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1

Apparent Linear Attenuation Coefficients in Phase Contrast X-Ray Tomography  

PubMed Central

In the inline phase contrast x-ray tomography the reconstructed apparent linear attenuation coefficient values may be greatly larger than sample’s linear attenuation coefficients or even be negative. In this work we present a general formula to quantitatively relate the apparent linear attenuation coefficient values in cone-beam phase contrast tomography to sample’s linear attenuation coefficients and refractive indices. This formula overcomes the gross inaccuracy of the existing formula in the literature in analyzing high-resolution phase contrast tomography, and it will be useful for correctly interpreting and quantifying the apparent linear attenuation coefficients in cone-beam x-ray phase contrast tomography.

Yan, Aimin; Wu, Xizeng

2011-01-01

2

Experimental X-ray attenuation coefficients at low photon energies for substances of medical importance.  

PubMed

Recent experimental values of X-ray mass attenuation coefficients for the elements zota = 6 to zota = 18 in the energy range from 4 to 25 keV suggest improvements to the data set presented in the ICRU Report 17. The results are, however, in excellent agreement with the theoretical data of Storm and Israel (1970). Values of mass attenuation coefficient for these elements and for a selection of materials of medical and biological importance are presented. PMID:1202514

Millar, R H

1975-11-01

3

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

4

Measurement of the x-ray mass attenuation coefficient and the imaginary part of the form factor of silicon using synchrotron radiation  

SciTech Connect

We used the x-ray extended-range technique to measure the x-ray mass attenuation coefficients of silicon with an accuracy between 0.27% and 0.5% in the 5 keV-20 keV energy range. Subtraction of the x-ray scattering contribution enabled us to derive the corresponding x-ray photoelectric absorption coefficients and determine the absolute value of the imaginary part of the atomic form factor of silicon. Discrepancies between the experimental values of the mass attenuation coefficients and theoretically calculated values are discussed. New approaches to the theoretical calculation will be required to match the precision and accuracy of the experimental results.

Tran, C.Q.; Chantler, C.T.; Barnea, Z.; Paterson, D.; Cookson, D.J. [School of Physics, University of Melbourne, Victoria 3010 (Australia); SRI-CAT, APS, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439 (United States); 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)

2003-04-01

5

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

6

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

7

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

NASA Astrophysics Data System (ADS)

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

Midgley, S. M.

2005-03-01

8

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

9

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

10

X-Ray Attenuation and Absorption for Materials of Dosimetric Interest  

National Institute of Standards and Technology Data Gateway

SRD 126 X-Ray Attenuation and Absorption for Materials of Dosimetric Interest (Web, free access)   Tables and graphs of the photon mass attenuation coefficient and the mass energy-absorption coefficient are presented for all of the elements Z = 1 to 92, and for 48 compounds and mixtures of radiological interest. The tables cover energies of the photon (x-ray, gamma ray, bremsstrahlung) from 1 keV to 20 MeV.

11

X-ray attenuation properties of stainless steel (u)  

SciTech Connect

Stainless steel vessels are used to enclose solid materials for studying x-ray radiolysis that involves gas release from the materials. Commercially available stainless steel components are easily adapted to form a static or a dynamic condition to monitor the gas evolved from the solid materials during and after the x-ray irradiation. Experimental data published on the x-ray attenuation properties of stainless steel, however, are very scarce, especially over a wide range of x-ray energies. The objective of this work was to obtain experimental data that will be used to determine how a poly-energetic x-ray beam is attenuated by the stainless steel container wall. The data will also be used in conjunction with MCNP (Monte Carlos Nuclear Particle) modeling to develop an accurate method for determining energy absorbed in known solid samples contained in stainless steel vessels. In this study, experiments to measure the attenuation properties of stainless steel were performed for a range of bremsstrahlung x-ray beams with a maximum energy ranging from 150 keV to 10 MeV. Bremsstrahlung x-ray beams of these energies are commonly used in radiography of engineering and weapon components. The weapon surveillance community has a great interest in understanding how the x-rays in radiography affect short-term and long-term properties of weapon materials.

Wang, Lily L [Los Alamos National Laboratory; Berry, Phillip C [Los Alamos National Laboratory

2009-01-01

12

X-ray phase-attenuation duality and phase retrieval  

Microsoft Academic Search

Phase retrieval is the key to quantitative x-ray phase-contrast imaging. To retrieve the phase image of an x-ray wave field, in general one needs multiple phase-contrast images. We have made a new observation of phase-attenuation duality for soft tissues, and we show how only a single phase-contrast image is needed for successful phase retrieval based on this duality. The phase-retrieval

Xizeng Wu; Hong Liu; Aimin Yan

2005-01-01

13

Effective x-ray attenuation measurements with full field digital mammography  

SciTech Connect

This work shows that effective x-ray attenuation coefficients may be estimated by applying Beer's Law to phantom image data acquired with the General Electric Senographe 2000D full field digital mammography system. Theoretical developments are provided indicating that an approximate form of the Beer's relation holds for polychromatic x-ray beams. The theoretical values were compared with experimentally determined measured values, which were estimated at various detector locations. The measured effective attenuation coefficients are in agreement with those estimated with theoretical developments and numerical integration. The work shows that the measured quantities show little spatial variation. The main ideas are demonstrated with polymethylmethacrylate and breast tissue equivalent phantom imaging experiments. The work suggests that the effective attenuation coefficients may be used as known values for radiometric standardization applications that compensate for the image acquisition influences. The work indicates that it is possible to make quantitative attenuation coefficient measurements from a system designed for clinical purposes.

Heine, John J.; Behera, Madhusmita [The H. Lee Moffitt Cancer Center and Research Institute, 12902 Magnolia Drive, Tampa, Florida 33612-4799 (United States)

2006-11-15

14

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

15

Novel x-ray attenuation mechanism: Role of interatomic distance  

SciTech Connect

Little progress has been made over the last 30 years for improving attenuation by x-ray contrast agents, in part because the mechanisms of x-ray attenuation are thought to be well understood. We hypothesized that x-ray absorbance can be modulated by altering the interatomic spacing between K-edge attenuating atoms. Iodomethane, diiodomethane, 2,6-diiodo-4-nitroanaline, and diiodobenzene isomers were dissolved in DMSO and imaged with an OEC Compact 7600 fluoroscope. At a tube voltage of 42 kVp, absorbance of equimolar diiodomethane (150 mM) was significantly (p<0.01) greater than iodomethane (150 mM) by 45%. Interestingly, 150 mM diiodomethane absorbance was significantly greater than 300 mM iodomethane (by 5%, p<0.01) despite equal amounts of iodine in both solutions. 1,3-diiodobenzene absorbance was significantly greater than 1,2- and 1,4-diiodobenzene (p<0.01). However, 2,6-diiodo-4-nitroanaline absorbance was similar to 1,3-diiodobenzene. When a linear model was fit for absorbance as a function of density and harmonic error (the fractional remainder of the inter-iodine distance and the K-shell ionizing wavelength) at different beam energies, a significant overall fit was obtained for both unfiltered and hardened beams (p<0.01). While the slope of absorbance as a function of harmonic error was significant for all conditions (p<0.01), the slope with respect to density was significant only when the beam was unfiltered (p<0.05). Also harmonic error, but not density, displayed significant energy-dependent effects on absorbance (p<0.01). These data suggest that harmonic error is a strong determinant of absorbance, particularly when the beam energy is concentrated near the iodine K-edge and is likely a descriptor of K-characteristic photon interactions. Therefore, x-ray absorbance may be modulated by the distance between covalently linked x-ray K-edge attenuating atoms. This finding has important implications for increasing contrast agent absorbance as well as for designing molecular transducers capable of modulating K-edge attenuating atomic distances and thereby x-ray absorbance.

Poelzing, Steven; Smoot, Adam F.; Veeraraghavan, Rengasayee [Nora Eccles Harrison Cardiovascular Research and Training Institute and Bioengineering, University of Utah, 95 South 2000 East, Salt Lake City, Utah 84112 (United States)

2008-10-15

16

Resonant X-Ray Attenuation by Highly Ionized Ions of High-Z Elements  

NASA Astrophysics Data System (ADS)

Heavy elements interact very efficiently with X-rays with large attenuation coefficients. Ionization and excitation of extended electronic shells have large photoabsorption cross sections up to very high energies. It is shown that X-ray absorption in gold ions is considerably enhanced by factors of up to 1000 or more at energies of K-shell resonances from the K-alpha excitation energy to the K-ionization edge at ˜80 keV. Such large enhancements may be realized by X-ray irradiation in the 67-80 keV range creating inner-shell vacancies below the K-edge. We calculate the Auger resonant probabilities and cross sections to obtain total mass attenuation coefficients with detailed resonance structures for the K ---> L,M,N,O,P shell transitions. This work may be potentially useful in the calculation of resonant plus non-resonant attenuation coefficients by high-Z elements in plasmas created with high-intensity lasers, monochromatic synchrotron light sources, and electron-beam-ion-traps. Spectral models for X-ray absorption and transmission, and properties of chemical compounds of high-Z elements for applications in medical and nanotechnology research are also under investigation.

Pradhan, Anil; Nahar, Sultana; Yu, Yan; Sur, C.; Montenegro, M.; Mrozik, M.; Pitzer, R.

2008-05-01

17

Determination of total x-ray absorption coefficient using non-resonant x-ray emission  

PubMed Central

An alternative measure of x-ray absorption spectroscopy (XAS) called inverse partial fluorescence yield (IPFY) has recently been developed that is both bulk sensitive and free of saturation effects. Here we show that the angle dependence of IPFY can provide a measure directly proportional to the total x-ray absorption coefficient, µ(E). In contrast, fluorescence yield (FY) and electron yield (EY) spectra are offset and/or distorted from µ(E) by an unknown and difficult to measure amount. Moreover, our measurement can determine µ(E) in absolute units with no free parameters by scaling to µ(E) at the non-resonant emission energy. We demonstrate this technique with measurements on NiO and NdGaO3. Determining µ(E) across edge-steps enables the use of XAS as a non-destructive measure of material composition. In NdGaO3, we also demonstrate the utility of IPFY for insulating samples, where neither EY or FY provide reliable spectra due to sample charging and self-absorption effects, respectively.

Achkar, A. J.; Regier, T. Z.; Monkman, E. J.; Shen, K. M.; Hawthorn, D. G.

2011-01-01

18

On the attenuation of X-rays and ?-rays for aqueous solutions of salts  

NASA Astrophysics Data System (ADS)

Disparities in the linear attenuation coefficients of X-rays and gamma rays for aqueous solutions of soluble salts arising from the nonequality of volume of the solution with the sum of volumes of its components are analysed and the mixture rule is reformulated. The disparities are illustrated for NaCl solution for concentrations c=0 to 1gm/cm3 which indicates that the mixture rule of Teli et al. works well within generally acceptable limits.

Teli, M. T.

1998-12-01

19

Contribution of near-edge processes to attenuation of the characteristic X-rays in elements with 48 ? Z ? 83  

NASA Astrophysics Data System (ADS)

Attenuation of the characteristic K X-rays in the 48Cd, 50Sn, 52Te, 64Gd, 65Tb, 66Dy, 68Er, 74Ta, 75Re, 79Au, 82Pb and 83Bi elements have been measured with especial emphasis for the X-ray energies (Ein) in the region of respective K-shell/Li subshell (i = 1, 2, 3) ionization threshold (BK/BLi). The characteristic X-rays were obtained from different fluorescent target elements excited by the X-rays and ?-rays emitted from the 55Fe and 241Am radioisotopes, respectively. The measurements were performed using an energy-dispersive detection set up involving a low-energy Ge detector. The measured attenuation coefficients for the X-rays with energies away from ionization thresholds of the attenuator element are found to be in good agreement with the available theoretical coefficients, which incorporate contributions of the photoionization, and the Rayleigh and Compton scattering processes. However, the measured attenuation coefficients are found to deviate significantly from the theoretical values for the X-rays with energies in vicinity of BK/Li. The observed alteration is attributed to the X-ray Absorption Fine Structure (XAFS) for negative BK/Li - Ein values, and the K-shell/Li subshell resonant Raman scattering (RRS) process for positive BK/Li - Ein values. Systematic of the K-shell/Li subshell RRS contribution to attenuation of the X-rays are discussed in terms of the respective oscillator density and fraction of electrons available in the K-shell/Li subshell Lorentzian profile of the attenuation element below Ein.

Kumar, Sunil; Alrakabi, Muhanad; Kumar, Sanjeev; Mehta, D.; Bedi, S. C.; Singh, Nirmal

2010-03-01

20

Estimating photon interaction coefficients from single energy x-ray CT  

NASA Astrophysics Data System (ADS)

Single energy x-ray analysis is explored in the context of computed tomography (CT), whereby Hounsfield numbers (HN) are used to estimate electron density Ne and parameters that describe composition. We examine measurements with tissue substitute materials and theoretical HN for a broad range of tissues. Results are combined with parametric models for the x-ray linear attenuation coefficient ? and energy absorption coefficient ?en to predict values at energies 10 keV to 20 MeV. At photon energies employed for CT, the fractional contribution to ? from composition is 0.1-0.4 for soft tissues to bone respectively, and is responsible for strong correlations between HN and Ne. The atomic density of tissues excluding lung is near constant allowing the models to be re-expressed as a function of Ne alone. The transformed model is subjected to propagation of error analysis and results are presented as the ratio of uncertainties for ? or ?en to those for Ne. For soft tissues to bone the ratios are as follows: at photon energies 20-100 keV the ratio is 5.0-2.0, at intermediate energies it is unity and increases above 4 MeV to reach 1.5-2.0 at 20 MeV. Results are discussed in the context of attenuation correction and dosimetry calculations for the same range of photon energies.

Midgley, S. M.

2012-12-01

21

Attenuation characteristics of fiberoptic plates for digital mammography and other X-ray imaging applications.  

PubMed

Spatially coherent fiberoptic plates are important components of some charge-coupled device (CCD)-based x-ray imaging systems. These plates efficiently transmit scintillations from the phosphor, and also filter out x-rays not absorbed by the phosphor, thus protecting the CCD from direct x-ray interaction. The thickness of the fiberoptic plate and the CCD package present a significant challenge in the design of a digital x-ray cassette capable of insertion into the existing film-screen cassette holders of digital mammography systems. This study was performed with an aim to optimize fiberoptic plate thickness. Attenuation measurements were performed on nine fiberoptic plates varying in material composition that exhibit desirable optical characteristics such as good coupling efficiency. Mammographic spectra from a clinical mammographic system and an Americium-241 (Am-241) source (59.54 KeV) were used. The spectra were recorded with a high-resolution cadmium zinc telluride (CZT)-based spectrometer and corrected for dead time and pile-up. The linear attenuation coefficients varied by a factor of 3 in the set of tested fiberoptic plates at both mammographic energies and 59.54 keV. Our results suggest that a 3-mm thick high-absorption plate might provide adequate for shielding at mammographic energies. A thickness of 2-mm is feasible for mammographic applications with further optimization of the fiberoptic plate composition by incorporating non-scintillating, high-atomic number material. This would allow more space for cooling components of the cassette and for a more compact device, which is critical for clinical implementation of the technology. PMID:22388292

Vedantham, S; Karellas, A; Suryanarayanan, S

2003-01-01

22

Phase Effects on Mesoscale Object X-ray Attenuation Radiographs  

SciTech Connect

Digital x-ray radiography and computed tomography methods are commonly used to characterize mesoscale objects (mm size objects with {micro}m size features). However the ability of these methods to provide high spatial resolution images is dependent, in part, on object recovery algorithms that account for phase effects [1]. The objective of this work is the development and validation of algorithms to model phase-contrast effects observed in x-ray radiographic systems, and to use these algorithms for quantitative object recovery. This work has three distinct tasks. First, we are modifying HADES [2,3] to model x-ray phase contrast and are investigating whether multislice techniques within the object are needed to fully capture the physics seen in x-ray data. Second, we are developing object recovery approaches. Third, we are validating these simulations against x-ray systems using well-known objects. At the end of this R&D, we will have a set of validated x-ray forward modeling codes including the effects of phase and an understanding of the current object recovery methods limitations.

Martz, Jr., H E; Aufderheide, M B; Barty, A; Hau-Riege, S; Lehman, S K; Kozioziemski, B J; Schneberk, D J

2005-11-08

23

Phase Effects on Mesoscale Object X-ray Attenuation Radiographs.  

National Technical Information Service (NTIS)

Digital x-ray radiography and computed tomography methods are commonly used to characterize mesoscale objects (mm size objects with (micro)m size features). However the ability of these methods to provide high spatial resolution images is dependent, in pa...

A. Barty B. J. Kozioziemski D. J. Schneberk H. E. Martz M. B. Aufderheide S. Hau-Riege S. K. Lehman

2005-01-01

24

NIST: X-Ray Form Factor, Attenuation, and Scattering Tables  

NSDL National Science Digital Library

This site gives the interactions of x-rays with isolated atoms, computed within a self-consistent Dirac-Hartree-Fock framework, across the range from 1-10 eV to 400-1000 keV. A reference paper gives information about the computation. A database of calculation results can be searched.

Chantler, C. T.; Olsen, K.; Dragoset, R. A.; Chang, J.; Kishore, A. R.; Kotochigova, S. A.

2003-10-10

25

An indirect method of X-ray spectra measurement by simultaneous attenuations of the scattered beam  

NASA Astrophysics Data System (ADS)

Direct and indirect methods of X-ray spectra determination present obstacles to their practical use since they must position either the collimator-detector assembly or the attenuators-ionization chamber, respectively, along the X-ray beam direction. These arrangements require considerable space and in many instances the detectors promptly saturate. An indirect procedure, which overcomes the aforementioned problems, is developed. It consists of the scattering of the X-ray beam from a carbon disk, which is detected simultaneously by several detectors placed away from the beam. The X-ray flux reaching each of these detectors is attenuated in metal sheets of different thicknesses, thus obtaining simultaneously the attenuation curve values. A set of analytical equations are derived to calculate attenuation curves by taking into account all the absorption and elastic and inelastic scattering processes that a beam of photons undergoes when going from the X-ray tube to the detector. Users, even those who are not well acquainted with computer programming, can easily obtain the X-ray spectrum by a least square fitting of a measured attenuation curve to a previously derived analytical expression. A simulated Monte Carlo program of photon transport from the X-ray tube to the detector provided simulated attenuation curves data. Analytically calculated and simulated attenuation curves for the same input spectrum wholly overlap and furthermore, reconstructed spectra from both sets of curves for different kilovoltages are also in full agreement. Finally, in addition to the importance of having the detectors out of the beam direction, the proposed arrangement features other main advantages, namely, only one X-ray tube shot is needed to obtain the required data, the physical processes involved are very well known, analytical equations are easily interpreted, and the measuring apparatuses can be comparatively simple to assemble and operate.

Mainardi, Raśl T.; Bonzi, Edgardo V.

2008-05-01

26

Broad beam attenuation of cobalt-60 gamma rays and 6-, 18-, and 25-MV x rays by lead  

SciTech Connect

The measurement of photon attenuation by absorbing materials in radiation beams is usually performed using narrow beam geometry. However, radiotherapy treatments rarely simulate narrow beam conditions. The effect of broad beams on the attenuation of cobalt-60 gamma rays and 6-, 18-, and 25-MV x rays by lead is considered both theoretically and experimentally. The theoretical calculations are based on first-scatter considerations and indicate a dependence on treatment geometry (i.e., maximum scattering angle). Measured attenuation coefficients vary by as much as 16%, comparing narrow and broad beam data for typical treatment conditions. Broad beam attenuation coefficients, calculated from the measured zero-area values agree with the measured results to within 2% on average with a maximum deviation of 5%. A very simple empirical procedure is proposed to determine attenuation coefficients for a wide range of field sizes. This agrees with the measured data to within 0.5% on average and 4% at worst. With irregularly shaped absorbers, a sector integration technique is considered in combination with a first-scatter calculation. For a long rectangular field, the agreement between measured and calculated attenuation coefficients is better than 1.5% for all energies. The question of accuracy in attenuation coefficients needed to give an accuracy of 3% in relative transmission is addressed and shows a dependence on absorber thickness. For 75% transmission, the required accuracy in attenuation coefficient is 10%, whereas for 25% transmission, it should be improved to 2%.

Van Dyk, J.

1986-01-01

27

X-Ray Form Factor, Attenuation, and Scattering Tables  

NSDL National Science Digital Library

This site, created by C.T. Chantler of the National Institute of Standards and Technology (NIST), gives the interactions of x-rays with isolated atoms, computed within a self-consistent Dirac-Hartree-Fock framework, across the range from 1-10 eV to 400-1000 keV. A reference paper gives information about the computation. A database of results to the calculation can be searched. External references are included for further research on the topic.

Chantler, C. T.

2009-05-05

28

Attenuation correction of SPECT using X-ray CT on an emission-transmission CT system: myocardial perfusion assessment  

Microsoft Academic Search

The authors present experimental results for attenuation correction of emission tomography through use of an attenuation map derived from X-ray CT data. The X-ray and gamma-ray data were obtained from a third-generation X-ray CT scanner and a single-headed SPECT Scanner juxtaposed to enable systematic registration of SPECT and X-ray CT Images. CT measurements were obtained from known materials at a

S. C. Blankespoor; X. Xu; K. Kaiki; J. K. Brown; H. R. Tang; C. E. Cann; B. H. Hasegawa

1996-01-01

29

X-ray-based attenuation correction for positron emission tomography\\/computed tomography scanners  

Microsoft Academic Search

A synergy of positron emission tomography (PET)\\/computed tomography (CT) scanners is the use of the CT data for x-ray-based attenuation correction of the PET emission data. Current methods of measuring transmission use positron sources, gamma-ray sources, or x-ray sources. Each of the types of transmission scans involves different trade-offs of noise versus bias, with positron transmission scans having the highest

Paul E. Kinahan; Bruce H. Hasegawa; Thomas Beyer

2003-01-01

30

The Calculation of X-Ray Mass Absorption Coefficients  

Microsoft Academic Search

An empirical method of calculating mass absorption coefficients is given. Complete tables of constants are presented for calculating ??&rgr; for all elements and for wave-lengths less than the K critical absorption wave-length. Partial tables give constants for wave-lengths between the L1 and M1 critical wave-lengths.Calculated mass absorption coefficients are given for the common elements.

John A. Victoreen

1949-01-01

31

Determination of mineral concentration in dental enamel from X-ray attenuation measurements.  

PubMed

The mineral content of dental enamel is commonly measured by X-ray attenuation experiments. Most studies have used contact microradiography in which intensities are measured with photographic film which is convenient and gives high spatial resolution. However photon counting intensity measurements are to be preferred in many experiments (longitudinal and scanning microradiography, and microtomography), as illustrated here, because they have a larger dynamic range and greater sensitivity to small intensity changes. Additionally, the detector and specimen are well separated which allows the pseudo-continuous study of de- and remineralization. The mineral content is often quoted as 95 wt% or 87 vol% hydroxyapatite for permanent human enamel. This determination from attenuation experiments requires accurate values of elemental mass attenuation coefficients and a number of assumptions. The effects of possible choices of these are considered and it is shown that the most important is the density of enamel mineral used in conversion of wt% to vol%. If the density is taken as 2.99 g cm(-3), as recently suggested (J.C. Elliott, Dental Enamel, Ciba Foundation Symposium 205, Wiley, Chichester, pp. 54-72, 1997), instead of 3.15 g cm(-3) as for hydroxyapatite, the calculated vol% is approximately 93 instead of approximately 87. PMID:11063016

Elliott, J C; Wong, F S; Anderson, P; Davis, G R; Dowker, S E

1998-01-01

32

Characteristics of X-ray attenuation in electrospun bismuth oxide/polylactic acid nanofibre mats.  

PubMed

The characteristics of the X-ray attenuation in electrospun nano(n)- and micro(m)-Bi2O3/polylactic acid (PLA) nanofibre mats with different Bi2O3 loadings were compared as a function of energy using mammography (i.e. tube voltages of 22-49?kV) and X-ray absorption spectroscopy (XAS) (7-20?keV). Results indicate that X-ray attenuation by electrospun n-Bi2O3/PLA nanofibre mats is distinctly higher than that of m-Bi2O3/PLA nanofibre mats at all energies investigated. In addition, with increasing filler loading (n-Bi2O3 or m-Bi2O3), the porosity of the nanofibre mats decreased, thus increasing the X-ray attenuation, except for the sample containing 38?wt% Bi2O3 (the highest loading in the present study). The latter showed higher porosity, with some beads formed, thus resulting in a sudden decrease in the X-ray attenuation. PMID:23955038

Noor Azman, Nurul Z; Siddiqui, Salim A; Haroosh, Hazim J; Albetran, Hani M M; Johannessen, Bernt; Dong, Yu; Low, It M

2013-07-13

33

Determination of multiwavelength anomalous diffraction coefficients at high x-ray intensity  

NASA Astrophysics Data System (ADS)

The high-intensity version of multiwavelength anomalous diffraction (MAD) has a potential for solving the phase problem in femtosecond crystallography with x-ray free-electron lasers (XFELs). For MAD phasing, it is required to calculate or measure the MAD coefficients involved in the key equation, which depend on XFEL pulse parameters. In this work, we revisit the generalized Karle-Hendrickson equation to clarify the importance of configurational fluctuations of heavy atoms induced by intense x-ray pulses, and investigate the high-intensity cases of transmission and fluorescence measurements of samples containing heavy atoms. Based on transmission/fluorescence and diffraction experiments with crystalline samples of known structures, we propose an experimental procedure to determine all MAD coefficients at high x-ray intensity, which can be used in ab initio phasing for unknown structures.

Son, Sang-Kil; Chapman, Henry N.; Santra, Robin

2013-08-01

34

KDP:Mn piezoelectric coefficients obtained by X-ray diffraction.  

PubMed

Crystals of pure potassium dihydrogen phosphate KH(2)PO(4) (KDP) and Mn-doped KDP (KDP:Mn) were grown from a water solution by the slow evaporation method and their piezoelectric properties were studied by X-ray diffraction methods. The results have shown an increase in the piezoelectric coefficients with the doping. PMID:20975229

Gomes, E J L; Moreira, S G C; de Menezes, A S; Dos Santos, A O; Pereira, D P; de Oliveira, P C; Remédios, C M R

2010-10-14

35

X-ray photon spectroscopy calculations  

Microsoft Academic Search

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

J. E. Fernandez; V. G. Molinari

1991-01-01

36

New techniques provide low-cost X-ray inspection of highly attenuating materials  

SciTech Connect

As a result of an arms reduction treaty between the United States and the Russian Federation, both countries will each be storing over 40,000 containers of plutonium. To help detect any deterioration of the containers and prevent leakage, the authors are designing a digital radiography and computed tomography system capable of handling this volume reliably, efficiently, and at a lower cost. The materials to be stored have very high x-ray attenuations, and, in the past, were inspected using 1- to 24-MV x-ray sources. This inspection system, however, uses a new scintillating (Lockheed) glass and an integrating CCD camera. Preliminary experiments show that this will permit the use of a 450-kV x-ray source. This low-energy system will cost much less than others designed to use a higher-energy x-ray source because it will require a less expensive source, less shielding, and less floor space. Furthermore, they can achieve a tenfold improvement in spatial resolution by using their knowledge of the point-spread function of the x-ray imaging system and a least-squares fitting technique.

Stupin, D.M.; Mueller, K.H.; Viskoe, D.A. [Los Alamos National Lab., NM (United States); Howard, B.; Poland, R.W. [Westinghouse Savannah River Lab., Aiken, SC (United States); Schneberk, D.; Dolan, K. [Lawrence Livermore National Lab., CA (United States); Thompson, K.; Stoker, G. [Sandia National Labs., Albuquerque, NM (United States)

1995-12-31

37

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

38

In vivo observing x-ray attenuation of intratumor injection of indocyanine green  

NASA Astrophysics Data System (ADS)

We report our experimental results of in vivo observing x-ray attenuation of intra-tumor injection of indocyanine green (ICG). An eight- to nine-week-old male BALB/c mouse weighting between 15 and 20 g is used in the experiments, which has been implanted with myeloma cell line (SP2/0) two week before. The system used to monitor the intratumor diffusion of ICG is a digital x-ray imaging system. It works at 33kVp, 0.3mAs, 4 seconds and 1.5×magnification. The objective of this research is to study the x-ray attenuation at different area, which represented by gray-scale value. Compare to the ROI in the tissue without ICG and ROI of black background in the image, there is an obvious change before and after injecting ICG in the tumor, which is the area ICG can diffuse to. It shows the feasibility of using digital x-ray imaging system to dynamically, effectively and noninterventionly monitor the diffusion of the ICG.

Ye, Chang; Luo, Qingming; Liang, Wenxi; Lu, Jinling

2003-12-01

39

X-ray absorption coefficient of iodine in the K edge region  

NASA Astrophysics Data System (ADS)

X-ray absorption spectroscopy of iodine vapour is used for absolute determination of the absorption coefficient of iodine within a region of 4.3 keV around the K edge. The comparison with data in available compilations is given, together with the compressed form of the Victoreen asymptotics below and above the edge. The deviation from the asymptotics due to multielectron excitations and virtual processes immediately above the edge is discussed.

Padežnik Gomilšek, J.; Ar?on, I.; de Panfilis, S.; Kodre, A.

2008-01-01

40

The criteria for measuring average density by x-ray attenuation: The role of spatial resolution  

SciTech Connect

It is well known that the attenuation of X-rays as they pass through a material can be used to quantify the amount of matter in their path. This is the basis for the gamma ray densitometer which can measure the amount of material on a moving conveyor belt. It is also the rationale for using X-rays for medical imaging as the attenuation can discriminate between tissue of different density and composition, yielding images of great diagnostic utility. Spatial resolution is obviously important with regard to detecting small features. However, it is less obvious that it plays an important role in obtaining quantitative information from the X-ray transmission data since the spatial resolution of the instrument can affect the accuracy of those measurements. This problem is particularly severe in the case of computed tomography where the accuracy of the reconstruction is dependent on the accuracy of the initial projection data. It should be noted that spatial resolution is not a concern for the case where the material is uniform. Here uniform is defined by small variations related to either the scale size of the resolution element in the detector, or to the size of a collimated X-ray beam. However, if the material has non-homogeneous composition or changes in density on the scale size of the systems spatial resolution, then there can be effects that will compromise the transmission data before it is acquired and these errors can not be corrected by any subsequent data processing. A method is presented for computing the density measurement error which parameterizes the effect in terms of the actual modulation on the face of the detector and the attenuation in the material. For cases like stacks of lead plates the errors can exceed 80%.

Friedman, W.

1999-07-29

41

Contribution of near-edge processes to attenuation of the characteristic X-rays in elements with 48 ? Z ? 83  

Microsoft Academic Search

Attenuation of the characteristic K X-rays in the 48Cd, 50Sn, 52Te, 64Gd, 65Tb, 66Dy, 68Er, 74Ta, 75Re, 79Au, 82Pb and 83Bi elements have been measured with especial emphasis for the X-ray energies (Ein) in the region of respective K-shell\\/Li subshell (i=1, 2, 3) ionization threshold (BK\\/BLi). The characteristic X-rays were obtained from different fluorescent target elements excited by the X-rays

Sunil Kumar; Muhanad Alrakabi; Sanjeev Kumar; D. Mehta; S. C. Bedi; Nirmal Singh

2010-01-01

42

NAD+ administration significantly attenuates synchrotron radiation X-ray-induced DNA damage and structural alterations of rodent testes  

PubMed Central

Synchrotron radiation (SR) X-ray has great potential for its applications in medical imaging and cancer treatment. In order to apply SR X-ray in clinical settings, it is necessary to elucidate the mechanisms underlying the damaging effects of SR X-ray on normal tissues, and to search for the strategies to reduce the detrimental effects of SR X-ray on normal tissues. However, so far there has been little information on these topics. In this study we used the testes of rats as a model to characterize SR X-ray-induced tissue damage, and to test our hypothesis that NAD+ administration can prevent SR X-ray-induced injury of the testes. We first determined the effects of SR X-ray at the doses of 0, 0.5, 1.3, 4 and 40 Gy on the biochemical and structural properties of the testes one day after SR X-ray exposures. We found that 40 Gy of SR X-ray induced a massive increase in double-strand DNA damage, as assessed by both immunostaining and Western blot of phosphorylated H2AX levels, which was significantly decreased by intraperitoneally (i.p.) administered NAD+ at doses of 125 and 625 mg/kg. Forty Gy of SR X-ray can also induce marked increases in abnormal cell nuclei as well as significant decreases in the cell layers of the seminiferous tubules one day after SR X-ray exposures, which were also ameliorated by the NAD+ administration. In summary, our study has shown that SR X-ray can produce both molecular and structural alterations of the testes, which can be significantly attenuated by NAD+ administration. These results have provided not only the first evidence that SR X-ray-induced tissue damage can be ameliorated by certain approaches, but also a valuable basis for elucidating the mechanisms underlying SR X-ray-induced tissue injury.

Sheng, Caibin; Chen, Heyu; Wang, Ban; Liu, Tengyuan; Hong, Yunyi; Shao, Jiaxiang; He, Xin; Ma, Yingxin; Nie, Hui; Liu, Na; Xia, Weiliang; Ying, Weihai

2012-01-01

43

X-ray attenuation cross sections for energies 100 eV to 100 keV and elements Z = 1 to Z = 92  

Microsoft Academic Search

This work presents for the energy range 0.1--100 keV the National Bureau of Standards (NBS) database of experimental x-ray attenuation coefficients (total absorption cross sections) and cross sections calculated using a relativistic Hartree--Slater model for the photoelectric cross section for all elements of atomic number Z = 1--92. The information is displayed in both tabular and graphical form. Also shown

E. B. Saloman; J. H. Hubbell; J. H. Scofield

1988-01-01

44

Ultraprecise studies of the thermal expansion coefficient of diamond using backscattering x-ray diffraction.  

SciTech Connect

The linear thermal expansion coefficient of diamond crystals of type IIa and type Ia was measured in the temperature range from 10 to 295 K. Neither negative thermal expansion nor any substantial difference in the thermal expansion coefficient in crystals of the different types were observed. An empirical expression was obtained that approximates the temperature dependence of the thermal expansion coefficient of diamond. The T{sup 3} temperature dependence of a Debye solid holds below {approx}100 K with an accuracy of {approx}10{sup -8} K{sup -1}. A slight increase in the value of the lattice parameter was found for the Ia-type crystal, which suggests lattice dilatation by nitrogen impurity. The measurements were performed using Bragg diffraction in backscattering from diamond crystals of highly monochromatic 23.7 keV x rays with the recently demonstrated high relative accuracy of 1.2 x 10{sup -8} in the determination of the lattice parameter.

Stoupin, S.; Shvyd'ko, Y. (X-Ray Science Division)

2011-03-17

45

X ray attenuation measurements for high-temperature materials characterization and in situ monitoring of damage accumulation  

NASA Astrophysics Data System (ADS)

The development and application is examined of x ray attenuation measurement systems that are capable of (1) characterizing density variations in high temperature materials, e.g., monolithic ceramics, ceramic and intermetallic matrix composites and (2) noninvasively monitoring damage accumulation and failure sequences in ceramic matrix composites under room temperature tensile testing. Results are presented in the development of (1) a point scan digital radiography system and (2) an in-situ x ray material testing system. The former is used to characterize silicon carbide and silicon nitride specimens and the latter is used to image the failure behavior of silicon carbide fiber reinforced reaction bonded silicon nitride matrix composites. Further, state of the art x ray computed tomography is studied to determine its capabilities and limitations in characterizing density variations of subscale engine components, e.g., a silicon carbide rotor, a silicon nitride blade, and a silicon carbide fiber reinforced beta titanium matrix rod, rotor, and ring. Microfocus radiography, conventional radiography, scanning acoustic microscopy, and metallography are used to substantiate the x ray computed tomography findings. Point scan digital radiography is a viable technique for characterization density variations in monolithic ceramic specimens. But it is very limited and time consuming in characterizing ceramic matrix composities. Precise x ray attenuation measurements, reflecting minute density variations, are achieved by photon counting and by using micro collimators at the source and the detector. X ray computed tomography is found to be a unique x ray attenuation measurement technique capable of providing cross sectional spatial density information in monolithic ceramics and metal matrix composites. X ray computed tomography is proven to accelerate generic composite component development. Radiographic evaluation before, during and after loading show the effect of preexisting volume flaws on the fracture behavior of composites. Results from one ply, three ply, five ply, and eight ply ceramic composite specimens show that x ray film radiography can monitor damage accumulation during tensile loading.

Baaklini, George Youssef

1991-10-01

46

Beamline fast and automatic attenuation system for X-Ray detectors at Synchrotron Soleil  

NASA Astrophysics Data System (ADS)

Attenuators are commonly used on beamlines to control incident photon flux. Attenuators are mainly controlled by software. In some experimental cases using various diffraction techniques, this architecture is not fast enough to manage high flux variation. The fast attenuation system inserts and extracts filters quickly, allowing very fast beam attenuation at the maximum rate allowed by the filter mechanism and the beam detector response. To build the solution, we used an off-the-shelf CPCI General Purpose board (GPIO) from TEWS that is based on a SPARTAN-3 Xilinx FPGA: We have developed a daughter board and an embedded VHDL program. The logic is dedicated to maintaining incident detector photon flux within an acceptable range for optimized measurements and protecting the X ray detector against over-exposure. This system is part of a continuous scan process. Some low level process logic is also embedded in order to optimize data exchange. During continuous scanning, this process allows each experimental data item collected to be associated with its corresponding photon flux value. This system is in operation on the SIXS beamline and will be soon installed on the DIFFABS beamline. This paper describes the principle and the results obtained with this solution and the possible improvements and perspectives (interfacing more complex detectors such as XPad).

Renaud, G.; Garreau, Y.; Betinelli, P.; Tournieux, A.; Bisou, J.; Monteiro, P.; Elattaoui, X.

2013-03-01

47

Three-dimensional x-ray microtomography  

SciTech Connect

The new technique of x-ray microtomography nondestructively generates three-dimensional maps of the x-ray attenuation coefficient inside small samples with approximately 1 percent accuracy and with resolution approaching 1 micrometer. Spatially resolved elemental maps can be produced with synchrotron x-ray sources by scanning samples at energies just above and below characteristic atomic absorption edges. The system consists of a high-resolution imaging x-ray detector and high-speed algorithms for tomographic image reconstruction. The design and operation of the microtomography device are described, and tomographic images that illustrate it performance with both synchrotron and laboratory x-ray sources are presented.

Flannery, B.P.; Deckman, H.W.; Roberge, W.G.; D'Amico, K.L.

1987-09-18

48

Attenuation coefficients of Rayleigh and Lg waves  

Microsoft Academic Search

Analysis of the frequency dependence of the attenuation coefficient leads to significant changes in interpretation of seismic\\u000a attenuation data. Here, several published surface-wave attenuation studies are revisited from a uniform viewpoint of the temporal\\u000a attenuation coefficient, denoted by ?. Theoretically, ?( f) is expected to be linear in frequency, with a generally non-zero intercept ??=??(0) related to the variations of

Igor B. Morozov

2010-01-01

49

Ultraprecise Studies of the Thermal Expansion Coefficient of Diamond using Backscattering X-ray Diffraction  

SciTech Connect

The linear thermal expansion coefficient of diamond crystals of type IIa and type Ia was measured in the temperature range from 10 to 295 K. Neither negative thermal expansion nor any substantial difference in the thermal expansion coefficient in crystals of the different types were observed. An empirical expression was obtained that approximates the temperature dependence of the thermal expansion coefficient of diamond. The T{sup 3} temperature dependence of a Debye solid holds below {approx}100 K with an accuracy of {approx}10{sup -8} K{sup -1}. A slight increase in the value of the lattice parameter was found for the Ia-type crystal, which suggests lattice dilatation by nitrogen impurity. The measurements were performed using Bragg diffraction in backscattering from diamond crystals of highly monochromatic 23.7 keV x rays with the recently demonstrated high relative accuracy of 1.2 x 10{sup -8} in the determination of the lattice parameter [S. Stoupin and Yu. Shvyd'ko Phys. Rev. Lett. 104 085901 (2010)].

S Stoupin; Y Shvydko

2011-12-31

50

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

51

Measurement of atomic number and mass attenuation coefficient in magnesium ferrite  

Microsoft Academic Search

Pure magnesium ferrite sample was prepared by standard ceramic technique and characterized by X-ray diffraction method. XRD pattern revealed that the sample possess single-phase cubic spinel structure. The linear attenuation coefficient (mu), mass attenuation coefficient (mu\\/rho), total atomic cross-section (sigma_{tot}), total electronic cross-section (sigma_{ele}) and the effective atomic number (Z_{eff}) were calculated for pure magnesium ferrite (MgFe_{2}O_{4}). The values of

R. H. Kadam; S. T. Alone; G. K. Bichile; K. M. Jadhav

2007-01-01

52

Prediction coefficient estimation in Markov random fields for iterative x-ray CT reconstruction  

NASA Astrophysics Data System (ADS)

Bayesian estimation is a statistical approach for incorporating prior information through the choice of an a priori distribution for a random field. A priori image models in Bayesian image estimation are typically low-order Markov random fields (MRFs), effectively penalizing only differences among immediately neighboring voxels. This limits spectral description to a crude low-pass model. For applications where more flexibility in spectral response is desired, potential benefit exists in models which accord higher a priori probability to content in higher frequencies. Our research explores the potential of larger neighborhoods in MRFs to raise the number of degrees of freedom in spectral description. Similarly to classical filter design, the MRF coefficients may be chosen to yield a desired pass-band/stop-band characteristic shape in the a priori model of the images. In this paper, we present an alternative design method, where high-quality sample images are used to estimate the MRF coefficients by fitting them into the spatial correlation of the given ensemble. This method allows us to choose weights that increase the probability of occurrence of strong components at particular spatial frequencies. This allows direct adaptation of the MRFs for different tissue types based on sample images with different frequency content. In this paper, we consider particularly the preservation of detail in bone structure in X-ray CT. Our results show that MRF design can be used to obtain bone emphasis similar to that of conventional filtered back-projection (FBP) with a bone kernel.

Wang, Jiao; Sauer, Ken; Thibault, Jean-Baptiste; Yu, Zhou; Bouman, Charles

2012-02-01

53

Investigation of photon attenuation coefficients for marble.  

PubMed

The total linear attenuation coefficients micro (cm(-1)) have been obtained using the XCOM program at photon energies of 1 keV to 1 GeV for six different natural marbles produced in different places in Turkey. The individual contribution of photon interaction processes to the total linear attenuation coefficients for marble has been investigated. The calculated results were also compared with the measurements. The results obtained for marble were also compared with concrete. PMID:15942062

Basyigit, C; Akkurt, I; Kilincarslan, S; Akkurt, A

2005-06-07

54

Repetitive exposures to low-dose X-rays attenuate testicular apoptotic cell death in streptozotocin-induced diabetes rats  

Microsoft Academic Search

To define whether repetitive exposures to low-dose radiation (LDR) can attenuate diabetes-induced testicular cell death, Type 1 diabetic rats were produced by single injection of streptozotocin (STZ). Once hyperglycemia was diagnosed, diabetic rats were treated with and without LDR (25 and 50mGy X-rays) daily for 4 weeks. Eight and 12 weeks after diabetes onset, testicular apoptotic cell death was examined

Hongguang Zhao; Songbai Xu; Zhicheng Wang; Yanbo Li; Wei Guo; Chenghe Lin; Shouliang Gong; Cai Li; Guanjun Wang; Lu Cai

2010-01-01

55

X-ray multiple diffraction as a probe to determine all the piezoelectric coefficients of a crystal: Rochelle salt case  

Microsoft Academic Search

The x-ray multiple diffraction method, which allows us to determine the piezoelectric coefficients of a single crystal under an external electric field (E), was applied to Rochelle salt (dos Santos et al 2001 J.Phys.:Condens.Matter13 10497) for E parallel to the piezoelectric Y direction. In this work, the theory was extended to consider an observed monoclinic–triclinic distortion under E application into

A O dos Santos; L P Cardoso; J M Sasaki; M A R Miranda; F E A Melo

2003-01-01

56

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

57

Determination of Soret coefficient and heat of transport in a binary liquid mixture using X-ray microscopy  

NASA Astrophysics Data System (ADS)

With a laboratory built X-ray microscope, analysis of a thermal diffusion process in a KBr solution has been performed. A solution of a salt submitted to a constant temperature gradient gives rise to a stationary concentration gradient of the species after a few hours: this is the so called Soret effect. From the digital image of the liquid, acquired in the steady state of the process, it is easy to obtain the concentration map of the species in the solution. The average concentration profile then deduced permits to reach the value of the Soret coefficient and the heat of transport of the binary compound. X-ray radiography is an alternative powerful technique to analyse this kind of complicated phenomenon where composition matter fluxes are driven by both temperature and composition gradient.

Rondot, S.; Aaboubi, O.; Baudart, P.; Erre, D.; Mérienne, E.; Patat, J. M.

2002-01-01

58

A program for calculating and plotting soft-X-ray optical interaction coefficients for molecules  

NASA Astrophysics Data System (ADS)

Comprehensive tables for atomic scattering factor components f1 and f2 were compiled by Henke et al. for the extended photon region of 350-10000 eV. Accurate calculations of optical interaction coefficients for absorption, reflection and scattering by material systems (e.g. filters, multi-layers, etc.), which have widespread application, can be based simply upon the atomic scattering factors for the elements comprising the material, except near the absorption threshold energies. These calculations based upon the weighted sum of f1 and f2 for each atomic species present can be very tedious if done by hand. This led us to develop Optical Constants Grapher (OCG), a user-friendly program to perform these calculations on an IBM PC or compatible computer. By entering the chemical formula, density and thickness of up to six molecules, values of f1, f2, mass absorption, transmission efficiencies, attenuation lengths, mirror reflectivities and complex indices of refraction can be calculated and plotted as a function of energy or wavelength. This program and its user's manual are available from the authors.

Thomas, M. M.; Davis, J. C.; Jacobsen, C. J.; Perera, R. C. C.

1990-05-01

59

X-ray absorption in matter. Reengineering XCOM  

NASA Astrophysics Data System (ADS)

A Windows version of XCOM, the well-known program for calculating X-ray and gamma-ray attenuation coefficients and interaction cross sections, has been developed. The new program, called WinXCom, has an improved user interface.

Gerward, L.; Guilbert, N.; Bjųrn Jensen, K.; Levring, H.

2001-01-01

60

Measurement of atomic number and mass attenuation coefficient in magnesium ferrite  

Microsoft Academic Search

Pure magnesium ferrite sample was prepared by standard ceramic technique and characterized by X-ray diffraction method. XRD\\u000a pattern revealed that the sample possess single-phase cubic spinel structure. The linear attenuation coefficient (µ), mass attenuation coefficient (µ\\/?), total atomic cross-section (?\\u000a tot), total electronic cross-section (?\\u000a ele) and the effective atomic number (Z\\u000a eff) were calculated for pure magnesium ferrite (MgFe2O4).

R H Kadam; S T Alone; G K Bichile; K M Jadhav

2007-01-01

61

Scattered X-ray beam nondestructive testing  

Microsoft Academic Search

X-ray scatter interactions generally dominate the linear attenuation coefficient at the photon energies typical of medical and industrial radiography. Specific advantages of X-ray scatter imaging, including a flexible choice of measurement geometry, direct 3D-imaging capability (tomography) and improved information for material characterization, are illustrated with results from Compton and coherent scatter devices. Applications of a Compton backscatter scanner (ComScan) in

G. Harding; J. Kosanetzky

1989-01-01

62

X-ray multiple diffraction as a probe to determine all the piezoelectric coefficients of a crystal: Rochelle salt case  

NASA Astrophysics Data System (ADS)

The x-ray multiple diffraction method, which allows us to determine the piezoelectric coefficients of a single crystal under an external electric field (E), was applied to Rochelle salt (dos Santos et al 2001 J. Phys.: Condens. Matter 13 10497) for E parallel to the piezoelectric Y direction. In this work, the theory was extended to consider an observed monoclinic-triclinic distortion under E application into the other two piezoelectric X and Z directions. Renninger scans carried out using the chosen (060) primary reflection have provided the four remaining coefficients through the measurement of the properly chosen secondary peaks. so that all eight piezoelectric coefficients (d14, d16, d21, d22, d23, d25, d34 and d36) for Rochelle salt were determined.

dos Santos, A. O.; Cardoso, L. P.; Sasaki, J. M.; Miranda, M. A. R.; Melo, F. E. A.

2003-11-01

63

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

64

Quantitative assessment of the effect of x-ray CT attenuation correction on myocardial perfusion in patients with single vessel coronary artery disease  

Microsoft Academic Search

Background: Attenuation artifacts diminish the diagnostic accuracy of myocardial perfusion imaging (MPI). Little quantitative data exist regarding the effect of x-ray CT based attenuation correction (AC) on regional tracer distribution. The purpose of this study is to quantitatively evaluate the effect of AC on MPI in individual vascular territories.Methods: In this study we selected patients with known single vessel disease

E. J Kostacos; L. I Araujo

2004-01-01

65

Measurement of atomic number and mass attenuation coefficient in magnesium ferrite  

NASA Astrophysics Data System (ADS)

Pure magnesium ferrite sample was prepared by standard ceramic technique and characterized by X-ray diffraction method. XRD pattern revealed that the sample possess single-phase cubic spinel structure. The linear attenuation coefficient (?), mass attenuation coefficient (?/?), total atomic cross-section (?_{tot}), total electronic cross-section (?_{ele}) and the effective atomic number (Z_{eff}) were calculated for pure magnesium ferrite (MgFe_{2}O_{4}). The values of ?-ray mass attenuation coefficient were obtained using a NaI energy selective scintillation counter with radioactive ?-ray sources having energy 0.36, 0.511, 0.662, 1.17 and 1.28 MeV. The experimentally obtained values of ?/? and Z_{eff} agreed fairly well with those obtained theoretically.

Kadam, R. H.; Alone, S. T.; Bichile, G. K.; Jadhav, K. M.

2007-05-01

66

Statistical image reconstruction for polyenergetic X-ray computed tomography  

Microsoft Academic Search

This paper describes a statistical image reconstruction method for X-ray computed tomography (CT) that is based on a physical model that accounts for the polyenergetic X-ray source spectrum and the measurement nonlinearities caused by energy-dependent attenuation. We assume that the object consists of a given number of nonoverlapping materials, such as soft tissue and bone. The attenuation coefficient of each

Idris A. Elbakri; Jeffrey A. Fessler

2002-01-01

67

X-ray induced transient attenuation at low temperatures in polymer clad silica \\/PCS\\/ fibers  

Microsoft Academic Search

In a number of applications considered for fiber optic data transmission links, the fibers must transmit light signals in a radiation environment. Studies of radiation effects in optoelectronic components have shown that one of the most severe problems caused by radiation is long lasting attenuation in fibers. Studies involving a wide variety of fibers have demonstrated that polymer clad silica

C. E. Barnes; J. J. Wiczer

1982-01-01

68

Spatial Gradients in Particle Reinforced Polymers Characterized by X-Ray Attenuation and Laser Confocal Microscopy  

Microsoft Academic Search

The goal of this work is to develop techniques for measuring gradients in particle concentration within filled polymers, such as encapsulant. A high concentration of filler particles is added to such materials to tailor physical properties such as thermal expansion coefficient. Sedimentation and flow-induced migration of particles can produce concentration gradients that are most severe near material boundaries. Therefore, techniques

ROBERT R. LAGASSE; KYLE R. THOMPSON

2000-01-01

69

Spatial gradients in particle reinforced polymers characterized by X-ray attenuation and laser confocal microscopy  

Microsoft Academic Search

The goal of this work is to develop techniques for measuring gradients in particle concentration within filled polymers, such as thermosetting polymer encapsulants. A high concentration of filler particles is added to such materials to tailor physical properties such as thermal expansion coefficient. Sedimentation and flow-induced migration of particles can produce concentration gradients that are most severe near boundaries. Therefore,

R. R Lagasse; K. R Thompson

2002-01-01

70

Measurement of the attenuation coefficient for Livermore Thoracic Phantom lungs fabricated using contemporary materials.  

PubMed

The University of Cincinnati has reproduced the original formulation for the Livermore Thoracic Phantom lungs using contemporary materials and has adopted the linear attenuation coefficient as the primary quality assurance parameter for evaluating the performance capabilities of these new lung phantoms. The Livermore Thoracic Phantom was originally fabricated in 1978 to intercalibrate detector systems used to measure plutonium and other low-energy, photon emitting radionuclides deposited in the respiratory tract. The linear attenuation coefficient is a critical performance indicator for these phantom lungs since the presence of any material with a high effective atomic number (where Z > or = 20) will make a significant change in the photoelectric cross section, the predominant mode of interaction for plutonium x rays. A set of test lungs was fabricated with KCl to introduce a known quantity of 40K in the phantom and to determine, by measurement and calculations, what change would be made to the attenuation coefficient at photon energies below 100 keV as a result of the modified formulation. The KCl increased the linear attenuation coefficient below 60 keV by more than a factor of two, which would produce a substantial systematic error in any subsequent calibration measurements performed with these modified phantom lungs. These results support use of the attenuation coefficient as an important performance indicator for the Livermore Thoracic Phantom lungs and also suggest that KCl not be added to the lung tissue substitute formulation as a means to incorporate 40K in the phantom for low energy calibrations. PMID:8200800

Spitz, H; Glover, S; Liu, N; Smith, B; Hickman, D; Kruchten, D; Anderson, L

1994-07-01

71

Evaluation of soft x-ray average recombination coefficient and average charge for metallic impurities in beam-heated plasmas  

SciTech Connect

The soft x-ray continuum radiation in TFTR low density neutral beam discharges can be much lower than its theoretical value obtained by assuming a corona equilibrium. This reduced continuum radiation is caused by an ionization equilibrium shift toward lower states, which strongly changes the value of the average recombination coefficient of metallic impurities anti ..gamma.., even for only slight changes in the average charge, anti Z. The primary agent for this shift is the charge exchange between the highly ionized impurity ions and the neutral hydrogen, rather than impurity transport, because the central density of the neutral hydrogen is strongly enhanced at lower plasma densities with intense beam injection. In the extreme case of low density, high neutral beam power TFTR operation (energetic ion mode) the reduction in anti ..gamma.. can be as much as one-half to two-thirds. We calculate the parametric dependence of anti ..gamma.. and anti Z for Ti, Cr, Fe, and Ni impurities on neutral density (equivalent to beam power), electron temperature, and electron density. These values are obtained by using either a one-dimensional impurity transport code (MIST) or a zero-dimensional code with a finite particle confinement time. As an example, we show the variation of anti ..gamma.. and anti Z in different TFTR discharges.

Sesnic, S.S.; Bitter, M.; Hill, K.W.; Hiroe, S.; Hulse, R.; Shimada, M.; Stratton, B.; von Goeler, S.

1986-05-01

72

Quasimonochromatic x-ray computed tomography by the balanced filter method using a conventional x-ray source  

SciTech Connect

A quasimonochromatic x-ray computed tomography (CT) system utilizing balanced filters has recently been developed for acquiring quantitative CT images. This system consisted of basic components such as a conventional x-ray generator for radiography, a stage for mounting and rotating objects, and an x-ray line sensor camera. Metallic sheets of Er and Yb were used as the balanced filters for obtaining quasimonochromatic incident x rays that include the characteristic lines of the W K{alpha} doublet from a tungsten target. The mean energy and energy width of the quasimonochromatic x rays were determined to be 59.0 and 1.9 keV, respectively, from x-ray spectroscopic measurements using a high-purity Ge detector. The usefulness of the present x-ray CT system was demonstrated by obtaining spatial distributions of the linear attenuation coefficients of three selected samples--a 20 cm diameter cylindrical water phantom, a 3.5 cm diameter aluminum rod, and a human head phantom. The results clearly indicate that this apparatus is surprisingly effective for estimating the distribution of the linear attenuation coefficients without any correction of the beam-hardening effect. Thus, implementing the balanced filter method on an x-ray CT scanner has promise in producing highly quantitative CT images.

Saito, Masatoshi [Department of Radiological Technology, School of Health Sciences, Faculty of Medicine, Niigata University, Niigata 951-8518 (Japan)

2004-12-01

73

Dose Reduction Technique Using a Combination of a Region of Interest (ROI) Material X-Ray Attenuator and Spatially Different Temporal Filtering for Fluoroscopic Interventions  

PubMed Central

We demonstrate a novel approach for achieving patient dose savings during image-guided neurovascular interventions, involving a combination of a material x-ray region of interest (ROI) attenuator and a spatially different ROI temporal filtering technique. The part of the image under the attenuator is reduced in dose but noisy and less bright due to fewer x-ray quanta reaching the detector, as compared to the non-attenuating (or less attenuating) region. First the brightness is equalized throughout the image by post processing and then a temporal filter with higher weights is applied to the high attenuating region to reduce the noise, at the cost of increased lag; however, in the regions where less attenuation is present, a lower temporal weight is needed and is applied to preserve temporal resolution. A simulation of the technique is first presented on an actual image sequence obtained from an endovascular image guided interventional (EIGI) procedure. Then the actual implementation of the technique with a physical ROI attenuator is presented. Quantitative analysis including noise analysis and integral dose calculations are presented to validate the proposed technique.

Vasan, S.N Swetadri; Panse, A.; Jain, A.; Sharma, P.; Ionita, Ciprian N.; Titus, A.H.; Cartwright, A.N.; Bednarek, D.R; Rudin, S.

2012-01-01

74

Calculation of radiation attenuation coefficients, effective atomic numbers and electron densities for some building materials.  

PubMed

Some building materials, regularly used in Turkey, such as sand, cement, gas concrete (lightweight, aerated concrete), tile and brick, have been investigated in terms of mass attenuation coefficient (?/?), effective atomic, numbers (Z(eff)), effective electron densities (N(e)) and photon interaction cross section (?(a)) at 14 different energies from 81- to 1332-keV gamma-ray energies. The gamma rays were detected by using gamma-ray spectroscopy, a High Purity Germanium (HPGe) detector. The elemental compositions of samples were analysed using an energy dispersive X-ray fluorescence spectrometer. Mass attenuation coefficients of these samples have been compared with tabulations based upon the results of WinXcom. The theoretical mass attenuation coefficients were estimated using the mixture rule and the experimental values of investigated parameters were compared with the calculated values. The agreement of measured values of mass attenuation coefficient, effective atomic numbers, effective electron densities and photon interaction cross section with the theory has been found to be quite satisfactory. PMID:22128356

Damla, N; Baltas, H; Celik, A; Kiris, E; Cevik, U

2011-11-28

75

The performance of the INER improved free-air ionization chamber in the comparison of air kerma calibration coefficients for medium-energy X-rays  

Microsoft Academic Search

This paper describes modifications to an original design, correction factors and uncertainty evaluations for an improved free-air ionization chamber constructed at the Institute of Nuclear Energy Research (INER, Taiwan). In addition, a comparison of secondary standard air kerma calibration coefficients for 100–250kV medium-energy X-rays was performed to verify the experimental accuracy and measurement consistency of the improved chamber. The comparison

Jeng-Hung Lee; Lew H. Kotler; Ludwig Büermann; Wen-Song Hwang; Jih-Hung Chiu; Chu-Fang Wang

2005-01-01

76

X ray attenuation measurements for high-temperature materials characterization and in-situ monitoring of damage accumulation. Ph. D. Thesis - Cleveland State Univ. , 1991  

SciTech Connect

The scope of this dissertation is to develop and apply x ray attenuation measurement systems that are capable of: (1) characterizing density variations in high-temperature materials, e.g., monolithic ceramics, ceramic and intermetallic matrix composites, and (2) noninvasively monitoring damage accumulation and failure sequences in ceramic matrix composites under room temperature tensile testing. This dissertation results in the development of: (1) a point scan digital radiography system, and (2) an in-situ x ray material testing system. Radiographic evaluation before, during, and after loading shows the effect of preexisting volume flaws on the fracture behavior of composites. Results show that x ray film radiography can monitor damage accumulation during tensile loading. Matrix cracking, fiber matrix debonding, fiber bridging, and fiber pullout are imaged throughout the tensile loading of the specimens. Further in-situ radiography is found to be a practical technique for estimating interfacial shear strength between the silicon carbide fibers and the reaction bonded silicon nitride matrix. It is concluded that pretest, in-situ, and post test x ray imaging can provide for greater understanding of ceramic matrix composite mechanical behavior.

Baaklini, G.Y.

1992-03-01

77

Development of in vivo characterization of breast tissues through absolute attenuation coefficients using dedicated cone-beam CT  

NASA Astrophysics Data System (ADS)

With advances in 3D in vivo imaging technology, non-invasive procedures can be used to characterize tissues to identify tumors and monitor changes over time. Using a dedicated breast CT system with a quasi-monochromatic cone-beam x-ray source and flat-panel digital detector, this study was performed in an effort to directly characterize different materials in vivo based on their absolute attenuation coefficients. CT acquisitions were first acquired using a multi-material rod phantom with acrylic, delrin, polyethylene, fat-equivalent, and glandular-equivalent plastic rods, and also with a human cadaver breast. Projections were collected with and without a beam stop array for scatter correction. For each projection, the 2D scatter was estimated with cubic spline interpolation of the average values behind the shadow of each beam stop overlapping the object. Scatter-corrected projections were subsequently calculated by subtracting the scatter images containing only the region of the object from corresponding projections (consisting of primary and scatter x-rays) without the beam stop array. Iterative OSTR was used to reconstruct the data and estimate the non-uniform attenuation distribution. Preliminary results show that with reduced beam hardening from the x-ray beam, scatter correction further reduces the cupping artifact, improves image contrast, and yields attenuation coefficients < 8% of narrow-beam values of the known materials (range 1.2 - 7.8%). Peaks in the histogram showed clear separation between the different material attenuation coefficients. These findings indicate that minimizing beam hardening and applying scatter correction make it practical to directly characterize different tissues in vivo using absolute attenuation coefficients.

Madhav, Priti; Li, Christina M.; Tornai, Martin P.

2010-03-01

78

Using Variable Temperature Powder X-Ray Diffraction to Determine the Thermal Expansion Coefficient of Solid MgO  

ERIC Educational Resources Information Center

|A laboratory exercise was developed by using variable temperature powder X-ray diffraction (XRD) to determine [alpha] for MgO (periclase)and was tested in the Applied Physical Chemistry and Materials Characterization Laboratories at James Madison University. The experiment which was originally designed to provide undergraduate students with a…

Corsepius, Nicholas C.; DeVore, Thomas C.; Reisner, Barbara A.; Warnaar, Deborah L.

2007-01-01

79

Hygrothermal degradation of 3-glycidoxypropyltrimethoxysilane films studied by neutron and X-ray reflectivity and attenuated total reflection infrared spectroscopy.  

SciTech Connect

Thin films of organosilanes have great technological importance in the areas of adhesion promotion, durability, and corrosion resistance. However, it is well-known that water can degrade organosilane films, particularly at elevated temperatures. In this work, X-ray and neutron reflectivity (XR and NR) were combined with attenuated total reflection infrared (ATR-IR) spectroscopy to study the chemical and structural changes within thin films of (3-glycidoxypropyl)trimethoxysilane (GPS) after exposure for various periods of time to air saturated with either D{sub 2}O or H{sub 2}O at 80 C. For NR and XR, ultrathin ({approx}100 {angstrom}) films were prepared by spin-coating. Both D{sub 2}O and H{sub 2}O provide neutron scattering contrast with GPS. Variations in the neutron scattering length density (SLD) profiles (a function of mass density and atomic composition) with conditioning time were measured after drying the samples out and also swelled with H{sub 2}O or D{sub 2}O vapor at room temperature. For samples that were dried out prior to measurement, little or no change was observed for H{sub 2}O conditioning up to 3.5 days, but large changes were observed after 30 days of conditioning. The range of conditioning time for this structural change was narrowed to between 4 and 10 days with XR. The SLD profiles indicated that the top portion of the GPS film was transformed into a thick low-density layer after conditioning, but the bottom portion showed little structural change. A previous NR study of as-prepared GPS films involving swelling with deuterated nitrobenzene showed that the central portion of the film has much lower cross-link density than the region nearest the substrate. The present data show that the central portion also swells to a much greater extent with water and hydrolyzes more rapidly. The chemical degradation mechanism was identified by IR as hydrolysis of siloxane bonds. For ATR-IR, GPS films were prepared by dip-coating, which resulted in a greater and more variable thickness than for the spin-coated samples. The IR spectra revealed an increase in vicinal silanol generation over the first 3 days of conditioning followed by geminal silanol generation. Thus, the structural change detected by NR and XR roughly coincided with the onset of geminal silanol generation. Finally, little change in the reflectivity data was observed for films conditioned with D{sub 2}O at 80 C for 1 month. This indicates that hydrolysis of Si-O-Si is much slower with D{sub 2}O than with H{sub 2}O.

Tallant, David Robert; Garcia, Manuel Joseph; Majewski, Jaroslaw (Los Alamos National Lab, Los Alamos, NM); Kent, Michael Stuart; Yim, Hyun

2005-05-01

80

Gamma ray attenuation coefficient measurement for neutron-absorbent materials  

NASA Astrophysics Data System (ADS)

The compounds Na2B4O7, H3BO3, CdCl2 and NaCl and their solutions attenuate gamma rays in addition to neutron absorption. These compounds are widely used in the shielding of neutron sources, reactor control and neutron converters. Mass attenuation coefficients of gamma related to the four compounds aforementioned, in energies 662, 778.9, 867.38, 964.1, 1085.9, 1173, 1212.9, 1299.1,1332 and 1408 keV, have been determined by the ? rays transmission method in a good geometry setup; also, these coefficients were calculated by MCNP code. A comparison between experiments, simulations and Xcom code has shown that the study has potential application for determining the attenuation coefficient of various compound materials. Experiment and computation show that H3BO3 with the lowest average Z has the highest gamma ray attenuation coefficient among the aforementioned compounds.

Jalali, Majid; Mohammadi, Ali

2008-05-01

81

Application of x-ray techniques in precision farming  

NASA Astrophysics Data System (ADS)

The precision farming is a relatively new concept basing farming upon quantitative determination of various parameters in the farming practices. One of these parameters is accurate measurement of grain flow rates on real time basis. Although there are various techniques already available for this purpose, x-rays provide a very competitive alternative to the current state of art. In this work, the use of low energy bremsstrahlung x-ray, up to 30 keV, densitometry is demonstrated for grain flow rate measurements. Mass flow rates for corn are related to measured x-ray intensity in gray scale units with a 0.99 correlation coefficient for flow rates ranging from 2 kg/s to 6 kg/s. Higher flow rate values can be measured by using slightly more energetic x-rays or a higher tube current. Measurements were done in real time at a 30 Hz sampling rate. Flow rate measurements are independent of grain moisture due to a negligible change in the x-ray attenuation coefficients at typical moisture content values from 15% to 25%. Grain flow profile changes do not affect measurement accuracy. X-rays easily capture variations in the corn stream. Due to the low energy of the x-ray photons, biological shielding can easily be accomplished with 2 mm thick lead foil or 5 mm of steel. .

Arslan, Selcuk; Inanc, Feyzi; Gray, Joseph N.; Colvin, Thomas S.

2000-05-01

82

6 MV x-ray spectra obtained by small field size attenuation measurements in water and their use in small field size dosimetry  

NASA Astrophysics Data System (ADS)

Direct measurement of x-ray spectra produced by medical linear accelerators is not possible because of high intensity and energy of the radiation involved. Knowledge of energy spectra are very useful in determination of parameters that convert from ionization chamber measurements to absorbed dose. Many indirect methods for determination of x-ray spectra in therapy beams have been developed. In the present work photon beams generated by a 6-MV Varian 6000 linear accelerator were used to obtain small field (0.5 x 0.5 to 4.0 x 4.0 cm 2 at 0.5 cm increments per side) attenuation values in water for the depths from 5 to 30 cm, at 5 cm increments. Attenuation values lying between those depths were interpolated using the Newton-Coates method and attenuation data of zero-field was obtained by extrapolation. Based on the measured attenuation curves, the relative air kerma and photon energy x-ray spectra were derived for all investigating fields using a user input parameter program and an iterative procedure. The attenuation curves of the radiation fields were calculated using the reconstructed spectrum. They were compared with the measured attenuation data at each iteration step until a satisfactory fit between the measured and calculated attenuation curves was obtained. In order for derived spectra to be of practical use in radiotherapy treatment planning, they must accurate reproduce measured dose distribution data. From the knowledge of the incident beam attenuation and the incident x-ray energy spectrum for the zero-field, the percentage depth dose of the zero-field was calculated at different points along the Central Axis. The percentage depth doses of larger fields were calculated by applying of the Relative Scatter Factor to the percentage depth dose of the zero-field. The agreement was within 1.11% for all fields, ranging from 0.5 x 0.5 to 4.0 x 4.0 cm2 at 0.5 cm increments per side. Further, the reconstructed spectrum for 4 x 4 cm2 field size was used in Monte Carlo simulations performed with MCNP5. The MCNP-calculated and measured transmission curves differ by 4--7% for the 4.0 x 4.0 cm 2 field. The MCNP-calculated and the measured PDDs differ by 1--7% for 4.0 x 4.0 cm2 field. The discrepancies could be explained by the simplicity of the MCNP model that didn't take into account the complex geometry of the treatment head of the linear accelerator. The algorithm presented in this research provides a practical option to derive the beam spectrum and calculate radiation dose in the community hospitals.

Lu, Cenney W.

83

The Pore3D library package for the textural analysis of X-ray computed microtomographic images of rocks  

Microsoft Academic Search

Many research fields in Geosciences require the knowledge of the three-dimensional (3D) texture of rocks. X-ray computed microtomography (muCT) supplies an effective method to directly acquire 3D information. Transmission X-ray muCT is a non-destructive technique based on the mapping of the linear attenuation coefficient of X-rays crossing the investigated sample. The 3D distribution of constituents and the contrast based on

Daria Zandomeneghi; Lucia Mancini; Marco Voltolini; Francesco Brun; Margherita Polacci

2010-01-01

84

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

85

Determination of mass attenuation coefficients for threshold contrast evaluation in digital mammography  

NASA Astrophysics Data System (ADS)

According to the 'European protocol for the quality control of the physical and technical aspects of mammography screening' (EPQC) image quality digital mammography units has to be evaluated at different breast thicknesses. At the standard thickness of 50 mm polymethyl methacrylate (PMMA) image quality is determined by the analysis of CDMAM contrast detail phantom images where threshold contrasts are calculated for different gold disc diameters. To extend these results to other breast thicknesses contrast-to-noise ratios (CNR) and threshold contrast (TC) visibilities have to be calculated for all required thicknesses. To calculate the latter the mass attenuation coefficient (MAC) of gold has to be known for all possible beam qualities in the tube voltage range between 26 and 32 kV. In this paper we first determined the threshold contrast visibility using the CDMAM phantom with the same beam quality at different current-time products (mAs). We can derive from Rose theory that CNR • CT • ? = const, where ? is the diameter of the gold cylinder. From this the corresponding attenuation coefficients can be calculated. This procedure was repeated for four different beam qualities (Mo/Mo 27kV, Rh/Rh 29kV, Rh/Rh 31 kV, and W/Rh 29 kV)). Next, we measured the aluminium half value layer (HVL) of all x-ray spectra relevant for mammography. Using a first order Taylor expansion of MAC as a function of HVL, all other desired MAC can be calculated. The MAC as a function of the HVL was derived to MAChvl = -286.97 * hvl+186.03 with R2 = 0.997, where MAChvl indicates the MAC for all specific x-ray spectrum defined by its aluminium half value layer. Based on this function all necessary MACs needed for quality assurance (QA) were calculated. The results were in good agreement with the data found in the protocol.

Hummel, Johann; Semturs, Friedrich; Menhart, Susanne; Figl, Michael

2010-03-01

86

Revealing the powdering methods of black makeup in Ancient Egypt by fitting microstructure based Fourier coefficients to the whole x-ray diffraction profiles of galena  

NASA Astrophysics Data System (ADS)

Galena (PbS) is a major ingredient in ancient Egyptian eye makeup. The microstructure of PbS in Egyptian cosmetic powders is used as a fingerprint and is matched with the microstructures produced artificially in geological galena minerals. The microstructure of PbS is determined by x-ray diffraction peak profile analysis in terms of dislocation density, crystallite size, and size distribution. High-resolution powder diffractograms were measured at the ESRF Grenoble synchrotron source with high resolution and high peak-to-background ratios. The Fourier coefficients of the first nine measured reflections of galena are fitted using physically based Fourier coefficients of strain and size functions. Strain anisotropy is accounted for by the dislocation model of the mean square strain. The x-ray data are supplemented by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) micrographs, and are compared with archęological documents. It enables us to describe the procedures of eye makeup manufacturing in the Middle and New Kingdoms of Egypt some 2000 years before Christ.

Ungįr, T.; Martinetto, P.; Ribįrik, G.; Dooryhée, E.; Walter, Ph.; Anne, M.

2002-02-01

87

The closed-form expressions for the neutron and x-ray reflection and transmission coefficients of a one-dimensional profile  

SciTech Connect

As the first part of an effort to systematically study the inversion problem in x-ray and neutron reflectivity experiments, the closed-form expressions are derived for the reflection and transmission coefficients as functionals of the sample profile. The assumption used is that the reflection is mainly due to the first- and the second-order derivatives of the profile and thus the third-and higher-order derivatives are negligible. One of the two major characteristics of the formulas is that the reflection and transmission coefficients are explicitly expressed in terms of the profile; the other is that the formulas are valid over the entire range of momentum transfer Q. This procedure enables the straight-forward calculation of the real space profile using the reflectivity data as the computer input, with an accuracy that still remains to be evaluated through both analytical and numerical analyses with the aid of model profiles.

Zhou, Xiao-Lin (Argonne National Lab., IL (USA) Massachusetts Inst. of Tech., Cambridge, MA (USA). Dept. of Nuclear Engineering); Felcher, G.P. (Argonne National Lab., IL (USA)); Chen, Sow-Hsin (Massachusetts Inst. of Tech., Cambridge, MA (USA). Dept. of Nuclear Engineering)

1990-11-01

88

X-ray transmissive debris shield  

DOEpatents

An X-ray debris shield for use in X-ray lithography that is comprised of an X-ray window having a layer of low density foam exhibits increased longevity without a substantial increase in exposure time. The low density foam layer serves to absorb the debris emitted from the X-ray source and attenuate the shock to the window so as to reduce the chance of breakage. Because the foam is low density, the X-rays are hardly attenuated by the foam and thus the exposure time is not substantially increased.

Spielman, R.B.

1996-05-21

89

Bibliography of photon total cross section (attenuation coefficient) measurements 10 eV to 13. 5 Gev  

SciTech Connect

The authors present a bibliography of papers reporting absolute measurements of photon (XUV, x-ray, gamma-ray, bremsstrahlung) total interaction cross sections or attenuation coefficients for the elements and some compounds. The energy range covered is from 10 eV to above 10 GeV. The papers are part of the reference collection of the National Bureau of Standards Photon and Charged Particle Data Center. They cover the period from 1907 to March 1986. Included with each reference are annotations specifying the substances studied and the duplicative references to a total of about 20,000 data points. All these data are available in machine-readable form.

Hubbell, J.H.; Gerstenberg, H.M.; Saloman, E.B.

1986-10-01

90

A model for the diffuse attenuation coefficient of downwelling irradiance  

Microsoft Academic Search

The diffuse attenuation coefficient for downwelling irradiance (Kd) is an important parameter for ocean studies. For the vast ocean the only feasible means to get fine-scale measurements of Kd is by ocean color remote sensing. At present, values of Kd from remote sensing are estimated using empirical algorithms. Such an approach is insufficient to provide an understanding regarding the variation

Zhong-Ping Lee; Ke-Ping Du; Robert Arnone

2005-01-01

91

Gamma-ray attenuation coefficients in bismuth borate glasses  

NASA Astrophysics Data System (ADS)

Mass attenuation coefficients of glasses in the system: xBi2O3(1-x)B2O3 (x=0.30, 0.35, 0.40, 0.45 and 0.55) were determined at 356, 662, 1173 and 1332 keV photon energies using a narrow beam transmission method. Appreciable variations were observed in these coefficients due to changes in the chemical composition of glasses. These coefficients were then used to determine effective atomic numbers of glass samples, which were found to be constant with bismuth concentration and energy.

Singh, Kulwant; Singh, Harvinder; Sharma, Vishal; Nathuram, Rohila; Khanna, Atul; Kumar, Rajesh; Singh Bhatti, Surjit; Singh Sahota, Hari

2002-07-01

92

X-ray microtomography at high pressure  

NASA Astrophysics Data System (ADS)

X-ray microtomography at high pressure is now possible with the rotating anvil apparatus (RAA) on the 13-BM- D beamline at the Advanced Photon Source (Argonne National Lab). The high-pressure X-ray tomography microscope (HPXTM) can be used to determine densities of amorphous materials (glasses and melts) and in situ characterization of 3D microstructure of multiphase materials subject to temperature and shear deformation [1, 2]. Densities may be obtained directly by volume rendering or from X-ray absorption. The rotating anvil apparatus is compressed by a 250-ton hydraulic press between concentric thrust bearings. Toroidal and truncated cylindrical (Drickamer) anvils can be accommodated. The latter anvils perform well up to 11.5 GPa and 1873K, using boron epoxy/diamond epoxy gaskets and X-ray transparent aluminum or polytherimide plastic containment rings. Differential rotation allows for controlled sample deformation. Pressure is determined by energy dispersive diffraction of an internal standard by convenient switching from monochromatic and polychromatic radiation. In-situ calibrations of linear attenuation coefficient permit bracketing of natural basalt density to better than 1 percent relative, while [2] used volume rendering to determine the compressibility of magnesium silicate glasses and supercooled liquid. The utility of the RRA to characterize microstructural evolution will be discussed. [1] Wang et al., Rev. Sci. Instrum., 76, 073709, 2005. [2] Lesher et al., PEPI, in press, DOI: 10.1016/j.pepi.2008.10.023, 2009

Lesher, C. E.; Wang, Y.; Gaudio, S.; Clark, A.; Yamada, A.; Sanehira, T.; Rivers, M.

2009-05-01

93

X-ray attenuation around K -edge of Zr, Nb, Mo and Pd: A comparative study using proton-induced X-ray emission and 241 Am gamma rays  

Microsoft Academic Search

Mass attenuation coefficients (µ\\/?) for Zr, Nb, Mo and Pd elements around their K-edges are measured at 14 energies in the range 15.744–28.564 keV using secondary excitation from thin Zr, Nb, Mo, Rh, Pd,\\u000a Cd and Sn foils. The measurements were carried out at the K\\u000a \\u000a ?\\u000a and K\\u000a \\u000a ?\\u000a energy values of the target elements by two techniques: (1)

K. K. Abdullah; K. Karunakaran Nair; N. Ramachandran; K. M. Varier; B. R. S. Babu; Antony Joseph; Rajive Thomas; P. Magudapathy; K. G. M. Nair

2010-01-01

94

Gamma ray attenuation coefficient measurement for neutron-absorbent materials  

Microsoft Academic Search

The compounds Na2B4O7, H3BO3, CdCl2 and NaCl and their solutions attenuate gamma rays in addition to neutron absorption. These compounds are widely used in the shielding of neutron sources, reactor control and neutron converters. Mass attenuation coefficients of gamma related to the four compounds aforementioned, in energies 662, 778.9, 867.38, 964.1, 1085.9, 1173, 1212.9, 1299.1,1332 and 1408keV, have been determined

Majid Jalali; Ali Mohammadi

2008-01-01

95

Measurements of the hard-x-ray reflectivity of iridium  

SciTech Connect

In connection with the design of a hard-x-ray telescope for the Constellation X-Ray Observatory we measured the reflectivity of an iridium-coated zerodur substrate as a function of angle at 55, 60, 70, and 80 keV at the National Synchrotron Light Source of Brookhaven National Laboratory. The optical constants were derived from the reflectivity data. The real component of the index of refraction is in excellent agreement with theoretical values at all four energies. However, the imaginary component, which is related to the mass attenuation coefficient, is 50% to 70% larger at 55, 60, and 70 keV than theoretical values.

Romaine, S.; Bruni, R.; Gorenstein, P.; Zhong, Z

2007-01-10

96

Synthesis and characterisation of ion-implanted epoxy composites for X-ray shielding  

NASA Astrophysics Data System (ADS)

The epoxy samples were implanted with heavy ions such as tungsten (W), gold (Au) and lead (Pb) to investigate the attenuation characteristics of these composites. Near-surface composition depth profiling of ion-implanted epoxy systems was studied using Rutherford Backscattering Spectroscopy (RBS). The effect of implanted ions on the X-ray attenuation was studied with a general diagnostic X-ray machine with X-ray tube voltages from 40 to 100 kV at constant exposure 10 mAs. Results show that the threshold of implanted ions above which X-ray mass attenuation coefficient, ?m of the ion-implanted epoxy composite is distinguishably higher than the ?m of the pure epoxy sample is different for W, Au and Pb.

Noor Azman, N. Z.; Siddiqui, S. A.; Ionescu, M.; Low, I. M.

2012-09-01

97

Temporal variations of coda Q: An attenuation-coefficient view  

NASA Astrophysics Data System (ADS)

Spatial and temporal variations of coda wave attenuation were identified in many studies, and particularly in relation to major earthquakes and volcanic eruptions. Both the coda quality factor, Qc, and its frequency dependence often change following such events, which is often attributed to variations in the properties of large volumes of the subsurface. However, Qc is also strongly sensitive to the assumed theoretical models, which are usually insufficiently accurate for constraining the actual relationships between the geometrical spreading, anelastic dissipation, and scattering. This inaccuracy often leads to significant exaggeration of attenuation effects and complicates the interpretation of temporal variations. To resolve this problem, this study uses a phenomenological approach based on the temporal attenuation coefficient ? instead of Qc. The attenuation coefficient often linearly depends on frequency f, with intercept ?=?(0) related to the geometrical spreading and slope giving the "effective quality" factor Qe as d?/df=?Qe-1. Two published examples of temporal variations of local-earthquake coda are revisited: a non-volcanic (Stone Canyon in central California) and volcanic area (Mount St. Helens, Washington). In both cases, linear ?(f) patterns are found, with the effects of ? on coda decay rates being significantly stronger than those of Qe-1. At Stone Canyon, ? ranged from 0.035 to 0.06 s -1 and Qe varied from 3000 to 10,000, with ? increasing and Qe decreasing during the winter season. At Mount St. Helens, ? remained constant at ˜0.18 s -1, and Qe changed from 400 before the eruption to 750 after it. The observed temporal variations are explained by the near-surface changes caused by seasonal variations in the non-volcanic case and gas-, magma-, and geothermal-system related in the volcanic case. Scattering attenuation does not appear to be a significant factor in these areas, or otherwise it may be indistinguishable due to its fundamental trade-off with the background structure and anelastic attenuation in the data.

Morozov, Igor B.

2011-07-01

98

Probable X-Ray Mass Absorption Coefficients for Wave-Lengths Shorter Than the K Critical Absorption Wave-Length  

Microsoft Academic Search

Absorption coefficients of all elements may be calculated, from short wave-lengths up to the K critical absorption wave-length by the expression: ??&rgr;=??3Z2(2Z?A)???4Z5(2Z?A)+?eN0(Z?A). This formula holds for all elements when suitable values for ? and ? are chosen. Factors ? and ? are related to the atomic number, Z, by the expressions ?=(aZ2+bZ?c), and ?=(dZ2?eZ+f). Different values of the constants a,

John A. Victoreen

1943-01-01

99

Hard X-ray phase imaging and tomography using a grating interferometer  

Microsoft Academic Search

An interferometric technique for hard X-rays is presented. It is based on two transmission gratings and a phase-stepping technique, and it provides separate radiographs of the phase and absorption profiles of bulk samples. Tomographic reconstruction yields quantitative three-dimensional maps of the X-ray refractive index and of the attenuation coefficient, with a spatial resolution down to a few microns. The method

C. David; T. Weitkamp; F. Pfeiffer; A. Diaz; J. Bruder; T. Rohbeck; A. Groso; O. Bunk; M. Stampanoni; P. Cloetens

2007-01-01

100

MEDICAL X-RAY IMAGING, CURRENT STATUS AND SOME FUTURE CHALLENGES  

Microsoft Academic Search

Biomedical x-ray imaging has proven to be an indispensable component of many medical diagnostic and treatment techniques. Major technical advances over the years, culminating in helical scanning, multi slice, x-ray computed tomography, can now provide ? 0.5 mm3 resolution 3D images of the spatial distribution of tissue attenuation coefficients of an entire adult human thorax or abdomen. The utility of

Erik L. Ritman

2006-01-01

101

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 ...

102

The Influence of X-Ray Spectra Filtration on Image Quality and Patient Dose in the GE VCT 64Slice Cardiac CT Scanner  

Microsoft Academic Search

The polyenergetic X-ray spectra used during CT imaging makes it subject to beam hardening artefacts caused by the absorption of low energy X-rays as they pass through the patient. The direct consequence is that the linear attenuation coefficient calculated for thick body regions is lower than in thin regions. This effect generates cupping and streak artefacts in the reconstructed CT

M. R. Ay; A. Ahmadian; H. Ghadiri; A. Maleki; P. Ghafarian; Habib Zaidi

2009-01-01

103

Attenuation Coefficient of Single-Mode Periodic Waveguides  

NASA Astrophysics Data System (ADS)

It is widely accepted that, on ensemble average, the transmission T of guided modes decays exponentially with the waveguide length L due to small imperfections, leading to the important figure of merit defined as the attenuation-rate coefficient ?=-?ln?(T)?/L. In this Letter, we evidence that the exponential-damping law is not valid in general for periodic monomode waveguides, especially as the group velocity decreases. This result, that contradicts common beliefs and experimental practices aiming at measuring ?, is supported by a theoretical study of light transport in the limit of very small imperfections, and by numerical results obtained for two waveguide geometries that offer contrasted damping behaviors.

Baron, A.; Mazoyer, S.; Smigaj, W.; Lalanne, P.

2011-10-01

104

Reference Materials for the Measurement of Acoustic Attenuation Coefficients  

NASA Astrophysics Data System (ADS)

In this work, we present a reference material for measuring the acoustic attenuation coefficient of biological tissues or tissue-mimicking materials by a transmission method. Accurate measurements by the method require a reference material that has the same acoustic velocity and density as the biological tissue. The newly developed reference material was prepared from NaCl and MgSO4 aqueous solutions. The inorganic material is stable through time. To formulate materials with the desired acoustic velocity and density, the ratio of three constituents (i.e., water, NaCl, and MgSO4) can be determined depending on the method of experiments with mixtures by Scheffe.

Yoshida, Tomoji; Gotow, Akari; Tanaka, Kouhei; Kondo, Toshio

2011-07-01

105

Vertical profiles of beam attenuation coefficients in East China Sea  

NASA Astrophysics Data System (ADS)

The vertical profiles of beam attenuation coefficient (c) can provide information about the distribution and variability of suspended particles in the water column. Vertical profiles of particulate beam attenuation coefficient at 660 nm (cp(660)), Chlorophyll a (chla) and Particulate Organic Carbon(POC) were analyzed to examine patterns and controlling factors of vertical distributions in the East China Sea (ECS), based on two cruises in summer and late autumn. In late autumn, the cp(660) profiles showed uniform distribution with depth in most of shelf regions, and high value of cp(660) was observed in some inshore stations caused by strong resuspension. In summer, cp(660) exhibited weak subsurface maxima phenomenon in outer shelf, while with the well vertical mixed structures in the northern coast areas of ECS. The variability of cp(660) between summer and autumn were mainly influenced by the changes of thermocline distribution in the ECS. In the late autumn, water potential density were characterized as fully vertical mixed, on the contrary, the strong stratifications of water column were observed in summer. Except for several inshore stations with highly influenced by terrestrial input, significant relationships between POC and cP(660) were observed in both late autumn and summer. The close relationship between POC and cp(660) could be an potential application to retrieve the POC profiles from in situ cP(660) measurements, and be applied to the surface POC estimated from space.

Liu, Qiong; Pan, Delu; Bai, Yan; Zhang, Xuan; Zhang, Lin; Zhu, Qiankun

2012-09-01

106

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

107

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

Microsoft Academic Search

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

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

2002-01-01

108

Quantitative phase-contrast tomography of a liquid phantom using a conventional x-ray tube source.  

PubMed

Over the last few years, differential phase-contrast x-ray computed tomography (PC-CT) using a hard x-ray grating interferometer and polychromatic x-ray tube sources has been developed. The method allows for simultaneous determination of the attenuation coefficient and the refractive index decrement distribution inside an object in three dimensions. Here we report experimental results of our investigation on the quantitativeness and accuracy of this method. For this study, a phantom consisting of several tubes filled with chemically well-defined liquids was built and measured in PC-CT. We find, that the measured attenuation coefficients and refractive index decrements closely match calculated, theoretical values. Moreover, the study demonstrates, how substances with similar attenuation coefficient or refractive index decrement, can be uniquely distinguished by the simultaneous, quantitative measurement of both quantities. PMID:19506651

Herzen, Julia; Donath, Tilman; Pfeiffer, Franz; Bunk, Oliver; Padeste, Celestino; Beckmann, Felix; Schreyer, Andreas; David, Christian

2009-06-01

109

Biomedical elemental analysis and imaging using synchrotron x-ray microscopy  

SciTech Connect

The application of synchrotron x-ray microscopy to biomedical research is currently in progress at the Brookhaven National Synchrotron Light Source (NSLS). The current status of the x-ray microscope (XRM) is reviewed from a technical standpoint. Some of the items considered are photon flux, spatial resolution, quantitation, minimum detection limits, and beam-induced specimen damage. Images can be produced by measurement of fluorescent x rays or of the attenuation of the incident beam by the specimen. Maps of the elemental distributions or linear attenuation of the incident beam by the specimen. Maps of the elemental distributions or linear attenuation coefficients can be made by scanning the specimen past the beam. Computed microtomography (CMT) can be used for non- destructive images through the specimen in either the emission or absorption mode. Examples of measurements made with the XRM are given.

Jones, K.W.; Gordon, B.M.; Schidlovsky, G.; Spanne, P.; Dejun, Xue (Brookhaven National Lab., Upton, NY (USA)); Bockman, R.S. (Hospital for Special Surgery, New York, NY (USA)); Saubermann, A.J. (State Univ. of New York, Stony Brook, NY (USA). Health Science Center)

1990-01-01

110

K-shell absorption jump factors and jump ratios in elements between Tm (Z = 69) and Os (Z = 76) derived from new mass attenuation coefficient measurements  

NASA Astrophysics Data System (ADS)

The K-shell absorption jump factors and jump ratios were derived from new mass attenuation coefficients measured using an energy dispersive X-ray fluorescence (EDXRF) spectrometer for Tm, Yb elements being Tm2O3, Yb2O3 compounds and pure Lu, Hf, Ta, W, Re and Os. The measurements, in the region 56 77 keV, were done in a transmission geometry utilizing the K?1, K?2, K?1 and K?2 X- rays from different secondary source targets (Yb, Ta, Os, W, Re and Ir, etc.) excited by the 123.6 keV ?-photons from an 57Co annular source and detected by an Ultra-LEGe solid state detector with a resolution of 150 eV at 5.9 keV. Experimental results have been compared with theoretically calculated values. The measured values of Tm, Yb, Lu, Hf, Ta, W, Re and Os are reported here for the first time.

Kaya, Necati; T?ra?o?lu, Engin; Apayd?n, Gökhan; Ayl?kc?, Volkan; Cengiz, Erhan

2007-08-01

111

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

112

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 ...

113

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

114

X-ray fluorescence solution semi-microanalysis of the luminophore type materials using scattered radiation and attenuation coefficients  

Microsoft Academic Search

A method to determine zinc, yttrium and europium in luminophore type materials: ZnS:Cu+, ZnS:Ag+, Y2O2S:Eu3+ in solution is presented in this paper. Scattered radiation was used to correct for the influence of the acid matrix. The results obtained using the W L?1 Compton scatter peak were compared with these obtained using the coherent scattered L?1 and L?1 as well as

Rafal Sitko; Beata Zawisza; Jerzy Jurczyk; Franciszek Buhl

2003-01-01

115

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

116

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 ...

117

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 ...

118

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 ...

119

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

120

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 ...

121

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

Microsoft Academic Search

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

Orhan ?ēelli; Salih Erzeneo?lu; Recep Boncukēuo?lu

2003-01-01

122

X-ray properties of an anthropomorphic breast phantom for MRI and x-ray imaging  

NASA Astrophysics Data System (ADS)

The purpose of this study is to characterize the x-ray properties of a dual-modality, anthropomorphic breast phantom whose MRI properties have been previously evaluated. The goal of this phantom is to provide a platform for optimization and standardization of two- and three-dimensional x-ray and MRI breast imaging modalities for the purpose of lesion detection and discrimination. The phantom is constructed using a mixture of lard and egg whites, resulting in a variable, tissue-mimicking structure with separate adipose- and glandular-mimicking components. The phantom can be produced with either a compressed or uncompressed shape. Mass attenuation coefficients of the phantom materials were estimated using elemental compositions from the USDA National Nutrient Database for Standard Reference and the atomic interaction models from the Monte Carlo code PENELOPE and compared with human values from the literature. The image structure was examined quantitatively by calculating and comparing spatial covariance matrices of the phantom and patient mammography images. Finally, a computerized version of the phantom was created by segmenting a computed tomography scan and used to simulate x-ray scatter of the phantom in a mammography geometry. Mass attenuation coefficients of the phantom materials were within 20% and 15% of the values for adipose and glandular tissues, respectively, which is within the estimation error of these values. Matching was improved at higher energies (>20 keV). Tissue structures in the phantom have a size similar to those in the patient data, but are slightly larger on average. Correlations in the patient data appear to be longer than those in the phantom data in the anterior-posterior direction; however, they are within the error bars of the measurement. Simulated scatter-to-primary ratio values of the phantom images were as high as 85% in some areas and were strongly affected by the heterogeneous nature of the phantom. Key physical x-ray properties of the phantom have been quantitatively evaluated and shown to be comparable to those of breast tissue. Since the MRI properties of the phantom have been previously evaluated, we believe it is a useful tool for quantitative evaluation of two- and three-dimensional x-ray and MRI breast imaging modalities for the purpose of lesion detection and characterization.

Freed, Melanie; Badal, Andreu; Jennings, Robert J.; de las Heras, Hugo; Myers, Kyle J.; Badano, Aldo

2011-06-01

123

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

124

Can the Lambert-Beer law be applied to the diffuse attenuation coefficient of ocean water?  

Microsoft Academic Search

Radiative transfer theory is combined with a bio-optical model of Case 1 waters and an optical model of the atmosphere to simulate the transport of radiation in the ocean-atmosphere system. The results are treated as experimental data to study the downwelling irradiance attenuation coefficient. It is shown that the downwelling irradiance attenuation coefficient just beneath the surface and the mean

HOWARD R. GORDON

1989-01-01

125

Microtomography using an x-ray tube  

SciTech Connect

A computerized tomographic (CT) scanner has been assembled with a geometric resolution of [approximately]25 to 50 [mu]m. This CT scanner, designed and built at the University of Rome [open quotes]La Sapienza[close quotes] has the following components: (1) X-ray tube working between 20 and 55 key with a maximum current of 30 mA; this tube used bremsstrahlung radiation and filtered the primary radiation with absorbers composed of an element or elements to quasi monochromatize the primary radiation; (2) single X-ray Nal(TI), high-purity germanium detector, or an array of detectors; (3) electronic chain with an amplifier, a single-channel analyzer, and a programmable timer-scaler; (4) translation-rotation system allowing for [approximately]1-m error for linear positioning and the equivalent for rotation; (5) IBM-compatible 286 personal computer, which drives both the translation-rotation system and the timer-scaler; and (6) reconstruction program, written in turbo-Pascal, which is able not only to give the reconstructed matrix of linear attenuation coefficients but also to simulate the matrix and the related tomography.

Cesareo, R. (Univ. of Rome (Italy)); Appoloni, C.R. (Univ. of Londrina (Brazil)); Giannini, M. (Univ. of Rome (Italy))

1992-01-01

126

Determination of the attenuation coefficients by visible and ultraviolet radiation in heavy water  

Microsoft Academic Search

A long-path-length transmission cell has been used to measure the attenuation coefficients of purified HāO and DāO at various wavelengths between 250 and 580 nm. The principles governing the procedures and corrections for various sources of light attenuation in the transmission cell components are discussed. Detailed chemical histories of the HāO and DāO samples are given. The measured attenuation coefficients

L. P. Boivin; W. F. Davidson; R. S. Storey; D. Sinclair; E. D. Earle

1986-01-01

127

Determination of the polymorphic forms of bicifadine hydrochloride by differential scanning calorimetry-thermogravimetric analysis, X-ray powder diffraction, attenuated total reflectance-infrared spectroscopy, and attenuated total reflectance-near-infrared spectroscopy.  

PubMed

The pharmaceutical compound bicifadine hydrochloride, which has been found to crystallize in two polymorphic forms, has been characterized by thermal analysis, X-ray powder diffraction (XRPD), infrared (IR) spectroscopy, and near-infrared (NIR) spectroscopy. A series of 22 sample mixtures of polymorph 1 and polymorph 2 were prepared and calibration models for the quantitation of these binary mixtures have been developed for each of the XRPD, attenuated total reflectance (ATR)-IR, and ATR-NIR analytical techniques. The quantitative results were obtained using a partial least squares (PLS) algorithm, which predicted the concentration of polymorph 1 from the XRPD spectra with a root mean standard error of prediction (RMSEP) of 4.4%, from the IR spectra with a RMSEP of 3.8%, and from the NIR spectra with a RMSEP of 1.4%. The studies indicate that when analyses are carried out on equivalent sets of spectra, NIR spectroscopy offers significant advantages in quantitative accuracy as a tool for the determination of polymorphs in the solid state and is also more convenient to use than both the ATR-IR and XRPD methods. Density functional theory (DFT) B3LYP calculations and IR spectral simulation have been used to determine the nature of the vibrational modes that are the most sensitive in the analysis. PMID:16316514

McArdle, Patrick; Gilligan, Karen; Cunningham, Desmond; Ryder, Alan

2005-11-01

128

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

129

Sliced multilayer grating x-ray spectroscopy  

Microsoft Academic Search

Low energy monochromatic x rays can be ]used to detect the attenuation differences between fibrous, fat, and cancerous tissues in mammography, evaluation of computer processor chips, as well as quality control for micro components. At 17 keV, carcinomas, fibrous and fatty tissues attenuate incident radiation to different degrees which permits non invasive detection of cancerous tissue. A sliced transmission multilayer

Michele M. Wilson; Muamer Zukic; Jongmin Kim; Douglas G. Torr; Alphonsus J. Fennelly; Edward L. Fry

1994-01-01

130

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

131

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

132

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

133

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

134

Determination of Body Fat Distribution by Dual-Energy X-ray Absorptiometry and Attenuation of Visceral Fat Vasoconstriction by Enalapril  

Microsoft Academic Search

Use of dual-energy X-ray absorptiometry (DEXA) data to calculate the percent of body fat in the visceral (%VF) and subcutaneous\\u000a (%SF) compartments and the mechanism of visceral fat vasoconstriction when intestinal mucosal afferent nerves are stimulated\\u000a has not been reported. The aim of this sudy was to compare visceral fat weight determined by DEXA and direct weighing and\\u000a determine whether

Felix W. Leung; Samuel Murray; Elsa Murray; Vay Liang Go

2008-01-01

135

X-Ray Optics.  

National Technical Information Service (NTIS)

A technique has been developed to improve the spatial resolving power of a Type 1 X-ray telescope while reducing its size and weight by an appreciable amount. While X-ray telescopy appears to have little attraction industrially, the same basic optical man...

1969-01-01

136

X-Rays  

NSDL National Science Digital Library

This problem set is designed to test students' understanding of x-rays. Students are given wavelengths and asked to calculate minimum potential energy, radiation frequency, and whether or not the mineral can be used as a radiation filter. They are also asked to determine the 2-theta for different crystal face x-ray diffractions given cell edge length and radiation wavelength.

137

X-ray Equipment  

Microsoft Academic Search

A method is described of determining the area of a body to be subjected to irradiation by x-rays. A calibrated system of shutters is provided, which is used in conjunction with a source of ordinary light placed in the same position as the source of x-rays. Thus from the image formed by the ordinary light, one can determine the region

Hollstein

1949-01-01

138

X-ray calorimeters  

Microsoft Academic Search

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

F. Scott Porter

2010-01-01

139

X-ray beamsplitter  

DOEpatents

An x-ray beamsplitter which splits an x-ray beam into two coherent parts by reflecting and transmitting some fraction of an incident beam has applications for x-ray interferometry, x-ray holography, x-ray beam manipulation, and x-ray laser cavity output couplers. The beamsplitter is formed of a wavelength selective multilayer thin film supported by a very thin x-ray transparent membrane. The beamsplitter resonantly transmits and reflects x-rays through thin film interference effects. A thin film is formed of 5-50 pairs of alternate Mo/Si layers with a period of 20-250 A. The support membrane is 10-200 nm of silicon nitride or boron nitride. The multilayer/support membrane structure is formed across a window in a substrate by first forming the structure on a solid substrate and then forming a window in the substrate to leave a free-standing structure over the window.

Ceglio, Natale M. (Livermore, CA); Stearns, Daniel S. (Mountain View, CA); Hawryluk, Andrew M. (Modesto, CA); Barbee, Jr., Troy W. (Palo Alto, CA)

1989-01-01

140

Water equivalence of micelle gels for x-ray beams  

NASA Astrophysics Data System (ADS)

Micelle gel is a radiochromic hydrogel with the potential to be used as a three dimensional (3D) radiation dosimeter. Since an ideal dosimeter should present water equivalent properties, in this study the water equivalence of two formulations of micelle gel has been investigated by calculating electron density, effective atomic number, fractional interaction probabilities, mass attenuation coefficient. The depth doses for kilovoltage and megavoltage x-ray beams have also modelled using Monte Carlo code. Based on the results of this work, micelle gels can be considered as water equivalent dosimeters.

Gorjiara, T.; Hill, R.; Kuncic, Z.; Bosi, S.; Baldock, C.

2013-06-01

141

Multilayer mirrors and beam splitters for soft X-rays  

Microsoft Academic Search

X-ray transmission coefficients for perfect multilayers have been derived based upon the optics of thin films at large angles of incidence. The new transmission coefficient together with the previously given diffraction coefficient can now be used to characterize the optical properties of multilayers. Applications of flat multilayer as X-ray beam splitters, polarizers and normal incidence mirrors are also presented.

P. Lee

1982-01-01

142

Multilayer mirrors and beam splitters for soft X-rays  

NASA Astrophysics Data System (ADS)

X-ray transmission coefficients for perfect multilayers have been derived based upon the optics of thin films at large angles of incidence. The new transmission coefficient together with the previously given diffraction coefficient can now be used to characterize the optical properties of multilayers. Applications of flat multilayer as X-ray beam splitters, polarizers and normal incidence mirrors are also presented.

Lee, P.

1982-10-01

143

Thoracic spine x-ray  

MedlinePLUS

Vertebral radiography; X-ray - spine; Thoracic x-ray; Spine x-ray; Thoracic spine films; Back films ... The test is done in a hospital radiology department or in the health care provider's office. You will lie on the x-ray table in different positions. If the x-ray ...

144

Two means method for the attenuation coefficient determination of archaeological ceramics from the North of Parana.  

National Technical Information Service (NTIS)

This work reports an alternative methodology for the linear attenuation coefficient determination ((mu) (rho)) of irregular form samples, in such a way that is not necessary to consider the sample thickness. With this methodology, indigenous archaeologica...

R. M. C. Silva

1997-01-01

145

X ray laser  

NASA Astrophysics Data System (ADS)

An X-ray laser that lases between the K edges of carbon and oxygen, i.e., between 44 and 23 Angstroms, is provided. The laser comprises a silicon and dysprosium foil combustion that is driven by two beams of intense line focused optical laser radiation. Ground state nickel-like dysprosium ions are resonantly photo-pumped to their upper X-ray laser state by line emission from hydrogen-like silicon ions. The novel X-ray laser should prove especially useful for the microscopy of biological specimens.

Nilsen, J.

1991-10-01

146

X-ray laser  

DOEpatents

An X-ray laser that lases between the K edges of carbon and oxygen, i.e. between 44 and 23 Angstroms, is provided. The laser comprises a silicon and dysprosium foil combustion that is driven by two beams of intense line focused optical laser radiation. Ground state nickel-like dysprosium ions are resonantly photo-pumped to their upper X-ray laser state by line emission from hydrogen-like silicon ions. The novel X-ray laser should prove especially useful for the microscopy of biological specimens.

Nilsen, J.

1991-10-12

147

Study on Z dependence of partial and total mass attenuation coefficients  

NASA Astrophysics Data System (ADS)

The partial and total mass attenuation coefficients ?/?(cmg) of photons at energy of 1 keV 100 GeV have been calculated as a function of atomic number and photon energies using the XCOM program (version 3.1) and data base and the calculated results were compared with the measurement. The results show that the mass attenuation coefficients (?/?) depend on incoming photon energies and Z numbers of the target nuclei.

Akkurt, I.; Mavi, B.; Akkurt, A.; Basyigit, C.; Kilincarslan, S.; Yalim, H. A.

2005-09-01

148

Ultrasonic computed tomography reconstruction of the attenuation coefficient using a linear array.  

PubMed

The attenuation coefficient distribution and sound velocity distribution in the breast can be used to complement B-mode ultrasound imaging in the detection of breast cancer. This study investigated an approach for reconstructing the attenuation coefficient distribution in the breast using a linear array. The imaging setup was identical to that for conventional B-mode breast imaging, and the same setup has been used for reconstruction of sound velocity distributions in previous studies. In this study, we further developed a reconstruction method for the attenuation coefficient distribution. In particular, the proposed method incorporates the segmentation information from B-mode images and uses the sound velocity distribution to compensate for refraction effects. Experiments were conducted with a setup consisting of a 5-MHz, 128-channel linear array, a programmable digital array system, a phantom, and a computer. The constructed phantom contained materials mimicking the following breast tissues: glandular tissue, fat, cysts, high-attenuation tumors, and irregular tumors. Application of the proposed technique resulted in all the cysts and tumors (including high-attenuation and irregular tumors) being distinguished by thresholding the reconstructed attenuation coefficients. We have demonstrated that it is possible to use the same imaging setup to acquire data for B-mode image, sound velocity distribution, and attenuation coefficient distribution simultaneously. Moreover, the experimental data indicate its potential in improving the detection of breast cancer. PMID:16422413

Huang, Sheng-Wen; Li, Pai-Chi

2005-11-01

149

X-ray grid-detector apparatus  

DOEpatents

A hybrid grid-detector apparatus for x-ray systems wherein a microchannel plate structure has an air-interspaced grid portion and a phosphor/optical fluid-filled grid portion. The grids are defined by multiple adjacent channels separated by lead-glass septa. X-rays entering the air-interspaced grid portion at an angle of impingement upon the septa are attenuated, while non-impinging x-rays pass through to the phosphor/fluid filled portion. X-ray energy is converted to luminescent energy in the phosphor/fluid filled portion and the resultant beams of light are directed out of the phosphor/optical fluid filled portion to an imaging device.

Boone, John M. (Folsom, CA); Lane, Stephen M. (Oakland, CA)

1998-01-27

150

A patient-equivalent attenuation phantom for estimating patient exposures from automatic exposure controlled x-ray examinations of the abdomen and lumbo-sacral spine  

SciTech Connect

The Joint Commission on Accreditation of Healthcare Organizations requires diagnostic radiology facilities to known the approximate amount of radiation received by an average patient during radiographic examinations at the facility. Automatic exposure controlled (AEC) techniques are used for many of these exams, and a standard patient-equivalent phantom is necessary when estimating patient exposure on such systems. This is of particular importance if exposures are to be compared among AEC systems with different entrance x-ray spectra. We have developed a phantom, LucA1 Abdomen, to facilitate determining the average patient exposure from AEC anteroposterior (AP) abdomen and lumbo-sacral (LS) spine radiography. The phantom is relatively lightweight, transportable, sturdy, and made of readily available inexpensive materials (Lucite and aluminum). It accurately simulates the primary and scatter transmission through the soft tissue and L-4 spinal regions of a patient-equivalent anthropomorphic phantom for x-ray spectra typically used in abdomen/LS spine radiography. A clinical evaluation to verify the patient-equivalence of three commercial anthropomorphic phantoms (Humanoid, Rando, 3-M) and two acrylic/aluminum phantoms (ANSI and LucA1 Abdomen) has been conducted. The design and development of the LucA1 Abdomen phantom and the evaluation of all phantoms is described.

Conway, B.J.; Duff, J.E.; Fewell, T.R.; Jennings, R.J.; Rothenberg, L.N.; Fleischman, R.C. (Food and Drug Administration, Rockville, MD (USA))

1990-05-01

151

The X-ray universe  

NASA Astrophysics Data System (ADS)

This book is a selective and personal history of X-ray astronomy. The X-ray universe is considered along with the sensible world, historical aspects regarding the discovery and utilization of X-rays, the pioneers of X-ray astronomy, the discovery of an X-ray star, the riddle of the X-ray stars, developments leading to the Uhuru (X-ray Explorer) satellite and the study of neutron stars and black holes, the X-ray sky, a telescope for X-rays, the Einstein observatory (HEAO-2), stellar coronas and supernovas, active galaxies and quasars, clusters of galaxies and the missing mass, and the cosmic X-ray background. Attention is also given to NASA's Advanced X-Ray Astrophysics Facility, which will open a permanent window on the X-ray universe.

Tucker, Wallace; Giacconi, Riccardo

152

X-Ray Diffraction  

NSDL National Science Digital Library

This site from the University of London presents a tutorial on several methods of X-ray diffraction, including the powder, rotating crystal, and Laue methods Each section includes interactive Java applets, exercises, and links to a glossary of terms.

Matter.org

153

X-ray (image)  

MedlinePLUS

... bone) will block most of the x-ray particles, and will appear white. Metal and contrast media (special dye used to highlight areas of the body) will also appear white. Structures containing air will be black and muscle, fat, ...

154

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

155

X-ray laser  

Microsoft Academic Search

This invention is directed towards a scalable x-ray laser comprising means for providing an active medium of lithium-like atoms or ions, means for producing in the active medium a population of low density ions in an excited intermediate metastable state and a visible or near infrared laser to stimulate x-ray lasing by resonant or non-resonant antistokes Raman process to the

J. D. Daugherty; H. A. Hyman; S. A. Mani

1980-01-01

156

X-ray binaries  

Microsoft Academic Search

The various types and classes of X-ray binary are reviewed high-lighting recent results. The high mass X-ray binaries (HMXRBs) can be used to probe the nature of the mass loss from the OB star in these systems. Absorption measurements through one orbital cycle of the supergiant system X1700-37 are well modelled by a radiation driven wind and also require a

N. E. White

1989-01-01

157

Fabrication of large area X-ray diffraction grating for X-ray phase imaging  

SciTech Connect

X-ray lithography, which uses highly directional synchrotron radiation, is one of the technologies that can be used for fabricating micrometer-sized structures. In X-ray lithography, the accuracy of the fabricated structure depends largely on the accuracy of the X-ray mask. Since X-ray radiation is highly directional, a micro-fabrication technology that produces un-tapered and high aspect ratio highly absorbent structures on a low absorbent membrane is required. Conventionally, a resin material is used as the support membrane for large area X-ray masks. However, resin membranes have the disadvantage that they can sag after several cycles of X-ray exposure due to the heat generated by the X-rays. Therefore, we proposed and used thin carbon wafers for the membrane material because carbon has an extremely small thermal expansion coefficient. We fabricated new carbon membrane X-ray masks, and these results of X-ray lithography demonstrate the superior performance.

Noda, Daiji; Tokuoka, Atsushi; Katori, Megumi; Minamiyama, Yasuto; Yamashita, Kenji; Nishida, Satoshi; Hattori, Tadashi [Laboratory of Advanced Science and Technology for Industry, University of Hyogo, 3-1-2 Koto, Kamigori, Ako, Hyogo 678-1205 (Japan); Nanocreate Co., Ltd, 9-8-6 Tsujii, Himeji, Hyogo 670-0083 (Japan)

2012-07-31

158

Fabrication of large area X-ray diffraction grating for X-ray phase imaging  

NASA Astrophysics Data System (ADS)

X-ray lithography, which uses highly directional synchrotron radiation, is one of the technologies that can be used for fabricating micrometer-sized structures. In X-ray lithography, the accuracy of the fabricated structure depends largely on the accuracy of the X-ray mask. Since X-ray radiation is highly directional, a micro-fabrication technology that produces un-tapered and high aspect ratio highly absorbent structures on a low absorbent membrane is required. Conventionally, a resin material is used as the support membrane for large area X-ray masks. However, resin membranes have the disadvantage that they can sag after several cycles of X-ray exposure due to the heat generated by the X-rays. Therefore, we proposed and used thin carbon wafers for the membrane material because carbon has an extremely small thermal expansion coefficient. We fabricated new carbon membrane X-ray masks, and these results of X-ray lithography demonstrate the superior performance.

Noda, Daiji; Tokuoka, Atsushi; Katori, Megumi; Minamiyama, Yasuto; Yamashita, Kenji; Nishida, Satoshi; Hattori, Tadashi

2012-07-01

159

Development of a model of an x-ray tube transmission source  

SciTech Connect

In support of the development of an x-ray tube based source for transmission measurements of UF6 gas, we have developed a one-dimensional, spreadsheet-based model of the source. Starting with the spectrum produced by an x-ray tube we apply the linear attenuation coefficients for various notch filters, the aluminum pipe, and UF6 gas. This model allows calculation of the transmitted spectrum based on the type of filter, the thickness of the filter, the x-ray tube high voltage, the Al pipe thickness, and the UF6 gas pressure. The sensitivity of the magnitude of the transmission peak produced by the notch filter to any of these variables can be explored quickly and easily to narrow the choices for experimental measurements. To validate the spreadsheet based model, comparisons have been made to various experimental data.

Goda, Joetta M [Los Alamos National Laboratory; Ianakiev, Kiril D [Los Alamos National Laboratory; Moss, Cal E [Los Alamos National Laboratory

2009-01-01

160

Comparison between different spectral models of the diffuse attenuation and absorption coefficients of seawater  

NASA Astrophysics Data System (ADS)

The goal of this work is to verify different spectral models of the diffuse attenuation and absorption coefficients of sea water and to work out a recommendation for their use. It is shown that the spectral models of the diffuse attenuation coefficient Kd((lambda) ) developed by Austin, Petzold, 1984 and by Volynsky, Sud'bin, 1992 correspond with each other, as well the models of Ivanov, Shemshura, 1973 and of Kopelevich, Shemshura, 1988 for calculation of the spectral absorption coefficient a((lambda) ) on the values of Kd((lambda) ). Theoretical foundation of the relation between a((lambda) ) and Kd((lambda) ) is given. The up-to-date physical model of the sea water light absorption is considered and checked by means of comparison with measured values of the attenuation coefficient at the ultraviolet and visible spectral ranges.

Kopelevich, Oleg V.; Filippov, Yury V.

1994-10-01

161

Assessment of errors caused by X-ray scatter and use of contrast medium when using CT-based attenuation correction in PET  

Microsoft Academic Search

Purpose  Quantitative image reconstruction in positron emission tomography (PET) requires an accurate attenuation map of the object under study for the purpose of attenuation correction. Current dual-modality PET\\/CT systems offer significant advantages over stand-alone PET, including decreased overall scanning time and increased accuracy in lesion localisation and detectability. However, the contamination of CT data with scattered radiation and misclassification of contrast

Mohammad Reza Ay; Habib Zaidi

2006-01-01

162

Refractive Optics for Hard X-ray Transmission Microscopy  

Microsoft Academic Search

For hard x-ray transmission microscopy at photon energies higher than 15 keV we design refractive condenser and imaging elements to be used with synchrotron light sources as well as with x-ray tube sources. The condenser lenses are optimized for low x-ray attenuation--resulting in apertures greater than 1 mm--and homogeneous intensity distribution on the detector plane, whereas the imaging enables high-resolution

M. Simon; G. Ahrens; A. Last; J. Mohr; V. Nazmov; E. Reznikova; A. Voigt

2011-01-01

163

Effective recombination coefficient and solar zenith angle effects on low-latitude D-region ionosphere evaluated from VLF signal amplitude and its time delay during X-ray solar flares  

NASA Astrophysics Data System (ADS)

Excess solar X-ray radiation during solar flares causes an enhancement of ionization in the ionospheric D-region and hence affects sub-ionospherically propagating VLF signal amplitude and phase. VLF signal amplitude perturbation (?A) and amplitude time delay (?t) (vis-į-vis corresponding X-ray light curve as measured by GOES-15) of NWC/19.8 kHz signal have been computed for solar flares which is detected by us during Jan-Sep 2011. The signal is recorded by SoftPAL facility of IERC/ICSP, Sitapur (22? 27'N, 87? 45'E), West Bengal, India. In first part of the work, using the well known LWPC technique, we simulated the flare induced excess lower ionospheric electron density by amplitude perturbation method. Unperturbed D-region electron density is also obtained from simulation and compared with IRI-model results. Using these simulation results and time delay as key parameters, we calculate the effective electron recombination coefficient (? eff ) at solar flare peak region. Our results match with the same obtained by other established models. In the second part, we dealt with the solar zenith angle effect on D-region during flares. We relate this VLF data with the solar X-ray data. We find that the peak of the VLF amplitude occurs later than the time of the X-ray peak for each flare. We investigate this so-called time delay (?t). For the C-class flares we find that there is a direct correspondence between ?t of a solar flare and the average solar zenith angle Z over the signal propagation path at flare occurrence time. Now for deeper analysis, we compute the ?t for different local diurnal time slots DT. We find that while the time delay is anti-correlated with the flare peak energy flux ? max independent of these time slots, the goodness of fit, as measured by reduced-? 2, actually worsens as the day progresses. The variation of the Z dependence of reduced-? 2 seems to follow the variation of standard deviation of Z along the T x -R x propagation path. In other words, for the flares having almost constant Z over the path a tighter anti-correlation between ?t and ? max was observed.

Basak, Tamal; Chakrabarti, Sandip K.

2013-09-01

164

Monte Carlo simulation of x-ray spectra in electron probe microanalysis: Comparison of continuum with experiment  

NASA Astrophysics Data System (ADS)

A Monte Carlo simulation code has been developed to describe the x-ray generation in a specimen for electron probe microanalysis (EPMA), enabling x-ray spectra observed by EPMA to be reproduced theoretically. The Monte Carlo simulation is based on the use of the Mott cross section and Bethe stopping power equation in describing elastic and inelastic scattering processes, respectively. With respect to x-ray generation the Sommerfeld theory for bremsstrahlung radiation was described by equations of Kirkpatrick-Wiedmann and of Statham for bremsstrahlung cross section. The up-to-date compilation of mass absorption coefficient by Henke, Gullikson, and Davis is used to evaluate attenuation of x-ray intensity. To verify the present Monte Carlo simulation measurements of x-ray spectra for Cu and Rh targets have been performed for primary electron energies of 10-30 keV by energy-dispersive x-ray spectrometry of an electron probe microanalyzer. Excellent agreement between experimental spectra and calculated results has been confirmed in the cases investigated, leading to the conclusion that the Monte Carlo simulation technique will be a powerful tool for more comprehensive understanding of x-ray generation in EPMA specimens.

Ding, Z.-J.; Shimizu, R.; Obori, K.

1994-12-01

165

X-Rays for Children  

MedlinePLUS

... for your child, depending on the goal: Bitewing X-rays (also called cavity-detecting X-rays) — These X-rays are used to view the ... called the 6-year molar) has erupted. Periapical X-rays — These are used to view the entire crowns ...

166

Magnified hard x-ray image in one dimension  

SciTech Connect

The possibility of magnified x-ray imaging is explored, by the near-field attenuation of a sample intercepting a spherical wave-front, plus the beam profile modulation by Borrmann pyramid based on dynamic x-ray scattering. It is verified by experiments in one dimension as well as numerical simulation.

Britten, James [Department of Chemistry, McMaster University, Hamilton, Ontario L8S4L8 (Canada); Feng Zhechuan [Department of Electrical Engineering, National Taiwan University, Taipei 106-17, Taiwan (China); Xu Gu [Department of Materials Science and Engineering, McMaster University, Hamilton, Ontario L8S4L7 (Canada)

2010-06-28

167

Modeling X-Ray Photoionized Plasmas: Ion Storage Ring Measurements of Low Temperature Dielectronic Recombination Rate Coefficients for L-Shell Iron  

Microsoft Academic Search

Iron L-shell ions (Fe XVII to Fe XXIV) play an important role in determining the line emission and thermal and ionization structures of photoionized gases. Existing uncertainties in the theoretical low temperature dielectronic recombination (DR) rate coefficients for these ions significantly affects our ability to model and interpret observations of photoionized plasmas. To help address this issue, we have initiated

D. W. Savin; N. R. Badnell; T. Bartsch; C. Brandau; M. H. Chen; M. Grieser; G. Gwinner; A. Hoffknecht; S. M. Kahn; J. Linkemann; A. Müller; R. Repnow; A. A. Saghiri; S. Schippers; M. Schmitt; D. Schwalm; A. Wolf; P. A. Zįvodszky

2000-01-01

168

Measuring the X-ray transmission function of the ACIS UV/Optical blocking filters at the National Synchrotron Light Source.  

NASA Astrophysics Data System (ADS)

The 0.26 to 3 keV X-ray transmission of the AXAF/ACIS UV/Optical blocking filters was measured at the National Synchrotron Light Source (NSLS) at Brookhaven. The main objective of the calibration was to determine an X-ray transmission function with an uncertainty of less than 1%. The ACIS UV/Optical Imager and Spectrometer blocking filters consist of LEXAN,a polycarbonate plastic with a chemical composition of C16H14O3, with a layer of aluminum coated on each side to provide optical light blocking. The X-ray transmission data can not be well fitted, especially at fine energy scales, with models that incorporate Henke absorption coefficients alone. Residuals between the X-ray transmission data and models that utilize the Henke absorption coefficients are as high as 50% and are mostly due to extended X-ray absorption fine structure (EXAFS) that appears above the C, O and Al absorption edges. We provide an analytic expression for the transmission function of the ACIS UV/Optical blocking filters which combines an X-ray transmission derived from Henke mass attenuation coefficients with a component to characterize the EXAFS contribution. EXAFS theory predicts a temperature dependence on the amplitude of the EXAFS oscillations. This dependence arises from the fact that thermal vibrations of the atoms in a solid produce a phase mismatch of the backscattered electron wave function. We derive a simple expression to predict the on-orbit X-ray transmission from the X-ray transmission measured on ground. Finally we present several examples where the presence of EXAFS in the X-ray transmission of a filter may significantly influence the interpretation of spectral data originating from celestial X-ray sources.

Chartas, G.; Garmire, G.; Nousek, J.; Graessle, D.; Furenlid, L.

1996-05-01

169

Bibliography of photon total cross section (attenuation coefficient) measurements 10 eV to 13. 5 GeV, 1907-1993  

SciTech Connect

A bibliography is presented of papers reporting absolute measurements of photon (XUV, x-ray, gamma-ray, bremsstrahlung) total interaction cross sections or attenuation coefficients for the elements and some compounds. The energy range covered is from 10 eV to above 10 GeV. These papers are part of the reference collection of the National Institute of Standards and Technology Photon and Charged Particle Data Center. They cover the period from 1907 through 1993 and into 1994. Thus this report is an update of the 1986 earlier report NBSIR 86-3461 (PB87-116141), and also includes additional papers dating back as far as 1966 which have since been found or brought to the attention of the author. Included with each reference are annotations specifying the energy range covered and the substances studied. This updated bibliography now includes 573 non-duplicative references to available measured data, plus 42 references to critical evaluations and review articles.

Hubbell, J.H.

1994-05-01

170

Trends in attenuation coefficients in Athens, Greece, from 1954 to 1991  

SciTech Connect

Unsworth and Monteith`s attenuation coefficient T{sub UM} was calculated from midday cloudless sky data in Athens, Greece, for the period 1954 to 1991. An interdependence between T{sub UM} and the Linke factor T{sub L} was found and is expressed as a mathematical function. It was also shown that the minimum turbidity levels occur during the winter and maximum levels occur during summer. An analysis of the long-term variation of the attenuation coefficients depicts the deterioration of air quality during the same period. The dependence of the ratio of diffuse to global radiation on the attenuation coefficient T{sub UM}, is also presented. 26 refs., 4 figs., 1 tab.

Jacovides, C.P.; Kaltsounides, N.A.; Giannourakos, G.P.; Kallos, G.B. [Univ. of Athens (Greece)

1995-06-01

171

Synoptic water clarity assessment in the Florida Keys using diffuse attenuation coefficient estimated from Landsat imagery  

Microsoft Academic Search

The diffuse attenuation coefficient, K (m–1), is a measure of the effective attenuation of light in the water column. It characterizes water clarity and is used as a\\u000a proxy for water quality. Mapping of shallow water benthic habitats using optical means, including daytime visible satellite\\u000a imagery, requires knowledge of K to correct for water column effects such as light absorption

D. Palandro; C. Hu; S. Andréfouėt; F. E. Muller-Karger

172

Diffraction enhanced x-ray imaging  

SciTech Connect

Diffraction enhanced imaging (DEI) is a new x-ray radiographic imaging modality using synchrotron x-rays which produces images of thick absorbing objects that are almost completely free of scatter. They show dramatically improved contrast over standard imaging applied to the same phantoms. The contrast is based not only on attenuation but also the refraction and diffraction properties of the sample. The diffraction component and the apparent absorption component (absorption plus extinction contrast) can each be determined independently. This imaging method may improve the image quality for medical applications such as mammography.

Thomlinson, W.; Zhong, Z. [Brookhaven National Lab., Upton, NY (United States). National Synchrotron Light Source; Chapman, D. [Illinois Inst. of Tech., Chicago, IL (United States); Johnston, R.E. [Univ. of North Carolina, Chapel Hill, NC (United States). Dept. of Radiology; Sayers, D. [North Carolina State Univ., Raleigh, NC (United States). Dept. of Physics

1997-09-01

173

X-ray Diffraction  

NSDL National Science Digital Library

A series of laboratory activities on x-ray diffraction physics using the Teltron Tel-X-Ometer System. Detailed explanations on the production and delivery of the beam is included, as well as a very complete safety protocol for conducting the experiments.

Langan, Shawn

2012-03-08

174

X-ray detector  

Microsoft Academic Search

An ionization chamber for use in determining the spatial distribution of x-ray photons in tomography systems comprises a plurality of substantially parallel, planar anodes separated by parallel, planar cathodes and enclosed in a gas of high atomic weight at a pressure from approximately 10 atmospheres to approximately 50 atmospheres. The cathode and anode structures comprise metals which are substantially opaque

N. R. Whetten; J. M. Houston

1977-01-01

175

The x-ray fovea, a device for reducing x-ray dose in fluoroscopy.  

PubMed

The x-ray fovea (U.S. patents pending) is a device for reducing x-ray dose to patients and operations during x-ray fluoroscopy. It consists of a semitransparent collimator with an open, circular, central hole. The fovea collimator is placed at the exit of the x-ray tube, and the attenuation of the peripheral x-ray beam reduces x-ray exposure to patients and operators. The shadow caused by the x-ray fovea can be compensated using real-time image processing hardware. Accurate compensation is demonstrated for both linearly and logarithmically acquired images using a model that accounts for beam hardening in the fovea collimator. The central fovea region has improved image quality due to reduced scatter and veiling glare from the periphery. From beam-stop measurements, a 40% reduction in scatter plus veiling glare is measured using the fovea. A contrast improvement ratio of 1.5 is measured throughout the central region. In the compensated periphery, noise is increased by a factor of 1.66 because fewer photons are detected, but a small amount of temporal filtering compensates this degradation. The Roentgen area product (RAP) exposure to patients is reduced by approximately 70%, while scattered exposure to operators is reduced by approximately 60%. PMID:8208223

Labbe, M S; Chiu, M Y; Rzeszotarski, M S; Bani-Hashemi, A R; Wilson, D L

1994-03-01

176

High-energy synchrotron radiation x-ray microscopy: Present status and future prospects  

SciTech Connect

High-energy radiation synchrotron x-ray microscopy is used to characterize materials of importance to the chemical and materials sciences and chemical engineering. The x-ray microscope (XRM) forms images of elemental distributions fluorescent x rays or images of mass distributions by measurement of the linear attenuation coefficient of the material. Distributions of sections through materials are obtained non-destructively using the technique of computed microtomography. The energy range of the x rays used for the XRM ranges from a few keV at the minimum value to more than 100 keV, which is sufficient to excite the K-edge of all naturally occurring elements. The work in progress at the Brookhaven NSLS X26 and X17 XRM is described in order to show the current status of the XRM. While there are many possible approaches to the XRM instrumentation, this instrument gives state-of-the-art performance in most respects and serves as a reasonable example of the present status of the instrumentation in terms of the spatial resolution and minimum detection limits obtainable. The examples of applications cited give an idea of the types of research fields that are currently under investigation. They can be used to illustrate how the field of x-ray microscopy will benefit from the use of bending magnets and insertion devices at the Advanced Photon Source. 8 refs., 5 figs.

Jones, K.W.; Gordon, B.M.; Spanne, P. (Brookhaven National Lab., Upton, NY (United States)); Rivers, M.L.; Sutton, S.R. (Illinois Univ., Chicago, IL (United States))

1991-01-01

177

21 CFR 1020.40 - Cabinet x-ray systems.  

Code of Federal Regulations, 2013 CFR

... PERFORMANCE STANDARDS FOR IONIZING RADIATION EMITTING PRODUCTS Ā§ 1020.40 Cabinet...which remains open during generation of x radiation. (3) Cabinet x-ray system means...a material being irradiated, provide radiation attenuation, and exclude personnel...

2013-04-01

178

Fluorescent computer tomography; A model for correction of x-ray absorption  

SciTech Connect

The distributions of individual trace elements within a sample can be found using fluorescent computed tomography (FCT). The absorption of incident and fluorescent X-rays results in degraded reconstructions of the distributions. The proposed method uses the absorption density, measured using conventional absorption tomography, to remove absorption effects. A model for FCT with absorption is developed and simulated. The resulting corrected reconstructions are compared to the reconstructions degraded by attenuation effects. In this paper a comparison is made with other methods which utilize knowledge of the sample composition and a standard source to estimate the absorption coefficients used to correct for attenuation effects.

Hogan, J.P.; Gonsalves, R.A. (Electro-Optics Technology Center, Tufts Univ., Medford, MA (US)); Krieger, A.S. (Radiation Science, Inc., Belmont, MA (US))

1991-12-01

179

Abnormal breast tissue imaging based on multi-energy x-ray  

NASA Astrophysics Data System (ADS)

The dual or multi-energy x-ray technique facilitates to generate tissue-selective images, by exploiting tissue-specific energy dependence of x-ray attenuation. An abnormal breast is considered to be a mixture of adipose, glandular, and abnormal tissues, but three tissues cannot be selectively decomposed because the total attenuation of a tissue is represented by only two attenuation basis functions at diagnostic energy range. This paper presents a novel method to selectively represent abnormal breast tissue, using polyenergetic multi-energy x-ray. We show that an abnormal tissue can be revealed from the total thickness map, which is virtually constructed by assuming a healthy and compressed breast. Specifically, regression analysis is first performed using the multi-energy images of the prepared calibration phantom that consists of two basis materials. Total thickness map is then constructed by linearly combining thickness maps of basis materials, where the optimal weights for combination are determined so that the uniformity of total breast thickness is maximized. It is noted that the proposed method does not need accurate attenuation coefficients of breast tissues. Simulation results show that the proposed method dramatically improves the detectability of mass that is obscured by normal structures.

Kang, Dong-Goo; Han, Seok-Min; Sung, Younghun; Lee, Seongdeok

2011-03-01

180

X-ray lithography using holographic images  

DOEpatents

Methods for forming X-ray images having 0.25 {micro}m minimum line widths on X-ray sensitive material are presented. A holographic image of a desired circuit pattern is projected onto a wafer or other image-receiving substrate to allow recording of the desired image in photoresist material. In one embodiment, the method uses on-axis transmission and provides a high flux X-ray source having modest monochromaticity and coherence requirements. A layer of light-sensitive photoresist material on a wafer with a selected surface is provided to receive the image(s). The hologram has variable optical thickness and variable associated optical phase angle and amplitude attenuation for transmission of the X-rays. A second embodiment uses off-axis holography. The wafer receives the holographic image by grazing incidence reflection from a hologram printed on a flat metal or other highly reflecting surface or substrate. In this second embodiment, an X-ray beam with a high degree of monochromaticity and spatial coherence is required. 15 figs.

Howells, M.S.; Jacobsen, C.

1997-03-18

181

X-ray lithography using holographic images  

DOEpatents

Methods for forming X-ray images having 0.25 .mu.m minimum line widths on X-ray sensitive material are presented. A holgraphic image of a desired circuit pattern is projected onto a wafer or other image-receiving substrate to allow recording of the desired image in photoresist material. In one embodiment, the method uses on-axis transmission and provides a high flux X-ray source having modest monochromaticity and coherence requirements. A layer of light-sensitive photoresist material on a wafer with a selected surface is provided to receive the image(s). The hologram has variable optical thickness and variable associated optical phase angle and amplitude attenuation for transmission of the X-rays. A second embodiment uses off-axis holography. The wafer receives the holographic image by grazing incidence reflection from a hologram printed on a flat metal or other highly reflecting surface or substrate. In this second embodiment, an X-ray beam with a high degree of monochromaticity and spatial coherence is required.

Howells, Malcolm S. (Berkeley, CA); Jacobsen, Chris (Sound Beach, NY)

1997-01-01

182

Comparison of attenuation coefficients for VVER-440 and VVER-1000 pressure vessels  

SciTech Connect

The paper summarizes the attenuation coefficient of the neutron fluence with E > 0.5 MeV through a reactor pressure vessel for vodo-vodyanoi energetichesky reactor (VVER) reactor types measured and/or calculated for mock-up experiments, as well as for operated nuclear power plant (NPP) units. The attenuation coefficient is possible to evaluate directly only by using the retro-dosimetry, based on a combination of the measured activities from the weld sample and concurrent ex-vessel measurement. The available neutron fluence attenuation coefficients (E > 0.5 MeV), calculated and measured at a mock-up experiment simulating the VVER-440-unit conditions, vary from 3.5 to 6.15. A similar situation is used for the calculations and mock-up experiment measurements for the VVER-1000 RPV, where the attenuation coefficient of the neutron fluence varies from 5.99 to 8.85. Because of the difference in calculations for the real units and the mock-up experiments, the necessity to design and perform calculation benchmarks both for VVER-440 and VVER-1000 would be meaningful if the calculation model is designed adequately to a given unit. (authors)

Marek, M.; Rataj, J.; Vandlik, S. [Reactor Physics Dept., Research Centre Rez, Husinec 130, 25068 (Czech Republic)

2011-07-01

183

Measurements of rain drop size distributions and estimation of radio-wave attenuation coefficients  

NASA Astrophysics Data System (ADS)

Results of photoelectron-detector measurements of rain drop size distributions carried out near Dubna, USSR during May-September, 1987 are presented. It is shown that, for large and small drop diameters, these distributions differ from the Marshall-Palmer ones. Radio-wave attenuation coefficients are evaluated for such distributions.

Zakharian, M. V.; Kornilov, L. N.; Pozhidaev, V. N.

1989-10-01

184

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

Microsoft Academic Search

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

J. E. McAninch; G. S. Bench; S. P. H. T. Freeman; M. L. Roberts; J. R. Southon; J. S. Vogel; I. D. Proctor

1994-01-01

185

X-ray Dinosaurs  

NSDL National Science Digital Library

In this activity, learners explore dinosaur fossils and skeletons. First, learners listen to "Tyrannosaurus Rex" by Daniel Cohen to learn about T. rex dinosaurs specifically. Then, learners make dinosaur tracings and drawings similar to x-rays. Learners can repeat the activity using pictures of other dinosaurs to compare and contrast various dinosaurs. This activity is featured on page 38 of the "Dinosphere" unit of study for K-2 learners.

Crosslin, Rick; Fortney, Mary; Indianapolis, The C.

2004-01-01

186

Stereoscopic x-ray device  

SciTech Connect

A stereoscopic x-ray device used for stereoscopic radiography generates x-rays from a pair of x-ray focal spots. The x-ray device is provided with an evacuated envelope, an x-ray target within the evacuated envelope, and a cathode structure having at least two pairs of filaments. The first pair of filaments form relatively large size x-ray focal spots on the target. The second pair of the filaments form relatively small size x-ray focal spots on the target and are situated between the first pair of filaments on the cathode structure. As a result of these two pairs of focal spots on the x-ray target, a relatively small xray device can be used to provide magnification of stereoscopic images of high stereo quality.

Muraki, T.; Yamamura, T.

1981-09-01

187

Soft X-ray Imaging  

SciTech Connect

The contents of this report cover the following: (1) design of the soft x-ray telescope; (2) fabrication and characterization of the soft x-ray telescope; and (3) experimental implementation at the OMEGA laser facility.

Seely, John

1999-05-20

188

Tunable X-ray source  

Microsoft Academic Search

A method for the production of X-ray bunches tunable in both time and energy level by generating multiple photon, X-ray, beams through the use of Thomson scattering. The method of the present invention simultaneously produces two X-ray pulses that are tunable in energy and\\/or time.

Boyce; James R

2011-01-01

189

Multilayer X-ray optics  

SciTech Connect

The principles, state of the art, and problems of multilayer X-ray optics are analysed. Among its applications, the projection X-ray lithography and mirrors for a repetitively pulsed capillary-discharge X-ray laser are considered. (special issue devoted to the 80th anniversary of academician n g basov's birth)

Vinogradov, Aleksandr V [P.N. Lebedev Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)

2002-12-31

190

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

191

Multiwavelength Anomalous Diffraction at High X-Ray Intensity  

NASA Astrophysics Data System (ADS)

The multiwavelength anomalous diffraction (MAD) method is used to determine phase information in x-ray crystallography by employing anomalous scattering from heavy atoms. X-ray free-electron lasers (FELs) show promise for revealing the structure of single molecules or nanocrystals, but the phase problem remains largely unsolved. Because of the ultrabrightness of x-ray FEL, samples experience severe electronic radiation damage, especially to heavy atoms, which hinders direct implementation of MAD with x-ray FELs. Here, we propose a generalized version of MAD phasing at high x-ray intensity. We demonstrate the existence of a Karle-Hendrickson-type equation in the high-intensity regime and calculate relevant coefficients with detailed electronic damage dynamics of heavy atoms. The present method offers a potential for ab initio structural determination in femtosecond x-ray nanocrystallography.

Son, Sang-Kil; Chapman, Henry N.; Santra, Robin

2011-11-01

192

Comparison of dual-window scatter correction and effective attenuation coefficients for quantification in dedicated breast SPECT  

Microsoft Academic Search

Correction for scattered and attenuated photons is necessary for accurate quantification in dedicated breast SPECT. An implemented dual energy window (DEW) scatter correction method along with attenuation correction has been shown to be accurate to within 10% of true values; however, the DEW method requires multiple processing steps, and thus more time, than an effective attenuation coefficient (EAC) method. This

Steve Mann; Kristy Perez; Martin Tornai

2011-01-01

193

Quantitative RNFL attenuation coefficient measurements by RPE-normalized OCT data  

NASA Astrophysics Data System (ADS)

We demonstrate significantly different scattering coefficients of the retinal nerve fiber layer (RNFL) between normal and glaucoma subjects. In clinical care, SD-OCT is routinely used to assess the RNFL thickness for glaucoma management. In this way, the full OCT data set is conveniently reduced to an easy to interpret output, matching results from older (non- OCT) instruments. However, OCT provides more data, such as the signal strength itself, which is due to backscattering in the retinal layers. For quantitative analysis, this signal should be normalized to adjust for local differences in the intensity of the beam that reaches the retina. In this paper, we introduce a model that relates the OCT signal to the attenuation coefficient of the tissue. The average RNFL signal (within an A-line) was then normalized based on the observed RPE signal, resulting in normalized RNFL attenuation coefficient maps. These maps showed local defects matching those found in thickness data. The average (normalized) RNFL attenuation coefficient of a fixed band around the optic nerve head was significantly lower in glaucomatous eyes than in normal eyes (3.0mm-1 vs. 4.9mm-1, P<0.01, Mann-Whitney test).

Vermeer, K. A.; van der Schoot, J.; Lemij, H. G.; de Boer, J. F.

2012-02-01

194

Parametric imaging of the local attenuation coefficient in human axillary lymph nodes assessed using optical coherence tomography  

PubMed Central

We report the use of optical coherence tomography (OCT) to determine spatially localized optical attenuation coefficients of human axillary lymph nodes and their use to generate parametric images of lymphoid tissue. 3D-OCT images were obtained from excised lymph nodes and optical attenuation coefficients were extracted assuming a single scattering model of OCT. We present the measured attenuation coefficients for several tissue regions in benign and reactive lymph nodes, as identified by histopathology. We show parametric images of the measured attenuation coefficients as well as segmented images of tissue type based on thresholding of the attenuation coefficient values. Comparison to histology demonstrates the enhancement of contrast in parametric images relative to OCT images. This enhancement is a step towards the use of OCT for in situ assessment of lymph nodes.

Scolaro, Loretta; McLaughlin, Robert A.; Klyen, Blake R.; Wood, Benjamin A.; Robbins, Peter D.; Saunders, Christobel M.; Jacques, Steven L.; Sampson, David D.

2012-01-01

195

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

196

X-ray lithography source  

DOEpatents

A high-intensity, inexpensive X-ray source for X-ray lithography for the production of integrated circuits is disclosed. Foil stacks are bombarded with a high-energy electron beam of 25 to 250 MeV to produce a flux of soft X-rays of 500 eV to 3 keV. Methods of increasing the total X-ray power and making the cross section of the X-ray beam uniform are described. Methods of obtaining the desired X-ray-beam field size, optimum frequency spectrum and eliminating the neutron flux are all described. A method of obtaining a plurality of station operation is also described which makes the process more efficient and economical. The satisfying of these issues makes transition radiation an excellent moderate-priced X-ray source for lithography. 26 figures.

Piestrup, M.A.; Boyers, D.G.; Pincus, C.

1991-12-31

197

X-ray lithography source  

DOEpatents

A high-intensity, inexpensive X-ray source for X-ray lithography for the production of integrated circuits. Foil stacks are bombarded with a high-energy electron beam of 25 to 250 MeV to produce a flux of soft X-rays of 500 eV to 3 keV. Methods of increasing the total X-ray power and making the cross section of the X-ray beam uniform are described. Methods of obtaining the desired X-ray-beam field size, optimum frequency spectrum and elminating the neutron flux are all described. A method of obtaining a plurality of station operation is also described which makes the process more efficient and economical. The satisfying of these issues makes transition radiation an exellent moderate-priced X-ray source for lithography.

Piestrup, Melvin A. (Woodside, CA); Boyers, David G. (Mountain View, CA); Pincus, Cary (Sunnyvale, CA)

1991-01-01

198

Refractive Optics for Hard X-ray Transmission Microscopy  

SciTech Connect

For hard x-ray transmission microscopy at photon energies higher than 15 keV we design refractive condenser and imaging elements to be used with synchrotron light sources as well as with x-ray tube sources. The condenser lenses are optimized for low x-ray attenuation--resulting in apertures greater than 1 mm--and homogeneous intensity distribution on the detector plane, whereas the imaging enables high-resolution (<100 nm) full-field imaging. To obtain high image quality at reasonable exposure times, custom-tailored matched pairs of condenser and imaging lenses are being developed. The imaging lenses (compound refractive lenses, CRLs) are made of SU-8 negative resist by deep x-ray lithography. SU-8 shows high radiation stability. The fabrication technique enables high-quality lens structures regarding surface roughness and arrangement precision with arbitrary 2D geometry. To provide point foci, crossed pairs of lenses are used. Condenser lenses have been made utilizing deep x-ray lithographic patterning of thick SU-8 layers, too, whereas in this case, the aperture is limited due to process restrictions. Thus, in terms of large apertures, condenser lenses made of structured and rolled polyimide film are more attractive. Both condenser types, x-ray mosaic lenses and rolled x-ray prism lenses (RXPLs), are considered to be implemented into a microscope setup. The x-ray optical elements mentioned above are characterized with synchrotron radiation and x-ray laboratory sources, respectively.

Simon, M.; Last, A.; Mohr, J.; Nazmov, V.; Reznikova, E. [Institute for Microstructure Technology, Karlsruhe Institute of Technology Kaiserstrasse 12, 76131 Karlsruhe (Germany); Ahrens, G.; Voigt, A. [Microresist Technology, Koepenikerstrasse 325, 12555 Berlin (Germany)

2011-09-09

199

Refractive Optics for Hard X-ray Transmission Microscopy  

NASA Astrophysics Data System (ADS)

For hard x-ray transmission microscopy at photon energies higher than 15 keV we design refractive condenser and imaging elements to be used with synchrotron light sources as well as with x-ray tube sources. The condenser lenses are optimized for low x-ray attenuation--resulting in apertures greater than 1 mm--and homogeneous intensity distribution on the detector plane, whereas the imaging enables high-resolution &lpar<100 nm) full-field imaging. To obtain high image quality at reasonable exposure times, custom-tailored matched pairs of condenser and imaging lenses are being developed. The imaging lenses (compound refractive lenses, CRLs) are made of SU-8 negative resist by deep x-ray lithography. SU-8 shows high radiation stability. The fabrication technique enables high-quality lens structures regarding surface roughness and arrangement precision with arbitrary 2D geometry. To provide point foci, crossed pairs of lenses are used. Condenser lenses have been made utilizing deep x-ray lithographic patterning of thick SU-8 layers, too, whereas in this case, the aperture is limited due to process restrictions. Thus, in terms of large apertures, condenser lenses made of structured and rolled polyimide film are more attractive. Both condenser types, x-ray mosaic lenses and rolled x-ray prism lenses (RXPLs), are considered to be implemented into a microscope setup. The x-ray optical elements mentioned above are characterized with synchrotron radiation and x-ray laboratory sources, respectively.

Simon, M.; Ahrens, G.; Last, A.; Mohr, J.; Nazmov, V.; Reznikova, E.; Voigt, A.

2011-09-01

200

Direct three-dimensional coherently scattered x-ray microtomography  

SciTech Connect

Purpose: It has been shown that coherently scattered x rays can be used to discriminate and identify specific components in a mixture of low atomic weight materials. The authors demonstrated a new method of doing coherently scattered x-ray tomography with a thin sheet of x ray. Methods: A collimated x-ray fan-beam, a parallel polycapillary collimator, and a phantom consisting of several biocompatible materials of low attenuation-based contrast were used to investigate the feasibility of the method. Because of the particular experimental setup, only the phantom translation perpendicular to the x-ray beam is needed and, thus, there is no need of Radon-type tomographic reconstruction, except for the correction of the attenuation to the primary and scattered x rays, which was performed by using a conventional attenuation-based tomographic image data set. The coherent scatter image contrast changes with momentum transfer among component materials in the specimen were investigated with multiple x-ray sources with narrow bandwidth spectra generated with anode and filter combinations of Cu/Ni (8 keV), Mo/Zr (18 keV), and Ag/Pd (22 keV) and at multiple scatter angles by orienting the detector and polycapillary collimator at different angles to the illuminating x ray. Results: The contrast among different materials changes with the x-ray source energy and the angle at which the image was measured. The coherent scatter profiles obtained from the coherent scatter images are consistent with the published results. Conclusions: This method can be used to directly generate the three-dimensional coherent scatter images of small animal, biopsies, or other small objects with low atomic weight biological or similar synthetic materials with low attenuation contrast. With equipment optimized, submillimeter spatial resolution may be achieved.

Cui Congwu; Jorgensen, Steven M.; Eaker, Diane R.; Ritman, Erik L. [Department of Medical Physics, CancerCare Manitoba, 675 McDermot Avenue, Winnipeg, Manitoba R3E 0V9 (Canada); Department of Physiology and Biomedical Engineering, Mayo Clinic, 200 First Street Southwest, Alfred Building 2-409, Rochester, Minnesota 55905 (United States)

2010-12-15

201

Comparison of photon attenuation coefficients (2-150 KeV) for diagnostic imaging simulations  

NASA Astrophysics Data System (ADS)

The Radiology Research Laboratory at the Henry Ford Hospital has been involved in modeling x-ray units in order to predict image quality. A critical part of that modeling process is the accurate choice of interaction coefficients. This paper serves as a review and comparison of existing interaction models. Our objective was to obtain accurate and easily calculated interaction coefficients, at diagnostically relevant energies. We obtained data from: McMaster, Lawrence Berkeley Lab data (LBL), XCOM and FFAST Data from NIST, and the EPDL-97 database via LLNL. Our studies involve low energy photons; therefore, comparisons were limited to Coherent (Rayleigh), Incoherent (Compton) and Photoelectric effects, which were summed to determine a total interaction cross section. Without measured data, it becomes difficult to definitively choose the most accurate method. However, known limitations in the McMaster data and smoothing of photo-edge transitions can be used as a guide to establish more valid approaches. Each method was compared to one another graphically and at individual points. We found that agreement between all methods was excellent when away from photo-edges. Near photo-edges and at low energies, most methods were less accurate. Only the Chanter (FFAST) data seems to have consistently and accurately predicted the placement of edges (through M-shell), while minimizing smoothing errors. The EPDL-97 data by LLNL was the best over method in predicting coherent and incoherent cross sections.

Dodge, Charles W., III; Flynn, Michael J.

2004-05-01

202

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

203

Total attenuation coefficients and scattering phase functions of tissues and phantom materials at 633 nm  

SciTech Connect

Measurements have been made of the total attenuation coefficient sigma t and the scattering phase function, S(theta), of 632.8 nm of light for a number of animal model tissues, blood, and inert scattering and absorbing media. Polystyrene microspheres of known size and refractive index, for which sigma t and S(theta) can be calculated by Mie theory, were used to test the experimental methods. The purpose of the study was to define typical ranges for these optical properties of tissues, as a contribution to the development of experimental and theoretical methods of light dosimetry in tissue, particularly related to photodynamic therapy of solid tumors. The results demonstrate that, for the representative tissues studied, the total attenuation coefficients are of the order of 10-100 mm-1, and that the scattering is highly forward peaked, with average cosine of scatter in the range 0.6-0.97.

Flock, S.T.; Wilson, B.C.; Patterson, M.S.

1987-09-01

204

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

205

Imaging modalities in x-ray computerized tomography and in selected volume tomography.  

PubMed

This review of different principles used in x-ray computerized tomography (CT) starts with attenuation (transmission) CT. The pros and cons of different geometrical solutions, single-ray, fan-beam and cone-beam, are discussed. Attenuation CT measures the spatial distribution of the linear attenuation coefficient, mu. The contributions of different interaction processes to mu have also been used for CT. Fluorescence CT is based on measurements of the contribution, cZtauZ/rho, from an element Z with concentration cZ, to the linear attenuation coefficient. Diffraction CT measures the differential coherent cross section d sigma (theta)(coh)/d omega, Compton CT the incoherent scatter cross section sigma. The usefulness of these modalities is illustrated. CT methods based on secondary photons have a competitor in selected volume tomography. These two tomography methods are compared. A proposal to perform Compton profile tomography is also discussed, as is the promising method of phase-contrast x-ray CT. PMID:10211798

Carlsson, C A

1999-03-01

206

Total mass attenuation coefficient evaluation of ten materials commonly used to simulate human tissue  

NASA Astrophysics Data System (ADS)

To study the doses received by patient submitted to ionizing radiation, several materials are used to simulate the human tissue and organs. The total mass attenuation coefficient is a reasonable way for evaluating the usage in dosimetry of these materials. The total mass attenuation coefficient is determined by photon energy and constituent elements of the material. Currently, the human phantoms are composed by a unique material that presents characteristics similar to the mean proprieties of the different tissues within the region. Therefore, the phantoms are usually homogeneous and filled with a material similar to soft tissue. We studied ten materials used as soft tissue-simulating. These materials were named: bolus, nylon®, orange articulation wax, red articulation wax, PMMA, modelling clay, bee wax, paraffin 1, paraffin 2 and pitch. The objective of this study was to verify the best material to simulate the human cerebral tissue. We determined the elementary composition, mass density and, therefore, calculated the total mass attenuation coefficient of each material. The results were compared to the values established by the International Commission on Radiation Units and Measurements - ICRU, report n° 44, and by the International Commission on Radiation Protection - ICRP, report n° 89, to determine the best material for this energy interval. These results indicate that new head phantoms can be constructed with nylon®.

Ferreira, C. C.; Ximenes, R. E.; Garcia, C. A. B.; Vieira, J. W.; Maia, A. F.

2010-11-01

207

Critical analysis of soft X-ray cross section data  

NASA Astrophysics Data System (ADS)

A project is in progress in the national Bureau of Standards (NBS) Photon and Charged Particle Data Center to collect and evaluate photon cross section data in the X-ray region 100 eV to 100 keV. This project complements earlier NBS evaluations and compilations which focused primarily on energies above 10 keV. The NBS collection of experimental total attenuation coefficients (10 eV to above 10 GeV) abstracted from the literature is now computerized to facilitate use and for future updates. These experimental results have been compared systematically with a theoretical photoabsorption calculation by Scofield, and also with a semi-empirical compilation by Henke et al. Sample graphical comparisons of measured data with the Scofield theoretical results are presented here for silicon and uranium. Silicon data from an International Union of Crystallography project are also presented. Discrepancies and uncertainties in the various experimental data sets are typically 5 to 50% or more in the soft X-ray region. However, systematic trends can be seen which suggest that the Scofield theoretical values, taken as a whole, are not improved by the Hartree-Slater to Hartree-Fock renormalization in this photon energy region.

Saloman, E. B.; Hubbell, J. H.

1987-03-01

208

Solar X-ray physics  

SciTech Connect

Research on solar X-ray phenomena performed by American scientists during 1987-1990 is reviewed. Major topics discussed include solar images observed during quiescent times, the processes observed during solar flares, and the coronal, interplanetary, and terrestrial phenomena associated with solar X-ray flares. Particular attention is given to the hard X-ray emission observed at the start of the flare, the energy transfer to the soft X-ray emitting plasma, the late resolution of the flare as observed in soft X-ray, and the rate of occurrence of solar flares as a function of time and latitude. Pertinent aspects of nonflaring, coronal X-ray emission and stellar flares are also discussed. 175 refs.

Bornmann, P.L. (USAF, Geophysics Laboratory, Hanscom AFB, MA (United States))

1991-01-01

209

British X-ray astronomy  

NASA Astrophysics Data System (ADS)

The development of solar and cosmic X-ray studies in the UK, in particular the Skylark and Ariel programs, is discussed. The characteristics and capabilities of the X-ray emulsion detector developed to monitor the solar X-radiation in the Skylark program, and of the proportional counter spectrometer developed for solar X-ray measurements on the Ariel I satellite are described. The designs and functions of the pin-hole camera, the Bragg crystal spectrometer, and the X-ray spectroheliograph are exmained. The Skylark observations of cosmic X-ray sources and high-resolution solar spectra, and the Ariel 5 data on cosmic X-ray sources are presented. Consideration is given to the Ariel 6, the U.S. Einstein Observatory, Exosat, and ASTRO-C.

Pounds, K. A.

1986-09-01

210

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

211

Results of a monte carlo investigation of the diffuse attenuation coefficient.  

PubMed

There has been a large effort to relate the apparent optical properties of ocean water to the inherent optical properties, which are the absorption coefficient a, the scattering coefficient b, and the scattering phase function rho(theta). The diffuse attenuation coefficient kdiff' has most often been considered an apparent optical property. However, kdiff' can be considered a quasi-inherent property kdiff' when defined as a steady-state light distribution attenuation coefficient. The Honey-Wilson research empirically relates kdiff' to a and b. The Honey-Wilson relation most likely applies to a limited range of water types because it does not include dependence on rho(theta). A series of Monte Carlo simulations were initiated to calculate kdiff' in an unstratified water column. The calculations, which reflected open ocean water types, used ranges of the single-scattering albedo omega(0) and the mean forward-scattering angle theta(m) for two analytic phase functions with different shapes. It was found that kdiff' is nearly independent of the shape of rho(theta) and can be easily parameterized in terms of a, b, and theta(m) for 0.11

Concannon, B M; Davis, J P

1999-08-20

212

X-ray imaging system  

DOEpatents

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 so that the divergent x-ray wavefronts are transformed into convergent wavefronts and are brought to focus to form an image of the object with a large depth of field. 6 figs.

Sommargren, G.E.; Weaver, H.J.

1990-01-01

213

X-ray imaging system  

DOEpatents

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 so that the divergent x-ray wavefronts are transformed into convergent wavefronts and are brought to focus to form an image of the object with a large depth of field. 6 figs.

Sommargren, G.E.; Weaver, H.J.

1990-12-31

214

Topological X-Rays Revisited  

ERIC Educational Resources Information Center

|We continue our study of topological X-rays begun in Lynch ["Topological X-rays and MRI's," iJMEST 33(3) (2002), pp. 389-392]. We modify our definition of a topological magnetic resonance imaging and give an affirmative answer to the question posed there: Can we identify a closed set in a box by defining X-rays to probe the interior and without…

Lynch, Mark

2012-01-01

215

Whitebeam X-ray topography  

Microsoft Academic Search

After radiography, white-beam X-ray topography (XRT) is the simplest X-ray imaging technique for crystals. An X-ray topograph is formed by a Bragg reflexion and is in effect a high-spatial-resolution Laue ‘spot’. Synchrotron radiation has given XRT additional powers, with its broad continuous spectrum, small beam divergence, high intensity, strong polarization and regular pulsed time structure. Each Laue image, however, may

Moreton Moore

2012-01-01

216

Pulsed X-ray tube  

Microsoft Academic Search

This is an invention in the field of pulsed X-ray tubes, specifically, pulsed X-ray tubes with a cold cathode. We are familiar with pulsed X-ray tubes with a cold cathode, designed for work with a high voltage transformer source with an anode in the form of a metal rod, sharpened on the end, and a cathode in the form of

N. I. Komyak; N. A. Dron; Y. A. Peliks; V. M. Kurbatov; Y. I. Bichenkov

1977-01-01

217

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

218

X-ray Absorption Spectroscopy  

SciTech Connect

This review gives a brief description of the theory and application of X-ray absorption spectroscopy, both X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS), especially, pertaining to photosynthesis. The advantages and limitations of the methods are discussed. Recent advances in extended EXAFS and polarized EXAFS using oriented membranes and single crystals are explained. Developments in theory in understanding the XANES spectra are described. The application of X-ray absorption spectroscopy to the study of the Mn4Ca cluster in Photosystem II is presented.

Yano, Junko; Yachandra, Vittal K.

2009-07-09

219

Determination of mass attenuation coefficients, effective atomic numbers, effective electron numbers and kermas for Earth and Martian soils  

NASA Astrophysics Data System (ADS)

Total mass attenuation coefficients, effective atomic numbers, effective electron numbers and kerma values for Earth and Martian soils are calculated in the energy range from 1 keV to 100 GeV. The values of mass attenuation and absorption coefficients used in calculations are taken from the WinXCOM program and correct data base. Contributions of different scatterings on the total mass attenuation coefficients of the soils are presented. In addition, the obtained results for Martian soils are compared with the results for Earth soils. The similarities of Earth and Martian soils are also investigated.

Un, A.; Sahin, Y.

2012-10-01

220

Generation of first hard X-ray pulse at Tsinghua Thomson Scattering X-ray Source.  

PubMed

Tsinghua Thomson Scattering X-ray Source (TTX) is the first-of-its-kind dedicated hard X-ray source in China based on the Thomson scattering between a terawatt ultrashort laser and relativistic electron beams. In this paper, we report the experimental generation and characterization of the first hard X-ray pulses (51.7 keV) via head-on collision of an 800 nm laser and 46.7 MeV electron beams. The measured yield is 1.0 × 10(6) per pulse with an electron bunch charge of 200 pC and laser pulse energy of 300 mJ. The angular intensity distribution and energy spectra of the X-ray pulse are measured with an electron-multiplying charge-coupled device using a CsI scintillator and silicon attenuators. These measurements agree well with theoretical and simulation predictions. An imaging test using the X-ray pulse at the TTX is also presented. PMID:23742539

Du, Yingchao; Yan, Lixin; Hua, Jianfei; Du, Qiang; Zhang, Zhen; Li, Renkai; Qian, Houjun; Huang, Wenhui; Chen, Huaibi; Tang, Chuanxiang

2013-05-01

221

Generation of first hard X-ray pulse at Tsinghua Thomson Scattering X-ray Source  

NASA Astrophysics Data System (ADS)

Tsinghua Thomson Scattering X-ray Source (TTX) is the first-of-its-kind dedicated hard X-ray source in China based on the Thomson scattering between a terawatt ultrashort laser and relativistic electron beams. In this paper, we report the experimental generation and characterization of the first hard X-ray pulses (51.7 keV) via head-on collision of an 800 nm laser and 46.7 MeV electron beams. The measured yield is 1.0 × 106 per pulse with an electron bunch charge of 200 pC and laser pulse energy of 300 mJ. The angular intensity distribution and energy spectra of the X-ray pulse are measured with an electron-multiplying charge-coupled device using a CsI scintillator and silicon attenuators. These measurements agree well with theoretical and simulation predictions. An imaging test using the X-ray pulse at the TTX is also presented.

Du, Yingchao; Yan, Lixin; Hua, Jianfei; Du, Qiang; Zhang, Zhen; Li, Renkai; Qian, Houjun; Huang, Wenhui; Chen, Huaibi; Tang, Chuanxiang

2013-05-01

222

X-ray fluorescence and the study of microcirculation  

Microsoft Academic Search

The feasibility of using K-shell X-ray fluorescence (XRF) technique for study of subchondral bone microcirculation in ex vivo samples is examined. Studies have been carried out at the Daresbury Laboratory Synchrotron Radiation Source (SRS) ultra-dilute extended X-ray absorption fine structure beamline. Initial investigations were made on fine-bore capillaries with diameters of either 500 or 200 ?m, attenuated by up to

P. Muthuvelu; R. P. Hugtenburg; D. A. Bradley; C. P. Winlove

2004-01-01

223

New large-area x-ray image sensor  

NASA Astrophysics Data System (ADS)

A new high speed/high resolution X-ray detector called the XEBIT (X-ray sensitive Electron Beam Image Tube) is currently under development at the University of Connecticut Health Center. This large area (9' diameter) direct conversion detector is based on an X-ray photoconductor called thallium bromide. The device utilizes cathode ray tube technology to provide a 30 frame per second raster scanned electron beam to both charge and readout the photoconductor. Thallium bromide is a high Z material with a linear attenuation coefficient of 28.11 cm-1 at 60 kev. This high stopping power results in a quantum efficiency of 57% at 60 kev for 300 micron thick layers. Thallium bromide is a very good X-ray photoconductor that requires 6.5 ev to create an electron-hole pair. For 60 kev photons, this results in a gain 9230 per absorbed photon. With a hole-mobility lifetime product of 1.5 X 10-6 cm2/volt, good charge collection can be achieved at reasonable field strengths. Thallium bromide has a very high band gap of 2.7 ev and a dielectric constant of 33. Its resistivity, which is 5 X 109 ohm-cm at room temperature, is dominated by ionic conductivity. Fortunately, ionic conductivity has a strong temperature dependence that can be significantly reduced with moderate cooling to -25 degrees centigrade. The XEBIT uses thallium bromide as an X- ray photoconductor in a vidicon type image tube. Its principals of operation are very similar to the standard light sensitive vidicon that were utilized extensively in the commercial television industry. A scanning electron beam charges the TlBr surface, with respect to the positively biased front surface, providing the necessary electric field across the photoconductor for charge transport. X-rays then penetrate the window and are absorbed by the thallium bromide. The absorbed photons generate large numbers of electron-hole pairs due to the high conversion gain. Electrons drift under the electric field to the positive bias electrode and the holes drift to the vacuum surface and annihilate stored charge. This results in an image dependent charge pattern on the vacuum surface of the photoconductor. A subsequent scan of the photoconductor generates the capacitively coupled signal by replacing the annihilated electrons. The XEBIT utilizes well-developed display tube technology to provide a very cost effective alternative to image intensifier and screen/film based systems. The XEBIT is currently under development as a replacement for X-ray Image Intensifiers in medical imaging applications. The first devices are 9 inch prototypes designed to be no larger than standard intensifiers. It will replace the image intensifier/optics/video camera with one direct conversion device. The XEBIT suffers from no veiling glare and has far superior contrast resolution with over 50 percent modulation at 5 line pairs per millimeter. The XEBIT is capable of full field imaging as well as under scanning to view smaller regions with higher detail.

Ouimette, Donald R.; Nudelman, Sol; Aikens, Richard S.

1998-07-01

224

Effect of x-ray tube window thickness of detection limits for light elements in XRF analysis  

SciTech Connect

Widespread interest in light element analysis using XRF has stimulated the development of thin x-ray tube windows. Thinner windows enhance the soft x-ray output of the tube, which more efficiently excite the light elements in the sample. A computer program that calculates the effect of window thickness on light element sample fluorescence has been developed. The code uses an NIST algorithm to calculate the x-ray tube spectrum given various tube parameters such as beryllium window thickness, operating voltage, anode composition, and take-off angle. The interaction of the tube radiation with the sample matrix is modelled to provide the primary and secondary fluorescence from the sample. For x-rays in the energy region 30 - 1000 eV the mass attenuation coefficients were interpolated from the photoabsorption data compilation of Henke, el al. The code also calculates the x-ray background due to coherent and incoherent scatter from the sample, as well as the contribution of such scatter to the sample fluorescence. Given the sample fluorescence and background the effect of tube window thickness on detection limits for light elements can be predicted. 17 refs., 3 figs., 2 tabs.

Whalen, D.J.; Turner, D.C. [MOXTEK, Inc., Orem, UT (United States)

1995-12-31

225

The effect of scintillator response on signal difference to noise ratio in X-ray medical imaging  

NASA Astrophysics Data System (ADS)

The aim of the present study was to examine the effect of scintillator material properties on the signal difference to noise ratio (SdNR) under X-ray imaging conditions. To this aim, SdNR was modelled in terms of scintillator material properties such as the quantum detection efficiency (QDE), the intrinsic energy conversion efficiency (ICE) and the light transmission efficiency (LTE). Scintillators were assumed to be in the form of scintillator layers (phosphor screens) with various thicknesses ranging from 70 to 110 mg/cm2. Data on the X-ray absorption and optical properties of the scintillators were either calculated from tabulated data, i.e. X-ray attenuation coefficients for QDE estimation, or were obtained from previous experimental studies. It was found that in a wide range of X-ray tube voltages the Gd2O2S:Tb scintillator produced higher SdNR values, while the CsI:Tl scintillator was better at lower voltages (below 65 kVp). It was additionally verified that, in the range of X-ray diagnostic energies, SdNR increases with the thickness of the scintillator layer screen. In conclusion, SdNR may be critically affected by scintillator properties and, hence, it may be significantly improved by appropriately selecting the type and thickness of the phosphor screen to be integrated into an imaging system.

Ninos, K.; Cavouras, D.; Fountos, G.; Kandarakis, I.

2010-10-01

226

Soft X-ray shock loading and momentum coupling in meteorite and planetary materials  

NASA Astrophysics Data System (ADS)

X-ray momentum coupling coefficients, CM, were determined by measuring stress waveforms in planetary materials subjected to impulsive radiation loading from the SNL Z-machine. Targets were prepared from iron and stone meteorites, dunite (primarily magnesium rich olivine) in solid and powder forms (~5 - 300 ?m grains), and Si, Al, and Fe. All samples were ~1 mm thick and, except for Si, backed by LiF single-crystal windows. The spectra of the incident x-rays included thermal radiation (blackbody 170 - 237 eV) and line emissions from the pinch material (Cu, Ni, Al, or stainless steel). Target fluences of 0.4 - 1.7 kJ/cm2 at intensities 43 - 260 GW/cm2 produced front surface plasma pressures of 2.6 - 12.4 GPa. Stress waves driven into the samples were attenuating due to the short ~5 ns duration of the drive pulse. CM was determined using the fact that an attenuating wave impulse is constant, and accounted for the mechanical impedance mismatch between samples and window. Values ranged from 0.8 - 3.1 x 10-5 s/m. CTH hydrocode modeling of x-ray coupling to porous and fully dense silica corroborated experimental results and extrapolations to other materials.

Remo, J. L.; Furnish, M. D.; Lawrence, R. J.

2012-03-01

227

X-Ray Exam: Foot  

MedlinePLUS

What It Is A foot X-ray is a safe and painless test that uses a small amount of radiation to make an image of a person's foot. During the examination, an X-ray machine sends a beam of radiation through the ...

228

X-Ray Exam: Ankle  

MedlinePLUS

What It Is An ankle X-ray is a safe and painless test that uses a small amount of radiation to make an image of the ankle. The ... back part of the foot (tarsal bones). An X-ray machine sends a beam of radiation through the ...

229

X-Ray Exam: Hip  

MedlinePLUS

What It Is A hip X-ray is a safe and painless test that uses a small amount of radiation to make images of a person's hip joints ( ... attach to the pelvis). During the examination, an X-ray machine sends a beam of radiation through the ...

230

X-Ray Exam: Wrist  

MedlinePLUS

What It Is A wrist X-ray is a safe and painless test that uses a small amount of radiation to make an image of a person's wrist. During the examination, an X-ray machine sends a beam of radiation through the ...

231

Ultrafast X-ray Sources.  

National Technical Information Service (NTIS)

During the contract period we made progress in six areas: development of ultrashort pulse x-ray sources; generation of subpicosecond, unicycle electromagnetic pulses; propagation of intense short pulse lasers in plasmas; new x-ray lasers; new high-intensi...

R. W. Falcone

1993-01-01

232

X-RAY SPOT MEASUREMENT  

Microsoft Academic Search

The so-called roll bar measurement uses a heavy metal material, optically thick to x-rays, to form a shadow of the x-ray origination spot. This spot is where an energetic electron beam interacts with a high Z target. The material (the \\

Roger A. Richardson; Stephen Sampayan; John Weir

233

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

234

An Instrument for the Measurement of Spectral Attenuation Coefficient and Narrow Angle Volume Scattering Function of Ocean Waters.  

National Technical Information Service (NTIS)

A new instrument has been developed for the study of those optical properties of ocean water that affect the transmission of image-forming light. The instrument performs simultaneous measurements of the volume attenuation coefficient and the volume scatte...

R. W. Austin T. J. Petzold

1975-01-01

235

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

236

X-ray spectra and quality parameters from Monte Carlo simulation and analytical filters.  

PubMed

BEAMnrc was used to derive the X-ray spectra, from which HVL and homogeneity coefficient were determined, for different kVp and filtration settings. Except for the peak at 61 keV, the spectra are in good agreement with the IPEM report 78 data for the case of filtered beams, whereas the unfiltered beams exhibit softer spectra. Although the current attenuation data deviates from the IPEM 78 data by ~±0.5%, this has negligible effects on the calculated HVL values. PMID:22940409

Salehi, Z; Ya Ali, N K; Yusoff, A L

2011-12-13

237

X-ray diagnostics for TFTR  

SciTech Connect

A short description of the x-ray diagnostic preparation for the TFTR tokamak is given. The x-ray equipment consists of the limiter x-ray monitoring system, the soft x-ray pulse-height-analysis-system, the soft x-ray imaging system and the x-ray crystal spectrometer. Particular attention is given to the radiation protection of the x-ray systems from the neutron environment.

von Goeler, S.; Hill, K.W.; Bitter, M.

1982-12-01

238

Nonthermal X-ray astronomy  

NASA Astrophysics Data System (ADS)

We provide a concise review of X-ray observations of synchrotron and inverse Compton radiation from relativistic electrons in cosmic sources, in the context of synergies between X-ray and ?-ray astronomy. Particular emphasis is placed on the cases of supernova remnants, pulsar wind nebulae, and relativistic jets of quasars. We discuss that imaging spectroscopy of synchrotron X-ray emission plays key roles in studying acceleration and transport of high-energy electrons, as well as in probing the magnetic field through a comparison with TeV ?-ray data. To demonstrate some prospects for future X-ray observations, we showcase the scientific capabilities of the next major X-ray observatory, ASTRO-H, which is a joint JAXA-NASA mission to be launched in 2014.

Uchiyama, Yasunobu

2012-12-01

239

X-ray spectrometry using polycapillary X-ray optics and position sensitive detector  

Microsoft Academic Search

Polycapillary X-ray optics (capillary X-ray lens) are now popular in X-ray fluorescence (XRF) analysis. Such an X-ray lens can collect X-rays emitted from an X-ray source in a large solid angle and form a very intense X-ray microbeam which is very convenient for microbeam X-ray fluorescence (MXRF) analysis giving low minimum detection limits (MDLs) in energy dispersive X-ray fluorescence (EDXRF).

Xunliang Ding; Jingdong Xie; Yejun He; Quili Pan; Yiming Yan

2000-01-01

240

Bone age assessment by dual-energy X-ray absorptiometry in children: an alternative for X-ray?  

PubMed Central

Objective The aim of the study was to validate dual-energy X-ray absorptiometry (DXA) as a method to assess bone age in children. Methods Paired dual-energy X-ray absorptiometry (DXA) scans and X-rays of the left hand were performed in 95 children who attended the paediatric endocrinology outpatient clinic of University Hospital Rotterdam, the Netherlands. We compared bone age assessments by DXA scan with those performed by X-ray. Bone age assessment was performed by two blinded observers according to the reference method of Greulich and Pyle. Intra-observer and interobserver reproducibility were investigated using the intraclass correlation coefficient (ICC), and agreement was tested using Bland and Altman plots. Results The intra-observer ICCs for both observers were 0.997 and 0.991 for X-ray and 0.993 and 0.987 for DXA assessments. The interobserver ICC was 0.993 and 0.991 for X-ray and DXA assessments, respectively. The mean difference between bone age assessed by X-ray and DXA was 0.11 years. The limits of agreement ranged from ?0.82 to 1.05 years, which means that 95% of all differences between the methods were covered by this range. Conclusions Results of bone age assessment by DXA scan are similar to those obtained by X-ray. The DXA method seems to be an alternative for assessing bone age in a paediatric hospital-based population.

Heppe, D H M; Taal, H R; Ernst, G D S; Van Den Akker, E L T; Lequin, M M H; Hokken-Koelega, A C S; Geelhoed, J J M; Jaddoe, V W V

2012-01-01

241

Studies on mass attenuation coefficient, effective atomic number and electron density of some thermoluminescent dosimetric compounds  

NASA Astrophysics Data System (ADS)

Mass attenuation coefficient, ?m , effective atomic number, Zeff, and effective electron density, Nel, were determined experimentally and theoretically for some thermoluminescent dosimetric (TLD) compounds such as MgSO4, CdSO4, Al2O3, Mg2SiO4, ZnSO4, CaSO4, CaF2, NaSO4, Na4P2O7, Ca5F(PO4)3, SiO2, CaCO3 and BaSO4 at 8.04, 8.91, 13.37, 14.97, 17.44, 19.63, 22.10, 24.90, 30.82, 32.06, 35.40, 36.39, 37.26, 43.74, 44.48, 50.38, 51.70, 53.16, 80.99, 276.40, 302.85, 356.01, 383.85 and 661.66 keV photon energies by using an HPGe detector with a resolution of 182 eV at 5.9 keV. The theoretical mass attenuation coefficients were estimated using mixture rule. The calculated values were compared with the experimental values for all compounds. Good agreement has been observed between experimental and theoretical values within experimental uncertainties.

Önder, P.; Tur?ucu, A.; Demir, D.; Gürol, A.

2012-12-01

242

X-ray Scattering in X-ray Binary Pulsars  

Microsoft Academic Search

In x-ray pulsars, the emission from the bottom of the accretion column in the magnetic pole propagates to the observers through the surrounding environment: the magnetosphere, the accretion disk and the disk corona, the stellar wind, the companion’s atmosphere, and finally the interstellar medium. The photoionization zone of the stellar wind, which is formed surrounding the neutron star by x-ray

Fumiaki Nagase

1994-01-01

243

Dissociative X-ray Lasing  

NASA Astrophysics Data System (ADS)

X-ray lasing is predicted to ensue when molecules are pumped into dissociative core-excited states by a free-electron-laser pulse. The lasing is due to the population inversion created in the neutral dissociation product, and the process features self-trapping of the x-ray pulse at the gain ridge. Simulations performed for the HCl molecule pumped at the 2p1/2?6? resonance demonstrate that the scheme can be used to create ultrashort coherent x-ray pulses.

Miao, Q.; Liu, J.-C.; Ågren, H.; Rubensson, J.-E.; Gel'mukhanov, F.

2012-12-01

244

Application-Oriented X-ray Grating Interferometer  

Microsoft Academic Search

Grating-based Differential Phase Contrast X-ray imaging (DPCi) provides, in one measurement, unique information about the absorption coefficient, the index of refraction and the microscopic structure of a sample at hard X-ray frequencies11-17. For this reason, DPCi can potentially overcome the limitations of classical absorption-based radiography, notably for weakly absorbing materials. However, the implementation of the technology in industrial applications is

V. Revol; C. Kottler; R. Kaufmann; I. Jerjen; T. Lüthi; F. Cardot; Ph. Niedermann; U. Sennhauser; U. Straumann; C. Urban

2010-01-01

245

Grain flow measurements with X-ray techniques  

Microsoft Academic Search

The use of low energy X-rays, up to 30 keV, densitometry is demonstrated for grain flow rate measurements through laboratory experiments. Mass flow rates for corn were related to measured X-ray intensity in gray scale units with a 0.99 correlation coefficient for flow rates ranging from 2 to 6 kg\\/s. Larger flow rate values can be measured by using higher

Selcuk Arslan; Feyzi Inanc; Joseph N. Gray; Thomas S. Colvin

2000-01-01

246

Order of magnitude reduction of fluoroscopic x-ray dose  

NASA Astrophysics Data System (ADS)

The role of fluoroscopic imaging is critical for diagnostic and image guided therapy. However, fluoroscopic imaging can require significant radiation leading to increased cancer risk and non-stochastic effects such as radiation burns. Our purpose is to reduce the exposure and dose to the patient by an order of magnitude in these procedures by use of the region of interest method. Method and Materials: Region of interest fluoroscopy (ROIF) uses a partial attenuator. The central region of the image has full exposure while the image periphery, there to provide context only, has a reduced exposure rate. ROIF using a static partial attenuator has been shown in our previous studies to reduce the dose area product (DAP) to the patient by at least 2.5 times. Significantly greater reductions in DAP would require improvements in flat panel detectors performance at low x-ray exposures or a different x-ray attenuation strategy. Thus we have investigated a second, dynamic, approach. We have constructed an x-ray shutter system allowing a normal x-ray exposure in the region of interest while reducing the number of x-ray exposures in the periphery through the rapid introduction, positioning and removal of an x-ray attenuating shutter to block radiation only for selected frames. This dynamic approach eliminates the DQE(0) loss associated with the use of static partial attenuator applied to every frame thus permitting a greater reduction in DAP. Results: We have compared the two methods by modeling and determined their fundamental limits.

Bal, Abhinav; Robert, Normand; Machan, Lindsay; Deutsch, Meir; Kisselgoff, David; Babyn, Paul; Rowlands, John A.

2012-02-01

247

Relationships between water attenuation coefficients derived from active and passive remote sensing: a case study from two coastal environments.  

PubMed

Relationships between the satellite-derived diffuse attenuation coefficient of downwelling irradiance (K(d)) and airborne-based vertical attenuation of lidar volume backscattering (?) were examined in two coastal environments. At 1.1 km resolution and a wavelength of 532 nm, we found a greater connection between ? and K(d) when ? was computed below 2 m depth (Spearman rank correlation coefficient up to 0.96), and a larger contribution of K(d) to ? with respect to the beam attenuation coefficient as estimated from lidar measurements and K(d) models. Our results suggest that concurrent passive and active optical measurements can be used to estimate total scattering coefficient and backscattering efficiency in waters without optical vertical structure. PMID:21691366

Montes, Martin A; Churnside, James; Lee, Zhongping; Gould, Richard; Arnone, Robert; Weidemann, Alan

2011-06-20

248

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

249

X-ray fluorescence microscopy  

SciTech Connect

Synchrotron x-ray fluorescence microscopy is used to quantitatively measure and image the distribution of trace elements in biological, geological and materials science specimens. The design and performance of the x-ray fluorescence (XFR) microprobe at the NSLS are discussed and compared with other XRF microprobe design. An example of a trace element image obtained with this instrument if presented. 6 refs., 5 figs.

Rivers, M.L.; Sutton, S.R. (Chicago Univ., IL (USA). Dept. of Geophysical Sciences); Jones, K.W. (Brookhaven National Lab., Upton, NY (USA))

1990-10-01

250

X-ray computed tomography  

NASA Astrophysics Data System (ADS)

The primary advantage of the X-ray computed tomography (XRCT) NDE method is that features are not superposed in the image, thereby rendering them easier to interpret than radiographic projection images. Industrial XRCT systems, unlike medical diagnostic systems, have no size and dosage constraints; they are accordingly used for systems from the scale of gas turbine blades, with hundreds-of-kV energies, to those of the scale of ICBMs, requiring MV-level X-ray energies.

1993-05-01

251

X Rays: Another Form of Light  

NSDL National Science Digital Library

This Chandra X-ray Observatory website gives a brief history on the discovery of X-rays and how they are produced. There is also information on other forms of light. This website includes illustrations and information on X- ray production, inverse Compton scattering, atomic emission, and synchrotron radiation. There are also links to learn more about the differences between x-ray astronomy and medical x-rays, and to a word search for x-rays and light.

2004-11-17

252

[Performance evaluation of X-ray CT using visible scintillation light].  

PubMed

We proposed a new method of performance evaluation for X-ray CT using visible scintillation light and examined its usefulness in this study. When we scanned a plastic scintillator disk in a gantry opening of the X-ray CT, we could observe visible scintillation light. The rotation of the light-emitting area of the disk corresponded to that of the X-ray tube. We were able to record the scintillation light by digital video camera. By analyzing the area of visible scintillation light, the rotation speed of the X-ray tube, angular spread of the X-ray beam, uniformity of the incident X-rays, and change in X-ray energy were measured. No other method is available to obtain the above parameters of X-ray CT during a single CT scan. In the measurements of the uniformity of incident X-rays and change of X-ray energy, our method showed good accuracy in detecting the attenuation caused by the couch between the X-ray tube and the plastic scintillator disc. The proposed method is inexpensive and easy-to-use. We conclude that the method is a useful tool for performance evaluation as well as a maintenance tool for X-ray CT. PMID:15565012

Kodama, Kiyoyuki; Hamada, Minoru; Suzuki, Tamotsu; Hashimoto, Masatoshi; Hanada, Takashi; Ide, Tatsuya; Maruyama, Koichi

2004-10-01

253

Soft x-ray laser microscopy  

SciTech Connect

Microscopes based on soft X-ray lasers possess unique advantages in bridging the gap between high resolution electron microscopy of dehydrated, stained cells and light microscopy at comparatively low resolution of unaltered live cells. The high brightness and short pulse duration of soft X-ray lasers make them ideal for flash imaging of live specimens. The Princeton soft X-ray laser is based on a magnetically confined laser produced carbon plasma. Radiation cooling after the laser pulse produces rapid recombination which produces a population inversion and high gain. A full account is given in a companion paper in this volume. The important characteristics of the laser beam produced by this device are 1 to 3 mJ of 18.2 nm radiation in a 10 to 30 nsec pulse with a divergence of 5 mrad. The 18.2 nm wavelength, while outside the water window, does provide a factor of 3 difference in absorption coefficients between oxygen and carbon.

DiCicco, D. (Princeton X-Ray Laser, Inc., Monmouth Junction, NJ (United States)); Meixler, L.; Skinner, C.H.; Suckewer, S. (Princeton Univ., NJ (United States). Plasma Physics Lab.); Hirschberg, J.; Kohen, E. (Miami Univ., Coral Gables, FL (United States). Dept. of Physics)

1987-01-01

254

Soft x-ray laser microscopy  

SciTech Connect

Microscopes based on soft X-ray lasers possess unique advantages in bridging the gap between high resolution electron microscopy of dehydrated, stained cells and light microscopy at comparatively low resolution of unaltered live cells. The high brightness and short pulse duration of soft X-ray lasers make them ideal for flash imaging of live specimens. The Princeton soft X-ray laser is based on a magnetically confined laser produced carbon plasma. Radiation cooling after the laser pulse produces rapid recombination which produces a population inversion and high gain. A full account is given in a companion paper in this volume. The important characteristics of the laser beam produced by this device are 1 to 3 mJ of 18.2 nm radiation in a 10 to 30 nsec pulse with a divergence of 5 mrad. The 18.2 nm wavelength, while outside the water window, does provide a factor of 3 difference in absorption coefficients between oxygen and carbon.

DiCicco, D. [Princeton X-Ray Laser, Inc., Monmouth Junction, NJ (United States); Meixler, L.; Skinner, C.H.; Suckewer, S. [Princeton Univ., NJ (United States). Plasma Physics Lab.; Hirschberg, J.; Kohen, E. [Miami Univ., Coral Gables, FL (United States). Dept. of Physics

1987-12-31

255

X-ray computerized tomography analysis and density estimation using a sediment core from the Challenger Mound area in the Porcupine Seabight, off Western Ireland  

NASA Astrophysics Data System (ADS)

X-ray computerized tomography (CT) analysis was used to image a half-round core sample of 50 cm long recovered from near Challenger Mound in the Porcupine Seabight, off western Ireland during the Integrated Ocean Drilling Program Expedition 307. This allowed three-dimensional examination of complex shapes of pebbles and ice-rafted debris in sedimentary sequences. X-ray CT analysis was also used for the determination of physical properties; a comparison between bulk density by the mass-volume method and estimated density based on linear attenuation coefficients of X-ray CT images provides insight into a spatially detailed and precise map of density variation in samples through the distribution of CT numbers.

Tanaka, A.; Nakano, T.; Ikehara, K.

2011-02-01

256

Effective atomic numbers and mass attenuation coefficients of some thermoluminescent dosimetric compounds for total photon interaction  

SciTech Connect

Effective atomic numbers for total gamma-ray interaction with some selected thermoluminescent dosimetric compounds such as barium acetate, barium sulfate, calcium carbonate, calcium sulfate, calcium sulfate dihydrate, cadmium sulfate (anhydrous), cadmium sulfate, strontium sulfate, and lithium fluoride have been calculated in the 1-keV to 20-MeV energy region. Experimental mass attenuation coefficients and effective atomic numbers for these compounds at selected photon energies of 26.3, 33.2, 59.54, and 661.6 keV have been obtained from good geometry transmission measurements and compared with theoretical values. The effect of absorption edge on effective atomic numbers and its variation with energy, and nonvalidity of the Bragg`s mixture rule at incident photon energies closer to the absorption edges of constituent elements of compounds are discussed.

Shivaramu; Amutha, R.; Ramprasath, V. [Indira Gandhi Centre for Atomic Research, Kalpakkam (India). Safety Research and Health Physics Group

1999-05-01

257

The effects of image acquisition control of digital X-ray system on radiodensity quantification  

PubMed Central

Objectives Aluminum step wedge (ASW) equivalent radiodensity (eRD) has been used to quantify restorative material's radiodensity. The aim of this study was to evaluate the effects of image acquisition control (IAC) of a digital X-ray system on the radiodensity quantification under different exposure time settings. Materials and Methods Three 1-mm thick restorative material samples with various opacities were prepared. Samples were radiographed alongside an ASW using one of three digital radiographic modes (linear mapping (L), nonlinear mapping (N), and nonlinear mapping and automatic exposure control activated (E)) under 3 exposure time settings (underexposure, normal-exposure, and overexposure). The ASW eRD of restorative materials, attenuation coefficients and contrasts of ASW, and the correlation coefficient of linear relationship between logarithms of gray-scale value and thicknesses of ASW were compared under 9 conditions. Results The ASW eRD measurements of restorative materials by three digital radiographic modes were statistically different (p = 0.049) but clinically similar. The relationship between logarithms of background corrected grey scale value and thickness of ASW was highly linear but attenuation coefficients and contrasts varied significantly among 3 radiographic modes. Varying exposure times did not affect ASW eRD significantly. Conclusions Even though different digital radiographic modes induced large variation on attenuation of coefficient and contrast of ASW, E mode improved diagnostic quality of the image significantly under the under-exposure condition by improving contrasts, while maintaining ASW eRDs of restorative materials similar. Under the condition of this study, underexposure time may be acceptable clinically with digital X-ray system using automatic gain control that reduces radiation exposure for patient.

Seong, Wook-Jin; Jeong, Soocheol; Heo, Youngcheul; Song, Woo-Bin; Ahmad, Mansur

2013-01-01

258

Simulation study of a quasi-monochromatic beam for x-ray computed mammotomography.  

PubMed

The purpose of this simulation study was to evaluate the feasibility, benefits, and potential operating parameters of a quasi-monochromatic beam from a tungsten-target x-ray source yielding projection images. The application is intended for newly developed cone beam computed mammotomography (CmT) of an uncompressed breast. The value of a near monochromatic x-ray source for a fully 3D CmT application is the expected improved ability to separate tissues with very small differences in attenuation coefficients. The quasi-monochromatic beam is expected to yield enhanced tomographic image quality along with a low dose, equal to or less than that of dual view x-ray mammography. X-ray spectra were generated with a validated projection x-ray simulation tool (XSpect) for a range of tungsten tube potentials (40-100 kVp), filter materials (Z=51-65), and filter thicknesses (10th to 1000th value layer determined at 60 kVp). The breast was modeled from ICRU-44 breast tissue specifications, and a breast lesion was modeled as a 0.5 cm thick mass. The detector was modeled as a digital flat-panel detector with a 0.06 cm thick CsI x-ray absorption layer. Computed figures of merit (FOMs) included the ratio of mean beam energy post-breast to pre-breast and the ratio of lesion contrasts for edge-located and center-located lesions as indices of breast beam hardening, and SNR2/exposure and SNR2/dose as indices of exposure and dose efficiencies. The impact of optimization of these FOMs on lesion contrast is also examined. For all simulated filter materials at each given attenuation thickness [10th, 100th, 500th, 1000th value layers (VLs)], the mean and standard deviation of the pre-breast spectral full-width at tenth-maximum (FWTM) were 16.1 +/- 2.4, 10.3 +/- 2.2, 7.3 +/- 1.4, and 6.5 +/- 1.5 keV, respectively. The change in beam width at the tenth maximum from pre-breast to post-breast spectra ranged from 4.7 to 1.1 keV, for the thinnest and thickest filters, respectively. The higher Z filters (Z=57-63) produced a quasi-monochromatic beam that allowed the widest tube potential operating range (50-70 kVp) while maintaining minimal beam hardening and maximal SNR2/exposure and SNR2/dose, and providing a contrast greater than that obtained in the unfiltered case. Figures of merit improved with increasing filter thickness, with diminishing returns beyond the 500th value layer attenuation level. Operating parameters required to produce optimal spectra, while keeping exposures equal to that of dual view mammography, are within the capability of the commercial x-ray tube proposed for our experimental study, indicating that use of these highly attenuating filters is viable. Additional simulations comparing Mo/Mo, Mo/Rh, and W/Rh target/filter combinations indicate that they exhibit significantly lower SNR2/exposure than the present approach, precluding them from being used for computed mammotomography, while maintaining dose limitations and obtaining sufficient SNR. Beam hardening was also much higher in the existing techniques (17%-42%) than for our technique (2%). Simulations demonstrate that this quasi-monochromatic x-ray technique may enhance tissue separation for a newly developed cone beam computed mammotomography application for an uncompressed breast. PMID:15124997

McKinley, Randolph L; Tornai, Martin P; Samei, Ehsan; Bradshaw, Marques L

2004-04-01

259

Astrophysical Observations with High Resolution X-ray Telescopes  

Microsoft Academic Search

In slightly less than twenty years, from its birth in 1962, X-ray astronomy has developed into a major branch of astronomy, equalling in importance the more established disciplines for the study of astrophysical problems. This has resulted from two major technological advances: 1) the capability of placing into space, above the Earth's attenuating atmosphere, large and sophisticated scientific payloads, and

M. V. Zombeck

1981-01-01

260

Highly-Iodinated Fullerene as a Contrast Agent For X-ray Imaging  

Microsoft Academic Search

The first fullerene-based X-ray contrast agent (CA) has been designed, synthesized, and characterized. The new CA is an externally functionalized derivative of C60 that is conceptually based on contemporary X-ray CA, all of which use iodine as the X-ray attenuating vehicle and are based on the 2,4,6-triiodinated-benzene-ring substructure. Using a modified Bingel-type reaction, a single addend containing 6 iodine atoms

Tim Wharton; Lon J. Wilson

2002-01-01

261

Automatic detection of bone fragments in poultry using multi-energy x-rays  

DOEpatents

At least two linear arrays of x-ray detectors are placed below a conveyor belt in a poultry processing plant. Multiple-energy x-ray sources illuminate the poultry and are detected by the detectors. Laser profilometry is used to measure the poultry thickness as the x-ray data is acquired. The detector readout is processed in real time to detect the presence of small highly attenuating fragments in the poultry, i.e., bone, metal, and cartilage.

Gleason, Shaun S [Knoxville, TN; Paulus, Michael J [Knoxville, TN; Mullens, James A [Knoxville, TN

2002-04-09

262

X-ray dark-field imaging modeling.  

PubMed

Dark-field images are formed from x-ray small-angle scattering signals. The small-angle scattering signals are particularly sensitive to structural variation and density fluctuation on a length scale of several tens to hundreds of nanometers, offering a unique contrast mechanism to reveal subtle structural features of an object. In this study, based on the principle of energy conservation, we develop a physical model to describe the relationship between x-ray small-angle scattering coefficients of an object and dark-field intensity images. This model can be used to reconstruct volumetric x-ray small-angle scattering images of an object using classical tomographic algorithms. We also establish a relationship between the small-angle scattering intensity and the visibility function measured with x-ray grating imaging. The numerical simulations and phantom experiments have demonstrated the accuracy and practicability of the proposed model. PMID:22673420

Cong, W; Pfeiffer, F; Bech, M; Wang, G

2012-06-01

263

X-ray diodes for laser fusion plasma diagnostics  

NASA Astrophysics Data System (ADS)

Photodiodes with X-ray sensitive photocathodes used as broadband X-ray detectors in fusion plasma diagnostics are discussed. The risetime of the detector system and the quantum efficiency between 1 to 500 A of numerous photocathode materials of practical interest were measured. The materials studied included aluminum, copper, nickel, gold, three forms of carbon, chromium, and cesium iodide. The results of the measurements are compared with Henke's semiempirical model of photoyield. The effects of long-term cathode aging were studied. In addition, the X-ray mass-absorption coefficient of several ultrasoft X-ray windows were measured in energy regions where data were unavailable. Windows studied were made of aluminum, Formvar, polypropylene, and Kimfoil.

Day, R. H.; Lee, P.; Salloman, E. B.; Nagel, D. J.

1981-02-01

264

Water equivalence of NIPAM based polymer gel dosimeters with enhanced sensitivity for x-ray CT  

NASA Astrophysics Data System (ADS)

Two new formulations of N-isopropylacrylamide (NIPAM) based three dimensional (3D) gel dosimeters have recently been developed with improved sensitivity to x-ray CT readout, one without any co-solvent and the other one with isopropanol co-solvent. The water equivalence of the NIPAM gel dosimeters was investigated using different methods to calculate their radiological properties including: density, electron density, number of electrons per grams, effective atomic number, photon interaction probabilities, mass attenuation and energy absorption coefficients, electron collisional, radiative and total mass stopping powers and electron mass scattering power. Monte Carlo modelling was also used to compare the dose response of these gel dosimeters with water for kilovoltage and megavoltage x-ray beams and for megavoltage electron beams. We found that the density and electron density of the co-solvent free gel dosimeter are more water equivalent with less than a 2.6% difference compared to a 5.7% difference for the isopropanol gel dosimeter. Both the co-solvent free and isopropanol solvent gel dosimeters have lower effective atomic numbers than water, differing by 2.2% and 6.5%, respectively. As a result, their photoelectric absorption interaction probabilities are up to 6% and 19% different from water, respectively. Compton scattering and pair production interaction probabilities of NIPAM gel with isopropanol differ by up to 10% from water while for the co-solvent free gel, the differences are 3%. Mass attenuation and energy absorption coefficients of the co-solvent free gel dosimeter and the isopropanol gel dosimeter are up to 7% and 19% lower than water, respectively. Collisional and total mass stopping powers of both gel dosimeters differ by less than 2% from those of water. The dose response of the co-solvent free gel dosimeter is water equivalent (with <1% discrepancy) for dosimetry of x-rays with energies <100 keV while the discrepancy increases (up to 5%) for the isopropanol gel dosimeter over the same energy range. For x-ray beams over the energy range 180 keV-18 MV, both gel dosimeters have less than 2% discrepancy with water. For megavoltage electron beams, the dose differences with water reach 7% and 14% for the co-solvent free gel dosimeter and the isopropanol gel dosimeter, respectively. Our results demonstrate that for x-ray beam dosimetry with photon energies higher than 100 keV and megavoltage electron beams, correction factors are needed for both NIPAM gels to be used as water equivalent dosimeters.

Gorjiara, Tina; Hill, Robin; Bosi, Stephen; Kuncic, Zdenka; Baldock, Clive

2013-10-01

265

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

266

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

267

Exploring the X-ray Universe  

NASA Astrophysics Data System (ADS)

1. Birth and childhood of X-ray astronomy; 2. X-ray emission and interaction with matter; 3. Tools and techniques; 4. Solar System X-rays; 5. X-ray absorption and scattering in the interstellar medium; 6. Active stellar coronae; 7. Early-type stars; 8. Supernova explosions and their remnants; 9. Neutron stars, pulsars, pulsar wind nebulae, more supernova remnants; 10. Cataclysmic variable stars; 11. X-ray binaries; 12. Black-hole X-ray binaries; 13. Normal and starburst galaxies; 14. Active galactic nuclei; 15. Clusters of galaxies; 16. The diffuse X-ray background; 17. Gamma-ray bursts; Index.

Seward, Frederick D.; Charles, Philip A.

2010-08-01

268

X ray laser with enhanced x ray gain through photodepopulation  

Microsoft Academic Search

The present invention relates to x ray lasers employing hydrogenic lasing ions of nuclear charge Z, for n=2 to 4 or 6 excitation, and radiating ions of nuclear charge Z\\/2 for decreasing the n=2 population density of the hydrogenic lasing ions of nuclear charge Z. It is an object of the invention to increase the population inversion and gain to

Raymond C. Elton

1989-01-01

269

Attenuation coefficients and absorbed gamma radiation energy of different varieties of potato, mango and prawn at different storage time and physiological condition.  

PubMed

Attenuation coefficients of different varieties of gamma irradiated potato (Kufri Chandramukhi, Kufri Jyoti, and Kufri Sindhuri), mango (Himsagar, Langra, Dashehri and Fazli) and prawn (Tiger prawn and Fresh water prawn) of different storage time and physiological stages were determined. After six months storage attenuation coefficient of Kufri Chandramukhi was decreased by 30.8% with decrease of density and moisture content. Decreasing trend of attenuation coefficient during storage was more prominent (almost 50%) in other two varieties of potato. On the other hand in all four varieties, unripe mango consisted of significantly less (p?0.05) attenuation coefficient (around 11-14%) than the ripe one due to changes in physiological properties and density. Different varieties of prawn had different attenuation coefficients due to subtle differences in their proximate composition. Due to having different attenuation coefficients, different food components, even different varieties of same food component absorbed different gamma radiation energy though exposed to same radiation dose. PMID:24128533

Ghosh, Sayanti; Das, M K

2013-09-04

270

Compound refractive X-ray lens  

Microsoft Academic Search

An apparatus and method are disclosed for focusing X-rays. In one embodiment, his invention is a commercial-grade compound refractive X-ray lens. The commercial-grade compound refractive X-ray lens includes a volume of low-Z material. The volume of low-Z material has a first surface which is adapted to receive X-rays of commercially-applicable power emitted from a commercial-grade X-ray source. The volume of

D. R. Nygren; R. Cahn; B. Cederstrom; M. Danielsson; J. Vestlund

2000-01-01

271

X-ray laser microscope apparatus  

Microsoft Academic Search

A microscope consisting of an x-ray contact microscope and an optical microscope. The optical, phase contrast, microscope is used to align a target with respect to a source of soft x-rays. The source of soft x-rays preferably comprises an x-ray laser but could comprise a synchrotron or other pulse source of x-rays. Transparent resist material is used to support the

Szymon Suckewer; Darrell S. DiCicco; Joseph G. Hirschberg; Lewis D. Meixler; Robert Sathre; Charles H. Skinner

1990-01-01

272

A three-dimensional x-ray scattering system for multi-parameter imaging of the human head.  

PubMed

This work examines the suitability of a non-rotating one-side 3D x-ray scatter system for imaging the human head. The system simultaneously produces images of the x-ray attenuation coefficients at two photon energies, as well as an image of the electron density. The system relies on measuring the scattered radiation at two directions orthogonal to an incident beam that scans the object from one side, in addition to the traditionally recorded transmitted radiation. Algorithms for this multi-parameter imaging process are presented, and their numerical viability is demonstrated, using both idealized detector responses and those independently estimated from Monte Carlo simulations. The absorbed radiation dose is also calculated, and was shown to be about one quarter of that of conventional CT systems, for 5 mm spatial-resolution images. The introduced system can therefore be useful in radiotherapy planning, and in post-treatment imaging. PMID:14620068

El Khettabi, Faysal; Yaar, Ilan; Hussein, Esam M A

2003-10-21

273

Compact x-ray source and panel  

DOEpatents

A compact, self-contained x-ray source, and a compact x-ray source panel having a plurality of such x-ray sources arranged in a preferably broad-area pixelized array. Each x-ray source includes an electron source for producing an electron beam, an x-ray conversion target, and a multilayer insulator separating the electron source and the x-ray conversion target from each other. The multi-layer insulator preferably has a cylindrical configuration with a plurality of alternating insulator and conductor layers surrounding an acceleration channel leading from the electron source to the x-ray conversion target. A power source is connected to each x-ray source of the array to produce an accelerating gradient between the electron source and x-ray conversion target in any one or more of the x-ray sources independent of other x-ray sources in the array, so as to accelerate an electron beam towards the x-ray conversion target. The multilayer insulator enables relatively short separation distances between the electron source and the x-ray conversion target so that a thin panel is possible for compactness. This is due to the ability of the plurality of alternating insulator and conductor layers of the multilayer insulators to resist surface flashover when sufficiently high acceleration energies necessary for x-ray generation are supplied by the power source to the x-ray sources.

Sampayon, Stephen E. (Manteca, CA)

2008-02-12

274

Cooled window for X-rays or charged particles  

DOEpatents

A window is disclosed that provides good structural integrity and a very high capacity for removal of the heat deposited by x-rays, electrons, or ions, with minimum attenuation of the desired beam. The window is cooled by providing microchannels therein through which a coolant is pumped. For example, the window may be made of silicon with etched microchannels therein and covered by a silicon member. A window made of silicon with a total thickness of 520 {micro}m transmits 96% of the x-rays at an energy of 60 keV, and the transmission is higher than 90% for higher energy photons. 1 fig.

Logan, C.M.

1996-04-16

275

X-Ray Detector: An x-ray radiation detector design code.  

National Technical Information Service (NTIS)

X-Ray Detector (XRD) is an x-ray detector design code. It is intended to aid in the rapid design of x-ray detector packages. The design capabilities of XRD include filters, x-ray mirrors, x-ray diodes, silicon PIN diodes, GaAs PIN diodes, photoconducting ...

R. B. Spielman

1990-01-01

276

X-ray computed tomography  

Microsoft Academic Search

X-ray computed tomography (CT), introduced into clinical practice in 1972, was the first of the modern slice-imaging modalities. To reconstruct images mathematically from measured data and to display and to archive them in digital form was a novelty then and is commonplace today. CT has shown a steady upward trend with respect to technology, performance and clinical use independent of

Willi A Kalender

2006-01-01

277

Hyperphysics: X-ray tube  

NSDL National Science Digital Library

This Hyperphysics webpage provides an explanation of how an x-ray tube works. An accompanying diagram shows the parts of the tube and how the photons are produced. Two links within Hyperphysics supply further information. This page page is part of the HyperPhysics Collection, which contains many short, illustrated pages on various areas of physics and astronomy.

Nave, Carl R.

2012-03-23

278

Alpha Proton X ray Spectrometer.  

National Technical Information Service (NTIS)

Mars Pathfinder will carry an alpha-proton x ray spectrometer (APX) for the determination of the elemental chemical composition of Martian rocks and soils. The instrument will measure the concentration of all major and some minor elements, including C, N,...

R. Rieder H. Waeke T. Economou

1994-01-01

279

Alpha proton x ray spectrometer  

NASA Astrophysics Data System (ADS)

Mars Pathfinder will carry an alpha-proton x ray spectrometer (APX) for the determination of the elemental chemical composition of Martian rocks and soils. The instrument will measure the concentration of all major and some minor elements, including C, N, and O at levels above typically 1 percent.

Rieder, Rudi; Waeke, H.; Economou, T.

280

Applications of Hard X-ray Full-Field Transmission X-ray Microscopy at SSRL  

NASA Astrophysics Data System (ADS)

State-of-the-art hard x-ray full-field transmission x-ray microscopy (TXM) at beamline 6-2C of Stanford Synchrotron Radiation Lightsource has been applied to various research fields including biological, environmental, and material studies. With the capability of imaging a 32-micron field-of-view at 30-nm resolution using both absorption mode and Zernike phase contrast, the 3D morphology of yeast cells grown in gold-rich media was investigated. Quantitative evaluation of the absorption coefficient was performed for mercury nanoparticles in alfalfa roots exposed to mercury. Combining XANES and TXM, we also performed XANES-imaging on an ancient pottery sample from the Roman pottery workshop at LaGraufesenque (Aveyron).

Liu, Y.; Andrews, J. C.; Meirer, F.; Mehta, A.; Gil, S. Carrasco; Sciau, P.; Mester, Z.; Pianetta, P.

2011-09-01

281

Applications of Hard X-ray Full-Field Transmission X-ray Microscopy at SSRL  

SciTech Connect

State-of-the-art hard x-ray full-field transmission x-ray microscopy (TXM) at beamline 6-2C of Stanford Synchrotron Radiation Lightsource has been applied to various research fields including biological, environmental, and material studies. With the capability of imaging a 32-micron field-of-view at 30-nm resolution using both absorption mode and Zernike phase contrast, the 3D morphology of yeast cells grown in gold-rich media was investigated. Quantitative evaluation of the absorption coefficient was performed for mercury nanoparticles in alfalfa roots exposed to mercury. Combining XANES and TXM, we also performed XANES-imaging on an ancient pottery sample from the Roman pottery workshop at LaGraufesenque (Aveyron).

Liu, Y.; Andrews, J. C.; Mehta, A.; Pianetta, P. [Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, CA 94025 (United States); Meirer, F. [Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, CA 94025 (United States); MiNALab, CMM-Irst, Fondazione Bruno Kessler, Via Sommarive 18, 38123 Povo, Trento (Italy); Gil, S. Carrasco [CIEMAT, Avda Complutense 22, MADRID 28040 (Spain); Sciau, P. [CEMES (UPR 8011 CNRS), 29 rue J. Marvig, 31055 Toulouse Cedex 4 (France); Mester, Z. [Institute for National Measurement Standards, National Research Council, Ottawa ON K1A0R6 (Canada)

2011-09-09

282

New soft x-ray spectrometer on MST  

NASA Astrophysics Data System (ADS)

Measurements of x-ray spectra in the MST are used to investigate the transport of energetic electrons and to estimate the effective charge Zeff. A new set of x-ray detectors is being implemented on the MST to detect x-rays in the energy range of 2-10,. The new detectors are six Amptek XR-100CR modules with preamplifier and cooling. The detectors are connected to Cremat Gaussian shaping amplifiers with shaping times of either 500 or 100,. The shaping amplifier output is directly digitized at 60,, and the x-ray pulses are processed using a new code capable of correctly fitting multiple overlapping pulses. This configuration should allow a maximum count rate of 2-5,. The detectors can be placed in any of 17 ports covering r/a values from 0.87 inboard to 0.84 outboard allowing measurements of inboard-outboard symmetry. The new detectors compliment the current system composed of 13 CdZnTe detectors detecting hard x-rays in the 10-150, energy range. The composite energy spectra of these x-ray diagnostics will be used with CQL3D Fokker-Planck modeling to constrain key parameters such as the electron radial diffusion coefficient and Zeff.

Lee, J. D.; Almagri, A. F.; Burke, D. R.; Chapman, B. E.; Clayton, D. J.; Forest, C. B.; Sarff, J. S.

2010-11-01

283

Mass attenuation coefficients, effective atomic numbers and effective electron densities for some polymers.  

PubMed

In this study, the total mass attenuation coefficients (?(m)) for some homo- and hetero-chain polymers, namely polyamide-6 (PA-6), poly-methyl methacrylate (PMMA), low-density polyethylene (LDPE), polypropylene (PP) and polystyrene (PS) were measured at 59.5, 511, 661.6, 1173.2, 1274.5 and 1332.5 keV photon energies. The samples were separately irradiated with (241)Am, (22)Na, (137)Cs and (60)Co (638 kBq) radioactive gamma sources. The measurements were made by performing transmission experiments with a 2?×2? NaI(Tl) scintillation detector having an energy resolution of 7 % at 662 keV gamma ray from the decay of (137)Cs. The effective atomic numbers (Z(eff)) and the effective electron densities (N(eff)) were determined experimentally and theoretically using the obtained ?(m) values for the investigated samples. Furthermore, Z(eff) and N(eff) of each polymer were computed for total photon interaction cross-sections using theoretical data over a wide energy region from 1 keV to 10 MeV. The experimental values of the selected polymers were found to be in good agreement with the theoretical values. PMID:22645382

Kucuk, Nil; Cakir, Merve; Isitman, Nihat Ali

2012-05-29

284

Radiation dose estimation and mass attenuation coefficients of cement samples used in Turkey.  

PubMed

Different cement samples commonly used in building construction in Turkey have been analyzed for natural radioactivity using gamma-ray spectrometry. The mean activity concentrations observed in the cement samples were 52, 40 and 324 Bq kg(-1) for (226)Ra, (232)Th and (40)K, respectively. The measured activity concentrations for these radionuclides were compared with the reported data of other countries and world average limits. The radiological hazard parameters such as radium equivalent activities (Ra(eq)), gamma index (I(gamma)) and alpha index (I(alpha)) indices as well as terrestrial absorbed dose and annual effective dose rate were calculated and compared with the international data. The Ra(eq) values of cement are lower than the limit of 370 Bq kg(-1), equivalent to a gamma dose of 1.5 mSv y(-1). Moreover, the mass attenuation coefficients were determined experimentally and calculated theoretically using XCOM in some cement samples. Also, chemical compositions analyses of the cement samples were investigated. PMID:20018450

Damla, N; Cevik, U; Kobya, A I; Celik, A; Celik, N; Van Grieken, R

2009-12-16

285

X ray laser with enhanced x ray gain through photodepopulation  

NASA Astrophysics Data System (ADS)

The present invention relates to x ray lasers employing hydrogenic lasing ions of nuclear charge Z, for n=2 to 4 or 6 excitation, and radiating ions of nuclear charge Z/2 for decreasing the n=2 population density of the hydrogenic lasing ions of nuclear charge Z. It is an object of the invention to increase the population inversion and gain to saturation, to improve the overall efficiency, and to increase the plasma size by decreasing the population density N2.

Elton, Raymond C.

1989-09-01

286

Heuristic model for understanding x-ray film characteristics.  

PubMed

A simple, heuristic model of a photographic emulsion is described for the purpose of illustrating the fundamental physical processes and emulsion properties which determine the characteristics of an x-ray film (viz., the shape of the H - D curve, film gamma, and film speed). By means of this model, it is shown that the contrast multiplication afforded by an x-ray film (i.e., a film gamma greater than unity) is a direct result of the exponential attenuation of the viewing light by the developed film, and that film gamma is proportional to grain size, grain density, and emulsion thickness. The difference in the H - D curve that is observed when the same film is exposed to light from an intensifying screen or directly to x rays is also predicted by the model. PMID:979925

Dixon, R L; Ekstrand, K E

287

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

SciTech Connect

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

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

1997-02-01

288

Center for X-Ray Optics, 1986  

SciTech Connect

The Center for X-Ray Optics has made substantial progress during the past year on the development of very high resolution x-ray technologies, the generation of coherent radiation at x-ray wavelengths, and, based on these new developments, had embarked on several scientific investigations that would not otherwise have been possible. The investigations covered in this report are topics on x-ray sources, x-ray imaging and applications, soft x-ray spectroscopy, synchrotron radiation, advanced light source and magnet structures for undulators and wigglers. (LSP)

Not Available

1987-07-01

289

Spectral characterization of 4 MV Bremsstrahlung by attenuation analysis.  

PubMed

The "quality of radiation" for a high energy x-ray beam can be specified by its attenuation curve in a selected material. The inverse Laplace transform of the attenuation curve can be used as an approximate indication of the energy spectrum of the beam. Existing mathematical procedures for this purpose have been evaluated and were found to poorly represent measured transmission data for 4 MV x-rays from a linear accelerator. The transmission data between 1 and 0.002 could be fitted within the experimental uncertainty by expressing the logarithmic transmission as a second order polynomial of attenuator thickness. The inverse Laplace transform them becomes a Gaussian function of the attenuation coefficient. This new version of "attenuation analysis" provides a practical method for specification of the quality of the radiation in this energy range. PMID:6798393

Huang, P H; Kase, K R; Bjärngard, B E

290

X-Ray Phase-Contrast Imaging Methods for Biological Structures  

Microsoft Academic Search

X-ray imaging is of paramount importance for clinical and preclinical imaging but it is fundamentally restricted by the attenuation-based contrast mechanism, which has remained essentially the same since Roentgen's discovery a century ago. Different from the conventional method based on the attenuation contrast mechanism, X-ray phase-contrast imaging (XPCI) is proposed for the study of biological tissues and structures. This technique

Fu Jian; Li Jian; Zhu Jian; Zhou Xingyu; Zhou Zhenggan; Wei Dongbo

2009-01-01

291

Human soft tissue analysis using x-ray or gamma-ray techniques.  

PubMed

This topical review is intended to describe the x-ray techniques used for human soft tissue analysis. X-ray techniques have been applied to human soft tissue characterization and interesting results have been presented over the last few decades. The motivation behind such studies is to provide improved patient outcome by using the data obtained to better understand a disease process and improve diagnosis. An overview of theoretical background as well as a complete set of references is presented. For each study, a brief summary of the methodology and results is given. The x-ray techniques include x-ray diffraction, x-ray fluorescence, Compton scattering, Compton to coherent scattering ratio and attenuation measurements. The soft tissues that have been classified using x-rays or gamma rays include brain, breast, colon, fat, kidney, liver, lung, muscle, prostate, skin, thyroid and uterus. PMID:18451465

Theodorakou, C; Farquharson, M J

2008-05-01

292

TOPICAL REVIEW: Human soft tissue analysis using x-ray or gamma-ray techniques  

NASA Astrophysics Data System (ADS)

This topical review is intended to describe the x-ray techniques used for human soft tissue analysis. X-ray techniques have been applied to human soft tissue characterization and interesting results have been presented over the last few decades. The motivation behind such studies is to provide improved patient outcome by using the data obtained to better understand a disease process and improve diagnosis. An overview of theoretical background as well as a complete set of references is presented. For each study, a brief summary of the methodology and results is given. The x-ray techniques include x-ray diffraction, x-ray fluorescence, Compton scattering, Compton to coherent scattering ratio and attenuation measurements. The soft tissues that have been classified using x-rays or gamma rays include brain, breast, colon, fat, kidney, liver, lung, muscle, prostate, skin, thyroid and uterus.

Theodorakou, C.; Farquharson, M. J.

2008-06-01

293

Fabrication of High Aspect Ratio X-ray Grating Using X-ray Lithography  

Microsoft Academic Search

X-ray radiographic imaging technique has found applications in various fields. However, it is not enough to get clear X-ray images of samples with low absorbance, such as biological soft tissues. To resolve this problem, we proposed a method using an X-ray Talbot interferometer of X-ray phase imaging. In this X-ray Talbot interferometer, X-ray gratings were required to have a fine,

Daiji Noda; Hiroshi Tsujii; Kazuma Shimada; Wataru Yashiro; Atsushi Momose; Tadashi Hattori

2009-01-01

294

Development of an X-ray photoelectron microscopic system with a compact X-ray source  

Microsoft Academic Search

We have constructed an X-ray photoelectron microscopic system. An X-ray source is a laser-produced plasma in a scheme of an X-ray laser experiment. X rays involving amplified spontaneous emissions (ASE) at 15.47 nm were delivered with a 10-Hz repetition rate from a compact X-ray laser system. X rays were collected and focused by a Schwarzschild optics coated with Mo\\/Si multilayers

Chiemi Fujikawa; Naohiro Yamaguchi; Tadayuki Ohchi; Tamio Hara; Katsumi Watanabe; Ibuki Tanaka; Masami Taguchi

2002-01-01

295

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

296

Recent advances in X-ray photoconductors for direct conversion X-ray image detectors  

Microsoft Academic Search

Recent research on flat panel X-ray image detectors has shown their potential for replacing existing X-ray film\\/screen cassettes and capturing X-ray images electronically, thus enabling the clinical transition to digital radiography. The present work examines the imaging properties of a number of potential X-ray photoconductors for these new X-ray image detectors. The X-ray sensitivity is discussed in terms of the

S. O. Kasap; M. Zahangir Kabir; J. A. Rowlands

2006-01-01

297

X-ray microprobe for micro x-ray fluorescence and absorption spectroscopies at GSECARS  

Microsoft Academic Search

The hard x-ray microprobe for x-ray fluorescence and absorption spectroscopy at GeoSoilEnviroCARS is presented. Using focused synchrotron radiation from an undulator beamline at the Advanced Photon Source at Argonne National Lab, the x-ray microprobe provides bright, monochromatic x-rays with typical spot sizes down to 1x1 mum for x-ray fluorescence and absorption spectroscopies. Quantitative x-ray fluorescence (XRF) analysis gives precise elemental

M. Newville; S. Sutton; M. Rivers

2002-01-01

298

Aspects of x-ray microtomography equipment design  

NASA Astrophysics Data System (ADS)

We have developed a high definition X-ray microtomography scanner using time-delay integration CCD readout mode, whereby the camera is moved through the X-ray "shadow" during simultaneous readout. This method eliminates ring artefacts in the reconstructed image and allows the recorded image to be larger than the CCD itself. To maximise dynamic range, the reflective coated scintillator was lens coupled (two back-to-back 50mm f1.2 camera lenses). Equivalent X-ray photons per pixel were derived from noise measurements in specimen-absent projections. This was typically 600,000 for a 10 second exposure (90kV, 200?A, 25 cm source to camera). To quantify relay lens efficiency, this was re-measured at aperture settings from f1.2 to f11. The results closely fitted a model based on two noise sources (one from finite X-ray photons and one from finite light photons per X-ray photon), yielding an efficiency of 60% at f1.2. Although higher efficiency is desirable, this is a good compromise that avoids CCD saturation. This suggests that when using the more efficient direct fibre-optic coupling, a reflective scintillator coating may be undesirable, as the marginal increase in efficiency would not justify any loss of resolution or dynamic range. Correction for beam hardening is currently carried out using a 7 step Al wedge to measure experimental attenuation vs theoretical attenuation for monochromatic radiation. We intend to modify this method to improve accuracy in a more diverse range of materials. Dishing artefacts were decreased further by using a moving X-ray aperture to reduce scattered radiation.

Davis, Graham R.; Elliott, James C.

2004-10-01

299

Operational characteristics of a prototype x-ray needle device  

NASA Astrophysics Data System (ADS)

A prototype x-ray needle, which emits 62.5 kVp x-rays at the tip of a 20 cm long, 4 mm diameter steel needle, has been developed by Titan Pulse Sciences Incorporated (PSI) (Albuquerque, NM) and was tested for its suitability in brachytherapy applications in comparison with a similar device by the Photoelectron Corporation. The depth dose profiles were also compared with those of two common brachytherapy sources (125I and 192Ir). The depth dose characteristics of the radiation were comparable with the two brachytherapy sources with a slightly reduced attenuation gradient. The dose rate from the x-ray needle tip was relatively isotropic at the needle tip and was continuously adjustable over the range of 0 cGy min-1 to upwards of 62 cGy min-1 at a reference distance of 1 cm in air. We detected a significant proportion of x-rays generated along the needle shaft, and not at the needle tip, as intended. The energy spectrum emitted from this device had a peak intensity at 21 keV and an average energy of 28 keV. The beam was attenuated in both aluminium (the first half-value layer being less than 0.1 mm) and in water (50% dose at approximately 2 mm). These studies confirm that although there is potential for a system similar to this one for clinical applications, the simplistic electron guidance used in this particular prototype device limits it to research applications. Further optimization is required in focusing and steering the electron beam to the target, improving x-ray production efficiency and using x-ray target cooling to achieve higher dose rates.

Karnas, S. J.; Avvakumov, N.; Yu, E.; Battista, J. J.

2001-01-01

300

Multiple Diffuse Small Angle Scattering of X-Rays  

Microsoft Academic Search

The problem of multiple x-ray scattering from spherical particles of radius much larger than the wave-length is treated using the Guinier approximate scattering function. The total scattered intensity is found to be a sum of Gaussians in the polar angle with coefficients dependent on the sample thickness. A method is discussed for determining particle sizes from the variation of the

David L. Dexter; W. W. Beeman

1949-01-01

301

Investigating the feasibility of photon-counting K-edge imaging at high x-ray fluxes using nonlinearity corrections.  

PubMed

Purpose: Pulse pileup occurring at high x-ray fluxes can severely degrade the energy resolution provided by a photon counting detector, which can represent a problem in spectroscopic CT when performing quantitative material discrimination tasks. As the effects of pileup can be most easily seen as a degradation of a detector's count rate linearity at high fluxes, it has been proposed previously to quantify and correct these nonlinearities. While this strategy has been applied successfully to materials without K-edges, it is currently unknown if this still prevails when using medical contrast agents. The purpose of this study is to close this gap.Methods: A Medipix2MXR Hexa detector was employed, featuring a pixel pitch of 165 [micro sign]m and a 1 mm thick CdTe sensor. A phantom containing various concentrations of iodine and gadolinium contrast agents was subject to energy selective CT acquisitions, using a pulsable x-ray source operated at 70 kVp. These acquisitions were obtained at low and high photon fluxes of 1.0 × 10(6) and 1.3 × 10(7) mm(-2) s(-1), respectively. Nonlinearity corrections were applied to the high-flux projections and for each pixel separately. The results were compared to the results at low photon fluxes.Results: At high fluxes, a general reduction of the reconstructed attenuation coefficients was observed, which could be partially recovered using the correction strategy applied. The spectroscopic separation of iodine from the phantom material, however, degraded with increasing x-ray flux. In contrast to this, gadolinium could still be discriminated almost as well as in the low flux case.Conclusions: Nonlinearity corrections applied to high flux measurements can help to recover attenuation coefficients normally obtained at low fluxes for low-Z materials, which do not exhibit an absorption edge in the relevant energy range. However, as a result of a significant change of the x-ray spectrum, the spectroscopic contrast normally observed for iodine was found to vanish with increasing x-ray flux. In other words, the authors' results indicate that nonlinearity corrections may be feasible only when the K-edge of interest is sufficiently high compared to the mean photon energy, and that spectroscopic CT at high x-ray fluxes may suffer from less limitations when using high-Z materials as contrast agents. A future study should aim to confirm these findings under clinical conditions. PMID:24089910

Rink, Kristian; Oelfke, Uwe; Fiederle, Michael; Zuber, Marcus; Koenig, Thomas

2013-10-01

302

Hard X-ray astronomy with balloons  

NASA Astrophysics Data System (ADS)

The hard X-ray studies of cosmic X-ray sources carried out with the balloon-borne instruments launched from Hyderabad (India) during 1968-1990 period are discussed. Advantages of making hard X-ray astronomy observations from Hyderabad are pointed out and the X-ray telescopes used in these studies are briefly described. A summary of the important results obtained from these studies on the galactic binary X-ray sources, a few extragalactic objects and the diffuse cosmic X-ray background, is presented. The important results include detection of hard X-ray flares in Sco X-1 and Cyg X-1, 4.8 hr intensity modulation in Cyg X-3, hard X-ray pulsations in the X-ray pulsars, energy spectra of Cyg X-1, Her X-1, 3C 273 and the diffuse Cosmic X-ray background, the correlated optical and hard X-ray intensity variations and the size of the hard X-ray emitting region in the Crab Nebula. Future hard X-ray studies planned to be carried out from Hyderabad are briefly described.

Agrawal, P. C.

1991-08-01

303

Phase-Sensitive X-ray Imaging of Synovial Joints  

PubMed Central

Objective To test the efficacy of phase-sensitive x-ray imaging for intact synovial joints, whereby refraction effects, along with the attenuation of conventional radiography, can be exploited. Design Intact cadaveric human knee joints were imaged, in the computed tomographic mode, using an analyzer based x-ray system at the National Synchrotron Light Source, Brookhaven National Laboratory. A collimated fan beam of 51 keV X-rays was prepared by a silicon [1,1,1 reflection] double-crystal monochromator. The x-ray beam transmitted through the specimen was imaged after diffraction in the vertical plane by means of the analyzer crystal with the analyzer crystal tuned to its half-reflectivity point (6.5 microradians). A two-dimensional filtered backprojection (FBP) algorithm was used for reconstructing transverse slices of images. Results The resulting images demonstrate simultaneous soft-tissue and bone contrast at a level that has not been achieved previously. Identifiable structures include articular cartilage, cruciate ligaments, loose connective tissue, menisci, and chondrocalcinosis. Conclusion Phase-sensitive x-ray imaging using an analyzer-based system renders exceptionally high quality images of soft and hard tissues within synovial joints, with high contrast and resolution, and thus holds promise for the eventual clinical utility.

Li, Jun; Zhong, Zhong; Connor, Dean; Mollenhauer, Jorgen; Muehleman, Carol

2009-01-01

304

Energy-resolved interferometric x-ray imaging  

NASA Astrophysics Data System (ADS)

Interferometric X-ray imaging becomes more and more attractive for applications such as medical imaging or non-destructive testing, where a compact setup is needed. Therefore a so-called Talbot-Lau interferometer in combination with a conventional X-ray tube is used. Thereby, three different kinds of images can be obtained. An attenuation image like in conventional X-ray imaging, an image of the differential phase-shifts caused by the object and the so-called dark-field image. The dark-field image shows information about the object's granularity even in sub-pixel dimensions what especially seems very promising for applications like mammography. With respect to optimizing the output of interferometric X-ray imaging in any application, it is inevitable to know the energy response of the interferometer as well as the energy dependence of the interactions of X- rays with matter. In this contribution, simulations and measurements using a Medipix 2 and a Timepix detector are presented.

Pelzer, Georg; Bayer, Florian; Gödel, Karl; Haas, Wilhelm; Horn, Florian; Rieger, Jens; Ritter, André; Sievers, Peter; Weber, Thomas; Zang, Andrea; Durst, Jürgen; Michel, Thilo; Anton, Gisela

2013-03-01

305

Unfolding X-ray spectra using a flat panel detector.  

PubMed

It is difficult to measure the energy spectrum of X-ray tubes due to the pile up effect produced by the high fluence of photons. Using attenuating materials, appropriate detector devices and the Monte Carlo method, primary X-ray spectrum of these devices can be estimated. In this work, a flat panel detector with a PMMA wedge has been used to obtain a dose curve corresponding to certain working conditions of a radiodiagnostic X-ray tube. The relation between the dose curve recorded by the flat panel and the primary X-ray spectrum is defined by a response function. Normally this function can be approximated by a matrix, which can be obtained by means of the Monte Carlo method. Knowing the measured dose curve and the response matrix, the primary X-ray spectrum can be unfolded. However, there are some problems that strongly affect the applicability of this method: i.e. technical features of the flat panel and inherent characteristics of the involved radiation physics (ill-posed problem). Both aspects are analyzed in this work, concluding that the proposed method can be applied with an acceptable accuracy for spectra without characteristic lines, for instance, tungsten anode in the 50-70 kVp range. PMID:24110205

Gallardo, Sergio; Juste, Belen; Pozuelo, Fausto; Rodenas, Jose; Querol, Andrea; Verdu, Gumersindo

2013-07-01

306

X-Ray Tomography: The Ultimate Petrographic Tool for Studying Pumice  

NASA Astrophysics Data System (ADS)

Over the last several years, we have been studying pumice from large-volume tuffs using synchrotron-based x- ray computed microtomography. Our goal is to document in detail and quantitatively crystal and bubble textures in pumice to retrieve information on the evolution of giant magma bodies over time, particularly for the stages leading to supereruptions. X-ray tomography yields 3D maps of x-ray linear attenuation coefficients, allowing documentation and visualization of textures in 3D, with resolution down to micrometer scale or better. X-ray tomography is ideal for the study of pumice, where crystals are sparse and mostly separated from each other by low-density vesicular glass. This is particularly fortunate because (a) pumice is poorly suited to being studied using thin-sections due to the low abundance of crystals, and (b) stereological corrections are unnecessary. Imaging is non-destructive, can be performed quickly (minutes to hours), and with little or no sample preparation. X-ray tomography is the perfect complement to physical separation methods (e.g. crushing, sieving and winnowing), which do allow extraction of individual crystals for detailed study, but also cause crystal breakage and yield little to no information on the vesicle populations. The application of x-ray tomography to pumice from the Bishop Tuff (California) and Peach Spring Tuff (Nevada-Arizona-California) reveals that, at the energies of interest, contrasts in attenuation are such that resulting tomograms enable the distinction of at least 5-6 of the most abundant phases present (i.e. void space, glass, quartz, feldspar, 1-2 mafic minerals, oxides). Using differential absorption x-ray tomography, we can map the distribution of key chemical elements in 3D, notably Zr and Ce, allowing the unambiguous identification and quantification of the sizes and spatial distribution of important accessory minerals such as zircon, titanite, and allanite (± chevkinite), for which textural information is almost completely lacking. Study of pumice from the Bishop Tuff shows that: (1) crystal fragmentation is an important magmatic process, with fragment size distributions following power laws typical of fractal processes; (2) quartz + feldspar crystal size distributions reveal two distinct crystal populations, one formed by crystallization under low supersaturation over millennial timescales, and another formed under high supersaturation (possibly reflecting decompression crystallization) within the final years to months before eruption; (3) a large vesicle with >50 magnetite crystals attached to its wall likely represents the first textural evidence for the presence of pre-eruptive bubbles in Bishop magma; (4) it may be possible to retrieve information on the pre-and syn-eruptive bubble populations from the study of vesicle size distributions. Study of pumice from the Peach Spring Tuff using Zr and Ce maps reveals that, surprisingly, most of the zircon crystals are included in large titanite crystals (also attached to allanite), while only a small number of zircon crystals occur isolated within the glassy matrix. This suggests that different zircon crystals may record different aspects of the crystallization history of pumice. Our ongoing studies of pumice from the Bishop and Peach Spring Tuff show that, especially when combined to crystal chemistry information, x-ray tomography provides invaluable information on the evolution of magmatic systems, with unprecedented level of detail.

Gualda, G. A.; Pamukcu, A. S.; Rivers, M. L.

2009-05-01

307

Soft X-ray Polarimetry  

NASA Astrophysics Data System (ADS)

We developed an instrument design capable of measuring linear X-ray polarization over a broad-band using conventional spectroscopic optics. A set of multilayer-coated flats reflects the dispersed X-rays to the instrument detectors. The intensity variation with position angle is measured to determine three Stokes parameters: I, Q, and U -- all as a function of energy. By laterally grading the multilayer optics and matching the dispersion of the gratings, one may take advantage of high multilayer reflectivities and achieve modulation factors >50% over the entire 0.2 to 0.8 keV band. This instrument could be used in a small orbiting mission or the approach could be used on a large dispersive spectrometric facility. We present progress on laboratory work to demonstrate the capabilities of key components.

Marshall, Herman; Schulz, Norbert S.; Heilmann, Ron; Kochanski, Kelly

2012-09-01

308

Microgap x-ray detector  

DOEpatents

An x-ray detector is disclosed which provides for the conversion of x-ray photons into photoelectrons and subsequent amplification of these photoelectrons through the generation of electron avalanches in a thin gas-filled region subject to a high electric potential. The detector comprises a cathode (photocathode) and an anode separated by the thin, gas-filled region. The cathode may comprise a substrate, such a beryllium, coated with a layer of high atomic number material, such as gold, while the anode can be a single conducting plane of material, such as gold, or a plane of resistive material, such as chromium/silicon monoxide, or multiple areas of conductive or resistive material, mounted on a substrate composed of glass, plastic or ceramic. The charge collected from each electron avalanche by the anode is passed through processing electronics to a point of use, such as an oscilloscope. 3 figures.

Wuest, C.R.; Bionta, R.M.; Ables, E.

1994-05-03

309

Microgap x-ray detector  

DOEpatents

An x-ray detector which provides for the conversion of x-ray photons into photoelectrons and subsequent amplification of these photoelectrons through the generation of electron avalanches in a thin gas-filled region subject to a high electric potential. The detector comprises a cathode (photocathode) and an anode separated by the thin, gas-filled region. The cathode may comprise a substrate, such a beryllium, coated with a layer of high atomic number material, such as gold, while the anode can be a single conducting plane of material, such as gold, or a plane of resistive material, such as chromium/silicon monoxide, or multiple areas of conductive or resistive material, mounted on a substrate composed of glass, plastic or ceramic. The charge collected from each electron avalanche by the anode is passed through processing electronics to a point of use, such as an oscilloscope.

Wuest, Craig R. (Danville, CA); Bionta, Richard M. (Livermore, CA); Ables, Elden (Livermore, CA)

1994-01-01

310

Soft x-ray microscopy  

Microsoft Academic Search

Summary form only given. Soft X-ray microscopy is at the forefront of research with spatial resolution approaching 10 nm, and wide ranging applications to the physical and life sciences, including the dynamics of magnetic nanostructures, three-dimensional biotomography at the sub-cellular level, elemental and chemically specific environmental studies. Examples of recent work are shown below in figures 1-3. Figure 1 shows

David Attwood; Peter Fischer; Erik Anderson; Carolyn Larabell; Mark LeGros; Paulo Monteiro; Weilun Chao; Anne Sakdinawat; Brooke Mesler

2008-01-01

311

X-ray Diode Preparation  

SciTech Connect

A rod pinch x-ray diode assembly culminates in a coaxial anode cathode arrangement where a small anode rod extends through the aperture of a cathode plate. Shotto- shot repeatability in rod placement, and thus x-ray source spot position, has potential to positively affect radiographic image quality. Thus, how to both control and measure, according to a Cartesian coordinate system, anode rod tip displacement (x, y) (off the beam line-of-sight retical) and also anode rod tip extension (z) (along the line-of-sight center line) become salient issues relative to radiographic image set utility. To address these issues both hardware fabrication and x-ray diode assembly methods were reviewed, and additional controls were introduced. A photogrammetric procedure was developed to quantify anode rod tip position in situ. Computer models and mock-up assemblies with precision fiducials were produced to validate this procedure. Therefore, both anode rod tip displacement and anode rod tip extension parameters were successfully controlled. Rod position was measured and met the required specifications: (1) radial displacement <0.25 mm and (2) axial placement of ±0.25 mm. We demonstrated that precision control and measurement of large scale components is achievable in a pulse power system (i.e., hardware and operations). Correlations with diode performance and radiography are presented.

Henderson, D J; Good, D E; Hogge, K W; Molina, I; Howe, R A; Lutz, S S; Flores, P A; McGillivray, K D; Skarda, W M; Nelson, D S; Ormond, E S

2011-06-16

312

X-ray integrated digital imaging system based on a-si flat panel detector  

NASA Astrophysics Data System (ADS)

X-ray phase contrast imaging (X-PCI) is one of the novel imaging methods. For the low density substance, it provides better images than the conventional X-ray attenuation imaging. In order to get a high-quality image, X-PCI adopts the high spatial resolution image intensifier as the detector. However, the X-ray attenuation imaging usually adopts the high sensitivity a-si flat panel detector (FPD) as the detector. So it is currently one of the questions in the field of X-ray imaging how to realize these two functions at a system: X-ray attenuation imaging and X-PCI. An X-ray integrated digital imaging system based on FPD is designed and developed after analyzing the imaging principle of X-PCI and the imaging feature of FPD. The results from simulation and experiments in this system show that the X-PCI image can be acquired without affecting the quality of the conventional X-ray attenuation image. It demonstrates the possibility to realize these two functions at a system.

Fu, Jian; Li, Bin; Jiang, Baihong

2010-05-01

313

Producing X-rays at the APS  

ScienceCinema

An introduction and overview of the Advanced Photon Source at Argonne National Laboratory, the technology that produces the brightest X-ray beams in the Western Hemisphere, and the research carried out by scientists using those X-rays.

314

Recent Advances in X-Ray Optics.  

National Technical Information Service (NTIS)

Recent developments in x-ray optics are reviewed. Specific advances in coded aperture imaging, zone plate lens fabrication, time and space resolved spectroscopy, and CCD x-ray detection are discussed. (ERA citation 09:036219)

N. M. Ceglio

1983-01-01

315

X-ray Photography: Inner Beauty  

NSDL National Science Digital Library

This article from TIME features Nick Veasey, an x-ray photographer who combines art and science through his photographs. The short article explains how Veasey started his work and includes a link to more x-ray photographs.

2009-10-15

316

Aspergillosis - chest x-ray (image)  

MedlinePLUS

... usually occurs in immunocompromised individuals. Here, a chest x-ray shows that the fungus has invaded the lung ... are usually seen as black areas on an x-ray. The cloudiness on the left side of this ...

317

5.8 X-ray Calorimeters.  

National Technical Information Service (NTIS)

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 detecti...

F. S. Porter

2008-01-01

318

X-rays, CT Scans and MRIs  

MedlinePLUS

... 2007 American Academy of Orthopaedic Surgeons X-rays, CT Scans and MRIs Diagnostic imaging techniques help narrow ... accurate. These techniques include X-rays, computed tomography (CT) scans, magnetic resonance imaging (MRI). These imaging tools ...

319

Using water quality variables to predict light attenuation coefficient: case study in Shihmen Reservoir  

Microsoft Academic Search

The amount of photosynthetically active radiation (PAR) in the water column is of fundamental importance in determining the\\u000a growth of aquatic plant and aquatic primary production. Light attenuation in aquatic ecosystems has important ecological implication\\u000a and water quality applications. In the present study, the light attenuation through the water column in the Shihmen Reservoir,\\u000a Taiwan was measured. A light attenuation

Wen-Cheng Liu; Ray-Shyan Wu; Edward Ming-Yang Wu; Yu-Pei Chang; Wei-Bo Chen

2010-01-01

320

L -subshell vacancy decay processes for elements with 52?Z?57 following ionization using Mn K? x rays  

NASA Astrophysics Data System (ADS)

The Li - (i=1-3) subshell x-ray spectra for the T52e , I53 , C55s , B56a , and L57a elements excited by Mn K? ( EK?2=5.888keV and EK?1=5.899keV ) x rays have been investigated using the F55e radioisotope in conjunction with a Cr absorber. A low-energy Ge detector was used to measure the L x rays at an emission angle ?=126° , where the second-order Legendre polynomial term P2 (cos?) associated with the angular distribution is annulled. In the case of the B56a and L57a elements, alignment of the L3 -subshell vacancy states was investigated through angular distribution measurements of the emitted L3 -subshell x rays. The L?1,2 and L?2,15 x-ray groups are observed to be nearly isotropic, while the data for the pure Ll (L3-M1) x-ray emission are indicative of a small anisotropic trend, though within experimental error. The integral x-ray fluorescence cross sections are deduced and interpreted in terms of Li -subshell photoionization cross sections, fluorescence and Coster-Kronig yields, and x-ray emission rates. The L2 -subshell x-ray cross sections for L57a measured using targets of lanthanum (III) fluoride and dilanthanum (III) trioxide are found to be unusually higher. The enhancement is observed due to the contribution of the L2 -subshell radiative resonant Raman scattering (RRS) of Mn K? x rays having energy around the L2 -subshell binding energy of L57a in these compounds. Also, the observed enhancement of the L3 -subshell x-ray cross sections in L57a is suggestive of intrashell vacancy transfer via L2-L3 Coster-Kronig RRS transitions. The L2 -subshell total RRS cross sections in L57a have been deduced from the present measured attenuation coefficients for Mn K? x rays in La2O3 and LaF3 . The L2 -subshell radiative and total RRS cross sections in L57a using LaF3 are higher by ˜30% than those using La2O3 . The contribution of processes predicted in the framework of Mozouchi’s four-band model involving inner subshells along with the valence and conduction bands of these wide-band-gap insulator compounds is likely to account for the observed results. The L2 -subshell radiative and L2-L3 Coster-Kronig yields and the ratio of the L2-M4 and L2-N4 radiative RRS intensities in both La compounds are found to be same and are consistent with values from photoexcited vacancy decay. The L2 -subshell radiative RRS was also observed to be isotropic.

Sharma, Veena; Kumar, Sanjeev; Mehta, D.; Singh, Nirmal

2008-07-01

321

X-ray lithography-an overview  

Microsoft Academic Search

The fundamentals of X-ray lithography are reviewed. Issues associated with resolution, wafer throughput, and process latitude are discussed. X-ray lithography is compared with other lithographic technologies; future advancements, such as X-ray projection lithography, are described. It is shown that the major barrier to the near-term success for X-ray lithography is the requirement for a defect-free one-to-one mask which satisfies the

MARTIN C. PECKERAR; JUAN R. MALDONADO

1993-01-01

322

Controlling X-rays with light  

Microsoft Academic Search

Ultrafast X-ray science is an exciting frontier that promises the visualization of electronic, atomic and molecular dynamics on atomic time and length scales. A largely unexplored area of ultrafast X-ray science is the use of light to control how X-rays interact with matter. To extend control concepts established for long-wavelength probes to the X-ray regime, the optical control field must

T. E. Glover; Marcus Hertlein; Steve Southworth; Tom Allison; Jeroen van Tilborg; Elliot Kanter; B. Krässig; H. R. Varma; Bruce Rude; Robin Santra; Ali Belkacem; Linda Young

2010-01-01

323

Material separation in x-ray CT with energy resolved photon-counting detectors  

PubMed Central

Purpose: The objective of the study was to demonstrate that, in x-ray computed tomography (CT), more than two types of materials can be effectively separated with the use of an energy resolved photon-counting detector and classification methodology. Specifically, this applies to the case when contrast agents that contain K-absorption edges in the energy range of interest are present in the object. This separation is enabled via the use of recently developed energy resolved photon-counting detectors with multiple thresholds, which allow simultaneous measurements of the x-ray attenuation at multiple energies. Methods: To demonstrate this capability, we performed simulations and physical experiments using a six-threshold energy resolved photon-counting detector. We imaged mouse-sized cylindrical phantoms filled with several soft-tissue-like and bone-like materials and with iodine-based and gadolinium-based contrast agents. The linear attenuation coefficients were reconstructed for each material in each energy window and were visualized as scatter plots between pairs of energy windows. For comparison, a dual-kVp CT was also simulated using the same phantom materials. In this case, the linear attenuation coefficients at the lower kVp were plotted against those at the higher kVp. Results: In both the simulations and the physical experiments, the contrast agents were easily separable from other soft-tissue-like and bone-like materials, thanks to the availability of the attenuation coefficient measurements at more than two energies provided by the energy resolved photon-counting detector. In the simulations, the amount of separation was observed to be proportional to the concentration of the contrast agents; however, this was not observed in the physical experiments due to limitations of the real detector system. We used the angle between pairs of attenuation coefficient vectors in either the 5-D space (for non-contrast-agent materials using energy resolved photon-counting acquisition) or a 2-D space (for contrast agents using energy resolved photon-counting acquisition and all materials using dual-kVp acquisition) as a measure of the degree of separation. Compared to dual-kVp techniques, an energy resolved detector provided a larger separation and the ability to separate different target materials using measurements acquired in different energy window pairs with a single x-ray exposure. Conclusions: We concluded that x-ray CT with an energy resolved photon-counting detector with more than two energy windows allows the separation of more than two types of materials, e.g., soft-tissue-like, bone-like, and one or more materials with K-edges in the energy range of interest. Separating material types using energy resolved photon-counting detectors has a number of advantages over dual-kVp CT in terms of the degree of separation and the number of materials that can be separated simultaneously.

Wang, Xiaolan; Meier, Dirk; Taguchi, Katsuyuki; Wagenaar, Douglas J.; Patt, Bradley E.; Frey, Eric C.

2011-01-01

324

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

325

Large Area X-Ray Spectroscopy Mission.  

National Technical Information Service (NTIS)

The Large Area X-ray Spectroscopy (LAXS) mission concept study continues to evolve strongly following the merging of the LAXS mission with the Next Generation X-ray Observatory (NGXO, PI: Nick White) into the re-named High Throughput X-ray Spectroscopy (H...

H. Tananbaum

1997-01-01

326

Center for X-ray Optics, 1988.  

National Technical Information Service (NTIS)

This report briefly reviews the following topics: soft-x-ray imaging; reflective optics for hard x-rays; coherent XUV sources; spectroscopy with x-rays; detectors for coronary artery imaging; synchrotron-radiation optics; and support for the advanced ligh...

1989-01-01

327

Cryotomography x-ray microscopy state  

DOEpatents

An x-ray microscope stage enables alignment of a sample about a rotation axis to enable three dimensional tomographic imaging of the sample using an x-ray microscope. A heat exchanger assembly provides cooled gas to a sample during x-ray microscopic imaging.

Le Gros, Mark (Berkeley, CA); Larabell, Carolyn A. (Berkeley, CA)

2010-10-26

328

Measurements of polycapillary x-ray optics  

Microsoft Academic Search

Assemblies of hollow capillary tubes, termed ‘‘Kumakhov optics,’’ can be used to control x rays for a large variety of applications. Measurements of x-ray transmission in polycapillary glass tubes were performed for the purpose of understanding their behavior in such devices. X-ray transmission was measured for straight, uniformly curved, and nonuniformly bent fibers. The data agree well with a computer

J. B. Ullrich; V. Kovantsev; C. A. MacDonald

1993-01-01

329

X-ray Topography in Protein Crystals  

NASA Astrophysics Data System (ADS)

X-ray topography, especially synchrotron X-ray topography, provides a useful tool for the characterization of protein crystals in order to characterize the defects. We observed clear images of dislocations in hen-egg white lysozyme crystals. In this article we overviewed the research on crystal defects, especially dislocations of protein crystals by synchrotron X-ray topography.

Kojima, Kenichi; Tachibana, Masaru

330

Novel x-ray mask structure with low out-of-plane distortion  

Microsoft Academic Search

During the process of an x-ray mask, anodic bonding makes the wafer to be distorted largely because of the difference between thermal coefficient of a wafer and Pyrex. A novel structure which has an additional wafer on the lower surface of Pyrex was suggested to reduce x-ray mask OPD and the case calculations have been made in this paper. For

Young Jin Jeon; Sang-Soo Choi; Il Yong Kim; Hai Bin Chung; Bo Woo Kim

1998-01-01

331

X-ray Bragg diffraction profiles from unstrained layered single-crystal structures: theoretical considerations, simulation and reconstruction using phase-retrieval X-ray diffractometry  

Microsoft Academic Search

The X-ray Bragg diffraction intensity profile for a model strain-compensated single-crystal structure consisting of a thin alloy layer grown on a thick substrate is derived using a Laplace transform interpretation of the kinematical approximation of X-ray diffraction theory, assuming a step-like attenuation depth-profile. The effects of the model physical parameters on the measurable Bragg diffraction intensity profile are discussed. The

A. Y. Nikulin; R. Steinfeld

2004-01-01

332

Validation of CALIPSO space-borne-derived attenuated backscatter coefficient profiles using a ground-based lidar in Athens, Greece  

Microsoft Academic Search

We present initial aerosol validation results of the space-borne lidar CALIOP -onboard the CALIPSO satellite- Level 1 attenuated backscatter coefficient profiles, using coincident observations performed with a ground-based lidar in Athens, Greece (37.9° N, 23.6° E). A multi-wavelength ground-based backscatter\\/Raman lidar system is operating since 2000 at the National Technical University of Athens (NTUA) in the framework of the European

R. E. Mamouri; V. Amiridis; A. Papayannis; E. Giannakaki; G. Tsaknakis; D. S. Balis

2009-01-01

333

Application-Oriented X-ray Grating Interferometer  

NASA Astrophysics Data System (ADS)

Grating-based Differential Phase Contrast X-ray imaging (DPCi) provides, in one measurement, unique information about the absorption coefficient, the index of refraction and the microscopic structure of a sample at hard X-ray frequencies11-17. For this reason, DPCi can potentially overcome the limitations of classical absorption-based radiography, notably for weakly absorbing materials. However, the implementation of the technology in industrial applications is still restricted due to the limited field of view and the insufficient contrast at high X-ray energies. Here, we report on a new experimental setup with field of view 5×7 cm2 that acquires single projections as well as Computerized Tomographic (CT) measurements of the sample. New micro-fabrication processes were developed to manufacture X-ray gratings with few defects. This allows the instrument to deliver images of industrial quality when operated with a conventional x-ray tube at 40 kV. The complementarity of DPCi with conventional absorption-based radiography was experimentally demonstrated.

Revol, V.; Kottler, C.; Kaufmann, R.; Jerjen, I.; Lüthi, T.; Cardot, F.; Niedermann, Ph.; Sennhauser, U.; Straumann, U.; Urban, C.

2010-04-01

334

An upgraded x-ray spectroscopy diagnostic on MST.  

PubMed

An upgraded x-ray spectroscopy diagnostic is used to measure the distribution of fast electrons in MST and to determine Z(eff) and the particle diffusion coefficient D(r). A radial array of 12 CdZnTe hard-x-ray detectors measures 10-150 keV Bremsstrahlung from fast electrons, a signature of reduced stochasticity and improved confinement in the plasma. A new Si soft-x-ray detector measures 2-10 keV Bremsstrahlung from thermal and fast electrons. The shaped output pulses from both detector types are digitized and the resulting waveforms are fit with Gaussians to resolve pileup and provide good time and energy resolution. Lead apertures prevent detector saturation and provide a well-known etendue, while lead shielding prevents pickup from stray x-rays. New Be vacuum windows transmit >2?keV x-rays, and additional Al and Be filters are sometimes used to reduce low energy flux for better resolution at higher energies. Measured spectra are compared to those predicted by the Fokker-Planck code CQL3D to deduce Z(eff) and D(r). PMID:21034007

Clayton, D J; Almagri, A F; Burke, D R; Forest, C B; Goetz, J A; Kaufman, M C; O'Connell, R

2010-10-01

335

A whole-system approach to x-ray spectroscopy in cargo inspection systems  

NASA Astrophysics Data System (ADS)

The bremsstrahlung x-ray spectrum used in high-energy, high-intensity x-ray cargo inspection systems is attenuated and modified by the materials in the cargo in a Z-dependent way. Therefore, spectroscopy of the detected x rays yields information about the Z of the x-rayed cargo material. It has previously been shown that such ZSpectroscopy (Z-SPEC) is possible under certain circumstances. A statistical approach, Z-SCAN (Z-determination by Statistical Count-rate ANalysis), has also been shown to be effective, and it can be used either by itself or in conjunction with Z-SPEC when the x-ray count rate is too high for individual x-ray spectroscopy. Both techniques require fast x-ray detectors and fast digitization electronics. It is desirable (and possible) to combine all techniques, including x-ray imaging of the cargo, in a single detector array, to reduce costs, weight, and overall complexity. In this paper, we take a whole-system approach to x-ray spectroscopy in x-ray cargo inspection systems, and show how the various parts interact with one another. Faster detectors and read-out electronics are beneficial for both techniques. A higher duty-factor x-ray source allows lower instantaneous count rates at the same overall x-ray intensity, improving the range of applicability of Z-SPEC in particular. Using an intensity-modulated advanced x-ray source (IMAXS) allows reducing the x-ray count rate for cargoes with higher transmission, and a stacked-detector approach may help material discrimination for the lowest attenuations. Image processing and segmentation allow derivation of results for entire objects, and subtraction of backgrounds. We discuss R&D performed under a number of different programs, showing progress made in each of the interacting subsystems. We discuss results of studies into faster scintillation detectors, including ZnO, BaF2 and PbWO4, as well as suitable photo-detectors, read-out and digitization electronics. We discuss high-duty-factor linear-accelerator x-ray sources and their associated requirements, and how such sources improve spectroscopic techniques. We further discuss how image processing techniques help in correcting for backgrounds and overlapping materials. In sum, we present an integrated picture of how to optimize a cargo inspection system for x-ray spectroscopy.

Langeveld, Willem G. J.; Gozani, Tsahi; Ryge, Peter; Sinha, Shrabani; Shaw, Tim; Strellis, Dan

2013-04-01

336

X-ray Spectroscopy of Cooling Cluster  

SciTech Connect

We review the X-ray spectra of the cores of clusters of galaxies. Recent high resolution X-ray spectroscopic observations have demonstrated a severe deficit of emission at the lowest X-ray temperatures as compared to that expected from simple radiative cooling models. The same observations have provided compelling evidence that the gas in the cores is cooling below half the maximum temperature. We review these results, discuss physical models of cooling clusters, and describe the X-ray instrumentation and analysis techniques used to make these observations. We discuss several viable mechanisms designed to cancel or distort the expected process of X-ray cluster cooling.

Peterson, J.R.; /SLAC; Fabian, A.C.; /Cambridge U., Inst. of Astron.

2006-01-17

337

Compound refractive X-ray lens  

Microsoft Academic Search

An apparatus and method for focusing X-rays. In one embodiment, his invention is a commercial-grade compound refractive X-ray lens. The commercial-grade compound refractive X-ray lens includes a volume of low-Z material. The volume of low-Z material has a first surface which is adapted to receive X-rays of commercially-applicable power emitted from a commercial-grade X-ray source. The volume of low-Z material

David R. Nygren; Robert Cahn; Bjorn Cederstrom; Mats Danielsson; Jonas Vestlund

2000-01-01

338

X-ray holography of biological specimens  

SciTech Connect

The author reviews the reasons for x-ray imaging of biological specimens and the techniques presently being used for x-ray microscopy. The author points out the advantages of x-ray holography and the difficulties of obtaining the requisite coherence with conventional sources. The author discusses the problems of radiation damage and the remarkable fact that short pulse x-ray sources circumvent these problems and obtain high-resolution images of specimens in the living state. Finally, the author reviews some of the efforts underway to develop high-intensity coherent x-ray sources for the laboratory. 14 references, 5 figures, 2 tables.

Solem, J.C.

1984-01-01

339

A computer code to simulate X-ray imaging techniques  

Microsoft Academic Search

A computer code was developed to simulate the operation of radiographic, radioscopic or tomographic devices. The simulation is based on ray-tracing techniques and on the X-ray attenuation law. The use of computer-aided drawing (CAD) models enables simulations to be carried out with complex three-dimensional (3D) objects and the geometry of every component of the imaging chain, from the source to

Philippe Duvauchelle; Nicolas Freud; Valérie Kaftandjian; Daniel Babot

2000-01-01

340

Transmission of x-ray polarization through glass capillary fibers  

Microsoft Academic Search

Synchrotron radiation beams at energies of 7, 8, and 11.5 keV were transmitted through straight and bent capillary fibers of the type used to focus or collimate x rays. The purpose was to learn if the multiple wall collisions during transmission would attenuate the polarization of the incident beam. The emergent polarization was determined using 90° Rayleigh-Thomson scattering by a

R. E. Benenson; Jianming Bai; Walter M. Gibson

2003-01-01

341

Parametrization of the total photon mass attenuation coefficients in the energy range 0.1-1000 keV  

NASA Astrophysics Data System (ADS)

It is convenient to generate mass attenuation coefficients using semi-empirical schemes. The validity of most of the existing schemes is limited to a relatively narrow energy interval (1-40 keV) and their accuracies are poor in some energy regions. In this work, a semi-empirical scheme flexible enough to give a good fit to data in a very wide photon energy range (0.1-1000 keV) was employed. Fitting coefficients for the entire range were obtained by utilizing mass attenuation data from two sources: (1) semi-empirical data of Henke et al. in the low photon energy region, and (2) theoretical values generated with the XCOM code for fitting in the high energy region. The root mean square of the fit is generally less than 0.2% except for energies below 1 keV where the available data are scattered. A computer code for generating mass attenuation coefficients based on the proposed scheme has been developed.

Orlic, I.; Loh, K. K.; Sow, C. H.; Tang, S. M.; Thong, P.

1993-05-01

342

X-Ray Photoelectron Spectroscopy  

NASA Astrophysics Data System (ADS)

Available from UMI in association with The British Library. Glasses of the systems Ge-Se-X (X = Ga, Sn, Bi, Sb), Ge-S-Y (Y = Ag, Ga, Sn, Bi) and Se-S have been examined using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), density and differential scanning calorimetry (DSC). Two of the compositions, GeSe_2 and (GeSe_2)_{92}Ga _8, have also been examined by extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge structure (XANES). The emphasis of the XPS measurements was on the changes in the binding energies with composition of the core peaks of the glasses, and on the plasmon energy losses from the L_3M_ {4,5}M_{4,5} Auger lines of Se and Ge. It was found that there were small shifts in the binding energies of the core peaks on substitution but the plasmon energy changed markedly with composition. For the XRD measurements, the focus was on two features: (a) to ensure that the samples prepared were truly amorphous and (b) to confirm the presence of the first sharp diffraction peak (FSDP) on the interference functions. The density measurements showed that the addition of the third element (X or Y) to the binary resulted in an increase in the relative density except for one system, Ge-Se-Sn, which showed the opposite behaviour. The DSC measurements showed that the addition of the third element to the binary resulted in a decrease in the glass transition temperatures. The EXAFS and XANES measurements of GeSe _2 and (GeSe_2)_ {92}Ga_8 glasses showed that there was very little change in the local order around the Ge atom in GeSe_2 glass with increase in temperature and that the local order around the Ge atom changes on alloying GeSe_2 with Ga. Correlations between parameters and measured properties of the ternary alloys have been investigated. It has been found that the parameter < m>, the average coordination number, correlates well with certain structural properties but badly with others. Suggestions are made for an alternative to .

Saffarini, Ghassan

343

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

344

Wavelength dispersive X-ray fluorescence imaging.  

PubMed

A new wavelength-dispersive X-ray fluorescence (WD-XRF) imaging spectrometer equipped with a two-dimensional X-ray detector was developed in the laboratory. Straight polycapillary optics was applied instead of a soller slit, which is used in conventional WD-XRF spectrometers. X-rays were guided through the straight polycapillary to the exit of the optics by X-ray external total reflections. X-ray fluorescence was dispersed by an analyzing crystal (LiF(200)), keeping the information of elemental distribution on the surface of the sample. The energy resolution of the developed spectrometer was 130-152 eV at the Zn K? peak. X-ray elemental images of Cu K? and Ni K? were successfully obtained by an X-ray CCD detector at the corresponding diffraction angles. The analytical performance of this technique, and further improvements are discussed. PMID:21749148

Tsuji, Kouichi; Ohmori, Takashi; Yamaguchi, Makoto

2011-07-27

345

Concepts in x-ray physics.  

SciTech Connect

A basic introduction to the theory underlying x-ray processes is provided. After general remarks on the practical advantages of using x-rays for probing matter, the derivation of the minimal-coupling Hamiltonian within nonrelativistic quantum electrodynamics is outlined. Perturbation theory is reviewed and applied to describe x-ray-induced processes. In connection with x-ray absorption, inner-shell binding energies and the photon energy dependence of the x-ray absorption cross section are discussed. In the context of x-ray scattering, atomic and molecular scattering factors are introduced, the complex index of refraction is derived, and the nonrelativistic theory of Compton scattering is described. The final topic is x-ray fluorescence and Auger decay of inner-shell-excited systems.

Santra, R.; Chemical Sciences and Engineering Division

2009-01-28

346

X-ray laser developments at PHELIX  

NASA Astrophysics Data System (ADS)

Development of x-ray lasers using the PHELIX laser at the GSI Helmholtz center for heavy-ion research [1] is targeting a number of applications of novel x-ray sources in combination with energetic heavy-ion beams. This includes Thomson scattering diagnostics of heavy-ion driven plasmas, x-ray opacity measurements, and x-ray laser spectroscopy of highly-charged ions. Developments centered on the application of a novel double-pulse GRIP-like pumping scheme, DGRIP, where nonnormal incidence geometry is used for both the pre- and the main pulse for transient pumped Ni-like x-ray lasers [2,3]. This scheme was used at lower energy levels to pump soft x-ray lasers in the 50 - 100 eV regime as well as for pulse energies above 100 J for the pumping of shorter wavelength soft x-ray lasers [4].

Zielbauer, B.; Kuehl, T.; Aurand, B.; Bagnoud, V.; Ecker, B.; Eisenbarth, U.; Hochhaus, D. C.; Neumayer, P.; Zimmer, D.; Cassou, K.; Daboussi, S.; Guilbaud, O.; Habib, J.; Kazamias, S.; Ros, D.; Seres, J.; Spielmann, C.

347

X-ray spectroscopy of low-mass X-ray binaries  

Microsoft Academic Search

I present high-resolution X-ray grating spectroscopy of neutron stars in low-mass X-ray binaries (LMXBs) using instruments onboard the Chandra X-ray Observatory and the X-ray Multi-Mirror Mission (XMM-Newton). The first part of this thesis concentrates on results from the subset of LMXBs with orbital periods less than an hour, known as ultracompact binaries. Previous low- resolution X-ray spectra of four systems

Adrienne Marie Juett

2004-01-01

348

Bone cartilage imaging with x-ray interferometry using a practical x-ray tube  

Microsoft Academic Search

The purpose of this study was to design an X-ray Talbot-Lau interferometer for the imaging of bone cartilage using a practical X-ray tube and to develop that imaging system for clinical use. Wave-optics simulation was performed to design the interferometer with a practical X-ray tube, a source grating, two X-ray gratings, and an X-ray detector. An imaging system was created

Kazuhiro Kido; Chiho Makifuchi; Junko Kiyohara; Tsukasa Itou; Chika Honda; Atsushi Momose

2010-01-01

349

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

350

Soft x-ray microscopy with a 182-angstrom soft x-ray laser  

Microsoft Academic Search

The high brightness and short pulse duration of soft x-ray lasers provide unique advantages for x-ray microscopy. We briefly review soft x-ray laser development at Princeton University and present results from the development of novel soft x-ray microscopes. The Princeton soft x- ray laser at 18.2 nm has been used to record high resolution contact images of biological specimens. More

Darrell S. Dicicco; Dong-Su Kim; Leonid Y. Polonski; Charles H. Skinner; Szymon Suckewer

1993-01-01

351

Water-window flash x-ray production from linear plasma x-ray source  

Microsoft Academic Search

The fundamental study on a high-intensity flash water-window x-ray generator is describe. This flash x-ray generator was improved in order to increase the x-ray intensity and to produce high-intensity characteristic x-rays by forming the linear plasma x-ray source. The generator consists of a high-voltage power supply, a polarity-inversion ignitron pulse generator, an oil-diffusion pump, and a radiation tube with a

Eiichi Sato; Michiaki Sagae; Hiroyuki Toriyabe; Wataru Awaji; Yasuomi Hayasi; Kazuyoshi Takayama; Hideaki Ido; Yoshiharu Tamakawa

2000-01-01

352

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

353

Development of x-ray photoelectron microscope with an x-ray laser source  

Microsoft Academic Search

We have constructed an x-ray photoelectron microscopic system with an x-ray laser as an x-ray source. The lasing line is the Li-like Al 3d-4f transition at 15.47 nm where the recombining Al plasma is used as the x-ray laser medium. The beam from the x-ray laser cavity was then focused by using a Schwarzschild mirror coated with Mo\\/Si multilayers. The

Tadayuki Ohchi; Naohiro Yamaguchi; Chiemi Fujikawa; Tamio Hara; Katsumi Watanabe; Ibuki Tanaka; Masami Taguchi

2000-01-01

354

Full-field transmission x-ray imaging with confocal polycapillary x-ray optics  

NASA Astrophysics Data System (ADS)

A transmission x-ray imaging setup based on a confocal combination of a polycapillary focusing x-ray optic followed by a polycapillary collimating x-ray optic was designed and demonstrated to have good resolution, better than the unmagnified pixel size and unlimited by the x-ray tube spot size. This imaging setup has potential application in x-ray imaging for small samples, for example, for histology specimens.

Sun, Tianxi; MacDonald, C. A.

2013-02-01

355

Full-field transmission x-ray imaging with confocal polycapillary x-ray optics.  

PubMed

A transmission x-ray imaging setup based on a confocal combination of a polycapillary focusing x-ray optic followed by a polycapillary collimating x-ray optic was designed and demonstrated to have good resolution, better than the unmagnified pixel size and unlimited by the x-ray tube spot size. This imaging setup has potential application in x-ray imaging for small samples, for example, for histology specimens. PMID:23460760

Sun, Tianxi; Macdonald, C A

2013-02-04

356

Soft x-ray projection lithography using an x-ray reduction camera  

Microsoft Academic Search

Soft x-ray projection lithography can now be realized with recent developments in x-ray optics. Using new x-ray optical components and spherical imaging optics, we have designed an x-ray reduction camera which is capable of projecting with soft x-ray radiation, a 5 x demagnified image of a mask onto a resist coated wafer. The resolution of this design is \\/similar to\\/00

Andrew M. Hawryluk; L. G. Seppala

1988-01-01

357

Coated x-ray filters  

DOEpatents

A radiation filter for filtering radiation beams of wavelengths within a preselected range of wavelengths comprises a radiation transmissive substrate and an attenuating layer deposited on the substrate. The attenuating layer may be deposited by a sputtering process or a vacuum process. Beryllium may be used as the radiation transmissive substrate. In addition, a second radiation filter comprises an attenuating layer interposed between a pair of radiation transmissive layers. 4 figs.

Steinmeyer, P.A.

1991-02-07

358

Roles of oxidative stress in synchrotron radiation X-ray-induced testicular damage of rodents  

PubMed Central

Synchrotron radiation (SR) X-ray has characteristic properties such as coherence and high photon flux, which has excellent potential for its applications in medical imaging and cancer treatment. However, there is little information regarding the mechanisms underlying the damaging effects of SR X-ray on biological tissues. Oxidative stress plays an important role in the tissue damage induced by conventional X-ray, while the role of oxidative stress in the tissue injury induced by SR X-ray remains unknown. In this study we used the male gonads of rats as a model to study the roles of oxidative stress in SR X-ray-induced tissue damage. Exposures of the testes to SR X-ray at various radiation doses did not significantly increase the lipid peroxidation of the tissues, assessed at one day after the irradiation. No significant decreases in the levels of GSH or total antioxidation capacity were found in the SR X-ray-irradiated testes. However, the SR X-ray at 40 Gy induced a marked increase in phosphorylated H2AX – a marker of double-strand DNA damage, which was significantly decreased by the antioxidant N-acetyl cysteine (NAC). NAC also attenuated the SR X-ray-induced decreases in the cell layer number of seminiferous tubules. Collectively, our observations have provided the first characterization of SR X-ray-induced oxidative damage of biological tissues: SR X-ray at high doses can induce DNA damage and certain tissue damage during the acute phase of the irradiation, at least partially by generating oxidative stress. However, SR X-ray of various radiation doses did not increase lipid peroxidation.

Ma, Yingxin; Nie, Hui; Sheng, Caibin; Chen, Heyu; Wang, Ban; Liu, Tengyuan; Shao, Jiaxiang; He, Xin; Zhang, Tingting; Zheng, Chaobo; Xia, Weiliang; Ying, Weihai

2012-01-01

359

Submicron X-ray diffraction  

SciTech Connect

At the Advanced Light Source in Berkeley the authors have instrumented a beam line that is devoted exclusively to x-ray micro diffraction problems. By micro diffraction they mean those classes of problems in Physics and Materials Science that require x-ray beam sizes in the sub-micron range. The instrument is for instance, capable of probing a sub-micron size volume inside micron sized aluminum metal grains buried under a silicon dioxide insulating layer. The resulting Laue pattern is collected on a large area CCD detector and automatically indexed to yield the grain orientation and deviatoric (distortional) strain tensor of this sub-micron volume. A four-crystal monochromator is then inserted into the beam, which allows monochromatic light to illuminate the same part of the sample. Measurement of diffracted photon energy allows for the determination of d spacings. The combination of white and monochromatic beam measurements allow for the determination of the total strain/stress tensor (6 components) inside each sub-micron sized illuminated volume of the sample.

MacDowell, Alastair; Celestre, Richard; Tamura, Nobumichi; Spolenak, Ralph; Valek, Bryan; Brown, Walter; Bravman, John; Padmore, Howard; Batterman, Boris; Patel, Jamshed

2000-08-17

360

3D investigation of inclusions in diamonds using X-ray micro-tomography  

NASA Astrophysics Data System (ADS)

The study of mineral inclusions in diamonds is providing invaluable insights into the geochemistry, geodynamics and geophysics of the Earth's mantle. Over the last two decades, the identification of different inclusion assemblages allowed to recognize diamonds deriving from the deep upper mantle, the transition zone and even the lower mantle. In such research field the in-situ investigation of inclusions using non-destructive techniques is often essential but still remains a challenging task. In particular, conventional 2D imaging techniques (e.g. SEM) are limited to the investigation of surfaces and the lack of access to the third dimension represents a major limitation when trying to extract quantitative information. Another critical aspect is related to sample preparation (cutting, polishing) which is typically very invasive. Nowadays, X-ray computed micro-tomography (X-?CT) allows to overcome such limitations, enabling the internal microstructure of totally undisturbed samples to be visualized in a three-dimensional (3D) manner at the sub-micrometric scale. The final output of a micro-tomography experiment is a greyvalue 3D map of the variations of the X-ray attenuation coefficient (µ) within the studied object. The high X-ray absorption contrast between diamond (almost transparent to X-rays) and the typical inclusion-forming minerals (olivines, garnets, pyroxenes, oxides and sulphides) makes X-?CT a straightforward method for the 3D visualization of inclusions and for the study of their spatial relationships with the diamond host. In this work we applied microfocus X-?CT to investigate silicate inclusions still trapped in diamonds, in order to obtain in-situ information on their exact position, crystal size, shape and X-ray absorption coefficient (which is related to their composition). We selected diamond samples from different deposits containing mainly olivine and garnet inclusions. The investigated samples derived from the Udachnaya pipe (Siberia, Russia), the Jericho Kimberlite (Slave Craton, Canada) and Sćo Luiz-Juina (Brazil). The information obtained by tomographic experiments were combined with X-ray single-crystal diffraction data (see Nestola et al 2011) in order to identify the inclusion parageneses (peridotitic, eclogitic or websteritic) and to finally determine the origin of the studied diamonds. Our results showed that, by combining X-?CT with X-ray diffraction data, it is possible to exactly determine the 3D position of each inclusion together with their crystal size, even though they cannot be detected by using an optical microscope. In addition, such method could have strong crystallographic implications for inclusions still trapped in diamonds as it enables the application of a reliable numerical absorption correction to the 3D intensity data collections. REF. Nestola, F., Nimis, P., Ziberna, L., Longo, M., Marzoli, A., Harris, J.W., Manghnani, M.H., Fedortchouk, Y. (2011): First crystal-structure determination of olivine in diamond: composition and implications for provenance in the Earth's mantle. Earth Planet. Sci. Lett., 305, 249-255.

Parisatto, M.; Nestola, F.; Artioli, G.; Nimis, P.; Harris, J. W.; Kopylova, M.; Pearson, G. D.

2012-04-01

361

Controlling X-rays With Light  

SciTech Connect

Ultrafast x-ray science is an exciting frontier that promises the visualization of electronic, atomic and molecular dynamics on atomic time and length scales. A largelyunexplored area of ultrafast x-ray science is the use of light to control how x-rays interact with matter. In order to extend control concepts established for long wavelengthprobes to the x-ray regime, the optical control field must drive a coherent electronic response on a timescale comparable to femtosecond core-hole lifetimes. An intense field is required to achieve this rapid response. Here an intense optical control pulse isobserved to efficiently modulate photoelectric absorption for x-rays and to create an ultrafast transparency window. We demonstrate an application of x-ray transparencyrelevant to ultrafast x-ray sources: an all-photonic temporal cross-correlation measurement of a femtosecond x-ray pulse. The ability to control x-ray/matterinteractions with light will create new opportunities at current and next-generation x-ray light sources.

Glover, Ernie; Hertlein, Marcus; Southworth, Steve; Allison, Tom; van Tilborg, Jeroen; Kanter, Elliot; Krassig, B.; Varma, H.; Rude, Bruce; Santra, Robin; Belkacem, Ali; Young, Linda

2010-08-02

362

A comparative study of X-ray shielding capability in ion-implanted acrylic and glass  

NASA Astrophysics Data System (ADS)

Samples of acrylic and glass were implanted with tungsten (W) and lead (Pb) to investigate their X-ray attenuation characteristics. The near-surface composition depth profiles of ion-implanted acrylic and glass samples were studied using ion-beam analysis (Rutherford backscattering spectroscopy—RBS). The effect of implanted ions on the X-ray attenuation ability was studied using a conventional laboratory X-ray machine with X-ray tube voltages ranging from 40 to 100 kV at constant exposure 10 mAs. The results were compared with previous work on ion-implanted epoxy. As predicted, the RBS results and X-ray attenuation for both ion-implanted acrylic and glass increase with the type of implanted ions when compared to the controls. However, since the glass is denser than epoxy or acrylic, it has provided the higher X-ray attenuation property and higher RBS ion concentration implanted with a shorter range of the ion depth profile when compared to epoxy and acrylic. A prolonged time is necessary for implanting acrylic with a very high nominal dose to minimize a high possibility of acrylic to melt during the process.

Noor Azman, N. Z.; Siddiqui, S. A.; Ionescu, M.; Low, I. M.

2013-04-01

363

Resonant X-ray Enhancement of the Auger Effect in High-Z Atoms, Molecules, and Nanoparticles: Potential Biomedical Applications  

NASA Astrophysics Data System (ADS)

It is shown that X-ray absorption can be considerably enhanced at resonant energies corresponding to K-shell excitation into higher shells with electron vacancies following Auger emissions in high-Z elements and compounds employed in biomedical applications. We calculate Auger resonant probabilities and cross sections to obtain total mass attenuation coefficients with resonant cross sections and detailed resonance structures corresponding to K?, K?, K?, K?, and K? complexes lying between 6.4-7.1 keV in iron and 67-80 keV in gold. The basic parameters were computed using the relativistic atomic structure codes and the R-matrix codes. It is found that the average enhancement at resonant energies is up to a factor of 1000 or more for associated K ? L, M, N, O, P transitions. The resonant energies in high-Z elements such as gold are sufficiently high to ensure significant penetration in body tissue, and hence the possibility of achieving X-radiation dose reduction commensurate with resonant enhancements for cancer theranostics using high-Z nanoparticles and molecular radiosensitizing agents embedded in malignant tumors. The in situ deposition of X-ray energy, followed by secondary photon and electron emission, will be localized at the tumor site. We also note the relevance of this work to the development of novel monochromatic or narrow-band X-ray emission sources for medical diagnostics and therapeutics.

Pradhan, Anil K.; Nahar, Sultana N.; Montenegro, Maximiliano; Yu, Yan; Zhang, H. L.; Sur, Chiranjib; Mrozik, Michael; Pitzer, Russell M.

2009-08-01

364

Nuclear waste drum characterization with 2 MeV x-ray and gamma-ray tomography  

NASA Astrophysics Data System (ADS)

This paper describes the progress of a multi-modality (three detector type) system for x-rays and gamma-rays developed for the waste inspection tomography (WIT) program. WIT provides mobile semi-trailer mounted nondestructive examination (NDE) and assay (NDA) for nuclear waste drum characterization. WIT uses various computed tomography (CT) methods for both NDE and NDA of nuclear waste drums. Without opening waste drums, WIT inspects and characterizes radioactive waste, including low level (LLW), transuranic (TRU), and mixed waste. With externally transmitted x-ray NDE techniques, WIT has the ability to identify high density waste materials like heavy metals, define drum contents in 2D and 3D space, quantify free liquid volumes through density and x-ray attenuation coefficient discrimination, and measure drum wall thickness. With waste emitting gamma-ray NDA techniques, WIT can locate gamma emitting radioactive sources in 2D and 3D space, identify gamma emitting isotopic species, identify gamma emitting isotopic species, identify the extermal activity approximations, and provide the data needed for waste classification as LLW or TRU.

Bernardi, Richard T.; Martz, Harry E.

1995-06-01

365

Resonant X-ray enhancement of the Auger effect in high-Z atoms, molecules, and nanoparticles: potential biomedical applications.  

PubMed

It is shown that X-ray absorption can be considerably enhanced at resonant energies corresponding to K-shell excitation into higher shells with electron vacancies following Auger emissions in high-Z elements and compounds employed in biomedical applications. We calculate Auger resonant probabilities and cross sections to obtain total mass attenuation coefficients with resonant cross sections and detailed resonance structures corresponding to Kalpha, Kbeta, Kgamma, Kdelta, and Keta complexes lying between 6.4-7.1 keV in iron and 67-80 keV in gold. The basic parameters were computed using the relativistic atomic structure codes and the R-matrix codes. It is found that the average enhancement at resonant energies is up to a factor of 1000 or more for associated K --> L, M, N, O, P transitions. The resonant energies in high-Z elements such as gold are sufficiently high to ensure significant penetration in body tissue, and hence the possibility of achieving X-radiation dose reduction commensurate with resonant enhancements for cancer theranostics using high-Z nanoparticles and molecular radiosensitizing agents embedded in malignant tumors. The in situ deposition of X-ray energy, followed by secondary photon and electron emission, will be localized at the tumor site. We also note the relevance of this work to the development of novel monochromatic or narrow-band X-ray emission sources for medical diagnostics and therapeutics. PMID:19888772

Pradhan, Anil K; Nahar, Sultana N; Montenegro, Maximiliano; Yu, Yan; Zhang, H L; Sur, Chiranjib; Mrozik, Michael; Pitzer, Russell M

2009-11-12

366

Extending the methodology of X-ray crystallography to allow X-ray microscopy without X-ray optics  

Microsoft Academic Search

We demonstrate that the soft X-ray diffraction pattern from a micron-size noncrystalline specimen can be recorded and inverted to form a high-resolution image. The phase problem is overcome by oversampling the diffraction pattern. The image is obtained using an iterative algorithm. The technique provides a method for X-ray microscopy requiring no high-resolution X-ray optical elements or detectors. In the present

Jianwei Miao; Pambos Charalambous; Janos Kirz; David Sayre

2000-01-01

367

Applications of x rays in art authentication: radiography, x-ray diffraction, and x-ray fluorescence  

Microsoft Academic Search

Several techniques involving X-rays are routinely applied in the study of works of art. These include radiography, X-ray diffraction, and X-ray fluorescence (often coupled with an electron beam instrument such as a scanning electron microscope or microprobe). Radiography provides information on condition and previous restorations or repairs. In the case of sculptures, the technique also sheds light on the manufacturing

Richard Newman

1998-01-01

368

The Physics of the Gas Attenuator for the Linac Coherent Light Source (LCLS)  

SciTech Connect

A systematic assessment of a variety of physics issues affecting the performance of the LCLS X-ray beam attenuator is presented. Detailed analysis of the gas flow in the gas attenuator and in the apertures is performed. A lot of attention is directed towards the gas ionization and heating by intense X-ray pulses. The role of these phenomena in possible deviations of the attenuation coefficient from its 'dialed in' value is evaluated and found small in most cases. Other sources of systematic and statistical errors are also discussed. The regimes where the errors may reach a few percent correspond to the lower X-ray energies (less than 2 keV) and highest beam intensities. Other effects discussed include chemical interaction of the gas with apertures, shock formation in the transonic flow in the apertures of the attenuator, generation of electromagnetic wakes in the gas, and head-to-tail variation of the attenuation caused by the ionization of gas or solid. Possible experimental tests of the consistency of the physics assumptions used in the concept of the gas attenuator are discussed. Interaction of X-rays with the solid attenuator (that will be used at higher X-ray energies, from 2.5 to 8 keV) is considered and thermo-mechanical effects caused by the beam heating are evaluated. Wave-front distortions induced by non-uniform heating of both the solid and the gas are found to be small. An overall conclusion drawn from the analysis presented is that the attenuator will be a reliable and highly versatile device, provided that some caution is exercised in its use for highest beam intensities at lowest X-ray energies.

Not Available

2011-02-07

369

Diffusive transport within dentinal tubules: an X-ray microtomographic study.  

PubMed

The hydrodynamic theory of dentine hypersensitivity proposes that external stimuli cause dentinal fluid movement within dentinal tubules thereby triggering mechanosensitive nerves and eliciting a pain response. The aim of this study was to employ X-ray microtomography (XMT) to monitor diffusion of caesium acetate through dentine to investigate the extent to which transport occurs within the primary tubules compared to that through branched microtubules believed to run perpendicular to the direction of the primary dentinal tubules. 2.0-mm thick coronal dentine disks masked to leave half of the upper surface exposed were imaged by XMT, initially in water, which was then replaced with an aqueous solution of 0.50 mol l(-1) caesium acetate. Further XMT images were acquired after 1 and 6 days immersion. The XMT images were used to measure the change in the X-ray linear attenuation coefficient resulting from caesium acetate ingress into dentine. There was clearly considerable ingress of caesium acetate into the dentine lying below the exposed surface, but considerably less beneath the sealed surface, suggesting that diffusive transport occurs predominantly in the direction of the primary dentinal tubules, with no significant lateral transport. Primary tubules are clearly the dominant transmission route for triggering the mechanosensitive nerves present at the dentine-pulp interface, and for delivery of nerve desensitising agents. PMID:18485329

Kawabata, Masako; Hector, Mark P; Davis, Graham R; Parkinson, Charles R; Rees, Gareth D; Anderson, Paul

2008-05-15

370

Compact soft X-ray laser  

NASA Astrophysics Data System (ADS)

For the first time, amplified spontaneous emission of Al ions was observed in a recombining plasma produced by a low-power driving laser of only 2 joules. This lasing was achieved by sharply focusing a pumping glass laser (5 ns FWHM) to a line 40 ?m wide and 12 mm long onto a slab target. The spectral lines (time integrated in the 5-50 nm region were recorded on Kodak SWR plates with a flat-field-type grazing incidence spectrograph which axially viewed the plasma at a distance (z) of 0.8 mm from a target surface with a spatial resolution of 200 ?m. The measured gain coefficients are 3.4, 4.5, 3.4 and 3.5 for the 10.57 nm 3d-5f and 15.47 nm 3d-4f transitions in Al XI and for the 12.35 nm 3d-5f and 17.78 nm 3d-4f transitions in Al X, respectively. The gain was observed in large area of 500 ?m ×600 ?m around z=0.8 mm. As Al XI line emissions continue during about 6 ns (FWHM), soft-X-ray laser resonator is expected to be effective. The electron temperatures in the plasma in the neighborhood of the target was estimated by the filter absorption method to be 400+/-100 eV, which is hot enough to produce Al11+ ions with high density. this result can pave the way to a low-power-pumped X-ray laser.

Hara, Tamio; Ando, Kozo; Aoyagi, Yoshinobu; Yashiro, Hidehiko

1990-12-01

371

X-ray dynamical diffraction from multilayer Laue lenses with rough interfaces  

SciTech Connect

A modeling approach for x-ray dynamical diffraction from multilayer Laue lenses (MLLs) with rough interfaces is developed. Although still based on the principle of the distorted-wave Born approximation (DWBA), this model is formulated from the perspective of the physical scattering process, very different from the conventional DWBA formalism. Using this model, one can study x-ray scattering from rough interfaces in the regime of Fresnel diffraction and in the case of absorptive samples, for example, x-ray dynamical diffraction from MLLs with rough interfaces, which is hard to handle in the framework of the conventional DWBA. Theoretical simulations for various MLLs with rough interfaces are conducted. It is found that interfacial roughness results in a decrease in the local diffraction intensity, where the attenuation factor is a function of the root-mean-square (rms) roughness versus the local zone width ratio. This study shows that if all zones possess an identical rms roughness value that is less than half of the outmost MLL zone width, the focal broadening effect due to roughness is almost unnoticeable, provided that the mean position of the interface does not deviate from the required zone plate law. A further study shows that uncorrelated interfacial roughness can be treated the same as interfacial diffusion, in which case a roughness factor similar to the ''Debye-Waller factor'' can be used, and the pseudo-Fourier coefficients of the susceptibility function for an MLL [H. F. Yan et al., Phys. Rev. B 76, 115438 (2007)] have to be multiplied by this factor.

Yan Hanfei [National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, New York 11973 (United States)

2009-04-15

372

Short-period X-ray multilayers based on Cr Sc  

Microsoft Academic Search

New experimental results on fabrication and investigations of the X-ray properties of multilayer X-ray mirrors based on CrSc for close-to-normal and Brewster's angles of incidence are presented. It is experimentally shown that the peak reflection coefficient of mirrors with periods of 1.6–1.7 nm for the wavelength 3.14 nm reaches 10% at a resolution ??? up to 175. The reflection coefficient

N. N. Salashchenko; E. A. Shamov

1997-01-01

373

X-rays for medical use  

NASA Astrophysics Data System (ADS)

1995 is the centenary of the discovery of X-rays by the German physicist Wilhelm C Rontgen. In the past hundred years, the new rays have developed from being unknown to finding application in many walks of life, not least in medicine. This is so much so that in common speech the word `x-ray` refers not to a form of radiation but to an X-ray photograph taken for the purposes of diagnosis (as in: `I had an X-ray done to see if my leg was broken`). X-rays are now used routinely, and they are used both for diagnosis and for therapy. This paper will give an outline of the use of X-rays in medicine throughout our present century.

Hessenbruch, A.

1995-11-01

374

Time resolved x-ray detection  

NASA Astrophysics Data System (ADS)

The goal of the project was to design, develop and construct an x-ray detector with high sensitivity and picosecond time resolution. This was achieved. A Ford Aerospace Charged Coupled Device, CCD, was utilized as the x-ray sensitive material around which the design and construction of the picosecond x-ray detector was built. This device has now become a commercial product sold, among other companies, by Photometrics Inc., and Princeton Research Inc. In addition we designed and built the first picosecond x-ray system. This system was utilized for the first ever picosecond x-ray diffraction experiments. The picosecond x-ray system was utilized in the oxidative fuel cell project to measure the decomposition of methanol and the change of the structure of its platinum catalyst. Another direct product of the work is the publication of 36 papers, in major scientific journals, and two patents.

Rentzepis, Peter M.

1994-04-01

375

The ELAIS deep X-ray survey  

NASA Astrophysics Data System (ADS)

We present initial follow-up results of the ELAIS Deep X-ray Survey which is being undertaken with the Chandra and XMM-Newton Observatories. 235 X-ray sources are detected in our two 75 ks ACIS-I observations in the well-studied ELAIS N1 and N2 areas. 90% of the X-ray sources are identified optically to R=26 with a median magnitude of R=24. We show that objects which are unresolved optically (i.e. quasars) follow a correlation between their optical and X-ray fluxes, whereas galaxies do not. We also find that the quasars with fainter optical counterparts have harder X-ray spectra, consistent with absorption at both wavebands. Initial spectroscopic follow-up has revealed a large fraction of high-luminosity Type 2 quasars. The prospects for studying the evolution of the host galaxies of X-ray selected Type 2 AGN are considered.

Willott, C. J.; Almaini, O.; Manners, J.; Johnson, O.; Lawrence, A.; Dunlop, J. S.; Mann, R. G.; Perez-Fournon, I.; Gonzalez-Solares, E.; Cabrera-Guerra, F.; Serjeant, S.; Oliver, S. J.; Rowan-Robinson, M.

376

Soft x-ray polarimeter laboratory tests  

NASA Astrophysics Data System (ADS)

Multilayer-coated optics can strongly polarize X-rays and are central to a new design of a broad-band, soft X-ray polarimeter. We have begun laboratory work to verify the performance of components that could be used in future soft X-ray polarimetric instrumentation. We have reconfigured a 17 meter beamline facility, originally developed for testing transmission gratings for Chandra, to include a polarized X-ray source, an X-ray-dispersing transmission grating, and a multilayer-coated optic that illuminates a CCD detector. The X-rays produced from a Manson Model 5, multi-anode source are polarized by a multilayer-coated flat mirror. The current configuration allows for a 180 degree rotation of the source in order to rotate the direction of polarization. We will present progress in source characterization and system modulation measurements as well as null and robustness tests.

Murphy, Kendrah D.; Marshall, Herman L.; Schulz, Norbert S.; Jenks, Kevin; Sommer, Sophie J. B.; Marshall, Eric A.

2010-07-01

377

Establishment of ANSI N13.11 X-ray radiation fields for personal dosimetry performance test by computation and experiment.  

PubMed Central

This paper describes establishment by computational and experimental methods of the American National Standard Institute (ANSI) N13.11 X-ray radiation fields by the Korea Atomic Energy Research Institute (KAERI). These fields were used in the standard irradiations of various personal dosimeters for the personal dosimetry performance test program performed by the Ministry of Science and Technology of Korea in the autumn of 1995. Theoretical X-ray spectra produced from two KAERI X-ray generators were estimated using a modified Kramers' theory with target attenuation and backscatter correction and their spectral distributions experimentally measured by a high-purity germanium semiconductor detector through proper corrections for measured pulse height distributions with photopeak efficiency, Compton fraction, and K-escape fraction. The average energies and conversion coefficients obtained from the computation and experimental methods, when compared with ANSI N13.11 and the recently published National Institute of Standards and Technology X-ray beams, appeared to be in good agreement--(+/-)3% between corresponding values--and thus, could be satisfactorily applied in the performance test of personal dosimeters.

Kim, J L; Kim, B H; Chang, S Y; Lee, J K

1997-01-01

378

Lobster eye x-ray optics  

Microsoft Academic Search

The imaging x-ray telescopes in current use mostly have limited field of view. The alternative x-ray optics geometries achieving very large fields of view have been theoretically suggested in the 70's but have been not constructed and used so far. We review the design and basic properties of the wide-field x-ray optical system based on one- and two-dimensional lobster-eye geometry

Adolf Inneman; Rene Hudec; Ladislav Pina; Paul Gorenstein

1999-01-01

379

X-Ray Spectroscopy of Gold Nanoparticles  

Microsoft Academic Search

Inner shell transitions, such as 1s-2p, in heavy elements can absorb or produce hard X-rays, and hence are widely used in nanoparticles. Bio-medical research for cancer treatment has been using heavy element nanoparticles, embeded in malignant tumor, for efficient absorption of irradiated X-rays and leading emission of hard X-rays and energetic electrons to kill the surrounding cells. Ejection of a

Sultana N. Nahar; M. Montenegro; A. K. Pradhan; R. Pitzer

2009-01-01

380

The X-ray Polarimeter Experiment (XPE)  

Microsoft Academic Search

Polarimetric studies will provide a new probe of cosmic x-ray sources, supplying important clues to source geometries and emission mechanisms. However, at the present time there is only one measurement of x-ray polarization from a cosmic source, the OSO-8 detection of 19% linear polarization from the Crab Nebula. We propose a new low cost x-ray polarimeter experiment (XPE), ideally sized

R. F. Elsner; B. D. Ramsey; S. L. O'dell; M. Sulkanen; A. F. Tennant; M. C. Weisskopf; S. Gunji; T. Minamitani; R. A. Austin; J. Kolodziejczak; D. Swartz; G. Garmire; P. Meszaros; G. G. Pavlov

1997-01-01

381

The Stellar X-Ray Polarimeter  

Microsoft Academic Search

The Stellar X-Ray Polarimeter (SXRP) will provide an order of magnitude increase in sensitivity compared to previous astronomical x-ray polarimeters. The SXRP uses a graphite Bragg crystal and a lithium Thomson scattering target as polarization analyzers and is sensitive in an energy band from 2.6 to 15 keV. Candidate targets include binary x-ray pulsars, supernova remnants, and accretion disk sources

J. Tomsick; P. Kaaret; E. Ford; J. Dwyer; R. Novick; E. Silver; M. Weisskopf; R. Elsner; K. Ziock; E. Costa; P. Soffitta

1996-01-01

382

A Plethora of X-ray Telescopes  

NSDL National Science Digital Library

This explanation describes the observatories we are currently using to study X-rays from space. Chandra, named for Nobel prize winner Subrahmanyan Chandrasekhar, was launched from the space shuttle in 1999. Current X-ray observatories include The Rossi X-ray Timing Explorer (RXTE), named after astronomer Bruno Rossi, and The Advanced Satellite for Cosmology and Astrophysics (ASCA). The site also discusses what observatories we will use in the coming years to explore the structure and evolution of the Universe.

383

X-ray scatter removal by deconvolution  

Microsoft Academic Search

The distribution of scattered x rays detected in a two-dimensional projection radiograph at diagnostic x-ray energies is measured as a function of field size and object thickness at a fixed x-ray potential and air gap. An image intensifier-TV based imaging system is used for image acquisition, manipulation, and analysis. A scatter point spread function (PSF) with an assumed linear, spatially

J. A. Seibert; J. M. Boone

1988-01-01

384

Topological X-Rays and MRIs  

ERIC Educational Resources Information Center

|Let K be a compact subset of the interior of the unit disk D in the plane and suppose one can't see through the boundary of D and identify K. However, assume that one can take "topological X-rays" of D which measure the "density" of K along the lines of the X-rays. By taking these X-rays from all directions, a "topological MRI" is generated for…

Lynch, Mark

2002-01-01

385

Lobster-Eye X-Ray Astronomy  

SciTech Connect

We report on technical and astrophysical aspects of Lobster-Eye wide-field X-ray telescopes expected to monitor the sky with high sensitivity and angular resolution of order of 1 arcmin. They will contribute essentially to study of various astrophysical objects such as AGN, SNe, Gamma-ray bursts (GRBs), X-ray flashes (XRFs), galactic binary sources, stars, CVs, X-ray novae, various transient sources, etc.

Hudec, R. [Astronomical Institute, AS CR, 25165 Ondrejov (Czech Republic); Czech Technical University in Prague, Faculty of Electrical Engineering (Czech Republic); Pina, L. [Czech Technical Universiry in Prague, Faculty of Nuclear Science, Prague (Czech Republic); Rigaku Innovative Technologies Europe, Prague (Czech Republic); Marsikova, V.; Inneman, A. [Rigaku Innovative Technologies Europe, Prague (Czech Republic)

2010-07-15

386

Lobster-Eye X-Ray Astronomy  

Microsoft Academic Search

We report on technical and astrophysical aspects of Lobster-Eye wide-field X-ray telescopes expected to monitor the sky with high sensitivity and angular resolution of order of 1 arcmin. They will contribute essentially to study of various astrophysical objects such as AGN, SNe, Gamma-ray bursts (GRBs), X-ray flashes (XRFs), galactic binary sources, stars, CVs, X-ray novae, various transient sources, etc.

R. Hudec; L. Pina; V. Marsikova; A. Inneman

2010-01-01

387

Ultrashort x-ray pulse science  

Microsoft Academic Search

A variety of phenomena involves atomic motion on the femtosecond time-scale. These phenomena have been studied using ultrashort optical pulses, which indirectly probe atomic positions through changes in optical properties. Because x-rays can more directly probe atomic positions, ultrashort x-ray pulses are better suited for the study of ultrafast structural dynamics. One approach towards generating ultrashort x-ray pulses is by

Alan Hap Chin

1998-01-01

388

Phase contrast X-ray imaging  

Microsoft Academic Search

In the last decade X-ray imaging based on phase contrast greatly advanced thanks to the use of unmonochromatic synchrotron hard X-rays. The recent advances are going beyond microradiology and microtomography to reach nanometre scale. This paper reviews basic theory and selected applications to biomedical and materials sciences. The forthcoming improvements in phase contrast X-ray imaging will lead to even better

Byung Mook Weon; Jung Ho Je; Yeukuang Hwu

2006-01-01

389

Time Resolved X-Ray Spot Diagnostic  

Microsoft Academic Search

A diagnostic was developed for the determination of temporal history of an X-ray spot. A pair of thin (0.5 mm) slits image the x-ray spot to a fast scintillator which is coupled to a fast detector, thus sampling a slice of the X-ray spot. Two other scintillators\\/detectors are used to determine the position of the spot and total forward dose.

R. Richardson; G. Guethlein; S. Falabella; F. Chambers; B. Raymond; J. Weir

2005-01-01

390

X-ray imaging with coded masks  

SciTech Connect

How can one image objects from which high-energy X rays emanate Actually the imaging is made possible by a technique that is similar to the one applied in making medical X-ray photographs. To make such photographs a film with an X-ray sensitive emulsion is placed directly behind a body part that is irradiated from the front by a small point source of X rays. The film in effect records the shadow cast by those components of the part that absorb X rays. A somewhat old-fashioned word for the technique is skiagraphy, from the Greek skia, meaning shadow. Now suppose the X rays come not from a point source such as a medical X-ray tube but from an extended source of unknown shape-perhaps a huge cloud of hot intergalactic plasma. Because the extended source can be envisioned as consisting of numerous point sources, the shadow of any intervening object is blurred. The reason is that each component point source causes a slightly different shadow to be cast on the film. Yet if one knows the shape of the intervening object precisely, one can easily predict the form of the shadow it would cast when illuminated by a single point source of X rays. By comparsing the shadows produced by all possible combinations of point sources with the actual recorded shadow, it might then be possible to reconstruct the shape of the extended source. That, in fact, is the operating principle of coded-mask X-ray imaging. The known object between the X-ray source and the detector is a coded mask: an X-ray-opaque plate that has a pattern of holes. The key to this type of imaging lies in the selection of a pattern that enables one to reconstruct an image of the X-ray source from the form of the mask's shadow.

Skinner, G.K.

1988-08-01

391

Soft x-ray polarimeter laboratory tests  

Microsoft Academic Search

Multilayer-coated optics can strongly polarize X-rays and are central to a new design of a broad-band, soft X-ray polarimeter. We have begun laboratory work to verify the performance of components that could be used in future soft X-ray polarimetric instrumentation. We have reconfigured a 17 meter beamline facility, originally developed for testing transmission gratings for Chandra, to include a polarized

Kendrah D. Murphy; Herman L. Marshall; Norbert S. Schulz; Kevin Jenks; Sophie J. B. Sommer; Eric A. Marshall

2010-01-01

392

High speed x-ray beam chopper  

DOEpatents

A fast, economical, and compact x-ray beam chopper with a small mass and a small moment of inertia whose rotation can be synchronized and phase locked to an electronic signal from an x-ray source and be monitored by a light beam is disclosed. X-ray bursts shorter than 2.5 microseconds have been produced with a jitter time of less than 3 ns.

McPherson, Armon (Oswego, IL); Mills, Dennis M. (Naperville, IL)

2002-01-01

393

X-ray source for mammography  

Microsoft Academic Search

An x-ray source utilizing anode material which shifts the output spectrum to higher energy and thereby obtains higher penetrating ability for screening mammography application, than the currently utilized anode material. The currently used anode material (molybdenum) produces an energy x-ray spectrum of 17.5\\/19.6 keV, which using the anode material of this invention (e.g. silver, rhodium, and tungsten) the x-ray spectrum

Logan; Clinton M

1994-01-01

394

Magnified hard X-ray microtomography  

Microsoft Academic Search

Summary form only given. In the field of hard X-ray microtomography one goal is the enhancement of resolution. Several ways can be followed to obtain this objective. One possibility is the use of high-resolution X-ray films or detector screens coupled with a microscope optical system. The limitation of resolution is either given by the grain size of the X-ray film

C. Rau; T. Weitkamp; A. Snigirev; C. G. Schroer; J. Tummler; B. Lengeler

2000-01-01

395

Ti X-Ray Laser Shadowgraphy Experiment  

Microsoft Academic Search

An x-ray laser shadowgraphy experiment was conducted on Xingguang-II laser facility in 1996. A multi-layer spherical mirror was used as an imaging element and a high sensitivity CCD camera as a detector. We measured the near-field image of the Ti x-ray laser beam. With a Ti x-ray laser beam as a backlight source, we obtained a clear Cu mesh image,

Wen-zhong Huang; Su-ping Liu; Han-sheng Peng; Yu-qiu Gu; Qi-ren Zhang; Yu-qin Cai; Yong-lu You; Wei Hong; Yu-tong Li; Shu-tai Chunyu; Shang-jin Yang; Chuan-fei Zhang; Yong-kuan Zhao; Shu-huai Wen; Jie Zhang; Guo-ping Zhang; Tan-xin Zhang

1996-01-01

396

The USA X-ray timing experiment  

Microsoft Academic Search

The USA Experiment is a new X-ray timing experiment with large collecting area and microsecond time resolution capable of conducting a broad program of studies of galactic X-ray binaries. USA is one of nine experiments aboard the Advanced Research and Global Observation Satellite which was launched February 23, 1999. USA is a collimated proportional counter X-ray telescope with about 1000

P. S. Ray; K. S. Wood; G. Fritz; P. Hertz; M. Kowalski; W. N. Johnson; M. N. Lovellette; M. T. Wolff; D. Yentis; R. M. Bandyopadhyay; E. D. Bloom; B. Giebels; G. Godfrey; K. Reilly; P. Saz Parkinson; G. Shabad; P. Michelson; M. Roberts; D. A. Leahy; L. Cominsky; J. Scargle; J. Beall; D. Chakrabarty; Y. Kim

2001-01-01

397

The USA X-ray Timing Experiment  

Microsoft Academic Search

The USA Experiment is a new X-ray timing experiment with large collecting area and microsecond time resolution capable of conducting a broad program of studies of galactic X-ray binaries. USA is one of nine experiments aboard the Advanced Research and Global Observation Satellite which was launched February 23, 1999. USA is a collimated proportional counter X-ray telescope with about 1000

P. S. Ray; K. S. Wood; G. Fritz; P. Hertz; M. Kowalski; W. N. Johnson; M. N. Lovellette; M. T. Wolff; D. Yentis; R. M. Bandyopadhyay; E. D. Bloom; B. Giebels; G. Godfrey; K. Reilly; P. Saz Parkinson; G. Shabad; P. Michelson; M. Roberts; D. A. Leahy; L. Cominsky; J. Scargle; J. Beall; D. Chakrabarty; Y. Kim

1999-01-01

398

HEATING THE SOLAR X-RAY CORONA  

Microsoft Academic Search

The X-ray corona of the Sun consists of the diffuse X-ray background and the bright X-ray loops (107 erg\\/cm2sec) confined in the strong (100 Gauss) bipolar fields of mag- netic active regions. The bipolar fields are rooted in the solar granules which continually intermix the photo- spheric footpoints of the bipolar fields and progressively interlace the field lines. The intermixing

E. N. Parker

399

Deriving attenuation coefficients from 3D CT data for SPECT Monte Carlo simulations  

Microsoft Academic Search

Quantitation of nuclear medicine data is a major goal in medical imaging. It implies that photon attenuation, scatter and depth dependent spatial resolution be corrected for. Realistic, anthropomorphic numerical phantoms are needed to understand how these phenomena degrade nuclear medicine images, and to validate correction methods. We developed a Monte Carlo simulator which simulates photon transport in an anthropomorphic phantom.

Veronique Baccarne; A. Turzo; Y. Bizais; M. Farine

1997-01-01

400

X-ray lithography sources: A review  

SciTech Connect

Synchrotron from dipole magnets in electron storage rings has emerged as a useful source of x-rays for lithography. To meet the need for these sources numerous groups around the world have embarked on projects to design and construct storage rings for x-ray lithography. Both conventional electromagnets as well as superconducting (SC) dipoles have been incorporated into the various designs. An overview of the worldwide effort to produce commercial x-ray sources will be presented. To better illustrate the elements involved in these sources a closer examination of the Superconducting X-ray Lithography Source Project (SXLS) at BNL will be presented. 11 refs., 1 fig., 5 tabs.

Murphy, J.B.

1989-01-01

401

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

402

Ultrashort X-ray pulse science  

SciTech Connect

A variety of phenomena involves atomic motion on the femtosecond time-scale. These phenomena have been studied using ultrashort optical pulses, which indirectly probe atomic positions through changes in optical properties. Because x-rays can more directly probe atomic positions, ultrashort x-ray pulses are better suited for the study of ultrafast structural dynamics. One approach towards generating ultrashort x-ray pulses is by 90{sup o} Thomson scattering between terawatt laser pulses and relativistic electrons. Using this technique, the author generated {approx} 300 fs, 30 keV (0.4 {angstrom}) x-ray pulses. These x-ray pulses are absolutely synchronized with ultrashort laser pulses, allowing femtosecond optical pump/x-ray probe experiments to be performed. Using the right-angle Thomson scattering x-ray source, the author performed time-resolved x-ray diffraction studies of laser-perturbated InSb. These experiments revealed a delayed onset of lattice expansion. This delay is due to the energy relaxation from a dense electron-hole plasma to the lattice. The dense electron-hole plasma first undergoes Auger recombination, which reduces the carrier concentration while maintaining energy content. Longitudinal-optic (LO) phonon emission then couples energy to the lattice. LO phonon decay into acoustic phonons, and acoustic phonon propagation then causes the growth of a thermally expanded layer. Source characterization is instrumental in utilizing ultrashort x-ray pulses in time-resolved x-ray spectroscopies. By measurement of the electron beam diameter at the generation point, the pulse duration of the Thomson scattered x-rays is determined. Analysis of the Thomson scattered x-ray beam properties also provides a novel means of electron bunch characterization. Although the pulse duration is inferred for the Thomson scattering x-ray source, direct measurement is required for other x-ray pulse sources. A method based on the laser-assisted photoelectric effect (LAPE) has been demonstrated as a means of measuring ultrashort x-ray pulse durations. LAPE may also serve as the basis for a gated x-ray detector.

Chin, A.H. [Univ. of California, Berkeley, CA (US). Dept. of Physics]|[Lawrence Berkeley National Lab., CA (US). Materials Science Div.

1998-05-01

403

The Planetary X-ray Emission  

Microsoft Academic Search

\\u000a With the advent of Chandra and XMM-Newton X-ray observatories, several new solar system bodies have been discovered to be\\u000a an X-ray source at energies below 2?keV: leading to significant advances in the field of planetary X-ray emission and astronomy\\u000a during the last one decade. Apart from the Sun, the known X-ray emitters now include Venus, Earth, Mars, Jupiter, and Saturn,

Anil Bhardwaj

2010-01-01

404

X-ray emission from comets.  

PubMed

The discovery of x-ray emission from comet Hyakutake was surprising given that comets are known to be cold. Observations by x-ray satellites such as the Röntgen Satellite (ROSAT) indicate that x-rays are produced by almost all comets. Theoretical and observational work has demonstrated that charge-exchange collisions of highly charged solar wind ions with cometary neutral species can explain this emission. X-ray observations of comets and other solar system objects may be used to determine the structure and dynamics of the solar wind. PMID:12004110

Cravens, T E

2002-05-10

405

Imaging with x-ray lasers  

SciTech Connect

Collisionally pumped soft x-ray lasers now operate over a wavelength range extending from 35--300 {Angstrom}. These sources have high peak brightness and are now being utilized for x-ray imaging and plasma interferometry. In this paper we will describe our efforts to probe long scalelength plasmas using Moire deflectrometry and soft x-ray imaging. The progress in the development of short pulse x-ray lasers using a double pulse irradiation technique which incorporates a travelling wave pump will also be presented.

Da Silva, L.B.; Cauble, B.; Frieders, G.; Koch, J.A.; MacGowan, B.J.; Matthews, D.L.; Mrowka, S.; Ress, D.; Trebes, J.E.; Weiland, T.L.

1993-11-01

406

X-rays from the youngest stars  

NASA Astrophysics Data System (ADS)

The X-ray properties of classical and weak-lined T Tauri stars are briefly reviewed, emphasizing recent results from the ROSAT satellite and prospects for ASCA. The interpretation of the high level of T Tauri X-rays as enhanced solar-type magnetic activity is discussed and criticized. The census of X-ray emitters is significantly increasing estimates of galactic star formation efficiency, and X-ray emission may be important for self-regulation of star formation. ASCA images will detect star formation regions out to several kiloparsecs and will study the magnetically heated plasma around T Tauri stars. However, images will often suffer from crowding effects.

Feigelson, Eric D.

1994-01-01

407

The possibilities for using x-ray radioscopy in thin wood inspection  

NASA Astrophysics Data System (ADS)

The aim of this study was to discover possibilities for using x-ray radioscopy in thin wood inspection. The main goal was to find a suitable x-ray imaging method to define the variations in wood density. In x-ray imaging radiation is sent through an object where radiation weakens proportionally to the object's thickness, density and moisture content. By sensing differences in attenuation an image can be created, allowing for the study of these properties. Because x-rays can penetrate deeply, x-ray imaging can be used for various materials and for many different imaging applications. The energy level of x-ray must be fairly low when imaging thin wood, as the level of attenuation is low due to the wood's thinness and low density. Some different imaging devices were tried in order to find suitable method for the task, and the best quality images were obtained with a mammography x-ray device. Digital out processing was used to enhance image contrast and density variations, respectively.

Ervasti, Tuomas H.; Mäkynen, Anssi J.

2008-06-01

408

Gold nanoparticle contrast agents in advanced X-ray imaging technologies.  

PubMed

Recently, there has been significant progress in the field of soft- and hard-X-ray imaging for a wide range of applications, both technically and scientifically, via developments in sources, optics and imaging methodologies. While one community is pursuing extensive applications of available X-ray tools, others are investigating improvements in techniques, including new optics, higher spatial resolutions and brighter compact sources. For increased image quality and more exquisite investigation on characteristic biological phenomena, contrast agents have been employed extensively in imaging technologies. Heavy metal nanoparticles are excellent absorbers of X-rays and can offer excellent improvements in medical diagnosis and X-ray imaging. In this context, the role of gold (Au) is important for advanced X-ray imaging applications. Au has a long-history in a wide range of medical applications and exhibits characteristic interactions with X-rays. Therefore, Au can offer a particular advantage as a tracer and a contrast enhancer in X-ray imaging technologies by sensing the variation in X-ray attenuation in a given sample volume. This review summarizes basic understanding on X-ray imaging from device set-up to technologies. Then this review covers recent studies in the development of X-ray imaging techniques utilizing gold nanoparticles (AuNPs) and their relevant applications, including two- and three-dimensional biological imaging, dynamical processes in a living system, single cell-based imaging and quantitative analysis of circulatory systems and so on. In addition to conventional medical applications, various novel research areas have been developed and are expected to be further developed through AuNP-based X-ray imaging technologies. PMID:23685939

Ahn, Sungsook; Jung, Sung Yong; Lee, Sang Joon

2013-05-17

409

Measurements of attenuation coefficient for evaluating the hardness of a cataract lens by a high-frequency ultrasonic needle transducer  

PubMed Central

A cataract is a clouding of the lens in the eye that affects vision. Phacoemulsification is the mostly common surgical method for treating cataracts, and determining that the optimal phacoemulsification energy is dependent on measuring the hardness of the lens. This study explored the use of an ultrasound needle transducer for invasive measurements of ultrasound attenuation coefficient to evaluate the hardness of the cataract lens. A 47 MHz high-frequency needle transducer with a diameter of 0.9 mm was fabricated by a polarized PMN-33%PT single crystal in the present study. The attenuation coefficients at different stages of an artificial porcine cataract lens were measured using the spectral shift approach. The hardness of the cataract lens was also evaluated by mechanical measurement of its elastic properties. The results demonstrated that the ultrasonic attenuation coefficient was increased from 0.048 ± 0.02 to 0.520 ± 0.06 dB mm?1 MHz?1 corresponding to an increase in Young’s modulus from 6 ± 0.4 to 96 ± 6.2 kPa as the cataract further developed. In order to evaluate the feasibility of combining needle transducer and phacoemulsification probe for real-time measurement during cataract surgery, the needle transducer was mounted on the phacoemulsification probe for a vibration test. The results indicated that there was no apparent damage to the tip of the needle transducer and the pulse–echo test showed that a good performance in sensitivity was maintained after the vibration test.

Chen, Ruimin; Tsui, Po-Hsiang; Zhou, Qifa; Humayun, Mark S; Shung, K Kirk

2010-01-01

410

X-ray spectrometry using polycapillary X-ray optics and position sensitive detector.  

PubMed

Polycapillary X-ray optics (capillary X-ray lens) are now popular in X-ray fluorescence (XRF) analysis. Such an X-ray lens can collect X-rays emitted from an X-ray source in a large solid angle and form a very intense X-ray microbeam which is very convenient for microbeam X-ray fluorescence (MXRF) analysis giving low minimum detection limits (MDLs) in energy dispersive X-ray fluorescence (EDXRF). A new method called position sensitive X-ray spectrometry (PSXS) which combines an X-ray lens used to form an intense XRF source and a position sensitive detector (PSD) used for wavelength dispersive spectrometry (WDS) measurement was developed recently in the X-ray Optics Laboratory of Institute of Low Energy Nuclear Physics (ILENP) at Beijing Normal University. Such a method can give high energy and spacial resolution and high detection efficiency simultaneously. A short view of development of both the EDXRF using a capillary X-ray lens and the new PSXS is given in this paper. PMID:18968083

Ding, X; Xie, J; He, Y; Pan, Q; Yan, Y

2000-10-01

411

Three-dimensional analysis of plant structure using high-resolution X-ray computed tomography  

Microsoft Academic Search

High-resolution X-ray computed tomography (HRCT) is a non-invasive approach to 3D visualization and quantification of biological structure. The data, based on differential X-ray attenuation, are analogous to those otherwise obtainable only by serial sectioning. Requiring no fixing, sectioning or staining, HRCT produces a 3D digital map of the specimen that allows measurements and visualizations, including arbitrarily oriented sections. In spite

Wolfgang H Stuppy; Jessica A Maisano; Matthew W Colbert; Paula J Rudall; Timothy B Rowe

2003-01-01

412

High contrast soft tissue imaging based on multi-energy x-ray  

NASA Astrophysics Data System (ADS)

Breast soft tissues have similar x-ray attenuations to mass tissue. Overlapping breast tissue structure often obscures mass and microcalcification, essential to the early detection of breast cancer. In this paper, we propose new method to generate the high contrast mammogram with distinctive features of a breast cancer by using multiple images with different x-ray energy spectra. On the experiments with mammography simulation and real breast tissues, the proposed method has provided noticeable images with obvious mass structure and microcalifications.

Oh, Hyun-Hwa; Sung, Young-Hun; Kim, Sung-Su; Kwon, Jae-Hyun; Lee, Seong-Deok; Kim, Chang-Yeong

2011-03-01

413

The Columbia University proton-induced soft x-ray microbeam  

PubMed Central

A soft x-ray microbeam using proton-induced x-ray emission (PIXE) of characteristic titanium (K? 4.5 keV) as the x-ray source has been developed at the Radiological Research Accelerator Facility (RARAF) at Columbia University. The proton beam is focused to a 120 ?m × 50 ?m spot on the titanium target using an electrostatic quadrupole quadruplet previously used for the charged particle microbeam studies at RARAF. The proton induced x-rays from this spot project a 50 ?m round x-ray generation spot into the vertical direction. The x-rays are focused to a spot size of 5 ?m in diameter using a Fresnel zone plate. The x-rays have an attenuation length of (1/e length of ~145 ?m) allowing more consistent dose delivery across the depth of a single cell layer and penetration into tissue samples than previous ultra soft x-ray systems. The irradiation end station is based on our previous design to allow quick comparison to charged particle experiments and for mixed irradiation experiments.

Harken, Andrew D.; Randers-Pehrson, Gerhard; Johnson, Gary W.; Brenner, David J.

2011-01-01

414

The Columbia University proton-induced soft x-ray microbeam.  

PubMed

A soft x-ray microbeam using proton-induced x-ray emission (PIXE) of characteristic titanium (K(?) 4.5 keV) as the x-ray source has been developed at the Radiological Research Accelerator Facility (RARAF) at Columbia University. The proton beam is focused to a 120 ?m × 50 ?m spot on the titanium target using an electrostatic quadrupole quadruplet previously used for the charged particle microbeam studies at RARAF. The proton induced x-rays from this spot project a 50 ?m round x-ray generation spot into the vertical direction. The x-rays are focused to a spot size of 5 ?m in diameter using a Fresnel zone plate. The x-rays have an attenuation length of (1/e length of ~145 ?m) allowing more consistent dose delivery across the depth of a single cell layer and penetration into tissue samples than previous ultra soft x-ray systems. The irradiation end station is based on our previous design to allow quick comparison to charged particle experiments and for mixed irradiation experiments. PMID:21811347

Harken, Andrew D; Randers-Pehrson, Gerhard; Johnson, Gary W; Brenner, David J

2011-09-15

415

Demonstration of a soft x-ray amplifier  

Microsoft Academic Search

We report observations of amplified spontaneous emission at soft x-ray wavelengths. An optical laser ionized thin foils of selenium to produce a population inversion of the 2p āµ3p and 2p āµ3s levels of the neonlike ion. Using three time-resolved, spectroscopic measurements we demostrated gain-length products up to 6.5 and gain coefficients of 5.5 +- 1.0 cmā»Ā¹ for the J =

D. L. Matthews; P. L. Hagelstein; M. D. Rosen; M. J. Eckart; N. M. Ceglio; A. U. Hazi; H. Medecki; B. J. MacGowan; J. E. Trebes; B. L. Whitten; E. M. Campbell; C. W. Hatcher; A. M. Hawryluk; R. L. Kauffman; L. D. Pleasance; G. Rambach; J. H. Scofield; G. Stone; T. A. Weaver

1985-01-01

416

An Empirical Expression to Estimate Specific Attenuation Coefficient due to fog at Frequencies from 100 to 300GHz  

NASA Astrophysics Data System (ADS)

A simple expression is presented to quickly estimate specific attenuation coefficient due to fog within the ranges of 100~300GHz and -8~20°C based on the Rayleigh approximation which is not very convenient. To evaluate the expression's estimation performance, the Pearson correlation coefficient (PCC) and maximal absolute value of the relative errors (MAVRE) are calculated. The maximum value of PCC is 1 and it reflects the fitting performance of an empirical expression. MAVRE denotes the largest deviation between a set of estimated values and corresponding theoretical values. Calculations show the PCC and MAVRE of the proposed expression are 0.99985 and 4.162%, respectively. Furthermore, a comparison analysis shows that the new expression has much better estimation performance than other two empirical expressions: the modified Mao expression and the Zhao expression.

Liu, Yun-Long; Hu, Meng-Hao

2013-08-01

417

A comfortable procedure for correcting X-ray detector backlight  

NASA Astrophysics Data System (ADS)

A novel approach is suggested to strongly suppress artifacts in radiography and computed tomography caused by the effect of diffuse background signals "backlighting" of 2D X-ray detectors. Depending on the detector geometry the mechanism may be different. Either based on the optical scattering of the fluorescent screen materials into the optical detection devices or Compton or X-ray fluorescence scattering by the detector components. Consequently, these erroneous intensity portions result in locally different violations of Lambert Beer's law in single projections (radiographs) as a function of the detector area coverage and the magnitude of the attenuation. The absorption of multiple metal sheets is investigated by monochromatic synchrotron radiation, thus excluding beam hardening. The proposed correction procedure simply requires the individual subtraction of one and the same fraction of the primary and transmitted mean intensity, as a constant (non-local) scattering mechanism is assumed.

Müller, Bernd R.; Lange, Axel; Hentschel, Manfred P.; Kupsch, Andreas

2013-03-01

418

Silicon Refractive optics for hard X-rays  

NASA Astrophysics Data System (ADS)

X-rays refractive optics has made a real success in a hard radiation domain promising for many applications. An analysis made of refractive materials properties, which are most suitable for this new kind of X-ray focusing optics shows that in silicon refraction effects prevail on attenuation. A wide variety of technologies dedicated to microstructure formation on Si make it as a most suitable one. Using electron beam lithography and deep plasma etching planar parabolic profiles are produced with the focal distance 1 m on 17.4 keV radiation. They are tested on synchrotron radiation at beamline X47 SPRING-8. Experiments carried out open the way to construct kinoform refracting profiles, which exceed simple parabolas in gain and aperture. A number of kinoform profiles on silicon is created for energies up to 50 keV, which at apertures 2 mm have calculated gain up to 5000. Some focusing properties of such planar refracting profiles are discussed. .

Aristov, V.; Firsov, A.; Grigoriev, M.; Ishikawa, T.; Kikuta, S.; Kohmura, Y.; Kuznetsov, S.; Shabelnikov, L.; Yunkin, V.

2000-05-01

419

Grating-Based X-ray Phase Imaging Using Multiline X-ray Source  

Microsoft Academic Search

Differential phase-contrast X-ray imaging has been performed in a Talbot-Lau configuration, where a multiline X-ray source was used instead of a combination of a hard-X-ray multiple slit and a normal focus X-ray generator. When the multiple slit is used, a high aspect ratio structure is needed and slit width should be below 10 mum for its function. The fabrication and

Atsushi Momose; Wataru Yashiro; Hiroaki Kuwabara; Katsuyuki Kawabata

2009-01-01

420

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

421

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

422

Wide field x-ray telescopes: Detecting x-ray transients\\/afterglows related to GRBs  

Microsoft Academic Search

The recent discovery of X-ray afterglows of GRBs opens the possibility of analyses of GRBs by their X-ray detections. However, imaging X-ray telescopes in current use mostly have limited fields of view. Alternative X-ray optics geometries achieving very large fields of view have been theoretically suggested in the 70's but not constructed and used so far. We review the geometries

René Hudec; Ladislav Pina; Adolf Inneman; Paul Gorenstein

1998-01-01

423

Hybrid X-ray Imaging Spectrometer for the Next Generation X-ray Satellites  

Microsoft Academic Search

We introduce a proposal of a new wide band hybrid X-ray imaging spectro polarimeter. This camera is realized by the combination of thin X-ray CCDs for 0.1-10 keV band and a Micro Pixel Gas Chamber (MPGC) detecting X-rays at 10-40 keV. The X-ray CCD is a backside illumination type and thinned leaving only depletion layer of 100micron. The small pixel

T. Tsuru; T. Tanimori; M. Ueno; T. Nagayoshi; R. Orito; T. Kubo; H. Matsumoto; K. Koyama; H. Tsunemi

2002-01-01

424

Development of x-ray mirrors for x-ray telescopes  

Microsoft Academic Search

We have been developing X-ray mirrors for X-ray telescope using a ion-beam sputtering system. X-rays can be reflected by two processes, one is total reflection, and another is Bragg reflection. Total reflection is used for previous telescope below 10 keV. Its reflectivity determined by the optical constant. We suggests composite-layer mirror for soft X-ray optics, which has consists some different

Keisuke Tamura; Chiaki Sakai; Nubuaki Yamada; Yasushi Ogasaka; Ryo Shibata

2005-01-01

425

X-ray waveguides for high resolution x-ray analysis  

Microsoft Academic Search

The project goals were to model, synthesize, and characterize thin-film, x-ray waveguide structures to determine whether such nanostructurcs can be fabricated with the precision required for true waveguide operation at x-ray energies. In FY98, we designed, fabricated, and characterized (at the Stanford Synchrotron Radiation Laboratory) optimized. thin-film, x-ray waveguide structures (XWGs) as resonant concentrators of x-rays which may be applied

Barbee

1999-01-01

426

Optical and X-ray properties of X-ray selected active galactic nuclei  

Microsoft Academic Search

X-ray data and optical spectrophotometric data are presented for 25 newly identified X-ray selected active nuclei (AGN). This sample is combined with another, more comprehensive sample, and correlations are studied between the X-ray continuum, the optical continuum, and various optical emission lines. The implications for the physical processes at work in AGN are discussed, as is the X-ray luminosity function

G. A. Kriss; C. R. Canizares

1982-01-01

427

The Distant X-ray Universe as seen by the Chandra X-ray Observatory  

Microsoft Academic Search

The Chandra X-ray Observatory has completed two 1 Ms exposures to the X-ray sky. These very deep exposures have detected over 700 X-ray sources, most of which appear to be AGN and QSOs. The mean X-ray luminosity of the sources rises rapidly from the local value to a maximum at a redshift of 3 and then appears to fall off.

G. Garmire

2001-01-01

428

Flash X-ray diagnostics of argon jets: X-ray induced fluorescence imaging and radiography  

Microsoft Academic Search

Summary form only given. In this work we report on the development and application of two flash X-ray diagnostic techniques. A compact X-ray source specially designed for these studies was used to characterize argon flows at atmospheric pressure in ambient air. The table-top X-ray source emits strong doses of X-ray photons of about 10 keV in pulses of 20 ns

L. Hure; E. Robert; C. Cachoncinlle; R. Viladrosa; J. M. Pouvesle

1999-01-01

429

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

430

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

431

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

432

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

433

A microfocus X-ray tube based on a microstructured X-ray target  

Microsoft Academic Search

We present a novel concept to develop a microfocus X-ray tube based on a microstructured X-ray target that is irradiated with a nonfocused electron beam. X-ray emissions from the microstructured targets with various morphologies were studied using Monte-Carlo simulation code MCNP5. The calculations revealed that the microstructured targets are quite capable of minimizing the effective X-ray spot size compared with

Aamir Ihsan; Sung Hwan Heo; Sung Oh Cho

2009-01-01

434

X-ray imaging with compound refractive lens and microfocus x-ray tube  

Microsoft Academic Search

Compound refractive lenses (CRL), consisting of a lot number in-line concave microlenses made of low-Z material were studied. Lenses with focal length 109 mm and 41 mm for 8-keV X-rays, microfocus X-ray tube and X-ray CCD camera were used in experiments. Obtained images show intensity distribution of magnified microfocus X-ray source focal spot. Within the experiments, one lens was also

Ladislav Pina; Yury Dudchik; Vaclav Jelinek; Libor Sveda; Jiri Marsik; Martin Horvath; Ondrej Petr

2008-01-01

435

Ultrafast X-ray diffraction and X-ray absorption spectroscopy  

Microsoft Academic Search

Summary form only given. Recently developed ultrafast laser-driven X-ray sources enable the observation of atomic motions in crystals and in solutions on the timescale of chemical bond formation and breakage. Using such a laboratory-based X-ray source the propagation of coherent phonon wave packets through GaAs(111) crystals after photo excitation has been imaged by ultrafast X-ray difraction. While ultrafast x-ray diffraction

C. Rose-Petruck

2000-01-01

436

Statistical data of X-ray emission from laboratory sparks  

NASA Astrophysics Data System (ADS)

In this study we present a summary of the data of 1331 long laboratory sparks in atmospheric pressure intended for a statistical analysis. A 2 MV, 17kJ Marx generator were used to generate 1.2/52?s shape pulses positive and negative polarity. The generator was connected to a spark gap with cone-shaped electrodes. The distance between high-voltage and grounded electrodes was 1.08 meters. Breakdown voltage between electrodes was about 1MV. X-rays have been detected during the development of the discharge channel. The currents through the grounded electrode and through the high-voltage electrode were recorded separately and simultaneously with the voltage and the X-ray signal. X-rays were registered by two LaBr3(Ce+) scintillation detectors in different positions with respect to the forming discharge channel. Detector D1 was placed immediately under the grounded electrode at 15cm distance. Detector D2 was placed at horizontal distances of 143cm and 210cm, at mid-gap height. We also used lead shields of 1.5, 3, and 4 mm thickness for radiation attenuation measurements. For detector collimation we used shields up to 2 cm thickness. Also no metallic objects with pointed surfaces were present within 2 m from the spark gap. Typical plot of positive discharge presented in Figure 1a. Table 1 shows the summary of the X-ray registrations. Signal detection occurred significantly more for positive polarity discharges than for negative. This dependence was observed for both detectors. For detector D2 the probability of X-ray registration decreased proportional to 1/d2 with increasing the distance d to the breakdown gap from 1m43 to 2m10. Detailed energy spectra and time distribution of X-ray emission were obtained; see for example Fig. 1b. For both polarities of the high voltage, the X-rays only occurred when there was a current at the cathode.

Kochkin, P.; Deursen, D. V.

2011-12-01

437

X-Ray Fluorescence (XRF) spectrometry for materials analysis and discovering "the atomic number"  

NSDL National Science Digital Library

In this experiment students use XRF spectroscopy to analyze a sampleās elemental composition. From the characteristic X-ray energies, Moseleyās Law, a proof of the existence of the atomic number, is verified. The atomic number increases in regular steps with an increase in the characteristic X-ray energy. We will use this relationship to find the Rydbergās energy constant and screening coefficient for K X-rays. This lab is designed for the student to learn to: 1. differentiate between characteristic X-rays and Bremsstrahlung radiations, 2. use characteristic X-rays to identify elements, 3. acquire a spectrum, calibrate it and use it for qualitative (element identification) as well as quantitative (elemental concentration) analysis, and finally, 4. verify Moseleyās law and the validity of an atomic number.

Khalid, Asma; Khan, Aleena T.; Anwar, Muhammad S.

2012-06-06

438

Simulation-based design of a MEMS X-ray optic for X-ray astronomy  

Microsoft Academic Search

An ultra light-weight X-ray optic using MEMS technologies was designed for X-ray astronomy. Numerical simulation was utilized to estimate allowable fabrication accuracies. Obtained X-ray images with a fabricated optic were consistent with the design.

M. Koshiishi; Y. Ezoe; I. Mitsuishi; M. Mita; K. Mitsuda; T. Takano; R. Maeda

2008-01-01

439

Development of X-Ray Polarimeter by Detecting Secondary Fluorescent X-Rays.  

National Technical Information Service (NTIS)

A new kind of X-ray polarimeter, which was successfully operated below 2 KeV X-ray, is described. The angular distribution of secondary fluorescent X-rays emitted in the process of photoelectric effect is expected to exhibit an asymmetry correlated with t...

T. Kifune

1972-01-01

440

Low Power X-Ray Tube for Use in Energy Dispersive X-Ray Fluorescence Analysis.  

National Technical Information Service (NTIS)

A low power X-ray tube with thin molybdenum transmission target for use in energy dispersive X-ray fluorescence (ENDXRF) element analysis has been indigenously built, along with its power supply. The X-ray tube has been in operation since August 1979, and...

S. K. Kataria R. Govil M. Lal

1980-01-01

441

X ray lithography in Japan  

NASA Astrophysics Data System (ADS)

Integrated circuits (semiconductors) are the key components of modern computers, communication systems, consumer electronics, and the new generations of smart machines and instruments. Japan's strong position and growing influence in the manufacture of semiconductors and systems based on them is well known and well documented. Microlithography is one the most critical elements of the semiconductor manufacturing process because it determines the minimum feature size and the functional capabilities of the semiconductor. Because it is used many times in the manufacturing sequence, the quality of the microlithography process (i.e., number of defects, control for feature size, etc.) is critical in determining the yield and cost of semiconductors and hence the competitiveness of the electronics industry. At present all volume semiconductor manufacturing is done with optical UV (ultraviolet) projection lithography, twenty-year-old photographic technology which has been and is still evolving. There are many issues that limit the technical capability and cost-effectiveness of UV lithography, and thus, alternate lithographic techniques are continuously being researched and developed. X-ray lithography, which was invented in the early 1970's, holds the promise of providing higher yields in manufacturing semiconductors by virtue of enhanced process latitude, process robustness, and resolution.

Clemens, James T.; Hill, Robert W.; Cerrina, Franco; Fuller, Gene E.; Pease, R. F.

1991-10-01

442

GEMS X-ray Polarimeter Performance Simulations.  

National Technical Information Service (NTIS)

The Gravity and Extreme Magnetism Small explorer (GEMS) is an X-ray polarization telescope selected as a NASA small explorer satellite mission. The X-ray Polarimeter on GEMS uses a Time Projection Chamber gas proportional counter to measure the polarizati...

J. Hill J. Swank J. K. Black T. Kallman T. Strohmayer W. H. Baumgartner

2012-01-01

443

X-Ray Exam: Femur (Upper Leg)  

MedlinePLUS

... asked to remove some clothing, jewelry, or any metal objects that might interfere with the image. If your daughter is pregnant, it's important to tell the X-ray technician or her doctor. X-rays are usually avoided during pregnancy because there's a small chance the radiation may ...

444

Advanced Cold X-Ray Source Program.  

National Technical Information Service (NTIS)

This report, the final technical report for the Advanced Cold X-Ray Source Program, describes experimental research efforts to develop plasma radiation sources (PRS) for the simulation of cold x-ray effects. On the Double- EAGLE generator we have investig...

J. C. Riordan P. D. LePell C. Deeney B. H. Failor C. A. Coverdale

2000-01-01

445

MSGC tests with X-rays  

NASA Astrophysics Data System (ADS)

Tests of MSGC detectors using an X-ray generator are reported. Results are presented for gas mixtures composed of Ar or Ne and dimethylether. The influence of the drift field and of the X-ray beam intensity is investigated.

Boulogne, Isabelle; Daubie, Evelyne

1998-02-01

446

Advanced multilayer x-ray optics.  

National Technical Information Service (NTIS)

Multilayer optics for the x-ray, soft x-ray and extreme ultra violet is a rapidly expanding and maturing field. A large part of the effort in this field is directed to improving the quality of multilayer structures by developing a better understanding of ...

T. W. Barbee

1990-01-01

447

X-Ray Spectrum of Kepler's SNR.  

National Technical Information Service (NTIS)

Observations made with the solid state spectrometer aboard the Einstein Observatory confirm Kepler's SNR as an X-ray source with an intensity between 1-3 KeV of 7.2 x 10 to the-11th power ergs/sq cm-s. The X-ray spectrum is similar to those of Cas A and T...

R. H. Becker E. A. Boldt S. S. Holt P. J. Serlemitsos N. E. White

1980-01-01

448

X-Ray Exam: Neck (For Parents)  

MedlinePLUS

What It Is A neck X-ray is a safe and painless test that uses a small amount of radiation to make images of the soft tissues in the neck. During the examination, an X-ray machine sends a beam of radiation through the ...

449

Coccidioidomycosis - chest x-ray (image)  

MedlinePLUS

This chest x-ray shows the affects of a fungal infection, coccidioidomycosis. In the middle of the left lung (seen on the ... defined borders. Other diseases that may explain these x-ray findings include lung abscesses, chronic pulmonary tuberculosis, chronic ...

450

Adenocarcinoma - chest x-ray (image)  

MedlinePLUS

This chest x-ray shows adenocarcinoma of the lung. There is a rounded light spot in the right upper lung (left side ... density. Diseases that may cause this type of x-ray result would be tuberculous or fungal granuloma, and ...

451

Ginga Observations of X ray Pulsars.  

National Technical Information Service (NTIS)

Data from Ginga observations of X-ray pulsars is discussed. They include the detection of a finite rate of change of the orbital period in Her X-1, the determination of the braking index of PSR 0540-69 from X-ray pulse timing, the discoveries of new trans...

F. Nagase

1989-01-01

452

LOBSTER – New Space X–Ray telescopes  

Microsoft Academic Search

We discuss the technological and scientific aspects of fully innovative very wide field X ray telescopes with high sensitivity. The prototypes of Lobster telescopes designed, developed and tested are very promising, allowing the proposals for space projects with very wide field Lobster Eye X ray optics to be considered for the first time. The novel telescopes will monitor the sky

R. Hudec; L. Pina; V. Šimon; L. Švéda; A. Inneman; V. Semencovį; M. Skulinovį

2007-01-01

453

Course Manual for X-Ray Applications.  

ERIC Educational Resources Information Center

|This publication is the third of three sequential course manuals for instructors in x-ray science and engineering. This course manual has been tested by introducing it into the Oregon State University curriculum. The publication is prepared for the purpose of improving the qualifications of x-ray users and to reduce the ionizing radiation…

Food and Drug Administration (DHEW), Rockville, MD. Bureau of Radiological Health.

454

Handbook of X-Ray Astronomy.  

National Technical Information Service (NTIS)

X-ray astronomy was born in the aftermath of World War II as military rockets were repurposed to lift radiation detectors above the atmosphere for a few minutes at a time. These early flights detected and studied X-ray emission from the Solar corona. The ...

A. Siemiginowska K. A. Arnaud R. K. Smith

2011-01-01

455

Device for detecting x-ray radiation  

Microsoft Academic Search

X rays detection devices, either for dose metering purposes or for display purposes are described. The device in accordance with the invention comprises a thin plate of ferroelectric material upon the faces of which electrical charges are deposited. X ray radiation produces an increase in the conductivity of the material and, consequently, modulation of the distribution of the charges. Determination

C. Mayeux; F. Micheron; J. P. Vasseur

1977-01-01

456

X-Ray Exam: Cervical Spine  

MedlinePLUS

... the bones, appear white on the X-ray image. Hollow body parts, such as the airways, allow X-ray ... lead apron to protect certain parts of your body. Your child's reproductive ... few minutes while the images are processed. If any are blurred or unclear, ...

457

Elliptical X-Ray Spot Measurement  

Microsoft Academic Search

The so-called roll bar measurement uses a heavy metal material, optically\\u000athick to x-rays, to form a shadow of the x-ray origination spot. This spot is\\u000awhere an energetic electron beam interacts with a high Z target. The material\\u000a(the \\

Roger A. Richardson; Stephen Sampayan; John T. Weir

2000-01-01

458

Optics for coherent x-ray sources  

Microsoft Academic Search

Several laboratories are now in the process of designing and constructing coherent x-ray sources, and application of these beams for radiography and material studies is facilitated by having appropriate optical components to provide collimation or focusing. Control of x-rays can be achieved by employing elements that perform refraction, diffraction or reflection, as exemplified by a lens, grating or mirror, respectively.

Richard H. Pantell; Joseph Feinstein; J. Theodore Cremer; Melvin A. Piestrup; H. R. Beguiristain; Charles K. Gary

2001-01-01

459

Proton induced x ray emission analysis  

Microsoft Academic Search

A solid mathematical basis is established for the use of thick target Proton Induced X ray Emission (PIXE) analysis to determine the trace element concentrations in solid samples. With the advent of high resolution Si(Li) detectors there was a revival of interest in the use of characteristic x ray induced by high energy particle beams. It was shown that it

Eric Clayton

1988-01-01

460

Phased Contrast X-Ray Imaging  

ScienceCinema

The Pacific Northwest National Laboratory is developing a range of technologies to broaden the field of explosives detection. Phased contrast X-ray imaging, which uses silicon gratings to detect distortions in the X-ray wave front, may be applicable to mail or luggage scanning for explosives; it can also be used in detecting other contraband, small-parts inspection, or materials characterization.