11 eV, is in good agreement with the accepted value when both are calculated in the same frame of reference.

Christian, G.; Hutcheon, D.; Akers, C.; Connolly, D.; Fallis, J.; Ruiz, C.

2013-09-01

259

Preliminary resolved resonance region evaluation of copper-63 from 0 to 300 keV  

SciTech Connect

A new preliminary evaluation of Cu-63 was done in the energy region from 0 to 300 keV extending the resolved resonance region of the previous, ENDF/B-VII.0, evaluation three-fold. The new evaluation was based on three experimental transmission data sets; two measured at the Oak Ridge Electron Linear Accelerator (ORELA) and one from the Massachusetts Inst. of Technology Nuclear Reactor (MITR). A total of 275 new resonances were identified and a corresponding set of external resonances was approximated to mock up the external levels. The negative external levels (bound level) were modified to match the thermal cross section values. A preliminary benchmarking calculation was made using 11 ICSBEP benchmarks. This work is in support of the DOE Nuclear Criticality Safety Program. (authors)

Sobes, V.; Forget, B. [Dept. of Nuclear Science and Engineering, Massachusetts Inst. of Technology, Bldg. 24, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States); Leal, L.; Guber, K. [Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831 (United States)

2012-07-01

260

Modification of poly(methyl methacrylate) by keV Ar deposition  

NASA Astrophysics Data System (ADS)

Classical molecular dynamics simulations are used to examine 1 keV Ar atom bombardment on the surface of poly(methyl methacrylate) (PMMA), which induces sputtering and chemical modifications to the surface. The simulations are carried out at various surface temperatures that range from 200 to 600 K. The results indicate that different fragments of PMMA, as characterized by their mass, are preferentially sputtered from the surface at the various temperatures considered. In addition, the simulations predict that small fragments are produced by the high energy deposition process. However, larger sized fragments are generated when the surface temperature is close to the glass transition temperature of PMMA. The atomic-scale processes by which these occur are elucidated by the simulations.

Su, Ya-Ting; Shan, Tzu-Ray; Sinnott, Susan B.

2009-08-01

261

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

262

Imaging Observations of X-Ray Quasi-periodic Oscillations at 3 - 6 keV in the 26 December 2002 Solar Flare  

NASA Astrophysics Data System (ADS)

Quasi-periodic oscillations in soft X-rays (SXR) are not well known due to the instrument limitations, especially the absence of imaging observations of SXR oscillations. We explore the quasi-periodic oscillations of SXR at 3 - 6 keV in a solar flare observed by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) on 26 December 2002. This was a B8.1 class event and showed three X-ray sources (S1, S2, and S3) at 3 - 6 keV and two sources (S1 and S2) at 12 - 25 keV. The light curves of the total fluxes display a two-minute oscillation at 3 - 6 keV, but not in the energy bands above 8 keV. To investigate imaging observations of the oscillations, we prepared CLEAN images at seven energy bands between 3 keV and 20 keV with an eight-second integration. The light curves of three sources were analyzed after integrating the flux of each source region. We used the Fourier method to decompose each source light curve into rapidly varying and slowly varying components. The rapidly varying components show seven individual peaks which are well fitted with a sine function. Then we used the wavelet method to analyze the periods in the rapidly varying component of each source. The results show that three sources display damped quasi-periodic oscillations with a similar two-minute period. The damped oscillations timescale varies between 2.5 to 6 minutes. Source S1 oscillates with the same phase as S3, but is almost in anti-phase with S2. Analyzing the flaring images in more detail, we found that these oscillation peaks are well consistent with the appearance of S3, which seems to split from or merge with S2 with a period of two minutes. The flare images with a high cadence of one second at 3 - 6 keV show that source S3 appears with a rapid period of 25 seconds. The two-minute oscillation shows the highest spectral power. Source S3 seems to shift its position along the flare loop with a mean speed of 130 km s-1, which is of the same order as the local sound speed. This connection between the oscillation peaks and emission enhancement appears to be an observational constraint on the emission mechanism at 3 - 6 keV.

Ning, Zongjun

2014-04-01

263

Motion of 3-6 keV Nonthermal Sources Along the Legs of a Flare Loop  

NASA Technical Reports Server (NTRS)

Observations of nonthermal X-ray sources me critical to studying electron acceleration and transport in solar flares. Strong thermal emission radiated from the preheated plasma before the flare impulsive phase often makes it difficult to detect low-energy X-ray sources that are produced by relatively low-energy nonthermal electrons. Knowledge of the distribution of these low-energy nonthermal electrons is particularly important in determining the total nonthermal electron energy in solar flares. We report on an 'early impulsive flare' in which impulsive hard X-ray emission was seen early in the flare before the soft X-ray emission had risen significantly, indicating limited plasma pre-heating. Early in the flare, RHESSI < 25 keV images show coronal sources that moved first downward and then upwards along the legs of a flare loop. In particular, the 3-6 keV source appeared as a single coronal source at the start of the flare, and then it involved into two coronal sources moving down along the two legs of the loop. After nearly reaching the two footpoints at the hard X-ray peak, the two sources moved back up to the looptop again. RHESSI images and light curves all indicate that nonthermal emission dominated at energies as low as 3-6 keV. We suggest that the evolution of both the spectral index and the low-energy cutoff of the injected electron distribution could result in the accelerated electrons reaching a lower altitude along the legs of the dense flare loop and hence result in the observed downward and upward motions of the nonthermal sources.

Sui, Linhui; Holman, Gordon D.; Dennis, Brian R.

2007-01-01

264

The structure and dynamics of the radiation belts from 10 keV to 2 MeV  

NASA Astrophysics Data System (ADS)

The Van Allen Probes mission measures the Earth’s radiation belts with very high spatial, temporal, and energy resolution. Recent analysis has taken advantage of the capability of the ECT/MagEIS instrument’s ability to directly measure penetrating background radiation contributions to the electron count rates - and subtract it - providing spectral measurements that are essentially free of background contamination [Claudepierre et al., 2014]. The “background-subtracted” measurements show a surprising lack of MeV electrons in inner zone of the radiation belt [Fennell et al., 2014]. However at energies below ~1 MeV electrons can be injected through the slot region into the inner belt.Our analysis of these deep particle injections shows (1) there is great variability in the location of the inner edge of the outer zone - both from one event to another and from one energy to another, (2) lower energy electrons (e.g. <300 keV) are injected into the inner zone (e.g. L<2) more often than higher energy electrons (3) electrons with energies as low as 50 keV are frequently injected into the inner zone. We discuss the implications of these new observations for our understanding of radiation belt acceleration and transport.

Reeves, Geoffrey D.; Larsen, Brian A.; Friedel, Reiner H. W.; Claudepierre, Seth G.; Fennell, Joseph F.; Spence, Harlan E.; Turner, Drew L.

2015-04-01

265

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

SciTech Connect

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

Li, G.; Kong, X.; Zank, G. [Department of Physics and CSPAR, University of Alabama in Huntsville, Huntsville, AL 35899 (United States); Chen, Y., E-mail: gang.li@uah.edu [Institute of Space Sciences and School of Space Sciences and Physics, Shandong University, 264209 Weihai (China)

2013-05-20

266

Capture of a neutron to excited states of a {sup 9}Be nucleus taking into account resonance at 622 keV  

SciTech Connect

Radiative capture of a neutron to the ground and excited states of the 9Be nucleus is considered using the potential cluster model with forbidden states and with classification of cluster states by the Young schemes taking into account resonance at 622 keV for thermal and astrophysical energies.

Dubovichenko, S. B., E-mail: dubovichenko@gmail.com [National Space Agency of the Republic of Kazakhstan, Fessenkov Astrophysical Institute, National Space Research and Technologies Center (Kazakhstan)

2013-10-15

267

Efficient Production of 4-KeV X Rays from Laser-Heated Xe Gas = Confined Within a Hohlraum  

NASA Astrophysics Data System (ADS)

Clean (debris-free) and efficient multi-kilovolt x-ray sources are needed for irradiating large military test objects and for use as backlighters in future Inertial Confinement Fusion experiments. Laser-plasma x-ray sources are particularly attractive for these uses since their spectrum can be controlled by proper choice of plasma material and laser intensity; and because many laser-plasma sources can be designed to produce little or no particulate debris. We report on an experiment in which we measured the production-efficiency, spectrum, and time history of 1-4 KeV x-rays from beryllium hohlraums which were filled with 1 and 2 atm of Xe gas and then irradiated by a 2-nsec pulse from the NOVA laser. It is predicted that 17be converted into > 4KeV x rays and 30history of >4KeV part of the spectrum is predicted to exhibit a dip in intensity whose depth and location vary with fill pressure and hohlraum size.. We also measured the debris produced by these sources. Work supported by the Defense Special Weapons Agency and the U.S. Department of Energy at LLNL under W-7405-ENG-48.

Grun, Jacob; Suter, Larry J.; Back, Christina A.; Decker, Chris; Kauffman, Robert L.; Davis, John F.

1996-11-01

268

RHESSI Observations of the Solar Flare Iron-line Feature at 6.7 keV  

E-print Network

Analysis of RHESSI 3--10 keV spectra for 27 solar flares is reported. This energy range includes thermal free--free and free--bound continuum and two line features, at 6.7keV and 8keV, principally due to highly ionized iron (Fe). We used the continuum and the flux in the so-called Fe-line feature at 6.7keV to derive the electron temperature T_e, the emission measure, and the Fe-line equivalent width as functions of time in each flare. The Fe/H abundance ratio in each flare is derived from the Fe-line equivalent width as a function of T_e. To minimize instrumental problems with high count rates and effects associated with multi-temperature and nonthermal spectral components, spectra are presented mostly during the flare decay phase, when the emission measure and temperature were smoothly varying. We found flare Fe/H abundance ratios that are consistent with the coronal abundance of Fe (i.e. 4 times the photospheric abundance) to within 20% for at least 17 of the 27 flares; for 7 flares, the Fe/H abundance ratio is possibly higher by up to a factor of 2. We find evidence that the Fe XXV ion fractions are less than the theoretically predicted values by up to 60% at T_e=25 MK appear to be displaced from the most recent theoretical values by between 1 and 3 MK.

K. J. H. Phillips; C. Chifor; B. R. Dennis

2006-07-13

269

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

270

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

271

Characterizations of MCP performance in the hard x-ray range (6–25 keV)  

SciTech Connect

MCP detector performance at hard x-ray energies from 6 to 25 keV was recently investigated using NSLS beamline X15A at BNL. Measurements were made with an NSTec Gen-II (H-CA-65) framing camera, based on a Photonis MCP with ?10 ?m in diameter pores, ?12 ?m center-center spacing, an L/D ratio of 46, and a bias angle of 8°. The MCP characterizations were focused on (1) energy and angle dependent sensitivity, (2) energy and angle dependent spatial resolution, (3) energy dependent gain performance, and (4) energy dependent dynamic range. These measurement corroborated simulation results using a Monte Carlo model that included hard x-ray interactions and the subsequent electron cascade in the MCP.

Wu, Ming, E-mail: minwu@sandia.gov; Rochau, Greg [Sandia National Laboratory, Albuquerque, New Mexico 87185 (United States); Moy, Ken [Special Technology Laboratories, NSTec, Santa Barbara, California 93111-2335 (United States); Kruschwitz, Craig [National Security Technologies, LLC, Los Alamos Operations, Los Alamos, New Mexico 87544 (United States)

2014-11-15

272

Characterizations of MCP performance in the hard x-ray range (6-25 keV)  

NASA Astrophysics Data System (ADS)

MCP detector performance at hard x-ray energies from 6 to 25 keV was recently investigated using NSLS beamline X15A at BNL. Measurements were made with an NSTec Gen-II (H-CA-65) framing camera, based on a Photonis MCP with ˜10 ?m in diameter pores, ˜12 ?m center-center spacing, an L/D ratio of 46, and a bias angle of 8°. The MCP characterizations were focused on (1) energy and angle dependent sensitivity, (2) energy and angle dependent spatial resolution, (3) energy dependent gain performance, and (4) energy dependent dynamic range. These measurement corroborated simulation results using a Monte Carlo model that included hard x-ray interactions and the subsequent electron cascade in the MCP.

Wu, Ming; Moy, Ken; Kruschwitz, Craig; Rochau, Greg

2014-11-01

273

Black-hole binaries: life begins at 40 keV  

E-print Network

In the study of black-hole transients, an important problem that still needs to be answered is how the high-energy part of the spectrum evolves from the low-hard to the high-soft state, given that they have very different properties. Recent results obtained with RXTE and INTEGRAL have given inconsistent results. With RXTE, we have found that the high-energy cutoff in GX 339-4 during the transition first decreases (during the low-hard state), then increases again across the Hard-Intermediate state, to become unmeasurable in the soft states (possibly because of statistical limitations). We show Simbol-X will be able to determine the spectral shape with superb accuracy. As the high-energy part of the spectrum is relatively less known than the one below 20 keV, Simbol-X will provide important results that will help out understanding of the extreme physical conditions in the vicinity of a stellar-mass black hole.

Belloni, Tomaso M

2009-01-01

274

ART: Surveying the Local Universe at 2-11 keV  

NASA Technical Reports Server (NTRS)

The Astronomical Rontgen Telescope (ART) is a medium-energy x-ray telescope system proposed for the Russian-led mission Spectrum Rontgen-Gamma (SRG). Optimized for performance over the 2-11-keV band, ART complements the softer response of the SRG prime instrument-the German eROSITA x-ray telescope system. The anticipated number of ART detections is 50,000-with 1,000 heavily-obscured (N(sub H)> 3x10(exp 23)/sq cm) AGN-in the SRG 4-year all-sky survey, plus a comparable number in deeper wide-field (500 deg(sup 2) total) surveys. ART's surveys will provide a minimally-biased, nearly-complete census of the local Universe in the medium-energy x-ray band (including Fe-K lines), at CCD spectral resolution. During long (approx.100-ks) pointed observations, ART can obtain statistically significant spectral data up to about 15 keY for bright sources and medium-energy x-ray continuum and Fe-K-line spectra of AGN detected with the contemporaneous NuSTAR hard-x-ray mission.

O'Dell, S. L.; Ramsey, B. D.; Adams, M. L.; Brandt, W. N.; Bubarev, M. V.; Hassinger, G.; Pravlinski, M.; Predehl, P.; Romaine, S. E.; Swartz, D. A.; Urry, C. M.; Vikhlinin, A.; Weisskopf, M. C.

2008-01-01

275

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

276

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

NASA Astrophysics Data System (ADS)

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 (Ix ? IL?) for 45 fs and optimized pulse duration were measured for laser intensities in the region of 3 × 1014 - 8 × 1017. 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 ?Mg = 1.2 × 10-5, ?Ti = 3.1 × 10-5, ?Fe = 2.7 × 10-5, ?Cu = 1.9 × 10-5. 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.; Naik, P. A.; Chakera, J. A.; Bagchi, S.; Tayyab, M.; Gupta, P. D.

2014-04-01

277

The Technique of Genetic Transformation Mediated by keV Ion Beam  

Microsoft Academic Search

The application of keV ion beam in life science started in China several decades ago. In 1986, researchers initially studied the mutagenic effect of ion beam, and successfully applied it to plant breeding. Nowadays, ion beam implantation technique has been extensively applied to many biological fields. This paper mainly introduces one of its important applications: Genetic transformation mediated by keV

Po Bian; Zengliang Yu

2005-01-01

278

The Physical Nature of the Sharp Spectral Feature at 7 keV Detected in 1H0707-495  

NASA Technical Reports Server (NTRS)

XMM-Newton acquired data on the accepted target, 1H0707-495, on 2002 October 13 during revolution 0521. The observation was successful, with only about 5% data loss due to background flaring. We compared the data from this observation with earlier data taken on this Narrow-Line Seyfert 1 about two years before, performing interpretation studies in the context of the partial-covering model. Our second longer observation once again displays a sharp (< 200 eV) spectral drop above 7 keV. However, in comparison to the first observation, the edge depth and energy have changed significantly. In addition to changes in the edge parameters, the high-energy spectrum appears steeper. The changes in the high-energy spectrum can be adequately explained in terms of a partial-covering absorber out-flowing from the central region. The low-energy spectrum also shows significant long-term spectral variability, including (1) a substantial increase in the disk temperature, (2) detection of an approx. 0.9 keV emission feature, and (3) the presence of ionized absorption that was detected during the ASCA mission. The large increase in disk temperature, and the more modest rise in luminosity, can be understood if we consider a slim-disk model for 1H0707-495. In addition, the higher disk luminosity could be the driving force behind the outflow and the re-appearance of an ionized medium during the second XMM-Newton observation.

Brandt, Niel

2005-01-01

279

Impact of IUdR on Rat 9L glioma cell survival for 25-35 keV photon-activated auger electron therapy.  

PubMed

The goal of the current study was to measure the energy dependence of survival of rat 9L glioma cells labeled with iododeoxyuridine (IUdR) that underwent photon-activated Auger electron therapy using 25-35 keV monochromatic X rays, i.e., above and below the K-edge energy of iodine. Rat 9L glioma cells were selected because of their radioresistance, ability to be implanted for future in vivo studies and analogy to radioresistant human gliomas. Survival curves were measured for a 4 MV X-ray beam and synchrotron produced monochromatic 35, 30 and 25 keV X-ray beams. IUdR was incorporated into the DNA at levels of 0, 9 and 18% thymidine replacement for 4 MV and 35 keV and 0 and 18% thymidine replacement for 30 and 25 keV. For 10 combinations of beam energy and thymidine replacement, 62 data sets (3-13 per combination) provided 776 data points (47-148 per combination). Survival versus dose data taken for the same combination, but on different days, were merged by including the zero-dose points in the nonlinear, chi-squared data fitting using the linear-quadratic model and letting the best estimate to the zero-dose plating efficiency for each of the different days be a fitting parameter. When comparing two survival curves, the ratio of doses resulting in 10% survival gave sensitization enhancement ratios (SER10) from which contributions due to linear energy transfer (LET) (SER10,LET), IUdR radiosensitization (SER10,RS), the Auger effect (SER10,AE) and the total of all effects (SER10,T) were determined. At 4 MV and 35, 30 and 25 keV, SER10,LET values were 1.00, 1.08 ± 0.03, 1.22 ± 0.02 and 1.37 ± 0.02, respectively. At 4 MV SER10,RS values for 9 and 18% IUdR were 1.28 ± 0.02 and 1.40 ± 0.02, respectively. Assuming LET effects were independent of percentage IUdR and radiosensitization effects were independent of energy, SER10,AE values for 18% IUdR at 35, 30 and 25 keV were 1.35 ± 0.05, 1.06 ± 0.03 and 0.98 ± 0.03, respectively. The value for 9% IUdR at 35 keV was 1.01 ± 0.04. First, we found the radioresistant rat 9L glioma cell line exhibited an SER10 due to the Auger effect of 1.35 at (35 keV, 18% IUdR) and an SER10 due to the radiosensitizing effect of 1.40 at (4 MV, 18% IUdR), both significantly less than values for previously reported cell lines. These low individual values emphasize the benefit of their combined value (SER10 of approximately 1.9) for achieving clinical benefit. Second, as expected, we observed that energies below the K-edge of iodine (25 and 30 keV), for which there are L, M and higher shell photoelectric events creating Auger electrons, show no promise for Auger electron therapy. Third, to proceed with future in vivo studies, additional data from 35-65 keV are needed to determine the optimal X-ray energy for IUdR Auger electron therapy. Only then can there be an answer to the question, how well the energy dependence of in vitro survival data supports the potential for photon-activated Auger electron therapy with IUdR in cancer radiotherapy. PMID:25409122

Alvarez, Diane; Hogstrom, Kenneth R; Brown, Thomas A D; Ii, Kenneth L Matthews; Dugas, Joseph P; Ham, Kyungmin; Varnes, Marie E

2014-12-01

280

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

281

New Approach for Measuring the (n,?) Cross Section of a Nucleus by a Few keV Neutron  

NASA Astrophysics Data System (ADS)

We have for the first time determined with high precision the energy spectrum of low-energy neutrons (En<10 keV) which are produced in the 7Li( p,n)7Be reaction, by detecting ?-rays of the 197Au(n,?)198Au reaction whose cross section is known. An anti-Compton NaI(Tl) spectrometer played an essential role in detecting the ?-rays with a good signal to noise ratio by discriminating large background due to thermalized neutrons in the measurement room. The low energy neutrons thus derived were successfully used to measure the 62Ni(n,?)63Ni reaction cross section. The present low energy neutrons could be extensively used for cross section measurements for neutron capture reactions and elastic scatterings from nuclei of nuclear astrophysical interests.

Segawa, Mariko; Tomyo, Atsushi; Nagai, Yasuki; Temma, Yasuyuki; Masaki, Tomohiro; Shima, Tatsushi; Nishiyama, Jun; Ohsaki, Toshiro; Igashira, Masayuki

2005-11-01

282

Phenomenological treatments of cross-sections for proton and hydrogen impact below 1 keV on molecular nitrogen  

NASA Technical Reports Server (NTRS)

An analytic independent-particle model is used to construct static potentials to describe the interaction of hydrogen-like ions with atoms and molecules. Parameters of the ion-atom potential are determined from ab initio total energy minimization procedure. The elastic scattering of He(+) from Ne and Ar is investigated as a test case and comparison is made with experiment. The model is then used in conjunction with low energy H(+)-N2 experimental data to construct differential and total cross-sections for the scattering of protons and hydrogen in the energy range of 10 eV to 1 keV from molecular nitrogen. Analytic forms are used to parametrize these cross-sections to facilitate their use in the calculation of energy deposition by protons and hydrogen atoms in atmospheric gases.

Porter, H. S.; Green, A. E. S.; Szydlik, P. P.

1975-01-01

283

M Sub-Shell Cross Sections For 75-300 keV Proton Impact On W, Pt And Pb  

SciTech Connect

M sub-shell x-ray production cross sections from 75-300 keV proton bombardment of thick elemental targets of W, Pt, and Pb were measured and compared with ECPSSR and relativistic RPWBA-BC cross sections using different data bases of fluorescence yields, Coster-Kronig factors, and x-ray transition rates. With a few exceptions, the differences between the various data base comparisons were not significant. For different sub-shells, either ECPSSR or RPWBA-BC compared better with the measurements. In all cases, agreement with theory improved as the collision energy increased.

Cipolla, Sam J. [Physics Department, Creighton University, Omaha, NE 68178 (United States)

2011-06-01

284

Production of ^13N Using a 400keV Van de Graaff Positive Ion Accelerator  

NASA Astrophysics Data System (ADS)

A target system has been developed to study the production and extraction of ^13N, a short-lived radioisotope of nitrogen (t1/2 9.6 minutes), formed via the ^12C(d,n)^13N reaction. The target is comprised of a graphite rod positioned in a custom-built target chamber where it is irradiated by a deuteron beam. Post irradiation, the target is flushed with H2 or CO2 gas, and heated via a large applied current producing ^13NH3 or HC^13N and ^13NO2 respectively. Radiolabeled ^13N compounds are used for physiological imaging using Positron Emission Tomography (PET). The production system used the 400keV Van de Graaff Positive Ion Accelerator housed in the Applied Nuclear Science Lab at Minnesota State University, Mankato. While this energy, slightly above threshold, is too low to make sufficient amounts of ^13N for imaging work, the system and procedure can be implemented on higher energy machines. Preliminary system results will be presented as well as accelerator calibration and reaction data.

Prokop, Christopher; Clymer, John; Compton, Nicholas; Dam, Henry; Hanson, Adam; Pautzke, Justen; Roberts, Andrew

2011-04-01

285

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

SciTech Connect

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

Janousch, M.; Schmidt, Th.; Wetter, R.; Grolimund, G.; Scheidegger, A.M. [Paul Scherrer Institute (PSI), CH-5232 Villigen PSI (Switzerland); Flank, A.-M.; Lagarde, P.; Cauchon, G.; Bac, S. [LURE, Bat 209d, Centre Universitaire Paris-Sud, BP 34, 91898 Orsay Cedex (France); Dubuisson, J.M. [Synchrotron SOLEIL, L'Orme de Merisiers, Saint-Aubin, BP 48, 91192 Gif-sur-Yvette Cedex (France)

2004-05-12

286

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

287

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

288

H- ion source development for the FNAL 750keV injector upgrade  

NASA Astrophysics Data System (ADS)

The new FNAL 750keV injector upgrade for the replacement of the 40 year old Fermi National Laboratory (FNAL) Cockcroft-Walton accelerators with a new ion source and 200MHz Radio Frequency Quadrupole (RFQ), Low Energy Beam Transport (LEBT) and Medium Energy Beam Transport (MEBT) [1], has been built and is now being tested prior to installation during the 2012 shutdown. The new H- ion source is a round aperture magnetron which was developed at Brookhaven National Lab (BNL) by Jim Alessi[2]. Operational experience from BNL has shown that this type of source is more reliable with a longer lifetime (on the order of 6 to 9 months) due to better power efficiency. With a similar duty factor to BNL, we expect to have a comparable lifetime between source changes. The new source design reliably produces 90mA of H- beam current at 15Hz rep-rate, 250?s pulse width, and a duty factor of 0.38%. The measured emittances at the end of the LEBT are horizontally ?H = 0.21? mm* mrad and vertically ?V = 0.17? mm* mrad. With 35kV extraction the power efficiency is 60mA/kW. The source design, along with data from a test stand and the LEBT, will be presented in this paper.

Bollinger, D. S.

2013-02-01

289

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

290

Revisiting the relationship between 6 ?m and 2-10 keV continuum luminosities of AGN  

NASA Astrophysics Data System (ADS)

We have determined the relation between the AGN luminosities at rest-frame 6 ?m associated with the dusty torus emission and at 2-10 keV energies using a complete, X-ray-flux-limited sample of 232 AGN drawn from the Bright Ultra-hard XMM-Newton Survey. The objects have intrinsic X-ray luminosities between 1042 and 1046 erg s-1 and redshifts from 0.05 to 2.8. The rest-frame 6 ?m luminosities were computed using data from the Wide-field Infrared Survey Explorer and are based on a spectral energy distribution decomposition into AGN and galaxy emission. The best-fitting relationship for the full sample is consistent with being linear, L6 ?m ? L_{2-10 keV}^{0.99± 0.03}, with intrinsic scatter, ? log L6 ?m ˜ 0.35 dex. The L_{6 ? m}/L_{2-10 keV} luminosity ratio is largely independent of the line-of-sight X-ray absorption. Assuming a constant X-ray bolometric correction, the fraction of AGN bolometric luminosity reprocessed in the mid-IR decreases weakly, if at all, with the AGN luminosity, a finding at odds with simple receding torus models. Type 2 AGN have redder mid-IR continua at rest-frame wavelengths <12 ?m and are overall ˜1.3-2 times fainter at 6 ?m than type 1 AGN at a given X-ray luminosity. Regardless of whether type 1 and type 2 AGN have the same or different nuclear dusty toroidal structures, our results imply that the AGN emission at rest-frame 6 ?m is not isotropic due to self-absorption in the dusty torus, as predicted by AGN torus models. Thus, AGN surveys at rest-frame ˜6 ?m are subject to modest dust obscuration biases.

Mateos, S.; Carrera, F. J.; Alonso-Herrero, A.; Rovilos, E.; Hernán-Caballero, A.; Barcons, X.; Blain, A.; Caccianiga, A.; Della Ceca, R.; Severgnini, P.

2015-05-01

291

Photon-attenuation cross sections for beryllium from 1.5 to 8.0 keV  

NASA Astrophysics Data System (ADS)

The photon-attenuation cross sections for beryllium have been measured with use of a Si(Li) detector spectrometer in the energy range 1.5-8.0 keV. The K? and L? x-ray lines produced by the heavy-ion interaction with the thick targets of different materials have been used as the low-energy photon sources. High-purity (99.8%) beryllium foils are used. The experimental errors are less than 2.5%, except when stacked foils were used for the Cu K? line, in which case the error was 2.9%. The results are compared with the available measured values in this energy region and also with widely used tabulated values of Storm and Israel, of Veigele, and with recent tabulations of Hubbell. Furthermore, the photoeffect cross sections are derived from the total attenuation cross sections by subtracting the scattering cross sections and are compared with Scofield's theoretical calculations.

Gowda, R.; Powers, D.

1985-11-01

292

Measurement of the 10 keV resonance in the $^{10}$B($p, \\alpha_0$)$^7$Be reaction via the Trojan Horse Method  

E-print Network

The $^{10}$B(p,$\\alpha_0$)$^7$Be 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 $^{11}$C level (J$^{\\pi}$=$\\frac{5}{2}$$^+$), producing an s-wave resonance centered at about 10 keV in the entrance channel. Up to now, only the high energy tail of this resonant has been measured, while the low-energy trend is extrapolated from the available direct data. The THM has been applied to the quasi-free $^2$H($^{10}$B,$\\alpha_0$$^7$Be)n reaction induced at a boron-beam energy of 24.5 MeV. An accurate analysis brings to the determination of the $^{10}$B(p,$\\alpha_0$)$^7$Be S(E)-factor and of the corresponding electron screening potential $U_e$, thus giving for the first time an independent evaluation of it.

Spitaleri, C; Puglia, S M R; Romano, S; La Cognata, M; Crucilla, V; Pizzone, R G; Rapisarda, G G; Sergi, M L; Del Santo, M Gimenez; Carlin, N; Munhoz, M G; Souza, F A; de Toledo, A Szanto; 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

2014-01-01

293

Measurement of the 10 keV resonance in the $^{10}$B($p, ?_0$)$^7$Be reaction via the Trojan Horse Method  

E-print Network

The $^{10}$B(p,$\\alpha_0$)$^7$Be 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 $^{11}$C level (J$^{\\pi}$=$\\frac{5}{2}$$^+$), producing an s-wave resonance centered at about 10 keV in the entrance channel. Up to now, only the high energy tail of this resonant has been measured, while the low-energy trend is extrapolated from the available direct data. The THM has been applied to the quasi-free $^2$H($^{10}$B,$\\alpha_0$$^7$Be)n reaction induced at a boron-beam energy of 24.5 MeV. An accurate analysis brings to the determination of the $^{10}$B(p,$\\alpha_0$)$^7$Be S(E)-factor and of the corresponding electron screening potential $U_e$, thus giving for the first time an independent evaluation of it.

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

2014-07-17

294

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

295

Revisiting the relationship between 6 {\\mu}m and 2-10 keV continuum luminosities of AGN  

E-print Network

We have determined the relation between the AGN luminosities at rest-frame 6 {\\mu}m associated to the dusty torus emission and at 2-10 keV energies using a complete, X-ray flux limited sample of 232 AGN drawn from the Bright Ultra-hard XMM-Newton Survey. The objects have X-ray luminosities corrected for intrinsic absorption between 10^42 and 10^46 erg/s and redshifts from 0.05 to 2.8. The rest-frame 6 {\\mu}m luminosities were computed using data from the Wide-Field Infrared Survey Explorer and are based on a spectral energy distribution decomposition into AGN and galaxy emission. The best-fit relationship for the full sample is consistent with being linear, L_6 {\\mu}m $\\propto$ L_2-10 keV^0.99$\\pm$0.032, but has significant intrinsic scatter, ~0.35 dex in log L_6 {\\mu}m. Assuming a constant X-ray bolometric correction, the fraction of AGN bolometric luminosity reprocessed in the mid-IR decreases weakly, if at all, with the AGN luminosity, a finding at odds with simple receding torus models. Type 2 AGN have re...

Mateos, S; Alonso-Herrero, A; Rovilos, E; Hernán-Caballero, A; Barcons, X; Blain, A; Caccianiga, A; Della Ceca, R; Severgnini, P

2015-01-01

296

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

297

Solar Wind ?20–200 keV Superhalo Electrons at Quiet Times  

NASA Astrophysics Data System (ADS)

High-energy superhalo electrons are present in the interplanetary medium (IPM) even in the absence of any significant solar activity, carrying important information on electron acceleration in the solar wind. We present a statistical survey of ?20–200 keV superhalo electrons measured at 1 AU by the WIND 3D Plasma & Energetic Particle instrument during quiet-time periods from 1995 January through 2013 December. The selected 242 quiet-time samples mostly occur during the rising, maximum and decay phases of solar cycles. The observed omnidirectional differential flux of these quiet-time superhalo electrons generally fits to a power-law spectrum J=A× {{(\\frac{E}{{{m}e}{{c}2}})}-? }, with ? ranging from ?1.6 to ?3.7 and the integrated density nsup ranging from 10?8 to 10?5 cm?3. In solar cycle 23 (24), the distribution of ? has a broad maximum between 2.4 and 2.8 (2.0 and 2.4). Both ? and the logarithm of nsup show no obvious correlation with sunspot number, solar flares, solar wind core population, etc. These superhalo electrons may form a quiet-time energetic electron background/reservoir in the IPM. We propose that they may originate from nonthermal processes related to the acceleration of the solar wind such as nanoflares, or could be formed in the IPM due to further acceleration and/or long-distance propagation effects.

Wang, Linghua; Yang, Liu; He, Jiansen; Tu, Chuanyi; Pei, Zhongtian; Wimmer-Schweingruber, Robert F.; Bale, Stuart D.

2015-04-01

298

The System of Nanosecond 280-KeV He+ Pulsed Beam  

SciTech Connect

At Fast Neutron Research Facility, the 150 kV-pulses neutron generator is being upgraded to a 280-kV-pulsed-He beam for time-of-flight Rutherford backscattering spectrometry. It involves replacing the existing beam line elements by a multicusp ion source, a 400-kV accelerating tube, 45{sup o}-double focusing dipole magnet and quadrupole lens. The multicusp ion source is a compact filament-driven of 2.6 cm in diameter and 8 cm in length. The current extracted is 20.4 {micro}A with 13 kV of extraction voltage and 8.8 kV of Einzel lens voltage. The beam emittance has found to vary between 6-12 mm mrad. The beam transport system has to be redesigned based on the new elements. The important part of a good pulsed beam depends on the pulsing system. The two main parts are the chopper and buncher. An optimized geometry for the 280 keV pulsed helium ion beam will be presented and discussed. The PARMELA code has been used to optimize the space charge effect, resulting in pulse width of less than 2 ns at a target. The calculated distance from a buncher to the target is 4.6 m. Effects of energy spread and phase angle between chopper and buncher have been included in the optimization of the bunch length.

Junphong, P.; Ano, V.; Lekprasert, B.; Suwannakachorn, D.; Thongnopparat, N.; Vilaithong, T.; /Chiang Mai U.; Wiedemann, H.; /SLAC /SLAC, SSRL

2006-05-01

299

Multipolarity of the 228.5-keV transition in {sup 80}Y  

SciTech Connect

We have unambiguously characterized the deexcitation of the 228.5-keV T{sub 1/2}=4.7-s isomer in {sup 80}Y as an M3 transition. This result determines, in conjunction with other experimental data, the spin and parity of the 228.5-keV isomer and the {sup 80}Y ground state as 1{sup -} and 4{sup -}, respectively. (c) 2000 The American Physical Society.

Piechaczek, A. [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803-4001 (United States)] [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803-4001 (United States); Zganjar, E. F. [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803-4001 (United States)] [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803-4001 (United States); Batchelder, J. C. [UNIRIB, Oak Ridge Associated Universities, Oak Ridge, Tennessee 37831 (United States)] [UNIRIB, Oak Ridge Associated Universities, Oak Ridge, Tennessee 37831 (United States); Bingham, C. R. [Department of Physics and Astronomy, University of Tennessee, Tennessee 37996-1200 (United States) [Department of Physics and Astronomy, University of Tennessee, Tennessee 37996-1200 (United States); Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6371 (United States); Ginter, T. N. [Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235 (United States)] [Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235 (United States); Gross, C. J. [Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6371 (United States) [Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6371 (United States); Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee 37831-0117 (United States); Grzywacz, R. [Department of Physics and Astronomy, University of Tennessee, Tennessee 37996-1200 (United States)] [Department of Physics and Astronomy, University of Tennessee, Tennessee 37996-1200 (United States); Macdonald, B. D. [School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332-0430 (United States)] [School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332-0430 (United States); Paul, S. D. [Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6371 (United States) [Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6371 (United States); UNIRIB, Oak Ridge Associated Universities, Oak Ridge, Tennessee 37831 (United States); Rykaczewski, K. [Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6371 (United States) [Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6371 (United States); Warsaw University, PL-00681 Warsaw, (Poland)] (and others)

2000-04-01

300

10–100 keV electron acceleration and emission from solar flares  

Microsoft Academic Search

We present an analysis of spacecraft observations of non-thermal X-rays and escaping electrons for 5 selected small solar flares in 1967. OSO-3 multi-channel energetic X-ray measurements during the non-thermal component of the solar flare X-ray bursts are used to derive the parent electron spectrum and emission measure. IMP-4 and Explorer-35 observations of > 22 keV and > 45 keV electrons

R. P. Lin; H. S. Hudson

1971-01-01

301

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

302

INTEGRAL observations of the cosmic X-ray background in the 5-100 keV range via occultation by the Earth  

E-print Network

We study the spectrum of the cosmic X-ray background (CXB) in energy range $\\sim$5-100 keV. Early in 2006 the INTEGRAL observatory performed a series of four 30ksec observations with the Earth disk crossing the field of view of the instruments. The modulation of the aperture flux due to occultation of extragalactic objects by the Earth disk was used to obtain the spectrum of the Cosmic X-ray Background(CXB). Various sources of contamination were evaluated, including compact sources, Galactic Ridge emission, CXB reflection by the Earth atmosphere, cosmic ray induced emission by the Earth atmosphere and the Earth auroral emission. The spectrum of the cosmic X-ray background in the energy band 5-100 keV is obtained. The shape of the spectrum is consistent with that obtained previously by the HEAO-1 observatory, while the normalization is $\\sim$10% higher. This difference in normalization can (at least partly) be traced to the different assumptions on the absolute flux from the Crab Nebulae. The increase relative to the earlier adopted value of the absolute flux of the CXB near the energy of maximum luminosity (20-50 keV) has direct implications for the energy release of supermassive black holes in the Universe and their growth at the epoch of the CXB origin.

E. Churazov; R. Sunyaev; M. Revnivtsev; S. Sazonov; S. Molkov; S. Grebenev; C. Winkler; A. Parmar; A. Bazzano; M. Falanga; A. Gros; F. Lebrun; L. Natalucci; P. Ubertini; J. -P. Roques; L. Bouchet; E. Jourdain; J. Knoedlseder; R. Diehl; C. Budtz-Jorgensen; S. Brandt; N. Lund; N. J. Westergaard; A. Neronov; M. Turler; M. Chernyakova; R. Walter; N. Produit; N. Mowlavi; J. M. Mas-Hesse; A. Domingo; N. Gehrels; E. Kuulkers; P. Kretschmar; M. Schmidt

2007-02-12

303

Kinematics and dissociation dynamics of a water molecule under the impact of 10 keV electrons  

NASA Astrophysics Data System (ADS)

The kinematics and dissociation dynamics of a H2O molecule induced by 10 keV electrons are studied using a time-of-flight mass spectrometer in conjunction with a position-sensitive detector in multi-hit coincidence mode. Five dissociative channels arising from the complete as well as the incomplete Coulomb explosions of H2Oq+ (q = 2, 3) ions are observed and identified. The dissociation mechanisms (concerted and/or sequential) for these channels are examined. Further, the angular correlation of different fragment ions and the geometrical structure of the precursor ion are studied. The kinetic energy release distributions for the observed channels are also determined. It is found that the pure Coulomb explosion model is insufficient to explain the observed kinetic release distributions. The mean kinetic energy release for these channels is compared with the available data reported by earlier workers who have employed different charged projectiles and sources of photons.

Singh, Raj; Bhatt, Pragya; Yadav, Namita; Shanker, R.

2013-04-01

304

Compact femtosecond electron diffractometer with 100 keV electron bunches approaching the single-electron pulse duration limit  

NASA Astrophysics Data System (ADS)

We present the design and implementation of a highly compact femtosecond electron diffractometer working at electron energies up to 100 keV. We use a multi-body particle tracing code to simulate electron bunch propagation through the setup and to calculate pulse durations at the sample position. Our simulations show that electron bunches containing few thousands of electrons per bunch are only weakly broadened by space-charge effects and their pulse duration is thus close to the one of a single-electron wavepacket. With our compact setup, we can create electron bunches containing up to 5000 electrons with a pulse duration below 100 fs on the sample. We use the diffractometer to track the energy transfer from photoexcited electrons to the lattice in a thin film of titanium. This process takes place on the timescale of few-hundred femtoseconds and a fully equilibrated state is reached within 1 ps.

Waldecker, Lutz; Bertoni, Roman; Ernstorfer, Ralph

2015-01-01

305

Study of K-line radiation of thick titanium produced in collisions of keV electrons.  

PubMed

The characteristic K-line yields Y(E?) of a pure thick titanium (Z=22) element target are measured for 8-18 keV electron impact and compared with the simulation calculations using PENELOPE code. A fair agreement between experiment and simulation results is found within the existing experimental uncertainty of measurements. The ratio F of indirectly produced characteristic Ti K X-ray yield to its total (directly+indirectly) yield is determined by employing an approximate analytical formulation of Hanson and Cowan (Hanson, H.P., Cowan, D.J., 1961. Phys. Rev. 124, 22-26). It is found that F changes strongly with impact energy E? for normal angle of incidence in contrast to a mild change predicted by the simulation calculations. Furthermore, experimental and simulation results for peak to effective continuum ratio R of Ti K-line are compared and discussed for the energy range of impact of the present investigation. PMID:21723738

Yadav, Namita; Bhatt, Pragya; Singh, Raj; Llovet, X; Shanker, R

2011-10-01

306

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

307

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

SciTech Connect

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.

Baronova, E. O.; Stepanenko, A. M. [RNC “Kurchatov Institute”, 123098 Moscow (Russian Federation); Pereira, N. R., E-mail: ninorpereira@gmail.com [Ecopulse, Inc., 7844 Vervain Ct, Springfield, Virginia 22152 (United States)

2014-11-15

308

The 0.1-100 keV spectral shape and variability of Mkn421 in high state  

E-print Network

The results of a BeppoSAX TOO observation of the BL Lac object Mkn421 during a high intensity state are reported and compared with monitoring X-ray data collected with the BeppoSAX Wide Field Cameras (WFC) and the RXTE All Sky Monitor(ASM). The 0.1-100 keV spectrum of Mkn421 shows continuous convex curvature that can be interpreted as the high-energy end of the synchrotron emission. The source shows significant short-term temporal and spectral variability, which can be interpreted in terms of synchrotron cooling. The comparison of our results with those of previous observations when the source was a factor 3-5 fainter shows evidence for strong spectral variability, with the maximum of the synchrotron power shifting to higher energy during high states. This behaviour suggest an increase in the number of energetic electrons during high states.

A. Malizia; M. Capalbi; F. Fiore; P. Giommi; G. Gandolfi; A. Tesseri; L. A. Antonelli; R. C. Butler; G. Celidonio; A. Coletta; L. Di Ciolo; J. M. Muller; L. Piro; S. Rebecchi; D. Ricci; R. Ricci; M. Smith; V. Torroni

1999-09-13

309

Injection and diffusive transport of suprathermal through energetic solar flare protons (35 keV to 20 MeV)  

NASA Technical Reports Server (NTRS)

Consideration is given to the injection and interplanetary propagation of low-energy protons caused by the solar particle event of July 20, 1981, in which flare protons in the range from 35 keV to 20 MeV were observed by instruments on ISEE 3. The observed time-intensity and time-anisotropy profiles were fitted over the entire energy range using a model based on the spherically symmetric Fokker-Plank equation, including convection, diffusion, and adiabatic deceleration. The results are used to discuss the behavior of the radial interplanetary diffusion coefficient and the scattering mean free path for protons. Also, evidence is found for diffusive coronal shock acceleration of protons during the event.

Beeck, J.; Mason, G. M.; Hamilton, D. C.; Marsden, R. G.; Sanderson, T. R.

1990-01-01

310

Lifetime of 981-Kev State in Li-8  

E-print Network

to that for the solid target except for pressurization with D, gas and substitution of a beam stop consisting of an -100-gg/cm layer of undeuterated Zr on a 10-mil Pt backing (Fig. 1). The energy lost by the incoming 8.0-MeV Li7 beam as it traversed the 0.57-mg/cm2....50? I.o I 2.0 I 3.0 V/V I 4.0 I 5.0 6.0 FIG. 5. Calculated stopping power vs velocity (v/vp, where vp=c/137) for Li stopping in the ZrOD target layer and the Pt backing. Vertical lines at v/vp= 6 indi- cate uncertainty in the stopping power...

Throop, M. J.; Youngblood, David H.; Morrison, G. C.

1971-01-01

311

950 keV, 3.95 MeV and 6 MeV X-band linacs for nondestructive evaluation and medicine  

Microsoft Academic Search

We are developing compact X-band linac X-ray sources for nondestructive evaluation and medicine. First, we develop a portable X-ray system by a 950keV 9.4GHz X-band linac to realize on-site inspection. We use a low power (250kW) magnetron as an RF source for compactness of the whole system. Since the RF power source is quite small and the stored energy in

Mitsuru Uesaka; Takuya Natsui; Kiwoo Lee; Katsuhiro Dobashi; Tomohiko Yamamoto; Takeshi Fujiwara; Haito Zhu; Kazuyuki Demachi; Eiji Tanabe; Masashi Yamamoto; Naoki Nakamura; Joichi Kusano; Toshiyasu Higo; Shigeki Fukuda; Mitsuhiro Yoshida; Shuji Matsumoto

2011-01-01

312

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

313

Measurement of L X-ray production cross sections by 400-700 keV proton impact on rare earth elements  

Microsoft Academic Search

The L-shell X-ray production cross sections of rare earth elements Dy, Ho, Er, Tm, Yb, and Lu by the impact of protons with energies between 400 and 700 keV have been measured. Thin films of the rare earth fluorides have been employed as targets. A comparison with the predictions given by the ECPSSR theory of Brandt and Lapicki, following the

L. Rodríguez-Fernández; J. Miranda; A. Oliver; F. Cruz; J. R. Pegueros

1993-01-01

314

Structural investigation of keV Ar-ion-induced surface ripples in Si by cross-sectional transmission electron microscopy  

E-print Network

O2, Ge, and GaAs, though rippling has been been observed recently in metals Ag and Cu as well.4 Amorphization of Si Refs. 15,16 by heavy ion such as Ar bombardment at keV energies occurs in a dose range 1014 have to be the same everywhere. This is a very relevant question be- cause quite recently ion-enhanced

Nordlund, Kai

315

Neutron capture cross section measurements for 197Au from 3.5 to 84 keV at GELINA  

NASA Astrophysics Data System (ADS)

Cross section measurements have been performed at the time-of-flight facility GELINA to determine the average capture cross section for 197Au in the energy region between 3.5 keV and 84 keV. Prompt ?-rays, originating from neutron-induced capture events, were detected by two C6 D6 liquid scintillators. The sample was placed at about 13m distance from the neutron source. The total energy detection principle in combination with the pulse height weighting technique was applied. The energy dependence of the neutron flux was measured with a double Frisch-gridded ionization chamber based on the 10B(n,?) reaction. The data have been normalized to the well-isolated and saturated 197Au resonance at 4.9 eV. Special care was taken to reduce bias effects due to the weighting function, normalization, dead time and background corrections. The total uncertainty due to normalization, neutron flux and weighting function is 1.0%. An additional uncertainty of 0.5% results from the correction for self-shielding and multiple interaction events. Fluctuations due to resonance structures have been studied by complementary measurements at a 30m flight path station. The results reported in this work deviate systematically by more than 5% from the cross section that is recommended as a reference for astrophysical applications. They are about 2% lower compared to an evaluation of the 197Au(n, ?) cross section, which was based on a least squares fit of experimental data available in the literature prior to this work. The average capture cross section as a function of neutron energy has been parameterized in terms of average resonance parameters. Maxwellian average cross sections at different temperatures have been calculated.

Massimi, C.; Becker, B.; Dupont, E.; Kopecky, S.; Lampoudis, C.; Massarczyk, R.; Moxon, M.; Pronyaev, V.; Schillebeeckx, P.; Sirakov, I.; Wynants, R.

2014-08-01

316

NeXT (New Exploration X-ray Telescope) 10-80 keV0.3-300  

E-print Network

: SXS x1 XX: SXI x1 XX: HXI x2 : SGD x1 NeXTNeXT-SXS He-like ISAS/JAXA NASA NeXT-SXS z ~ 1 IIXT () NeXT 1E10 1E15 1E20 1E25 [Hz] HXI keV MeV SGD NeXT SXI SXS NeXT M82 TeVHESS XDark Particle. of WisconsinMITNASA/GSFCSLAC 550 cm (6 keV) 0.3-10 keV 10 eV(7 keV) (SGD) 120 cm2 () (100 keV) 15 cm2

Enomoto, Ryoji

317

Dark matter in galaxies: the dark matter particle mass is about 7 keV  

E-print Network

Warm dark matter (WDM) means DM particles with mass m in the keV scale. For large scales, (structures beyond ~ 100 kpc) WDM and CDM yield identical results which agree with observations. For intermediate scales, WDM gives the correct abundance of substructures. Inside galaxy cores, below ~ 100 pc, N-body WDM classical physics simulations are incorrect because at such scales quantum WDM effects are important. WDM quantum calculations (Thomas-Fermi approach) provide galaxy cores, galaxy masses, velocity dispersions and density profiles in agreement with the observations. For a dark matter particle decoupling at thermal equilibrium (thermal relic), all evidences point out to a 2 keV particle. Remarkably enough, sterile neutrinos decouple out of thermal equilibrium with a primordial power spectrum similar to a 2 keV thermal relic when the sterile neutrino mass is about 7 keV. Therefore, WDM can be formed by 7 keV sterile neutrinos. Excitingly enough, Bulbul et al. (2014) announced the detection of a cluster X-ray emission line that could correspond to the decay of a 7.1 keV sterile neutrino and to a neutrino decay mixing angle of \\sin^2 2 \\theta ~ 7 10^{-11} . This is a further argument in favour of sterile neutrino WDM. Baryons, represent 10 % of DM or less in galaxies and are expected to give a correction to pure WDM results. The detection of the DM particle depends upon the particle physics model. Sterile neutrinos with keV scale mass (the main WDM candidate) can be detected in beta decay for Tritium and Renium and in the electron capture in Holmiun. The sterile neutrino decay into X rays can be detected observing DM dominated galaxies and through the distortion of the black-body CMB spectrum. So far, not a single valid objection arose against WDM.

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

2014-11-11

318

The complex 0.1-200 keV spectrum of the Seyfert 1 Galaxy NGC 4593  

NASA Astrophysics Data System (ADS)

We report on the first observation of the Seyfert 1 galaxy NGC 4593 in the 0.1-200 keV band, performed with the BeppoSAX observatory. Its spectral components are for the first time simultaneously measured: a power-law with photon spectral index Gamma =~ 1.9; the Compton-reflection of the primary power-law; a moderately broad (sigma > 60 eV) K_? fluorescent line from neutral iron; and an absorption edge, whose threshold energy is consistent with K-shell photoionization from Ovii. The amount of reflection and the iron line properties are consistent with both being produced in a plane-parallel, X-ray illuminated relativistic accretion disc surrounding the nuclear black hole, seen at an inclination of =~ 30(deg) . Any cutoff of the intrinsic continuum is constrained to lay above 150 keV. The claim for a strongly variable soft excess is dismissed by our data and by a reanalysis of archival ASCA and ROSAT data.

Guainazzi, M.; Perola, G. C.; Matt, G.; Nicastro, F.; Bassani, L.; Fiore, F.; dal Fiume, D.; Piro, L.

1999-06-01

319

A possible cyclotron resonance scattering feature near 0.7 keV in X1822-371  

E-print Network

We analyse all available X-ray observations of X1822-371 made with XMM-Newton, Chandra, Suzaku and INTEGRAL satellites. The observations were not simultaneous. The Suzaku and INTEGRAL broad band energy coverage allows us to constrain the spectral shape of the continuum emission well. We use the model already proposed for this source, consisting of a Comptonised component absorbed by interstellar matter and partially absorbed by local neutral matter, and we added a Gaussian feature in absorption at $\\sim 0.7$ keV. This addition significantly improves the fit and flattens the residuals between 0.6 and 0.8 keV. We interpret the Gaussian feature in absorption as a cyclotron resonant scattering feature (CRSF) produced close to the neutron star surface and derive the magnetic field strength at the surface of the neutron star, $(8.8 \\pm 0.3) \\times 10^{10}$ G for a radius of 10 km. We derive the pulse period in the EPIC-pn data to be 0.5928850(6) s and estimate that the spin period derivative of X1822-371 is $(-2.55...

Iaria, R; Matranga, M; Galiano, C G; D'Aì, A; Riggio, A; Burderi, L; Sanna, A; Ferrigno, C; Del Santo, M; Pintore, F; Robba, N R

2015-01-01

320

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

321

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

PubMed

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. PMID:24689570

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

2014-03-01

322

3.5 keV X-ray line and R-parity conserving supersymmetry  

NASA Astrophysics Data System (ADS)

We present some R-parity conserving supersymmetric models which can accommodate the 3.5 keV X-ray line reported in recent spectral studies of the Perseus galaxy cluster and the Andromeda galaxy. Within the Minimal Supersymmetric Standard Model (MSSM) framework, the dark matter (DM) gravitino (or the axino) with mass of around 7 keV decays into a massless neutralino (bino) and a photon with lifetime ˜ 1028 sec. The massless bino contributes to the effective number of neutrino species N eff and future data will test this prediction. In the context of NMSSM, we first consider scenarios where the bino is massless and the singlino mass is around 7 keV. We also consider quasi-degenerate bino-singlino scenarios where the mass scale of DM particles are O(GeV) or larger. In such a scenario we require the mass gap to generate the 3.5 keV line. We comment on the possibility of a 7 keV singlino decaying via R parity violating couplings while all other neutralinos are heavy.

Dutta, Bhaskar; Gogoladze, Ilia; Khalid, Rizwan; Shafi, Qaisar

2014-11-01

323

Probing the nature of IGR J16493-4348: Spectral and temporal analysis of the 1-100 keV emission  

E-print Network

IGR J16493-4348 was one of the first new sources to be detected by the INTEGRAL gamma-ray telescope in the 18-100 keV energy band. Based upon spatial coincidence the source was originally associated with the free radio pulsar PSR J1649-4349. Presented here are the results of 2.8 Ms of observations made by the INTEGRAL mission and a 5.6 ks observation with the Swift X-ray Telescope. Spectral analysis indicates that the source is best modeled by an absorbed power law with a high energy cut-off at E$_{cut}$~15 keV and a hydrogen absorbing column of NH=5.4$^{+1.3}_{-1}$ x 10$^{22}$ cm$^{-2}$. Analysis of the light curves indicates that the source is a weak, persistent gamma-ray emitter showing indications of variability in the 2-9 and 22-100 keV bands. The average source flux is ~1.1 x 10^{-10} erg cm$^{-2}$ s$^{-1}$ in the 1-100 keV energy band. No coherent timing signal is identified at any timescale in the INTEGRAL or Swift data. The refined source location and positional uncertainty of IGR J16493-4348 places PSR J1649-4349 outside of the 90% error circle. We conclude that IGR J16493-4348 is not associated with PSR J1649-4349. Combining the INTEGRAL observations with Swift/XRT data and information gathered by RXTE and Chandra we suggest that IGR J16493-4348 is an X-ray binary; and that the source characteristics favour a high mass X-ray binary although an LMXB nature cannot be ruled out.

A. B. Hill; A. J. Dean; R. Landi; V. A. McBride; A. De Rosa; A. J. Bird; A. Bazzano; V. Sguera

2007-12-13

324

Development of heavy mineral and heavy element database of soil sediments in Japan using synchrotron radiation X-ray powder diffraction and high-energy (116 keV) X-ray fluorescence analysis: 1. Case study of Kofu and Chiba region.  

PubMed

We have started the construction of a nationwide forensic soil sediment database for Japan based on the heavy mineral and trace heavy element compositions of stream sediments collected at 3024 points all over Japan obtained by high-resolution synchrotron X-ray powder diffraction (SR-XRD) and high-energy synchrotron X-ray fluorescence analysis (HE-SR-XRF). In this study, the performance of both techniques was demonstrated by analyzing soil sediments from two different geological regions, the Kofu and Chiba regions in Kanto province, to construct database that can be applied in the future to provenance analysis of soil evidence from a crime scene. The sediments from the quaternary volcanic lithology of the Chiba region were found to be dominated by heavy minerals of volcanic origin - orthopyroxene, clinopyroxene, and amphibole, and the REEs (rare earth elements) within the region showed similar geochemical behavior. On the other hand, four distinct heavy mineral groups were identified in the sediments of the Kofu region, where there is a great variety of underlying bedrock, and the geochemical behavior of the REEs in the sediments also varied accordingly to their geological origins. As such, our study shows that high-resolution SR-XRD data can provide information on the spatial distribution patterns of heavy minerals in stream sediments, playing an important role in determining their likely geographical origin. Meanwhile, the highly sensitive HE-SR-XRF data allow us to study the geochemical behavior of trace heavy elements, especially the REEs in the sediments, providing additional support to further constrain the likely geographical origin of the sediments determined by heavy minerals. PMID:22445767

Bong, Willy Shun Kai; Nakai, Izumi; Furuya, Shunsuke; Suzuki, Hiroko; Abe, Yoshinari; Osaka, Keiichi; Matsumoto, Takuya; Itou, Masayoshi; Imai, Noboru; Ninomiya, Toshio

2012-07-10

325

Detection of 1 - 100 keV x-rays from high intensity, 500 fs laser- produced plasmas using charge-coupled devices  

SciTech Connect

We describe a compact, vacuum compatible, large format, charge- coupled device (CCD) camera for scientific imaging and detection of 1- 100 keV x rays in experiments at LLNL JANUS-1ps laser. A standard, front-illuminated, multi-pin phase device with 250 k electron full well capacity, low dark current (10 pA/cm{sup 2} at 20 C) and low read noise (5 electron rms) is cooled to -35 C to give the camera excellent 15-bit dynamic range and signal-to-noise response. Intensity and x-ray energy linear response were determined for optical and x-ray (<65 keV) photons and are in excellent agreement. Departure from linearity was less than 0.7%. Inherent linearity and energy dispersive characteristics of CCD cameras are well suited for hard x-ray photon counting. X-rays absorbed within the depletion and field-free regions can be distinguished by studying the pulse height spectrum. Results are presented for the detection of 1-100 keV Bremsstrahlung continuum, K-shell and L-shell fluorescence spectra emitted from high intensity (10{sup 18}W cm{sup -2}), 500 fs laser- produced plasmas.

Dunn, J.; Young, B.K.F.; Conder, A.D.; Stewart, R.E.

1996-01-01

326

Cell survival measurements in an argon, aluminium and sulphur filtered neutron beam: a comparison with 24 keV neutrons and relevance to boron neutron capture therapy.  

PubMed

Boron neutron capture therapy (BNCT) has been advanced as a suitable alternative therapy for the treatment of glioma. BNCT involves the selective uptake of a tumour with a boron-bearing substance and subsequent irradiation with a beam of neutrons. Previous attempts with BNCT have utilized thermal neutrons, but this involves resection of the scalp prior to treatment and is only possible with superficial tumours. An alternative is to use a beam of intermediate-energy neutrons which will produce a peak in the thermal neutron fluence at depth in tissue and so enable deep-seated tumours to be treated. A neutron beam with a mean energy of approximately 9 keV, obtained by filtering neutrons from a reactor with aluminium, argon and sulphur, has been used to explore the radiobiological advantage over thermal and 24 keV neutrons for BNCT. Irradiation of V79 and HeLa cells at various positions in a polythene phantom suggest that the beam is less cytotoxic for a given neutron fluence than the 24 keV neutron beam previously considered as an alternative to thermal neutrons for BNCT. However, optimization of boron distribution via the development of new compounds still appears to be necessary for BNCT to become a safe alternative option for the treatment of glioma. PMID:8000825

Mill, A J; Morgan, G R; Newman, S M

1994-10-01

327

Measurement of the MACS of Ta181(n,?) at kT=30 keV as a test of a method for Maxwellian neutron spectra generation  

NASA Astrophysics Data System (ADS)

Measurement of the Maxwellian-Averaged Cross-Section (MACS) of the Ta(n,?)181 reaction at kT=30 keV by the activation technique using an innovative method for the generation of Maxwellian neutron spectra is presented. The method is based on the shaping of the proton beam to produce a desired neutron spectrum using the 7Li(p,n) reaction as a neutron source. The characterization of neutron spectra has been performed by combining measured proton distributions, an analytical description of the differential neutron yield in angle and energy of the 7Li(p,n) reaction, and with Monte Carlo simulations of the neutron transport. A measured value equal to 815±73 mbarn is reported for the MACS of the reaction Ta(n,?)181 at kT=30 keV. The MACS of the reaction Au(n,?)197 provided by KADoNiS has been used as a reference.

Praena, J.; Mastinu, P. F.; Pignatari, M.; Quesada, J. M.; García-López, J.; Lozano, M.; Dzysiuk, N.; Capote, R.; Martín-Hernández, G.

2013-11-01

328

Properties of the 5{sup -} state at 839 keV in {sup 176}Lu and the s-process branching at A=176  

SciTech Connect

The s-process branching at mass number A=176 depends on the coupling between the high-K ground state and a low-lying low-K isomer in {sup 176}Lu. This coupling is based on electromagnetic transitions via intermediate states at higher energies. The properties of the lowest experimentally confirmed intermediate state at 839 keV are reviewed, and the transition rate between low-K and high-K states under stellar conditions is calculated on the basis of new experimental data for the 839-keV state. Properties of further candidates for intermediate states are briefly analyzed. It is found that the coupling between the high-K ground state and the low-K isomer in {sup 176}Lu is at least one order of magnitude stronger than previously assumed, leading to crucial consequences for the interpretation of the {sup 176}Lu/{sup 176}Hf pair as an s-process thermometer.

Mohr, P. [Diakonie-Klinikum Schwaebisch Hall, D-74523 Schwaebisch Hall (Germany); Bisterzo, S.; Gallino, R. [Dipartimento di Fisica Generale, Universita di Torino, Via P. Giuria 1, I-10125 Torino (Italy); Kaeppeler, F. [Forschungszentrum Karlsruhe, Institut fuer Kernphysik, P. O. Box 3640, D-76021 Karlsruhe (Germany); Kneissl, U. [Institut fuer Strahlenphysik, Universitaet Stuttgart, Allmandring 3, D-70569 Stuttgart (Germany); Winckler, N. [GSI, Planckstrasse 1, D-64291 Darmstadt (Germany)

2009-04-15

329

Realistic sterile neutrino dark matter with keV mass does not contradict cosmological bounds.  

PubMed

Previous fits of sterile neutrino dark matter (DM) models to cosmological data ruled out masses smaller than approximately 8 keV, assuming a production mechanism that is not the best motivated from a particle physics point of view. Here we focus on a realistic extension of the standard model with three sterile neutrinos, consistent with neutrino oscillation data and baryogenesis, with the lightest sterile neutrino being the DM particle. We show that for each mass >or= 2 keV there exists at least one model accounting for 100% of DM and consistent with Lyman-alpha and other cosmological, astrophysical, and particle physics data. PMID:19519017

Boyarsky, Alexey; Lesgourgues, Julien; Ruchayskiy, Oleg; Viel, Matteo

2009-05-22

330

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

SciTech Connect

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

Boyarsky, Alexey [ETHZ, Zuerich, CH-8093 (Switzerland); Bogolyubov Institute for Theoretical Physics, Kiev 03680 (Ukraine); Lesgourgues, Julien [PH-TH, CERN, CH-1211 Geneve 23 (Switzerland); Ecole Polytechnique Federale de Lausanne, FSB/ITP/LPPC, BSP, CH-1015, Lausanne (Switzerland); LAPTH, Universite de Savoie, CNRS, B.P.110, F-74941 Annecy-le-Vieux Cedex (France); Ruchayskiy, Oleg [Ecole Polytechnique Federale de Lausanne, FSB/ITP/LPPC, BSP, CH-1015, Lausanne (Switzerland); Viel, Matteo [INAF-Osservatorio Astronomico di Trieste, Via G.B. Tiepolo 11, I-34131 Trieste (Italy); INFN-National Institute for Nuclear Physics, Via Valerio 2, I-34127 Trieste (Italy)

2009-05-22

331

A high-sensitivity search for a 17keV neutrino  

NASA Astrophysics Data System (ADS)

A negative result for the existence of a 17keV neutrino was obtained by a very high-statistical measurement of the 63Ni ?-spectrum and a response function using an iron-free magnetic spectrometer. The obtained mixing strength is |U| 2 = (1.8±3.3(stat.)±3.3(sys.))×10 -4, which strongly excludes the existence of a 17keV neutrino with an admixture of 1%. We set the upper limit to 0.095% on |U| 2 with a 95% confidence level.

Shirai, J.

1993-05-01

332

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

333

Analysis of photon emission from 50--350-keV proton impact on H{sub 2}O  

SciTech Connect

We have measured photon emission cross sections from neutral fragments produced by collisions of 50-350 keV protons with H{sub 2}O molecules. Balmer {alpha}-{delta} emissions from both the target and projectile were recorded. We also analyzed A {sup 2}{Sigma}{sup +}-X {sup 2}{Pi} (0,0) and (1,0) emission from the excited OH fragment produced during target dissociation. Trends in the cross sections revealed two key properties of the collision process: (1) The Bethe theory accurately describes target emission from both H and OH fragments and (2) the ratio of any two Balmer emission cross sections for both the target and projectile can be approximated by simple functions of the respective optical oscillator strengths. Finally, we provide the Bethe fit parameters necessary to calculate the target emission cross sections at all nonrelativistic impact energies.

Goldman, Benjamin D.; Timpone, Stephanie A.; Monce, Michael N.; Mitchell, Laurel; Griffin, Brian [Daghlian Accelerator Laboratory, Department of Physics, Astronomy, and Geophysics, Connecticut College, New London, Connecticut 06320 (United States)

2011-04-15

334

The search for absorption of 1 keV X-rays by the Small Magellanic Cloud  

NASA Technical Reports Server (NTRS)

The contribution of the extragalactic component of the diffuse background to the 1 keV energy band remains unknown. An effective way to ascertain this contribution is to measure the absorption of the extragalactic component by the neutral hydrogen in the Small Magellanic Cloud (SMC) with an instrument capable of eliminating point sources from the X-ray data that compensate for absorption. The image proportional counter data from the Einstein observatory can be used for this purpose. Additionally, any extended emission must also be eliminated. The resulting source free data can be compared to the neutral hydrogen and the amount of absorption can then be obtained when compared to the diffuse flux away from the SMC. However, due to other types of radiation contaminating the X-ray data, a true measure of the X-ray absorption was not obtained.

Marazas, Brad

1989-01-01

335

Effective atomic number of composite materials for Compton effect in the gamma ray region 280-1115 keV.  

PubMed

In this paper, we report the effective atomic number, Z(eff), of composite materials for Compton effect in the gamma ray region 280-1115 keV based on the theoretically obtained Klein-Nishina scattering cross sections in the angular range 50-100° as well as experimentally measured differential incoherent (Compton) scattering cross sections of some composite materials at three scattering angles of 60°, 80°, and 100°. The Z(eff) values so obtained were found to be both angle and energy independent in the region of interest so that it could be concluded that it is possible to represent such composite materials by a mean atomic number in this region as suggested in earlier reports recently. PMID:20702099

Kumar, S Prasanna; Umesh, T K

2010-12-01

336

Fragmentation of OCS3+ formed by 150 keV Ar+ ion impact on OCS  

NASA Astrophysics Data System (ADS)

The dissociation of OCS3+ formed in ion impact ionization of OCS has been studied using the technique of multi-ion time of flight mass spectroscopy employing 150 keV Ar+ ions as projectiles. The coincidence plot reveals several fragmentation channels for the decay of this transient molecular ion with different possible decay mechanisms.

Safvan, C. P.; Jana, M. R.

2012-11-01

337

keV Ag ion irradiation induced damage on multiwalled carbon nanotubes  

Microsoft Academic Search

The stability of carbon nanotubes (CNTs) under ion irradiation is an important parameter for the performance of CNT devices under extreme conditions of heat, radiation, etc. In order to investigate the stability and the evolution of nature of bonding, multiwalled carbon nanotubes were irradiated using 21 keV Ag- ions with fluences of 1 × 1013, 5 × 1013, 7 ×

S. Mathew; U. M. Bhatta; B. Joseph; B. N. Dev

2007-01-01

338

A Dynamical Framework for KeV Dirac Neutrino Warm Dark Matter  

E-print Network

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

Dean J. Robinson; Yuhsin Tsai

2014-08-06

339

Dynamical framework for KeV Dirac neutrino warm dark matter  

NASA Astrophysics Data System (ADS)

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

Robinson, Dean J.; Tsai, Yuhsin

2014-08-01

340

Diffuse x-ray background spectrum from 3 to 50 keV  

SciTech Connect

The spectrum of the extragalactic diffuse X-ray background has been measured with the GSFC Cosmic X-Ray Experiment on HEAO 1 for regions of the sky away from known point sources and more than 20 /sup 0/ from the galactic plane. A total exposure of 80 m/sup 2/-s-sr is available at present. Free-free emission from an optically thin plasma of 40 +- 5 keV provides an excellent description of the observed spectrum from 3 to 50 keV. This spectral shape is confirmed by measurements from five separate layers of three independent detectors. With an estimated absolute precision of approx.10%, the intensity of the emission at 10 keV is 3.2 keV keV/sup -1/ cm/sup -2/ s/sup -1/ sr/sup -1/, a value consistent with the average of previously reported spectra. No other spectral features, such as iron line emission, are evident. This spectrum is not typical of known extra-galactic objects. A uniform hot intergalactic medium of approximately 36% of the closure density of the universe would produce such a flux, although nonuniform models indicating less total matter are probably more realistic.

Marshall, F.E.; Boldt, E.A.; Holt, S.S.; Miller, R.B.; Mushotzky, R.F.; Rose, L.A.; Rothschild, R.E.; Serlemitsos, P.J.

1980-01-01

341

A Strong Excess in the 20-100 keV Emission of NGC 1365  

NASA Astrophysics Data System (ADS)

We present a new Suzaku observation of the obscured active galactic nucleus in NGC 1365, revealing an unexpected excess of X-rays above 20 keV of at least a factor ~2 with respect to the extrapolation of the best-fitting 3-10 keV model. Additional Swift-BAT and Integral-IBIS observations show that the 20-100 keV is concentrated within ~1.5 arcmin from the center of the galaxy, and is not significantly variable on timescales from days to years. A comparison of this component with the 3-10 keV emission, which is characterized by a rapidly variable absorption, suggests a complex structure of the circumnuclear medium, consisting of at least two distinct components with rather different physical properties, one of which covers >80% of the source with a column density N H ~ 3-4×1024 cm-2. An alternative explanation is the presence of a double active nucleus in the center of NGC 1365.

Risaliti, G.; Braito, V.; Laparola, V.; Bianchi, S.; Elvis, M.; Fabbiano, G.; Maiolino, R.; Matt, G.; Reeves, J.; Salvati, M.; Wang, J.

2009-11-01

342

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

PubMed

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. PMID:10442709

Britten, A J; Klie, R

1999-07-01

343

Total Cross Sections for Multiple Electron Stripping in Atomic Collisions at Energies to 100 kev  

Microsoft Academic Search

Total cross sections have been measured for electron capture and stripping of He+, Ne+, and A+ ions in single collisions of He+ on He, Ne, and A; Ne+ on Ne and A; and A+ on A. Where He+ ions are incident, the cross sections are given for electron capture, sigma10 for electron loss, sigma12 and for \\

P. R. Jones; F. P. Ziemba; H. A. Moses; E. Everhart

1959-01-01

344

TOTAL CROSS SECTIONS FOR MULTIPLE ELECTRON STRIPPING IN ATOMIC COLLISIONS AT ENERGIES TO 100 kev  

Microsoft Academic Search

Total cross sections were measured for electron capture and stripping of ; He\\/sup +\\/, Ne\\/sup +\\/, and Ar\\/sup +\\/ ions in single collisions of He\\/sup +\\/ on He, ; Ne, and Ar, Ne\\/sup +\\/ on Ne and Ar and Ar\\/sup +\\/ on Ar. Where He\\/sup +\\/ ions are ; incident, the cross sections are given for electron capture, sigma ââ;

P. R. Jones; F. P. Ziemba; H. A. Moses; E. Everhart

1959-01-01

345

Modeling the Chandra High Energy Transmission Gratings below 2 keV  

E-print Network

-mail: kaf©space.mit.edu X-Ray and Gamma-Ray Instrumentation for Astronomy XI, Kathryn A. Flanagan, Oswald H and suggesting where the model might be improved. Keywords: X-ray, X-ray astronomy, X-ray spectroscopy, Germany dCenter for X-Ray Optics Lawrence Berkeley National Laboratory, Berkeley, CA 94720 ABSTRACT

346

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

PubMed

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

Yücel, H; Dikmen, H

2009-04-30

347

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

348

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

349

Incomplete guiding of 300-900 keV O6+ ions through a glass macrocapillary due to saturated charging-up  

NASA Astrophysics Data System (ADS)

The transmissions of 300, 600 and 900 keV O6+ ions through a single borosilicate glass macrocapillary with a diameter of 0.6 mm and a length of 31 mm were studied. The ions went out neither along the macrocapillary axis nor along the incident direction, but still kept their initial charge state and energies. The higher the energy, the smaller the deflection angle. With the present conditions, the incident energies exceed the higher energy limit of the self-organizing charge-up mechanism. This incomplete guiding phenomenon is considered to be a consequence of the saturated charge-up at the macrocapillary inner wall, which cannot compensate the transverse momentum of the ions. In the present work, there is a saturated potential difference almost independent of the incident ion energy and current. It implies the existence of an intrinsic limit of the guiding ability of a capillary, depending on its shape, material, boundary conditions and temperature.

Wu, Yehong; Yu, Deyang; Xue, Yingli; Chen, Jing; Liu, Junliang; Zhang, Mingwu; Wang, Wei; Lu, Rongchun; Ruan, Fangfang; Du, Fan; Shao, Caojie; Li, Jinyu; Kang, Long; Cai, Xiaohong

2014-09-01

350

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

351

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

352

Search for 14.4 keV solar axions from M1 transition of Fe-57 with CUORE crystals  

E-print Network

We report the results of a search for axions from the 14.4 keV M1 transition from Fe-57 in the core of the sun using the axio-electric e?ect in TeO2 bolometers. The detectors are 5x5x5 cm3 crystals operated at about 10 mK in a facility used to test bolometers for the CUORE experiment at the Laboratori Nazionali del Gran Sasso in Italy. An analysis of 43.65 kg d of data was made using a newly developed low energy trigger which was optimized to reduce the detectors energy threshold. An upper limit of 0.63 c kg-1 d-1 was established at 95% C.L.. From this value, a lower bound at 95% C.L. was placed on the Peccei-Quinn energy scale of fa >= 0.76 10**6 GeV for a value of S=0.55 for the flavor-singlet axial vector matrix element. Bounds are given for the interval 0.15 < S < 0.55.

,

2012-01-01

353

Ionization and Fragmentation of Anthracene upon Interaction with keV Protons and ? Particles  

NASA Astrophysics Data System (ADS)

The interaction of keV ions with polyaromatic hydrocarbons is dominated by charge exchange and electronic stopping. We have studied the response of the polyaromatic hydrocarbon anthracene (C14H10) upon keV H+ and He2+ impact using high-resolution time-of-flight mass spectrometry. Extensive fragmentation into small C n H q+ m as well as formation of up to triply charged parent ions is observed. Ab initio electron densities are used to calculate the molecular excitation due to electronic stopping. Fragment yields increase with the increase of electronic stopping as a function of projectile velocity. For equal electronic stopping, He2+ is found to induce more fragmentation than H+. The difference in fragmentation is concluded to be due to two electron processes, which are relevant channels only for He2+.

Postma, J.; Bari, S.; Hoekstra, R.; Tielens, A. G. G. M.; Schlathölter, T.

2010-01-01

354

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

355

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

PubMed

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. PMID:24593645

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

356

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

357

keV Ag ion irradiation induced damage on multiwalled carbon nanotubes  

Microsoft Academic Search

The stability of carbon nanotubes (CNTs) under ion irradiation is an important parameter for the performance of CNT devices under extreme conditions of heat, radiation, etc. In order to investigate the stability and the evolution of nature of bonding, multiwalled carbon nanotubes were irradiated using 21keV Ag? ions with fluences of 1×1013, 5×1013, 7×1013 and 1×1014ions\\/cm2. The samples were characterized

S. Mathew; U. M. Bhatta; B. Joseph; B. N. Dev

2007-01-01

358

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

359

The diffuse X-ray background spectrum from 3 to 50 keV  

NASA Technical Reports Server (NTRS)

The spectrum of the extragalactic diffuse X-ray background has been measured with the GSFC Cosmic X-ray Experiment on HEAO 1 for regions of the sky away from known point sources and more than 20 deg from the galactic plane. A total exposure of 80 sq m-s-sr is available at present. Free-free emission from an optically thin plasma of 40 plus or minus 5 keV provides an excellent description of the observed spectrum from 3 to 50 keV. This spectral shape is confirmed by measurements from five separate layers of three independent detectors. With an estimated absolute precision of about 10%, the intensity of the emission at 10keV is 3.2 keV/keV/sq cm/s/sr, a value consistent with the average of previously reported spectra. A uniform hot intergalactic medium of approximately 36% of the closure density of the universe would produce such a flux, although nonuniform models indicating less total matter are probably more realistic.

Marshall, F. E.; Boldt, E. A.; Holt, S. S.; Miller, R. B.; Mushotzky, R. F.; Rose, L. A.; Rothschild, R. E.; Serlemitsos, P. J.

1980-01-01

360

L Sub-Shell Cross Sections measured for 75-300 keV protons on Selected Rare-Earth Elements.  

NASA Astrophysics Data System (ADS)

L sub-shell x-ray production cross sections were measured for 75-300 keV proton impact on thick elemental targets ranging from Gd through Yb. X-ray yields were measured using a high-resolution Si(Li) detector with an ultra-thin window. The results were compared with ECPSSR theory with and without the united-atom approximation for the binding-energy effect and the relativistic correction. Multiple ionization effects are also taken into account.

Cipolla, Sam J.

2007-06-01

361

Position detection of 17-25 keV x-rays in krypton and xenon with a resolution of 18-50 m (FWHM)  

SciTech Connect

Measurements have been made of x-ray position resolution in a proportional chamber with both Kr/10% CO2 and Xe/10% CO2, for the x-ray energy region 17 to 25 keV. Position resolutions in the range of 18 to 50 m (FWHM) are obtained in krypton, and in the range 50 to 100 m (FWHM) for xenon. These results are interpreted in terms of the physical limitation to resolution due to the range of photoelectrons and Auger electrons emitted from the x-ray absorbing atom.

Fischer, J.; Radeka, V.; Smith, G.C.

1985-10-01

362

Measurement of the 20 and 90 keV Resonances in the {sup 18}O(p,{alpha}){sup 15}N Reaction via the Trojan Horse Method  

SciTech Connect

The {sup 18}O(p,{alpha}){sup 15}N 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 {sup 18}O(p,{alpha}){sup 15}N 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.

La Cognata, M.; Spitaleri, C.; Cherubini, S.; Crucilla, V.; Gulino, M.; Lamia, L.; Pizzone, R. G.; Puglia, S. M. R.; Rapisarda, G. G.; Romano, S.; Sergi, M. L.; Tumino, A. [INFN Laboratori Nazionali del Sud and DMFCI Universita di Catania, 95123 Catania (Italy); Mukhamedzhanov, A. M.; Tribble, R. E.; Banu, A.; Goldberg, V. Z.; Tabacaru, G.; Trache, L. [Cyclotron Institute, Texas A and M University, College Station, 77843 Texas (United States); Irgaziev, B. [GIK Institute of Engineering Sciences and Technology, Topi (23640), NWFP Pakistan (Pakistan); Coc, A. [CSNSM, CNRS/IN2P3 Universite Paris Sud, F-91405 Orsay (France)] (and others)

2008-10-10

363

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

2008-02-11

364

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

365

Dosimetry of ultrasoft x-rays (1.5 keV Al(Kalpha)) using radiochromatic films and colour scanners.  

PubMed

This work explores the possibility of measuring the absorbed dose of ultrasoft x-rays (USX, 1.5 keV Al(Kalpha)) with GAFCHROMIC HD-810 radiochromatic dosimetry films (HD-810 films) and colour scanners. HD-810 films were exposed to USX, soft x-rays (14.8 keV) and gamma-rays (60Co) for various times. The response of HD-810 films to absorbed doses of gamma-rays in water was calibrated with Fricke dosimetry and used for the calibration of USX. The optical density of the HD-810 films was quantified with an HP ScanJet 6100C scanner and Corel Picture Paint 7. The choice of the reading channel and colour adjustment settings were optimized to either improve sensitivity or expand the measurable dose range. The response of the HD-810 films to the absorbed dose in water decreased by 50% when the effective photon energy decreased from 1.25 MeV to 14.8 keV. The ratio of the mass energy absorption coefficient of the active layer of HD-810 films to that of water was found to play a major role in this decrease. The mean absorbed doses of the active layer of the HD-810 films exposed to USX were derived. The calculation of the initial photon fluence rate and the mean absorbed doses of USX to biological samples such as plasmid DNA is discussed. This study suggests that radiochromatic dosimetry films are promising secondary dosimeters for measuring the absorbed dose of USX. PMID:14727755

Cai, Zhongli; Pan, Xiaoning; Hunting, Darel; Cloutier, Pierre; Lemay, Rosalie; Sanche, Léon

2003-12-21

366

X-ray Full Field Microscopy at 30 keV  

NASA Astrophysics Data System (ADS)

In our X-ray full field microscopy experiments, we demonstrated a resolution better than 260 nm over the entire field of view of 80 ?m × 80 ?m at 30 keV. Our experimental setup at PETRA III, P05, had a length of about 5 m consisting of an illumination optics, an imaging lens and a detector. For imaging, we used a compound refractive lens (CLR) consisting of mr-L negative photo resist, which was fabricated by deep X-ray lithography. As illumination optics, we choose a refractive rolled X-ray prism lens, which was adapted to the numerical aperture of the imaging lens.

Marschall, F.; Last, A.; Simon, M.; Kluge, M.; Nazmov, V.; Vogt, H.; Ogurreck, M.; Greving, I.; Mohr, J.

2014-04-01

367

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

368

Implications of the broad Al-26 1809 keV line observed by GRIS  

NASA Technical Reports Server (NTRS)

The astrophysical implications of the large width of the 1809 keV gamma ray line from the decay of radioactive Al-26, recently observed with the gamma ray imaging spectrometer (GRIS), are discussed. While there may be no apparent single mechanism that can explain the observed broadening, high speed dust grains, extremely hot superbubbles and a large, low density gaseous halo were identified in the Galactic center region as the possible origins. The implications of these observations on the hot gas content in the interstellar medium are discussed.

Chen, Wan; Diehl, Roland; Gehrels, Neil; Hartmann, Dieter; Leising, Mark; Naya, Juan E.; Prantzos, Nikos; Tueller, Jack; vanBallmoos, Peter

1997-01-01

369

Scattering Of KeV Neutrons And The Problem Of Quantum Entanglement  

NASA Astrophysics Data System (ADS)

A scattering study of ˜ 30 keV neutrons from H2O, D2O and H2O/D2O mixtures was carried out to search for a ˜ 40% anomalous drop in the n-p scattering cross section. Such an anomaly was reported using 10-200eV neutrons scattered from many H-containing compounds. The anomaly was attributed to n-scattering from quantum entangled proton pairs in the sample. In the present measurement no anomaly was observed.

Moreh, R.; Block, R. C.; Danon, Y.; Neuman, M.

2006-03-01

370

On the vectorial photoelectric effect at 2.69 keV  

NASA Technical Reports Server (NTRS)

Recent experiments conducted to study the vectorial photoelectric effect with CsI, Al2O3 and Si photocathodes at 2.69 keV indicate null results. Detailed analysis shows that previously measured modulation can be well explained by geometrical misalignment and a combination of the asymmetric shape of the incident X-ray beam and a small detection area of the photoelectron detector. After the elimination of the sources of spurious modulation, we observed a modulation factor of less than 3 percent for a grazing incidence angle as small as 5 deg. There is no observable difference in the pulse height distribution between s and p states.

Shaw, P. S.; Hanany, S.; Liu, Y.; Church, E. D.; Fleischman, J.; Kaaret, P.; Novick, R.; Santangelo, A.

1991-01-01

371

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

372

Mutual ionization in 200-keV H-+He collisions  

NASA Astrophysics Data System (ADS)

We studied mutual ionization in 200-keV H-+He collisions in a kinematically complete experiment by measuring the fully momentum-analyzed recoil ions and both active electrons in coincidence. Comparison of the data to our calculations, based on various theoretical models, show that mutual ionization proceeds predominantly through the interaction between both electrons. The post-collision interaction between the outgoing ejected electrons as well as higher order processes involving the interaction between the core of both collision partners are also important.

Ferger, T.; Fischer, D.; Schulz, M.; Moshammer, R.; Voitkiv, A. B.; Najjari, B.; Ullrich, J.

2005-12-01

373

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

374

3-200 keV spectral states and variability of the INTEGRAL Black Hole binary IGR J17464-3213  

E-print Network

On March 2003, IBIS, the gamma-ray imager on board the INTEGRAL satellite, detected an outburst from a new source, IGR J17464-3213, that turned out to be a HEAO-1 transient, H1743-322. In this paper we report on the high energy behaviour of this BHC studied with the three main instruments onboard INTEGRAL. The data, collected with unprecedented sensitivity in the hard X-Ray range, show a quite hard Comptonised emission from 3 keV up to 150 keV during the rising part of the source outburst, with no thermal emission detectable. A few days later, a prominent soft disk multicolour component appears, with the hard tail luminosity almost unchanged: 10-9 erg*cm-2*s-1. Two months later, during a second monitoring campaign near the end of the outburst, the observed disk component was unchanged. Conversely, the Comptonised emission from the central-hot part of the disk reduced by a factor of 10. We present here its long term behaviour in different energy ranges and the combined JEM-X, SPI and IBIS wide band spectral ev...

Capitanio, F; Bazzano, A; Kretschmar, P; Zdziarski, A A; Joinet, A; Barlow, E J; Bird, A J; Dean, A J; Jourdain, E; De Cesare, G; Santo, M D; Natalucci, L; Bel, M C; Goldwurm, A

2004-01-01

375

3-200 keV spectral states and variability of the INTEGRAL Black Hole binary IGR J17464-3213  

E-print Network

On March 2003, IBIS, the gamma-ray imager on board the INTEGRAL satellite, detected an outburst from a new source, IGR J17464-3213, that turned out to be a HEAO-1 transient, H1743-322. In this paper we report on the high energy behaviour of this BHC studied with the three main instruments onboard INTEGRAL. The data, collected with unprecedented sensitivity in the hard X-Ray range, show a quite hard Comptonised emission from 3 keV up to 150 keV during the rising part of the source outburst, with no thermal emission detectable. A few days later, a prominent soft disk multicolour component appears, with the hard tail luminosity almost unchanged: 10-9 erg*cm-2*s-1. Two months later, during a second monitoring campaign near the end of the outburst, the observed disk component was unchanged. Conversely, the Comptonised emission from the central-hot part of the disk reduced by a factor of 10. We present here its long term behaviour in different energy ranges and the combined JEM-X, SPI and IBIS wide band spectral evolution of this source.

F. Capitanio; P. Ubertini; A. Bazzano; P. Kretschmar; A. A. Zdziarski; A. Joinet; E. J. Barlow; A. J. Bird; A. J. Dean; E. Jourdain; G. De Cesare; M. Del Santo; L. Natalucci; M. Cadolle Bel; A. Goldwurm

2004-11-30

376

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

377

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

378

Effect on number albedo values for 662 keV photons from radiation shielding materials stratified with lead  

NASA Astrophysics Data System (ADS)

Albedo measurements for backscattered gamma rays from semi-infinite scatterers have suitable applications in the design of gamma ray shields particularly in nuclear reactor and accelerator shields and in many other nuclear installations. The insertion of lead slabs into stratified combination with other shielding materials has been found to increase the shielding property appreciably. The stratified slabs of alternating heterogeneous layers have been found in this investigation to have a virtual homogeneous property with a definite effective atomic number. The purpose of the present investigation is to find out the extent to which the shielding property increases in binary configuration with lead and to investigate into the dependence of the saturation thickness of the shielding media on the effective atomic number of each configuration. The indigeneously designed Uniform Sensitivity Photon Counter used in this investigation has an edge over all previous methods of experimental measurements that it is independent of response correction. The number albedo values as well as angular distribution of backscattered photons for iron, aluminium and concrete stratified with lead slabs at 662 keV energy have been reported here.

Bhattacharjee, A.; Sinha, A. K.

1988-07-01

379

Construction of 144, 565 keV and 5.0 MeV monoenergetic neutron calibration fields at JAERI.  

PubMed

Monoenergetic neutron calibration fields of 144, 565 keV and 5.0 MeV have been developed at the Facility of Radiation Standards of JAERI using a 4 MV Pelletron accelerator. The 7Li(p,n)7Be and 2H(d,n)3He reactions are employed for neutron production. The neutron energy was measured by the time-of-flight method with a liquid scintillation detector and calculated with the MCNP-ANT code. A long counter is employed as a neutron monitor because of the flat response. The monitor is set up where the influence of inscattered neutrons from devices and their supporting materials at a calibration point is as small as possible. The calibration coefficients from the monitor counts to the neutron fluence at a calibration point were obtained from the reference fluence measured with the transfer instrument of the primary standard laboratory (AIST), a 24.13 cm phi Bonner sphere counter. The traceability of the fields to AIST was established through the calibration. PMID:15353627

Tanimura, Y; Yoshizawa, M; Saegusa, J; Fujii, K; Shimizu, S; Yoshida, M; Shibata, Y; Uritani, A; Kudo, K

2004-01-01

380

Bent-crystal Laue spectrograph for measuring x-ray spectra (15keV)  

NASA Astrophysics Data System (ADS)

A bent-crystal Laue {or Cauchois [J. Phys. Radium 3, 320 (1932)] geometry} spectrograph is a good compromise between sensitivity and spectral resolution for measuring x-ray spectra (15keV) from large area x-ray sources because source-size spectral broadening is mitigated. We have designed, built, and tested such a spectrograph for measuring the spectra from electron-beam x-ray sources with diameters as large as 30cm. The same spectrograph geometry has also been used to diagnose (with higher spectral resolution) smaller sources, such as x-ray tubes for mammography and laser-driven inertial fusion targets. We review our spectrograph design and describe the performance of different components. We have compared the reflectivity and spectral resolution of LiF, and Ge diffracting crystals. We have also measured the differences in sensitivity and spectral resolution using different x-ray to light converters (plastic scintillator, CsI, and Gd2O2S) fiber optically coupled to an intensified charge-coupled device camera. We have also coupled scintillating fibers to photomultiplier tubes to obtain temporal records for discrete energy channels.

Failor, B. H.; Wong, S.; Riordan, J. C.; Hudson, L. T.; O'Brien, C. M.; Seltzer, S. M.; Seiler, S.; Pressley, L.; Lojewski, D. Y.

2006-10-01

381

Set-up of an XAFS beamline for measurements between 2.4-8 keV at DORIS III  

SciTech Connect

In this paper results from the commissioning phase and from first user experiments of a new EXAFS beamline at the DORIS III storage ring are presented. The bending magnet EXAFS beamline A1 underwent a complete rebuild and now covers the energy range 2.4-8 keV. A Ni-coated toroidal mirror, placed in a 2:1 focusing position and a plane mirror with one Ni coated stripe and one uncoated (SiO{sub 2}) stripe are used for effective higher harmonics suppression and focusing. The UHV-compatible fixed-exit Double Crystal Monochromator (DCM) is equipped with two Si(111) crystal pairs. The second crystal of one of the two crystal pairs is tilted by 90 deg. around the surface normal to shift the position of glitches. It allows Bragg angles between 5 deg. and 55.5 deg. and continuous scans in quick-EXAFS mode. Test measurements during the commissioning phase proved the excellent performance of the monochromator and a high quality of the XAFS spectra over the entire working range.

Welter, Edmund [Deutsches Elektronen-Synchrotron A Research Centre of the Helmholtz Association, Notkestrasse 85, D-22607 Hamburg (Germany)

2010-06-23

382

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

383

60 keV Ar{sup +}-ion induced modification of microstructural, compositional, and vibrational properties of InSb  

SciTech Connect

Room temperature irradiation of InSb(111) by 60?keV Ar{sup +}-ions at normal (0°) and oblique (60°) angles of incidence led to the formation of nanoporous structure in the high fluence regime of 1?×?10{sup 17} to 3?×?10{sup 18} ions cm{sup ?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 In{sub 2}O{sub 3} and Sb{sub 2}O{sub 3} 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.; Som, T., E-mail: tsom@iopb.res.in [SUNAG Laboratory, Institute of Physics, Bhubaneswar, Odisha 751005 (India); Satpati, B. [Surface Physics and Materials Science Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064 (India); Sahoo, P. K. [School of Physical Sciences, National Institute of Science Education and Research, Bhubaneswar 751005, Odisha (India); Kanjilal, A. [Department of Physics, Shiv Nadar University, Uttar Pradesh 203207 (India); Dhara, S. [Surface and Nanoscience Division, Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India); Kanjilal, D. [Inter-University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067 (India)

2014-10-14

384

Influence of a keV sterile neutrino on neutrinoless double beta decay: How things changed in recent years  

NASA Astrophysics Data System (ADS)

Earlier studies of the influence of dark matter keV sterile neutrinos on neutrinoless double beta decay concluded that there is no significant modification of the decay rate. These studies have focused only on a mass of the keV sterile neutrino above 2 and 4 keV, respectively, as motivated by certain production mechanisms. On the other hand, alternative production mechanisms have been proposed, which relax the lower limit for the mass, and new experimental data are available, too. For this reason, an updated study is timely and worthwhile. We focus on the most recent data, i.e., the newest Chandra and XMM-Newton observational bounds on the x-ray line originating from radiative keV sterile neutrino decay, as well as the new measurement of the previously unknown leptonic mixing angle ?13. While the previous works might have been a little short-sighted, the new observational bounds do indeed render any influences of keV sterile neutrinos on neutrinoless double beta decay small. This conclusion even holds in case not all the dark matter is made up of keV sterile neutrinos.

Merle, Alexander; Niro, Viviana

2013-12-01

385

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

386

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

387

Strength of the ER=127 keV, Al26(p,?)Si27 resonance  

NASA Astrophysics Data System (ADS)

We examine the impact of the strength of the ER=127 keV, Al26(p,?)Si27 resonance on Al26 production in classical nova explosions and asymptotic giant branch (AGB) stars. Thermonuclear Al26(p ,?)Si27 reaction rates are determined using different assumed strengths for this resonance and representative stellar model calculations of these astrophysical environments are performed using these different rates. Predicted Al26 yields in our models are not sensitive to differences in rates determined using zero and a commonly stated upper limit corresponding to ??UL=0.0042 ?eV for this resonance strength. Yields of Al26 decrease by 6% and, more significantly, up to 30%, when a strength of 24×??UL=0.1 ?eV is assumed in the adopted nova and AGB star models, respectively. Given that the value of ??UL was deduced from a single, background-dominated Al26(He3,d )Si27 experiment where only upper limits on differential cross sections were determined, we encourage new experiments to confirm the strength of the 127-keV resonance.

Parikh, A.; José, J.; Karakas, A.; Ruiz, C.; Wimmer, K.

2014-09-01

388

keV Warm Dark Matter via the Supersymmetric Higgs Portal  

E-print Network

Warm dark matter (WDM) may resolve the possible conflict between observed galaxy halos and the halos produced in cold dark matter (CDM) simulations. Here we present an extension of MSSM to include WDM by adding a gauge singlet fermion, \\bar{\\chi}, with a portal-like coupling to the MSSM Higgs doublets. This model has the property that the dark matter is {\\it necessarily warm}. In the case where M_{\\bar{\\chi}} is mainly due to electroweak symmetry breaking, the \\bar{\\chi} mass is completely determined by its relic density and the reheating temperature, T_R. For 10^2 GeV < T_{R} < 10^{5} GeV$, the range allowed by \\bar{chi} production via thermal Higgs annihilation, the \\bar{\\chi} mass is in the range 0.3-4 keV, precisely the range required for WDM. The primordial phase-space density, Q, can directly account for that observed in dwarf spheroidal galaxies, Q \\approx 5 x 10^{6}(eV/cm^3)/(km/s)^3,, when the reheating temperature is in the range T_R \\approx 10-100 TeV, in which case M_{\\bar{\\chi}} \\approx 0.45 keV. The free-streaming length is in the range 0.3-4 Mpc, which can be small enough to alleviate the problems of overproduction of galaxy substructure and low angular momentum of CDM simulations.

John McDonald; Narendra Sahu

2009-05-14

389

Nuclear microanalysis by means of 350 keV Van de Graaf accelerator  

NASA Astrophysics Data System (ADS)

An inexpensive and quantitative method to depth profile hydrogen and helium isotopes in low- Z materials ( Z ? 25) by ERD E × B and, simultaneously, elements heavier than the substrate by RBS, has been developed. It uses a 350 keV He + beam, low-noise ion-implanted detectors and a filter built out of crossed magnetic and electric fields. Typically, with this setup, the depth resolution (which depends significantly on the materials) is ? 4 nm at the surface degrading to ? 15 nm at a depth of 100 nm, while the depth probed is ? 100 nm for H and He and ? 500 nm for heavier elements. The sensitivity is ? 1 at.% for H and He, ? 0.1 at.% for other light elements (e.g.: C, N, O, etc.) and 1 ppm for heavier elements such as gold. It is also possible to use a 350 keV 1H + beam to simultaneously depth profile heavier elements by RBS and identify them by PIXE. These combined techniques are especially useful to detect elements with neighbouring Z, such as stainless steel components.

Ross, G. G.; Leblanc, L.; Terreault, B.; Pageau, J. F.; Gollier, P. A.

1992-03-01

390

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

391

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, Calvin E [Los Alamos National Laboratory; Goda, Joetta M [Los Alamos National Laboratory; Favalli, Andrea [Los Alamos National Laboratory; Lombardi, Marcie [Los Alamos National Laboratory; Paffett, Mark T [Los Alamos National Laboratory; Hill, Thomas R [Los Alamos National Laboratory; MacArthur, Duncan W [Los Alamos National Laboratory; Smith, Morag K [Los Alamos National Laboratory

2010-04-13

392

Cross calibration of new x-ray films against direct exposure film from 1 to 8 keV using the X-pinch x-ray source  

NASA Astrophysics Data System (ADS)

A cross calibration of readily available x-ray sensitive films has been carried out against the calibrated direct exposure film (DEF) which is no longer being manufactured by Kodak. Four-wire X pinches made from various metal wires were used as x-ray sources for this purpose. Tests were carried out for the Kodak films Biomax MS, Biomax XAR, M100, Technical Pan, and T-Max over the energy range of 1-8keV (12.4-1.5Å wavelength). The same hand-development procedures as described by Henke et al. [J. Opt. Soc. Am. B 3, 1540 (1986)] were followed for all films in every test. Sensitivity curves as a function of wavelength for these films relative DEF are presented. These relative calibrations show that Biomax MS is likely to be the best replacement film for DEF for most purposes over the energy range tested here.

Chandler, K. M.; Pikuz, S. A.; Shelkovenko, T. A.; Mitchell, M. D.; Hammer, D. A.; Knauer, J. P.

2005-11-01

393

Fragmentation of doubly charged HDO, H2O, and D2O molecules induced by proton and monocharged fluorine beam impact at 3 keV  

NASA Astrophysics Data System (ADS)

Doubly charged ions HDO2+, H2O2+, and D2O2+ were prepared selectively to triplet or singlet excited states in collisions with F+ or H+ projectiles at 3 keV. Excitation energies of dications following two-body or three-body dissociation channels were measured and compared with recent calculations using ab initio multi-reference configuration interaction method [Gervais et al., J. Chem. Phys. 131, 024302 (2009)]. For HDO2+, preferential cleavage of O-H rather than O-D bond has been observed and the ratio between the populations of the fragmentation channels OD+_H+ and OH+_D+ were measured. The kinetic energy release has been measured and compared with previous experiments.

Martin, S.; Chen, L.; Brédy, R.; Bernard, J.; Cassimi, A.

2015-03-01

394

Fragmentation of doubly charged HDO, H2O, and D2O molecules induced by proton and monocharged fluorine beam impact at 3 keV.  

PubMed

Doubly charged ions HDO(2+), H2O(2+), and D2O(2+) were prepared selectively to triplet or singlet excited states in collisions with F(+) or H(+) projectiles at 3 keV. Excitation energies of dications following two-body or three-body dissociation channels were measured and compared with recent calculations using ab initio multi-reference configuration interaction method [Gervais et al., J. Chem. Phys. 131, 024302 (2009)]. For HDO(2+), preferential cleavage of O-H rather than O-D bond has been observed and the ratio between the populations of the fragmentation channels OD(+)_H(+) and OH(+)_D(+) were measured. The kinetic energy release has been measured and compared with previous experiments. PMID:25747080

Martin, S; Chen, L; Brédy, R; Bernard, J; Cassimi, A

2015-03-01

395

Close-packed arrays of transition-edge x-ray microcalorimeters with high spectral resolution at 5.9 keV  

SciTech Connect

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. [NASA/Goddard Space Flight Center, Greenbelt, Maryland 20771 (United States); Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

2008-01-07

396

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

397

Effect of sample thickness on the measured mass attenuation coefficients of some compounds and elements for 59.54, 661.6 and 1332.5 keV \\/gamma-rays  

Microsoft Academic Search

Measurements have been made to determine \\/gamma-rays attenuation coefficients very accurately by using an extremely narrow-collimated-beam transmission method. The effect of the sample thickness on the measured values of the mass attenuation coefficients (mu\\/rho)cm2\\/g of perspex, bakelite, paraffin, Al, Cu, Pb and Hg have been investigated at three different \\/gamma-ray energies (59.54, 661.6 and 1332.5 keV). It is seen that

M. A. Abdel-Rahman; E. A. Badawi; Y. L. Abdel-Hady; N. Kamel

2000-01-01

398

Charge transfer in collisions of B{sup 2+}({sup 2}{ital S},{sup 2}{ital P}) and B{sup 3+}({sup 1}{ital S}) ions with He atoms below 200 keV  

SciTech Connect

Charge transfer in B{sup 2+}({sup 2}{ital S},{sup 2}{ital P})+He and in B{sup 3+}({sup 1}{ital S})+He collisions is studied theoretically by using a semiclassical molecular representation with 8 and 12 molecular channels for B{sup 2+} and B{sup 3+} on He systems, respectively, at collision energies between 200 eV and 200 keV for the former and between 600 eV and 50 keV for the latter. The {ital ab} {ital initio} potential curves and nonadiabatic coupling matrix elements are obtained from the multireference single- and double-excitation configuration-interaction (MRD-CI) calculations for the B{sup 2+}-He system and a pseudopotential-modified configuration-interaction method for the B{sup 3+}-He system. The present cross sections for charge transfer by the ground state B{sup 2+} ions are found to have a broad maximum with a magnitude as large as 2{times}10{sup {minus}15} cm{sup 2} at 100 keV and those by an excited B{sup 2+}({sup 2}{ital P}) state are found to be larger by a factor of 6 than those by the ground state in the same energy regime. B{sup 2+}-excitation cross sections are smaller than those for charge transfer below 1 keV, while they increasingly dominate above this energy. The present total charge-transfer cross section for B{sup 3+} in collisions with He is similar to that obtained in earlier work by Gargaud {ital et} {ital al}. [J. Phys. B {bold 27}, 3985 (1994)] both in magnitude and energy dependence, but is found to show slightly different B{sup 2+}(2{ital s}) and B{sup 2+}(2{ital p}) production ratio. {copyright} {ital 1996 The American Physical Society.}

Kimura, M. [School of Allied Health Sciences, Yamaguchi University, 755 Ube, Yamaguchi (Japan)] [School of Allied Health Sciences, Yamaguchi University, 755 Ube, Yamaguchi (Japan); [The Institute of Physical and Chemical Research (RIKEN), Wako, Saitama 351-01 (Japan); Suzuki, S.; Shimakura, N. [Department of Chemistry, Niigata University, Niigata (Japan)] [Department of Chemistry, Niigata University, Niigata (Japan); Gu, J.P.; Hirsch, G.; Buenker, R.J. [Theoretische Chemie, Bergische Universitaet-Gesamthochschule Wuppertal, D-42097 Wuppertal (Germany)] [Theoretische Chemie, Bergische Universitaet-Gesamthochschule Wuppertal, D-42097 Wuppertal (Germany); Shimamura, I. [The Institute of Physical and Chemical Research (RIKEN), Wako, Saitama 351-01 (Japan)] [The Institute of Physical and Chemical Research (RIKEN), Wako, Saitama 351-01 (Japan)

1996-10-01

399

Measurement of the 13C(?,n)16O reaction with the Trojan horse method: Focus on the sub threshold resonance at -3 keV  

NASA Astrophysics Data System (ADS)

The 13C(?,n)16O 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 17O. 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 13C(6Li,n16O)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.; 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.

2014-05-01

400

An accuracy assessment of photo-ionization cross-section datasets for 1-2 keV x-rays in light elements using PIXE  

NASA Astrophysics Data System (ADS)

Proton-induced x-ray emission (PIXE) was used to assess the accuracy of the National Institute of Standards and Technology XCOM and FFAST photo-ionization cross-section databases in the low energy region (1-2 keV) for light elements. Characteristic x-ray yields generated in thick samples of Mg, Al and Si in elemental and oxide form, were compared to fundamental parameters computations of the expected x-ray yields; the database for this computation included XCOM attenuation coefficients. The resultant PIXE instrumental efficiency constant was found to differ by 4-6% between each element and its oxide. This discrepancy was traced to use of the XCOM Hartree-Slater photo-electric cross-sections. Substitution of the FFAST Hartree-Slater cross-sections reduced the effect. This suggests that for 1-2 keV x-rays in light element absorbers, the FFAST predictions of the photo-electric cross-sections are more accurate than the XCOM values.

Heirwegh, C. M.; Pradler, I.; Campbell, J. L.

2013-09-01

401

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

402

Fabrication and evaluation of transmissive multilayer optics for 8 keV x rays. [Zone plates  

SciTech Connect

We have investigated an alternative technique for fabricating zone plates that operate in the 5 to 10 keV regime. Ultimately we plan to make zone plates by sputtering alternating layers of opaque and transparent materials onto a thin wire core, then slicing perpendicular to the core axis to produce many zone plates. This technique shows promise for making x-ray optical elements that can be used in industrial crystallography, microprobe and radiography equipment. In a previous publication we reported on the favorable comparison between the measured performance of an Al/Ta diffraction grating and our numerical simulation. In this report we concentrate on the fabrication techniques used to produce diffraction gratings and linear zone plates. 2 refs., 10 figs.

Bionta, R.M.; Jankowski, A.F.; Makowiecki, D.M.

1987-12-01

403

Neutral beam injector for 475 keV MARS sloshing ions  

SciTech Connect

A neutral beam injector system which produces 5 MW of 475 keV D/sup 0/ neutrals continuously on target has been designed. The beamline is intended to produce the sloshing ion distribution required in the end plug region of the conceptual MARS tandem mirror commercial reactor. The injector design utilizes the LBL self-extraction negative ion source and Transverse Field Focusing (TFF) accelerator to generate a long, ribbon ion beam. A laser photodetachment neutralizer strips over 90% of the negative ions. Magnetic and neutron shield designs are included to exclude the fringe fields of the end plug and provide low activation by the neutron flux from the target plasma. The use of a TFF accelerator and photodetachment neutralizer produces a total system electrical efficiency of about 63% for this design.

Goebel, D.M.; Hamilton, G.W.

1983-12-13

404

Tip-based source of femtosecond electron pulses at 30 keV  

NASA Astrophysics Data System (ADS)

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; Krüger, Michael; Förster, Michael; Hammer, Jakob; Ehberger, Dominik; Baum, Peter; Hommelhoff, Peter

2014-03-01

405

Direct Laser Acceleration of 28 keV Electrons at a Single Dielectric Grating  

NASA Astrophysics Data System (ADS)

Direct laser acceleration exploiting the large optical field strength of short laser pulses and the proximity of a dielectric structure can support high acceleration gradients and may therefore lead to much smaller accelerators, with potential application in table-top free electron lasers. We report a proof-of-concept experiment demonstrating direct laser acceleration of non-relativistic 28 keV electrons derived from a conventional scanning electron microscope column at a single fused-silica grating. The electrons pass the grating as closely as 50 nm and interact with the third spatial harmonic, which is excited by 100 fs Titanium:sapphire laser pulses with a peak electric field of 2.85 GV/m. The observed maximum acceleration gradient of 25 MeV/m is already comparable to state- of-the-art RF structures. This work represents the first demonstration of scalable laser acceleration and of the inverse Smith-Purcell effect in the optical regime.

Breuer, John; Hommelhoff, Peter

406

Precision Measurements of {sup 56}Fe Cross Sections for the 847-keV Gamma Transition  

SciTech Connect

At the First Research Coordination Meeting of the IAEA/NDS CRP on Measurement, Calculation and Evaluation of Photon Production Data an experiment to measure with high precision the cross sections of the production of the 847-keV gamma ray due to inelastic neutron scattering with iron was proposed and discussed. The main justification for the proposed improved precision was the need for improved calculations of radiation transport through thick iron components of nuclear reactors. Present evaluated data for the subject reaction in the ENDF/B-VI files have evaluated uncertainties {approx} 10%; consequently, the results of computation of deep penetration of radiation in iron can have quite large uncertainties -- larger than 100%, for example, for an attenuation of {approximately} three orders of magnitude -- which can be a serious problem when one considers the magnitude of the radiation field inside a pressure vessel. This report describes progress toward obtaining more precise data. 13 refs., 1 fig.

Dickens, J.K.

1997-12-31

407

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

408

Mechanisms of O2 sputtering from water ice by keV ions  

NASA Astrophysics Data System (ADS)

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.

2005-12-01

409

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

410

Ion Source Development For The Proposed FNAL 750 keV Injector Upgrade  

NASA Astrophysics Data System (ADS)

Currently there is a Proposed FNAL 750 keV Injector Upgrade for the replacement of the 40 year old Fermi National Laboratory (FNAL) Cockcroft-Walton accelerators with a new ion source and 200 MHz Radio Frequency Quadruple (RFQ). [1] The slit type magnetron being used now will be replaced with a round aperture magnetron similar to the one used at Brookhaven National Lab (BNL). Operational experience from BNL has shown that this type of source is more reliable with a longer lifetime due to better power efficiency [2]. The current source development effort is to produce a reliable source with >60 mA of H- beam current, 15 Hz rep-rate, 100 ?s pulse width, and a duty factor of 0.15%. The source will be based on the BNL design along with development done at FNAL for the High Intensity Neutrino Source (HINS) [3].

Bollinger, D. S.

2011-09-01

411

Growth of Sn whiskers after low temperature implantation of 20 keV He or H  

SciTech Connect

Single crystalline whiskers have been observed to form on thin films (approx.100 nm) of Sn following implantation of 20-keV H or He at temperatures below 15/sup 0/K. Rapid warming prevented the formation of whiskers, indicating that the growth occurs predominatly during the warming, and not during implantation. Samples that had been warmed rapidly did show whisker growth only after several days in air at room temperature. The adhesion of the films to the substrate is remarkably enhanced by the irradiation, as measured by scratch tests. Thicker films produced progressively fewer whiskers, and none were observed on implanted foils, or films of In, Bi, Zn, or Pb. Possible origins of the driving force for whisker growth are discussed. Whiskers grew on Sn films on all of the substrates that were tested: quartz, sapphire, glass, Si, Cu, stainless steel, and NaCl.

Poker, D.B.; Schubert, J.; Alexandrou, A.; Froehlingsdorf, J.; Stritzker, B.

1986-01-01

412

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

413

Observation of the galactic 1809 keV gamma-ray line with the HEXAGONE spectrometer. [Milky Way  

SciTech Connect

We report an observation of the galactic 1809 keV gamma-ray line produced by radioactive {sup 26}Al in the interstellar medium. The measurement was performed with our high resolution germanium spectrometer HEXAGONE on a balloon flight in May 1989 from Alice Springs, Australia. Our differential spectrum of the Galactic Center region shows a narrow line at 1809 keV corresponding to a flux of (1.9 +/{minus} 0.9) {center dot} 10{sup {minus}4} photons {center dot} cm{sup {minus}2} s{sup {minus}1} assuming a source at the Galactic Center. We discuss the available observations of the 1809 keV line in the context of models that have been proposed for the origin of the galactic {sup 26}Al.

Malet, I.; Niel, M.; Vedrenne, G.; von Ballmoos, P. (Centre d'Etude Spatiales des Rayonnements, 31029 Toulouse Cedex (France)); Bowman, B.; Briggs, M.; Gruber, D.; Matteson, J.; Pelling, M.; Peterson, l. (Center for Astrophysics and Space Sciences, University of California, San Deigo, La Jolla, California 92093 (United States)); Feffer, P.; Hurley, K.; Lin, R.; Smith, D. (Space Science Laboratory, University of California, Berkeley, Berkeley, California 94720 (United States)); Cork, C.; Landis, D.; Luke, P.; Madden, N.; Malone, D.; Pehl, R.; Pollard, M. (Lawrence Berkeley Laboratory, Berkeley, California 94720 (United States)); Chapuis, C.; Durouchoux, P. (Service d'Astrophysique, Centre d'Etudes Nucleaires de Saclay, 91191 Gif-sur-Yvette Cedex (France))

1991-08-01

414

Analysis of 6.4 KEV Moessbauer Spectra Obtained with MIMOS II on MER on Cobbles at Meridiani Planum, Mars and Considerations on Penetration Depths  

NASA Technical Reports Server (NTRS)

The miniaturized Moessbauer (MB) spectrometers MIMOS II [1] on board of the two Mars Exploration Rovers Spirit and Opportunity have obtained more than 600 spectra of more than 300 different rock and soil targets [2-7]. Both instruments have simultaneously collected 6.4 keV X-ray and 14.4 keV .-ray spectra in backscattering geometry [1]. With Spirit's MB spectrometer, 6.4 keV and 14.4 keV spectra have been obtained for all targets through sol 461. After this date, only 14.4 keV spectra were collected. With Opportunity's spectrometer, 6.4 keV and 14.4 keV spectra have been collected for all targets to date. The Fe-mineralogy of rock and soil targets at both landing sites reported to date has been exclusively extracted from 14.4 keV spectra [2-5]. The comparison of 6.4 keV and 14.4 keV spectra provides depth selective information about a sample, but interpretation is not always straightforward [8].

Fleischer, I.; Klingelhoefer, G.; Morris, R. V.; Schroder, C.; Rodionov, D.; deSouza, P.

2008-01-01

415

Measurement of the MACS of 159Tb(n, ?) at kT=30 keV by Activation  

NASA Astrophysics Data System (ADS)

The measurement of the Maxwellian-Averaged Cross-Section (MACS) of the 159Tb(n, ?) reaction at kT=30 keV by the activation technique is presented. An innovative method for the generation of Maxwellian neutron spectra at kT=30 keV is used. An experimental value of 2166±181 mb agrees well with the MACS value derived from the ENDF/B-VII.1 evaluation, but is higher than KADoNiS recommended value of 1580±150 mb. Astrophysical implications are studied.

Praena, J.; Mastinu, P. F.; Pignatari, M.; Quesada, J. M.; Capote, R.; Morilla, Y.

2014-06-01

416

K and L-shell X-ray production cross sections for 50-250 keV proton impact on elements with Z = 26-30  

NASA Astrophysics Data System (ADS)

The K and L-shell X-ray production cross sections of Fe, Co, Ni, Cu and Zn elements are measured by 50-250 keV proton impact. The results are compared with Binary Encounter Approximation (BEA), Plane Wave Born Approximation (PWBA) and Energy loss Coulomb repulsion Perturbed Stationary State Relativistic (ECPSSR) theoretical predictions, as well as with experimental data of other authors. The ECPSSR theory agrees well with the K-shell cross section, but it overestimates the L-shell cross section by a maximum factor of about 7. The ECPSSR theory predicts a good trend to the production cross section ratio of the L to K-shell X-ray.

Zhou, Xianming; Zhao, Yongtao; Cheng, Rui; Wang, Yuyu; Lei, Yu; Wang, Xing; Sun, Yuanbo

2013-03-01

417

On-site nondestructive inspection by upgraded portable 950 keV/3.95 MeV X-band linac x-ray sources  

NASA Astrophysics Data System (ADS)

We have developed and upgraded portable 950 keV/3.95 MeV X-band (9.3 GHz) linac x-ray sources for on-site nondestructive testing (NDT) for social and industrial infrastructures. We integrated the hardware devices as well as software systems. For the hardware, we established all designed parameters including x-ray intensities of 0.05/2 Gy min?1 at 1 m for 950 keV/3.95 MeV systems, respectively. Concerning the software, we adopted the wavelet analysis for enhanced image contrast and partial angle computed tomography (CT) for a small region of interest. The wavelet analysis is effective to reduce scattered low energy x-ray noise in addition to using physical filters and collimators. The partial CT is inevitable to reconstruct an inner reinforced iron tube in concrete. We successfully performed on-site inspection three times, namely of a nitrogen acid distillation tower, a reinforced concrete pier and a large sample cut from a bridge. We obtained the x-ray images of the inner tube, determined the sizes of reinforced iron parts and evaluated the mechanical tolerance. Moreover, we are developing a new x-ray camera specified for MeV x-rays used for NDT of heavy objects. Then, our system will become a self-consisting and specialized high energy x-ray on-site inspection system. We are going to promote an application to NDT of social and industrial infrastructures in Japan and around the world.

Ueaska, Mitsuru; Dobashi, Katsuhiro; Fujiwara, Takeshi; Pei, Cuixiang; Wu, Wenjing; Kusano, Joichi; Nakamura, Naoki; Yamamoto, Masashi; Tanabe, Eiji; Ohya, Seiji; Hattori, Yukiya; Miura, Itaru; Honma, Hidetaka; Ishida, Masahiro; Kimura, Yoshitomi

2014-12-01

418

keV Sterile Neutrino Dark Matter from Singlet Scalar Decays: Basic Concepts and Subtle Features  

E-print Network

We perform a detailed and illustrative study of the production of keV sterile neutrino Dark Matter (DM) by decays of singlet scalars in the early Universe. In the current study we focus on providing a clear and general overview of this production mechanism. For the first time we study all regimes possible on the level of momentum distribution functions, which we obtain by solving a system of Boltzmann equations. These quantities contain the full information about the production process, which allows us to not only track the evolution of the DM generation but to also take into account all bounds related to the spectrum, such as constraints from structure formation or from avoiding too much dark radiation. In particular we show that this simple production mechanism can, depending on the regime, lead to strongly non-thermal DM spectra which may even feature more than one peak in the momentum distribution. These cases could have particularly interesting consequences for cosmological structure formation, as their ...

Merle, Alexander

2015-01-01

419

A comparison of the theoretical and experimental results for keV electron scattering from argon  

NASA Astrophysics Data System (ADS)

Experiments studying the scattering of keV electrons from noble gas atoms have been performed in the past, as the first Born approximation (FBA) was thought to be valid under these conditions, and hence it was expected that these experiments could be modelled relatively straightforwardly by theory. Somewhat surprisingly these experiments have so far attracted only very limited theoretical interest and the ability of modern scattering theory to describe them has not been firmly established. In our earlier study of the cross section for the resonant transitions, we established that the FBA was sufficient to describe the results for small scattering angles, but it did not account for the observed intensity at larger angles. Here we extend this comparison for the case of argon to monopole, quadrupole and octopole transitions below the continuum. The experimental results show differential cross sections spanning many orders of magnitude for these transitions. The relativistic distorted wave theory developed here describes these experiments for many transitions and a large range of scattering angles reasonably well.

Vos, M.; McEachran, R. P.; Zhu, Lin-Fan

2014-03-01

420

Dielectric laser acceleration of 28 keV electrons with the inverse Smith-Purcell effect  

NASA Astrophysics Data System (ADS)

Dielectric laser acceleration exploiting the large optical field strength of short laser pulses and the proximity of a dielectric structure can support high acceleration gradients may therefore lead to much smaller accelerators, with future potential application in table-top free electron lasers. We report a proof-of-concept experiment demonstrating dielectric laser acceleration of non-relativistic 28 keV electrons derived from a conventional scanning electron microscope column at a single fused-silica grating. The electrons pass the grating as closely as 50 nm and interact with the third spatial harmonic, which is excited by 110 fs long 800 nm laser pulses with a peak electric field of 2.85 GV/m. The observed maximum acceleration gradient of 25 MeV/m is already comparable to state-of-the-art radio-frequency structures. This work thus represents a demonstration of scalable laser acceleration and of the inverse Smith-Purcell effect in the optical regime. For relativistic electrons and otherwise identical conditions up to two orders of magnitude larger acceleration gradients are expected.

Breuer, John; Hommelhoff, Peter

2014-03-01

421

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

422

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

423

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

424

Maskless implants of 20 keV Ga+ in thin crystalline silicon on insulator  

NASA Astrophysics Data System (ADS)

A nano-sized ion beam apparatus has been used as maskless lithography to implant 20 keV Ga+ 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 × 1014/cm2. 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 °C temperature range and the interfaces with the surrounding crystalline regions sharpen. A temperature as high as 600 °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 °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.; Milazzo, R. G.; Rimini, E.; Spinella, C.; Peto, L.; Nadzeyka, A.; Bauerdick, S.

2013-01-01

425

Rolling down from the 30 keV peak: modelling the hard X-ray and gamma-ray backgrounds  

E-print Network

We will briefly discuss the importance of sensitive X-ray observations above a few tens of keV for a better understanding of the physical mechanisms associated to the Supermassive Black Hole primary emission in both radio quiet and radio loud AGN and to the cosmological evolution of the most obscured sources.

Andrea Comastri; Roberto Gilli; Guenther Hasinger

2006-04-25

426

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

NASA Astrophysics Data System (ADS)

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

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

2015-04-01

427

A comparison of the bremsstrahlung yields from 53 keV electrons on gold targets produced by PENELOPE and experiment  

NASA Astrophysics Data System (ADS)

We compare the predictions for the bremsstrahlung probability densities for 53 keV electrons on gold targets produced by the Monte Carlo program, PENELOPE, to experimental results. A comparison of the results indicates that bremsstrahlung produced by solid targets is best described by ordinary bremsstrahlung alone and that there are no significant polarizational bremsstrahlung contributions.

Requena, S.; Williams, S.; Quarles, C. A.

2010-12-01

428

ANL/APS/LS-313 Short-Period APPLE II Undulator for Generating 12-15 keV  

E-print Network

ANL/APS/LS-313 Short-Period APPLE II Undulator for Generating 12-15 keV X-Rays at the Advanced APPLE II design. In this note, we present magnet design calculations and radiation calculations are not important for the first harmonic and for the issues discussed in this note). Magnet Modeling of APPLE II

Kemner, Ken

429

DOSIMTRIE ABSOLUE POUR DES RAYONS X D'NERGIE MOYENNE 23 keV TALONNAGE DU SULFATE FERREUX  

E-print Network

516. DOSIMÉTRIE ABSOLUE POUR DES RAYONS X D'ÉNERGIE MOYENNE 23 keV ÉTALONNAGE DU SULFATE FERREUXV, valeur légèrement inférieure à celle des rayons 03B3 du radiocobalt. On discute les variations de ce chimiques de dosimétrie de rayons X ou y les plus universellement adoptées [1]. D'autre part la densité

Boyer, Edmond

430

OSSE observations of Galactic 511 keV positron annihilation radiation - Initial phase 1 results. [Oriented Scintillation Spectrometer Experiment  

NASA Technical Reports Server (NTRS)

The Oriented Scintillation Spectrometer Experiment (OSSE) on the Compton Gamma-Ray Observatory (GRO) has performed numerous observations of the Galactic plane and Galactic center region to measure the distribution of Galactic 511 keV positron annihilation radiation and to search for time variability of the emission. The initial 511 keV line fluxes for the observations performed during the first 18 months of the GRO mission are presented. The 511 keV line flux for a typical Galactic center observation is (2.5 +/- 0.3) x 10 exp -4 gamma/sq cm per sec, where the quoted uncertainty represents the 1 sigma statistical uncertainty. No statistically significant time variability of the line flux has been observed; the 3 sigma upper limit to daily variations from the mean is 3 x 10 exp -4 gamma/sq cm per sec. The distribution of Galactic 511 keV positron annihilation radiation implied by the OSSE observations is discussed and compared with observations by other instruments.

Purcell, W. R.; Grabelsky, D. A.; Ulmer, M. P.; Johnson, W. N.; Kinzer, R. L.; Kurfess, J. D.; Strickman, M. S.; Jung, G. V.

1993-01-01

431

2-20 ns interframe time 2-frame 6.151 keV x-ray imaging on the recently upgraded Z Accelerator: a progress report.  

PubMed

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(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(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.]. PMID:19044569

Bennett, G R; Smith, I C; Shores, J E; Sinars, D B; Robertson, G; Atherton, B W; Jones, M C; Porter, J L

2008-10-01

432

2-20 ns interframe time 2-frame 6.151 keV x-ray imaging on the recently upgraded Z Accelerator: A progress report  

NASA Astrophysics Data System (ADS)

When used for the production of an x-ray imaging backlighter source on Sandia National Laboratories' recently upgraded 26MA Z Accelerator, the terawatt-class, multikilojoule, 526.57nm Z-Beamlet laser (ZBL) [P. K. Rambo et al., Appl. Opt. 44, 2421 (2005)], in conjunction with the 6.151keV (1s2-1s2p 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 1mg 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 2-20ns. 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 6.151keV two frame technique has recently been used to image imploding wire arrays, using a 7.3ns 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 6.181keV Mn 1s2-1s2p singlet line), to increase x-ray yields. Also, a highly sensitive inline multiframe ultrafast (1ns 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.

2008-10-01

433

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

434

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

435

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.