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1

Spectral characteristics of plane multilayer amplitude diffraction gratings for the soft x-ray range  

NASA Astrophysics Data System (ADS)

Several spectral characteristics of plane multilayer amplitude molybdenum—silicon diffraction gratings (1000 and 2000 lines mm-1), fabricated by electron-beam lithography, were determined with a broadband laser-plasma source of soft x-rays. The gratings, with the multilayer structure period 11.5 nm, were investigated at near-normal incidence and at an angle of incidence of 36o in a quasi-stigmatic spectrograph system with moderate dispersion. The spectral profile of resonant reflection by the gratings was determined in the first and second interference orders of the multilayer structure for different angles of incidence. The line spectrum of multiply charged F(V) and F(VI) ions was recorded in the 16.0-18.5 nm range by means of these multilayer gratings and the resolving power of the gratings was estimated.

Troussel, P.; Bac, S.; Kolachevsky, Nikolai N.; Mitropol'skii, M. M.; Ragozin, Evgenii N.

1996-10-01

2

CO-ANALYSIS OF SOLAR MICROWAVE AND HARD X-RAY SPECTRAL EVOLUTIONS. I. IN TWO FREQUENCY OR ENERGY RANGES  

SciTech Connect

Solar microwave and hard X-ray spectral evolutions are co-analyzed in the 2000 June 10 and 2002 April 10 flares, and are simultaneously observed by the Owens-Valley Solar Array in the microwave band and by Yohkoh/Hard X-ray Telescope or RHESSI in the hard X-ray band, with multiple subpeaks in their light curves. The microwave and hard X-ray spectra are fitted by a power law in two frequency ranges of the optical thin part and two photon energy ranges, respectively. Similar to an earlier event in Shao and Huang, the well-known soft-hard-soft pattern of the lower energy range changed to the hard-soft-hard (HSH) pattern of the higher energy range during the spectral evolution of each subpeak in both hard X-ray flares. This energy dependence is actually supported by a positive correlation between the overall light curves and spectral evolution in the lower energy range, while it becomes an anti-correlation in the higher energy range. Regarding microwave data, the HSH pattern appears in the spectral evolution of each subpeak in the lower frequency range, which is somewhat similar to Huang and Nakajima. However, it returns back to the well-known pattern of soft-hard-harder for the overall spectral evolution in the higher frequency range of both events. This frequency dependence is confirmed by an anti-correlation between the overall light curves and spectral evolution in the lower frequency range, but it becomes a positive correlation in the higher frequency range. The possible mechanisms are discussed, respectively, for reasons why hard X-ray and microwave spectral evolutions have different patterns in different energy and frequency intervals.

Song Qiwu; Huang Guangli [Purple Mountain Observatory, Nanjing 210008 (China); Nakajima, Hiroshi, E-mail: songqw@pmo.ac.cng, E-mail: lhuang@pmo.ac.cn, E-mail: nakaji15@dia.janis.or.jp [Nobeyama Solar Radio Observatory, Nobeyama, Minamisaku, Nagano 384-1305 (Japan)

2011-06-20

3

Response of diamond photoconductors to soft x-ray in the spectral range 125 {angstrom} to 240 {angstrom}  

SciTech Connect

Due to the large bandgap of diamond, it is transparent to the visible spectrum, making it an attractive material for soft x-ray detection. Response of diamond photoconductors fabricated using Polycrystalline chemical-vapor-deposited (CVD) diamond to soft x-rays has been measured using x-rays emitted from a laser-produced plasma source in the spectral range 125 {Angstrom} to 240 {Angstrom}. These photoconductors have interdigitated electrode structure in order to increase the active area as well as detector sensitivity. Contributions to the detector sensitivity by the photoelectrons is discussed.

Han, S.; Wagner, R.S. [Los Alamos National Lab., NM (United States); Gullikson, E. [Lawrence Berkeley Lab., CA (United States)

1995-12-01

4

Spectral characteristics of plane multilayer amplitude diffraction gratings for the soft x-ray range  

Microsoft Academic Search

Several spectral characteristics of plane multilayer amplitude molybdenum---silicon diffraction gratings (1000 and 2000 lines mm-1), fabricated by electron-beam lithography, were determined with a broadband laser-plasma source of soft x-rays. The gratings, with the multilayer structure period 11.5 nm, were investigated at near-normal incidence and at an angle of incidence of 36o in a quasi-stigmatic spectrograph system with moderate dispersion. The

P. Troussel; S. Bac; Nikolai N. Kolachevsky; M. M. Mitropol'skii; Evgenii N. Ragozin

1996-01-01

5

An in-vacuum wiggler for SOLEIL Hard X-rays spectral range  

SciTech Connect

The production of Hard X-rays has become a tricky problem on medium energy storage rings. It requires Insertion Devices (IDs) with high magnetic field and a large number of periods. To cover the 20-50 keV photon energy range at SOLEIL (2.75 GeV), an in-vacuum wiggler (WSV50) has been preferred to a superconducting ID. The wiggler is composed of 38 periods of 50 mm producing a 2.1 T field at a minimum magnetic gap of 5.5 mm. To minimize the magnetic forces acting between magnet arrays (8.5 tons), a compensation system composed of non magnetic springs has been mounted apart from the magnet system to reduce the mechanical deformations. The wiggler has been assembled step by step by means of a genetic algorithm which minimizes the magnetic errors measured with a flipping coil. This paper presents the mechanical and magnetic design of the wiggler as well as the construction and the magnetic measurements.

Marcouille, O.; Chapuis, L.; Brunelle, P.; Berteaud, P.; Couprie, M.-E.; Filhol, J.-M.; Herbeaux, C.; Marlats, J.-L.; Massal, M.; Mary, A.; Tavakoli, K.; Valleau, M.; Veteran, J. [Synchrotron SOLEIL, L'Orme des Merisiers, Bat. A, Saint-Aubin, Gif-sur-Yvette- 9119 (France)

2010-06-23

6

Freestanding multilayer films for application as phase retarders and spectral purity filters in the soft x-ray and EUV ranges  

Microsoft Academic Search

A technique for fabrication of freestanding multilayers which are able to be used as optical elements in the soft X-ray and EUV ranges is reported. Two types of transmission mode elements have been developed: phase retarders for the aims of soft X-ray polarimetry and thin film spectral filters. A variety of phase retarders on the base of Cr\\/Sc, Cr\\/C, V\\/B4C

N. I. Chkhalo; M. N. Drozdov; S. A. Gusev; E. B. Kluenkov; A. Ya. Lopatin; V. I. Luchin; N. N. Salashchenko; L. A. Shmaenok; N. N. Tsybin; B. A. Volodin

2011-01-01

7

Tomographic imaging of coherent x-ray scatter momentum transfer distribution using spectral x-ray detection and polycapillary optic  

Microsoft Academic Search

Quantitation of coherent x-ray scatter traditionally involves measuring the intensity of the scattered x-ray over a range of angles (theta) from the illuminating monochromatic x-ray beam. Spectral x-ray imaging produces the same information at a single theta when bremsstrahlung x-ray exposure is used. We used a 200mum thick sheet-illumination of a phantom (lucite cylinder containing holes with water, polyethylene, collagen,

Diane R. Eaker; Steven M. Jorgensen; Anthony P. H. Butler; Erik L. Ritman

2010-01-01

8

The X-Ray Spectral Evolution of Galactic Black Hole X-Ray Binaries toward Quiescence  

NASA Astrophysics Data System (ADS)

Most transient black hole X-ray binaries (BHXBs) spend the bulk of their time in a quiescent state, where they accrete matter from their companion star at highly sub-Eddington luminosities (we define quiescence here as a normalized Eddington ratio lx = L 0.5-10 keV/L Edd < 10-5). Here, we present Chandra X-ray imaging spectroscopy for three BHXB systems (H 1743-322, MAXI J1659-152, and XTE J1752-223) as they fade into quiescence following an outburst. Multiple X-ray observations were taken within one month of each other, allowing us to track each individual system's X-ray spectral evolution during its decay. We compare these three systems to other BHXB systems. We confirm that quiescent BHXBs have softer X-ray spectra than low-hard-state BHXBs, and that quiescent BHXB spectral properties show no dependence on the binary system's orbital parameters. However, the observed anti-correlation between X-ray photon index (?) and lx in the low-hard state does not continue once a BHXB enters quiescence. Instead, ? plateaus to an average lang?rang = 2.08 ± 0.07 by the time lx reaches ~10-5. lx ~ 10-5 is thus an observationally motivated upper limit for the beginning of the quiescent spectral state. Our results are discussed in the context of different accretion flow models and across the black hole mass scale.

Plotkin, Richard. M.; Gallo, Elena; Jonker, Peter G.

2013-08-01

9

THE SECOND STAGE OF FERMI@ELETTRA: A SEEDED FEL IN THE SOFT X-RAY SPECTRAL RANGE  

SciTech Connect

The second stage of the FERMI FEL, named FEL-2, is based on the principle of high-gain harmonic generation and relies on a double-seeded cascade. Recent developments stimulated a revision of the original setup, which was designed to cover the spectral range between 40 and 10 nm. The numerical simulations we present here show that the nominal (expected) electron-beam performance allows extension of the FEL spectral range down to 4 nm. A significant amount of third harmonic power can be also expected. We also show that the proposed setup is flexible enough for exploiting future developments of new seed sources, e.g., high harmonic generation in gases.

Allaria, E.; DeNinno, G.; Fawley, W. M.

2009-08-14

10

Freestanding multilayer films for application as phase retarders and spectral purity filters in the soft x-ray and EUV ranges  

NASA Astrophysics Data System (ADS)

A technique for fabrication of freestanding multilayers which are able to be used as optical elements in the soft X-ray and EUV ranges is reported. Two types of transmission mode elements have been developed: phase retarders for the aims of soft X-ray polarimetry and thin film spectral filters. A variety of phase retarders on the base of Cr/Sc, Cr/C, V/B4C and W/B4C freestanding multilayers were designed for a spectral region of "water window" (?~ 2-4.5nm) 2 - 4.5 nm). The possibility to yield the phase shift between s- and p-polarizations as high as 90º at equal transparencies of these polarizations of 0.4% was experimentally demonstrated with Cr/Sc phase retarder close to the Sc L-edge of absorption (? = 3.11 nm). The set of freestanding absorption filters Cr/Sc, Mo/C, Zr/Si, Zr/Al with spectral windows within 2.2 to 22 nm wavelength range was developed for the aims of hot plasma diagnostics. We also fabricated Al/Si structures with supported mesh, which are transparent in the range ? = 17 - 60 nm, for application in the sun astronomy. The sample of 160 mm in diameter Mo/ZrSi2 spectral purity filters with transparency of 70% (? = 13 nm) was fabricated as the probable component part of industrial EUV lithography tool. The preliminary testing of heat load withstandability was fulfilled for a number of freestanding multilayers consisting of Si, Zr, Mo and silicides of both metals. It was found that Mo/ZrSi2 structure is the challenge to withstand intensive heating up to 800 - 850°C.

Chkhalo, N. I.; Drozdov, M. N.; Gusev, S. A.; Kluenkov, E. B.; Lopatin, A. Ya.; Luchin, V. I.; Salashchenko, N. N.; Shmaenok, L. A.; Tsybin, N. N.; Volodin, B. A.

2011-05-01

11

Tomographic imaging of coherent x-ray scatter momentum transfer distribution using spectral x-ray detection and polycapillary optic  

NASA Astrophysics Data System (ADS)

Quantitation of coherent x-ray scatter traditionally involves measuring the intensity of the scattered x-ray over a range of angles (?) from the illuminating monochromatic x-ray beam. Spectral x-ray imaging produces the same information at a single ? when bremsstrahlung x-ray exposure is used. We used a 200?m thick sheet-illumination of a phantom (lucite cylinder containing holes with water, polyethylene, collagen, polycarbonate, and nylon) and a polycapillary x-ray optic collimator to provide measurements at a fixed ?. A Medipix2 x-ray detection array (2562 (55?m)2 pixels) provided the spectral (E, 10 - 22 keV in 3keV energy bins) spread needed to generate the momentum transfer (q) profile information at one angle. The tungsten x-ray source anode (aluminum filter) was operated at 35kVp at 20mA. The detected scatter intensity was corrected for attenuation of the incident and the scattered x-ray by use of the regular CT image of the phantom generated at the same energy bins. The phantom was translated normal to the plane of the fan beam in 65, 0.2mm, steps to generate the 3D image data. The momentum transfer profiles generated with this approach were compared to published momentum transfer profiles obtained by other methods.

Eaker, Diane R.; Jorgensen, Steven M.; Butler, Anthony P. H.; Ritman, Erik L.

2010-08-01

12

THE DERIVATION OF APPROXIMATE X-RAY SPECTRAL DISTRIBUTIONS AND AN ANALYSIS OF X-RAY \\  

Microsoft Academic Search

Methods of deriving and specifying approximate methods of x-ray spectral ; distribution if either the time or facilities are not available for obtaining ; complete spectra are discussed and compared. Tables are provided that simplify ; the representation of an x-ray beam by three monoenergetic components when the ; transmission curve of the radiation in a suitable absorber is known.

J. R. Greening

1963-01-01

13

A new technique for X-ray spectroscopy of laser-plasmas with simultaneous 2D spatial resolution over a broad spectral range  

SciTech Connect

Over the past few years, a new X-ray diagnostic technique has been developed by the group of the Intense Laser Irradiation Laboratory of the CNR in Pisa. Here we give a brief description of this new diagnostic tool, which basically allows X-ray spectroscopy of laser-produced plasmas to be performed over a broad photon energy range with a simultaneous 2D spatial resolution. An outline of recent results will be also given in order to assess the diagnostic capabilities.

Labate, L.; Cecchetti, C. A.; Giulietti, A.; Giulietti, D.; Koester, P.; Levato, T.; Pathak, N.; Gizzi, L. A. [Istituto Nazionale di Ottica, Consiglio Nazionale delle Ricerche, Pisa (Italy); Dipartimento di Fisica, Universita di Pisa (Italy); Istituto Nazionale di Ottica, Consiglio Nazionale delle Ricerche, Pisa (Italy); Laboratori Nazionali di Frascati, Istituto Nazionale di Fisica Nucleare (Italy); Istituto Nazionale di Ottica, Consiglio Nazionale delle Ricerche, Pisa (Italy)

2012-05-25

14

Absolyutnaya spektral'naya chuvstvitel'nost' fotodiodnykh lineek v rentgenovskom diapazone 7-20 kehV. (Absolute spectral sensitivity of photodiode arrays in the X-ray energy range 7-20 keV).  

National Technical Information Service (NTIS)

The results of the investigation of absolute spectral sensitivity of linear photodiode arrays (the kind LF1024-25/2) as X-ray one-coordinate detectors in the energy range from 7 to 20 keV are presented. The measurements have been carried out with the use ...

I. P. Dolbnya S. G. Kurylo

1991-01-01

15

Extended Range X-Ray Telescope.  

National Technical Information Service (NTIS)

An X-ray telescope system is described which is designed for use on sounding rockets and satellites to investigate solar X-ray phenomena and cosmic X-ray sources. The system comprises a tubular mount having a collecting region at one axial end for receivi...

R. B. Hoover

1981-01-01

16

X-ray spectral properties of {gamma}-ray bursts  

SciTech Connect

The authors summarize the spectral characteristics of a sample of 22 bright gamma-ray bursts detected with the gamma-ray burst sensors aboard the satellite Ginga. This instrument employed a proportional and scintillation counter to provide sensitivity to photons in the 2--400 keV range, providing a unique opportunity to characterize the largely unexplored X-ray properties of gamma-ray bursts. The photon spectra of the Ginga bursts are well described by a low energy slope, a bend energy, and a high energy slope. In the energy range where they can be compared, this result is consistent with burst spectral analyses obtained from the BATSE experiment aboard the Compton Observatory. However, below 20 keV they find evidence for a positive spectral number index in approximately 40% of their burst sample, with some evidence for a strong rolloff at lower energies in a few events. They find that the distribution of spectral bend energies extends below 10 keV. The observed ratio of energy emitted in the X-rays relative to the gamma-rays can be much larger than a few percent and, in fact, is sometimes larger than unity. The average for their sample is 24%.

Strohmayer, T.E. [National Aeronautics and Space Administration, Greenbelt, MD (United States). Goddard Space Flight Center; Fenimore, E.E. [Los Alamos National Lab., NM (United States); Murakami, Toshio [ISAS, Sagamihara, Kanagawa (Japan); Yoshida, Atsumasa [RIKEN, Wako, Saitama (Japan)

1997-09-01

17

Spectral unfolds of PITHON Flash X-ray source.  

SciTech Connect

Using a differential absorption spectrometer we obtained experimental spectral information for the PITHON Flash X-ray Machine located in San Leandro, California at L-3 Communications. Spectral information we obtained pertained to the 200 keV to 800 keV endpoint operation of PITHON. We also obtained data on the temporal behavior of high energy and low energy spectral content.

Zarick, Thomas Andrew; Sheridan, Timothy J.; Hartman, E. Frederick; Riordan, John C. (L-3 Pulse Sciences)

2007-11-01

18

EXSAA: Environmentally-Induced X-ray Spectral Analysis Automation  

NASA Astrophysics Data System (ADS)

X-ray fluorescence (XRF) spectrometry is one of the principal means of compositional analysis in the lab and in the field: it will be a central tool in NASA's Exploration Initiative (EI) missions. No currently available XRF software has the generic functionality to provide the basis for XRF experiment design, instrument development, and data interpretation for the suite of prospective EI missions. In response to this need, we have developed EXSAA (Environmentally-induced X-ray Spectral Analysis Automation), a generic, fast, interactive spectral simulation tool which can be used in assessing broadband continuous spectra being generated and detected during reconnaissance missions and field campaigns involving planetary surfaces. The software produces model spectra of detectable environmentally-induced X-ray spectra from fundamental principles for target characteristics and conditions likely to be experienced in remote or in situ planetary missions. Fluorescence is modeled following Jenkins and DeVries (1967); coherent and Compton scattering following Hubbell (1969). The modeling provided is extensible, and a user interface provides for selection of source, detector characteristics, compositional components, and geometry for known targets. An immediate application of the tool is the prediction for mission planning purposes of X-ray flux to be expected for a range of targets and instrumentation. A longer-term application is the model basis for the recovery of surface composition from actual missions, where some parameters (e.g. source flux) will be known, and others obtained from a Bayesian analysis of the observations. Ultimately, EXSAA could function as part of the agent-based SAA Toolkit being developed by a group of physical scientists, systems engineers, and AI practitioners to automate portions of the spectral analysis process. EXSAA could be called on by human or machine agents to provide an understanding of XRF phenomena for tasks including specifically (1) instrument and mission design and planning, or (2) model-based data analysis. Thus EXSAA could support traditional design methods and enable a variety of experiments in automated design and operation. The far term objective is to develop a toolkit for use at the human/robotic interface during exploration of lunar or Martian surfaces.

Fallon, F. W.; Clark, P. E.; Rilee, M. L.; Truszkowski, W.

2005-05-01

19

Spectral Variation of Hard X-Ray Emission from the Crab Nebula with the Suzaku Hard X-Ray Detector  

NASA Astrophysics Data System (ADS)

The Crab Nebula is one of the brightest and most stable sources in the X-ray sky. Year-scale flux variation from the object was recently revealed in the hard X-ray band by four satellites. This marked the first detection of year-scale variability from pulsar wind nebulae in the hard X-ray band. The Crab Nebula has been observed at least once a year for calibration purposes with the Suzaku Hard X-ray Detector (HXD) since its launch in 2005. In order to investigate possible spectral changes as well as flux variation, archival data of the HXD were analyzed. The flux variation reported by other instruments was confirmed in the 25-100 keV band by the HXD at a few percent level, but flux above 100 keV did not follow the trend in variation below 100 keV. The hardness ratios produced utilizing the PIN and GSO sensors installed in the HXD exhibit significant scattering, thereby indicating spectral variations in the hard X-ray band. The spectral changes were quantified by spectral fitting with a broken power-law model. The difference between the two photon indexes of the broken power-law model in harder and softer energy bands is in the range of < 2.54. Taking into account a flux variation of 6.3% and a spectral variation time-scale of a few days, multi components of the broken power-law-shaped synchrotron emission with different cooling times are suggested.

Kouzu, Tomomi; Tashiro, Makoto S.; Terada, Yukikatsu; Yamada, Shin'ya; Bamba, Aya; Enoto, Teruaki; Mori, Koji; Fukazawa, Yasushi; Makishima, Kazu

2013-08-01

20

The X-Ray Spectral Changes of Scorpius X-1  

Microsoft Academic Search

Rossi X-Ray Timing Explorer (RXTE) observations of Sco X-1 during 1997-1999 have been analyzed for spectral characteristics. All the X-ray branches of Sco X-1 were observed during these epochs. On the basis of our observations, we present a simple model for the behavior of Sco X-1 as a function of accretion rate and angle of the observer's line of sight

C. F. Bradshaw; B. J. Geldzahler; E. B. Fomalont

2003-01-01

21

Fabrication of diffractive optical elements for x-ray range  

Microsoft Academic Search

Problems of microelectronics technology applications for diffractive optical elements fabrication have been considered. The results on x-ray diffractive focusing elements are described: amplitude and phase-contrast Fresnel zone plates as well as freestanding gold gratings. The creation of reflected Bragg-Fresnel lenses for soft x-ray range was made on the basis of multilayer x-ray mirrors. Considerable attention was paid to the correction

Yu A. Agafonov; Sergey V. Babin; Alexei I. Erko; A. A. Shestakov; Igor A. Schelokov

1993-01-01

22

Fabrication of diffractive optical elements for x-ray range  

NASA Astrophysics Data System (ADS)

Problems of microelectronics technology applications for diffractive optical elements fabrication have been considered. The results on x-ray diffractive focusing elements are described: amplitude and phase-contrast Fresnel zone plates as well as freestanding gold gratings. The creation of reflected Bragg-Fresnel lenses for soft x-ray range was made on the basis of multilayer x-ray mirrors. Considerable attention was paid to the correction of different distortion factors involved in the electron beam lithography process.

Agafonov, Yu A.; Babin, Sergey V.; Erko, Alexei I.; Shestakov, A. A.; Schelokov, Igor A.

1993-12-01

23

Optimal material discrimination using spectral x-ray imaging  

NASA Astrophysics Data System (ADS)

Spectral x-ray imaging using novel photon counting x-ray detectors (PCDs) with energy resolving abilities is capable of providing energy-selective images. PCDs have energy thresholds, enabling the classification of photons into multiple energy bins. The extra energy information provided may allow materials such as iodine and calcium, or water and fat to be distinguishable. The information content of spectral x-ray images, however, depends on how the photons are grouped together. In this work, we present a model to optimize energy windows for maximum material discrimination. Multivariate statistics allows the confidence region of the correlated uncertainties to be mapped in the thickness space. Minimization of the uncertainties enables optimization of energy windows. Applications related to small animal imaging and breast imaging are considered.

Nik, S. J.; Meyer, J.; Watts, R.

2011-09-01

24

X-ray spectral components of starburst galaxies  

NASA Astrophysics Data System (ADS)

X-ray emission processes in starburst galaxies (SBGs) are assessed, with the aim of identifying and characterizing the main spectral components. Our survey of spectral properties, complemented with a model for the evolution of galactic stellar populations, leads to the prediction of a complex spectrum. Comparing the predicted spectral properties with current X-ray measurements of the nearby SBGs M 82 and N253, we draw the following tentative conclusions: 1) X-ray binaries with accreting neutron stars are the main contributors in the 2-15 keV band, and could be responsible for the yet uninterpreted hard component required to fit the observed 0.5-10 keV spectra of SBGs; 2) diffuse thermal plasma contributes at energies la 1 keV; 3) nonthermal emission, from Compton scattering of FIR and CMB radiation fields photons off supernova-accelerated relativistic electrons, and AGN-like emission, are likely be the dominant emission at energies ga 30 keV; 4) supernova remnants make a relatively minor contribution to the X-ray continuum but may contribute appreciably to the Fe-K emission at 6.7 keV.

Persic, M.; Rephaeli, Y.

2002-02-01

25

Single-step absorption and phase retrieval with polychromatic x-rays using a spectral detector  

PubMed Central

In this letter we present a single-step method to simultaneously retrieve x-ray absorption and phase images valid for a broad range of imaging energies and material properties. Our method relies on the availability of spectrally resolved intensity measurements, which is now possible using semiconductor x-ray photon counting detectors. The new retrieval method is derived and presented with results showing good agreement.

Gursoy, Dogga; Das, Mini

2013-01-01

26

Spectral Properties of X-ray-Emitting Quasars  

NASA Astrophysics Data System (ADS)

I present spectral indices obtained from 112 X-ray-selected and fully optically-identified quasars in four sky fields in the southern hemisphere, detected by the Rosat Position Sensitive Proportional Counters. These fields were originally studied by Boyle et al. (1990) for the ultraviolet-excess properties of objects in the fields; only 47 of the quasars in the field were listed in Boyle et al. I determine the quasars' power-law spectral index alpha_E with three different methods: spectral ``stacking'', hardness ratios, and direct fitting. Both spectral stacking and the hardness ratio methods are used because several of the quasars were too dim to reliably calculate spectral indices individually. The spectral stacking method, which involves co-adding quasar spectra energy bins, shows a definite change in quasar spectral index with redshift.

Morgan, W. A., Jr.

1996-12-01

27

BROADBAND SPECTRAL ANALYSIS OF THE GALACTIC RIDGE X-RAY EMISSION  

SciTech Connect

Detailed spectral analysis of the Galactic X-ray background emission, or the Galactic Ridge X-ray Emission (GRXE), is presented. To study the origin of the emission, broadband and high-quality GRXE spectra were produced from 18 pointing observations with Suzaku in the Galactic bulge region, with a total exposure of 1 Ms. The spectra were successfully fitted by a sum of two major spectral components: a spectral model of magnetic accreting white dwarfs with a mass of 0.66{sup +0.09}{sub -0.07} M{sub Sun} and a softer optically thin thermal emission with a plasma temperature of 1.2-1.5 keV that is attributable to coronal X-ray sources. When combined with previous studies that employed high spatial resolution of the Chandra satellite, the present spectroscopic result gives stronger support to the scenario that the GRXE is essentially an assembly of numerous discrete faint X-ray stars. The detected GRXE flux in the hard X-ray band was used to estimate the number density of the unresolved hard X-ray sources. When integrated over a luminosity range of {approx}10{sup 30}-10{sup 34} erg s{sup -1}, the result is consistent with a value that was reported previously by directly resolving faint point sources.

Yuasa, Takayuki; Makishima, Kazuo; Nakazawa, Kazuhiro, E-mail: yuasa@astro.isas.jaxa.jp [Department of Physics, School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033 (Japan)

2012-07-10

28

Spectral Properties of X-Ray Binaries in Centaurus A  

NASA Astrophysics Data System (ADS)

We present a spectral investigation of X-ray binaries (XBs) in NGC 5128 (Cen A), using six 100 ks Chandra observations taken over two months in 2007. We divide our sample into thermally and non-thermally dominated states based on the behavior of the fitted absorption column N H, and present the spectral parameters of sources with Lx >~ 2 × 1037 erg s-1. The majority of sources are consistent with being neutron star low-mass X-ray binaries (NS LMXBs) and we identify three transient black hole (BH) LMXB candidates coincident with the dust lane, which is the remnant of a small late-type galaxy. Our results also provide tentative support for the apparent "gap" in the mass distribution of compact objects between ~2-5 M ?. We propose that BH LMXBs are preferentially found in the dust lane, and suggest this is because of the younger stellar population. The majority (~70%-80%) of potential Roche lobe filling donors in the Cen A halo are >~ 12 Gyr old, while BH LMXBs require donors >~ 1 M ? to produce the observed peak luminosities. This requirement for more massive donors may also explain recent results that claim a steepening of the X-ray luminosity function with age at Lx >= 5 × 1038 erg s-1 for the XB population of early-type galaxies; for older stellar populations, there are fewer stars >~ 1 M ?, which are required to form the more luminous sources.

Burke, Mark J.; Raychaudhury, Somak; Kraft, Ralph P.; Maccarone, Thomas J.; Brassington, Nicola J.; Hardcastle, Martin J.; Kainulainen, Jouni; Woodley, Kristin A.; Goodger, Joanna L.; Sivakoff, Gregory R.; Forman, William R.; Jones, Christine; Murray, Stephen S.; Birkinshaw, Mark; Croston, Judith H.; Evans, Daniel A.; Gilfanov, Marat; Jordán, Andrés; Sarazin, Craig L.; Voss, Rasmus; Worrall, Diana M.; Zhang, Zhongli

2013-04-01

29

X-ray Spectral Formation In High-mass X-ray Binaries: The Case Of Vela X-1  

NASA Astrophysics Data System (ADS)

We are working to develop improved models of radiatively-driven mass flows in the presence of an X-ray source -- such as in X-ray binaries, cataclysmic variables, and active galactic nuclei -- in order to infer the physical properties that determine the X-ray spectra of such systems. The models integrate a three-dimensional time-dependent hydrodynamics capability (FLASH); a comprehensive and uniform set of atomic data, improved calculations of the line force multiplier that account for X-ray photoionization and non-LTE population kinetics, and X-ray emission-line models appropriate to X-ray photoionized plasmas (HULLAC); and a Monte Carlo radiation transport code that simulates Compton scattering and recombination cascades following photoionization. As a test bed, we have simulated a high-mass X-ray binary with parameters appropriate to Vela X-1. While the orbital and stellar parameters of this system are well constrained, the physics of X-ray spectral formation is less well understood because the canonical analytical wind velocity profile of OB stars does not account for the dynamical and radiative feedback effects due to the rotation of the system and to the irradiation of the stellar wind by X-rays from the neutron star. We discuss the dynamical wind structure of Vela X-1 as determined by the FLASH simulation, where in the binary the X-ray emission features originate, and how the spatial and spectral properties of the X-ray emission features are modified by Compton scattering, photoabsorption, and fluorescent emission. This work was performed under the auspices of the U.S. Department of Energy by University of California, Lawrence Livermore National Laboratory under Contract W-7405-Eng-48.

Akiyama, Shizuka; Mauche, C. W.; Liedahl, D. A.; Plewa, T.

2007-05-01

30

Experimental investigation of X-ray spectral absorption coefficients in heated Al and Ge on the Iskra-5 laser facility  

SciTech Connect

We set forth the data of experimental investigation of X-ray spectral absorption coefficients in the 1.1 - 1.6 keV photon energy range for Al and Ge specimens bulk heated by soft X-ray radiation. Two experimental techniques are described: with the use of one facility channel and the heating of specimens by the X-ray radiation from a plane burnthrough target, as well as with the use of four channels and the heating by the radiation from two cylindrical targets with internal input of laser radiation. The X-ray radiation absorption coefficients were studied by way of transmission absorption spectroscopy using backlighting X-ray radiation from a point source. The results of investigation of X-ray spectral absorption coefficients on the 1s - 2p transitions in Al atoms and the 2p - 3d transitions in Ge atoms are presented.

Bondarenko, S V; Garanin, Sergey G; Zhidkov, N V; Pinegin, A V; Suslov, N A [Russian Federal Nuclear Center 'All-Russian Research Institute of Experimental Physics', Sarov, Nizhnii Novgorod region (Russian Federation)

2012-01-31

31

X-ray observations of spiral galaxies. II. Images and spectral parameters of 13 galaxies  

SciTech Connect

The results of a spatial and spectral analysis of a sample of spiral galaxies observed in X-rays with the Einstein satellite indicate that the X-ray emission is generally extended and complex. In some cases, discrete, very bright X-ray sources are detected, some of these coincident with the nuclear regions. The spectral fit of the IPC data to a thermal bremsstrahlung spectrum with a low-energy absorption cutoff shows that the average spectrum could be rather hard with kT greater than 2 keV, and with low-energy cutoff consistent with line-of-sight absorption. Results on NGC 4631, NGC 6946, and the nuclei of IC 342 and NGC 1313 are discussed and compared with previous observations in different energy ranges. 75 references.

Fabbiano, G.; Trinchieri, G.

1987-04-01

32

The Extended Range X-Ray Telescope center director's discretionary fund report  

NASA Astrophysics Data System (ADS)

An Extended Range X-Ray Telescope (ERXRT) of high sensitivity and spatial resolution capable of functioning over a broad region of the X-ray/XUV portion of the spectrum has been designed and analyzed. This system has been configured around the glancing-incidence Wolter Type I X-ray mirror system which was flown on the Skylab Apollo Telescope Mount as ATM Experiment S-056. Enhanced sensitivity over a vastly broader spectral range can be realized by the utilization of a thinned, back-illuminated, buried-channel Charge Coupled Device (CCD) as the X-ray/XUV detector rather than photographic film. However, to maintain the high spatial resolution inherent in the X-ray optics when a CCD of 30 micron pixel size is used, it is necessary to increase the telescope plate scale. This can be accomplished by use of a glancing-incidence X-ray microscope to enlarge and re-focus the primary image onto the focal surface of the CCD.

Hoover, R. B.; Cumings, N. P.; Hildner, E.; Moore, R. L.; Tandberg-Hanssen, E. A.

1985-03-01

33

X-Ray Spectral Variation of ? Carinae through the 2003 X-Ray Minimum  

NASA Astrophysics Data System (ADS)

We report the results of an observing campaign on ? Car around the 2003 X-ray minimum, mainly using the XMM-Newton observatory. These are the first spatially resolved X-ray monitoring observations of the stellar X-ray spectrum during the minimum. The hard X-ray emission, associated with the wind-wind collision (WWC) in the binary system, varied strongly in flux on timescales of days, but not significantly on timescales of hours. The X-ray flux in the 2-10 keV band seen by XMM-Newton was only 0.7% of the flux maximum seen by RXTE. The slope of the X-ray continuum above 5 keV did not vary in any observation, which suggests that the electron temperature of the hottest plasma did not vary significantly at any phase. Through the minimum, the absorption to the stellar source increased by a factor of 5-10 to NH~(3-4)×1023 cm-2. These variations were qualitatively consistent with emission from the WWC plasma entering into the dense wind of the massive primary star. During the minimum, X-ray spectra also showed significant excesses in the thermal Fe XXV emission line on the red side, while they showed only a factor of 2 increase in equivalent width of the Fe fluorescence line at 6.4 keV. These features are not fully consistent with the eclipse of the X-ray plasma and may suggest an intrinsic fading of the X-ray emissivity. The drop in the WWC emission revealed the presence of an additional X-ray component that exhibited no variation on timescales of weeks to years. This component may be produced by the collision of high-speed outflows at v~1000-2000 km s-1 from ? Car with ambient gas within a few thousand AU from the star.

Hamaguchi, Kenji; Corcoran, Michael F.; Gull, Theodore; Ishibashi, Kazunori; Pittard, Julian M.; Hillier, D. John; Damineli, Augusto; Davidson, Kris; Nielsen, Krister E.; Kober, Gladys Vieira

2007-07-01

34

Temporal and spectral variability in luminous X ray binaries  

NASA Astrophysics Data System (ADS)

A variety of timing analyses have been applied to data from recent Ginga observations of Galactic Black Hole Candidates (BHC) and Low Mass X-ray Binaries (LMXB) to probe spectral and temporal variability. (1) A cross spectral analysis of Cyg X-1 and GX 339-4. The cross spectral coherence function is used to study temporal correlations between hard and soft photons from Cyg X-1 and GX 339-4. A technique is developed to correct for counting noise and applied to Cyg X-1 to estimate the extent of the Compton scattering region. The region size is found to be of order .014 light seconds. (2) Correlation between QPO and LFN in GX 5-1. Statistical tests are developed to probe correlations between the QPO and LFN in GX 5-1 on the horizontal branch. At long time scales, QPO and LFN amplitudes are found to be correlated, but below 8 seconds the correlation disappears. Tests are calibrated through extensive simulations. We place severe constraints on the Beat Frequency model. (3) X-ray variability of Sco X-1 during a multiwavelength campaign. We present results of a March 1989 Ginga observation of Sco X-1 as part of a simultaneous worldwide multiwavelength campaign. We see both normal and flaring branch QPO. To test Z-diagram position as a state variable, we probe for correlation between velocity along the diagram and measurable quantities. Finally, we perform a search for coherent oscillation and find none, with an upper limit of 0.2 percent. (4) Search for coherent oscillations in Low Mass X-ray Binaries. Using Ginga and HEAO-1 data, we have performed the most sensitive search to date for coherent oscillations in LMXB. We describe a technique to compensate for Doppler smearing by source orbital motion with a single correction parameter, and obtain modulation depth limits for Sco X-1, GX 5-1, Cyg X-2, GX 340 + 0, GX 9 + 1 and 1820-30.

Vaughan, Brian Alexander

35

A wide dynamic range x-ray streak camera system  

SciTech Connect

An x-ray streak camera with wide dynamic range and a large slit photocathode of 30 mm length has been developed and calibrated. In order to achieve wide dynamic range, a conventional streak tube has been improved and the camera system has been designed without microchannel plate electron amplifier. As a result, a dynamic range of 922 is achieved in a single shot mode with laser pulse of 30 ps (full width at half maximum) at time resolution of better than 31 ps.

Niu Lihong; Yang Qinlao; Niu Hanben; Liao Hua; Zhou Junlan; Ding Yunkun [Institute of Optoelectronics, Shenzhen University, Guangdong 518060 (China); Laser Fusion Research Center, China Academy of Engineering Physics, Mianyang 621900 (China)

2008-02-15

36

The nature of X-ray spectral variability in Seyfert galaxies  

NASA Astrophysics Data System (ADS)

We use a model-independent technique to investigate the nature of the 2-15 keV X-ray spectral variability in four Seyfert galaxies and distinguish between spectral pivoting and the two-component model for spectral variability. Our analysis reveals conclusively that the softening of the X-ray continuum with increasing flux in MCG-6-30-15 and NGC 3516 is a result of summing two spectral components: a soft varying component (SVC) with spectral shape independent of flux and a hard constant component (HCC). In contrast, the spectral variability in NGC 4051 can be well described by simple pivoting of one component, together with an additional hard constant component. The spectral variability model for NGC 5506 is ambiguous, due to the smaller range of fluxes sampled by the data. We investigate the shape of the hard spectral component in MCG-6-30-15 and find that it appears similar to a pure reflection spectrum, but requires a large reflected fraction (R > 3). We briefly discuss physical interpretations of the different modes of spectral variability.

Taylor, Richard D.; Uttley, Philip; McHardy, Ian M.

2003-06-01

37

High dynamic range streak camera for subpicosecond time-resolved x-ray spectroscopy  

SciTech Connect

The full characterization of a time resolved x-ray spectrometer is presented. It is based on the coupling of a conical crystal with a subpicosecond x-ray streak camera. The detector is designed to operate in accumulation mode at high repetition rate (up to 1 kHz) allowing signal to noise ratio as high as 10{sup 4}:1. Optical switches have been used to limit the jitter induced in the subpicosecond range, demonstrating the very long term stability (a few hours) of the entire device. The data analysis have been developed to get the spectral and temporal resolution of an ultrashort laser-plasma-based x-ray source.

Bonte, C.; Harmand, M.; Dorchies, F.; Magnan, S.; Pitre, V.; Kieffer, J.-C.; Audebert, P.; Geindre, J.-P. [Universite Bordeaux I, CNRS, CEA, CELIA UMR 5107, 351 cours de la Liberation, Talence, F-33405 (France); I.N.R.S.-Energie, Materiaux et Telecommunications, 1650 boul. Lionel-Boulet, Varennes, Qc, J3X 1S2 (Canada); Laboratoire pour l'Utilisation des Lasers Intenses (LULI), Ecole Polytechnique, 91128 Palaiseau (France)

2007-04-15

38

STATISTICAL STUDY of HARD X-RAY SPECTRAL CHARACTERISTICS OF SOLAR FLARES  

NASA Astrophysics Data System (ADS)

We investigate the spectral characteristics of 75 solar flares at the hard X-ray peak time observed by RHESSI (Ramaty High Energy Solar Spectroscopic Imager) in the energy range 12-150keV. At energies above 40keV, the Hard X-ray emission is mostly produced by bremsstrahlung of suprathermal electrons as they interact with the ambient plasma in the chromosphere. The observed photon spectra therefore provide diagnostics of electron acceleration processes in Solar flares. We will present statistical results of spectral fitting using two models: a broken power law plus a thermal component which is a direct fit of the photon spectrum and a thick target model plus a thermal component which is a fit of the photon spectra with assumptions on the electrons emitting bremsstrahlung in the thick target approximation.

Alaoui, M.; Krucker, S.; Saint-Hilaire, P.; Lin, R. P.

2009-12-01

39

Development of Multilayer Optics in EUV, Soft X-Ray and X-Ray Range at IPOE  

Microsoft Academic Search

Multilayer coatings are key optical components in the EUV, soft X-ray and X-ray range. At Institute of Precision Optical Engineering\\u000a (IPOE), the development of multilayer optics has been impelled for their wide applications in X-ray laser, plasma diagnostics,\\u000a astronomical observation and synchrotron radiation. The paper presents our recent results of periodic multilayers of Mo\\/Si,\\u000a Cr\\/C, Cr\\/Sc, La\\/B4C, Mo\\/B4C, Si\\/C, Si\\/SiC,

Zhanshan Wang; Jingtao Zhu; Zhong Zhang; Xinbin Cheng; Jing Xu; Fengli Wang; Xiaoqiang Wang; Lingyan Chen

2009-01-01

40

The spectral archive of cosmic X-ray sources observed by the Einstein Observatory Focal Plane Crystal Spectrometer  

Microsoft Academic Search

The Einstein Observatory Focal Plane Crystal Spectrometer (FPCS) used the technique of Bragg spectroscopy to study cosmic X-ray sources in the 0.2-3 keV energy range. The high spectral resolving power (E\\/Delta-E is approximately equal to 100-1000) of this instrument allowed it to resolve closely spaced lines and study the structure of individual features in the spectra of 41 cosmic X-ray

Kenneth S. K. Lum; Claude R. Canizares; George W. Clark; Joan M. Coyne; Thomas H. Markert; Pablo J. Saez; Mark L. Schattenburg; P. F. Winkler

1992-01-01

41

Spectral-based 2D/3D X-ray to CT image rigid registration  

NASA Astrophysics Data System (ADS)

We present a spectral-based method for the 2D/3D rigid registration of X-ray images to a CT scan. The method uses a Fourier-based representation to decompose the six rigid transformation parameters problem into a twoparameter out-of-plane rotation and a four-parameter in-plane transformation problems. Preoperatively, a set of Digitally Reconstructed Radiographs (DRRs) are generated offline from the CT in the expected in-plane location ranges of the fluoroscopic X-ray imaging devices. Each DRR is transformed into a imaging device in-plane invariant features space. Intraoperatively, a few 2D projections of the patient anatomy are acquired with an X-ray imaging device. Each projection is transformed into its in-plane invariant representation. The out-of-plane parameters are first computed by maximization of the Normalized Cross-Correlation between the invariant representations of the DRRs and the X-ray images. Then, the in-plane parameters are computed with the phase correlation method based on the Fourier-Mellin transform. Experimental results on publicly available data sets show that our method can robustly estimate the out-of-plane parameters with accuracy of 1.5° in less than 1sec for out-of-plane rotations of 10° or more, and perform the entire registration in less than 10secs.

Freiman, M.; Pele, O.; Hurvitz, A.; Werman, M.; Joskowicz, L.

2011-03-01

42

Microwave Kinetic Inductance Detectors: Large Format X-ray Spectral Imagers for the Next Generation of X-ray Telescopes  

Microsoft Academic Search

Microwave Kinetic Inductance Detectors (MKIDs) have the potential to provide megapixel imagers with few eV spectral resolution for future X-ray missions such as Gen-X. MKIDs offer the advantage over many other cryogenic detector technologies that they can be easily multiplexed, so that arrays with many thousand pixels are readily achievable. In addition, the readout electronics can be operated at room

Megan E. Eckart; B. A. Mazin; B. Bumble; S. R. Golwala; J. Zmuidzinas; P. K. Day; F. A. Harrison

2006-01-01

43

X-Ray Spectral Variability in NGC 7469  

NASA Astrophysics Data System (ADS)

We present analyses of two Ginga observations and two observations from the ROSAT database of NGC 7469, focusing on the spectral variability observed on timescales of days and longer. During the 1988 Ginga observation, the hardness ratio (8-21 keV/3.4-5.7 keV) increased significantly as the total flux decreased by 30%. As the spectrum is well fit by the reflection model and since the spectra variability dominates the higher energy band, this could be explained by either a variation in the power law index or in the effective covering fraction of the reflecting material. This ambiguity is inherent in reflection modeling of Ginga spectra from moderate flux Seyfert 1 galaxies. Assuming that the power law index did not change, we find that the reflected flux is consistent with being constant, suggesting that much of the reflecting material may be located more than 3 light-days from the continuum source with the molecular torus being a plausible site. This scenario is also supported by the report of a narrow rather than broad iron K-alpha line in the ASCA data by Guainazzi et al. NGC 7469 was faint during the 1989 Ginga observation, but variability was observed with doubling timescale of 5 hr, and the spectrum was harder. A reflection component could not be constrained, and the change in the spectrum could be explained by an increase in neutral absorption. The brighter of two ROSAT spectra was significantly softer, and in both spectra there was evidence of spectral complexity, as has been previously reported by Turner, George, & Mushotzky and Brandt et al. The spectrum could be fit by a variety of two-component models, including a warm absorber model, an ionized disk model, and a thermal model with single-component blackbody spectrum, but joint fitting of the 1988 average Ginga spectrum and the nonsimultaneous ROSAT spectra favored thermal models, and other models required an anomalously high reflection ratio. This model is supported by the observation of a soft excess component and the lack of ionized absorption edges in the ASCA spectrum by Guainazzi et al. The long-term spectral variability could be explained by relative variability between the power-law and soft excess component normalizations, perhaps implying that hard X-ray reprocessing in thermal material does not dominate on long timescales.

Leighly, Karen; Kunieda, Hideyo; Awaki, Hisamitsu; Tsuruta, Sachiko

1996-05-01

44

X-Ray Spectral Study of the Photoionized Stellar Wind in Vela X-1  

SciTech Connect

We present results from quantitative modeling and spectral analysis of the high mass X-ray binary system Vela X-1 obtained with the Chandra High Energy Transmission Grating Spectrometer. The observations cover three orbital phase ranges within a single binary orbit. The spectra exhibit emission lines from H-like and He-like ions driven by photoionization, as well as fluorescent emission lines from several elements in lower charge states. The properties of these X-ray lines are measured with the highest accuracy to date. In order to interpret and make full use of the high-quality data, we have developed a simulator, which calculates the ionization and thermal structure of a stellar wind photoionized by an X-ray source, and performs Monte Carlo simulations of X-ray photons propagating through the wind. The emergent spectra are then computed as a function of the viewing angle accurately accounting for photon transport in three dimensions including dynamics. From comparisons of the observed spectra with results from the simulator, we are able to find the ionization structure and the geometrical distribution of material in the stellar wind of Vela X-1 that can reproduce the observed spectral line intensities and continuum shapes at different orbital phases remarkably well. We find that the stellar wind profile can be represented by a CAK-model with a star mass loss rate of (1.5-2.0) x 10{sup -6} M{sub {circle_dot}} yr{sup -1}, assuming a terminal velocity of 1100 km s{sup -1}. It is found that a large fraction of X-ray emission lines from highly ionized ions are formed in the region between the neutron star and the companion star. We also find that the fluorescent X-ray lines must be produced in at least three distinct regions: (1) the extended stellar wind, (2) reflection off the stellar photosphere, and (3) in a distribution of dense material partially covering and possibly trailing the neutron star, which may be associated with an accretion wake. Finally, from detailed analysis of the emission line profiles, we demonstrate that the stellar wind dynamics is affected by X-ray photoionization.

Watanabe, Shin; Sako, Masao; Ishida, Manabu; Ishisaki, Yoshitaka; Kahn, Steven M.; Kohmura, Takayoshi; Nagase, Fumiaki; Paerels, Frederik; Takahashi, Tadayuki; /JAXA, Sagamihara /KIPAC, Menlo Park /Tokyo Metropolitan U. /Kogakuin U. /Columbia U., Astron. Astrophys.

2006-07-10

45

X-ray multilayer mirrors with an extended angular range  

Microsoft Academic Search

The shape of the reflection curve of depth-graded X-ray multilayer mirrors may be controlled in an angular region several times greater than the angular width of traditionally periodical X-ray multilayer mirrors. Mirrors of this type may be used in X-ray collimators, focusing devices and scanners. In addition, very narrow angular gaps in the reflection curves may be obtained, which may

V. V. Protopopov; V. A. Kalnov

1998-01-01

46

SPECTRAL SURVEY OF X-RAY BRIGHT ACTIVE GALACTIC NUCLEI FROM THE ROSSI X-RAY TIMING EXPLORER  

SciTech Connect

Using long-term monitoring data from the Rossi X-ray Timing Explorer (RXTE), we have selected 23 active galactic nuclei (AGNs) with sufficient brightness and overall observation time to derive broadband X-ray spectra from 3 to {approx}>100 keV. Our sample includes mainly radio-quiet Seyferts, as well as seven radio-loud sources. Given the longevity of the RXTE mission, the greater part of our data is spread out over more than a decade, providing truly long-term average spectra and eliminating inconsistencies arising from variability. We present long-term average values of absorption, Fe line parameters, Compton reflection strengths, and photon indices, as well as fluxes and luminosities for the hard and very hard energy bands, 2-10 keV and 20-100 keV, respectively. We find tentative evidence for high-energy rollovers in three of our objects. We improve upon previous surveys of the very hard X-ray energy band in terms of accuracy and sensitivity, particularly with respect to confirming and quantifying the Compton reflection component. This survey is meant to provide a baseline for future analysis with respect to the long-term averages for these sources and to cement the legacy of RXTE, and especially its High Energy X-ray Timing Experiment, as a contributor to AGN spectral science.

Rivers, Elizabeth; Markowitz, Alex; Rothschild, Richard, E-mail: erivers@ucsd.edu [University of California, San Diego, Center for Astrophysics and Space Sciences, 9500 Gilman Dr., La Jolla, CA 92093-0424 (United States)

2011-03-15

47

An X-ray spectral model for Compton-thick toroidal reprocessors  

NASA Astrophysics Data System (ADS)

The central engines of both type 1 and type 2 active galactic nuclei are thought to harbour a toroidal structure that absorbs and reprocesses high-energy photons from the central X-ray source. Unique features in the reprocessed spectra can provide powerful physical constraints on the geometry, column density, element abundances and orientation of the circumnuclear matter. If the reprocessor is Compton-thick, the calculation of emission-line and continuum spectra that are suitable for direct fitting to X-ray data is challenging because the reprocessed emission depends on the spectral shape of the incident continuum, which may not be directly observable. We present new Monte Carlo calculations of Green's functions for a toroidal reprocessor that provide significant improvements over currently available models. The Green's function approach enables the construction of X-ray spectral fitting models that allow arbitrary incident spectra as part of the fitting process. The calculations are fully relativistic and have been performed for column densities that cover the Compton-thin to Compton-thick regime, for incident photon energies up to 500 keV. The Green's function library can easily be extended cumulatively to provide models that are valid for higher input energies and a wider range of element abundances and opening angles of the torus. The reprocessed continuum and fluorescent line emission due to Fe K?, Fe K? and Ni K? are treated self-consistently, eliminating the need for ad hoc modelling that is currently common practice. We find that the spectral shape of the Compton-thick reflection spectrum in both the soft and hard X-ray bands in our toroidal geometry is different compared with that obtained from disc models. A key result of our study is that a Compton-thick toroidal structure that subtends the same solid angle at the X-ray source as a disc can produce a reflection spectrum that is ~6 times weaker than that from a disc. This highlights the widespread and erroneous interpretation of the so-called `reflection-fraction' as a solid angle, obtained from fitting disc-reflection models to Compton-thick sources without regard for proper consideration of geometry.

Murphy, Kendrah D.; Yaqoob, Tahir

2009-08-01

48

An XMM-Newton spectral survey of 12 mum selected galaxies - I. X-ray data  

Microsoft Academic Search

We present an X-ray spectral analysis of 126 galaxies of the 12 mum galaxy sample. By studying this sample at X-ray wavelengths, we aim to determine the intrinsic power, continuum shape and obscuration level in these sources. We improve upon previous works by the use of superior data in the form of higher signal-to-noise ratio spectra, finer spectral resolution and

Murray Brightman; Kirpal Nandra

2011-01-01

49

X-ray-sensitive device based on a linear CCD for recording the radiation in the energy range 0.20 to 40.00 keV  

Microsoft Academic Search

The C(Pi) M11 x-ray sensitive device is intended for recording the one-dimensional space distribution of x-radiation fluence in the spectral energy range from 0.2 to 40.0 keV and can be used as a part of x-ray spectrometers of different types instead of the photographic film and for measurement of spatial parameters of x-ray beams and oth.

B. F. Voronov; M. V. Emelyanov; Yu. I. Kozhunov; O. B. Kozlov; S. I. Rybin; A. E. Favorski

1999-01-01

50

Spectral filtering optimization of a measuring channel of an x-ray broadband spectrometer  

NASA Astrophysics Data System (ADS)

A new channel of an X-ray broadband spectrometer has been developed for the 2 - 4 keV spectral range. It uses a spectral filtering by using a non-periodic multilayer mirror. This channel is composed by a filter, an aperiodic multilayer mirror and a detector. The design and realization of the optical coating mirror has been defined such as the reflectivity is above 8% in almost the entire bandwidth range 2 - 4 keV and lower than 2% outside. The mirror is optimized for working at 1.9° grazing incidence. The mirror is coated with a stack of 115 chromium / scandium (Cr / Sc) non-periodic layers, between 0.6 nm and 7.3 nm and a 3 nm thick top SiO2 layer to protect the stack from oxidization. To control thin thicknesses, we produced specific multilayer mirrors which consist on a superposition of two periodic Cr / Sc multilayers with the layer to calibrate in between. The mirror and subnanometric layers characterizations were made at the "Laboratoire Charles Fabry" (LCF) with a grazing incidence reflectometer working at 8.048 keV (Cu K? radiation) and at the synchrotron radiation facility SOLEIL on the hard X-ray branch of the "Metrology" beamline. The reflectivity of the mirrors as a function of the photon energy was obtained in the Physikalisch Technische Bundesanstalt (PTB) laboratory at the synchrotron radiation facility Bessy II.

Emprin, B.; Troussel, Ph.; Villette, B.; Delmotte, F.

2013-05-01

51

Characteristics of transition radiation in the x-ray spectral region  

SciTech Connect

Measurements of soft x-ray production by transition radiation have been performed in a series of experiments at the Lawrence Livermore National Laboratory. The results have shown that transition radiation is an intense and predictable source of photons in the soft x-ray energy range. This paper will give a brief review of the general properties of the x-ray distributions generated by these sources. 9 refs., 9 figs.

Moran, M.J.

1986-06-06

52

TW Hya: SPECTRAL VARIABILITY, X-RAYS, AND ACCRETION DIAGNOSTICS  

SciTech Connect

The nearest accreting T Tauri star, TW Hya was intensively and continuously observed over {approx}17 days with spectroscopic and photometric measurements from four continents simultaneous with a long segmented exposure using the Chandra satellite. Contemporaneous optical photometry from WASP-S indicates a 4.74 day period was present during this time. The absence of a similar periodicity in the H{alpha} flux and the total X-ray flux which are dominated by accretion processes and the stellar corona, respectively, points to a different source of photometric variations. The H{alpha} emission line appears intrinsically broad and symmetric, and both the profile and its variability suggest an origin in the post-shock cooling region. An accretion event, signaled by soft X-rays, is traced spectroscopically for the first time through the optical emission line profiles. After the accretion event, downflowing turbulent material observed in the H{alpha} and H{beta} lines is followed by He I ({lambda}5876) broadening near the photosphere. Optical veiling resulting from the heated photosphere increases with a delay of {approx}2 hr after the X-ray accretion event. The response of the stellar coronal emission to an increase in the veiling follows {approx}2.4 hr later, giving direct evidence that the stellar corona is heated in part by accretion. Subsequently, the stellar wind becomes re-established. We suggest a model that incorporates the dynamics of this sequential series of events: an accretion shock, a cooling downflow in a supersonically turbulent region, followed by photospheric and later, coronal heating. This model naturally explains the presence of broad optical and ultraviolet lines, and affects the mass accretion rates determined from emission line profiles.

Dupree, A. K.; Brickhouse, N. S.; Cranmer, S. R.; Luna, G. J. M.; Schneider, E. E. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Bessell, M. S. [Australian National Observatory, Mount Stromlo Observatory, Canberra, ACT 2611 (Australia); Bonanos, A. [Institute of Astronomy and Astrophysics, National Observatory of Athens, 15236 Athens (Greece); Crause, L. A. [South African Astronomical Observatory, P.O. Box 9, Observatory 7935, Cape Town (South Africa); Lawson, W. A. [School of Physical, Environmental, and Math Sciences, University of New South Wales, Canberra, ACT 2600 (Australia); Mallik, S. V. [Indian Institute of Astrophysics, Bangalore 560034 (India); Schuler, S. C. [National Optical Astronomy Observatory, Tucson, AZ 85719 (United States)

2012-05-01

53

Power Density Spectral Analysis as a Method of Compact Object Determination in X-ray Binary Systems  

NASA Astrophysics Data System (ADS)

Mass determinations and X-ray energy spectral analyses are among the methods used to distinguish between the types of compact objects present in X-ray binary systems. We test a method of distinguishing between neutron stars and black holes proposed by Sunyaev and Revnivtsev where power density spectra are used, particularly in the 500-1000Hz range. Sunyaev and Revnivtsev found that only neutron stars appear to have significant power in this frequency range. We apply this criterion to 12 X-ray binary systems (six neutron stars and six black holes) using USA data and cannot reproduce Sunyaev and Revnivtsev's result. The reason for this discrepancy is most likely a USA instrumental effect which manifests itself as excess power in the frequency range of interest. Future work on correcting this problem should provide more accurate analyses that may yield a different result.

Lee, J.

2002-08-01

54

Hysteresis in X-ray Transient Spectral Transitions  

NASA Astrophysics Data System (ADS)

We present hardness-intensity plots for several soft X-ray transients (the neutron star Aql X-1 and the black hole candidates 1748-288, 1859+226, 2012+381 and 1550-564) from pointed RXTE observations and RXTE All-Sky Monitor Observations. We show that in all cases for which there is good data, the hardness intensity diagrams over the course of the outburst cycle map out a loop, indicating that hysteresis is present and that the state transitions from hard-to-soft occur at a different luminosity than those from soft-to-hard. We show that this observation (1) rules out propeller effects as the sole cause of state transitions in Aql X-1 and (2) implies a common origin for the state transitions in accreting black holes and neutron stars. We discuss the implications for popular models of state transitions, such as the onset of an adiabatic or advection dominated accretion flow. We discuss the similarities between these results and the similar loop in the diagram of X-ray intensity versus radio intensity previously reported in GX 339-4.

Maccarone, Thomas; Coppi, Paolo

2002-04-01

55

Efficient, high-spectral-resolution Bragg crystal x-ray polarimeter  

Microsoft Academic Search

Utilizing Bragg scattering near 90°, an x-ray polarimeter is described that has high spectral resolution and reasonable efficiency. The latter is achieved by using a position-sensitive proportional counter to discriminate spatially resolved x rays dispersed by the crystal. This instrument has been used to measure the linear polarization of lines from one- and two-electron oxygen ions. For this study, aligned

B. L. Doyle; U. Schiebel; L. D. Ellsworth; James R. MacDonald

1978-01-01

56

An XMM-Newton spectral survey of 12 micron selected galaxies. I. X-ray data  

Microsoft Academic Search

We present an X-ray spectral analysis of 126 galaxies of the 12 micron galaxy\\u000asample. We pay particular attention to Compton thick AGN with the help of new\\u000aspectral fitting models that we have produced, which are based on Monte-Carlo\\u000asimulations of X-ray radiative transfer, using both a spherical and torus\\u000ageometry, and taking into account Compton scattering and Fe

Murray Brightman; Kirpal Nandra

2010-01-01

57

A Study of the Discontinuous Drop in X-ray Emission at Spectral Type B1  

Microsoft Academic Search

B supergiants display a discontinuous drop in X-ray emission along a dividing line in the H-R diagram (analogous to the one for K giants) which is referred to as the bistability jump at spectral type B1. Our XMM study of the X-ray properties on both sides of the jump have revealed several interesting results, but some uncertainties have arisen since

Wayne Waldron

2006-01-01

58

Experimental investigation of capillaries and focusing systems in soft x-ray range  

NASA Astrophysics Data System (ADS)

The results of an experimental investigation of transporting soft x-rays through quartz capillaries are presented. These results are used to design a capillary focusing system in the soft x-ray range. Monolithic and assembled x-ray lenses for AlK(alpha )- and MoL(alpha )-radiation are also investigated. These result are compared to those obtained with multilayer structures.

Arkadiev, Vladimir A.; Beckhoff, Burkhard; Bzhaumikhov, Aniuar A.; Gorny, Hans E.; Kanngiesser, Birgit

1996-07-01

59

X-Ray Detector Calibrations in the 280-Ev to 100-Kev Energy Range.  

National Technical Information Service (NTIS)

The absolute sensitivity for several different types of radiation detectors has been measured using x-rays in the energy range of 280 eV to 100 keV. The photons in this energy range are produced using three separate x-ray-generating facilities. The detect...

J. L. Gaines R. W. Kuckuck R. D. Ernst

1976-01-01

60

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

61

THE OPTX PROJECT. III. X-RAY VERSUS OPTICAL SPECTRAL TYPE FOR ACTIVE GALACTIC NUCLEI  

SciTech Connect

We compare the optical spectral types with the X-ray spectral properties for a uniformly selected (sources with fluxes greater than the 3sigma level and above a flux limit of f {sub 2-8keV} > 3.5 x 10{sup -15} erg cm{sup -2} s{sup -1}), highly spectroscopically complete (>80% for f {sub 2-8keV} > 10{sup -14} erg cm{sup -2} s{sup -1} and >60% below) 2-8 keV X-ray sample observed in three Chandra fields (CLANS, CLASXS, and the CDF-N) that cover approx1.2 deg{sup 2}. For our sample of 645 spectroscopically observed sources, we confirm that there is significant overlap of the X-ray spectral properties, as determined by the effective photon indices, GAMMA{sub eff}, obtained from the ratios of the 0.5-2 keV to 2-8 keV counts, for the different optical spectral types. For example, broad-line active galactic nuclei (AGNs) are expected to be unobscured and hence X-ray soft (GAMMA{sub eff} >= 1.2), yet we find 20%+- 3% have GAMMA{sub eff} <1.2. Non-broad-line AGNs are expected to be obscured and hence X-ray hard (GAMMA{sub eff} < 1.2), yet we find 33% +- 4% have GAMMA{sub eff} >= 1.2. Thus, one cannot use the X-ray spectral classifications and the optical spectral classifications equivalently. Since it is not understood how X-ray and optical classifications relate to the obscuration of the central engine, we strongly advise against a mixed classification scheme, as it can only complicate the interpretation of X-ray AGN samples. We confirm the dependence of optical spectral type on X-ray luminosity, and for z < 1, we find a similar luminosity dependence of GAMMA{sub eff}. However, this dependence breaks down at higher redshifts due to the highly redshift-dependent nature of GAMMA{sub eff}. We therefore also caution that any classification scheme which depends on GAMMA{sub eff} is likely to suffer from serious redshift bias.

Trouille, L.; Barger, A. J. [Department of Astronomy, University of Wisconsin-Madison, 475 North Charter Street, Madison, WI 53706 (United States); Cowie, L. L. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Yang, Y. [Department of Astronomy, University of Illinois, 1002 West Green Street, Urbana, IL 61801 (United States); Mushotzky, R. F. [NASA Goddard Space Flight Center, Code 662, Greenbelt, MD 20771 (United States)

2009-10-01

62

The OPTX Project. III. X-ray Versus Optical Spectral Type for Active Galactic Nuclei  

NASA Astrophysics Data System (ADS)

We compare the optical spectral types with the X-ray spectral properties for a uniformly selected (sources with fluxes greater than the 3? level and above a flux limit of f 2-8 keV > 3.5 × 10-15 erg cm-2 s-1), highly spectroscopically complete (>80% for f 2-8 keV > 10-14 erg cm-2 s-1 and >60% below) 2-8 keV X-ray sample observed in three Chandra fields (CLANS, CLASXS, and the CDF-N) that cover ~1.2 deg2. For our sample of 645 spectroscopically observed sources, we confirm that there is significant overlap of the X-ray spectral properties, as determined by the effective photon indices, ?eff, obtained from the ratios of the 0.5-2 keV to 2-8 keV counts, for the different optical spectral types. For example, broad-line active galactic nuclei (AGNs) are expected to be unobscured and hence X-ray soft (?eff >= 1.2), yet we find 20%± 3% have ?eff <1.2. Non-broad-line AGNs are expected to be obscured and hence X-ray hard (?eff < 1.2), yet we find 33% ± 4% have ?eff >= 1.2. Thus, one cannot use the X-ray spectral classifications and the optical spectral classifications equivalently. Since it is not understood how X-ray and optical classifications relate to the obscuration of the central engine, we strongly advise against a mixed classification scheme, as it can only complicate the interpretation of X-ray AGN samples. We confirm the dependence of optical spectral type on X-ray luminosity, and for z < 1, we find a similar luminosity dependence of ?eff. However, this dependence breaks down at higher redshifts due to the highly redshift-dependent nature of ?eff. We therefore also caution that any classification scheme which depends on ?eff is likely to suffer from serious redshift bias. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The observatory was made possible by the generous financial support of the W. M. Keck Foundation.

Trouille, L.; Barger, A. J.; Cowie, L. L.; Yang, Y.; Mushotzky, R. F.

2009-10-01

63

THE CORRELATION BETWEEN X-RAY LINE IONIZATION AND OPTICAL SPECTRAL TYPES OF THE OB STARS  

SciTech Connect

Marked correlations are reported between the ionization of the X-ray line spectra of normal OB stars, as observed by the Chandra X-Ray Observatory, and their optical spectral types. These correlations include the progressive weakening of the higher ionization relative to the lower ionization X-ray lines with advancing spectral type, and the similarly decreasing intensity ratios of the H-like to He-like lines of the alpha ions. These relationships were not predicted by models, nor have they been clearly evident in astrophysical studies of a few objects; rather, they have emerged from morphological analysis of an adequate (albeit still small) sample, from which known peculiar objects such as magnetic stars and very rapid rotators have been isolated to reveal the normal trends. This process is analogous to that which first demonstrated the strong relationships between the UV wind profiles and the optical spectral types of normal OB stars, which likely bear a physical as well as a historical connection to the present X-ray results. Since the optical spectral types are calibrated in terms of fundamental stellar parameters, it follows that the winds and X-ray spectra are determined by the latter. These observations provide strong guidance for further astrophysical modeling of these phenomena.

Walborn, Nolan R. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Nichols, Joy S. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Waldron, Wayne L., E-mail: walborn@stsci.ed, E-mail: jnichols@cfa.harvard.ed, E-mail: wwaldron@satx.rr.co [Eureka Scientific, Inc., 2452 Delmer Street, Suite 100, Oakland, CA 94602 (United States)

2009-09-20

64

Spectrally resolving and scattering-compensated x-ray luminescence/fluorescence computed tomography  

PubMed Central

The nanophosphors, or other similar materials, emit near-infrared (NIR) light upon x-ray excitation. They were designed as optical probes for in vivo visualization and analysis of molecular and cellular targets, pathways, and responses. Based on the previous work on x-ray fluorescence computed tomography (XFCT) and x-ray luminescence computed tomography (XLCT), here we propose a spectrally-resolving and scattering-compensated x-ray luminescence/fluorescence computed tomography (SXLCT or SXFCT) approach to quantify a spatial distribution of nanophosphors (other similar materials or chemical elements) within a biological object. In this paper, the x-ray scattering is taken into account in the reconstruction algorithm. The NIR scattering is described in the diffusion approximation model. Then, x-ray excitations are applied with different spectra, and NIR signals are measured in a spectrally resolving fashion. Finally, a linear relationship is established between the nanophosphor distribution and measured NIR data using the finite element method and inverted using the compressive sensing technique. The numerical simulation results demonstrate the feasibility and merits of the proposed approach.

Cong, Wenxiang; Shen, Haiou; Wang, Ge

2011-01-01

65

Spectrally resolving and scattering-compensated x-ray luminescence/fluorescence computed tomography  

NASA Astrophysics Data System (ADS)

The nanophosphors, or other similar materials, emit near-infrared (NIR) light upon x-ray excitation. They were designed as optical probes for in vivo visualization and analysis of molecular and cellular targets, pathways, and responses. Based on the previous work on x-ray fluorescence computed tomography (XFCT) and x-ray luminescence computed tomography (XLCT), here we propose a spectrally-resolving and scattering-compensated x-ray luminescence/fluorescence computed tomography (SXLCT or SXFCT) approach to quantify a spatial distribution of nanophosphors (other similar materials or chemical elements) within a biological object. In this paper, the x-ray scattering is taken into account in the reconstruction algorithm. The NIR scattering is described in the diffusion approximation model. Then, x-ray excitations are applied with different spectra, and NIR signals are measured in a spectrally resolving fashion. Finally, a linear relationship is established between the nanophosphor distribution and measured NIR data using the finite element method and inverted using the compressive sensing technique. The numerical simulation results demonstrate the feasibility and merits of the proposed approach.

Cong, Wenxiang; Shen, Haiou; Wang, Ge

2011-06-01

66

Experimental measurements of selenium x-ray laser spectral line profiles  

SciTech Connect

The authors discuss their recent measurements of the spectral width of the 206.38 {Angstrom} x-ray laser transition in Ne-like Se. These measurements used a high-resolution grating spectrometer and were performed over a wide range of laser amplifier lengths. The data have enabled them to extrapolate the intrinsic line width and to observe the effects of gain-narrowing and saturation on the line profile. They find an intrinsic width which is 1.4 times the Doppler width, they observe gain-narrowing in intermediate length amplifiers, and they observe no re-broadening in long, saturated amplifiers. These results suggest that collisional line-broadening has a significant effect on the line profile and saturation behavior of this laser.

Koch, J.A.; MacGowan, B.J.; Da Silva, L.B.; Matthews, D.L.; London, R.A.; Lee, R.W.; Mrowka, S. [Lawrence Livermore National Lab., CA (US); Underwood, J.H.; Batson, P.J. [Lawrence Berkeley Lab., CA (US)

1993-03-01

67

An XMM-Newton spectral survey of 12 ?m selected galaxies - I. X-ray data  

NASA Astrophysics Data System (ADS)

We present an X-ray spectral analysis of 126 galaxies of the 12 ?m galaxy sample. By studying this sample at X-ray wavelengths, we aim to determine the intrinsic power, continuum shape and obscuration level in these sources. We improve upon previous works by the use of superior data in the form of higher signal-to-noise ratio spectra, finer spectral resolution and a broader bandpass from XMM-Newton. We pay particular attention to Compton thick active galactic nucleus (AGN) with the help of new spectral fitting models that we have produced, which are based on Monte Carlo simulations of X-ray radiative transfer, using both a spherical and torus geometry, and taking into account Compton scattering and iron fluorescence. We use this data to show that with a torus geometry, unobscured sightlines can achieve a maximum equivalent width of the Fe K? line of ˜150 eV, originally shown by Ghisellini et al. In order for this to be exceeded, the line of sight must be obscured with NH > 1023 cm-2, as we show for one case, NGC 3690. We also calculate flux suppression factors from the simulated data, the main conclusion from which is that for NH? 1025 cm-2, the X-ray flux is suppressed by a factor of at least 10 in all X-ray bands and at all redshifts, revealing the biases present against these extremely heavily obscured systems inherent in all X-ray surveys. Furthermore, we confirm previous results from Murphy & Yaqoob that show that the reflection fraction determined from slab geometries is underestimated with respect to toroidal geometries. For the 12 ?m selected galaxies, we investigate the distribution of X-ray power-law indices, finding that the mean (= 1.90+0.05-0.07 and ??= 0.31+0.05-0.05) is consistent with previous works, and that the distribution of ? for obscured and unobscured sources is consistent with the source populations being the same, in general support of unification schemes. We determine a Compton thick fraction for the X-ray AGN in our sample to be 18 ± 5 per cent which is higher than the hard X-ray (>10 keV) selected samples. Finally we find that the obscured fraction for our sample is a strong function of X-ray luminosity, peaking at a luminosity of ˜1042-43 erg s-1.

Brightman, Murray; Nandra, Kirpal

2011-05-01

68

X-ray Spectral Formation In High-mass X-ray Binaries: The Case Of Vela X-1  

Microsoft Academic Search

We are working to develop improved models of radiatively-driven mass flows in the presence of an X-ray source -- such as in X-ray binaries, cataclysmic variables, and active galactic nuclei -- in order to infer the physical properties that determine the X-ray spectra of such systems. The models integrate a three-dimensional time-dependent hydrodynamics capability (FLASH); a comprehensive and uniform set

Shizuka Akiyama; C. W. Mauche; D. A. Liedahl; T. Plewa

2007-01-01

69

Possible application of X-ray optical elements for reducing the spectral bandwidth of an X-ray SASE FEL  

Microsoft Academic Search

A new design for a single pass X-ray Self-Amplified Spontaneous Emission (SASE) FEL is proposed. The scheme consists of two undulators and an X-ray monochromator located between them. The first stage of the FEL amplifier operates in the SASE linear regime. After the exit of the first undulator the electron bunch is guided through a non-isochronous bypass and the X-ray

J Feldhaus; E. L Saldin; J. R Schneider; E. A Schneidmiller; M. V Yurkov

1997-01-01

70

Simulation of experimental investigations of X-ray spectral path lengths on Iskra-5 laser facility  

SciTech Connect

We describe an improved Slater average-ion model employed in the numerical-theoretical analysis of experimental data, which were obtained in the investigation of X-ray spectral path lengths performed on the Iskra-5 laser facility at the All-Russian Scientific Research Institute of Experimental Physics (VNIIEF). The proposed model permits determining the spectral characteristics of the X-ray radiation with an accuracy of a few electronvolts. We outline the results of simulations of experiments with X-ray radiation-heated aluminium and germanium specimens of initial thickness of {approx}0.1 mm, in which absorption lines arising from 1s-2p transitions in Al and the absorption band arising from 2p-3d transitions in Ge were recorded.

Bel'kov, S A; Sharov, O O [Russian Federal Nuclear Center 'All-Russian Research Institute of Experimental Physics', Sarov, Nizhnii Novgorod region (Russian Federation)

2011-10-31

71

A High Spatial Resolution X-Ray and H? Study of Hot Gas in the Halos of Star-forming Disk Galaxies. I. Spatial and Spectral Properties of the Diffuse X-Ray Emission  

NASA Astrophysics Data System (ADS)

We present arcsecond resolution Chandra X-ray and ground-based optical H? imaging of a sample of 10 edge-on star-forming disk galaxies (seven starburst and three ``normal'' spiral galaxies), a sample that covers the full range of star formation intensity found in disk galaxies. The X-ray observations make use of the unprecedented spatial resolution of the Chandra X-ray observatory to more robustly than before remove X-ray emission from point sources and hence obtain the X-ray properties of the diffuse thermal emission alone. We have combined the X-ray observations with existing, comparable-resolution, ground-based H? and R-band imaging and present a mini-atlas of images on a common spatial and surface brightness scale to aid cross-comparison. In general, the morphology of the extraplanar diffuse X-ray emission is very similar to the extraplanar H? filaments and arcs, on both small and large scales (scales of tens of parsecs and kiloparsecs, respectively). The most spectacular cases of this are found in NGC 1482 (for which we provide the first published X-ray observation) and NGC 3079. We provide a variety of quantitative measures of how the spectral hardness and surface brightness of the diffuse X-ray emission varies with increasing height z above the plane of each galaxy. Of the eight galaxies in which diffuse X-ray emitting halos are found (the starbursts and the normal spiral NGC 891), significant spatial variation in the spectral properties of the extraplanar emission (|z|>=2 kpc) is only found in two cases: NGC 3628 and NGC 4631. In general, the vertical distribution of the halo-region X-ray surface brightness is best described as an exponential, with the observed scale heights of the sample galaxies lying in the range Heff~2-4 kpc. The presence of extraplanar X-ray emission is always associated with the presence of extraplanar optical line emission of similar vertical extent. No X-ray emission was detected from the halos of the two low-mass normal spiral galaxies NGC 6503 and NGC 4244. Active galactic nuclei, where present, appear to play no role in powering or shaping the outflows from the starburst galaxies in this sample. The Chandra ACIS X-ray spectra of extraplanar emission from all these galaxies can be fitted with a common two-temperature spectral model with an enhanced ?-to-iron element ratio. This is consistent with the origin of the X-ray emitting gas being either metal-enriched merged SN ejecta or shock-heated ambient halo or disk material with moderate levels of metal depletion onto dust. Our favored model is that SN feedback in the disks of star-forming galaxies create, via blow-out and venting of hot gas from the disk, tenuous exponential atmospheres of density scale height Hg~4-8 kpc. The soft thermal X-ray emission observed in the halos of the starburst galaxies is either this preexisting halo medium, which has been swept up and shock-heated by the starburst-driven wind, or wind material compressed near the walls of the outflow by reverse shocks within the wind. In either case, the X-ray emission provides us with a powerful probe of the properties of gaseous halos around star-forming disk galaxies.

Strickland, David K.; Heckman, Timothy M.; Colbert, Edward J. M.; Hoopes, Charles G.; Weaver, Kimberly A.

2004-04-01

72

High spectral resolution x-ray optics with highly oriented pyrolytic graphite.  

PubMed

Thin films of highly oriented pyrolytic graphite (HOPG) give the opportunity to realize crystal optics with arbitrary geometry by mounting it on a mould of any shape. A specific feature of HOPG is its mosaicity accompanied by a high integral reflectivity, which is by an order of magnitude higher than that of all other known crystals in an energy range between 2 keV up to several 10 keV. These characteristics make it possible to realize highly efficient collecting optics, which could be also relevant for compact x-ray diagnostic tools and spectrometers. For these applications the achievable spectral resolution of the crystal optics is of interest. In this article measurements with a spectral resolution of E/DeltaE=2900 in the second order reflection and E/DeltaE=1800 in the first order reflection obtained with HOPG crystals are presented. These are by far the highest spectral resolutions reported for HOPG crystals. The integral reflectivity of these very thin films is still comparable with that of ideal Ge crystals. The trade-off between energy resolution and high integral reflectivity for HOPG is demonstrated by determining these parameters for HOPG films of different thickness. PMID:19516609

Legall, H; Stiel, H; Arkadiev, V; Bjeoumikhov, A A

2006-05-15

73

Spatial and Spectral Features of Soft Diffuse X Ray Background Seen by the Einstein Observatory.  

National Technical Information Service (NTIS)

A survey of the diffuse soft X-ray background as seen directly by the Einstein Observatory Imaging Proportional Counter (IPC) is presented. A source free region of the detector 1 by 1 degree field is used. The background in the 0.16 to 3.5 keV spectral re...

G. Micela F. R. Harnden R. Rosner S. Sciortino G. S. Vaiana

1989-01-01

74

Experimental spectral measurements of heavy K-edge filtered beams for x-ray computed mammotomography  

PubMed Central

A dual modality computed mammotomography (CmT) and single photon emission computed tomography (SPECT) system for dedicated 3D breast imaging is in development. Using heavy K-edge filtration, the CmT component narrows the energy spectrum of the cone-shaped x-ray beam incident on the patient’s pendant, uncompressed breast. This quasi-monochromatic beam is expected to improve discrimination of tissue with similar attenuation coefficients while restraining absorbed dose to below that of dual view mammography. Previous simulation studies showed the optimal energy that maximizes dose efficiency for a 50/50% adipose/glandular breast is between 30 and 40 keV. This study experimentally validates these results using pre-breast and post-breast spectral measurements made under tungsten tube voltages between 40 and 100 kVp using filter materials with K-edge values ranging from 15 to 70 keV. Different filter material thicknesses are used, approximately equivalent to the 200th and 500th attenuating value layer (VL) thickness. Cerium (K = 40.4 keV) filtered post-breast spectra for 8–18 cm breasts are measured for a range of breast compositions. Figures of merit include mean beam energy, spectral full-width at tenth-maximum, beam hardening and dose for the range of breast sizes. Measurements corroborate simulation results, indicating that for a given dose, a 200th VL of cerium filtration may have optimal performance in the dedicated mammotomography paradigm.

Crotty, D J; McKinley, R L; Tornai, M P

2012-01-01

75

Methods for deconvoluting and interpreting complex gamma- and x-ray spectral regions  

SciTech Connect

Germanium and silicon detectors are now widely used for the detection and measurement of x and gamma radiation. However, some analysis situations and spectral regions have heretofore been too complex to deconvolute and interpret by techniques in general use. One example is the L x-ray spectrum of an element taken with a Ge or Si detector. This paper describes some new tools and methods that were developed to analyze complex spectral regions; they are illustrated with examples.

Gunnink, R.

1983-06-01

76

New consistency tests for high-accuracy measurements of X-ray mass attenuation coefficients by the X-ray extended-range technique  

SciTech Connect

An extension of the X-ray extended-range technique is described for measuring X-ray mass attenuation coefficients by introducing absolute measurement of a number of foils - the multiple independent foil technique. Illustrating the technique with the results of measurements for gold in the 38-50 keV energy range, it is shown that its use enables selection of the most uniform and well defined of available foils, leading to more accurate measurements; it allows one to test the consistency of independently measured absolute values of the mass attenuation coefficient with those obtained by the thickness transfer method; and it tests the linearity of the response of the counter and counting chain throughout the range of X-ray intensities encountered in a given experiment. In light of the results for gold, the strategy to be ideally employed in measuring absolute X-ray mass attenuation coefficients, X-ray absorption fine structure and related quantities is discussed.

Chantler, C.T.; Islam, M.T.; Rae, N.A.; Tran, C.Q.; Glover, J.L.; Barnea, Z. (La Trobe); (Melbourne)

2012-09-25

77

Spin and spectral variations of a peculiar high-mass X-ray binary 4U 2206+54  

NASA Astrophysics Data System (ADS)

Spin properties and spectral variations of a high-mass X-ray binary 4U 2206+54 are studied with long-term hard X-ray monitoring observations by INTEGRAL. A long-period X-ray pulsar of Pspin ˜ 5558 s has been identified in 4U 2206+54. The spin evolution of the neutron star in 4U 2206+54 is detected with the INTEGRAL/IBIS data. From 2005 to 2011, the spin period of the neutron star in 4U 2206+54 varies from ˜5558 to ˜5588 s. The average spin-down rate in the last 20 years is derived as ˜5 × 10-7 s s-1. 4U 2206+54 is a variable source with luminosities of ˜1035-1036 erg s-1 in the range of 3-100 keV. Its spectrum can be described by an absorbed power-law model with exponential rolloff. The hydrogen column density and photon index show the anticorrelations with hard X-ray luminosity: low column density and small photon index at maximum of luminosity. This spectral variation pattern suggests that 4U 2206+54 would be a highly obscured binary system. Furthermore, the possible cyclotron line features are searched for in the spectra of different luminosities. The possible cyclotron absorption feature around 30 keV is not confirmed in our work. The physical origin and evolutional track of this very slow pulsation neutron star are still unclear. We suggest that 4U 2206+54 would be a young system with the long-term spin-down trend, would evolve to a longer spin-period range and transit to the spin-up phase similar to 2S 0114+65. These very slow pulsation X-ray pulsars would belong to a new class of compact objects - accreting magnetars.

Wang, Wei

2013-06-01

78

Parameterized algorithms for quantitative differentials in spectrally equivalent medical diagnostic x-ray beams  

SciTech Connect

Qualitative and quantitative equivalence of spectra transmitted by two different elemental filters require a good match in terms of shape and size over the entire energy range of 0-150 keV used in medical diagnostic radiology. However, the photoelectric absorptions and Compton scattering involved in the interaction of x rays with matter at these relatively low photon energies differ in a nonuniform manner with energy and atomic number. By careful choice of thicknesses for filter materials with an atomic number between 12 and 39, when compared with aluminum, it is possible to obtain transmitted beams of the same shape (quality) but not of the same size (quantity). In this paper, calculations have been carried out for the matching of the shapes and sizes of beams transmitted through specified thicknesses of aluminium filter and spectrally equivalent thicknesses of other filter materials (different from aluminium) using FORTRAN source codes traceable to the American Association of Physics in Medicine (AAPM), College Park, MD, USA. Parametrized algorithms for the evaluation of quantitative differentials (deficit or surplus) in radiation output (namely, photon fluence, exposure, kerma, energy imparted, absorbed dose, and effective dose) from these transmitted spectrally equivalent beams were developed. These differentials range between 1%, and 4% at 1 mm Al filtration and between 8%, and 25% for filtration of 6 mm Al for different filter materials in comparison with aluminum. Also developed were models for factors for converting measures of photon fluence, exposure-area product, (EAP), and kerma-area product (KAP) to risk related quantities such as energy imparted, absorbed dose, and effective dose from the spectrally equivalent beams. The thicknesses of other filter materials that are spectrally equivalent to given thicknesses of aluminum filter were characterized using polynomial functions. The fact that the use of equivalent spectra in radiological practice can provide means of ranking the differentials in radiographic image quality and stochastic risk is discussed.

Okunade, Akintunde Akangbe [Department of Physics, Obafemi Awolowo University, Ile-Ife, Osun State (Nigeria)

2005-06-15

79

C IV EMISSION AND THE ULTRAVIOLET THROUGH X-RAY SPECTRAL ENERGY DISTRIBUTION OF RADIO-QUIET QUASARS  

SciTech Connect

In the rest-frame ultraviolet (UV), two of the parameters that best characterize the range of emission-line properties in quasar broad emission-line regions are the equivalent width and the blueshift of the C IV {lambda}1549 line relative to the quasar rest frame. We explore the connection between these emission-line properties and the UV through X-ray spectral energy distribution (SED) for radio-quiet (RQ) quasars. Our sample consists of a heterogeneous compilation of 406 quasars from the Sloan Digital Sky Survey (at z > 1.54) and Palomar-Green survey (at z < 0.4) that have well-measured C IV emission-line and X-ray properties (including 164 objects with measured {Gamma}). We find that RQ quasars with both strong C IV emission and small C IV blueshifts can be classified as 'hard-spectrum' sources that are (relatively) strong in the X-ray as compared to the UV. On the other hand, RQ quasars with both weak C IV emission and large C IV blueshifts are instead 'soft-spectrum' sources that are (relatively) weak in the X-ray as compared to the UV. This work helps to further bridge optical/soft X-ray 'eigenvector 1' relationships to the UV and hard X-ray. Based on these findings, we argue that future work should consider systematic errors in bolometric corrections (and thus accretion rates) that are derived from a single mean SED. Detailed analysis of the C IV emission line may allow for SED-dependent corrections to these quantities.

Kruczek, Nicholas E.; Richards, Gordon T.; Deo, Rajesh P.; Krawczyk, Coleman M. [Department of Physics, Drexel University, Philadelphia, PA 19104 (United States); Gallagher, S. C. [Department of Physics and Astronomy, The University of Western Ontario, London, ON N6A 3K7 (Canada); Hall, Patrick B. [Department of Physics and Astronomy, York University, Toronto, Ontario M3J 1P3 (Canada); Hewett, Paul C. [Institute of Astronomy, Cambridge CB3 0HA (United Kingdom); Leighly, Karen M. [Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, Norman, OK 73019 (United States); Proga, Daniel [Department of Physics and Astronomy, University of Nevada Las Vegas, Las Vegas, NV 891541 (United States)

2011-10-15

80

A new soft X-ray spectral model for polars with an application to AM Herculis  

NASA Astrophysics Data System (ADS)

We present a simple heuristic model for the time-averaged soft X-ray temperature distribution in the accretion spot on the white dwarf in polars. The model is based on the analysis of the Chandra LETG spectrum of the prototype polar AM Her and involves an exponential distribution of the emitting area vs. blackbody temperature a(T) = a0 exp( - T/T0). With one free parameter besides the normalization, it is mathematically as simple as the single blackbody, but is physically more plausible and fits the soft X-ray and far-ultraviolet spectral fluxes much better. The model yields more reliable values of the wavelength-integrated flux of the soft X-ray component and the implied accretion rate than reported previously. Based on observations with the Chandra and ROSAT satellites.

Beuermann, K.; Burwitz, V.; Reinsch, K.

2012-07-01

81

Spatial resolution of synchrotron x-ray microtomography in high energy range: Effect of x-ray energy and sample-to-detector distance  

NASA Astrophysics Data System (ADS)

Spatial resolution of three-dimensional images obtained by synchrotron X-ray microtomography technique is evaluated using cyclic bar patterns machined on a steel wire. Influences of X-ray energy and the sample-to-detector distance on spatial resolution were investigated. High X-ray energies of 33-78 keV are applied due to the high X-ray absorption of transition metals. Best spatial resolution of about 1.2 ?m pitch was observed at the sample-to-detector distance range of 20-110 mm and at the energy range of 68-78 keV. Several factors such as X-ray scattering and diffraction phenomena affecting the degradation of spatial resolution are also discussed.

Seo, D.; Tomizato, F.; Toda, H.; Uesugi, K.; Takeuchi, A.; Suzuki, Y.; Kobayashi, M.

2012-12-01

82

Spatial resolution of synchrotron x-ray microtomography in high energy range: Effect of x-ray energy and sample-to-detector distance  

SciTech Connect

Spatial resolution of three-dimensional images obtained by synchrotron X-ray microtomography technique is evaluated using cyclic bar patterns machined on a steel wire. Influences of X-ray energy and the sample-to-detector distance on spatial resolution were investigated. High X-ray energies of 33-78 keV are applied due to the high X-ray absorption of transition metals. Best spatial resolution of about 1.2 {mu}m pitch was observed at the sample-to-detector distance range of 20-110 mm and at the energy range of 68-78 keV. Several factors such as X-ray scattering and diffraction phenomena affecting the degradation of spatial resolution are also discussed.

Seo, D.; Tomizato, F.; Toda, H.; Kobayashi, M. [Department of Mechanical Engineering, Toyohashi University of Technology, Toyohashi, Aichi 441-8580 (Japan); Uesugi, K.; Takeuchi, A.; Suzuki, Y. [Japan Synchrotron Radiation Research Institute, Mikazuki, Sayo, Hyogo 679-5198 (Japan)

2012-12-24

83

Processing of spectral X-ray data with principal components analysis  

NASA Astrophysics Data System (ADS)

The goal of the work was to develop a general method for processing spectral x-ray image data. Principle component analysis (PCA) is a well understood technique for multivariate data analysis and so was investigated. To assess this method, spectral (multi-energy) computed tomography (CT) data was obtained using a Medipix2 detector in a MARS-CT (Medipix All Resolution System). PCA was able to separate bone (calcium) from two elements with k-edges in the X-ray spectrum used (iodine and barium) within a mouse. This has potential clinical application in dual-energy CT systems and future Medipix3 based spectral imaging where up to eight energies can be recorded simultaneously with excellent energy resolution.

Butler, Anthony P. H.; Butzer, Jochen; Schleich, Nanette; Cook, Nicholas J.; Anderson, Nigel G.; Scott, Nicola; de Ruiter, Niels; Grasset, Raphael; Tlustos, Lukas; Butler, Philip H.

2011-05-01

84

Modelling The Coupling Of Variability And Spectral Emission In Black Hole X-ray Binaries  

NASA Astrophysics Data System (ADS)

The emission properties of Black Hole X-ray Binaries (BHXRBs) are commonly studied either in terms of their energy spectrum (counts per energy channel) or in terms of their variability properties by means of power spectral density. Each of these can be modelled separately using X-ray analysis packages, however energy spectra and frequency power spectra have not been modelled simultaneously so far to produce a self-consistent picture of the origin and transfer of variability in these systems. We discuss new techniques that use frequency and energy-dependent cross-spectra in different energy channels to model variability and spectral information simultaneously. The powerful combination of spectral and timing information will allow us to 'reverberation map' the emitting regions close to the black hole and measure the propagation of signals through the accretion flow.

Cassatella, Pablo; Uttley, P.; Houck, J.; Davis, J. E.

2012-01-01

85

X-ray temporal and spectral studies of blazars with the GINGA satellite  

NASA Astrophysics Data System (ADS)

This is the final report to the National Aeronautics and Space Administration (NASA) concerning NASA grant NAG8-697. This grant was awarded to Dr. C. Megan Urry of the Space Telescope Science Institute in response to a proposal, entitled 'X-Ray Temporal and Spectral Studies of Blazars with the Ginga Satellite', to collaborate with Japanese colleagues in using the Ginga X-ray satellite. The grant was originally awarded on 2/27/88 and expired on 3/31/94. The Ginga X-ray satellite had unprecedented sensitivity in the 2-20 keV energy band, allowing us to make detailed temporal and spectral studies of a large number of blazars, which are a kind of unusually luminous and variable active galactic nuclei. We were successful with several proposals and were able to observe a number of different active galactic nuclei. Our investigations under this grant fall broadly into two categories: (1) Ginga observations of blazars, usually in conjunction with simultaneous multiwavelength observations using other facilities; and (2) the application of calculated pair plasma spectra to the X-ray colors of active galactic nuclei. These are described in turn.

Urry, C. Megan

1994-03-01

86

Electron-beam lithography of optical elements for x-ray range (Poster Paper)  

Microsoft Academic Search

Experimental investigations and special software for the e-beam exposure system gives the possibility of decreasing the influence of proximity effects and field distortion. The results of creating a focusing element for the soft x-ray range are described: amplitude and phase- contrast Fresnel zone plates as well as reflected Bragg-Fresnel lenses on the base of multilayer x-ray mirrors.

Sergey V. Babin; Alexei I. Erko

1992-01-01

87

Creating an X-ray Nebula in the Laboratory: Spectral Diagnostics of Neon Photoionization Experiments on the Z-machine  

Microsoft Academic Search

We report on initial spectroscopic studies of an X-ray photoionized neon plasma, in an attempt to study spectral properties of X-ray nebulae in the laboratory. These experiments, carried out on the Z-machine at Sandia, are optimized to produce a gradient free, X-ray heated and ionized plasma, and to approximate as closely as possible the photoionization-dominated regime. We present results of

D. S. Conners; D. H. Cohen; J. J. MacFarlane; D. A. Liedahl; J. E. Bailey

2002-01-01

88

Spatial and spectral features of soft diffuse X ray background seen by the Einstein observatory  

Microsoft Academic Search

A survey of the diffuse soft X-ray background as seen directly by the Einstein Observatory Imaging Proportional Counter (IPC) is presented. A source free region of the detector 1 by 1 degree field is used. The background in the 0.16 to 3.5 keV spectral region is viewed. The data covers roughly 5 percent of the sky, with some bias in

G. Micela; F. R. Harnden; R. Rosner J; S. Sciortino; G. S. Vaiana

1989-01-01

89

XOP: A graphical user interface for spectral calculations and x-ray optics utilities  

Microsoft Academic Search

A graphical user interface, using the Interactive Data Language (IDL) widget toolkit, for calculation of spectral properties of synchrotron radiation sources and for interaction of x-rays with optical elements has been developed. The interface runs presently on three different computer architectures under the Unix operating system -- the Sun-OS, the HP-UX, and the DEC-Unix operating systems. The point-and-click interface is

Roger J. Dejus; Manuel Sanchez del Rio

90

Soft X-Ray Spectral Analysis of the North Polar Spur  

NASA Astrophysics Data System (ADS)

I present a soft X-ray spectral observation of the North Polar Spur (NPS), an enhanced feature in the Soft X-ray Background. The observation was made with a Charge Coupled Device (CCD) aboard a sounding rocket on May 2, 1997. CCD temperature during flight was -72°C, approximately 15° higher than optimal. A total of 330 seconds of data was collected. The spectrum, in the 0.22-10 keV energy range, was analyzed using the XSPEC data package. The data were fit by a three component model: an absorbed power law representing the extragalactic emission, a thermal plasma model representing the foreground emission from the Local Hot Bubble and a thermal plasma model representing emission from the North Polar Spur. The extragalactic component was fit with an absorbed power law, using a column density of 2 × 1020cm -2. The best fit gave a spectral index of 1.391 and a normalization of 11.11. The local component was fit with a Raymond and Smith thermal plasma model. The best fit resulted in a temperature of 1.5 × 106 K and an emission measure of 6.76 × 103cm-6 pc. The NPS component was fit with an absorbed Raymond and Smith thermal plasma model with a temperature of 3.5 × 106 K and an emission measures of 3.53 × 103cm-6 pc. The fit was significantly improved with the addition of Gaussians at energies of known astrophysical lines corresponding to N VII, Ne IX, Mg XI and Si Ly?. It was also significantly improved when the abundances of N, O, Ne, Ar, Fe, and Ni were allowed to vary using a variable Raymond and Smith thermal plasma model for the NPS component. Both fits are evidence of abundance variations in the North Polar Spur. An NEI (nonequilibrium ionization) model for the NPS component did not result in a significant improvement of the fit, suggesting that the NPS plasma is already in collisional ionization equilibrium.

Cawley, Laura Joan

91

A MIDEX Mission to Spectrally Analyze the Diffuse X-ray and Ultraviolet Background  

NASA Astrophysics Data System (ADS)

BEST (Baryonic Extragalactic Structure Tracer) is a proposed Medium-class Explorer (MIDEX) that is focused on mapping diffuse hot intergalactic and interstellar gas with high spectral resolution. We describe the four spectrographs and an imager that can over a three-year mission map the entire sky and conduct deep pointed observations of selected regions to profoundly extend, and possibly to fundamentally change, our understanding of hot matter in the Universe. This tremendously versatile suite of instruments addresses a wide range of scientific issues. We highlight areas where we believe BEST will have greatest scientific impact: detect and characterize the ``missing baryons" in the current epoch, which are primarily in moderately overdense intergalactic regions and are predicted to account for 10 - 20% of the soft X-ray background; measure accurately the extragalactic diffuse ultraviolet background, probably produced by the ensemble of intergalactic gas and galaxies over cosmological space; determine properties of the hot Galactic halo and the hot Galactic gas, crucial to understanding the evolution and dynamics of the ISM; and map H_2, a fundamental constituent of the ISM, over the entire sky.

Sanders, Wilton; Henry, Richard

2002-04-01

92

Search for Discrete X-ray Spectral Features in a Sample of Bright Gamma-ray Burst Afterglows.  

National Technical Information Service (NTIS)

We present uniform, detailed spectral analyses of gamma-ray burst (GRB) X-ray afterglows observed with ASCA, Beppo-SAX, Chandra, and XMM-Newton, and critically evaluate the statistical significances of X-ray emission and absorption features in these spect...

M. Sako

2004-01-01

93

Spectral change in X-ray absorption near edge structure of DNA thin films irradiated with monochromatic soft X-rays  

NASA Astrophysics Data System (ADS)

To reveal the chemical changes induced in DNA by irradiation with ionizing radiation, we have investigated the spectral change in the X-ray absorption near edge structure (XANES) of DNA resulting from exposure to monochromatic soft X-rays. We used a thin film of calf thymus DNA as a sample and observed nitrogen K-shell and oxygen K-shell XANES spectra. The typical monochromatic soft X-ray energies used for the irradiation (395, 408, 528, and 538 eV) were obtained from a soft X-ray beamline (BL23SU, SPring-8). These energies correspond to those just below or just above the nitrogen and oxygen K-shell ionization energy, respectively. The obtained XANES spectra show significant changes by irradiation. Particularly a new ?* resonance peak in oxygen XANES spectra evidently appeared by the irradiation above oxygen K-shell ionization potential. These results suggest that carbonyl groups, presumably a propenal group (OC-CC), may be produced in the sample by oxygen ionization. Thus characteristic damage induced by induction in the DNA molecule would be predicted following exposure to monochromatized synchrotron soft X-rays.

Fujii, Kentaro; Yokoya, Akinari

2009-12-01

94

High-spatial resolution and high-spectral resolution detector for use in the measurement of solar flare hard X-rays  

NASA Astrophysics Data System (ADS)

In the areas of high spatial resolution, the evaluation of a hard X-ray detector with 65 micron spatial resolution for operation in the energy range from 30 to 400 keV is proposed. The basic detector is a thick large-area scintillator faceplate, composed of a matrix of high-density scintillating glass fibers, attached to a proximity type image intensifier tube with a resistive-anode digital readout system. Such a detector, combined with a coded-aperture mask, would be ideal for use as a modest-sized hard X-ray imaging instrument up to X-ray energies as high as several hundred keV. As an integral part of this study it was also proposed that several techniques be critically evaluated for X-ray image coding which could be used with this detector. In the area of high spectral resolution, it is proposed to evaluate two different types of detectors for use as X-ray spectrometers for solar flares: planar silicon detectors and high-purity germanium detectors (HPGe). Instruments utilizing these high-spatial-resolution detectors for hard X-ray imaging measurements from 30 to 400 keV and high-spectral-resolution detectors for measurements over a similar energy range would be ideally suited for making crucial solar flare observations during the upcoming maximum in the solar cycle.

Desai, U. D.; Orwig, Larry E.

1988-11-01

95

Spectral evolution of active galactic nuclei: A unified description of the X-ray and gamma  

NASA Astrophysics Data System (ADS)

A model for spectral evolution is presented whereby active galactic nuclei (AGN) of the type observed individually emerge from an earlier stage at z approx = 4 in which they are the thermal X-ray sources responsible for most of the cosmic X-ray background (CXB). The conjecture is pursued that these precursor objects are initially supermassive Schwarzschild black holes with accretion disks radiating near the Eddington luminosity limit. It is noted that after approx. 10 to the 8th power years these central black holes are spun-up to a canonical Kerr equilibrium state (A/M = 0.998; Thorne 1974) and shown how they then can lead to spectral evolution involving non-thermal emission extending to gamma rays, at the expense of reduced thermal disk radiation. That major portion of the CXB remaining after the contribution of usual AGN are considered, while a superposition of AGN sources at z 1 can account for the gamma ray background. Extensive X-ray measurements carried out with the HEAO 1 and 2 missions as well as gamma ray and optical data are shown to compare favorably with principal features of this model.

Leiter, D.; Boldt, E.

1982-02-01

96

Efficient, high-spectral-resolution Bragg crystal x-ray polarimeter.  

PubMed

Utilizing Bragg scattering near 90 degrees , an x-ray polarimeter is described that has high spectral resolution and reasonable efficiency. The latter is achieved by using a position-sensitive proportional counter to discriminate spatially resolved x rays dispersed by the crystal. This instrument has been used to measure the linear polarization of lines from one- and two-electron oxygen ions. For this study, aligned initial states have been populated in oxygen beams by various excitation processes in foil, gas, and thick solid targets. In spite of the small probability for the production and radiative decay of few-electron excited states in the presence of intense background radiation, the instrument resolution and efficiency are sufficient to permit polarization measurements. PMID:18699186

Doyle, B L; Schiebel, U; Ellsworth, L D; Macdonald, J R

1978-06-01

97

The X-ray pulsar A0535+26 in hard X-rays - Average spectrum, pulse-phase spectroscopy, and spectral time variability  

NASA Astrophysics Data System (ADS)

A hard X-ray (30-190 keV) observation of A0535+26 in outburst was performed during a balloon flight on October 4, 1980. Detailed spectral analysis shows that the average photon spectrum of A0535+26 can be well fitted by a Wein law with kT = 7.68 + or - 0.035 keV. This spectral law is in good agreement with theoretical model spectra of X-ray pulsars. The energy spectra over 51 phase bins are also well fitted by a Wein law with a kT variable with pulse phase from 7.3 to about 8.5 keV. Apart from this spectral variability, photon spectra averaged over a pulse period strongly suggest that chaotic spectral variability is also present. A simple geometrical model for the X-ray emission and modulation with pulse phase from A0535+26 is presented. This model gives good qualitative agreement with the present observations.

dal Fiume, D.; Frontera, F.; Morelli, E.

1988-08-01

98

X-RAY PROPERTIES OF INTERMEDIATE-MASS BLACK HOLES IN ACTIVE GALAXIES. III. SPECTRAL ENERGY DISTRIBUTION AND POSSIBLE EVIDENCE FOR INTRINSICALLY X-RAY-WEAK ACTIVE GALACTIC NUCLEI  

SciTech Connect

We present a systematic X-ray study, the third in a series, of 49 active galactic nuclei with intermediate-mass black holes (IMBH; {approx}10{sup 5}-10{sup 6} M{sub Sun }) using Chandra observations. We detect 42 out of 49 targets with a 0.5-2 keV X-ray luminosity 10{sup 41}-10{sup 43} erg s{sup -1}. We perform spectral fitting for the 10 objects with enough counts (>200), and they are all well fit by a simple power-law model modified by Galactic absorption, with no sign of significant intrinsic absorption. While we cannot fit the X-ray spectral slope directly for the rest of the sample, we estimate it from the hardness ratio and find a range of photon indices consistent with those seen in more luminous and massive objects. The X-ray-to-optical spectral slope ({alpha}{sub ox}) of our IMBH sample is systematically flatter than in active galaxies with more massive black holes, consistent with the well-known correlation between {alpha}{sub ox} and UV luminosity. Thanks to the wide dynamic range of our sample, we find evidence that {alpha}{sub ox} increases with decreasing M{sub BH} as expected from accretion disk models, where the UV emission systematically decreases as M{sub BH} decreases and the disk temperature increases. We also find a long tail toward low {alpha}{sub ox} values. While some of these sources may be obscured, given the high L{sub bol}/L{sub Edd} values in the sample, we argue that some may be intrinsically X-ray-weak, perhaps owing to a rare state that radiates very little coronal emission.

Dong Ruobing; Greene, Jenny E. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); Ho, Luis C., E-mail: rdong@princeton.edu, E-mail: jgreene@princeton.edu, E-mail: lho@obs.carnegiescience.edu [Observatories of the Carnegie Institution for Science, 813 Santa Barbara St., Pasadena, CA 91101 (United States)

2012-12-10

99

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.  

PubMed

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. PMID:20515133

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

2010-05-01

100

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  

SciTech Connect

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. [Commissariat a l'Energie Atomique, DAM, CESTA, BP 2, Le Barp 33114 (France); Gontier, D.; Lidove, G.; Reverdin, C.; Soullie, G.; Stemmler, P.; Villette, B. [Commissariat a l'Energie Atomique, DAM, DIF, Arpajon F-91290 (France)

2010-05-15

101

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

102

Multicolor operation and spectral control in a gain-modulated x-ray free-electron laser.  

PubMed

We show that the spectral properties of a self-amplified spontaneous emission x-ray free-electron laser can be controlled by modulating the gain in magnetic undulators, thus producing one or several spectral lines within a single few femtosecond pulse. By varying the magnetic field along the undulator and the electron beam transport line, the system we demonstrate can tailor the x-ray spectrum to optimally meet numerous experimental requirements for multicolor operation. PMID:24116783

Marinelli, A; Lutman, A A; Wu, J; Ding, Y; Krzywinski, J; Nuhn, H-D; Feng, Y; Coffee, R N; Pellegrini, C

2013-09-24

103

Multicolor Operation and Spectral Control in a Gain-Modulated X-Ray Free-Electron Laser  

NASA Astrophysics Data System (ADS)

We show that the spectral properties of a self-amplified spontaneous emission x-ray free-electron laser can be controlled by modulating the gain in magnetic undulators, thus producing one or several spectral lines within a single few femtosecond pulse. By varying the magnetic field along the undulator and the electron beam transport line, the system we demonstrate can tailor the x-ray spectrum to optimally meet numerous experimental requirements for multicolor operation.

Marinelli, A.; Lutman, A. A.; Wu, J.; Ding, Y.; Krzywinski, J.; Nuhn, H.-D.; Feng, Y.; Coffee, R. N.; Pellegrini, C.

2013-09-01

104

X-Ray Timing and Spectral Evolution of Circinus X-1 versus Orbital Phase with the Rossi X-Ray Timing Explorer  

Microsoft Academic Search

We have carried out a study of Cir X-1 through (1) detailed sampling over a single 16.5 day intensity cycle with the Rossi X-Ray Timing Explorer (RXTE) proportional counter array and (2) complementary monitoring over six such cycles with the RXTE all-sky monitor (ASM). We report here the temporal and spectral evolution at nonflaring phases, during which Cir X-1 remained

Robert E. Shirey; Hale V. Bradt; Alan M. Levine; Edward H. Morgan

1996-01-01

105

Spontaneous and X-ray?Triggered Crystallization at Long Range in Self-Assembling Filament Networks  

SciTech Connect

We report here crystallization at long range in networks of like-charge supramolecular peptide filaments mediated by repulsive forces. The crystallization is spontaneous beyond a given concentration of the molecules that form the filaments but can be triggered by x-rays at lower concentrations. The crystalline domains formed by x-ray irradiation, with interfilament separations of up to 320 angstroms, can be stable for hours after the beam is turned off, and ions that screen charges on the filaments suppress ordering. We hypothesize that the stability of crystalline domains emerges from a balance of repulsive tensions linked to native or x-ray-induced charges and the mechanical compressive entrapment of filaments within a network. Similar phenomena may occur naturally in the cytoskeleton of cells and, if induced externally in biological or artificial systems, lead to possible biomedical and lithographic functions.

Cui, Honggang; Pashuck, E. Thomas; Velichko, Yuri S.; Weigand, Steven J.; Cheetham, Andrew G.; Newcomb, Christina J.; Stupp, Samuel I. (NWU)

2010-03-16

106

PASS, an extended-range Ge spectrometer for radionuclide analysis via L X-, ?-ray spectrometry  

NASA Astrophysics Data System (ADS)

PASS (Photon Analysis Spectrometer System) is a pulser-equipped, extended range, thin-window, Ge detector spectrometer that is capable of automatically measuring radionuclide activity concentrations in up to 100 samples per day at remediation sites. No operator intervention is required after the counting queue for the sample changer has been setup. Actinides are measured from L X-rays following ? decay such as APu --> A-4U and 241Am --> 237Np and from low-energy ?-rays by spectral component analysis. Activation, fission products and a few actinides (e.g., 241Am) are measured from their characteristic ?-ray emission by fitting the associated peaks. Pulses from a precision, dual-energy pulser can be used to determine the energy scale, provide documentation of the data quality, and provide a correction for pulse pileup. Soil, smear, and air particulate samples can be counted. For an 11-g sample counted for 15 min the lower-limits-of-detection are 50, 1, and 5 pCi/g for plutonium, americium, and several ?-ray emitting radionuclides, respectively.

Gehrke, R. J.; Watts, K. D.; Killian, E. W.; Putnam, M. H.; Helmer, R. G.

1994-12-01

107

The X-ray spectrum and spectral energy distribution of FIRST J155633.8+351758: a LoBAL quasar with a probable polar outflow  

NASA Astrophysics Data System (ADS)

We report the results of a new 60 ks Chandra X-ray Observatory Advanced CCD Imaging Spectrometer S-array (ACIS-S) observation of the reddened, radio-selected, highly polarized `FeLoBAL' quasar FIRST J1556+3517. We investigated a number of models of varied sophistication to fit the 531-photon spectrum. These models ranged from simple power laws to power laws absorbed by hydrogen gas in differing ionization states and degrees of partial covering. Preferred fits indicate that the intrinsic X-ray flux is consistent with that expected for quasars of similarly high luminosity, i.e. an intrinsic, dereddened and unabsorbed optical to X-ray spectral index of -1.7. We cannot tightly constrain the intrinsic X-ray power-law slope, but find indications that it is flat (photon index ? = 1.7 or flatter at a >99 per cent confidence for a neutral hydrogen absorber model). Absorption is present, with a column density a few times 1023 cm-2, with both partially ionized models and partially covering neutral hydrogen models providing good fits. We present several lines of argument that suggest the fraction of X-ray emissions associated with the radio jet is not large. We combine our Chandra data with observations from the literature to construct the spectral energy distribution of FIRST J1556+3517 from radio to X-ray energies. We make corrections for Doppler beaming for the pole-on radio jet, optical dust reddening and X-ray absorption, in order to recover a probable intrinsic spectrum. The quasar FIRST J1556+3517 seems to be an intrinsically normal radio-quiet quasar with a reddened optical/UV spectrum, a Doppler-boosted but intrinsically weak radio jet and an X-ray absorber not dissimilar from that of other broad absorption line quasars.

Berrington, Robert C.; Brotherton, Michael S.; Gallagher, Sarah C.; Ganguly, Rajib; Shang, Zhaohui; DiPompeo, Michael; Chatterjee, Ritaban; Lacy, Mark; Gregg, Michael D.; Hall, Patrick B.; Laurent-Muehleisen, S. A.

2013-10-01

108

Imaging by parabolic refractive lenses in the hard X-ray range  

Microsoft Academic Search

The manufacture and properties of compound refractive lenses (CRLs) for hard X-rays with parabolic profile are described. These novel lenses can be used up to60 keV. A typical focal length is 1 m. They have a geometrical aperture of 1 mm and are best adapted to undulator beams at synchrotron radiation sources. The transmission ranges from a few % in

Bruno Lengeler; Christian Schroer; Johannes Tummler; Boris Benner; Matthias Richwin; Anatoly Snigirev; Irina Snigirevab; Michael Drakopoulosb

1999-01-01

109

Crosscheck of different techniques for two dimensional power spectral density measurements of x-ray optics  

SciTech Connect

The consistency of different instruments and methods for measuring two-dimensional (2D) power spectral density (PSD) distributions are investigated. The instruments are an interferometric microscope, an atomic force microscope (AFM) and the X-ray Reflectivity and Scattering experimental facility, all available at Lawrence Berkeley National Laboratory. The measurements were performed with a gold-coated mirror with a highly polished stainless steel substrate. It was shown that these three techniques provide essentially consistent results. For the stainless steel mirror, an envelope over all measured PSD distributions can be described with an inverse power-law PSD function. It is also shown that the measurements can be corrected for the specific spatial frequency dependent systematic errors of the instruments. The AFM and the X-ray scattering measurements were used to determine the modulation transfer function of the interferometric microscope. The corresponding correction procedure is discussed in detail. Lower frequency investigation of the 2D PSD distribution was also performed with a long trace profiler and a ZYGO GPI interferometer. These measurements are in some contradiction, suggesting that the reliability of the measurements has to be confirmed with additional investigation. Based on the crosscheck of the performance of all used methods, we discuss the ways for improving the 2D PSD characterization of X-ray optics.

Yashchuk, Valeriy V.; Irick, Steve C.; Gullikson, Eric M.; Howells, Malcolm R.; MacDowell, Alastair A.; McKinney, Wayne R.; Salmassi, Farhad; Warwick, Tony

2005-07-12

110

THE X-RAY POWER SPECTRAL DENSITY FUNCTION OF THE SEYFERT ACTIVE GALACTIC NUCLEUS NGC 7469  

SciTech Connect

We present the broadband X-ray power spectral density (PSD) function of the X-ray-luminous Seyfert 1.2 NGC 7469, measured from Rossi X-ray Timing Explorer monitoring data and two XMM-Newton observations. We find significant evidence for a turnover in the 2-10 keV PSD at a temporal frequency of 2.0{sup +3.0}{sub -0.8} x 10{sup -6} Hz or 1.0{sup +3.0}{sub -0.6} x 10{sup -6} Hz, depending on the exact form of the break (sharply broken or slowly bending power law, respectively). The 'surrogate' Monte Carlo method of Press et al. was used to map out the probability distributions of PSD model parameters and obtain reliable uncertainties (68% confidence limits quoted here). The corresponding break timescale of 5.8 {+-} 3.5 days or 11.6{sup +17.5}{sub -8.7} days, respectively, is consistent with the empirical relation between PSD break timescale, black hole mass, and bolometric luminosity of McHardy et al. Compared to the 2-10 keV PSD, the 10-20 keV PSD has a much flatter shape at high temporal frequencies, and no PSD break is significantly detected, suggesting an energy-dependent evolution not unlike that exhibited by several Galactic black hole systems.

Markowitz, A. [Center for Astrophysics and Space Sciences, University of California, San Diego, Mail Code 0424, La Jolla, CA 92093-0424 (United States)

2010-11-20

111

Spectral-luminosity evolution of active galactic nuclei and the cosmic X-ray background  

NASA Astrophysics Data System (ADS)

Black hole accretion disk dynamo processes are generally regarded as the central power source for AGN (Rees, 1984). If the precursor active galaxies for such AGN are formed at redshift z greater than about 4 and contain initial central seed black holes about 10 exp 6 solar masses, then the Eddington limited X-ray radiation emitted during their lifetime will undergo the phenomenon of 'spectral-luminosity evolution'. When accretion disks are first formed at the onset of galaxy formation, the accretion rate occurs at high values of luminosity/size compactness parameter L/R greater than 10 exp 30 erg/cm-sec. Such high values of L/R generate dynamic constraints which suppress nonthermal black hole accretion disk dynamo processes in favor of thermal processes. This causes the spectrum of X-radiation emitted by early AGN to be predominantly thermal. A superposition of such thermal, comptonized PAG sources can account for the residual cosmic X-ray background and can act as a source of X-ray heating of the intergalactic medium for z greater than about 4.

Leiter, Darryl; Boldt, Elihu

1991-04-01

112

THE NEXT GENERATION ATLAS OF QUASAR SPECTRAL ENERGY DISTRIBUTIONS FROM RADIO TO X-RAYS  

SciTech Connect

We have produced the next generation of quasar spectral energy distributions (SEDs), essentially updating the work of Elvis et al. by using high-quality data obtained with several space- and ground-based telescopes, including NASA's Great Observatories. We present an atlas of SEDs of 85 optically bright, non-blazar quasars over the electromagnetic spectrum from radio to X-rays. The heterogeneous sample includes 27 radio-quiet and 58 radio-loud quasars. Most objects have quasi-simultaneous ultraviolet-optical spectroscopic data, supplemented with some far-ultraviolet spectra, and more than half also have Spitzer mid-infrared Infrared Spectrograph spectra. The X-ray spectral parameters are collected from the literature where available. The radio, far-infrared, and near-infrared photometric data are also obtained from either the literature or new observations. We construct composite SEDs for radio-loud and radio-quiet objects and compare these to those of Elvis et al., finding that ours have similar overall shapes, but our improved spectral resolution reveals more detailed features, especially in the mid- and near-infrared.

Shang Zhaohui; Li Jun; Xie Yanxia [Department of Physics, Tianjin Normal University, Tianjin 300387 (China); Brotherton, Michael S.; Cales, Sabrina L.; Dale, Daniel A.; Runnoe, Jessie C.; Kelly, Benjamin J. [Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82071 (United States); Wills, Beverley J.; Wills, D. [Department of Astronomy, University of Texas at Austin, 1 University Station, C1400 Austin, TX 78712 (United States); Green, Richard F. [Large Binocular Telescope Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Nemmen, Rodrigo S. [NASA/Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Gallagher, Sarah C. [Department of Physics and Astronomy, University of Western Ontario, London, ON N6A 3K7 (Canada); Ganguly, Rajib [Department of Computer Science, Engineering, and Physics, University of Michigan-Flint, 213 Murchie Science Building, 303 Kearsley Street, Flint, MI 48502 (United States); Hines, Dean C. [Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, CO 80301 (United States); Kriss, Gerard A. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Tang, Baitian, E-mail: zshang@gmail.com [Department of Physics, 1245 Webster Hall, Washington State University, Pullman, WA 99164-2814 (United States)

2011-09-01

113

X-RAY SPECTRAL STATE IS NOT CORRELATED WITH LUMINOSITY IN HOLMBERG II X-1  

SciTech Connect

The ultraluminous X-ray source (ULX) Holmberg II X-1 has been observed over four months in 2009/2010 by the Swift observatory. The source luminosity varied by a factor of up to 14, reaching a maximum 0.3-10 keV luminosity of {approx}3.0 x 10{sup 40} erg s{sup -1}. The spectral properties do not vary much over these four months, with only a slight monotonic increase of the hardness ratio with the count rate. This means that the erratic flaring activity of the source is not associated with spectral changes, as seen in other ULXs. Conversely, comparison with data obtained by Swift in 2006 shows a completely different picture: while at a luminosity also seen in the 2009/2010 data, the source appears with a hard spectrum. Thus, it appears that, as in Galactic black hole binaries, spectral states in this ULX are not determined only by the X-ray luminosity.

Grise, F.; Kaaret, P. [Department of Physics and Astronomy, University of Iowa, Van Allen Hall, Iowa City, IA 52242 (United States); Feng, H. [Department of Engineering Physics and Center for Astrophysics, Tsinghua University, Beijing 100084 (China); Kajava, J. J. E. [Department of Physics, Astronomy Division, P.O. Box 3000, 90014 University of Oulu (Finland); Farrell, S. A. [Department of Physics and Astronomy, University of Leicester, University Road, Leicester, LE1 7RH (United Kingdom)

2010-12-01

114

Temporal resolved x-ray penumbral imaging technique using heuristic image reconstruction procedure and wide dynamic range x-ray streak camera  

SciTech Connect

Temporal resolved x-ray penumbral imaging has been developed using an image reconstruction procedure of the heuristic method and a wide dynamic range x-ray streak camera (XSC). Reconstruction procedure of the penumbral imaging is inherently intolerant to noise, a reconstructed image is strongly distorted by artifacts caused by noise in a penumbral image. Statistical fluctuation in the number of detected photon is the dominant source of noise in an x-ray image, however acceptable brightness of an image is limited by dynamic range of an XSC. The wide dynamic range XSC was used to obtain penumbral images bright enough to be reconstructed. Additionally, the heuristic method was introduced in the penumbral image reconstruction procedure. Distortion of reconstructed images is sufficiently suppressed by these improvements. Density profiles of laser driven brominated plastic and tin plasma were measured with this technique.

Fujioka, Shinsuke; Shiraga, Hiroyuki; Azechi, Hiroshi; Nishimura, Hiroaki; Izawa, Yasukazu; Nozaki, Shinya; Chen, Yen-wei [Institute of Laser Engineering, Osaka University, 2-6 Yamada-Oka, Suita, Osaka 565-0871 (Japan); Information and Communication Systems Engineering, Okinawa National College of Technology, 2-19-2 Daito, Nago, Okinawa 905-0016 (Japan); College of Information Science and Engineering, Ritsumeikan University, 525-8577 (Japan)

2004-10-01

115

An X-Ray Spectral Analysis of the Central Regions of NGC 4593  

NASA Astrophysics Data System (ADS)

We present a detailed analysis of XMM-Newton EPIC-pn data for the Seyfert 1 galaxy NGC 4593. We discuss the X-ray spectral properties of this source, as well as its variations with time. The 0.5-10 keV spectrum shows significant complexity beyond a simple power-law form, with clear evidence existing for a ``soft excess,'' as well as absorption by highly ionized plasma (a warm absorber) within the central engine of this active galactic nucleus. We show that the soft excess is best described as originating from thermal Comptonization by plasma that is appreciably cooler than the primary X-ray-emitting plasma; we find that the form of the soft excess cannot be reproduced adequately by reflection from an ionized accretion disk. The only measurable deviation from the power-law continuum in the hard spectrum comes from the presence of cold and ionized fluorescent iron K? emission lines at 6.4 and 6.97 keV, respectively. While constraints on the ionized iron line are weak, the cold line is found to be narrow at CCD resolution with a flux that does not track the temporal changes in the underlying continuum, implying an origin in the outer radii of the accretion disk or the putative molecular torus of Seyfert unification schemes. The X-ray continuum itself varies on all accessible timescales. We detect a ~230 s time lag between soft and hard EPIC-pn bands that, if interpreted as scattering timescales within a Comptonizing disk corona, can be used to constrain the physical size of the primary X-ray source to a characteristic length scale of ~2rg. Taken together, the small implied coronal size and the large implied iron-line emitting region indicate a departure from the current picture of a ``typical'' AGN geometry.

Brenneman, Laura W.; Reynolds, Christopher S.; Wilms, Jörn; Kaiser, Mary Elizabeth

2007-09-01

116

Diffractive lenses for photon energies ranging from the extreme ultraviolet to hard x rays  

NASA Astrophysics Data System (ADS)

Diffractive optics for the x-ray range have to meet the various requirements of experimental set-ups at synchrotron or other light sources. In the case of focusing elements it is essential that the devices are matched to parameters such as the photon energy and spatial coherence of the source, as well as the required spatial resolution, working distance, and diffraction efficiency. In some cases, a suppression of disturbing diffraction orders requires additional features such as an opaque central stop integrated into the lens. The Laboratory for Micro- and Nanotechnology provides the essential technologies necessary for the design and fabrication of diffractive x-ray lenses for a wide range of photon energies and applications. Over the past years, a large variety of optics tailored to the specific needs of x-ray optical experiments have been fabricated and tested. These include transmission Fresnel phase zone plate for microscopy, microprobe, or beam monitoring applications, as well as condensers to increase the flux in waveguiding experiments in the hard x-ray range. An overview of the nanofabrication technologies and a selection of experiments demonstrating the devices performance are presented.

David, Christian; Noehammer, Bernd; Solak, Harun H.; Haas, Bianca; Glaus, Fredy; van der Veen, J. Friso; Schlott, Volker; Bongaerts, Jeroen; Kaulich, Burkhard; Susini, Jean

2001-12-01

117

pyblocxs: Bayesian Low-Counts X-ray Spectral Analysis in Sherpa  

NASA Astrophysics Data System (ADS)

Typical X-ray spectra have low counts and should be modeled using the Poisson distribution. However, ?2 statistic is often applied as an alternative and the data are assumed to follow the Gaussian distribution. A variety of weights to the statistic or a binning of the data is performed to overcome the low counts issues. However, such modifications introduce biases or/and a loss of information. Standard modeling packages such as XSPEC and Sherpa provide the Poisson likelihood and allow computation of rudimentary MCMC chains, but so far do not allow for setting a full Bayesian model. We have implemented a sophisticated Bayesian MCMC-based algorithm to carry out spectral fitting of low counts sources in the Sherpa environment. The code is a Python extension to Sherpa and allows to fit a predefined Sherpa model to high-energy X-ray spectral data and other generic data. We present the algorithm and discuss several issues related to the implementation, including flexible definition of priors and allowing for variations in the calibration information.

Siemiginowska, A.; Kashyap, V.; Refsdal, B.; van Dyk, D.; Connors, A.; Park, T.

2011-07-01

118

Determination of electron energy, spectral width, and beam divergence at the exit window for clinical megavoltage x-ray beams  

SciTech Connect

Monte Carlo simulations of x-ray beams typically take parameters of the electron beam in the accelerating waveguide to be free parameters. In this paper, a methodology is proposed and implemented to determine the energy, spectral width, and beam divergence of the electron source. All treatment head components were removed from the beam path, leaving only the exit window. With the x-ray target and flattener out of the beam, uncertainties in physical characteristics and relative position of the target and flattening filter, and in spot size, did not contribute to uncertainty in the energy. Beam current was lowered to reduce recombination effects. The measured dose distributions were compared with Monte Carlo simulation of the electron beam through the treatment head to extract the electron source characteristics. For the nominal 6 and 18 MV x-ray beams, the energies were 6.51{+-}0.15 and 13.9{+-}0.2 MeV, respectively, with the uncertainties resulting from uncertainties in the detector position in the measurement and in the stopping power in the simulations. Gaussian spectral distributions were used, with full widths at half maximum ranging from 20{+-}4% at 6 MV to 13{+-}4% at 18 MV required to match the fall-off portion of the percent-depth ionization curve. Profiles at the depth of maximum dose from simulations that used the manufacturer-specified exit window geometry and no beam divergence were 2-3 cm narrower than measured profiles. Two simulation configurations yielding the measured profile width were the manufacturer-specified exit window thickness with electron source divergences of 3.3 degree sign at 6 MV and 1.8 deg. at 18 MV and an exit window 40% thicker than the manufacturer's specification with no beam divergence. With the x-ray target in place (and no flattener), comparison of measured to simulated profiles sets upper limits on the electron source divergences of 0.2 deg. at 6 MV and 0.1 deg. at 18 MV. A method of determining source characteristics without mechanical modification of the treatment head, and therefore feasible in clinics, is presented. The energies and spectral widths determined using this method agree with those determined with only the exit window in the beam path.

Sawkey, D. L.; Faddegon, B. A. [Department of Radiation Oncology, University of California San Francisco, 1600 Divisadero Street, San Francisco, California 94143 (United States)

2009-03-15

119

Analysis of nuclear materials by energy dispersive x-ray fluorescence and spectral effects of alpha decay  

SciTech Connect

Energy dispersive X-ray fluorescence (EDXRF) spectra collected from alpha emitters are complicated by artifacts inherent to the alpha decay process, particularly when using portable instruments. For example, {sup 239}Pu EDXRF spectra exhibit a prominent uranium L X-ray emission peak series due to sample alpha decay rather than source-induced X-ray fluorescence. A portable EDXRF instrument was used to collect spectra from plutonium, americium, and a Pu-contaminated steel sample. The plutonium sample was also analyzed by wavelength dispersive XRF to demonstrate spectral differences observed when using these very different instruments.

Worley, Christopher G [Los Alamos National Laboratory

2009-01-01

120

MCP image intensifier in the 100-KeV to 1-MeV x-ray range  

NASA Astrophysics Data System (ADS)

A high gain x-ray image intensifier with high sensitivity in the 1 MeV x-ray range is presented and a good spatial resolution developed in order to improve the radiographic detection in the experiments. In particular the gold photocathode and MCP thickness have been optimized to give the best trade-off between the dose sensitivity and the spatial resolution. The large useful 60 mm diameter photocathode set on the MCP input converts the x-ray emission into electrons which are multiplied in the MCP and proximity-focused onto the P11 phosphor screen deposited on a fiber optic plate. For x-ray quanta of 1 MeV energy the x-ray image converter is more sensitive than the most sensitive x-ray screen-film systems. Using, for instance, a pulsed x-ray source the authors were able to record pictures of a sphere or of a testing metallic chart for a dose lower than 100 (mu) rad; under these conditions the spatial resolution was greater than 1 lp/mm and the dynamic range was still around 10. Using an x-ray screen film under the same input level the authors have obtained a very low dynamic range and density values actually equal to the noise level. These unique performances fulfill the requirements of a large number of detonic experiments needing a high sensitivity in the 1 Mev x-ray range.

Veaux, Jacqueline; Cavailler, Claude; Gex, Jean-Pierre; Hauducoeur, Alain; Hivernage, M.

1991-06-01

121

The MultiSpectral Solar Telescope Array. II - Soft X-ray\\/EUV reflectivity of the multilayer mirrors  

Microsoft Academic Search

We have developed seven compact soft X-ray\\/EUV (XUV) multilayer coated and two compact FUV interference film coated Cassegrain and Ritchey-Chretien telescopes for a rocket borne observatory, the Multi-Spectral Solar Telescope Array. We report here on extensive measurements of the efficiency and spectral bandpass of the XUV telescopes carried out at the Stanford Synchrotron Radiation Laboratory.

Troy W. Barbee Jr.; J. W. Weed; Richard B. C. Hoover Jr.; Max J. Allen; Joakim F. Lindblom; Ray H. O'Neal; Charles C. Kankelborg; Craig E. Deforest; Elizabeth S. Paris; Arthur B. C. Walker

1992-01-01

122

The MultiSpectral Solar Telescope Array II: Soft X-ray\\/EUV reflectivity of the multilayer mirrors  

Microsoft Academic Search

The authors have developed seven compact soft X-ray\\/EUV (XUV) multilayer coated and two compact FUV interference film coated Cassegrain and Ritchey-Chrétien telescopes for a rocket borne observatory, the Multi-Spectral Solar Telescope Array. They report on extensive measurements of the efficiency and spectral bandpass of the XUV telescopes.

T. W. Barbee; J. W. Weed; R. B. Hoover; M. J. Allen; J. F. Lindblom; R. H. O'Neal; C. C. Kankelborg; C. E. Deforest; E. S. Paris; A. B. C. Walker Jr.; T. D. Willis; E. Gluskin; P. Pianetta; P. C. Baker

1992-01-01

123

Pockels readout optical modulator: An x-ray imaging detector that maintains good efficiency over a broad energy range  

Microsoft Academic Search

We present measurements of the performance of a Pockels readout optical modulator (PROM) x-ray imaging detector using a 30-kV constant potential bremsstrahlung source. A nickel step wedge was used to measure the spatial resolution and noise of the PROM image. PROMs are unique high-efficiency x-ray detectors that image with good spatial resolution over a wide range of x-ray energy. The

Grant H. Stokes; David M. Stupin; Norman E. Elliott; Michael Graser

1985-01-01

124

X-RAY VARIABILITY AND HARDNESS OF ESO 243-49 HLX-1: CLEAR EVIDENCE FOR SPECTRAL STATE TRANSITIONS  

SciTech Connect

The ultraluminous X-ray (ULX) source ESO 243-49 HLX-1, which reaches a maximum luminosity of 10{sup 42} erg s{sup -1} (0.2-10 keV), currently provides the strongest evidence for the existence of intermediate-mass black holes (IMBHs). To study the spectral variability of the source, we conduct an ongoing monitoring campaign with the Swift X-ray Telescope (XRT), which now spans more than two years. We found that HLX-1 showed two fast rise and exponential decay type outbursts in the Swift XRT light curve with increases in the count rate of a factor {approx}40 separated by 375 {+-} 13 days. We obtained new XMM-Newton and Chandra dedicated pointings that were triggered at the lowest and highest luminosities, respectively. From spectral fitting, the unabsorbed luminosities ranged from 1.9 Multiplication-Sign 10{sup 40} to 1.25 Multiplication-Sign 10{sup 42} erg s{sup -1}. We confirm here the detection of spectral state transitions from HLX-1 reminiscent of Galactic black hole binaries (GBHBs): at high luminosities, the X-ray spectrum showed a thermal state dominated by a disk component with temperatures of 0.26 keV at most, and at low luminosities the spectrum is dominated by a hard power law with a photon index in the range 1.4-2.1, consistent with a hard state. The source was also observed in a state consistent with the steep power-law state, with a photon index of {approx}3.5. In the thermal state, the luminosity of the disk component appears to scale with the fourth power of the inner disk temperature, which supports the presence of an optically thick, geometrically thin accretion disk. The low fractional variability (rms of 9% {+-} 9%) in this state also suggests the presence of a dominant disk. The spectral changes and long-term variability of the source cannot be explained by variations of the beaming angle and are not consistent with the source being in a super-Eddington accretion state as is proposed for most ULX sources with lower luminosities. All this indicates that HLX-1 is an unusual ULX as it is similar to GBHBs, which have non-beamed and sub-Eddington emission, but with luminosities three orders of magnitude higher. In this picture, a lower limit on the mass of the black hole of >9000 M{sub Sun} can be derived, and the relatively low disk temperature in the thermal state also suggests the presence of an IMBH of a few 10{sup 3} M{sub Sun }.

Servillat, Mathieu [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-67, Cambridge, MA 02138 (United States); Farrell, Sean A. [Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH (United Kingdom); Lin Dacheng; Godet, Olivier; Barret, Didier; Webb, Natalie A., E-mail: mservillat@cfa.harvard.edu [Universite de Toulouse, Universite Paul Sabatier-Observatoire Midi-Pyrenees, Institut de Recherche en Astrophysique et Planetologie (IRAP), Toulouse (France)

2011-12-10

125

Artificial Temperature Anisotropy of Crystals in X-Ray Frequency Range  

SciTech Connect

The effect of artificial temperature anisotropy of crystals in X-ray frequency range was observed for the first time and an effort to theoretically interpret this effect in Bragg-Laue diffraction case was made. It was established that an isotropic crystal optically turns into an artificially anisotropic one with optical axis along the direction of applied external influence as a symmetry axis, giving rise to the double refraction.

Mkrtchyan, Vahram P.; Gasparyan, Laura G.; Balyan, Minas K. [Department of solid state physics, Yerevan State University, Alex Manoogian 1, 0025 Yerevan (Armenia)

2010-04-06

126

Processing of spectrally resolved x-ray images of inertial confinement fusion implosion cores recorded with multimonochromatic x-ray imagers  

SciTech Connect

We discuss the processing of data recorded with multimonochromatic x-ray imagers (MMI) in inertial confinement fusion experiments. The MMI records hundreds of gated, spectrally resolved images that can be used to unravel the spatial structure of the implosion core. In particular, we present a new method to determine the centers in all the array of images, a better reconstruction technique of narrowband implosion core images, two algorithms to determine the shape and size of the implosion core volume based on reconstructed broadband images recorded along three-quasiorthogonal lines of sight, and the removal of artifacts from the space-integrated spectra.

Nagayama, T.; Mancini, R. C.; Florido, R. [Department of Physics, University of Nevada, Reno, Nevada 89557 (United States); Tommasini, R.; Koch, J. A. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Delettrez, J. A.; Regan, S. P.; Smalyuk, V. A. [Laboratory for Laser Energetics, University of Rochester, New York 14623 (United States)

2011-05-01

127

The First Hard X-Ray Power Spectral Density Functions of Active Galactic Nucleus  

NASA Astrophysics Data System (ADS)

We present results of our power spectral density (PSD) analysis of 30 active galactic nuclei (AGNs) using the 58 month light curves from Swift's Burst Alert Telescope (BAT) in the 14-150 keV band. PSDs were fit using a Monte Carlo based algorithm to take into account windowing effects and measurement error. All but one source were found to be fit very well using an unbroken power law with a slope of ~ - 1, consistent at low frequencies with previous studies in the 2-10 keV band, with no evidence of a break in the PSD. For five of the highest signal-to-noise ratio sources, we tested the energy dependence of the PSD and found no significant difference in the PSD at different energies. Unlike previous studies of X-ray variability in AGNs, we do not find any significant correlations between the hard X-ray variability and different properties of the AGN including luminosity and black hole mass. The lack of break frequencies and correlations seem to indicate that AGNs are similar to the high state of Galactic black holes.

Shimizu, T. Taro; Mushotzky, Richard F.

2013-06-01

128

The Northern Galactic Cap AGN from the 58-month BAT Catalogue: A Comprehensive X-ray Spectral Study  

NASA Astrophysics Data System (ADS)

The all-sky hard X-ray Swift/BAT survey has provided the most complete census of local AGN activity to date, unbiased to all but the most heavy absorption levels. Continual monitoring in the 14--195 keV band has allowed the assembly of hard X-ray detected AGN catalogues after 9, 22, 36, 58 and 70 months of operation, increasing the sample size by probing to fainter fluxes. The seminal study of Winter et al. (2009) presented a comprehensive X-ray analysis of the AGN in the 9-month catalogue, providing their absorption and luminosity distributions, characterising the spectral shape for each source in the catalogue, and allowing the determination of sample-wide properties for an unbiased AGN sample. We present a timely revision of this exercise for the latest publicly available 58-month BAT catalogue (flux limit 4 x 10^-12 erg/s/cm^2 in the 14-195 keV band), focusing on the Northern Galactic Cap (b>50 degrees). This sky area has excellent potential for further dedicated study due to a wide range of multi-wavelength data that are already available, and we propose it as a low-redshift analogue to the ‘deep field’ observations of AGN at higher redshifts. We consistently fit all the 100 objects in this sky region with a suite of models to determine the best fitting column densities, luminosities and spectral features (Iron lines, soft excesses and warm absorber edges). Comparison with previous works on the 9-month and 36-month catalogues now allows a better understanding of whether the deepening exposure of the BAT catalogue uncovers progressively different AGN properties. We find that ~60% of the sample is absorbed above logNH=22, 9% is Compton thick, and Compton reflection is significant for the sample overall (average reflection amplitude = 2.7). The sample is complete down to fluxes 4 times fainter than the 9-month catalogue in the 2--10 keV band. We emphasise the utility of this Northern Galactic Cap sample for a wide variety of future studies on AGN, and outline one such current project on the stacked emission from this sample and the connections with X-ray background synthesis models.

Vasudevan, Ranjan; Brandt, W. N.; Mushotzky, R.; Winter, L. M.; Baumgartner, W. H.; Shimizu, T.; Nousek, J. A.; Schneider, D. P.; Gandhi, P.

2013-04-01

129

Exploring the accessible frequency range of phase-resolved ferromagnetic resonance detected with x-rays  

NASA Astrophysics Data System (ADS)

We present time- and element-resolved measurements of the magnetization dynamics in a ferromagnetic trilayer structure. A pump-probe scheme was utilized with a microwave magnetic excitation field phase-locked to the photon bunches and x-ray magnetic circular dichroism in transmission geometry. Using a relatively large photon bunch length with a full width at half maximum of 650 ps, the precessional motion of the magnetization was resolved up to frequencies of 2.5 GHz, thereby enabling sampling at frequencies significantly above the inverse bunch length. By simulating the experimental data with a numerical model based on a forced harmonic oscillator, we obtain good correlation between the two. The model, which includes timing jitter analysis, is used to predict the accessible frequency range of x-ray detected ferromagnetic resonance.

Warnicke, P.; Knut, R.; Wahlström, E.; Karis, O.; Bailey, W. E.; Arena, D. A.

2013-01-01

130

FIRST EVIDENCE FOR SPECTRAL STATE TRANSITIONS IN THE ESO 243-49 HYPERLUMINOUS X-RAY SOURCE HLX-1  

SciTech Connect

The brightest ultra-luminous X-ray source, ESO 243-49 HLX-1, with a 0.2-10 keV X-ray luminosity of up to 10{sup 42} erg s{sup -1}, provides the strongest evidence to date for the existence of intermediate mass black holes (BHs). Although small-scale X-ray spectral variability has already been demonstrated, we have initiated a monitoring campaign with the X-ray Telescope (XRT) onboard the Swift satellite to search for luminosity-related spectral changes and to compare its behavior with the better-studied stellar mass BHs. In this Letter, we report a drop in the XRT count rate by a factor of approx8 which occurred simultaneously with a hardening of the X-ray spectrum. A second observation found that the source had re-brightened by a factor of approx21 which occurred simultaneously with a softening of the X-ray spectrum. This may be the first evidence for a transition between the low/hard and high/soft states.

Godet, O.; Barret, D.; Webb, N. A. [Universite de Toulouse, UPS, CESR, 9 Avenue du Colonel Roche, F-31028 Toulouse Cedex 9 (France); Farrell, S. A. [Department of Physics and Astronomy, University of Leicester, University Road, Leicester, LE1 7RH (United Kingdom); Gehrels, N. [NASA/Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

2009-11-10

131

Spectral fingerprint in X-ray absorption for hydrogen-bonded dimer formation of acetic acids in solution  

NASA Astrophysics Data System (ADS)

We have measured X-ray absorption spectra for acetic acid molecules in an organic solvent in order to study the effect of hydrogen-bonding formation. The spectral shapes distorted by saturation effect were compensated by using a new correction procedure for X-ray absorption based on the changes in the concentration of the samples. A resonance peak shift was observed when the acetic acid molecules formed a cyclic dimer in hexane solution, which is similar to the behavior of cluster molecules in vacuum. This is the first report on the XAS spectral changes due to cyclic dimer formation in a solution.

Horikawa, Y.; Arai, H.; Tokushima, T.; Shin, S.

2012-01-01

132

The Hot--blackbody Spectral Excess in Low--luminosity High--Mass X--Ray Binaries  

NASA Astrophysics Data System (ADS)

We report on the main results obtained thanks to an observation campaign with XMM-Newton of four persistent, low-luminosity (L_{X} ˜ 10^{34} erg s^{-1}) and long-period (P > 200 s) Be accreting pulsars. We found that all sources considered here are characterized by a spectral excess that can be described with a blackbody component of high temperature (kT_{BB} > 1 keV) and small area (R_{BB} < 0.5 km). We show that: 1) this feature is a common property of several low-luminosity X-ray binaries; 2) for most sources the blackbody parameters (radius and temperature) are within a narrow range of values; 3) it can be interpreted as emission from the NS polar caps.

La Palombara, N.; Mereghetti, S.; Sidoli, L.; Tiengo, A.; Esposito, P.

133

Modeling the image quality of enhanced reflectance x-ray multilayers as a surface power spectral density filter function  

NASA Astrophysics Data System (ADS)

Residual surface roughness over the entire range of relevant spatial frequencies must be specified and controlled in many high-performance optical systems. This is particularly true for enhanced reflectance multilayers if both high reflectance and high spatial resolution are desired. If we assume that the interfaces making up a multilayer coating are uncorrelated at high spatial frequencies (microroughness) and perfectly correlated at low spatial and midspatial frequencies, then the multilayer can be thought of as a surface power spectral density (PSD) filter function. Multilayer coatings thus behave as a low-pass spatial frequency filter acting on the substrate PSD, with the exact location and shape of this cutoff being material and process dependent. This concept allows us to apply conventional linear systems techniques to the evaluation of image quality and to the derivation of optical fabrication tolerances for applications utilizing enhanced reflectance x-ray multilayers.

Harvey, James E.

1995-07-01

134

Modeling the image quality of enhanced reflectance x-ray multilayers as a surface power spectral density filter function.  

PubMed

Residual surface roughness over the entire range of relevant spatial frequencies must be specified and controlled in many high-performance optical systems. This is particularly true for enhanced reflectance multilayers if both high reflectance and high spatial resolution are desired. If we assume that the interfaces making up a multilayer coating are uncorrelated at high spatial frequencies (microroughness) and perfectly correlated at low spatial and midspatial frequencies, then the multilayer can be thought of as a surface power spectral density (PSD) filter function. Multilayer coatings thus behave as a low-pass spatial frequency filter acting on the substrate PSD, with the exact location and shape of this cutoff being material and process dependent. This concept allows us to apply conventional linear systems techniques to the evaluation of image quality and to the derivation of optical fabrication tolerances for applications utilizing enhanced reflectance x-ray multilayers. PMID:21052193

Harvey, J E

1995-07-01

135

RXTE/ASM and Swift/BAT observations of spectral transitions in bright X-ray binaries in 2005-2010  

NASA Astrophysics Data System (ADS)

We have studied X-ray spectral state transitions that can be seen in the long-term monitoring light curves of bright X-ray binaries from the All-Sky Monitor (ASM) onboard the Rossi X-ray Timing Explorer (RXTE) and the Burst Alert Telescope (BAT) onboard Swift during a period of five years from 2005 to 2010. We have applied a program to automatically identify the hard-to-soft (H-S) spectral state transitions in the bright X-ray binaries monitored by the ASM and the BAT. In total, we identified 128 hard-to-soft transitions, of which 59 occurred after 2008. We also determined the transition fluxes and the peak fluxes of the following soft states, updated the measurements of the luminosity corresponding to the H-S transition and the peak luminosity of the following soft state in about 30 bright persistent and transient black hole and neutron star binaries following Yu & Yan, and found the luminosity correlation and the luminosity range of spectral transitions in data between 2008-2010 are about the same as those derived from data before 2008. This further strengthens the idea that the luminosity at which the H-S spectral transition occurs in the Galactic X-ray binaries is determined by non-stationary accretion parameters such as the rate-of-change of the mass accretion rate rather than the mass accretion rate itself. The correlation is also found to hold in data of individual sources 4U 1608-52 and 4U 1636-53.

Tang, Jing; Yu, Wen-Fei; Yan, Zhen

2011-04-01

136

Polarization, temporal, and spectral parameters of solar flare hard X-rays as measured by the SPR-N instrument onboard the CORONAS-F satellite  

NASA Astrophysics Data System (ADS)

The SPR-N polarimeter onboard the CORONAS-F satellite allows the X-ray polarization degree to be measured in energy ranges of 20 40, 40 60, and 60 100 keV. To measure the polarization, the method based on the Thompson scattering of solar X-ray photons in beryllium plates was used; the scattered photons were detected with a system of six CsI(Na) scintillation sensors. During the observation period from August 2001 to January 2005, the SPR-N instrument detected the hard X-rays of more than 90 solar flares. The October 29, 2003, event showed a significant polarization degree exceeding 70% in channels of E = 40 60 and 60 100 keV and about 50% in the 20-to 40-keV channel. The time profile of the polarization degree and the projection of the polarization plane onto the solar disk were determined. For 25 events, the upper limits of the part of polarized X-rays were estimated at 8 to 40%. For all the flares detected, time profiles (with a resolution of up to 4 s), hard X-ray radiation fluxes, and spectral index estimates were obtained.

Zhitnik, I. A.; Logachev, Yu. I.; Bogomolov, A. V.; Denisov, Yu. I.; Kavanosyan, S. S.; Kuznetsov, S. N.; Morozov, O. V.; Myagkova, I. N.; Svertilov, S. I.; Ignat'ev, A. P.; Oparin, S. N.; Pertsov, A. A.; Tindo, I. P.

2006-03-01

137

Measuring the absolute sensitivity of an X-ray electron-optical image converter in the range 7-20 keV  

Microsoft Academic Search

The absolute sensitivity of an X-ray electron-optical image converter with a MCP used as both photocathode and amplifier has been investigated using synchrotron radiation from the VEPP-3 storage ring (INP, Novosibirsk) in the energy range of 7 to 20 keV. In this spectral range the response of the converter increases from 1200 to 2200 blue photons at the output per

I. P. Dolbnya; B. A. Knyazev; V. P. Simonov; G. G. Feldman

1991-01-01

138

HARD X-RAY AND MICROWAVE EMISSIONS FROM SOLAR FLARES WITH HARD SPECTRAL INDICES  

SciTech Connect

We analyze 10 flare events that radiate intense hard X-ray (HXR) emission with significant photons over 300 keV to verify that the electrons that have a common origin of acceleration mechanism and energy power-law distribution with solar flares emit HXRs and microwaves. Most of these events have the following characteristics. HXRs emanate from the footpoints of flare loops, while microwaves emanate from the tops of flare loops. The time profiles of the microwave emission show delays of peak with respect to those of the corresponding HXR emission. The spectral indices of microwave emissions show gradual hardening in all events, while the spectral indices of the corresponding HXR emissions are roughly constant in most of the events, though rather rapid hardening is simultaneously observed in some for both indices during the onset time and the peak time. These characteristics suggest that the microwave emission emanates from the trapped electrons. Then, taking into account the role of the trapping of electrons for the microwave emission, we compare the observed microwave spectra with the model spectra calculated by a gyrosynchrotron code. As a result, we successfully reproduce the eight microwave spectra. From this result, we conclude that the electrons that have a common acceleration and a common energy distribution with solar flares emit both HXR and microwave emissions in the eight events, though microwave emission is contributed to by electrons with much higher energy than HXR emission.

Kawate, T. [Kwasan and Hida Observatory, Kitashirakawa-oiwakecho, Sakyo, Kyoto 606-8502 (Japan); Nishizuka, N. [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 229-8510 (Japan); Oi, A. [College of Science, Ibaraki University, Mito, Ibaraki 310-8512 (Japan); Ohyama, M. [Faculty of Education, Shiga University, 2-5-1 Hiratsu, Otsu, Shiga 1-1, Baba Hikone city, Siga 522-8522 (Japan); Nakajima, H., E-mail: kawate@kusastro.kyoto-u.ac.jp [Nobeyama Solar Radio Observatory, NAOJ, Nobeyama, Minamisaku, Nagano 384-1305 (Japan)

2012-03-10

139

Resonant soft X-ray scattering, stripe order, and the electron spectral function in  

SciTech Connect

We review the current state of efforts to use resonant soft X-ray scattering (RSXS), which is an elastic, momentum-resolved, valence band probe of strongly correlated electron systems, to study stripe-like phenomena in copper-oxide superconductors and related materials. We review the historical progress including RSXS studies of Wigner crystallization in spin ladder materials, stripe order in 214-phase nickelates, 214-phase cuprates, and other systems. One of the major outstanding issues in RSXS concerns its relationship to more established valence band probes, namely angle-resolved photoemission (ARPES) and scanning tunneling microscopy (STM). These techniques are widely understood as measuring a one-electron spectral function, yet a relationship between RSXS and a spectral function has so far been unclear. Using physical arguments that apply at the oxygen K edge, we show that RSXS measures the square modulus of an advanced version of the Green’s function measured with STM. This indicates that, despite being a momentum space probe, RSXS is more closely related to STM than to ARPES techniques. Finally, we close with some discussion of the most promising future directions for RSXS. We will argue that the most promising area lies in high magnetic field studies, particularly of edge states in strongly correlated heterostructures, and the vortex state in superconducting cuprates, where RSXS may clarify the anomalous periodicities observed in recent quantum oscillation experiments.

Abbamonte, P.; Demler, E.; Davis, J.C. Seamus; Campuzano, J.-C.

2012-01-01

140

Advection-dominated Accretion and the Spectral States of Black Hole X-Ray Binaries: Application to Nova MUSCAE 1991  

Microsoft Academic Search

Black hole X-ray binaries (BHXBs) are known to display five distinct spectral states. In order of increasing luminosity these are the quiescent state, low state, intermediate state, high state, and very high state. We present a self-consistent model of accretion flows around black holes that unifies all of these states except the very high state. The model is an extension

Ann A. Esin; Jeffrey E. McClintock; Ramesh Narayan

1997-01-01

141

Morphometry, scanning electron microscopy and x-ray spectral microanalysis of protostylid pits on human lower third molars  

Microsoft Academic Search

Protostylid pits on 50 lower third molars were studied. The depth and width of the pits, the thickness of the enamel at the pit bottom and the concavity of the dentino-enamel junction under the pit were measured by light microscopy. The pit content was examined by scanning electron microscopy and X-ray spectral microanalysis. The results show that the morphometric variables

Dominik Gašperši?

1996-01-01

142

Instrumental aspects of x-ray microbeams in the range above 1 keV  

Microsoft Academic Search

X-ray microscopy has the capability of looking into normally opaque samples with high resolution. X rays are sensitive to elemental, structural, and chemical content and thus can provide microscopic maps of the composition and structure of a sample. X-ray microscopy has seen great growth in the last two decades in the number and types of operating instruments as well as

P. Dhez; P. Chevallier; T. B. Lucatorto; C. Tarrio

1999-01-01

143

Laser-induced fluorescence and X-ray spectral analysis of carious process in hard dental tissues.  

PubMed

Morphological and spectral X-ray analysis of carious and noncarious extracted teeth showed the patterns of dentin ossification in caries of different degree. Parietal ectopic ossification of the canal and cavity lumens in stages III and IV dental caries is regarded as a specific structural marker of pathological regeneration. The X-ray spectral analysis showed that the progress of carious process is paralleled by loss of mineral components. Laser-induced fluorescent study of tissues in extracted teeth showed 4 spectral bands corresponding to mineral and protein components of the tooth. The progress of carious process was associated with reduction of the fluorescence intensities of the spectral bands characteristic of dental collagen and mineral components. PMID:21246104

Lidman, G Yu; Larionov, P M; Savchenko, S V; Lushnikova, E L; Orishich, A M; Rozhin, I A; Malov, A N; Maslov, N A; Titov, A T; Kositsyna, I G

2010-09-01

144

X-ray spectral diagnostics of neon photoionization experiments on the Z-machine  

Microsoft Academic Search

We report on an initial spectroscopic study of low-density, x-ray photoionized neon with x-ray spectroscopy. These experiments, carried out on the Z-machine at Sandia, are optimized to produce a gradient-free, collisionless plasma, and to explore issues related to the rapid x-ray photoionization of relatively cold, low-density plasmas. The initial experiments used time-integrated absorption spectroscopy, backlit by the pinch radiation, to

David H. Cohen; Joseph J. Macfarlane; James E. Bailey; Duane A. Liedahl

2003-01-01

145

X-ray spectral diagnostics of neon photoionization experiments on the z- machine  

Microsoft Academic Search

We report on an initial spectroscopic study of low-density, x-ray photoionized neon with x ray spectroscopy. These experiments, carried out on the Z-machine at Sandia, are optimized to produce a gradient free, collisionless plasma, and to explore issues related to the rapid x-ray photoionization of relatively cold, low-density plasmas. The initial experiments used time-integrated absorption spectroscopy, backlit by the pinch

David H. Cohen; Joseph J. MacFarlane; James E. Bailey; Duane A. Liedahl

146

Image-based spectral distortion correction for photon-counting x-ray detectors  

PubMed Central

Purpose: To investigate the feasibility of using an image-based method to correct for distortions induced by various artifacts in the x-ray spectrum recorded with photon-counting detectors for their application in breast computed tomography (CT). Methods: The polyenergetic incident spectrum was simulated with the tungsten anode spectral model using the interpolating polynomials (TASMIP) code and carefully calibrated to match the x-ray tube in this study. Experiments were performed on a Cadmium-Zinc-Telluride (CZT) photon-counting detector with five energy thresholds. Energy bins were adjusted to evenly distribute the recorded counts above the noise floor. BR12 phantoms of various thicknesses were used for calibration. A nonlinear function was selected to fit the count correlation between the simulated and the measured spectra in the calibration process. To evaluate the proposed spectral distortion correction method, an empirical fitting derived from the calibration process was applied on the raw images recorded for polymethyl methacrylate (PMMA) phantoms of 8.7, 48.8, and 100.0 mm. Both the corrected counts and the effective attenuation coefficient were compared to the simulated values for each of the five energy bins. The feasibility of applying the proposed method to quantitative material decomposition was tested using a dual-energy imaging technique with a three-material phantom that consisted of water, lipid, and protein. The performance of the spectral distortion correction method was quantified using the relative root-mean-square (RMS) error with respect to the expected values from simulations or areal analysis of the decomposition phantom. Results: The implementation of the proposed method reduced the relative RMS error of the output counts in the five energy bins with respect to the simulated incident counts from 23.0%, 33.0%, and 54.0% to 1.2%, 1.8%, and 7.7% for 8.7, 48.8, and 100.0 mm PMMA phantoms, respectively. The accuracy of the effective attenuation coefficient of PMMA estimate was also improved with the proposed spectral distortion correction. Finally, the relative RMS error of water, lipid, and protein decompositions in dual-energy imaging was significantly reduced from 53.4% to 6.8% after correction was applied. Conclusions: The study demonstrated that dramatic distortions in the recorded raw image yielded from a photon-counting detector could be expected, which presents great challenges for applying the quantitative material decomposition method in spectral CT. The proposed semi-empirical correction method can effectively reduce these errors caused by various artifacts, including pulse pileup and charge sharing effects. Furthermore, rather than detector-specific simulation packages, the method requires a relatively simple calibration process and knowledge about the incident spectrum. Therefore, it may be used as a generalized procedure for the spectral distortion correction of different photon-counting detectors in clinical breast CT systems.

Ding, Huanjun; Molloi, Sabee

2012-01-01

147

X-ray and EUV spectral instruments for plasma source characterization  

Microsoft Academic Search

A set of spectral analytic instruments has been developed for absolute intensity measurements in a spectral range of 1 - 600 Å: (1) several modifications of grazing incidence spectrographs; (2) EUV monochromator- spectrometer with a constant angle of deviation; (3) focusing crystal von Hamos spectrometer using cylindrical mica and pyrolytic graphite crystals and a CCD linear array as a detector.

Alexander P. Shevelko; Yuri S. Kasyanov; Larry V. Knight; James Phillips; R. Steven Turley; D. Clark Turner; Oleg F. Yakushev

2004-01-01

148

Structure Analysis of Nylon6Clay Hybrid by Spectral Reflectance of Laser-Plasma Soft X-Rays  

Microsoft Academic Search

Structure analysis of nylon6-clay hybrid (NCH) was carried out by means of spectral reflectance of soft X-rays between 8 and 17 nm wavelength from laser-produced plasma. Spectral reflectance composed of specular reflectance and Bragg reflectance was measured by a flat field XUV spectrometer equipped with a toroidal mirror. The observed Bragg reflectance was very weak, but it suggested that NCH

Hirozumi Azuma; Akihiro Takeichi; Shoji Noda

1993-01-01

149

Multi-spectral solar telescope array II; Soft x-ray/euv reflectivity of the multilayer mirrors  

SciTech Connect

In this paper, the authors have developed seven compact soft x-ray/EUV (XUV) multilayer-coated and two compact FUV interference-film-coated Cassegrain and Ritchey-Chretien telescopes for a rocket-borne observatory, the Multi-Spectral Solar Telescope Array. The authors report on extensive measurements of the efficiency and spectral bandpass of the XUV telescopes carried out at the Stanford Synchrotron Radiation Laboratory.

Barbee, T.W. Jr.; Weed, J.W. (Lawrence Livermore National Lab., Livermore, CA (US)); Hoover, R.M. (NASA Marshall Space Flight Center, Space Science Lab., Huntsville, AL (US)); Allen, M.J.; Lindblom, J.F.; O'Neal, R.H.; Kankelborg, C.C.; DeForest, C.E.; Paris, E.S.; Walker, A.B.C. Jr.; Willis, T.D. (Stanford Univ., Center for Space Science and Astrophysics, Stanford, CA (US)); Gluskin, E. (Argonne National Lab., Argonne, IL (US)); Pianetta, P. (Stanford Univ., Stanford Synchrotron Radiation Lab., Stanford, CA (US)); Baker, P.C. (Baker Consulting, Walnut Creek, CA (US))

1991-08-01

150

Time-Resolved Measurements of Polarized X-Ray Spectral Lines Emitted from Discharges of the Plasma-Focus Type  

SciTech Connect

The paper presents results of experimental studies of the polarization of the X-ray spectral lines observed during high-current Plasma-Focus (PF) discharges. Time-resolved measurements of the highly-ionized argon lines were performed within the MAJA-PF facility operated at 44 kJ. The detailed studies confirmed considerable differences in relative intensities of the investigated spectral lines, what could be treated as an evidence of their different polarization.

Jakubowski, L.; Sadowski, M. J.; Stanislawski, J. [Andrzej Soltan Institute for Nuclear Studies, 05-400 Swierk (Poland); Baronova, E. O. [Nuclear Fusion Institute, NRC Kurchatov Institute, 123182 Moscow (Russian Federation)

2006-01-15

151

The Drop in X-ray Flux at Spectral Type B1: Evidence for a B-Star Dividing Line?  

Microsoft Academic Search

All B star luminosity classes show a substantial drop in their X-ray emission between spectral type B1 and B2 suggesting an H-R diagram B-star dividing line somewhat analogous to the one for K giants. This emission appears to be related to the bi-stability jump at spectral type B1. But our analyses of B supergiant and giant XMM data revealed several

Wayne Waldron

2009-01-01

152

The Drop in X-ray Flux at Spectral Type B1: Evidence for a B-Star Dividing Line?  

Microsoft Academic Search

All B star luminosity classes show a substantial drop in their X-ray emission between spectral type B1 and B2 suggesting an H-R diagram B-star dividing line somewhat analogous to the one for K giants. This emission appears to be related to the bi-stability jump at spectral type B1. But our analyses of B supergiant and giant XMM data revealed several

Wayne Waldron

2010-01-01

153

EFFECT OF LASER LIGHT ON MATTER. LASER PLASMAS: X-ray spectral diagnostics of plasmas heated by picosecond laser pulses  

NASA Astrophysics Data System (ADS)

The properties of a magnesium plasma heated by picosecond laser pulses have been determined by x-ray spectral methods. Experiments were carried out at a laser power density ~ 1.5 · 1018 W/cm2. The x-ray spectra were detected by spectrographs with a plane CsAP crystal and a mica crystal bent into part of a spherical surface 10 cm in radius. The experimental data are compared with predictions of a calculation on the time-varying kinetics of multiply charged magnesium ions.

Bryunetkin, B. A.; Skobelev, I. Yu; Faenov, A. Ya; Khakhalin, S. Ya; Kalashnikov, M. P.; Nickles, P. V.; Schnürer, M.

1993-06-01

154

X-Ray Spectral Diagnostics of Gamma-Ray Burst Environments  

Microsoft Academic Search

Recently, detection of discrete features in the X-ray afterglow spectra of GRB 970508 and GRB 970828 was reported. The most natural interpretation of these features is that they are redshifted Fe K emission complexes. The identification of the line emission mechanism has drastic implications for the inferred mass of radiating material and hence the nature of the burst site. X-ray

Frits Paerels; Erik Kuulkers; John Heise; Duane A. Liedahl

2000-01-01

155

Can We Reproduce the X-Ray Background Spectral Shape Using Local Active Galactic Nuclei?  

NASA Astrophysics Data System (ADS)

The X-ray background (XRB) is due to the aggregate of active galactic nuclei (AGNs), which peak in activity at z ~ 1 and is often modeled as the sum of different proportions of unabsorbed, moderately, and heavily absorbed AGN. We present the summed spectrum of a complete sample of local AGN (the Northern Galactic Cap of the 58 month Swift/BAT catalog, z < 0.2) using 0.4-200 keV data and directly determine the different proportions of unabsorbed, moderately and heavily absorbed AGN that make up the summed spectrum. This stacked low redshift AGN spectrum is remarkably similar in shape to the XRB spectrum (when shifted to z ~ 1), but the observed proportions of different absorption populations differ from most XRB synthesis models. AGN with Compton-thick absorption account for only ~12% of the sample, but produce a significant contribution to the overall spectrum. We confirm that Compton reflection is more prominent in moderately absorbed AGN and that the photon index differs intrinsically between unabsorbed and absorbed AGN. The AGN in our sample account for only ~1% of the XRB intensity. The reproduction of the XRB spectral shape suggests that strong evolution in individual AGN properties is not required between z ~ 0 and 1.

Vasudevan, Ranjan V.; Mushotzky, Richard F.; Gandhi, Poshak

2013-06-01

156

Short-range structure of ?-V2D: Pair distribution function analysis of x-ray and neutron diffraction  

NASA Astrophysics Data System (ADS)

X-ray and neutron diffraction experiments using pair distribution function (PDF) analysis were used to elucidate the short-range structure of ?-V2D. The PDF obtained by x-ray diffraction indicated the displacement of the vanadium atoms from the ideal body-centered-tetragonal lattice positions; the displacement was evaluated to be 0.008(2) nm. Reverse Monte Carlo simulation based on x-ray and neutron PDFs was also used to determine the locations of the deuterium atoms. Results suggest that the deuterium atoms are displaced from the centers of the octahedral sites and are surrounded by four vanadium atoms at equal average distances.

Itoh, Keiji; Fukunaga, Toshiharu

2007-06-01

157

Simulations of X-ray spectral/timing properties in a propagation model of variability of accreting black holes  

NASA Astrophysics Data System (ADS)

A phenomenological model of X-ray variability of accreting black holes is considered, where the variable emission is attributed to multiple active regions/perturbations moving radially towards the central black hole. The hard X-rays are produced by inverse Compton upscattering of soft photons coming from reprocessing/thermalization of the same hard X-rays. The heating rate of the Comptonizing plasma is assumed to scale with the rate of dissipation of gravitational energy while the supply of soft photons is assumed to diminish towards the centre. Two scenarios are considered: (1) an inner hot flow with outer truncated standard accretion disc and (2) an accretion disc with an active corona and a thick hot ionized skin. A variant of the model is also considered, which is compatible with the currently discussed multi-Lorentzian description of power spectral densities of X-ray light curves. In the inner hot flow scenario the model can reproduce the observed Fourier frequency resolved spectra observed in X-ray binaries, in particular the properties of the reprocessed component as functions of Fourier frequency. In the accretion disc with ionized skin scenario the reduction of soft photons owing to the ionized skin is insufficient to produce the observed characteristics.

?ycki, Piotr T.

2003-04-01

158

Flat panel X-ray detector with reduced internal scattering for improved attenuation accuracy and dynamic range  

SciTech Connect

An x-ray detector is disclosed that has had all unnecessary material removed from the x-ray beam path, and all of the remaining material in the beam path made as light and as low in atomic number as possible. The resulting detector is essentially transparent to x-rays and, thus, has greatly reduced internal scatter. The result of this is that x-ray attenuation data measured for the object under examination are much more accurate and have an increased dynamic range. The benefits of this improvement are that beam hardening corrections can be made accurately, that computed tomography reconstructions can be used for quantitative determination of material properties including density and atomic number, and that lower exposures may be possible as a result of the increased dynamic range.

Smith, Peter D. (Santa Fe, NM); Claytor, Thomas N. (White Rock, NM); Berry, Phillip C. (Albuquerque, NM); Hills, Charles R. (Los Alamos, NM)

2010-10-12

159

Novel instrumentation for spectrally resolved soft x-ray plasma tomography: Development and pilot results on TEXTOR  

NASA Astrophysics Data System (ADS)

A novel instrumentation for wavelength- and time-resolved plasma emission tomography in the range 0.1-4 keV has been demonstrated on the Torus Experiment for Technology Oriented Research (TEXTOR). The technique is intended for reconstruction of distributions of local emission coefficients (LEC) for selected spectral lines of impurity ions. Further determination (with additional data on electron density and temperature) of spatial distributions of impurity ions at particular ionization stages will become feasible. Spectrally selective plasma images at several viewpoints around plasma are obtained with miniature pinhole cameras supplemented with multilayer mirrors as dispersion elements. The x-ray image is converted to a visible image and transported by a fiber bundle to a gain enhanced recording camera with an electron bombarded charge coupled device tube. A part of the system has been installed on temporary TEXTOR ports. First demonstration results have been obtained on plasma imaging and on subsequent LEC reconstruction using a modified iterative sinogram restoration tomography algorithm. The complete diagnostics will be operational after the TEXTOR shutdown in 2001.

Shmaenok, L. A.; Golovkin, S. V.; Govorun, V. N.; Ekimov, A. V.; Salashchenko, N. N.; Pickalov, V. V.; Belik, V. P.; Schüller, F. C.; Donné, A. J. H.; Oomens, A. A. M.; Prokhorov, K. A.; Andreev, S. S.; Sorokin, A. A.; Podlaskin, B. G.; Khasanov, L. V.

2001-02-01

160

Evaluating the impact of x-ray spectral shape on image quality in flat-panel CT breast imaging  

SciTech Connect

In recent years, there has been an increasing interest in exploring the feasibility of dedicated computed tomography (CT) breast imaging using a flat-panel digital detector in a truncated cone-beam imaging geometry. Preliminary results are promising and it appears as if three-dimensional tomographic imaging of the breast has great potential for reducing the masking effect of superimposed parenchymal structure typically observed with conventional mammography. In this study, a mathematical framework used for determining optimal design and acquisition parameters for such a CT breast imaging system is described. The ideal observer signal-to-noise ratio (SNR) is used as a figure of merit, under the assumptions that the imaging system is linear and shift invariant. Computation of the ideal observer SNR used a parallel-cascade model to predict signal and noise propagation through the detector, as well as a realistic model of the lesion detection task in breast imaging. For all evaluations, the total mean glandular dose for a CT breast imaging study was constrained to be approximately equivalent to that of a two-view conventional mammography study. The framework presented was used to explore the effect of x-ray spectral shape across an extensive range of kVp settings, filter material types, and filter thicknesses. The results give an indication of how spectral shape can affect image quality in flat-panel CT breast imaging.

Glick, Stephen J.; Thacker, Samta; Gong Xing; Liu, Bob [Department of Radiology, University of Massachusetts Medical School, Worcester, Massachusetts 01655 (United States); Radiation Monitoring Devices, Inc., 44 Hunt Street, Watertown, Massachusetts 02172 (United States); Department of Medical Physics and Radiation Oncology, Rush University Medical Center, Chicago, Illinois, 60612 (United States); Massachusetts General Hospital, Boston, Massachusetts 02114 (United States)

2007-01-15

161

MCP image intensifier in the 100KeV to 1MeV x-ray range  

Microsoft Academic Search

A high gain x-ray image intensifier with high sensitivity in the 1 MeV x-ray range is presented and a good spatial resolution developed in order to improve the radiographic detection in the experiments. In particular the gold photocathode and MCP thickness have been optimized to give the best trade-off between the dose sensitivity and the spatial resolution. The large useful

Jacqueline Veaux; Claude Cavailler; Jean-Pierre Gex; Alain Hauducoeur; M. Hivernage

1991-01-01

162

Sensitivity study of ignition capsule implosion performance on the hard x-ray spectral distribution of hohlraum  

SciTech Connect

The paper investigates theoretically the sensitivities of ignition capsule implosion performance on the hard x-ray spectral distribution of hohlraum. In the simulation, the hohlraum radiation is represented by a Planckian spectrum for the main drive plus a gaussian bump centered at energy E{sub c} for preheating x-rays. Simulation results show that with the increasing of center energy E{sub c}, the Atwood number at the fuel-ablator interface increases rapidly due to the preheating and expanding of the inner undoped CH layer. The growing of Atwood number indicates the hydrodynamic instability (HI) growth and mixing at this interface. On the other hand, the increasing of E{sub c} results in a large density gradient scale length of ablation front and stabilizes the HI growth at ablation front. The changes of the hard x-ray spectrum have significant influences on other important implosion parameters including the ablator mass remaining, shock timing, implosion velocity, and yield as well. High-precision results on the hard x-ray spectral distribution of hohlraum are thus critical for optimizing the ignition capsule design to limit the HI growth.

Gu Jianfa; Zou Shiyang; Li Yongsheng; Dai Zhensheng; Ye Wenhua [Institute of Applied Physics and Computational Mathematics, Beijing 100088 (China)

2012-12-15

163

Characterisation of spectral performance of pixellated X-ray imaging detectors in a microscopy setup  

NASA Astrophysics Data System (ADS)

In order to achieve energy resolved X-ray imaging with small pixel resolution, physical processes in the detector material such as fluorescence and charge sharing must be considered. This paper presents characterisation measurements performed with an X-ray microscopy setup for energy resolved imaging. The microscopy setup consists of a nanofocus X-ray source capable of 160 kV anode voltage, ESRF-type collimating slits and Medipix2 detectors. The detector systems developed in the Medipix collaboration are capable of energy resolved imaging. The measurements were performed by scanning an energy window through the spectrum. In this paper we have considered detectors made of Si, GaAs and CdTe for use in the microscopy setup. Both measurements and theoretical simulations are considered. For high X-ray energies, it is essential to consider fluorescence from the shielding and Compton scattering in silicon detectors.

Norlin, Börje; Fröjdh, Christer

2009-08-01

164

Spektr: A computational tool for x-ray spectral analysis and imaging system optimization  

SciTech Connect

A set of computational tools are presented that allow convenient calculation of x-ray spectra, selection of elemental and compound filters, and calculation of beam quality characteristics, such as half-value layer, mR/mAs, and fluence per unit exposure. The TASMIP model of Boone and Seibert is adapted to a library of high-level language (Matlab{sup TM}) functions and shown to agree with experimental measurements across a wide range of kVp and beam filtration. Modeling of beam filtration is facilitated by a convenient, extensible database of mass and mass-energy attenuation coefficients compiled from the National Institute of Standards and Technology. The functions and database were integrated in a graphical user interface and made available online at http://www.aip.org/epaps/epaps.html. The functionality of the toolset and potential for investigation of imaging system optimization was illustrated in theoretical calculations of imaging performance across a broad range of kVp, filter material type, and filter thickness for direct and indirect-detection flat-panel imagers. The calculations reveal a number of nontrivial effects in the energy response of such detectors that may not have been guessed from simple K-edge filter techniques, and point to a variety of compelling hypotheses regarding choice of beam filtration that warrant future investigation.

Siewerdsen, J.H.; Waese, A.M.; Moseley, D.J.; Richard, S.; Jaffray, D.A. [Ontario Cancer Institute, Princess Margaret Hospital, Toronto, Ontario M5G 2M9 (Canada); Departments of Medical Biophysics and Radiation Oncology, University of Toronto, Toronto, Ontario M5G 2M9 (Canada); Department of Medical Biophysics, University of Toronto, Toronto, Ontario M5G 2M9 (Canada); Ontario Cancer Institute, Princess Margaret Hospital, Toronto, Ontario M5G 2M9 (Canada); Department of Medical Biophysics, University of Toronto, Toronto, Ontario M5G 2M9 (Canada); Ontario Cancer Institute, Princess Margaret Hospital, Toronto, Ontario M5G 2M9 (Canada); Departments of Medical Biophysics and Radiation Oncology, University of Toronto, Toronto, Ontario M5G 2M9 (Canada); Radiation Medicine Program, Princess Margaret Hospital, Toronto, Ontario M5G 2M9 (Canada)

2004-11-01

165

GX17+2: X-ray spectral and timing behaviour of a bursting Z source  

Microsoft Academic Search

We have investigated the properties of the Z pattern of the low-mass X-ray binary GX17+2 in the X-ray colour-colour diagrams (CDs) and hardness-intensity diagrams (HIDs), and of the power spectra as a function of position in the Z. We used all EXOSAT ME data on GX17+2, a total of six observations during 1983-86. We find that the Z pattern in

E. Kuulkers; M. van der Klis; T. Oosterbroek; J. van Paradijs; W. H. G. Lewin

1997-01-01

166

X-ray Spectral Classification of Chandra Orion Ultradeep Project (COUP) Sources  

Microsoft Academic Search

The Chandra X-ray Observatory is producing images with outstanding spatial resolution using low-noise, fast-readout CCDs. Techniques than can objectively and efficiently classify X-ray sources in large images of rich fields of sources are needed to analyze the growing Chandra image archive. One such dataset, the Chandra Orion Ultradeep Project (COUP) dataset, was compiled from an 850 ks Chandra observation of

S. M. Hojnacki; J. H. Kastner; S. M. LaLonde; G. Micela; E. D. Feigelson

2005-01-01

167

The broad band spectral properties of binary X-ray pulsars  

Microsoft Academic Search

The X-ray telescopes on board BeppoSAX are an optimal set of instruments to observe bright galactic binary pulsars. These sources emit very hard and quite complex X-ray spectra that can be accurately measured with BeppoSAX between 0.1 and 200 keV. A prototype of this complexity, the source Her X?1, shows at least seven different components in its spectrum. A broad

D. Dal Fiume; M. Orlandini; S. Del Sordo; F. Frontera; T. Oosterbroek; E. Palazzi; A. N. Parmar; S. Piraino; A. Santangelo; A. Segreto

2000-01-01

168

Spectral measurements of galactic and extragalactic sources in the hard X-ray region of 20-200 keV using balloon borne telescope  

Microsoft Academic Search

The spectral and temporal measurements in the hard X-ray region between 20-200 keV not only determines the extended behaviour of thermal X-ray spectrum below 10 keV but also provide a unique insight into the non-thermal processes in relativistic astrophysical plasma. From our present understanding of the X-ray sources, a significant flux in the 20-200 keV band is expected from a

R. K. Manchanda

2002-01-01

169

X-ray and UV spectral features of matter in the environment of the central source in AGN.  

NASA Astrophysics Data System (ADS)

Several spectral features from the optical region to X-rays provide informations about matter in the environment of the "powerhouse" in the center of active galactic nuclei from outer regions down to the innermost regions around the massive black hole. The authors review some of the relevant results that, over the last years, have allowed to construct a scenario of the AGN environment, with particular regard to the innermost regions.

Piro, L.; Matsuoka, M.; Yamauchi, M.

170

Cross-check of different techniques for two-dimensional power spectral density measurements of x-ray optics  

Microsoft Academic Search

The consistency of different instruments and methods for measuring two-dimensional (2D) power spectral density (PSD) distributions are investigated. The instruments are an interferometric microscope, an atomic force microscope (AFM) and the X-ray Reflectivity and Scattering experimental facility, all available at Lawrence Berkeley National Laboratory. The measurements were performed with a gold-coated mirror with a highly polished stainless steel substrate. It

Valeriy V. Yashchuk; Steve C. Irick; Eric M. Gullikson; Malcolm R. Howells; Alastair A. MacDowell; Wayne R. McKinney; Farhad Salmassi; Tony Warwick

2005-01-01

171

Reducing Poisson noise and baseline drift in x-ray spectral images with bootstrap Poisson regression and robust nonparametric regression  

NASA Astrophysics Data System (ADS)

X-ray spectral imaging provides quantitative imaging of trace elements in a biological sample with high sensitivity. We propose a novel algorithm to promote the signal-to-noise ratio (SNR) of x-ray spectral images that have low photon counts. Firstly, we estimate the image data area that belongs to the homogeneous parts through confidence interval testing. Then, we apply the Poisson regression through its maximum likelihood estimation on this area to estimate the true photon counts from the Poisson noise corrupted data. Unlike other denoising methods based on regression analysis, we use the bootstrap resampling method to ensure the accuracy of regression estimation. Finally, we use a robust local nonparametric regression method to estimate the baseline and subsequently subtract it from the x-ray spectral data to further improve the SNR of the data. Experiments on several real samples show that the proposed method performs better than some state-of-the-art approaches to ensure accuracy and precision for quantitative analysis of the different trace elements in a standard reference biological sample.

Zhu, Feng; Qin, Binjie; Feng, Weiyue; Wang, Huajian; Huang, Shaosen; Lv, Yisong; Chen, Yong

2013-03-01

172

Saturation and Dynamic Range of Microchannel Plate-Based X-Ray Imagers  

SciTech Connect

This paper describes recent advances in Monte Carlo simulations of microchannel plate (MCP)–based x-ray detectors, a continuation of ongoing work in this area. A Monte Carlo simulation model has been developed over the past several years by National Security Technologies, LLC (NSTec). The model simulates the secondary electron emission process in an MCP pore and includes the effects of gain saturation. In this work we focus on MCP gain saturation and dynamic range. We have performed modeling and experimental characterizations of L/D = 46, 10-micron diameter, MCP-based detectors. The detectors are typically operated by applying a subnanosecond voltage pulse, which gates the detector on. Agreement between the simulations and experiment is very good for a variety of voltage pulse waveforms ranging in width from 150 to 300 ps. The results indicate that such an MCP begins to show nonlinear gain around 5 × 10^4 electrons per pore and hard saturation around 105 electrons per pore. The simulations show a difference in MCP sensitivity vs voltage for high flux of photons producing large numbers of photoelectrons on a subpicosecond timescale. Simulations and experiments both indicate an MCP dynamic range of 1 to 10,000, and the dynamic range depends on how the voltage is applied.

,

2012-05-04

173

High-resolution x-ray spectra of solar flares. IV. General spectral properties of M type flares  

Microsoft Academic Search

High-resolution x-ray spectra of class M flares have been recorded by four Bragg crystal spectrometers (SOLFLEX = solar flare x-rays) flown by NRL on an Air Force spacecraft. The wavelength ranges are 1.82 to 1.97 A, 2.98 to 3.07 A, 3.14 to 3.24 A, and 8.26 to 8.53 A. Electron temperatures are derived from dielectronic satellite-line-to-resonance-line ratios as a function

U. Feldman; G. A. Doschek; R. W. Kreplin; J. T. Mariska

1980-01-01

174

The wide band spectral observation of high mass x-ray binary 4u1700-37 with suzaku (II)  

NASA Astrophysics Data System (ADS)

4U1700-37 is a high mass X-ray binary discovered by Uhuru satellite, whose companion star HD153919 is the brightest one in the visible light. 4U1700-37 was observed with Suzaku from September 13th to 14th, 2006. The observational period corresponded to an orbital phase of 0.30-0.72, and the XIS mode was set to be 1/4 window mode with 1 sec Burst mode. We have divided all observation data into 1000 sec periods and individually fitted the extracted spectra by the cut off power-law model. Several results were obtained from light curves of the best-fit parameters. The normalization of power-law and line flux was fluctuating by a factor of 10, and the absorption was also making a variation such order. On the other hand, the power-law index approximately stayed in a range of 0.7-1.2, except a short period in which the value dropped smaller than 0. The cutoff and folding energy stayed comparatively flat, changing between 4 and 14 keV, 5 and 25 keV, respectively. The line center energy almost remained constant. We will report these results on the wide-band spectral properties and temporal behaviors of 4U1700-37.

Koseki, Yuu; Sasaki, Chikako; Kokubun, Motohide

175

X-ray spectral line coincidences between fluorine VIII (and IX) and transition metal lines  

SciTech Connect

X-ray spectroscopy was performed in the 12 to 15 A region, recording L-shell lines from selected laser-irradiated transition metals. Line coincidences and near coincidences were identified between Fe, Cr, Mn, and Ni L-spectra, and F VIII and F IX K-shell lines. Wavelengths were determined to accuracies of 1 to 3 mA and will be utilized in selecting potential pumping candidates in future x-ray lasing schemes. High-resolution x-ray spectra were collected under controlled illumination and target conditions using 1.05 ..mu..m and 0.527 ..mu..m laser excitation with the KMS CHROMA laser.

Charatis, G.; Rockett, P.D.; Burkhalter, P.G.

1983-01-01

176

X-Ray Spectral Diagnostics of Gamma-Ray Burst Environments.  

PubMed

Recently, detection of discrete features in the X-ray afterglow spectra of GRB 970508 and GRB 970828 was reported. The most natural interpretation of these features is that they are redshifted Fe K emission complexes. The identification of the line emission mechanism has drastic implications for the inferred mass of radiating material and hence the nature of the burst site. X-ray spectroscopy provides a direct observational constraint on these properties of gamma-ray bursters. We briefly discuss how these constraints arise in the context of an application to the spectrum of GRB 970508. PMID:10829000

Paerels; Kuulkers; Heise; Liedahl

2000-05-20

177

X-ray characteristics and the spectral energy distribution of AE Aquarii  

NASA Astrophysics Data System (ADS)

Using data from contemporaneous observations with Chandra and Swift, it is shown that the X-ray emission below 10 keV is predominantly thermal, characterized by flares and emission lines and dominated by the soft component. The Chandra and Swift X-ray spectra (EX? 10 keV) can be reproduced by multicomponent thermal emission models with a time-averaged X-ray luminosity of LX˜ 1031 erg s-1. The pulsed 33-s soft X-ray emission below 10 keV is confirmed in both the Chandra and Swift data sets. The epoch of pulse maximum of the 33-s white dwarf spin period is consistent with the recently derived ephemeris based upon Suzaku measurements. The recently detected Suzaku hard X-ray component above 10 keV shows a non-thermal power-law nature, with a photon index of ?˜ 1.2, possibly the result of synchrotron emission of high-energy electrons in the white dwarf magnetosphere. The hard X-ray luminosity of LX,hard? 5 × 1030 erg s-1 also constitutes ?˜ 0.1 per cent of the total spin-down luminosity of the white dwarf. This places AE Aquarii in the same category as young spin-powered pulsars between 2 and 20 keV. Additionally, it is shown that electrons can be accelerated to energies in excess of 10 TeV outside the light cylinder radius, providing interesting possibilities for VHE-TeV follow-up observations. The X-ray emission below EX? 10 keV, on the other hand, is explained in terms of plasma heating at the magnetospheric radius, the result of the dissipation of gravitational potential energy. It is found that a conversion efficiency of ?˜ 0.01 is sufficient to heat the plasma at the magnetospheric boundary to temperatures kT? 10 keV, sufficient to drive the X-ray emission below 10 keV. Only a small fraction (?˜ 0.3 per cent) of the mass flow at the magnetospheric radius eventually accretes on to the surface of the white dwarf, emphasizing the very effective magnetospheric propeller process in the system.

Oruru, B.; Meintjes, P. J.

2012-04-01

178

High Spectral Resolution X-ray Observation of Magnetic CVs: EX Hya  

SciTech Connect

In magnetic cataclysmic variables (CVs) the primary is a highly magnetized white dwarf (WD) whose field controls the accretion flow close to the WD, leading to a shock and accretion column that radiate chiefly in X-rays. We present preliminary results from a 500 ks Chandra HETG observation of the brightest magnetic CV EX Hya. From the observational dataset we are able to measure the temperature and density at different points of the cooling accretion column using sensitive line ratios. We also construct line-based light curves to search for rotational modulation of the X-ray emission.

Luna, G; Brickhouse, N S; Mauche, C W

2008-04-07

179

How to Build a Time Machine: Interfacing Hydrodynamics, Ionization Calculations and X-ray Spectral Codes for Supernova Remnants  

NASA Astrophysics Data System (ADS)

Thanks to Chandra and XMM-Newton, spatially resolved spectroscopy of SNRsin the X-ray band has become a reality. Several impressive data sets forejecta-dominated SNRs can now be found in the archives, the Cas A VLP justbeing one (albeit probably the most spectacular) example. However, it isoften hard to establish quantitative, unambiguous connections between theX-ray observations of SNRs and the dramatic events involved in a corecollapse or thermonuclear SN explosion. The reason for this is that thevery high quality of the data sets generated by Chandra and XMM for thelikes of Cas A, SNR 292.0+1.8, Tycho, and SN 1006 has surpassed our abilityto analyze them. The core of the problem is in the transient nature of theplasmas in SNRs, which results in anintimate relationship between the structure of the ejecta and AM, the SNRdynamics arising from their interaction, and the ensuing X-rayemission. Thus, the ONLY way to understand the X-ray observations ofejecta-dominated SNRs at all levels, from the spatially integrated spectrato the subarcsecond scales that can be resolved by Chandra, is to couplehydrodynamic simulations to nonequilibrium ionization (NEI) calculationsand X-ray spectral codes. I will review the basic ingredients that enterthis kind of calculations, and what are the prospects for using them tounderstand the X-ray emission from the shocked ejecta in young SNRs. Thisunderstanding (when it is possible), can turn SNRs into veritable timemachines, revealing the secrets of the titanic explosions that generatedthem hundreds of years ago.

Badenes, Carlos

2006-02-01

180

An active-optic x-ray fluorescence analyzer with high energy resolution, large solid angle coverage, and a large tuning range  

SciTech Connect

A crystal-optic x-ray fluorescence energy analyzer has been designed and tested, which combines the features of electron-volt energy resolution, large solid angle coverage, and tunability over several kilo-electron-volts. The design is based upon the principle of active optics, with ten actuators available to optimally adjust the shape of a silicon crystal used in the Bragg geometry. In most applications the shape is that of a logarithmic spiral for high energy resolution with a spatially nonresolving detector, but a wide range of other shapes is also possible for applications such as imaging or single-shot spectroscopy in a spectral range of the operator's choosing.

Adams, Bernhard W.; Attenkofer, Klaus [Argonne National Laboratory, Argonne, Illinois 60439 (United States)

2008-02-15

181

Soft X-ray spectral FITS of Geminga with model neutron star atmospheres  

NASA Astrophysics Data System (ADS)

The spectrum of the soft X-ray pulsar Geminga consists of two components, a softer one which can be interpreted as thermal-like radiation from the surface of the neutron star, and a harder one interpreted as radiation from a polar cap heated by relativistic particles. We have fitted the soft spectrum using a detailed magnetized hydrogen atmosphere model. The fitting parameters are the hydrogen column density, the effective temperature Teff, the gravitational redshift z, and the distance to radius ratio, for different values of the magnetic field B. The best fits for this model are obtained when B less than or approximately 1 x 1012 G and z lies on the upper boundary of the explored range (z = 0.45). The values of Teff approximately = (2-3) x 105 K are a factor of 2-3 times lower than the value of Teff obtained for blackbody fits with the same z. The lower Teff increases the compatibility with some proposed schemes for fast neutrino cooling of neutron stars (NSs) by the direct Urca process or by exotic matter, but conventional cooling cannot be excluded. The hydrogen atmosphere fits also imply a smaller distance to Geminga than that inferred from a blackbody fit. An accurate evaluation of the distance would require a better knowledge of the ROSAT Position Sensitive Proportional Counter (PSPC) response to the low-energy region of the incident spectrum. Our modeling of the soft component with a cooler magnetized atmosphere also implies that the hard-component fit requires a characteristic temperature which is higher (by a factor of approximately 2-3) and a surface area which is smaller (by a factor of 103, compared to previous blackbody fits.

Meyer, R. D.; Pavlov, G. G.; Meszaros, P.

1994-09-01

182

Spectral Resolution for Five-Element, Filtered, X-Ray Detector (XRD) Arrays Using the Methods of Backus and Gilbert  

SciTech Connect

The generalized method of Backus and Gilbert (BG) is described and applied to the inverse problem of obtaining spectra from a 5-channel, filtered array of x-ray detectors (XRD's). This diagnostic is routinely fielded on the Z facility at Sandia National Laboratories to study soft x-ray photons ({le}2300 eV), emitted by high density Z-pinch plasmas. The BG method defines spectral resolution limits on the system of response functions that are in good agreement with the unfold method currently in use. The resolution so defined is independent of the source spectrum. For noise-free, simulated data the BG approximating function is also in reasonable agreement with the source spectrum (150 eV black-body) and the unfold. This function may be used as an initial trial function for iterative methods or a regularization model.

FEHL,DAVID LEE; BIGGS,F.; CHANDLER,GORDON A.; STYGAR,WILLIAM A.

2000-01-17

183

Proposed SMEX to spectrally analyze the diffuse x-ray background: The Baryonic Extragalactic Structure Tracer (BEST)  

NASA Astrophysics Data System (ADS)

The Baryonic Extragalactic Structure Tracer (BEST) is a SMEX-class mission that is designed to map the hot million-degree diffuse intergalactic and interstellar gas with high spectral resolution. It consists of an imaging X ray spectrometer that can, over a 1-2 year mission, map the entire sky and conduct deep pointed observations of selected regions to profoundly extend our understanding of hot matter in the Universe. BEST will be able to detect and characterize the missing baryons in the current epoch, which are primarily in moderately overdense intergalactic regions and are predicted to account for 10 - 20% of the soft X-ray background, and also determine the properties of the hot Galactic halo and the hot Galactic gas, crucial to understanding the evolution and dynamics of our Galaxy and its interstellar medium.

Sanders, Wilton T.; Henry, Richard C.; Bregman, Joel N.; Cen, Renyue; Cox, Donald P.; Croft, Rupert A. C.; Hammond, Ernest C.; Hurwitz, Mark V.; Kimble, Randy A.; McCammon, Dan; McKee, Christopher; Murthy, Jayant; Phillips, Lara A.; Porter, Frederick S.; Raymond, John C.; Serlemitsos, Peter J.; Shelton, Robin L.; Smith, Randall K.; Stahle, Caroline K.; Szymkowiak, Andrew E.

2003-03-01

184

X-ray spectral investigations of cobalt germanides and nickel germanides  

Microsoft Academic Search

X-ray emission bands of germanides of cobalt and nickel are analyzed in terms of shape, width, energy shift, and integrated intensities. The energy band structure is represented as three strongly overlapping bands corresponding to collectivized, locally bound, and rigidly bound electrons. Some striking changes in the outer energy band distinguish the spectra of the germanides from spectra of the elements.

Ia. I. Dutchak; I. V. Kavich; V. G. Siniushko; B. M. Iatsik

1977-01-01

185

Numerical solution of the radiative transfer equation: X-ray spectral formation from cylindrical accretion onto a magnetized neutron star  

NASA Astrophysics Data System (ADS)

Context. Predicting the emerging X-ray spectra in several astrophysical objects is of great importance, in particular when the observational data are compared with theoretical models. This requires developing numerical routines for the solution of the radiative equation according to the expected physical conditions of the systems under study. Aims: We have developed an algorithm solving the radiative transfer equation in the Fokker-Planck approximation when both thermal and bulk Comptonization take place. The algorithm is essentially a relaxation method, where stable solutions are obtained when the system has reached its steady-state equilibrium. Methods: We obtained the solution of the radiative transfer equation in the two-dimensional domain defined by the photon energy E and optical depth of the system ? using finite-differences for the partial derivatives, and imposing specific boundary conditions for the solutions. We treated the case of cylindrical accretion onto a magnetized neutron star. Results: We considered a blackbody seed spectrum of photons with exponential distribution across the accretion column and for an accretion where the velocity reaches its maximum at the stellar surface and at the top of the accretion column, respectively. In both cases higher values of the electron temperature and of the optical depth ? produce flatter and harder spectra. Other parameters contributing to the spectral formation are the steepness of the vertical velocity profile, the albedo at the star surface, and the radius of the accretion column. The latter parameter modifies the emerging spectra in a specular way for the two assumed accretion profiles. Conclusions: The algorithm has been implemented in the xspec package for X-ray spectral fitting and is specifically dedicated to the physical framework of accretion at the polar cap of a neutron star with a high magnetic field (? 1012 G). This latter case is expected to be typical of accreting systems such as X-ray pulsars and supergiant fast X-ray transients.

Farinelli, R.; Ceccobello, C.; Romano, P.; Titarchuk, L.

2012-02-01

186

Soft X-ray Scanning Transmission Microscope Working in an Extended Energy Range at the Advanced Light Source  

SciTech Connect

One of the ALS scanning transmission x-ray microscopes (STXMs) has been moved to the new ALS molecular environmental science beamline 11.0.2. The STXM is located on the microscopy branchline downstream of an elliptically-polarizing undulator delivering x-rays from 80 eV to 1900 eV. The wide energy range allows STXM operations with the current zone plate from 190 eV to about 1900 eV, the highest accessible energy with sufficient flux.

Tyliszczak, T.; Warwick, T.; Kilcoyne, A.L.D.; Fakra, S.; Shuh, D.K. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Yoon, T.H. [Dept. of Geological and Environmental Sciences, Stanford University, Stanford, CA 94305 (United States); Brown, G.E. Jr. [Dept. of Geological and Environmental Sciences, Stanford University, Stanford, CA 94305 (United States); Stanford Synchrotron Radiation Laboratory, SLAC, Menlo Park, CA 94025 (United States); Andrews, S. [Materials Sciences Dept., Stanford University, Stanford, CA 94305 (United States); Chembrolu, V.; Strachan, J. [Applied Physics Dept., Stanford University, Stanford, CA 94305 (United States); Acremann, Y. [Stanford Synchrotron Radiation Laboratory, SLAC, Menlo Park, CA 94025 (United States)

2004-05-12

187

High spatial/spectral resolution x-ray observations and volumetric 3d modeling of superheated plasma in the planetary nebula BD+3003639  

NASA Astrophysics Data System (ADS)

Planetary nebulae (PNs) represent the last dying stages of evolution for sun-like stars. Though astronomers have traditionally studied PNs in optical emission lines, which mainly probe UV-photoionized gas, the study of X-ray emission from PNs offers insight into much more energetic process associated with stellar death. I present and analyze the results of multiple Chandra X-ray observations of the X-ray-bright, young PN BD+30.3639°. The Chandra datasets analyzed include a 3.5-day gratings spectroscopy observation for a total of 300 ks exposure and two direct CCD imaging observations. This thesis is based primarily on a detailed spatial/spectral analysis of the gratings data. Modeling of this gratings spectrum indicates the presence of a range of plasma temperatures from Tx ~1.7 × 10^6 K to 2.9 × 10^6 K and conclusively demonstrates that C and Ne are highly enhanced, while N and Fe are depleted. These results are generally consistent with earlier results obtained from X-ray CCD imaging spectroscopy of BD+30.3639°, but are far more precise. I obtained a direct Chandra CCD image in 2009 to compare with the Chandra CCD image obtained in 2000 and thereby to test the hypothesis that the X-ray emission could be due to fast-expanding jets. The error normalized difference image (2009 - 2000) does not reveal an apparent expansion signature, and comparison of flux images does not show any significant change in surface brightness over the 9 year span, indicating that the X-rays are generated by a quasi-spherical wind from the present-day central star. I argue that an exponential decline in flux below ~1 keV is caused by the contamination of the CCD imaging detector rather than a real decline in flux from the PN, and suggest that BD+30.3639° is a good candidate for the long-term calibration of this Chandra instrument. I construct 3-dimensional plasma models to describe the intrinsic structure of the X-ray-emitting region of BD+30.3639° by reproducing the grating spectroscopy results (both the 0th order image and dispersed images), taking into account the physical/chemical plasma components and intervening absorption obtained from spectral model fitting and Chandra's instrumental characteristics. This approach takes advantage of volumetric 3D modeling (V3D) routines under development at MIT's Kavli Institute. I present results in the form of X-ray spectra and images synthesized using spectral-V3D models. I outline how these studies of BD+30.3639° serve to constrain models of stellar evolution and PN morphologies and to guide the development of sophisticated models of the wind interactions responsible for the superheated gas within PNs.

Yu, Young Sam

188

High-Resolution Soft X-Ray Spectral Analysis in the CK Region of Titanium Carbide (TiC) using the DV-X alpha Molecular Orbital Method  

SciTech Connect

We used the DV-X alpha method to analyze the high-resolution soft X-ray emission and absorption spectra in the CK region of titanium carbide (TiC). The spectral profiles of the X-ray emission and absorption can be ssuscfucelly reproduced by the occupied and unoccupied density of states (DOS ), respectively, in the C2p orbitals of the center carbon atoms in a Ti62C63 cluster model, suggesting that the center carbon atom in a large cluster model expanded to the cubic-structured 53 (= 125) atoms provides sufficient DOS for the X-ray spectral analysis of rock-salt structured metal carbides.

Shimomura, Kenta; Muramatsu, Yasuji; Denlinger, Jonathan D.; Gullikson, Eric M.

2008-10-31

189

High resolution instruments based on X-ray multilayer gratings  

Microsoft Academic Search

New possibilities in the development of spectral instruments with high resolution and efficiency are opened up by the X-ray multilayer gratings. The main advantage of such gratings in the range of the soft X-ray radiation is their greater operating angles and high reflection coefficients. The high spectral resolution is provided by the large number of operating grooves with the same

V. I. Erofeev; N. V. Kovalenko; E. P. Kruglyakov; O. K. Myskinand; N. I. Chkhalo

1999-01-01

190

Measurements of x-ray spectral flux and intensity distribution of APS/CHESS undulator radiation  

SciTech Connect

Absolute radiation flux and polarization measurements of the APS undulators may have to be made under high thermal loading conditions. A method that may circumvent the high-heat-load problem was tested during a recent APS/CHESS undulator run. The technique makes use of a Si(Li) energy-dispersive detector to measure 5--35 keV x-rays scattered from a well-defined He gas volume at controlled pressure.

Ilinski, P.; Yun, W.; Lai, B.; Gluskin, E.; Cai, Z.

1994-09-01

191

Measurements of x-ray spectral flux of high brightness undulators by gas scattering  

SciTech Connect

Absolute radiation flux and polarization measurements of the Advanced Photon Source (APS) undulators may have to be made under high thermal loading conditions. A method that may circumvent the high-heat-load problem was tested during a recent APS/CHESS undulator run. The technique makes use of a Si(Li) energy-dispersive detector to measure 5--35 keV x rays scattered from a well-defined He gas volume at controlled pressure.

Ilinski, P.; Yun, W.; Lai, B.; Gluskin, E.; Cai, Z. (Advanced Photon Source, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439 (United States))

1995-02-01

192

A detailed X-ray investigation of ? Puppis. III. Spectral analysis of the whole RGS spectrum  

NASA Astrophysics Data System (ADS)

Context. ? Pup is the X-ray brightest O-type star of the sky. This object was regularly observed with the RGS instrument onboard XMM-Newton for calibration purposes, which led to an unprecedented set of high-quality spectra. Aims: We have previously reduced and extracted this data set and integrated it into the most detailed high-resolution X-ray spectrum of any early-type star so far. Here we present the analysis of this spectrum, taking into account for the presence of structures in the stellar wind. Methods: For this purpose, we used our new modeling tool that allows fitting the entire spectrum with a multi-temperature plasma. We illustrate the impact of a proper treatment of the radial dependence of the X-ray opacity of the cool wind on the best-fit radial distribution of the temperature of the X-ray plasma. Results: The best-fit of the RGS spectrum of ? Pup is obtained assuming no porosity. Four plasma components at temperatures between 0.10 and 0.69 keV are needed to adequately represent the observed spectrum. Whilst the hardest emission is concentrated between ~3 and 4 R?, the softer emission starts already at 1.5 R? and extends to the outer regions of the wind. Conclusions: The inferred radial distribution of the plasma temperatures agrees rather well with theoretical expectations. The mass-loss rate and CNO abundances corresponding to our best-fit model also agree quite well with the results of recent studies of ? Pup in the UV and optical domain. Based on observations collected with XMM-Newton, an ESA Science Mission with instruments and contributions directly funded by ESA Member States and the USA (NASA).

Hervé, A.; Rauw, G.; Nazé, Y.

2013-03-01

193

Spectral Transitions of an Ultraluminous X-Ray Source, NGC 2403 Source 3  

NASA Astrophysics Data System (ADS)

A Suzaku observation of an ultraluminous X-ray source, NGC 2403 Source 3, performed on 2006 March 16-17, is reported. The Suzaku XIS spectrum of Source 3 was described as multi-color black-body-like emission from an optically thick accretion disk. The innermost disk temperature and radius were measured to be Tin = 1.08-0.03+0.02keV and Rin = 122.1-6.8+7.7?1/2km, respectively, where ? = (cos 60°/cos i) with i being the disk inclination. Its bolometric luminosity was estimated to be Lbol = 1.82 ×1039?erg s-1. Archival Chandra and XMM-Newton data of the source were analyzed. In almost all observations, the source showed multi-color black-body-like X-ray spectra with parameters similar to those of the Suzaku observation. In only one Chandra observation, however, Source 3 exhibited a power-law-like spectrum, with a photon index of ? = 2.37±0.08, when it was fainter by ˜15% than in the Suzaku observation. This behavior is explained in terms of a transition between a slim-disk state and ``very high'' states, both found in Galactic black hole binaries, when their luminosity apporached the Eddington limit. These results are utilized to argue that ultraluminous X-ray sources generally have significantly higher masses than ordinary stellar-mass black holes.

Isobe, Naoki; Makishima, Kazuo; Takahashi, Hiromitsu; Mizuno, Tsunefumi; Miyawaki, Ryouhei; Gandhi, Poshak; Kawaharada, Madoka; Senda, Atsushi; Yoshida, Tessei; Kubota, Aya; Kobori, Hiroshi

2009-01-01

194

High-Latitude Emission of a Non-Power-Law Spectrum and Spectral Evolution of GRB X-Ray Tails  

SciTech Connect

The apparent spectral evolution observed in the steep decay phase of many GRB earlyX-ray afterglows raises a great concern of the high-latitude ''curvature effect'' interpretation of this phase. However, previous curvature effect models only invoked a simple power law spectrum upon the cessation of the prompt internal emission. We investigate the 'curvature effect' model of a more general non-power-law spectrum and and test this model with the Swift/XRT observations By comparing the simulated lightcurves/spectra with the observed ones, we show that one can reproduce both the observed lightcurve and the apparent spectral evolution of GRB 050814 using a model invoking a cut-off power-law spectrum. This suggests that at least for some GRBs, the fast spectral evolution in the steep-decay phase can be explained by the curvature effect of a non-power-law spectrum.

Zhang Binbin; Zhang Bing [Department of Physics and Astronomy, University of Nevada, Las Vegas, NV 89154 (United States); Liang Enwei [Department of Physics, Guangxi University, Nanning 530004 (China); Wang Xiangyu [Department of Astronomy, Nanjing University, Nanjing 210093 (China)

2009-05-25

195

Study on the influence of X-ray tube spectral distribution on the analysis of bulk samples and thin films: Fundamental parameters method and theoretical coefficient algorithms  

NASA Astrophysics Data System (ADS)

Knowledge of X-ray tube spectral distribution is necessary in theoretical methods of matrix correction, i.e. in both fundamental parameter (FP) methods and theoretical influence coefficient algorithms. Thus, the influence of X-ray tube distribution on the accuracy of the analysis of thin films and bulk samples is presented. The calculations are performed using experimental X-ray tube spectra taken from the literature and theoretical X-ray tube spectra evaluated by three different algorithms proposed by Pella et al. (X-Ray Spectrom. 14 (1985) 125-135), Ebel (X-Ray Spectrom. 28 (1999) 255-266), and Finkelshtein and Pavlova (X-Ray Spectrom. 28 (1999) 27-32). In this study, Fe-Cr-Ni system is selected as an example and the calculations are performed for X-ray tubes commonly applied in X-ray fluorescence analysis (XRF), i.e., Cr, Mo, Rh and W. The influence of X-ray tube spectra on FP analysis is evaluated when quantification is performed using various types of calibration samples. FP analysis of bulk samples is performed using pure-element bulk standards and multielement bulk standards similar to the analyzed material, whereas for FP analysis of thin films, the bulk and thin pure-element standards are used. For the evaluation of the influence of X-ray tube spectra on XRF analysis performed by theoretical influence coefficient methods, two algorithms for bulk samples are selected, i.e. Claisse-Quintin (Can. Spectrosc. 12 (1967) 129-134) and COLA algorithms (G.R. Lachance, Paper Presented at the International Conference on Industrial Inorganic Elemental Analysis, Metz, France, June 3, 1981) and two algorithms (constant and linear coefficients) for thin films recently proposed by Sitko (X-Ray Spectrom. 37 (2008) 265-272).

Sitko, Rafa?

2008-11-01

196

Near-Field Stacking of Zone Plates in the X-Ray Range.  

National Technical Information Service (NTIS)

We use Fresnel zone plates as focusing optics in hard x-ray microprobes at energies typically between 6 and 30 keV. While a spatial resolution close to 0.1 microm can currently be achieved, highest spatial resolution is obtained only at reduced diffractio...

J. Maser B. Lai W. Yun S. D. Shastri Z. Cai

2002-01-01

197

Extragalactic X-ray Background in the 0.2-2 keV Range.  

National Technical Information Service (NTIS)

We made the first measurement of the extragalactic 0.7 keV background. We detected the X-ray shadow of a neutral gas cloud in the Magellanic Bridge. We further constrained the point-like source contribution based on the mean spectrum of detected sources a...

D. Q. Wang

1997-01-01

198

Spectral classification of the mass donors in the high-mass X-ray binaries EXO 1722-363 and OAO 1657-415  

NASA Astrophysics Data System (ADS)

Aims: We report near-infrared (NIR) observations of the mass donors of the eclipsing high-mass X-ray binary (HMXB) systems EXO 1722-363 and OAO 1657-415 in order to derive their accurate spectral classifications. Methods: ESO/VLT observations of the targets with the NIR spectrometer ISAAC were compared with several published NIR spectral atlases of O and B supergiants, an identification of each object's spectral characteristics was made, enabling the refinement of spectral classification of the mass donors. Results: We determined that EXO 1722-363 was of spectral type B0-B1Ia, positioned at a distance 8.0-2.0+2.5 kpc with a progenitor mass in the range 30-40 M?. Luminosity calculations imply that LX ~ 1035-1037 erg s-1 for this distance range. We conclude that EXO 1722-363 shares many of the properties associated with other X-ray binary B-type supergiant donors. We found that OAO 1657-415 correlates closely with the spectra of a class of transitional objects, the Ofpe/WNL stars, an intermediate evolutionary stage between massive O type stars leaving the main sequence and evolving into Wolf-Rayets. Due to the wide range in luminosity displayed by Ofpe/WNL stars, (log(L/L?) ~ 5.3-6.2) distance determinations are problematic. For OAO 1657-415 we report a distance of 4.4 ? d ? 12 kpc, implying an X-ray luminosity of 1.5 × 1036 ? LX ? 1037 erg s-1. We have used our new classification of OAO 1657-415 to explain the physical processes responsible for its unique position within the Corbet diagram. Ofpe/WNL stars demonstrate a high rate of mass-loss through a dense stellar wind combined with a low terminal velocity. This combination of wind properties leads to a high accretion rate and transfer of angular momentum to the neutron star in this system. We believe this in turn leads to a smaller instantaneous equilibrium spin period with respect to normal OB supergiants. Based on observations carried out at the European Southern Observatory under programme ID 081.D-0073(A).

Mason, A. B.; Clark, J. S.; Norton, A. J.; Negueruela, I.; Roche, P.

2009-10-01

199

EVIDENCE FOR THE FULL HARD X-RAY SPECTRAL SIGNATURE OF NONUNIFORM IONIZATION IN A SOLAR FLARE  

SciTech Connect

The hard X-ray (HXR) emission from solar flares is observed primarily from the footpoints of flare magnetic loops, where nonthermal electrons are understood to emit thick-target bremsstrahlung as they stream from the fully ionized hot corona to the denser, cooler, and partially ionized chromosphere. The change in the plasma ionization along the path of the electrons should result in a characteristic upward break and corresponding flattening of the X-ray spectrum with increasing energy at lower energies, and a downward break at higher energies. Due to the presence of thermal emission, the upward break usually cannot be observed. We report the first evidence for both breaks in spectra measured with the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) during the GOES X1.2 class flare that happened on 2002 October 31. The RHESSI X-ray spectral analysis shows both the breakup at {approx}49 keV and the breakdown at {approx}134 keV at the HXR peak time. The time evolution of both breaks also agrees with the nonuniform ionization (NUI) model. Other possible explanations for the breaks are considered, but the NUI model provides the simplest explanation for the spectral shape and its time evolution. We find that the average column density of the fully ionized plasma changed from 2 x10{sup 19} cm{sup -2} in the rise phase to 7 x10{sup 21} cm{sup -2} after the peak. This indicates that plasma in the target was heated and became ionized during the flare, in agreement with heating by the nonthermal electrons and chromospheric evaporation expected in the collisional thick-target model.

Su Yang [Department of Physics, Catholic University of America, Washington, DC 20064 (United States); Holman, Gordon D.; Dennis, Brian R., E-mail: yang.su@nasa.gov, E-mail: gordon.d.holman@nasa.gov [NASA Goddard Space Flight Center, Solar Physics Laboratory, Code 671, Greenbelt, MD 20771 (United States)

2011-04-20

200

Improving the spectral resolution of soft x-ray flat-field spectrometer with multi-area gratings  

NASA Astrophysics Data System (ADS)

The ideal focal curve for the soft x-ray flat-field spectrometer is a straight line, but the real one is not, thus the inconformity of aberrations between different wavelengths in the working waveband is inevitable. In order to further reduce aberrations and improve spectral resolutions, multi-area gratings (divided perpendicular the direction of grating grooves) are devised. Firstly, the grating is divided into three areas, and the spectral aberrations for these areas are analyzed by means of ray tracing. Then, diffraction efficiencies for the areas with worse aberrations should be reduced to lower the proportion regional aberrations contributing to the overall aberration, therefore better spectral image could be obtained and the spectral resolution would be improved. Theoretical analysis demonstrates that: using multi-area grating, the spectral resolutions at wavelength of 0.8 and 1.1nm are increased from 123 and 333 to 401 and 671, respectively. At the same time, the spectral resolutions at other wavelengths are not reduced.

Chen, Huoyao; Liu, Zhengkun; Wang, Qingbo; Fu, Shaojun

2013-08-01

201

Long-range density fluctuations in orthoterphenyl as studied by means of ultrasmall-angle x-ray scattering  

Microsoft Academic Search

The structure factor of a fragile glass-forming liquid orthoterphenyl was measured in the previously inaccessible intermediate q range between the conventional light scattering (LS) and small-angle x-ray scattering (SAXS) q ranges using the low-angle scattering beam line at the European Synchrotron Radiation Facility. At low q the structure factor exhibits an excess scattering and matches well the LS data. This

A. Patkowski; Th. Thurn-Albrecht; E. Banachowicz; W. Steffen; P. Bösecke; T. Narayanan; E. W. Fischer

2000-01-01

202

Spectral sampling of a soft X-ray tube emission by a lamellar multilayer grating in standard and conical mountings  

NASA Astrophysics Data System (ADS)

A Lamellar Multilayer Amplitude Grating (LMAG) etched in a multilayer mirror was designed for an efficient use in the 1 keV region, through a multistep process involving sputtering coating, electron lithography and reactive ion etching. The multilayer structure has 115 W/B4C bilayers of 3.1 nm thickness, and the grating of period 1.33 ?m has a small line-to-period ratio ? equal to about 0.10. The properties of a LMAG illuminated in standard and conical mountings by a polychromatic radiation are given, and the concept of a “polychromator” based on a LMAG is presented. Taking benefit from the specific properties of a LMAG, the emission of a soft X-ray tube equipped with a copper target is spectrally analyzed with our LMAG in the Cu-L (930 eV) region in standard and conical mountings. This experiment shows that a LMAG could be an interesting spectral analyzer for short-duration X-ray sources.

Krastev, K.; LeGuern, F.; Coat, K.; Barchewitz, R.; André, J.-M.; Ravet, M. F.; Cambril, E.; Rousseaux, F.; Davi, P.

1996-01-01

203

Spectral linewidth measurement of an injection-seeded transient 18.9 nm soft X-ray laser  

Microsoft Academic Search

The linewidth of an injection-seeded 18.9nm molybdenum soft x-ray laser (SXRL) was measured to be significantly wider than seeded optical field ionization SXRLs that use gaseous targets, an advantage for the development of sub-picosecond SXRLs. OCIS codes: (140.7240) UV, EUV and X-ray lasers; (340.7480) X-rays, soft x-rays, extreme ultraviolet (EUV) The demonstration of injection-seeded soft X-ray lasers (SXRL), generated by

D. Alessi; L. M. Meng; Y. Wang; O. Guilbaud; M. Berrill; S. R. Domingue; D. H. Martz; B. M. Luther; D. Joyeux; S. De Rossi; A. Klisnick; J. J. Rocca

2011-01-01

204

Extension of dynamic range in X-ray radiography using multi-color scintillation detector  

Microsoft Academic Search

A new imaging system using the multi-color scintillator Gd2O2S:Eu has been developed for the X-ray radiography. In this method a color Charge Coupled Device detects the weak blue and green photons associated with the transitions from the terms like 5D1 and 5D2 in the Eu-ions as well as the dominant red photons. As these transitions become appreciable and saturate at

Koichi Nittoh; Eiji Oyaizu; Tetsuo Sakurai; Tadashi Yoshida; Koh-Ichi Mochiki

2003-01-01

205

X-ray Si-based Integrated Lens System for Wide Range of Hard Synchrotron Radiation  

Microsoft Academic Search

We present integrated lens system (ILS), which consists of 6 compound refractive lenses with the same focal distance of 0.5m, but optimized for discrete set of energies such as 10, 12, 14, 16, 18, 20 keV. Focusing properties were tested at the ESRF BM-5 and ID18F beamlines. It was shown, that all compound refractive lenses in the system focus X-rays

I. Snigireva; A. Snigirev; V. Yunkin; M. Drakopoulos; M. Grigoriev; S. Kuznetsov; M. Chukalina; M. Hoffmann; D. Nuesse; E. Voges

2004-01-01

206

Production of spectrally narrow soft-x-ray radiation through the use of broadband laser-produced plasma sources and multilayer-coated reflecting optics.  

PubMed

We describe a special filter design that produces spectrally narrow soft-x-ray radiation by using a broadband laser-produced plasma source and multilayer-coated reflecting optics. Calculations for the design were carried out at several laser-produced plasma-source temperatures and various multilayermirror combinations with and without a soft-x-ray filter. We determined that the best arrangement for a laser-produced plasma source consists of two multilayer mirrors and one soft-x-ray filter for each temperature investigated. PMID:21052324

Eligon, A M; Gruber, N; Silfvast, W T

1995-08-01

207

Spectral measurements of galactic and extragalactic sources in the hard X-ray region of 20-200 keV using balloon borne telescope  

Microsoft Academic Search

The spectral and temporal measurements in the hard X-ray region between 20-200 keV not only determines the extended behaviour\\u000a of thermal X-ray spectrum below 10 keV but also provide a unique insight into the non-thermal processes in relativistic astrophysical\\u000a plasma. From our present understanding of the X-ray sources, a significant fluxin the 20-200 keV band is expected from a variety

R. K. Manchanda

2002-01-01

208

Versatile high-repetition-rate phase-locked chopper system for fast timing experiments in the vacuum ultraviolet and x-ray spectral region  

NASA Astrophysics Data System (ADS)

A novel light chopper system for fast timing experiments in the vacuum-ultraviolet (VUV) and x-ray spectral region has been developed. It can be phase-locked and synchronized with a synchrotron radiation storage ring, accommodating repetition rates in the range of ~8 to ~120 kHz by choosing different sets of apertures and subharmonics of the ring frequency (MHz range). Also the opening time of the system can be varied from some nanoseconds to several microseconds to meet the needs of a broad range of applications. Adjusting these parameters, the device can be used either for the generation of single light pulses or pulse packages from a microwave driven, continuous He gas discharge lamp or from storage rings which are otherwise often considered as quasi-continuous light sources. This chopper can be utilized for many different kinds of experiments enabling, for example, unambiguous time-of-flight (TOF) multi-electron coincidence studies of atoms and molecules excited by a single light pulse as well as time-resolved visible laser pump x-ray probe electron spectroscopy of condensed matter in the valence and core level region.

Plogmaker, Stefan; Linusson, Per; Eland, John H. D.; Baker, Neville; Johansson, Erik M. J.; Rensmo, Ha?Kan; Feifel, Raimund; Siegbahn, Hans

2012-01-01

209

Versatile high-repetition-rate phase-locked chopper system for fast timing experiments in the vacuum ultraviolet and x-ray spectral region  

SciTech Connect

A novel light chopper system for fast timing experiments in the vacuum-ultraviolet (VUV) and x-ray spectral region has been developed. It can be phase-locked and synchronized with a synchrotron radiation storage ring, accommodating repetition rates in the range of {approx}8 to {approx}120 kHz by choosing different sets of apertures and subharmonics of the ring frequency (MHz range). Also the opening time of the system can be varied from some nanoseconds to several microseconds to meet the needs of a broad range of applications. Adjusting these parameters, the device can be used either for the generation of single light pulses or pulse packages from a microwave driven, continuous He gas discharge lamp or from storage rings which are otherwise often considered as quasi-continuous light sources. This chopper can be utilized for many different kinds of experiments enabling, for example, unambiguous time-of-flight (TOF) multi-electron coincidence studies of atoms and molecules excited by a single light pulse as well as time-resolved visible laser pump x-ray probe electron spectroscopy of condensed matter in the valence and core level region.

Plogmaker, Stefan; Johansson, Erik M. J.; Rensmo, Haakan; Feifel, Raimund; Siegbahn, Hans [Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala (Sweden); Linusson, Per [Department of Physics, Stockholm University, AlbaNova University Center, SE-106 91 Stockholm (Sweden); Eland, John H. D. [Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala (Sweden); Department of Chemistry, Physical and Theoretical Chemistry Laboratory, Oxford University, South Parks Road, Oxford OX1 3QZ (United Kingdom); Baker, Neville [Department of Chemistry, Physical and Theoretical Chemistry Laboratory, Oxford University, South Parks Road, Oxford OX1 3QZ (United Kingdom)

2012-01-15

210

Versatile high-repetition-rate phase-locked chopper system for fast timing experiments in the vacuum ultraviolet and x-ray spectral region.  

PubMed

A novel light chopper system for fast timing experiments in the vacuum-ultraviolet (VUV) and x-ray spectral region has been developed. It can be phase-locked and synchronized with a synchrotron radiation storage ring, accommodating repetition rates in the range of ~8 to ~120 kHz by choosing different sets of apertures and subharmonics of the ring frequency (MHz range). Also the opening time of the system can be varied from some nanoseconds to several microseconds to meet the needs of a broad range of applications. Adjusting these parameters, the device can be used either for the generation of single light pulses or pulse packages from a microwave driven, continuous He gas discharge lamp or from storage rings which are otherwise often considered as quasi-continuous light sources. This chopper can be utilized for many different kinds of experiments enabling, for example, unambiguous time-of-flight (TOF) multi-electron coincidence studies of atoms and molecules excited by a single light pulse as well as time-resolved visible laser pump x-ray probe electron spectroscopy of condensed matter in the valence and core level region. PMID:22299937

Plogmaker, Stefan; Linusson, Per; Eland, John H D; Baker, Neville; Johansson, Erik M J; Rensmo, Håkan; Feifel, Raimund; Siegbahn, Hans

2012-01-01

211

Developing a Compton polarimeter to measure polarization of hard x-rays in the 50-300 keV energy range  

Microsoft Academic Search

This paper discusses the latest progress in the development of GRAPE (Gamma-Ray Polarimeter Experiment), a hard X-ray Compton Polarimeter. The purpose of GRAPE is to measure the polarization of hard X-rays in the 50-300 keV energy range. We are particularly interested in X-rays that are emitted from solar flares and gamma-ray bursts (GRBs). Accurately measuring the polarization of the emitted

Jason Legere; Peter L. Bloser; John R. Macri; Mark L. McConnell; Tomohiko Narita; James M. Ryan

2005-01-01

212

SWIFT OBSERVATIONS OF THE 2006 OUTBURST OF THE RECURRENT NOVA RS OPHIUCHI. III. X-RAY SPECTRAL MODELING  

SciTech Connect

Following the Swift X-ray observations of the 2006 outburst of the recurrent nova RS Ophiuchi, we developed hydrodynamical models of mass ejection from which the forward shock velocities were used to estimate the ejecta mass and velocity. In order to further constrain our model parameters, we present synthetic X-ray spectra from our hydrodynamical calculations, which we compare to the Swift data. An extensive set of simulations was carried out to find a model that best fits the spectra up to 100 days after outburst. We find a good fit at high energies but require additional absorption to match the low energy emission. We estimate the ejecta mass to be in the range (2-5) x 10{sup -7} M{sub sun} and the ejection velocity to be greater than 6000 km s{sup -1} (and probably closer to 10, 000 km s{sup -1}). We also find that estimates of shock velocity derived from gas temperatures via standard model fits to the X-ray spectra are much lower than those of the true shock velocities.

Vaytet, N. M. H. [CEA/DSM/IRFU, Service d'Astrophysique, Laboratoire AIM, CNRS, Universite Paris Diderot, 91191 Gif-sur-Yvette, Cedex (France); O'Brien, T. J.; Lloyd, M. [Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL (United Kingdom); Page, K. L.; Beardmore, A. P. [Department of Physics and Astronomy, University of Leicester, Leicester, LE1 7RH (United Kingdom); Bode, M. F., E-mail: neil.vaytet@cea.fr, E-mail: tim.obrien@manchester.ac.uk, E-mail: kpa@star.le.ac.uk, E-mail: mfb@astro.livjm.ac.uk [Astrophysics Research Institute, Liverpool John Moores University, Birkenhead, CH41 1LD (United Kingdom)

2011-10-10

213

Investigation of multilayer X-ray optics for the 6 keV to 20 keV energy range.  

PubMed

The X-ray optics group at the Swiss Light Source in co-operation with RIT (Rigaku Innovative Technologies) have investigated seven different multilayer samples. The goal was to find an ideal multilayer structure for the energy range between 6?keV and 20?keV in terms of energy resolution and reflectivity. Such multilayer structures deposited on substrates can be used as X-ray monochromators or reflecting synchrotron mirrors. The measured reflectivities agree with the simulated ones. They cover a reflectivity range from 45% to 80% for energies between 6?keV and 10?keV, and 80% to 90% for energies between 10?keV and 20?keV. The experimentally measured energy resolution of the samples lies between 0.3% and 3.5%. PMID:22898944

Oberta, P; Platonov, Y; Flechsig, U

2012-08-03

214

Micro-X-ray spectral determination of iodine in alloys based on bismuth telluride  

SciTech Connect

The authors have developed a procedure for determining the iodine content in Bi/sub 2/Te/sub 3/ single crystals and solid solutions based on it with the help of an x-ray microanalyzer. The crystals were grown by Czochralski's method with the liquid phase fed from a floating crucible. the iodine was injected into the alloys in the form of the compound SbI/sub 3/. It is evident, according to the authors, that changing the iodine content from 0.08 to 0.12 mass % appreciably affects the electrophysical properties of the melt. The amount of iodine determined using the procedure developed corresponds well with its content in the starting charge.

Kul'bachevskaya, E.V.; Chizhevskaya, S.N.; Svechnikova, T.E.

1986-08-01

215

Spectral evolution in black hole accretion powered AGN and the cosmic X-ray background  

NASA Astrophysics Data System (ADS)

If AGN contain supermassive black holes of pregalactic origin, then the radiation emitted during their lifetime will undergo spectral evolution. For AGN black-hole-accretion disk dynamo power sources, the dynamic parameters relevant to spectral evolution are the electron crossing time in the dynamo, the electron radiative loss time, the compactness parameter, and the photon-photon pair production optical depth. It is suggested that both spectral and luminosity evolution may be required to explain the evolutionary properties of AGN.

Leiter, D.; Boldt, E.

216

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

Microsoft Academic Search

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

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

2004-01-01

217

Spectral and temporal behavior of low mass X ray binaries observed with the Einstein SSS and MPC, and the Broad Band X Ray Telescope  

Microsoft Academic Search

An extensive survey of 50 low mass X-ray binaries was carried out using the HEAO-2 Einstein Solid State Spectrometer data (0.5-4.5 keV) with the Monitor Proportional Counter data (1.2-20.0 keV). The SSS provided 160 eV resolution below 4.5 keV with about 200 sq cm of area, 100 times that of grating instruments on Einstein and EXOSAT. Additional observations were obtained

Damian Joseph Christian

1993-01-01

218

X-ray Absorption Fine Structure Combined with X-ray Fluorescence Spectrometry. Improvement of Spectral Resolution at the Absorption Edges of 9?29 keV  

Microsoft Academic Search

X-ray absorption near-edge structure (XANES) suffers from core-hole lifetime broadening at a higher energy absorption edge, such as Sn K (29 keV, ¡K ) 8.49 eV). To overcome this problem, emitted Sn Kr1 fluorescence from sample was counted using high-energy-resolution fluorescence spectrometer in the XANES measurements. Experimental energy resolution (5.0 eV) was consistent with theoretical values based on the Rowland

Yasuo Izumi; Hiroyasu Nagamori; Fumitaka Kiyotaki; Dilshad Masih; Taketoshi Minato; Eric Roisin; Jean-Pierre Candy; Hajime Tanida; Tomoya Uruga

2005-01-01

219

Timing and spectral analysis of the X-ray binary pulsar XTE J1829-098  

NASA Astrophysics Data System (ADS)

We have used the archival RXTE PCA data to investigate timing and spectral characteristics of the Pulsar XTE J1829-098. Spectral analysis confirmed the present discovery of Cyclotron line at ˜18 keV and detection of Iron line at around 6.4 keV. We have performed multi-wavelength studies to study the properties of the source.

Roy, Jayashree; Tanti, Kamal Kumar; Agrawal, P. C.; Duorah, Kalpana

220

Two dimensional power spectral density measurements of X-ray optics with the Micromap interferometric microscope  

Microsoft Academic Search

A procedure and software have been developed to transform the area distribution of the residual surface heights available from the measurement with the Micromap interferometric microscope into a two-dimensional (2D) power spectral density (PSD) distribution of the surface height. The procedure incorporates correction of one of the spectral distortions of the PSD measurement. The distortion appears as a shape difference

Valeriy V. Yashchuk; Andrew D. Franck; Steve C. Irick; Malcolm R. Howells; Alastair A. MacDowell; Wayne R. McKinney

221

Short-range order in amorphous SiO{sub x} by x ray photoelectron spectroscopy  

SciTech Connect

The Si 2p x ray photoelectron spectra of SiO{sub x} with a different composition of 0 {<=} x {<=} 2 have been studied experimentally and theoretically. The SiO{sub x} films were prepared by low-pressure chemical vapor deposition from SiH{sub 4} and N{sub 2}O source at 750 deg. C. Neither random bonding nor random mixture models can adequately describe the structure of these compounds. The interpretation of the experimental results is discussed according to a large scale potential fluctuation due to the spatial variation of chemical composition in SiO{sub x}.

Novikov, Yu. N.; Gritsenko, V. A. [Institute of Semiconductor Physics, Novosibirsk 630090 (Russian Federation)

2011-07-01

222

X-ray Spectral Analysis of Dim Type Ia Supernova Remnant Candidates in the Small Magellanic Cloud  

NASA Astrophysics Data System (ADS)

We report on the statistical analyses of three morphologically asymmetric low-count supernova remnants, designated IKT 5, IKT 25, and DEM S 128 in the Small Magellanic Cloud (SMC). These remnants have been previously identified as Type Ia candidates based on the presumed overabundance of iron in their XMM CCD spectra. We have used archived Chandra data to perform spectral analyses on these three remnants. Their tentative Type Ia designation and morphological asymmetry is in contrast to more recent findings that soft x-ray morphology is generally more symmetric in Type Ia remnants in the Large Magellanic Cloud and Milky Way. We combine the Chandra data with Spitzer data to show that the morphology is affected by complicated environmental interactions with these remnants. Moreover, by performing a maximum-likelihood analysis fitting technique on the soft X-ray spectra of these remnants, we find that these remnants are dominated by surrounding ISM emission, as opposed to being iron ejecta-dominated, as expected for younger Type Ia supernova remnants.

Roper, Quentin; McEntaffer, R.; DeRoo, C.

2012-01-01

223

A highly-ionized absorber as a new explanation for the spectral changes during dips from X-ray binaries  

NASA Astrophysics Data System (ADS)

Until now, the spectral changes observed from persistent to dipping intervals in dipping low-mass X-ray binaries were explained by invoking progressive and partial covering of an extended emission region. Here, we propose a novel and simpler way to explain these spectral changes, which does not require any partial covering and hence any extended corona, and further has the advantage of explaining self-consistently the spectral changes both in the continuum and the narrow absorption lines that are now revealed by XMM-Newton. In 4U 1323-62, we detect Fe XXV and Fe XXVI absorption lines and model them for the first time by including a complete photo-ionized absorber model rather than individual Gaussian profiles. We demonstrate that the spectral changes both in the continuum and the lines can be simply modeled by variations in the properties of the ionized absorber. From persistent to dipping the photo-ionization parameter decreases while the equivalent hydrogen column density of the ionized absorber increases. In a recent work (Díaz Trigo et al. 2005), we show that our new approach can be successfully applied to all the other dipping sources that have been observed by XMM-Newton.

Boirin, L.; Méndez, M.; Díaz Trigo, M.; Parmar, A.; Kaastra, J.

2005-12-01

224

Studies on x-ray and UV emissions in electron cyclotron resonance x-ray source  

NASA Astrophysics Data System (ADS)

A novel electron cyclotron resonance x-ray source is constructed based on the ECR technique. In this paper, the possibility of using the ECR x-ray source for producing UV rays by optimizing the plasma parameters is explored. X-ray and UV emissions from the ECR x-ray source are carried out for argon, nitrogen, and CO2 plasma. The x-ray spectral and dose measurements are carried with NaI(Tl) based spectrometer and dosimeter, respectively. For UV measurement, a quartz window arrangement is made at the exit port and the UV intensity is measured at 5 cm from the quartz plate using UV meter. The x-ray and UV emissions are carried out for different microwave power levels and gas pressures. The x-ray emission is observed in the pressure range <=10-5 Torr, whereas the UV emission is found to be negligible for the gas pressures <10-5 Torr and it starts increasing in the pressure range between 10-5 and 10-3 Torr. At high-pressure range, collision frequency of electron-atom is large which leads to the higher UV flux. At low pressure, the electron-atom collision frequency is low and hence the electrons reach high energy and by hitting the cavity wall produces higher x-ray flux. By choosing proper experimental conditions and plasma gas species, the same source can be used as either an x-ray source or an UV source.

Baskaran, R.; Selvakumaran, T. S.

2008-02-01

225

Two Dimensional Power Spectral Density Measurement of X-ray Optics with the Micromap Interferometric Microscope.  

National Technical Information Service (NTIS)

A procedure and software have been developed to transform the area distribution of the residual surface heights available from the measurement with the Micromap interferometric microscope into a two-dimensional (2D) power spectral density (PSD) distributi...

V. V. Yashchuk A. D. Franck S. C. Irick M. R. Howells A. A. MacDowell

2006-01-01

226

OSO7 observations of solar x-rays in the energy range 10–100 keV  

Microsoft Academic Search

The solar X-ray experiment on the satellite OSO-7 has provided extensive observations of hard and soft X-ray bursts. We give a general description of the hard X-ray data here, in parallel with the description of the soft X-ray data already published (Datlowe et al., 1974). The data for this study consist of 123 hard X-ray bursts which occurred between 10

D. W. Datlowe; M. J. Elcan; H. S. Hudson

1974-01-01

227

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

PubMed

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

Yücel, H; Dikmen, H

2008-11-27

228

CANDIDATE X-RAY-EMITTING OB STARS IN THE CARINA NEBULA IDENTIFIED VIA INFRARED SPECTRAL ENERGY DISTRIBUTIONS  

SciTech Connect

We report the results of a new survey of massive, OB stars throughout the Carina Nebula using the X-ray point source catalog provided by the Chandra Carina Complex Project (CCCP) in conjunction with infrared (IR) photometry from the Two Micron All-Sky Survey and the Spitzer Space Telescope Vela-Carina survey. Mid-IR photometry is relatively unaffected by extinction, hence it provides strong constraints on the luminosities of OB stars, assuming that their association with the Carina Nebula, and hence their distance, is confirmed. We fit model stellar atmospheres to the optical (UBV) and IR spectral energy distributions (SEDs) of 182 OB stars with known spectral types and measure the bolometric luminosity and extinction for each star. We find that the extinction law measured toward the OB stars has two components: A{sub V} = 1-1.5 mag produced by foreground dust with a ratio of total-to-selective absorption R{sub V} = 3.1 plus a contribution from local dust with R{sub V} > 4.0 in the Carina molecular clouds that increases as A{sub V} increases. Using X-ray emission as a strong indicator of association with Carina, we identify 94 candidate OB stars with L{sub bol} {approx}> 10{sup 4} L{sub sun} by fitting their IR SEDs. If the candidate OB stars are eventually confirmed by follow-up spectroscopic observations, the number of cataloged OB stars in the Carina Nebula will increase by {approx}50%. Correcting for incompleteness due to OB stars falling below the L{sub bol} cutoff or the CCCP detection limit, these results potentially double the size of the young massive stellar population.

Povich, Matthew S.; Townsley, Leisa K.; Broos, Patrick S.; Getman, Konstantin V. [Department of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802 (United States); Gagne, Marc [Department of Geology and Astronomy, West Chester University, West Chester, PA 19383 (United States); Babler, Brian L.; Meade, Marilyn R.; Townsend, Richard H. D. [Department of Astronomy, University of Wisconsin, 475 N. Charter Street, Madison, WI 53706 (United States); Indebetouw, Remy; Majewski, Steven R. [Department of Astronomy, University of Virginia, P.O. Box 400325, Charlottesville, VA 22904-4325 (United States); Robitaille, Thomas P., E-mail: povich@astro.psu.edu [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

2011-05-01

229

Development of high spectral resolution CdZnTe pixel detectors for astronomical hard X-ray telescopes  

NASA Astrophysics Data System (ADS)

Cadmium zinc telluride detectors (CdZnTe) offer the possibility of achieving excellent spectral and spatial resolution for compact hard X-ray sensors operated without cryogenics. These characteristics make these detectors ideal for several astrophysical applications, including focal plane sensors for multilayer hard X-ray telescopes, and in the image plane of coded-aperture imagers. We are developing a CdZnTe pixel detector and low-noise VLSI readout for use at the focal plane of the balloon-borne High Energy Focusing Telescope (HEFT). In particular, we have concentrated on achieving excellent spectral resolution in a device with 600?m pixels. Here we report results from the testing of our fully functional prototype hybrid detector. The detector (an 8×7×2mm3 single crystal of CdZnTe with an 8×8 pattern of platinum contacts on one side and a monolithic contact on the other) is indium bump-bonded to our 64-channel readout chip, which contains a charge-sensitive preamplifier, shaping amplifier, and combination peak stretcher/discriminator for each pixel. In this paper, we present results taken at room temperature, demonstrating a low-energy threshold near 5keV and electronic noise of 1.5keV FWHM at 60keV. Subsequent testing of this detector at -10°C, reported in Cook et al. [Proc. SPIE 3769 (1999) 92], achieved 670eV FWHM resolution at 60keV, with electronic noise of 340eV.

Bolotnikov, A. E.; Cook, W. R.; Boggs, S. E.; Harrison, F. A.; Schindler, S. M.

2001-02-01

230

Search for X-ray emission from Nova Cygni 1975  

Microsoft Academic Search

A search for X-rays from Nova Cygni 1975 was carried out before, during, and after the time of optical maximum. No X-rays were detected over the spectral range 0.1-50 keV. On the basis of these results a strong upper limit of .0001 has been placed on the ratio of X-ray to optical luminosity for this nova, consistent with effective temperatures

J. A. Hoffman; W. H. G. Lewin; K. Brecher; J. Buff; G. W. Clark; P. C. Joss; T. Matilsky

1976-01-01

231

Recent activity of the black hole X-ray binary IGR J17091-3624 as observed with the SWIFT/XRT : spectral hardening following the sharp drop in X-ray intensity  

NASA Astrophysics Data System (ADS)

The last X-ray activity of the transient, Galactic, black hole X-ray binary IGR J17091-3624 was reported by Altamirano et al. (Atel #3913), where, using SWIFT/XRT data, they showed the source count rate of 15 +/- 2 cts/s on 31st January, 2012. Using INTEGRAL and IBIS detector, Drave et al. (Atel# 3916) detected the source activity in the 18-40 keV and 40-100 keV energy range respectively. Here, we are briefly summarizing the source activity using all observations from February 2012 onwards by the SWIFT/XRT.

Pahari, Mayukh; Bhattacharyya, Sudip; Yadav, J. S.

2012-07-01

232

Task-based weights for photon counting spectral x-ray imaging  

SciTech Connect

Purpose: To develop a framework for taking the spatial frequency composition of an imaging task into account when determining optimal bin weight factors for photon counting energy sensitive x-ray systems. A second purpose of the investigation is to evaluate the possible improvement compared to using pixel based weights. Methods: The Fourier based approach of imaging performance and detectability index d' is applied to pulse height discriminating photon counting systems. The dependency of d' on the bin weight factors is made explicit, taking into account both differences in signal and noise transfer characteristics across bins and the spatial frequency dependency of interbin correlations from reabsorbed scatter. Using a simplified model of a specific silicon detector, d' values for a high and a low frequency imaging task are determined for optimal weights and compared to pixel based weights. Results: The method successfully identifies bins where a large point spread function degrades detection of high spatial frequency targets. The method is also successful in determining how to downweigh highly correlated bins. Quantitative predictions for the simplified silicon detector model indicate that improvements in the detectability index when applying task-based weights instead of pixel based weights are small for high frequency targets, but could be in excess of 10% for low frequency tasks where scatter-induced correlation otherwise degrade detectability. Conclusions: The proposed method makes the spatial frequency dependency of complex correlation structures between bins and their effect on the system detective quantum efficiency easier to analyze and allows optimizing bin weights for given imaging tasks. A potential increase in detectability of double digit percents in silicon detector systems operated at typical CT energies (100 kVp) merits further evaluation on a real system. The method is noted to be of higher relevance for silicon detectors than for cadmium (zink) telluride detectors.

Bornefalk, Hans [Department of Physics, Royal Institute of Technology, SE-106 91 Stockholm (Sweden)

2011-11-15

233

X-ray structural studies of quinone reductase 2 nanomolar range inhibitors  

SciTech Connect

Quinone reductase 2 (QR2) is one of two members comprising the mammalian quinone reductase family of enzymes responsible for performing FAD mediated reductions of quinone substrates. In contrast to quinone reductase 1 (QR1) which uses NAD(P)H as its co-substrate, QR2 utilizes a rare group of hydride donors, N-methyl or N-ribosyl nicotinamide. Several studies have linked QR2 to the generation of quinone free radicals, several neuronal degenerative diseases, and cancer. QR2 has been also identified as the third melatonin receptor (MT3) through in cellulo and in vitro inhibition of QR2 by traditional MT3 ligands, and through recent X-ray structures of human QR2 (hQR2) in complex with melatonin and 2-iodomelatonin. Several MT3 specific ligands have been developed that exhibit both potent in cellulo inhibition of hQR2 nanomolar, affinity for MT3. The potency of these ligands suggest their use as molecular probes for hQR2. However, no definitive correlation between traditionally obtained MT3 ligand affinity and hQR2 inhibition exists limiting our understanding of how these ligands are accommodated in the hQR2 active site. To obtain a clearer relationship between the structures of developed MT3 ligands and their inhibitory properties, in cellulo and in vitro IC{sub 50} values were determined for a representative set of MT3 ligands (MCA-NAT, 2-I-MCANAT, prazosin, S26695, S32797, and S29434). Furthermore, X-ray structures for each of these ligands in complex with hQR2 were determined allowing for a structural evaluation of the binding modes of these ligands in relation to the potency of MT3 ligands.

Pegan, Scott D.; Sturdy, Megan; Ferry, Gilles; Delagrange, Philippe; Boutin, Jean A.; Mesecar, Andrew D. (IdRS); (Purdue); (Colorado); (UIC)

2011-09-06

234

Multifrequency observations of blazars. III - The spectral shape of the radio to X-ray continuum  

Microsoft Academic Search

Multifrequency, quasi-simultaneous spectra for a sample of 11 blazars are presented. The spectral shape of the violently variable millimeter to ultraviolet flux is consistent with emission from a very compact single component which becomes self-absorbed at wavelengths longer than about 3 mm. The centimeter emission can be attributed to a separate, more slowly varying component. Three out of four optically

L. M. J. Brown; E. I. Robson; W. K. Gear; D. H. Hughes; M. J. Griffin; B. J. Geldzahler; P. R. Schwartz; M. G. Smith; A. G. Smith; D. W. Shepherd; J. R. Webb; E. Valtaoja; H. Terasranta; E. Salonen

1989-01-01

235

Discovery of a quasi-periodic oscillation in the X-ray pulsar 1A 1118-615: correlated spectral and aperiodic variability  

NASA Astrophysics Data System (ADS)

Aims: Our goal is to investigate the X-ray timing and spectral variability of the high-mass X-ray binary 1A 1118-615 during a type-II outburst. Methods: We performed a detailed color, spectral, and timing analysis of a giant outburst from 1A 1118-615 using RXTE data. Results: We report the discovery of a variable quasi-periodic oscillation (QPO) in the power spectral density of 1A 1118-615, with a centroid frequency of ~0.08 Hz. The centroid frequency of the QPO correlates with the X-ray flux, as expected according to the most accredited models for QPO production. For energies above ~4 keV, the QPO rms variability decreases as the energy increases. Pulse profiles display an energy dependence with a two-peak profile at lower energies and a single peak at higher energies. From the spectral analysis we confirm the presence of a cyclotron absorption feature at ~60 keV, the highest value measured for an X-ray pulsar. We find that the spectral parameters (photon index, cutoff energy, iron fluorescence line strength) display a marked dependence with flux. We detect two different levels of neutral hydrogen column density, possibly owing to to the Be companion activity. We report for the first time a correlation between the timing and spectral parameters in an X-ray pulsar. All correlations found between spectral/timing parameters and X-ray flux are present up to a flux of ~6 × 10-9 erg cm-2 s-1, when a saturation level is reached. We propose that the observed saturation corresponds to the minimum extent of the neutron star magnetosphere. We estimate the magnetic field of the neutron star from two independent ways, using results from spectral (cyclotron line energy) and timing (QPO frequency) analysis, obtaining consistent values of ~7-8 × 1012 G. Results from the comprehensive spectral and timing analysis are discussed in comparison with other X-ray pulsars.

Nespoli, E.; Reig, P.

2011-02-01

236

Spectral separation of the efficiencies of the inside and outside orders of soft-x-ray-extreme-ultraviolet gratings at near normal incidence  

SciTech Connect

It is shown from both a phenomenological study and exact modeling that the reason for the experimentally observed substantial (a few angstroms or nanometers) separation in wavelength between the maxima of the inside (negative numbered) and outside (positive numbered) diffraction orders of a multilayer-coated grating, operating at near normal incidence and close to the Bragg condition in the soft-x-ray and extreme-ultraviolet (EUV) regions, is related to the different angles of deviation of the orders. This wavelength separation is also a feature of uncoated diffraction gratings, although not clearly noticeable. The widely used approximate approach for calculating the absolute efficiency, the product of the relative grating efficiency and the reflectance of its multilayer coating, has until recently been considered accurate enough for the analysis of soft-x-ray and EUV near-normal-incidence multilayer-coated gratings. The inapplicability of this approximation for the analysis of the precise positions and shapes of the efficiency curves for the inside and outside orders, despite the small ratios of wavelength and groove depth to period and the small angles of incidence, is demonstrated using gratings with realistic groove profiles and operating in the EUV region. The rigorous modified integral method (MIM), which is a variant of boundary integral equation methods and is designed for the calculation of the efficiency of multilayer gratings with arbitrary layer thicknesses and boundary shapes (including microroughness) and over a wide wavelength range, is proposed in a general operator formalism. An analysis of a derived simple phenomenological expression and the exact numerical study indicates that the spectral separation between the inside and the outside orders grows with increasing either wavelength, angle of incidence, groove frequency, or diffraction order number |m|. The efficiency modeling carried out with the commercial program PCGRATE-SX, based on the MIM, gave not only the exact values of the spectral separation between the inside and outside orders of Mo{sub 4}Ru{sub 6}/Be, Mo/Si, and Mo/Y multilayer-coated gratings with various real groove profiles measured using atomic force microscopy (AFM) but also good agreement with synchrotron radiation measurements, including high orders as well. To determine the shapes and positions of efficiency curves in the soft-x-ray-EUV range of close to normal-incidence bulk and multilayer-coated gratings with real groove profiles (measured by AFM), one should use codes based on rigorous electromagnetic theory such as the MIM. The modeling is important for developing high efficiency and dispersion gratings for high-resolution spectroscopic studies of laboratory, solar, and astrophysical radiation sources.

Goray, Leonid I.; Seely, John F.; Sadov, Sergey Yu. [International Intellectual Group, Inc., P.O. Box 335, Penfield, New York 14526 and Institute for Analytical Instrumentation, Russian Academy of Sciences, Rizhsky Prospect 26, Saint-Petersburg 190103 (Russian Federation); Space Science Division, Naval Research Laboratory, Washington, DC 20375 (United States); Department of Mathematics and Statistics, Memorial University of Newfoundland, St. John's, Newfoundland A1C 5S7 (Canada)

2006-11-01

237

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

238

Two-dimensional power spectral density measurements of x-ray optics with the Micromap interferometric microscope  

NASA Astrophysics Data System (ADS)

A procedure and software have been developed to transform the area distribution of the residual surface heights available from the measurement with the Micromap interferometric microscope into a two-dimensional (2D) power spectral density (PSD) distribution of the surface height. The procedure incorporates correction of one of the spectral distortions of the PSD measurement. The distortion appears as a shape difference between the tangential and sagittal PSD spectra deduced from the 2D PSD distribution for an isotropic surface. A detailed investigation of the origin of the anisotropy was performed, and a mathematical model was developed and used to correct the distortion. The correction employs a modulation transfer function (MTF) of the detector deduced analytically based on an experimentally confirmed assumption about the origin of the anisotropy due to the asymmetry of the read-out process of the instrument's CCD camera. The correction function has only one free parameter, the effective width of the gate-shaped apparatus function which is the same for both directions. The value of the parameter, equal to 1.35 pixels, was found while measuring the 2D PSD distribution of the instrument self-noise, independent of spatial frequency. The effectiveness of the developed procedure is demonstrated with a number of PSD measurements with different X-ray optics including mirrors and a grating.

Yashchuk, Valeriy V.; Franck, Andrew D.; Irick, Steve C.; Howells, Malcolm R.; MacDowell, Alastair A.; McKinney, Wayne R.

2005-08-01

239

Long-range density fluctuations in orthoterphenyl as studied by means of ultrasmall-angle x-ray scattering.  

PubMed

The structure factor of a fragile glass-forming liquid orthoterphenyl was measured in the previously inaccessible intermediate q range between the conventional light scattering (LS) and small-angle x-ray scattering (SAXS) q ranges using the low-angle scattering beam line at the European Synchrotron Radiation Facility. At low q the structure factor exhibits an excess scattering and matches well the LS data. This excess scattering is due to long-range density fluctuations also observed in the isotropic component of scattered light. At high q the structure factor decays to a plateau corresponding to the isothermal compressibility in agreement with the conventional SAXS data. In the intermediate q range, the structure factor exhibits a power law q dependence which indicates that the excess scattering is due to fractal aggregates of denser domains. PMID:11088383

Patkowski, A; Thurn-Albrecht, T; Banachowicz, E; Steffen, W; Bösecke, P; Narayanan, T; Fischer, E W

2000-06-01

240

X-RAY SPECTRAL VARIATIONS IN THE YOUNGEST GALACTIC SUPERNOVA REMNANT G1.9+0.3  

SciTech Connect

The discovery of the youngest Galactic supernova remnant (SNR) G1.9+0.3 has allowed a look at a stage of SNR evolution never before observed. We analyze the 50 ks Chandra observation with particular regard to spectral variations. The very high column density (N{sub H} {approx} 6 x 10{sup 22} cm{sup -2}) implies that dust scattering is important, and we use a simple scattering model in our spectral analysis. The integrated X-ray spectrum of G1.9+0.3 is well described by synchrotron emission from a power-law electron distribution with an exponential cutoff. Using our measured radio flux and including scattering effects, we find a rolloff frequency of 5.4(3.0, 10.2) x 10{sup 17} Hz (h{nu}{sub roll} = 2.2 keV). Including scattering in a two-region model gives lower values of {nu}{sub roll} by over a factor of 2. Dividing G1.9+0.3 into six regions, we find a systematic pattern in which spectra are hardest (highest {nu}{sub roll}) in the bright southeast and northwest limbs of the shell. They steepen as one moves around the shell or into the interior. The extensions beyond the bright parts of the shell have the hardest spectra of all. We interpret the results in terms of dependence of shock acceleration properties on the obliquity angle {theta}{sub Bn} between the shock velocity and a fairly uniform upstream magnetic field. This interpretation probably requires a Type Ia event. If electron acceleration is limited by synchrotron losses, the spectral variations require obliquity-dependence of the acceleration rate independent of the magnetic-field strength.

Reynolds, Stephen P.; Borkowski, Kazimierz J. [Department of Physics, North Carolina State University, Raleigh, NC 27695-8202 (United States); Green, David A. [Cavendish Laboratory, 19 J.J. Thomson Avenue, Cambridge CB3 0HE (United Kingdom); Hwang, Una; Harrus, Ilana; Petre, Robert [NASA/GSFC, Code 660, Greenbelt, MD 20771 (United States)], E-mail: stephen_reynolds@ncsu.edu

2009-04-20

241

A digital x-ray tomosynthesis coupled near infrared spectral tomography system for dual-modality breast imaging.  

PubMed

A Near Infrared Spectral Tomography (NIRST) system has been developed and integrated into a commercial Digital Breast Tomosynthesis (DBT) scanner to allow structural and functional imaging of breast in vivo. The NIRST instrument uses an 8-wavelength continuous wave (CW) laser-based scanning source assembly and a 75-element silicon photodiode solid-state detector panel to produce dense spectral and spatial projection data from which spectrally constrained 3D tomographic images of tissue chromophores are produced. Integration of the optical imaging system into the DBT scanner allows direct co-registration of the optical and DBT images, while also facilitating the synergistic use of x-ray contrast as anatomical priors in optical image reconstruction. Currently, the total scan time for a combined NIRST-DBT exam is ~50s with data collection from 8 wavelengths in the optical scan requiring ~42s to complete. The system was tested in breast simulating phantoms constructed using intralipid and blood in an agarose matrix with a 3 cm x 2 cm cylindrical inclusion at 1 cm depth from the surface. Diffuse image reconstruction of total hemoglobin (HbT) concentration resulted in accurate recovery of the lateral size and position of the inclusion to within 6% and 8%, respectively. Use of DBT structural priors in the NIRST reconstruction process improved the quantitative accuracy of the HbT recovery, and led to linear changes in imaged versus actual contrast, underscoring the advantages of dual-modality optical imaging approaches. The quantitative accuracy of the system can be further improved with independent measurements of scattering properties through integration of frequency or time domain data. PMID:23038553

Krishnaswamy, Venkataramanan; Michaelsen, Kelly E; Pogue, Brian W; Poplack, Steven P; Shaw, Ian; Defrietas, Ken; Brooks, Ken; Paulsen, Keith D

2012-08-13

242

Accretion flow diagnostics with X-ray spectral timing: the hard state of SWIFT J1753.5-0127  

NASA Astrophysics Data System (ADS)

Recent XMM-Newton studies of X-ray variability in the hard states of black hole X-ray binaries (BHXRBs) indicate that the variability is generated in the 'standard' optically thick accretion disc that is responsible for the multi-colour blackbody emission. The variability originates in the disc as mass-accretion fluctuations and propagates through the disc to 'light up' inner disc regions, eventually modulating the power-law emission that is produced relatively centrally. Both the covariance spectra and time-lags that cover the soft bands strongly support this scenario. Here, we present a comparative spectral-timing study of XMM-Newton data from the BHXRB SWIFT J1753.5-0127 in a bright 2009 hard state with that from the significantly fainter 2006 hard state to show for the first time the change in disc spectral-timing properties associated with a global increase in both the accretion rate and the relative contribution of the disc emission to the bolometric luminosity. We show that, although there is strong evidence for intrinsic disc variability in the more luminous hard state, the disc variability amplitude is suppressed relative to that of the power-law emission, which contrasts with the behaviour at lower luminosities where the disc variability is slightly enhanced when compared with the power-law variations. Furthermore, in the higher luminosity data the disc variability below 0.6 keV becomes incoherent with the power-law and higher energy disc emission at frequencies below 0.5 Hz, in contrast with the coherent variations seen in the 2006 data. We explain these differences and the associated complex lags in the 2009 data in terms of the fluctuating disc model, where the increase in accretion rate seen in 2009 leads to more pronounced and extended disc emission. If the variable signals are generated at small radii in the disc, the variability of disc emission can be naturally suppressed by the fraction of unmodulated disc emission arising from larger radii. Furthermore, the drop in coherence can be produced by disc accretion fluctuations arising at larger radii which are viscously damped and hence unable to propagate to the inner, power-law emitting region.

Cassatella, P.; Uttley, P.; Maccarone, T. J.

2012-12-01

243

Evolution of long-range myofibrillar crystallinity in insect flight muscle as examined by X-ray cryomicrodiffraction.  

PubMed

Insect flight muscle is known for its crystal-quality regularity of contractile protein arrangement within a sarcomere. We have previously shown by X-ray microdiffraction that the crystal-quality regularity in bumble-bee flight muscle is not confined within a sarcomere, but extends over the entire length of a myofibril (>1000 sarcomeres connected in series). Because of this, the whole myofibril may be regarded as a millimetre-long, natural single protein crystal. Using bright X-ray beams from a synchrotron radiation source, we examined how this long-range crystallinity has evolved among winged insects. We analysed >4600 microdiffraction patterns of quick-frozen myofibrils from 50 insect species, covering all the major winged insect orders. The results show that the occurrence of such long-range crystallinity largely coincides with insect orders with asynchronous muscle operation. However, a few of the more skilled fliers among lower-order insects apparently have developed various degrees of structural regularity, suggesting that the demand for skillful flight has driven the lattice structure towards increased regularity. PMID:16608686

Iwamoto, Hiroyuki; Inoue, Katsuaki; Yagi, Naoto

2006-03-22

244

High reflectivity optics for the extreme ultraviolet and soft X-ray spectral regions  

Microsoft Academic Search

The wavelengths in the region between 35 nm and 50 nm are too short to be reflected at normal incidence by any bulk material and too long for standard multilayer reflective coatings. The practical interest to this range was stimulated by the development of 46.9 nm capillary discharge laser that is working in a repetitive mode with an average power

A. V. Vinogradov

2001-01-01

245

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

Microsoft Academic Search

This paper discusses the latest progress in the development of GRAPE\\u000a(Gamma-Ray Polarimeter Experiment), a hard X-ray Compton Polarimeter. The\\u000apurpose of GRAPE is to measure the polarization of hard X-rays in the 50-300\\u000akeV energy range. We are particularly interested in X-rays that are emitted\\u000afrom solar flares and gamma-ray bursts (GRBs). Accurately measuring the\\u000apolarization of the emitted

J. S. Legerea; P. Bloser; J. R. Macri; M. L. McConnella; T. Narita; J. M. Ryan

2005-01-01

246

Examinations of tRNA Range of Motion Using Simulations of Cryo-EM Microscopy and X-Ray Data.  

PubMed

We examined tRNA flexibility using a combination of steered and unbiased molecular dynamics simulations. Using Maxwell's demon algorithm, molecular dynamics was used to steer X-ray structure data toward that from an alternative state obtained from cryogenic-electron microscopy density maps. Thus, we were able to fit X-ray structures of tRNA onto cryogenic-electron microscopy density maps for hybrid states of tRNA. Additionally, we employed both Maxwell's demon molecular dynamics simulations and unbiased simulation methods to identify possible ribosome-tRNA contact areas where the ribosome may discriminate tRNAs during translation. Herein, we collected >500?ns of simulation data to assess the global range of motion for tRNAs. Biased simulations can be used to steer between known conformational stop points, while unbiased simulations allow for a general testing of conformational space previously unexplored. The unbiased molecular dynamics data describes the global conformational changes of tRNA on a sub-microsecond time scale for comparison with steered data. Additionally, the unbiased molecular dynamics data was used to identify putative contacts between tRNA and the ribosome during the accommodation step of translation. We found that the primary contact regions were H71 and H92 of the 50S subunit and ribosomal proteins L14 and L16. PMID:21716650

Caulfield, Thomas R; Devkota, Batsal; Rollins, Geoffrey C

2011-03-28

247

Optical CCD photometry and Rosat X-ray spectral analysis of the shortest period CV EI Psc (1RXS J232953.9 + 062814)  

NASA Astrophysics Data System (ADS)

We present here the optical observations of EI Psc (1RXS J232953.9 + 062814) through Turkish National Observatory (TUG) with RTT150 cm Russian-Turkish joint telescope and its X-ray observation using the ROSAT archival data. Our optical observations reveal a period of 0.0408 days (58.75 min) which is rather different from its early value of 0.046 days (66.24 min) as reported by [Schmeer, P., 2001. vsnet-alert6830, < http://www.kusastro.kyoto-u.ac.jp/vsnet/Mail/vsnet-alert/mgs06830.html>]. Also possible periodicities as well as any QPOs are studied without having any clear indication of it. Archival ROSAT RASS data are also analyzed for its X-ray spectra. The raw data were fitted with various spectral models and the best fit models are found to be that of Blackbody and Raymond-Smith with best fit temperatures of kT=(0.07±0.02)keV for blackbody model and kT=(0.13±0.04)keV for Raymond-Smith model while the column density fixed at 0.54×10-21cm. The estimated 0.1-2.4 keV flux is found to be in the range of between logF=-13 and logF=-14ergcm-2s-1. The model dependent luminosity values were in the range of log L=29ergs-1 for Raymond-Smith model and logL=31ergs-1 for blackbody model. Using the well fitted temperature values, the mass of the primary value that is obtained by [Uemura, M., Kato, T., Ishioka, R., Yamaoka, H., Scgmeer, P., Starkey, D.R., Torii, K., Kawai, N., Urata, Y., Kohama, M., Yoshida, A., Ayani, K., Kawabata, T., Tanabe, K., Matsumoto, K., Kiyota, S., Pietz, J., Vanmunster, T., Krajci, T., Oksanen, A., Giambersio, A., 2002b. Superhump Evolution in the Ultrashort Period Dwarf Nova 1RXS J232953.9 + 062814. PASJ 54, 599-607] and the equations taken from literature, the mass accretion rate in the boundary layer is obtained to be (1.58±0.14)×1021gs-1 for the blackbody model and (2.2±0.052)×1019gs-1 for Raymond-Smith model. As a result of our study it seems that the system EI Psc has a very high mass accretion rate; and because of the observed soft X-ray photons and high mass accretion rates it has an optically thick boundary layer and M-type secondary star which can be a Brown Dwarf.

Gök, F.; Gün, G. ?kis; Aktekin, E.; Sezer, A.; Altan, M.

2009-02-01

248

Syntheses, spectral characterization, single crystal X-ray diffraction and DFT computational studies of novel thiazole derivatives  

NASA Astrophysics Data System (ADS)

A novel thiazole (E)-1-((E)-2-methyl-3-phenylallylidene)-2-(4-phenylthiazole-2-yl)hydrazine 2 and its derivatives 3-8 were synthesized by cyclo condensation of (1E)-1-((E)-2-methyl-3-phenylallylidene)thiosemicarbazide 1 with substituted 2-bromoacetophenones. The synthesized thiazole derivatives were characterized by FT-IR, 1H NMR and 13C NMR analyses. For compound 8 single crystals X-ray diffraction analysis and density functional theory (DFT) calculation were carried out. The compound 8 crystallizes in the monoclinic space group P21/c with a = 7.4601 (3) Å, b = 5.7259 (2) Å, c = 41.0823 (13) Å, ? = 90°, ? = 91.715 (2)° and ? = 90°. The molecular geometrical parameters, frontier molecular orbital energies (HOMO, LUMO), their energy gap (?E), molecular electrostatic potential (MEP) and natural bond orbital (NBO) analysis of the compounds 2 and8 have been calculated by using DFT/B3LYP with 6-311G (d, p) level. In addition, IR frequencies, 1H and 13C NMR chemical shifts of compound 8 were also calculated by using DFT calculations at the same level basis set. The calculated geometrical parameters, IR frequencies, 1H and 13C NMR chemical shifts of the compound 8 were in good agreement with the observed single crystal-XRD data, IR, 1H and 13C NMR spectral values.

Anbazhagan, R.; Sankaran, K. R.

2013-10-01

249

X-ray calorimeters  

NASA Astrophysics Data System (ADS)

X-ray calorimeter instruments for astrophysics have seen rapid development since they were invented in 1984. The prime instrument on all currently planned X-ray spectroscopic observatories is based on calorimeter technology. This relatively simple detection concept that senses the energy of an incident photon by measuring the temperature rise of an absorber material at very low temperatures can form the basis of a very high-performance, non-dispersive spectrometer. State-of-theart calorimeter instruments have resolving powers of over 3000, large simultaneous bandpasses, and near unit efficiency. This coupled with the intrinsic imaging capability of a pixilated X-ray calorimeter array, allows true spectral-spatial instruments to be constructed. This chapter briefly reviews the detection scheme, the state of the art in X-ray calorimeter instruments and the future outlook for this technology.

Porter, F. Scott

250

The orbital solution and spectral classification of the high-mass X-ray binary IGR J01054-7253 in the Small Magellanic Cloud  

NASA Astrophysics Data System (ADS)

We present X-ray and optical data on the Be/X-ray binary (BeXRB) pulsar IGR J 01054-7253= SXP11.5 in the Small Magellanic Cloud (SMC). Rossi X-ray Timing Explorer (RXTE) observations of this source in a large X-ray outburst reveal an 11.483 ± 0.002 s pulse period and show both the accretion-driven spin-up of the neutron star and the motion of the neutron star around the companion through Doppler shifting of the spin period. Model fits to these data suggest an orbital period of 36.3 ± 0.4 d and ? of (4.7 ± 0.3) × 10-10 seconds s-1. We present an orbital solution for this system, making it one of the best-described BeXRB systems in the SMC. The observed pulse period, spin-up and X-ray luminosity of SXP11.5 in this outburst are found to agree with the predictions of neutron star accretion theory. Timing analysis of the long-term optical light curve reveals a periodicity of 36.70 ± 0.03 d, in agreement with the orbital period found from the model fit to the X-ray data. Using blue-end spectroscopic observations we determine the spectral type of the counterpart to be O9.5-B0 IV-V. This luminosity class is supported by the observed V-band magnitude. Using optical and near-infrared photometry and spectroscopy, we study the circumstellar environment of the counterpart in the months after the X-ray outburst.

Townsend, L. J.; Coe, M. J.; Corbet, R. H. D.; McBride, V. A.; Hill, A. B.; Bird, A. J.; Schurch, M. P. E.; Haberl, F.; Sturm, R.; Pathak, D.; van Soelen, B.; Bartlett, E. S.; Drave, S. P.; Udalski, A.

2011-01-01

251

The X-ray spectral signatures from the complex circumnuclear regions in NGC424  

NASA Astrophysics Data System (ADS)

We propose a 100 ks observation of NGC424 to exploit the full range of XMM-Newton capabilities (RGS+EPIC) by studying the properties of the different materials found in the nucleus of this object. NGC424 is one of the brightest Compton-thick AGN, thus being one of the few sources which presently permit this kind of analysis. The proposed 100 ks EPIC spectrum will allow us to study in detail the properties of the torus, by measuring: the iron Kalpha/Kbeta ratio and the iron Kalpha centroid energy, to determine its ionization state and then estimate its distance from the Black Hole; the Compton Shoulder, to check if the cold reflecting matter is indeed the inner wall of the obscuring torus. On the other hand, the RGS high resolution spectrum will allow us to take advantage of

Bianchi, Stefano

2006-10-01

252

The X-ray spectral signatures from the complex circumnuclear regions in NGC424  

NASA Astrophysics Data System (ADS)

We propose a 100 ks observation of NGC424 to exploit the full range of XMM-Newton capabilities (RGS+EPIC) by studying the properties of the different materials found in the nucleus of this object.NGC424 is one of the brightest Compton-thick AGN,thus being one of the few sources which presently permit this kind of analysis.The proposed 100 ks EPIC spectrum will allow us to study in detail the properties of the torus,by measuring:the iron Kalpha/Kbeta ratio and the iron Kalpha centroid energy,to determine its ionization state and then estimate its distance from the Black Hole;the Compton Shoulder,to check if the cold reflecting matter is indeed the inner wall of the obscuring torus.On the other hand, the RGS high resolution spectrum will allow us to take advantage of

Bianchi, Stefano

2007-10-01

253

X-ray detection, possible variability and spectral evolution of Nova Del 2013 observed with Swift  

NASA Astrophysics Data System (ADS)

Nova Del 2013 has been the target of a monitoring campaign by Swift since 2013 August 14. In the first days the source was not detected by the XRT, both in the PC and WT modes (ATel #5283, #5305, #5318). Starting with an observation on 2013 August 27 (2 ks exposure), and then on September 6 (1 ks) and 8 (1 ks), a handful of counts have been recorded by the XRT/PC at the position of the Nova. Although in all these observations the significance of detection is less than 3 in the 0.3-10 keV range, we estimated a corrected count rate of ~(8+-3)x10^-3 c/s, but we noted that almost all the counts are in the soft band (<2 keV).

Donato, D.

2013-09-01

254

Timing and spectral studies of the transient X-ray pulsar GX 304-1 during an outburst  

NASA Astrophysics Data System (ADS)

We present the timing and spectral properties of the transient X-ray pulsar GX 304-1 during its recent outburst in 2010 August, using observations carried out with the Proportional Counter Array (PCA) instrument on board the Rossi X-ray Timing Explorer (RXTE) satellite. We detected strong intensity- and energy-dependent variations in the pulse profiles during the outburst. The pulse profile showed significant evolution over the outburst. It showed complex structures consisting of a main peak with steps on both sides during the start of the outburst. On some days, a sharp dip-like feature was seen which disappeared at the end of the outburst when the profile evolved into a sinusoidal shape. At low energies, the pulse profiles appeared complex, consisting of multiple peaks and a narrow minimum. The amplitude of the second brightest peak in low energies decreased with energy, and above 12 keV the shape of the pulse profile changed to a single broad peak with a dip-like feature. The dip had energy dependence, both in phase and in width. We detected quasi-periodic oscillations (QPOs) at 0.125 Hz with a harmonic. The QPO feature had a low rms value of 2.9 per cent and it showed a positive energy dependence up to 40 keV with the rms value increasing to 9 per cent at 40 keV. The QPO frequency decreased from 0.128 to 0.108 Hz in 12 days. During most of the outburst, the 3-30 keV spectrum of GX 304-1 can be well fitted with a partial covering power-law model with a high-energy cut-off and iron fluorescent line emission. For a few of the observations carried out during the decay of the outburst, the partial covering absorption component is found to change to single-component absorption. We also found that the partial covering and high-energy cut-off parameters vary significantly with the pulse phase.

Devasia, Jincy; James, Marykutty; Paul, Biswajit; Indulekha, Kavila

2011-10-01

255

X-ray timing and spectral observations of galactic black hole candidate XTE J1550-564 during outburst  

NASA Astrophysics Data System (ADS)

The timing and spectral properties of the soft X-ray transient (SXT) and microquasar XTE J1550-564 during outburst are studied, emphasizing observations made by the Unconventional Stellar Aspect (USA) Experiment. USA data show a low-frequency quasi-periodic oscillation (LFQPO) with a centroid frequency that tends to increase with increasing flux and a fractional rms amplitude which is correlated with the USA hardness ratio. Several high- frequency quasi-periodic oscillations (HFQPOs) were detected by RXTE, during periods where the LFQPO is seen to be weakening or not detectable at all. The evolution of the USA hardness ratio with time and source flux is examined. The hardness-intensity diagram shows counterclockwise cyclical evolution and possibly indicates the presence of two independent accretion flows: a geometrically thin, optically thick accretion disk and a hot sub-Keplerian flow. A model for production of the LFQPO in XTE J1550-564 is proposed, assuming that the LFQPO is a result of acoustic oscillations in a hot sub-Keplerian transition layer (TL). Under this acoustic oscillation model (AOM), the TL is an acoustic cavity having an outer boundary at RTL, where R TL ? Rinner, with Rinner being the radius of the accretion disk inner edge. TL resonance is interpreted as a mechanism for the LFQPO and the eigenfrequencies are associated with the LFQPO frequencies, ? LFQPO. This LFQPO mechanism requires the presence of a TL, capable of inverse-Compton scattering, with RTL regulated by a cool Keplerian accretion disk. Support for the AOM is provided by the correlation of the LFQPO percent rms amplitude with the USA hardness ratio, and other correlations and anti-correlations found in the USA, RXTE and BATSE observations. LFQPO data show increasing rms amplitude with increasing high energy flux and increasing ?LFQPO with increasing low energy flux. These observations indicate that ? LFQPO is set by the accretion disk inner edge. The spectrally inferred Rinner is commensurate, showing a decrease with increasing ? LFQPO. Finally, RXTE spectral data indicate that the LFQPO is detectable only when the power law contribution is greater than 20% of the low energy flux, providing evidence that the LFQPO mechanism is dependent on the TL. The AOM is consistent with all of the above observations and it has the ability to predict the approximate value of Rinner. Comparison between spectrally determined Rinner and the AOM measurement of RTL shows good agreement.

Reilly, Kaice Theodore

2003-09-01

256

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

NASA Astrophysics Data System (ADS)

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

2012-07-01

257

Feedback at the Working Surface: A Joint X-ray and Low-Frequency Radio Spectral Study of the Cocoon Shock in Cygnus A  

NASA Astrophysics Data System (ADS)

We report on preliminary results from a joint spectral analysis of the cocoon shock region in Cygnus A using deep archival Chandra data and new low-frequency radio data from LOFAR. Being both bright in X-rays and the most powerful radio source in the local universe, the FRII radio galaxy Cygnus A represents an ideal opportunity to study the interaction between the jets produced by the central AGN and the surrounding intracluster medium (ICM) in which that AGN is embedded. Using the entire 235 ksec archival Chandra exposure, we have performed a spatially resolved, X-ray spectral analysis of the ICM in Cygnus A. By combining the resulting X-ray images and temperature maps with spectral index maps between 30-80 MHz and 120-180 MHz calculated from a recent, deep LOFAR observation, we can resolve the X-ray and radio emitting plasmas in any given region on spatial scales of 3-4 kpc over the central 100 kpc. We clearly resolve the cocoon shock surrounding Cygnus A and determine the Mach number of the shock as a function of position angle. Temperature jumps associated with this shock are detected over a large fraction of the total shock circumference. Significant non-thermal emission is also detected in the regions surrounding the SE and NW leading edges of the shock near the hotspots. In this talk, we will present a detailed analysis of the energetics of this interface region between the radio plasma inside the cocoon shock and the X-ray emitting gas outside the shock. Inside the shock, we will present constraints on the emission mechanisms in the jet, counter-jet, and hotspots based on the combined radio and X-ray spectra. Using maps of the spectral age derived from the LOFAR data and independent age estimates based on various cavity features seen in the X-ray image, we will present a picture of the evolution of the shock region in Cygnus A over the past 50 Myr. Finally, we will discuss the implications these observations have for AGN feedback models as well as the energy transfer mechanism itself.

Wise, Michael W.; Rafferty, D. A.; McKean, J. P.

2013-04-01

258

CO-ANALYSIS OF SOLAR MICROWAVE AND HARD X-RAY SPECTRAL EVOLUTIONS. II. IN THREE SOURCES OF A FLARING LOOP  

SciTech Connect

Based on the spatially resolvable data of the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) and Nobeyama Radio Heliograph (NoRH), co-analysis of solar hard X-ray and microwave spectral evolution is performed in three separate sources located in one looptop (LT) and two footpoints (FPs) of a huge flaring loop in the 2003 October 24 flare. The RHESSI image spectral evolution in 10-100 keV is always fitted by the well-known soft-hard-soft (SHS) pattern in the three sources. When the total energy is divided into four intervals similar to the Yohkoh/Hard X-ray Telescope, i.e., 12.5-32.5 keV, 32.5-52.5 keV, 52.5-72.5 keV, and 72.5-97.5 keV, the SHS pattern in lower energies is converted gradually to the hard-soft-hard (HSH) pattern in higher energies in all three sources. However, the break energy in the LT and the northeast FP ({approx}32.5 keV) is evidently smaller than that in the southwest FP ({approx}72.5 keV). Regarding microwave spectral evolution of the NoRH data, the well-known soft-hard-harder pattern appeared in the southwest FP, while the HSH pattern coexisted in the LT and the northeast FP. The different features of the hard X-ray and microwave spectral evolutions in the three sources may be explained by the loop-loop interaction with another huge loop in the LT and with a compact loop in the northeast FP, where the trapping effect is much stronger than that in the southwest FP. The comparison between the LT and FP spectral indices suggests that the radiation mechanism of X-rays may be quite different in different energy intervals and sources. The calculated electron spectral indices from the predicted mechanisms of X-rays gradually become closer to those from the microwave data with increasing X-ray energies.

Huang Guangli; Li Jianping, E-mail: glhuang@pmo.ac.cn, E-mail: jpli@pmo.ac.cn [Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China)

2011-10-10

259

Design and performance of a versatile curved-crystal spectrometer for high-resolution spectroscopy in the tender x-ray range  

SciTech Connect

A complete in-vacuum curved-crystal x-ray emission spectrometer in Johansson geometry has been constructed for a 2-6 keV energy range with sub natural line-width energy resolution. The spectrometer is designed to measure x-ray emission induced by photon and charged particle impact on solid and gaseous targets. It works with a relatively large x-ray source placed inside the Rowland circle and employs position sensitive detection of diffracted x-rays. Its compact modular design enables fast and easy installation at a synchrotron or particle accelerator beamline. The paper presents main characteristics of the spectrometer and illustrates its capabilities by showing few selected experimental examples.

Kavcic, M.; Budnar, M.; Muehleisen, A.; Gasser, F.; Zitnik, M.; Bucar, K.; Bohinc, R. [J. Stefan Institute, Jamova 39, SI-1001, Ljubljana (Slovenia)

2012-03-15

260

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

261

The X-ray Spectrum and Spectral Energy Distribution of FIRST J155633.8+351758: A Beamed Radio-Quiet Quasar with a Polar Outflow  

NASA Astrophysics Data System (ADS)

We report the results of a 60 ks Chandra X-ray Observatory ACIS-S observation of the reddened, radio-selected, highly polarized "FeLoBAL" quasar FIRST J155633.8+351758. Our analyses of the 531 photon spectrum indicate that the intrinsic X-ray flux is consistent with that expected for quasars of similarly high luminosity. We cannot tightly constrain the intrinsic X-ray power-law slope, but find indications that it is flat (photon index ? = 1.7 or flatter). No iron K-? line is detected, and the X-rays appear to be down by only an order of magnitude below their intrinsic unabsorbed levels. Absorption is present with both partially ionized models and neutral hydrogen models with partial covering providing good fits. The level of partial covering in the latter model is consistent with the rest-frame ultraviolet maximum polarization of 13%, in the sense that light scattered by electrons around the X-ray absorber could account for both results. We present the spectral energy distribution (SED) of FIRST J155633.8+351758 from radio through X-ray energies, and make corrections for Doppler beaming for the pole-on radio-quiet jet, optical dust reddening, and X-ray absorption. The corrected SED appears to be that of a luminous radio-quiet quasar deficient in the mid and far-infrared, suggesting that the dust covering fraction of the quasar is not large and that star formation is not excessive. FIRST J155633.8+351758 seems to be an intrinsically normal radio-quiet quasar with an X-ray absorber not dissimilar from that of other broad absorption line quasars studied in detail at X-ray wavelengths. We acknowledge support from Chandra Award No. GO6-7105X, from the US NSF (grant AST 05-07781), from NASA under the grant NNG05GD03G, and from the National Natural Science Foundation of China (grant 10643001). This work was performed under the auspices of the US DOE by the University of California, LLNL (Contract No. W-7405-Eng-48).

Berrington, Robert C.; Brotherton, M. S.; Gallagher, S. C.; Ganguly, R.; Shang, Z.; Lacy, M.; Gregg, M. D.; Hall, P. B.; Laurent-Muehleisen, S. A.

2007-12-01

262

X-ray lasing in the CO molecule  

NASA Astrophysics Data System (ADS)

We theoretically demonstrate the feasibility of x-ray lasing in the CO molecule by the core ionization of the C K- and O K-shell by x-ray free-electron laser sources. Our numerical simulations are based on the solution of generalized Maxwell-Bloch equations, accounting for the electronic and nuclear degrees of freedom. The amplified x-ray emission pulses have an extremely narrow linewidth of about 0.1 eV and a pulse duration shorter than 30 fs. We compare x-ray lasing transitions to the three lowest electronic states of singly ionized CO. The dependence of the lasing efficiency on the spectral width of the x-ray fluorescence band, value and orientation of the electronic transition dipole moment, lifetime of the core-excited state and the duration of the pump pulse is analysed. Using a pre-aligned molecular ensemble substantially increases the amplified emission. Moreover, by controlling the molecular alignment and thereby the alignment of the transition dipole moment polarization, the control of the emitted x-ray radiation is achievable. Preparing the initial vibrational quantum state, the x-ray emission frequency can be tuned within the fluorescence band. The present scheme is applicable to other diatomic systems, thereby extending the spectral range of coherent x-ray radiation sources based on stimulated x-ray emission on bound transitions.

Kimberg, Victor; Zhang, Song Bin; Rohringer, Nina

2013-08-01

263

The contribution of AGNs to the X-ray background.  

NASA Astrophysics Data System (ADS)

We report the results of a detailed analysis of the contribution of various classes of AGNs (Seyfert galaxies and quasars) to the extragalactic X-ray background (XRB). The model is based on the unification schemes of AGNs, on their related X-ray spectral properties in the light of recent observational results and on the X-ray luminosity function derived by Boyle et al. (1993). The integrated emission from AGNs, when folded with an appropriate cosmological evolution law, can provide a good fit to the XRB over a wide energy range, from several to ~100keV, while it contributes only about 74% of the ROSAT soft XRB. The baseline model predictions have been checked against all available observational constraints from both hard and soft X-ray surveys (counts, redshift distributions and average X-ray source spectral properties).

Comastri, A.; Setti, G.; Zamorani, G.; Hasinger, G.

1995-04-01

264

A compton polarimeter for synchrotron radiation in the x-ray energy range  

Microsoft Academic Search

A polarimeter for synchrotron radiation in the energy range E >~ 15 keV is described. It utilizes 90° Compton scattering by low Z atoms in a thin organic foil. The effect of double scattering on the analyzing power is calculated. The instrument can be used for continuously monitoring the intensity and the polarization of a photon beam during an experiment.

F. Smend; D. Schaupp; H. Czerwinski; A. H. Millhouse; H. Schenk-Strauss

1985-01-01

265

Numerical Solution of the Radiative Transfer Equation: X-Ray Spectral Formation from Cylindrical Accretion onto a Magnetized Neutron Star.  

National Technical Information Service (NTIS)

Predicting the emerging X-ray spectra in several astrophysical objects is of great importance, in particular when the observational data are compared with theoretical models. This requires developing numerical routines for the solution of the radiative tr...

C. Ceccobello L. Titarchuk P. Romano R. Fairnelli

2011-01-01

266

X-Ray, Optical, and Infrared Imaging and Spectral Properties of the 1 Ms Chandra Deep Field North Sources  

Microsoft Academic Search

We present the optical, near-infrared, submillimeter, and radio follow-up catalog of the X-ray-selected sources from an ~1 Ms Chandra observation of the Hubble Deep Field North region. We have B, V, R, I, and z' magnitudes for the 370 X-ray point sources, HK' magnitudes for 276, and spectroscopic redshifts for 182. We present high-quality spectra for 175 of these. The

A. J. Barger; L. L. Cowie; W. N. Brandt; P. Capak; G. P. Garmire; A. E. Hornschemeier; A. T. Steffen; E. H. Wehner

2002-01-01

267

An X-ray Spectral Analysis of the Nucleus of NGC 1052: What is the Nature of the Accretion Flow?  

Microsoft Academic Search

The LINER galaxy NGC 1052 represents the rare case of a radio-loud AGN with a prominent compact jet structure and a broad Fe K line. As part of a multi-mission monitoring program begun in 2005, including VLBI radio observations and several pointings with different X-ray missions, a 101 ks Suzaku spectrum has yielded the highest signal-to-noise X-ray spectrum of NGC

Laura Brenneman; K. Weaver; M. Kadler; J. Tueller; A. Marscher; E. Ros; A. Zensus; Y. Kovalev; M. Aller; H. Aller; J. Irwin; J. Kerp; S. Kaufmann

2009-01-01

268

Relativistic Short-Range-Order X-ray Photoelectron Diffraction Theory  

Microsoft Academic Search

In this paper we discuss relativistic short-range-order XPD theory applicable to the XPD from heavy elements (Z>50), where relativistic effects play some important roles. The 4 × 4 Dirac Green's function can be expanded in terms of full non-relativistic 2 × 2 Green's functions using Gestzesy expansion, which enables us to use well-defined Debye-Waller factors and optical potentials developed within

Takashi Fujikawa; Takehisa Konishi

2003-01-01

269

Simultaneous X-ray\\/optical\\/UV snapshots of active galactic nuclei from XMM-Newton: spectral energy distributions for the reverberation mapped sample  

Microsoft Academic Search

We employ contemporaneous optical, ultraviolet (UV) and X-ray observations from the XMM-Newton European Photon Imaging Camera (EPIC-pn) and Optical Monitor (OM) archives to present, for the first time, simultaneous spectral energy distributions (SEDs) for the majority of the Peterson et al. reverberation mapped sample of active galactic nuclei (AGN). The raw data were reduced using the latest pipelines and are

R. V. Vasudevan; A. C. Fabian

2009-01-01

270

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  

Microsoft Academic Search

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

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

2010-01-01

271

Extended dynamic range of ultra-high speed gated microchannel plate for x-ray framing camera  

NASA Astrophysics Data System (ADS)

X-ray framing cameras (XFC) based on an ultra-high speed gated microchannel plate (MCP) as a routine diagnostic in laser-driven Inertial Confinement Fusion (ICF) experiment have deployed on domestic facility for several years, typically, these XFC devices used a normal MCP with 500?m thick and 12?m pore size, and achieved an optical temporal gate leas than 100 picoseconds, but which are vulnerable to suffer a time broadened temporal response when encounter heavy expose, due to the limited dynamic range of the normal MCP. We developed a 56mm format MCP with 250?m thickness and 6?m pore diameter, which objective is to promote the optical temporal gate and dynamic range for the upgrade XFC, this MCP is fabricated by a special designed low resistance glass, the reduced thickness, small pore size and increased gain linearity, offered which with ultra-fast temporal response and extended dynamic range characters. In this paper, we review the mechanisms that limiting the temporal response and gain linearity of this ultra-high speed gated MCP applied to XFC, and describe the design principle and development work of this ultra-fast temporal response, extended dynamic range and larger format MCP, this MCP will assemble to the upgrade XFC which is designed by CAEP and is currently in the final design stages.

Pan, Jingsheng; Lv, Jingwen; Cao, Zhurong; Liu, Shenye; Liu, Shulin; Li, Yanhong

2009-07-01

272

Testing MOND over a Wide Acceleration Range in X-Ray Ellipticals  

NASA Astrophysics Data System (ADS)

The gravitational fields of two isolated ellipticals, NGC 720 and NGC 1521, have been recently measured to very large galactic radii (˜100 and ˜200kpc), assuming hydrostatic balance of the hot gas enshrouding them. They afford, for the first time to my knowledge, testing modified Newtonian dynamics (MOND) in ellipticals with force and quality that, arguably, approach those of rotation-curve tests in disk galaxies. In the context of MOND, it is noteworthy that the measured accelerations span a wide range, from more than 10a0 to about 0.1a0, unprecedented in individual ellipticals. I find that MOND predicts correctly the measured dynamical mass runs (apart from a possible minor tension in the inner few kpc of NGC 720, which might be due to departure from hydrostatic equilibrium): The predicted mass discrepancy increases outward from none near the center, to ˜10 at the outermost radii. The implications for the MOND-versus-dark-matter controversy go far beyond the simple fact of two more galaxies conforming to MOND.

Milgrom, Mordehai

2012-09-01

273

Studies on x-ray and UV emissions in electron cyclotron resonance x-ray source  

SciTech Connect

A novel electron cyclotron resonance x-ray source is constructed based on the ECR technique. In this paper, the possibility of using the ECR x-ray source for producing UV rays by optimizing the plasma parameters is explored. X-ray and UV emissions from the ECR x-ray source are carried out for argon, nitrogen, and CO{sub 2} plasma. The x-ray spectral and dose measurements are carried with NaI(Tl) based spectrometer and dosimeter, respectively. For UV measurement, a quartz window arrangement is made at the exit port and the UV intensity is measured at 5 cm from the quartz plate using UV meter. The x-ray and UV emissions are carried out for different microwave power levels and gas pressures. The x-ray emission is observed in the pressure range {<=}10{sup -5} Torr, whereas the UV emission is found to be negligible for the gas pressures <10{sup -5} Torr and it starts increasing in the pressure range between 10{sup -5} and 10{sup -3} Torr. At high-pressure range, collision frequency of electron-atom is large which leads to the higher UV flux. At low pressure, the electron-atom collision frequency is low and hence the electrons reach high energy and by hitting the cavity wall produces higher x-ray flux. By choosing proper experimental conditions and plasma gas species, the same source can be used as either an x-ray source or an UV source.

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

2008-02-15

274

Spectral and Timing Properties of the Low-mass X-ray Binary 4U 0614+09 with XMM-Newton  

NASA Astrophysics Data System (ADS)

4U 0614+09 is a low-mass X-ray binary with a weakly magnetized neutron star primary. It shows variability on time scales that range from years down to ~0.8 milliseconds. Before the Chandra and XMM-Netwon era, emission features around 0.7 keV have been reported from this source, but recent Chandra observations failed to detect them. Instead, these observations suggest an overabundance of Ne in the absorbing material, which may be common to ultracompact (P_orb < 1 hour) systems with a neon-rich degenerate dwarf secondary. We observed 4U 0614+09 with XMM-Newton in March 2001. Here we present the energy spectra, both from the RGS and EPIC cameras, and the Fourier power spectra from EPIC high-time resolution light curves, which we use to characterize the spectral state of the source, and to understand the geometry of the accretion flow in the vicinity of the neutron star in this system.

Mendez, Mariano; Cottam, Jean; Paerels, Frits

2002-04-01

275

HARD-SOFT-HARD FLARE SPECTRA AND THEIR ENERGY DEPENDENCE IN SPECTRAL EVOLUTION OF A SOLAR HARD X-RAY FLARE  

SciTech Connect

In this Letter, we studied the time evolution of the energy-dependent spectral indices for the 2004 November 3 solar hard X-ray flare observed by RHESSI. The common soft-hard-soft (SHS) pattern spectra were found at the lower energies, while a new feature, hard-soft-hard (HSH), was found at higher energies for each subpeak. As the energy increases, the SHS pattern is gradually converted into the HSH pattern. Some possible explanations for the spectral evolution and its energy dependence are discussed, such as the return current.

Shao Chengwen; Huang Guangli [Purple Mountain Observatory, Chinese Academy of Sciences (CAS), Nanjing, 210008 (China)], E-mail: chengwenshao@yahoo.com.cn, E-mail: glhuang@pmo.ac.cn

2009-04-01

276

Large-Area X-ray Lithography System for LIGA Process Operating in Wide Energy Range of Synchrotron Radiation  

Microsoft Academic Search

We developed a new X-ray lithography system for the lithographite, galvanoformung and abformung process (LIGA process) using synchrotron radiation at the NewSUBARU facility of the University of Hyogo. The X-ray lithography system can utilize two different energy regions: one is a high-energy region: from 2 keV to 12 keV, and the other is a low-energy region from 1 to 2

Yuichi Utsumi; Takefumi Kishimoto; Tadashi Hattori; Hirotsugu Hara

2005-01-01

277

X-ray, Optical, and Infrared Imaging and Spectral Properties of the 1 Ms Chandra Deep Field North Sources  

Microsoft Academic Search

We present the optical, near-infrared, submillimeter, and radio follow-up\\u000acatalog of the X-ray selected sources from the 1 Ms Chandra observation of the\\u000aHubble Deep Field North region. We have B, V, R, I, and z' magnitudes for the\\u000a370 X-ray point sources, HK' magnitudes for 276, and spectroscopic redshifts\\u000afor 182. We present high-quality spectra for 175 of these.

A. J. Barger; L. L. Cowie; W. N. Brandt; P. Capak; G. P. Garmire; A. E. Hornschemeier; A. T. Steffen; E. H. Wehner

2002-01-01

278

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

SciTech Connect

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

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

2010-11-12

279

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

NASA Astrophysics Data System (ADS)

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

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

2010-02-01

280

X-ray polarization detector  

SciTech Connect

We designed and constructed a cylindrical gas proportional counter that can be used to analyze the linear polarization of x rays with a wide range of energy from 2 keV to 10 keV. The polarization sensitivity is based on the highly nonisotropic scattering of polarized x rays from a gas or solid target. The gas proportional counter surrounds the scattering chamber and measures the scattered x rays as a function of the azimuthal angle. The angle of scattered x rays is determined by the charge division of the anode resistive wire. This polarimeter without any moving parts can measure x rays with continuous energies. It is specially suitable for synchrotron x rays. We discuss the testing and performance of such an x-ray polarimeter. {copyright} {ital 1996 American Institute of Physics.}

Shaw, P.; Arp, U.; Henins, A. [National Institute of Standards and Technology, Building 221, Room B206, Gaithersburg, MD 20899 (United States); Southworth, S. [Physics Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States)

1996-09-01

281

Evaluation of field-portable X-ray fluorescence spectrometry for the determination of lead contamination on small-arms firing ranges  

SciTech Connect

Field analytical methods for the characterization of lead contamination in soil are being developed. In this study, the usefulness of a commercially available, field-portable energy-dispersive X-ray fluorescence spectrometer (XRF) is evaluated for determining the extent of lead contamination in soils on small-arms firing ranges at a military installation. This field screening technique provides significant time and cost savings for the study of sites with lead-contaminated soil. Data obtained with the XRF unit in the field are compared with data obtained from soil samples analyzed in an analytical laboratory by inductively coupled plasma atomic emission spectroscopy. Results indicate that the field-portable XRF unit evaluated in this study provides data that are useful in determining the extent and relative magnitude of lead contamination. For the commercial unit used in this study, improvements in the spectral resolution and in the limit of detection would be required to make the unit more than just a screening tool.

Schneider, J.F.; Taylor, J.D.; Bass, D.A.; Zellmer, D. [Argonne National Lab., IL (United States); Rieck, M. [U.S. Army, Grafenwoehr Training Area (Germany)

1995-02-01

282

Characterization of ripple-trapped suprathermal electron losses by their bremsstrahlung emission in the soft x-ray range at the TJ-II stellarator  

NASA Astrophysics Data System (ADS)

Here we present the first observations in TJ-II of suprathermal electron convective losses by means of their bremsstrahlung emission in the range of soft x-rays. Spectra and spatial distribution intensity have been obtained. Their dependence with density, Zeff, magnetic field ripple, heating method and radial electric field is discussed.

Medina, F.; Ochando, M. A.; Baciero, A.; Guasp, J.

2007-04-01

283

Structural state of Ni-Mn solid solutions in a wide range of concentrations based on the data of scattering and absorption of X-rays  

NASA Astrophysics Data System (ADS)

It has been demonstrated that Ni-Mn alloys prepared from elemental powders by the method of mechanical alloying appear to be fcc solid solutions in a wide concentration range. Structural studies of samples with the amount of Ni from 50 to 95 at % were carried out by the methods of X-ray diffraction, electron microscopy, and EXAFS spectroscopy.

Ryazhkin, A. V.; Miyanaga, T.; Ogasawara, T.; Patselov, A. M.; Chernyshev, E. G.; Babanov, Yu. A.; Pilyugin, V. P.

2009-02-01

284

Comparison of the air-kerma standards of the PTB and the BIPM in the low-energy x-ray range  

Microsoft Academic Search

Abstract A,direct comparison,has been made,between,the air-kerma standards of the ,PTB and the BIPM in the low-energy x-ray range. The results show,the standards to be in agreement,at the level of one standard uncertainty.

D. T. Burns; L. Bueermann; H.-M. Kramer; B. Lange

285

Imaging X-ray detector front-end with high dynamic range: IDeF-X HD  

NASA Astrophysics Data System (ADS)

Presented circuit, IDeF-X HD (Imaging Detector Front-end) is a member of the IDeF-X ASICs family for space applications. It has been optimized for a half millimeter pitch CdTe or CdZnTe pixelated detector arranged in 16×16 array. It is aimed to operate in the hard X-ray range from few keV up to 250 keV or more. The ASIC has been realized in AMS 0.35 ?m CMOS process.The IDeF-X HD is a 32 channel analog front-end with self-triggering capability. The architecture of the analog channel includes a chain of charge sensitive amplifier with continuous reset system and non-stationary noise suppressor, adjustable gain stage, pole-zero cancellation stage, adjustable shaping time low pass filter, baseline holder and peak detector with discriminator. The power consumption of the IDeF-X HD is 800 ?W per channel. With the in-channel variable gain stage the nominal 250 keV dynamic range of the ASIC can be extended up to 1 MeV anticipating future applications using thick sensors. Measuring the noise performance without a detector at the input with minimized leakage current (programmable) at the input, we achieved ENC of 33 electrons rms at 10.7 ?s peak time. Measurements with CdTe detector show good energy resolution FWHM of 1.1 keV at 60 keV and 4.3 keV at 662 keV with detection threshold below 4 keV. In addition, an absolute temperature sensor has been integrated with resolution of 1.5 °C.

Gevin, O.; Lemaire, O.; Lugiez, F.; Michalowska, A.; Baron, P.; Limousin, O.; Delagnes, E.

2012-12-01

286

High-power high-quality lenses of infrared and visible range for thermovision and x-ray TV systems  

NASA Astrophysics Data System (ADS)

Fast perfection of sensors has caused a significant growth of the usage of the methods of testing, based on the visualization. Among the most popular are the methods of visualization based on registration of the IR radiation of the object under investigation and x-ray examination. An increase of sensors characteristics is putting a demanding task to the development of the optic systems matching parameters of conventional detectors. The paper presents the results of development of some precise lenses, which are used in some complicated applications of thermovision and x-ray projection systems.

Archipova, Ludmila; Savelyev, Sergey; Shevtsov, Sergey

1998-02-01

287

Soft X-ray Analysis and Multiwavelength Modeling of X-ray Selected Active Galactic Nuclei  

Microsoft Academic Search

We survey the broadband spectral properties of ~500 X-ray-selected Active Galactic Nuclei (AGN) observed with the Einstein X-ray Observatory in order to better understand the X-ray emission characteristics of this population as compared to previously studied optically- and radio-selected populations. We further select a subsample of X-ray-selected AGN which possess strong components of soft X-ray emission below ~0.5 keV. This

Richard J. Thompson

1994-01-01

288

Studies on x-ray and UV emissions in electron cyclotron resonance x-ray source  

Microsoft Academic Search

A novel electron cyclotron resonance x-ray source is constructed based on the ECR technique. In this paper, the possibility of using the ECR x-ray source for producing UV rays by optimizing the plasma parameters is explored. X-ray and UV emissions from the ECR x-ray source are carried out for argon, nitrogen, and CO2 plasma. The x-ray spectral and dose measurements

R. Baskaran; T. S. Selvakumaran

2008-01-01

289

Timing and Spectral Properties of Be/X-Ray Pulsar EXO 2030+375 during a Type I Outburst  

NASA Astrophysics Data System (ADS)

We present results from a study of broadband timing and spectral properties of EXO 2030+375 using a Suzaku observation. Pulsations with a period of 41.41 s and strong energy-dependent pulse profiles were clearly detected up to 100 keV. Narrow dips are seen in the profiles up to ~70 keV. The presence of prominent dips at several phases in the profiles up to such high energy ranges was not seen before. At higher energies, these dips gradually disappeared and the profile appeared to be single-peaked. The 1.0-200.0 keV broadband spectrum is found to be well described by a partial covering high-energy cutoff power-law model. Several low-energy emission lines are also detected in the pulsar spectrum. We fitted the spectrum using neutral as well as partially ionized absorbers along with the above continuum model yielding similar parameter values. The partial covering with a partially ionized absorber resulted in a marginally better fit. The spectral fitting did not require any cyclotron feature in the best-fit model. To investigate the changes in spectral parameters at dips, we carried out pulse-phase-resolved spectroscopy. During the dips, the value of the additional column density was estimated to be high compared to other pulse phases. While using a partially ionized absorber, the value of the ionization parameter is also higher at the dips. This may be the reason for the presence of dips up to higher energies. No other spectral parameters show any systematic variation with pulse phases of the pulsar.

Naik, Sachindra; Maitra, Chandreyee; Jaisawal, Gaurava K.; Paul, Biswajit

2013-02-01

290

The X-Ray Power Spectral Density Function and Black Hole Mass Estimate for the Seyfert Active Galactic Nucleus IC 4329a  

NASA Astrophysics Data System (ADS)

We present the X-ray broadband power spectral density function (PSD) of the X-ray-luminous Seyfert IC 4329a, constructed from light curves obtained via Rossi X-ray Timing Explorer monitoring and an XMM-Newton observation. Modeling the 3-10 keV PSD using a broken power-law PSD shape, a break in power-law slope is significantly detected at a temporal frequency of 2.5+2.5 -1.7 × 10-6 Hz, which corresponds to a PSD break timescale T b of 4.6+10.1 -2.3 days. Using the relation between T b, black hole mass M BH, and bolometric luminosity as quantified by McHardy and coworkers, we infer a black hole mass estimate of M BH = 1.3+1.0 -0.3 × 108 M sun and an accretion rate relative to Eddington of 0.21+0.06 -0.10 for this source. Our estimate of M BH is consistent with other estimates, including that derived by the relation between M BH and stellar velocity dispersion. We also present PSDs for the 10-20 and 20-40 keV bands; they lack sufficient temporal frequency coverage to reveal a significant break, but are consistent with the same PSD shape and break frequency as in the 3-10 keV band.

Markowitz, A.

2009-06-01

291

X-ray spectral analysis of YOHKOH BCS data on Sep. 6, 1992 flares: Blue shift component and ion abundances  

NASA Astrophysics Data System (ADS)

We have studied the time evolution of BCS spectra of He - like S (15), Ca(19) and Fe(25) ions observed by the Yohkoh satellite for solar flares on 6th September 1992 at 05:05 (M2.4 class) and 08:59(M3.3 class). Electron temperatures are derived through the fit of the synthetic spectra to the observed ones. Apparent ion temperatures are derived from the line width of S(15) and Ca(19) spectra. The blue shifted component in the rising phase is separated from the main component of the Ca(19) spectra. The emission measures are derived from the spectra without assuming ionization equilibrium and solar abundances for the first time. The time variation of these parameters are compared with hard X-rays, soft X-rays and radio measurements. In the preheating phase, the moderate increase of thermal plasma with turbulence indicated from the line width is observed. The time evolution of the blue shift component coincides with that of the burst in hard X-rays and microwaves which are produced by non-thermal high energy electrons. The ion density ratios derived from the spectra show a time-dependent non equilibrium ionization. They are shifted from the equilibrium values indicating an ionizing plasma.

Kato, T.; Fujiwara, T.; Hanaoka, Y.

1996-02-01

292

The X-ray Evolution of Normal Galaxies  

NASA Astrophysics Data System (ADS)

We combine optical data from the NOAO Deep Wide Field Survey (NDWFS), X-ray data from the XBoötes X-ray survey and redshifts from the AGN and Galaxy Evolution Survey (AGES) to measure the X-ray evolution of normal galaxies as a function of absolute luminosity and spectral type over the range 0 < z < 0.5. We discuss the implications of our results for the star formation and nuclear accretion rates of normal galaxies. Our research is supported by the National Optical Astronomy Observatory which is operated by the Association of Universities for Research in Astronomy, Inc. (AURA) under a cooperative agreement with the National Science Foundation.

Watson, C. R.; Kochanek, C. S.; Brand, K.; Dey, A.; Brown, M.; Jannuzi, B.; Najita, J.; Eisenstein, D.; Vikhlinin, A.; Fazio, G.; Forman, W. R.; Green, P. J.; Jones, C. J.; Kenter, A. T.; Murray, S.; McNamara, B. R.; Rieke, M.; Shields, J. C.

2004-12-01

293

Towards attosecond X-ray pulses from the FEL  

SciTech Connect

The ability to study ultrafast phenomena has been recently advanced by the demonstrated production and measurement of a single, 650-attosecond (10{sup 18} sec), VUV x-ray pulse[1] and, latter, a 250-attosecond pulse[2]. The next frontier is a production of the x-ray pulses with shorter wavelengths and in a broader spectral range. Several techniques for a generation of an isolated, attosecond duration, short-wavelength x-ray pulse based upon the ponderomotive laser acceleration [3], SASE and harmonic cascade FELs ([4] - [6]) had been already proposed. In this paper we briefly review a technique proposed in [5] and present some new results.

Zholents, Alexander A.; Fawley, William M.

2004-07-01

294

X-ray imaging with laser-Compton scattering X-ray at AIST  

Microsoft Academic Search

An X-ray facility with a compact electron linear accelerator via laser-Compton scattering (LCS X-ray) is recently installed at AIST. The LCS X-ray facility in approximately 8-m square consists of a 40-MeV linac, a femtosecond terawatt laser and an X-ray beamline. The LCS X-ray facility produces quasi-monochromatic X-rays with energy in the range of 12 ~ 40 keV which are commonly

M. Yasumoto; R. Kuroda; H. Ikeura-Sekiguchi; H. Toyokawa; N. Sei; H. Ogawa; M. Koike; K. Yamada; K. Mori; F. Sakai; S. Tamura

2009-01-01

295

X-ray scattering in X-ray fluorescence spectra with X-ray tube excitation – Modelling, experiment, and Monte-Carlo simulation  

Microsoft Academic Search

X-ray scattering may contribute significantly to the spectral background of X-ray fluorescence (XRF) spectra. Based on metrological measurements carried out with a scanning electron microscope (SEM) having attached a well characterised X-ray source (polychromatic X-ray tube) and a calibrated energy dispersive X-ray spectrometer (EDS) the accuracy of a physical model for X-ray scattering is systematically evaluated for representative samples. The

V.-D. Hodoroaba; M. Radtke; L. Vincze; V. Rackwitz; D. Reuter

2010-01-01

296

An accurate X-ray spectrographic method for the analysis of a wide range of geological samples  

Microsoft Academic Search

For accurate X-ray spectrographic analysis of geological samples of widely varying composition, a fusion with lithium borate containing lanthanum oxide is used to make a suitable glass disc. Mg, Al, Si, P, K, Ca, Ti, Mn and Fe are determined on this disc, using similar discs made with pure chemicals for calibration. \\

K. Norrish; J. T. Hutton

1969-01-01

297

PXAMS -- Projectile X ray AMS: X ray yields and applications  

SciTech Connect

Characteristic x rays have recently been explored as a method for the detection and identification of ions in accelerator mass spectrometry (AMS). After analysis in the AMS spectrometer, the ions stop in an appropriately chosen target and the induced x rays identify the ions by atomic number. For the application of AMS to higher mass isotopes, characteristic x rays allow significantly better discrimination of competing atomic isobars than is possible using energy loss detectors. Characteristic x rays also show promise as a convenient component in hybrid detection systems. Measurements of x ray yields are presented for Si, Fe, Ni, Se, Mo, and Pd ions of 0.5--2 MeV/AMU. The yields rise by more than a factor of 10 over this energy range, and approach 1 x-ray per incident ion at 2 MeV/AMU for the lighter ions. Preliminary work on the application of PXAMS to the detection of {sup 79}Se is described.

McAninch, J.E.; Bench, G.S.; Freeman, S.P.H.T.; Roberts, M.L.; Southon, J.R.; Vogel, J.S.; Proctor, I.D. [Lawrence Livermore National Lab., CA (United States). Center for Accelerator Mass Spectrometry

1994-10-07

298

Application of Nanometer-Multilayer Optics for X-Ray Analysis  

Microsoft Academic Search

With the growing number of applications in X-ray analysis, more and more dedicated X-ray optics are required, optimized for the spectral range they are intended to be used for. Three different types of curvature of laterally graded multilayer mirrors are used for X-ray analysis experiments: parabolic, elliptic and planar, which result in parallel, focusing and divergent beam conditions, respectively. Ni\\/C-multilayer-optics

Reiner Dietsch; Thomas Holz; Stefan Braun; Andreas Leson

2003-01-01

299

Miniature x-ray source  

Microsoft Academic Search

A miniature x-ray source utilizing a hot filament cathode. The source has a millimeter scale size and is capable of producing broad spectrum x-ray emission over a wide range of x-ray energies. The miniature source consists of a compact vacuum tube assembly containing the hot filament cathode, an anode, a high voltage feedthru for delivering high voltage to the cathode,

James E. Trebes; Perry M. Bell; Ronald B. Robinson

2000-01-01

300

Low Energy X-Ray Spectrometer  

NASA Astrophysics Data System (ADS)

A subkilovolt spectrometer has been produced to permit high-energy-resolution, time-dependent x-ray intensity measurements. The diffracting element is a curved mica (d=9.95A?) crystal. To preclude higher order (n>~1) diffractions, a carbon x-ray mirror that reflects only photons with energies less than ~1.1 keV is utilized ahead of the diffracting element. The nominal energy range of interest is 800 to 900 eV. The diffracted photons are detected by a gold-surfaced photoelectric diode designed to have a very good frequency response, and whose current is recorded on an oscilloscope. A thin, aluminum light barrier is placed between the diffracting crystal and the photoelectric diode detector to keep any UV generated on or scattered by the crystal from illuminating the detector. High spectral enegy resolution is provided by many photocathodes between 8- and 50-eV wide placed serially along the diffracted x-ray beam at the detector position. The spectrometer was calibrated for energy and energy dispersion using the Ni L?1,2 lines produced in the LLNL IONAC accelerator and in third order using a molybdenum target x-ray tube. For the latter calibration the carbon mirror was replaced by one surfaced with rhodium to raise the cut-off energy to about 3 keV. The carbon mirror reflection dependence on energy was measured using one of our Henke x-ray sources. The curved mica crystal diffraction efficiency was measured on our Low-Energy X-ray (LEX) machine. The spectrometer performs well although some changes in the way the x-ray mirror is held are desirable.

Woodruff, Wayne R.

1981-10-01

301

Spectral and Timing Properties of the Low-mass X-ray Binary 4U 0614+09 with XMM-Newton  

Microsoft Academic Search

4U 0614+09 is a low-mass X-ray binary with a weakly magnetized neutron star primary. It shows variability on time scales that range from years down to ~0.8 milliseconds. Before the Chandra and XMM-Netwon era, emission features around 0.7 keV have been reported from this source, but recent Chandra observations failed to detect them. Instead, these observations suggest an overabundance of

Mariano Mendez; Jean Cottam; Frits Paerels

2002-01-01

302

Bone densitometry using x-ray spectra  

NASA Astrophysics Data System (ADS)

In contrast to the two distinct energy regions that are involved in dual-energy x-ray absorptiometry for bone densitometry, the complete spectrum of a beam transmitted through two layers of different materials is utilized in this study to calculate the areal density of each material. Test objects constructed from aluminum and Plexiglas were used to simulate cortical bone and soft tissue, respectively. Solid-state HPGe (high-purity germanium) detectors provided high-resolution x-ray spectra over an energy range of approximately 20-80 keV. Areal densities were obtained from spectra using two methods: a system of equations for two spectral regions and a nonlinear fit of the entire spectrum. Good agreement with the known areal densities of aluminum was obtained over a wide range of PMMA thicknesses. The spectral method presented here can be used to decrease beam hardening at a small number of bodily points selected for examination.

Krmar, M.; Shukla, S.; Ganezer, K.

2010-10-01

303

Short-range order in crystalline, amorphous, liquid, and supercooled germanium probed by x-ray-absorption spectroscopy  

NASA Astrophysics Data System (ADS)

A detailed experimental investigation of the short-range structural properties in condensed phases of germanium is presented. X-ray-absorption measurements at the Ge K edge have been collected in a wide temperature range for different samples. Polycrystalline c-Ge was measured at 77, 296, 450, 620, 782, 920, and 1110 K, close to the Ge melting-point temperature Tm=1210.4 K. Evaporated amorphous Ge was measured at 297 K. Eight independent measurements for liquid germanium have been collected from about 950 K in highly supercooled conditions up to about 1600 K. The spectra show a remarkable temperature trend. By comparison, previous diffraction measurements on l-Ge were limited to two narrow temperature regions only, either above Tm or around 1500 K, and no measurements in the supercooled liquid region existed. Data analysis has been performed with the GNXAS approach and account has been taken for the presence of double-excitation channels involving 3d and 3p electrons in addition to the 1s. The c-Ge structural results are found in excellent agreement with the known properties. The expansion of the average bond length R is in agreement with thermal expansion data. Mean-square vibrational amplitudes are in excellent agreement with both previous measurements and calculations in the harmonic approximation. The analysis of the signal in liquid Ge has been performed using a technique that allows to extract information on the radial distribution function g(r) directly comparable with molecular dynamics (MD) simulations or previous diffraction determinations. A regular trend is observed in the intensity of the first g(r) peak that decreases from 2.3 to 950 K to about 1.8 at 1610 K. At the same time a widening of the peak and a shift of the rising short distance edge is clearly detected. The data are in excellent agreement with diffraction measurements and recent ab initio MD results by Kresse and Hafner [Phys. Rev. B 49, 14 251 (1994)]. The general relevance of these findings, in connection with the possibility to obtain structural information for liquid systems complementary to that contained in diffraction measurements, is addressed.

Filipponi, A.; di Cicco, A.

1995-05-01

304

Normal-incidence reflectance of optimized W\\/B4C x-ray multilayers in the range 1.4 nm < lambda < 2.4 nm  

Microsoft Academic Search

We have fabricated W\\/B4C multilayers having periods in the range d = 0.8-1.2 nm and measured their soft-x-ray performance near normal incidence in the wavelength range 1.4 < lambda < 2.4 nm. By adjusting the fractional layer thickness of W we have produced structures having interface widths sigma ~ 0.29 nm (i.e., as determined from normal-incidence reflectometry), thus having optimal

David L. Windt; Eric M. Gullikson; Christopher C. Walton

2002-01-01

305

Miniature x-ray source  

DOEpatents

A miniature x-ray source capable of producing broad spectrum x-ray emission over a wide range of x-ray energies. The miniature x-ray source comprises a compact vacuum tube assembly containing a cathode, an anode, a high voltage feedthru for delivering high voltage to the anode, a getter for maintaining high vacuum, a connection for an initial vacuum pump down and crimp-off, and a high voltage connection for attaching a compact high voltage cable to the high voltage feedthru. At least a portion of the vacuum tube wall is highly x-ray transparent and made, for example, from boron nitride. The compact size and potential for remote operation allows the x-ray source, for example, to be placed adjacent to a material sample undergoing analysis or in proximity to the region to be treated for medical applications.

Trebes, James E. (Livermore, CA); Stone, Gary F. (Livermore, CA); Bell, Perry M. (Tracy, CA); Robinson, Ronald B. (Modesto, CA); Chornenky, Victor I. (Minnetonka, MN)

2002-01-01

306

The BeppoSAX High Energy Large Area Survey (HELLAS) - II. Number counts and X-ray spectral properties  

Microsoft Academic Search

The BeppoSAX High Energy Large Area Survey (HELLAS) has surveyed about 85deg2 of sky in the 5-10keV band down to a flux of 4-5×10-14ergcm-2s-1. The source surface density of 16.9+\\/-6.4deg-2 at the survey limit corresponds to a resolved fraction of the 5-10keV X-ray background (XRB) of the order of 20-30 per cent. Hardness ratio analysis indicates that the spectra of

F. Fiore; P. Giommi; C. Vignali; A. Comastri; G. Matt; G. C. Perola; F. La Franca; S. Molendi; F. Tamburelli; L. A. Antonelli

2001-01-01

307

2-Acylamino- and 2,4-bis(acylamino)pyrimidines as supramolecular synthons analyzed by multiple noncovalent interactions. DFT, X-ray diffraction, and NMR spectral studies.  

PubMed

Intermolecular interactions of ten 2-acylamino and 2,4-bis(acylamino)pyrimidines (7 of which are previously unknown) have been investigated by X-ray structural, quantum chemical (DFT), and NMR spectral methods. Especially the concentration dependencies of the (1)H NMR chemical shifts and titrations with other molecules capable of multiple hydrogen bonding provided useful information regarding their association via triple or quadruple hydrogen bonding, which is controlled by the conformational preferences of 2-acylamino- and 2,4-bis(acylamino)pyrimidines. On comparison of the properties of 2-acylamino- and 2,4-bis(acylamino)pyrimidines with the corresponding pyridines, an additional nitrogen in the heterocyclic ring is the crucial factor in explaining the stability of various conformers and dimers of pyrimidines. Computational modeling of their dimerization (self-association) and heteroassociation supports the experimental findings. The substituent effects in 2-acylamino- and 2,4-bis(acylamino)pyrimidines are discussed via inter- and intramolecular terms. The subtle balance between several structural factors and their influence on the aggregation of studied pyrimidines was confirmed also by variable-temperature NMR and NOE experiments. X-ray structures of 2-methyl- and 2-adamantyl-CONH-pyrimidines revealed very different intermolecular interactions, showing the importance of the substituent size on the self-assembly process. As a whole NMR spectral, X-ray structural, and computational data of 2-acylamino- and 2,4-bis(acylamino)pyrimidines can be interpreted in terms of multiple intra-/intermolecular interactions. PMID:23020688

O?mia?owski, Borys; Kolehmainen, Erkki; Ikonen, Satu; Valkonen, Arto; Kwiatkowski, Adam; Grela, Izabela; Haapaniemi, Esa

2012-10-11

308

X-Ray Data Booklet  

NSDL National Science Digital Library

The X-Ray Data Booklet is provided by the Center for X-ray Optics and Advanced Light Source of the Lawrence Berkeley National Laboratory, which is funded by the US Department of Energy. The online publication contains topics such as x-ray properties of elements, mass absorption coefficients, synchrotron radiation, scattering processes, low-energy electron ranges in matter, optics and detectors, specular reflectivities for grazing-incidence mirrors, and other practical information that has been produced and gathered as a result of research at the center. Additional features of the informative site include an interactive periodic table of X-Ray properties and free deliverable hardcopies of the document.

Lindau, Ingolf.; Kortright, Jeff.; Kim, Kwang-Je.; Howells, Malcolm.; Gullikson, Eric.; Attwood, David.

2000-01-01

309

VARIABILITY AND SPECTRAL MODELING OF THE HARD X-RAY EMISSION OF GX 339-4 IN A BRIGHT LOW/HARD STATE  

SciTech Connect

We study the high-energy emission of the Galactic black hole candidate GX 339-4 using INTEGRAL/SPI and simultaneous RXTE/PCA data. By the end of 2007 January, when it reached its peak luminosity in hard X-rays, the source was in a bright hard state. The SPectrometer on INTEGRAL (SPI) data from this period show a good signal-to-noise ratio, allowing a detailed study of the spectral energy distribution up to several hundred keV. As a main result, we report on the detection of a variable hard spectral feature ({>=}150 keV) which represents a significant excess with respect to the cutoff power-law shape of the spectrum. The SPI data suggest that the intensity of this feature is positively correlated with the 25-50 keV luminosity of the source and the associated variability timescale is shorter than 7 hr. The simultaneous Proportional Counter Array data, however, show no significant change in the spectral shape, indicating that the source is not undergoing a canonical state transition. We analyzed the broadband spectra in the lights of several physical models, assuming different heating mechanisms and properties of the Comptonizing plasma. For the first time, we performed quantitative model fitting with the new versatile Comptonization code BELM, accounting self-consistently for the presence of a magnetic field. We show that a magnetized medium subject to pure non-thermal electron acceleration provides a framework for a physically consistent interpretation of the observed 4-500 keV emission. Moreover, we find that the spectral variability might be triggered by the variations of only one physical parameter, namely the magnetic field strength. Therefore, it appears that the magnetic field is likely to be a key parameter in the production of the Comptonized hard X-ray emission.

Droulans, R.; Belmont, R.; Malzac, J.; Jourdain, E. [CESR, Universite de Toulouse, UPS, 9 avenue du Colonel Roche, F-31028 Toulouse (France)

2010-07-10

310

A combined optical and X-ray study of unobscured type 1 active galactic nuclei - I. Optical spectra and spectral energy distribution modelling  

NASA Astrophysics Data System (ADS)

We present modelling and interpretation of the continuum and emission lines for a sample of 51 unobscured type 1 active galactic nuclei (AGNs). All of these AGNs have high-quality spectra from both XMM-Newton and the Sloan Digital Sky Survey. We extend the wavelength coverage where possible by adding simultaneous ultraviolet data from the OM onboard XMM-Newton. Our sample is selected based on low reddening in the optical and low gas columns implied by their X-ray spectra, except for one case, the broad absorption line quasar PG 1004+130. They also lack clear signatures for the presence of a warm absorber. Therefore, the observed characteristics of this sample are likely to be directly related to the intrinsic properties of the central engine. To determine the intrinsic optical continuum, we subtract the Balmer continuum and all major emission lines (including Fe II). We also consider possible effects of contamination from the host galaxy. The resulting continuum is then used to derive the properties of the underlying accretion disc. We constrain the black hole masses from spectral fits of the Balmer emission lines and determine the best-fitting value from the modelling of broad-band spectral energy distributions (SEDs). In addition to the disc component, many of these SEDs also exhibit a strong soft X-ray excess, plus a power law extending to higher X-ray energies. We fit these SEDs by applying a new broad-band SED model which comprises accretion disc emission, low-temperature optically-thick Comptonization and a hard X-ray tail by introducing the concept of a corona radius. We find that in order to fit the data, the model often requires an additional long-wavelength optical continuum component, whose origin is discussed in this paper. We also find that the photorecombination edge of the Balmer continuum shifts and broadens beyond the standard limit of 3646 Å, implying an electron number density which is far higher than that in the broad-line-region clouds. Our results indicate that the narrow-line type 1 Seyfert galaxies in this sample tend to have lower black hole masses, higher Eddington ratios, softer 2-10 keV band spectra, lower 2-10 keV luminosities and higher ?ox, compared with typical broad-line type 1 Seyfert galaxies, although their bolometric luminosities are similar. We illustrate these differences in properties by forming an average SED for three subsamples, based on the full width at half-maximum velocity width of the H? emission line.

Jin, Chichuan; Ward, Martin; Done, Chris; Gelbord, Jonathan

2012-03-01

311

Bragg reflection x ray optics  

Microsoft Academic Search

After a brief summary of the properties of x rays and of materials in the x ray frequency range, the ray optics and microscopic wavefield optics of Bragg reflection in perfect crystals are reviewed. Particular attention is given to the phase relationships between fields, to the spatial modulation of wavefields and to the role of the structure amplitude in determining

M. Hart

1971-01-01

312

Spatial resolution of a hard x-ray CCD detector  

SciTech Connect

The spatial resolution of an x-ray CCD detector was determined from the widths of the tungsten x-ray lines in the spectrum formed by a crystal spectrometer in the 58 to 70 keV energy range. The detector had 20{mu}m pixel, 1700 by 1200 pixel format, and a CsI x-ray conversion scintillator. The spectral lines from a megavolt x-ray generator were focused on the spectrometer's Rowland circle by a curved transmission crystal. The line shapes were Lorentzian with an average width after removal of the natural and instrumental line widths of 95{mu}m (4.75 pixels). A high spatial frequency background, primarily resulting from scattered gamma rays, was removed from the spectral image by Fourier analysis. The spectral lines, having low spatial frequency in the direction perpendicular to the dispersion, were enhanced by partially removing the Lorentzian line shape and by fitting Lorentzian curves to broad unresolved spectral features. This demonstrates the ability to improve the spectral resolution of hard x-ray spectra that are recorded by a CCD detector with well-characterized intrinsic spatial resolution.

Seely, John F.; Pereira, Nino R.; Weber, Bruce V.; Schumer, Joseph W.; Apruzese, John P.; Hudson, Lawrence T.; Szabo, Csilla I.; Boyer, Craig N.; Skirlo, Scott

2010-08-10

313

Establishment of Age-Specified Bone Mineral Density Reference Range for Indian Females Using Dual-Energy X-ray Absorptiometry  

Microsoft Academic Search

We undertook this study to establish age-specified bone mineral density (BMD) reference range for Indian females using dual-energy X-ray absorptiometry. BMD at multiple skeletal sites was measured in 2034 healthy women aged 18–85yr. The effect of anthropometry and biochemical parameters on BMD was determined. Peak BMD was observed between 30 and 35yr at the hip, lumbar spine, and radius. Significant

Raman K. Marwaha; Nikhil Tandon; Parjeet Kaur; Aparna Sastry; Kuntal Bhadra; Archna Narang; Saurav Arora; Kalaivani Mani

314

Hydrostatic low-range pressure applications of the Paris-Edinburgh cell utilising polymer gaskets for diffuse x-ray scattering measurements  

Microsoft Academic Search

The use of a polymeric Torlon (polyamide-imide) gasket material in a Paris-Edinburgh pressure cell for in situ high-pressure X-ray scattering measurements is demonstrated. The relatively low bulk modulus of the gasket allows for fine control of the sample pressure over the range 0.01-0.42 GPa. The quality of the data obtained in this way is suitable for Bragg and pair distribution

Karena W. Chapman; Peter J. Chupas; Charles A. Kurtz; Darren R. Locke; J. B. Parise; J. A. Hriljac

2007-01-01

315

Skull x-ray  

MedlinePLUS

X-ray - head; X-ray - skull; Skull radiography; Head x-ray ... You will be asked to lie on the x-ray table or sit in a chair. Your head ... there is little or no discomfort during an x-ray. If there is a head injury , positioning the ...

316

The X-ray-to-Optical Properties of Optically-Selected Active Galaxies Over Wide Luminosity and Redshift Ranges  

Microsoft Academic Search

We present partial-correlation analyses that examine the strengths of the\\u000arelationships between L_UV, L_X, Alpha_OX, and redshift for optically-selected\\u000aAGNs. We extend the work of Strateva et al. (2005), that analyzed\\u000aoptically-selected AGNs from the Sloan Digital Sky Survey (SDSS), by including\\u000a52 moderate-luminosity, optically-selected AGNs from the COMBO-17 survey with\\u000acorresponding deep (~250 ks to 1 Ms) X-ray observations

A. T. Steffen; I. Strateva; W. N. Brandt; D. M. Alexander; A. M. Koekemoer; B. D. Lehmer; D. P. Schneider; C. Vignali

2006-01-01

317

X-ray spectrum in the range (6-12) A emitted by laser-produced plasma of samarium  

SciTech Connect

A detailed analysis of the x-ray spectrum emitted by laser-produced plasma of samarium (6-12 A) is presented, using ab initio calculations with the HULLAC relativistic code and isoelectronic considerations. Resonance 3d-nf (n=4 to 7), 3p-4d, 3d-4p, and 3p-4s transitions in Ni samarium ions and in neighboring ionization states (from Mn to Zn ions) were identified. The experiment results show changes in the fine details of the plasma spectrum for different laser intensities.

Louzon, Einat; Henis, Zohar; Levi, Izhak; Hurvitz, Gilad; Ehrlich, Yosi; Fraenkel, Moshe; Maman, Shlomo [Soreq Research Center, Yavne 81800 (Israel); Mandelbaum, Pinchas [Jerusalem College of Engineering, Ramat Beth Hakerem, Jerusalem 91035 (Israel)

2009-05-15

318

Millisecond-Range Time-Resolved Small-Angle X-Ray Scattering Studies of Micellar Transformations  

NASA Astrophysics Data System (ADS)

The transformation of mixtures of cationic and anionic micelles to vesicles has been studied by time-resolved small-angle x-ray scattering (SAXS). Equimolar amounts of ionic surfactant solutions, the anionic TexaponN70-H and the cationic TTAOH, were mixed by a stopped-flow device. Time-resolved SAXS patterns reveal that within the mixing time (<10 ms) mixed micelles are formed. These globular micelles dissolve within about 400-1000 ms and form monodisperse unilamellar vesicles in a much slower process of 5-100 s duration.

Schmölzer, St.; Gräbner, D.; Gradzielski, M.; Narayanan, T.

2002-06-01

319

Mapping of auroral x-rays from rocket overflights  

SciTech Connect

In March 1978, two Nike Tomahawk payloads were launched from Poker Flat, Alaska, to observe the structure of bremsstrhlung x rays and precipitating particles during both nighttime and daytime observe x rays in four spectral ranges (5--10 keV, 10--20 keV, 20--40 keV, and >40 keV). Particle contamination of the detectors was avoided with broom magnet shielding techniques. By virtue of the payloads' approximate 20/sup 0/ coning angle (about 10.5-s period), the detectors scanned wide regions on either side of the trajectory paths. This has permitted construction (using computer color graphics) of the time averaged (approx.4 min) x ray source regions near 100 km, a height consistent with Chatanika radar electron density maps obtained during each flight period. X ray image maps for both flights exhibit enhanced source regions well outside the rocket trajectory planes. For the nighttime overflight, Chatanika radar scan data and Fort Yukon riometer data were used to verify the presence of an x ray imaged enhancement of electron precipitation, approximately 30 km to the east of the rocket trajectory plane. The daytime x ray data also exhibited several regions of enhanced emission, but outside the region scanned by Chatanika radar. A comparison of the x ray emissions from the two events shows the daytime x ray spectral distributions to be significantly harder but less intense that the nighttime distributions. Furthermore, for both events, spectra compared within and nearby each enhanced emitting region exhibit characteristics of a two component spectrum, such that the bright regions show an increased flux primarily in the low-energy component. Electron fluxes measured on each of the two flights with Geiger tubes are mainly isotropic over the downward hemisphere at night but show anisotropic pitch angle characteristics by day, consistent with the concept that the enhancement of the low-energy x ray flux component is predominantly induced by electrons filling the loss cone.

Goldberg, R.A.; Barcus, J.R.; Treinish, L.A.; Vondrak, R.R.

1982-04-01

320

Mass attenuation coefficients in the range 3.8?E?11keV, K fluorescence yield and K?/K? relative X-ray emission rate for Ti, V, Fe, Co, Ni, Cu and Zn measured with a tunable monochromatic X-ray source  

NASA Astrophysics Data System (ADS)

This work presents new measurements of mass attenuation coefficients in the range 3.8?E?11keV, K-absorption jump-ratios, K? and K? fluorescence yields for Ti, V, Fe, Co, Ni, Cu and Zn. We use the experimental facility SOLEX, a tunable monochromatic X-ray source combined with an energy-dispersive high-purity germanium detector. The results are compared with theoretical values as well as with other experimental data and show a relatively good agreement. However, the derived K-jump-ratios appear larger than those widely used in the XCOM database. The K? and K? fluorescence yields and the corresponding relative emission rates K?/K? are also derived, which was made possible by the use of energy-dispersive detectors with good spectral resolution.

Ménesguen, Y.; Lépy, M.-C.

2010-08-01

321

Z-dependence and collective analysis of M x-ray production cross sections for a wide range of elements (60?Z?90) by proton impact  

NASA Astrophysics Data System (ADS)

Based on the remarkable spread of the ratios of the experimental to theoretical M-shell x-ray production cross section, where they are usually analyzed by a function depending only on the scaled velocity parameter, we attempt to deduce new semi-empirical cross sections by introducing the dependence of these ratios on the atomic number of the target, noted as "Z-dependence". For this effect, the ECPSSR model and the updated experimental data (from 1980 till 2009) of the M-shell x-ray production cross sections are combined to calculate the semi-empirical cross sections for a wide range of heavy elements (60?Z?90) by proton impact. A brief discussion of the agreement between our results and earlier theoretical as well as experimental works has been demonstrated.

Deghfel, B.; Kahoul, A.; Kerai, S.; Saadaoui, M.; Dechoucha, S.; Nekkab, M.

2013-11-01

322

X-Rays from Young Stars and Eggs in the Eagle Nebula (M16)  

NASA Astrophysics Data System (ADS)

The Chandra X-ray Observatory observed the Eagle Nebula (M16) a young star forming region containing the dark columns of dust and cold molecular gas known as the ""Pillars of Creation"" or ""elephant trunks"". We identify more than 1000 X-ray sources coincident with K-band stars that are premain sequence stars ranging in spectral type from O to M. A handful of the hard X-ray sources in the pillars are spatially coincident with deeply embedded young stellar objects seen in JHK images. However none of the X-ray sources are associated with the evaporating gaseous globules (EGGs) first observed by Hester et al. (1996).

Linsky, Jeffrey L.; Gagne, Marc; Mytyk, Anna

323

X-ray luminescence based spectrometer for investigation of scintillation properties  

SciTech Connect

A new x-ray luminescence based spectrometer was developed and installed to examine the scintillation properties of materials while revealing the origins of luminescence and investigating trapping defects. Measurements were performed on a number of undoped and Ce doped yttrium aluminum garnet crystals and various luminescence centers were characterized. The measured x-ray luminescence spectra provide information about the spectral range and the scintillation efficiency and linearity. The efficiency of charge-carriers production due to x ray, their energy transfer to the luminescence centers, and the efficiency of luminescence are all reflected in the efficiency of x-ray luminescence.

Varney, C. R.; Khamehchi, M. A.; Ji, Jianfeng; Selim, F. A. [Department of Physics and Astronomy, Washington State University, Pullman, Washington 99164-2814 (United States)

2012-10-15

324

The BeppoSAX High Energy Large Area Survey (HELLAS) - II. Number counts and X-ray spectral properties  

NASA Astrophysics Data System (ADS)

The BeppoSAX High Energy Large Area Survey (HELLAS) has surveyed about 85deg2 of sky in the 5-10keV band down to a flux of 4-5×10-14ergcm-2s-1. The source surface density of 16.9+/-6.4deg-2 at the survey limit corresponds to a resolved fraction of the 5-10keV X-ray background (XRB) of the order of 20-30 per cent. Hardness ratio analysis indicates that the spectra of a substantial fraction of the HELLAS sources (at least one-third) are harder than a ?E=0.6 power law. This hardness may be caused by large absorbing columns. The hardness ratio analysis also indicates that many HELLAS sources may have a spectrum more complex than a single absorbed power law. A soft component, superimposed on a strongly cut-off power law, is likely to be present in several sources.

Fiore, F.; Giommi, P.; Vignali, C.; Comastri, A.; Matt, G.; Perola, G. C.; La Franca, F.; Molendi, S.; Tamburelli, F.; Antonelli, L. A.

2001-11-01

325

Hydrodynamics of X-ray induced stellar winds  

SciTech Connect

We present new theoretical models for X-ray induced stellar winds in binary systems. We numerically solve the hydrodynamic equations in one dimension, utilizing a simplified model of the physics of an X-ray heated plasma. The character of the solutions depends on three dimensionless parameters: (1) the ratio of the X-ray spectral temperature to the photospheric temperature; (2) the ratio of the X-ray temperature to a temperature characterizing the escape energy from the stellar surface; and (3) the ratio of the flow time to the heating time. Holding the first parameter fixed at a high value ( = 100), we explore the complete range of solutions produced by variations in the other two parameters.

London, R.A.; Flannery, B.P.

1982-07-01

326

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

327

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

PubMed

A dedicated in-vacuum coherent x-ray diffraction microscope was installed at the 2-ID-B beamline of the Advanced Photon Source for use with 0.7-2.9 keV x-rays. The instrument can accommodate three common implementations of diffractive imaging; plane wave illumination; defocused-probe (Fresnel diffractive imaging) and scanning (ptychography) using either a pinhole, focused or defocused probe. The microscope design includes active feedback to limit motion of the optics with respect to the sample. Upper bounds on the relative optics-to-sample displacement have been measured to be 5.8 nm(v) and 4.4 nm(h) rms/h using capacitance micrometry and 27 nm/h using x-ray point projection imaging. The stability of the measurement platform and in-vacuum operation allows for long exposure times, high signal-to-noise and large dynamic range two-dimensional intensity measurements to be acquired. Finally, we illustrate the microscope's stability with a recent experimental result. PMID:22462925

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

2012-03-01

328

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

SciTech Connect

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

Vine, D. J. [Australian Research Council Centre of Excellence for Coherent X-ray Science (Australia); School of Physics, University of Melbourne, Victoria 3010 (Australia); Argonne National Laboratory, Argonne, Illinois 60439 (United States); Williams, G. J. [Australian Research Council Centre of Excellence for Coherent X-ray Science (Australia); SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Clark, J. N. [Australian Research Council Centre of Excellence for Coherent X-ray Science (Australia); Department of Physics, La Trobe University, Bundoora, Victoria 3086 (Australia); London Centre for Nanotechnology, University College, London WC1E 6BT (United Kingdom); Putkunz, C. T.; Abbey, B.; Nugent, K. A. [Australian Research Council Centre of Excellence for Coherent X-ray Science (Australia); School of Physics, University of Melbourne, Victoria 3010 (Australia); Pfeifer, M. A. [Australian Research Council Centre of Excellence for Coherent X-ray Science (Australia); Cornell High Energy Synchrotron Source, Cornell University, Ithaca, New York 14850 (United States); Legnini, D.; Roehrig, C.; Wrobel, E.; McNulty, I. [Argonne National Laboratory, Argonne, Illinois 60439 (United States); Huwald, E. [Department of Physics, La Trobe University, Bundoora, Victoria 3086 (Australia); Riessen, G. van; Peele, A. G. [Australian Research Council Centre of Excellence for Coherent X-ray Science (Australia); Department of Physics, La Trobe University, Bundoora, Victoria 3086 (Australia); Beetz, T.; Irwin, J.; Feser, M.; Hornberger, B. [Xradia, Inc., 4385 Hopyard Road, Pleasanton, California 94588 (United States)

2012-03-15

329

Measurement of the mass attenuation coefficient for elemental materials in the range 6 < or = Z < or = 82 using X-rays from 13 up to 50 kev.  

PubMed

The mass attenuation coefficients for 22 high purity elemental materials (C, Al, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Rh, Pd, Ag, Cd, In, Ta, Pt, Au, Pb) were measured in the X-ray energy range from 13 up to 50 keV using a high purity germanium detector with thin (50 microm) Be window and a variable-energy X-ray source. The measured values are compared with the theoretical ones obtained using the XCOM code and data base, as well as with other experimental data showing a general agreement within +/- 5%. The mass attenuation cross-sections were thus derived and compared with other experimental data available on the 1988 NBS database of X-ray attenuation cross-sections. The agreement is always within +/- 8%, but for a few points the discrepancies are up to +/- 18%. The data analysis has also shown that some measurements performed at 50.65 keV as well as at 36.65 keV are to be considered as new data for most of the measured materials. PMID:11545503

Angelone, M; Bubba, T; Esposito, A

2001-10-01

330

Recent X-ray Variability of Eta Car Approaching The X-ray Eclipse  

Microsoft Academic Search

We discuss recent X-ray spectral variability of the supermassive star Eta Car in the interval since the last X-ray eclipse in 1998. We concentrate on the interval just prior to the next X-ray eclipse which is expected to occur in June 2003. We compare the X-ray behavior during the 2001-2003 cycle with the previous cycle (1996-1998) and note similarities and

M. Corcoran; J. H. Swank; K. Ishibashi; T. Gull; R. Humphreys; A. Damineli; N. Walborn; D. J. Hillier; K. Davidson; S. M. White; R. Petre; J. Pittard; Y. Butt; K. Verner

2002-01-01

331

X-rays of a Monster Star: Eta Car Approaching The X-ray Eclipse  

Microsoft Academic Search

We discuss recent X-ray spectral variability of the supermassive star Eta Car in the interval since the last X-ray eclipse in 1998. We concentrate on the interval just prior to the next X-ray eclipse which is expected to occur in June 2003. We compare the X-ray behavior during the 2001-2003 cycle with the previous cycle (1996-1998) and note similarities and

M. F. Corcoran

2003-01-01

332

X-Ray Morphology,Kinematics and Geometry of the Eridanus Soft X-Ray Enhancement  

Microsoft Academic Search

We present mosaics of X-ray intensity maps and spectral fit results for selected regions of the Eridanus soft X-ray Enhancement (EXE), as well as kinematics of the X-ray absorbing clouds in the EXE region and geometrical properties of this X-ray emitting bubble. The work is based on pointed observations with the ROSAT Position Sensitive Proportional Counter, 21 cm observations with

Zhiyu Guo; David N. Burrows; Wilton T. Sanders; Steve L. Snowden; Bryan E. Penprase

1994-01-01

333

Novel X-Ray Source Using Rear Side X-Ray Emission from the Foil Target  

Microsoft Academic Search

Development of a novel and compact x-ray source is described. The first direct evidence of L-shell x-ray transport through an Al foil target was determined by observing the soft x-ray spectra from the rear side and this is explained in terms of ionization burnthrough. In contrast to other work, the x-ray spectral profile from the rear side of the target

H. Hirose; K. Ando; K. Miyazawa; T. Hara; K. Kodate; Y. Aoyagi

1996-01-01

334

X-ray Spectroscopy of Neutron Star Low-Mass X-ray Binaries  

Microsoft Academic Search

In this thesis, I present work spanning a variety of topics relating to neutron star low-mass X-ray binaries (LMXBs) and utilize spectral information from X-ray observations to further our understanding of these sources. First, I give an overview of important X-ray astrophysics relevant to the work I present in subsequent chapters, as well as information about the X-ray observatories from

M. I. Krauss

2007-01-01

335

Novel x-ray source using rear side x-ray emission from the foil target  

Microsoft Academic Search

Development of a novel and compact x-ray source is described. The first direct evidence of L-shell x-ray transport through an Al foil target was determined by observing the soft x-ray spectra from the rear side and this is explained in terms of ionization hurnthrough. Contrary to the other works, the x-ray spectral protile from the rear side of the target

H. Hirose; K. Ando; Y. Aoyagi

1996-01-01

336

Frequency Filter of Seed X-ray by Use of X-ray Laser Medium: Toward the Generation of the Temporally Coherent X-ray Laser  

Microsoft Academic Search

We evaluate the characteristics of a higher-order harmonics light as a seed X-ray amplified through a laser-produced X-ray amplifier. The narrow spectral bandwidth of the X-ray amplifier works as the frequency filter of the seed X-ray, resulting in that only the temporally coherent X-ray is amplified. Experimental investigation using the 29th-order harmonic light of the Ti:sapphire laser at a wavelength

Noboru Hasegawa; Tetsuya Kawachi; Maki Kishimoto; Kouta Sukegawa; Momoko Tanaka; Tai Renzhong; Yoshihiro Ochi; Masaharu Nishikino; Keisuke Nagashima; Yoshiaki Kato

2009-01-01

337

The ASTRO-H X-ray Observatory  

NASA Astrophysics Data System (ADS)

The joint JAXA/NASA ASTRO-H mission is the sixth in a series of highly successful X-ray missions initiated by the Institute of Space and Astronautical Science (ISAS). ASTRO-H will investigate the physics of the highenergy universe via a suite of four instruments, covering a very wide energy range, from 0.3 keV to 600 keV. These instruments include a high-resolution, high-throughput spectrometer sensitive over 0.3-12 keV with high spectral resolution of ?E ? 7 eV, enabled by a micro-calorimeter array located in the focal plane of thin-foil X-ray optics; hard X-ray imaging spectrometers covering 5-80 keV, located in the focal plane of multilayer-coated, focusing hard X-ray mirrors; a wide-field imaging spectrometer sensitive over 0.4-12 keV, with an X-ray CCD camera in the focal plane of a soft X-ray telescope; and a non-focusing Compton-camera type soft gamma-ray detector, sensitive in the 40-600 keV band. The simultaneous broad bandpass, coupled with high spectral resolution, will enable the pursuit of a wide variety of important science themes.

Takahashi, Tadayuki; Mitsuda, Kazuhisa; Kelley, Richard; Aarts, Henri; Aharonian, Felix; Akamatsu, Hiroki; Akimoto, Fumie; Allen, Steve; Anabuki, Naohisa; Angelini, Lorella; Arnaud, Keith; Asai, Makoto; Audard, Marc; Awaki, Hisamitsu; Azzarello, Philipp; Baluta, Chris; Bamba, Aya; Bando, Nobutaka; Bautz, Mark; Blandford, Roger; Boyce, Kevin; Brown, Greg; Cackett, Ed; Chernyakova, Mara; Coppi, Paolo; Costantini, Elisa; de Plaa, Jelle; den Herder, Jan-Willem; DiPirro, Michael; Done, Chris; Dotani, Tadayasu; Doty, John; Ebisawa, Ken; Eckart, Megan; Enoto, Teruaki; Ezoe, Yuichiro; Fabian, Andrew; Ferrigno, Carlo; Foster, Adam; Fujimoto, Ryuichi; Fukazawa, Yasushi; Funk, Stefan; Furuzawa, Akihiro; Galeazzi, Massimiliano; Gallo, Luigi; Gandhi, Poshak; Gendreau, Keith; Gilmore, Kirk; Haas, Daniel; Haba, Yoshito; Hamaguchi, Kenji; Hatsukade, Isamu; Hayashi, Takayuki; Hayashida, Kiyoshi; Hiraga, Junko; Hirose, Kazuyuki; Hornschemeier, Ann; Hoshino, Akio; Hughes, John; Hwang, Una; Iizuka, Ryo; Inoue, Yoshiyuki; Ishibashi, Kazunori; Ishida, Manabu; Ishimura, Kosei; Ishisaki, Yoshitaka; Ito, Masayuki; Iwata, Naoko; Iyomoto, Naoko; Kaastra, Jelle; Kallman, Timothy; Kamae, Tuneyoshi; Kataoka, Jun; Katsuda, Satoru; Kawahara, Hajime; Kawaharada, Madoka; Kawai, Nobuyuki; Kawasaki, Shigeo; Khangaluyan, Dmitry; Kilbourne, Caroline; Kimura, Masashi; Kinugasa, Kenzo; Kitamoto, Shunji; Kitayama, Tetsu; Kohmura, Takayoshi; Kokubun, Motohide; Kosaka, Tatsuro; Koujelev, Alex; Koyama, Katsuji; Krimm, Hans; Kubota, Aya; Kunieda, Hideyo; LaMassa, Stephanie; Laurent, Philippe; Lebrun, Francois; Leutenegger, Maurice; Limousin, Olivier; Loewenstein, Michael; Long, Knox; Lumb, David; Madejski, Grzegorz; Maeda, Yoshitomo; Makishima, Kazuo; Marchand, Genevieve; Markevitch, Maxim; Matsumoto, Hironori; Matsushita, Kyoko; McCammon, Dan; McNamara, Brian; Miller, Jon; Miller, Eric; Mineshige, Shin; Minesugi, Kenji; Mitsuishi, Ikuyuki; Miyazawa, Takuya; Mizuno, Tsunefumi; Mori, Hideyuki; Mori, Koji; Mukai, Koji; Murakami, Toshio; Murakami, Hiroshi; Mushotzky, Richard; Nagano, Hosei; Nagino, Ryo; Nakagawa, Takao; Nakajima, Hiroshi; Nakamori, Takeshi; Nakazawa, Kazuhiro; Namba, Yoshiharu; Natsukari, Chikara; Nishioka, Yusuke; Nobukawa, Masayoshi; Nomachi, Masaharu; O'Dell, Steve; Odaka, Hirokazu; Ogawa, Hiroyuki; Ogawa, Mina; Ogi, Keiji; Ohashi, Takaya; Ohno, Masanori; Ohta, Masayuki; Okajima, Takashi; Okamoto, Atsushi; Okazaki, Tsuyoshi; Ota, Naomi; Ozaki, Masanobu; Paerels, Fritzs; Paltani, Stéphane; Parmar, Arvind; Petre, Robert; Pohl, Martin; Porter, F. Scott; Ramsey, Brian; Reis, Rubens; Reynolds, Christopher; Russell, Helen; Safi-Harb, Samar; Sakai, Shin-ichiro; Sameshima, Hiroaki; Sanders, Jeremy; Sato, Goro; Sato, Rie; Sato, Yohichi; Sato, Kosuke; Sawada, Makoto; Serlemitsos, Peter; Seta, Hiromi; Shibano, Yasuko; Shida, Maki; Shimada, Takanobu; Shinozaki, Keisuke; Shirron, Peter; Simionescu, Aurora; Simmons, Cynthia; Smith, Randall; Sneiderman, Gary; Soong, Yang; Stawarz, Lukasz; Sugawara, Yasuharu; Sugita, Hiroyuki; Sugita, Satoshi; Szymkowiak, Andrew; Tajima, Hiroyasu; Takahashi, Hiromitsu; Takeda, Shin-ichiro; Takei, Yoh; Tamagawa, Toru; Tamura, Takayuki; Tamura, Keisuke; Tanaka, Takaaki; Tanaka, Yasuo; Tashiro, Makoto; Tawara, Yuzuru; Terada, Yukikatsu; Terashima, Yuichi; Tombesi, Francesco; Tomida, Hiroshi; Tsuboi, Yohko; Tsujimoto, Masahiro; Tsunemi, Hiroshi; Tsuru, Takeshi; Uchida, Hiroyuki; Uchiyama, Yasunobu; Uchiyama, Hideki; Ueda, Yoshihiro; Ueno, Shiro; Uno, Shinichiro; Urry, Meg; Ursino, Eugenio; de Vries, Cor; Wada, Atsushi; Watanabe, Shin; Werner, Norbert; White, Nicholas; Yamada, Takahiro; Yamada, Shinya; Yamaguchi, Hiroya; Yamasaki, Noriko; Yamauchi, Shigeo; Yamauchi, Makoto; Yatsu, Yoichi; Yonetoku, Daisuke; Yoshida, Atsumasa; Yuasa, Takayuki

2012-09-01

338

FY06 LDRD Final Report Next-generation x-ray optics: focusing hard x-rays  

SciTech Connect

The original goal of our research was to open up a new class of scientific experiments by increasing the power of newly available x-ray sources by orders of magnitude. This was accomplished by developing a new generation of x-ray optics, based on hard x-ray (10-200 keV) reflective and diffractive focusing elements. The optical systems we envision begin with a core reflective optic, which has the ability to capture and concentrate x-rays across a wide range of energies and angles band, combined with diffractive optics, based on large-scale multilayer structures, that will further enhance the spatial, spectral and temporal resolving power of the system. Enabling technologies developed at LLNL such as precise mounting of thermally formed substrates, smoothing techniques and multilayer films of ultra-high reflectance and precision were crucial in the development and demonstration of our research objectives. Highlights of this phase of the project include: the design and fabrication of a concentrator optic for the Pleiades Thomson X-ray source located at LLNL, smoothing of glass substrates through application of polyimide films, and the design, fabrication and testing of novel volume multilayers structures. Part of our research into substrate smooth led to the development of a new technique (patent pending) to construct high-quality, inexpensive x-ray optics. This innovation resulted in LLNL constructing a x-ray optic for the CERN Axion Solar Telescope (CAST) and allowed LLNL to join the international experiment.

Pivovaroff, M; Soufli, R

2007-03-01

339

An advanced multivariate approach for processing X-ray fluorescence spectral and hyperspectral data from non-invasive in situ analyses on painted surfaces.  

PubMed

In the last decades, in situ non-invasive analytical techniques have been widely used for the analysis of paintings. These techniques are useful to extensively map the surface in a non-invasive way, in order to identify the most representative areas to be sampled. When spectroscopic investigations, such as X ray fluorescence (XRF), are conducted, they usually imply the acquisition of a huge amount of measurements. Subsequently, all these data should be processed in situ, in order to immediately support the sampling strategies. To this aim, an appropriate and fast strategy for multivariate treatment of XRF spectral and hyperspectral data sets is presented, able to account for inter-correlation among variables, which is an issue of high importance for elemental analyses. The main advantage of the approach is that XRF spectral profiles are analysed directly, without computation of derived parameters, by means of principal component analysis (PCA). This procedure allows a fast interpretation of results that can be accomplished in situ. Particular attention was paid to the selection of proper spectral pre-treatments to be applied on data together with the use of several chemometric tools (peak alignment, spectra normalisation and exploratory analysis) aimed at improving the interpretation of XRF results. In addition, the application of multivariate exploratory analysis on XRF hyperspectral maps was studied by using an interactive brushing procedure. The multivariate approach was validated on data obtained from the analysis of the famous Renaissance panel painting "The Ideal City", exhibited in Palazzo Ducale of Urbino, Italy. PMID:23101649

Sciutto, Giorgia; Oliveri, Paolo; Prati, Silvia; Quaranta, Marta; Bersani, Silvia; Mazzeo, Rocco

2012-10-02

340

The feasibility of independent observations/detections of GRBs in X-rays  

SciTech Connect

According to the observational statistics a large majority of all GRBs exhibit X-ray emission. In addition, a dedicated separate group of GRB, the XRFs, exists which emission dominates in the X-ray spectral range. And the third group of GRB related objects (yet hypothetical) are the group of off-axis observed GRBs (orphan afterglows). These facts justify the consideration of an independent experiment for monitoring, detection and analyses of GRBs and others fast X-ray transients in X-rays. We will present and discuss such experiment based on wide-field X-ray telescopes of Lobster Eye type. The wide field and fine sensitivity of Lobster Eye X-ray All-Sky Monitor make such instruments important tools in study of GRBs and related objects.

Hudec, R.; Skulinova, M. [Astronomical Institute, Academy of Sciences of the Czech Republic, 251 65 Ondrejov (Czech Republic); Pina, L.; Sveda, L. [Czech Technical University, Prague (Czech Republic); Semencova, V.; Inneman, A. [Rigaku Innovative Techniologies Europe, Prague (Czech Republic)

2009-05-25

341

STEND-70: multifunction arrangement for the x-ray capillary products testing  

NASA Astrophysics Data System (ADS)

In the report we consider the experimental set-up for measuring the main characteristics of X-ray capillary products in the X-ray energy band ranging from 4 keV up to 60 keV. These characteristic are: 1) the capillary/lens transmission coefficient; 2) X-ray focal spot sizes of lenses and conical capillaries; 3) focal distances of lenses; 4) the transmission coefficient and the scatter reduction factor (for anti scatter grids). The arrangement is designed to allow measuring spectral dependence of the above characteristics. Example of the measurement of the X-ray poly-capillary transmission coefficient is given. The influence of mechanical and electronic stability on the measured values is discussed. Examples of the designed and manufactured gimbal mounts, translation stages, X-ray collimators and X-ray detectors that were produced by IRO in collaboration with 'Kurchatov Institute' are presented.

Shovkun, V. Y.; Moseiko, N. I.; Moseiko, L. A.; Brovchenko, V. G.; Kirichenko, A. M.; Puhov, A. V.; Markelov, A. A., Jr.; Molchanov, Yu. D.; Shimchenco, T. F.

2005-07-01

342

The feasibility of independent observations/detections of GRBs in X-rays  

NASA Astrophysics Data System (ADS)

According to the observational statistics a large majority of all GRBs exhibit X-ray emission. In addition, a dedicated separate group of GRB, the XRFs, exists which emission dominates in the X-ray spectral range. And the third group of GRB related objects (yet hypothetical) are the group of off-axis observed GRBs (orphan afterglows). These facts justify the consideration of an independent experiment for monitoring, detection and analyses of GRBs and others fast X-ray transients in X-rays. We will present and discuss such experiment based on wide-field X-ray telescopes of Lobster Eye type. The wide field and fine sensitivity of Lobster Eye X-ray All-Sky Monitor make such instruments important tools in study of GRBs and related objects.

Hudec, R.; Pina, L.; Marsikova, V.; Inneman, A.; Skulinova, M.

2011-08-01

343

Be/X-ray binaries  

NASA Astrophysics Data System (ADS)

The interest in X/ ?-ray Astronomy has grown enormously in the last decades thanks to the ability to send X-ray space missions above the Earth’s atmosphere. There are more than half a million X-ray sources detected and over a hundred missions (past and currently operational) devoted to the study of cosmic X/ ? rays. With the improved sensibilities of the currently active missions new detections occur almost on a daily basis. Among these, neutron-star X-ray binaries form an important group because they are among the brightest extra-solar objects in the sky and are characterized by dramatic variability in brightness on timescales ranging from milliseconds to months and years. Their main source of power is the gravitational energy released by matter accreted from a companion star and falling onto the neutron star in a relatively close binary system. Neutron-star X-ray binaries divide into high-mass and low-mass systems according to whether the mass of the donor star is above ˜8 or below ˜2 M?, respectively. Massive X-ray binaries divide further into supergiant X-ray binaries and Be/X-ray binaries depending on the evolutionary status of the optical companion. Virtually all Be/X-ray binaries show X-ray pulsations. Therefore, these systems can be used as unique natural laboratories to investigate the properties of matter under extreme conditions of gravity and magnetic field. The purpose of this work is to review the observational properties of Be/X-ray binaries. The open questions in Be/X-ray binaries include those related to the Be star companion, that is, the so-called “Be phenomenon”, such as, timescales associated to the formation and dissipation of the equatorial disc, mass-ejection mechanisms, V/ R variability, and rotation rates; those related to the neutron star, such as, mass determination, accretion physics, and spin period evolution; but also, those that result from the interaction of the two constituents, such as, disc truncation and mass transfer. Until recently, it was thought that the Be stars’ disc was not significantly affected by the neutron star. In this review, I present the observational evidence accumulated in recent years on the interaction between the circumstellar disc and the compact companion. The most obvious effect is the tidal truncation of the disc. As a result, the equatorial discs in Be/X-ray binaries are smaller and denser than those around isolated Be stars.

Reig, Pablo

2011-03-01

344

A high spatial resolution X-ray and H-alpha study of hot gas in the halos of star-forming disk galaxies. I. Spatial and spectral properties of the diffuse X-ray emission  

Microsoft Academic Search

We present arcsecond resolution Chandra X-ray and ground-based optical\\u000aH-alpha imaging of a sample of ten edge-on star-forming disk galaxies (seven\\u000astarburst and three ``normal'' spiral galaxies), a sample which covers the full\\u000arange of star-formation intensity found in disk galaxies. We use the\\u000aunprecedented spatial resolution of the Chandra X-ray observatory to robustly\\u000aremove point sources, and hence obtain

David K. Strickland; Timothy M. Heckman; Edward J. M. Colbert; Charles G. Hoopes; Kimberly A. Weaver

2003-01-01

345

Influence of laser focal position on X-ray and ion emission of copper plasma  

NASA Astrophysics Data System (ADS)

X-ray emission from copper plasma produced by a sub-nanosecond Nd:glass laser was studied as a function of distance of the target from the focus position. Optimization of soft (0.7-1.56 keV) and hard (3.2-5 keV) X-ray emissions as a function of the laser focal position was studied. In addition, a thallium acid phthalate (TAP) crystal spectrometer with spectral resolution of 30 mÅ was also developed to study variation in X-ray line emission in the spectral range of 1.291-1.610 keV (7.7-9.6 Å) as a function of laser focal position. It is observed that the maximum soft X-ray emission is on either sides of the focus, indicating a dependence on plasma volume, whereas hard X-ray emission shows a single peak close to the ‘best focus’ position. The line X-ray emission intensity with respect to laser focal position also shows a double hump structure as in the case of soft X-ray emission. This indicates that the line emission is also a function of plasma volume. Scaling of X-ray yield with laser intensity has also been determined. Ion emission was also studied as a function of focal position variation. It is observed to match well with the trend shown by X-ray emission.

Chaurasia, S.; Tripathi, S.; Ryc, L.; Dhareshwar, L. J.

2011-05-01

346

Quantitative extraction of spectral line intensities and widths from x-ray spectra recorded with gated microchannel plate detectors  

NASA Astrophysics Data System (ADS)

Plasma spectroscopy requires determination of spectral line intensities and widths. At Sandia National Laboratories Z facility we use elliptical crystal spectrometers equipped with gated microchannel plate detectors to record time and space resolved spectra. We collect a large volume of data typically consisting of five to six snapshots in time and five to ten spectral lines with 30 spatial elements per frame, totaling to more than 900 measurements per experiment. This large volume of data requires efficiency in processing. We have addressed this challenge by using a line fitting routine to automatically fit each spectrum using assumed line profiles and taking into account photoelectron statistics to efficiently extract line intensities and widths with uncertainties. We verified that the random data noise obeys Poisson statistics. Rescale factors for converting film exposure to effective counts required for understanding the photoelectron statistics are presented. An example of the application of these results to the analysis of spectra recorded in Z experiments is presented.

Dunham, Greg; Bailey, J. E.; Rochau, G. A.; Lake, P. W.; Nielsen-Weber, L. B.

2007-06-01

347

X-ray observations of 4U 1626-67 by the monitor counter on the Einstein \\/HEAO 2\\/ observatory  

Microsoft Academic Search

The pulsing X-ray source 4U 1626-67 was observed with the Monitor Proportional Counter (MPC) on board the Einstein X-Ray Observatory on three occasions in early 1979. The MPC is a sealed, argon-filled proportional counter with a 1.5 mil beryllium window and is coaligned with the X-ray telescope on board the observatory. The spectral data spanning the energy range from 1.1

R. F. Elsner; W. Darbro; D. Leahy; M. C. Weisskopf; S. M. Kahn; P. G. Sutherland; J. E. Grindlay

1983-01-01

348

Einstein Observatory survey of X-ray emission from solar-type stars - The late F and G dwarf stars  

Microsoft Academic Search

Results of a volume-limited X-ray survey of stars of luminosity classes IV and V in the spectral range F7-G9 observed with the Einstein Observatory are presented. Using survival analysis techniques, the stellar X-ray luminosity function in the 0.15-4.0 keV energy band for both single and multiple sources. It is shown that the difference in X-ray luminosity between these two classes

A. Maggio; S. Sciortino; G. S. Vaiana; P. Majer; J. Bookbinder; L. Golub; F. R. Harnden Jr.; R. Rosner

1987-01-01

349

A Chandra/HETGS Census of X-Ray Variability from Sgr A* during 2012  

NASA Astrophysics Data System (ADS)

We present the first systematic analysis of the X-ray variability of Sgr A* during the Chandra X-ray Observatory's 2012 Sgr A* X-ray Visionary Project. With 38 High Energy Transmission Grating Spectrometer observations spaced an average of 7 days apart, this unprecedented campaign enables detailed study of the X-ray emission from this supermassive black hole at high spatial, spectral and timing resolution. In 3 Ms of observations, we detect 39 X-ray flares from Sgr A*, lasting from a few hundred seconds to approximately 8 ks, and ranging in 2-10 keV luminosity from ~1034 erg s–1 to 2 × 1035 erg s–1. Despite tentative evidence for a gap in the distribution of flare peak count rates, there is no evidence for X-ray color differences between faint and bright flares. Our preliminary X-ray flare luminosity distribution dN/dL is consistent with a power law with index -1.9^{+0.3}_{-0.4}; this is similar to some estimates of Sgr A*'s near-IR flux distribution. The observed flares contribute one-third of the total X-ray output of Sgr A* during the campaign, and as much as 10% of the quiescent X-ray emission could be comprised of weak, undetected flares, which may also contribute high-frequency variability. We argue that flares may be the only source of X-ray emission from the inner accretion flow.

Neilsen, J.; Nowak, M. A.; Gammie, C.; Dexter, J.; Markoff, S.; Haggard, D.; Nayakshin, S.; Wang, Q. D.; Grosso, N.; Porquet, D.; Tomsick, J. A.; Degenaar, N.; Fragile, P. C.; Houck, J. C.; Wijnands, R.; Miller, J. M.; Baganoff, F. K.

2013-09-01

350

X-ray optics  

Microsoft Academic Search

Developments related to X-ray reflection are considered. The discovery that X-rays could be reflected at glancing incidence from polished surfaces opened up the possibility of making true X-ray imaging optics. However, to design usable X-ray optical systems, approaches had to be found for overcoming difficulties related to aberrations. The first X-ray microscope was constructed in 1948. Attention is also given

J. H. Underwood

1978-01-01

351

Impact of laser and x-ray irradiation on C60 films  

NASA Astrophysics Data System (ADS)

The modification of C60-film structure under laser and x-ray irradiation has been investigated. The wide spectral and dose ranges of irradiation have been applied: from visible light to hard x-ray and from low to high intensity, when the optical nonlinear effects appear. The structure changes manifesting close to nonlinear threshold have been found. They have exhibited the nonreversible effect contribution to the nonlinear parameters of initial C60- films. The dependence of C60-film structure modification on irradiation wavelength has been demonstrated by the photoluminescence and transmission spectral measurements, the solubility controlling, and data of x-ray diffractometry as well. The contribution of x-ray and a secondary electron flow to polymerization of the C60-film has bene determined. The information about C60- film modification may be used for optical limiting devices and for the development of UV and x-ray resists.

Kognovitsky, Sergey O.; Kamanina, Natalia V.; Seisyan, Ruben P.; Gaevski, Michael E.; Nesterov, S. I.; Baidakova, M. V.; Rymalis, M. R.

2001-06-01

352

The Current Performance of the Wide Range (90-2500 eV) Soft X-ray Beamline at the Australian Synchrotron  

SciTech Connect

The Soft X-ray beamline at the Australian synchrotron has been constructed around a collimated light Plane Grating Monochromator taking light from an Elliptically Polarized Undulator (EPU). The beamline covers a wide photon energy range between 90 to 2500 eV, using two gratings of 250 l/mm and 1200 l/mm. At present the output from the monochromator is directed into one branchline with a dedicated UHV endstation. The measured performance of the beamline in flux and resolution is shown to be very close to that of theoretical calculations.

Cowie, B. C. C.; Tadich, A.; Thomsen, L. [Australian Synchrotron, 800 Blackburn Road, Clayton, Victoria (Australia)

2010-06-23

353

Directional Bremsstrahlung from a Ti Laser-Produced X-Ray Source at Relativistic Intensities in the 3-12 keV Range  

SciTech Connect

Front and rear side x-ray emission from thin titanium foils irradiated by ultraintense laser pulses at intensities up to {approx_equal}5x10{sup 19} W/cm{sup 2} was measured using a high-resolution imaging system. Significant differences in intensity, dimension, and spectrum between front and rear side emission intensity in the 3-12 keV photon energy range was found even for 5 {mu}m thin Ti foils. Simulations and analysis of space-resolved spectra explain this behavior in terms of directional bremsstrahlung emission from fast electrons generated during the interaction process.

Zamponi, F.; Luebcke, A.; Kaempfer, T.; Uschmann, I.; Foerster, E. [Institut fuer Optik und Quantenelektronik, Friedrich-Schiller-Universitaet Jena, Max-Wien-Platz 1, 07743 Jena (Germany); Robinson, A. P. L. [Central Laser Facility, STFC Rutherford-Appleton Laboratory, Chilton, OX11 0QX (United Kingdom); Giulietti, A.; Koester, P.; Labate, L.; Levato, T.; Gizzi, L. A. [ILIL, Istituto Nazionale di Ottica, UOS 'Adriano Gozzini', CNR, Via G. Moruzzi 1, Pisa (Italy); INFN, Sezione di Pisa, Largo B. Pontecorvo 3, Pisa (Italy)

2010-08-20

354

STELLAR X-RAY SOURCES IN THE CHANDRA COSMOS SURVEY  

SciTech Connect

We present an analysis of the X-ray properties of a sample of solar- and late-type field stars identified in the Chandra Cosmic Evolution Survey (COSMOS), a deep (160 ks) and wide ({approx}0.9 deg{sup 2}) extragalactic survey. The sample of 60 sources was identified using both morphological and photometric star/galaxy separation methods. We determine X-ray count rates, extract spectra and light curves, and perform spectral fits to determine fluxes and plasma temperatures. Complementary optical and near-IR photometry is also presented and combined with spectroscopy for 48 of the sources to determine spectral types and distances for the sample. We find distances ranging from 30 pc to {approx}12 kpc, including a number of the most distant and highly active stellar X-ray sources ever detected. This stellar sample extends the known coverage of the L{sub X}-distance plane to greater distances and higher luminosities, but we do not detect as many intrinsically faint X-ray sources compared to previous surveys. Overall the sample is typically more luminous than the active Sun, representing the high-luminosity end of the disk and halo X-ray luminosity functions. The halo population appears to include both low-activity spectrally hard sources that may be emitting through thermal bremsstrahlung, as well as a number of highly active sources in close binaries.

Wright, N. J.; Drake, J. J.; Civano, F., E-mail: nwright@cfa.harvard.ed [Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

2010-12-10

355

EUV spectroscopy of high-redshift x-ray objects  

NASA Astrophysics Data System (ADS)

As astronomical observations are pushed to cosmological distances (z>3) the spectral energy distributions of X-ray objects, AGN for example, will be redshifted into the EUV waveband. Consequently, a wealth of critical spectral diagnostics, provided by, for example, the Fe L-shell complex and the O VII/VIII lines, will be lost to future planned X-ray missions (e.g., IXO, Gen-X) if operated at traditional X-ray energies. This opens up a critical gap in performance located at short EUV wavelengths, where critical X-ray spectral transitions occur in high-z objects. However, normal-incidence multilayer-grating technology, which performs best precisely at such wavelengths, together with advanced nanolaminate replication techniques have been developed and are now mature to the point where advanced EUV instrument designs with performance complementary to IXO and Gen-X are practical. Such EUV instruments could be flown either independently or as secondary instruments on these X-ray missions. We present here a critical examination of the limits placed on extragalactic EUV measurements by ISM absorption, the range where high-z measurements are practical, and the requirements this imposes on next-generation instrument designs. We conclude with a discussion of a breakthrough technology, nanolaminate replication, which enables such instruments.

Kowalski, M. P.; Wolff, M. T.; Wood, K. S.; Barbee, T. W., Jr.; Barstow, M. A.

2010-07-01

356

Electron-positron processes and spectral evolution in black hole accretion disk dynamo models for AGN sources of the cosmic X-ray and. gamma. ray backgrounds  

SciTech Connect

This work discusses a black hole accretion disk dynamo model for Active Galactic Nuclei (AGN) sources of the cosmic X-ray and ..gamma.. ray backgrounds which involves both thermal and nonthermal accretion disk processes around greater than or equal to 10/sup 8/M/sub sun/ Kerr black holes. Before black hole spin-up to the Kerr metric state, the large value of the compactness parameter L(luminosity)/r(size of emitting region) > 10/sup 30/erg/cm-sec associated with the L/L/sub Edd/ less than or equal to l luminosity ratio in Precursor Active Galaxies (PAG) suppresses all nonthermal emission mechanisms. In this PAG state the resulting emission is predominantly thermal and is due to Comptonization of soft photons by an electron-positron plasma, generated within the hot accretion disk region by ..gamma.. + ..gamma.. reversible e+/- processes in the transrelativistic regime. While the underlying plasma in the PAG accretion disk hot inner region may be optically thin initially, the overall effect of the copious ..gamma.. + ..gamma.. reversible e+/- generated electron-positron plasma is to push the overall optical depth to tau greater than or equal to 1. This has two main effects: a) it causes the resulting Comptonized spectrum of X-radiation from PAG to be associated with a flat spectral index comparable to that of the residual Cosmic X-ray Background (CXB), and b) the copious ..gamma.. + ..gamma.. reversible e+/- within the hot accretion disk region play the role of a phase transition thermostat, and act to maintain the temperature of the hot inner region at greater than or equal to 109/sup 0/K. 16 references.

Leiter, D.

1983-01-01

357

Continuous hard x-ray imager for astrophysics  

NASA Astrophysics Data System (ADS)

CHIP -- the continuous hard x-ray imager for astrophysics) -- is a powerful hard x ray imaging spectroscopy mission, an order of magnitude more sensitive to hard x rays than XTE, comprised of the large uniform coverage imager (LUCY) for all-sky coverage and the deep extragalactic survey imager (DESI) for more sensitive pointed observations. Both instrument complements will utilize the room temperature semiconductor CdZnTe in mosaiced arrays of position sensitive devices in conjunction with coded masks. Each unit will provide imaging from 2 - 100 keV with approximately 1 keV energy resolution throughout the entire energy range and few arcminute intrinsic spatial resolution. LUCY will provide (1) a complete flux- limited sample of the hard x-ray contents of our galaxy as well as of the extragalactic sky, (2) alarms and precise positions for transient phenomena on all timescales from seconds to days, and (3) continuous spectral/temporal studies of these objects over a vast range of timescales from seconds to days, to months, to years. DESI will extend LUCY's coverage even deeper by viewing a small portion of the hard x-ray sky (0.01 sr) for background limited studies of individual objects considerably deeper than present or future hard x-ray instruments.

Rothschild, Richard E.; Matteson, James L.; Heindl, W.; Peterson, Lawrence E.; Hink, Paul L.

1995-09-01

358

Spectral differences between the radio-loud and radio-quiet low-hard states of GRS 1915+105: Possible detection of synchrotron radiation in X-rays  

NASA Astrophysics Data System (ADS)

The Galactic microquasar GRS 1915+105 exhibits several episodes of steady X-ray emission characterized by a hard power-law spectrum and intense Quasi Periodic Oscillations. It is known that there are two types of such low-hard states, one with steady radio emission and the other without any significant radio emission. We present the results of a detailed X-ray spectroscopic study of GRS 1915+105, using data from the Rossi X-ray Timing Explorer obtained during various episodes of the low-hard states of the source. We show that there are distinct X-ray spectral differences between the radio-quiet and radio-loud low-hard states of the source. The X-ray spectra of the radio-quiet low-hard state is best described by a model consisting of a multicolor disk-blackbody and a Comptonized component, whereas the X-ray spectra of radio-loud low-hard state requires a model consisting of three components: a multicolor disk-blackbody, a Comptonized component and a power-law, for statistically and physically acceptable fits. We attempt to model the presence of this additional power-law component as due to synchrotron radiation which is responsible for the radio and infrared radiation from the source. We show that a simple adiabatically expanding jet model for the synchrotron radiation can account for the observed X-ray flux for reasonable values of the magnetic field and the mass outflow rate. This is the first report of detection of the synchrotron radiation in the X-ray band for this source.

Vadawale, S. V.; Rao, A. R.; Chakrabarti, S. K.

2001-06-01

359

Nanoscale X-ray imaging  

Microsoft Academic Search

Recent years have seen significant progress in the field of soft- and hard-X-ray microscopy, both technically, through developments in source, optics and imaging methodologies, and also scientifically, through a wide range of applications. While an ever-growing community is pursuing the extensive applications of today's available X-ray tools, other groups are investigating improvements in techniques, including new optics, higher spatial resolutions,

Anne Sakdinawat; David Attwood

2010-01-01

360

The Emission from an Inner Disk and a Corona in the Low and Intermediate Spectral States of Black Hole X-Ray Binaries  

NASA Astrophysics Data System (ADS)

Recent observations reveal that a cool disk may survive in the innermost stable circular orbit (ISCO) for some black hole X-ray binaries (BHXRBs) in the canonical low/hard state. The spectrum is characterized by a power law with a photon index ? ~ 1.5-2.1 in the range of 2-10 keV and a weak disk component with a temperature of ~0.2 keV. In this work, we revisit the formation of such a cool, optically thick, geometrically thin disk in the innermost region of BHXRBs at the low/hard state within the context of disk accretion fed by condensation of the hot corona. By taking into account the cooling process associated with both Compton and conductive processes in a corona and the irradiation of the hot corona to the disk, we calculate the structure of the corona. For viscosity parameter ? = 0.2, it is found that the inner disk can exist for an accretion rate ranging from \\dot{M} \\sim 0.006{ to }0.03 \\,\\dot{M}_Edd, over which the electron temperatures of the corona are in the range of 1-5 × 109 K producing the hard X-ray emission. We calculate the emergent spectra of the inner disk and corona for different mass accretion rates. The effect of viscosity parameter ? and albedo a (a is defined as the energy ratio of reflected radiation from the surface of the thin disk to incident radiation upon it from the corona) on the emergent spectra is also presented. Our model is used to explain the recent observations of GX 339-4 and Cyg X-1, in which the thin disk may exist at the ISCO region in the low/hard state at a luminosity around a few percent of L Edd. It is found that the observed maximal effective temperature of the thermal component and the hard X-ray photon index ? can be matched well by our model.

Qiao, Erlin; Liu, B. F.

2012-01-01

361

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

SciTech Connect

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; Guo Liang [Department of Modern Physics and CAS Key Laboratory of Basic Plasma Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang, Sichuan 621900 (China); Jiang Xiaohua; Liu Shenye; Huang Tianxuan; Yang Jiamin; Li Sanwei; Zhao Xuefeng; Du Huabin; Song Tianming; Yi Rongqing; Liu Yonggang; Jiang Shaoen; Ding Yongkun [Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang, Sichuan 621900 (China); Zheng Jian [Department of Modern Physics and CAS Key Laboratory of Basic Plasma Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China)

2010-07-15

362

An observational study of the 2B/X2.8 flare of 30 March, 1982 in optical, radio, and X-ray ranges  

NASA Astrophysics Data System (ADS)

The 2B/X2.8 double-ribbon flare of 30 March, 1982 is investigated using H?, white light, X-rays and microwaves. The X-ray burst seems to consist of two components, i.e., an impulsive component showing a long chain of peaks and a thermal component (T ? 2×107K). A peak of one-directional intensity distribution at 35 GHz always lies on the core of the hard X-ray source, showing a shift of the position synchronous with the hard X-ray core. This may imply a common source for the radio waves and the hard X-rays. The source of the thermal component observed at the soft X-rays (7 - 14 keV) after the early phase covers a whole H? patch. This may imply a physical relation between the thermal X-ray loops and the H? brightening.

Wang, J. L.; Liu, J. Q.; Takakura, T.; Ohki, K.; Kawabata, K.

1987-03-01

363

Comparison of polychromatic and monochromatic x-rays for imaging  

NASA Astrophysics Data System (ADS)

Monochromatic X-rays have been proposed for medical imaging, especially in the mammographic energy range. Our previous investigations have shown that the contrast of objects such as lesions or contrast media can be enhanced considerably by using monochromatic X-rays instead of the common polychromatic spectra. Admittedly, only one specific polychromatic spectrum and one monochromatic energy have been compared so far. In this work, we investigated the contrast yielded by a series of different X-ray spectra obtained by varying tube voltage and beam filtering. This resulted in spectra of different mean energies and spectral widths. The objects under examination were aqueous solutions containing different chemical elements such as I, Gd, Dy, Yb, and Bi. A monoenergetic spectrum at 17.5 keV was obtained using a mammographic X-ray tube with a Mo anode and a monochromator equipped with a HOPG crystal. Moreover, we simulated quasi-monoenergetic spectra at different energies and with different widths. As a result, we demonstrated that in many cases spectra with an energetic width of some keV yield an equivalent contrast to monoenergetic radiation at the same energy. Therefore, the advantage in image contrast of monochromatic X-rays at 17.5 keV over narrow-band polychromatic X-ray spectra obtained by appropriate filtering is only slight. Thus, the additional expenditure on a mammography system with HOPG monochromator that can deliver only a small X-ray dose and the unfavorable slot-scan geometry can be avoided. Moreover, we carried out simulations of monochromatic versus polychromatic spectra throughout the whole radiographic energy range. We found advantages in using monochromatic X-rays at higher energies and thicker objects that will justify their application for diagnostic imaging in a number of specific cases.

Hoheisel, M.; Bernhardt, P.; Lawaczeck, R.; Pietsch, H.

2006-03-01

364

The Off-Plane X-ray Grating Spectrometer for the International X-ray Observatory  

NASA Astrophysics Data System (ADS)

The baseline configuration for the International X-ray Observatory (IXO) includes a soft x-ray grating spectrometer as part of its instrument complement to provide a spectral resolution of R >3000 over the 0.3 - 1 keV band with >1000 square cm effective collecting area. Using the current generation of reflection gratings flown on rocket experiments as a point of departure, an Off-Plane X-ray Grating Spectrometer (OP-XGS) is being proposed to the project to meet this need. These rocket experiments have demonstrated R of >100 with wire grid collimators and objective gratings that produce large point spread functions. Prototype gratings fabricated for the IXO project have achieved adequate throughput to obtain the IXO effective area requirement while resolution tests have demonstrated ?/?? > 200 when used with a 3 arc minute (angular resolution) telescope. When combined with the IXO telescope performance, the resulting spectral resolution is well over the IXO requirement. The OP-XGS will thus provide higher spectral resolution (over a slightly smaller energy range) than the Chandra LETGS instrument but with a larger effective collecting area providing improved sensitivity. The conceptual design and predicted performance of this system is presented here, along with the technology developments that will be needed to achieve the desired performance.

Casement, Suzanne; Johnson, T.; Lillie, C.; McEntaffer, R.; Cash, W.

2009-09-01

365

Electron-positron pairs, Compton reflection, and the X-ray spectra of active galactic nuclei  

Microsoft Academic Search

It is shown here that reprocessing of radiation fron nonthermal pair cascades by cold material in the central parts of active galactic nuclei (AGN) gives rise to X-ray and gamma-ray spectra that satisfy current observational constraints. An average 1-30 keV X-ray spectral index alpha(x) of about 0.7 in the compact range 30-300 is obtained for a wide range of Lorentz

Andrzej A. Zdziarski; Gabriele Ghisellini; Ian M. George; A. C. Fabian; Roland Svensson; Chris Done

1990-01-01

366

X-Ray Optics.  

National Technical Information Service (NTIS)

This final scientific report covers research activities on X-Ray Optics. The report description is contained in the following sections: Preliminary Study of Source Coherency; Lloyd's Mirror Experiment; X-Ray Speckle; Measurement of Film Resolution; Experi...

N. George

1981-01-01

367

X-ray (image)  

MedlinePLUS

X-rays are a form of ionizing radiation that can penetrate the body to form an image on ... will be shades of gray depending on density. X-rays can provide information about obstructions, tumors, and other ...

368

X Ray Topography  

ERIC Educational Resources Information Center

|Discusses some aspects in X-ray topography, including formation of dislocations, characteristics of stacking faults, x-ray contrast in defect inspection, Berg-Barrett technique, and Lang traversing crystal and Borrmann's methods. (CC)|

Balchin, A. A.

1974-01-01

369

Millimetre Observations of X-Ray Bl-Lacertae  

NASA Astrophysics Data System (ADS)

I present the first 1.3-mm observations of a complete sample of 10 X-ray- selected BL Lacertae objects (XBLs), together with complementary measurements of a complete sample of nine radio-selected BL Lacs (RBLs). Three XBLs have firm detections and one has a marginally significant detection. None of the XBLs has a radio spectrum rising steeply into the millimetre region, and the radio-millimetre spectral indices of the XBLs detected are within the range found for the RBLs. However, the overall millimetre-X-ray spectra of the XBLs are much flatter than for any RBL.

Gear, W. K.

1993-10-01

370

X-Ray Telescopes  

NASA Astrophysics Data System (ADS)

X-ray telescopes produce images of x-ray-emitting objects within the telescope's FIELD OF VIEW by reflection from precisely shaped mirrors. Hans Wolter's design in the early 1950s of an x-ray microscope using reflective optics led Riccardo GIACCONI to suggest an `inverted' set of optics, not subject to the fabrication limitations of the microscope, could be used as a cosmic x-ray telescope. As de...

Reid, P.; Murdin, P.

2000-11-01

371

Studies of X-ray Spectral Lines Polarization in Correlation with the Emission of Supra-thermal Electrons in Plasma-Focus Discharges  

Microsoft Academic Search

The correlation of the emission of polarized X-ray lines from highly-ionized argon ions and the emission of intense electron pulses has been observed. The paper presents a review of research on the polarization of the selected X-ray lines and their correlation with pulsed electron beams investigated within the MAJA-PF facility at SINS in Swierk, Poland.

L. Jakubowski; M. J. Sadowski; E. O. Baronova

2006-01-01

372

Studies of X-ray Spectral Lines Polarization in Correlation with the Emission of Supra-thermal Electrons in Plasma-Focus Discharges  

SciTech Connect

The correlation of the emission of polarized X-ray lines from highly-ionized argon ions and the emission of intense electron pulses has been observed. The paper presents a review of research on the polarization of the selected X-ray lines and their correlation with pulsed electron beams investigated within the MAJA-PF facility at SINS in Swierk, Poland.

Jakubowski, L.; Sadowski, M. J. [Andrzej Soltan Institute for Nuclear Studies, 05-400 Otwock-Swierk (Poland); Baronova, E. O. [Nuclear Fusion Institute, NRC Kurchatov Institute, 123182 Moscow (Russian Federation)

2006-12-04

373

Studies of X-ray Spectral Lines Polarization in Correlation with the Emission of Supra-thermal Electrons in Plasma-Focus Discharges  

NASA Astrophysics Data System (ADS)

The correlation of the emission of polarized X-ray lines from highly-ionized argon ions and the emission of intense electron pulses has been observed. The paper presents a review of research on the polarization of the selected X-ray lines and their correlation with pulsed electron beams investigated within the MAJA-PF facility at SINS in Swierk, Poland.

Jakubowski, L.; Sadowski, M. J.; Baronova, E. O.

2006-12-01

374

Comparison of mammography radiation dose values obtained from direct incident air kerma measurements with values from measured X-ray spectral data  

Microsoft Academic Search

The application of X-rays and ionising radiations for diagnostic radiology requires that the procedure is justified and optimised and that the exposure to the patient is kept as low as possible, without compromising image information. X-ray mammography is considered to be the most sensitive technique currently available for early detection of breast cancer. The magnitude of the absorbed radiation dose

M. Assiamah; T. L. Nam; R. J. Keddy

2005-01-01

375

Provenance of Holocene sediment on the Chukchi-Alaskan margin based on combined diffuse spectral reflectance and quantitative X-Ray Diffraction analysis  

USGS Publications Warehouse

Sediment clay and silt mineral assemblages provide an excellent means of assessing the provenance of fine-grained Arctic sediment especially when a unique mineral assemblage can be tied to specific source areas. The diffuse spectral reflectance (DSR) first derivative measurements and quantitative X-Ray Diffraction (qXRD) on a high-resolution sediment core from the continental slope north of Alaska constrain the sediment mineralogy. DSR results are augmented by measurements on several adjacent cores and compared to surface sediment samples from the northern Alaskan shelf and slope. Using Principal Component Analysis (PCA), we infer that the three leading DSR modes relate to mixtures of smectite + dolomite, illite + goethite, and chlorite + muscovite. This interpretation is consistent with the down core qXRD results. While the smectite + dolomite, and illite + goethite factors show increased variability down core, the chlorite + muscovite factor had highest positive loadings in the middle Holocene, between ca. 6.0 and 3.6??ka. Because the most likely source of the chlorite + muscovite suite in this vicinity lies in the North Pacific, we argue that the oscillations in chlorite + muscovite values likely reflect an increase in the inflow of Pacific water to the Arctic through the Bering Strait. The time interval of this event is associated in other parts of the globe with a non-linear response of the climate system to the decrease in insolation, which may be related to changes in water exchange between the Pacific and Arctic Ocean. ?? 2009 Elsevier B.V.

Ortiz, J. D.; Polyak, L.; Grebmeier, J. M.; Darby, D.; Eberl, D. D.; Naidu, S.; Nof, D.

2009-01-01

376

Provenance of Holocene sediment on the Chukchi-Alaskan margin based on combined diffuse spectral reflectance and quantitative X-Ray Diffraction analysis  

NASA Astrophysics Data System (ADS)

Sediment clay and silt mineral assemblages provide an excellent means of assessing the provenance of fine-grained Arctic sediment especially when a unique mineral assemblage can be tied to specific source areas. The diffuse spectral reflectance (DSR) first derivative measurements and quantitative X-Ray Diffraction (qXRD) on a high-resolution sediment core from the continental slope north of Alaska constrain the sediment mineralogy. DSR results are augmented by measurements on several adjacent cores and compared to surface sediment samples from the northern Alaskan shelf and slope. Using Principal Component Analysis (PCA), we infer that the three leading DSR modes relate to mixtures of smectite + dolomite, illite + goethite, and chlorite + muscovite. This interpretation is consistent with the down core qXRD results. While the smectite + dolomite, and illite + goethite factors show increased variability down core, the chlorite + muscovite factor had highest positive loadings in the middle Holocene, between ca. 6.0 and 3.6 ka. Because the most likely source of the chlorite + muscovite suite in this vicinity lies in the North Pacific, we argue that the oscillations in chlorite + muscovite values likely reflect an increase in the inflow of Pacific water to the Arctic through the Bering Strait. The time interval of this event is associated in other parts of the globe with a non-linear response of the climate system to the decrease in insolation, which may be related to changes in water exchange between the Pacific and Arctic Ocean.

Ortiz, Joseph D.; Polyak, Leonid; Grebmeier, Jacqueline M.; Darby, Dennis; Eberl, Dennis D.; Naidu, Sathy; Nof, Doron

2009-07-01

377

Imaging and spectral performance of CdTe double-sided strip detectors for the hard x-ray imager onboard ASTRO-H  

NASA Astrophysics Data System (ADS)

The imaging and spectral performance of CdTe double-sided strip detectors (CdTe-DSDs) was evaluated for the ASTRO-H mission. The charcterized CdTe-DSDs have a strip pitch of 0.25 mm, an imaging area of 3.2 cm × 3.2 cm and a thickness of 0.75 mm. The detector was successfully operated at a temperature of -20°C and with an applied bias voltage of 250 V. By using two-strip events as well as one-strip events for the event reconstruction, a good energy resolution of 2.0 keV at 59.5 keV and a sub-strip spatial resolution was achieved. The hard X-ray and gamma-ray response of CdTe-DSDs is complex due to the properties of CdTe and the small pixel effect. Therefore, one of the issues to investigate is the response of the CdTe-DSD. In order to investigate the spatial dependence of the detector response, we performed fine beam scan experiments at SPring-8, a synchrotron radiation facility. From these experiments, the depth structure of the electric field was determined as well as properties of carriers in the detector and successfully reproduced the experimental data with simulated spectra.

Hagino, Kouichi; Odaka, Hirokazu; Sato, Goro; Watanabe, Shin; Takeda, Shin'ichiro; Kokubun, Motohide; Fukuyama, Taro; Saito, Shinya; Sato, Tamotsu; Ichinohe, Yuto; Takahashi, Tadayuki; Nakano, Toshio; Nakazawa, Kazuhiro; Makishima, Kazuo; Tajima, Hiroyasu; Tanaka, Takaaki; Ishibashi, Kazunori; Miyazawa, Takuya; Sakai, Michito; Sakanobe, Karin; Kato, Hiroyoshi; Takizawa, Shunya; Uesugi, Kentaro

2012-09-01

378

Optical properties of silicon nanocrystals in silica: Results from spectral filtering effect, m-line technique, and x-ray photoelectron spectroscopy  

NASA Astrophysics Data System (ADS)

The optical properties of silica layers containing silicon nanocrystals are analyzed in terms of spectral filtering in absorbing planar waveguides (cutoff spectra), m-line measurements, and x-ray photoelectron spectroscopy (XPS). The effects of optical dispersion, approximation of weak guiding, and depth dependence of refractive index in a planar waveguide are studied. We compare the measured optical properties of silicon-rich silicon oxide samples with the values estimated by the Bruggeman theory using the XPS structural components. A good agreement between the measured and calculated refractive indices is found. The results for absorption suggest high transparency of the nanoscale-suboxide component in contrast to the corresponding bulk material. The Raman intensity of silicon nanocrystals is proportional to the XPS amount of bulk silicon. The extinction coefficient extracted for the Si component is between the values for crystalline and amorphous silicon. Annealing at higher temperatures decreases the Si component extinction coefficient, which is interpreted as a decrease in the amorphous Si fraction. The XPS method surprisingly suggests a large proportion of silicon suboxide even after annealing at 1200 °C.

Khriachtchev, Leonid; Nikitin, Timur; Oton, Claudio J.; Velagapudi, Rama; Sainio, Jani; Lahtinen, Jouko; Novikov, Sergei

2008-11-01

379

Precise measurement of the lattice spacing of LaB{sub 6} standard powder by the x-ray extended range technique using synchrotron radiation  

SciTech Connect

We used the basis of the x-ray extended range technique to measure the lattice spacing of LaB{sub 6} standard powder samples relative to silicon 640b standard powder samples with an accuracy of 5x10{sup -5} A. Measurements were not constrained to one energy but were carried out over a 5 keV-20 keV energy range. These measurements used powder diffraction to determine the synchrotron beam energy, to diagnose discrepancies in the nominal calibrated beam energies, and to determine beam energy bandwidths as a function of energy. More specifically, this technique is able to yield a result independent of certain energy-dependent systematics and to yield the most accurate determination of the lattice spacing of NIST SRM 660 LaB{sub 6} standard powder so far undertaken. This has direct application to beam line energy calibration, structural evaluation, edge energy calibration, and lattice spacing determinations.

Chantler, C.T.; Tran, C.Q. [School of Physics, University of Melbourne, Victoria 3010 (Australia); Cookson, D.J. [ANSTO, Private Mail Bag 1, Menai, New South Wales 2234 (Australia); Chem-Mat-CARS-CAT (Sector 15, Building 434D), Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 6043 (United States)

2004-04-01

380

Soft X-ray microscopy in the spectral region of 'carbon window' with the use of multilayer optics and a laser-plasma source  

SciTech Connect

This paper reports on the fabrication and testing of multilayer mirrors for X-ray optical systems operating in the 'carbon window' region (at wavelengths from 4.5 to 5.0 nm) and the results of their application in soft X-ray imaging of the internal structure of organic objects. The developed approaches to the fabrication and control of graded Co/C multilayer coatings have made it possible to create an X-ray multimirror system with a maximum known entrance aperture and throughput. The use of the developed high-spatial-resolution X-ray optics can significantly extend the field of practical application of soft X-ray absorption microscopy based on compact laser-plasma sources.

Artyukov, I. A., E-mail: iart@sci.lebedev.ru; Vinogradov, A. V. [Russian Academy of Sciences, P.N. Lebedev Physical Institute (Russian Federation); Bugayev, Ye. A.; Devizenko, A. Yu.; Kondratenko, V. V. [National Technical University 'Kharkiv Polytechnical Institute' (Ukraine); Kasyanov, Yu. S. [Russian Academy of Sciences, A.M. Prokhorov General Physics Institute (Russian Federation)

2009-11-15

381

Hand x-ray  

MedlinePLUS

X-ray - hand ... X-rays are a form of electromagnetic radiation like light, but of higher energy. They can pass through ... structures will be shades of gray. A hand x-ray is taken in a hospital radiology department or ...

382

X-Rays  

MedlinePLUS

X-rays are a type of radiation called electromagnetic waves. X-ray imaging creates pictures of the inside of your ... different amounts of radiation. Calcium in bones absorbs x-rays the most, so bones look white. Fat and ...

383

Pelvis x-ray  

MedlinePLUS

X-ray - pelvis ... in the health care provider's office by an x-ray technician. You will be asked to lie down ... The x-ray is used to detect fractures , tumors, or degenerative conditions of bones in the hips, pelvis, and upper ...

384

X-ray spectropolarimeter.  

PubMed

We have constructed a novel single-crystal x-ray spectropolarimeter that separates spatially the two perpendicularly polarized components of an x-ray beam. We have tested this device by using an x-ray tube, and confirmed its performance to be satisfactory as expected from its design. PMID:19044334

Baronova, E O; Stepanenko, M M; Stepanenko, A M

2008-08-01

385

X-Rays  

MedlinePLUS

... X-Rays htmProcedureXray X-rays are waves of electromagnetic radiation that are used to form images of structures ... What Is It? X-rays are waves of electromagnetic radiation that are used to create images of organs ...

386

ROSAT soft X-ray properties of the Large Bright Quasar Survey: modelling of stacked X-ray spectra  

Microsoft Academic Search

We develop and apply a novel method of analysis to study the X-ray spectral properties of 908 QSOs in the Large Bright Quasar Survey (LBQS) that were observed during the soft X-ray ROSAT All-Sky Survey (RASS). Due to the relatively short (<=600s) RASS exposure times, only 10 per cent of the QSOs are detected in X-rays, so X-ray spectral model

Norbert Schartel; Paul J. Green; Scott F. Anderson; Paul C. Hewett; Craig B. Foltz; Bruce Margon; Wolfgang Brinkmann; Henner Fink; Joachim Trumper

1996-01-01

387

ROSAT Soft X-Ray Properties of the Large Bright Quasar Survey: Modeling of Stacked X-Ray Spectra  

Microsoft Academic Search

We develop and apply a novel method of analysis to study the X-ray spectral\\u000aproperties of 908 QSOs in the Large Bright Quasar Survey (LBQS) that were\\u000aobserved during the soft X-ray ROSAT All-Sky Survey (RASS). Due to the\\u000arelatively short (<600sec) RASS exposure times, only 10% of the QSOs are\\u000adetected in X-rays, so X-ray spectral model fits for

Norbert Schartel; Paul J. Green; Scott F. Anderson; Paul C. Hewett; Craig B. Foltz; Bruce Margon; Wolfgang Brinkmann; Henner Fink; Joachim Truemper

1996-01-01

388

Symbiotic stars in X-rays  

NASA Astrophysics Data System (ADS)

Until recently, symbiotic binary systems in which a white dwarf accretes from a red giant were thought to be mainly a soft X-ray population. Here we describe the detection with the X-ray Telescope (XRT) on the Swift satellite of nine white dwarf symbiotics that were not previously known to be X-ray sources and one that had previously been detected as a supersoft X-ray source. The nine new X-ray detections were the result of a survey of 41 symbiotic stars, and they increase the number of symbiotic stars known to be X-ray sources by approximately 30%. The Swift/XRT telescope detected all of the new X-ray sources at energies greater than 2 keV. Their X-ray spectra are consistent with thermal emission and fall naturally into three distinct groups. The first group contains those sources with a single, highly absorbed hard component that we identify as probably coming from an accretion-disk boundary layer. The second group is composed of those sources with a single, soft X-ray spectral component that probably originates in a region where low-velocity shocks produce X-ray emission, i.e., a colliding-wind region. The third group consists of those sources with both hard and soft X-ray spectral components. We also find that unlike in the optical, where rapid, stochastic brightness variations from the accretion disk typically are not seen, detectable UV flickering is a common property of symbiotic stars. Supporting our physical interpretation of the two X-ray spectral components, simultaneous Swift UV photometry shows that symbiotic stars with harder X-ray emission tend to have stronger UV flickering, which is usually associated with accretion through a disk. To place these new observations in the context of previous work on X-ray emission from symbiotic stars, we modified and extended the ?/?/? classification scheme for symbiotic-star X-ray spectra that was introduced by Muerset et al. based upon observations with the ROSAT satellite, to include a new ? classification for sources with hard X-ray emission from the innermost accretion region. Because we have identified the elusive accretion component in the emission from a sample of symbiotic stars, our results have implications for the understanding of wind-fed mass transfer in wide binaries, and the accretion rate in one class of candidate progenitors of type Ia supernovae. Tables 1 and 3 are available in electronic form at http://www.aanda.org

Luna, G. J. M.; Sokoloski, J. L.; Mukai, K.; Nelson, T.

2013-11-01

389

Solar flare hard and soft X ray relationship determined from SMM HXRBS and BCS data  

NASA Astrophysics Data System (ADS)

The exact nature of the solar flare process is still somewhat a mystery. A key element to understanding flares if the relationship between the hard x rays emitted by the most energetic portions of the flare and the soft x rays from other areas and times. This relationship was studied by comparing hard x ray light curved from the Hard X-Ray Burst Spectrometer (HXRBS) with the soft x ray light curve and its derivation from the Bent Crystal Spectrometer (BCS) which is part of the X-Ray Polychrometer (XRP), these instruments being on the Solar Maximum Mission spacecraft (SMM). Data sample was taken from flares observed with the above instruments during 1980, the peak of the previous maximum of solar activity. Flares were chosen based on complete coverage of the event by several instruments. The HXRBS data covers the x ray spectrum from about 25 keV to about 440 keV in 15 spectral channels, while the BCS data used covers a region of the Spectrum around 3 angstroms including emission from the Ca XIX ion. Both sets of data were summed over their spectral ranges and plotted against time at a maximum time resolution of around 3 seconds. The most popular theory of flares holds that a beam of electrons produces the hard x rays by bremsstrahlung while the soft x rays are the thermal response to this energy deposition. The question is whether the rate of change of soft x ray emission might reflect the variability of the electron beam and hence the variability of the hard x rays. To address this, we took the time derivative of the soft x ray light curve and compared it to the hard flares, 12 of them showed very closed agreement between the soft x ray derivative and the hard x ray light curve. The other five did not show this behavior but were similar to each other in general soft x ray behavior. Efforts to determine basic differences between the two kinds of flares continue. In addition the behavior of soft x ray temperature of flares was examined.

Toot, G. David

1989-09-01

390

X-Ray Spectra  

NSDL National Science Digital Library

In this activity, learners use simple materials to simulate the effect of X-rays in a safe way. Learners place a piece of window screen over a box and a cardboard pattern on top of the screen. They sprinkle sand over the area of the box. The sand simulates X-rays passing through the screen to the bottom of the box, except where they are blocked by the cardboard. Use this activity to demonstrate how X-rays create an image, including "soft" and shorter wavelength X-rays as well as X-rays from space.

Fetter, Neil

2007-01-01

391

Flat Field Anomalies in an X-ray CCD Camera Measured Using a Manson X-ray Source  

SciTech Connect

The Static X-ray Imager (SXI) is a diagnostic used at the National Ignition Facility (NIF) to measure the position of the X-rays produced by lasers hitting a gold foil target. The intensity distribution taken by the SXI camera during a NIF shot is used to determine how accurately NIF can aim laser beams. This is critical to proper NIF operation. Imagers are located at the top and the bottom of the NIF target chamber. The CCD chip is an X-ray sensitive silicon sensor, with a large format array (2k x 2k), 24 ?m square pixels, and 15 ?m thick. A multi-anode Manson X-ray source, operating up to 10kV and 10W, was used to characterize and calibrate the imagers. The output beam is heavily filtered to narrow the spectral beam width, giving a typical resolution E/?E?10. The X-ray beam intensity was measured using an absolute photodiode that has accuracy better than 1% up to the Si K edge and better than 5% at higher energies. The X-ray beam provides full CCD illumination and is flat, within ±1% maximum to minimum. The spectral efficiency was measured at 10 energy bands ranging from 930 eV to 8470 eV. We observed an energy dependent pixel sensitivity variation that showed continuous change over a large portion of the CCD. The maximum sensitivity variation occurred at 8470 eV. The geometric pattern did not change at lower energies, but the maximum contrast decreased and was not observable below 4 keV. We were also able to observe debris, damage, and surface defects on the CCD chip. The Manson source is a powerful tool for characterizing the imaging errors of an X-ray CCD imager. These errors are quite different from those found in a visible CCD imager.

M. J. Haugh and M. B. Schneider

2008-10-31

392

X-ray lithography using holographic images  

DOEpatents

A non-contact X-ray projection lithography method for producing a desired X-ray image on a selected surface of an X-ray-sensitive material, such as photoresist material on a wafer, the desired X-ray image having image minimum linewidths as small as 0.063 .mu.m, or even smaller. A hologram and its position are determined that will produce the desired image on the selected surface when the hologram is irradiated with X-rays from a suitably monochromatic X-ray source of a selected wavelength .lambda.. On-axis X-ray transmission through, or off-axis X-ray reflection from, a hologram may be used here, with very different requirements for monochromaticity, flux and brightness of the X-ray source. For reasonable penetration of photoresist materials by X-rays produced by the X-ray source, the wavelength X, is preferably chosen to be no more than 13.5 nm in one embodiment and more preferably is chosen in the range 1-5 nm in the other embodiment. A lower limit on linewidth is set by the linewidth of available microstructure writing devices, such as an electron beam.

Howells, Malcolm R. (Berkeley, CA); Jacobsen, Chris (Sound Beach, NY)

1995-01-01

393

Automated software for the recovery of the short range order parameters from diffuse X-ray scattering data  

NASA Astrophysics Data System (ADS)

We have developed software to accelerate the analysis of the diffuse scattering data and to recover the short-range-order (SRO) and other parameters. The software is applied to data collected from a Cu50Au50 single crystal.

Puzyrev, Y. S.; Ice, G. E.; Sparks, C. J.; Robertson, L.

2007-11-01

394

Monte Carlo Simulations of High-Speed, Time-Gated MCP-based X-ray Detectors: Saturation Effects in DC Pulsed Modes and Detector Dynamic Range  

SciTech Connect

We present here results of continued efforts to understand the performance of microchannel plate (MCP)–based, high-speed, gated, x-ray detectors. This work involves the continued improvement of a Monte Carlo simulation code to describe MCP performance coupled with experimental efforts to better characterize such detectors. Our goal is a quantitative description of MCP saturation behavior in both static and pulsed modes. A new model of charge buildup on the walls of the MCP channels is briefly described. The simulation results agree favorably with experimental data obtained with a short-pulse, high-intensity ultraviolet (UV) laser. These results indicate that a weak saturation can change the exponent of gain with voltage and that a strong saturation lead to a gain plateau. These results also demonstrate that the dynamic range of an MCP in pulsed mode has a value of between 10^2 and 10^3.

Craig Kruschwitz, Ming Wu, Ken Moy, Greg Rochau

2008-05-30

395

Mass attenuation coefficients of natural Rhizophora spp. wood for X-rays in the 15.77-25.27 keV range.  

PubMed

The mass attenuation coefficients (mu/rho) of Rhizophora spp. were determined for photons in the energy range of 15.77-25.27 keV. This was carried out by studying the attenuation of X-ray fluorescent photons from zirconium, molybdenum, palladium, silver, indium and tin targets. The results were compared with theoretical values for average breast tissues in young-age, middle-age and old-age groups calculated using photon cross section database (XCOM), the well-known code for calculating attenuation coefficients and interaction cross-sections. The measured mass attenuation coefficients were found to be very close to the calculated XCOM values in breasts of young-age group. PMID:19482883

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

2009-05-29

396

Comparison of the NIST and BIPM air-kerma standards for measurements in the low-energy x-ray range  

SciTech Connect

A direct comparison was made between the air-kerma standards used for the measurement of low-energy x rays at the National Institute of Standards and Technology (NIST) and the Bureau International des Poids et Mesures (BIPM). The comparison was carried out at the BIPM using the BIPM reference beam qualities in the range from 10kV to 100 kV. The results show the standards to be in agreement to around 0.5% at reference beam qualities up to 50kV and at 100 kV. The result at the 80kV beam quality is less favorable, with agreement at the 1% level.

Burns, D.T. [Bureau International des Poids et Mesures, Sevres (France); Lamperti, P.; O`Brien, M. [National Inst. of Standards and Technology, Gaithersburg, MD (United States)

1999-03-01

397

Structure and Orientation of the Mn4Ca Cluster in PlantPhotosystem II Membranes Studied by Polarized Range-Extended X-rayAbsorption Spectroscopy  

SciTech Connect

X-ray absorption spectroscopy has provided importantinsights into the structure and function of the Mn4Ca cluster in theoxygen-evolving complex (OEC) of Photosystem II (PS II). The range of Mnextended X-ray absorption fine structure (EXAFS) data collected from PSII until now has been, however, limited by the presence of Fe in PS II.Using a crystal spectrometer with high energy resolution to detect solelythe Mn K alpha fluorescence, we are able to extend the EXAFS range beyondthe onset of the Fe absorption edge. This results in improvement inresolution of the Mn-backscatterer distances in PS II from 0.14 Angstromto 0.09 Angstrom. The high-resolution data obtained from oriented spinachPS II membranes in the S1 state show that there are threedi-?-oxo-bridged Mn-Mn distances of ~;2.7 Angstrom and ~;2.8 Angstrom ina 2:1 ratio and that these three Mn-Mn vectors are aligned at an averageorientation of ~;60 deg relative to the membrane normal. Furthermore, weare able to observe the separation of the Fourier peaks corresponding tothe ~;3.2 Angstrom Mn-Mn and the ~;3.4 Angstrom Mn-Ca interactions inoriented PS II samples and determine their orientation relative to themembrane normal. The average of the Mn-Ca vectors at ~;3.4 Angstrom isaligned along the membrane normal, while the ~;3.2 Angstrom Mn-Mn vectoris oriented near the membrane plane. A comparison of this structuralinformation with the proposed Mn4Ca cluster models based on spectroscopicand diffraction data provide input for refining and selecting among thesemodels.

Pushkar, Yulia; Yano, Junko; Glatzel, Pieter; Messinger,Johannes; Lewis, Azul; Sauer, Kenneth; Bergmann, Uwe; Yachandra, Vittal K.

2006-11-10

398

Resonant Compton Scattering and the Hard X-ray Tails of Anomalous X-ray Pulsars  

Microsoft Academic Search

A significant new development in the study of Anomalous X-ray Pulsars (AXPs) has been the recent discovery by INTEGRAL and RXTE of flat, hard X-ray components in three AXPs. These non-thermal spectral components differ dramatically from the steeper quasi-power-law tails seen in the classic X-ray band in these sources. A prime candidate mechanism for generating this new component is resonant,

Matthew G. Baring; A. K. Harding

2006-01-01

399

Heavy X-Ray Absorption in Soft X-Ray-weak Active Galactic Nuclei  

Microsoft Academic Search

Recent ROSAT studies have identified a significant population of active galactic nuclei (AGNs) that are notably faint in soft X-rays relative to their optical fluxes. Are these AGNs intrinsically X-ray weak or are they highly absorbed? Brandt, Laor, & Wills have systematically examined the optical and UV spectral properties of a well-defined sample of these soft X-ray-weak (SXW) AGNs drawn

S. C. Gallagher; W. N. Brandt; A. Laor; M. Elvis; S. Mathur; Beverley J. Wills; N. Iyomoto

2001-01-01

400

Creation of Bragg x-ray optics for imaging spectroscopy of plasma microsources  

Microsoft Academic Search

Creation of Bragg X-ray optics based on transmitted and reflection crystals, bent on cylindrical or spherical surfaces, is discussed. Application of such optics for obtaining one and two dimensional monochromatic images of different plasma sources in the wide spectral range 1 - 20 angstroms are described. Samples of spectra obtained with spectral resolution up to (lambda) \\/(Delta) (lambda) approximately 1000

Tatyana A. Pikouz; B. A. Bryunetkin; Anatoly Y. Faenov; S. A. Pikuz; V. M. Romanova; T. A. Shelkovenko

1994-01-01

401

Optics-free x-ray FEL oscillator  

SciTech Connect

There is a need for an Optics-Free FEL Oscillators (OFFELO) to further the advantages of free-electron lasers and turning them in fully coherent light sources. While SASE (Self-Amplified Spontaneous Emission) FELs demonstrated the capability of providing very high gain and short pulses of radiation and scalability to the X-ray range, the spectra of SASE FELs remains rather wide ({approx}0.5%-1%) compared with typical short wavelengths FEL-oscillators (0.01%-0.0003% in OK-4 FEL). Absence of good optics in VUV and X-ray ranges makes traditional oscillator schemes with very high average and peak spectral brightness either very complex or, strictly speaking, impossible. In this paper, we discuss lattice of the X-ray optics-free FEL oscillator and present results of initial computer simulations of the feedback process and the evolution of FEL spectrum in X-ray OFFELO. We also discuss main limiting factors and feasibility of X-ray OFFELO.

Litvinenko, V.N.; Hao, Y.; Kayran, D.; Trbojevic, D.

2011-03-28

402

Microsecond Z-pinch as ultrasoft X-ray radiation source  

Microsoft Academic Search

Spectral characterictics of plasma radiation of a gas Z-pinch with a rise time of 1 µs and current amplitude of 250 kA have been measured. The measurements were performed in the range of X-ray energy quanta from 30 eV to 600 eV. A spectrograph with a transmission grating and a polychromator on the basis of multilayer X-ray mirrors served as

G. S. Volkov; V. I. Zaitsev; A. V. Kartashov; N. I. Lahtushko; A. A. Rupasov; A. S. Shikanov

2004-01-01

403

Synchrotron Tests of a 3D Medipix2 X-Ray Detector  

Microsoft Academic Search

Three-dimensional (3D) photodiode detectors offer advantages over standard planar photodiodes in a range of applications, including X-ray detection for synchrotrons and medical imaging. The principal advantage of these sensors for X-ray imaging is their low charge sharing between adjacent pixels, which could improve spatial and spectral resolution. A 'double-sided' 3D detector has been bonded to a Medipix2 single-photon-counting readout chip,

David Pennicard; Julien Marchal; Celeste Fleta; Giulio Pellegrini; Manuel Lozano; Chris Parkes; Nicola Tartoni; Damien Barnett; Igor Dolbnya; Kawal Sawhney; Richard Bates; Val O'Shea; Victoria Wright

2010-01-01

404

Einstein Observatory X-Ray Spectra of Bl-Lacertae Objects  

Microsoft Academic Search

In this paper, we summarize the spectral X-ray data obtained with the Imaging Proportional Counter flown on the Einstein Observatory and interpret that data in the context of the overall electromagnetic distribution. The X-ray spectra in the IPC (0.2 - 4.0 keV) range are generally well represented by a model incorporating an intrinsic power law with a mean value of

G. M. Madejski; D. A. Schwarz

1989-01-01

405

Ultrahigh resolution photographic films for X-ray\\/EUV\\/FUV astronomy  

Microsoft Academic Search

The quest for ultrahigh resolution full-disk images of the sun at soft X-ray\\/EUV\\/FUV wavelengths has increased the demand for photographic films with broad spectral sensitivity, high spatial resolution, and wide dynamic range. These requirements were made more stringent by the recent development of multilayer telescopes and coronagraphs capable of operating at normal incidence at soft X-ray\\/EUV wavelengths. Photographic films are

Richard B. Hoover; Arthur B. C. Walker Jr.; Craig E. Deforest; Richard Watts; Charles Tarrio

1993-01-01

406

X-ray fluorescence holography  

NASA Astrophysics Data System (ADS)

X-ray fluorescence holography (XFH) is a method of atomic resolution holography which utilizes fluorescing atoms as a wave source or a monitor of the interference field within a crystal sample. It provides three-dimensional atomic images around a specified element and has a range of up to a few nm in real space. Because of this feature, XFH is expected to be used for medium-range local structural analysis, which cannot be performed by x-ray diffraction or x-ray absorption fine structure analysis. In this article, we explain the theory of XFH including solutions to the twin-image problem, an advanced measuring system, and data processing for the reconstruction of atomic images. Then, we briefly introduce our recent applications of this technique to the analysis of local lattice distortions in mixed crystals and nanometer-size clusters appearing in the low-temperature phase of a shape-memory alloy.

Hayashi, Kouichi; Happo, Naohisa; Hosokawa, Shinya; Hu, Wen; Matsushita, Tomohiro

2012-03-01

407

Calibration of a high resolution grating soft x-ray spectrometer.  

PubMed

The calibration of the soft x-ray spectral response of a large radius of curvature, high resolution grating spectrometer (HRGS) with a back-illuminated charge-coupled device detector is reported. The instrument is cross-calibrated for the 10-50 A? waveband at the Lawrence Livermore National Laboratory electron beam ion trap (EBIT) x-ray source with the EBIT calorimeter spectrometer. The HRGS instrument is designed for laser-produced plasma experiments and is important for making high dynamic range measurements of line intensities, line shapes, and x-ray sources. PMID:21034013

Magee, E W; Dunn, J; Brown, G V; Cone, K V; Park, J; Porter, F S; Kilbourne, C A; Kelley, R L; Beiersdorfer, P

2010-10-01

408

Broad Band Long Term Monitoring of X-Ray Bursters.  

National Technical Information Service (NTIS)

We have analysed the BATSE (Burst and Transient Source Experiment) long term monitoring data of X-ray bursters. We generated the long-term light-curves of several X-ray bursters and studied their spectral evolution and compared them with black hole X-ray ...

S. N. Zhang

2001-01-01

409

X-ray Polarimetry  

NASA Astrophysics Data System (ADS)

1. X-ray polarimetry: historical remarks and other considerations; Part I. Polarimetry Techniques: 2. Scattering polarimetry in high energy astronomy; 3. Photoelectric polarimeters; 4. Bragg crystal polarimeters; 5. X-ray polarimetry with the photon counting pixel detector timepix; 6. HE polarized photon interactions with matter: simulations with geant4; 7. The GPD as a polarimeter: theory and facts; 8. Ideal gas electron multipliers (GEMs) for x-ray polarimeters; 9. Broad-band soft x-ray polarimetry; 10. Feasibility of x-ray photoelectric polarimeters with large field of view; 11. Angular resolution of a photoelectric polarimeter; 12. Development of a Thomson x-ray polarimeter; 13. Hard x / soft gamma ray polarimetry using a Laue lens; Part II. Polarized Emission in X-ray Sources: 14. Probing strong gravity effects with x-ray polarimetry; 15. X-ray polarization from black holes in the thermal state; 16. Strong-gravity effects acting on polarization from orbiting spots; 17. Polarization of thermal emission from accreting black holes; 18. X-ray polarimetry and radio-quiet AGN; 19. The soft x-ray polarization in obscured AGN; 20. The polarization of complex x-ray sources; 21. Polarization of Compton x-rays from jets in AGN; 22. Polarization of x-ray lines from galaxy clusters and elliptical galaxies; 23. Polarization characteristics of rotation-powered pulsars; 24. Polarized x-rays from magnetized neutron stars; 25. Polarization properties of x-ray millisecond pulsars; 26. X-ray polarization signatures of neutron stars; 27. Polarization from the oscillating magnetized accretion torus; 28. X-ray polarization from accreting white dwarfs and associated systems; 29. Polarization of pulsar wind nebulae; 30. X-ray polarization of gamma-ray bursts; 31. Central engine afterglow from GRBs and the polarization signature; 32. GRB afterglow polarimetry. Past, present and future; 33. Gamma-ray polarimetry with SPI; 34. INTEGRAL/IBIS observations of the Crab Nebula and GRB 041219A; 35. Fermi results on the origin of high energy emission in pulsars; 36. Diagnostics of the evolution of spiral galaxies in a cluster environment; Part III. Future Missions: 37. Gravity and extreme magnetism SMEX (GEMS); 38. Programs of x-ray polarimetry in Italy; 39. A polarimeter for IXO; 40. Polarimetry with ASTRO-H soft gamma-ray detector; 41. EXIST and its polarization sensitivity; 42. PoGOLite: a balloon-borne soft gamma-ray polarimeter; 43. Studies of neutron background rejection in the PoGOLite polarimeter; 44. Observing polarized x-rays with PoGOLite; 45. Pre-flight qualification tests of the PoGOLite detector system; 46. The gamma-ray polarimeter experiment (GRAPE) Balloon Payload; 47. POLAR: an instrument dedicated to GRB polarization measurement; 48. Polarisation detection capability of GRIPS; 49. X-ray and y-ray polarimetry small satellite mission polaris; 50. GAP aboard the solar powered sail mission; 51. Hard x-ray polarimeter for small satellite missions; 52. Performance of hard x-ray polarimeter: PHENEX; 53. GRB polarimetry with POET; Index.

Bellazzini, Ronaldo; Costa, Enrico; Matt, Giorgio; Tagliaferri, Gianpiero

2010-07-01

410

X-ray microscopy  

Microsoft Academic Search

Ever since W. C. Röntgen discovered his x-rays there was a desire to create a useful x-ray microscopy. The fact that the index of refraction deviates so little from that of vacuum causes, however, great difficulties in developing suitable x-ray optical elements. Quite generally, the low efficiency even of the now existing optical elements and the low brilliance of classical

C. Kunz

1996-01-01

411

X ray imaging system  

NASA Astrophysics Data System (ADS)

The invention provides a method and apparatus for focusing and imaging x-rays. An opaque sphere is used as a diffractive imaging element to diffract x-rays from an object. The divergent x-ray wavefronts are then transformed into convergent wavefronts. The convergent wavefronts are brought into focus to form an image of the object. The new image has a large depth of field.

Sommargren, G. E.; Weaver, H. J.

1990-04-01

412

X ray imaging system  

Microsoft Academic Search

The invention provides a method and apparatus for focusing and imaging x-rays. An opaque sphere is used as a diffractive imaging element to diffract x-rays from an object. The divergent x-ray wavefronts are then transformed into convergent wavefronts. The convergent wavefronts are brought into focus to form an image of the object. The new image has a large depth of

G. E. Sommargren; H. J. Weaver

1990-01-01

413

THE EFFECT OF CORONAL RADIATION ON A RESIDUAL INNER DISK IN THE LOW/HARD SPECTRAL STATE OF BLACK HOLE X-RAY BINARY SYSTEMS  

SciTech Connect

Thermal conduction between a cool accretion disk and a hot inner corona can result in either evaporation of the disk or condensation of the hot corona. At low mass accretion rates, evaporation dominates and can completely remove the inner disk. At higher mass accretion rates, condensation becomes more efficient in the very inner regions, so that part of the mass accretes via a weak (initially formed) inner disk which is separated from the outer disk by a fully evaporated region at mid radii. At still higher mass accretion rates, condensation dominates everywhere, so there is a continuous cool disk extending to the innermost stable circular orbit. We extend these calculations by including the effect of irradiation by the hot corona on the disk structure. The flux which is not reflected is reprocessed in the disk, adding to the intrinsic thermal emission from gravitational energy release. This increases the seed photons for Compton cooling of the hot corona, enhancing condensation of the hot flow, and reinforcing the residual inner disk rather than evaporating it. Our calculations confirm that a residual inner disk can coexist with a hard, coronally dominated spectrum over the range of 0.006< m-dot <0.016 (for {alpha} = 0.2). This provides an explanation for the weak thermal component seen recently in the low/hard state of black hole X-ray binary systems.

Liu, B. F. [National Astronomical Observatories/Yunnan Observatory, Chinese Academy of Sciences, P.O. Box 110, Kunming 650011 (China); Done, C. [Department of Physics, University of Durham, South Road, Durham, DH1 3LE (United Kingdom); Taam, Ronald E., E-mail: bfliu@ynao.ac.cn, E-mail: r-taam@northwestern.edu, E-mail: bfliu@nao.cas.cn [Department of Physics and Astronomy, Northwestern University, 2131 Tech Drive, Evanston, IL 60208 (United States)

2011-01-01

414

X-ray Astronomy and the Analysis of X-ray Data  

Microsoft Academic Search

The Chandra X-ray Observatory, launched in 1999, continues to return spectacular scientific results thanks to its combination of high spatial and spectral resolution. I will discuss a selection of these results, and draw attention to the specific data analysis challenges posed by X-ray observatories in general, leading to the identification of the spatial distribution of elements in supernova remnants, the

J. C. McDowell

2006-01-01

415

Multilayer X-ray Optical Systems for Future X-ray Astronomy Missions  

Microsoft Academic Search

The development of multilayers makes it possible to construct a normal incidence soft X ray telescope with high angular resolution and a grazing incidence hard X ray telescope sensitive up to 100 keV using a multilayer supermirror. A multilayer coated grating is also a useful dispersive element with high efficiency and spectral resolution in the Extreme Ultraviolet Radiation (EUV) and

Koujun Yamashita

1997-01-01

416

X-ray Interferometry  

NASA Astrophysics Data System (ADS)

X-ray interferometry is well on its way to becoming a reality. We present an update on MAXIM, the Micro-Arcsecond X-ray Imaging Mission. With the eventual goal of imaging the event horizon of a black hole, MAXIM will require a phased array of x-ray mirrors across a one kilometer aperture. Recent design advances, backed by demonstrations in the laboratory have established that such a mission is not only feasible, but affordable. Soon, x-ray observatories may rise to the standards set by radio astronomers.

Cash, W.

2005-12-01

417

Einstein Observatory magnitude-limited X-ray survey of late-type giant and supergiant stars  

SciTech Connect

Results are presented of an extensive X-ray survey of 380 giant and supergiant stars of spectral types from F to M, carried out with the Einstein Observatory. It was found that the observed F giants or subgiants (slightly evolved stars with a mass M less than about 2 solar masses) are X-ray emitters at the same level of main-sequence stars of similar spectral type. The G giants show a range of emissions more than 3 orders of magnitude wide; some single G giants exist with X-ray luminosities comparable to RS CVn systems, while some nearby large G giants have upper limits on the X-ray emission below typical solar values. The K giants have an observed X-ray emission level significantly lower than F and F giants. None of the 29 M giants were detected, except for one spectroscopic binary. 79 refs.

Maggio, A.; Vaiana, G.S.; Haisch, B.M.; Stern, R.A.; Bookbinder, J. (Osservatorio Astronomico, Palermo (Italy) Lockheed Research Laboratories, Palo Alto, CA (USA) Joint Institute for Laboratory Astrophysics, Boulder, CO (USA) Smithsonian Astrophysical Observatory, Cambridge, MA (USA))

1990-01-01

418

X-ray photon spectroscopy calculations  

SciTech Connect

X-ray photons - as many other particles - interact with matter producing secondary radiation that carries useful information about the atoms comprising the target. The availability of intense sources of highly monochromatic X-rays and the great improvement in detector technology intensified research in X-ray spectrometry in the last twenty years. New techniques allowed the attenuation coefficients and the physics of the atom to be better known: Extended X-ray Absorption Fine Structure (EXAFS), X-ray Absorption Near Edge Structure (XANES), and Inelastic X-ray Scattering Spectroscopy (IXSS). Old techniques, like X-ray Fluorescence (XRF), gained in precision thus extending the horizon of applicability to new elements and energy ranges, and consequently Energy Dispersive X-ray Fluorescence (EDXRF) and Synchrotron Radiation X-ray Fluorescence (SRXRF) were evolved. Particle induced X-ray emission spectroscopy also benefited from this improvement. The field of application of X-ray spectrometry has grown from atomic, to nuclear, to plasma physics, to astrophysics. In this work the authors summarize the knowledge recently gained about how the intensity due to multiple scattering perturbs the first-order terms of the three processes of main interest in X-ray spectrometry between 1 keV and 100 keV: the photoelectric, the Rayleigh and the Compton effects. They show that the contribution of a few orders of scattering, calculated in the frame of transport theory, allows the construction of a theoretical X-ray spectrum that matches well experimental data from targets of homogeneous composition and infinite thickness. 99 refs., 15 figs.

Fernandez, J.E.; Molinari, V.G. [Univ. of Bologna (Italy)

1991-12-31

419

Instrumentation for Microfabrication with Deep X-ray Lithography  

Microsoft Academic Search

Deep X-ray lithography for microfabrication is performed at least at ten synchrotron radiation centers worldwide. The characteristic energies of these sources range from 1.4 keV up to 8