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1

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

2

Measurement of the x-ray mass energy-absorption coefficient of air using 3 keV to 10 keV synchrotron radiation.  

PubMed

For the first time absolute photon mass energy-absorption coefficients of air in the energy range 3 keV to 10 keV have been measured with relative standard uncertainties less than 1%, significantly smaller than those of up to 5% assumed hitherto for calculated data. Monochromatized synchrotron radiation was used to measure both the total radiant energy by means of silicon photodiodes calibrated against a cryogenic radiometer and the fraction of radiant energy that is deposited in dry air by means of a free air ionization chamber. The measured ionization charge was converted into energy absorbed in air by calculated effective W values of photons as a function of their energy based on new measurements of the W values in dry air for electron kinetic energies between 1 keV and 7 keV, also presented in this work. The measured absorption coefficients were compared with state-of-the art calculations and found to agree within 0.7% with data calculated earlier by Hubbell at energies above 4 keV but were found to differ by values up to 2.1% at 10 keV from more recent calculations of Seltzer. PMID:17019029

Büermann, L; Grosswendt, B; Kramer, H-M; Selbach, H-J; Gerlach, M; Hoffmann, M; Krumrey, M

2006-10-21

3

Modeling the Chandra High Energy Transmission Gratings below 2 keV  

E-print Network

The High Energy Transmission Grating Spectrometer of the Chandra X-Ray Observatory is a high spectral The High Energy Transmission Grating Spectrometer (HETGS) of the Chandra X-Ray Observatory is a highModeling the Chandra High Energy Transmission Gratings below 2 keV K.A. Flanagana, T.H. Markerta, J

4

Low energy electrons (less than 200 keV) in the inner Earth's magnetosphere  

NASA Astrophysics Data System (ADS)

The version of IMPTAM (Inner Magnetosphere Particle Transport ans Acceleration Model) which simulates the transport and acceleration of the electrons from the plasma sheet to the inner magnetosphere regions is presented. The low energy electron fluxes (< 200 keV) constitute the seed population for the high energy MeV particles in the radiation belts and they are responsible for hazardous phenomena such as surface charging. We show the results of modeling of 5 storm events during the year of 2013. The model output is compared with measurements made at geostationary orbit (1) at the AMC 12 geostationary spacecraft by the CEASE II ESA instrument (ten energy ranges from 5 to 50 keV), and (2) at the GOES 13 data (three energy channels, 30-50 keV, 50-100 keV, 100-200 keV). We introduced the substorm-associated electromagnetic fields by launching several electromagnetic pulses at the substorm onsets during the modeled periods. At the same time, we present the nowcast model of IMPTAM for low energy (< 200 keV) electrons in the inner magnetosphere, operating online under the SPACECAST project (http://fp7-spacecast.eu). The presented model provides the low energy electron flux at all L-shells and at all satellite orbits, when necessary. The model is driven by the real time solar wind and Interplanetary Magnetic Field (IMF) parameters with 1 hour time shift for propagation to the Earth's magnetopause, and by the real time Dst index. Real time geostationary GOES 13 or GOES 15 (whenever which available) data on electron fluxes are used for comparison and validation of IMPTAM running online. The output of this model can serve as an input of electron seed population for the higher-energy radiation belt modeling.

Ganushkina, Natalia

5

A proton polarimeter for beam energies below 300 keV  

Microsoft Academic Search

A nuclear polarimeter based on the low energy analyzing power of the 6Li(p, 3He)alpha reaction has been developed and tested for proton energies below Ep = 300 keV. The polarimeter uses a 6LiF target evaporated on a water-cooled tantalum backing. The target is observed at backward angles by four silicon surface barrier detectors. The energy dependence of the analyzing power

L. Buchmann

1991-01-01

6

Energy loss of 100 keV protons in single collisions with argon atoms  

NASA Astrophysics Data System (ADS)

We have measured energy loss spectra of 100 keV protons interacting with argon atoms in small angle scattering under single collision conditions. The high overall energy resolution and the geometry of our setup allow a reliable determination of the mean energy loss and straggling. We have measured these quantities in dependence on the angle of scattering and find good agreement with recent calculations by Kabachnik et al.

Auth, C.; Winter, H.

1993-05-01

7

Statistical Analysis of Solar Electron Bursts at Energies Below 1.4 keV  

Microsoft Academic Search

The SWEPAM experiment aboard the ACE spacecraft has observed approximately 300 solar electron bursts below 1.4 keV. These low energy solar electron bursts are detected on interplanetary field lines connected to, or surrounding, solar active regions and are usually associated with solar type III radio bursts. Detailed statistical analysis can aid in understanding the physical mechanisms governing the acceleration and

C. A. de Koning; J. T. Gosling; R. M. Skoug; J. T. Steinberg

2003-01-01

8

Surface damage studies of ETFE polymer bombarded with low energy Si ions (?100 keV)  

NASA Astrophysics Data System (ADS)

Surface studies of ethylenetetrafluoroethylene (ETFE), bombarded with Si in a high-energy tandem Pelletron accelerator, have recently been reported. Si ion bombardment with a few MeV to a few hundred keV energies was shown to be sufficient to produce damage on ETFE film. We report here the use of a low energy implanter with Si ion energies lower than 100 keV, to induce changes on ETFE films. In order to determine the radiation damage, ETFE bombarded films were simulated with SRIM software and analyzed with optical absorption photometry (OAP), Raman and Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy to show quantitatively the physical and chemical property changes. Carbonization occurs following higher dose implantation, and hydroperoxides were formed following dehydroflorination of the polymer.

Minamisawa, Renato Amaral; De Almeida, Adelaide; Budak, Satilmis; Abidzina, Volha; Ila, Daryush

2007-08-01

9

Study of the Ar LMM spectra by He + projectile at 1250 keV, 1500 keV and 2000 keV bombardment energies  

NASA Astrophysics Data System (ADS)

The influence of He + ion impact on the Ar LMM spectra was investigated at the ESA-21 electron spectrometer using three different ion energies. Observed line relative energies to the L 3M 2,3( 1D 2) line agree well with other results, but the relative intensities of five angular-isotropic lines deviate significantly from other measurements and theory. The angular dependence of energy shifts agrees with the quantum PCI theory of Barrachina and Macek, except for directions close to 180°, where a slight enhancement of energy shift was observed. Finally, the angular distributions of the L 2M 2,3( 1S 0), ( 1d 2) and ( 3P 0,1,2) line intensities were compared to the alignment theory of Sizov and Kabachnik.

Tóth, L.; Víkor, Gy.; Ricz, S.; Pelicon, P.; Miller, R.

1994-03-01

10

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

11

Multilayer optics for monochromatic high-resolution X-ray imaging diagnostic in a broad photon energy range from 2 keV to 22 keV  

NASA Astrophysics Data System (ADS)

The “Commissariat à l’énergie atomique et aux énergies alternatives” (CEA) studies and designs advanced X-ray diagnostics to probe dense plasmas produced at the future Laser MegaJoule (LMJ) facility. Mainly for X-ray imaging with high spatial resolution, different types of multilayer mirrors were developed to provide broadband X-ray reflectance at grazing incidence. These coatings are deposited on two toroidal mirror substrates that are then mounted into a Wolter-type geometry (working at a grazing angle of 0.45°) to realize an X-ray microscope. Non-periodic (depth graded) W/Si multilayer can be used in the broad photon energy range from 2 keV to 22 keV. A third flat mirror can be added for the spectral selection of the microscope. This mirror is coated with a Mo/Si multilayer for which the d-spacing varies in the longitudinal direction to satisfy the Bragg condition within the angular acceptance of the microscope and also to compensate the angular dispersion due to the field of the microscope. We present a study of such a so-called Göbel mirror which was optimized for photon energy of 10.35 keV. The three mirrors were coated using magnetron sputtering technology by Xenocs SA. The reflectance in the entire photon energy range was determined in the laboratory of the Physikalisch-Technische Bundesanstalt (PTB) at the synchrotron radiation facility BESSY II in Berlin.

Troussel, Ph.; Dennetiere, D.; Maroni, R.; Høghøj, P.; Hedacq, S.; Cibik, L.; Krumrey, M.

2014-12-01

12

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

SciTech Connect

The compounds, Na{sub 2}B{sub 4}O{sub 7}, H{sub 3}BO{sub 3}, CdCl{sub 2} 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 and agree very well with the results obtained by Xcom code. Experiment and computation show that, H{sub 3}BO{sub 3} has the highest gamma ray attenuation coefficient among the aforementioned compounds. (author)

Jalali, Majid [Esfahan Nuclear Technology Center - ENTC (Iran, Islamic Republic of)

2006-07-01

13

Energy loss of 18 keV electrons in gaseous T2 and quench condensed D2 lms  

Microsoft Academic Search

Measurements of the energy loss of fast electrons at an energy of 18 keV have been performed on molecules of hydrogen isotopes, gaseous T2 and frozen D2. Whereas in the case of gaseous T2 the values of total inelastic cross-section (tot; gaseous =( 3:40 0:07) 10 18 cm2 for E =1 8:6 keV), average energy loss (\\

V. N. Aseev; A. I. Belesev; A. I. Berlev; E. V. Geraskin; O. V. Kazachenko; Yu. E. Kuznetsov; V. M. Lobashev; R. P. Ostroumov; N. A. Titov; S. V. Zadorozhny; Yu. I. Zakharov; J. Bonn; B. Bornschein; L. Bornschein; E. W. Otten; M. Przyrembel; Ch. Weinheimer; A. Saenz

14

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

15

The Perseus and Coma clusters of galaxies at energies above 20 keV  

NASA Technical Reports Server (NTRS)

Observations of the Perseus and Coma clusters of galaxies were made on June 21, 1974, with a balloon-borne X-ray telescope (energies of approximately 20-150 keV). No positive detection was made. The data favor a thermal bremsstrahlung mechanism for the X-ray production in the Perseus cluster of galaxies over the inverse Compton mechanism. In the case of the Coma cluster of galaxies, the data are inconclusive with respect to determining the origin of the X-rays.

Scheepmaker, A.; Ricker, G. R.; Brecher, K.; Ryckman, S. G.; Ballintine, J. E.; Doty, J. P.; Downey, P. M.; Lewin, W. H. G.

1976-01-01

16

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

17

Reflection electron energy loss spectroscopy of keV bombarded polystyrene at high ion fluences  

NASA Astrophysics Data System (ADS)

Reflection Electron Energy Loss Spectroscopy (REELS) is used to characterize the surface of thin films of polystyrene bombarded with keV ion beams in the fluence range 1 × 10 14-1 × 10 16 ions/cm 2. The characteristic features of REELS spectra of irradiated samples are in agreement with the formation of a hydrogenated amorphous carbon phase. The bulk plasmon shift and the inelastic scattering increase in the low-energy range of REELS spectra showed that the final structure is correlated to the total ion energy loss ( St) and to the predominant elastic or inelastic stopping regime. In particular, samples irradiated at a high St an predominant elastic regime show a higher film density and a higher valence electron density with respect to those irradiated at a low St and a predominant inelastic regime.

Marletta, Giovanni; Licciardello, Antonino; Calcagno, Lucia; Foti, Gaetano

1989-02-01

18

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

19

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

E-print Network

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

Fu, Jun

2004-11-15

20

High-resolution 17-75 keV backlighters for high energy density experiments  

NASA Astrophysics Data System (ADS)

17-75keV one- and two-dimensional high-resolution (<10?m) radiography has been developed using high-intensity short pulse lasers. High energy K? sources are created by fluorescence from hot electrons interacting in the target material after irradiation by lasers with intensity IL>1017W /cm2. High-resolution point projection one- and two-dimensional radiography has been achieved using microfoil and microwire targets attached to low-Z substrate materials. The microwire size was 10?m×10?m×300?m on a 300?m×300?m×5?m polystyrene substrate. The radiography experiments were performed using the Titan laser at Lawrence Livermore National Laboratory. The results show that the resolution is dominated by the microwire 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 microwire volume. There are enough K? photons created with a 300J, 1-?, 40ps 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 experiments at many new high-power laser facilities.

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

2008-07-01

21

Structural characterization of negatively charged glycosaminoglycans using high-energy (50–150 keV) collisional activation  

Microsoft Academic Search

Anionic glycosaminoglycan mono- and disaccharides (IVA, IH and IS) were subjected to very high-energy collisions (50–150 keV ion kinetic energy prior to collision) with Neon gas in an accelerator mass spectrometer, to explore the possibility of using this method to structurally characterize anionic sugars. Experiments were also conducted for the Na+·IH2? and Na+·IS3? sodiated complexes. This high-energy ion collision technique

Christopher J. Taylor; Ruth M. Burke; Bohan Wu; Subhasis Panja; Steen Brøndsted Nielsen; Caroline E. H. Dessent

2009-01-01

22

Structural characterization of negatively charged glycosaminoglycans using high-energy (50-150 keV) collisional activation  

Microsoft Academic Search

Anionic glycosaminoglycan mono- and disaccharides (IVA, IH and IS) were subjected to very high-energy collisions (50-150 keV ion kinetic energy prior to collision) with Neon gas in an accelerator mass spectrometer, to explore the possibility of using this method to structurally characterize anionic sugars. Experiments were also conducted for the Na+.IH2- and Na+.IS3- sodiated complexes. This high-energy ion collision technique

Christopher J. Taylor; Ruth M. Burke; Bohan Wu; Subhasis Panja; Steen Brøndsted Nielsen; Caroline E. H. Dessent

2009-01-01

23

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

24

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

25

Experimental investigation of ?130 keV kinetic energy antiprotons annihilation on nuclei  

NASA Astrophysics Data System (ADS)

The study of the antiproton ( bar {p}) annihilation cross section on nuclei at low energies (eV-MeV region) has implications for fundamental cosmology as well as for nuclear physics. Concerning the former, different models try to explain the matter/antimatter asymmetry in the universe assuming the existence of the so-called "islands" where antinucleon-nucleon annihilations occur in the border region (Cohen et al. Astrophys. J. 495, 539-549, 1998), while, from the nuclear physics point of view, the annihilation process is a valuable tool to evaluate the neutron/proton ratio in order to probe the external region of the nucleus (Gupta et al. Nucl. Phys. B 70(3), 414-424, 1974). The existing data of antinucleon-nucleon (or -nucleus) annihilation cross-sections are mainly confined to energies above ?1 MeV, while the cross section measured at LEAR in the 80's-90's (mostly with light targets Agnello et al. Phys. Lett. B 256, 349-353, 1991; Bertin et al. Phys. Lett. B 369, 77-85, 1996; Bertin et al. Phys. Lett. B 414, 220-228, 1997; Zenoni et al. Phys. Lett. B 461, 405-412, 1999; Bianconi et al. Phys. Lett. B 481, 194-198, 2000; Bianconi et al. Phys. Lett. B 492, 254-258, 2000) showed an unexpected behaviour for energies below 1 MeV (Bianconi et al. Phys. Lett. B 483, 353-359, 2000; Bianconi et al. Phys. Rev. C 62, 014611-7, 2000; Batty et al. Nucl. Phys. A 689, 721-740, 2001). The results showed a saturation with the atomic mass number against the A 2/3 trend which is observed for higher energies (being A the target mass number). The ASACUSA collaboration at CERN recently measured antiproton annihilation cross section on different kinds of nuclei with a bar {p} kinetic energy of 5.3 MeV (Bianconi et al. Phys. Lett. B 704, 461-466, 2011; Corradini et al. Nucl. Instr. Methods A 711, 12-20, 2013). Such results proved compatibility with the black-disk model with the Coulomb correction. But till now experimental difficulties prevented the investigation at energies below ?1 MeV. In 2012, the 100 keV region has been investigated for the first time (Aghai-Khozani et al. Eur. Phys. J. Plus 127, 125-128, 2012). We present here the first preliminary results of this experiment.

Aghai-Khozani, H.; Barna, D.; Corradini, M.; Hayano, R.; Hori, M.; Kobayashi, T.; Leali, M.; Lodi-Rizzini, E.; Mascagna, V.; Prest, M.; Soter, A.; Todoroki, K.; Vallazza, E.; Venturelli, L.; Zurlo, N.

2014-04-01

26

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

27

"Sweet spot" for endoleak detection: Optimizing contrast to noise using low keV reconstructions from fast-switch kVp dual energy CT  

PubMed Central

Objective To assess endoleak detection and conspicuity using low keV monochromatic reconstructions of single source (fast-switch kVp) dual energy datasets. Methods With IRB approval, multiphasic dual energy CT scans for aortic endograft surveillance were retrospectively reviewed for 39 patients. Two abdominal radiologists each performed two separate reading sessions, at 55 keV and standard 75 keV reconstruction, respectively. Readers tabulated endoleak presence, conspicuity on 1-5 scale, and type overall and in arterial and venous phases. Originally dictated reports in medical records were used as gold standard. Results Original dictations identified 19 endoleaks (9 abdominal and 10 thoracic), 13 of which were Type II. The blinded readers (R1 and R2) exhibited good to very good intraobserver and interobserver agreement. Endoleak detection was higher at 55 keV than 75 keV (sensitivity 100% (CI 82.4-100.0%) and 84.2% (CI 60.4-96.6%)at 55 keV vs. 79% (CI 54.4-94.0%)and 68.4% (CI 43.5-87.4%) at 75 keV in venous phase). Further, endoleak conspicuity ratings (where original dictation showed positive leak) were higher at 55 keV than 75 keV, which was a significant difference for R2 in the overall ratings (p=.03) and for both readers in the venous phase ratings (R1:p=.01; R2: p=.004). There was no difference in endoleak type characterization between the keV levels. Conclusion Sensitivity for endoleak detection and overall endoleak conspicuity ratings were both higher at 55 keV than 75 keV, favoring the inclusion of a lower energy monochromatic reconstruction for endoleak surveillance protocols with dual energy CT. PMID:22261775

Kaza, Ravi K; Liu, Peter S; Quint, Leslie E; Khalatbari, Shokoufeh H; Platt, Joel F

2012-01-01

28

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

29

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

30

Double ionization of helium in the 8--25keV x-ray energy range% (Work supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under contract W-31-109ENG38)  

Microsoft Academic Search

X rays in the keV energy regime interact only very weakly with helium atoms. Starting at about 6 keV x-ray energy, the absorption of x rays becomes less important in the ionization of helium than Compton scattering. Whereas for photoabsorption the high-energy asymptotic value for the fraction of helium double ionization is practically reached for keV x rays, the fraction

B. Krässig; R. W. Dunford; D. S. Gemmell; S. Hasegawa; E. P. Kanter; S. H. Southworth; L. Young; T. Weber; H. Schmidt-Böcking; W. Schmitt

1998-01-01

31

Energy loss distributions for 625 keV H + ions channeled near the <100> axis in silicon  

NASA Astrophysics Data System (ADS)

An angular dependence of the energy distributions for 625 keV H + ions transmitted through a 0.57 ?m thick Si(100) single crystal is studied. The angular scans have been taken through the <100> axis along the {110} plane and through the {110} plane at an angle of 6° with respect to the <100> axis. The experimental distributions have been reproduced by a Monte Carlo simulation assuming individual contributions to the energy loss due to close and distant collisions of the H ion with inner-shell as well as valence electrons. The relative contributions of core and valence electrons to the stopping have been investigated.

Dygo, A.; Boshart, M. A.; Grant, M. W.; Seiberling, L. E.

1994-07-01

32

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

NASA Technical Reports Server (NTRS)

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

Bai, Taeil

1986-01-01

33

Gaseous Detector with sub keV Threshold to Study Neutrino Scattering at Low Recoil Energies  

E-print Network

Gaseous detector with a sub keV electron equivalent threshold is a very perspective tool for the precision measurement of the neutrino magnetic moment and to observe coherent scattering of neutrinos on nuclei. The progress in the development of low noise electronics makes it possible to register the rare events at the threshold less than 100 eV. The construction of the gaseous detector is given and the typical pulses with amplitudes of a few eV observed on a bench scale installation are presented. The possible implications for future experiments are discussed.

Kopylov, A V; Petukhov, V V; Solomatin, A E

2014-01-01

34

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

35

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

36

Evaluation of resonance parameters for neutron interaction with iron isotopes for energies up to 400 keV  

SciTech Connect

The evaluation of the resolved resonance parameters of iron isotopes 54, 56, and 57 in the neutron energy region below 400 keV is documented. Estimates of the uncertainties in the resonance parameters and correlation between the partial widths GAMMA/sub n/ and GAMMA/sub ..gamma../ are given when significant. Some details about the procedures used to evaluate the resonance parameters, their uncertainties, and correlations are reported. This evaluation was performed for the general-purpose file of the Evaluated Nuclear Data File (ENDF/B-V MAT 1326). 4 figures, 7 tables.

Perey, C.M.; Perey, F.G.

1980-09-01

37

Ionic fragmentation of CO and H2O under impact of 10 keV electrons: kinetic energy release distributions  

NASA Astrophysics Data System (ADS)

Dissociative ionization of COq+ (q=2-4) and H2Oq+ (q=2-3) molecular ions produced from the collisions of CO and H2O with 10 keV electrons is studied using time-of-flight mass spectrometer and position sensitive detector with multi-hit ability, respectively. The kinetic energy release distributions for these channels are obtained. We found that a pure Coulomb explosion model is insufficient to explain the observed kinetic release distributions for the Coulomb explosion channels. A detail of this study is given in references [3, 4].

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

2014-04-01

38

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

PubMed

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

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

2013-02-01

39

Application of the HOTWAXS detector for imaging at higher X-ray energies (10-30 keV)  

NASA Astrophysics Data System (ADS)

The high overall throughput wide angle X-ray scattering (HOTWAXS) gas detector system, aimed at X-ray diffraction (XRD) and wide angle X-ray scattering (WAXS) applications has been a successful user facility on stations 2.1 and 9.3 at the Daresbury SRS offering high-speed data acquisition. The facility has been duplicated on station I22 of the Diamond light source. The energy range covered by stations I22 and 9.3 is very similar varying from 6 to 30 keV, well above the energy range conventionally covered by gas detectors. Here, we report studies of the options for successful operation of HOTWAXS at the upper end of this energy range, made possible by this particular design.

Bateman, J. E.; Duxbury, D. M.; Harvey, I.; Helsby, W. I.; Spill, E. J.

2009-06-01

40

Impact-parameter dependence of energy loss for 625-keV H+ ions in Si single crystals  

NASA Astrophysics Data System (ADS)

The energy distributions for 625-keV H+ ions transmitted through thin Si single crystals are studied for detailed angular scans through the <110> and <100> axial as well as the \\{111\\} and \\{110\\} planar channels. Well-resolved structures in the distributions taken near the <110> axial direction are observed. The experimental energy-loss distributions are very well reproduced by a Monte Carlo simulation using the semiclassical approximation model for core electrons and the two-component free-electron-gas model for valence electrons. The best fit to the data is obtained if the model energy losses are scaled up for core electrons and down for valence electrons by several percent. The experimental distributions can also be reproduced by assuming the mean excitation energy for distant collisions of the ion with core electrons equal to 1.4 times the binding energy for a given shell. No significant differences between the distributions obtained using the solid-state and free-atom valence electron densities have been found. The evolution of the distributions for the <110> axial scan is discussed in terms of ion trajectories and the flux distribution. Also, the azimuthally averaged mean energy loss is studied as a function of tilt angle with respect to the <110> axis.

Dygo, A.; Boshart, M. A.; Seiberling, L. E.; Kabachnik, N. M.

1994-12-01

41

Impact-parameter dependence of energy loss for 625-keV H[sup +] ions in Si single crystals  

SciTech Connect

The energy distributions for 625-keV H[sup +] ions transmitted through thin Si single crystals are studied for detailed angular scans through the [l angle]110[r angle] and [l angle]100[r angle] axial as well as the [l brace]111[r brace] and [l brace]110[r brace] planar channels. Well-resolved structures in the distributions taken near the [l angle]110[r angle] axial direction are observed. The experimental energy-loss distributions are very well reproduced by a Monte Carlo simulation using the semiclassical approximation model for core electrons and the two-component free-electron-gas model for valence electrons. The best fit to the data is obtained if the model energy losses are scaled up for core electrons and down for valence electrons by several percent. The experimental distributions can also be reproduced by assuming the mean excitation energy for distant collisions of the ion with core electrons equal to 1.4 times the binding energy for a given shell. No significant differences between the distributions obtained using the solid-state and free-atom valence electron densities have been found. The evolution of the distributions for the [l angle]110[r angle] axial scan is discussed in terms of ion trajectories and the flux distribution. Also, the azimuthally averaged mean energy loss is studied as a function of tilt angle with respect to the [l angle]110[r angle] axis.

Dygo, A.; Boshart, M.A.; Seiberling, L.E. (Department of Physics, University of Florida, P.O. Box 118440, Gainesville, Florida 32611-8440 (United States)); Kabachnik, N.M. (Institute of Nuclear Physics, Moscow State University, 119899 Moscow (Russian Federation))

1994-12-01

42

Ionic fragmentation of the CO molecule by impact of 10-keV electrons: Kinetic-energy-release distributions  

NASA Astrophysics Data System (ADS)

The ionic fragmentation of a multiply charged CO molecule is studied under impact of 10-keV electrons using recoil-ion momentum spectroscopy. The kinetic-energy-release distributions for the various fragmentation channels arising from the dissociation of COq+ (q = 2-4) are measured and discussed in light of theoretical calculations available in the literature. It is observed that the present kinetic-energy-release values are much smaller than those predicted by the Coulomb explosion model. The kinetic-energy-release distribution for the C++O+ channel is suggested to arise from the tunneling process. It is seen that the peak of kinetic-energy-release distribution is larger for that dissociation channel that arises from the same molecular ion which has higher charge on the oxygen atom. Further, the relative ionic fractions for seven ion species originating from ionization and subsequent dissociation of the CO molecule are obtained and compared with the existing data reported at low energy of the electron impact. The precursor-specific relative partial ionization cross sections are also obtained and shown to be about 66.4% from single ionization, 29.9% from double ionization, 3.3% from triple ionization, and about 0.4% from quadruple ionization of the precursor CO molecule contributing to the total fragment ion yield.

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

2013-02-01

43

Study of the surface activation of ETFE by low energy (keV) Si and N bombardment  

NASA Astrophysics Data System (ADS)

The ethylenetetrafluoroethylene (ETFE) is a polymer formed by alternating ethylene and tetrafluoroethylene segments. It can be applied in the field of medical physics as intra venous catheters and as radiation dosimeters. The increasing application of polymeric materials in technological and scientific fields has motivated the use of surface treatments to modify the physical and chemical properties of polymer surfaces. When a material is exposed to ionizing radiation, it suffers damage leading to surface activation depending on the type, energy and intensity of the applied radiation. In order to determine the radiation damage and the surface activation mechanism ETFE films were bombarded with keV Si and N at various fluences. The bombarded film was also analyzed with optical absorption photospectrometry (OAP), Raman and Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy showing quantitatively the chemical nature at the damage caused by the Si and N bombardment.

Parada, M. A.; de Almeida, A.; Muntele, C.; Muntele, I.; Delalez, N.; Ila, D.

2005-12-01

44

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

NASA Astrophysics Data System (ADS)

The current goals of the TEXONO research program 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 WIMP dark matter searches. An energy threshold of 220 eV was achieved with a four-channel ultra-low-energy germanium prototype detector each with an active mass of 5 g at the Kuo-Sheng Neutrino Laboratory. New limits were placed for the couplings of low-mass WIMPs with matter with a ultra-low-energy germanium prototype detector. Data are being taken with a 500 g Point Contact Germanium detector, where a threshold of ~350 eV was demonstrated. The dark matter program will evolve into a dedicated experiment at an underground laboratory under construction in Sichuan, China.

Lin, Shin-Ted; Wong, Henry T.

2011-03-01

45

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

SciTech Connect

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

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

1988-09-25

46

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

47

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

48

The low energy particle detector sled (~30 keV3.2 MeV) and its performance on the phobos mission to mars and its moons  

Microsoft Academic Search

A low energy particle detector system (SLED) is described which was designed to measure the flux densities of electrons and ions in the energy range from ~30 keV to a few MeV in (a) the varying solar aspect angles and temperatures pertaining during the Cruise Phase of the Phobos Mission and (b) in the low temperature environment (reaching -25° C)

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

1990-01-01

49

A survey of energy loss calculations for heavy ions between 1 and 100 keV  

E-print Network

The original Lindhard-Scharff-Schi{\\o}tt (LSS) theory and the more recent Tilinin theory for calculating the nuclear and electronic stopping powers of slow heavy ions are compared with predictions from the SRIM code by Ziegler. While little discrepancies are present for the nuclear contribution to the energy loss, large differences are found in the electronic one. When full ion recoil cascade simulations are tested against the elastic neutron scattering data available in the literature, it can be concluded that the LSS theory is the more accurate.

A. Mangiarotti; M. I. Lopes; M. L. Benabderrahmane; V. Chepel; A. Lindote; J. Pinto da Cunha; P. Sona

2006-10-31

50

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

51

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

52

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

SciTech Connect

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

Jimenez-Rey, D. [Centro de Micro-Analisis de Materiales, Universidad Autonoma de Madrid, C/ Faraday 3, Campus de Cantoblanco, E-28049 Madrid (Spain); Zurro, B.; Baciero, A.; Navarro, M. [Laboratorio Nacional de Fusion, Asociacion Euratom-CIEMAT, Av. Complutense 22, E-28040 Madrid (Spain); Rodriguez-Barquero, L. [Laboratorio de Metrologia de Radiaciones lonizantes, CIEMAT, Av. Complutense 22, E-28040 Madrid (Spain)

2010-10-15

53

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

54

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

55

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

56

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

57

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

Microsoft Academic Search

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

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

2004-01-01

58

Analysis of initial energies of fragments produced by 65keV proton-molecule collisions using a time-of-flight mass spectrometer  

Microsoft Academic Search

A method is described to evaluate initial-energy distributions of fragments produced by proton-molecule collisions. The fragments are analysed by means of a time-of-flight mass spectrometer and their initial energies are evaluated from their time-of-flight spectrum. These energies are presented for various fragments of H2, N2, O2, CO2, CH3Cl, CH3Br, CH3I, C2H6 and C3H8 produced with 65-keV protons. The results indicate

K. Schäfer; W. Y. Baek; K. Förster; D. Gassen; W. Neuwirth

1991-01-01

59

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

60

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

SciTech Connect

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

Friedman, P.G.

1986-11-25

61

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

62

High-energy-resolution monochromator for nuclear resonant scattering of synchrotron radiation by Te-125 at 35.49 keV  

NASA Astrophysics Data System (ADS)

We have developed a high-resolution monochromator (HRM) for the measurement of nuclear resonant scattering (NRS) of synchrotron radiation by Te-125 at 35.49 keV using the backscattering of sapphire (9 1 -10 68). HRMs for nuclei with excitation energies less than 30 keV have been successfully developed using high angle diffractions by silicon crystals. Nearly perfect silicon crystal, however, is not suitable for high efficient HRMs at higher energy regions because the symmetry of the crystal structure is high and the Debye-temperature is low. Therefore, we used high quality synthetic sapphire crystal, which has low symmetry of crystal structure and high Debye-temperature. The temperature of the crystal was precisely controlled around 218 K to diffract synchrotron radiation with a Bragg angle of ?/2 - 0.52 mrad. Energy was tuned by changing the crystal temperature under the condition of constant diffraction angle. Energy resolution was measured by detecting nuclear forward scattering by Te-125 in enriched TeO II. The relative energy resolution of 2.1×10 -7 is achieved, that is 7.5 meV in energy bandwidth. This HRM opens studies on element-specific dynamics and electronic state of substances containing Te-125.

Imai, Yasuhiko; Yoda, Yoshitaka; Kitao, Shinji; Masuda, Ryo; Higashitaniguchi, Satoshi; Inaba, Chika; Seto, Makoto

2007-09-01

63

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

PubMed

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

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

2011-02-01

64

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

65

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

66

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

67

Measurement of mass attenuation coefficients of Eremurus-Rhizophora spp. particleboards for X-ray in the 16.63-25.30 keV energy range  

NASA Astrophysics Data System (ADS)

The roots of Eremurus spp. were used as a bio-adhesive in the fabrication of Rhizophora spp. particleboards. The mass attenuation coefficients of Eremurus-Rhizophora spp. particleboard of six samples with two different weight percentages of the Eremurus spp. root (6% and 12%) and three various Rhizophora spp. particle sizes (?149 ?m, 149-500 ?m and 500-1000 ?m) were determined by using X-ray fluorescence (XRF) photons in 16.63 keV and 25.30 keV of the photon energy range. The results were compared with theoretically calculated mass attenuations using the XCOM computer program for younger-age (breast 1: 75% muscle+25% fat), middle-age (breast 2: 50% muscle+50% fat), and old-age (breast 3: 25% muscle+75% fat) breasts. The results indicated that Eremurus-Rhizophora spp. particleboard is the appropriate suitable phantom in the diagnostic energy region. The mass attenuation coefficient in the low weight percentage of the bio-adhesive and the large Rhizophora spp. particle size were found very close to breast 1. Moreover the mass attenuation coefficient of the sample with high weight percentage of the bio-adhesive and small Rhizophora spp. particle size was found very close to water as a standard material phantom. In addition, the viscosity of dissolved Eremurus spp. root in water could be considerably higher than that of formaldehyde-based adhesives, which affects on some properties such as high strength and high binding.

Tousi, E. T.; Bauk, S.; Hashim, R.; Jaafar, M. S.; Abuarra, A.; Aldroobi, K. S. A.; Al-Jarrah, A. M.

2014-10-01

68

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

NASA Astrophysics Data System (ADS)

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

Maddox, Brian

2010-11-01

69

TEC evidence for near-equatorial energy deposition by 30 keV electrons in the topside ionosphere  

NASA Astrophysics Data System (ADS)

Observations of energetic electrons (10 - 300 keV) by NOAA/POES and DMSP satellites at heights <1000 km during the period from 1999 to 2010 allowed finding abnormal intense fluxes of ~106 - 107 cm-2 s-1 sr-1 for quasi-trapped electrons appearing within the forbidden zone of low latitudes over the African, Indo-China, and Pacific regions. Extreme fluxes appeared often in the early morning and persisted for several hours during the maximum and recovery phase of geomagnetic storms. We analyzed nine storm time events when extreme electron fluxes first appeared in the Eastern Hemisphere, then drifted further eastward toward the South-Atlantic Anomaly. Using the electron spectra, we estimated the possible ionization effect produced by quasi-trapped electrons in the topside ionosphere. The estimated ionization was found to be large enough to satisfy observed storm time increases in the ionospheric total electron content (TEC) determined for the same spatial and temporal ranges from global ionospheric maps. Additionally, extreme fluxes of quasi-trapped electrons were accompanied by the significant elevation of the low-latitude F-layer obtained from COSMIC/FORMOSAT-3 radio occultation measurements. We suggest that the storm time ExB drift of energetic electrons from the inner radiation belt is an important driver of positive ionospheric storms within low-latitude and equatorial regions.

Suvorova, A. V.; Dmitriev, A. V.; Tsai, L.-C.; Kunitsyn, V. E.; Andreeva, E. S.; Nesterov, I. A.; Lazutin, L. L.

2013-07-01

70

Prompt gamma ray analysis of Portland cement sample using keV neutrons with a Maxwellian energy spectrum—a Monte Carlo study  

NASA Astrophysics Data System (ADS)

Monte Carlo calculations have been carried out to determine the prompt gamma ray yield from a Portland cement sample using keV neutrons from a 3H(p,n) reaction with a Maxwellian energy distribution with kT=52 keV. This work is a part of wider Monte Carlo studies being conducted at the King Fahd University of Petroleum and Minerals (KFUPM) in search of a more efficient neutron source for its D(d,n) reaction based (2.8 MeV neutrons) Prompt Gamma Ray Neutron Activation Analysis (PGNAA) facility. In this study a 3H(p,n) reaction based prompt gamma ray PGNAA setup was simulated. For comparison purposes, the diameter of a cylindrical external moderator of the 3H(p,n) reaction based PGNAA setup was assumed to be similar to the one used in the KFUPM PGNAA setup. The results of this study revealed that the optimum geometry of the 3H(p,n) reaction based setup is different from that of the KFUPM PGNAA facility. The performance of the 3H(p,n) reaction based setup is also better than that of the 2.8 MeV neutrons based KFUPM facility and its prompt gamma ray yield is about 60-70% higher than that from the 2.8 MeV neutrons based facility. This study has provided a theoretical base for experimental test of a 3H(p,n) reaction based setup.

Naqvi, A. A.

2003-08-01

71

{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

72

Absolute differential cross sections for elastic and inelastic electron scattering from benzene with 1 kev impact energy  

NASA Astrophysics Data System (ADS)

The absolute generalized oscillator strength and absolute inelastic differential cross section have been determined, as a function of the momentum transfer, for the 1E1u + 1B1u larr 1Ag transition in the benzene molecule. A previously described electron energy-loss spectrometer, featuring a Wien-filter velocity analyser, has been used. Employing 1000 eV incident electron energy and 1.0 eV energy resolution, absolute oscillator strength distribution as a function of electron energy loss was obtained in the 2-8° scattering angle range. The absolute elastic differential cross section was also determined spanning an angular range of 2°-14°. The photoabsorption spectrum converted from the electron energy-loss spectrum was compared with the interstellar extinction curve where we confirm the proportionality between the cross section and extinction.

Boechat-Roberty, H. M.; Rocco, M. L. M.; Lucas, C. A.; de Souza, G. G. B.

2004-04-01

73

Trajectory dependent energy loss in grazing collisions of keV He atoms from a LiF(0 0 1) surface  

NASA Astrophysics Data System (ADS)

Angular distributions for scattering of 12 keV He atoms from a LiF(0 0 1) surface under a grazing angle of incidence were recorded in coincidence with the projectile energy loss and the number of electrons emitted from the target surface during the collision. For scattering along the low indexed <1 1 0> and <1 0 0> directions of the crystal surface collisional rainbow peaks were observed. For scattering along a <1 1 0> direction the resulting rainbow peaks can be attributed to scattering from strings of anions which form active sites for charge exchange and emission of electrons. The data can be interpreted by trajectory computer simulations where charge transfer takes place from F- sites.

Lienemann, J.; Hülsewede, D.; Seifert, J.; Maass, K.; Busch, M.; Winter, H.

2013-11-01

74

A Novel Approach to Measure the Cross Section of the 18O(p, ?)15N Resonant Reaction in the 0-200 keV Energy Range  

NASA Astrophysics Data System (ADS)

The 18O(p, ?)15N reaction is of primary importance to pin down the uncertainties, due to nuclear physics input, affecting present-day models of asymptotic giant branch stars. Its reaction rate can modify both fluorine nucleosynthesis inside such stars and oxygen and nitrogen isotopic ratios, which allow one to constrain the proposed astrophysical scenarios. Thus, an indirect measurement of the low-energy region of the 18O(p, ?)15N reaction has been performed to access, for the first time, the range of relevance for astrophysical application. In particular, a full, high-accuracy spectroscopic study of the 20 and 90 keV resonances has been performed and the strengths deduced to evaluate the reaction rate and the consequences for astrophysics.

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

2010-01-01

75

plutonium isotopic analysis in the 30 KeV to 210 KeV range  

SciTech Connect

Low-Energy Gamma-ray Spectroscopy (LEGS) is a nondestructive assay (NDA) technique developed in the 1980s. In 1999, it was modified to include a physical-based model for the energy dependent efficiency. It uses the gamma rays in the energy range from approximately 30 keV to 210 keV, except the 100-keV region. This energy region provides intense, well-separated gamma rays from the principal isotopes of plutonium. For applications involving small quantities (mg to g) of freshly separated plutonium in various chemical forms, it is ideally suited for accurate real-time or near real-time isotopic analysis. Since the last modification, LEGS has been incorporated into the FRAM code (Fixed-energy Response-function Analysis with Multiple efficiency), version 4. FRAM v4 is capable of analyzing the peaks in the whole energy range from 30 keV to 1 MeV, including the X-ray region. The new capability of analyzing the peaks in the 100-keV region greatly enhances the plutonium analysis in the 30 keV to 2 10 keV ranges of the traditional LEGS. We now can analyze both the freshly separated and aged plutonium with greater accuracy.

Vo, Duc T.; Li, T. K. (Tien K.)

2001-01-01

76

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

SciTech Connect

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

Imazono, T.; Koike, M.; Koeda, M.; Nagano, T.; Sasai, H.; Oue, Y.; Yonezawa, Z.; Kuramoto, S.; Terauchi, M.; Takahashi, H.; Handa, N.; Murano, T. [QuBS, Japan Atomic Energy Agency (JAEA), 8-1-7 Umemidai, Kizugawa, Kyoto 619-0215 (Japan); Device Dept., Shimadzu Corp., 1 Nishinokyo-Kuwabarcho, Nakagyo-ku, Kyoto 604-8511 (Japan); IMRAM, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); EC Business Unit, JEOL Ltd., 3-1-2 Musashino, Akishima, Tokyo 196-8558 (Japan)

2012-05-17

77

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

78

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

79

Reevaluation of 58Ni and 60Ni Resonance Parameters in the Energy Range Thermal to 800 keV  

SciTech Connect

The previous 58Ni and 60Ni set of resonance parameters (ENDF/B-VII-0, JEFF-3, etc.) was based on the SAMMY analysis of Oak Ridge National Laboratory neutron transmission, scattering cross section and capture cross section measurements by C. M. Perey et al. The present results were obtained by adding to the SAMMY experimental data base the capture cross sections measured recently at the Oak Ridge Linear Electron Accelerator by Guber et al. and the Geel Electron Linear Accelerator very high-resolution neutron transmission measurements performed by Brusegan et al. A complete resonance parameter covariance matrix (RPCM) was obtained from the SAMMY analysis of the experimental database. The data sets were made consistent, when needed, by adjusting the neutron energy scales, the normalization coefficients, and the background corrections. The RPCM allows the calculation of the cross section uncertainties due mainly to statistical errors in the experimental data. The systematic uncertainties of the experimental data, estimated from the preliminary analyses of the experimental database, were taken into account in the cross section covariance matrix (CSCM) for total, scattering, and capture cross sections. The diagonal elements of the CSCM were obtained by quadratic combination of the different components of the uncertainties. Because of a lack of experimental information, the energy correlations were not obtained, and a value of 0.5 was arbitrarily taken for all the CSCM nondiagonal elements.

Derrien, Herve [ORNL; Leal, Luiz C [ORNL; Guber, Klaus H [ORNL; Wiarda, Dorothea [ORNL; Arbanas, Goran [ORNL

2009-01-01

80

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

81

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

82

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

83

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

84

Disappearance and reappearance of particles of energies 50 keV as seen by P78-2 (SCATHA) near geosynchronous orbit  

NASA Technical Reports Server (NTRS)

The nightside particle environment as observed by the AFGL Rapid Scan Particle Detector on SCATHA showing large, sudden simultaneous changes in the fluxes of electrons and protons with energies above 50 keV (dropouts) is considered. An interesting feature of SCATHA dropouts is the quasiperiodic behavior of the particle flux amplitudes which often vary with a period of the order of 15 minutes both during the dropout and after the return. A flux return during eclipse caused a major spacecraft charging event of several kilovolts. The SCATHA observations are compared with those reported for other geosynchronous satellites. In agreement with ATS-5, a marked dependence in the frequency of occurrence due to an effect of the orbit is found. ATS-5 experienced few dropouts during quiet geomagnetic conditions. However, for an L shell greater than seven, SCATHA particle dropouts occur routinely during quiet conditions. Thus, for SCATHA's orbit, both the orbital position and geomagnetic conditions must be taken into account in evaluating the potential hazard of flux returns.

Feynman, J.; Saflekos, N. A.; Garrett, H. G.; Hardy, D. A.; Mullen, E. G.

1980-01-01

85

Size saturation in low energy ion beam synthesized nanoparticles in silica glass: 50 keV Ag{sup -} ions implantation, a case study  

SciTech Connect

Fluence-dependent formation of Ag nanoparticles (NPs) in silica glass by 50 keV Ag{sup -} ions implantation has been studied. Samples implanted with fluences of 2x10{sup 16} ions cm{sup -2} and above are found to show an absorption band at around 410 nm, corresponding to the surface plasmon resonance (SPR) of the Ag NPs in silica glass. An increase in SPR peak intensity with increase in fluence has been observed up to a fluence of 7x10{sup 16} ions cm{sup -2} (F7), after which the absorption intensity shows a saturation. Simulations of the optical absorption spectra also indicated an increase in the absorption intensity and hence the size of the NPs with increase in fluence up to F7, beyond which NP size is seen to saturate. The saturation of fluence and the SPR intensity (or NP size) have been explained as coming due to a break up of larger Ag NPs formed near the surface by displacement spikes induced by subsequently incident Ag ions against their regrowth from the movement of Ag atoms toward the surface and their sputtering loss. Further, we have compared our observations with the earlier data on saturation of fluence and size of NPs in cases of Au and Zn, and concluded that the saturation of both fluence and NP size are general phenomena for low energy high fluence metal ion implantation.

Kuiri, P. K. [Department of Physics, Achhruram Memorial College, P.O. Jhalda, Purulia 723202 (India)

2010-09-15

86

The effects of energy-loss straggling and elastic scattering models on Monte Carlo calculations of dose distribution functions for 10 keV to 1 MeV incident electrons in water  

NASA Astrophysics Data System (ADS)

Accurate simulation of the transport and energy-loss of energetic electrons is an important step in modeling ion-induced effects in materials. Dose distribution functions (or so-called dose point kernels, DPKs) represent one of the most basic and useful quantities for characterizing the spatial distribution of energy deposition in matter. In the present work we investigate the effect on DPK of various models for the elastic scattering cross-section and energy-loss straggling distribution widely used in Monte Carlo simulation of electron transport above a few keV. Our findings indicate that, overall, the DPK is not very sensitive to the examined physical models, except at the tail of the distribution where a strong dependence is observed. The present comparison can be useful for avoiding systematic errors in the simulation of electron transport at primary energies from several keV to a few MeV and to suggest further improvement in the existing codes.

Bousis, C.; Emfietzoglou, D.; Nikjoo, H.; Hadjidoukas, P.; Pathak, A.

2009-05-01

87

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

88

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

E-print Network

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

Geloni, Gianluca; Saldin, Evgeni

2012-01-01

89

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

90

Interplanetary variability in particle fluxes recorded by the low energy charged particle detector SLED (about 30 keV to greater than 30 MeV) during the Cruise Phase of the PHOBOS Mission to Mars and its moons  

Microsoft Academic Search

Two lightweight telescope detector systems, codenamed SLED-1 and SLED-2, with the capability to monitor electron and ion fluxes within an energy range spanning 34 keV to a few tens of MeV, were launched on the twin spacecraft of the Soviet Phobos Mission to Mars and its moons in July 1988. Solar-related particle enhancements recorded during the Cruise Phase, and also

S. M. P. McKenna-Lawlor; V. V. Afonin; K. I. Gringauz; E. Keppler; E. Kirsch; A. K. Richter; M. Witte; D. O'Sullivan; A. Thompson; K. Kecskemety

1991-01-01

91

Neutron physics of the Re/Os clock. II. The (n,n{sup '}) cross section of {sup 187}Os at 30 keV neutron energy  

SciTech Connect

The inelastic neutron-scattering cross section of {sup 187}Os has been determined in a time-of-flight experiment at the Karlsruhe 3.7-MV Van de Graaff accelerator. An almost monoenergetic beam of 30-keV neutrons was produced at the threshold of the {sup 7}Li(p,n){sup 7}Be reaction. Information on the inelastic channel is required for reliable calculations of the so-called stellar enhancement factor, by which the laboratory cross section of {sup 187}Os must be corrected in order to account for the thermal population of low-lying excited states at the temperatures of s-process nucleosynthesis, in particular of the important state at 9.75 keV. This correction represents a crucial step in the interpretation of the {sup 187}Os/{sup 187}Re pair as a cosmochronometer.

Mosconi, M.; Heil, M.; Kaeppeler, F.; Plag, R.; Mengoni, A. [Karlsruhe Institute of Technology (KIT), Campus Nord, Institut fuer Kernphysik, D-76021 Karlsruhe (Germany); International Atomic Energy Agency, Nuclear Data Section, A-1400 Vienna (Austria)

2010-07-15

92

Bromine--rare-gas electron-transfer and electron-loss cross sections at 15--130-keV collision energies  

SciTech Connect

Measurements are reported of the cross sections for the capture and loss of an electron by 15--130-keV bromine atoms during single collisions with rare-gas atoms. The bromine data fit well with similar data for the other halogens. The electron-capture cross sections peak at collision velocities that agree with the simple two-state model. Competition between target ionization and beam ionization, which is determined by relative ionization potentials, seems to account for the observed differences in the electron-loss cross sections.

Hird, B.; Elrick, B.M.; Lacasse, H.; LaCasse, J.H.; Tume, P. (Ottawa-Carleton Institute for Physics, Ottawa University Campus, Ottawa, Ontario, Canada K1N6N5 (CA))

1990-05-01

93

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

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

94

Stellar neutron capture on 180 Tam . I. Cross section measurement between 10 keV and 100 keV  

NASA Astrophysics Data System (ADS)

The neutron capture cross section of 180 Tam has been measured at energies between 10 keV and 100 keV in a time-of-flight experiment at the Karlsruhe 3.7 MV Van de Graaff accelerator. Neutrons were produced via the 7Li ( p,n ) 7Be reaction by bombarding metallic Li targets with a pulsed proton beam, and gold was used as a cross section standard. Though the world supply of enriched 180 Tam was available for this experiment, the sample consisted of only 150 mg Ta2 O5 with a 180 Tam content of only 5.5% . The difficult separation of the comparably few capture events in 180 Tam from the much larger background due to captures in 181 Ta could be achieved by means of the Karlsruhe 4? barium fluoride detector, taking advantage of its combination of high efficiency, good energy resolution, and high granularity. The cross section was determined with an overall uncertainty of better than 10% in the energy range from 30 keV to 100 keV and could be used for renormalizing statistical model calculations in the entire energy range of astrophysical interest, which had predicted about two times larger values. Based on these first experimental data, Maxwellian averaged neutron capture cross sections were calculated for thermal energies between kT=8 keV and 100 keV .

Wisshak, K.; Voss, F.; Arlandini, C.; Käppeler, F.; Heil, M.; Reifarth, R.; Krti?ka, M.; Be?vá?, F.

2004-05-01

95

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

E-print Network

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

Danon, Yaron

96

OSLD energy response performance and dose accuracy at 24 - 1250 keV: Comparison with TLD-100H and TLD-100  

SciTech Connect

OSLD was evaluated in terms of energy response and accuracy of the measured dose in comparison with TLD-100H and TLD-100. The OSLD showed a better energy response performance for H{sub p}(10) whereas for H{sub p}(0.07), TLD-100H is superior than the others. The OSLD dose accuracy is comparable with the other two dosimeters since it fulfilled the requirement of the ICRP trumpet graph analysis.

Kadir, A. B. A. [School of Applied Physics, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Malaysia and Secondary Standard Dosimetry Laboratory (SSDL), Malaysia Nuclear Agency, Bangi, 43000 Kajang (Malaysia); Priharti, W.; Samat, S. B. [School of Applied Physics, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 UKM Bangi (Malaysia); Dolah, M. T. [Secondary Standard Dosimetry Laboratory (SSDL), Malaysia Nuclear Agency, Bangi, 43000 Kajang (Malaysia)

2013-11-27

97

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

98

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

99

Grazing incidence imaging from 10 to 40 keV Martin Elvis, Daniel G. Fabricant, and Paul Gorenstein  

E-print Network

Grazing incidence imaging from 10 to 40 keV Martin Elvis, Daniel G. Fabricant, and Paul Gorenstein The prospects for imaging x rays at energies from 10 to 40 keV with grazing incidence optics are explored glass was measured at small grazing angles (25-5 min of arc) at energies of 8,17, and 26 keV. High

Elvis, Martin

100

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

101

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

NASA Technical Reports Server (NTRS)

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

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

1977-01-01

102

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

NASA Technical Reports Server (NTRS)

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

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

1977-01-01

103

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

NASA Astrophysics Data System (ADS)

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

Liamsuwan, T.; Nikjoo, H.

2013-02-01

104

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

SciTech Connect

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

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

2010-06-20

105

Quasistellar spectrum for neutron activation measurements at kT=5keV  

NASA Astrophysics Data System (ADS)

We have measured the neutron energy spectrum of the 18O(p,n)18F reaction at a proton energy of 2582 keV, 8 keV above the reaction threshold. At this energy the resulting neutron spectrum resembles almost perfectly a Maxwellian distribution at a thermal energy of kT=5.1±0.1keV. Since all neutrons are emitted in a forward cone of 140? opening angle, this reaction can be used for neutron activation measurements similar to the 7Li(p,n)7Be reaction, which is known for producing a thermal spectrum with kT=25keV. Measured neutron capture cross sections at kT=5.1keV and kT=25keV can be used to interpolate to kT=8keV, which characterizes the dominant neutron exposure during s-process nucleosynthesis in thermally pulsing low-mass AGB stars. In a first application of this new method the Maxwellian-averaged neutron capture cross section of 138Ba was measured to be /vT=13.0±0.5mb at kT=5.1keV.

Heil, M.; Dababneh, S.; Juseviciute, A.; Käppeler, F.; Plag, R.; Reifarth, R.; O'Brien, S.

2005-02-01

106

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

NASA Technical Reports Server (NTRS)

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

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

1972-01-01

107

Characterization of a silicon strip detector for photon-counting spectral CT using monoenergetic photons from 40 keV to 120 keV  

NASA Astrophysics Data System (ADS)

Background: We are developing a segmented silicon strip detector that operates in photon-counting mode and allows pulse-height discrimination with 8 adjustable energy bins. In this work, we determine the energy resolution of the detector using monoenergetic x-ray radiation from 40 keV to 120 keV. We further investigate the effects of pulse pileup and charge sharing between detector channels that may lead to a decreased energy resolution. Methods: For each incident monochromatic x-ray energy, we obtain count spectra at different photon fluxes. These spectra corresponds to the pulse-height response of the detector and allow the determination of energy resolution and charge-sharing probability. The energy resolution, however, is influenced by signal pileup and charge sharing. Both effects are quantified using Monte Carlo simulations of the detector that aim to reproduce the conditions during the measurements. Results: The absolute energy resolution is found to increase from 1.7 to 2.1 keV for increasing energies 40 keV to 120 keV at the lowest measured photon flux. The effect of charge sharing is found to increase the absolute energy resolution by a factor of 1.025 at maximum. This increase is considered as negligibly small. The pileup of pulses leads to a deterioration rate of the energy resolution of 4 · 10-3 keV Mcps-1 mm2, corresponding to an increase of 0.04keV per 10 Mcps increase of the detected count rate.

Liu, Xuejin; Bornefalk, Hans; Chen, Han; Danielsson, Mats; Karlsson, Staffan; Persson, Mats; Xu, Cheng; Huber, Ben

2014-03-01

108

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

SciTech Connect

A search for an anomalous n-p scattering from a polyethylene sample (CH{sub 2}) 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 H{sub 2}O 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. [Physics Department, Ben-Gurion University of the Negev, Beer-Sheva 84120 (Israel); Block, R. C.; Danon, Y. [Gaerttner LINAC Laboratory, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States)

2009-01-28

109

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

E-print Network

Sky maps are powerful visualisation tools for quicklook analysis of extended sources. The latest sky map in soft X-rays (0.1-2.4 keV) has been created in 90ies using ROSAT data. By analyzing publically available data from XMM-Newton X-ray mission we constructed new sky maps in two energy bands -- 2-5 keV and 5-10 keV, complementary to ROSAT data, covering about 1% of all sky, and included them to our web-based tool http://skyview.virgoua.org.

Savchenko, Denis

2014-01-01

110

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

NASA Technical Reports Server (NTRS)

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

Garmire, G. P.

1974-01-01

111

Experimental Research on 0.5 - 10 keV High-Energy Process Resulting from H2 and D2 Ions Flux Interaction with Cathode Solid in Electric Discharge  

Microsoft Academic Search

X-ray emission ranging 0.5 - 10.0 keV with the dose power rate up to 0.01 J\\/s emanating from the cathode solid in the high-current Glow Discharge has been registered in earlier experiments. The X-rays were recorded during the Glow Discharge operation and after the Glow Discharge current switch off. Presumably the observed X-ray emission proceeds as a result of relaxation

A. B. Karabut

112

Ultrafast 25 keV backlighting for experiments on Z.  

SciTech Connect

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

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

2010-11-01

113

Ultrafast 25 keV backlighting for experiments on Z.  

SciTech Connect

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

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

2010-10-01

114

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

115

The TIGRE desktop prototype results for 511 and 900 keV gamma rays  

Microsoft Academic Search

A small desktop prototype of the Tracking and Imaging Gamma-Ray Experiment (TIGRE) has been assembled and tested at 511 keV and 900 keV. TIGRE was designed to observe cosmic gamma ray sources at energies of 0.3 to 100 MeV. Its major feature is its use of multi-layer silicon strip detectors to track Compton recoil electrons and positron-electron pairs. Our small

T. J. O'Neill; D. Bhattacharya; S. Blair; G. Case; O. T. Tumer; R. S. White; A. D. Zych

1995-01-01

116

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

Microsoft Academic Search

Depth graded multilayer designs for hard x-ray telescopes in the 10 keV to 70-80 keV energy range have had either W or Pt as the heavy element. These materials have been chosen because of reasonable optical constants, the possibility to grow smooth interfaces with the spacer material, and the stability over time. On the flip side both W and Pt

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

2007-01-01

117

Measurement of the neutron capture cross section of the s-only isotope Pb204 from 1 eV to 440 keV  

Microsoft Academic Search

The neutron capture cross section of Pb204 has been measured at the CERN n_TOF installation with high resolution in the energy range from 1 eV to 440 keV. An R-matrix analysis of the resolved resonance region, between 1 eV and 100 keV, was carried out using the SAMMY code. In the interval between 100 keV and 440 keV we report

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

2007-01-01

118

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

SciTech Connect

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

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

2010-02-15

119

Electron bremsstrahlung angular-distribution fits for atomic numbers 1 less than or equal to Z less than or equal to 92, and incident-electron energies 1 keV less than or equal to T less than or equal to 500 keV  

SciTech Connect

The analytic fit of a simple expression to the electron bremsstrahlung angular distribution cross section d/sup 2/sigma/dkd..cap omega.. (differential in the emitted photon energy k and angle ..cap omega..) is investigated. Optimal choices for the fit parameters are determined and fit coefficients are tabulated for a large number of neutral-atom cases. Results are also presented for fits to the relativistic Coulomb-Born approximation. Comparisons between the screened neutral-atom results and the Coulomb-Born results are made. Discrepancies reported to exist between angular distribution cross sections and fit coefficients published by Tseng, Pratt and Lee are confirmed and understood in terms of their choice of fit weight function.

Kissel, L.

1982-01-01

120

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

121

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

122

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

123

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

NASA Technical Reports Server (NTRS)

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

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

2007-01-01

124

Scaling of keV HHG photon yield with drive wavelength.  

PubMed

We study semi-analytically and numerically the photon yield of high harmonic generation (HHG) on the level of the single atom response under ideal conditions: no initial depletion of the ground state prior to the main peak of the pump pulse. We show that the yield decreases exponentially as function of the cutoff energy starting at about 0.5keV in the case of a Ti:sapphire source and a helium target. We show that the yield in helium beyond the 1keV energy range can be increased by orders of magnitude when long wavelength driver sources in the range from 1.5 mum to 3 mum are used. This finding leads to the conclusion that significant HHG beyond 1keV is possible through long wavelength driver pulses. PMID:19495190

Gordon, Ariel; Kärtner, Franz

2005-04-18

125

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

126

Static and time-resolved 10-1000 keV x-ray imaging detector options for NIF  

SciTech Connect

High energy (>10 keV) x-ray self-emission imaging and radiography will be essential components of many NIF high energy density physics experiments. In preparation for such experiments, we have evaluated the pros and cons of various static [x-ray film, bare charge-coupled device (CCD), and scintillator + CCD] and time-resolved (streaked and gated) 10-1000 keV detectors.

Landen, O.L.; Bell, P.M.; McDonald, J.W.; Park, H.-S.; Weber, F.; Moody, J.D.; Lowry, M.E.; Stewart, R.E. [Lawrence Livermore National Laboratory, Livermore, California USA 94551-0808 (United States)

2004-10-01

127

Polarized Radiative Capture Reactions below 100 keV, a New Laboratory for Nuclear Physics.  

NASA Astrophysics Data System (ADS)

Despite the importance of low energy radiative capture reactions in nuclear astrophysics, very little is known and very few measurements have been made below 100 keV. The energy change of a factor of 100 as we go from 1 to 100 keV can be accompanied by huge changes in proton penetrabilities (of the order of 10^8), making extrapolations difficult. Although meson-exchange current effects are known to be important at thermal energies, no studies of these effects have been performed at finite low-energies. The availability of large high-resolution Germanium detectors (HPGe) and high intensity polarized beams has made it possible to begin to study these reactions between 10 and 100 keV in considerable detail. Our study of the D(p, ?)^3He and the ^1H(d, ?)^3He reactions using polarized beams below 80 keV has revealed a wealth of new information. The energy dependence of the cross section below 80 keV was determined experimentally for the first time. Our results indicate an astrophysical S-factor which is 34% smaller than the presently accepted value. Our detailed measurements of cross section, vector and tensor analyzing powers, and gamma-ray polarizations as a function of energy and angle have been compared with the results of new few-body calculations by Schiavilla et al.(R. Schiavilla, CEBAF Theory Group, private communication (1995).) which include Coulomb and MEC effects. Dramatic effects due to the tensor force and the associated two-body currents are observed in the vector and tensor analyzing powers for the first time. A detailed study of the ^7Li(p, ?)^8Be reaction has revealed the presence of a significant p-wave capture amplitude at these energies which affects the extrapolation used to obtain the S-factor. A recent measurement of the ^7Li(p, ?_3)^8Be (2^+, T=0+1) reaction has been performed using polarized protons below 80 keV. This reaction is especially interesting due to its close relationship to the ^7Be(p, ?)^8B (2^+, T=1) reaction, the source of high energy solar neutrinos. The results of this work and preliminary studies of several other reactions below 80 keV will be described. Work partially supported by USDOE grant No. DEFG05-91-ER40619

Weller, H. R.

1996-05-01

128

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

2013-12-16

129

Astrophysical radiative neutron capture on 10B taking into account resonance at 475 keV  

E-print Network

The possibility of the description of the available experimental data for cross sections of the neutron capture reaction on 10B at thermal and astrophysical energies, taking into account the resonance at 475 keV, was considered within the framework of the modified potential cluster model with forbidden states and accounting for the resonance behavior of the scattering phase shifts.

Sergey Dubovichenko; Albert Dzhazairov-Kakhramanov

2013-12-17

130

Degradation of 81 keV 133Xe Gamma-Rays into the 31 keV X-Ray Peak in CsI Scintillators  

SciTech Connect

ABSTRACT Pacific Northwest National Laboratory uses beta-gamma coincidence detectors in a number of xenon sampling and/or measurement systems to enable simultaneous, sensitive measurements of 131Xe, 133Xe, 133mXe, and 135Xe for treaty monitoring applications. In recent years, a new style of beta-gamma detector was developed to improve upon the detector module used in the Automated Radioxenon Sampler/Analyzer. The results of an MCNP5 Monte Carlo simulation of the new detector cell are presented, with particular emphasis on the identification of an energy deposition sequence with the potential to introduce significant error into the detector efficiency calibration. This sequence occurs when an 81 keV gamma from 133Xe is absorbed in an inactive region of the CsI(Na) scintillator, followed by emission of a 31 keV x-ray from cesium (or possibly a 28.5 keV x-ray from iodine). These x-rays add excess counts into the 31 keV peak observed in the decay of 133Xe. The impact of this effect on different efficiency calibration techniques is discussed.

Keillor, Martin E.; Cooper, Matthew W.; Hayes, James C.; McIntyre, Justin I.

2009-12-03

131

A 40 keV cyclotron for radioisotope dating  

NASA Astrophysics Data System (ADS)

We have built and begun testing a small low energy negative ion cyclotron for direct detection of 14C. At present, the cyclotron is operated in a high resolution mode at the 31st harmonic, with 1-2 kV on the dees. The high harmonic and a minimum number of turns of approximately 100, should give a fwhm mass resolution of about {1}/{30000} — sufficient to suppress the background from molecular ions such as 13CH -. Background such as scattered ions of 12C - and 13C - should be totally suppressed by the cyclotron acceleration process. (At the 88? cyclotron at LBL we found that ions only 1% off-resonance are suppressed by more than a factor of 10 17.) A miniature Cs sputter source located at the center of the cyclotron is expected to provide more than 1 ?A of negative carbon ions. Negative ions are used in order to eliminate the interference from 14N. Unlike high energy cyclotrons, focussing is obtained solely from the axial components of the accelerating electric field. The magnetic field is kept flat to within 1 part in 10 4 in order to maintain exact isochronism throughout the several thousand accelerating rf cycles. The low final energy of 40 keV eliminates any danger from radiation or need for shielding, and the final orbit radius of only 10.5 cm, reduce the size and cost of the machine to that of conventional mass spectrometers.

Welch, James J.; Bertsche, Kirk J.; Friedman, Peter G.; Morris, Donald E.; Muller, Richard A.; Tans, Pieter P.

1984-11-01

132

A neutron source to measure stellar neutron capture cross sections at kT=5 keV  

NASA Astrophysics Data System (ADS)

Since 1980 the 7Li(p,n)7Be reaction was intensively used for activation measurements. With a proton energy of E=1911 keV the resulting neutron spectrum resembles a Maxwell-Boltzmann distribution with a thermal energy of kT=25 keV. Therefore, this neutron source is ideal to determine Maxwellian-averaged neutron capture cross sections (MACS) close to a temperature of 250 million Kelvin (kT=23 keV) which is typical for the s process in red giant stars. Meanwhile, detailed stellar models indicate that the dominant neutron exposure of the main s-process component in low mass AGB stars occurs at a lower temperature of 90 million Kelvin (kT=8 keV). Hence, the necessary stellar reaction rates had to be extrapolated from 25 keV to the lower thermal energy. In order to avoid the corresponding additional uncertainties, we report on the 18O(p,n)18F neutron source, which allows one to produce a Maxwell-Boltzmann spectrum close to the lower thermal energy of kT=8 keV. First results of activation measurements for 138Ba(n,?)139Ba, 139La(n,?)140La, and 175Lu(n,?)176Lum will be presented.

Heil, M.; Dababneh, S.; Käppeler, F.; Plag, R.; Juseviciute, A.; Winckler, N.; Reifarth, R.; O'Brien, S.

2005-07-01

133

Special State Standard of absorbed dose unit of x-ray radiation with maximum photon energy from 3 to 9 fJ (20–60 keV)  

Microsoft Academic Search

The special State standard reproduces the absorbed dose unit of x-ray radiation in an absorber within the range from 1 to 5 J\\/kg. The unit is reproduced by calorimetric techniques which is the only method of direct and absolute measurement of absorbed radiation energy. In compliance with the ICRU recommendations, the absorber material is graphite. The block diagram of the

R. F. Kononova; A. P. Sebekin; V. I. Fominykh; M. F. Yudin

1976-01-01

134

The ^14N(p,?_o)^15O Reaction below 140 keV  

NASA Astrophysics Data System (ADS)

The capture reaction ^14N(p,?)^15O is the limiting reaction in the CNO cycle. Very little data exists at beam energies below the Ep = 278 keV resonance for this reaction(U. Schroder et al., Nucl. Phys. A467) 240 (1987).^,(W. Lamb and R. Hester, Phys. Rev. 108) 1304 (1957).. Using a 140 keV polarized proton beam and a thick frozen trideuterio ammonia (ND_3) target, we have measured the astrophysical S-factor for the reaction relative to the S-factor for the D(p,?)^3He reaction in this energy region. The outgoing gamma rays were detected in a 140% HPGe detector. The D(p,?)^3He reaction also provided a convenient reference for the energy calibration of this detector. Preliminary analysis suggests that the S-factor for the ^14N(p,?_o)^15O reaction in this energy range is significantly larger than previously assumed^2.

Nelson, S. O.; Kelley, J. H.; Canon, R. S.; Schreiber, E. C.; Saburov, K.; Wulf, E. A.; Weller, H. R.; Prior, R. M.; Spraker, M.; Tilley, D. R.

1999-10-01

135

Search for time variations in 511 KeV flux by ISEE-3 gamma-ray spectrometer  

Microsoft Academic Search

The ISEE-3 gamma-ray spectrometer has provided nearly continuous monitoring of the cosmic gamma-ray background in the energy regime 125 keV to 6.5 MeV since launch of the satellite in August 1978. The data has been analyzed for possible variations in the cosmic 511 keV line flux. The detector is an unshielded, radiatively-cooled, high-purity germanium crystal with a sensitive volume 33

Jay P. Norris; Thomas L. Cline; Bonnard J. Teegarden

1982-01-01

136

Modeling of the bremsstrahlung radiation produced in pure-element targets by 10-40 keV electrons  

Microsoft Academic Search

A new global relationship has been developed for predicting electron-excited bremsstrahlung intensities over a wide range of accelerating voltages 10--40 keV, atomic numbers 4--92, and x-ray energies 1.5--20 keV. The new relationship was determined empirically from the mathematical modeling of extensive data and is designed for calculating bremsstrahlung intensities in analytical procedures, such as those requiring peak-to-background measurements, where the

John A. Small; Stefan D. Leigh; Dale E. Newbury; Robert L. Myklebust

1987-01-01

137

Modeling of the bremsstrahlung radiation produced in pure-element targets by 10–40 keV electrons  

Microsoft Academic Search

A new global relationship has been developed for predicting electron-excited bremsstrahlung intensities over a wide range of accelerating voltages 10–40 keV, atomic numbers 4–92, and x-ray energies 1.5–20 keV. The new relationship was determined empirically from the mathematical modeling of extensive data and is designed for calculating bremsstrahlung intensities in analytical procedures, such as those requiring peak-to-background measurements, where the

John A. Small; Stefan D. Leigh; Dale E. Newbury; Robert L. Myklebust

1987-01-01

138

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

139

Quasi-monoenergetic 200 keV photon field using a radioactive source with backscatter layout  

NASA Astrophysics Data System (ADS)

A quasi-monoenergetic photon field with energy of ?200 keV was obtained using a radioactive source with a backscatter layout. The backscatter layout allows the calibration of a dosimeter for two different energies with a single radioactive source. The setup was optimized through calculations and experiments to minimize the low energy component and to obtain field uniformity. The optimal backscatter layout was found to comprise a 1 × 1 m2 steel floor, a radioactive source placed 20 cm above the floor, and a 10-cm cubic lead block placed directly above the source. Under the proposed layout and using a 208-MBq Cs-137 source, a monoenergetic photon field with 190 ± 9.6 keV (FWHM) and a dose rate of 3.18 ± 0.18 µSv/h was obtained within a 10 × 10 × 10 cm3 area, at a distance of 15 to 25 cm above the lead block.

Tajudin, Suffian M.; Namito, Yoshihito; Sanami, Toshiya; Hirayama, Hideo

2014-11-01

140

Monitoring the >100 keV Gamma-Ray Sky Using GBM: The First Two Years  

NASA Astrophysics Data System (ADS)

The Gamma-Ray Burst Monitor (GBM) onboard Fermi is being used to monitor hard x-ray/soft gamma-ray sources in the energy range of 8-1000 keV using the Earth occultation technique. Through the first two years of this monitoring program, eight sources have been detected at energies above 100 keV, including six persistent sources (Crab, Cyg X-1, Cen A, 1E 1740-29, SWIFT J1753.5-0127, and GRS 1915+105) and two transients (XTE J1752-223 and GX 339-4). Light curves of all eight sources using the GBM 8-channel CTIME data are presented along with discussion of the high energy behavior.

Case, G. L.; Camero-Arranz, A.; Chaplin, V.; Cherry, M. L.; Finger, M. H.; Jenke, P.; Rodi, J.; Wilson-Hodge, C. A.

2010-10-01

141

STEREO/IMPACT Observations of Foreshock Electrons from 10 eV-100 keV  

NASA Astrophysics Data System (ADS)

Solar wind electrons are accelerated and reflected back upstream by the terrestrial bow shock into a region known as the electron foreshock. Observed spectra at low energies are consistent with a fast Fermi process, which is dependent on the conservation of the adiabatic moment of the accelerated electrons. In the early part of its mission, the STEREO spacecraft observed many examples of electron beams in the terrestrial foreshock. The combined capabilities of the SWEA and STE instruments on STEREO can measure the electron foreshock spectrum from 10 eV to 100 keV. The highest observed accelerated electron energies can reach up to several tens of keV. These energies are of particular interest because electrons at keV energies and higher have Larmor radii of tens of km or greater, comparable to the scale sizes of the shock. Therefore, the adiabatic condition no longer applies. We compare the observed STEREO foreshock electron energy spectra with predictions based on a Liouville mapping of the observed upstream spectra through a shock interaction, and discuss implications for the fast Fermi theory.

Pulupa, M.; Bale, S.; Lin, R. P.; Larson, D. E.

2010-12-01

142

Implications of the 17 keV neutrino  

SciTech Connect

Constraints on the theoretical interpretation of the 17 keV neutrino are reviewed. A simple understanding of the 17 keV neutrino is provided by flavon models, which involve the spontaneous breaking of Abelian lepton symmetries and have only the usual three light neutrino species. Signatures for this class of models include neutrino oscillations, tau decay to an electron and a flavon, and invisible decay modes of the Higgs boson to two flavons.

Hall, L.J.

1991-06-01

143

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

144

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

PubMed Central

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

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

2014-01-01

145

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

146

Trapping and replacement of 1-14 keV hydrogen and deuterium in 316 stainless steel  

Microsoft Academic Search

Trapping of deuterium with energies between one and 14 keV implanted into 316 stainless steel has been studied as a function of implant energy at a target temperature of 150 K; replacement behavior occurring after saturation also receives attention. The replacement of trapped deuterium atoms in the saturated stainless steel lattice is investigated by switching the implant beam from D(+)

R. S. Blewer; R. Behrisch; B. M. U. Scherzer; R. Schulz

1978-01-01

147

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

148

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

Microsoft Academic Search

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

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

2003-01-01

149

Coherent keV backscattering from plasma-wave boosted relativistic electron mirrors  

E-print Network

A new parameter regime of laser wakefield acceleration driven by sub-petawatt femotsecond lasers is proposed, which enables the generation of relativistic electron mirrors further accelerated by the plasma wave. Integrated particle-in-cell simulation including the mirror formation and Thomson scattering demonstrates that efficient coherent backscattering up to keV photon energy can be obtained with moderate driver laser intensities and high density gas targets.

Li, F Y; Chen, M; Wu, H C; Liu, Y; Meyer-ter-Vehn, J; Mori, W B; Zhang, J

2014-01-01

150

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

NASA Astrophysics Data System (ADS)

The solar corona is the brightest source of X-rays in the solar system, and the X-ray emission is highly variable on many time scales. However, the actual solar soft X-ray (SXR) (0.5-5 keV) spectrum is not well known, particularly during solar quiet periods, as, with few exceptions, this energy range has not been systematically studied in many years. Previous observations include high-resolution but very narrow-band spectra from crystal spectrometers (e.g., Yohkoh/BCS), or integrated broadband irradiances from photometers (e.g., GOES/XRS, TIMED/XPS, etc.) that lack detailed spectral information. In recent years, broadband measurements with moderate energy resolution (~0.5-0.7 keV FWHM) were made by SphinX on CORONAS-Photon and SAX on MESSENGER, although they did not extend to energies below ~1 keV. We present observations of solar SXR emission obtained using new instrumentation flown on recent SDO/EVE calibration rocket underflights. The photon-counting spectrometer, a commercial Amptek X123 with a silicon drift detector and an 8 ?m Be window, measures the solar disk-integrated SXR emission from ~0.5 to >10 keV with ~0.15 keV FWHM resolution and 1 s cadence. A novel imager, a pinhole X-ray camera using a cooled frame-transfer CCD (15 ?m pixel pitch), Ti/Al/C filter, and 5000 line/mm Au transmission grating, images the full Sun in multiple spectral orders from ~0.1 to ~5 nm with ~10 arcsec/pixel and ~0.01 nm/pixel spatial and spectral detector scales, respectively, and 10 s cadence. These instruments are prototypes for future CubeSat missions currently being developed. We present new results of solar observations on 04 October 2013 (NASA sounding rocket 36.290). We compare with previous results from 23 June 2012 (NASA sounding rocket 36.286), during which solar activity was low and no signal was observed above ~4 keV. We compare our spectral and imaging measurements with spectra and broadband irradiances from other instruments, including SDO/EVE, GOES/XRS, TIMED/XPS, and RHESSI, as well as the SphinX observations during the deep solar minimum of 2009. Using newly-developed computational methods, we analyze the differential emission measure (DEM) of the solar corona, and discuss the possible implications for X-ray-producing physical processes in the quiescent corona.

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

2013-12-01

151

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

152

3 keV to 2 MeV observations of four gamma-ray bursts  

NASA Astrophysics Data System (ADS)

Simultaneous X and gamma ray spectra were obtained for four gamma ray burst events using satellite instrumentation. The P78-1 satellite proportional counters recorded X-ray data in the 3-10 keV range, while Pioneer Venus Orbiter and ISEE 3 sensors had a 3 keV lower limit for events. The positively correlated data covered the events GB 790307, 790325, 790504, and 790731. The time histories of the X and gamma ray energies did not correlate well. The post-gamma ray phase of GB 790307 displayed features of simple cooling, and in conjunction with soft X-ray data suggested an origin in an optically thin fireball. However, the data were equally well-fitted by a model of an emitting hot spot on a neutron star. The data negated any concept that gamma ray bursts evolve similarly to classical X-ray bursts.

Laros, J. G.; Evans, W. D.; Fenimore, E. E.; Klebesadel, R. W.; Shulman, S.; Fritz, G.

1984-11-01

153

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

NASA Astrophysics Data System (ADS)

We present a high-brightness 24-keV electron-impact microfocus x-ray source based on continuous operation of a heated liquid-indium/gallium-jet anode. The 30-70 W electron beam is magnetically focused onto the jet, producing a circular 7-13 ?m full width half maximum x-ray spot. The measured spectral brightness at the 24.2 keV In K? line is 3 × 109 photons/(s × mm2 × mrad2 × 0.1% BW) at 30 W electron-beam power. The high photon energy compared to existing liquid-metal-jet sources increases the penetration depth and allows imaging of thicker samples. The applicability of the source in the biomedical field is demonstrated by high-resolution imaging of a mammography phantom and a phase-contrast angiography phantom.

Larsson, D. H.; Takman, P. A. C.; Lundström, U.; Burvall, A.; Hertz, H. M.

2011-12-01

154

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

PubMed

We present a high-brightness 24-keV electron-impact microfocus x-ray source based on continuous operation of a heated liquid-indium/gallium-jet anode. The 30-70 W electron beam is magnetically focused onto the jet, producing a circular 7-13 ?m full width half maximum x-ray spot. The measured spectral brightness at the 24.2 keV In K(?) line is 3 × 10(9) photons?(s × mm(2) × mrad(2) × 0.1% BW) at 30 W electron-beam power. The high photon energy compared to existing liquid-metal-jet sources increases the penetration depth and allows imaging of thicker samples. The applicability of the source in the biomedical field is demonstrated by high-resolution imaging of a mammography phantom and a phase-contrast angiography phantom. PMID:22225218

Larsson, D H; Takman, P A C; Lundström, U; Burvall, A; Hertz, H M

2011-12-01

155

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

SciTech Connect

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

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

2011-12-15

156

Energetic (greater than 100 keV) O(+) ions in the plasma sheet  

NASA Technical Reports Server (NTRS)

The first measurements of very energetic (112 - 157 keV) O(+) ions in the earth's magnetosphere are presented. The observations were made with the UMd/MPE ULECA sensor on ISEE-1 on 5 March 1981 at geocentric distances approximately 20 R(E) in the earth's magnetotail. During this time period an Energetic Storm Particle event was observed by the nearly identical sensor on the ISEE-3 spacecraft, located approximately 250 R(E) upstream of the earth's magnetosphere. The ISEE-1 sensor observed a similar temporal profile except for several sharp intensity enhancements, corresponding to substorm recoveries during which the plasma sheet engulfed the spacecraft. During these plasma sheet encounters we observe O(+)/H(+) abundance ratios, at approximately 130 kev, as large as 0.35. In between plasma sheet encounters the O(+)/H(+) ratio at this energy is consistent with zero.

Ipavich, F. M.; Galvin, A. B.; Gloeckler, G.; Hovestadt, D.; Klecker, B.; Scholer, M.

1984-01-01

157

Energetic (>100 keV) 0/sup +/ ions in the plasma sheet  

SciTech Connect

We present the first measurements of very energetic (112-157 keV) 0/sup +/ ions in the earth's magnetosphere. The observations were made with the UMd/MPE ULECA sensor on ISEE-1 on 5 March 1981 at geocentric distances approx.20 R/sub E/ in the earth's magnetotail. During this time period an Energetic Storm Particle event was observed by our nearly identical sensor on the ISEE-3 space-craft, located approx.250 R/sub E/ upstream of the earth's magnetosphere. The ISEE-1 sensor observed a similar temporal profile except for several sharp intensity enhancements, corresponding to substorm recoveries during which the plasma sheet engulfed the spacecraft. During these plasma sheet encounters we observe 0/sup +//H/sup +/ abundance ratios, at approx.130 keV, as large as 0.35. In between plasma sheet encounters with 0/sup +//H/sup +/ ratio at this energy is consistent with zero.

Ipavich, F.M.; Galvin, A.B.; Gloeckler, G.; Hovestadt, D.; Klecker, B.; Scholer, M.

1984-05-01

158

The 511 keV emission from positron annihilation in the Galaxy  

SciTech Connect

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

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

2011-07-01

159

Comparison of solar flare X-ray producing and escaping electrons from about 2 to 100 keV  

NASA Technical Reports Server (NTRS)

Using observations from the ISEE-3 spacecraft, the X-ray producing electrons and escaping electons from a solar flare on November 8, 1978 are compared. The instantaneous 5 to 75 keV electron spectrum in the X-ray producing region is computed from the observed bremsstrahlung X-ray spectrum. Assuming that energy loss by Coulomb collisions (thick target) is the dominant electron loss process, the accelerated electron spectrum is obtained. The energy spectrum of the escaping electrons observed from 2 to 100 keV differs significantly from the spectra of the X-ray producing electrons and of the accelerated electrons, even when the energy loss which the escaping electrons experienced during their travel from the sun to the earth is taken into account. The observations are consistent with a model where the escaping electons come from an extended X-ray producing region, which ranges from the chromosphere to high in the corona. In this model, the low energy escaping electrons (2-10 keV) come from the higher part of the extended X-ray source where the overlying column density is low, while the high energy electrons (20-100 keV) come from the entire X-ray source.

Pan, L.-D.; Lin, R. P.; Kane, S. R.

1984-01-01

160

Secondary ion emission under keV carbon cluster bombardment  

E-print Network

projectile for SIMS. The secondary ion yields (i.e., the number of secondary ions detected per projectile impact) from impacts of 10-26 keV C24H12+, C60+, gramicidin S+ and C60F40+ projectiles were examined to compare the effectiveness of the projectiles...

Locklear, Jay Edward

2006-10-30

161

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

162

Origin of the 6.4-keV line of the Galactic Ridge X-ray Emission - First Report -  

NASA Astrophysics Data System (ADS)

We report the first results from high-statistics observation of the 6.4-keV line in the region of $l= +1.5^\\circ$ to $+3.5^\\circ$ (hereafter referred to as GC East), with the goal to uncover the origin of the Galactic ridge X-ray emission (GRXE). By comparing this data with that from the previous observations in the region $l=-1.5^\\circ$ to $-3.5^\\circ$ (hereafter referred to as GC West), we discovered that the 6.4-keV line is asymmetrically distributed with respect to the Galactic center, whereas the 6.7-keV line is symmetrically distributed. The distribution of the 6.4-keV line follows that of $^{13}$CO and its flux is proportional to the column density of the molecular gas. This correlation agrees with that seen between the 6.4-keV line and the cold interstellar medium (ISM) (H$_{\\rm I}$ $+$ H$_2$) in the region $|l|>4^\\circ$. This result suggests that the 6.4-keV emission is diffuse fluorescence from the cold ISM not only in GC East and West but also in the entire Galactic plane. This observational result suggests that the surface brightness of the 6.4-keV line is proportional to the column density of the cold ISM in the entire Galactic plane. For the ionizing particles, we consider X-rays and low energy cosmic-ray protons and electrons .

Tsuru, T. G.; Uchiyama, H.; Nobukawa, K. K.; Nobukawa, M.; Nakashima, S.; Koyama, K.; Torii, K.; Fukui, Y.

2014-09-01

163

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

NASA Technical Reports Server (NTRS)

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

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

2006-01-01

164

Depth selective Mössbauer spectroscopy: Analysis and simulation of 6.4 keV and 14.4 keV spectra obtained from rocks at Gusev Crater, Mars, and layered laboratory samples  

NASA Astrophysics Data System (ADS)

The miniaturized Mössbauer spectrometer (MIMOS) II Mössbauer spectrometers on the Mars Exploration Rovers (MER) simultaneously obtained 6.4 keV and 14.4 keV Mössbauer spectra from rock and soil targets. Because photons with lower energy have a shallower penetration depth, 6.4 keV spectra contain more mineralogical information about the near-surface region of a sample than do 14.4 keV spectra. The influence of surface layers of varying composition and thickness on Mössbauer spectra was investigated by Monte Carlo simulation and by measurement using a copy of the MER MIMOS II instrument and samples with one or two layers of known thicknesses. Thin sections of minerals or metallic Fe foil on top of a thick mineral sample were used to produce samples with thin layers of known thickness on a thick substrate. Monte Carlo simulation of MER spectra obtained on the rock Mazatzal, which displays a coating on a basaltic substrate, and other Adirondack Class rocks results in a calculated thickness of 10 ?m for the Mazatzal surface layer. The 6.4 keV spectra obtained on Adirondack Class rocks, on laboratory samples, and in Monte Carlo calculations show an apparent olivine enrichment which is not related to any observable surface layer.

Fleischer, I.; Klingelhöfer, G.; Schröder, C.; Morris, R. V.; Hahn, M.; Rodionov, D.; Gellert, R.; de Souza, P. A.

2008-06-01

165

Evidence for Electron Acceleration up to 300 keV in the Magnetic Reconnection Diffusion Region of Earth's Magnetotail  

E-print Network

the ion diffusion region for the 06:30­10:00 UT interval on 1 April 1999, from the 3D plasma and energeticEvidence for Electron Acceleration up to 300 keV in the Magnetic Reconnection Diffusion Region 2002) We report direct measurements of high-energy particles in a rare crossing of the diffusion region

California at Berkeley, University of

166

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

NASA Astrophysics Data System (ADS)

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

Zhao, Zilong; Li, Junqin; Zhang, Xuemei

2013-10-01

167

Possible Capture of keV Sterile Neutrino Dark Matter on Radioactive beta-decaying Nuclei  

E-print Network

There exists an observed "desert" spanning six orders of magnitude between O(0.5) eV and O(0.5) MeV in the fermion mass spectrum. We argue that it might accommodate one or more keV sterile neutrinos as a natural candidate for warm dark matter. To illustrate this point of view, we simply assume that there is one keV sterile neutrino nu_4 and its flavor eigenstate nu_s weakly mixes with three active neutrinos. We clarify different active-sterile neutrino mixing factors for the radiative decay of nu_4 and beta decays in a self-consistent parametrization. A direct detection of this keV sterile neutrino dark matter in the laboratory is in principle possible since the nu_4 component of nu_e can leave a distinct imprint on the electron energy spectrum when it is captured on radioactive beta-decaying nuclei. We carry out an analysis of its signatures in the capture reactions nu_e + ^{3}H \\to ^{3}He + e^- and nu_e + ^{106}Ru \\to ^{106}Rh + e^- against the beta-decay backgrounds, and conclude that this experimental approach might not be hopeless in the long run.

Y. F. Li; Zhi-zhong Xing

2010-09-29

168

Degeneracy at 1871 keV in {sup 112}Cd and implications for neutrinoless double electron capture  

SciTech Connect

High-statistics {beta}-decay measurements of {sup 112}Ag and {sup 112}In were performed to study the structure of the {sup 112}Cd nucleus. The precise energies of the doublet of levels at 1871 keV, for which the 0{sup +} member has been suggested as a possible daughter state following neutrinoless double electron capture of {sup 112}Sn, were determined to be 1871.137(72) keV (0{sub 4}{sup +} level) and 1870.743(54) keV (4{sub 2}{sup +} level). The nature of the 0{sub 4}{sup +} level, required for the calculation of the nuclear matrix element that would be needed to extract a neutrino mass from neutrinoless double electron capture to this state, is suggested to be of intruder origin.

Green, K. L.; Garrett, P. E.; Demand, G. A.; Grinyer, G. F.; Leach, K. G.; Phillips, A. A.; Schumaker, M. A.; Svensson, C. E.; Wong, J. [Department of Physics, University of Guelph, Guelph, Ontario, N1G 2W1 (Canada); Austin, R. A. E.; Colosimo, S. [Department of Astronomy and Physics, Saint Mary's University, Halifax, Nova Scotia, B3H 3C3 (Canada); Ball, G. C.; Bandyopadhyay, D. S.; Hackman, G.; Morton, A. C.; Pearson, C. J. [TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia, V6T 2A3 (Canada); Cross, D. [Department of Chemistry, Simon Fraser University, Burnaby, British Columbia, V5A 1S6 (Canada); Kulp, W. D.; Wood, J. L. [School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332-0430 (United States); Yates, S. W. [Departments of Chemistry and Physics and Astronomy, University of Kentucky, Lexington, Kentucky 40506-0055 (United States)

2009-09-15

169

Demonstration of a 13-keV Kr K-shell x-ray source at the National Ignition Facility  

NASA Astrophysics Data System (ADS)

We report 3% conversion efficiency of laser energy into Kr K-shell (?13 keV) radiation, consistent with theoretical predictions. This is ?10× greater than previous work. The emission was produced from a 4.1-mm-diameter, 4-mm-tall gas pipe target filled with 1.2 or 1.5 atm of Kr gas. 160 of the National Ignition Facility laser beams deposited ?700 kJ of 3? light into the target in an ?140 TW, 5.0-ns-duration square pulse. The Dante diagnostics measured ?5 TW into 4? solid angle of ?12 keV x rays for ?4 ns, which includes both continuum emission and flux in the Kr He? line at 13 keV.

Fournier, K. B.; May, M. J.; Colvin, J. D.; Barrios, M. A.; Patterson, J. R.; Regan, S. P.

2013-09-01

170

Reply to Two Comments on "Dark matter searches going bananas the contribution of Potassium (and Chlorine) to the 3.5 keV line"  

E-print Network

We respond to two comments on our recent paper, Jeltema & Profumo (2014). The first comment by Boyarsky et al. confirms the absence of a line from M31 in the 3-4 keV energy range, but criticizes the energy range for spectral fitting on the basis that (i) the background model adopted between 3-4 keV is invalid outside that range and that (ii) extending the energy range multiple features appear, including a 3.5 keV line. Point (i) is manifestly irrelevant (the 3-4 keV background model was not meant to extend outside that range), while closer inspection of point (ii) shows that the detected features are inconsistent and likely unphysical. We demonstrate that the existence of an excess near 3.5 keV in the M31 data requires fitting a broad enough energy range such that the background modeling near 3.5 keV is poor to a level that multiple spurious residual features become significant. Bulbul et al. criticize our use of WebGuide instead of the full AtomDB package. While a technically correct remark, this is only...

Jeltema, Tesla

2014-01-01

171

Magnetospheric plasma modeling (0-100 keV)  

Microsoft Academic Search

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

H. B. Garrett; G. C. Spitale

1985-01-01

172

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

173

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

174

Rise time in 20-32 keV impulsive X-radiation  

NASA Technical Reports Server (NTRS)

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

Vorpahl, J. A.; Takakura, T.

1974-01-01

175

Attenuation in the Chest Wall of 20 keV X-rays from an Inhaled Radioactive Aerosol  

Microsoft Academic Search

EXTERNAL counting of the low intensity L uranium X-rays (energies 13.6, 16.9 and 20.2 keV) is a promising technique for the estimation of insoluble compounds of plutonium in the human lung. These low energy radiations are, however, very easily absorbed in the tissues of the chest wall; the half-value thickness (HVT) is about 0.7 cm of soft tissue and only

J. Rundo; B. T. Taylor; D. V. Booker; D. Newton; D. Scargill

1968-01-01

176

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

177

On the effective anisotropy of the 91-1,094 keV ??-cascade in 172Yb  

NASA Astrophysics Data System (ADS)

The suitability of the 91-1,094 keV ??-cascade in 172Lu(172Yb) for perturbed angular correlation studies has been demonstrated several decades ago. In comparison with widely used probe nuclei like 111In or 181Hf its quadrupole moment and anisotropy coefficient are quite large and the life time of the intermediate state is sufficiently long. However, the effective anisotropy observed in actual experiments is generally much lower than the literature value. If this isotope is to be used for any quantitative analysis, especially in solid state investigations, it is very important to understand the origin of this discrepancy since the ratio of these values is directly related to the fraction of probe atoms in any given lattice environment. To this end, the influence of Compton events from competing cascades in the 91 keV start energy window of the 91-1,094 keV ??-cascade was studied in a numerical simulation. It is shown that this Compton background is the main reason for the strong reduction of the observable anisotropy. A relation between the width of the 91 keV energy window and the effective anisotropy is established.

Nédélec, R.; Vianden, R.

2009-07-01

178

Development of a modular CdTe detector plane for gamma-ray burst detection below 100 keV  

E-print Network

We report on the development of an innovative CdTe detector plane (DPIX) optimized for the detection and localization of gamma-ray bursts in the X-ray band (below 100 keV). DPIX is part of an R&D program funded by the French Space Agency (CNES). DPIX builds upon the heritage of the ISGRI instrument, currently operating with great success on the ESA INTEGRAL mission. DPIX is an assembly of 200 elementary modules (XRDPIX) equipped with 32 CdTe Schottky detectors (4x4 mm2, 1 mm thickness) produced by ACRORAD Co. LTD. in Japan. These detectors offer good energy response up to 100 keV. Each XRDPIX is readout by the very low noise front-end electronics chip IDeF-X, currently under development at CEA/DSM/DAPNIA. In this paper, we describe the design of XRDPIX, the main features of the IDeF-X chip, and will present preliminary results of the reading out of one CdTe Schottky detector by the IDeF-X V1.0 chip. A low-energy threshold around 2.7 keV has been measured. This is to be compared with the 12-15 keV threshold of the ISGRI-INTEGRAL and BAT-SWIFT instruments, which both use similar detector material.

M. Ehanno; C. Amoros; D. Barret; K. Lacombe; R. Pons; G. Rouaix; O. Gevin; O. Limousin; F. Lugiez; A. Bardoux; A. Penquer

2007-01-15

179

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

180

Acceleration theory for 5-40 keV ions at interplanetary shocks  

NASA Technical Reports Server (NTRS)

A theory is presented to explain the acceleration of suprathermal ions observed near propagating shocks in the solar wind. The hard power-law spectra of ions of energies 5 to 40 keV are shown to be accounted for by diffusive scattering across a plane shock with a small amount of adiabatic deceleration losses on both sides of the shock. The theory fits the observations of the event of November 25, 1977, which followed a large solar flare, and indicates a mean free path perpendicular to the shock of less than 0.0003 AU behind the shock and 0.01 AU in front of it. The theory also predicts a steepening ion energy spectrum at higher energies.

Forman, M. A.

1981-01-01

181

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

182

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

E-print Network

computed by a partial-wave version of the exact (for hydrogen) technique of Merzbacher and Lewis. ' The agreement was excellent (-2% difference). Our ionization cross section results are given in Fig. 3. Our theoretical curve was determined.... Bransden, J. Phys. B Proc. Phys. Soc. Lond. 5, 2061 (1972). ~E. Merzbacher and H. W, Lewis, in Handbuch der Physik, edited by S. Flugge (Springer, Berlin, 1958), Vol. 24, p. 166ff. W. L. Fite, R. F. Stebbings, D. G. Hummer, and: R. T. Brackmann, Phys...

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

1977-01-01

183

Proposed FNAL 750 KeV Linac Injector Upgrade  

SciTech Connect

The present FNAL linac H{sup -} injector has been operational since 1978 and consists of a magnetron H{sup -} source and a 750 keV Cockcroft-Walton Accelerator. The proposed upgrade to this injector is to replace the present magnetron source having a rectangular aperture with a circular aperture, and to replace the Cockcroft-Walton with a 200 MHz RFQ. Operational experience at other laboratories has shown that the upgraded source and RFQ will be more reliable and require less manpower than the present system.

Tan, C.Y.; Bollinger, D.S.; Schmidt, C.W.; /Fermilab

2009-04-01

184

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

185

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

186

Full characterization of a laser-produced keV x-ray betatron source  

NASA Astrophysics Data System (ADS)

This paper presents the complete characterization of a kilo-electron-volt laser-based x-ray source. The main parameters of the electron motion (amplitude of oscillations and initial energy) in the laser wakefield have been investigated using three independent methods relying on spectral and spatial properties of this betatron x-ray source. First we will show studies on the spectral correlation between electrons and x-rays that is analyzed using a numerical code to calculate the expected photon spectra from the experimentally measured electron spectra. High-resolution x-ray spectrometers have been used to characterize the x-ray spectra within 0.8-3 keV and to show that the betatron oscillations lie within 1 µm. Then we observed Fresnel edge diffraction of the x-ray beam. The observed diffraction at the center energy of 4 keV agrees with the Gaussian incoherent source profile of full width half maximum <5 µm, meaning that the amplitude of the betatron oscillations is less than 2.5 µm. Finally, by measuring the far field spatial profile of the radiation, we have been able to characterize the electron's trajectories inside the plasma accelerator structure with a resolution better than 0.5 µm.

Albert, F.; Phuoc, K. Ta; Shah, R.; Corde, S.; Fitour, R.; Tafzi, A.; Burgy, F.; Douillet, D.; Lefrou, T.; Rousse, A.

2008-12-01

187

Absolute detection efficiencies of a microchannel plate detector for 0.5-5 keV neutrals  

NASA Astrophysics Data System (ADS)

The absolute detection efficiencies of a microchannel plate detector for neutral atoms were measured using the coincidence method for neutralized incident ions and ionized target atoms in electron capture collisions. This method does not require knowledge of the absolute electron-capture rates for determination of the detection efficiencies. Results for Ne, Ar, and Kr atoms at energies of 0.5-5 keV are reported. The detection efficiencies for all atomic species increase concomitantly with increasing impact energy and plateau at the efficiency of about 50%. For low impact energies, the efficiency decreases with increasing mass of the impact atom at a given energy.

Hosokawa, S.; Takahashi, N.; Saito, M.; Haruyama, Y.

2010-06-01

188

keV photon emission from light nonthermal dark matter  

NASA Astrophysics Data System (ADS)

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 O(GeV) and its relic density has a nonthermal origin. The model includes two colored scalars of O(TeV) mass (X1,2), and two singlet fermions that are almost degenerate in mass with the proton (N1,2). The heavier fermion N2 undergoes radiative decay to the lighter one N1 that is absolutely stable. Radiative decay with a lifetime ˜1023 seconds can account for the claimed 3.5 keV line, which requires couplings ˜10-3-10-1 between X1,2, N1,2 and the up-type quarks. The model also gives rise to potentially detectable monojet, dijet, and monotop signals at the LHC.

Allahverdi, Rouzbeh; Dutta, Bhaskar; Gao, Yu

2014-06-01

189

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.

Allahverdi, Rouzbeh; Gao, Yu

2014-01-01

190

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

191

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

192

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

193

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

2014-08-13

194

Single Ionization of He and H by 75 keV Proton Impact  

NASA Astrophysics Data System (ADS)

Recoil-ion momentum spectroscopy and projectile momentum spectroscopy have been applied to the study of single ionization of He and H by 75keV proton impact. Doubly differential cross sections as a function of the projectile energy loss (or equivalently electron energy) and the scattering angle will be discussed. The results will be compared to earlier doubly differential data for ionization of helium [1]. There, qualitative discrepancies to various theories were observed. Here, we will discuss to what extent these discrepancies can be attributed to an insufficient description of the initial target state. Analyzing the recoil-ion momenta will eventually enable us to obtain fully differential cross sections. [1] Vajnai, T. et al. Phys. Rev. Lett. 74 3588 (1995)

Alexander, Jason; Laforge, Aaron; Schulz, Michael

2007-10-01

195

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

196

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

197

Cross sections for ionizaton of gases by 5--4000-keV protons and for electron capture by 5--150-keV protons  

SciTech Connect

Using the parallel-plate-capacitor method and a capacitance manometer to determine pressures, total cross sections for the production of positive and negative charges were measured for 5--4000-keV-proton impact on He, Ne, Ar, Kr, H/sub 2/, N/sub 2/, CO, O/sub 2/, CH/sub 4/, and CO/sub 2/. From these, ionization and electron-capture cross sections were obtained and fitted to semiempirical equations describing the energy dependence in terms of a few parameters. At high energies very good agreement is obtained in the comparison of the ionization cross sections to earlier proton- and electron-impact measurements and with theoretical treatments where they are available, but discrepancies exist for some targets at low energy. Above 10 keV the electron-capture cross sections are in agreement with earlier work for all the targets except CO and CH/sub 4/ for which they are (20--40)% higher.

Rudd, M.E.; DuBois, R.D.; Toburen, L.H.; Ratcliffe, C.A.; Goffe, T.V.

1983-12-01

198

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

SciTech Connect

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

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

2012-11-06

199

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

Microsoft Academic Search

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

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

1977-01-01

200

Fast neutron detection with germanium detectors: Unfolding the 692 keV peak response for fission neutron spectra  

Microsoft Academic Search

A new method is proposed for obtaining information on the spectral distribution of fast fission neutrons in the energy range from 0.7 MeV up to about 6 MeV from the shape of the Ge 692 keV inelastic scattering peak response e.g. in the pulse-height distribution measured with a portable Ge detector. In order to reduce photon background events, a lead

G. Fehrenbacher; R. Meckbach; H. G Paretzke

1997-01-01

201

Guiding of 60 keV O6+ Ions through Nanocapillaries in an Uncoated Al2O3 Membrane  

Microsoft Academic Search

We measure the transmission of O6+ ions with a higher energy of 60keV (in turn a higher value of Ep\\/q) through capillaries in an uncoated Al2O3 membrane, and obtain agreements with previously reported results in general angular distribution of the transmitted ions and the transmission profile width variation with capillary tilt angle. The transmission fractions as a function of the

Xi-Meng Chen; Fa-Yuan Xi; Xi-Yu Qiu; Jian-Xiong Shao; Ying Cui; Guang-Zhi Sun; Jun Wang; Yi-Feng Chen; Hui-Ping Liu; Yong-Zhi Yin; Feng-Jun Lou; Xing-An Wang; Jun-Kui Xu; Chun-Lin Zhou

2008-01-01

202

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

203

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

204

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

205

Evaluation of neutron cross sections for fissile and fertile nuclides in the keV range  

SciTech Connect

Procedures for evaluation of radiative capture, elastic and inelastic processes, and fission in the keV region of neutron energies are described. The use of theoretical tools along with the available ENDF utility codes allows the evaluator to extend and expand upon the experimental data, which are often sparse or discrepant. A few problems with the utility codes are noted, and suggestions, made for improvement and extension. Some ENDF/B-V cross sections for important nuclei are plotted in detail, and show significant need for improvement in the shape of the individual partial cross sections to be consistent with theoretical predictions within the constraints of the experimental data. In particular, uranium and plutonium isotopic evaluations, which are of critical importance to fast reactors, deserve careful attention with improved methodology. 8 figures.

Weston, L.W.

1980-01-01

206

Single Ionization of Molecular Hydrogen by 75 keV Proton Impact  

NASA Astrophysics Data System (ADS)

Triply differential cross sections (DDCS) for single ionization of molecular hydrogen by 75keV proton impact have been measured and calculated as a function of the projectile scattering angle, energy loss, and longitudinal recoil momentum. Earlier, we reported interference structures in the DDCS resulting from coherent diffraction of the incoming projectile wave from the two atomic centers in the molecule. In the experimental data these structures disappeared near vel vproj. It seems plausible that this disappearance may be caused by the PCI, which is known to maximize at vel vproj. In order to test this hypothesis we have measured the recoil-ion momenta in addition to the projectile momenta in a kinematically complete experiment. Indeed, in the TDCS a weak interference structure is recovered if large longitudinal recoil-ion momenta p^recz are selected, which kinematically suppress PCI. In contrast, for small p^recz, which kinematically favor PCI, no structure is observed.

Egodapitiya, K.; Laforge, A.; Alexander, J.; Schulz, M.; Hasan, A.; Ciappini, M.; Khakoo, M.

2009-10-01

207

K-Ionization probability across the 460-keV12C( p, p 0) resonance  

NASA Astrophysics Data System (ADS)

We have remeasured the K-shell vacancy production probability P K across the 460-keV12C( p, p 0) resonance, previously investigated by Duinker et al. We are unable to confirm the large (˜70 %) variation of P K across the resonance, found by Duinker et al. for protons elastically scattered at 125°. Our values for the ratio P K (142°)/ P K (16°) are independent (within±20%) of the proton bombarding energy over the resonance region, in agreement with theoretical predictions by Blair and Anholt, Feagin and Kocbach, McVoy and Weidenmüller. Our average value for this ratio, equal to 0.88 ±0.06, agrees with the value 0.88 calculated by Amundsen and Aashamar.

Meyerhof, W. E.; Astner, G.; Hofmann, D.; Groeneveld, K. O.; Chemin, J. F.

1982-06-01

208

Continuous slowing-down approximation range of 50-keV--100-MeV electrons  

SciTech Connect

The Wilson theory has been modified for the calculation of the continuous slowing-down approximation (CSDA) range of 50-keV--100-MeV electrons in the absorbers of atomic numbers from 1 to 92 and in some detector materials, minerals, organic compounds, and gaseous compounds. A correction factor which depends on energy as well as on atomic number is evaluated. Values of the CSDA range obtained by the present approach have shown an agreement with reported values within a discrepancy of 6--7%. An attempt has also been made to correlate the CSDA range with the available experimentally measured projected range. Calculated projected range and experimentally measured projected range are found to be in good agreement.

Gupta, S.K.; Gupta, D.K.

1981-03-01

209

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

210

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

211

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

212

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

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

213

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

SciTech Connect

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

Tanuma, S. [Materials Analysis Station, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Powell, C. J.; Penn, D. R. [National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8370 (United States)

2008-03-15

214

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

SciTech Connect

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

Kaya, N.; Tirasoglu, E.; Apaydin, G.; Kobya, A. I. [Karadeniz Technical University, Faculty of Arts and Sciences, Department of Physics, Trabzon, 61080 (Turkey)

2007-04-23

215

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

216

GBM detection of XTE J1752-223 to above 100 keV  

NASA Astrophysics Data System (ADS)

The new transient black hole candidate XTE J1752-223 (ATel. #2258; see also ATels. #2259, #2261, #2263, #2268, #2269, #2278), is also detected using the Earth occultation technique with the Gamma Ray Burst Monitor (GBM) on Fermi. We detect the source to above 100 keV, with a mean 100-300 keV flux for 2009 Oct 30 - November 2 of 740+/-120 mCrab. The transient rose from undetectable on 2009 October 24 to 560+/-55 mCrab (12-25 keV), 510+/-80 mCrab (25-50 keV), 970+/-120 mCrab (50-100 keV), and 770+/-230 mCrab (100-300 keV) on 2009 November 2.

Wilson-Hodge, C. A.; Camero-Arranz, A.; Case, G.; Chaplin, V.; Connaughton, V.

2009-11-01

217

Observations of 10-eV to 25-keV electrons in steady diffuse aurora from Atmosphere Explorer C and D  

NASA Technical Reports Server (NTRS)

Electron energy spectra from 10 eV to 25 keV have been obtained from steady diffuse auroral forms at altitudes above 150 km by the Atmosphere Explorer C and D spacecraft. Overlapping coverage of the energy range was provided by the photoelectron spectrometer experiment (10-500 eV) and the low-energy electron experiment (0.2-25 keV). The spectral shape between 10 and 20 eV is independent of altitude between 150 and 270 km, has variable energy dependence between about 20 and 150 eV, and above approximately 150 eV has energy dependence determined primarily by the details of the energy spectrum of electrons incident on the atmosphere. The observed results are in satisfactory agreement with two recently published model calculations.

Peterson, W. K.; Doering, J. P.; Potemra, T. A.; Mcentire, R. W.; Bostrom, C. O.; Hoffman, R. A.; Janetzke, R. W.; Burch, J. L.

1977-01-01

218

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

219

Spectral properties of ~0.03-6 keV Energetic Neutral Atoms Measured by the Interstellar Boundary Explorer (IBEX) Along the Lines-of-Sight of Voyager  

NASA Astrophysics Data System (ADS)

Energetic Neutral Atoms (ENAs) observed by the Interstellar Boundary Explorer (IBEX) provide powerful diagnostics about the origin of the progenitor ion populations and the physical mechanisms responsible for their production. Here we survey the fluxes, energy spectra, and energy-dependence of the spectral indices of ~0.03-6 keV ENAs measured by IBEX-Hi and IBEX-Lo along the lines-of-sight of Voyager 1 and 2. We compare the ENA spectra observed at IBEX with predictions of models that simulate the microphysics of the heliospheric termination shock to predict the shape and relative contributions of a variety of heliosheath ion populations. We show: (1) The ENA spectra between ~0.7-6 keV do not exhibit sharp cut-offs at ~twice the solar wind speed as is typically observed for shell-like PUI distributions in the heliosphere and are reasonably well accounted for by most of the models. (2) The ~0.03-0.7 keV ENA intensities are larger by more than an order of magnitude compared with most existing models that do not include contributions from ENAs generated in the outer heliosheath. We conclude that the ~0.7-5 keV ENAs at IBEX are generated by inner heliosheath PUIs in the ~0.5-5 keV energy range that are transmitted through the termination shock; the PUI population being a superposition of Maxwellian or kappa distributions and partially filled shell distributions in velocity space. In contrast, the parent PUI proton population for the <0.7 keV ENAs observed at IBEX most likely originates in the outer heliosheath and is substantially hotter compared with the thermal plasma component. In this paper, we explore the physical processes that could contribute to the origin of the different proton populations that are likely to be present in the heliosheath.

Desai, M. I.; Allegrini, F.; Dayeh, M. A.; Funsten, H. O.; Heerikhuisen, J.; McComas, D. J.; Pogorelov, N. V.; Schwadron, N. A.; Fuselier, S. A.; Zank, G. P.; Zirnstein, E. J.

2013-05-01

220

First Results from Fermi Gamma-ray Burst Monitor Earth Occultation Monitoring: Observations of Soft Gamma-ray Sources Above 100 keV  

NASA Astrophysics Data System (ADS)

The NaI and BGO detectors on the Gamma-ray Burst Monitor (GBM) on Fermi are now being used for long-term monitoring of the hard X-ray/low-energy gamma-ray sky. Using the Earth occultation technique as demonstrated previously by the BATSE instrument on the Compton Gamma-Ray Observatory, GBM can be used to produce multiband light curves and spectra for known sources and transient outbursts in the 8 keV to 1 MeV energy range with its NaI detectors and up to 40 MeV with its BGO detectors. Over 85% of the sky is viewed every orbit, and the precession of the Fermi orbit allows the entire sky to be viewed every ~26 days with sensitivity exceeding that of BATSE at energies below ~25 keV and above ~1.5 MeV. We briefly describe the technique and present preliminary results using the NaI detectors after the first two years of observations at energies above 100 keV. Eight sources are detected with a significance greater than 7?: the Crab, Cyg X-1, SWIFT J1753.5-0127, 1E 1740-29, Cen A, GRS 1915+105, and the transient sources XTE J1752-223 and GX 339-4. Two of the sources, the Crab and Cyg X-1, have also been detected above 300 keV.

Case, G. L.; Cherry, M. L.; Wilson-Hodge, C. A.; Camero-Arranz, A.; Rodi, J. C.; Chaplin, V.; Finger, M. H.; Jenke, P.; Beklen, E.; Bhat, P. N.; Briggs, M. S.; Connaughton, V.; Greiner, J.; Kippen, R. M.; Meegan, C. A.; Paciesas, W. S.; Preece, R.; von Kienlin, A.

2011-03-01

221

LXT. The determination of the internal conversion coefficient and branching ratio for the 80 kev ?-ray emitted by I by means of X-ray-?-ray coincidence measurements  

Microsoft Academic Search

The investigation of primary and secondary electron spectra as a means of determining conversion coefficients becomes difficult at low ?-ray energies. A method relying on the measurement of the ?-rays emitted as a result of internal conversion does not suffer from this disadvantage. Such a method has been applied to the 80 kev ?-ray emitted by I. This is believed

Patrick E. Cavanagh

1952-01-01

222

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

223

Discovery of a 6.4 keV Emission Line in a Burst from SGR 1900+14  

NASA Technical Reports Server (NTRS)

We present evidence of a 6.4 key emission line during a burst from the soft gamma repeater SGR 1900+14. The Rossi X-Ray Timing Explorer (RXTE) monitored this source extensively during its outburst in the summer of 1998. A strong burst observed on 1998 August 29 revealed a number of unique properties. The burst exhibits a precursor and is followed by a long (approx. 10(exp 3) s) tail modulated at the 5.16 s stellar rotation period. The precursor has a duration of approx. equals 0.85 s and shows both significant spectral evolution as well as an emission feature centered near 6.4 keV during the first 0.3 s of the event, when the X-ray spectrum was hardest. The continuum during the burst is well fit with an optically thin thermal bremsstrahlung spectrum with the temperature ranging from approx. equals 40 to 10 keV. The line is strong, with an equivalent width of approx. 400 eV, and is consistent with Fe K(alpha) fluorescence from relatively coot material. If the rest-frame energy is indeed 6.4 keV, then the lack of an observed redshift indicates that the source is at least approx. 80 km above the neutron star surface. We discuss the implications of the line detection in the context of models for SGRs.

Strohmayer, Tod E.; Ibrahim, Alaa I.

2000-01-01

224

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

SciTech Connect

We report on an experimental study of the ionization and fragmentation of clusters of k polycyclic aromatic hydrocarbon (PAH) molecules using anthracene, C{sub 14}H{sub 10}, or coronene, C{sub 24}H{sub 12}. These PAH clusters are moderately charged and strongly heated in small impact parameter collisions with 22.5-keV He{sup 2+} ions, after which they mostly decay in long monomer evaporation sequences with singly charged and comparatively cold monomers as dominating end products. We describe a simple cluster evaporation model and estimate the number of PAH molecules in the clusters that have to be hit by He{sup 2+} projectiles for such complete cluster evaporations to occur. Highly charged and initially cold clusters are efficiently formed in collisions with 360-keV Xe{sup 20+} ions, leading to cluster Coulomb explosions and several hot charged fragments, which again predominantly yield singly charged, but much hotter, monomer ions than the He{sup 2+} collisions. We present a simple formula, based on density-functional-theory calculations, for the ionization energy sequences as functions of coronene cluster size, rationalized in terms of the classic electrostatic expression for the ionization of a charged conducting object. Our analysis indicates that multiple electron removal by highly charged ions from a cluster of PAH molecules rapidly may become more important than single ionization as the cluster size k increases and that this is the main reason for the unexpectedly strong heating in these types of collisions.

Johansson, H. A. B.; Zettergren, H.; Holm, A. I. S.; Seitz, F.; Schmidt, H. T.; Cederquist, H. [Department of Physics, Stockholm University, SE-106 91, Stockholm (Sweden); Rousseau, P.; Lawicki, A.; Capron, M.; Domaracka, A.; Lattouf, E.; Maclot, S.; Maisonny, R.; Chesnel, J.-Y.; Adoui, L.; Huber, B. A. [CIMAP, UMR 6252, CEA/CNRS/ENSICAEN/Universite de Caen Basse-Normandie, Boulevard Henri Becquerel, BP5133, F-14070 Caen Cedex 5 (France); Manil, B. [Laboratoire de Physique des Laser, CNRS, UMR 7538, Institut Galilee, Universite Paris 13, F-93430, Villetaneuse (France)

2011-10-15

225

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

2014-07-02

226

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

227

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

NASA Technical Reports Server (NTRS)

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

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

1996-01-01

228

K X-ray production cross sections in aluminium for 15, 20 and 25 keV protons  

NASA Astrophysics Data System (ADS)

A low-energy particle accelerator has been used to determine experimentally low-energy X-ray production cross sections through the irradiation of thick targets with ions with energies up to 25 keV/ion charge by measuring thick target yields. We obtained aluminium K- X-ray production cross sections values of 8.4 × 10-4, 1.3 × 10-3 and 1.8 × 10-3 barn for 15, 20 and 25 keV protons, respectively. Although there are no results in the literature for such low-energy impinging protons for comparison, the results presented here are in good agreement with the general trend exhibited for higher energy ranges.

do Carmo, S. J. C.; Borges, F. I. G. M.; Trindade, A. M. F.; Conde, C. A. N.

2012-12-01

229

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

230

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

231

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

SciTech Connect

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

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

2010-07-15

232

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

E-print Network

On energetic electrons (>38 keV) in the central plasma sheet: Data analysis and modeling Bingxian] The spatial distribution of >38 keV electron fluxes in the central plasma sheet (CPS) and the statistical relationship between the CPS electron fluxes and the upstream solar wind and interplanetary magnetic field (IMF

Li, Xinlin

233

Design and fabrication of a Transverse Field Focussing (TFF) 180 keV negative ion accelerator  

SciTech Connect

The 180 keV Transverse Field Focussing (TFF) negative ion accelerator described is the final component of a negative ion based neutral beam acceleration system which is being developed as proof-of-principle demonstration of a radiation hardened neutral beamline. The 180 keV beamline consists of: a surface conversion negative ion source, a 80 keV pre-accelerator, a TFF pumping, matching, and transport section, and the 180 keV TFF accelerator presented. This beamline is expected to provide 1 A of H/sup -/ at 180 keV. In the design of the accelerator, particular importance was given to the rigidity of the accelerator electrode mounting structures and to the electrical isolation of the electrodes along with their related cooling lines. An optical alignment scheme was developed to assemble and to insure precision alignment of the electrodes. (LEW)

Matuk, C.A.; Anderson, O.A.; Owren, H.M.; Paterson, J.A.; Purgalis, P.

1985-11-01

234

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

235

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

PubMed

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

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

2013-06-21

236

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

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

237

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

238

Auger electron emission from a Si(1 1 1) surface during 11-keV Ar+ ion sputtering  

NASA Astrophysics Data System (ADS)

Ion sputtering experiments were carried out for a Si(1 1 1)-7 × 7 surface, irradiated with an 11-keV Ar+ beam. The energy spectra of secondary electrons were measured with a cylindrical mirror analyzer (CMA). The dependence of the Auger electron yield on the ion incidence angle, ?, measured from the surface normal, was studied by varying ? from 0° to 80°. The Auger electron yield increases with increasing incidence angle. This angular dependence is similar to that of the Si sputtering yield. Both angular dependences could be reasonably understood in terms of ion range, escape depths of the sputtered ion and the electron mean free path.

Kawai, K.; Sakuma, Y.; Kato, M.; Soda, K.

2013-11-01

239

Multiple ionization of diatomic molecules in collisions with 50-300-keV hydrogen and helium ions  

SciTech Connect

Measurements of relative multiple ionization cross sections have been performed for 50-300-keV H{sup +}, D{sup +}, and He{sup +} impact on N{sub 2}, O{sub 2}, CO, and NO molecules. Fragment ions with total charges up to Q=q{sub 1}+q{sub 2}=5 have been detected in coincidence using a position- and time-sensitive detector. Dependence of the cross section on the molecular orientation with respect to the ion beam is observed for all targets. The experimental data are compared with theoretical calculations based on the statistical energy deposition model.

Siegmann, B.; Werner, U.; Kabachnik, N.M.; Lutz, H.O. [Fakultaet fuer Physik, Universitaet Bielefeld, D-33615 Bielefeld (Germany); Kaliman, Z. [Faculty of Philosophy, University of Rijeka, 51000 Rijeka (Croatia); Roller-Lutz, Z. [Institute of Physics, Faculty of Medicine, University of Rijeka, 51000 Rijeka (Croatia)

2002-11-01

240

Two-color ionization of hydrogen close to threshold with keV photons  

NASA Astrophysics Data System (ADS)

In a recent Letter [H. Bachau, M. Dondera, and V. Florescu, Phys. Rev. Lett. 112, 073001 (2014), 10.1103/PhysRevLett.112.073001] we considered the hydrogen atom in interaction with an electromagnetic field consisting in the coherent superposition of two keV pulses centered around two frequencies ?1 and ?2 that differ by a few atomic units. The analysis of the results obtained from the resolution of the time-dependent Schrödinger equation focused on stimulated Compton scattering (SCS). We have developed in parallel an approach based on perturbation theory and it proved to be an appropriate and useful tool in complement to the nonperturbative approach. In this paper we present a detailed analysis of the electron spectra obtained for ??1= 55 a.u. and two values of ??2, 50 and 54 a.u. Emphasis is put on the case ??2=54 a.u., where the electron emitted through SCS has the lowest energy, showing in particular that in the vicinity of the ionization threshold the cross section increases as ??1-??2 decreases. We calculate photoelectron energy and angular distributions at various relative directions of propagation of the pulses. We discuss the limitations of the approximations underlying the numerical and analytical approaches used in this work.

Dondera, Mihai; Florescu, Viorica; Bachau, Henri

2014-09-01

241

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

242

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

243

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. Neither Jaffe model for nuclear recoil-induced ionization nor that of Thomas-Imel can consistently describe the energy dependence of the ionization yield.

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

2014-01-01

244

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

2014-07-28

245

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

246

Digging gold: keV He+ ion interaction with Au  

PubMed Central

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

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

2013-01-01

247

20-100 keV properties of cataclysmic variables detected in the INTEGRAL/IBIS survey  

E-print Network

Analysis of INTEGRAL/IBIS survey observations has revealed that the rare intermediate polar and asynchronous polar cataclysmic variables are consistently found to emit in the 20-100 keV energy band, whereas synchronous polars and the common non-magnetic CVs rarely do so. From the correlation of a candidate INTEGRAL/IBIS survey source list with a CV catalogue, 15 CV detections by IBIS have been established including a new INTEGRAL source IGR J06253+7334. The properties of these sources and 4 additional CV candidates are discussed in the context of their 20-100 keV emission characteristics and we conclude that the INTEGRAL mission is an important tool in the detection of new magnetic CV systems. Furthermore, analysis of the time-averaged spectra of CVs detected by INTEGRAL indicate that although there is little difference between the spectral slopes of the different sub-types, intermediate polars may be considerably more luminous than polars in the soft gamma-ray regime. We also present the detection of an unusual high-energy burst from V1223 Sgr discovered by inspection of the IBIS light-curve. Additionally, we have compared the IBIS and optical AAVSO light-curves of SS Cyg and extracted IBIS spectra during single periods of optical outburst and quiescence. We find that the 20-100 keV flux is an order of magnitude greater during optical quiescence. This is in agreement with previous studies which show that the hard X-ray component of SS Cyg is suppressed during high accretion states

E. J. Barlow; C. Knigge; A. J. Bird; A. J. Dean; D. J. Clark; A. B. Hill; M. Molina; V. Sguera

2006-07-20

248

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

249

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

250

A 40 keV cyclotron for radioisotope dating  

Microsoft Academic Search

We have built and begun testing a small low energy negative ion cyclotron for direct detection of 14C. At present, the cyclotron is operated in a high resolution mode at the 31st harmonic, with 1-2 kV on the dees. The high harmonic and a minimum number of turns of approximately 100, should give a fwhm mass resolution of about 1\\/30000

James J. Welch; Kirk J. Bertsche; Peter G. Friedman; Donald E. Morris; Richard A. Muller; Pieter P. Tans

1984-01-01

251

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

NASA Technical Reports Server (NTRS)

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

Stanford, John M.; Caillault, Jean-Pierre

1994-01-01

252

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

SciTech Connect

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

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

2012-10-15

253

Beam profile monitor for annihilation cross section measurements of antiprotons at 100 keV  

NASA Astrophysics Data System (ADS)

The ASACUSA (the Atomic Spectroscopy And Collisions Using Slow Antiprotons) collaboration is planning to measure the cross sections of antiproton annihilations at kinetic energy 100 keV on targets of various mass numbers (C, Ni, Sn, and Pt) using the Antiproton Decelerator (AD) of CERN. No previous measurement exists in this region where the A-dependence of the cross section is expected to deviate from the A^{2/3} (Batty et al, Nucl Phys A 689:721, 2001) as reported by the Obelix collaboration. A beam profile monitor based on secondary electron emission with a grid of electrode pads fabricated on an FR4-type glass-epoxy circuit board was developed for this measurement. The advantage of this kind of detector is that it is simple, lightweight, and low cost. It was used to measure the spatial profile of 100-ns-long beam pulses containing > 6 × 104 antiprotons with an active area of 40 mm × 40 mm and a spatial resolution of 4 mm.

Todoroki, Koichi; Corradini, Maurizio; Hayano, Ryugo S.; Kobayashi, Takumi; Leali, Marco; Lodi Rizzini, Evandro; Mascagna, Valerio; Soter, Anna; Venturelli, Luca; Zurlo, Nicola; Hori, Masaki

254

Desorption of large organic molecules induced by keV projectiles  

NASA Astrophysics Data System (ADS)

In order to understand the emission of organic molecules in sputtering, classical molecular dynamics (MD) is used to model the 5 keV Ar atom bombardment of polystyrene oligomers adsorbed on Ag{1 1 1}. The analysis of the results shows that a significant fraction of the trajectories generates high action events in the sample. These events are characterized by the simultaneous motion of several hundreds of substrate atoms and, oftentimes, by high emission yields of substrate atoms, clusters and polystyrene molecules. Collision trees representing the energetic part of the cascades confirm that high sputtering yields of molecules occur when a large portion of the primary particle energy is quickly dissipated in the upper layers of the silver substrate. This class of events where high action occurs in the surface region might explain the ejection of organic species with a mass of several kilodaltons such as biomolecules and synthetic polymers. In the simulation, these events are capable of desorbing polystyrene molecules of ˜2 kDa.

Delcorte, A.; Garrison, B. J.

2001-06-01

255

The TIGRE prototype results for 511 and 900 keV gamma rays  

Microsoft Academic Search

A small prototype of the Tracking and Imaging Gamma-Ray Experiment (TIGRE) has been assembled and tested at 511 keV and 900 keV. TIGRE uses multi-layers of silicon strip detectors both as a gamma ray converter and to track Compton recoil electrons and positron-electron pairs. Our prototype consists of 7 double sided silicon strip detectors 3.2 cm×3.2 cm×300 micron with 1

T. J. O'Neill; D. Bhattacharya; S. Blair; G. Case; O. T. Tumer; R. S. White; A. D. Zych

1994-01-01

256

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

257

Laser streaking of free electrons at 25 keV  

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

258

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

259

Study of the spectrum beyond 200 keV of second-stage solar flare X-ray emission  

SciTech Connect

We have studied the spectra of three solar flares with second-stage hard X-ray emission observed by instruments on board the OSO 5 spacecraft. Using a Monte Carlo program, we have calculated the expected flux of solar X-rays reflected from the Earth's atmosphere for the observed solar X-ray spectra. The results have been compared with the observed reflected fluxes, which were also detected by the above instruments. We show that for the events considered here, which are necessarily intense and have hard spectra, the simple extrapolation of the observed solar spectrum to higher energies cannot explain the observed flux of the reflected radiation. Instead, we find the need to postulate the existence of a solar X-ray flux at energies above 200 keV larger than that obtained from simple extrapolation. In particular, we find evidence against a thermal spectrum in at least one of the events considered.

Langer, S.H.; Petrosian, V.; Frost, K.J.

1980-02-01

260

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

261

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

262

Dense ion clouds of 0.1 - 2 keV ions inside the CPS-region observed by Astrid2  

Microsoft Academic Search

Data from the Astrid-2 satellite taken between April and July 1999 show several examples of dense ion clouds in the 0.1 2 keV energy range inside the inner mag-netosphere, both in the northern and southern hemispheres. These inner magnetospheric ion clouds are found predomi-nantly in the early morning sector, suggesting that they could have originated from substorm-related ion injections on

S. H. Høymork; M. Yamauchi; Y. Ebihara; Y. Narita; O. Norberg; D. Winningham

2001-01-01

263

A 400keV X-ray generator with the pulse duration variable within 10–80 ns and an up to 70-Gy radiation dose  

Microsoft Academic Search

A high-power X-ray generator is created based on a universal setup for the experimental development of components of electrophysical\\u000a installations (spark gaps, insulators, liquid resistors, etc.). The maximum energy of X-ray quanta is 400 keV, the pulse duration\\u000a can be varied in steps from 10 to 80 ns, the radiation dose in the atmosphere near the exit window is ?70

A. I. Gerasimov; V. S. Gordeev; V. V. Kul’gavchuk; S. A. Lazarev

2000-01-01

264

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

NASA Astrophysics Data System (ADS)

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

De Cesare, G.

2011-09-01

265

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

266

Microcollimator for micrometer-wide stripe irradiation of cells using 20-30 keV X rays.  

PubMed

Abstract Pataky, K., Villanueva, G., Liani, A., Zgheib, O., Jenkins, N., Halazonetis, D. J., Halazonetis, T. D. and Brugger, J. Microcollimator for Micrometer-Wide Stripe Irradiation of Cells Using 20-30 keV X Rays. Radiat. Res. 172, 252-259 (2009). The exposure of subnuclear compartments of cells to ionizing radiation is currently not trivial. We describe here a collimator for micrometer-wide stripe irradiation designed to work with conventional high-voltage X-ray tubes and cells cultured on standard glass cover slips. The microcollimator was fabricated by high-precision silicon micromachining and consists of X-ray absorbing chips with grooves of highly controlled depths, between 0.5-10 microm, along their surfaces. These grooves form X-ray collimating slits when the chips are stacked against each other. The use of this device for radiation biology was examined by irradiating human cells with X rays having energies between 20-30 keV. After irradiation, p53 binding protein 1 (53BP1), a nuclear protein that is recruited at sites of DNA double-strand breaks, clustered in lines corresponding to the irradiated stripes. PMID:19630530

Pataky, Kristopher; Villanueva, Guillermo; Liani, Andre; Zgheib, Omar; Jenkins, Nathan; Halazonetis, Demetrios J; Halazonetis, Thanos D; Brugger, Juergen

2009-08-01

267

A method to obtain a Maxwell-Boltzmann neutron spectrum at kT=30 keV for nuclear astrophysics studies  

NASA Astrophysics Data System (ADS)

A method based on shaping the proton beam energy in order to shape the neutron beam energy to a desired form for accelerator-based neutron sources is proposed. An application to a superconductive RFQ proton accelerator of 5 MeV and 50 mA for the production of a stellar neutron spectrum at thermal energy equal to 30 keV using the 7Li(p,n)7Be reaction is investigated. The chosen energy beam shaper is a carbon foil which shapes the quasi-monochromatic proton beam to a quasi-Gaussian distribution: after the carbon foil, the beam is still shaped by chopping the Gaussian distribution at the reaction energy threshold. The obtained proton beam is impinged in a metallic lithium target. The concepts of the energy shaper, the proposed lithium target and the calculations performed to remove their power load are presented. Calculations show that a power density of 3 kW/cm2 can be sustained by the target which produces a forward-directed neutron source of 7.3×1010 neutrons/s. The obtained neutron spectrum resembles a Maxwell-Boltzmann distribution at kT=30 keV with a coefficient of determination of 0.997. The method is intended to be applied in activation analysis for measuring the Maxwellian-averaged neutron capture cross-section of elements of interest for astrophysics and validation of integral neutron data in the epithermal energy range.

Mastinu, P. F.; Martín Hernández, G.; Praena, J.

2009-04-01

268

Lifetime and conversion coefficient for the 17 keV level in 52V  

Microsoft Academic Search

Using thermal neutron capture on natural vanadium targets, the lifetime and conversion coefficient for the 17 keV level in 52V have been measured: T1\\/2 = 1.08 +\\/-0.22 ns and alphaexp = 4.6+\\/-1.8. The conversion coefficient implies an (89+\\/-8)% M1 and (11+\\/-8)% E2 assignment for the 17 keV gamma-ray. The experimental reduced M1 transition probability, B (M1) = 0.66+\\/-0.30 W.u., is

J. F. Boulter; W. V. Prestwich

1972-01-01

269

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

NASA Astrophysics Data System (ADS)

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

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

2004-11-01

270

Comparison of measured parameters from a 24-keV and a broad spectrum epithermal neutron beam for neutron capture therapy: an identification of consequential parameters.  

PubMed

Epithermal neutron beams are under development in a number of locations in the U.S. and abroad. The increased penetration in tissue provided by these neurons should circumvent problems associated with the rapid attenuation of thermal neutron beams encountered in previous clinical trials of neutron capture therapy (NCT). Physical and radiobiological experiments with two "intermediate energy" or "epithermal" beams have been reported. A comparison is made here between the 24-keV iron-filtered beam at Harwell, England, and the broad-spectrum Al2 O3 moderated beam at the Brookhaven Medical Research Reactor (BMRR). In addition, parameters which are relevant for NCT, and which are best suited for evaluation and comparison of beams, are discussed. Particular attention is paid to the mean neutron energy which can be tolerated without significant reduction of therapeutic gain (TG), where TG is the ratio of tumor dose to maximum normal tissue dose. It is suggested that the simplest and most meaningful parameters for comparison of beam intensity and purity are the epithermal neutron fluence rate, and the fast neutron dose per epithermal neutron (4.2 X 10(-11) rad/neutron for the broad-spectrum beam and 29 X 10(-11) rad/neutron for the 24-keV beam). While the Al2O3 beam is close to optimal, the 24-keV beam produces a significant fast neutron dose which results in a lower TG.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2280734

Fairchild, R G; Saraf, S K; Kalef-Ezra, J; Laster, B H

1990-01-01

271

Studies of Transport Properties and Critical Temperature Suppression Mechanism in Yttrium BARIUM(2) COPPER(3) Oxygen(x) Thin Films Irradiated with 20 TO 120 KEV Electrons  

NASA Astrophysics Data System (ADS)

We present comprehensive studies of the effects of 20 to 120 keV electron irradiation on rm YBa_2Cu_3O_{x} thin films. Above 60 keV, T_{c } of irradiated samples is suppressed accompanied by a significant increase in residual resistivity, while the carrier concentration remains relatively unchanged. The plane oxygen defects produced by irradiation are found to be responsible for T_{c} suppression. The II suppression mechanism is discussed within several theoretical frameworks. Though in qualitative agreement with d-wave pairing symmetry, our results show a T_{c} suppression rate three times as slow as predicted by the theory when resistivity data are used to extract the impurity scattering rate. Alternatively, phase fluctuations theory gives a qualitative description as well. The displacement energy of plane oxygen is found to be 8.3 eV, which corresponds to a threshold electron energy 58 keV. Finally, an empirical relation is proposed to describe the temperature dependence of the Hall coefficient.

Lin, Jiunn-Yuan

272

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

NASA Astrophysics Data System (ADS)

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

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

2010-01-01

273

Molecular dynamics simulations of sputtering of Langmuir-Blodgett multilayers by keV C60 projectiles  

PubMed Central

Coarse-grained molecular dynamics computer simulations are applied to investigate fundamental processes induced by an impact of keV C60 projectile at an organic overlayer composed of long, well-organized linear molecules. The energy transfer pathways, sputtering yields, and the damage induced in the irradiated system, represented by a Langmuir-Blodgett (LB) multilayers composed from molecules of bariated arachidic acid, are investigated as a function of the kinetic energy and impact angle of the projectile and the thickness of the organic system. In particular, the unique challenges of depth profiling through a LB film vs. a more isotropic solid are discussed. The results indicate that the trajectories of projectile fragments and, consequently, the primary energy can be channeled by the geometrical structure of the overlayer. Although, a similar process is known from sputtering of single crystals by atomic projectiles, it has not been anticipated to occur during C60 bombardment due to the large size of the projectile. An open and ordered molecular structure of LB films is responsible for such behavior. Both the extent of damage and the efficiency of sputtering depend on the kinetic energy, the impact angle, and the layer thickness. The results indicate that the best depth profiling conditions can be achieved with low-energy cluster projectiles irradiating the organic overlayer at large off-normal angles. PMID:20174461

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

2009-01-01

274

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

275

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

276

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

277

Decline of the 2-10 keV Emission from Eta Carinae  

NASA Astrophysics Data System (ADS)

Analysis of Eta Car's X-ray spectrum in the 2-10 keV band using processed data from the X-ray Telescope on Swift reveals a peak flux on July 16, 2014 of 0.046 photons s-1cm-2 (3.37 & plusmn0.15 & times;10-10 ergs s-1cm-2).

Liburd, Jamar; Corcoran, Michael F.; Hamaguchi, Kenji; Gull, Theodore; Madura, Thomas; Teodoro, Mairan; Moffat, Anthony; Richardson, Noel; Russell, Chris; Pollock, Andrew; Owocki, Stan

2014-07-01

278

A study on the microstructural parameters of 550 keV electron irradiated Lexan polymer films  

SciTech Connect

Lexan polymer films irradiated with 550 keV Electron Beam (EB) were characterized using Wide Angle Xray Scattering (WAXS) data to study the microstructural parameters. The crystal imperfection parameters like crystal size , lattice strain (g in %) and enthalpy ({alpha}) have been determined by Line Profile Analysis (LPA) using Fourier method of Warren.

Hareesh, K.; Pramod, R.; Petwal, V. C.; Dwivedi, Jishnu; Sangappa; Sanjeev, Ganesh [Microtron Centre, Department of Physics, Mangalore University, Mangalagangotri-574199 (India); PSIA Division, Raja Rammana Centre for Advanced Technology, Indore-452013 (India); Department of Physics, Mangalore University, Mangalagangotri-574199 (India); Microtron Centre, Department of Physics, Mangalore University, Mangalagangotri-574199 (India)

2012-06-05

279

The Discovery and Nondiscovery of Neutrinos: The Reines Cowan Experiment and the 17Kev Neutrino  

SciTech Connect

In this paper I discuss the first observation of the neutrino by Frederick Reines, Clyde Cowan, and their collaborators. I also discuss how the physics community decided to reject the claim that a new, heavy, 17-keV neutrino had been observed. Both are examples of good science.

Franklin, Allan [Department of Physics, University of Colorado, Boulder, CO 80309-0390 (United States)

2007-06-19

280

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

281

On the 110 keV Feature From A0535+26: Direct Evidence For A Near-Critical Magnetic Field  

E-print Network

A recent high resolution measurement of an absorption line at 110 keV in the phase-averaged spectrum of A0535+26 (Grove et al. 1994) and the conspicuous absence of a previously reported harmonic feature at around 50 keV (Kendziorra et al. 1992, 1994) are indicative of cyclotron scattering in a magnetic field of about $10^{13}$G. However, controversy has risen over whether a lower field scenario may account for the alleged absence or weakness of a lower energy fundamental harmonic feature. This work explores these two alternatives through the generation of theoretical cyclotron spectra. For lower field models, a cylindrical geometry of the line forming region and the strong angle dependence of the cross section for resonant scattering conspire to fill in a first harmonic at around 57 keV. Higher field models (B $\\simeq$ 10.75 TG), however, yield significantly better fits (${\\cal X}^2_{low}/{\\cal X}^2_{high} \\sim 71$), thus strengthening the case for a near-critical field ($B_{crit} \\simeq 44$ TG). Phase-resolved OSSE spectra are not yet available but would greatly help in resolving this issue.

Rafael A. Araya; Alice K. Harding

1996-03-15

282

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

PubMed

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

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

2013-06-01

283

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

PubMed

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

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

2012-12-01

284

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.

The Cuore Collaboration; F. Alessandria; R. Ardito; D. R. Artusa; F. T. Avignone III; O. Azzolini; M. Balata; T. I. Banks; G. Bari; J. Beeman; F. Bellini; A. Bersani; M. Biassoni; T. Bloxham; C. Brofferio; C. Bucci; X. Z. Cai; L. Canonica; S. Capelli; L. Carbone; L. Cardani; M. Carrettoni; N. Casali; N. Chott; M. Clemenza; C. Cosmelli; O. Cremonesi; R. J. Creswick; I. Dafinei; A. Dally; V. Datskov; A. De Biasi; M. P. Decowski; M. M. Deninno; S. Di Domizio; M. L. di Vacri; L. Ejzak; R. Faccini; D. Q. Fang; H. A. Farach; E. Ferri; F. Ferroni; E. Fiorini; M. A. Franceschi; S. J. Freedman; B. K. Fujikawa; A. Giachero; L. Gironi; A. Giuliani; J. Goett; P. Gorla; C. Gotti; E. Guardincerri; T. D. Gutierrez; E. E. Haller; K. Han; K. M. Heeger; H. Z. Huang; R. Kadel; K. Kazkaz; G. Keppel; L. Kogler; Yu. G. Kolomensky; D. Lenz; Y. L. Li; C. Ligi; X. Liu; Y. G. Ma; C. Maiano; M. Maino; M. Martinez; R. H. Maruyama; N. Moggi; S. Morganti; T. Napolitano; S. Newman; S. Nisi; C. Nones; E. B. Norman; A. Nucciotti; F. Orio; D. Orlandi; J. L. Ouellet; M. Pallavicini; V. Palmieri; L. Pattavina; M. Pavan; M. Pedretti; G. Pessina; S. Pirro; E. Previtali; V. Rampazzo; F. Rimondi; C. Rosenfeld; C. Rusconi; S. Sangiorgio; N. D. Scielzo; M. Sisti; A. R. Smith; L. Taffarello; M. Tenconi; W. D. Tian; C. Tomei; S. Trentalange; G. Ventura; M. Vignati; B. S. Wang; H. W. Wang; C. A. Whitten Jr.; T. Wise; A. Woodcraft; L. Zanotti; C. Zarra; B. X. Zhu; S. Zucchelli

2012-09-13

285

Destruction of 18F via 18F(p,a)15O Burning Through the Ec.m. = 665 keV Resonance  

SciTech Connect

Knowledge of the astrophysical rate of the {sup 18}F(p,a){sup 15}O reaction is important for understanding the {gamma}-ray emission expected from novae and heavy-element production in x-ray bursts. The rate of this reaction is dominated at temperatures above {approx}0.4 GK by a resonance near 7.08 MeV excitation energy in {sup 19}Ne. The {sup 18}F(p,a){sup 15}O rate has been uncertain in part because of disagreements among previous measurements concerning the resonance strength and excitation energy of this state. To resolve these uncertainties, we have made simultaneous measurements of the {sup 1}H({sup 18}F,p){sup 18}F and {sup 1}H({sup 18}F,a){sup 15}O excitation functions using a radioactive {sup 18}F beam at the ORNL Holifield Radioactive Ion Beam Facility. A simultaneous fit of the data sets has been performed, and the best fit was obtained with a center-of-mass resonance energy of 664.7 {+-} 1.6 keV (E{sub x} = 7076 {+-} 2 keV), a total width of 39.0 {+-} 1.6 keV, a proton branching ratio of {Lambda}{sub p}/{Lambda} = 0.39 {+-} 0.02, and a resonance strength of {omega}{gamma} = 6.2 {+-} 0.3 keV.

Bardayan, D.W.

2001-06-01

286

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

287

Blistering of GaAs by low keV H, D, and He ions  

NASA Astrophysics Data System (ADS)

The thermally activated blistering of the GaAs (100) surface after 5- and 10keV H, D, and He ion implantations was investigated. A large isotope effect is observed as the critical blistering fluences are two to three times higher for D than for H ions. Blistering and exfoliation are also obtained for very low He ion fluence, contrary to Si which is impervious to He blistering in the same conditions. The exfoliated crater depth depends strongly on the He fluence, varying, at 10keV, from 75±10nm (for 1.6×1016He/cm2), consistent with the ion projected range determined by computation, to a saturation value of 155±10nm for doses >4×1016He/cm2. Our results suggest that the fracture leading to cleavage is triggered at a local He concentration of about 2at.%, where dislocations and nanocavities are created.

Giguère, Alexandre; Desrosiers, Nicholas; Terreault, Bernard

2005-11-01

288

870. 8-keV gamma ray from PuO/sub 2/  

SciTech Connect

A /sup 252/Cf neutron source and an /sup 241/Am alpha source were used with isotopically enriched water containing 43.9% /sup 17/O and 43.1% /sup 18/O, to study the (n,n'UPSILON) and (..cap alpha..,..cap alpha..'UPSILON) reactions in /sup 17/O and /sup 18/O. The production yields for the 870.8-keV gamma ray from /sup 17/O and the 1982.2-keV gamma ray from /sup 18/O were measured. In addition, the average cross sections over the /sup 252/Cf fission neutron spectrum for /sup 17/O(n,n'UPSILON)/sup 17/O and /sup 18/O(n,n'UPSILON)/sup 18/O were determined.

Hsu, H.H.

1981-01-01

289

Questioning a 3.5 keV dark matter emission line  

E-print Network

Recent results of line emission at 3.5 keV in both individual and stacked X-ray spectra of galaxy clusters has been speculated to have dark matter origin. We analyse Chandra X-ray observations of the Milky Way where, if the origin is indeed dark matter, such a line should be very strong. We find no clear evidence for its presence but the results are strongly dependent on the assumptions about the astrophysical sources, that goes into the spectral modelling. For the most conservative assumptions the Milky Way observations are consistent with a line at 3.5 keV but when excluding known emission lines, the allowed extra emission significantly decreases and rules out the predicted line at 95% confidence level. We present flux limits and interpretations for various scenarios (decaying and annihilating dark matter).

Riemer-Sorensen, Signe

2014-01-01

290

A large scale height galactic component of the diffuse 2-60 keV background  

NASA Technical Reports Server (NTRS)

The diffuse 2-60 keV X-ray background has a galactic component clearly detectable by its strong variation with both galactic latitude and longitude. This galactic component is typically 10 percent of the extragalactic background toward the galactic center, half that strong toward the anticenter, and extrapolated to a few percent of the extragalactic background toward the galactic poles. It is acceptably modeled by a finite radius emission disk with a scale height of several kiloparsecs. The averaged galactic spectrum is best fitted by a thermal spectrum of kT about 9 keV, a spectrum much softer than the about 40 keV spectrum of the extragalactic component. The most likely source of this emission is low luminosity stars with large scale heights such as subdwarfs. Inverse Compton emission from GeV electrons on the microwave background contributes only a fraction of the galactic component unless the local cosmic ray electron spectrum and intensity are atypical.

Iwan, D.; Marshall, F. E.; Boldt, E. A.; Mushotzky, R.; Shafer, R. A.; Stottlemyer, A.

1982-01-01

291

Determination of the branching ratio for the {sup 209}Bi (n, {gamma}) {sup 210}Bi reaction from 500 eV to 20 keV  

SciTech Connect

Energy differential neutron capture cross section measurements have been performed to determine the branching ratio for the {sup 209}Bi(n, {gamma}) reaction. The measurements were carried out at the time-of-flight facility GELINA of the IRMM in Geel (Belgium). The capture measurements were performed at a 12 m flight path using three High-Purity Germanium detectors. The experimental set-up was optimized to reduce the prompt background due to scattered neutrons. Several {gamma}-ray spectra corresponding to the {sup 209}Bi + n resonances up to 20 keV were deduced. The results of a preliminary data analysis are given in this paper. (authors)

Borella, A. [CEA/Saclay, DSM/DAPNIA/SPhN, F-91911 Gif-sur-Yvette (France); Belgya, T. [II, CRC HAS, P.O. Box 77, H-1525 Budapest (Hungary); Berthomieux, E. [CEA/Saclay, DSM/DAPNIA/SPhN, F-91911 Gif-sur-Yvette (France); Colonna, N. [Istituto Nazionale di Fisica Nucleare, Bari (Italy); Domingo-Pardo, C. [Instituto de Fisica Corpuscular, CSIC-Universidad de Valencia (Spain); Gunsing, F. [II, CRC HAS, P.O. Box 77, H-1525 Budapest (Hungary); Marrone, S. [Istituto Nazionale di Fisica Nucleare, Bari (Italy); Martinez, T. [Centro de Investigaciones Energeticas Medioambientales y Technologicas, Madrid (Spain); Massimi, C. [Istituto Nazionale di Fisica Nucleare, Bologna (Italy); Mastinu, P. M. [Laboratori Nazionali di Legnaro, Legnaro (Italy); Milazzo, P. M. [Istituto Nazionale di Fisica Nucleare, Trieste (Italy); Schillebeeckx, P. [EC-JRC-IRMM, Retieseweg 111, B-2440 Geel (Belgium); Tagliente, G. [Istituto Nazionale di Fisica Nucleare, Bari (Italy); Tain, J. [Instituto de Fisica Corpuscular, CSIC-Universidad de Valencia (Spain); Terlizzi, R. [Istituto Nazionale di Fisica Nucleare, Bari (Italy); Wynants, R. [EC-JRC-IRMM, Retieseweg 111, B-2440 Geel (Belgium)

2006-07-01

292

X-ray fluorescence in some rare earth and high Z elements excited by 661.6 keV g-rays  

NASA Astrophysics Data System (ADS)

The K-shell X-ray fluorescence cross sections are determined experimentally for 10 elements such as Pb, Hg, Ir, W, Lu, Tm, Dy, Tb, Gd and Nd at excitation energy of 661.6 keV associated with g-rays of 137Cs radioisotope. The technique employed involves the measurement of total intensity of fluorescent K X-rays that follow the photoeffect absorption of a known flux of g-rays using a well type NaI(Tl) detector. The obtained results are compared with the available theoretical values and other measured values.

Yashoda, T.; Krishnaveni, S.; Gowda, Shivalinge; Umesh, T. K.; Gowda, Ramakrishna

2002-01-01

293

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

E-print Network

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

E. Churazov; S. Sazonov; R. Sunyaev; M. Revnivtsev

2006-08-11

294

Alignment of the 1[ital s]2[ital p] vacancy states of Ne doubly ionized by 700--2000-keV proton impact  

SciTech Connect

The angular distribution of [ital KL][sub 23-][ital LLL][sub 23] Auger electrons emitted from the decay of 1[ital s]2[ital p] vacancy states of Ne doubly ionized by 700--2000-keV protons has been measured. From the measured anisotropy of the Auger lines the alignment of the double-vacancy states has been deduced. Our data compared with different theories indicate that the shake-off plays an important role in the double-ionization process at these energies.

Takacs, E.; Ricz, S.; Vegh, J.; Kadar, I.; Palinkas, J.; Sulik, B.; Toth, L.; Berenyi, D. (Institute of Nuclear Research of the Hungarian Academy of Sciences (ATOMKI), POB 51, H-4001 Debrecen (Hungary)); Kabachnik, N.M. (Institute of Nuclear Physics, Moscow State University, Moscow 119899 (Russian Federation))

1994-08-01

295

New emission line at ~3.5 keV - observational status, connection with radiatively decaying dark matter and directions for future studies  

E-print Network

Recent works of [1402.2301,1402.4119], claiming the detection of extra emission line with energy ~3.5 keV in X-ray spectra of certain clusters of galaxies and nearby Andromeda galaxy, have raised considerable interest in astrophysics and particle physics communities. A number of new observational studies claim detection or non-detection of the extra line in X-ray spectra of various cosmic objects. In this review I summarize existing results of these studies, overview possible interpretations of the extra line, including intriguing connection with radiatively decaying dark matter, and show future directions achievable with existing and planned X-ray cosmic missions.

Iakubovskyi, Dmytro

2014-01-01

296

Experimental study of the {sup 91}Zr(n,{gamma}) reaction up to 26 keV  

SciTech Connect

The neutron capture cross sections of the Zr isotopes are relevant to studies in nuclear structure, nuclear astrophysics, and nuclear technology. The valence neutron of {sup 91}Zr with respect to the neutron magic nucleus {sup 90}Zr has interesting implications for the statistical analysis in the proximity of shell closures. In stellar nucleosynthesis, the Zr isotopes are important for the s-process reaction flow between the Fe seeds and the heavier isotopes. Because of its relatively small (n,{gamma}) cross sections, Zr represents also an interesting structural material for nuclear reactors. For the same reason, these cross sections are difficult to measure and reliable data are sparse. Therefore, the (n,{gamma}) cross sections of the Zr isotopes have been remeasured at the CERN n{sub T}OF facility. Thanks to its high instantaneous flux, good energy resolution, and low background, this facility is particularly suited for the determination of small, resonance-dominated cross sections. In this work, results for the {sup 91}Zr(n,{gamma}){sup 92}Zr reaction are reported in the neutron energy range from thermal to 26 keV. In this region, accurate data of 157 resonances could be obtained, 33 of these resonances are not present in the main databases and/or were observed for the first time.

Tagliente, G.; Colonna, N.; Marrone, S.; Terlizzi, R. [Istituto Nazionale di Fisica Nucleare (INFN), Bari (Italy); Milazzo, P. M.; Fujii, K.; Abbondanno, U.; Belloni, F.; Moreau, C. [Istituto Nazionale di Fisica Nucleare (INFN), Trieste (Italy); Aerts, G.; Andriamonje, S.; Berthoumieux, E.; Dridi, W.; Gunsing, F.; Pancin, J.; Perrot, L.; Plukis, A. [CEA/Saclay-DSM/DAPNIA, Gif-sur-Yvette (France); Alvarez, H.; Duran, I.; Paradela, C. [Universidade de Santiago de Compostela (Spain)] (and others)

2008-10-15

297

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

SciTech Connect

Fragmentation ratios and branching ratios are measured for ionization and dissociative ionization for 20-150 keV (0.9-2.4v{sub 0}) proton collisions with gas-phase uracil molecules. Through event-by-event determination of the postcollision projectile charge, it is possible for such a key biomolecule to distinguish between electron capture (EC) by the incident proton and direct ionization (DI) without projectile neutralization. While the same fragment ion groups are observed in the mass spectra for both processes, EC induces dissociation with greater efficiency than DI in the impact energy range of 35-150 keV (1.2-2.4v{sub 0}). In this range EC is also less abundant than DI with a branching ratio for EC/total ionization of <50%. Moreover, whereas fragmentation ratios do not change with energy in the case of EC, DI mass spectra show a tendency for increased fragmentation at lower impact energies.

Tabet, J.; Eden, S.; Feil, S.; Abdoul-Carime, H.; Farizon, B.; Farizon, M.; Ouaskit, S.; Maerk, T. D. [Universite de Lyon, F-69003, Lyon (France); Universite Lyon 1, Villeurbanne, CNRS/IN2P3, UMR5822, Institut de Physique Nucleaire de Lyon, F-69622 Villeurbanne (France)

2010-01-15

298

A CHANDRA OBSERVATION OF 3C 288-REHEATING THE COOL CORE OF A 3 keV CLUSTER FROM A NUCLEAR OUTBURST at z = 0.246  

SciTech Connect

We present results from a 42 ks Chandra/ACIS-S observation of the transitional FR I/FR II radio galaxy 3C 288 at z = 0.246. We detect {approx}3 keV gas extending to a radius of {approx}0.5 Mpc with a 0.5-2.0 keV luminosity of 6.6 x 10{sup 43} erg s{sup -1}, implying that 3C 288 lies at the center of a poor cluster. We find multiple surface brightness discontinuities in the gas indicative of either a shock driven by the inflation of the radio lobes or a recent merger event. The temperature across the discontinuities is roughly constant with no signature of a cool core, thus disfavoring either the merger cold front or sloshing scenarios. We argue therefore that the discontinuities are shocks due to the supersonic inflation of the radio lobes. If they are shocks, the energy of the outburst is {approx}10{sup 60} erg, or roughly 30% of the thermal energy of the gas within the radius of the shock, assuming that the shocks are part of a front produced by a single outburst. The cooling time of the gas is {approx}10{sup 8} yr, so that the energy deposited by the nuclear outburst could have reheated and efficiently disrupted a cool core.

Lal, D. V.; Kraft, R. P.; Forman, W. R.; Jones, C.; Nulsen, P. E. J.; Evans, D. A.; Lee, J. C. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Hardcastle, M. J. [School of Physics, Astronomy, and Mathematics, University of Hertfordshire, Hatfield, AL 10 9AB (United Kingdom); Croston, J. H. [School of Physics and Astronomy, University of Southampton, Southampton, SO17 1SJ (United Kingdom)

2010-10-20

299

High Energy Transients! Neil Gehrels  

E-print Network

Detection ! X-rays! -rays! OSO-7 Dec 20, 1972 .! Time ! Countss-1.! RHESSI July 23, 2002! Countscm-2s-1keV-1! Energy (keV)! OSO-7 Detector! #12;Teegarden, Tueller et al. 1988! Early Supernova -Ray Detection! GRIS

Hinton, Jim

300

Prospects For Gamma-ray Focusing Telescopes Beyond 70/100 Kev  

NASA Astrophysics Data System (ADS)

I will report on the LAUE project, devoted to the development of a lens petal with 20 m focal length. The final goal is to develop a technology for building Laue lenses with a passband from 70/100 to 600 keV. The project is on the way in a synergic collaboration between scientific institutions (University of Ferrara; INAF/IASF, Bologna; CNR/IMEM, Parma; DTM, Modena; Thales-Alenia Space Italy). The LAUE project is supported by the Italian Space Agency ASI.

Frontera, F.

2011-09-01

301

A 9 keV electron-impact liquid-gallium-jet x-ray source  

Microsoft Academic Search

We demonstrate a high-brightness compact 9 keV electron-impact microfocus x-ray source based on a liquid-gallium-jet anode. A ~30 W, 50 kV electron gun is focused onto the ~20 m\\/s, 30 mum diameter liquid-gallium-jet anode to produce an ~10 mum full width at half maximum x-ray spot. The peak spectral brightness is >2×1010 photons\\/(s mm2 mrad2×0.1% BW). Calculation and experiments show

M. Otendal; T. Tuohimaa; U. Vogt; H. M. Hertz

2008-01-01

302

Setup of an 8 keV laboratory transmission x-ray microscope  

NASA Astrophysics Data System (ADS)

This article presents a concept and the first results for the setup of an 8keV laboratory transmission x-ray microscope with a polycapillary optic as condenser at the BliX in Berlin. The incentive of building such a microscope is that the penetration depth for hard x-rays is much higher than in the soft x-ray range, e.g. the water window. Therefore, it is possible to investigate even dense materials such as metal compounds, bones or geological samples. The future aim is to achieve a spatial resolution better than 200 nm.

Baumbach, S.; Kanngießer, B.; Malzer, W.; Stiel, H.; Bjeoumikhova, S.; Wilhein, T.

2014-04-01

303

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

304

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

305

Three-Dimensional Fully Differential Single Ionization Cross Sections for 75 keV p + He collisions  

NASA Astrophysics Data System (ADS)

Single ionization of a neutral atom by a charged particle impact is a most suitable process to study the fundamentally important few-body problem. The most detailed information can be obtained from fully differential cross section (FDCS). FDCS for single ionization can be obtained by measuring the momenta of any two of three particles involved in the interaction. In our experiment we measured the complete momentum vector of the projectile and the ionized target. The electron momentum is then readily determined by momentum conservation. The ionized target momentum was obtained using cold-target recoil-ion momentum spectroscopy (COLTRIMS) while the projectile momentum was obtained using ion energy-loss spectroscopy. Using this experimental technique, we studied single ionization of He by proton impact at 75 keV. Such collision system corresponds to a perturbation of 0.6, defined as Q_p/vp (where Qp and vp are the projectile charge and velocity, respectively) and small relative speed between the projectile and the ionized electron. At these kinematic conditions, the post-collision interaction (PCI) is particularly important. The experimental results are compared to various theoretical models including a CDW calculation with the n-n interaction included. Good agreement in shape but poor agreement in magnitude is found.

Maydanyuk, N.; Hasan, A.; Fendler, B.; Schulz, M.; Voitkiv, A.

2004-05-01

306

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

NASA Astrophysics Data System (ADS)

Room temperature irradiation of InSb(111) by 60 keV Ar+-ions at normal (0°) and oblique (60°) angles of incidence led to the formation of nanoporous structure in the high fluence regime of 1 × 1017 to 3 × 1018 ions cm-2. While a porous layer comprising of a network of interconnected nanofibers was generated by normal ion incidence, evolution of plate-like structures was observed for obliquely incident ions. Systematic studies of composition and structure using energy dispersive x-ray spectroscopy, Raman spectroscopy, x-ray photoelectron spectroscopy, Raman mapping, grazing incidence x-ray diffraction, and cross-sectional transmission electron microscopy revealed a high degree of oxidation of the ion-induced microstructures with the presence of In2O3 and Sb2O3 phases and presence of nanocrystallites within the nanoporous structures. The observed structural evolution was understood in terms of processes driven by ion-induced defect accumulation within InSb.

Datta, D. P.; Garg, S. K.; Satpati, B.; Sahoo, P. K.; Kanjilal, A.; Dhara, S.; Kanjilal, D.; Som, T.

2014-10-01

307

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

308

Abundance of 766.6 and 1001 keV ?-Quanta in the 238U Decay Chain  

Microsoft Academic Search

The abundances of 63.3, 185.7, 766.6, 1001 keV ?-quanta in the 238U decay chain, determinedby semiconductor ?-ray spectrometry of metallic uranium foil, are 4.2, 48, 0.39, and 1.12%, respectively.The abundance of 766.6 and 1001 keV ?-ray quanta is higher than the generally accepted values by a factor of 1.9.

S. I. Ushakov

2002-01-01

309

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

310

Improving accuracy and reliability of 186-keV measurements for unattended enrichment monitoring  

SciTech Connect

Improving the quality of safeguards measurements at Gas Centrifuge Enrichment Plants (GCEPs), whilst reducing the inspection effort, is an important objective given the number of existing and new plants that need to be safeguarded. A useful tool in many safeguards approaches is the on-line monitoring of enrichment in process pipes. One aspect of this measurement is a simple, reliable and precise passive measurement of the 186-keV line from {sup 235}U. (The other information required is the amount of gas in the pipe. This can be obtained by transmission measurements or pressure measurements). In this paper we describe our research efforts towards such a passive measurement system. The system includes redundant measurements of the 186-keV line from the gas and separately from the wall deposits. The design also includes measures to reduce the effect of the potentially important background. Such an approach would practically eliminate false alarms and can maintain the operation of the system even with a hardware malfunction in one of the channels. The work involves Monte Carlo modeling and the construction of a proof-of-principle prototype. We will carry out experimental tests with UF{sub 6} gas in pipes with and without deposits in order to demonstrate the deposit correction.

Ianakiev, Kiril D [Los Alamos National Laboratory; Boyer, Brian D [Los Alamos National Laboratory; Swinhoe, Martyn T [Los Alamos National Laboratory; Moss, Cal E [Los Alamos National Laboratory; Goda, Joetta M [Los Alamos National Laboratory; Favalli, Andrea [Los Alamos National Laboratory; Lombardi, Marcie [Los Alamos National Laboratory; Paffet, Mark T [Los Alamos National Laboratory; Hill, Thomas R [Los Alamos National Laboratory; Mac Arthur, Duncan W [Los Alamos National Laboratory; Smith, Morag K [Los Alamos National Laboratory

2010-01-01

311

7 keV Sterile neutrino dark matter in $U(1)_R-$ lepton number model  

E-print Network

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 $\\sim$ 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 $\\sim \\mathcal O$(GeV).

Chakraborty, Sabyasachi; Roy, Sourov

2014-01-01

312

7 keV Sterile neutrino dark matter in $U(1)_R-$ lepton number model  

E-print Network

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 $\\sim$ 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 $\\sim \\mathcal O$(GeV).

Sabyasachi Chakraborty; Dilip Kumar Ghosh; Sourov Roy

2014-05-27

313

Emission Lines between 1 and 2 keV in Cometary X-Ray Spectra  

NASA Astrophysics Data System (ADS)

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.; Bodewits, Dennis; Dennerl, Konrad; Lisse, Carey M.; Wolk, Scott J.

2013-01-01

314

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

315

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

NASA Astrophysics Data System (ADS)

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

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

1981-05-01

316

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

317

Non-abelian Dark Matter Solutions for Galactic Gamma-ray Excess and Perseus 3.5 keV X-ray Line  

E-print Network

We attempt to explain simultaneously the Galactic center gamma-ray excess and the 3.5 keV X-ray line from the Perseus cluster based on a class of non-abelian $SU(2)$ DM models, in which the dark matter and an excited state comprise a "dark" $SU(2)$ doublet. The non-abelian group kinetically mixes with the standard model gauge group via dimensions-5 operators. The dark matter particles annihilate into standard model fermions, followed by fragmentation and bremsstrahlung, and thus producing a continuous spectrum of gamma-rays. On the other hand, the dark matter particles can annihilate into a pair of excited states, each of which decays back into the dark matter particle and an X-ray photon, which has an energy equal to the mass difference between the dark matter and the excited state, which is set to be 3.5 keV. The large hierarchy between the required X-ray and $\\gamma$-ray annihilation cross-sections can be achieved by a very small kinetic mixing between the SM and dark sector, which effectively suppresses t...

Cheung, Kingman; Tsai, Yue-Lin Sming

2014-01-01

318

Interacting dark matter contribution to the galactic 511 keV gamma ray emission: constraining the morphology with INTEGRAL/SPI observations  

NASA Astrophysics Data System (ADS)

We compare the full-sky morphology of the 511 keV gamma ray excess measured by the INTEGRAL/SPI experiment to predictions of models based on dark matter (DM) scatterings that produce low-energy positrons: either MeV-scale DM that annihilates directly into e+e- pairs, or heavy DM that inelastically scatters into an excited state (XDM) followed by decay into e+e- and the ground state. By direct comparison to the data, we find that such explanations are consistent with dark matter halo profiles predicted by numerical many-body simulations for a Milky Way-like galaxy. Our results favor an Einasto profile over the cuspier NFW distribution and exclude decaying dark matter scenarios whose predicted spatial distribution is too broad. We obtain a good fit to the shape of the signal using six fewer degrees of freedom than previous empirical fits to the 511 keV data. We find that the ratio of flux at Earth from the galactic bulge to that of the disk is between 1.9 and 2.4, taking into account that 73% of the disk contribution may be attributed to the beta decay of radioactive 26Al.

Vincent, Aaron C.; Martin, Pierrick; Cline, James M.

2012-04-01

319

Characteristic Behavior and Scaling Studies of Self Organized InP Nano-dots formed via keV and MeV irradiations  

NASA Astrophysics Data System (ADS)

The controlled formation of nano-dots, using ion beams as tool, has become important as it offers a unique method to generate non-equilibrium phases with novel physical properties and structures with nano-dimensions. We have investigated the creation of self assembled nano- dots on InP(111) surfaces after 3 keV as well as 1.5 MeV ion beams at a large range of fluences. We have studied the Scaling exponents of the evolved surfaces by utilizing the technique of Scanning Probe Microscopy (SPM). At keV energies ripening of the nano-dots is seen below a critical time whereas an inverse ripening is observed for longer durations. At the critical time square shaped array of nano --dots are observed. The dots are characterized by narrow height and size distributions. Nano dots have also been observed at MeV ion irradiations. Their size distribution though broad at lowest fluence decreases for larger fluences.

Paramanik, Dipak; Varma, Shikha

2008-04-01

320

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

321

The 3.5 keV X-ray line signature from annihilating and decaying dark matter in Weinberg model  

E-print Network

Recently two groups independently observed unidentified X-ray line signal at the energy 3.55 keV from the galaxy clusters and Andromeda galaxy. We show that this anomalous signal can be explained in annihilating dark matter model, for example, fermionic dark matter model in hidden sector with global $U(1)_X$ symmetry proposed by Weinberg. There are two scenarios for the production of the annihilating dark matters. In the first scenario the dark matters with mass 3.55 keV decouple from the interaction with Goldstone bosons and go out of thermal equilibrium at high temperature ($>$ 1 TeV) when they are still relativistic, their number density per comoving volume being essentially fixed to be the current value. The correct relic abundance of this warm dark matter is obtained by assuming that about ${\\cal O}(10^3)$ relativistic degrees of freedom were present at the decoupling temperature or alternatively large entropy production occurred at high temperature. In the other scenario, the dark matters were absent at...

Baek, Seungwon; Park, Wan-Il

2014-01-01

322

Solar energetic photon transients - 50 keV-100 MeV  

NASA Technical Reports Server (NTRS)

The observed properties of solar transient photon impulses between a few keV and 100 MeV recorded by the SMM are compared and reasons for continued monitoring of solar photon transients are discussed. Various solar flare events observed are reviewed, along with gamma ray measurements. It is calculated that the emission of energetic photons is due to ion and electron interactions with matter, with both species undergoing acceleration at close time intervals. The gamma ray events and microwave emissions showed time structures similar to previously recorded X ray emissions. Bursts of all three radiation types have displayed a quasi-periodicity of less than 10 sec. Data on the 2.223 MeV neutron capture line have shown a decay in line intensity to take about 50 sec, consistent with Monte Carlo calculation for a He-3/H abundance of 0.00005.

Chupp, E. L.

1982-01-01

323

Ion beam mixing of marker layers in Al and Si. [300 keV Ar ions  

SciTech Connect

Ion beam mixing experiments on thin Pt, Au, and Ni markers in Al and Si have performed at 17, 85, and 300 K. After irradiation with 300-keV Ar ions the broadening and relative shifts of the markers have been determined by RBS measurements. The marker broadenings are more pronounced in Si than in Al; in both matrices the broadenings decrease in the following order: Au, Pt, and Ni. No dependence of mixing on irradiation temperature was observed between 17 and 300 K. The shifts of the heavy Au and Pt markers relative to the Ni markers are approximately equal to the experimental accuracy. However, a shift of the Ni marker toward the surface relative to the heavier Au and Pt markers was consistently observed. 13 references, 2 figures.

Mantl, S.; Rehn, L.E.; Averback, R.S.; Thompson, L.J. Jr.

1984-07-01

324

Silicon-carbon bond inversions driven by 60-keV electrons in graphene.  

PubMed

We demonstrate that 60-keV electron irradiation drives the diffusion of threefold-coordinated Si dopants in graphene by one lattice site at a time. First principles simulations reveal that each step is caused by an electron impact on a C atom next to the dopant. Although the atomic motion happens below our experimental time resolution, stochastic analysis of 38 such lattice jumps reveals a probability for their occurrence in a good agreement with the simulations. Conversions from three- to fourfold coordinated dopant structures and the subsequent reverse process are significantly less likely than the direct bond inversion. Our results thus provide a model of nondestructive and atomically precise structural modification and detection for two-dimensional materials. PMID:25259987

Susi, Toma; Kotakoski, Jani; Kepaptsoglou, Demie; Mangler, Clemens; Lovejoy, Tracy C; Krivanek, Ondrej L; Zan, Recep; Bangert, Ursel; Ayala, Paola; Meyer, Jannik C; Ramasse, Quentin

2014-09-12

325

Silicon-Carbon Bond Inversions Driven by 60-keV Electrons in Graphene  

NASA Astrophysics Data System (ADS)

We demonstrate that 60-keV electron irradiation drives the diffusion of threefold-coordinated Si dopants in graphene by one lattice site at a time. First principles simulations reveal that each step is caused by an electron impact on a C atom next to the dopant. Although the atomic motion happens below our experimental time resolution, stochastic analysis of 38 such lattice jumps reveals a probability for their occurrence in a good agreement with the simulations. Conversions from three- to fourfold coordinated dopant structures and the subsequent reverse process are significantly less likely than the direct bond inversion. Our results thus provide a model of nondestructive and atomically precise structural modification and detection for two-dimensional materials.

Susi, Toma; Kotakoski, Jani; Kepaptsoglou, Demie; Mangler, Clemens; Lovejoy, Tracy C.; Krivanek, Ondrej L.; Zan, Recep; Bangert, Ursel; Ayala, Paola; Meyer, Jannik C.; Ramasse, Quentin

2014-09-01

326

SIMPle Dark Matter: Self-Interactions and keV Lines  

E-print Network

We consider a simple supersymmetric hidden sector: pure SU(N) gauge theory. Dark matter is made up of hidden glueballinos with mass $m_X$ and hidden glueballs with mass near the confinement scale $\\Lambda$. For $m_X \\sim 1~\\text{TeV}$ and $\\Lambda \\sim 100~\\text{MeV}$, the glueballinos freeze out with the correct relic density and self-interact through glueball exchange to resolve small-scale structure puzzles. An immediate consequence is that the glueballino spectrum has a hyperfine splitting of order $\\Lambda^2 / m_X \\sim 10~\\text{keV}$. We show that the radiative decays of the excited state can explain the observed 3.5 keV X-ray line signal from clusters of galaxies, Andromeda, and the Milky Way.

Boddy, Kimberly K; Kaplinghat, Manoj; Shadmi, Yael; Tait, Timothy M P

2014-01-01

327

Interaction of 30 keV O3+ ions with Al2O3 nanocapillaries  

NASA Astrophysics Data System (ADS)

Interaction of 30 keV O3+ ions with capillaries in an Al2O3 membrane was studied. The charge state distribution and the angular distribution of the ions transmitted through the capillaries were measured. Shifts of the transmission profile centroid by twice of the capillary tilt angle ? and double-peak structure in the transmission profile were found. Difficulties exist in determination of the impact point location on the capillary wall and the scattering angle for each collision to interpret the observed 2? shift phenomenon. The transmission profile width and ion guiding ability of the concerned capillaries for the used projectile ions were analyzed. Comparison of the present guiding angle and the prediction of scaling laws was conducted. Further work concerning the influence of the material and its surface treatment on the guiding properties is needed.

Xi, F. Y.; Lv, H. Y.

2014-11-01

328

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

329

keV warm dark matter via the supersymmetric Higgs portal  

SciTech Connect

Warm dark matter (WDM) may resolve the possible conflict between observed galaxy halos and the halos produced in cold dark matter simulations. Here, we present an extension of the minimal supersymmetric standard model to include WDM by adding a gauge singlet fermion, {chi}, with a portal-like coupling to the minimal supersymmetric standard model Higgs doublets. This model has the property that the dark matter is necessarily warm. In the case where M{sub {chi}} is mainly due to electroweak symmetry breaking, the {chi} mass is completely determined by its relic density and the reheating temperature T{sub R}. For 10{sup 2} GeV < or approx. T{sub R} < or approx. 10{sup 5} GeV, the range allowed by {chi} production via thermal Higgs annihilation, the {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_equal}5x10{sup 6}(eV/cm{sup 3})/(km/s){sup 3}, when the reheating temperature is in the range T{sub R}{approx_equal}10-100 TeV, in which case M{sub {chi}}{approx_equal}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 cold dark matter simulations.

McDonald, John; Sahu, Narendra [Cosmology and Astroparticle Physics Group, University of Lancaster, Lancaster LA1 4YB (United Kingdom)

2009-05-15

330

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

331

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

332

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

333

Excited dark matter reconciles conflicting observations of 3.5 keV X-rays  

E-print Network

Tentative evidence of a 3.5 keV X-ray line has been found in the stacked spectra of galaxy clusters, individual clusters, the Andromeda galaxy and the galactic center, leading to speculation that it could be due to decays of metastable dark matter such as sterile neutrinos. However searches for the line in other systems such as dwarf satellites of the Milky Way have given negative or ambiguous results. We reanalyze both the positive and negative searches from the point of view that the line is due to inelastic scattering of dark matter to an excited state that subsequently decays---the mechanism of excited dark matter (XDM). Unlike the metastable dark matter scenario, XDM gives a stronger signal in systems with higher velocity dispersions, such as galaxy clusters. We show that the predictions of XDM can be consistent with null searches from dwarf satellites, while the signal from the closest individual galaxies can be detectable having a flux consistent with that from clusters. We discuss the impact of our ne...

Cline, James M

2014-01-01

334

The poker face of the Majoron dark matter model: LUX to keV line  

NASA Astrophysics Data System (ADS)

We study the viability of pseudo Nambu-Goldstone bosons (Majorons) arising in see-saw models as dark matter candidates. Interestingly the stability of the Majoron as dark matter is related to the scale that sets the see-saw and leptogenesis mechanisms, while its annihilation and scattering cross section off nuclei can be set through the Higgs portal. For O(GeV)-O(TeV) Majorons, we compute observables such as the abundance, scattering cross section, Higgs invisible decay width, and emission lines and compare with current data in order to outline the excluded versus still viable parameter space regions. We conclude that the simplest Majoron dark matter models coupling through the Higgs portal, except at the Higgs resonance, are excluded by current direct detection data for Majorons lighter than 225 GeV and future runnings are expected to rule out decisively the 1 GeV-1 TeV window. Lastly, we point out that light keV-scale Majorons whose relic density is set by thermal freeze-in from sterile neutrinos can account for the keV line observed by XMM-Newton observatory in the spectrum of 73 galaxy clusters, within a see-saw model with a triplet Higgs.

Queiroz, Farinaldo S.; Sinha, Kuver

2014-07-01

335

100 keV electron backscattered range and coefficient for silicon.  

SciTech Connect

The authors have measured the range and intensity of backscattered electrons in silicon from a 100 keV source using a process independent method. Backscattered electrons contributed to the total dose of features written in a negative tone electron beam resist. Instead of measuring the height of the resist and using a contrast curve to convert the resist height to dose, the heights of the features were made equal by adjusting the backscattered contribution through dose assignments. Creating features of equal height eliminated the need to use a contrast curve to convert from resist height to total dose. Also, it allowed for measurements of the backscattered contribution from larger distances. Using a circularly symmetric torus pattern, the three-dimensional backscatter problem was reduced to a 1-dimensional Gaussian form. The authors measured the range of the backscattered electrons, {beta}, to be 31.08 {+-} 0.06 {micro}m. By varying the writing dose of the pattern, we determined the backscatter coefficient, {eta}, to be 0.63 {+-} 0.03.

Czaplewski, D.A.; Ocola, L.E. (Center for Nanoscale Materials)

2012-01-01

336

Nonabelian dark matter models for 3.5 keV X-rays  

NASA Astrophysics Data System (ADS)

A recent analysis of XXM-Newton data reveals the possible presence of an X-ray line at approximately 3.55 keV, which is not readily explained by known atomic transitions. Numerous models of eV-scale decaying dark matter have been proposed to explain this signal. Here we explore models of multicomponent nonabelian dark matter with typical mass ~ 1-10 GeV (higher values being allowed in some models) and eV-scale splittings that arise naturally from the breaking of the nonabelian gauge symmetry. Kinetic mixing between the photon and the hidden sector gauge bosons can occur through a dimension-5 or 6 operator. Radiative decays of the excited states proceed through transition magnetic moments that appear at one loop. The decaying excited states can either be primordial or else produced by upscattering of the lighter dark matter states. These models are significantly constrained by direct dark matter searches or cosmic microwave background distortions, and are potentially testable in fixed target experiments that search for hidden photons. We note that the upscattering mechanism could be distinguished from decays in future observations if sources with different dark matter velocity dispersions seem to require different values of the scattering cross section to match the observed line strengths.

Cline, James M.; Frey, Andrew R.

2014-10-01

337

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

338

Measuring the 511 keV emission in the direction of 1E1740.7-2942 with BATSE  

NASA Technical Reports Server (NTRS)

Observations of the 511 keV emission in the direction of 1E 1740.7-2942 (1E) using the earth burst and transient source experiment (BATSE) onboard the Compton Gamma Ray Observatory (CGRO), are presented. The CGRO phase 1 average spectrum of 1E is calculated using a method which assumes that a given source spectrum is the sum of the flux coming directly from the object and the contribution from the surrounding diffuse emission. The 1E light curve is calculated in the 40 to 150 keV range. It presents a constant flux excess of 70 mCrab in comparison with observations from the SIGMA gamma ray telescope onboard the GRANAT observatory. By removing this contribution, the 1E spectral transition from the low state to the high standard state observed by SIGMA is confirmed, and it is shown that the 511 keV flux is independent of the 1E long term evolution from low state to high standard state. It is concluded that the 511 keV emission of (4.2 +/- 1.3) x 140(exp -4) photons/sq cm s observed in the direction of 1E is mainly diffuse and spatially extended.

Wallyn, P.; Ling, J. C.; Mahoney, W. A.; Wheaton, W. A.; Durouchoux, P.; Corbel, S.; Astier-Perret, L.; Poirot, L.

1997-01-01

339

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

340

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

341

Desorption of large organic molecules induced by keV projectiles A. Delcorte *, B.J. Garrison  

E-print Network

Desorption of large organic molecules induced by keV projectiles A. Delcorte *, B.J. Garrison in the sample. These events are char- acterized by the simultaneous motion of several hundreds of substrate and synthetic polymers. In the simulation, these events are capable of desorbing polystyrene molecules of 2 k

342

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 Short title: ENERGETIC ELECTRONS AT GEOSYNCHRONOUS ORBIT #12;2 Abstract. Using simultaneous measurements of the upstream solar wind and of energetic electrons at geosynchronous orbit, we analyze the response

Li, Xinlin

343

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

344

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

345

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

346

The INTEGRAL/SPI 511 keV Signal from Hidden Valleys  

SciTech Connect

We examine under what circumstances the INTEGRAL/SPI 511 keV signal can originate from decays of MeV-scale composite states produced by: (A) thermonuclear (type Ia) or (B) core collapse supernovae (SNe). The requisite dynamical properties that would account for the observed data are quite distinct, for cases (A) and (B). We determine these requirements in simple hidden valley models, where the escape fraction problem is naturally addressed, due to the long lifetime of the new composite states. A novel feature of scenario (A) is that the dynamics of type Ia SNe, standard candles for cosmological measurements, might be affected by our mechanism. In case (A), the mass of the state mediating between the hidden sector and the SM e{sup +}e{sup -} could be a few hundred GeV and within the reach of a 500GeV e{sup +}e{sup -} linear collider. We also note that kinetic mixing of the photon with a light vector state may provide an interesting alternate mediation mechanism in this case. Scenarios based on case (B) are challenged by the need for a mechanism to transport some of the produced positrons toward the Galactic bulge, due to the inferred distribution of core collapse sources. The mass of the mediator in case (B) is typically hundreds of TeV, leading to long-lived particles that could, under certain circumstances, include a viable dark matter candidate. The appearance of long-lived particles in typical models leads to cosmological constraints and we address how a consistent cosmic history may be achieved.

Davoudiasl, H.; Perez, G.

2009-12-01

347

Destabilization of olivine by 30-keV electron irradiation: a possible mechanism of space weathering affecting interplanetary dust particles and planetary surfaces  

NASA Astrophysics Data System (ADS)

Electron irradiation experiments were performed using a 30-keV electron beam on single crystals of olivine in a scanning electron microscope (SEM) and in an electron microprobe (EMP). We determined that, under certain conditions, structural damage is caused to the irradiated surface of iron-bearing olivines. The irradiated areas comprise spherules with sizes of hundreds of nanometers and micrometer-sized holes. In the immediate vicinities of the irradiated areas, droplets with sizes of tens of nanometers and branching tracks are observed. With increasing total charge, the hundreds of nanometer-sized spherules become larger and more irregular in shape. The size and shape of the nanometer-sized droplets remain almost constant, but their surface density increases (in m -2). Chemical fractionations compared to the initial olivine were found: the irradiated areas are slightly enriched in MgO, whereas the deposits are enriched in SiO 2. Destabilization of olivine is not due to the dissipation of the implanted energy as heat, but results most probably from electrostatic discharges leading to the breakdown of the dielectric lattice. The possibility that such processes could be responsible for significant space weathering of interplanetary dust particles and regoliths of planetary surfaces should be taken into account. In the interplanetary medium, 10-keV range electrons are carried by the solar wind, whereas at 1 AU from the Sun, the lifetime of cometary dust and the exposure time of lunar regolith are, at least, 10 to 100 times greater than the duration required to accumulate the damaging electronic doses applied in this study. Moreover, the comparison of the microstructures of samples irradiated in the present study with features of lunar regolith grains reveals several chemical and structural similarities.

Lemelle, L.; Beaunier, L.; Borensztajn, S.; Fialin, M.; Guyot, F.

2003-05-01

348

The 3.5 keV X-ray line signature from annihilating and decaying dark matter in Weinberg model  

E-print Network

Recently two groups independently observed unidentified X-ray line signal at the energy 3.55 keV from the galaxy clusters and Andromeda galaxy. We show that this anomalous signal can be explained in annihilating dark matter model, for example, fermionic dark matter model in hidden sector with global $U(1)_X$ symmetry proposed by Weinberg. There are two scenarios for the production of the annihilating dark matters. In the first scenario the dark matters with mass 3.55 keV decouple from the interaction with Goldstone bosons and go out of thermal equilibrium at high temperature ($>$ 1 TeV) when they are still relativistic, their number density per comoving volume being essentially fixed to be the current value. The correct relic abundance of this warm dark matter is obtained by assuming that about ${\\cal O}(10^3)$ relativistic degrees of freedom were present at the decoupling temperature or alternatively large entropy production occurred at high temperature. In the other scenario, the dark matters were absent at high temperature, and as the universe cools down, the SM particles annihilate or decay to produce the dark matters non-thermally as in `freeze-in' scenario. It turns out that the DM production from Higgs decay is the dominant one. In the model we considered, only the first scenario can explain both X-ray signal and relic abundance. The X-ray signal arises through $p$-wave annihilation of dark matter pair into two photons through the scalar resonance without violating the constraints from big bang nucleosynthesis, cosmic microwave background, and astrophysical objects such as red giants or white dwarfs. We also discuss the possibility that the signal may result from a decaying dark matter in a simple extension of Weinberg model.

Seungwon Baek; P. Ko; Wan-Il Park

2014-05-15

349

Structural and optical properties of 70-keV carbon ion beam synthesized carbon nanoclusters in thermally grown silicon dioxide  

NASA Astrophysics Data System (ADS)

The structural and optical properties of carbon nanoclusters formed in thermally grown silicon dioxide film via the ion beam synthesis process have been investigated. A low-energy (70 keV) carbon ion beam (C-) at a fluence of 3 × 1017 atoms/cm2 was used for implantation into a thermally grown silicon dioxide layer (500 nm thick) on a Si (100) wafer. Several parts of the implanted samples were subsequently annealed in a gas mixture (4 % H2 + 96 % Ar) at 900 °C for different time periods. The as-implanted and annealed samples were characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy, Raman spectroscopy, transmission electron microscopy (TEM), and photoluminescence spectroscopy (PL). The carbon ion implantation depth profile was simulated using a widely used Monte Carlo-based simulation code SRIM-2012. Additionally, the elemental depth profile of the implanted carbon along with host elements of silicon and oxygen were simulated using a dynamic ion-solid interaction code T-DYN, which incorporates the effects of the surface sputtering and gradual change in the elemental composition in the implanted layers due to high-fluence ion implantation. The elemental depth profile obtained from the XPS measurements matches closely to the T-DYN predictions. Raman measurements indicate the formation of graphitic phases in the annealed samples. The graphitic peak (G-peak) was found to be increased with the annealing time duration. In the sample annealed for 10 min, the sizes of the carbon nanoclusters were found to be 1-4 nm in diameter using TEM. The PL measurements at room temperature using a 325-nm laser show broad-band emissions in the ultraviolet to visible range in the as-implanted sample. Intense narrow bands along with the broad bands were observed in the annealed samples. The defects present in the as-grown samples along with carbon ion-induced defect centers in the as-implanted samples are the main contributors to the observed broad-band luminescence centered around 2.4 and 2.9 eV. The intense narrow peaks observed in the PL spectra centered on ~2.67 and 2.8 eV with full width at half maxima ? 150 meV are believed to be mainly due to the quantum size effects of the carbon nanoclusters formed in the annealed samples. The relative intensities of the narrow peaks are seen to be changing with the annealing time interval. This may be due to the change in the size distribution of the carbon nanoclusters.

Poudel, P. R.; Poudel, P. P.; Paramo, J. A.; Strzhemechny, Y. M.; Rout, B.; McDaniel, F. D.

2014-09-01

350

The 2-79 keV X-Ray Spectrum of the Circinus Galaxy with NuSTAR, XMM-Newton, and Chandra: A Fully Compton-thick Active Galactic Nucleus  

NASA Astrophysics Data System (ADS)

The Circinus galaxy is one of the closest obscured active galactic nuclei (AGNs), making it an ideal target for detailed study. Combining archival Chandra and XMM-Newton data with new NuSTAR observations, we model the 2-79 keV spectrum to constrain the primary AGN continuum and to derive physical parameters for the obscuring material. Chandra's high angular resolution allows a separation of nuclear and off-nuclear galactic emission. In the off-nuclear diffuse emission, we find signatures of strong cold reflection, including high equivalent-width neutral Fe lines. This Compton-scattered off-nuclear emission amounts to 18% of the nuclear flux in the Fe line region, but becomes comparable to the nuclear emission above 30 keV. The new analysis no longer supports a prominent transmitted AGN component in the observed band. We find that the nuclear spectrum is consistent with Compton scattering by an optically thick torus, where the intrinsic spectrum is a power law of photon index ? = 2.2-2.4, the torus has an equatorial column density of N H = (6-10) × 1024 cm-2, and the intrinsic AGN 2-10 keV luminosity is (2.3-5.1) × 1042 erg s-1. These values place Circinus along the same relations as unobscured AGNs in accretion rate versus ? and LX versus L IR phase space. NuSTAR's high sensitivity and low background allow us to study the short timescale variability of Circinus at X-ray energies above 10 keV for the first time. The lack of detected variability favors a Compton-thick absorber, in line with the spectral fitting results.

Arévalo, P.; Bauer, F. E.; Puccetti, S.; Walton, D. J.; Koss, M.; Boggs, S. E.; Brandt, W. N.; Brightman, M.; Christensen, F. E.; Comastri, A.; Craig, W. W.; Fuerst, F.; Gandhi, P.; Grefenstette, B. W.; Hailey, C. J.; Harrison, F. A.; Luo, B.; Madejski, G.; Madsen, K. K.; Marinucci, A.; Matt, G.; Saez, C.; Stern, D.; Stuhlinger, M.; Treister, E.; Urry, C. M.; Zhang, W. W.

2014-08-01

351

Diagnostics for the optimization of an 11 keV inverse Compton scattering x-ray source  

NASA Astrophysics Data System (ADS)

In a scope of a collaboration between Thales Communications & Security and CEA DAM DIF, 11 keV Xrays were produced by inverse Compton scattering on the ELSA facility. In this type of experiment, X-ray observation lies in the use of accurate electron and laser beam interaction diagnostics and on fitted X-ray detectors. The low interaction probability between < 100 ?m width, 12 ps [rms] length electron and photon pulses requires careful optimization of pulse spatial and temporal covering. Another issue was to observe 11 keV X-rays in the ambient radioactive noise of the linear accelerator. For that, we use a very sensitive detection scheme based on radio luminescent screens.

Chauchat, A.-S.; Brasile, J.-P.; Le Flanchec, V.; Nègre, J.-P.; Binet, A.; Ortega, J.-M.

2013-04-01

352

An experimental study of 1.5 keV X-ray radiation effects on CMOS devices  

Microsoft Academic Search

The total dose radiation effects are studied on CMOS devices consisting of n- and p-MOSFETs and logic circuits. The devices on a test chip were designed in two micron, double metal, single polysilicon, p-well CMOS technology and fabricated through the Metal-Oxide Semiconductor Implementation System (MOSIS) foundry. Effects of 1.5 keV Al?Ka X-ray irradiation on the threshold voltage of n- and

A. Srivastava; R. Nema; P. K. Bhattacharya

1996-01-01

353

Performance characteristics of a 511keV collimator for imaging positron emitters with a standard gamma-camera  

Microsoft Academic Search

Line-source experiments were conducted to assess the performance of a gamma-camera equipped with a specially designed 511-keV collimator for the planar imaging of positron emitters. The results were compared with the camera performance with routinely used collimators and radionuclides (thallium-201, technetium-99m and gallium-67). With positron emitters, scatter contributed less to the widening of the line spread function than with radionuclides

Arthur Van Lingen; Peter C. Huijgens; Frans C. Visser; Gert J. Ossenkoppele; Otto S. Hoekstra; Harry J. M. Martens; Hans Huitink; Koos D. M. Herscheid; Michael V. Greens; Gerrit J. J. Teule

1992-01-01

354

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

E-print Network

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 $\\mu$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 flu...

Alvarez, Pedro D; Day, Francesca V; Marsh, M C David; Rummel, Markus

2014-01-01

355

Galaxy Clusters in the Swift/BAT era II: 10 more Clusters detected above 15 keV  

SciTech Connect

We report on the discovery of 10 additional galaxy clusters detected in the ongoing Swift/BAT all-sky survey. Among the newly BAT-discovered clusters there are: Bullet, Abell 85, Norma, and PKS 0745-19. Norma is the only cluster, among those presented here, which is resolved by BAT. For all the clusters we perform a detailed spectral analysis using XMM-Newton and Swift/BAT data to investigate the presence of a hard (non-thermal) X-ray excess. We find that in most cases the clusters emission in the 0.3-200 keV band can be explained by a multi-temperature thermal model confirming our previous results. For two clusters (Bullet and Abell 3667) we find evidence for the presence of a hard X-ray excess. In the case of the Bullet cluster, our analysis confirms the presence of a non-thermal, power-law like, component with a 20-100 keV flux of 3.4 x 10{sup -12} erg cm{sup -2} s{sup -1} as detected in previous studies. For Abell 3667 the excess emission can be successfully modeled as a hot component (kT = {approx}13 keV). We thus conclude that the hard X-ray emission from galaxy clusters (except the Bullet) has most likely thermal origin.

Ajello, M.; /SLAC /KIPAC, Menlo Park; Rebusco, P.; /KIPAC, Menlo Park; Cappelluti, N.; /Garching, Max Planck Inst., MPE /Maryland U., Baltimore County; Reimer, O.; /SLAC /Palermo Observ.; Boehringer, H.; /Garching, Max Planck Inst., MPE; La Parola, V.; Cusumano, G.; /Palermo Observ.; ,

2010-10-27

356

GALAXY CLUSTERS IN THE SWIFT/BAT ERA. II. 10 MORE CLUSTERS DETECTED ABOVE 15 keV  

SciTech Connect

We report on the discovery of 10 additional galaxy clusters detected in the ongoing Swift/Burst Alert Telescope (BAT) all-sky survey. Among the newly BAT-discovered clusters there are Bullet, A85, Norma, and PKS 0745-19. Norma is the only cluster, among those presented here, which is resolved by BAT. For all the clusters, we perform a detailed spectral analysis using XMM-Newton and Swift/BAT data to investigate the presence of a hard (non-thermal) X-ray excess. We find that in most cases the clusters' emission in the 0.3-200 keV band can be explained by a multi-temperature thermal model confirming our previous results. For two clusters (Bullet and A3667), we find evidence for the presence of a hard X-ray excess. In the case of the Bullet cluster, our analysis confirms the presence of a non-thermal, power-law-like, component with a 20-100 keV flux of 3.4 x 10{sup -12} erg cm{sup -2} s{sup -1} as detected in previous studies. For A3667, the excess emission can be successfully modeled as a hot component (kT {approx} 13 keV). We thus conclude that the hard X-ray emission from galaxy clusters (except the Bullet) has most likely a thermal origin.

Ajello, M.; Reimer, O. [SLAC National Laboratory and Kavli Institute for Particle Astrophysics and Cosmology, 2575 Sand Hill Road, Menlo Park, CA 94025 (United States); Rebusco, P. [Kavli Institute for Astrophysics and Space Research, MIT, Cambridge, MA 02139 (United States); Cappelluti, N.; Boehringer, H. [Max Planck Institut fuer Extraterrestrische Physik, P.O. Box 1603, 85740, Garching (Germany); La Parola, V.; Cusumano, G., E-mail: majello@slac.stanford.ed [INAF, Istituto di Astrofisica Spaziale e Fisica Cosmica di Palermo, via U. La Malfa 153, 90146 Palermo (Italy)

2010-12-20

357

A novel approach to generating time of flight mass spectra for low energy neutral atom detection  

Microsoft Academic Search

Low energy neutral atom detectors traditionally use a surface to convert the neutrals into negative ions. The negative ions are then accelerated with an acceleration potential of at least 15 keV to allow them to penetrate a thin carbon foil used to create the start signal for a time of flight (TOF) spectrometer. The 15 keV accelerating potential prevents energy

J. Kubit; M. A. Coplan; M. Shappirio; D. J. Chornay

2009-01-01

358

Sensitivity variation of doped Fricke gel irradiated with monochromatic synchrotron X rays between 33.5 and 80 keV.  

PubMed

An experimental binary radiotherapy proposes the concomitant use of a high-Z compound and synchrotron X rays for enhancing radiation dose selectively in tumours by a photoelectric effect. This study aimed at measuring the resulting dose enhancement in irradiated material. A doped Fricke gel dosemeter model was manufactured with 10 mg ml(-1) of iodine (Telebrix) or barium (Micropaque). Samples were irradiated with a monochromatic synchrotron beam at 33.5, 50, 65 and 80 keV. The ensuing enhancement of the sensitivity of the dosemeter was derived from the nuclear magnetic resonance relaxation rates measured at different X-ray doses. Our results demonstrate (1) the preservation of a linear relationship between relaxation rates and X-ray doses for dosemeters doped with high-Z atoms and (2) a clear energy-dependent sensitivity enhancement for barium-doped Fricke gels. This enhancement was neither reproducible with iodinated compounds nor clearly related to the expected dose enhancement factor. However 1% barium sulphate in the gel could significantly improve the gel's response when it was irradiated by low-energy X rays. PMID:15956218

Corde, Stéphanie; Adam, Jean-François; Biston, Marie-Claude; Joubert, Aurélie; Charvet, Anne-Marie; Estève, François; Le Bas, Jean-François; Elleaume, Hélène; Balosso, Jacques

2005-01-01

359

ENA Images of the Heliosheath (5-55 keV) from Cassini/INCA: Updated with data 2010-2012  

NASA Astrophysics Data System (ADS)

We have published energetic neutral atom (ENA) images of the heliosheath from cumulative observations (2003 through 2009) of the Cassini/INCA ENA imager in orbit around Saturn. We have now augmented the data set to include observations during 2010-2012. All-sky maps are made in four energy channels (5-55 keV). The spatial coverage for a given year period depends upon the INCA viewing directions, which vary considerably from year to year due to the evolution of the Cassini orbit. Contamination due to the Sun (which moves 12deg/yr along the ecliptic) and to Saturn's magnetosphere must be carefully removed, but fortunately the obscurations due the Sun and Saturn move across the sky. Consequently, some regions of the sky are sampled in a half-year by the 90degx120deg INCA field of view with sufficient (6° x 6°) pixel statistics to allow quantitative interpretation of spatial structure and energy spectral dependence in these individual regions. The most recent data (2010-2012) contains some of the best ENA samplings of regions so far. Of particular interest are the regions associated with the pixels containing Voyager 1 and Voyager 2. We will report on this work in progress. See also the poster by Dialynas et al. (this Conference).

Roelof, E.; Krimigis, S.; Mitchell, D.; Decker, R.; Dialynas, K.

2012-04-01

360

Measurement of the -3 keV resonance in the {sup 13}C({alpha},n){sup 16}O reaction and its influence on the synthesis of s-process nuclei  

SciTech Connect

The {sup 13}C({alpha},n){sup 16}O reaction is the neutron source for the main component of the s-process, responsible of the production of most nuclei in the mass range 90 < A < 204. It is active inside the helium-burning shell in asymptotic giant branch stars, at temperatures < 10{sup 8} K, corresponding to an energy interval where the {sup 13}C({alpha},n){sup 16}O is effective 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 {sup 17}O, giving rise to a steep increase of the S-factor. Notwithstanding that it plays a crucial role in astrophysics, no direct measurements exist. Therefore, we have applied the Trojan Horse Method (THM) to the {sup 13}C({sup 6}Li,n{sup 16}O)d quasi-free reaction to achieve an experimental estimate of such contribution. For the first time, the ANC for the 6.356 MeV level has been deduced through the THM as well as the n-partial width, allowing to attain an unprecedented accuracy in the {sup 13}C({alpha},n){sup 16}O study. Though a larger ANC for the 6.356 MeV level is measured, our experimental S(E) factor agrees with the most recent extrapolation in the literature in the 140 - 230 keV energy interval, the accuracy being greatly enhanced thanks to this innovative approach.

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.; Sparta, R. [Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali del Sud, Catania (Italy); Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali del Sud, Catania (Italy) and Dipartimento di Fisica e Astronomia, Universita di Catania, Catania (Italy); and others

2012-11-20

361

Gold-thiolate cluster emission from SAMs under keV ion bombardment: Experiments and molecular  

E-print Network

on gold is investigated using time-of-flight secondary ion mass spectrometry (ToF-SIMS). Layers out concerning the origin of the gold-thiolate cluster ions observed in the SIMS mass spectra-ordered molecular monolayers on gold. First, we compare and interpret the yields and energy spectra of gold

362

Constraints on 3.55 keV line emission from stacked observations of dwarf spheroidal galaxies  

NASA Astrophysics Data System (ADS)

Several recent works have reported the detection of an unidentified x-ray line at 3.55 keV, which could possibly be attributed to the decay of dark matter (DM) particles in the halos of galaxy clusters and in the M31 galaxy. We analyze all publicly available XMM-Newton satellite data of dwarf spheroidal galaxies to test the possible DM origin of the line. Dwarf spheroidal galaxies have high mass-to-light ratios, and their interstellar medium is not a source of diffuse x-ray emission; thus, they are expected to provide the cleanest DM decay line signal. Our analysis shows no evidence for the presence of the line in the stacked spectra of the dwarf galaxies. It excludes the sterile neutrino DM decay origin of the 3.5 keV line reported by Bulbul et al. (2014) at the level of 4.1 ? under standard assumptions about the Galactic DM column density in the direction of selected dwarf galaxies and at the level of 3.2 ? assuming minimal Galactic DM column density. Our analysis is still consistent with the estimate of sterile neutrino DM parameters by Boyarsky et al. (2014) because of its larger uncertainty. However, the central value of their estimate of the mixing angle is inconsistent with our dwarf spheroidals data at the 3.4 ? (2.5 ? ) level assuming the mean (minimal) Galactic DM column density. As a byproduct of our analysis, we provide updated upper limits to the mixing angle of sterile neutrino DM in the mass range between 2 and 20 keV.

Malyshev, D.; Neronov, A.; Eckert, D.

2014-11-01

363

Spectral reflectance change and luminescence of selected salts during 2-10 KeV proton bombardment - Implications for Io  

NASA Technical Reports Server (NTRS)

Radiation damage and luminescence caused by magnetospheric charged particles have been suggested by several investigators as mechanisms that are capable of explaining some of the peculiar spectral/albedo features of Io. In the present paper, this possibility is pursued by measuring the UV-visual spectral reflectance and luminescent efficiency of several proposed Io surface constituents during 2 to 10 keV proton irradiation at room and low temperatures. The luminescence efficiencies of pure samples, studied in the laboratory, suggest that charged-particle induced luminescence from Io's surface might be observable by spacecraft such as Voyager when viewing Io's dark side.

Nelson, R. M.; Nash, D. B.

1979-01-01

364

3.55 keV X-ray line signal from excited dark matter in radiative neutrino model  

NASA Astrophysics Data System (ADS)

We study an exciting dark matter scenario in a radiative neutrino model to explain the X-ray line signal at 3.55 keV recently reported by XMN-Newton X-ray observatory using data of various galaxy clusters and Andromeda galaxy. We show that the required large cross section for the up-scattering process to explain the X-ray line can be obtained via the resonance of the pseudo-scalar. Moreover, this model can be compatible with the thermal production of dark matter and the constraint from the direct detection experiment.

Okada, Hiroshi; Toma, Takashi

2014-10-01

365

Enhanced keV peak power and yield using twisted pair 'cables' in a z-pinch  

SciTech Connect

Individual wires in a z-pinch were replaced with twisted pair 'cables' of similar linear mass on the COBRA pulsed power generator, resulting in peak power and yield increases in radiation above 1 keV. A cable is defined here as two or more fine wires twisted together to form a continuous strand with a wavelength ({lambda}{sub t}) dependent on the twists per unit length. The magnitude of {lambda}{sub t} appears to play a strong role in these increases, with the largest gains found for a {lambda}{sub t} of Almost-Equal-To 0.75 mm.

Hoyt, C. L.; Knapp, P. F.; Pikuz, S. A.; Shelkovenko, T. A.; Cahill, A. D.; Gourdain, P.-A.; Greenly, J. B.; Kusse, B. R.; Hammer, D. A. [Laboratory of Plasma Studies, Cornell University, 439 Rhodes Hall, Ithaca, New York 14853 (United States)

2012-06-11

366

Enhanced keV peak power and yield using twisted pair ``cables'' in a z-pinch  

NASA Astrophysics Data System (ADS)

Individual wires in a z-pinch were replaced with twisted pair "cables" of similar linear mass on the COBRA pulsed power generator, resulting in peak power and yield increases in radiation above 1 keV. A cable is defined here as two or more fine wires twisted together to form a continuous strand with a wavelength (?t) dependent on the twists per unit length. The magnitude of ?t appears to play a strong role in these increases, with the largest gains found for a ?t of ?0.75 mm.

Hoyt, C. L.; Knapp, P. F.; Pikuz, S. A.; Shelkovenko, T. A.; Cahill, A. D.; Gourdain, P.-A.; Greenly, J. B.; Kusse, B. R.; Hammer, D. A.

2012-06-01

367

KeV right-handed neutrinos from type II seesaw mechanism in a 3-3-1 model  

E-print Network

We adapt the type II seesaw mechanism to the framework of the 3-3-1 model with right-handed neutrinos. We emphasize that the mechanism is capable of generating small masses for the left-handed and right-handed neutrinos and the structure of the model allows that both masses arise from the same Yukawa coupling. For typical values of the free parameters of the model we may obtain at least one right-handed neutrino with mass in the KeV range. Right-handed neutrino with mass in this range is a viable candidate for the warm component of the dark matter existent in the universe.

D. Cogollo; H. Diniz; C. A. de S. Pires

2009-03-02

368

IonCCD Detector for Miniature Sector-Field Mass Spectrometer: Investigation of Peak Shape and Detector Surface Artifacts Induced by keV Ion Detection  

NASA Astrophysics Data System (ADS)

A recently described ion charge coupled device detector IonCCD (Sinha and Wadsworth, Rev. Sci. Instrum. 76(2), 2005; Hadjar, J. Am. Soc. Mass Spectrom. 22(4), 612-624, 2011) is implemented in a miniature mass spectrometer of sector-field instrument type and Mattauch-Herzog (MH)-geometry (Rev. Sci. Instrum. 62(11), 2618-2620, 1991; Burgoyne, Hieftje and Hites J. Am. Soc. Mass Spectrom. 8(4), 307-318, 1997; Nishiguchi, Eur. J. Mass Spectrom. 14(1), 7-15, 2008) for simultaneous ion detection. In this article, we present first experimental evidence for the signature of energy loss the detected ion experiences in the detector material. The two energy loss processes involved at keV ion kinetic energies are electronic and nuclear stopping. Nuclear stopping is related to surface modification and thus damage of the IonCCD detector material. By application of the surface characterization techniques atomic force microscopy (AFM) and X-ray photoelectrons spectroscopy (XPS), we could show that the detector performance remains unaffected by ion impact for the parameter range observed in this study. Secondary electron emission from the (detector) surface is a feature typically related to electronic stopping. We show experimentally that the properties of the MH-mass spectrometer used in the experiments, in combination with the IonCCD, are ideally suited for observation of these stopping related secondary electrons, which manifest in reproducible artifacts in the mass spectra. The magnitude of the artifacts is found to increase linearly as a function of detected ion velocity. The experimental findings are in agreement with detailed modeling of the ion trajectories in the mass spectrometer. By comparison of experiment and simulation, we show that a detector bias retarding the ions or an increase of the B-field of the IonCCD can efficiently suppress the artifact, which is necessary for quantitative mass spectrometry.

Hadjar, Omar; Schlathölter, Thomas; Davila, Stephen; Catledge, Shane A.; Kuhn, Ken; Kassan, Scott; Kibelka, Gottfried; Cameron, Chad; Verbeck, Guido F.

2011-10-01

369

International Fusion Materials Irradiation Facility injector acceptance tests at CEA/Saclay: 140 mA/100 keV deuteron beam characterizationa)  

NASA Astrophysics Data System (ADS)

In the framework of the ITER broader approach, the International Fusion Materials Irradiation Facility (IFMIF) deuteron accelerator (2 × 125 mA at 40 MeV) is an irradiation tool dedicated to high neutron flux production for future nuclear plant material studies. During the validation phase, the Linear IFMIF Prototype Accelerator (LIPAc) machine will be tested on the Rokkasho site in Japan. This demonstrator aims to produce 125 mA/9 MeV deuteron beam. Involved in the LIPAc project for several years, specialists from CEA/Saclay designed the injector based on a SILHI type ECR source operating at 2.45 GHz and a 2 solenoid low energy beam line to produce such high intensity beam. The whole injector, equipped with its dedicated diagnostics, has been then installed and tested on the Saclay site. Before shipment from Europe to Japan, acceptance tests have been performed in November 2012 with 100 keV deuteron beam and intensity as high as 140 mA in continuous and pulsed mode. In this paper, the emittance measurements done for different duty cycles and different beam intensities will be presented as well as beam species fraction analysis. Then the reinstallation in Japan and commissioning plan on site will be reported.

Gobin, R.; Bogard, D.; Cara, P.; Chauvin, N.; Chel, S.; Delferrière, O.; Harrault, F.; Mattei, P.; Mosnier, A.; Senée, F.; Shidara, H.; Okumura, Y.

2014-02-01

370

The improvement of mechanical properties of aluminum nitride and alumina by 1 keV Ar{sup +} ion irradiation in reactive gas environment  

SciTech Connect

Ar ions with 1 keV energy was irradiated on aluminum nitride in an O{sub 2} environment to increase the bonding strength with Cu and also on alumina in an N{sub 2} environment to increase the bending strength. Cu(1,000 {angstrom}) films were deposited by ion-beam sputter on Ar{sup +} irradiated/unirradiated AlN surfaces and the change of the bond strength was investigated by a scratch test. For the study of chemical structural change don the Ar{sup +} irradiated AlN surface. Cu(50{angstrom}) were deposited on an AlN substrate and XPS depth profile analysis was performed. Cu films deposited on Ar{sup +} irradiated AlN under an O{sub 2} environment showed the bond strength of 30 Newton by a scratch test. On the basis of Cu3p, Al2p near core levels and O1s, N1s core level spectra, it was found that the improvement of bond strength of Cu films on the AlN surface resulted from the formation of intermediate layers such as copper oxide and aluminum oxynitride. The bending strength of polycrystalline alumina irradiated by Ar ions in an N{sub 2} environment was also increased.

Koh, S.K.; Son, Y.B.; Gam, J.S.; Kim, C.J.; Choi, W.K.; Jung, H.J. [Korea Inst. of Science and Technology, Seoul (Korea, Republic of). Div. of Ceramics

1996-12-31

371

Target dependence of state selective single- and double-electron capture in 150-keV Ne^10++X (X=He, Ne, Ar) collisions  

NASA Astrophysics Data System (ADS)

High-resolution cold-target recoil-ion momentum spectroscopy (COLTRIMS) measurements of single- and double-electron capture in 150-keV Ne^10++X (X=He, Ne, Ar) collisions have been performed at the UNR 14 GHz ECR ion source research facility. The measured recoil-ion momenta provide Q-values and angular distributions that provide information on the projectile state population (and possible target excitation) and electron capture mechanisms. Single-electron capture from He dominantly populates the n=4 and 5 levels on the projectile, while that from Ne populates the n=5 and 6 levels, and from Ar the n=6 and 7 levels. Target excitation accompanying single-electron capture is a very weak channel in these collision systems. Double-electron capture from He populates the (3,n>= 4), (4,4) and (4,5) doubly excited states, from Ne the (4,n>= 4) states, and from Ar the (4,n>= 5) and (5,5) states. A signature of target excitation accompanying the population of the (4,5) and (4,6) doubly excited states is observed in double-electron capture from Ar. Capture mechanisms and the dependence of the relaxation properties of the doubly excited states on the binding energies of the captured electrons on the projectile will be discussed.

Hasan, A. A.; Emmons, E. D.; Hinojosa, G.; Ali, R.

2000-06-01

372

A new study of the $^{22}$Ne(p,$?$)$^{23}$Na reaction deep underground: Feasibility, setup, and first observation of the 186 keV resonance  

E-print Network

The $^{22}$Ne(p,$\\gamma$)$^{23}$Na reaction takes part in the neon-sodium cycle of hydrogen burning. This cycle is active in asymptotic giant branch stars as well as in novae and contributes to the nucleosythesis of neon and sodium isotopes. In order to reduce the uncertainties in the predicted nucleosynthesis yields, new experimental efforts to measure the $^{22}$Ne(p,$\\gamma$)$^{23}$Na cross section directly at the astrophysically relevant energies are needed. In the present work, a feasibility study for a $^{22}$Ne(p,$\\gamma$)$^{23}$Na experiment at the Laboratory for Underground Nuclear Astrophysics (LUNA) 400\\,kV accelerator deep underground in the Gran Sasso laboratory, Italy, is reported. The ion beam induced $\\gamma$-ray background has been studied. The feasibility study led to the first observation of the $E_{\\rm p}$ = 186\\,keV resonance in a direct experiment. An experimental lower limit of 0.12\\,$\\times$\\,10$^{-6}$\\,eV has been obtained for the resonance strength. Informed by the feasibility study, a dedicated experimental setup for the $^{22}$Ne(p,$\\gamma$)$^{23}$Na experiment has been developed. The new setup has been characterized by a study of the temperature and pressure profiles. The beam heating effect that reduces the effective neon gas density due to the heating by the incident proton beam has been studied using the resonance scan technique, and the size of this effect has been determined for a neon gas target.

F. Cavanna; R. Depalo; M. -L. Menzel; M. Aliotta; M. Anders; D. Bemmerer; C. Broggini; C. G. Bruno; A. Caciolli; P. Corvisiero; T. Davinson; A. di Leva; Z. Elekes; F. Ferraro; A. Formicola; Zs. Fülöp; G. Gervino; A. Guglielmetti; C. Gustavino; Gy. Gyürky; G. Imbriani; M. Junker; R. Menegazzo; P. Prati; C. Rossi Alvarez; D. A. Scott; E. Somorjai; O. Straniero; F. Strieder; T. Szücs; D. Trezzi

2014-11-11

373

International Fusion Materials Irradiation Facility injector acceptance tests at CEA/Saclay: 140 mA/100 keV deuteron beam characterization.  

PubMed

In the framework of the ITER broader approach, the International Fusion Materials Irradiation Facility (IFMIF) deuteron accelerator (2 × 125 mA at 40 MeV) is an irradiation tool dedicated to high neutron flux production for future nuclear plant material studies. During the validation phase, the Linear IFMIF Prototype Accelerator (LIPAc) machine will be tested on the Rokkasho site in Japan. This demonstrator aims to produce 125 mA/9 MeV deuteron beam. Involved in the LIPAc project for several years, specialists from CEA/Saclay designed the injector based on a SILHI type ECR source operating at 2.45 GHz and a 2 solenoid low energy beam line to produce such high intensity beam. The whole injector, equipped with its dedicated diagnostics, has been then installed and tested on the Saclay site. Before shipment from Europe to Japan, acceptance tests have been performed in November 2012 with 100 keV deuteron beam and intensity as high as 140 mA in continuous and pulsed mode. In this paper, the emittance measurements done for different duty cycles and different beam intensities will be presented as well as beam species fraction analysis. Then the reinstallation in Japan and commissioning plan on site will be reported. PMID:24593497

Gobin, R; Bogard, D; Cara, P; Chauvin, N; Chel, S; Delferrière, O; Harrault, F; Mattei, P; Mosnier, A; Senée, F; Shidara, H; Okumura, Y

2014-02-01

374

A new study of the $^{22}$Ne(p,$\\gamma$)$^{23}$Na reaction deep underground: Feasibility, setup, and first observation of the 186 keV resonance  

E-print Network

The $^{22}$Ne(p,$\\gamma$)$^{23}$Na reaction takes part in the neon-sodium cycle of hydrogen burning. This cycle is active in asymptotic giant branch stars as well as in novae and contributes to the nucleosythesis of neon and sodium isotopes. In order to reduce the uncertainties in the predicted nucleosynthesis yields, new experimental efforts to measure the $^{22}$Ne(p,$\\gamma$)$^{23}$Na cross section directly at the astrophysically relevant energies are needed. In the present work, a feasibility study for a $^{22}$Ne(p,$\\gamma$)$^{23}$Na experiment at the Laboratory for Underground Nuclear Astrophysics (LUNA) 400\\,kV accelerator deep underground in the Gran Sasso laboratory, Italy, is reported. The ion beam induced $\\gamma$-ray background has been studied. The feasibility study led to the first observation of the $E_{\\rm p}$ = 186\\,keV resonance in a direct experiment. An experimental lower limit of 0.12\\,$\\times$\\,10$^{-6}$\\,eV has been obtained for the resonance strength. Informed by the feasibility study,...

Cavanna, F; Menzel, M -L; Aliotta, M; Anders, M; Bemmerer, D; Broggini, C; Bruno, C G; Caciolli, A; Corvisiero, P; Davinson, T; di Leva, A; Elekes, Z; Ferraro, F; Formicola, A; Fülöp, Zs; Gervino, G; Guglielmetti, A; Gustavino, C; Gyürky, Gy; Imbriani, G; Junker, M; Menegazzo, R; Prati, P; Alvarez, C Rossi; Scott, D A; Somorjai, E; Straniero, O; Strieder, F; Szücs, T; Trezzi, D

2014-01-01

375

Perturbed angular correlation measurements on the 40.9 keV level of62Cu. A preliminary study of 2Zn-insulin  

NASA Astrophysics Data System (ADS)

Time-differential PAC measurements have been made using62Zn, both in aqueous solution at pH ˜ 6.0 and also incorporated into crystalline 2Zn-insulin. Three Nal(Tl) detectors were used — a 2.54 cm thick scintillator detecting the ‘stop’ 41 keV gamma ray and two 5.0 cm thick scintillators at 90‡ and 135‡ detecting the ‘start’ 597 keV gamma rays. The need to separate the 597 keV line from the 511 keV background was found to require very careful setting-up conditions in the case of a fixed-detector spectrometer. The solution data produced a fast relaxation time of (75±25) ns, while the three 2Zn-insulin batches gave data which were analyzed using a static interaction with an assumed axial symmetry to give an electric quadrupole frequency of (77±8) MHz.

Smith, F. A.; Martin, P. W.; Shukri, A.

1985-12-01

376

Calibration of Xray CCDs with an ErectField Grating Spectrometer in the 0.2 1.5 keV band.  

E-print Network

Calibration of X­ray CCDs with an Erect­Field Grating Spectrometer in the 0.2 ­ 1.5 keV band. G been calibrated in the 0.25­1.5 keV spectral range using an erect­field grating spectrometer X­ray CCDs developed at MIT Lincoln Laboratories for the AXAF CCD Imaging Spectrometer (ACIS) have

377

New measurement of the emission probability of the 63.290 keV 234Th ?-ray from 238U ? decay  

Microsoft Academic Search

The measurement of nanogram and microgram quantities of 241Am can be carried out by comparing its rate of 59.541keV ? emission to that of known amount of 238U emitting a 63.290keV ?-ray following ? decay to 234Th. As the accuracy of the method appears to be limited by the relatively high uncertainty of the literature value for this emission probability,

S. Abousahl; P. van Belle; B. Lynch; H. Ottmar

2004-01-01

378

Ion and photon emission from keV cluster impacts on surfaces  

E-print Network

and cluster ions as projectiles. The primary ions used were C?H, (Csl)?I- cluster ions and H, I- monoatomic ions. The targets studied were CsI and phenylalanine. The yields of secondary ions and photons induced by different primary ions were obtained using...keV) studied, the photon yield is directly proportional to the energy per mass ratio of the projectiles. Heavier ions such as Csin'- and Cs2I3- are efficient projectiles for secondary ion production but generated a barely detectable emission from CsI...

Yau, Alice Yau-Lic

2012-06-07

379

Interactions of neutral and singly charged keV atomic particles with gas-phase adenine molecules  

SciTech Connect

KeV atomic particles traversing biological matter are subject to charge exchange and screening effects which dynamically change this particle's effective charge. The understanding of the collision cascade along the track thus requires a detailed knowledge of the interaction dynamics of radiobiologically relevant molecules, such as DNA building blocks or water, not only with ionic but also with neutral species. We have studied collisions of keV H{sup +}, He{sup +}, and C{sup +} ions and H{sup 0}, He{sup 0}, and C{sup 0} atoms with the DNA base adenine by means of high resolution time-of-flight spectrometry. For H{sup 0} and H{sup +} we find qualitatively very similar fragmentation patterns, while for carbon, strong differences are observed when comparing C{sup 0} and C{sup +} impact. For collisions with He{sup 0} and He{sup +} projectiles, a pronounced delayed fragmentation channel is observed, which has not been reported before.

Alvarado, Fresia; Bari, Sadia; Hoekstra, Ronnie; Schlathoelter, Thomas [KVI Atomic Physics, University of Groningen, Zernikelaan 25, NL-9747AA Groningen (Netherlands)

2007-07-21

380

A possible link between the GeV excess and the 511 keV emission line in the Galactic Centre  

E-print Network

The morphology and characteristics of the so-called GeV gamma-ray excess detected in the Milky Way lead us to speculate about a possible common origin with the 511 keV line mapped by the SPI experiment about ten years ago. In the previous version of our paper, we assumed 30 GeV dark matter particles annihilating into $b \\bar{b}$ and obtained both a morphology and a 511 keV flux (\\phi_{511 keV} ~ 10^{-3} ph/cm^2/s) in agreement with SPI observation. However our estimates assumed a negligible number density of electrons in the bulge which lead to an artificial increase in the flux (mostly due to negligible Coulomb losses in this configuration). Assuming a number density greater than $n_e > 10^{-3} cm^{-3}$, we now obtain a flux of 511 keV photons that is smaller than \\phi_{511 keV} ~ 10^{-6} ph/cm^2/s and is essentially in agreement with the 511 keV flux that one can infer from the total number of positrons injected by dark matter annihilations into $b \\bar{b}$. We thus conclude that -- even if 30 GeV dark matter particles were to exist-- it is impossible to establish a connexion between the two types of signals, even though they are located within the same 10 deg region in the galactic centre.

Celine Boehm; Paolo Gondolo; Pierre Jean; Thomas Lacroix; Colin Norman; Joseph Silk

2014-06-18

381

An Electromagnet-based Mass Spectrometer for Magnetospheric keV Ion Measurements  

NASA Astrophysics Data System (ADS)

A mass spectrometer based on a 3/4 sphere electrostatic analyzer, with a radial magnetic field located 180 degrees from the entrance aperture, is to be flown on the upcoming sounding rocket project TRICE. Ion optics simulations, used to optimise the geometric factor and mass resolution, will be described. The imaging scheme is based on multiple low-resolution imaging areas, each one corresponding to a mass distribution, and each with its own low-power digital imaging electronics. The lack of postacceleration high voltage supplies, together with the simplified imaging, allow this instrument and its electronics to be kept very compact and inexpensive. The trade-off is that magnetic mass analysis at variable energies requires an electromagnet. The power of this electromagnet is kept at reasonable levels by using one compact magnetic field region for particles at multiple angles.

Tornquist, M.; Boehm, M. H.; Hooli, S.

2006-05-01

382

Determining 234Th and 238U in rocks, soils, and sediments via the doublet gamma at 92.5 keV.  

PubMed

Efficient and accurate measurements of uranium (U) and U-series radionuclides in earth's materials are needed to assess its environmental impact, reconstruct geochemical histories, and quantify heat production in the crust. To date, measurements of 234Th and 238U by gamma spectrometry have relied on the quantification of 234Th gamma emissions at approximately 63 keV (absolute intensity = 3.7%) and the (234m)Pa gamma at 1001 keV (absolute intensity = 0.84%). However, use of the 63 keV emissions can be hampered by 232Th interferences and self absorption, and the 1001 keV photon has a very low yield. Here we describe the effective use of the 234Th doublet gamma emission at approximately 92.5 keV (total absolute intensity = 4.8%) for 234Th and 238U measurements. This doublet has been largely ignored because of its proximity to the Th K(alpha1) (93.3 keV) and thus its vulnerability to a Th self-fluorescence interference. We demonstrate that additions of U and 40K to a Th ore sample do not increase the count rate at 92-93 keV above that which would be expected from the associated additions of U and 234Th. We also show that the Th self-fluorescence interference appears to be an anomaly associated only with the analysis of relatively thick (>1 mm) Th minerals, and suggest that fluorescence will not complicate the 92-93 keV region in most environmental samples. A review of decay data reveals that Th K(alpha1) X-rays associated with the decay of 235U and 228Ac can significantly interfere with quantification of the 92.5 keV 234Th doublet. We show that simple experimentally-derived correction factors for these X-rays can be used to accurately determine 234Th using its strongest gammas, resulting in higher count rates and smaller self-absorption corrections relative to the traditional analytical lines. Total 1 sigma analytical error associated with U measurements at 92.5 keV ranged from 1 to 9% and is dominated by the relative size of the 228Ac interference. Detection limits for U in environmental samples using this technique are on the order of 50 ppb. PMID:16732365

Kaste, James M; Bostick, Benjamin C; Heimsath, Arjun M

2006-06-01

383

Sub-Angstrom transmission electron microscopy at 300keV  

SciTech Connect

We have demonstrated sub-Angstrom TEM to a resolution of 0.78 Angstrom with the one-Angstrom microscope (OAM) project at the National Center for Electron Microscopy. The OAM combines a modified CM300FEG-UT with computer software able to generate sub-Angstrom images from experimental image series. We achieved sub-Angstrom resolution with the OAM by paying close attention to detail. We placed the TEM in a favorable environment. We reduced its three-fold astigmatism A2 from 2.46mm to 300 Angstrom (corresponding to transfer of 0.68 Angstrom spacings at a pi/4 phase limit). We improved its information limit by minimizing high-voltage and lens current ripple. Energy spread of 0.93eV FWHH gave a focus spread of 20 Angstrom and an information limit of 0.78 Angstrom, allowing successful resolution of the 0.89 Angstrom (400) atom spacings in [110] diamond. As a further test, we reduced the electron gun extraction voltage to 3kV to improve our information limit to 0.75 Angstrom, and then imaged 0 .7 Angstrom (444) atom spacings in [112] silicon as distinct pairs of 'white atoms' near an alpha-null defocus of -3783 Angstrom.

O'Keefe, Michael A.; Nelson, E. Christian; Turner, John H.; Thust, Andreas

2001-02-14

384

Single track nanodosimetry of low energy electrons  

NASA Astrophysics Data System (ADS)

Auger-electron-emitting radionuclides (for instance, 125I) with a predominant energy spectrum below 3 keV are an active area of research towards the clinical application of radiopharmaceuticals. Hence, the necessity for an adequate description of the effects of radiation by low-energy electrons on nanometric biological targets seems to be unquestionable. Experimental nanodosimetry for low-energy electrons has been accomplished with a device named JET COUNTER. The present paper describes, for the first time, nanodosimetric experiments in nanometer-sized cavities of nitrogen using low energy electrons ranging from 100 eV to 2 keV.

Bantsar, A.; Grosswendt, B.; Pszona, S.; Kula, J.

2009-02-01

385

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

SciTech Connect

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

Savelov, A. S., E-mail: vniia@vniia.ru; Salakhutdinov, G. Kh. [National Research Nuclear Center 'MIFI,' (Russian Federation); Koltunov, M. V.; Lemeshko, B. D.; Yurkov, D. I.; Sidorov, P. P. [Federal State Unitary Enterprise 'VNII Avtomatiki,' (Russian Federation)

2011-12-15

386

Energy!  

NSDL National Science Digital Library

Students will be introduced to energy, what it is and the different forms of energy. Energy - the ability to do work! Energy is necessary to our everyday lives and is found all around us all the time. We can not do anything without using energy. For the purposes of this class it is important that we understand there are ...

Larsen, Mr.

2009-09-24

387

Modification of the mechanical and optical properties of a polycarbonate by 50 keV Ar+ and H+ ion implantation  

NASA Astrophysics Data System (ADS)

The effects of 50 keV H+ and Ar+ ions on the mechanical properties and ultraviolet-visible absorption of the polymer CR39 were investigated. It was found that the H+ implantation produced a yellow-brown material with optical properties similar to amorphous hydrogenated carbon, whereas Ar+ implantation produced a material with optical properties more like evaporated amorphous carbon. The mechanical properties of the implanted material were measured using a nanoindentation technique and increases in both the elastic modulus and hardness (maximum sustainable contact pressure) were observed following irradiation with both ion species. Compared to Ar+ implantation, H+ implantation of CR39 was found to produce a more transparent material at an equivalent maximum sustainable contact pressure and therefore H+ ions were found to be more desirable than Ar+ ions for the treatment of CR39 optical components.

Yap, E.; McCulloch, D. G.; McKenzie, D. R.; Swain, M. V.; Wielunski, L. S.; Clissold, R. A.

1998-03-01

388

X-ray Filament with a Strong 6.7 keV Line in the Galactic Center Region  

E-print Network

An elongated X-ray source with a strong K-shell line from He-like iron (Fe XXVI) is found at (RA, Dec)_{J2000.0}=(17h44m00s.0, -29D13'40''.9) in the Galactic center region. The position coincides with the X-ray thread, G359.55+0.16, which is aligned with the radio non-thermal filament. The X-ray spectrum is well fitted with an absorbed thin thermal plasma (apec) model. The best-fit temperature, metal abundance, and column density are 4.1^{+2.7}_{-1.8} keV, 0.58^{+0.41}_{-0.32} solar, and 6.1^{+2.5}_{-1.3}x10^{22} cm^{-2}, respectively. These values are similar to those of the largely extended Galactic center X-ray emission.

Yamauchi, Shigeo; Nakashima, Shinya; Nobukawa, Masayoshi; Tsuru, Takeshi Go; Koyama, Katsuji

2014-01-01

389

Desorption of nanoclusters from gold nanodispersed layers by 72 keV Au 400 ions: Experiment and molecular dynamics simulation  

NASA Astrophysics Data System (ADS)

The interaction of 72 keV Au 400 ions (with a diameter of approximately 2 nm) with nanodispersed gold targets has been studied. These interactions are dominated by elastic collisions. The gold nanodispersed target with 2-12 nm nanoislets was bombarded with a fluence of 1.7 × 10 12 ions/cm 2. The desorbed nanoclusters were collected on carbon foils supported by TEM-grids. Intact 29 nm gold nanoclusters were found on the collectors. The desorption yield (normalized to the total cross-section of the projectile-cluster interaction) was estimated to be 0.62 nanocluster/projectile. Preliminary estimates were made using molecular dynamic simulations for comparison with the experimental results.

Baranov, I.; Della-Negra, S.; Domaratsky, V.; Chemezov, A.; Novikov, A.; Obnorsky, V.; Pautrat, M.; Anders, Chr.; Urbassek, H. M.; Wien, K.; Yarmiychuk, S.; Zhurkin, E.

2008-05-01

390

Low energy tracking and particles identification in the MUNU Time Projection Chamber at 1 bar. Possible application in low energy solar neutrino spectroscopy  

E-print Network

In this paper we present the results from the measurements made with the MUNU TPC at 1bar pressure of CF4 in the energy region below 1 MeV. Electron events down to 80 keV are successfully measured. The electron energy and direction are reconstructed for every contained single electron above 200 keV. As test the 137Cs photopeak is reconstructed by measuring both the energy and direction of the Compton electrons in the TPC.

Z. Daraktchieva; C. Amsler; M. Avenier; C. Broggini; J. Busto; C. Cerna; F. Juget; D. H. Koang; J. Lamblin; D. Lebrun; O. Link; G. Puglierin; A. Stutz; A. Tadsen; J. -L. Vuilleumier; J. -M. Vuilleumier; V. Zacek

2007-10-04

391

Studies on the effective energy of x-rays generated by ECR and their use for the calibration of thermoluminescent dosimeter badges in low energy region  

SciTech Connect

The effective energy of electron cyclotron resonance (ECR) x-ray source has been altered by keeping a target disk at the cavity wall in the exit port. The source has been tuned for the effective energy of 40 and 70 keV. The use of the source for the calibration of thermoluminescent dosimeter badges in the low energy region (<150 keV) has been explored.

Baskaran, R.; Selvakumaran, T.S. [Radiological Safety Division, Safety Group Indira Gandhi Center for Atomic Research, Kalpakkam, 603 102, Tamil Nadu (India)

2005-04-01

392

IonCCD™ for direct position-sensitive charged-particle detection: from electrons and keV ions to hyperthermal biomolecular ions.  

PubMed

A novel, low-cost, pixel-based detector array (described elsewhere Sinha and Wadsworth (76(2), 1) is examined using different charged particles, from electrons to hyperthermal (<100 eV) large biomolecular positive and negative ions, including keV small atomic and molecular ions. With this in mind, it is used in instrumentation design (beam profiling), mass spectrometry, and electron spectroscopy. The array detector is a modified light-sensitive charge-coupled device (CCD) that was engineered for direct charged-particle detection by replacing the semiconductor part of the CCD pixel with a conductor Sinha and Wadsworth (76(2), 1). The device is referred to as the IonCCD. For the first time, we show the direct detection of 250-eV electrons, providing linearity response of the IonCCD to the electron beam current. We demonstrate that the IonCCD detection efficiency is virtually independent from the particle energy (250 eV, 1250 eV), impact angle (45(o), 90(o)) and flux. By combining the IonCCD with a double-focusing sector field mass spectrometer (MS) of Mattauch-Herzog geometry (MH-MS), we demonstrate fast data acquisition. Detection of hyperthermal biomolecular ions produced using an electrospray ionization source (ESI) is also presented. In addition, the IonCCD was used as a beam profiler to characterize the beam shape and intensity of 15 eV protonated and deprotonated biomolecular ions at the exit of an rf-only collisional quadrupole. This demonstrates an ion-beam profiling application for instrument design. Finally, we present simultaneous detection of 140 eV doubly protonated biomolecular ions when the IonCCD is combined with the MH-MS. This demonstrates the possibility of simultaneous separation and micro-array deposition of biological material using a miniature MH-MS. PMID:21472600

Hadjar, Omar; Johnson, Grant; Laskin, Julia; Kibelka, Gottfried; Shill, Scott; Kuhn, Ken; Cameron, Chad; Kassan, Scott

2011-04-01

393

Effect of gold on keV x-ray emission yield from laser produced plasma of gold-copper mix-Z targets  

SciTech Connect

The effect of gold on keV x-ray emission from gold-copper (Au-Cu) mix-Z plasma has been experimentally studied. The intensity of the copper L-shell line radiation ({lambda}{approx}7.8-10.9 A) as well as the integrated keV x-ray yield were observed to decrease sharply with increasing atomic fraction of gold in the mix-Z target. The decrease was observed to be by a factor of {approx}2.1 for 0.12 atomic fraction of gold in the Au-Cu mix-Z target with respect to the pure copper target. The results can be explained from physical consideration of the high value of free-bound opacity of gold in the spectral region of the L-shell emission of copper ions and downconversion of the absorbed keV line radiation.

Arora, V.; Chakera, J. A.; Naik, P. A.; Kumbhare, S. R.; Gupta, P. D.; Gupta, N. K. [Laser Plasma Division, Raja Ramanna Centre for Advanced Technology, Indore 452 013 (India); Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India)

2006-08-01

394

Extra light fermions in E6-inspired models and the 3.5 keV X-ray line signal  

NASA Astrophysics Data System (ADS)

We propose a scenario in which extra light fermions in an E6-inspired U(1) extension of the standard model constitute the dark matter, as a simple variation of our model for dark radiation presented in 2010. Interestingly, for the light fermions of mass about 7 keV, we naturally obtain a desired mixing angle to explain the recently discovered 3.5 keV X-ray line signal through the radiative decay into active neutrinos and photons with a lifetime in the range of 1027-1028 seconds.

Nakayama, Kazunori; Takahashi, Fuminobu; Yanagida, Tsutomu T.

2014-10-01

395

Measurement of the {sup 237}Np(n,{gamma}) cross section from 20 meV to 500 keV with a high efficiency, highly segmented 4{pi} BaF{sub 2} detector  

SciTech Connect

The {sup 237}Np(n,{gamma}){sup 238}Np cross section has been measured in the neutron energy range from 20 meV to 500 keV using the DANCE array at the Los Alamos National Laboratory. This new facility allows experiments with submilligram samples and is therefore well suited to investigate isotopes with half-lives as low as a few hundred days. In this benchmark measurement, only 0.42 mg of {sup 237}Np was sufficient to determine differential cross sections relative to the well-known resonance at 0.5 eV. The thermal cross section was measured to {sigma}{sub 2200m/s}=177{+-}5 barn, {sigma}{sub kT=25.3meV}=167{+-}4 barn and the resonance integral to RI=693{+-}6 barn.

Esch, E.-I.; Bond, E. M.; Bredeweg, T. A.; Couture, A.; Glover, S. E.; Haight, R. C.; Jandel, M.; Kawano, T.; Mertz, A.; O'Donnell, J. M.; Rundberg, R. S.; Schwantes, J. M.; Ullmann, J. L.; Vieira, D. J.; Wilhelmy, J. B.; Wouters, J. M. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Reifarth, R. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Colorado School of Mines, Golden, Colorado 80401 (United States); Greife, U.; Hatarik, A. M.; Hatarik, R. [Colorado School of Mines, Golden, Colorado 80401 (United States)

2008-03-15

396

Relic gravity waves and 7 keV dark matter from a GeV scale inflaton  

NASA Astrophysics Data System (ADS)

We study the mechanism of generation of 7 keV sterile neutrino Dark Matter (DM) in the model with light inflaton ?, which serves as a messenger of scale invariance breaking. In this model the inflaton, in addition to providing reheating to the Standard Model (SM) particles, decays directly into sterile neutrinos. The latter are responsible for the active neutrino oscillations via seesaw type I mechanism. While the two sterile neutrinos may also produce the lepton asymmetry in the primordial plasma and hence explain the baryon asymmetry of the Universe, the third one being the lightest may be of 7 keV and serve as DM. For this mechanism to work, the mass of the inflaton is bound to be light (0.1-1 GeV) and uniquely determines its properties, which allows to test the model. For particle physics experiments these are: inflaton lifetime (10-5-10-12 s), branching ratio of B-meson to kaon and inflaton (10-6-10-4) and inflaton branching ratios into light SM particles like it would be for the SM Higgs boson of the same mass. For cosmological experiments these are: spectral index of scalar perturbations (ns?0.957-0.967), and amount of tensor perturbations produced at inflation (tensor-to-scalar ratio r?0.15-0.005). ? and ? are related from the CMB normalization. m? and ? are related by the requirement of the generation of proper abundance of DM (given DM mass M1 or coupling f1 is known). ? can be determined from the measurement of the tensor-to-scalar ratio r of the primordial perturbations. ? is bound from below from the requirement of sufficient reheating, ? is bound from above not to spoil the inflationary potential by radiative corrections, certain region in m? and ? (or, equivalently ?) is constrained from particle physics experiments. We show below that the first two are automatically satisfied with the parameters, leading to the proper DM generation, and the latter one leads to significant bound on the inflaton mass m? (and hence effective upper bound on r).

Bezrukov, F. L.; Gorbunov, D. S.

2014-09-01

397

The high energy X-ray tail of Eta Car revealed by BeppoSAX  

E-print Network

We report on the June 2000 long (100 ks) BeppoSAX exposure that has unveiled above 10 keV a new very high energy component of the X-ray spectrum of Eta Car extending to at least 50 keV. We find that the 2-150 keV spectrum is best reproduced by a thermal + non-thermal model. The thermal component dominates the 2-10 keV spectral range with kT_h=5.5 +/- 0.3 keV and log NH_h=22.68 +/- 0.01. The spectrum displays a prominent iron emission line centred at 6.70 keV. Its equivalent width of 0.94 keV, if produced by the thermal source, gives a slightly sub-solar iron abundance ([Fe/H]=-0.15 +/- 0.02). The high energy tail above 10 keV is best fitted by a power law with a photon index of 2.42 +/- 0.04. The integrated 13-150 keV luminosity of ~12 L-sun is comparable to that of the 2-10 keV thermal component. The present result can be explained, in the Eta Car binary star scenario, by Comptonisation of low frequency radiation by high energy electrons, probably generated in the colliding wind shock front, or in instabilities in the wind of the S Dor primary star. It is possible that the high energy tail had largely weakened near the minimum of the 5.53 yr cycle. With respect to the thermal component, it probably has a longer recovering time like that of the highest excitation optical emission lines. Both features can be associated with the large absorption measured by BeppoSAX at phase 0.05.

R. F. Viotti; L. A. Antonelli; C. Rossi; S. Rebecchi

2004-02-13

398

The response of polycrystalline tungsten to 30 keV helium ion implantation at normal incidence and high temperatures  

NASA Astrophysics Data System (ADS)

Polycrystalline tungsten samples were irradiated with 30 keV helium ions in the Materials Irradiation Experiment (MITE-E). Samples were held at temperatures of 500-900 °C while irradiated to fluences of ˜6 × 1016 to ˜4 × 1019 He/cm2. Drastic changes to the surface morphology were observed at implant doses exceeding ˜1 × 1018 He/cm2 and classified as blisters, pitting, or a highly directional surface structure dubbed "grass." Morphological details of the grass structure depended on the crystal orientation of the grains at the sample surface. A sub-surface semi-porous layer was formed during irradiation. Post-implantation analysis revealed that this layer extended up to ˜1000 nm below the surface in the highest fluence cases. Specimens irradiated to fluences in excess of ˜1 × 1018 He/cm2 experienced statistically significant mass loss which increased with higher implant dose. Implications of this mass loss are discussed for the plasma facing components of both magnetic and inertial fusion reactors.

Zenobia, Samuel J.; Garrison, Lauren M.; Kulcinski, Gerald L.

2012-06-01

399

X-ray backlighting sources of 4 to 10 keV for laser-fusion targets  

SciTech Connect

High-intensity, short-duration x-ray pulses are necessary to diagnose the compression of laser film targets. Present target designs are such that backlighting sources ranging from a few thousand electron volts to 100 keV will be necessary. The desired source durations range from a few tens of picoseconds for flash radiography to several nanoseconds for streaked backlighting, and the source occurrence must be tightly synchronized to that of the target-irradiating laser pulse. For the latter reason, a laser-induced x-ray pulse is preferred. An initial study of the K lines of Ti, Ni, and Zn as possible backlighting sources was conducted. The conversion efficiency of laser light into line radiation was obtained as a function of laser intensity, pulse length, and wavelength. A threshold laser intensity for x-ray line production was identified. Information was obtained on the size and duration of the x-ray emission source, in relation to laser parameters. The experimental results, and their impact on backlighting capability for high-density laser function targets, are discussed.

Rupert, V.C.; Matthews, D.L.; Koppel, L.N.

1981-05-12

400

Mechanical and elastic changes in cementite Fe3C subjected to cumulative 1 keV Fe recoils  

NASA Astrophysics Data System (ADS)

Carbon-bearing steels have a complex microstructure which involves cementite Fe3C. When these steels are used as construction materials for nuclear reactors they are subjected to continuous defect production due to neutron irradiation. Its effects on iron containing interstitial carbon have been studied previously. However, the evolution of Fe3C when subjected to these conditions is unknown, at any temperature, dose and dose rate. In this work we present results from molecular dynamics simulations of cumulative defect production in a pure single-crystal Fe3C sample subjected to a high dose-rate of 1 keV Fe recoils. The results indicate that Fe3C after an initial softening grows slightly harder after a dose of 0.1 dpa, and remains at this level for doses up to 0.7 dpa. Analysis indicates this effect may be due to C atoms getting closer to each other as the damage production increases. Results for the Young's moduli and the defect production are also presented. Due to the high dose-rate the effects on actual nuclear steels is unclear, but some estimates are discussed.

Henriksson, K. O. E.; Nordlund, K.

2014-11-01

401

Analysis of 20 KEV Electron Induced X-Ray Production in Skull, Femur/tibia Bones of Rats  

NASA Astrophysics Data System (ADS)

Hind-limb suspension (HLS) of rats is a NASA validated model of simulated weightlessness. This study examines the effects of microgravity on the skeletal system of rats to assess whether or not exposure of rats to HLS for one week will induce alteration of structural features in selected bones. Four groups of rats were used: two unsuspended controls and two suspended groups. Body weight, food, and water intake were monitored daily before and after suspension. X-rays were measured by a liquid nitrogen cooled Si(li) detector on a Scanning Electron Microscope (SEM) that provided the 20 keV electron beam. X-ray data were collected from square cross sections between 100 ?m2 and 104 ?m2. The bones were measured for elemental levels of calcium, phosphorus, oxygen and carbon from both control and HLS rats. The average body weight of all HLS groups decreased compared to their respective unsuspended controls. Food and water intake was also lower in both suspended groups. A correlation among HLS and control samples in terms of the distribution of the primary elements was found in the bone tissue when analyzed as a function of position along the hind-leg and within the cross sections.

Mehta, Rahul; Watson, Alec; Ali, Nawab; Soulsby, Michael; Chowdhury, Parimal

2010-04-01

402

Strength of the E_R = 127 keV, 26Al(p,g)27Si resonance  

E-print Network

We examine the impact of the strength of the E_R = 127 keV, 26Al(p,g)27Si resonance on 26Al production in classical nova explosions and asymptotic giant branch (AGB) stars. Thermonuclear 26Al(p,g)27Si 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 26Al yields in our models are not sensitive to differences in rates determined using zero and a commonly stated upper limit corresponding to wg_UL = 0.0042 micro-eV for this resonance strength. Yields of 26Al decrease by 6% and, more significantly, up to 30%, when a strength of 24 x wg_UL = 0.1 micro-eV is assumed in the adopted nova and AGB star models, respectively. Given that the value of wg_UL was deduced from a single, background-dominated 26Al(3He,d)27Si experiment where only upper limits on differential cross sections were determined, we encourage new experiments to confirm the strength of t...

Parikh, A; Karakas, A; Ruiz, C; Wimmer, K

2014-01-01

403

Remeasurement of the 193 keV resonance in {sup 17}O(p,{alpha}){sup 14}N  

SciTech Connect

A recently discovered resonance at 193 keV determines the thermonuclear rates of the {sup 17}O +p reactions at temperatures important for the nucleosynthesis in classical novae (T=0.1-0.4 GK). We report on a remeasurement of this resonance in the {sup 17}O(p,{alpha}){sup 14}N reaction by using a different kind of target compared to the previous study. Special emphasis is placed on Monte Carlo simulations of the experiment in order to better understand certain effects that have been disregarded previously. Our measured value of the resonance strength amounts to ({omega}{gamma}){sub p{alpha}}=(1.66{+-}0.17)x10{sup -3} eV, in agreement with the previously reported result. As a byproduct of our study, we find that the inhomogeneity of the foil placed in front of the {alpha}-particle detector determines the resolution in the pulse-height spectrum, and thus constrains the signal-to-noise ratio in searches of very weak (p,{alpha}) resonances.

Newton, J. R.; Iliadis, C.; Champagne, A. E.; Longland, R.; Ugalde, C. [Department of Physics and Astronomy, University of North Carolina, Chapel Hill, North Carolina 27599-3255 (United States) and Triangle Universities Nuclear Laboratory, Durham, North Carolina 27708-0308 (United States)

2007-05-15

404

PACT: a sensitive 100 keV-10 MeV all sky pairs and Compton telescope  

NASA Astrophysics Data System (ADS)

PACT is a Pair And Compton Telescope that aims to make a sensitive survey of the gamma-ray sky between 100 keV and 100 MeV. It will be devoted to the detection of radioactivity lines from present and past supernova explosions, the observation of thousands of new blazars, and the study of polarized radiations from gamma-ray bursts, pulsars and accreting black holes. It will reach a sensitivity of one to two orders of magnitude lower than COMPTEL/CGRO (e.g. about 50 times lower for the broad-band, survey sensitivity at 1 MeV after 5 years). The concept of PACT will be proposed for the AstroMeV mission in the framework of the M4 ESA Call. It is based upon three main components: a silicon-based gamma-ray tracker, a crystal-based calorimeter (e.g. CeBr3:Sr), and an anticoincidence detector made of plastic scintillator panels. Prototypes of these detector planes are currently tested in the laboratories.

Laurent, P.; Tatischeff, V.; de Seréville, N.; Limousin, O.; Bertoli, W.; Bréelle, E.; Dolgorouky, Y.; Gostojic, A.; Hamadache, C.; Khalil, M.; Kiener, J.

2014-07-01

405

Study of a high intensity 746 keV neutrino source for the calibration of solar neutrino detectors  

NASA Astrophysics Data System (ADS)

We describe the test production of a 0.94 PBq (25 400 Ci) source of 746 keV neutrinos coming from the electron capture decay of 51Cr. This is the first time that such a source has been produced. It was obtained by neutron activation of 12.5 kg of natural granular chromium at the Siloé reactor at Grenoble. If this nuclear reactor were devoted exclusively to the production of 51Cr from natural chromium, we calculate that the highest activity that could be produced would be around 29 PBq (0.8 MCi) in 45 days of irradiation, for 125 kg of target. With chromium enriched in 50Cr, we could get around 40 PBq (1.08 MCi) in an irradiation of 21 days, for 45 kg of target containing 17% 50Cr. Such sources are planned for use in calibrating forthcoming solar neutrino detectors, especially the gallium detector to be installed in the Gran Sasso Underground Laboratory. To obtain a precision of 10% in such calibrations would require either three sources made from natural chromium (i.e. three reactor irradiations of 45 days each) or two sources made from enriched chromium (two irradiations of 21 days each).

Cribier, M.; Pichard, B.; Rich, J.; Spiro, M.; Vignaud, D.; Besson, A.; Bevilacqua, A.; Caperan, F.; Dupont, G.; Sire, P.; Gorry, J.; Hampel, W.; Kirsten, T.

1998-03-01

406

FABRICATION AND REPAIR OF ION SOURCE COMPONENTS IN THE 80 keV NEUTRAL BEAM LINES FOR DIII-D  

SciTech Connect

OAK-B135 After 8 years of operation, leaks began to develop in critical components of the ion sources of the 80 keV neutral beam lines in DIII-D. Operational adjustments were made that seemed to remedy the problems, but five years later leaks began occurring again, this time with greater frequency. Failures occurred in the stainless steel bellows and molybdenum rails of the grid rail modules as well as in the Langmuir probes. Failure analyses identified several root causes of the leaks and operational adjustments were again made to mitigate the problems, but the rash of failures depleted the program's supply of spare grid rail modules and probes and removed one of the ion sources from regular operation. Fifteen years after their original fabrication, the ion source components were no longer commercially available. In 2001, a program was initiated to fabricate new grid rail modules, including new molybdenum grid rails, bellows, and stainless steel grid rail holders, as well as new Langmuir probes. In parallel, components removed from service due to leaks were to be repaired with new rails and bellows and returned to service. An overview of the root causes of the service failures is offered, details of the repair processes are described, and a summary and evaluation of the fabrication procedures for the new molybdenum rails, grid modules, and Langmuir probes are given.

GRUNLOH,H.J; BUSATH,J.L; CALLIS,R.W; CHIU,H.K; DiMARTINO,M; HONG,R; KLASEN,R; MOELLER,C.P; ROBINSON,J.I; STRECKERT,H.H; TAO,R; TRESTER,P.W

2003-10-01

407

Investigation of structural stability and magnetic properties of Fe/Ni multilayers irradiated by 300 keV Fe10+  

NASA Astrophysics Data System (ADS)

The effects of irradiation on the structural stability and magnetic properties of Fe/Ni multilayers, which are promising candidate magnet materials in fusion reactors, were investigated. Three types of Fe/Ni multilayers with different modulation periods ranging from 2 nm to 10 nm were deposited on Si (1 0 0) substrate through direct current magnetron sputtering. The multilayered samples were irradiated by 300 keV Fe10+ ions in a wide fluence range of 1.7 × 1018/m2 to 2 × 1019/m2. Magnetic hysteresis loops of pre- and post-irradiation samples were obtained using a vibrating sample magnetometer, and structural stability were analyzed by X-ray diffraction. Magnetic measurements showed that the coercive force of Fe/Ni multilayers remained stable with increasing irradiation fluence. However, saturation magnetization increased with increasing irradiation fluence. The samples with 5 nm modulation period were the least affected by irradiation among the three types of Fe/Ni multilayers. The effects of temperature during irradiation were also discussed to explore the optimum temperature of multilayers.

Chen, Feida; Tang, Xiaobin; Yang, Yahui; Huang, Hai; Chen, Da

2014-09-01

408

Scattering of 64 eV to 3 keV Neutrons from Polyethylene and Graphite and the Coherence Length Problem  

E-print Network

Scattering of 64 eV to 3 keV Neutrons from Polyethylene and Graphite and the Coherence Length 12180, USA (Received 31 August 2005; published 8 February 2006) We measured the neutron scattering. This experiment was carried out to search for any anomaly in the n-p scattered intensities from CH2 caused

Danon, Yaron

409

A statistical analysis of the lateral displacement of Si atoms in molecular dynamics simulations of successive bombardment with 20keV C60 projectiles  

Microsoft Academic Search

An important factor that determines the possible lateral resolution in sputter depth profiling experiments is ion induced lateral displacement of substrate atoms. Molecular dynamics (MD) simulations are performed to model the successive bombardment of Si with 20 keV C60 at normal incidence. A statistical analysis of the lateral displacement of atoms that originate from the topmost layer is presented and

K. D. Krantzman; E. L. Cook; A. Wucher; B. J. Garrison

2011-01-01

410

A statistical analysis of the lateral displacement of Si atoms in molecular dynamics simulations of successive bombardment with 20keV C 60 projectiles  

Microsoft Academic Search

An important factor that determines the possible lateral resolution in sputter depth profiling experiments is ion induced lateral displacement of substrate atoms. Molecular dynamics (MD) simulations are performed to model the successive bombardment of Si with 20keV C60 at normal incidence. A statistical analysis of the lateral displacement of atoms that originate from the topmost layer is presented and discussed.

K. D. Krantzman; E. L. Cook; A. Wucher; B. J. Garrison

2011-01-01

411

TEMPERATURE-DEPENDENT FORMATION OF OZONE IN SOLID OXYGEN BY 5 keV ELECTRON IRRADIATION AND IMPLICATIONS FOR SOLAR SYSTEM ICES  

E-print Network

TEMPERATURE-DEPENDENT FORMATION OF OZONE IN SOLID OXYGEN BY 5 keV ELECTRON IRRADIATION AND IMPLICATIONS FOR SOLAR SYSTEM ICES Bhalamurugan Sivaraman,1 Corey S. Jamieson,2 Nigel J. Mason,1 and Ralf I irradiation, two additional temperature-dependent reaction mechanisms were observed to synthesize ozone: (1

Kaiser, Ralf I.

412

Cross sections for the production of excited He{sup +} ({ital np}){sup 2}{ital P}{sup {ital o}} states by 50{endash}150-keV proton impact on helium  

SciTech Connect

Cross sections have been measured for the production of He{sup +} ({ital np}){sup 2}{ital P}{sup {ital o}} states, {ital n}=2,3,4, by proton impact on helium over a projectile velocity range of 1.42{endash}2.45 a.u. (50 {le}{ital E}{le}150 keV). Cross sections were determined by measuring the extreme ultraviolet photons emitted from excited He{sup +} ions. The data indicate a lower energy than expected for the maximum cross section. A comparison of the present results in terms of projectile energy dependance with the cross sections for excitation to He (1{ital snp}){sup 1}{ital P}{sup {ital o}}, ionization, and total electron capture suggests the primary mechanism for the production of excited He{sup +} at low energies is transfer excitation, with ionization excitation being the dominant mechanism at higher energies. {copyright} {ital 1996 The American Physical Society.}

Stolte, W.C.; Bruch, R. [Department of Physics, University of Nevada, Reno, Nevada 89557-0058 (United States)] [Department of Physics, University of Nevada, Reno, Nevada 89557-0058 (United States)

1996-09-01

413

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

PubMed Central

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

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

2013-01-01

414

Energy.  

PubMed

Energy is the capacity to do the things we are capable of and desire to accomplish. Most often this is thought of in terms of PEP--personal energy potential--a reservoir of individual vivacity and zest for work. Like a battery, energy can be conceived of as a resource that is alternatively used and replenished. Transitions between activities, variety of tasks, and choices of what to spend energy on are part of energy management. Energy capacity can be thought of at four levels: (a) so little that harm is caused and extraordinary steps are needed for recovery, (b) a deficit that slightly impairs performance but will recover naturally, (c) the typical range of functioning, and (d) a surplus that may or may not be useful and requires continual investment to maintain. "Flow" is the experience of optimal energy use when challenges balance capacity as a result of imposing order on our environment. There are other energy resources in addition to personal vim. Effective work design reduces demands on energy. Money, office design, and knowledge are excellent substitutes for personal energy. PMID:22856055

Chambers, David W

2012-01-01

415

Investigation of dual-energy X-ray photon counting using a cadmium telluride detector and two comparators and its application to photon-count energy subtraction  

NASA Astrophysics Data System (ADS)

To obtain two tomograms with two different photon energy ranges simultaneously, we have performed dual-energy X-ray photon counting using a cadmium telluride (CdTe) detector, two comparators, two frequency–voltage converters (FVCs), and an analog digital converter (ADC). X-ray photons are detected using the CdTe detector with an energy resolution of 1% at 122 keV, and the event pulses from a shaping amplifier are sent to two comparators simultaneously to regulate two thresholds of photon energy. The logical pulses from a comparator are sent to an FVC consisting of two integrators, a microcomputer, and a voltage–voltage amplifier. The smoothed outputs from the two FVCs are input to the ADC to carry out dual-energy imaging. To observe contrast variations with changes in threshold energy, we performed energy-dispersive computed tomography utilizing the dual-energy photon counting at a tube voltage of 70 kV and a current of 25 µA. Two tomograms were obtained simultaneously at two energy ranges of 20.0–70.0 keV and 33.2–70.0 keV. The photon-count subtraction was carried out using photon energies ranging from 20.0 to 33.2 keV. The maximum count rate was 5.4 kilocounts per second with energies of 20.0–70.0 keV, and the exposure time for tomography was 10 min.

Hagiwara, Osahiko; Sato, Eiichi; Watanabe, Manabu; Sato, Yuich; Oda, Yasuyuki; Matsukiyo, Hiroshi; Osawa, Akihiro; Enomoto, Toshiyuki; Kusachi, Shinya; Ehara, Shigeru

2014-10-01

416

Characterisation of PEEK, PET and PI implanted with 80 keV Fe+ ions to high fluencies  

NASA Astrophysics Data System (ADS)

Polyimide (PI), polyetheretherketone (PEEK) and polyethylene terephthalate (PET) foils were implanted with 80 keV Fe+ ions at room temperature at fluencies of 0.2 × 1016 cm-2- 5.0 × 1016 cm-2. The implanted polymers were subsequently annealed at 200 °C for 20 min. The depth profiles of implanted Fe atoms and compositional changes of the implanted polymers were characterised by RBS and ERDA methods. A significant shift of the Fe concentration maximum to the sample surface with increasing ion fluence was observed and annealing does not influence the Fe profiles. The implanted Fe profiles cannot be reproduced by SRIM and TRIDYN simulations. Hydrogen desorption from the surface layer of all polymers is observed, the effect being the most pronounced on PET. Desorption of oxygen from the samples implanted to lower fluences is observed too. On the samples implanted to the highest fluence of 5.0 × 1016 cm-2, however, oxygen concentration increases to the value close to that of pristine polymer, this phenomenon is strongly pronounced after the annealing, which is provided in the ambient atmosphere. The electrical, optical and structural properties of the implanted polymers were investigated by sheet resistance measurement and UV-Vis spectroscopy. With increasing ion fluence, the sheet resistance decreases, but a saturation effect is achieved at a fluence of 5.0 × 1016 cm-2. UV-Vis absorbance increases simultaneously with the decline of the optical band gap Eg. After annealing, no significant changes in UV-Vis spectra or in electrical properties were observed.

Mackova, A.; Malinsky, P.; Miksova, R.; Hnatowicz, V.; Khaibullin, R. I.; Slepicka, P.; Svorcik, V.

2014-07-01

417

Photoabsorption and Compton scattering in ionization of helium at high photon energies  

SciTech Connect

Production of singly and doubly charged helium ions by impact of keV photons is studied. The ratio R{sub ph} = {sigma}{sub ph}{sup ++}/{sigma}{sub ph}{sup +} for photoabsorption is calculated in the photon-energy range 2--18 keV using correlated initial- and final- state wave functions. Extrapolation towards asymptotic photon energies yields R{sub ph}({omega} {yields} {infinity}) = 1.66% in agreement with previous predictions. Ionization due to Compton scattering, which becomes comparable to photoabsorption above {omega} {approximately} 3 keV, is discussed.

Andersson, L.R.; Burgdoerfer, J. [Oak Ridge National Lab., TN (United States)]|[Tennessee Univ., Knoxville, TN (United States). Dept. of Physics and Astronomy

1993-10-01

418

Near-threshold emission of electrons during grazing scattering of keV Ne atoms from an Al(111) surface  

SciTech Connect

The number of electrons emitted during grazing scattering of Ne atoms with kilo-electron-volt energies from an Al(111) surface is recorded in coincidence with the energy loss of scattered projectiles. Irrespective of the total projectile energies used, we observe a pronounced increase of total electron emission yields when the energy for motion normal to the surface exceeds about 25 eV. Based on energy loss spectra and classical computer simulations of projectile trajectories we attribute electron emission under these scattering conditions to a promotion mechanism in binary collisions between Ne and Al target atoms resulting in single and double excitations of projectiles.

Matulevich, Y.; Lederer, S.; Winter, H. [Institut fuer Physik, Humboldt Universitaet zu Berlin, Brook-Taylor-Str. 6, D-12489 Berlin (Germany)

2005-01-15

419

Near-threshold emission of electrons during grazing scattering of keV Ne atoms from an Al(111) surface  

NASA Astrophysics Data System (ADS)

The number of electrons emitted during grazing scattering of Ne atoms with kilo-electron-volt energies from an Al(111) surface is recorded in coincidence with the energy loss of scattered projectiles. Irrespective of the total projectile energies used, we observe a pronounced increase of total electron emission yields when the energy for motion normal to the surface exceeds about 25eV . Based on energy loss spectra and classical computer simulations of projectile trajectories we attribute electron emission under these scattering conditions to a promotion mechanism in binary collisions between Ne and Al target atoms resulting in single and double excitations of projectiles.

Matulevich, Y.; Lederer, S.; Winter, H.

2005-01-01

420

Evaluation of powder/granular Gd2O2S:Pr scintillator screens in single photon counting mode under 140 keV excitation  

NASA Astrophysics Data System (ADS)

The aim of this paper is the evaluation of an alternative, low cost solution for the gamma detector in planar imaging. It is based on a powder scintillator, well established in X-ray imaging, and could be further exploited in simultaneous bimodal imaging systems. For this purpose, we have examined the performance of Gd2O2S:Pr powder scintillator, in the form of thick granular screens easily produced in the laboratory by commercially available Gd2O2S:Pr powder. The screen was coupled to a round position sensitive photomultiplier tube (R3292 PSPMT). The system's evaluation was performed in photon counting mode under 99mTc excitation. In all measurements, a general purpose hexagonal parallel collimator was used. Different samples of screens with coating thickness varying from 0.1 g/cm2 to 1.2 g/cm2 were tested. The 0.6 g/cm2 screen, corresponding to ~ 2 mm actual thickness, was found most efficient under 140 keV irradiation. The system`s performance with the proposed screen is reported with the modulation transfer function. Moreover sensitivity, spatial and energy resolution as well as the uniformity response using phantoms were measured. The performance of the proposed screen was compared with two CsI:Tl pixellated crystal arrays with 2 × 2 × 3 mm3 and 3 × 3 × 5 mm3pixel size. A spatial resolution, of 3 mm FWHM, for a 99mTc line source, was achieved at zero source to collimator distance. In addition, the Gd2O2S:Pr screen showed a slower degradation of the spatial resolution with increasing source to collimator distance e.g at 20 cm, the Gd2O2S:Pr screen showed aq spatial resolution of 8.4 mm while the spatial resolution of the pixellated crystals was 15 mm. Taking into account its easy production, its flexibility due to powder form, the very low cost and the good spatial resolution properties of the proposed alternative detector, powder scintillators could potentially be used for the construction of flexible detector geometries, such as ring type or gamma probes or as a low cost detector solution in educational photon counting imaging applications, complementary to standard X-ray imaging.

David, S.; Georgiou, M.; Loudos, G.; Michail, C.; Fountos, G.; Kandarakis, I.

2013-01-01

421

Effects of alpha, gamma, and alpha-recoil radiation on borosilicate glass containing Savannah River Plant defense high-level nuclear waste. [Lead ions-250 keV; xenon ions-160 keV  

SciTech Connect

At the Savannah River Plant, the reference process for the immobilization of defense high-level waste (DHLW) for geologic storage is vitrification into borosilicate glass. During geologic storage for 10/sup 6/ y, the glass would be exposed to approx. 3 x 10/sup 10/ rad of ..beta.. radiation, approx. 10/sup 10/ rad of ..gamma.. radiation, and 10/sup 18/ particles/g glass for both ..cap alpha.. and ..cap alpha..-recoil radiation. This paper discusses tests of the effect of these radiations on the leachability and density of the glass. Even though the doses were large, no effect of the radiations was detected that reduced the effectiveness of the glass for long-term storage of DHLW even at doses corresponding to 10/sup 6/ years storage for the actual glass. For the tests, glass containing simulated DHLW was prepared from frit of the reference composition. Three methods were used to irradiate the glass: external irradiations with beams of approx. 200 keV Xe or Pb ions, internal irradiations with Cm-244 doped glass, and external irradiations with Co-60 ..gamma.. rays. Results with both Xe and Pb ions indicate that a