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1

Hydrogen Backscattering on Gold: Charge State and Energy Distribution (300 EV - 10 KeV).  

National Technical Information Service (NTIS)

The charge state of hydrogen is investigated, that is backscattered after hydrogen ion shooting with a primal energy of 1-10 keV on a gold surface with in the energy range of 300 eV to 10 keV. No experimental sign of a volume effect at the formation of th...

F. E. P. Matschke

1977-01-01

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

Energy determination of the 6129 keV 16O transition  

Microsoft Academic Search

Using newly established energy standards, which are based upon a scale derived by means of mass-doublets, and two different source arrangements, the energy of the 16O transition has been determined to be (6129.119 +\\/- 0.040) keV. The Q value for the 19F(n, gamma)20F reaction was also evaluated and found to be (6601.344 +\\/- 0.055) keV.

T. J. Kennett; W. V. Prestwich; J. S. Tsai

1986-01-01

4

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

NASA Astrophysics Data System (ADS)

The PILATUS detector module was characterized in the PTB laboratory at BESSY II comparing modules with 320 ?m thick and newly developed 450 ?m and 1000 ?m thick silicon sensors. Measurements were carried out over a wide energy range, in-vacuum from 1.75 keV to 8.8 keV and in air from 8 keV to 60 keV. The quantum efficiency (QE) was measured as a function of energy and the spatial resolution was measured at several photon energies both in terms of the modulation transfer function (MTF) from edge profile measurements and by directly measuring the point spread function (PSF) of a single pixel in a raster scan with a pinhole beam. Independent of the sensor thickness, the measured MTF and PSF come close to those for an ideal pixel detector with the pixel size of the PILATUS detector (172 × 172 ?m2). The measured QE follows the values predicted by calculation. Thicker sensors significantly enhance the QE of the PILATUS detectors for energies above 10 keV without impairing the spatial resolution and noise-free detection. In-vacuum operation of the PILATUS detector is possible at energies as low as 1.75 keV.

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

2013-03-01

5

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

PubMed

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

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

2014-06-01

6

Channeled and random proton stopping power in the 30-1000 keV energy range  

Microsoft Academic Search

The stopping power of 30- to 1000-keV protons transmitted through silicon in random and channeling (, , and ) directions has been determined. It was found that the stopping power for random and all channeling directions reaches a maximum at about 50 keV. At nearly the same energy the ratio of the channeled-to-random stopping has the maximum value. Present results

A. Carnera; G. Della Mea; A. V. Drigo; S. Lo Russo; P. Mazzoldi; G. G. Bentini

1978-01-01

7

X-Ray Attenuation of Silicon in the Energy Range 25 - 50 KeV.  

National Technical Information Service (NTIS)

Precise measurements of the X-ray attenuation coefficient of crystalline silicon have been made in the energy range 25 to 50 keV. A systematic discrepancy between theory and experiment is observed. The most likely cause of the disagreement is thought to b...

J. F. Mika Z. Barnea

1984-01-01

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

Energy recovery experiments with a powerful 100 keV D[sup [minus  

SciTech Connect

Energy recovery experiments have been conducted for the first time with a negative ion based neutral beam injector. A new type of energy recovery system was utilized, which: (i) separates electrostatically the neutrals and charged components of the beam at the exit of the neutralizer; (ii) decelerates the residual unneutralized negative ions; (iii) prevents secondary emission of electrons from the negative ion collector by means of electrostatic trapping. With 102 keV, 1.2 A D[sup [minus

Fumelli, M.; Jequier, F.; Pamela, J. (Association EURATOM-CEA, CE Cadarache, 13108 St. Paul-Lez-Durance (France)); Hanada, M.; Okumura, Y.; Watanabe, K. (JAERI, Naka-machi, Naga-gun, Ibaraki-ken, 311-01 (Japan))

1992-10-05

10

A 0-30 keV low-energy focused ion beam system  

Microsoft Academic Search

Low-energy focused ion beam (FIB) is a useful tool for shallow doping, gas-assisted etching, and other uses to minimize substrate damage in semiconductor device fabrication. The possibility to form a finely FIB of low energy under 1 keV was suggested in the investigations on the retarding mode in electron optical systems. The abilities of the simplest type of retarding mode

H. Kasahara; H. Sawaragi; R. Aihara; K. Gamo; S. Namba; M. Hassel Shearer

1988-01-01

11

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

Microsoft Academic Search

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 L3M2,3(1D2) 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

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

1994-01-01

12

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

13

Energy loss of 450-2400 kev protons in Havar, Kapton and aluminized Mylar foils  

Microsoft Academic Search

The energy loss of 450-2400 keV protons in common exit foils used in external beam setups has been determined. The measured foils consisted of 2.4 mum Havar, 9.9 mum Kapton and 3.5 mum and 6.6 mum aluminized (40 nm Al) Mylar. Good agreement with the calculations by using Bragg's rule and the Andersen and Ziegler parameters was found in the

E. Rauhala; J. Räisänen

1985-01-01

14

Effects induced by keV low-energy ion irradiation in the nematode Caenorhabditis elegans  

Microsoft Academic Search

The nematode Caenorhabditis elegans is an excellent model organism with which to study the biological effects and mechanisms of ionizing irradiation. In this\\u000a study, using C. elegans as a model, the effects of keV low-energy argon ion irradiation were investigated, by examining cuticle damage, worm survival,\\u000a brood size, life span, and germ cell death. The surface etching of worm cuticle

Xuelan Liu; Kezhou Cai; Huiyun Feng; Hang Yuan; Mingguang Kong; Lijun Wu; Yuejin Wu; Zengliang Yu

2007-01-01

15

Polarized proton capture on tritium at proton energies below 80 keV  

NASA Astrophysics Data System (ADS)

The 3H (p,->g) 4He reaction was studied at energies below Ep = 80 keV at Triangle Universities Nuclear Laboratory (TUNL) using the polarized ion source. The current study was the logical progression of a previous study of the 2H (p->,g ) 3He reaction done by the radiative capture group at TUNL. One result from that study was the recognition of the importance of meson exchange currents (MEC) in that reaction. In fact, theoretical calculations have shown that approximately 50% of the magnetic dipole transition strength observed in that reaction at Ep = 80 keV can be attributed to MECs. The contribution of MECs to the M1 strength in the 3H (p->,g ) 4He reaction at very low energies is expected to be even stronger. The use of a polarized proton beam allows for the observation of the analyzing power in this reaction. The angular distribution of the cross section, ?(?), and the analyzing power, Ay(?), were measured at incident proton beam energies of 40 keV and 80 keV. In both cases the beam was stopped in the target. The angular distribution in the cross section and analyzing power were fit to a Legendre and Associated Legendre polynomial expansion, respectively. A transition matrix element analysis, which expands all of the observables as a set of amplitudes and phases, was performed on the data as well. The magnetic dipole transition strength was determined from this analysis. The explicit MEC effects are contained in this strength. By comparing this strength with similar reactions in the case of three- bodies, we are able to interpret the MEC origin of this strength. In addition, the absolute cross section has been determined. A parameterization of the Astrophysical S- factor, which factors out the rapidly varying effects due to the Coulomb potential from the cross section, has been performed. Previous measurements of the absolute cross section extended down to beam energies of 100 keV. The present study extends the measured cross section data closer to zero energy and, therefore, makes the extrapolation into the energy regime typically of interest to astrophysicists more reliable. Finally, this reaction can be used as a source of 20 MeV ?-rays. A reliable measurement of the cross-section at low energies will be very useful in future designs of sources using high-voltage power supplies to accelerate the proton beam.

Canon, Richard Shane

16

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

17

Synthesis of gold and silver nanoparticles by electron irradiation at 5 15 keV energy  

NASA Astrophysics Data System (ADS)

Thin coatings (~10 µm) made from a mixture of polyvinyl alcohol (PVA) and HAuCl4 or PVA and AgNO3 on quartz plates were irradiated with 5-15 keV electrons, at room temperature. The electron energy was varied from coating to coating in the range of 5-15 keV, but electron fluence was kept constant at ~1015 e cm-2. Samples were characterized by the UV-vis, XRD, SEM and TEM techniques. The plasmon absorption peaks at ~511 and ~442 nm confirmed the formation of gold and silver nanoparticles in the respective electron-irradiated coatings. The XRD, SEM and TEM measurements reveal that the average size of the particles could be tailored in the range of 130-50 nm for gold and from 150-40 nm for silver by varying the electron energy in the range of 5-15 keV. These particles of gold and silver embedded in the polymer could also be separated by dissolving the coatings in distilled water.

Mahapatra, S. K.; Bogle, K. A.; Dhole, S. D.; Bhoraskar, V. N.

2007-04-01

18

Absolute measurements of x-ray backlighter sources at energies above 10 keV  

SciTech Connect

Line emission and broadband x-ray sources with x-ray energies above 10 keV have been investigated using a range of calibrated x-ray detectors for use as x-ray backlighters in high energy density (HED) experiments. The conversion efficiency of short- and long-pulse driven Mo and Ag line-emission backlighters at 17 and 22 keV was measured to investigate the crossover region between short- and long-pulse conversion efficiency. It was found that significant 17 and 22 keV line emissions were observed using a 3 {omega}, 1 ns long-pulse drive for Mo and Ag targets and a comparison between the measured Mo x-ray spectrum and calculations using an atomic physics code suggests that the line emission is due to thermal emission from N-like Mo atoms. Electron temperatures derived from fits to the continuum region of the x-ray spectra agree well with the T{sub hot} scaling as 100x(I{lambda}{sup 2}){sup 1/3}. The continuum emissions from empty and 1 atm Kr-filled imploded CH shell targets were also measured for the use as broadband backlighters.

Maddox, B. R.; Park, H. S.; Remington, B. A.; Chen, C.; Chen, S.; Prisbrey, S. T. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Comley, A. [Atomic Weapons Establishment, Aldermasten, Reading RG7 4PR (United Kingdom); Back, C. A. [General Atomics, San Diego, California 92121 (United States); Szabo, C.; Seely, J. F. [Naval Research Laboratory, Washington D.C. 20375 (United States); Feldman, U. [ARTEP Inc., Ellicott City, Maryland 21042 (United States); Hudson, L. T.; Seltzer, S. [National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); Haugh, M. J.; Ali, Z. [NSTEC, Livermore, California 94550 (United States)

2011-05-15

19

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

NASA Technical Reports Server (NTRS)

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

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

1973-01-01

20

Efficiency of Scintillator Materials in the Energy Range 8.0-32.0 keV  

SciTech Connect

X-ray microtomography requires the measurement of x-ray attenuation along ray paths through a specimen, and on the inversion of these data to obtain a spatially resolved mapping of the microstructure of the specimen. To do this efficiently, two-dimensional array detectors are often used to measure the transmitted x-rays by capturing and recording each x-ray incident on the detector. The highest resolution CT instruments perform this by converting the incident x-rays to visible light, and then focusing this light onto a charge-coupled-device (CCD) detector. The light output of the scintillator (photons per incident x-ray), the numerical aperture of the optical lens system, and the quantum efficiency of the CCD govern the efficiency of the detection process. Several years earlier, our group performed an investigation aimed at determining the best scintillator material for high-resolution synchrotron CT. The selection criteria included light output in the 8-32 keV energy range, the spatial resolution of the scintillator, the wavelength of the scintillation radiation, and the stability and ease of polishing of the scintillator. A list of the scintillators that we considered, with the exceptions of the more recently developed glass scintillators, is provided in Table 1. Among these scintillators, we concluded that single crystal cadmium tungstate was optimum; we have used this material in all subsequent synchrotron CT systems. Since this original study, several doped-glass scintillators have become available. The LSO (Lu orthosilicates) scintillators, developed for PET scanning, show considerable light output at high energy (energies above 500 keV). Theoretically, the light output of these scintillators should be twice that of the cadmium tungstate. The purpose of this study was to determine the efficiency of two such scintillators (LSO:Yt and IQI-401 high density terbium activated glass) in the energy range from 8-32 keV.

Kinney, J H; Haupt, D L

2002-07-01

21

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

PubMed Central

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

Vigne, Jean-Denis; Briois, Francois; Zazzo, Antoine; Willcox, George; Cucchi, Thomas; Thiebault, Stephanie; Carrere, Isabelle; Franel, Yodrik; Touquet, Regis; Martin, Chloe; Moreau, Christophe; Comby, Clothilde; Guilaine, Jean

2012-01-01

22

Precise energy of the 9.4 keV gamma transition observed in the 83Rb decay  

NASA Astrophysics Data System (ADS)

The energy of the 9.4 keV ?-transition observed in the 83Rb decay was established to be 9405.8(3) eV. This energy value was obtained from photon spectrometry measurements of the differences in the energies of closely spaced lines. The result allows one to determine more precisely the energy of conversion electrons of the 9.4 keV transition, which represent a unique tool for energy calibration of the tritium beta spectrum and systematic measurements in the KATRIN neutrino mass determination experiment.

Slezák, M.; Vénos, D.; Lebeda, O.; Trojek, T.

2012-02-01

23

NOTE: DNA strand breaks induced by low keV energy heavy ions  

NASA Astrophysics Data System (ADS)

We present some results on the interaction of low energy atomic ions with DNA. Experiments consist of irradiation of dried DNA in vacuum with Ar ions at low keV energies for different time intervals. The DNA is placed back in solution and analysed by agarose gel electrophoresis. These experiments demonstrated the production of single and double strand breaks. The induction of these lesions could be due to several processes: direct collisions with DNA constituent atoms resulting in displacements, cascade recoil collisions of the constituent atoms, electron transfer processes between the ion and the DNA as well as breaks induced by molecular excitation and secondary electron interactions. Here we briefly discuss some aspects of direct and recoil collision processes.

Lacombe, S.; LeSech, C.; Esaulov, V. A.

2004-03-01

24

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

SciTech Connect

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

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

1997-10-01

25

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

NASA Astrophysics Data System (ADS)

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

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

2006-03-01

26

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

SciTech Connect

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

Kim, G. N. [School of Physics and Energy Science, Kyungpook National University, 1370 Sankyok-dong, Buk-gu, Daegu 702-701 (Korea, Republic of); Chung, W. C.; Ro, T. I. [Department of Physics, Dong-A University, 840 Hadan 2-dong, Saha-gu, Busan 604-714 (Korea, Republic of); Ohsaki, T.; Igashira, M. [Research Laboratory for Nuclear Reactors, Tokyo Institute of Technology, 2-12-1-N1-26, O-okayama, Meguro-ku, Tokyo 152-8550 (Japan)

2006-03-13

27

The response of a thermoluminescent dosimeter to low energy protons in the range 30–100 keV  

Microsoft Academic Search

This study demonstrates the thermoluminescence (TL) response of CaF2:Tm (commercial name TLD-300) to 30–100keV protons which were generated by means of a Cockcroft–Walton accelerator. The phenomenon in which the total thermoluminescent output from CaF2:Tm (TLD-300) decreases with proton energy from 30 to 100keV (with increase of LET) can be interpreted by the track structure theory (TST). The analysis of the

Tieh-Chi Chu; Sung-Yen Lin; Chu-Chung Hsu; Jao-Perng Lin

2001-01-01

28

Warm trapped plasmaspheric plume at keV energy confined near the equator  

NASA Astrophysics Data System (ADS)

Cluster perigee observation (at about 4 Earth radius) revealed that the trapped plasmaspheric plasma in a very limited region near the magnetic equator, that was reported by Olsen et al.( 1987) at tens eV range, are sometimes heated to more than hundred eV and up to keV, a much higher energy than plasmaspheric ions. Yet, the composition data confirms the plasmaspheric origin, with domination by H+ and existence of some amount of He+ without He++ or O+. The pitch angle of this warm plasma plume is nearly 90° and is consistent with the confinement within a few degrees latitude of the equator. In the energy-time domain, this warm plasma plume is structureless although various forms of energy-time (or energy-latitude) dispersion, including signatures of energy-dependent magnetic drift, are sometimes recognized. Together with this equatorially trapped warm plasma plume, electrostatic wave above the upper hybrid frequency at (n + 1 2)fce (Jones et al., 1987) are observed, indicating that the wave is directly related to this plume. The time scales of the plume formation and its decay are both about 1-2 hours, and the wave activity follows the change in the warm trapped plasma. The local time dependence and non-correlation to the substorm activity indicate that this phenomenon is different from the plasmaspheric drain. This phenomenon indicates the specialty of the equator even for hundreds eV ions.

Yamauchi, M.; Dandouras, I.; Mazouz, F.; Reme, H.; Grimald, S.; Pickett, J.; Nilsson, H.

2012-04-01

29

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

PubMed

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

Tan, Zhenyu; Liu, Wei

2014-05-01

30

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

SciTech Connect

17-75 keV one- and two-dimensional high-resolution (<10 {mu}m) radiography has been developed 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}. 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 {mu}mx10 {mu}mx300 {mu}m on a 300 {mu}mx300 {mu}mx5 {mu}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{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 experiments at many new high-power laser facilities.

Park, H.-S.; Maddox, B. R.; Hatchett, S. P.; Izumi, N.; Key, M. H.; Le Pape, S.; MacKinnon, A. J.; MacPhee, A. G.; Patel, P. K.; Phillips, T. W.; Remington, B. A.; Tommasini, R.; Town, R. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Giraldez, E. [General Atomics, San Diego, California 92121 (United States); Hudson, L. T. [NIST, Gaithersburg, Maryland 20899 (United States); Seely, J. F. [Naval Research Laboratory, Washington, D.C., 20375 (United States); Workman, J. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Brambrink, E. [Laboratoire pour l'Utilisation des Lasers Intenses, Ecole Polytechnique, 91128 Palaiseau Cedex (France)

2008-07-15

31

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

NASA Astrophysics Data System (ADS)

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

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

1997-07-01

32

Multiple scattering of 5-30 keV electrons in evaporated metal films II: Range-energy relations  

Microsoft Academic Search

The ranges of electrons in evaporated films of aluminium, copper, silver and gold have been measured for incident energies E0 between 5 and 20 keV. From electron transmission measurements the maximum range and the extrapolated range were determined. Energy loss measurements gave the mean range and the Thomson-Whiddington range, corresponding to the mean energy Em and the most probable energy

V. E. Cosslett; R. N. Thomas

1964-01-01

33

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

34

Studies on the effective atomic numbers of some human tissues in the energy region 15-100 keV  

NASA Astrophysics Data System (ADS)

The effective atomic numbers for total photon interaction in muscle, bone, brain, heart, kidney, liver, lungs, ovaries, pancreas, spleen and tongue are evaluated using three different methods, for practical use in the energy region 15-100 keV. Muscle, brain, heart, kidney, lungs, ovaries, pancreas, spleen, tongue and water; bone and silicon; liver and oxygen are found to behave in an approximately similar manner in this energy region.

Özyol, H.

1994-12-01

35

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

SciTech Connect

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

Babenko, V. A., E-mail: vladimir@ukr.net; Petrov, N. M., E-mail: pet2@ukr.ne [National Academy of Sciences of Ukraine, Bogolyubov Institute for Theoretical Physics (Ukraine)

2009-04-15

36

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

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

37

High-accuracy determination of the relative full energy peak efficiency curve of a coaxial HPGe detector in the energy range 700–1300 keV  

Microsoft Academic Search

A method for the high-accuracy determination of the relative full energy peak efficiency is established. Radionuclides that emit at least two gamma-ray lines for which the relative intensity can be found (from the decay scheme) to much better than ±0.1% were used as calibration standards. Specifically, the 889 and 1120 keV lines of 46Sc, the 983 and 1312 keV lines

Ayman Ibrahim Hawari; Ronald F. Fleming; Martin A. Ludington

1997-01-01

38

High-accuracy determination of the relative full energy peak efficiency curve of a coaxial HPGe detector in the energy range 700-1300 keV  

Microsoft Academic Search

A method for the high-accuracy determination of the relative full energy peak efficiency is established. Radionuclides that emit at least two gamma-ray lines for which the relative intensity can be found (from the decay scheme) to much better than +\\/-0.1% were used as calibration standards. Specifically, the 889 and 1120 keV lines of 46Sc, the 983 and 1312 keV lines

Ayman Ibrahim Hawari; Ronald F. Fleming; Martin A. Ludington

1997-01-01

39

Thick target DT neutron yield measurements using metal occluders of scandium, titanium, yttrium, zirconium, gadolinium, erbium, hafnium, and tantalum at energies from 25 to 200 keV  

Microsoft Academic Search

Deuterium-Tritium (D-T) neutron yields from thick films of scandium, titanium, yttrium, zirconium, gadolinium, erbium, hafnium, and tantalum were measured by the associated particle technique using the 200-keV accelerator at the Pinellas Plant. The neutron yields were measured for all targets at energies from 25 to 200 keV in 5-keV steps with an average uncertainty of ±6.8%. Tabulated results are presented

D. J. Malbrough; J. T. Jr. Molloy; R. H. Becker

1990-01-01

40

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

41

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

NASA Astrophysics Data System (ADS)

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

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

2006-11-01

42

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

NASA Astrophysics Data System (ADS)

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

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

2004-02-01

43

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

44

Charge transfer between alkali cluster ions and atoms in the 1 to 10 keV collisional energy range  

Microsoft Academic Search

:   The cross-sections for collisional charge transfer between singly charged free clusters M\\u000a n\\u000a \\u000a + (M = Li, Na; n=1...50) and atomic targets A (cesium, potassium) have been measured as a function of collisional relative velocity in laboratory\\u000a energy range 1–10 keV. For each cluster size, the experimental values of the charge transfer cross-section are fitted with an universal parametric

C. Bréchignac; Ph. Cahuzac; B. Concina; J. Leygnier; I. Tignères

2000-01-01

45

Mixing of binary metal systems by noble-gas ions of energies between 30 and 400 keV  

Microsoft Academic Search

Multilayered samples of the binary systems Au-Rh and Ni-Pt were bombarded at 77 K with He-, Ne-, Ar- and Kr-ions at energies between 30 and 400 keV. The maximum irradiation dose was 2 × 1017 ions\\/cm2. All samples were analysed by X-ray diffraction using a Seemann-Bohlin arrangement. In thermal equilibrium the system Au-Rh has vanishingly small mutual solid solubility whereas

W. Hiller; M. Buchgeister; P. Eitner; K. Kopitzki; V. Lilienthal; G. Mertler

1990-01-01

46

Novel Method to Study Neutron Capture of ^{235}U and ^{238}U 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

47

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

48

Synthesis of gold and silver nanoparticles by electron irradiation at 5-15 keV energy.  

PubMed

Thin coatings (?10 µm) made from a mixture of polyvinyl alcohol (PVA) and HAuCl(4) or PVA and AgNO(3) on quartz plates were irradiated with 5-15 keV electrons, at room temperature. The electron energy was varied from coating to coating in the range of 5-15 keV, but electron fluence was kept constant at ?10(15) e cm(-2). Samples were characterized by the UV-vis, XRD, SEM and TEM techniques. The plasmon absorption peaks at ?511 and ?442 nm confirmed the formation of gold and silver nanoparticles in the respective electron-irradiated coatings. The XRD, SEM and TEM measurements reveal that the average size of the particles could be tailored in the range of 130-50 nm for gold and from 150-40 nm for silver by varying the electron energy in the range of 5-15 keV. These particles of gold and silver embedded in the polymer could also be separated by dissolving the coatings in distilled water. PMID:21730380

Mahapatra, S K; Bogle, K A; Dhole, S D; Bhoraskar, V N

2007-04-01

49

X-ray attenuation coefficients and photoelectric cross sections of Cu, Fe and Sn for the energy range 3-29 KeV.  

National Technical Information Service (NTIS)

The document contains the following two papers: X-ray attenuation coefficient and photoelectric cross sections of Sn for the Energy Range 3.3 KeV to 29.1 KeV - by Wang Dachun, Yang Hua and Luo Pingan. X-ray attenuation coefficients and photoelectric cross...

Wang Dachun Yang Hua Luo Pingan Ding Xunliang Wang Xinfu

1991-01-01

50

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

51

Performance of a medical imaging system for photons in the 60-140 keV energy range  

NASA Astrophysics Data System (ADS)

We report the status of the art of a prototype based on a GaAs pixel detector bump-bonded to a dedicated VLSI chip to be possibly used for imaging in the nuclear medicine field. This device, with a 200 ?m thick pixel matrix (64×64 square pixels, 170 ?m side), has already been tested with very good results for digital mammography applications (mean energy 20 keV). For more energetic photons, as in nuclear medicine, a 600 ?m thick detector has been chosen. Using radioactive sources ( 241Am, 60 keV and 99 mTc, 140 keV photons) we have measured the performance of our prototype in terms of charge collection and detection efficiency of the detector, discrimination capability of the electronics and imaging properties of the whole system. In particular, we have evaluated the spatial resolution properties measuring the Point Spread Function and the imaging capabilities using a home made thyroid phantom. We present also the comparison between these results and those obtained with a traditional gamma camera and the evaluation, made by both experimental measurements and software simulations, of the geometry related to the use of a collimator.

Amendolia, S. R.; Bisogni, M. G.; Bottigli, U.; Ceccopieri, A.; Delogu, P.; Dipasquale, G.; Fantacci, M. E.; Maestro, P.; Marchi, A.; Marzulli, V. M.; Oliva, P.; Palmiero, R.; Pernigotti, E.; Rosso, V.; Stefanini, A.; Stumbo, S.

2001-04-01

52

Mixing of binary metal systems by noble-gas ions of energies between 30 and 400 keV  

NASA Astrophysics Data System (ADS)

Multilayered samples of the binary systems Au-Rh and Ni-Pt were bombarded at 77 K with He-, Ne-, Ar- and Kr-ions at energies between 30 and 400 keV. The maximum irradiation dose was 2 × 10 17 ions/cm 2. All samples were analysed by X-ray diffraction using a Seemann-Bohlin arrangement. In thermal equilibrium the system Au-Rh has vanishingly small mutual solid solubility whereas the phase diagram of the system Ni-Pt shows that the two metals form a continuous series of solid solutions. By irradiation of Au-Rh samples with Kr-ions a single-phase metastable solid solution was produced. Irradiation with Ar- and Ne-ions results in extension of the terminal solid solubilities. Irradiation with 400 keV He-ions did not cause any mixing. This is in contrast to the experiments with 30 keV He-ions for which we could observe partial mixing. By ion irradiation of Ni-Pt samples solid solutions were produced in all cases. The results are discussed in the frame of the thermal spike model of ion beam mixing.

Hiller, W.; Buchgeister, M.; Eitner, P.; Kopitzki, K.; Lilienthal, V.; Mertler, G.

1990-03-01

53

High-resolution 15-100 keV K-alpha radiography for high-energy density experiments  

NASA Astrophysics Data System (ADS)

We are developing 15-100 keV high-energy x-ray sources for diagnostic radiography for high energy density experiments on new facilities such as Omega-EP, Z-R and NIF. High-energy x-ray sources can be created from hot electron interactions with target materials when illuminated by high intensity lasers. We have performed experiments to characterize and optimize these sources. Our measurements show that the total K-? yield is independent of the target thickness, verifying that refluxing plays a major role in x-ray generation^1. We demonstrated that high energy (17 to 40 keV) 1-D radiography with the required brightness and spatial resolution for materials experiments on NIF is possible using small-thin foils viewed edge-on. Extending the 1-D concept, we created small point sources for 2-D radiography consisting of micro-wire targets attached to low-Z substrates. We will present absolute K-? yields from small wire targets and the resulting measured spatial resolution of radiographs. We will compare our measurements with hybrid-PIC LSP simulations. 1. H. S. Park et al., PoP, 13, 056309 (2006)

Park, Hye-Sook; Tommasini, R.; Key, M.; MacKinnon, A.; Patel, P.; Remington, B.; Tabak, M.; Towm, R.; Back, C. A.; Giraldez, E.; Stoeckl, C.; Theobald, W.

2006-10-01

54

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

55

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

56

Results of total cross section measurements for 197Au in the neutron energy region from 4 to 108 keV at GELINA  

NASA Astrophysics Data System (ADS)

Transmission measurements have been performed to determine the total cross section for neutron-induced reactions with 197Au in the energy region from 4keV to 108keV. The experiments were carried out at a 50m measurement station of the time-of-flight facility GELINA using a 6Li glass scintillator. The average total cross section as a function of neutron energy was derived after correcting the observed average transmission for cross section fluctuations due to resonance structures. The results have been compared with literature data and with the total cross section resulting from a dispersive coupled-channel optical model potential. The neutron strength function for s -wave neutrons and an orbital-independent scattering radius, together with their covariance matrix, have been derived in the neutron energy region between 4keV and 108keV through a parameterization of the total cross section based on a nuclear reaction theory.

Sirakov, I.; Becker, B.; Capote, R.; Dupont, E.; Kopecky, S.; Massimi, C.; Schillebeeckx, P.

2013-11-01

57

Amorphization of Si(0 0 1) by ultra low energy (0.5-5 keV) ion implantation observed with high-resolution RBS  

NASA Astrophysics Data System (ADS)

The process of amorphization of Si(0 0 1) by ultra low energy (0.5 keV B + and 5 keV Si +) ion implantation is investigated using high-resolution RBS/channeling with a depth resolution better than 1 nm. In contrast to observations at higher implantation energies, amorphization by the ultra low energy ion implantation appears to proceed from the SiO 2/c-Si interface. The threshold dose for amorphization is determined to be ˜1 × 10 15 cm -2 for 0.5 keV B + and ˜1.5 × 10 14 cm -2 for 5 keV Si +. Comparison of the experimental results with TRIM simulations suggests that the SiO 2/c-Si interface behaves as a nucleation site for amorphization.

Kimura, K.; Agarwal, A.; Toyofuku, H.; Nakajima, K.; Gossmann, H.-J.

1999-01-01

58

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

NASA Astrophysics Data System (ADS)

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

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

59

The characterization of X-ray photocathodes in the 0.1-10-keV photon energy region  

NASA Astrophysics Data System (ADS)

A method and an instrument are described for the measurement of the absolute quantum yield for front-surface and transmission photocathodes in the 0.1-10-keV photon energy region. Total and secondary electron photoemission yields have been measured for Al, Au, CuI, and CsI photocathodes for the absolute calibration of the X-ray diode detectors and for the X-ray streak cameras. The relative secondary electron yields have also been measured for the same photocathodes by high resolution electron spectroscopy of the secondary electron energy distributions. Cs I is shown to be an effective photocathode for sensitive, time-resolved spectroscopy into the picosecond region. A simple model for X-ray photoemission is described which leads to semiempirical equations for front and back surface secondary electron photoemission; model predictions are consistent with the experiment.

Henke, B. L.; Knauer, J. P.; Premaratne, K.

1981-03-01

60

Efficacy and Safety of 10,600-nm Carbon Dioxide Fractional Laser on Facial Skin with Previous Volume Injections  

PubMed Central

Background: Fractionated carbon dioxide (CO2) lasers are a new treatment modality for skin resurfacing. The cosmetic rejuvenation market abounds with various injectable devices (poly-L-lactic acid, polymethyl-methacrylate, collagens, hyaluronic acids, silicone). The objective of this study is to examine the efficacy and safety of 10,600-nm CO2 fractional laser on facial skin with previous volume injections. Materials and Methods: This is a retrospective study including 14 patients treated with fractional CO2 laser and who have had previous facial volume restoration. The indication for the laser therapy, the age of the patients, previous facial volume restoration, and side effects were all recorded from their medical files. Objective assessments were made through clinical physician global assessment records and improvement scores records. Patients’ satisfaction rates were also recorded. Results: Review of medical records of the 14 patients show that five patients had polylactic acid injection prior to the laser session. Eight patients had hyaluronic acid injection prior to the laser session. Two patients had fat injection, two had silicone injection and one patient had facial thread lift. Side effects included pain during the laser treatment, post-treatment scaling, post-treatment erythema, hyperpigmentation which spontaneously resolved within a month. Concerning the previous facial volume restoration, no granulomatous reactions were noted, no facial shape deformation and no asymmetry were encountered whatever the facial volume product was. Conclusion: CO2 fractional laser treatments do not seem to affect facial skin which had previous facial volume restoration with polylactic acid for more than 6 years, hyaluronic acid for more than 0.5 year, silicone for more than 6 years, or fat for more than 1.4 year. Prospective larger studies focusing on many other variables (skin phototype, injected device type) are required to achieve better conclusions.

Helou, Josiane; Maatouk, Ismael; Moutran, Roy; Obeid, Grace; Stephan, Farid

2013-01-01

61

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

SciTech Connect

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

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

2013-06-13

62

High energy resolution measurement of the ²³⁸U neutron capture yield from 1 keV to 100 keV  

Microsoft Academic Search

The purpose of this work is the precise determination of the ²³⁸U neutron capture yield (i.e., the probability of neutron absorption) as a function of neutron energy with the highest available neutron energy resolution. The motivation for this undertaking arises from the central role played by the ²³⁸U neutron capture process in the calculation of the neutron balance of both

R. L. Macklin; R. B. Perez; G. de Saussure; R. W. Ingle

1988-01-01

63

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

64

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

65

Range and Stopping Power Energy Relationships for 0.5-30 keV Electron Beams Slowing Down in Solids: Analytical Model  

NASA Astrophysics Data System (ADS)

The development of an analytical model for calculating the electron stopping power (SP) converging with the experimental data at lower energies is still not completed. The purpose of this work is to suggest a mathematical expression of the range and the stopping power of electrons impinging in solid targets in the energy range up to 30 keV based on the spherical geometric model [A. Bentabet, Vacuum86 (2012) 1855]. The results are in good agreement with those of the literature. The slight discrepancy between the obtained and both the theoretical and experimental results regarding the stopping power at very low energy (E<0.5 keV) is discussed.

Bentabet, A.

2014-01-01

66

Experimental study of interactions of highly charged ions with atoms at keV energies  

SciTech Connect

This Progress Report describes the experimental work carried out, and the work in progress, at the Cornell EBIS Laboratory during the period 7/1/1991 to 6/30/1992. During this period, a number of experiments were carried out. The absolute values of the total, one, two and three electron transfer cross sections for highly charged argon ions (8{le}q{le}16) colliding with argon at 2.3 qkev laboratory energy were measured. The distribution of recoil ions and molecular fragments formed in highly charged ion atom and molecule collisions was measured in order to help the interpretation of electron spectra in the 40--320 eV energy range emitted in Ar{sup q+}+Ar(8{le}q{le}16) collisions at 2.3 qkeV that were measured in our laboratory. The interpretation of the electron spectra is still under way. A new collision chamber was built which contains an ion decelerating lens system and a high resolution monochromator-analyzer combination. Ions extracted from the Cornell Electron Beam Ion Source were successfully decelerated from 2.3 qkeV down to 30 qeV Preliminary 0{degree} translational energy spectra for Ar{sup l2+} on Ar at a collision energy of 38.6 qeV show a 0.56 qeV resolution. Work is in progress to extend measurements of cross sections and recoil ion charge state distributions down to collision energies in the 10 eV/amu range.

Kostroun, V.O.

1992-07-05

67

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

68

Characteristic energy losses of 30 keV - electrons in vapours of aromatic hydrocarbons  

Microsoft Academic Search

Measurements are reported of 30 keV-electrons scattered at zero angle in vapours of benzene, naphthalene, anthracene, tetracene, phenanthrene, chrysene, pyrene and coronene. Comparison with optical absorption measurements and MO-calculations leads to the assignment of several losses due to pi-pi* single-electron transitions. The interpretation of some losses in the VUV region and at higher energies is still tentative. On leave from

E. E. Koch; A. Otto

1969-01-01

69

Measurement of the Scintillation Efficiency of Na Recoils in NaI(Tl) Down to 10 keV Nuclear Recoil Energy Relevant to Dark Matter Searches  

NASA Astrophysics Data System (ADS)

We present preliminary results of measurements of the quenching factor for Na recoils in NaI(Tl) at room temperature, made at a dedicated neutron facility at the University of Sheffield. Measurements have been performed with a 2.45 MeV mono-energetic neutron generator in the energy range from 10 keV to 100 keV nuclear recoil energy. A BC501A liquid scintillator detector was used to tag neutrons. Cuts on pulse-shape discrimination from the BC501A liquid scintillator detector and neutron time-of-flight were performed on pulses recorded by a digitizer with a 2 ns sampling time. Measured quenching factors range from 19% to 26%, in agreement with other experiments. From pulse-shape analysis, a mean time of pulses from electron and nuclear recoils are compared down to 2 keV electron equivalent energy.

Chagani, H.; Majewski, P.; Daw, E. J.; Kudryavtsev, V. A.; Spooner, N. J. C.

2007-08-01

70

Observations of solar X-ray bursts in the energy range 5-15 keV  

NASA Technical Reports Server (NTRS)

Bursts of solar X-rays in the energy range 5-15 keV are associated with flares and are due to thermal emission from a hot coronal plasma. The results of the first study of a large sample of separate bursts, 197 events associated with subflares, and of a few events of importance 1 are presented. The observations were made by a proportional counter on the satellite OSO-7 from October, 1971 to June, 1972. In most cases, the temperature characterizing the X-ray spectrum rises impulsively at the onset of the burst and then declines slowly throughout the remainder of the burst. The emission measure rises exponentially with a time scale of 30-100 sec and then declines slowly on a time scale of the order of 1,000 sec. It is shown that the growth of the thermal energy in the flare plasma throughout the burst can be due to the heating of new cool material.

Datlowe, D. W.; Hudson, H. S.; Peterson, L. E.

1974-01-01

71

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

72

Averaged Cross Section of the exp 95 Mo(n, alpha ) exp 92 Zr Reaction in the 30 KeV Neutron Energy.  

National Technical Information Service (NTIS)

The averaged cross section of the exp 95 Mo(n, a) exp 92 Zr reaction in the 30 keV neutron energy region is measured. The exp 7 Li(p, n) reaction served as neutron source. The measured cross section is in agreeemnt within errors with the averaged cross se...

Y. P. Popov V. I. Salatskij G. Khuukhehnkhuu I. Chadraabal

1982-01-01

73

Design and experiment of dual-energy X-ray material recognition using a 950 keV X-band Linac  

NASA Astrophysics Data System (ADS)

The 950 keV portable X-band (9.4 GHz) linear accelerator (Linac) provides on-site high-energy X-ray inspection, including material recognition up to a certain precision. We have developed an X-band Linac system and have achieved the maximum 950 keV X-ray by using the low-power magnetron (250 kW) in a 2-?s pulse length. We have already experimentally verified the dual-energy X-ray material recognition with and without an energy filter. Further, the array of the scintillator detector for dual-energy X-ray measurement without the energy filter is numerically analyzed and designed for much quicker measurements. Updated results will be presented.

Lee, Kiwoo; Hashimoto, Eiko; Yamamoto, Tomohiko; Natsui, Takuya; Mori, Azusa; Hirai, Shunsuke; Uesaka, Mitsuru

2011-05-01

74

Measurement of the optical constants of crystal quartz at 10 K and 300 K in the far infrared spectral range: 10–600 cm ?1  

Microsoft Academic Search

The optical constants of crystal quartz in the far infrared (10 – 600 cm?1) are reported at room temperature and at 10 K, for both polarizations parallel and perpendicular to the c-axis, respectively\\u000a extraordinary and ordinary ray. These constants are obtained from the analysis of the transmissivity channeled spectra below\\u000a 300 cm?1, and from the analysis of the reflectivity spectra

F. Bréhat; B. Wyncke

1997-01-01

75

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

NASA Astrophysics Data System (ADS)

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

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

2010-04-01

76

Strongly Enhanced Li + D Reaction in Pd Observed in Deuteron Bombardment on PdLix with Energies between 30 and 75 keV  

Microsoft Academic Search

Thick target yields of alpha particles emitted in the 6,7Li(d,alpha)4,5He reactions in PdLix and AuLix were measured as a function of the bombarding energy between 30 and 75 keV. It was found that the reaction rate in Pd at lower energies is enhanced strongly over the one predicted by the cross section for the reaction with bare nuclei, but no

Jirohta Kasagi; Hideyuki Yuki; Taiji Baba; Takashi Noda; Junji Taguchi; Masayoshi Shimokawa; Wilfried Galster

2004-01-01

77

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

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

78

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

79

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

80

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

NASA Technical Reports Server (NTRS)

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

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

1983-01-01

81

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

NASA Technical Reports Server (NTRS)

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

Kahler, S. W.

1973-01-01

82

Measurement of the ^17O(p,?)^18F nuclear reaction cross section in the energy range Elab=360 - 1625 keV  

NASA Astrophysics Data System (ADS)

The ^17O(p,?)^18F reaction influences hydrogen-burning nucleosynthesis in several stellar sites, such as red giants, asymptotic giant branch (AGB) stars, massive stars and classical novae. In the relevant temperature range for these environments (T9=0.01-0.4), the main contributions to the rate of this reaction are the direct capture process, two low lying narrow resonances (ER^lab=70 and 193 keV) and the low energy tails of two broad resonances (ER^lab=587 and 714 keV). Previous measurements and calculations give contradictory results for the direct capture contribution which in turn increases the uncertainty of the reaction rate. In addition, very few published cross section data exist for the high energy region that might affect the interpretation of the direct capture and the broad resonances contributions in the lower energy range. In this work we present a measurement of the reaction at a wide proton energy range (Elab=360 - 1625 keV) and at several angles (?lab=0^o,45^o,90^o,135^o). All detected primary transitions and all angles were fitted simultaneously and extrapolated to lower energies using the multi-level, multi-channel R-matrix code, AZURE.

Kontos, Antonios; Görres, Joachim; Best, Andreas; Li, Qian; Schürmann, Daniel; Stech, Ed; Uberseder, Ethan; Wiescher, Michael; Imbriani, Gianluca; Azuma, Richard

2011-10-01

83

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

84

GRB 980923, a burst with a hard spectrum in energies from KeV to MeV  

NASA Astrophysics Data System (ADS)

A detailed joint analysis of BATSE-LAD, BATSE-SD and EGRET-TASC of GRB 980923 was performed. The analysis yielded to the discovery of an anomalous short keV to MeV component in the spectra of the burst.

Sacahui, J. R.; Ramirez, J. L.; Kaneko, Y.; González, M. M.

2011-10-01

85

Investigating the Unknown Nuclear Reaction in a Low-Energy (E < 330 keV) p + Ti{sup 2}H{sub x} Experiment  

SciTech Connect

Charged-particle products with {approx}3.9-MeV energy were observed in a low-energy experiment (E{sub p} {<=} 330 keV) with a proton bombarding a Ti{sup 2}H{sub x} target. The features of the charged-particle products were the same as those of an alpha particle. The threshold of the reaction was {approx}150 keV. The maximum reaction rate reached more than 10{sup 5} r/s, while the proton energy and current were 324 keV and 1.2 mA, respectively. The excitation curve of this unknown reaction increased exponentially with the growth of proton energy. There is no known nuclear reaction induced by a proton that can be applied to interpret this experimental phenomenon. Some interpretations, e.g., an indirect secondary reaction and a multibody reaction model, are discussed, but the origin of this unknown nuclear reaction is still a mystery and under study.

Wang Tieshan [Chinese Academy of Sciences (China); Wang Zhiguo [Chinese Academy of Sciences (China); Chen Jingen [Lanzhou University (China); Jin Genming [Chinese Academy of Sciences (China); Piao Yubo [Lanzhou University (China)

2000-03-15

86

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

SciTech Connect

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

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

2008-07-15

87

Absolute detection efficiency of a micro-channel plate detector to x-rays in the 1--100 KeV energy range  

Microsoft Academic Search

There is little information in the literature on the performance of working micro-channel plate (MCP) detectors at high x-ray energies. We have measured the absolute efficiency of a microchannel-plate-intensified, subnanosecond, one dimensional unaging x-ray detector developed at LLNL in the 1 to 100 keV range and at 1.25 MeV. The detector consists of a gold photocathode deposited on the front

G. A. Burginyon; B. A. Jacoby; J. K. Wobser; R. D. Ernst; D. S. Ancheta; K. G. Tirsell

1992-01-01

88

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

Microsoft Academic Search

There is little information in the literature on the performance of working micro-channel plate (MCP) detectors at high x-ray energies. We have measured the absolute efficiency of a microchannel-plate-intensified, subnanosecond, one dimensional imaging x-ray detector developed at LLNL in the 1 to 100 keV range and at 1.25 MeV. The detector consists of a gold photocathode deposited on the front

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

1993-01-01

89

Absolute detection efficiency of a micro-channel plate detector to X-rays in the 1 - 100 keV energy range  

Microsoft Academic Search

There is little information in the literature on the performance of working micro-channel plate (MCP) detectors at high X-ray energies. The authors have measured the absolute efficiency of a microchannel-plate-intensified, subnanosecond, one dimensional imaging X-ray detector in the 1 to 100 keV range and at 1.25 MeV. The detector consists of a gold photocathode deposited on the front surface of

G. A. Burginyon; B. A. Jacoby; J. K. Wobser; R. D. Ernst; D. S. Ancheta; K. G. Tirsell

1993-01-01

90

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

Microsoft Academic Search

One of the advantages of applying X-band linear accelerator (Linac) is the compact size of the whole system. That shows us the possibility of on-site system such as the custom inspection system in an airport. As X-ray source, we have developed X-band Linac and achieved maximum X-ray energy 950 keV using the low power magnetron (250 kW) in 2 mus

Kiwoo Lee; Takuya Natsui; Shunsuke Hirai; Mitsuru Uesaka; Eiko Hashimoto

2011-01-01

91

Measurement of neutron capture cross-section of indium in the energy region from 0.003 eV to 30 keV  

Microsoft Academic Search

The neutron capture cross-section of indium (In) has been measured in the energy region from 0.003 eV to 30 keV by the neutron time-of-flight (TOF) method with a 46-MeV electron linear accelerator (linac) of the Research Reactor Institute, Kyoto University. An assembly of Bi4Ge3O12 (BGO) scintillators, which was composed of 12 pieces of BGO and placed at a distance of

Jungran Yoon; Taeik Ro; Samyol Lee; Shuji Yamamoto; Katsuhei Kobayashi

2002-01-01

92

Low-energy (30 keV) carbon ion induced mutation spectrum in the LacZ? gene of M13mp18 double-stranded DNA  

Microsoft Academic Search

Double-stranded M13mp18 DNA was irradiated with 30keV carbon ions in dry state under vacuum to investigate the low-energy heavy ion induced mutation spectra. When the irradiated DNA was used to transfect Escherichia coli JM105, 3.6–5.7-fold increases in mutation frequency were observed, in contrast to the spontaneous group. Sequences of the 92 induced mutants showed that the carbon ions in this

Quan Wang; Gang Zhang; Yan-hua Du; Yong Zhao; Guan-ying Qiu

2003-01-01

93

Studies on effective atomic numbers and electron densities in amino acids and sugars in the energy range 30–1333 keV  

Microsoft Academic Search

The effective atomic numbers and electron densities of the amino acids glycine, alanine, serine, valine, threonine, leucine, isoleucine, aspartic acid, lysine, glutamic acid, histidine, phenylalanine, arginine, tyrosine, tryptophane and the sugars arabinose, ribose, glucose, galactose, mannose, fructose, rhamnose, maltose, melibiose, melezitose and raffinose at the energies 30.8, 35.0, 81.0, 145, 276.4, 302.9, 356, 383.9, 661.6, 1173 and 1332.5keV were calculated

Shivalinge Gowda; S. Krishnaveni; Ramakrishna Gowda

2005-01-01

94

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

SciTech Connect

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

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

2013-09-15

95

Interferometric X-Ray Imaging of Breast Cancer Specimens at 51 keV X-Ray Energy  

Microsoft Academic Search

The feasibility of the interferometric X-ray imaging technique is examined for revealing the features of breast cancer specimens. The interferometric X-ray imaging system consisted of an asymmetrically cut silicon crystal, a monolithic X-ray interferometer, a phase-shifter, an object cell, and an X-ray CCD camera. Ten 10-mm-thick formalin-fixed breast cancer specimens were imaged at 51 keV, and these images were compared

Tohoru Takeda; Jin Wu; Yoshinori Tsuchiya; Akio Yoneyama; Thet Thet Lwin; Yuji Aiyoshi; Tsutomu Zeniya; Kazuyuki Hyodo; Ei Ueno

2004-01-01

96

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

SciTech Connect

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

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

2007-01-01

97

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

NASA Astrophysics Data System (ADS)

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

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

2006-10-01

98

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

99

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

100

Recent photoabsorption measurements in the rare gases and alkalis in the 3 to 15 keV photon energy region  

SciTech Connect

The attenuation cross-section of photons in helium in the range 3 to 14 keV has been measured. The results indicate the importance of Compton scattering in this range and show reasonable agreement with theory. The authors have also used a heat-pipe to measure absorption spectra in argon, potassium and rubidium near their respective K-edges and have made identifications using relativistic Hartree-Fock calculations. Some ion spectra near and below the K-edges of argon and potassium are also presented.

Berry, H.G. [Argonne National Lab., IL (United States). Physics Div.

1994-09-01

101

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

102

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

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

103

The response of a radiation resistant ceramic scintillator (Al{sub 2}O{sub 3}:Cr) to low energy ions (0-60 keV)  

SciTech Connect

This work extends a previous study on ionoluminescence of a radiation-hard ceramic scintillator, Al{sub 2}O{sub 3}:Cr, to ions accelerated to keV energies [K. J. McCarthy et al., J. Nucl. Mater. 321, 78 (2003)]. It is motivated by the identification of this material as a promising candidate for use in the fast-ion-loss detector for ITER [for the range of thermal (low energy) and suprathermal ions]. In the paper we quantify and compare its ionoluminescence with that of some common luminescent materials (YAG:Ce and ruby) when irradiated by H{sup +} ions accelerated to {<=}60 keV using a purpose built laboratory setup. Next, studies are made on the ceramic to quantify its response as a function of incident ion mass, i.e., to He{sup +}. For this, the absolute luminosities of the material are estimated in terms of the number of photons emitted per incident ion as a function of energy. Moreover, the radiation hardness and postirradiation recovery of the ceramic are investigated. Finally, from the studies it can be concluded that the ceramic ruby is a good candidate for detecting low energy ions as long as its temporal response (approximately several milliseconds) is not a constraint for specific ion measurements.

Jimenez-Rey, D.; Zurro, B.; McCarthy, K. J.; Baciero, A. [Laboratorio Nacional de Fusion por Confinamiento Magnetico, Asociacion Euratom-CIEMAT, Av. Complutense 22, E-28040, Madrid (Spain); Garcia, G. [Instituto de Matematicas y Fisica Fundamental, Consejo Superior de Investigaciones Cientificas, Serrano 113-bis, 20806, Madrid (Spain)

2008-10-15

104

The response of a radiation resistant ceramic scintillator (Al2O3:Cr) to low energy ions (0-60 keV).  

PubMed

This work extends a previous study on ionoluminescence of a radiation-hard ceramic scintillator, Al(2)O(3):Cr, to ions accelerated to keV energies [K. J. McCarthy et al., J. Nucl. Mater. 321, 78 (2003)]. It is motivated by the identification of this material as a promising candidate for use in the fast-ion-loss detector for ITER [for the range of thermal (low energy) and suprathermal ions]. In the paper we quantify and compare its ionoluminescence with that of some common luminescent materials (YAG:Ce and ruby) when irradiated by H(+) ions accelerated to < or = 60 keV using a purpose built laboratory setup. Next, studies are made on the ceramic to quantify its response as a function of incident ion mass, i.e., to He(+). For this, the absolute luminosities of the material are estimated in terms of the number of photons emitted per incident ion as a function of energy. Moreover, the radiation hardness and postirradiation recovery of the ceramic are investigated. Finally, from the studies it can be concluded that the ceramic ruby is a good candidate for detecting low energy ions as long as its temporal response (approximately several milliseconds) is not a constraint for specific ion measurements. PMID:19044498

Jimenez-Rey, D; Zurro, B; McCarthy, K J; Garcia, G; Baciero, A

2008-10-01

105

The Measurements of the Differential Elastic Neutron Cross-Sections of Carbon for Energies from 2 TO 133 keV  

NASA Astrophysics Data System (ADS)

The measurements of the differential elastic neutron cross-sections of carbon have been carried out at the Kyiv Research Reactor (KRR) using the neutron filter beam technique. Experimental set-up for detection of scattered neutrons has been installed at the eighth horizontal channel of the KRR. The quasi-mono-energetic neutron lines with mean energies 2, 59 and 133 keV were formed by composite filters. The measurements of the angle distribution of scattering neutrons on carbon samples were executed at angles 30°, 55°, 90°, 125° and 150° for three neutron energies. To determine the differential elastic neutron cross-section on carbon d?/d?, the relative method of measurement was used. The isotope 208Pb was used as a standard. The normalization factor, which is a function of detector efficiency, thickness of the carbon samples, thickness of the Pb-208 sample, geometry, etc., for each sample and for each filter energy has been obtained through Monte Carlo calculations by means of own codes. The results of measurements of the differential elastic neutron cross sections on carbon samples at reactor neutron filtered beams with energies 2, 59, and 133 keV have been compared with the known experimental data from database EXFOR/CSISRS.

Gritzay, Olena; Kolotyi, Volodymyr; Pshenychnyi, Volodymyr; Klimova, Nataliia; Libman, Volodymyr; Venedyktov, Vitalii; Richardson, Jeffery; Sale, Kenneth

2009-08-01

106

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

NASA Astrophysics Data System (ADS)

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

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

2005-10-01

107

Absolute detection efficiency of a micro-channel plate detector to x-rays in the 1--100 KeV energy range  

SciTech Connect

There is little information in the literature on the performance of working micro-channel plate (MCP) detectors at high x-ray energies. We have measured the absolute efficiency of a microchannel-plate-intensified, subnanosecond, one dimensional unaging x-ray detector developed at LLNL in the 1 to 100 keV range and at 1.25 MeV. The detector consists of a gold photocathode deposited on the front surface of the MCP (optimized for Ni K[sub [alpha

Burginyon, G.A.; Jacoby, B.A.; Wobser, J.K.; Ernst, R.D.; Ancheta, D.S.; Tirsell, K.G.

1992-09-03

108

Facilities and techniques for x-ray diagnostic calibration in the 100-eV to 100-keV energy range  

SciTech Connect

The Lawrence Livermore National Laboratory (LLNL) has been a pioneer in the field of x-ray diagnostic calibration for more than 20 years. We have built steady state x-ray sources capable of supplying fluorescent lines of high spectral purity in the 100-eV to 100-keV energy range, and these sources have been used in the calibration of x-ray detectors, mirrors, crystals, filters, and film. This paper discusses our calibration philosophy and techniques, and describes some of our x-ray sources. Examples of actual calibration data are presented as well.

Gaines, J.L.; Wittmayer, F.J.

1986-06-01

109

W values of protons in alkane-based TE gases and dimethylether in the energy range 1-100 keV: measurements and additivity models.  

PubMed

W values of tissue-equivalent gases based on propane and butane were measured for protons in the energy range 1-100 keV and compared with those of dimethylether and water vapour. The experimental values of the tissue-equivalent gas mixtures were compared with data calculated from the W values of the mixture components using five existing additivity models and two new models derived within the scope of the present work. Apart from one model--the simplest one--all models show a good agreement with the experimental data. PMID:15353623

Baek, W Y; Grosswendt, B; Willems, G

2004-01-01

110

Energy loss and straggling for 50- and 100-keV H{sup +} ions passing through the Si(001)2{times}1-Sb surface  

SciTech Connect

Surface stopping powers were measured for 50- and 100-keV H{sup +} ions passing through the Si(001)2{times}1-Sb surface. The energy losses as a function of the exit angle are fit successfully by a simple relationship involving the time spent near the surface. The fitting parameter is in agreement with the value expected from the bulk Sb stopping cross section and the areal Sb density. This result suggests continuity of the stopping power from the bulk to the surface. It provides a useful method for determining the distance between the plane of deposited atoms and of a substrate surface and for measuring the composition of the topmost atomic layer. The estimated energy loss by surface-plasmon excitation is negligibly small in the present system. The energy straggling as a function of exit angle was also measured for 50- and 100-keV H{sup +} incidence and the results are compared here with the bulk straggling values. {copyright} {ital 1997} {ital The American Physical Society}

Sumitomo, K.; Nishioka, T. [NTT Basic Research Laboratories, Atsugi, Kanagawa 243-01 (Japan)] [NTT Basic Research Laboratories, Atsugi, Kanagawa 243-01 (Japan); Ikeda, A.; Kido, Y. [Department of Physics, Ritsumeikan University, Kusatsu, Shiga 525-77 (Japan)] [Department of Physics, Ritsumeikan University, Kusatsu, Shiga 525-77 (Japan)

1997-09-01

111

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

112

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

NASA Astrophysics Data System (ADS)

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

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

2010-07-01

113

Ionization and fragmentation of RNA base molecule uracil in collisions with carbon ions of energies between 100 keV and 60 MeV  

NASA Astrophysics Data System (ADS)

We report here the first measurement of absolute single ionization cross-section of uracil (C4H4N2O2, m=112) in collisions with highly charged C ions of energy ranging between 100 keV to 60 MeV i.e. in the range of Bragg peak which is relevant for high energy hadron therapy. An ECR based low energy accelerator along with a 14 MV Pelletron accelerator were used to obtain a wide range of energies. Energy and charge state (representing perturbation strength) dependence of io-nization cross-section has been studied using a ToF mass spectrometer. In the low energy range, cross-section increases with energy and then saturates while in the high energy range it decreases with energy. Ionization cross-section found to increase linearly with charge-state. The CTMC and CDW-EIS models are used to compare with the data. The complementary experiment was also carried out to measure the low energy electron emission spectrum at different angles.

Tribedi, L. C.; Agnihotri, A. N.; Kasthurirangan, S.; Kumar, A.; Champion, C.; Rivarola, R.

2012-11-01

114

Reaction /sup 2/H(/sup 3/He,. gamma. ) /sup 5/Li at center-of-mass energies between 25 and 60 keV  

SciTech Connect

The gamma ray to proton branching ratio, GAMMA/sub ..gamma..//GAMMA/sub p/, of the /sup 2/H+ /sup 3/He reaction has been measured between center-of-mass energies of 25 and 60 keV. The ratio of the ground-state gamma reaction /sup 2/H(/sup 3/He,..gamma../sub 0/) /sup 5/Li to the dominant reaction /sup 2/H(/sup 3/He,p)/sup 4/He is observed to be roughly constant over this energy range with a best value of (4.5 +- 1.2) x 10/sup -5/. This ratio for the gamma-ray reaction to the /sup 5/Li first excited state is measured to have a value of (8 +- 3) x 10/sup -5/. The excitation energy of the first excited state is estimated to be 3.0 +- 1.0 MeV.

Cecil, F.E.; Cole, D.M.; Philbin, R.; Jarmie, N.; Brown, R.E.

1985-09-01

115

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

Friedman, P.G.

1986-01-01

116

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

SciTech Connect

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

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

2011-06-01

117

Refractive lenses fabricated by deep SR lithography and LIGA technology for X-ray energies from 1 keV to 1 MeV  

SciTech Connect

SU-8 polymer and Nickel were used to manufacture planar high aspect ratio X-ray refractive lenses by the LIGA process (Deep X-ray lithography, electroforming). The exposure of PMMA and highly sensitive SU-8 resist layers were carried out at the ANKA storage ring, Karlsruhe. Lenses of either round, segment or quasi-parabolic (kinoform) profiles have been designed, fabricated and tested at the ESRF and at the ANKA synchrotron sources with X-ray energies ranging from 12 to 55 keV. The SU-8 polymer lenses tested at ESRF showed an uniform focal line spot with FWHM of appr. 0.32 {mu}m and gains in the range of 320. The characteristics did not alter after an absorbed dose of 2 MJ/cm3. Lenses fabricated from electroplated Ni, 320 {mu}m thick, were tested at a photon energy of 212 keV. In this case the uniform focal line spot was about 5 {mu}m.

Nazmov, V.; Reznikova, E.; Boerner, M.; Mohr, J.; Saile, V. [Institut fuer Mikrostrukturtechnik/Forschungszentrum Karlsruhe GmbH, 76021 Karlsruhe (Germany); Snigirev, A.; Snigireva, I.; DiMichiel, M.; Drakopoulos, M. [ESRF, BP-220, Grenoble Cedex (France); Simon, R. [Institut fuer Synchrotron Strahlung/Forschungszentrum Karlsruhe GmbH, 76021 Karlsruhe (Germany); Grigoriev, M. [IMT RAS, Chernogolovka, 142432 (Russian Federation)

2004-05-12

118

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

NASA Astrophysics Data System (ADS)

One of the advantages of applying X-band linear accelerator (Linac) is the compact size of the whole system. That shows us the possibility of on-site system such as the custom inspection system in an airport. As X-ray source, we have developed X-band Linac and achieved maximum X-ray energy 950 keV using the low power magnetron (250 kW) in 2 ?s pulse length. The whole size of the Linac system is 1×1×1 m3. That is realized by introducing X-band system. In addition, we have designed two-fold scintillator detector in dual energy X-ray concept. Monte carlo N-particle transport (MCNP) code was used to make up sensor part of the design with two scintillators, CsI and CdWO4. The custom inspection system is composed of two equipments: 950 keV X-band Linac and two-fold scintillator and they are operated simulating real situation such as baggage check in an airport. We will show you the results of experiment which was performed with metal samples: iron and lead as targets in several conditions.

Lee, Kiwoo; Natsui, Takuya; Hirai, Shunsuke; Uesaka, Mitsuru; Hashimoto, Eiko

2011-06-01

119

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

120

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

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

121

14-pixel, multiplexed array of gamma-ray microcalorimeters with 47 eV energy resolution at 103 keV  

SciTech Connect

The authors present a prototype for a high-energy-resolution, high-count-rate, gamma-ray spectrometer intended for nuclear forensics and international nuclear safeguards. The prototype spectrometer is an array of 14 transition-edge-sensor microcalorimeters with an average energy resolution of 47 eV (full width at half maximum) at 103 keV. The resolution of the best pixel is 25 eV. A cryogenic, time-division multiplexer reads out the array. Several important topics related to microcalorimeter arrays are discussed, including cross-talk, the uniformity of detector bias conditions, fabrication of the arrays, and the multiplexed readout. The measurements and calculations demonstrate that a kilopixel array of high-resolution microcalorimeters is feasible.

Doriese, W. B.; Ullom, J. N.; Beall, J. A.; Duncan, W. D.; Ferreira, L.; Hilton, G. C.; Horansky, R. D.; Irwin, K. D.; Mates, J. A. B.; Reintsema, C. D.; Vale, L. R.; Xu, Y.; Zink, B. L.; Rabin, M. W.; Hoover, A. S.; Rudy, C. R.; Vo, D. T. [National Institute of Standards and Technology, 325 Broadway, MC 817.03, Boulder, Colorado 80305 (United States); Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2007-05-07

122

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

SciTech Connect

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

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

2006-09-18

123

26Al(n,p1) and (n,?0) cross sections from thermal energy to 70 keV and the nucleosynthesis of 26Al  

NASA Astrophysics Data System (ADS)

We have measured the 26Al(n,?0)23Mg and 26Al(n,p1)26Mg* cross sections from thermal energy to approximately 10 keV and 70 keV, respectively. These reactions are thought to be the major mechanisms for the destruction of 26Al in many nucleosynthesis environments; hence, an accurate determination of their rates is important for understanding the observations of ? rays from ``live'' 26Al in our galaxy and of ``extinct'' 26Al in meteorites. The astrophysical rate for the 26Al(n,?0)23Mg reaction determined from our measurements is in good agreement with the rate determined via inverse measurements. On the other hand, the rate we determined for the 26Al(n,p1)26Mg* reaction is significantly larger than previously reported. In addition, we were able to determine this rate in the temperature range below 0.2 GK which was not covered by previous measurements. This lower temperature range may be important for understanding the production of 26Al in Red Giant stars. Both of our rates are significantly different than the rates used in most nucleosynthesis calculations. We discuss the impact of our measurements on the nucleosynthesis of 26Al.

Koehler, P. E.; Kavanagh, R. W.; Vogelaar, R. B.; Gledenov, Yu. M.; Popov, Yu. P.

1997-08-01

124

Energy dependence of effective atomic numbers for photon energy absorption and photon interaction: studies of some biological molecules in the energy range 1 keV-20 MeV.  

PubMed

Effective atomic numbers for photon energy absorption, Z(PEA,eff), and for photon interaction, Z(PI,eff), have been calculated by a direct method in the photon-energy region from 1 keV to 20 MeV for biological molecules, such as fatty acids (lauric, myristic, palmitic, stearic, oleic, linoleic, linolenic, arachidonic, and arachidic acids), nucleotide bases (adenine, guanine, cytosine, uracil, and thymine), and carbohydrates (glucose, sucrose, raffinose, and starch). The Z(PEA,eff) and Z(PI,eff) values have been found to change with energy and composition of the biological molecules. The energy dependence of the mass attenuation coefficient, Z(PEA,eff), and the mass energy-absorption coefficient, Z(PI,eff), is shown graphically and in tabular form. Significant differences of 17%-38% between Z(PI,eff) and Z(PEA,eff) occur in the energy region 5-100 keV. The reasons for these differences, and for using Z(PEA,eff) rather than Z(PI,eff) in calculations of the absorbed dose, are discussed. PMID:18293593

Manohara, S R; Hanagodimath, S M; Gerward, L

2008-01-01

125

Yields of ions and excited states in nonpolar liquids exposed to x-rays of 1 to 30 kev energy.  

National Technical Information Service (NTIS)

When x-rays from a synchrotron source are absorbed in a liquid, the x-ray energy (E(sub x)) is converted by the photoelectric effect into the kinetic energy of the electrons released. For hydrocarbons, absorption by the K-electrons of carbon dominates. Th...

Holroyd

1999-01-01

126

Gamma Ray Intensity Standards for Calibrating Ge(Li) Detectors for the Energy Range 200-1700 KeV.  

National Technical Information Service (NTIS)

Gamma ray pulse height spectra for seven radioactive sources have been analyzed for the full energy peak areas. By using these areas in conjunction with the results of an extensive compilation of relative gamma ray intensities, a relatively simple efficie...

Roney W.M W. A. Seale

1978-01-01

127

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

128

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

PubMed Central

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

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

2014-01-01

129

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

SciTech Connect

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

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

2012-10-01

130

Calibrating of x-ray detectors in the 8 to 111 keV energy range and their application to diagnostics on the National Ignition Facility  

NASA Astrophysics Data System (ADS)

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

Lee, Joshua J.; Haugh, Michael J.; LaCaille, Greg; Torres, Peter

2012-10-01

131

Combining two types of molecular dynamics for rapid computation of high-energy displacement cascades. II. Application of the method to a 70-keV cascade in a simplified nuclear glass  

NASA Astrophysics Data System (ADS)

A combined molecular dynamics method is proposed to accelerate the computation of displacement cascades in nuclear glass arising from recoil nuclei in the 70-100 keV energy range. The method combines two types of molecular dynamics calculations: classical MD with standard empirical potentials and a simplified form with the potentials reduced to their short-range component to estimate the morphology of a displacement cascade. With this method we were able to reconstitute the behavior of a simplified oxide glass impacted by a 70-keV projectile. Compared with the results obtained by classical molecular dynamics, mechanisms observed at lower energies (temporary depolymerization followed by progressive structure recovery) are correctly reproduced at 70 keV; the number of atom displacements and the intermediate depolymerization peak intensity remain linear at energies ranging from 0 to 70 keV. The large volume of the 70-keV cascade allowed us to demonstrate that structure recovery was not homogeneous: the coolest regions were less annealed than the hottest regions. The residual depolymerization was more intense in regions struck by lower-energy projectiles—i.e., at the end of the cascade. Local thermal agitation in the hottest regions rapidly diminished as it propagated, and the neighboring regions were largely unaffected. Thermal agitation in the hottest regions thus had little effect on the recovery of regions impacted by low-energy projectiles.

Delaye, J.-M.; Ghaleb, D.

2005-06-01

132

Charge-transfer processes in collisions of H+ ions with H2, D2, CO, and CO2 molecules in the energy range 0.2-4.0 keV  

NASA Astrophysics Data System (ADS)

Charge-transfer processes resulting from collisions of H+ ions with H2, D2, CO, and CO2 molecules have been experimentally investigated in the energy range of 0.2-4.0 keV by using the initial growth-rate method. Theoretical analysis based on a molecular-orbital expansion method for H2 and CO targets was also carried out. The observed cross sections are compared with previous experimental and theoretical data. The present results for H2 are found to be in excellent accord with the recommended data by Barnett [Oak Ridge National Laboratory Report No. ORNL-6086 (1990)], and hence, confirm the accuracy of the recommended data. But, at 0.2 keV, the present data for D2 are found to be smaller than those for H2. For the CO molecule, the present data qualitatively agree well with most previous measurements, but show the stronger energy dependence, while the present theory shows a pronounced structure at around 0.25 keV and ties well with other low-energy measurements below 0.1 keV. For the CO2 molecule, the present results are in excellent accord with other measurements above 1 keV, while they show some differences below this energy where our experimental result displays the stronger energy dependence. These data are useful for various applications.

Kusakabe, Toshio; Asahina, Kensuke; Gu, Jiang P.; Hirsch, Gerhard; Buenker, Robert J.; Kimura, Mineo; Tawara, Hiroyuki; Nakai, Yohta

2000-12-01

133

Absolute detection efficiency of a micro-channel plate detector to x-rays in the 1--100 KeV energy range  

SciTech Connect

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

Burginyon, G.A.; Jacoby, B.A.; Wobser, J.K.; Ernst, R.D.; Ancheta, D.S.; Tirsell, K.G.

1992-09-03

134

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

135

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

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

136

Ionic fragmentation of a CH4 molecule induced by 10-keV electrons: Kinetic-energy-release distributions and dissociation mechanisms  

NASA Astrophysics Data System (ADS)

The dynamics of ionic fragmentation of CH4 molecules under impact of 10-keV electrons has been studied. The technique of recoil ion momentum spectroscopy is employed to obtain information about the kinetic energy release and the dissociation mechanisms of different pathways arising from the fragmentation of a CH4 dication. The results show that there are altogether eight dissociation pathways that arise from the complete and the incomplete Coulomb explosions of the CH42+ molecular ions. The kinetic energy release for these pathways is compared with earlier data from the literature for the impact of different charged particles, photons, and their impact energies. The present results indicate that mostly the lower electronic states of CH42+ are involved for the observed dissociation channels. Also, the dissociation mechanisms associated with these channels are suggested and discussed. Further, we have also estimated the relative ion intensities of different channels of fragmentation of CH4 dication produced under impact of considered energy of electrons.

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

2013-06-01

137

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

NASA Astrophysics Data System (ADS)

The recent completion and operation of the High Energy Stereoscopic System [1], an array of ground based imaging Cherenkov telescopes, has provided a survey with unprecedented sensitivity of the inner part of the Galaxy and revealed a new population of very high energy gamma-rays sources emitting at E > 100 GeV. Most of them were reported to have no known radio or X-ray counterpart and hypothesised to be representative of a new class of dark nucleonic cosmic sources. In fact, very high energy gamma-rays with energies E > 1011 eV are the best proof of non-thermal processes in the universe and provide a direct in-site view of matter-radiation interaction at energies by far greater than producible in ground accelerators. At lower energy INTEGRAL has regularly observed the entire galactic plane during the first 1000 day in orbit providing a survey in the 20 100 keV range resulted in a soft gamma-ray sky populated with more than 200 sources, most of them being galactic binaries, either Black Hole Candidates (BHC) or Neutron Stars (NS) [5]. Very recently, the INTEGRAL new source IGR J18135-1751 has been identified as the soft gamma-ray counterpart of HESS J1813-178 [18] and AXJ1838.0-0655 as the X/gamma-ray counterpart of HESS J1837-069 [14]. Detection of non-thermal radio, X and gamma-ray emission from these TeV sources is very important to discriminate between various emitting scenarios and, in turn, to fully understand their nature. The implications of these new findings in the high energy Galactic population will be addressed.

Ubertini, P.

2005-12-01

138

Modeling the energy response of pn-CCDs in the 0.2-10 keV band  

NASA Astrophysics Data System (ADS)

A simple analytical model has been developed to explain the shape of low-energy spectra taken with pn-CCDs, which are developed as imaging spectroscopic detectors for ESA's X-ray observatory satellite X-Ray Multimirror Mission (XMM). The model has been tested on experimental data taken with test devices at the German synchrotron Berliner Elektronen Speicherring für Synchrotronstrahlung (BESSY-I). It can be used to generate the response matrix function for pn-EPIC (European Photon Imaging Camera), one of the three X-ray cameras onboard XMM. First results in applying the model to polychromatic spectra are shown.

Popp, M.; Hartmann, R.; Soltau, H.; Strüder, L.; Meidinger, N.; Holl, P.; Krause, N.; von Zanthier, C.

2000-01-01

139

Probabilities of multiple electron emission from thin (˜ 50 Å) carbon foils after impact of neutral oxygen at energies between 30 and 200 keV  

NASA Astrophysics Data System (ADS)

The multiple secondary electron emission from a thin (˜ 50 Å) carbon foil has been measured for impacting primary oxygen atoms with energies of 30, 50, 100 and 200 keV. The absolute probabilities Pk, Pk', Pkk' of the emission of k, k' = 0, 1…numbers of electrons in forward (k'), and/or backward (k) directions from the foil have been derived. It is observed that (i) the probabilities Pk, Pk' disagree with those expected from Poisson statistics, (ii) there is an asymmetry in the forward/backward emission, (iii) the probabilities Pk(E) change in a different way with energy E than it is expected from the energy dependence of the stopping power dE/dx, (iv) in individual events there is no correlation between the numbers of electrons going in forward and/or backward directions. From these observations and further statistical analysis it is concluded that the emission of multiple electrons is not the result of only one primary process (ionization by collision between the projectile and target atoms). Rather, larger numbers of emitted electrons are mainly produced in an additional process (cascade electron production), in which the internal secondary electrons produce further (tertiary) electrons.

Kozochkina, A. A.; Leonas, V. B.; Witte, M.

1991-11-01

140

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

141

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

SciTech Connect

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

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

2010-10-15

142

6129keV line of 16O  

Microsoft Academic Search

The mass-doublet-scale based energy of the 6129-keV gamma ray of 16O is reevaluated in light of a recent determination of the deuteron binding energy. The result is 6129.142 +\\/- 0.032 keV. No serious descrepancy exists between this result and a recently measured value based on the wavelength (Au) standard. RADIOACTIVITY 16O, deduced energy of 6129-keV transition based on mass scale.

E. B. Shera

1982-01-01

143

Compton Scattering at Bound Electrons of Copper, Lead and Tin at the Primary Photon Energy Esub(Y1)=661,66 KeV and the Scattering Angle Theta=145 exp 0.  

National Technical Information Service (NTIS)

Double-differential cross sections for the inelastic scattering of photons with the primary energy 661.66 keV and a scattering angle theta = 145 exp 0 by copper, tin and lead were measured. Numerical methods were developed, which allow the calculation of ...

A. Reineking

1982-01-01

144

Experimental Determination of Sensitivity of DN-A-1 Dosimeter and exp 6 LiJ(Eu) Scintillation Detector in Sphere Polyethylene Moderators in the 30 KeV Neutron Energy Range.  

National Technical Information Service (NTIS)

DH-A-1 dosimeter and exp 6 LiJ(Eu) detector, located in the center of polyethylene spheres with various diameters, were calibrated by means of neutrons with the energy of about 30 keV. The data on the detectors responses enable one to determine the shape ...

V. E. Aleinikov L. G. Beskrovnaya M. M. Komochkov Y. V. Mokrov S. P. Prusachenkov

1979-01-01

145

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

NASA Astrophysics Data System (ADS)

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

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

2011-01-01

146

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

147

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

PubMed

Studies of materials under extreme conditions have relevance to a broad area of research, including planetary physics, fusion research, materials science, and structural biology with x-ray lasers. We study such extreme conditions and experimentally probe the interaction between ultrashort soft x-ray pulses and solid targets (metals and their deuterides) at the FLASH free-electron laser where power densities exceeding 10(17) W/cm(2) were reached. Time-of-flight ion spectrometry and crater analysis were used to characterize the interaction. The results show the onset of saturation in the ablation process at power densities above 10(16) W/cm(2). This effect can be linked to a transiently induced x-ray transparency in the solid by the femtosecond x-ray pulse at high power densities. The measured kinetic energies of protons and deuterons ejected from the surface reach several keV and concur with predictions from plasma-expansion models. Simulations of the interactions were performed with a nonlocal thermodynamic equilibrium code with radiation transfer. These calculations return critical depths similar to the observed crater depths and capture the transient surface transparency at higher power densities. PMID:21405780

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

2011-01-01

148

On the existence of low-energy photons (<150 keV) in the unflattened x-ray beam from an ordinary radiotherapeutic target in a medical linear accelerator  

Microsoft Academic Search

Low-energy photons (<150 keV) are essential for obtaining high quality x-ray radiographs. These photons are usually produced in the accelerator target, but are effectively absorbed by the flattening filter and, at least partially, by the target itself. Experimental proof is presented for the existence of low-energy photons in the unflattened x-ray beam produced by a 6 MeV electron beam normally

A. Tsechanski; Y. Krutman; S. Faermann

2005-01-01

149

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

Microsoft Academic Search

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

Pavel Dryak; Petr Kovar

2006-01-01

150

6129keV line of ¹⁶O  

Microsoft Academic Search

The mass-doublet-scale based energy of the 6129-keV ..gamma.. ray of ¹⁶O is reevaluated in light of a recent determination of the deuteron binding energy. The result is 6129.142 +- 0.032 keV. No serious discrepancy exists between this result and a recently measured value based on the wavelength (Au) standard.

Shera

1982-01-01

151

Multilayer diffraction at 104 keV  

NASA Technical Reports Server (NTRS)

We have measured the diffraction peak of a W:Si synthetic multilayer reflector at 104 keV using the High Energy Bonse-Hart Camera at the X-17B hard X-ray wiggler beam line of the National Synchrotron Light Source at Brookhaven National Laboratory. The characteristics of the diffraction peak are described and compared to theory.

Krieger, Allen S.; Blake, Richard L.; Siddons, D. P.

1993-01-01

152

On the 17-keV neutrino  

SciTech Connect

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

Hime, A.

1993-04-01

153

Formation and emission of gold and silver carbide cluster ions in a single C60- surface impact at keV energies: Experiment and calculations  

NASA Astrophysics Data System (ADS)

Impact of fullerene ions (C60-) on a metallic surface at keV kinetic energies and under single collision conditions is used as an efficient way for generating gas phase carbide cluster ions of gold and silver, which were rarely explored before. Positively and negatively charged cluster ions, AunCm+ (n = 1-5, 1 <= m <= 12), AgnCm+ (n = 1-7, 1 <= m <= 7), AunCm- (n = 1-5, 1 <= m <= 10), and AgnCm- (n = 1-3, 1 <= m <= 6), were observed. The Au3C2+ and Ag3C2+ clusters are the most abundant cations in the corresponding mass spectra. Pronounced odd/even intensity alternations were observed for nearly all AunCm+/- and AgnCm+/- series. The time dependence of signal intensity for selected positive ions was measured over a broad range of C60- impact energies and fluxes. A few orders of magnitude immediate signal jump instantaneous with the C60- ion beam opening was observed, followed by a nearly constant plateau. It is concluded that the overall process of the fullerene collision and formation/ejection of the carbidic species can be described as a single impact event where the shattering of the incoming C60- ion into small Cm fragments occurs nearly instantaneously with the (multiple) pickup of metal atoms and resulting emission of the carbide clusters. Density functional theory calculations showed that the most stable configuration of the AunCm+ (n = 1, 2) clusters is a linear carbon chain with one or two terminal gold atoms correspondingly (except for a bent configuration of Au2C+). The calculated AuCm adiabatic ionization energies showed parity alternations in agreement with the measured intensity alternations of the corresponding ions. The Au3C2+ ion possesses a basic Au2C2 acetylide structure with a ?-coordinated third gold atom, forming a ?-complex structure of the type [Au(?-Au2C2)]+. The calculation shows meaningful contributions of direct gold-gold bonding to the overall stability of the Au3C2+ complex.

Cohen, Y.; Bernshtein, V.; Armon, E.; Bekkerman, A.; Kolodney, E.

2011-03-01

154

Low Background-Rate Detector for Ions in the 5 to 50 KeV Energy Range to Be Used for Radioisotope Dating with a Small Cyclotron.  

National Technical Information Service (NTIS)

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 ...

P. G. Friedman

1986-01-01

155

Charge-transfer processes in collisions of ground-state C+ ions with H2, D2, CO, and CO2 molecules in the energy range from 0.15 to 4.5 keV  

NASA Astrophysics Data System (ADS)

Charge-transfer processes in collisions of C+ ions with H2, D2, CO, and CO2 molecules have been studied based on joint experimental and theoretical approaches in the collision energy from 0.15 to 4.5 keV. In the present experiment, the ground-state C+(2P) ion projectiles have been produced by carefully energy-controlled electron impact to minimize the influence of the metastable-state ions. The observed cross sections are compared with the present theoretical prediction, and while the theoretical results are somewhat smaller than the measurements, they are found to be in reasonable agreement for H2, D2, and CO above around 1 keV. The present experimental cross sections for CO and CO2 are smaller by a factor of 2 to 3 than those of earlier measurements. We provide some remarks on the effect of the metastable-state ions.

Kusakabe, Toshio; Hosomi, Kenji; Nakanishi, Hiroshi; Tawara, Hiroyuki; Sasao, Mamiko; Nakai, Yohta; Kimura, Mineo

1999-07-01

156

A Monte Carlo track structure code for electrons (~10 eV10 keV) and protons (~0.3-10 MeV) in water: partitioning of energy and collision events  

Microsoft Academic Search

An event-by-event Monte Carlo simulation code for track structure studies is described. In the present form the code transports protons (~0.3-10 MeV) and electrons (~10 eV-10 keV) in a water medium in the gas phase approximation. For the type of particles and energy range considered, ionization, electronic excitation and electron elastic scattering are the most important collision events accounted for

D. Emfietzoglou; G. Papamichael; K. Kostarelos; M. Moscovitch

2000-01-01

157

Radiative Capture of Neutrons in the Kev Region.  

National Technical Information Service (NTIS)

Essentially monoenergetic neutrons with keV energies can be obtained from a reactor by using suitable filters. To date, prompt gamma -ray spectra have been measured using 24-, 2-, and 1-keV neutrons, obtained through Fe + Al + S, Sc + Ti and exp 6 Li filt...

R. C. Greenwood R. E. Chrien K. Rimawi

1975-01-01

158

Half-life measurements for the 50 keV and 162 keV states in 132I  

NASA Astrophysics Data System (ADS)

132Te was produced via the 232Th (?, fission) reaction at the Variable Energy Cyclotron , Calcutta. 132Te was separated in carrier-free form from the fission products by radiochemical separation and the half-lives for the 50 keV and 162 keV states of 132I were determined to be 2.94±0.11 ns and 0.55±0.04 ns respectively. The present results differ significantly from the previously reported half-lives of 7.14 ns and 3.57 ns for the 50 keV and 162 keV states respectively.

Das, S. K.; Guin, R.; Saha, S. K.

1999-01-01

159

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

160

Rayleigh and Compton scattering cross sections for low, medium and high Z elements in the energy region 23.18 <= E <= 30.85 keV  

Microsoft Academic Search

Using nearly monoenergetic unpolarised Kalpha x-ray photons coherent (Rayleigh) and incoherent (atomic Compton) scattering cross sections in the atomic region 13 <= Z <= 82 have been measured at 23.18, 24.14, 25.19, 26.27 and 30.85 keV. Experimental scattering cross sections in the momentum transfer region 1.322 h Å-1 <= q <= 1.759 h Å-1 [q = sin (theta\\/2)lambda(Å)] were obtained

D. V. Rao; R. Cesareo; G. E. Gigante

1996-01-01

161

High-efficiency B?C/Mo?C alternate multilayer grating for monochromators in the photon energy range from 0.7 to 3.4 keV.  

PubMed

An alternate multilayer (AML) grating has been prepared by coating an ion etched lamellar grating with a B4C/Mo2C multilayer (ML) having a layer thickness close to the groove depth. Such a structure behaves as a 2D synthetic crystal and can reach very high efficiencies when the Bragg condition is satisfied. This AML coated grating has been characterized at the SOLEIL Metrology and Tests Beamline between 0.7 and 1.7 keV and at the four-crystal monochromator beamline of Physikalisch-Technische Bundesanstalt (PTB) at BESSY II between 1.75 and 3.4 keV. A peak diffraction efficiency of nearly 27% was measured at 2.2 keV. The measured efficiencies are well reproduced by numerical simulations made with the electromagnetic propagation code CARPEM. Such AML gratings, paired with a matched ML mirror, constitute efficient monochromators for intermediate energy photons. They will extend the accessible energy for many applications as x-ray absorption spectroscopy or x-ray magnetic circular dichroism experiments. PMID:24686695

Choueikani, Fadi; Lagarde, Bruno; Delmotte, Franck; Krumrey, Michael; Bridou, Françoise; Thomasset, Muriel; Meltchakov, Evgueni; Polack, François

2014-04-01

162

On the possibility of the generation of high harmonics with photon energies greater than 10 keV upon interaction of intense mid-IR radiation with neutral gases  

NASA Astrophysics Data System (ADS)

Based on the analytical quantum-mechanical description in the framework of the modified strong-field approximation, we have investigated high harmonic generation of mid-IR laser radiation in neutral gases taking into account the depletion of bound atomic levels of the working medium and the electron magnetic drift in a high-intensity laser field. The possibility is shown to generate high-order harmonics with photon energies greater than 10 keV under irradiation of helium atoms by intense femtosecond laser pulses with a centre wavelength of 8 – 10.6 ?m.

Emelina, A. S.; Emelin, M. Yu; Ryabikin, M. Yu

2014-05-01

163

Theoretical and experimental investigation of the triple-differential cross sections for electron-impact ionization of Kr(4{ital p}) and Xe(5{ital p}) at 1-keV impact energy  

SciTech Connect

The triple-differential cross sections for the ionization of Kr(4p) and Xe(5p) by a fast electron where the exiting electrons have energies of 20 eV and 1 keV have been measured and compared with distorted-wave Born calculations. Difficulties were encountered when trying to place the relative data on an absolute scale by extrapolation to the optical limit: an extensive study of this normalization process is presented and it is argued that it is not applicable to the heavier atoms considered here, but can be used effectively for helium targets. {copyright} {ital 1997} {ital The American Physical Society}

Rasch, J. [Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Silver Street, Cambridge CB3 9EW (England)] [Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Silver Street, Cambridge CB3 9EW (England); Zitnik, M. [J. Stefan Institute, University of Ljubljana, Ljubljana (Slovenia)] [J. Stefan Institute, University of Ljubljana, Ljubljana (Slovenia); Avaldi, L. [Istituto Metodologie Avanzate Inorganiche, Consiglio Nationale delle Ricerche, Area della Ricerca di Roma, Via Salaria km 29300, C.P. CP10, 00016 Monterotondo Scalo, Roma (Italy)] [Istituto Metodologie Avanzate Inorganiche, Consiglio Nationale delle Ricerche, Area della Ricerca di Roma, Via Salaria km 29300, C.P. CP10, 00016 Monterotondo Scalo, Roma (Italy); Whelan, C.T. [Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Silver Street, Cambridge CB3 9EW (England)] [Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Silver Street, Cambridge CB3 9EW (England); Stefani, G.; Camilloni, R. [Istituto Metodologie Avanzate Inorganiche, Consiglio Nationale delle Richerche, Area della Ricerca di Roma, Via Salaria km 29300, C.P. Box 10, 00016 Monterotondo Scalo, Roma (Italy)] [Istituto Metodologie Avanzate Inorganiche, Consiglio Nationale delle Richerche, Area della Ricerca di Roma, Via Salaria km 29300, C.P. Box 10, 00016 Monterotondo Scalo, Roma (Italy); Allan, R.J. [Department for Computation and Information, CCLRC Daresbury Laboratory, Warrington WA4 4AD (England)] [Department for Computation and Information, CCLRC Daresbury Laboratory, Warrington WA4 4AD (England); Walters, H.R. [Department of Applied Mathematics and Theoretical Physics, The Queens University of Belfast, Belfast BT7 1NN (Northern Ireland)] [Department of Applied Mathematics and Theoretical Physics, The Queens University of Belfast, Belfast BT7 1NN (Northern Ireland)

1997-12-01

164

Study of photon interactions and shielding properties of silicate glasses containing with Bi 2O 3, BaO and PbO in the energy region of 1 keV–100 GeV  

Microsoft Academic Search

The mass attenuation coefficient (?\\/?), effective atomic number (Zeff), effective electron density (Ne,eff) and half value layer (HVL) of xRmOn:(1-x)SiO2 glass system (where RmOn are Bi2O3, PbO and BaO, with 0.3?x?0.7 is fraction by weight) have been calculated by theoretical approach using WinXCom program in the energy region from 1 keV–100 GeV. Also the HVL of these glass samples has

N. Chanthima; J. Kaewkhao; P. Limsuwan

165

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

166

Design of the Experimental Apparatus to Obtain a Thermal Neutron Beam, Intermediate-Energy Neutrons (2-144 KeV) and High-Energy Photons (6 MeV) by Means of the Triga Reactor at the ENEA Casaccia Center.  

National Technical Information Service (NTIS)

Neutron beams in the energy range between 2 and 150 KeV can be obtained by suitably filtering the neutrons in the beam tubes of a nuclear research reactor. This method has been applied at the NBS and PTB reactors. Neutron beams in this energy range are ve...

R. F. Laitano C. Mancini

1987-01-01

167

Li(i=1-3) sub-shell x-ray relative intensities for some compounds of 66Dy at 22.6 and 59.54 keV incident photon energies  

NASA Astrophysics Data System (ADS)

The intensity ratios, ILk/IL? (k=l,?1,4,?3,6,?2,7,9,10,15,?1,5,?2,3,?4,?,?), have been measured for some compounds of 66Dy, namely, Dy2O3, Dy2(CO3)3, Dy2(SO4)3, DyI2 and Dy metal by creating the Li(i=1-3) sub-shell vacancies in widely different proportions at two incident photon energies of 22.6 keV and 59.54 keV, in order to check the predicted dependence of these ratios on the incident photon energy and also investigate the influence of chemical effects on these ratios for an f-block element. The measurements were performed using the EDXRF spectrometer involving disk type radioactive sources of Cd109 and Am241 and a Peltier cooled Si PIN x-ray detector arranged in the 90° reflection geometry. The measured intensity ratios have been compared with the theoretical ILk/IL? values and those calculated using the two sets of fluorescence and Coster-Kronig yields available in literature in order to check the reliability of the theoretical/calculated values. Further, the measured ratio, IL?4/IL?, was found to depend on the oxidation state of 66Dy as well as nature of ligand attached to it in a given compound.

Kumar, Anil; Puri, Sanjiv

2012-07-01

168

On the validity of trajectory methods for calculating the transport of very low energy (<1 keV) electrons in liquids and amorphous media  

NASA Astrophysics Data System (ADS)

It is easily demonstrated that a trajectory picture of low energy electron transport in condensed matter is not compatible with the Heisenberg uncertainty principle. The uncertainty in the position of a low energy electron is large and may in fact be larger than an entire simulated trajectory. This might be interpreted to mean that trajectory methods are not applicable. However, this conclusion is not correct. In the present paper, the evidence for the validity of low energy electron trajectory simulation is discussed, as well as the wave aspects and quantum nature of low energy electron transport in liquids and amorphous solids.

Liljequist, D.; Nikjoo, H.

2014-06-01

169

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

NASA Astrophysics Data System (ADS)

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

Oetliker, Michael

1993-12-01

170

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

SciTech Connect

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

Weston, L.W.

1990-12-21

171

Experimental Study of Interactions of Highly Charged Ions with Atoms at KeV Energies. Progress Report, May 15, 1984-May 14, 1985.  

National Technical Information Service (NTIS)

The interest, both theoretical and experimental, in interactions of low energy highly charged ions with electrons, atoms or ions is due to the importance of such interactions to controlled thermonuclear fusion research and to the intrinsically interesting...

V. O. Kostroun

1985-01-01

172

Experimental Study of Interactions of Highly Charged Ions with Atoms at KeV Energies: Progress Report for Period May 15, 1985-February 15, 1987.  

National Technical Information Service (NTIS)

Interest in interactions of low energy highly charged ions with electrons, atoms or ions is due to their importance to controlled thermonuclear fusion research and the interesting nature of the fundamental processes involved. Studies of such interactions ...

V. O. Kostroun

1987-01-01

173

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

NASA Astrophysics Data System (ADS)

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 Hp(10) whereas for Hp(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.; Priharti, W.; Samat, S. B.; Dolah, M. T.

2013-11-01

174

M-shell X-ray production cross-sections for elements with 67 {<=} Z {<=} 92 at incident photon energies E{sub M{sub 1}}keV  

SciTech Connect

The X-ray production cross-sections for the Mk (k = {xi}, {delta}, {alpha}, {beta}, {zeta}, {gamma}, m{sub 1} and m{sub 2}) groups of X-rays have been evaluated for all the elements with 67 {<=} Z {<=} 92 at incident photon energies ranging E{sub M{sub 1}}keV using currently available theoretical data sets of different physical parameters, namely, partial photoionization cross-sections, X-ray emission rates, fluorescence and Coster-Kronig yields, and the K-shell/L{sub j} (j = 1-3) subshell to the M{sub i} (i = 1-5) subshell vacancy transfer probabilities, based on the independent particle models.

Chauhan, Yogeshwar; Kumar, Anil [University College of Engineering, Punjabi University, Patiala 147002, Punjab (India); Puri, Sanjiv [University College of Engineering, Punjabi University, Patiala 147002, Punjab (India)], E-mail: sanjivpurichd@yahoo.com

2009-07-15

175

Evaluation of the use of sputter profiling with XPS or AES for the study of surface carburization resulting from high energy (>20 keV) ion implantation  

Microsoft Academic Search

Auger depth profiling was used previously with Xe ion etching to determine the extent of carburization resulting from ion implantation. In this report, the possibility of surface carburization resulting from the low-energy ion bombardment associated with sputter profiling was investigated. When a sample is analyzed by AES or XPS, a surface-contaminant layer of carbonaceous material is always observed. The source

1983-01-01

176

Experimental study of interactions of highly charged ions with atoms at keV energies. Progress report, July 1, 1991--June 30, 1992  

SciTech Connect

This Progress Report describes the experimental work carried out, and the work in progress, at the Cornell EBIS Laboratory during the period 7/1/1991 to 6/30/1992. During this period, a number of experiments were carried out. The absolute values of the total, one, two and three electron transfer cross sections for highly charged argon ions (8{le}q{le}16) colliding with argon at 2.3 qkev laboratory energy were measured. The distribution of recoil ions and molecular fragments formed in highly charged ion atom and molecule collisions was measured in order to help the interpretation of electron spectra in the 40--320 eV energy range emitted in Ar{sup q+}+Ar(8{le}q{le}16) collisions at 2.3 qkeV that were measured in our laboratory. The interpretation of the electron spectra is still under way. A new collision chamber was built which contains an ion decelerating lens system and a high resolution monochromator-analyzer combination. Ions extracted from the Cornell Electron Beam Ion Source were successfully decelerated from 2.3 qkeV down to 30 qeV Preliminary 0{degree} translational energy spectra for Ar{sup l2+} on Ar at a collision energy of 38.6 qeV show a 0.56 qeV resolution. Work is in progress to extend measurements of cross sections and recoil ion charge state distributions down to collision energies in the 10 eV/amu range.

Kostroun, V.O.

1992-07-05

177

Electron capture cross-sections between 3He + ion and rubidium vapor in the energy range 1.0–19 keV  

Microsoft Academic Search

Electron capture cross-sections have been measured for 3He+ ions in Rb vapor. The deduced data were used for evaluating the performance of the proposed polarized 3He ion source (SEPIS) based on the spin-exchange collisions. Measurements of the 3He+ beam components after passing through the target were made as a function of the Rb target thickness at energies ranging from 1.0

M. Tanaka; Y. Takahashi; T. Shimoda; T. Furukawa; M. Yosoi; K. Takahisa; N. Shimakura; S. Yasui

2006-01-01

178

X-ray transmission of Kumakhov polycapillary lens up to 50 keV  

Microsoft Academic Search

New series of polycapillary lens is developed for medium hard x-rays. At the x-ray energy about 50 keV these lenses give intensity gain in the focal spot (~O.15 mm dia.) at the distance ~0.5m more than two orders of magnitude compared to the direct beam through a pinhole. At 25 keV the gain exceeds 103. At 22 keV x-ray energy

S. M. Cheremisin; D. I. Gruev; S. V. Nikitina; D. V. Zaitsev

2005-01-01

179

Predissociation of the c 3? u state of H 2, populated after charge exchange of H 2+ with several targets at keV energies  

NASA Astrophysics Data System (ADS)

A detailed study of the predissocitation of the c 3? u state of H 2 has been made with a new, very sensitive, experimental technique. A resolution better than 1% is obtained in the measurement of the released kinetic energy of H?H pairs after charge exchange of H 2+ with Ar, H 2, Mg, Na and Cs by detecting both fragments with a time- and position-sensitive microchannel-plate detector. Eighteen vibrational levels of the c 3? u state can be clearly distinguished in the range of 7.2-10.2 eV. Detailed information is extracted from the spectra with the aid of a convolution procedure. The vibrational energy levels of the c 3? u state as calculated by Ko?os and Rychlewski are found to be correct within the experimental accuracy of 5 meV. Predissociative lifetimes are measured, yielding 6.2±0.5 ns for the lowest rovibrational level (? = 0, N = 1), which are in good agreement with theoretical calculations of Comtet and de Bruijn. The cross section for charge exchange is observed to increase gradually with the vibrational level and seems to follow the geometrical cross section of the molecule. Rotational excitation during the charge exchange is also found to increase considerably with the vibrational quantum number. The final rotational temperature further depends strongly on the target gas used and increases with the resonance energy defect ? I in the charge exchange collision.

de Bruijn, D. P.; Neuteboom, J.; Los, J.

1984-04-01

180

Multielectronic close-coupling treatment of atomic and molecular collisions: applications to H+-Li collisions in the keV energy range  

NASA Astrophysics Data System (ADS)

We present a new approach to describe electronic processes occurring in ion-atom and ion-molecule collisions at impact energies ranging from 50 eV.u?1 to 1 MeV.u?1. The treatment is based on the semiclassical approximation in which the time-dependent Schrödinger equation is solved non perturbatively, taking into account all the electrons of the collision system. This allows to describe exactly multielectronic processes and also, at the same footing, processes involving valence and inner shell electrons. We apply this model to describe electron transfer in a genuine three-electron system, H+-Li.

Labaigt, Gabriel; Dubois, Alain

2014-04-01

181

Carbon contamination of soft X-ray beamlines: dramatic anti-reflection coating effects observed in the 1 keV photon energy region.  

PubMed

Carbon contamination is a general problem of under-vacuum optics submitted to high fluence. In soft X-ray beamlines carbon deposit on optics is known to absorb and scatter radiation close to the C K-edge (280?eV), forbidding effective measurements in this spectral region. Here the observation of strong reflectivity losses is reported related to carbon deposition at much higher energies around 1000?eV, where carbon absorptivity is small. It is shown that the observed effect can be modelled as a destructive interference from a homogeneous carbon thin film. PMID:21862857

Chauvet, C; Polack, F; Silly, M G; Lagarde, B; Thomasset, M; Kubsky, S; Duval, J P; Risterucci, P; Pilette, B; Yao, I; Bergeard, N; Sirotti, F

2011-09-01

182

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

PubMed

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

Seidenbusch, M; Harder, D; Regulla, D

2014-05-01

183

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

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

184

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

185

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

186

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

187

The x-ray calibration facility of the laser integration line in the 0.9-10 keV range: The high energy x-ray source and some applications  

NASA Astrophysics Data System (ADS)

The laser integration line (LIL) located at CEA-CESTA is equipped with x-ray plasma diagnostics using different kinds of x-ray components such as filters, mirrors, crystals, detectors, and cameras. The CEA-DAM of Arpajon is currently developing x-ray calibration methods and carrying out absolute calibration of LIL x-ray photodetectors. To guarantee LIL measurements, detectors such as x-ray cameras must be regularly calibrated close to the facility. A new x-ray facility is currently available to perform these absolute x-ray calibrations. This paper presents the x-ray tube based high energy x-ray source delivering x-ray energies ranging from 0.9 to 10 keV by means of an anode barrel. The purpose of this source is mainly to calibrate LIL x-ray cameras but it can also be used to measure x-ray filter transmission of plasma diagnostics. Different x-ray absolute calibrations such as x-ray streak and framing camera yields, x-ray charge-coupled device quantum efficiencies, and x-ray filter transmissions are presented in this paper. A x-ray flat photocathode detector sensitivity calibration recently performed for a CEA Z-pinch facility is also presented.

Hubert, S.; Dubois, J. L.; Gontier, D.; Lidove, G.; Reverdin, C.; Soullié, G.; Stemmler, P.; Villette, B.

2010-05-01

188

A Monte Carlo track structure code for electrons (~10 eV-10 keV) and protons (~0.3-10 MeV) in water: partitioning of energy and collision events  

NASA Astrophysics Data System (ADS)

An event-by-event Monte Carlo simulation code for track structure studies is described. In the present form the code transports protons (~0.3-10 MeV) and electrons (~10 eV-10 keV) in a water medium in the gas phase approximation. For the type of particles and energy range considered, ionization, electronic excitation and electron elastic scattering are the most important collision events accounted for in the transport simulation. Efforts were made to ensure that the analytic representation of the various interaction cross sections rests on well established experimental data and theory. For example, the secondary-electron spectrum as well as partial and total ionization cross sections are represented by a semitheoretical formulation combining Bethe's asymptotic expansion and binary-encounter theory. Binding effects for five levels of ionization and eight levels of electronic excitation of the water molecule are explicitly considered. The validity of the model cross sections is examined against available experimental data and theoretical predictions from other similar studies. Results pertaining to the partitioning of energy loss and interaction events for the first-collision probability and nanometre-size track segments are presented.

Emfietzoglou, D.; Papamichael, G.; Kostarelos, K.; Moscovitch, M.

2000-11-01

189

A Monte Carlo track structure code for electrons (approximately 10 eV-10 keV) and protons (approximately 0.3-10 MeV) in water: partitioning of energy and collision events.  

PubMed

An event-by-event Monte Carlo simulation code for track structure studies is described. In the present form the code transports protons (approximately 0.3-10 MeV) and electrons (approximately 10 eV-10 keV) in a water medium in the gas phase approximation. For the type of particles and energy range considered, ionization, electronic excitation and electron elastic scattering are the most important collision events accounted for in the transport simulation. Efforts were made to ensure that the analytic representation of the various interaction cross sections rests on well established experimental data and theory. For example, the secondary-electron spectrum as well as partial and total ionization cross sections are represented by a semitheoretical formulation combining Bethe's asymptotic expansion and binary-encounter theory. Binding effects for five levels of ionization and eight levels of electronic excitation of the water molecule are explicitly considered. The validity of the model cross sections is examined against available experimental data and theoretical predictions from other similar studies. Results pertaining to the partitioning of energy loss and interaction events for the first-collision probability and nanometre-size track segments are presented. PMID:11098897

Emfietzoglou, D; Papamichael, G; Kostarelos, K; Moscovitch, M

2000-11-01

190

A 750 keV RFQ linac for the AGS polarized proton program  

Microsoft Academic Search

A radio-frequency quadrupole (RFQ) linac was chosen for use as the preaccelerator for the polarized H(-) beam. The low injection energy of 20 keV eliminates the need for installing the bulky and complex polarized ion source within a large high voltage dome. A preliminary design was completed which accelerates 1 mA of polarized H(-) from 20 keV to 750 keV

J. M. Watson; D. R. Moffett; A. Moretti; R. L. Stockley; T. P. Wangler

1982-01-01

191

Degeneracy at 1871 keV in Cd112 and implications for neutrinoless double electron capture  

Microsoft Academic Search

High-statistics beta-decay measurements of Ag112 and In112 were performed to study the structure of the Cd112 nucleus. The precise energies of the doublet of levels at 1871 keV, for which the 0+ member has been suggested as a possible daughter state following neutrinoless double electron capture of Sn112, were determined to be 1871.137(72) keV (04+ level) and 1870.743(54) keV (42+

K. L. Green; P. E. Garrett; R. A. E. Austin; G. C. Ball; D. S. Bandyopadhyay; S. Colosimo; D. Cross; G. A. Demand; G. F. Grinyer; G. Hackman; W. D. Kulp; K. G. Leach; A. C. Morton; C. J. Pearson; A. A. Phillips; M. A. Schumaker; C. E. Svensson; J. Wong; J. L. Wood; S. W. Yates

2009-01-01

192

Bremsstrahlung Energy Spectra from Electrons of Kinetic Energy 1 KeV Less Than or Equal to T Less Than or Equal to 2000 KeV Incident on Neutral Atoms 1 Less Than or Equal to Z Less Than or Equal to 92.  

National Technical Information Service (NTIS)

A tabulation is presented of theoretical predictions for the electron bremsstrahlung energy spectrum from neutral atoms as a function of atomic number Z, incident electron kinetic energy T, and fraction of energy radiated k/T (k is the emitted photon ener...

L. Kissel C. MacCallum R. H. Pratt

1981-01-01

193

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

SciTech Connect

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

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

2007-03-15

194

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

SciTech Connect

We use the x-ray extended-range technique (XERT) [Chantler et al., Phys. Rev. A 64, 062506 (2001)] to measure the mass attenuation coefficients of molybdenum in the x-ray energy range of 13.5-41.5 keV to 0.02-0.15 % accuracy. Measurements made over an extended range of the measurement parameter space are critically examined to identify, quantify, and correct where necessary a number of experimental systematic errors. These results represent the most extensive experimental data set for molybdenum and include absolute mass attenuation coefficients in the regions of the x-ray absorption fine structure (XAFS) and x-ray-absorption near-edge structure (XANES). The imaginary component of the atomic form-factor f{sub 2} is derived from the photoelectric absorption after subtracting calculated Rayleigh and Compton scattering cross sections from the total attenuation. Comparison of the result with tabulations of calculated photoelectric absorption coefficients indicates that differences of 1-15 % persist between the calculated and observed values.

Jonge, Martin D. de; Tran, Chanh Q.; Chantler, Christopher T.; Barnea, Zwi; Dhal, Bipin B.; Cookson, David J.; Lee, Wah-Keat; Mashayekhi, Ali [School of Physics, University of Melbourne, Melbourne, Victoria 3010 (Australia); Chem-Mat-CARS, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439 (United States); XOR 1-ID, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439 (United States)

2005-03-01

195

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

PubMed

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

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

2012-04-01

196

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

197

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

198

Pursuing the 17 keV Neutrino  

NASA Astrophysics Data System (ADS)

Evidence both for and against the existence of a 17 keV neutrino presents an unresolved conundrum. The experimental status is reviewed, emphasizing recent attempts to clarify the issue and thoughts on how the situation might be improved.

Hime, A.

199

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

NASA Astrophysics Data System (ADS)

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

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

2009-01-01

200

5 upgradable to 25Â keV free electron laser facility  

NASA Astrophysics Data System (ADS)

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

York, R. C.

2014-01-01

201

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

202

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

NASA Astrophysics Data System (ADS)

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

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

2012-07-01

203

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

204

Origin of 30-100 keV protons observed in the upstream region of the earth's bow shock  

Microsoft Academic Search

A Fermi-type acceleration model is constructed to explain the origin of energetic protons (30-100 keV) which have been observed upstream of the bow shock. It is shown that the suprathermal protons (with energy of several keV) can be accelerated up to several tens of keV through the Fermi-type process in which the reflection at the shock front and the scattering

T. Terasawa

1979-01-01

205

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

206

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

Microsoft Academic Search

A 110 mA, 75 keV dc proton injector is being developed at Los Alamos. A microwave proton source is coupled to a two solenoid, space-charge neutralized, low-energy beam transport (LEBT) system. The ion source produces 110 mA proton current at 75 keV using 600-800 W of 2.45 GHz discharge power. Typical proton fraction is 85%-90% of the total extracted ion

Joseph Sherman; Andrew Arvin; Lash Hansborough; David Hodgkins; Earl Meyer; J. David Schneider; H. Vernon Smith; Michael Thuot; Thomas Zaugg; Robin Ferdinand

1998-01-01

207

10 keV X-Ray Phase-Contrast Microscopy for Observing Transparent Specimens  

Microsoft Academic Search

Hard X-ray phase-contrast microscopy has been performed with phase plates of tantalum using an X-ray beam from an undulator in SPring-8. The photon energy was set at 10 keV near the L3 absorption edge of tantalum (9.9 keV) in order to increase the phase contrast. To demonstrate its capability, a transparent specimen was imaged clearly in the reverse contrast with

Yasushi Kagoshima; Takashi Ibuki; Yoshiyuki Yokoyama; Yoshiyuki Tsusaka; Junji Matsui; Kengo Takai; Masataka Aino

2001-01-01

208

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

Microsoft Academic Search

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

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

1974-01-01

209

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

Microsoft Academic Search

High-statistics -decay measurements of ¹¹²Ag and ¹¹²In were performed to study the structure of the ¹¹²Cd 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 ¹¹²Sn, were determined to be 1871.137(72) keV (0{sup +} level) and 1870.743(54)

K. L. Green; P. E. Garrett; G. A. Demand; G. F. Grinyer; K. G. Leach; A. A. Phillips; M. A. Schumaker; C. E. Svensson; J. Wong; R. A. E. Austin; S. Colosimo; G. C. Ball; D. S. Bandyopadhyay; G. Hackman; A. C. Morton; C. J. Pearson; D. Cross; W. D. Kulp; J. L. Wood; S. W. Yates

2009-01-01

210

Gel behavior of keV ion irradiated polystyrene  

SciTech Connect

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

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

1988-10-17

211

Stopping Power of Thin Aluminum Foils for 12 TO 127 KEV Electrons  

Microsoft Academic Search

The stopping power of aluminum for electrons having energies of 10 to ; 125 kev was studied by measuring the average energy loss directly by calorimetric ; means. Two differert aluminum foils were studied of thicknesses 50.3 and 107.8 ; mu g\\/cm². At these thicknesses the scattering was not excessive for the ; incident electron energies used. The maximum path

Ford Kalil; W. G. Stone; H. H. Jr. Hubbell; R. D. Birkhoff

1959-01-01

212

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

213

An experimental and theoretical study of electronic excitation and charge transfer processes in collisions between Cs( 6 2 S 1\\/2 ) atoms and Na +( 1 S 0) ions in the 0.30–4.00 keV energy range  

Microsoft Academic Search

The collisional system Cs+Na+ with both species in their ground electronic state, has been studied using the crossed molecular beams technique and measuring the resulting fluorescent decay. Emissions from electronically excited Cs(62P3\\/2) and Cs(72P1\\/2,3\\/2) atoms have been detected as well as those from excited Na(32P1\\/2,3\\/2) and Na(42D3\\/2,5\\/2) produced by electron transfer. Cross-section values in the 0.30–4.00 keV energy range have

J. de Andrés; M. Sabidó; M. E. Aricha; M. Albert??; J. M. Lucas; F. X. Gadea; A. Aguilar

2002-01-01

214

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

Code of Federal Regulations, 2013 CFR

...America-United States Free Trade Agreement Rules of Origin...customary for the good. (a) Regional value content. If the good is subject to a regional value content requirement...be, in calculating the regional value content of the...

2013-04-01

215

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

216

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

217

First measurement of ˜10 keV neutral atoms in the low-latitude ionosphere  

NASA Astrophysics Data System (ADS)

Energetic neutral atoms (ENAs) with energies of 4 to 35 keV were measured at altitudes of 170 to 570 km by a new ENA instrument on board a sounding rocket. The instrument measured particles precipitating into the ionosphere from the equatorial region of the magnetosphere at a magnetic local time of ˜1830. The geomagnetic activity was quiet for a prolonged period before the launch. The measured ENA flux was ˜10² (cm² s str keV)-1 at energies of ˜10 keV. The energy spectrum is in a good agreement with an expected spectrum of hydrogen atoms originating from the ring current region as reported by Milillo et al. [1996]. The altitude profile is also discussed in terms of collisional interaction of ENAs with upper-atmospheric constituents.

Asamura, K.; Mukai, T.; Saito, Y.; Kazama, Y.; Machida, S.

218

Field-aligned precipitation of greater than 30-keV electrons  

NASA Technical Reports Server (NTRS)

A search through 2-3 months of data from Ogo 6 has revealed about 10 cases of field-aligned precipitation of electrons at energies greater than 30 keV. Brief descriptions are given of the four most spectacular of these events, in which the ratio between precipitated and trapped fluxes reached about 100 in one case. Preliminary indications are that such events occur mainly in the evening and midnight sectors and at high geomagnetic latitudes (usually at or above the trapping boundary for electrons with energies greater than 30 keV).

Williams, D. J.; Trefall, H.

1976-01-01

219

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

220

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

221

Construcao, calibracao e teste de uma camara de ionizacao para medidas de exposicao de raios-x e gama na regiao de 40 keV ate 1250 keV. (Construction, calibration and test of an ionization chamber for exposure measurement of x and gamma radiation in region from 40 keV to 1250 keV).  

National Technical Information Service (NTIS)

An unsealed thimble ionization chamber with connecting cable was designed, manufactured and tested at the IRD=CNEN, for exposure or exposure rate measurement of X or gamma rays in the energy range from 40 KeV up to Cobalt-60. Recommendations given by IEC,...

C. A. A. Campos

1982-01-01

222

The BeppoSAX 2-10 keV Survey (Giommi+, 2000)  

NASA Astrophysics Data System (ADS)

File table contains the name of the sources, their coordinates (J2000.0) and the measured flux detected by the BeppoSAX MECS instrument in the 2-10 keV energy band. Additional information (other designation, class and redshift) if available in literature is also provided. (1 data file).

Giommi, P.; Perri, M.; Fiore, F.

2000-11-01

223

Energetic (approx. 100keV) tailward-directed ion beam outside the Jovian plasma boundary  

Microsoft Academic Search

The hot plasma instrument on the Voyager-2 spacecraft measured a nearly monoenergetic (approx.100 keV) ion beam several hours after crossing the Jovian plasma boundary on the nightside of the planet. The beam, deduced to consist primarily of heavy ions, persisted for about four hours and originated from the general direction of Jupiter. The energy density of the beam was approx.

S. M. Krimigis; T. P. Armstrong; W. I. Axford; C. O. Bostrom; C. Y. Fan; G. Gloeckler; L.J. Lanzerotti; D. C. Hamilton; R. D. Zwickl

1980-01-01

224

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

225

The 7 keV axion dark matter and the X-ray line signal  

NASA Astrophysics Data System (ADS)

We propose a scenario where the saxion dominates the energy density of the Universe and reheats the standard model sector via the dilatonic coupling, while its axionic partner contributes to dark matter decaying into photons via the same operator in supersymmetry. Interestingly, for the axion mass ma?7 keV and the decay constant fa?10 GeV, the recently discovered X-ray line at 3.5 keV in the XMM Newton X-ray observatory data can be explained. We discuss various cosmological aspects of the 7 keV axion dark matter such as the production of axion dark matter, the saxion decay process, hot dark matter and isocurvature constraints on the axion dark matter, and the possible baryogenesis scenarios.

Higaki, Tetsutaro; Jeong, Kwang Sik; Takahashi, Fuminobu

2014-06-01

226

Degeneracy at 1871 keV in Cd112 and implications for neutrinoless double electron capture  

NASA Astrophysics Data System (ADS)

High-statistics ?-decay measurements of Ag112 and In112 were performed to study the structure of the Cd112 nucleus. The precise energies of the doublet of levels at 1871 keV, for which the 0+ member has been suggested as a possible daughter state following neutrinoless double electron capture of Sn112, were determined to be 1871.137(72) keV (04+ level) and 1870.743(54) keV (42+ level). The nature of the 04+ 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.; Austin, R. A. E.; Ball, G. C.; Bandyopadhyay, D. S.; Colosimo, S.; Cross, D.; Demand, G. A.; Grinyer, G. F.; Hackman, G.; Kulp, W. D.; Leach, K. G.; Morton, A. C.; Pearson, C. J.; Phillips, A. A.; Schumaker, M. A.; Svensson, C. E.; Wong, J.; Wood, J. L.; Yates, S. W.

2009-09-01

227

A possible line feature at 73 keV from the Crab Nebula  

NASA Technical Reports Server (NTRS)

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

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

1979-01-01

228

30- to 100-keV protons upstream from the earth's bow shock  

NASA Technical Reports Server (NTRS)

Protons of 30 to 100 keV are found upstream from the bow shock whenever interplanetary magnetic fields connect the spacecraft and bow shock. The protons do not appear upstream of a boundary determined by the solar wind speed (the speed at which the interplanetary field is being convected) and an effective upstreaming velocity of 2.5 to 3 times the solar wind speed along the field lines. It is believed that (1) the lower-energy (3-4 keV) protons accelerated and reflected by the bow shock and (2) the Alfven waves observed upstream are in some way responsible for the origin of the 30- to 100-keV protons in very large regions upstream from the bow shock.

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

1974-01-01

229

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

SciTech Connect

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

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

2010-02-15

230

Tomographic All-sky Imaging Above 200 keV With BATSE  

NASA Astrophysics Data System (ADS)

We describe a tomographic method of mapping the gamma-ray sky above 200 keV with earth-occultation data from BATSE, the Burst And Transient Source Experiment on the Compton Gamma-Ray Observatory (CGRO). The method combines good sensitivity with 0.5° angular resolution over the whole sky. Our previous occultation analysis of the BATSE data indicates the presence of a significant number of unmodeled cosmic sources. The Earth's horizon cuts the sky in a cycle that repeats with the 51 day precession of the CGRO orbit plane, which is reflected in periodic effects due to the uncatalogued sources. Such cycles are then a natural data unit for all-sky mapping by a tomographic method using the Radon transform. Because the airmass profile of the horizon is nearly independent of energy, we obtain 0.5° angular resolution over the entire low-energy gamma-ray region. To improve sensitivity, we subtract a phenomenological model for the non-cosmic gamma-ray background from the raw count data before performing the imaging analysis, which uses a simple planar approximation to the inverse Radon transform on a tiling of the sky. We present images in four broad energy bands (23-98 keV, 98-230 keV, 230-595 keV and 595-1800 keV) centered on selected sources to illustrate the power of this approach. Our preliminary results tentatively show several sources in the 230-595 keV and 595-1800 keV bands, which will be presented. We easily image the Crab in the 595-1800 keV band in a single precession cycle. With 64 cycles in the 9 year CGRO data set, we expect a flux-complete survey of the entire sky, with multiple independent sky maps achieving a combined sensitivity typically less than 125 mCrab near 1 MeV. This work has been supported by grants from NASA, JPL, and LSU.

Wheaton, William A.; Case, G. L.; Cherry, M. L.; Ling, J. C.; Lo, M. W.; Roland, J. M.; Shimizu, T.

2010-02-01

231

Calibration of the Galileo micro channel plate with the Xe7+ +Xe43+ ions in the energy range from 2 keV\\/1 up to 154 keV\\/q  

Microsoft Academic Search

The procedure of calibration of the detector assembly consisting of the two Galileo micro channel plates (MCPs) operated in a Chevron configuration is described. The current gains and the analog particle gains of the MCPs for Xe ions with charge states from q=7+ to q=43+ and ion impact energies to charge state ratios from 2 keV\\/q to 154 keV\\/q have

W. Mroz; D. Fry; A. Prokopuik; M. P. Stockli; B. Walch

1998-01-01

232

New measurement of the relative scintillation efficiency of xenon nuclear recoils below 10 keV  

SciTech Connect

Liquid xenon is an important detection medium in direct dark matter experiments, which search for low-energy nuclear recoils produced by the elastic scattering of WIMPs with quarks. The two existing measurements of the relative scintillation efficiency of nuclear recoils below 20 keV lead to inconsistent extrapolations at lower energies. This results in a different energy scale and thus sensitivity reach of liquid xenon dark matter detectors. We report a new measurement of the relative scintillation efficiency below 10 keV performed with a liquid xenon scintillation detector, optimized for maximum light collection. Greater than 95% of the interior surface of this detector was instrumented with photomultiplier tubes, giving a scintillation yield of 19.6 photoelectrons/keV electron equivalent for 122-keV {gamma} rays. We find that the relative scintillation efficiency for nuclear recoils of 5 keV is 0.14, staying constant around this value up to 10 keV. For higher energy recoils we measure a value of 0.21, consistent with previously reported data. In light of this new measurement, the XENON10 experiment's upper limits on spin-independent WIMP-nucleon cross section, which were calculated assuming a constant 0.19 relative scintillation efficiency, change from 8.8x10{sup -44} cm{sup 2} to 9.9x10{sup -44} cm{sup 2} for WIMPs of mass 100 GeV/c{sup 2}, and from 4.5x10{sup -44} cm{sup 2} to 5.6x10{sup -44} cm{sup 2} for WIMPs of mass 30 GeV/c{sup 2}.

Aprile, E.; Choi, B.; Giboni, K. L.; Lim, K.; Monzani, M. E.; Plante, G.; Santorelli, R.; Yamashita, M. [Department of Physics, Columbia University, New York, New York 10027 (United States); Baudis, L. [Physik-Institut, Universitaet Zuerich, CH-8057 Zuerich (Switzerland); Manalaysay, A. [Physik-Institut, Universitaet Zuerich, CH-8057 Zuerich (Switzerland); Department of Physics, University of Florida, Gainesville, Florida 32611 (United States)

2009-04-15

233

Resonant photoemission study of the electronic structure of 3 keV nitrogen-implanted tantalum  

Microsoft Academic Search

The electronic properties of tantalum nitride thin films grown by 3keV nitrogen implantation have been studied with resonant photoemission using synchrotron radiation. Resonant photoemission from the valence band was observed when the photon energy was in the neighborhood of the Ta5p-->5d , 5p-->6sp and 4f-->5d transition energies. The constant initial state curves show multiple resonance maxima that are explained in

A. Arranz; C. Palacio; J. Avila

2005-01-01

234

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

235

X-ray transmission of Kumakhov polycapillary lens up to 50 keV  

NASA Astrophysics Data System (ADS)

New series of polycapillary lens is developed for medium hard x-rays. At the x-ray energy about 50 keV these lenses give intensity gain in the focal spot (~O.15 mm dia.) at the distance ~0.5m more than two orders of magnitude compared to the direct beam through a pinhole. At 25 keV the gain exceeds 103. At 22 keV x-ray energy (Ag line) these lenses transmit more than 25% of radiation falling onto entrance window with resultant effective capture solid angles up to 5•10-4 steradian (25 mrad or 1.4 degree flat angle) and up to 3% with effective capture angles 5"10-5 steradian (8 mrad or 0.45 degree flat) at 50 keV. Presented are spectral transmission data for such lenses with focal distances 100 to 250 mm. Radial distribution of transmission over the lens input window is also measured. Experimental results are compared with computer calculation.

Cheremisin, S. M.; Gruev, D. I.; Nikitina, S. V.; Zaitsev, D. V.

2005-07-01

236

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

NASA Technical Reports Server (NTRS)

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

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

1972-01-01

237

Lantanides' Experimental L X-ray Fluorescence Cross Sections at 9 keV and 12 keV with Synchrotron Radiation  

NASA Astrophysics Data System (ADS)

Experimental determinations of L X-ray fluorescence cross sections for elements with 64 ? Z ? 70 at 9 keV and 12 keV were carried out with synchrotron radiation. The experimental setup provided a linearly polarized monoenergetic photon beam producing a very low background, which improved the signal to noise ratio and reduced the experimental uncertainties. Results of the experimental cross sections obtained for the L lines were grouped considering the transitions scheme, the energies of the emission lines and the detector's resolution. The data obtained were compared with theoretical data using two different data tables. A very good agreement was found between our experimental values and the theoretical values calculated using Puri's data. A new set of ?L1, f12 and f13 coefficients for Gd were also used to calculate theoretical cross sections and the experimenal values are in excellent agreement with them.

Barrea, Raúl A.; Bonzi, Edgardo V.

238

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

239

Generation of a 500-keV electron beam from a high voltage photoemission gun  

NASA Astrophysics Data System (ADS)

High-brightness, high-current electron guns for energy recovery linac light sources and high repetition rate X-ray free-electron lasers require an exit beam energy of >=500 keV to reduce space-charge induced emittance growth in the drift space from the gun exit to the following superconducting accelerator entrance. At the Japan Atomic Energy Agency, we have developed a DC photoemission gun employing a segmented insulator to mitigate the field emission problem, which is a major obstacle for operation of DC guns at >=500 kV. The first demonstration of generating a 500-keV electron beam with currents up to 1.8 mA is presented.

Nishimori, Nobuyuki; Nagai, Ryoji; Matsuba, Shunya; Hajima, Ryoichi; Yamamoto, Masahiro; Miyajima, Tsukasa; Honda, Yosuke; Iijima, Hokuto; Kuriki, Masao; Kuwahara, Makoto

2013-06-01

240

Searching for the 511 keV annihilation line from galactic compact objects with the IBIS gamma ray telescope  

NASA Astrophysics Data System (ADS)

Context. The first detection of a gamma ray line with an energy of about 500 keV from the center of our Galaxy dates back to the early seventies. Thanks to the astrophysical application of high spectral resolution detectors, it was soon clear that this radiation was due to the 511 keV photons generated by electron-positron annihilation. Even though the physical process are known, the astrophysical origin of this radiation is still a mystery. Aims: The spectrometer SPI aboard the INTEGRAL gamma-ray satellite has been used to produce the first all-sky map in light of the 511 keV annihilation, but no direct evidence of any 511 keV galactic compact objects has been found. Owing to its moderate angular resolution, these SPI data are still compatible with a distribution of point sources clustered in the bulge of our Galaxy. Thanks to the fine angular resolution and the large field of view, the IBIS imager on the INTEGRAL satellite gives us the unique opportunity to search for a possible 511 keV line from point sources associated to known objects, such as X-ray binaries, or supernovae, or even new ones. Methods: We present the first deep IBIS 511 keV all-sky map, obtained by applying standard analysis to about 5 years of data. Possible 511 keV signals are also searched over hour-day-month timescales. The IBIS sensitivity at 511 keV depends on the detector quantum efficiency at this energy and on the background. Both these quantities were estimated in this work. Results: We find no evidence of Galactic 511 keV point sources. With an exposure of 10 Ms, in the center of the Galaxy, we estimate a 1.6 × 10-4 ph cm-2 s-1 flux 2 sigma upper limit. A similar limit is given in a wide area in the Galactic center region with similar exposures. The IBIS 511 keV flux upper limits for microquasars and supernova remnants detected in the hard X domain (E > 20 keV) are also reported. Conclusions: Our results are consistent with a diffuse e + e - annihilation scenario. If positrons are generated in compact objects, we expect that a significant fraction of them propagate in the interstellar medium before they are annihilated away from their birth places.

De Cesare, G.

2011-07-01

241

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.

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

2014-01-01

242

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

NASA Astrophysics Data System (ADS)

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

Natsui, Takuya; Uesaka, Mitsuru; Yamamoto, Tomohiko; Sakamoto, Fumito; Hashimoto, Eiko; Kiwoo, Lee; Nakamura, Naoki; Yamamoto, Masashi; Tanabe, Eiji; Yoshida, Mitsuhiro; Higo, Toshiyasu; Fukuda, Shigeki

2009-03-01

243

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

244

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

PubMed

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

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

2014-01-01

245

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

NASA Technical Reports Server (NTRS)

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

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

1997-01-01

246

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

Microsoft Academic Search

Using simultaneous measurements of the upstream solar wind and of energetic electrons at geosynchronous orbit, we analyze the response of electrons over a wide energy range, 50 keV to 6 MeV, to solar wind variations. Enhancements of energetic electron fluxes over this whole energy range are modulated by the solar wind speed and the polarity of the interplanetary magnetic field

Xinlin Li; D. N. Baker; M. Temerin; G. Reeves; R. Friedel; C. Shen

2005-01-01

247

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

NASA Astrophysics Data System (ADS)

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

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

2006-06-01

248

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

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

249

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

NASA Technical Reports Server (NTRS)

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

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

1973-01-01

250

Free-electron maser operation at the 1 GHz\\/1 keV regime  

Microsoft Academic Search

The paper describes a free-electron maser (FEM) experiment operating in the low-frequency (? 1 GHz) low-energy (? 1 keV) regime. The table-top FEM device consists of a non-dispersive parallel-stripline waveguide and a planar folded-foil wiggler. The experimental results show a super-regenerative amplification. Oscillations are observed above a threshold of the wiggler field.

R. Drori; E. Jerby; A. Shahadi; M. Einat; M. Sheinin

1996-01-01

251

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

252

A 20 keV electron gun system for the electron irradiation experiments  

Microsoft Academic Search

An electron gun consisting of cathode, focusing electrode, control electrode and anode has been designed and fabricated for the electron irradiation experiments. This electron gun can provide electrons of any energy over the range 1–20keV, with current upto 50?A. This electron gun and a Faraday cup are mounted in the cylindrical chamber. The samples are fixed on the Faraday cup

S. K. Mahapatra; S. D. Dhole; V. N. Bhoraskar

2005-01-01

253

Monte Carlo Simulation of 1 eV 35 keV Electron Scattering in Teflon  

Microsoft Academic Search

A simple physical model of ≈1 eV 35 keV electron scattering in insulating polymers was proposed. A new correction to Slater's exchange potential was used for the description of low-energy elastic electron scattering. The simulation of electron trajectories was performed using the Monte Carlo technique. The integral and differential characteristics such as the total secondary electron yield and elastic and

Alexandre Palov; Haruhisa Fujii; Sanju Hiro

1998-01-01

254

30 keV to 2 MeV Boron implantation profiles in solids  

Microsoft Academic Search

Boron was implanted into several solids in the dose regime 10 to 10 ions\\/cm and at energies between some 10 keV and some MeV. Measurements of the corresponding depth distributions were performed by means of the B(n, ?0)Li(gnd) and B(n, ?1)Li*(1st) nuclear reaction techniques with thermal neutrons, and by SIMS. The results are compared to theoretical predictions.

D. Fink; L. Wang; J. P. Biersack; F. Jahnel

1990-01-01

255

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

257

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

258

On the unusual properties of the 282 keV state in 135Sb  

NASA Astrophysics Data System (ADS)

Recently the first excited state in 135Sb has been observed at the unexpectedly low excitation energy of only 282keV and interpreted as mainly d 5/2 proton coupled to the 134Sn core. Based on theoretical considerations it was suggested that its low excitation energy is related to a relative shift of the proton d 5/2 and g 7/2 orbits induced by the neutron excess. We have measured the lifetime of the 282keV state by the advanced time-delayed ???( t) method. The measured half-life, T 1/2 = 6.1(4)ns, yields exceptionally low limits of B( M1;5/21 +?7/21 +)?3.0×10-4 ? 2 N and B( E2;5/21 +?7/21 +)?54 e 2 fm 4. These strongly hindered M1 and slow E2 transition rates are similar to those for the transition de-populating the first excited state at 405keV in 211Bi. Results of shell model calculations with realistic interactions are presented. The M1 decay rate was found to be extremely sensistive both to the wave function and to the M1 effective operator.

Korgul, A.; Mach, H.; Brown, B. A.; Covello, A.; Gargano, A.; Fogelberg, B.; Kurcewicz, W.; Werner-Malento, E.; Orlandi, R.; Sawicka, M.

2007-04-01

259

The 511 keV emission from positron annihilation in the Galaxy  

NASA Astrophysics Data System (ADS)

The first ?-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 (˜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.; Ferrière, K.; Guessoum, N.; Jean, P.; Knoedlseder, J.; Marcowith, A.; Moskalenko, I. V.; Strong, A.; Weidenspointner, G.

2011-07-01

260

Energetic /approximately 100-keV/ tailward-directed ion beam outside the Jovian plasma boundary  

NASA Technical Reports Server (NTRS)

The hot plasma instrument on the Voyager-2 spacecraft measured a nearly monoenergetic (100 keV) ion beam several hours after crossing the Jovian plasma boundary on the nightside of the planet. The beam, deduced to consist primarily of heavy ions, persisted for about four hours and originated from the general direction of Jupiter. The energy density of the beam was about several times the energy density of the magnetic field (beta greater than 1). This beam, a product of an as yet not understood Jovian plasma acceleration mechanism, provides a dramatic example of the energetic dynamics of Jupiter's magnetosphere.

Krimigis, S. M.; Bostrom, C. O.; Armstrong, T. P.; Axford, W. I.; Fan, C. Y.; Gloeckler, G.; Hamilton, D. C.; Lanzerotti, L. J.; Zwickl, R. D.

1980-01-01

261

The Measurement of X Rays 30 Kev in the Brazilian Magnetic Anomaly with Omnidirectional Detectors Medidas de Raios-X 30 Kev COM Detetores Oni Direcionais NA Anomalia Magnetica Brasileira.  

National Technical Information Service (NTIS)

Atmospheric X-Rays measurements, with energies or = 30 KeV, were performed at Sao Jose dos Campos-Brazil (23 S, 46 W Geographic) on April 14 and December 19, 1981, using omnidirectional NaI (Tl) scintillation counters on board stratospheric balloons. The ...

O. Pinto A. W. L. Gonzales A. L. D. Degonzales I. M. Martin S. L. G. Dutra

1982-01-01

262

Global Continuous Symmetry and the 17keV Neutrino.  

National Technical Information Service (NTIS)

The effects of a very small explicit breaking of a continuous global symmetry advocated in successful models for the 17 keV neutrino are discussed. It is shown that these effects are substantial, even if the explicit breaking terms are suppressed by power...

D. Grasso M. Lusignoli M. Roncadelli

1992-01-01

263

8 keV x-ray zone plates.  

National Technical Information Service (NTIS)

Sputtered-sliced transmissive x-ray zone plates consisting of concentric rings of Al and Cu have been fabricated and tested using the 8.04 keV k-(alpha) line from Cu. Due to the need for high aspect ratios for this 1.54 (Angstrom) radiation, magnetron spu...

R. M. Bionta E. Ables O. Clamp O. D. Edwards P. C. Gabriele

1989-01-01

264

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

265

Power Supply for the Lbl 40 Kev Neutral Beam Source.  

National Technical Information Service (NTIS)

A 20 keV, 50 Amp, 10 millisec pulse D exp 0 Neutral Beam Source at the Lawrence Berkeley Laboratory that serves as the prototype for 12 similar sources now in operation on the 2XIIB Mirror Machine at the Lawrence Livermore Laboratory has been recently upg...

W. R. Baker M. L. Fitzgerald V. J. Honey

1975-01-01

266

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

267

Use of 123 KeV gamma -Radiation for Investigation of Substance Near the Critical Point. Experimental Apparatus.  

National Technical Information Service (NTIS)

Experimental apparatus for investigation of substance near the critical point by transmission of gamma -rays with 123 keV energy has been designed and tested. The apparatus works within the 285-340 K temperature range, with the approach to critical temper...

B. P. Osipenko A. P. Simkina V. G. Tishin

1987-01-01

268

0-600 kev GAMMA-RAY SPECTRA FROM THERMAL NEUTRON CAPTURE IN THE REGION A = 104 TO 198  

Microsoft Academic Search

The energies and absolute intensities of prominent peaks in the 0-600 ; kev region of the gamma-ray spectrum following thermal neutron capture have been ; measured with a single NaI(T1) scintillation spectrometer. The elements ; investigated were rhodium, silver, cadmium, indium, antimony, tellurium, iodine, ; samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ; hafnium, tantalum, rhenium, iridium, platinum, and

James Draper

1959-01-01

269

0-600 kev Gamma-Ray Spectra from Thermal Neutron Capture in the Region A=104 to 198  

Microsoft Academic Search

The energies and absolute intensities of prominent peaks in the 0-600 kev region of the gamma-ray spectrum following thermal neutron capture have been measured with a single NaI(Tl) scintillation spectrometer. The elements investigated were rhodium, silver, cadmium, indium, antimony, tellurium, iodine, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, hafnium, tantalum, rhenium, iridium, platinum, and gold.

James E. Draper

1959-01-01

270

Multiple scattering of 5 - 30 keV electrons in evaporated metal films III: Backscattering and absorption  

Microsoft Academic Search

Measurements have been made of the fraction of an electron beam backscattered from thin films of copper and gold at incident energies from 5 to 25 kev. The results from very thin films indicate that approximately 50% of backscattering from a solid target must be due to single scattering. A comparison with existing theories shows that the results can be

V. E. Cosslett; R. N. Thomas

1965-01-01

271

OSSE observations of galactic 511 keV annihilation radiation  

NASA Technical Reports Server (NTRS)

The Oriented Scintillation Spectrometer Experiment (OSSE) on the Compton Gamma-Ray Observatory has performed several observations of the galactic plane and galactic center region to measure the distribution of galactic 511 keV positron annihilation radiation. Preliminary analysis of data collected during the observation of the galactic center region over the period 13-24 Jun. 1991, indicates the presence of a 511 keV line and positronium continuum superimposed on a power-law continuum. The line of flux was found to be (2.7 +/- 0.5) x 10(exp -4) gamma/sq cm sec, with a positronium fraction of (0.9 +/- 0.2). The 3(sigma) upper limit to daily variations in the 511 keV line flux from the mean during the observation interval is 3 x 10(exp -4) gamma/sq cm sec. If all of the observed annihilation radiation is assumed to originate from the x-ray source 1E 1740.7-2942, the corresponding 511 keV line flux would be (3.0 +/- 0.6) x 10(exp -4) gamma/sq cm sec. The 3(sigma) upper limit for 511 keV line emission from the x-ray binary GX1+4 is 6 x 10(exp -4) gamma/sq cm sec. Results from the galactic plane observations at galactic longitudes of 25 degrees (16-21 Aug. 1991) and 339 degrees (6-11 Sep. 1991) suggest that the emission is concentrated near the galactic center. The observations and the preliminary results are described.

Purcell, W. R.; Grabelsky, D. A.; Johnson, W. N.; Jung, G. V.; Kinzer, R. L.; Kurfess, J. D.; Strickman, M. S.; Ulmer, M. P.

1992-01-01

272

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

NASA Astrophysics Data System (ADS)

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

Midgley, S. M.

2013-02-01

273

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

PubMed

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

Midgley, S M

2013-02-21

274

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

275

Correlating few keV Energetic Neutral Atoms with soft x-rays  

NASA Astrophysics Data System (ADS)

The discovery of a bright 'ribbon' of Energetic Neutral Atom (ENA) emission by the Interstellar Boundary Explorer (IBEX) was both unexpected and exciting. Although there are a number of theories about the origin of this structure, none of them fully work, and the ribbon is still a puzzle. The ribbon is brightest at a few keV, which begs the question of whether it is visible in photons. Under a Science Innovation Fund grant at GSFC, we have performed detailed numeric correlation of the energetic data from IBEX and soft x-rays from ROSAT and present preliminary results from this study including upper limits on x-ray emission associated with the ENA ribbon. Figure 1: Energetic neutral atom emission map from IBEX in galactic coordinates. The energy range is 0.9 - 1.5 keV. Figure 2: Soft x-ray background emission from the ROSAT all-sky survey in galactic coordinates from .1-2 keV

Summerlin, E. J.; Christian, E. R.; Snowden, S. L.

2013-12-01

276

X-ray (17 -- 99-keV) diagnostics for the 200-TW Trident Laser  

NASA Astrophysics Data System (ADS)

The sub-ps Trident laser can deliver >100 J on target. The target irradiance is ˜10^20 W/cm^2. X-ray diagnostics include a Laue x-ray spectrograph, a Ross filter pair to measure conversion efficiency of laser light to K-shell emission, and a single-photon-counting x-ray CCD camera. For the Laue instrument, we discuss design features used to limit corruption of the recorded spectra by ˜MeV electrons and bremsstrahlung: a tungsten shield in the front, low-Z, thick-wall construction materials, magnetic traps, light traps, and a special sandwich-style film holder. For the Laue geometry where a LiF 200 crystal has a bandpass of 17 - 70 keV, LiF 220 shifts the bandpass to 24 - 99 keV. The sensitivity of Si p-i-n diodes is adequate to record x-ray emission up to ˜100 keV. With a carefully matched Ross filter pair, we may estimate the signal between the filter edges of two channels through subtraction of signals. The K-shell emission is expected to exceed the continuum contribution to the signal. These instruments will be employed to optimize the efficiency of x-ray backlighters in this energy range. The x-ray CCD is discussed in a parallel poster.

Cobble, James; Workman, Jonathan; Vutisalchavakul, Nalin

2008-11-01

277

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

NASA Technical Reports Server (NTRS)

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

Bleach, R. D.

1972-01-01

278

The X-ray spectrum of AM Herculis from 0.1 to 150 keV  

NASA Technical Reports Server (NTRS)

No significant flux at 100 keV was detected in the observations by the HEAO 1 satellite (March and April of 1978) and in several OSO 7 observations. The spectrum above 2 keV can be fitted by a composite thermal bremsstrahlung model that includes an approximation to the albedo expected from the white dwarf. The bremsstrahlung kT sub e from this model (30.9 + or - 4.5 keV) implies a white dwarf mass in excess of 0.6 solar mass. An emission feature at 6.5 + or - 0.15 keV and equivalent width of 0.8 + or - 0.1 keV is confirmed; it is thought that this might be due to fluorescence from the white dwarf by the bremsstrahlung from a small thin shocked region. It is noted that the continuum could also have been steepened at high energy in scattering in the accretion column, but the line photons cannot have gone through the same optical depths.

Rothschild, R. E.; Gruber, D. E.; Knight, F. K.; Matteson, J. L.; Nolan, P. L.; Swank, J. H.; Holt, S. S.; Serlemitsos, P. J.; Mason, K. O.; Tuohy, I. R.

1981-01-01

279

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

280

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

281

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

PubMed

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. PMID:24125368

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

2013-09-01

282

Study on the keV neutron capture reaction in 56Fe and 57Fe  

NASA Astrophysics Data System (ADS)

The neutron capture cross-sections and the radiative capture gamma-ray spectra from the broad resonances of 56Fe and 57Fe in the neutron energy range from 10 to 90keV and 550keV have been measured with an anti-Compton NaI(Tl) detector. Pulsed keV neutrons were produced from the 7Li 7Be reaction by bombarding the lithium target with the 1.5ns bunched proton beam from the 3MV Pelletron accelerator. The incident neutron spectrum on a capture sample was measured by means of a time-of-flight (TOF) method with a 6Li -glass detector. The number of weighted capture counts of the iron or gold sample was obtained by applying a pulse height weighting technique to the corresponding capture gamma-ray pulse height spectrum. The neutron capture gamma-ray spectra were obtained by unfolding the observed capture gamma-ray pulse height spectra. To achieve further understanding on the mechanism of neutron radiative capture reaction and study on physics models, theoretical calculations of the -ray spectra for 56Fe and 57Fe with the POD program have been performed by applying the Hauser-Feshbach statistical model. The dominant ingredients to perform the statistical calculation were the Optical Model Potential (OMP), the level densities described by the Mengoni-Nakajima approach, and the -ray transmission coefficients described by -ray strength functions. The comparison of the theoretical calculations, performed only for the 550keV point, show a good agreement with the present experimental results.

Wang, Taofeng; Lee, Manwoo; Kim, Guinyun; Ro, Tae-Ik; Kang, Yeong-Rok; Igashira, Masayuki; Katabuchi, Tatsuya

2014-03-01

283

The 2-10 keV emission properties of PSR B1937+21  

NASA Astrophysics Data System (ADS)

We present the results of a BeppoSAX observation of the fastest pulsar known: PSR B1937+21. The ~ 200 ks observation (78.5 (34) ks MECS (LECS) exposure times) allowed us to investigate with high statistical significance both the spectral properties and the pulse profile shape. The absorbed power law spectral model gave a photon index of ~1.7 and NH ~ 2.3 x 1022 cm-2. These values explain both a.) the ROSAT non-detection and b.) the deviant estimate of a photon index of 0.8 obtained by ASCA. The pulse profile appears, for the first time, clearly double peaked with the main component much stronger than the other. The statistical significance is 10 sigma (main peak) and 5 sigma (secondary peak). The 1.6-10 keV pulsed fraction is consistent with 100%; only in the 1.6-4 keV band there is a ~ 2sigma indication for a DC component. The secondary peak is detected significantly only for energies above 3-4 keV. The unabsorbed (2-10 keV) flux is F2-10 = 3.7 x 10-13 \\fu, implying a luminosity of LX = 4.6 x 1031 Theta (d/3.6 kpc)2 erg s-1 and an X-ray efficiency of ? = 4× 10-5, Theta, where Theta is the solid angle spanned by the emission beam. These results are in agreement with those obtained by ASCA.

Nicastro, L.; Cusumano, G.; Kuiper, L.; Becker, W.; Hermsen, W.; Kramer, M.

284

Relative detection efficiency of back- and front-illuminated charge-coupled device cameras for x-rays between 1 keV and 18 keV  

SciTech Connect

High-resolution x-ray measurements were performed with a von Hamos-type bent crystal spectrometer using for the detection of the diffracted photons either a back-illuminated charge-coupled device (CCD) camera or a front-illuminated one. For each CCD the main x-ray emission lines (e.g., K{alpha}, K{beta}, L{alpha}, and L{beta}) of a variety of elements were measured in order to probe the performances of the two detectors between 1 and 18 keV. From the observed x-ray lines the linearity of the energy response, the noise level, the energy resolution, and the quantum efficiency ratio of the two CCDs were determined.

Szlachetko, J.; Dousse, J.-Cl.; Hoszowska, J.; Berset, M.; Cao, W.; Szlachetko, M.; Kavcic, M. [Department of Physics, University of Fribourg, CH-1700 Fribourg (Switzerland); J. Stefan Institute, SI-1001 Ljubljana (Slovenia)

2007-09-15

285

Relative detection efficiency of back- and front-illuminated charge-coupled device cameras for X-rays between 1 keV and 18 keV.  

PubMed

High-resolution x-ray measurements were performed with a von Hamos-type bent crystal spectrometer using for the detection of the diffracted photons either a back-illuminated charge-coupled device (CCD) camera or a front-illuminated one. For each CCD the main x-ray emission lines (e.g., Kalpha, Kbeta, Lalpha, and Lbeta) of a variety of elements were measured in order to probe the performances of the two detectors between 1 and 18 keV. From the observed x-ray lines the linearity of the energy response, the noise level, the energy resolution, and the quantum efficiency ratio of the two CCDs were determined. PMID:17902942

Szlachetko, J; Dousse, J-Cl; Hoszowska, J; Berset, M; Cao, W; Szlachetko, M; Kavcic, M

2007-09-01

286

Relative detection efficiency of back- and front-illuminated charge-coupled device cameras for x-rays between 1 keV and 18 keV  

NASA Astrophysics Data System (ADS)

High-resolution x-ray measurements were performed with a von Hamos-type bent crystal spectrometer using for the detection of the diffracted photons either a back-illuminated charge-coupled device (CCD) camera or a front-illuminated one. For each CCD the main x-ray emission lines (e.g., K?, K?, L?, and L?) of a variety of elements were measured in order to probe the performances of the two detectors between 1 and 18 keV. From the observed x-ray lines the linearity of the energy response, the noise level, the energy resolution, and the quantum efficiency ratio of the two CCDs were determined.

Szlachetko, J.; Dousse, J.-Cl.; Hoszowska, J.; Berset, M.; Cao, W.; Szlachetko, M.; Kav?i?, M.

2007-09-01

287

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

SciTech Connect

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

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

1982-11-01

288

Analyzing power and yield measurements of the ^13C(d,n0)^14N Reaction between 280-460 keV  

Microsoft Academic Search

One of the poorly understood reactions that may contribute to heavy element inhomogeneous nucleosynthesis is the ^13C(d,n0)^14N reaction. To understand the dynamics of this reaction, we have measured the yield and vector analyzing power of the n0 group in the deuteron energy range from 280 keV to 460 keV. Neutrons were produced by a deuterium beam from the atomic beam

Evan Sand; S. Stave; M. W. Ahmed; S. S. Henshaw; H. R. Weller; R. M. Prior; M. C. Spraker

2008-01-01

289

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

Microsoft Academic Search

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

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

2002-01-01

290

Oscillations observed in electrons and scattered protons from 30–100 keV protons transiting a Si\\/Lexan\\/C layered foil  

Microsoft Academic Search

A layered foil of 4.5 ?g\\/cm2 Si, 3.6 ?g\\/cm2 Lexan, and 1.0 ?g\\/cm2 C was bombarded by protons between 30 and 100 keV. The electron yields from the Si and C surfaces at ? = 0° (unscattered), 45° (forward), and 135° (backward) with respect to the beam direction were measured at proton energies 30, 60 and 90 keV. The scattered-proton

C. C. Hsu; T. C. Chu; K. C. Hsieh; Y. C. Chang; C. C. Lo; W. C. Chiou

1996-01-01

291

511 keV photons from color superconducting dark matter.  

PubMed

We discuss the possibility that the recent detection of 511 keV gamma rays from the galactic bulge, as observed by the International Gamma-Ray Astrophysics Laboratory, can be naturally explained by the supermassive very dense droplets (strangelets) of dark matter. These droplets are assumed to be made of ordinary light quarks (or antiquarks) condensed in a nonhadronic color superconducting phase. The droplets can carry electrons (or positrons) in the bulk or/and on the surface. The e(+)e(-) annihilation events take place due to the collisions of electrons from the visible matter with positrons from dark matter droplets which may result in the bright 511 keV gamma-ray line from the bulge of the Galaxy. PMID:15783469

Oaknin, David H; Zhitnitsky, Ariel R

2005-03-18

292

Desorption Induced by KEV Molecular and Cluster Projectiles  

Microsoft Academic Search

A new experimental method has been developed for studying negative secondary ion (SI) emission from solid surfaces bombarded by polyatomic primary ions of 5 to 30 keV. The method is based on the time-of-flight (TOF) analysis of primary ions which are produced by either ^ {252}Cf fission fragment induced desorption or by extraction from a liquid metal ion source, and

Matthew Glenn Blain

1990-01-01

293

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

294

Zeptosecond high harmonic keV x-ray waveforms driven by midinfrared laser pulses.  

PubMed

We demonstrate theoretically that the temporal structure of high harmonic x-ray pulses generated with midinfrared lasers differs substantially from those generated with near-infrared pulses, especially at high photon energies. In particular, we show that, although the total width of the x-ray bursts spans femtosecond time scales, the pulse exhibits a zeptosecond structure due to the interference of high harmonic emission from multiple reencounters of the electron wave packet with the ion. Properly filtered and without any compensation of the chirp, regular subattosecond keV waveforms can be produced. PMID:23909315

Hernández-García, C; Pérez-Hernández, J A; Popmintchev, T; Murnane, M M; Kapteyn, H C; Jaron-Becker, A; Becker, A; Plaja, L

2013-07-19

295

Interaction of 662-keV photons with some solutions of urea  

SciTech Connect

Total mass attenuation coefficients of aqueous solutions of urea, having concentrations ranging from 0.06 to 0.22 g/cm{sup 3}, have been determined by performing transmission experiments in a narrow beam geometry at 662 keV. The sphere transmission method has also been employed for the direct measurement of mass energy absorption coefficients of these solutions by placing a point source of {sup 137}Cs inside a spherical shell. Analysis of the experimental data in terms of cross sections and effective atomic numbers is presented.

Singh, K.; Gagandeep; Lark, B.S. [Guru Nanak Dev Univ., Amritsar (India); Sahota, H.S. [Punjabi Univ., Patiala (India). Dept. of Physics

1999-05-01

296

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

NASA Technical Reports Server (NTRS)

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

Barengoltz, J. B.; Brady, J.

1977-01-01

297

Nuclear resonant scattering of synchrotron radiation from 161Dy at 25.61 keV  

NASA Astrophysics Data System (ADS)

Nuclear resonant scattering of synchrotron radiation from the 25.6 keV level of 161Dy is studied with two techniques: nuclear forward scattering (NFS) and nuclear incoherent scattering (NIS). NFS time spectra of Dy metal are measured at temperatures ranging from 15 K to 80 K. They reveal electron spin relaxation in ferromagnetic dysprosium with long relaxation times of simeq 10 30 ns. NIS energy spectra of Dy2O3 at room temperature are measured with meV resolution. Scattering accompanied by phonon excitation is observed.

Shvyd'ko, Yu. V.; Gerken, M.; Franz, H.; Lucht, M.; Gerdau, E.

2001-10-01

298

Metastable dark matter mechanisms for INTEGRAL 511 keV ? rays and DAMA/CoGeNT events  

NASA Astrophysics Data System (ADS)

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

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

2011-04-01

299

Application of keV and MeV ion microbeams through tapered glass capillaries  

NASA Astrophysics Data System (ADS)

We have developed a method to produce micrometer-sized beams of keV energy highly charged ions (HCIs) and MeV energy protons/helium ions with tapered glass capillary optics for the applications of micrometer sized surface modifications and a biological tool, respectively. The transmission experiments of keV HCIs through the glass capillaries show a density enhancement of about 10, beam guiding up to 5°, and the extracted beam keeping the initial charge-state. The combination of MeV ion beams and the capillary with a thin end window at its outlet was used for the irradiation of a part of nucleus of a HeLa cell in culture solution. Escherichia coli cells are irradiated by MeV proton microbeam to determine the minimum dose to stop the single flagellar motor. Scanning irradiation of polymer surface by the beam extracted from the capillary in solution containing acrylic acid was found to provide a deposition layer with large affinity with water.

Ikeda, T.; Kojima, T. M.; Kobayashi, T.; Meissl, W.; Mäckel, V.; Kanai, Y.; Yamazaki, Y.

2012-11-01

300

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

SciTech Connect

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

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

1998-02-01

301

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

SciTech Connect

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

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

1997-10-01

302

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

303

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

304

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

305

Cross section measurements of the B10(d,n0)C11 reaction below 160 keV  

NASA Astrophysics Data System (ADS)

New data were taken at the Triangle Universities Nuclear Laboratory to investigate the plausibility of using low energy deuterons and the B10(d,n)C11 reaction as a portable source of 6.3 MeV neutrons. Analysis of the data at and below incident deuteron energies of 160 keV indicates an n0 neutron cross section that is lower than previous estimates by at least three orders of magnitude. In separate runs, deuterons with two different energies (160 and 140 keV) were stopped in a B10 target. The resulting n0 neutrons of approximately 6.3 MeV were detected at angles between 0° and 150°. The angle integrated yields were used to determine the astrophysical S factor for this reaction assuming a constant value for the S factor below 160 keV. The cross sections reported between 130 and 160 keV were calculated using the extracted value of the S factor. The measured n0 cross section is several orders of magnitude smaller than previous results, thus eliminating B10(d,n)C11 as a portable source of intense neutrons with low energy deuteron beams on the order of tens of microamps. In order to gain insight into the reaction dynamics at these low energies the cross section results have been compared with results from calculations using the distorted wave Born approximation (DWBA) and a detailed Hauser-Feshbach calculation performed by the authors. The angular distribution is consistent with the Hauser-Feshbach calculation suggesting a statistical compound nucleus reaction rather than a direct reaction.

Stave, S.; Ahmed, M. W.; Antolak, A. J.; Blackston, M. A.; Crowell, A. S.; Doyle, B. L.; Henshaw, S. S.; Howell, C. R.; Kingsberry, P.; Perdue, B. A.; Rossi, P.; Prior, R. M.; Spraker, M. C.; Weller, H. R.

2008-05-01

306

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

307

Centaurus A (NGC 5128) at 2 keV--2. 3 MeV: HEAO 1 observations and implications  

SciTech Connect

The nearby active-nucleus galaxy Centaurus A (NGC 5128) has been studied at 2 keV--2.3 MeV using data from both the UCSD/MIT hard X-ray and low energy ..gamma..-ray instrument and from the GSFC/CIT cosmic X-ray experiment on HEAO 1. We find that an E/sup -1.60plus-or-minus0.03/ power law spectrum breaking to E/sup -2.0plus-or-minus0.2/ at 140 keV best describes the 1978 January and July data. The average intensity was 50% higher during the January observations. We have searched our data for faster variations and set limits in several energy ranges over times from fractions of a day to several days. Upper limits to unresolved lines at 511 keV and 1.6 MeV are 6.5 x 10/sup -4/ photons cm/sup -2/ s/sup -1/ and 2.2 x 10/sup -4/ photons cm/sup -2/ s/sup -1/, respectively, at the 90% confidence level. Continuation of the observed power law to higher energies is used to constrain various models of energy generation in the nucleus of NGC 5128.

Baity, W.A.; Rothschild, R.E.; Lingenfelter, R.E.; Stein, W.A.; Nolan, P.L.; Gruber, D.E.; Knight, F.K.; Matteson, J.L.; Peterson, L.E.; Primini, F.A.; Levine, A.M.; Lewin, W.H.G.; Mushotzky, R.F.; Tennant, A.F.

1981-03-01

308

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

309

Construction of a 300-keV compact ion microbeam system with a three-stage acceleration lens  

NASA Astrophysics Data System (ADS)

Hydrogen ion microbeams were experimentally formed at beam energies below 150 keV using a 300-keV compact microbeam system that was constructed at the Japan Atomic Energy Agency. This paper is a preliminary report on the performance of the three-stage acceleration lens used in the compact microbeam system. This system consists of a three-stage acceleration lens and a plasma-type ion source. Since the three-stage acceleration lens was designed to simultaneously accelerate and focus the ion beam, the compact microbeam system is only about 1-m high and can be placed in a small experimental room. To evaluate the effectiveness of the three-stage acceleration lens, experimentally measured beam sizes are compared with theoretically calculated ones. The calculated and measured beam sizes were consistent within 10%. This shows that the three-stage acceleration lens is effective as a focusing lens for forming microbeams.

Ishii, Yasuyuki; Ohkubo, Takeru; Kojima, Takuji; Kamiya, Tomihiro

2014-08-01

310

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

311

Detection of an Unexplained Emission Line at 3.56 keV  

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

312

The geographical distribution of difference 100-keV electrons above the earth's atmosphere  

NASA Technical Reports Server (NTRS)

Modern soft X-ray astronomical observations are made with large-area proportional counters that have very thin plastic windows. The counters are consequently very sensitive to low energy electrons. An electron with only a few keV of energy can penetrate a typical window, and a flux of approximately 100 electrons per square centimeter sec-ster can double the background counting rate during a typical observation. These electrons produce an undersiable effect which, is impossible to distinguish from X ray data. Consequently, an electron-free region is needed for accurate astronomical observations. Geographical regions of weak electron flux from low altitude satellite data are derived. These regions can be compared with the locations of rocket launching sites. The best sites should be those farthest from electron regions.

Seward, F. D.

1974-01-01

313

Current transmission and charge deposition in polyethyleneterephthalate (PETP) irradiated with 10–50 keV electrons  

Microsoft Academic Search

Electron transmission through and charge deposition in polyethyleneterephthalate (PETP) are investigated by means of current measurements on and behind 2 to 46µm thick absorber foils. The results obtained for electron-beam energies ranging from 10 to 50 keV can be represented in one single reduced transmission curve (master curve). The normalised charge-deposition profile in thin PETP is calculated from this curve.

B. Gross; R. Gerhard-Multhaupt; K. Labonte; A. Berraissoul

1984-01-01

314

keV electron heating in laser-cluster interaction probed by X-ray and electron spectroscopy  

NASA Astrophysics Data System (ADS)

The interaction of intense laser pulses with nanoscopic rare-gas clusters provides a testing ground for laser-atom interaction at solid-state densities. We investigate the driven electronic dynamics on the femtosecond time scale both experimentally and theoretically using two complementary observables: the laser intensity dependence of characteristic X-ray emission and of high-energy (keV) electron spectra.

Yin, H.; Wachter, G.; Deiss, C.; Lemell, C.; Burgdörfer, J.; Lamour, E.; Prigent, C.; Ramond, C.; Rozet, J. P.; Steydli, S.; Trassinelli, M.; Vernhet, D.

2014-04-01

315

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

316

The colouration of CaF2 crystals by keV and GeV ions  

Microsoft Academic Search

CaF2 crystals have been implanted with a variety of ions of widely different energies and mass. Effects have been monitored using optical absorption in the range 120-750 nm. This includes the vacuum UV region. For 100 keV ions (Al, Mg, Kr) we observe extrinsic colloid bands in the case of implanted metal ions at high fluences (10(17) ions cm(2) )

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

2002-01-01

317

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

NASA Technical Reports Server (NTRS)

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

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

1996-01-01

318

Elemental composition effects on self-absorption for photons below 100 keV in gamma-ray spectrometry  

NASA Astrophysics Data System (ADS)

The influence of elemental composition in the self-absorption phenomenon is observed. The effective atomic number (Zeff) is used to explain this influence for energies below 100 keV. Monte Carlo simulations based on MCNPX and GESPECOR are used to demonstrate the separate impact of Zeff and density ? on the self-absorption for a given extended sample. Results obtained by simulation are in good agreement with those obtained by the transmission method.

Dziri, S.; Nachab, A.; Nourreddine, A.; Sellam, A.; Pape, A.

2014-07-01

319

Energetic Particle Events (> or =30 keV) of Jovian origin observed by Voyager 1 and 2 in interplanetary space  

Microsoft Academic Search

Short-lived and long-lived ion flux increases (E> or =30 keV) of Jovian origin have been observed by the low energy charged particle (LECP) instrumnet on the Voyager 1 and 2 spacecraft. The short-lived events are observed more than 860 R\\/sub J\\/ upstream and more than 1500 R\\/sub J\\/ downstream of Jupiter. Observations of long-lived events appear to be confined to

R. D. Zwickl; S. M. Krimigis; J. F. Carbary; E. P. Keath; T. P. Armstrong; D. C. Hamilton; G. Gloeckler

1981-01-01

320

A Study of the Beam-Foil Excitation Mechanism Using 30-300 keV He+ Projectiles  

Microsoft Academic Search

Beam-foil excitation functions have been measured for some optical transitions in neutral He (singly as well as doubly excited) and ionized He in the projectile energy range 30-300 keV. The excitation functions have been converted into relative population functions, which for levels within individual level schemes are proportional. The three sets of population functions have been linked by two parameters,

B. Dynefors; I. Martinson; E. Veje

1976-01-01

321

Characteristic x-ray production by argon projectiles moving in graphite targets between 30 and 200 keV  

Microsoft Academic Search

Thick-target yields and x-ray spectra have been measured for argon ions ; impinging on graphite targets at energies between 30 and 200 keV. The thick-; target yields of carbon K-shell and argon L-shell x rays are analyzed on the ; basis of a simple model involving multiple collisions and molecular-orbital ; promotions. The analysis results in average argon L-shell fluorescence

R. J. Fortner; J. D. Garcia

1975-01-01

322

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

NASA Astrophysics Data System (ADS)

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

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

2011-10-01

323

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

PubMed

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

Tereshchenko, Evgeny E; Moiseev, Nikolay

2012-09-01

324

Sputtering of (100) Si by 350 keV Co implantation  

NASA Astrophysics Data System (ADS)

Silicon (100) substrates have been implanted with 350 keV Co to fluences in the range 7.2 × 10 15 to 3.3 × 10 17 Co/cm 2 at temperatures near 100 ° C and 450 ° C. Rutherford backscattering profiles of the implanted Co were analyzed by the computer code MEASTRI to extract values for the sputtering coefficient, S, of Si by Co at these temperatures. At the lower temperatures S =1.1± 0.2 results from the analysis, while at 450 °C we obtain S=1.8 ± 0.2. The value predicted by the Matsunanu/Yamamura formula is S = 1.6. Our results are consistent with those of Nizam and Benazeth-Colombie which show a similar variation in S for 40 keV Ar + bombardment of (100) Si in the temperature range 50-550 °C. This temperature variation is interpreted as due to an altered surface binding energy resulting from surface rearrangement at the higher temperatures.

Brice, D. K.; Barbour, J. C.

1989-04-01

325

A cryogenic electrostatic trap for long-time storage of keV ion beams.  

PubMed

We report on the realization and operation of a fast ion beam trap of the linear electrostatic type employing liquid helium cooling to reach extremely low blackbody radiation temperature and residual gas density and, hence, long storage times of more than 5 min which are unprecedented for keV ion beams. Inside a beam pipe that can be cooled to temperatures <15 K, with 1.8 K reached in some locations, an ion beam pulse can be stored at kinetic energies of 2-20 keV between two electrostatic mirrors. Along with an overview of the cryogenic trap design, we present a measurement of the residual gas density inside the trap resulting in only 2 x 10(3) cm(-3), which for a room temperature environment corresponds to a pressure in the 10(-14) mbar range. The device, called the cryogenic trap for fast ion beams, is now being used to investigate molecules and clusters at low temperatures, but has also served as a design prototype for the cryogenic heavy-ion storage ring currently under construction at the Max-Planck Institute for Nuclear Physics. PMID:20515170

Lange, M; Froese, M; Menk, S; Varju, J; Bastert, R; Blaum, K; López-Urrutia, J R Crespo; Fellenberger, F; Grieser, M; von Hahn, R; Heber, O; Kühnel, K-U; Laux, F; Orlov, D A; Rappaport, M L; Repnow, R; Schröter, C D; Schwalm, D; Shornikov, A; Sieber, T; Toker, Y; Ullrich, J; Wolf, A; Zajfman, D

2010-05-01

326

The 2-8 keV cosmic X-ray background spectrum as observed with XMM-Newton  

NASA Astrophysics Data System (ADS)

We have measured the spectrum of the Cosmic X-ray Background (CXB) in the 2-8 keV range with the high throughput EPIC/MOS instrument onboard XMM-Newton. A large sample of high galactic latitude observations was used, covering a total solid angle of 5.5 square degrees. Our study is based on a very careful characterization and subtraction of the instrumental background, which is crucial for a robust measurement of the faintest diffuse source of the X-ray sky. The CXB spectrum is consistent with a power law having a photon index ?=1.41 ± 0.06 and a normalization of 2.46 ± 0.09 photons cm-2 s-1 sr-1 keV-1 at 3 keV (˜11.6 photons cm-2 s-1 sr-1 keV-1 at 1 keV), corresponding to a 2-10 keV flux of (2.24 ± 0.16) × 10-11 erg cm-2 s-1 deg-1 (90% confidence level, including the absolute flux calibration uncertainty). Our results are in excellent agreement with two of the most recent CXB measurements, performed with BeppoSAX LECS/MECS data (Vecchi et al. \\cite{Vec99}) and with an independent analysis of XMM-Newton EPIC/MOS data (Lumb et al. \\cite{Lum02}), providing a very strong constraint to the absolute sky surface brightness in this energy range, so far affected by an ˜40% uncertainty. Our measurement implies that the fraction of CXB resolved by the recent deep X-ray observations in the 2-10 keV band is of 80 ± 7% (1?), suggesting the existence of a new population of faint sources, largely undetected within the current sensitivity limits of the deepest X-ray surveys. Based on observations with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA member states and the USA (NASA). Appendices A and B are only available in electronic form at http://www.edpsciences.org

De Luca, A.; Molendi, S.

2004-06-01

327

A very sensitive nonintercepting beam average velocity monitoring system for the TRIUMF 300-keV injection line  

SciTech Connect

A nonintercepting beam velocity monitoring system has been installed in the 300-keV injection line of the TRIUMF cyclotron to reproduce the injection energy for beam from different ion sources and to monitor any beam energy fluctuations. By using a programmable beam signal leveling method the system can work with a beam current dynamic range of 50 dB. Using synchronous detection, the system can detect 0.5 eV peak-to-peak energy modulation of the beam, sensitivity is 1.7{times}10{sup {minus}6}. The paper will describe the principle and beam measurement results. {copyright} {ital 1997 American Institute of Physics.}

Yin, Y.; Laxdal, R.E.; Zelenski, A. [TRIUMF, 4004 Wesbrook Mall, Vancouver, B.C., V6T 2A3 (CANADA); Ostroumov, P. [INR, 117312 Moscow (Russia)

1997-01-01

328

Cosmology, astrophysics, and a 17 keV neutrino  

NASA Astrophysics Data System (ADS)

Recent observations of structure below the endpoint in various beta decay spectra suggest that the cosmological consequences of a possible 17 keV neutrino admixture with the electron neutrino should be re-considered. We derive constraints coming from the evolution of the universe, large scale structure, and big bang nucleosynthesis. Whe these are combined with a constraints from astrophysical observables, including neutrinos from SN1987A, the restrictions on models are quiet severe. One model motivated by the recent data appears unacceptable, and the class of models which manages to cleanly satisfy all the constraints appears incompatible with the MSW solution to the solar neutrino problem. Research supported in part by an NSF Presidential Investigator Award, by the DOE, and by the Foundation for Physical Science.

Krauss, Lawrence M.

1991-07-01

329

Magnetospheric plasma modeling (0-100 keV)  

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

330

K-(alpha) Radiography at 20-100 keV Using Short-Pulse Lasers  

SciTech Connect

X-ray radiography is an important tool for diagnosing and imaging planar and convergent hydrodynamics phenomena for laser experiments. Until now, hydrodynamics experiments at Omega and NIF utilize E{sub x-ray} < 9 keV backlighter x-rays emitted by thermal plasmas. However, future experiments will need to diagnose larger and denser targets and will require x-ray probes of energies from 20-100 keV and possibly up to 1 MeV. Hard K-{alpha} x-ray photons can be created through high-energy electron interactions in the target material after irradiation by petawatt-class high-intensity-short-pulse lasers with > 10{sup 17} W/cm{sup 2}. We have performed several experiments on the JanUSP, and the Vulcan 100TW, and Vulcan Petawatt lasers to understand K-{alpha} sources and to test radiography concepts. 1-D radiography using an edge-on foil and 2-D radiography using buried wires and cone-fiber targets were tested. We find that 1-D thin edge-on foils can have imaging resolution better than 10 {micro}m. Micro volume targets produce bright sources with measured conversion efficiency from laser energy to x-ray photons of {approx} 1 x 10{sup -5}. This level of conversion may not be enough for 2-D point projection radiography. A comparison of our experimental measurements of small volume sources with the LSP/PIC simulation show similar K-{alpha} creation profiles but discrepancy in absolute yields.

Park, H S; Chambers, D; Clarke, R; Eagleton, R; Giraldez, E; Goldsack, T; Heathcote, R; Izumi, N; Key, M; King, J; Koch, J; Landen, O L; Mackinnon, A; Nikroo, A; Patel, P; Pasley, J; Remington, B; Robey, H; Snavely, R; Steinman, D; Stephenson, R; Stoeckl, C; Storm, M; Tabak, M; Theobald, W; Town, R J

2005-08-29

331

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

NASA Astrophysics Data System (ADS)

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

Hayashi, Toru; Takahashi, Yoko; Todoriki, Setsuko

1998-06-01

332

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

333

Neutron capture cross sections of {sup 74}Ge, {sup 76}Ge, and {sup 75}As at 25 keV  

SciTech Connect

The neutron capture cross sections of {sup 74}Ge, {sup 76}Ge, and {sup 75}As have been measured at the Karlsruhe Van de Graaff accelerator by means of the activation technique. The neutron source reaction {sup 7}Li(p,n){sup 7}Be was used for simulating a thermal energy distribution for kT=25 keV to determine the astrophysically relevant stellar cross sections directly. Based on an extended series of activations, consistent results could be obtained, corresponding to Maxwellian average cross sections at kT=30 keV of 37.6{+-}3.9 mb for {sup 74}Ge, 21.5{+-}1.8 mb for {sup 76}Ge, and 362{+-}19 mb for {sup 75}As. These results are more accurate than previous data and are, therefore, important for resolving previous discrepancies. By extrapolation Maxwellian averaged cross sections were derived for thermal energies from 5 to 100 keV. The implications of these results for the s-process abundances in massive stars and for the background conditions in double {beta} decay experiments are discussed.

Marganiec, J.; Dillmann, I.; Pardo, C. Domingo; Kaeppeler, F.; Reifarth, R.; Gallino, R.; Pignatari, M.; Grabmayr, P. [Forschungszentrum Karlsruhe, Institut fuer Kernphysik, D-76344 Eggenstein-Leopoldshafen (Germany); Gesellschaft fuer Schwerionenforschung, D-64291 Darmstadt (Germany) and Johann Wolfgang Goethe-Universitaet, D-60438 Frankfurt am Main (Germany); Dipartimento di Fisica Generale, Universita di Torino, Via P. Giuria 1, I-10125 Torino (Italy); Keele University, Keele, Staffordshire ST5 5BG (United Kingdom) and JINA, University of Notre Dame, Notre Dame, Indiana 46556 (United States); Physikalisches Institut der Universitaet Tuebingen, Auf der Morgenstelle 14, D-72076 Tuebingen (Germany)

2009-06-15

334

Neutron capture cross sections of Ge74, Ge76, and As75 at 25 keV  

NASA Astrophysics Data System (ADS)

The neutron capture cross sections of Ge74, Ge76, and As75 have been measured at the Karlsruhe Van de Graaff accelerator by means of the activation technique. The neutron source reaction Li7(p,n)Be7 was used for simulating a thermal energy distribution for kT=25 keV to determine the astrophysically relevant stellar cross sections directly. Based on an extended series of activations, consistent results could be obtained, corresponding to Maxwellian average cross sections at kT=30 keV of 37.6±3.9 mb for Ge74, 21.5±1.8 mb for Ge76, and 362±19 mb for As75. These results are more accurate than previous data and are, therefore, important for resolving previous discrepancies. By extrapolation Maxwellian averaged cross sections were derived for thermal energies from 5 to 100 keV. The implications of these results for the s-process abundances in massive stars and for the background conditions in double ? decay experiments are discussed.

Marganiec, J.; Dillmann, I.; Pardo, C. Domingo; Käppeler, F.; Reifarth, R.; Gallino, R.; Pignatari, M.; Grabmayr, P.

2009-06-01

335

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

336

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

337

150 keV Emission from PKS2149-306 with BeppoSAX: A Compton Suppressed Jet and the Origin of Radio-quiet Quasars  

NASA Astrophysics Data System (ADS)

A BeppoSAX observation of the z=2.34 quasar PKS2149-306 produced a strong signal in the high energy PDS instrument up to a maximum observed energy of nearly 50 keV, 150 keV in the quasar frame. The Beppo-SAX spectrum spans almost 3 decades (0.3-150 keV, quasar frame) and shows a hard (alpha =0.4+/-0.05) X-ray spectrum above 3 keV, and either a softer (alpha =1.0(+0.6}_{-0.3) ) low energy component, or an ionized absorber at zero redshift. An ionized absorber may be blueshifted from the quasar frame with v=0.6c. No evidence is seen of an Fe-K emission line (EW<50 eV at 6.5 keV rest) or a Compton hump (R<0.3). A bremsstrahlung fit gives kT(rest)=46(+32}_{-16) keV, similar to the X-ray background value. The SED of PKS 2149-306 shows two peaks at ~ 10({12+/-) 0.5}Hz and ~ 10({21+/-) 1.0}Hz ( ~ 0.3 mm and ~ 4 MeV), strongly resembling a low energy cutoff BL Lac object (LBL). The ratio of the two peaks shows an extreme Compton dominance (C_D=1.4+/- 0.4), as in flat spectrum radio quasars (FSRQs). The presence of an additional `optical/UV big bump' component may provide photons that cool the jet, suppressing the radio emission. Compton suppression amplifies changes in intrinsic jet power into a greater change in radio loudness. Hence a modest extension from conditions in PKS2149--306 may completely quench a radio jet. The result would be a radio-quiet quasar. Several predictions of the radio and X-ray properties of radio-quiet AGN follow from this picture.

Elvis, Martin; Fiore, Fabrizio; Siemiginowska, Aneta; Mathur, Smita; McDowell, Jonathan; Bechtold, Jill

1999-04-01

338

Two-photon coincident emission from thick targets for 70-keV incident electrons  

NASA Astrophysics Data System (ADS)

Two-photon coincidence yields have been measured in thick targets of C, Al, Ag, and Ta for 70 keV incident electrons and photons radiated at +/-45° to the incident beam. A theoretical model, which is more rigorous, has been developed to simulate the two-photon processes of coherent thick-target double bremsstrahlung (TTDB) and the incoherent emission of two single-bremsstrahlung (SBSB) photons in a thick-target environment. The model is based on an integration of the thin-target cross sections over the target thickness taking into account electron energy loss, electron backscattering, and photon attenuation. It predicts a yield that is much lower than that of the previous model. The prediction of the model fits the present experimental data well by adjusting the relative weight of the two competing processes, and we find that TTDB dominates at low Z and incoherent SBSB dominates at higher Z.

Liu, J.; Kahler, D. L.; Quarles, C. A.

1993-04-01

339

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

340

Desorption of neutral molecules from self-assembled monolayers subjected to keV ion bombardment  

NASA Astrophysics Data System (ADS)

Laser postionization in combination with mass spectrometry was used to detect neutral molecules desorbed from self-assembled monolayers of phenethyl mercaptan and benzyl mercaptan on gold upon 8 keV Ar + bombardment. From experimentally obtained time distributions, it was determined that the majority of the desorbed neutral molecules leave the surface with low translational energies of about 0.03 eV. As the substrate temperature is reduced, the distributions become broader and shift to longer flight times. In combination with mass distributions, these results indicate that the thermal desorption process is initiated by chemical reactions in the organic layer, creating fragments of the original molecule weakly bound to the surface, prior to release.

Meserole, C. A.; Vandeweert, E.; Chatterjee, R.; Winograd, N.; Postawa, Z.

1999-03-01

341

Monochromatic focusing of subpicosecond x-ray pulses in the keV range  

NASA Astrophysics Data System (ADS)

An effective x-ray optical method to focus keV x-ray pulses shorter than one picosecond by using spherically or toroidally bent crystals is presented. The spectral, spatial, and time-dependent properties of focusing by two-dimensional bent crystals are calculated by considering geometrical effects, physical limitation in high performance crystal optics, and reflectivities obtained by x-ray diffraction theory. These properties are compared with first experimental results of focusing x rays from a plasma created by a laser pulse with 4.5 mJ energy and 100 fs pulse length. The x-ray signals, simultaneously obtained from a von Hámos spectrometer and two-dimensional bent crystals are compared and found in good agreement with theoretical data. The possibilities and aspects of laser pump x-ray probe experiments using this type of x-ray optics system and currently available laser systems are discussed.

Missalla, T.; Uschmann, I.; Förster, E.; Jenke, G.; von der Linde, D.

1999-02-01

342

A Source Design Strategy Providing 5 eV-100 keV Photons.  

PubMed

The future requirements for synchrotron radiation facilities in the UK have been surveyed by consulting the large user community. Some of the results of this survey are presented and it is shown that all requirements could be satisfied by access to three synchrotron radiation sources covering the spectral range from 5 eV to 100 keV. These sources are the 6 GeV ESRF, MES (a new 3 GeV replacement for the SRS) and LES (a new low-energy source at 700 MeV). Outline plans for LES and MES and their optimization to generate the requisite radiation quality and spectral range are discussed. PMID:16728778

Suller, V P

1994-10-01

343

Spatial structure of greater than 100 keV X-ray sources in solar flares  

NASA Technical Reports Server (NTRS)

Recent ISEE 3 and Pioneer Venus Orbiter observations relevant to the altitude structure of the hard X-ray source down to 3000 km or less above the photosphere are reported. About 90 percent of the impulsive X-ray emission and about 70 percent of the gradual emission originates at altitudes 2500 km or less above the photosphere. In the 100-500 keV range, this altitude dependence is essentially independent of photon energy. Brightness of the impulsive X-ray source decreases rapidly with increase in altitude. As far as models of the impulsive phase are concerned, the thermal model with adiabatic compression and expansion of a magnetically confined plasma and the thin target model are not consistent with these observations. The thick target model and the dissipative thermal model are consistent with the observed low altitude of the hard X-ray source.

Kane, S. R.; Fenimore, E. E.; Klebesadel, R. W.; Laros, J. G.

1982-01-01

344

Efficient production of 100 keV deuterons in deuterium gas puff Z-pinches at 2 MA current  

NASA Astrophysics Data System (ADS)

Deuterium gas puff experiments were carried out on the S-300 Z-pinch at the Kurchatov Institute in Moscow. Gas puffs imploded onto the axis before a current peak at about 100 ns. Fusion neutrons were generated after the gas puff implosion during global expansion of a plasma column. Neutron emission lasted on average 35 ± 5 ns (full width half maximum, FWHM). In the downstream direction (on the Z-pinch axis behind the cathode), a mean neutron energy was 2.6 ± 0.1 MeV. Side-on neutron energy spectra peaked at 2.40 ± 0.05 MeV with about 600 ± 150 keV FWHM. A broad width of side-on neutron spectra implied a high radial component of deuteron velocities. An average kinetic energy of fast deuterons, which produced fusion neutrons, was 150 keV. A peak neutron yield reached a value of 6 × 1010 on a current level of 1.5 MA. It was by one order higher in comparison with other deuterated loads used on the same current generator. On the basis of experimental observations, we concluded that a total energy of deuterons accelerated to fusion energies was above 1.5 kJ. It is more than 15% of the energy input into a plasma. Therefore gas puff Z-pinches seem to be not only powerful sources of x-ray radiation but also efficient sources of 100 keV deuterons. Such a result is consistent with high neutron yields observed on the Angara Z-pinch and plasma foci with similar currents.

Klir, D.; Kravarik, J.; Kubes, P.; Rezac, K.; Cikhardt, J.; Litseva, E.; Hyhlik, T.; Ananev, S. S.; Bakshaev, Yu L.; Bryzgunov, V. A.; Chernenko, A. S.; Kalinin, Yu G.; Kazakov, E. D.; Korolev, V. D.; Ustroev, G. I.; Zelenin, A. A.; Juha, L.; Krasa, J.; Velyhan, A.; Vysin, L.; Sonsky, J.; Volobuev, I. V.

2010-06-01

345

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

346

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

NASA Technical Reports Server (NTRS)

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

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

2007-01-01

347

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

348

Direct evidence of doppler shift in 10 keV Ar + ion induced Si Auger emission  

NASA Astrophysics Data System (ADS)

Angle resolved Si L-shell Auger emission induced by 10 keV Ar ion bombardment has been reinvestigated to study the spatial distribution of sputtered Si particles. We confirm all the major Si atomic-like Auger features whose kinetic energies are independent of either ion beam incidence angle or electron emission angle. We find, however, that at near-normal incidence the Si Auger spectra undergo characteristic lineshape changes showing the growth of satellites on the high kinetic energy side as the take-off angle moves away from the surface normal. The gradual splitting of the satellites from their main peaks results in a continuous transition of Auger features from singlets at normal emission to well separated doublets at grazing emission. The Auger peaks with fixed kinetic energies are due to the de-excitation of the sputtered slow Si species occurring outside the solid with a typical cosine distribution while the satellites at higher energies are atributed to the Doppler effects of the ejected fast Si particles in a narrow cone along grazing direction. The effect of the ion beam incidence angle on the higly anisotropic distribution of the sputtered energetic Si ions and neutrals is also discussed.

Xu, F.; Siciliano, R.; Camarca, M.; Oliva, A.

1989-02-01

349

Direct evidence of Doppler shift in 10 keV Ar + ion induced Si Auger emission  

NASA Astrophysics Data System (ADS)

Angle resolved Si L-shell Auger emission induced by 10 keV Ar ion bombardment has been reinvestigated to study the spatial distribution of sputtered Si particles. We confirm all the major Si atomic-like Auger features whose kinetic energies are independent of either ion beam incidence angle or electron emission angle. We find, however, that at near-normal incidence the Si Auger spectra undergo characteristic lineshape changes showing the growth of satellites on the high kinetic energy side as the take-off angle moves away from the surface normal. The gradual splitting of the satellites from their main peaks results in a continuous transition of Auger features from singlets at normal emission to well separated doublets at grazing emission. The Auger peaks with fixed kinetic energies are due to the de-excitation of the sputtered slow Si species occuring outside the solid with a typical cosine distribution while the satellites at higher energies are atributed to the Doppler effects of the ejected fast Si particles in a narrow cone along grazing direction. The effect of the ion beam incidence angle on the higly anisotropic distribution of the sputtered energetic Si ions and neutrals is also discussed.

Xu, F.; Siciliano, R.; Camarca, M.; Oliva, A.

350

Stimulated Compton scattering in two-color ionization of hydrogen with keV electromagnetic fields.  

PubMed

We present a theoretical study of two-color ionization of hydrogen with keV photons at intensities ranging from 1016 to 1018??W/cm2. We consider the atom in interaction with a superposition of two electromagnetic pulses centered around two frequencies that differ by a few atomic units and we present in detail the case of the frequencies 55 and 50 a.u. We present the electron energy spectra, angular distributions, and ionization rates based on nonperturbative and perturbative calculations. Although the ejected electron energy distribution is dominated by one-photon ionization from each pulse, we are able to identify the contribution of stimulated Compton scattering, a process in which one photon is absorbed while the other is emitted, the photon energy difference being transferred to the electron. This leads to low-energy electrons, and we show in particular that it is of crucial importance to consider the retardation effects on the ionization rates and the electron angular distributions. The relative propagation direction of the two fields also plays an important role; in the case of counterpropagating fields, the ionization by stimulated Compton scattering is dominated by A2 and competes with one-photon ionization at high intensities. PMID:24579592

Bachau, H; Dondera, M; Florescu, V

2014-02-21

351

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

352

Primordial nucleosynthesis during the keV era  

SciTech Connect

Energetic hadronic and electromagnetic showers in the keV era of the hot big bang are produced by the decays of long lived particles. These showers initiate a new phase of nucleosynthesis. The abundance ratios of D, /sup 3/He, /sup 6/Li and /sup 7/Li are given by fixed points of rate equations, which are determined by nuclear physics not by the nature of the decaying particle. The fixed points are independent of prior abundances, so that constraints from the MeV era of nucleosynthesis evaporate, except for a requirement that /sup 4/He not be underproduced. For example, ..cap omega../sub B/ = 1 and many more than four neutrino species are both possible. Within the accuracy of our calculation (there are uncertainties of at least a factor of three), the abundances agree with those inferred from observations. Considerable /sup 6/Li is produced and must be depleted in both population II halo stars and in the galactic disk. We predict /sup 6/Li, /sup 3/He and D abundances in primordial material which are higher than conventional nucleosynthesis. 8 refs.

Dimopoulos, S.; Esmailzadeh, R.; Hall, L.J.; Starkman, G.D.

1987-09-09

353

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

Microsoft Academic Search

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

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

2009-01-01

354

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

Microsoft Academic Search

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 5MeV and 50mA for the production of a stellar neutron spectrum at thermal energy equal to 30keV using the 7Li(p,n)7Be reaction is investigated. The

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

2009-01-01

355

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

356

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

Microsoft Academic Search

We present a new method of utilizing a filter--fluorescer system for measuring high fluence x-rays above 120 keV, where there are no practical absorption edges available for conventional filter--fluorescer techniques. The absorption edge (E\\/sub p\\/ keV) of the prefilter is chosen to be less than that of the fluorescer (E\\/sub f\\/ keV), i.e., E\\/sub p\\/

C. L. Wang

1981-01-01

357

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

Microsoft Academic Search

We present a new method of utilizing a filter–fluorescer system for measuring high fluence x-rays above 120 keV, where there are no practical absorption edges available for conventional filter–fluorescer techniques. The absorption edge (Ep keV) of the prefilter is chosen to be less than that of the fluorescer (Ef keV), i.e., Ep

C. L. Wang

1981-01-01

358

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

359

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

360

Cross Sections for Positive-Ion and Electron Production in Collisions of 1-25 KeV Hydrogen Atoms with Atomic and Molecular Gases.  

National Technical Information Service (NTIS)

Cross sections are reported for production of positive ions and electrons in collisions of hydrogen atoms in the energy range 1-25 keV with He, Ne, A, Kr, Xe, H2, and O2. Slow, positive ions are produced by capture of an electron by the fast atom from the...

R. J. McNeal D. C. Clark R. A. Klingberg

1970-01-01

361

The 12.34keV Ml Transition in 133mBa  

Microsoft Academic Search

Halflives of a 12.34-keV level in 133mBa and two levels in 120Sn were measured by means of a delayed coincidence system which was accurately calibrated by use of a standard pulse generator: 18.0± 0.4 n sec for the 12.34-keV level in 133Ba, 11.96± 0.09 mu sec for the 2482.0-keV level in 120Sn, 5.55± 0.03 n sec for the 2284.6-keV level

Kazumasa Miyano; Yoshiaki Kato

1980-01-01

362

Comparison of the gamma-ray spectra from 2. 8keV neutron capture and thermal-neutron capture in sodium-23  

Microsoft Academic Search

The gamma-ray spectrum resulting from neutron capture in the 2.8-keV resonance of ²³Na has been measured with the high-resolution annihilation pair spectrometer at the internal-target facility of the CP-5 reactor. The 2.8-keV resonance was populated by using the boron-shielded target technique: A ¹\\/â-in.-thick filter of ¹°B surrounding the sodium sample selectively removes low-energy neutrons from the spectrum; the 1\\/E dependence

W. M. Wilson; H. E. Jackson; G. E. Thomas

1977-01-01

363

Centaurus A /NGC 5128/ at 2 keV-2.3 MeV - HEAO 1 observations and implications  

NASA Technical Reports Server (NTRS)

The active-nucleus galaxy Centaurus A has been studied at 2 keV-2.3 MeV using data from the UCSD/MIT hard X-ray and low-energy gamma-ray instrument and the GSFC/CIT cosmic X-ray experiment on HEAO-1. It is found that an E exp -1.60 + or - 0.03 power law spectrum breaking to E exp -2.0 + or - 0.2 at 140 keV best describes the January and July 1978 data. The average intensity was 50% higher during the January observations. Upper limits to unresolved lines at 511 keV and 1.6 MeV were found to be 6.5 x 10 to the -4th photons/sq cm-s and 2.2 x 10 to the -4th photons/sq cm-s, respectively, at the 90% confidence level. The present data are consistent with the detailed calculations of the synchrotron self-Compton mechanism; they may also agree, marginally, with the predictions of emission from spherical accretion onto black holes.

Baity, W. A.; Rothschild, R. E.; Lingenfelter, R. E.; Stein, W. A.; Nolan, P. L.; Gruber, D. E.; Knight, F. K.; Matteson, J. L.; Peterson, L. E.; Mushotzky, R. F.

1981-01-01

364

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

365

Proof-of-Principle Time-Resolved Bremsstrahlung Spectral Measurement for Intense, Low-Endpoint (<300 keV) Pulsed Sources  

NASA Astrophysics Data System (ADS)

In a proof-of-principle test, we measured how the L-3 Pulse Sciences MBS (~200 keV peak voltage) Bremsstrahlung spectrum changed in time using a pair of filter-fluorescer channels, one at 41 ± 18 keV and another at 87 ± 27 keV. This demonstrates an approach for measuring a time-resolved bremsstrahlung spectrum for SGEMP applications, albeit with coarse energy resolution (30-45%). Using filter fluorescers and detecting the resultant X-rays with plastic scintillator PMTs, there is adequate sensitivity and dynamic range to correlate spectra from two sources, MBS and PITHON, which differ by a factor of up to ~100× in brightness (from 1 to 100 rad CaF2 at the spectrometer entrance). For such a correlation, no hardware changes are required—only the PMT gains need to be changed. The time resolution of the measurement is expected to be 2 ns.

Failor, B. H.; Riordan, J. C.; Rodriguez, J. C.; Verma, A.; Lojewski, D. Y.

2009-03-01

366

Extended observations of higher than 7-keV X-rays from Centaurus X-3 by the OSO-7 satellite  

NASA Technical Reports Server (NTRS)

The UCSD X-ray telescope on board OSO-7 provided 43 days of continuous coverage of the variable X-ray source Cen X-3 at energies above 7 keV during December 1971 and January 1972. We detected the 4.8-sec pulsation period, the 2.087-day eclipse cycle, and an apparently nonperiodic, low-intensity state lasting more than 12 days. Spectra obtained over the 7-30 keV range during noneclipsed high-intensity states are steeper than those previously reported. Large changes, which may be characterized by a number spectral index alpha varying between 3.0 plus or minus 0.2 and 2.0 plus or minus 0.3, or by exponential spectra with kT varying from 6 plus or minus 2 to 13 plus or minus 3 keV, occur at different high-intensity states.

Baity, W. A.; Ulmer, M. P.; Wheaton, W. A.; Peterson, L. E.

1974-01-01

367

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

368

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

369

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

NASA Astrophysics Data System (ADS)

We report an experimental study on the optimization of a laser plasma based x-ray source of ultra-short duration K-? line radiation. The interaction of pulses from a CPA based Ti:sapphire laser (10 TW, 45 fs, 10 Hz) system with magnesium, titanium, iron and copper solid target generates bright 1-8 keV K-? x-ray radiation. The x-ray yield was optimized with the laser pulse duration (at fixed fluence) which is varied in the range of 45 fs to 1.4 ps. It showed a maximum at laser pulse duration of ˜740 fs, 420 fs, 350 and 250 fs for Mg (1.3 keV), Ti (4.5 keV), Fe (6.4 keV) and Cu (8.05 keV) respectively. The x-ray yield is observed to be independent of the sign of the chirp. The scaling of the K-? yield (Ix ? IL?) for 45 fs and optimized pulse duration were measured for laser intensities in the region of 3 × 1014 - 8 × 1017. The x-ray yield shows a much faster scaling exponent ? = 1.5, 2.1, 2.4 and 2.6 for Mg, Ti, Fe and Cu respectively at optimized pulse duration compared to scaling exponent of 0.65, 1.3, 1.5, and 1.7 obtained for 45 fs duration laser pulses. The laser to x-ray energy conversion efficiencies obtained for different target materials are ?Mg = 1.2 × 10-5, ?Ti = 3.1 × 10-5, ?Fe = 2.7 × 10-5, ?Cu = 1.9 × 10-5. The results have been explained from the efficient generation of optimal energy hot electrons at longer laser pulse duration. The faster scaling observed at optimal pulse duration indicates that the x-ray source is generated at the target surface and saturation of x-ray emission would appear at larger laser fluence. An example of utilization of the source for measurement of shock-wave profiles in a silicon crystal by time resolved x-ray diffraction is also presented.

Arora, V.; Naik, P. A.; Chakera, J. A.; Bagchi, S.; Tayyab, M.; Gupta, P. D.

2014-04-01

370

Electron events from the scattering with solar neutrinos in the search of keV scale sterile neutrino dark matter  

NASA Astrophysics Data System (ADS)

In a previous work, we showed that it is possible to detect keV scale sterile neutrino dark matter ?s in a ? decay experiment using radioactive sources such as T3 or Ru106. The signals of this dark matter candidate are monoenergetic electrons produced in the neutrino capture process ?s+ N'?N+e-. These electrons have energy greater than the maximum energy of the electrons produced in the associated decay process N'?N+e-+? ¯e. Hence, signal electron events are well beyond the end point of the ? decay spectrum and are not polluted by the ? decay process. Another possible background, which is a potential threat to the detection of ?s dark matter, is the electron event produced by the scattering of solar neutrinos with electrons in target matter. In this article, we study in detail this possible background and discuss its implications for the detection of keV scale sterile neutrino dark matter. In particular, bound state features of electrons in Ru atoms are considered with care in the scattering process when the kinetic energy of the final electron is the same order of magnitude of the binding energy.

Liao, Wei; Wu, Xiao-Hong; Zhou, Hang

2014-05-01

371

HEAO 1 observations of the Perseus cluster above 10 keV  

NASA Technical Reports Server (NTRS)

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

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

1981-01-01

372

Neutron capture cross sections near 30 keV using a Moxon-Rae detector  

Microsoft Academic Search

Neutron radiative capture cross sections were measured using a Moxon-Rae ; detector, for neutrons near 30 kev. A time-of-flight system with less than 3 ns ; resolution and a 7 cm flight path was shown applicable to small sample ; measurements. Cross sections at 30 kev for Mo, Cd, Sn, Ta, W, Pt, and Au and ; cross sections versus

R. L. Macklin; J. H. Gibbons; T. Inada

1963-01-01

373

Desorption Induced by KEV Molecular and Cluster Projectiles.  

NASA Astrophysics Data System (ADS)

A new experimental method has been developed for studying negative secondary ion (SI) emission from solid surfaces bombarded by polyatomic primary ions of 5 to 30 keV. The method is based on the time-of-flight (TOF) analysis of primary ions which are produced by either ^ {252}Cf fission fragment induced desorption or by extraction from a liquid metal ion source, and then accelerated into a field free region. The primary ions included organic monomer, dimer, and fragment ions of coronene and phenylalanine, (CsI)_ nCs ^{+} cluster ions, and Au _sp{n}{+} cluster ions. Secondary electrons, emitted from a target surface upon primary ion impact, are used to identify which primary ion has hit the surface. An event-by-event coincidence counting technique allows several secondary ion TOF spectra, correlated to several different primary ions, to be acquired simultaneously. Negative SI yields from organic (phenylalanine and dinitrostilbene), CsI, and Au surfaces have been measured for a number of different mono- and polyatomic primary ions. The results show, for example, yields ranging from 1 to 10% for phenylalanine (M-H) ^{ -}, 1 to 10% for I^{-} , and 1 to 5% for Au^{-} , with Cs_2I^ {+} and Cs_3I _sp{2}{+} clusters as projectiles. Yields for the same surfaces using Cs ^{+} primary ions are much less than 1%, indicating that SI yields are enhanced with clusters. A yield enhancement occurs when the SI yield per atom of a polyatomic projectile is greater than the SI yield of its monoatomic equivalent, at the same velocity. Thus, a (M-H) ^{-} yield increase of a factor of 50, when phenylalanine is bombarded with Cs_3I_sp{2} {+} instead of Cs^{+ }, represents a yield enhancement factor of 10. For the projectiles and samples studied, it was observed that the heavier the mass of the constituents of a projectile, the larger the enhancement effects, and that the largest yield enhancements (with CsI and Au _ n projectiles) occur for the organic target, phenylalanine. One possible explanation for the larger enhancements with organics, namely a thermal spike process, appears unlikely. Experiments with high and low melting point isomers of dinitrostilbene, bombarded with Cs _2I^{+} and Cs^{+} projectiles, showed larger Cs_2I^ {+} yield enhancements for the high melting point isomer.

Blain, Matthew Glenn

1990-01-01

374

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

375

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

376

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

NASA Technical Reports Server (NTRS)

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

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

1997-01-01

377

Electron impact excitation cross sections of sodium ? autoionizing state from threshold to 1.5 keV  

Microsoft Academic Search

Relative excitation cross sections of the lowest-lying autoionizing state 0953-4075\\/31\\/3\\/023\\/img2 of sodium are measured for electron impact in the range of incident energy 0953-4075\\/31\\/3\\/023\\/img3 from 1.5 keV down to the threshold. Absolute cross sections are obtained by normalization of the relative cross sections at 0953-4075\\/31\\/3\\/023\\/img4 to the theoretical cross section in the plane-wave Born approximation with accurate atomic wavefunctions. Negative

B. Feuerstein; A. N. Grum-Grzhimailo; W. Mehlhorn

1998-01-01

378

Single-Photon Entanglement in the keV Regime via Coherent Control of Nuclear Forward Scattering  

NASA Astrophysics Data System (ADS)

Generation of single-photon entanglement is discussed in nuclear forward scattering. Using successive switchings of the direction of the nuclear hyperfine magnetic field, the coherent scattering of photons on nuclei is controlled such that two signal pulses are generated out of one initial pump pulse. The two time-resolved correlated signal pulses have different polarizations and energy in the keV regime. Spatial separation of the entangled field modes and extraction of the signal from the background can be achieved with the help of state-of-the-art x-ray polarizers and piezoelectric fast steering mirrors.

Pálffy, Adriana; Keitel, Christoph H.; Evers, Jörg

2009-07-01

379

Electron-detachment spectroscopy of 20-100-keV H- projectiles interacting with thin Ar targets  

NASA Astrophysics Data System (ADS)

Energy and transformed-velocity spectra of electrons emitted in the forward direction have been experimentally determined for 20-120-keV H- projectiles traversing thin Ar targets. The spectra from H- are surprisingly cusplike in shape even though single-electron loss is known to dominate. In contrast to the findings of Menendez and Duncan, who performed similar measurements at higher projectile velocities, target-induced structures in the electron loss to the continuum spectra are not pronounced in this velocity regime.

Alton, G. D.; Compton, R. N.; Pegg, D. J.

1985-04-01

380

Search for Anomalous Scattering of keV Neutrons from H2O-D2O Mixtures  

NASA Astrophysics Data System (ADS)

We measured the neutron scattering intensities from pure liquid H2O relative to that of pure D2O and also relative to H2O-D2O mixtures, at room temperature. This study is relevant to the problem of quantum entanglement. The neutrons were generated from an electron Linac and the final energy of the scattered neutrons was fixed at 24.3 keV using a 20 cm thick pure iron filter. The scattering intensity ratios were found to agree with expected values deduced from the tabulated total cross sections within an accuracy of 3%. Thus no anomaly was observed.

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

2005-05-01

381

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

NASA Astrophysics Data System (ADS)

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

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

2001-01-01

382

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

383

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

NASA Astrophysics Data System (ADS)

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

Demir, Demet; Kele?, Gürbüz

2006-04-01

384

Energetic neutral atoms (E approximately 50 keV) from the ring current - IMP 7/8 and ISEE 1  

NASA Technical Reports Server (NTRS)

Energetic neutral atoms (ENA), emitted from the magnetosphere with energies of about 50 keV, have been measured with solid state detectors on the IMP 7/8 and ISEE 1 spacecraft; they are produced when singly charged trapped ions collide with the exosphere neutral hydrogen geocorona and the energetic ions are neutralized by charge exchange. ENA observations during the recovery phase of two moderate geomagnetic storms are analyzed: November 22-23, 1973, from IMP 8 at 33 earth radii and December 17, 1977, from ISEE 1 at 20 earth radii.

Roelof, E. C.; Mitchell, D. G.; Williams, D. J.

1985-01-01

385

Energy Levels of Ho166  

Microsoft Academic Search

The high-energy gamma-ray spectrum from thermal-neutron capture in natural holmium has been studied over the energy range of 5000 to 6200 keV. Low-energy gamma radiation of the same reaction has been measured from 30 to 750 keV and conversion electrons from 29 to 500 keV. Data from the reaction Ho165(d,p)Ho166 have been analyzed. The combination of the results of these

H. T. Motz; E. T. Jurney; O. W. Schult; H. R. Koch; U. Gruber; B. P. Maier; H. Baader; Gordon L. Struble; Jean Kern; R. K. Sheline; T. von Egidy; Th. Elze; E. Bieber; A. Bäcklin

1967-01-01

386

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

SciTech Connect

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

Imazono, Takashi; Koike, Masato; Kawachi, Tetsuya; Hasegawa, Noboru; Koeda, Masaru; Nagano, Tetsuya; Sasai, Hiroyuki; Oue, Yuki; Yonezawa, Zeno; Kuramoto, Satoshi; Terauchi, Masami; Takahashi, Hideyuki; Handa, Nobuo; Murano, Takanori [Quantum Beam Science Directorate, Japan Atomic Energy Agency, 8-1-7 Umemidai, Kizugawa, Kyoto 619-0215 (Japan); Device Dept., Shimadzu Corp., 1 Nishinokyo-Kuwabara-cho, Nakagyo-ku, Kyoto 604-8511 (Japan); IMRAM, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); ECBU, JEOL Ltd., 3-1-2 Musashino, Akishima, Tokyo 196-8558 (Japan)

2012-07-11

387

High accuracy measurements and Monte Carlo calculations of the relative efficiency curve of an HPGe detector from 433 to 2754 keV  

Microsoft Academic Search

The relative full-energy peak efficiency curve of a 280-cm3 coaxial HPGe detector was determined to an accuracy of about 0.1% over the energy range from 433 to 2754 keV from pairs of gamma-ray lines whose emission probabilities are very accurately known. The curve was extended from previous studies by the addition of lines from 108mAg and 24Na. Ratios of full-

Martin A. Ludington; Richard G. Helmer

2000-01-01

388

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

Microsoft Academic Search

The accurate characterization of material properties under extreme conditions is an important issue for the understanding of high energy density states of matter, from planetary interiors to capsule implosions relevant to inertial confinement fusion. High energy x-ray Thomson Scattering at 18 keV will make it possible to characterize very dense states of matter such as 50x compressed beryllium, ICF-like ablator

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

2010-01-01

389

Irradiation of Cu(In,Ga)Se\\/sub 2\\/ thin film solar cells with 110-, 210-, and 290- keV protons  

Microsoft Academic Search

This study presents irradiation experiments of Cu(In,Ga)Se\\/sub 2\\/ thin-film solar cells using protons with energies of 110, 210, and 290 keV, i.e., in an energy range that is expected to cause maximum damage in the Cu(In,Ga)Se\\/sub 2\\/ absorber layer. Monte-Carlo simulations predict the average depth of the irradiation induced vacancies as well as the integral number of generated vacancies. From

K. Weinert; M. Schwickert; U. Rau

2003-01-01

390

Cross sections for electron capture by Ne2+ in He, Ne, Ar, Kr and Xe between 60 and 200 keV  

Microsoft Academic Search

Measurements of the sigma 21 cross sections for Ne2+ ions in targets of helium, neon, argon, krypton and xenon have been made with an absolute accuracy of about 5% in the energy range between 60 and 200 keV. The two-state theory, in the form given by Rapp and Francis (1962) is able to account for the energy variation of the

H. C. Suk; A. Guilbaud; B. Hird

1978-01-01

391

INTEGRAL observations of Scorpius X-1: evidence for Comptonization up to 200 keV  

NASA Astrophysics Data System (ADS)

We have analyzed a long-term database for Sco X-1 obtained with the telescope IBIS onboard the INTEGRAL satellite in order to study the hard X-ray behavior of Sco X-1 from 20 up to 200 keV. Besides the data used for producing of the INTEGRAL catalog of sources, this is the longest (412 ks) database of IBIS on Sco X-1 up to date. The production of hard X-ray tails in low-mass X-ray binaries is still a matter of debate. Since most of the fits to the high-energy part of the spectra are done with powerlaw models, the physical mechanism for the hard X-ray tail production is unclear. The purpose of this study is to better constrain those possible mechanisms. Our main result shows a strong correlation between the fluxes in the thermal and nonthermal part of Sco X-1 spectra. We, thus, suggest that comptonization of lower energy photons is the mechanism for producing hard X-ray tails in Sco X-1.

Maiolino, T.; D'Amico, F.; Braga, J.

2013-03-01

392

Frequency analysis of 4- to 6-keV electrons associated with an auroral arc  

NASA Technical Reports Server (NTRS)

The high time resolution (HTR) experiment considered consists of four sections, including electrostatic deflection plates, electron multiplier, preamplifier-integrator, and frequency analyzer. Electrons in the energy range from 4 to 6 keV electrons are selected by the deflection system, after which they are detected, multiplied, and passed to the charge sensitive preamplifier. The charge pulses are amplified and integrated, and the resulting voltage pulse series is fed to the frequency analyzer. The experiment is essentially a flux detector, so that estimates of the input flux can be made from the mean value of the output spectrum. The results obtained with the HTR in a rocket flight on March 14, 1974, are discussed. The lack of modulation noticed in the high-frequency range indicates that there is insufficient wave energy available in the vicinity of the rocket to produce a wave-particle interaction which the HTR is able to observe. This finding is consistent with the stabilization of the plasma by the low flux of energetic electrons.

Murphree, J. S.; Anderson, H. R.

1978-01-01

393

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

394

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

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

395

3-10 keV Xe + ion beam machining of ultra low thermal expansion glasses for EUVL projection optics: Evaluation of surface roughness  

NASA Astrophysics Data System (ADS)

In order to obtain surface figure error of 0.15 nm rms and surface roughness ( R rms) of 0.12 nm rms for aspherical substrates in EUVL tools, ion beam figuring may be adopted to final surface figure error correction of aspherical substrates. During figure error correction, machined surface of the substrate becomes rougher than the pre-finished one. Therefore, we investigated the machined depth and ion energy dependences of R rms (measured by an AFM) of substrates machined by 3-10 keV Xe + ion beam, and compared them with the results obtained for Ar + ion beam. Result shows that the R of CLEARCERAM®-Z, Zerodur® and ULE® substrates machined to the depth of 50 nm by 3-10 keV Xe + ion beam at the normal ion incidence angle become approximately 0.25, 0.28 and 0.15 nm rms, respectively. Those values are larger than the pre-finished substrates (0.07-0.09 nm rms), but smaller than that (0.60 nm rms for CLEARCERAM®-Z, 0.61 nm rms for Zerodur® and 0.18 nm rms for ULE®) of the substrates machined by Ar + ion beam. Moreover, the R merely increase with increasing ion energy. The R of the ULE® substrate machined by 3-10 keV Xe + ion beam rapidly increase with increasing machined depth, then saturate at machined depth of 10-50 nm. The saturated values of the R are 0.12 and 0.15 nm rms for 3 and 10 keV Xe + ion beam respectively. We suggest that the 3 keV Xe + ion beam machining can be applicable for final shape correction of ULE® substrates for EUVL projection optics in association with considering further ultra smoothing process such as Si deposition or low energy ion beam smoothing.

Morikawa, K.; Kamijo, K.; Morijiri, K.; Pahlovy, S. A.; Aikawa, N.; Miyamoto, I.

2012-02-01

396

Microvariability of 0.3-10 keV Flux in Hbl Source PKS 2155-304  

NASA Astrophysics Data System (ADS)

The high energy peaked BL Lacertae object PKS 2155-304 has been observed 106-times by the X-ray Telescope onboard the Swift satellite through the 0.3-10 keV band since 2005 November 17. Among these observations, we have revealed 19 cases of the intraday flux variability at 99.9% confidence level with fractional rms amplitudes up to 30% and timescales ranging from 40 ks down to 0.4 ks. Flux changes were often accompanied by a spectral variability which showed a complex character in the presence of both clockwise and counter-clockwise evolution in a hardness ratio-flux plane. These events show rather curved spectra fitted well with the log-parabolic model. The curvature parameter ranged from 0.13 to 0.73 and showed different values for the spectra corresponding to the separate orbits of a single observation. The peak of spectral energy distribution ranged between 1.76 keV and 2.67 keV and generally was variable during the intraday flux changes. The soft and hard X-ray fluxes showed a strong correlation to each other. No correlation between the occurrence of intraday variations and source brightness state was seen — they are found as in flaring as well for intermediate and low states. The X-ray microvariability in PKS 2155-304 can be explained both with the shock-in-jet scenario and emergence of a "blob" of very energetic particles in the jet base.

Kapanadze, Bidzina; Kapanadze, Sergo; Vardosanidze, Manana

2014-03-01

397

HEAO 1 Observations of the Perseus cluster above 10 keV  

SciTech Connect

We present the results of HEAO 1 observations of the Perseus cluster from 10 to 150 keV in 1977 August and 1978 February and August. The spectrum exhibits a previously unknown hard (>25 keV) component in addition to the previously known thermal bremsstrahlung emission. The data presented show no significant evidence of variability from 10.5 keV to 93.5 keV, and a comparison of our results with earlier results indicates no strong evidence for variability above 25 keV over a time scale of approx. 4 yr. If the hard-component excess is due to NGC 1275, the data imply a 2--6 keV X-ray luminosity of approx.1 x 10/sup 44/ ergs s /sup -1/ for the galaxy, or approx.15% of the total cluster emission from 2 to 6 keV and a 25--40 luminosity of approx.8 x 10/sup 43/ ergs s/sup -1/. In the context of a model of hard-X-ray emission by inverse Compton scattering of relativistic electrons on the 2.7 K background, the X-ray spectrum, in conjuction with previously reported radio data, implies a magnetic field of B>10/sup -7/ gauss.

Primini, F.A.; Basinska, E.; Howe, S.K.; Land, F.; Levine, A.M.; Lewin, W.H.G.; Rothschild, R.; Baity, W.A.; Gruber, D.E.; Knight, F.K.; Matteson, J.L.; Lea, S.M.; Reichert, G.A.

1981-01-01

398

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

PubMed

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

Tan, Zhenyu; Liu, Wei

2013-12-01

399

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

NASA Astrophysics Data System (ADS)

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

Cazaux, J.

2012-10-01

400

Characterization of 1 MW, 40 keV, 1 s neutral beam for plasma heating  

NASA Astrophysics Data System (ADS)

Neutral beam with geometrical focusing for plasma heating in moderate-size plasma devices has been developed in Budker Institute of Nuclear Physics, Novosibirsk. When operated with hydrogen, the neutral beam power is 1 MW, pulse duration is 1 s, beam energy is 40 keV, and angular divergence is 1.2°. Initial ion beam is extracted and accelerated by triode multiapertures ion-optical system. To produce 1 MW neutral beam, about 40 A proton current is extracted with nominal current density of 320 mA/cm2. Ion-optical system has 200 mm diameter grids with 44% transparency. The grids have inertia cooling and heat is removed between the pulses by water flowing in channels placed on periphery of the grids. A plasma emitter for ion extraction is produced by rf-plasma box. Ion species mix of rf plasma source amounts to 70%, 20%, and 10% of H+, H2+, and H3+ ions, respectively, by current. Heavy impurities contribute less than 0.3%.

Sorokin, A.; Belov, V.; Davydenko, V.; Deichuli, P.; Ivanov, A.; Podyminogin, A.; Shikhovtsev, I.; Shulzhenko, G.; Stupishin, N.; Tiunov, M.

2010-02-01

401

Ionization and fragmentation of cold clusters of PAH molecules - collisions with keV ions  

NASA Astrophysics Data System (ADS)

We discuss the ionization and fragmentation of isolated monomers and cold clusters of polycyclic aromatic hydrocarbon (PAH) molecules in collisions with keV ions in low or high charge states. With low charge state projectile ions, PAH cluster or monomer targets are thermally excited through electronic stopping processes directly in close peripheral or penetrating collisions while only single or few electrons are removed. With high charge state projectiles, electrons are very effectively removed from both the cluster and the monomer target already at very large distances with very little direct target heating. Singly charged and internally very hot PAH monomers are dominant fragmentation products following collisions between Xe20+ ions and PAH clusters. We suggest that this due to an unusually strong dominance of multiple-ionization over single ionization for PAH clusters interacting with highly charged ions. Here, charge and excitation energy is very rapidly redistributed within the clusters before they Coulomb explode and we suggest that these Coulomb explosions induce strong internal heating in the individual PAH molecules. We thus conclude that PAH cluster fragmentation always dominates strongly for all ionization processes regardless if these are due to interactions with ions in high or low charge states. These findings are discussed in view of simple models for cluster evaporation or single and multiple ionizations of PAH clusters.

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

2012-11-01

402

Origins of Anisotropic 40 300 keV Electron Events Observed at Low and High Latitudes  

NASA Astrophysics Data System (ADS)

Using a survey of anisotropic electron events in the energy range of ˜40 300 keV observed by HI-SCALE on Ulysses, we have selected several time intervals during 1999 when Ulysses traveled from about 20° S at 5.2 AU (January 1999) to 42° S at 4.2 AU (January 2000). We compare these events with observations at ˜1 AU using the nearly identical instrument, EPAM on ACE. In order to study the solar origins of these electrons using the imaging Nançay Radioheliograph, we further restricted the list of events to those in which interplanetary magnetic field lines with origins on the visible solar disk, intersected Ulysses. We find that not all the anisotropic electron events are observed by both spacecraft and there exists a strong dependence on the spacecraft's magnetic connection back to the Sun. We have identified the solar origin for five electron events using radio observations, and correlate these with interplanetary type-III radio emissions using the WIND/WAVES experiment.

Hawkins, S. E., III; Gold, R. E.; Pick, M.; Maia, D.

2001-05-01

403

800-keV Electron Induction Injector with High Average Power  

NASA Astrophysics Data System (ADS)

Design parameters of the induction injector are 800 keV beam energy, 2...5 kA current, 80 ns pulse flat top and 100 Hz repetition rate. The average beam power of the series of pulses is 40 kW. The injector modules use metglass cores. The electron source mounted on the stem consists of a 80 mm diameter velvet cathode placed on a field forming electrode. The tapered insulator assembly separates the oil-filled induction modules from the vacuum diode. The magnetic field necessary for beam extraction is generated by two magntic cores. 150 kV, 40 kA, 100 ns, 100 Hz pulse generator has been designed in Radiotechnical institute. The generator is a two-stage magnetic power compressor with a thyratron switch. The voltage pulse is produced by the water-filled pulse forming line (PFL) with the impedance of 3.3 ohm. The calculated parameters of the injector, the design features of its modules and the experimental results of their testing are presented.

Mamaev, G. L.; Glazov, A. I.; Krasnopolsky, V. A.; Latypov, T. A.; Mamaev, S. L.; Puchkov, S. N.; Shcherbakov, A. M.; Tenyakov, I. E.; Terechkin, Y. M.; Vlasenko, S. I.

1997-05-01

404

Microstructural evolution in Cu-A125 alloy under 300 keV Cu + ion irradiation  

NASA Astrophysics Data System (ADS)

Dispersion strengthened (DS) Cu-Al25 alloy containing small Al 2O 3 particles (˜4 nm in diameter) was irradiated by 300 keV Cu + ion to doses of 10 dpa and 30 dpa with a displacement rate of 3.7×10 -2 dpa/s at room temperature, which simulates the effects of high energy primary knock-on atoms (PKA) produced by 14 MeV neutrons. Microstructural evolution was investigated by transmission electron microscopy (TEM). Selected area diffraction (SAD) was used to study the phase stability of alumina under irradiation. The defect cluster structure formed by irradiation was investigated by dynamic two-beam techniques. Small particles of Al 2O 3 were dissolved under ion irradiation with increasing fluences. A large number of small Frank vacancy and interstitial dislocation loops (˜5 nm in diameter) with different Burgers vectors of a/3 <1 1 1> are produced by ion irradiation. At the region adjacent to the irradiation surface the number of vacancy loops was greater than that of interstitial ones. This result is in good agreement with the computer simulation results.

Li, Jing; Xu, Hui; Yu, Jinnan; Wu, Baoli; He, Qingfu

1998-10-01

405

Characterization of 1 MW, 40 keV, 1 s neutral beam for plasma heating  

SciTech Connect

Neutral beam with geometrical focusing for plasma heating in moderate-size plasma devices has been developed in Budker Institute of Nuclear Physics, Novosibirsk. When operated with hydrogen, the neutral beam power is 1 MW, pulse duration is 1 s, beam energy is 40 keV, and angular divergence is 1.2 deg. Initial ion beam is extracted and accelerated by triode multiapertures ion-optical system. To produce 1 MW neutral beam, about 40 A proton current is extracted with nominal current density of 320 mA/cm{sup 2}. Ion-optical system has 200 mm diameter grids with 44% transparency. The grids have inertia cooling and heat is removed between the pulses by water flowing in channels placed on periphery of the grids. A plasma emitter for ion extraction is produced by rf-plasma box. Ion species mix of rf plasma source amounts to 70%, 20%, and 10% of H{sup +}, H{sub 2}{sup +}, and H{sub 3}{sup +} ions, respectively, by current. Heavy impurities contribute less than 0.3%.

Sorokin, A.; Belov, V.; Davydenko, V.; Deichuli, P.; Ivanov, A.; Podyminogin, A.; Shikhovtsev, I.; Shulzhenko, G.; Stupishin, N.; Tiunov, M. [Budker Institute of Nuclear Physics, Lavrentev Ave. 11, Novosibirsk 630090 (Russian Federation)

2010-02-15

406

Time-Of Mass Spectrometry with KEV and Mev Projectiles Using Coincidence Counting.  

NASA Astrophysics Data System (ADS)

The goal of this study was to explore sample-projectile interactions by examining secondary ion (SI) yields in an event-by-event impact and detection mode. Cluster secondary ion mass spectrometry (SIMS) was evaluated in comparison to plasma desorption mass spectrometry (PDMS) and monoatomic SIMS. A cluster ion source was designed based on the spontaneous desorption (SD) process. The parameters affecting the SD were studied to optimize the cluster source performance. These factors were extraction grid vs. aperture, aperture size, source bias, source distance, and time. Under optimized SD conditions signal-to-noise ratios (S/N) up to approximately 27 were obtained for the production of CsI cluster ions. The ions of interest from the source were I^ - and (CsI)_{rm n} I^- clusters (where n is the cluster order). For our source a 3 mm gridless aperture 8 mm from the source foil produced the highest signal-to -noise ratio at 18 kV on the source. A signal-to-noise maximum was reached after the sample was biased for 12 hours. The SI yields from organic targets were compared for monoatomic keV ions, MeV ions (^{252 }Cf fission fragments), and polyatomic keV ions. The energy range of the clusters used was 18 to 27 keV. This comparison was made by calculating secondary ion yields for the molecular ions from a given sample. The organic samples used were epinephrine, gamma -aminobutyric acid, phenylalanine, and valine. For cluster bombardment secondary ion yields ranged from 0.53% for epinephrine to 3.45% for phenylalanine. These yields are less than the molecular ion yields from PDMS which ranged from 3.09% for epinephrine to 7.00% for phenylalanine. The secondary ion yields for monoatomic bombardment were 0.05% for epinephrine and 0.29% for phenylalanine. The higher yields observed with cluster primary ions are attributed to an enhancement effect related to the number of constituents in a cluster. Multiple ions detected from individual desorption events are said to be in coincidence. Coincidence counting can monitor these secondary ions and from which primary ion impact they occurred. This information is used to calculate percent coincidence between secondary ions. Percent coincidence is defined as the percentage of a peak observed in coincidence with another peak. Given the spatial correlations of ions emitted from the same projectile impact, percent coincidence gives indications about the homogeneity of surfaces. We found a linear relationship between a homogeneity factor based on percent coincidences of the secondary ions and particle size. Two types of samples were used, the first of which was a NaF/poly(vinyl methyl ether) (PVME) sample. With these samples we were able to distinguish between the PVME substrate and NaF crystals with diameters down to 1 mum. The second sample was rhodamine doped polystyrene spheres/PVME. The smallest sphere we were able to distinguish had a diameter of 0.48 mum.

Inman, Mark Estes

407

Comparison of calculated spectra for the interaction of photons in a liquid scintillator. Example of 54Mn 835 keV emission.  

PubMed

The CIEMAT/NIST and TDCR methods in liquid scintillation counting, initially developed for the activity standardization of pure-beta radionuclides, have been extended to the standardization of electron capture and beta-gamma radionuclides. Both methods require the calculation of the energy spectrum absorbed by the liquid scintillator. For radionuclides emitting X-rays or gamma-rays, when the energy is greater than a few tens of keV the Compton interaction is important and the absorption is not total. In this case, the spectrum absorbed by the scintillator must be calculated using analytical or stochastic models. An illustration of this problem is the standardization of 54Mn, which is a radionuclide decaying by electron capture. The gamma transition, very weakly converted, leads to the emission of an 835 keV photon. The calculation of the detection efficiency of this radionuclide requires the calculation of the energy spectrum transferred to the scintillator after the absorption of the gamma ray and the associated probability of absorption. The validity of the method is thus dependent on the correct calculation of the energy transferred to the scintillator. In order to compare the calculation results obtained using various calculation tools, and to provide the metrology community with some information on the choice of these tools, the LS working group of the ICRM organised a comparison of the calculated absorbed spectra for the 835 keV photon of 54Mn. The result is the spectrum of the energy absorbed by the scintillator per emission of an 835 keV gamma ray. This exercise was proposed for a standard 20 ml LS glass vial and for LS cocktail volumes of 10 and 15 ml. The calculation was done for two different cocktails: toluene and a widely used commercial cocktail, Ultima Gold. The paper describes the results obtained by nine participants using a total of 12 calculation codes. PMID:16600600

Cassette, P; Ahn, G H; Alzitzoglou, T; Aubineau-Lanièce, I; Bochud, F; Garcia Torano, E; Grau Carles, A; Grau Malonda, A; Kossert, K; Lee, K B; Laedermann, J P; Simpson, B R S; van Wyngaardt, W M; Zimmerman, B E

2006-01-01

408

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

Microsoft Academic Search

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

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

1984-01-01

409

Power supply for the LBL 40 keV neutral beam source  

SciTech Connect

A 20 keV, 50 Amp, 10 millisec pulse D$sup 0$ Neutral Beam Source at the Lawrence Berkeley Laboratory that serves as the prototype for 12 similar sources now in operation on the 2XIIB Mirror Machine at the Lawrence Livermore Laboratory has been recently upgraded to operate at 40 keV. The system of electronically regulated and controlled power supplies that drive the Source is described. (auth)

Baker, W.R.; Fitzgerald, M.L.; Honey, V.J.

1975-11-01

410

D- PRODUCTION BY CHARGE TRANSFER OF 0.3-10 keV D+, D0, AND D- IN CESIUM, RUBIDIUM, AND SODIUM VAPOR TARGETS  

SciTech Connect

Equilibrium charge-state fractions for 0.3-10-keV D ions and atoms in cesium-, rubidium-, and sodium-vapor targets are reported. The D{sup -} yield from charge transfer in a thick cesium-vapor target exceeds 30 percent at energies below 800 eV. The high D{sup -} yield in cesium vapor is consistent with recent calculations of the cross sections {sigma}{sub 0-} and {sigma}{sub -0} at low energies; at energies above 2.5 keV, the D{sup -} yield is consistent with our measurements of {sigma}{sub 0-} and {sigma}{sub -0}. The D{sup -} yield from charge transfer in rubidium vapor is similar to that for cesium vapor. For sodium vapor, however, there is a broad maximum of about 10 percent D{sup -} yield at about 3 keV, with slight structure at lower energies, implying structure in one of the charge-transfer cross sections.

Schlachter, A.S.; Stalder, K.R.; Stearns, J.W.

1980-04-01

411

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

NASA Technical Reports Server (NTRS)

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

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

1990-01-01

412

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

413

Resonant photoemission study of the electronic structure of 3 keV nitrogen-implanted tantalum  

SciTech Connect

The electronic properties of tantalum nitride thin films grown by 3 keV nitrogen implantation have been studied with resonant photoemission using synchrotron radiation. Resonant photoemission from the valence band was observed when the photon energy was in the neighborhood of the Ta 5p{yields}5d, 5p{yields}6sp and 4f{yields}5d transition energies. The constant initial state curves show multiple resonance maxima that are explained in terms of the Ta 5p{yields}5d, 5p{yields}6sp and 4f{yields}5d photoabsorption mechanisms, the spin-orbit splitting of the Ta 5p and Ta 4f core levels, and the splitting of the N-Ta hybridized unoccupied states by crystal-field interactions. A strong resonance has been observed at the Ta4f{yields}5d transition. Resonant photoemission results suggest a strong hybridization of the Ta 5d and N 2p atomic orbitals along the main feature of the VB (between {approx}3-9 eV) due to the extended nature of Ta orbitals. Occupied vacancy states at {approx}2 eV show a resonance enhancement that supports the Ta character recently predicted for such states by Stampfl and Freeman. Stronger resonances are found for the hybridized Ta 5d-N 2p valence band features lying in the {approx}3-9 eV range, than for the essentially Ta-like ones just below the Fermi level. This suggests that an interatomic recombination mechanism in which N 2p states resonate themselves could also take place.

Arranz, A.; Palacio, C. [Departamento de Fisica Aplicada, Facultad de Ciencias, C-XII, Universidad Autonoma de Madrid, Cantoblanco, 28049-Madrid (Spain); Avila, J. [LURE, Centre Universitaire Paris-Sud, Bat. 209 D, B.P. 34, 91898 Orsay Cedex (France)

2005-01-15

414

1-40-keV fixed-exit monochromator for a wafer mapping TXRF facility  

NASA Astrophysics Data System (ADS)

An industrial facility for the mapping of trace impurities on the surface of 300 mm Silicon wafers will be commissioned at the end of 1998. The elements to be detected range from Na to Hg with a target routine detection limit of 108 atoms/cm2. The monochromator of the facility plays a central role and fulfills the following requirements: ease of operations and fast tuning (one single motor); extended energy range (1 - 40 KeV covered by a fixed exit Si(111) channel cut and multilayer pair); smooth and reliable running (water cooling even in the powerful ESRF undulator beams at high energies). The mechanical structure of the monochromator is based on well-established concepts: an external goniometer transfers the main rotation to the in-vacuum plateau via a hollow differentially pumped feed-through. The optical arrangement shows some novelties: the plateau can be cooled either by water or liquid nitrogen and it holds the convex- concave machined Si(111) channel-cut for fixed exit performances. The shape of the machined surfaces of the crystal helps also on to spread the power density of the beam on the silicon surface. A set of two identical multilayers are also mounted on the plateau and the transition from the Si(111) crystal to the multilayer operation is performed by rotating the wafer main axis by about 180 degrees. The whole facility is centered around the three main components: the monochromator, the wafer handling robots and the two linear arrays of solid state fluorescence detectors.

Comin, Fabio; Apostolo, G.; Freund, Andreas K.; Mangiagalli, P.; Navizet, M.; Troxel, C. L.

1998-12-01

415

On the Origin of the 6.4 keV line from the GRXE  

NASA Astrophysics Data System (ADS)

The Galactic Ridge X-ray Emission (GRXE) spectrum has strong iron emission lines at 6.4, 6.7, and 7.0 keV, each corresponding to the neutral (or low-ionized), He-like, and H-like iron ions. The 6.4 keV fluorescence line is due to irradiation of neutral (or low ionized) material (iron) by hard X-ray sources, indicating uniform presence of the cold matter in the Galactic plane. In order to resolve origin of the cold fluorescent matter, we examined the contribution of the 6.4 keV line emission from white dwarf surfaces in the hard X-ray emitting symbiotic stars (hSSs) and magnetic cataclysmic variables (mCVs) to the GRXE. In our spectral analysis of 4 hSSs and 19 mCVs observed with Suzaku, we were able to resolve the three iron emission lines. We found that the equivalent-widths (EWs) of the 6.4 keV lines of hSSs are systematically higher than those of mCVs, such that the average EWs of hSSs and mCVs are 180-10 +50 eV and 93-3 +20 eV, respectively. The EW of hSSs compares favorably with the typical EWs of the 6.4 keV line in the GRXE of 90-300 eV depending on Galactic positions. Average 6.4 keV line luminosities of the hSSs and mCVs are 9.2 × 1039 and 1.6 × 1039 photons s-1, respectively, indicating that hSSs are intrinsically more efficient 6.4 keV line emitters than mCVs. We estimated required space densities of hSSs and mCVs to account for all the GRXE 6.4 keV line emission flux to be 2 × 10-7 pc-3 and 1 × 10-6 pc-3, respectively. We also estimated the actual 6.4 keV line contribution from the hSSs, which is as much as 30% of the observed GRXE flux, and that from the mCV is about 50%. We therefore conclude that the GRXE 6.4 keV line flux is primarily explained by hSSs and mCVs.

Eze, Romanus; Saitou, Kei; Ebisawa, Ken

2012-09-01

416

A source\\/drain formation technology utilizing sub-10 keV arsenic and assist-phosphorus implantation for 0.13 ?m MOSFET  

Microsoft Academic Search

We have developed a novel technology for formation of source\\/drain regions in 0.13 ?m MOSFETs. A combination of low-energy arsenic (8 keV) implantation and assist-phosphorous implantation suppresses transient enchanted diffusion (TED) of boron, and this improves Ion -Ioff characteristics as well as Vth roll-off. Assisted by low-dose phosphorous implantation, this technology can minimize both junction-leakage current and gate-poly depletion. An

K. Imai; S. Shishiguchi; K. Yamaguchi; N. Kimizuka; H. Onishi; T. Horiuchi

1999-01-01

417

Measurement of88Sr K-shell ionization probability across the nuclear elastic-scattering resonance at 5060 keV  

NASA Astrophysics Data System (ADS)

We have measured the dependence of the Sr K-shell-ionization probability on the projectile energy in the vicinity of the d-wave iosobaric analog resonance at 5060 keV in the reaction 88Sr(p,p)88Sr. The variation of the ionization probability with projectile enegy is interpreted in terms of a phase shift between the incoming and outgoing atomic ionization amplitudes due to the nuclear time delay.

Chemin, J. F.; Anholt, R.; Stoller, Ch.; Meyerhot, W. E.; Amundsen, P. A.

1981-09-01

418

Charge transfer of 0.2-5.0 keV protons and hydrogen atoms in sodium-, potassium- and rubidium-vapour targets  

Microsoft Academic Search

Total cross sections sigma +0 and sigma +- for single- and double-electron capture by protons, and total cross sections sigma 0- and sigma 0+ for single-electron capture and single-electron loss by neutral hydrogen atoms in single collisions with atoms of sodium, potassium and rubidium have been measured in the energy range 0.2-5.0 keV. All electron capture cross sections show a

F. Ebel; E. Salzborn

1987-01-01

419

Experimental investigation of ligand effects on the conversion electron spectrum of the 22.5 keV M1 + E2 nuclear transition in 149 Sm  

Microsoft Academic Search

The conversion electron spectrum of the 22.5keV M1 + E2 nuclear transition in 149Sm from the electron capture decay of 149Eu was experimentally studied for the “Eu2O3” and “EuF3” compounds in which 149Eu ions have the same assumed oxidation number +3 . While the energies of the L, M, N, O, and P1 conversion lines for “EuF3” were lower, on

A. Kh. Inoyatov; L. L. Perevoshchikov; A. Kovalík; O. Dragoun; D. V. Filosofov

2011-01-01

420

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

Microsoft Academic Search

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

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

2011-01-01

421

Differential cross-section measurements of multiply charged xenon ions produced in 10-28keV eXe collisions  

Microsoft Academic Search

Partial single-differential ionization cross sections (PSDICSs) of a multiply ionized xenon atom ( Xen+ , n=1-7 ) are measured for impact of 10-28keV electrons with xenon by performing coincidences between the produced recoil ions and the electrons of indiscriminated energies detected at 90° with respect to the incident electron beam direction. Values of relative PSDICSs for doubly charged ions are

S. Mondal; R. Shanker

2005-01-01

422

Differential cross-section measurements of multiply charged xenon ions produced in 10-28keV e⁻Xe collisions  

Microsoft Academic Search

Partial single-differential ionization cross sections (PSDICSs) of a multiply ionized xenon atom (Xe{sup n+}, n=1-7) are measured for impact of 10-28 keV electrons with xenon by performing coincidences between the produced recoil ions and the electrons of indiscriminated energies detected at 90 deg. with respect to the incident electron beam direction. Values of relative PSDICSs for doubly charged ions are

S. Mondal; R. Shanker

2005-01-01

423

Neutron slowing-down time studies in iron: measurements from 1.46 eV to 847 keV  

Microsoft Academic Search

Two techniques are used to investigate time-dependent neutron behaviour in a large iron assembly. The first, covering the energy range from 1·4 to 132 eV, uses resonance absorbers in conjunction with either a Ge(Li) detector or a small BF3 counter whilst the second, from 110 to 846 keV, uses inelastic scattering indicators with a Ge(Li) detector. The measurements in the

J. P. Rippon; Malcolm C. Scott

1974-01-01

424

A search for a thermal spike effect in sputtering. I. Temperature dependence of the yield at low-kev, heavy-ion bombardment  

Microsoft Academic Search

The temperature dependence of the angular-differential sputtering yield of silver has been studied for low-keV, heavy ion bombardment in order to check whether thermal spikes contribute to sputtering in this energy regime. An oscillating quartz microbalance was used as detector for sputtered particles.The measurements reported in this work pertain to sputtering of polycrystalline samples bombarded by 8 keV Ar and

K. Besocke; S. Berger; W. O. Hofer; U. Littmark

1982-01-01

425

Range measurement of boron isotopes in silicon from 600 keV to 2 MeV  

NASA Astrophysics Data System (ADS)

Ranges of boron isotopes with masses 10 and 11 were measured in silicon for implantation energies of 600 keV, 1.0, 1.5 and 2.0 MeV by use of high-energy elastic recoil detection analysis (HE-ERDA). The measured ranges were compared with TRIM and PRAL calculations. The experimental data show a deviation to larger depth particularly at higher energies. The ratio of the ranges of the isotopes is always lower than theoretically predicted. The experimental results can be interpreted as follows: the electronic stopping, which dominates this energy regime, increases slower than expected. The maximum of the stopping power is shifted towards lower energies and is lower than calculated. In the lower energy range the stopping power must be larger than predicted leading to smaller ranges for energies up to 1 MeV. Our experiment is in good agreement with former range measurements of Behar et al. [Nucl. Instr. and Meth. B34 (1988) 316] who used the very reliable 10B(n, ?) 6Li nuclear reaction technique (neutron depth profiling: NDP), and of Svensson et al. [J. Appl. Phys. 68 (1990) 73] using secondary ion mass spectroscopy (SIMS), who both found this behavior, too.

Goppelt, P.; Biersack, J. P.; Gebauer, B.; Fink, D.; Bohne, W.; Wilpert, M.; Wilpert, Th.

1993-06-01

426

Ejection of nanoclusters from gold nanoislet layers by 38 keV Au ions in the elastic stopping mode.  

PubMed

Total absolute yields of the ejected gold were obtained regardless of the type of the particles are--atoms, clusters, nanoclusters,--as well as absolute yields of gold nanoclusters, from nanoislet gold targets under bombardment by monoatomic gold ions at 45 degrees to the target surface with the energy 38 keV, i.e., in the "purely" elastic stopping mode -6 keV/nm up to the fluence of 4 x 10(12) cm2. Three targets had gold nanoislets on the substrate surface: 2-12 nm; -18 nm; -35 nm, the most probable sizes being 7.1; 9.4; 17.5 nm respectively. The part of the surface area covered with gold was known. Total transfer of gold was determined by means of the neutron-activation analysis and decreased from 450 to 20 at/ion. The number of the ejected gold nanoclusters was determined using TEM and decreased from approximately 0.06 to < 0.01 per one 38 keV Au ion with the increase of the most probable sizes of the nanoislets on the target from 7.1 to 17.5 nm. The yields appeared to be surprisingly high, which is of scientific and practical importance. Tentative estimations were made using molecular dynamics simulations. PMID:19916412

Baranov, I A; Della-Negra, S; Domaratsky, V P; Chemezov, A V; Kirillov, S N; Novikov, A C; Obnorsky, V V; Pautrat, M; Urbassek, H M; Wien, K; Yarmiychuk, S V; Zhurkin, E E

2009-07-01

427

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

PubMed

We present experimental results for the angular scattering of ?1-50 keV H, He, C, O, N, Ne, and Ar ions transiting through graphene foils and compare them with scattering through nominal ?0.5 ?g?cm(-2) carbon foils. Thin carbon foils play a critical role in time-of-flight ion mass spectrometers and energetic neutral atom sensors in space. These instruments take advantage of the charge exchange and secondary electron emission produced as ions or neutral atoms transit these foils. This interaction also produces angular scattering and energy straggling for the incident ion or neutral atom that acts to decrease the performance of a given instrument. Our results show that the angular scattering of ions through graphene is less pronounced than through the state-of-the-art 0.5 ?g?cm(-2) carbon foils used in space-based particle detectors. At energies less than 50 keV, the scattering angle half width at half maximum, ?1/2, for ?3-5 atoms thick graphene is up to a factor of 3.5 smaller than for 0.5 ?g?cm(-2) (?20 atoms thick) carbon foils. Thus, graphene foils have the potential to improve the performance of space-based plasma instruments for energies below ?50 keV. PMID:24689570

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

2014-03-01

428

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

429

Origin of the 871-keV gamma ray and the ``oxide'' attribute  

SciTech Connect

This work concludes the investigation of the oxide attribute of current interest for the characterization of stored plutonium. Originally it was believed that the presence of oxide could be ascertained by measurement of the 871-keV line in a high-resolution gamma-ray spectrum. However, recent work has suggested that the 871-keV gamma ray in plutonium oxide arises from the reaction {sup 14}N({alpha},p){sup 17}O rather than the inelastic scattering reaction {sup 17}O({alpha},{alpha}{prime}){sup 17}O*. This conclusion, though initially surprising, was obtained during efforts to determine the relative importance of americium and plutonium alpha-particle decay for the production of the 871-keV gamma ray. Several questions were raised by previous experiments: What role, if any does {sup 17}O have in the generation of the 871-keV gamma ray? How does sufficient nitrogen come to be present in plutonium oxide? Under what conditions is the 871-keV gamma ray measurable in plutonium oxide? This paper describes the answers to these questions.

AJ Peurrung; RJ Arthur; BD Geelhood; RD Scheele; RJ Elovich; SL Pratt

2000-03-22

430

2-gamma decay of the 662-keV isomer in ^137Ba  

NASA Astrophysics Data System (ADS)

2-gamma decay of the 662-keV ^137Ba isomer following ^137Cs beta decay has been observed using two 3"x3" NaI detectors, a 20.5-?Ci source, and a Pb shielding geometry designed to minimize direct and sequential Compton scattering backgrounds. In runs totaling 144 days, a 662-keV peak has been observed in the profile across the diagonal connecting 662-keV axis points in a 2-dimensional coincidence pulse-height spectrum. A preliminary value of 2.0(6)x10-6 is derived for the 2-gamma/1-gamma intensity ratio. The distribution of 662-keV events along the 2D diagonal is a continuum centered at 331-331 keV with a shape favoring a double quadrupole E2-M2 or M2-E2 decay sequence. Our result compares with upper limits of < 10-5, our assessment of the Beusch experiment [1], and < 2.2x10-6 by Basenko et al. [2]. It will be compared with theoretical estimates. [4pt] [1] W. Beusch, Helv Phys. Acta 33, 363 (1960)[0pt] [2] V.K. Basenko, A.N. Berlizov, and G.A. Prokopets, Bull. Russ. Acad. Sci. 56, 94 (1992)

Millener, D. J.; Sutter, R. J.; Alburger, D. E.

2011-10-01

431

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

NASA Astrophysics Data System (ADS)

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

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

432

7 keV sterile neutrino dark matter from split flavor mechanism  

NASA Astrophysics Data System (ADS)

The recently discovered X-ray line at about 3.5 keV can be explained by sterile neutrino dark matter with mass, ms?7 keV, and the mixing, sin22?˜10?10. Such sterile neutrino is more long-lived than estimated based on the seesaw formula, which strongly suggests an extra flavor structure in the seesaw sector. We show that one can explain both the small mass and the longevity based on the split flavor mechanism where the breaking of flavor symmetry is tied to the breaking of the B?L symmetry. In a supersymmetric case we find that the 7 keV sterile neutrino implies the gravitino mass about 100 TeV.

Ishida, Hiroyuki; Jeong, Kwang Sik; Takahashi, Fuminobu

2014-05-01

433

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

SciTech Connect

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

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

1987-09-21

434

Evaluation of the 1077 keV ?-ray emission probability from 68Ga decay  

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

435

Measurement of the 183 keV Resonance in 17O(p,alpha)14N using a Novel Technique  

SciTech Connect

We have developed a novel technique for measurements of low energy (p,alpha) reactions using heavy ion beams and a differentially-pumped windowless gas target. We applied this new approach to study the 183 keV resonance in the 17O(p,alpha)14}N reaction. We report a resonance energy (center-of-mass) of 183.5{+0.1}{-0.4} keV, a resonance strength of 1.70 +/- 0.15 meV, and set an upper limit (95\\% confidence) on the total width of the state of < 0.1 keV. This resonance is important for the 17O(p,alpha)14}N reaction rate, and we find that 18F production is significantly decreased in low mass ONeMg novae but less affected in more energetic novae. We also report the first determination of the stopping power for oxygen ions in hydrogen gas near the peak of the Bragg curve (E=193 keV/u) to be (63+/-1)e-15 eV-cm2.

Moazen, Brian H [ORNL; Bardayan, Daniel W [ORNL; Blackmon, Jeff C [ORNL; Chae, Kyung Yuk [ORNL; Chipps, Kelly A [ORNL; Domizioli, Carlo P [ORNL; Fitzgerald, Ryan [ORNL; Greife, Uwe [ORNL; Hix, William Raphael [ORNL; Grzywacz-Jones, Kate L [ORNL; KOZUB, RAYMOND L [ORNL; Lingerfelt, Eric J [ORNL; Livesay, Jake [ORNL; Nesaraja, Caroline D [ORNL; Pain, Steven D [ORNL; Roberts, Luke F [ORNL; Shriner, Jr., John F [ORNL; Smith, Michael Scott [ORNL; Thomas, Jeffrey S [ORNL

2007-01-01

436

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

437

BeppoSAX observations in the 2-100 keV band of the nearby Seyfert galaxies: an atlas of spectra  

NASA Astrophysics Data System (ADS)

An atlas of high energy (E?2 keV) spectra of nearby (z?0.1) Seyfert galaxies observed with BeppoSAX is presented. The data have been analyzed in an homogeneous way. The final sample contains BeppoSAX MECS+PDS (LECS data were not used here) pointings of 113 objects. No useful X-ray data were present for eight targets. The catalog of X-ray spectra contains data for 43 type-I Seyfert (including Seyfert 1.0, 1.2, and 1.5) and for 62 type-II objects (including Seyfert 1.8, 1.9, and 2.0). A total of 163 X-ray spectra (84 for type-I and 79 for type-II objects) were analyzed, since some sources were observed several times. 81 sources were detected at high energy (above 10 keV) by the PDS: 39 are Seyfert I and 42 are Seyfert II. The broadband X-ray spectra covering the ~2-100 keV band are 130 in total. In a forthcoming paper, the statistical analysis of these data will be presented.

Dadina, M.

2007-01-01

438

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</