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1

X-ray diffraction-based electronic structure calculations and experimental x-ray analysis for medical and materials applications  

Microsoft Academic Search

This thesis includes x-ray experiments for medical and materials applications and the use of x-ray diffraction data in a first-principles study of electronic structures and hyperfine properties of chemical and biological systems. Polycapillary focusing lenses were used to collect divergent x rays emitted from conventional x-ray tubes and redirect them to form an intense focused beam. These lenses are routinely

Dip Narayan Mahato

2009-01-01

2

X-ray-spectroscopy analysis of electron-cyclotron-resonance ion-source plasmas  

SciTech Connect

Analysis of x-ray spectra emitted by highly charged ions in an electron-cyclotron-resonance ion source (ECRIS) may be used as a tool to estimate the charge-state distribution (CSD) in the source plasma. For that purpose, knowledge of the electron energy distribution in the plasma, as well as the most important processes leading to the creation and de-excitation of ionic excited states are needed. In this work we present a method to estimate the ion CSD in an ECRIS through the analysis of the x-ray spectra emitted by the plasma. The method is applied to the analysis of a sulfur ECRIS plasma.

Santos, J. P.; Martins, M. C.; Parente, F. [Centro de Fisica Atomica, CFA, Departamento de Fisica, Faculdade de Ciencias e Tecnologia, FCT, Universidade Nova de Lisboa, P-2829-516 Caparica (Portugal); Costa, A. M.; Marques, J. P. [Centro de Fisica Atomica, CFA, Departamento de Fisica, Faculdade de Ciencias, FCUL, Universidade de Lisboa, Campo Grande, P-1749-016 Lisboa (Portugal); Indelicato, P. [Laboratoire Kastler Brossel, Ecole Normale Superieure, CNRS, Universite P. et M. Curie - Paris 6, Case 74, 4, place Jussieu, F-75252 Paris CEDEX 05 (France)

2010-12-15

3

ELECTRON FLUX SPECTRAL IMAGING OF SOLAR FLARES THROUGH REGULARIZED ANALYSIS OF HARD X-RAY SOURCE VISIBILITIES  

E-print Network

ELECTRON FLUX SPECTRAL IMAGING OF SOLAR FLARES THROUGH REGULARIZED ANALYSIS OF HARD X-RAY SOURCE method for imaging spectroscopy analysis of hard X-ray emission during solar flares. The method avoids then yields images of the elec- tron flux that vary smoothly with energy. We apply the method to a solar flare

California at Berkeley, University of

4

ELECTRON FLUX SPECTRAL IMAGING OF SOLAR FLARES THROUGH REGULARIZED ANALYSIS OF HARD X-RAY SOURCE VISIBILITIES  

E-print Network

ELECTRON FLUX SPECTRAL IMAGING OF SOLAR FLARES THROUGH REGULARIZED ANALYSIS OF HARD X-RAY SOURCE a new method for imaging spectroscopy analysis of hard X-ray emission during solar flares. The method the method to a solar flare observed on 2002 February 20 by the RHESSI instrument. The event is characterized

Piana, Michele

5

Analysis of InGaN\\/GaN single quantum wells by X-ray scattering and transmission electron microscopy  

Microsoft Academic Search

A set of InxGa1-xN\\/GaN single quantum wells (SQWs) were analysed using X-ray reflectivity (XRR), high resolution X-ray diffraction (HRXRD) and high resolution transmission electron microscopy (HRTEM). A method for determining the thickness and composition of the single quantum well layers using only X-ray scattering measurements is described - the results agree very closely with those determined from HRTEM analysis of

T. M. Smeeton; M. J. Kappers; J. S. Barnard; M. E. Vickers; C. J. Humphreys

2003-01-01

6

12.141 Electron Microprobe Analysis by Wavelength Dispersive X-ray Spectrometry, January (IAP) 2006  

E-print Network

Introduction to the theory of x-ray microanalysis through the electron microprobe including ZAF matrix corrections. Techniques to be discussed are wavelength and energy dispersive spectrometry, scanning backscattered ...

Chatterjee, Nilanjan

7

Microfibrous quartz varieties: characterization by quantitative X-ray texture analysis and transmission electron microscopy  

NASA Astrophysics Data System (ADS)

Quantitative X-ray texture analysis was used to identify the fiber elongation direction of microfibrous quartz varieties in materials that contain narrow bands of closely spaced, radially divergent spherulitic fiber bundles. The statistical approach of X-ray texture analysis makes it possible to determine the fiber axis direction even when the maximum divergence angle of fibers within spherulitic fiber bundles diverge +/-20° from a common growth direction. Representative samples of chalcedony <11&2macr0>, quartzine [0001], and pseudochalcedony were selected for additional study with transmis-sion electron microscopy. All varieties of microfibrous quartz were found to contain high concentrations of polysynthetic Brazil twins and domains characterized by a modulated microstructure. Trace element profiles of aluminum and iron concentration were measured by electron microprobe analysis for an agate sample that contains alternating bands of chalcedony <11&2macr0> and quartzine fibers. The elemental concentration profiles were measured in a direction parallel to the growth direction of microfibrous quartz. Although fibers within the chalcedony bands initially displayed cooperative helical twisting, the fibers became untwisted during the later stages of growth within any one band. The trace element profiles revealed that higher concentrations of aluminum are associated with quartzine and non-twisted <11&2macr0> fibers, rather than twisted chalcedony <11&2macr0> fibers. Except for the presence of iron-rich inclusions between quartzine and chalcedony bands, trace concentrations of iron were below the detection limit for the different varieties of microfibrous quartz analyzed.

Cady, S. L.; Wenk, H.-R.; Sintubin, M.

8

12.141 Electron Microprobe Analysis by Wavelength Dispersive X-ray Spectrometry, January IAP 2010  

E-print Network

This lab-oriented course introduces the student to the subject of X-ray spectrometry and micro-scale chemical quantitative analysis of solid samples through an intensive series of hands-on laboratory exercises that use the ...

Chatterjee, Nilanjan

2010-01-01

9

Cadmium toxicity in perinatal rat hepatocytes: Electron microscopy, X-ray microanalysis, and morphometric analysis  

SciTech Connect

Effects of cadmium on the fetal and postnatal rat hepatocytes were studied with an electron microscope and an X-ray microanalyzer. Pregnant and lactating Wistar rat dams at 15 and 21 days of pregnancy and at 3 days after delivery received intraperitoneal injections of cadmium sulfate (1 mg/kg body weight) for 3 days. On the day following the last injection, the livers were isolated from the fetal and suckling rats and provided for electron microscopy. The livers from the untreated fetal and newborn rats served as control. Large bile canaliculi, which were formed by five or more hepatocytes, were frequently observed in the cadmium-treated perinatal rat livers. The intercellular space between each adjacent hepatocyte was widened. By X-ray microanalysis, cadmium peaks were preferentially detected out from intramitochondrial granules of the cadmium-treated hepatocytes. By morphometric analysis, the increase both in the mitochondria volume and in the number of intramitochondrial granules was evident in the cadmium-treated hepatocytes when compared to those of control. These data suggest the preferential accumulation of cadmium in mitochondria of the hepatocytes interferes with the morphogenesis of the perinatal rat liver.

Kawahara, A.; Yoshizuka, M.; Hirano, T.; Ohsato, K.; Fujimoto, S. (Univ. of Occupational and Environmental Health, Kitakyushu (Japan))

1990-10-01

10

A New Furnace For High-Temperature Synchrotron X-ray Powder Diffraction Experiments - Electron Density Analysis By Powder X-ray Diffraction At 1300 deg. C  

SciTech Connect

A new furnace for synchrotron X-ray powder diffraction experiments in a high-temperature range up to 1600 deg. C has been developed in order to obtain the detailed crystallographic information around high-temperature structural phase transition for the diffractometer of the beam-line 3A at the Photon Factory. The new furnace optical design is based on the flat-specimen reflection geometry using a parallel beam. We have successfully acquired the electron density distribution map of CaTiO3 at about 1300 deg. C with this new furnace using Rietveld and maximum-entropy-method analysis.

Tanaka, Masahiko; Mori, Takeharu [Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization, Oho, Tsukuba Ibaraki, 305-0801 (Japan); Yashima, Masatomo [Department of Material Science and Engineering, Interdisciplinary Graduate School and Engineering, Tokyo Institute of Technology 4259 Nagatuta-cho, Midori-ku, Yokohama 226-8502 (Japan)

2004-05-12

11

Application of scanning electron microscopy to x-ray analysis of frozen- hydrated sections. I. Specimen handling techniques  

PubMed Central

X-ray microanalysis of frozen-hydrated tissue sections permits direct quantitative analysis of diffusible elements in defined cellular compartments. Because the sections are hydrated, elemental concentrations can be defined as wet-weight mass fractions. Use of these techniques should also permit determination of water fraction in cellular compartments. Reliable preparative techniques provide flat, smooth, 0.5 micrometers-thick sections with little elemental and morphological disruption. The specimen support and transfer system described permits hydrated sections to be transferred to the scanning electron microscope cold stage for examination and analysis without contamination or water loss and without introduction of extraneous x- ray radiation. PMID:7204491

1981-01-01

12

Scanning electron microscopic and X-ray micro analysis on tooth enamel exposed to alkaline agents.  

PubMed

The background of this study comprises two clinical cases, where patients exposed to aerosols of an alkaline and surface active cleaning agent developed loss of enamel substance on their teeth, further resulting in loss of teeth and partially destroyed soft tissues. The alkaline cleaning agent consisted of potassium hydroxide and various surfactants. The purpose of this study was to investigate possible changes in morphology and composition in human teeth enamel exposed to alkaline solutions, by means of X-ray micro analysis (XRMA), FTIR-spectroscopic analyses and scanning electron microscopy (SEM). Extracted premolars, exposed to potassium hydroxide solutions and alkaline cleaning solution,were analyzed by means of XRMA and SEM. Enamel powder, exposed to cleaning solution, was analyzed by means of FTIR. The SEM analysis revealed an increased porosity of the enamel surface and partially loss of enamel substance after exposure to alkaline solutions. The XRMA analyses revealed a decrease in carbon concentration while phosphorous and calcium showed no marked changes. The FTIR analyses showed no significant changes in peak heights or peak positions for phosphate, carbonate or hydroxide. It was concluded that human teeth enamel exposed to alkaline solutions showed loss of organic substance, marked pores in enamel surface and loss of substance in the enamel surface. PMID:21121412

Taubee, Fabian; Steiniger, Frank; Nietzsche, Sandor; Norén, Jörgen G

2010-01-01

13

Distribution analysis of epoxy groups in polymers by derivatization-electron probe X-ray microanalysis.  

PubMed

An analytical method, referred to as "derivatization-electron probe X-ray micro-analysis (XMA)", has been developed to determine the distribution of a small amount of the functional groups in a polymer. The suitable conditions for the derivatization reaction with epoxy groups, which contribute to the hardening reactions of polymers, were investigated. It was found that epoxy groups in polymers were derivatized selectively using gas-phase esterification with hydrochloric acid (HCI). The most suitable amount of HCl in a 50 ml vial was 300 microl. After setting a sample in the vessel without directly contacting the reagent, by reacting the reagent and the sample at 25 degrees C for 1 h, the highest reaction yield and selectivity were obtained. By derivatization-XMA using this reaction condition, the measurement of the distribution of epoxy groups in the polymer became feasible. Actual applications to a depth analysis of epoxy groups in the hardened acrylic coating and epoxy resin proved that this method is useful for the characterization of polymers and for the study of the hardening reaction of polymers. PMID:11990569

Sugiura, M; Fukumoto, K; Murase, A; Ueda, K

2001-04-01

14

SCANNING ELECTRON MICROSCOPY AND X-RAY DIFFRACTION ANALYSIS OF TANK 18 SAMPLES  

SciTech Connect

The F-Area Tank Farm (FTF) Performance Assessment (PA) utilizes waste speciation in the waste release model used in the FTF fate and transport modeling. The waste release modeling associated with the residual plutonium in Tank 18 has been identified as a primary contributor to the Tank 18 dose uncertainty. In order to reduce the uncertainty related to plutonium in Tank 18, a better understanding of the plutonium speciation in the Tank 18 waste (including the oxidation state and stoichiometry) is desired. Savannah River National Laboratory (SRNL) utilized Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD) to analyze Tank 18 samples to provide information on the speciation of plutonium in the waste material. XRD analysis of the Tank 18 samples did not identify any plutonium mineral phases in the samples. These indicates the crystalline mineral phases of plutonium are below the detection limits of the XRD method or that the plutonium phase(s) lack long range order and are present as amorphous or microcrystalline solids. SEM analysis of the Tank 18 samples did locate particles containing plutonium. The plutonium was found as small particles, usually <1 {micro}m but ranging up to several micrometers in diameter, associated with particles of an iron matrix and at low concentration in other elemental matrices. This suggests the plutonium has an affinity for the iron matrix. Qualitatively, the particles of plutonium found in the SEM analysis do not appear to account for all of the plutonium in the sample based on concentrations determined from the chemical analysis of the Tank 18 samples. This suggests that plutonium is also distributed throughout the solids in low concentrations.

Hay, M.; O'Rourke, P.; Ajo, H.

2012-03-08

15

Comprehensive Study of Hydrated IDPs: X-Ray Diffraction, IR Spectroscopy and Electron Microscopic Analysis  

NASA Technical Reports Server (NTRS)

Chondritic hydrated interplanetary dust particles (IDPs) comprise up to 50% of all IDPs collected in the stratosphere(1). Although much is known about the mineralogy, chemistry and carbon abundance of hydrated IDPs (2-4) controversies still exist regarding their formation, history, and relationship to other primitive solar system materials. Hydrated IDPs are generally believed to be derived from asteroidal sources that have undergone some degree of aqueous alteration. However, the high C contents of hydrated IDPs (by 2 to 6X CI levels (3,4) indicate that they are probably not derived from the same parent bodies sampled by the known chondritic meteorites. We report the comprehensive study of individual hydrated IDPs. The strong depletion in Ca (I) has been used as a diagnostic feature of hydrated IDPs. The particles are embedded in elemental sulfur or low viscosity epoxy and ultramicrotomed thin sections are observed using a transmission electron microscope (TEM) equipped with an energy-dispersive X-ray detector (EDX) followed by other measurements including: 1) FTIR microspectroscopy to understand the significant constraints on the organic functionality and the nature of the C-bearing phases and 2) powder X-ray difiaction using a synchrotron X-ray source to understand the bulk mineralogy of the particles.

Nakamura, K.; Keller, L. P.; Nakamura, T.; Noguchi, T.; Nozaki, W.; Tomeoka, K.

2003-01-01

16

Stimulated Electronic X-Ray Raman Scattering  

NASA Astrophysics Data System (ADS)

We demonstrate strong stimulated inelastic x-ray scattering by resonantly exciting a dense gas target of neon with femtosecond, high-intensity x-ray pulses from an x-ray free-electron laser (XFEL). A small number of lower energy XFEL seed photons drive an avalanche of stimulated resonant inelastic x-ray scattering processes that amplify the Raman scattering signal by several orders of magnitude until it reaches saturation. Despite the large overall spectral width, the internal spiky structure of the XFEL spectrum determines the energy resolution of the scattering process in a statistical sense. This is demonstrated by observing a stochastic line shift of the inelastically scattered x-ray radiation. In conjunction with statistical methods, XFELs can be used for stimulated resonant inelastic x-ray scattering, with spectral resolution smaller than the natural width of the core-excited, intermediate state.

Weninger, Clemens; Purvis, Michael; Ryan, Duncan; London, Richard A.; Bozek, John D.; Bostedt, Christoph; Graf, Alexander; Brown, Gregory; Rocca, Jorge J.; Rohringer, Nina

2013-12-01

17

Synchrotron radiation induced x-ray micro analysis: A realistic alternative for electron- and ion beam microscopy?  

SciTech Connect

Synchrotron Radiation induced X-ray micro Fluorescence analysis ({mu}-SRXRF) is compared with more conventional microanalytical techniques such as Secondary Ion Microscopy (SIMS) and Electron Probe X-ray Microanalysis (EPXMA) for two typical microanalytical applications. SRXRF and EPXMA are employed for the analysis of individual particles, showing the complementary character of both techniques. By means of element mapping of trace constituents in a heterogeneous feldspar, the strong and weak points of SRXRF in comparison to EPXMA and SIMS are illustrated. The most striking difference between SRXRF and the other two microanalytical methods is the ability of SRXRF to probe deep into the investigated Material, whereas SIMS and EPXMA only investigate the upper surface of the material. The possibilities of SRXRF at third generation synchrotron rings is also briefly discussed.

Janssens, K.; Adams, F. [Universitaire Instelling Antwerpen, Antwerp (Belgium). Dept. of Chemistry; Rivers, M.L.; Jones, K.W. [Brookhaven National Lab., Upton, NY (United States)

1992-10-01

18

Synchrotron radiation induced x-ray micro analysis: A realistic alternative for electron- and ion beam microscopy  

SciTech Connect

Synchrotron Radiation induced X-ray micro Fluorescence analysis ([mu]-SRXRF) is compared with more conventional microanalytical techniques such as Secondary Ion Microscopy (SIMS) and Electron Probe X-ray Microanalysis (EPXMA) for two typical microanalytical applications. SRXRF and EPXMA are employed for the analysis of individual particles, showing the complementary character of both techniques. By means of element mapping of trace constituents in a heterogeneous feldspar, the strong and weak points of SRXRF in comparison to EPXMA and SIMS are illustrated. The most striking difference between SRXRF and the other two microanalytical methods is the ability of SRXRF to probe deep into the investigated Material, whereas SIMS and EPXMA only investigate the upper surface of the material. The possibilities of SRXRF at third generation synchrotron rings is also briefly discussed.

Janssens, K.; Adams, F. (Universitaire Instelling Antwerpen, Antwerp (Belgium). Dept. of Chemistry); Rivers, M.L.; Jones, K.W. (Brookhaven National Lab., Upton, NY (United States))

1992-01-01

19

Scanning electron microscopy, x-ray diffraction, and electron microprobe analysis of calcific deposits on intrauterine contraceptive devices  

SciTech Connect

Deposits found on intrauterine contraceptive devices (IUDs) were studied by scanning electron microscopy, x-ray diffraction, and energy dispersive x-ray microanalysis. All seven devices, including five plastic and two copper IUDs, were coated with a crust containing cellular, acellular, and fibrillar material. The cellular material was composed of erythrocytes, leukocytes, cells of epithelial origin, sperm, and bacteria. Some of the bacteria were filamentous, with acute-angle branching. The fibrillar material appeared to be fibrin. Most of the acellular material was amorphous; calcite was identified by x-ray diffraction, and x-ray microanalysis showed only calcium. Some of the acellular material, particularly that on the IUD side of the crust, was organized in spherulitic crystals and was identified as calcium phosphate by x-ray microanalysis. The crust was joined to the IUD surface by a layer of fibrillar and amorphous material. It is suggested that the initial event in the formation of calcific deposits on IUD surfaces is the deposition of an amorphous and fibrillar layer. Various types of cells present in the endometrial environment adhere to this layer and then calcify. Thus, the deposition of calcific material on the IUDs is a calcification phenomenon, not unlike the formation of plaque on teeth.

Khan, S.R.; Wilkinson, E.J.

1985-07-01

20

TEM (transmission electron microscopy) and x-ray analysis of multilayer mirrors and beamsplitters  

Microsoft Academic Search

Recent advances in the development of lasers at soft x-ray wavelengths has spurred increasing interest in the production of cavity components using multilayer technology. We have established a comprehensive capability to design, fabricate, and characterize multilayer x-ray optics directed towards the goal of building the first x-ray laser cavity. High quality multilayer structures have been fabricated using magnetron sputtering. In

D. G. Stearns; N. M. Ceglio; A. M. Hawryluk; M. B. Stearns; A. K. Petford-Long; C. H. Chang; K. Danzmann; M. Kuhne; P. Muller; B. Wende

1986-01-01

21

Single shot speckle and coherence analysis of the hard X-ray free electron laser LCLS.  

PubMed

The single shot based coherence properties of hard x-ray pulses from the Linac Coherent Light Source (LCLS) were measured by analyzing coherent diffraction patterns from nano-particles and gold nanopowder. The intensity histogram of the small angle x-ray scattering ring from nano-particles reveals the fully transversely coherent nature of the LCLS beam with a number of transverse mode ?Ms? = 1.1. On the other hand, the speckle contrasts measured at a large wavevector yields information about the longitudinal coherence of the LCLS radiation after a silicon (111) monochromator. The quantitative agreement between our data and the simulation confirms a mean coherence time of 2.2 fs and a x-ray pulse duration of 29 fs. Finally the observed reduction of the speckle contrast generated by x-rays with pulse duration longer than 30 fs indicates ultrafast dynamics taking place at an atomic length scale prior to the permanent sample damage. PMID:24150309

Lee, Sooheyong; Roseker, W; Gutt, C; Fischer, B; Conrad, H; Lehmkühler, F; Steinke, I; Zhu, D; Lemke, H; Cammarata, M; Fritz, D M; Wochner, P; Castro-Colin, M; Hruszkewycz, S O; Fuoss, P H; Stephenson, G B; Grübel, G; Robert, A

2013-10-21

22

Degradation of spatial resolution in thin-foil x-ray microchemical analysis due to plural scattering of electrons  

SciTech Connect

A computer-based Monte Carlo simulation of incoherent plural scattering of electrons has been developed in order to estimate the broadening of an electron probe as it propagates through a solid. By applying this approach to modeling the spreading of a fine (50 A) probe focused on a thin foil in a scanning transmission electron microscope (STEM), we have estimated the spatial resolution of the compositional analysis obtainable using energy dispersive x-ray spectroscopy (EDS). Specifically, an attempt has been made to determine how the apparent microchemistry of a feature of finer dimensions than the broadened beam differs from the actual composition of the given feature. The apparent Ge concentration profile in the vicinity of a 200 A wide Ge platelet in a 5000 A thick Al foil was measured, using STEM and EDS, and compared with the profile predicted by Monte Carlo calculations. Results are presented and discussed.

Twigg, Mark Erickson

1982-01-01

23

Measurements and analysis of bremsstrahlung x-ray spectrum obtained in NANOGAN electron cyclotron resonance ion source  

SciTech Connect

From the ECR plasma, hot electrons leak across the magnetic lines of force and by striking the plasma chamber produce bremsstrahlung x-rays. The wall bremsstrahlung gives information on the confinement status of hot electron. In our studies, experimental measurements are carried out in NANOGAN electron cyclotron resonance (ECR) ion source for the wall bremsstrahlung x-rays and the results are presented. While optimizing a particular charge state in ECR ion source, experimental parameters are adjusted to get a maximum current. The wall bremsstrahlung components are studied in these cases for understanding the hot electron confinement conditions.

Baskaran, R.; Selvakumaran, T. S.; Rodrigues, G.; Kanjilal, D.; Roy, A. [Radiological Safety Division, Indira Gandhi Center for Atomic Research, Kalpakkam 603 102 (India); Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067 (India)

2008-02-15

24

Convergent x-ray monochromator for molecular microprobe analysis  

SciTech Connect

An improved apparatus and method are provided for electron spectroscopy for chemical analysis which permits analysis of micron sized regions of a heterogeneous sample surface. The apparatus includes a source of multidirectional X-ray radiation. A hollow cylindrical body receives the multidirectional X-ray radiation. The hollow cylindrical body includes a plurality of beam directing Johannsen-type diffracting crystals elements arrayed symmetrically and circumferentially around an axis of symmetry extending from the source of X-ray radiation to a surface of the sample. The array of Johannsen-type diffracting crystals transforms the multidirectional X-ray radiation into a hollow cone of monochromatic X-ray radiation that converges on a micron sized region on the sample surface. A screen opaque to X-rays is located along the axis of symmetry between the source of X-ray radiation and the sample. The screen prevents X-rays from the source from reaching the sample without being directed and diffracted by the beam directing and diffracting elements. An electron detector located along the axis of symmetry detects electrons emitted from the micron sized region of the sample surface. The electron detector is located between the X-ray screen and the sample surface. 4 figs.

Gamba, O.O.M.

1990-01-01

25

X-ray topographic methods and application to analysis of electronic materials  

NASA Astrophysics Data System (ADS)

Three supplementary X-ray techniques new to semiconductor applications are discussed. These are the Computer Aided Rocking Curve Analyzer, the Divergent Beam Method and a new method based on enhanced X-ray flourescence. The first method is used for quantitative mapping of an elastic or plastic strain field while the other two methods are used only to measure elastic strains. The divergent beam method is used for measuring the full strain tensor while the microfluorescence method is useful for monitoring strain uniformity. These methods are discussed in detail and examples of their application is presented. Among these are determination of the full strain ellipsoid in state-of-the-art liquid phase epitaxy deposited III-V epitaxial films; mapping of the plastic strain concentrations in tensile deformed Si; and quantitative determination of damage in V3Si due to ion implantation.

Mayo, W. E.; Liu, H. Y.; Chaudhuri, J.

1984-04-01

26

Femtosecond laser-electron x-ray source  

DOEpatents

A femtosecond laser-electron X-ray source. A high-brightness relativistic electron injector produces an electron beam pulse train. A system accelerates the electron beam pulse train. The femtosecond laser-electron X-ray source includes a high intra-cavity power, mode-locked laser and an x-ray optics system.

Hartemann, Frederic V.; Baldis, Hector A.; Barty, Chris P.; Gibson, David J.; Rupp, Bernhard

2004-04-20

27

Characterization of zirconia–thoria–urania ceramics by X-ray and electron interactions  

Microsoft Academic Search

X-ray and electron interactions with matter were used as probes to characterize the structure and chemistry of zirconia–thoria–urania ceramics. The ceramics were prepared by coprecipitation of Zr, Th and U salts. In this study, transmission electron microscopy (TEM) techniques such as energy dispersive X-ray (EDX) analysis and electron energy loss spectroscopy (EELS) complement X-ray diffraction, extended X-ray absorption fine structure

Gini Curran; Y. Sevestre; Wendy Rattray; Patrick Allen; K. R. Czerwinski

2003-01-01

28

X-ray free-electron lasers  

NASA Astrophysics Data System (ADS)

In a free-electron laser (FEL) the lasing medium is a high-energy beam of electrons flying with relativistic speed through a periodic magnetic field. The interaction between the synchrotron radiation that is produced and the electrons in the beam induces a periodic bunching of the electrons, greatly increasing the intensity of radiation produced at a particular wavelength. Depending only on a phase match between the electron energy and the magnetic period, the wavelength of the FEL radiation can be continuously tuned within a wide spectral range. The FEL concept can be adapted to produce radiation wavelengths from millimetres to Ångstroms, and can in principle produce hard x-ray beams with unprecedented peak brightness, exceeding that of the brightest synchrotron source by ten orders of magnitude or more. This paper focuses on short-wavelength FELs. It reviews the physics and characteristic properties of single-pass FELs, as well as current technical developments aiming for fully coherent x-ray radiation pulses with pulse durations in the 100 fs to 100 as range. First experimental results at wavelengths around 100 nm and examples of scientific applications planned on the new, emerging x-ray FEL facilities are presented.

Feldhaus, J.; Arthur, J.; Hastings, J. B.

2005-05-01

29

X-ray Free-electron Lasers  

SciTech Connect

In a free-electron laser (FEL) the lasing medium is a high-energy beam of electrons flying with relativistic speed through a periodic magnetic field. The interaction between the synchrotron radiation that is produced and the electrons in the beam induces a periodic bunching of the electrons, greatly increasing the intensity of radiation produced at a particular wavelength. Depending only on a phase match between the electron energy and the magnetic period, the wavelength of the FEL radiation can be continuously tuned within a wide spectral range. The FEL concept can be adapted to produce radiation wavelengths from millimeters to Angstroms, and can in principle produce hard x-ray beams with unprecedented peak brightness, exceeding that of the brightest synchrotron source by ten orders of magnitude or more. This paper focuses on short-wavelength FELs. It reviews the physics and characteristic properties of single-pass FELs, as well as current technical developments aiming for fully coherent x-ray radiation pulses with pulse durations in the 100 fs to 100 as range. First experimental results at wavelengths around 100 nm and examples of scientific applications planned on the new, emerging x-ray FEL facilities are presented.

Feldhaus, J.; /DESY; Arthur, J.; Hastings, J.B.; /SLAC

2007-02-23

30

X-ray Analysis of Unknown Minerals  

NSDL National Science Digital Library

In this exercise, students use X-ray analysis to identify unknown minerals. They are given two samples to grind up and X-ray, using Jade to identify them. Once the minerals are identified, students make a spreadsheet and do a series of calculations.

Dexter Perkins

31

NASA Li/CF(x) cell problem analysis: Scanning electron microscopy with energy dispersive x ray spectrometry  

NASA Astrophysics Data System (ADS)

An analysis was made of Lithium/carbon fluoride cell parts for possible chloride contamination induced by exposure to thionyl chloride (SOCl2); various samples were submitted for analysis. Only a portion of the analysis which has been conducted is covered, herein, namely analysis by scanning electron microscopy with energy dispersive x ray spectrometry (SEM/EDS). A strip of nickel was exposed to SOCl2 vapors to observe variations in surface concentrations of sulfur and chlorine with time. By detecting chlorine one can not infer contamination by SOCl2 only that contamination is present. Six samples of stainless steel foil were analyzed for chlorine using EDS. Chlorine was not detected on background samples but was detected on the samples which had been handled including those which had been cleaned. Cell covers suspected of being contaminated while in storage and covers which were not exposed to the same storage conditions were analyzed for chlorine. Although no chlorine was found on the covers from cells, it was found on all stored covers. Results are presented with techniques shown for analysis and identification. Relevant photomicrographs are presented.

Baker, John

1991-05-01

32

STATISTICAL CONSIDERATIONS IN THE EMPLOYMENT OF SAX (SCANNING ELECTRON MICROSOPY WITH AUTOMATED IMAGE ANALYSIS AND X-RAY ENERGY SPECTROSCOPY) RESULTS FOR RECEPTOR MODELS  

EPA Science Inventory

Hundreds of thousands of individual particle measurements may be accumulated in a receptor model study employing Scanning electron microscopy with Automated image analysis and X-ray energy spectroscopy (SAX). At present, the summaries of these data are utilized in apportionment c...

33

X-ray Analysis of Sand  

NSDL National Science Digital Library

This is an x-ray diffraction analysis of six sand samples and comparison with hand specimens. Students look at each of the six samples under the binocular microscope and note such useful properties as number of minerals, cleavage/fracture, color, shape, grain size, roundness, and degree of sorting. Then they grind up small amounts of each sample and mount them on glass slides for X-ray. Students write all sample descriptions and X-ray analysis results in their lab notebook. Then they identify the minerals in each sample, determine where they are from, and write a report summarizing all results.

Dexter Perkins

34

X-ray Free-electron Lasers  

SciTech Connect

We review the present status and properties of X-ray free-electron lasers in operation or under construction in the nanometer and sub-nanometer wavelength range, and the novel possibilities they offer for the study of atomic and molecular processes. We also discuss recent developments in relativistic electron beam physics that give us the possibility of designing a new generation of X-ray free-electron lasers that: a. are more compact; b. reduce the radiation pulse duration to one femtosecond or below; c. extend the photon energy to the 50 keV region. These results are obtained by reducing the electron bunch charge while at same time maximizing the beam brightness and reducing the bunch length to a value near or smaller than the free-electron laser cooperation length. In the last case the radiation pulse is fully coherent in the longitudinal and transverse space. The increase in beam brightness can also be used to reduce the beam energy needed for a given radiation wavelength, when, at the same time, the undulator period is reduced. The simultaneous decrease in beam energy and undulator period leads to a more compact free-electron laser, while the high beam brightness reduces the gain length and increases the coherent radiation intensity.

Pellegrini, Claudio [UCLA Department of Physics and Astronomy, Los Angeles, CA 90095-1547 (United States)

2009-09-10

35

Scanning electron microscopy, X-ray diffraction and thermal analysis study of the TiH{sub 2} foaming agent  

SciTech Connect

The decomposition of commercially available TiH{sub 2} was investigated while performing different thermal treatments. TiH{sub 2} powder, which is widely used as a foaming agent, was heat treated at 450 Degree-Sign C for various times, from 15 min to 120 min. Scanning electron microscopy (SEM) images of the surfaces at different magnifications were obtained and interpreted. A Bragg-Brentano X-ray diffractometer was used to measure the X-ray diffraction (XRD) spectra on all five samples. A close examination of the diffraction spectra showed that for an as-received sample and samples undergoing the longest thermal treatment (1 and 2 h) these spectra can be explained as deriving from cubic TiH{sub 1.924}, while for the other two samples they can be explained as deriving from tetragonal TiH{sub 1.924}. A constant-unit-cell-volume phase transition between the cubic and tetragonal phases in TiH{sub 2-y}-type compounds had been described in the literature. The unit-cell parameters obtained from measured spectra confirm that within the measurement uncertainty the unit-cell volume is indeed constant in all five samples. Thermo-gravimetry (TG) and differential thermal analysis (DTA) measurements were performed on all the samples, showing that the intensity of the dehydrogenation depends on the previous treatment of the TiH{sub 2}. After the thermal analysis XRD of the samples was performed again and the material was found to exhibit a Ti-like unit cell, but slightly enlarged due to the unreleased hydrogen. - Highlights: Black-Right-Pointing-Pointer TiH{sub 2} samples were cubic or tetragonal TiH{sub 1.924} Black-Right-Pointing-Pointer Onset of the hydrogen release temperature increases with the pre-treatment time. Black-Right-Pointing-Pointer Thermal dehydrogenation for the as-prepared TiH{sub 2} is a three-step process. Black-Right-Pointing-Pointer After thermal analysis 2 residual hydrogen TiH{sub x} phases, close to {alpha}Ti, appeared.

Mandrino, Djordje, E-mail: djordje.mandrino@imt.si [Institute of Metals and Technology, Lepi pot 11, 1000 Ljubljana (Slovenia)] [Institute of Metals and Technology, Lepi pot 11, 1000 Ljubljana (Slovenia); Paulin, Irena [Institute of Metals and Technology, Lepi pot 11, 1000 Ljubljana (Slovenia)] [Institute of Metals and Technology, Lepi pot 11, 1000 Ljubljana (Slovenia); Skapin, Sreco D. [Jozef Stefan Institute, Jamova 39, 1000 Ljubljana (Slovenia)] [Jozef Stefan Institute, Jamova 39, 1000 Ljubljana (Slovenia)

2012-10-15

36

High resolution x-ray tomography in an electron microprobe  

Microsoft Academic Search

Conversion of an electron microprobe for use as an x-ray microtomograph is described. Only minor modifications are required, indeed several of the utilities of the microprobe can be used to ensure high resolution radiography and tomography. System performance was evaluated by analysis of glass fiber reinforced polymer composites and of a carbonate reservoir rock. Individual glass fibers of 10 and

Rogério Ferreira de Paiva; Michel Bisiaux; John Lynch; Elisabeth Rosenberg

1996-01-01

37

Maximum x-ray energy from compact electron cyclotron resonance based source of x rays  

NASA Astrophysics Data System (ADS)

The x-ray spectra from an electron cyclotron resonance argon plasma produced in a compact magnetic trap, containing a tungsten target, are reported. The maximum attainable x-ray energy was recorded for different magnetic field configurations and energies higher than 300 keV were found. The maximum x-ray energy is strongly peaked near the change of the resonance surface topology from a one sheet hyperboloid to a two sheet hyperboloid. This observation is explained theoretically. Different regimes of x-ray production are described. Two distinct pressure ranges where x rays are produced were found. The characteristic lines of metals, e.g., from the target (tungsten), protection (lead), are clearly resolved. The radiography of an integrated circuit is shown as an example of possible use of the x-ray source for nondestructive control.

Rouillé, C.; Serebrennikov, K.; Bacal, M.

2002-06-01

38

Application of scanning electron microscopy and X-ray analysis to urinary tract cancer in animals and humans.  

PubMed

Scanning electron microscopy (SEM) has proven useful in various aspects of urinary bladder carcinogenesis research and these are reviewed as they pertain to our research involving sodium saccharin in the rat. Sodium saccharin-carcinogenesis in rats requires administration at high doses beginning at birth or earlier. Administration beginning at ages of 5 weeks or later results in much lower incidences of bladder tumors. Methods were developed for examining the rat fetal and neonatal bladder to further evaluate effects at these critical ages. Several significant differences were found by SEM between the fetal bladder compared to the adult. The typical polygonal superficial cells of the bladder with asymmetric unit membrane were present before birth, but the slow turnover rate of the adult bladder did not occur until 3-4 weeks of age. Sodium saccharin causes increased proliferation rates and hyperplasia of the urothelium which is dose-dependent. SEM was found to be more sensitive than either light microscopy or labeling indices to detect the earliest lesions induced by sodium saccharin. More recently, amorphous and crystalline material in the urine of rats fed high doses of sodium saccharin were detected by SEM examinations which contained silicon as well as calcium, phosphate, and magnesium as detected by energy dispersive X-ray analysis (EDS) with the SEM. These parameters may be relevant to differences between rats and humans and pertain to extrapolations regarding risk assessment. PMID:8316805

Cano, M; Suzuki, T; Cohen, S M

1993-03-01

39

Use of electron microprobe x-ray analysis for determination of low calcium concentrations across leaves deficient in calcium  

NASA Technical Reports Server (NTRS)

An electron microprobe with wavelength-dispersive x-ray spectrometry (WDS) was found to be useful for the determination of Ca concentrations in leaf tissue deficient in Ca. WDS effectively detected Ca concentrations as low as 0.2 mg/g dry wt in the presence of high levels of K and Mg (120 and 50 mg/g dry wt, respectively). Leaf specimens were prepared for analysis by quick-freezing in liquid nitrogen and freeze-drying at -20 degrees C to maintain elemental integrity within the tissue. Because dry material was analyzed, sample preparation was simple and samples could be stored for long periods before analysis. A large beam diameter of 50 gm was used to minimize tissue damage under the beam and analyze mineral concentrations within several cells at one time. Beam penetration was between 50 and 55 microns, approximately one-third of the thickness of the leaf. For analysis of concentrations in interveinal areas, analyses directed into the abaxial epidermis were found most useful. However, because of limited beam penetration, analyses of veinal areas would require use of cross sections [correction of crosssections]. Solid mineral standards were used for instrument standardization. To prevent measurement errors resulting from differences between the matrix of the mineral standards and the analyzed tissue, concentrations in leaves were corrected using gelatin standards prepared and analyzed under the same conditions. WDS was found to be useful for documenting that very low Ca levels occur in specific areas of lettuce leaves exhibiting the Ca deficiency injury termed tipburn.

Barta, D. J.; Tibbitts, T. W.

1991-01-01

40

Lung dust content in idiopathic pulmonary fibrosis: a study with scanning electron microscopy and energy dispersive x ray analysis.  

PubMed Central

Examination with an optical microscope and polarised light is not sensitive enough to detect low diameter asbestos fibres. This limitation implies that some cases of asbestosis can be erroneously diagnosed as idiopathic pulmonary fibrosis (IPF) if asbestos bodies are not found in the standard examination of abnormal tissue. To determine whether IPF is over-diagnosed, a study was carried out with scanning electron microscopy (SEM) and energy dispersive x ray analysis (EDXA) on 25 samples previously diagnosed as IPF at the standard examination. Scanning electron microscopy will show the presence of low diameter fibres in the lung without tissue destruction, and these fibres can be identified using EDXA. The quantitative and qualitative results for lung tissue from patients diagnosed as having IPF were compared with the results of the examination of 25 samples of normal lung. Most of the samples from patients diagnosed as having IPF showed only occasional inorganic particles (less than 10 particles/SEM field at 160 x), results equivalent to the results obtained in normal lung. Two cases of IPF, however, showed innumerable asbestos fibres (greater than 100 fibres/SEM field). One of these two patients had an antecedent of brief exposure to asbestos. No environmental antecedent was found in the second patient. Asbestosis was the final diagnosis for these two patients. The examination of inorganic particles in normal lungs showed mainly non-fibrous silicates (61.4%) and particles of heavy elements (34.9%). Only one asbestos fibre was found (0.9%). It is concluded that standard pathological techniques overdiagnose IPF in a few cases in which asbestos bodies are not found with the optical microscope. Images PMID:2039745

Monsó, E; Tura, J M; Pujadas, J; Morell, F; Ruiz, J; Morera, J

1991-01-01

41

Analysis of a Novel Diffractive Scanning Wire Beam Position Monitor (BPM) for Discriminative Profiling of Electron Vs. X Ray Beams  

SciTech Connect

Recent numerical studies of Free Electron Lasers (FELs) operating in the Self Amplified Spontaneous Emission (SASE) regime indicate a large sensitivity of the gain to the degree of transverse overlap (and associated phase coherence) between the electron and photon beams traveling down the insertion device. Simulations of actual systems imply that accurate detection and correction for this relative loss of overlap, rather than correction for the absolute departure of the electron beam from a fixed axis, is the preferred function of an FEL amplifier's Beam Position Monitor (BPM) and corrector systems. In this note we propose a novel diffractive BPM with the capability of simultaneously detecting and resolving the absolute (and relative) transverse positions and profiles of electron and x-ray beams co-propagating through an undulator. We derive the equations governing the performance of the BPM and examine its predicted performance for the SLAC Linac Coherent Light Source (LCLS), viz., for profiling multi-GeV electron bunches co-propagating with one-to-several-hundred keV x-ray beams. Selected research and development (r&d) tasks for fabricating and testing the proposed BPM are discussed.

Tatchyn, Roman; /SLAC

2011-09-01

42

Femtosecond x-ray absorption spectroscopy with hard x-ray free electron laser  

SciTech Connect

We have developed a method of dispersive x-ray absorption spectroscopy with a hard x-ray free electron laser (XFEL), generated by a self-amplified spontaneous emission (SASE) mechanism. A transmission grating was utilized for splitting SASE-XFEL light, which has a relatively large bandwidth (?E/E ? 5 × 10{sup ?3}), into several branches. Two primary split beams were introduced into a dispersive spectrometer for measuring signal and reference spectra simultaneously. After normalization, we obtained a Zn K-edge absorption spectrum with a photon-energy range of 210 eV, which is in excellent agreement with that measured by a conventional wavelength-scanning method. From the analysis of the difference spectra, the noise ratio was evaluated to be ?3 × 10{sup ?3}, which is sufficiently small to trace minute changes in transient spectra induced by an ultrafast optical laser. This scheme enables us to perform single-shot, high-accuracy x-ray absorption spectroscopy with femtosecond time resolution.

Katayama, Tetsuo; Togashi, Tadashi; Tono, Kensuke; Kameshima, Takashi [Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan)] [Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan); Inubushi, Yuichi; Sato, Takahiro; Hatsui, Takaki; Yabashi, Makina [RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148 (Japan)] [RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148 (Japan); Obara, Yuki; Misawa, Kazuhiko [Department of Applied Physics, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo 184-8588 (Japan)] [Department of Applied Physics, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo 184-8588 (Japan); Bhattacharya, Atanu; Kurahashi, Naoya [Department of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-ku, Kyoto 606-8502 (Japan)] [Department of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-ku, Kyoto 606-8502 (Japan); Ogi, Yoshihiro [Molecular Reaction Dynamics Research Team, RIKEN Center for Advanced Photonics, 2-1 Hirosawa, Wako 351-0198 (Japan)] [Molecular Reaction Dynamics Research Team, RIKEN Center for Advanced Photonics, 2-1 Hirosawa, Wako 351-0198 (Japan); Suzuki, Toshinori [Department of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-ku, Kyoto 606-8502 (Japan) [Department of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-ku, Kyoto 606-8502 (Japan); Molecular Reaction Dynamics Research Team, RIKEN Center for Advanced Photonics, 2-1 Hirosawa, Wako 351-0198 (Japan)

2013-09-23

43

Muscle cell membranes from early degeneration muscle cell fibers in Solenopsis are leaky to lanthanum: electron microscopy and X-ray analysis  

SciTech Connect

Lanthanum infusion techniques, transmission electron microscopy, and X-ray microanalysis were utilized to compare the permeability of muscle cell membranes from normal and degenerating muscle fibers of Solenopsis spp. In normal fibers, the electron-dense tracer was limited to components of the sarcotubular system. However, the insemination-induced degeneration of muscle fibers was characterized by the presence of an electron-dense precipitate within the myofibrils and mitochondria as well as in the extramyofibrillar spaces. The electron-dense material was subsequently identified by elemental analysis to be lanthanum. Such data indicate that one of the earliest stages of muscle degeneration involves an alteration in cell membrane permeability.

Jones, R.G.; Davis, W.L.

1985-06-01

44

Opportunities for resonant elastic X-ray scattering at X-ray free-electron lasers  

NASA Astrophysics Data System (ADS)

X-ray Free-Electron Lasers (FELs) are beginning to deliver a revolution in X-ray experiments, thanks to their ultra-bright (peak brightness exceeding 1033 photons/s/mm2/mrad2/0.1%BW), ultrashort (down to a few fs), spatially coherent X-ray pulses. Presently operational facilities cover wide spectral ranges, from the VUV and soft X-ray wavelengths of FLASH in Hamburg (down to 4.2 nm), to the hard X-rays delivered by the LCLS in Stanford (wavelengths of 0.15 nm or shorter). The basic properties of the new sources are briefly reviewed, and the impact on resonant scattering experiments is discussed. The perspective of investigating ultrafast magnetism, and, more generally, the time-dependent response of strongly correlated electron systems, in a pump-and-probe mode at the L edges of 3d transition metals, would be very attractive. In the hard X-ray range, the very recent proposal of self-seeded X-ray FELs, with 10-5 intrinsic bandwidth, tunable wavelength, 100 fs pulses and number of photons per pulse of order 1012 also opens exciting possibilities for resonant scattering.

Altarelli, M.

2012-06-01

45

Stress Analysis by X-Ray Diffraction  

Microsoft Academic Search

A mathematical analysis is presented for the problem of determining stresses in a metal by x-ray diffraction. The treatment is a general one, including as special cases the various methods for the determination of uniaxial stresses or the sum of two principal stresses in the plane of the metal surface. The analysis is extended to the problem of determining the

C. S. Barrett; M. Gensamer

1936-01-01

46

Fundamental characteristics of hybrid X-ray focusing optics for micro X-ray fluorescence analysis  

NASA Astrophysics Data System (ADS)

We developed a hybrid X-ray focusing optics, which consisted of a polycapillary X-ray lens (PCXL) and a tungsten conical pinhole (WCP) for micro X-ray fluorescence (?-XRF) analysis. A single PCXL produced an X-ray micro beam with a spot size of 12 ?m. We developed a WCP by using a laser-ablation technique with an input diameter of 39 ?m, an output diameter of 2.5 ?m, and a thickness of 0.5 mm in a conical shape. This hybrid X-ray optics gave a small spot size of 2.8 ?m with a small divergent angle of 12 mrad.

Komatani, Shintaro; Nakamachi, Kazuo; Nakano, Kazuhiko; Ohzawa, Sumito; Uchihara, Hiroshi; Bando, Atsushi; Tsuji, Kouichi

2013-08-01

47

Fundamental physics with an X-ray free electron laser  

Microsoft Academic Search

Of late, laboratories around the world are considering building X-ray free electron lasers based on high energy electron accelerators\\u000a (with energies exceeding 10 GeV) to produce bright coherent X rays with wavelengths on the order of 1 . Because of the extremely\\u000a small wavelength and high brilliance of these coherent X rays, there is an unprecedented opportunity to explore new

T. Tajima

2003-01-01

48

Low energy X-ray and electron interactions within matter  

NASA Astrophysics Data System (ADS)

This research program is concerned with the physics and the application of low energy X-ray and associated electron interactions. It has been concentrated upon the sub-kilovolt energy region where the need has been greatest for the development of efficient and precise spectroscopic methods, for the measurement of fundamental interaction cross sections, and for the basic theoretical modeling of certain important X-ray and electron interaction processes as, for example, X-ray induced photo-emission and fluorescence. This work is applied to two areas of considerable present importance and need: the development of high efficiency spectroscopic methods that can be effectively applied to the diagnostics of high temperature plasmas - particularly as generated by high power pulsed lasers, electron or ion beams and by exploding wires, for which high temporal resolution as well as high spectral resolution is needed; and the testing and application of high-efficiency low-energy fluorescent spectroscopic measurement and analysis for valence and molecular orbital electron energy state studies, for the solid state characterization of surfaces, and for studies of the effects of radiation damage.

Henke, B. L.

1980-03-01

49

X-ray waveguides for high resolution x-ray analysis  

SciTech Connect

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 as diffraction-limited, linear x-ray sources. We fabricated nine waveguide structures that were optimized to operate in the cavity modes m = 1,2,3 and tested them at x-ray energies of 6 to 10 keV. The observed performances were compared to the calculations based on the design structures and excellent agreement was demonstrated. This project plan is presented in TABLE 1 that includes all aspects of the development of these unique thin film x-ray optical devices. X-ray waveguide designs were made using a standard x-ray multilayer x-ray optic Fresnel code. Materials were selected on the basis of calculated performance as well as sputter deposition characteristics. Laboratory x-ray reflectivity measurements were made prior to the SSRL experimental run to assess the quality of the samples. Cross-section Transmission Electron Microscopy observations of selected sample were made to enable assessment of the relationship between the design structures and the fabricated structures. The cross-section TEM observations correlated well with the waveguide fabrication parameters supporting the observed agreement between the experimental and calculated grazing incidence reflectivities and fluorescence as functions of both x-ray energy and grazing angle of incidence.

Barbee, T W

1999-06-28

50

A false report of product tampering involving a rodent and soft drink can: light microscopy, image analysis and scanning electron microscopy/energy dispersive X-ray analysis.  

PubMed

The "Pepsi Tamperings" of 1993 resulted in a large number of cases involving foreign objects reportedly found inside canned soft drinks. Although the majority of cases involved medical syringes and metallic objects, one case involved the report of a mouse found inside a can of Caffeine-Free Diet Pepsi. Using light and polarized light microscopy and computer-assisted image analysis, trace evidence and tooth structure from the suspect mouse were matched to scratches and indentions on the suspect can. Scanning electron microscopy and energy dispersive X-ray analysis were used to compare and match particles of gnawed metal from the lid of the suspect can to other particles recovered from the muzzle and stomach of the suspect mouse. The forensic analyses in this case proved the mouse could not have been canned in the soft drink product and refuted the defendant's sworn statements. PMID:9397564

Platek, F; Ranieri, N; Wolnik, K A

1997-11-01

51

Density gradient free electron collisionally excited X-ray laser  

DOEpatents

An operational X-ray laser (30) is provided that amplifies 3p-3s transition X-ray radiation along an approximately linear path. The X-ray laser (30) is driven by a high power optical laser. The driving line focused optical laser beam (32) illuminates a free-standing thin foil (34) that may be associated with a substrate (36) for improved structural integrity. This illumination produces a generally cylindrically shaped plasma having an essentially uniform electron density and temperature, that exists over a long period of time, and provides the X-ray laser gain medium. The X-ray laser (30) may be driven by more than one optical laser beam (32, 44). The X-ray laser (30) has been successfully demonstrated to function in a series of experimental tests.

Campbell, Edward M. (Pleasanton, CA); Rosen, Mordecai D. (Berkeley, CA)

1989-01-01

52

Density gradient free electron collisionally excited x-ray laser  

DOEpatents

An operational x-ray laser is provided that amplifies 3p-3s transition x-ray radiation along an approximately linear path. The x-ray laser is driven by a high power optical laser. The driving line focused optical laser beam illuminates a free-standing thin foil that may be associated with a substrate for improved structural integrity. This illumination produces a generally cylindrically shaped plasma having an essentially uniform electron density and temperature, that exists over a long period of time, and provides the x-ray laser gain medium. The x-ray laser may be driven by more than one optical laser beam. The x-ray laser has been successfully demonstrated to function in a series of experimental tests.

Campbell, E.M.; Rosen, M.D.

1984-11-29

53

Microspectroscopic soft X-ray analysis of keratin based biofibers.  

PubMed

Scanning soft X-ray transmission microspectroscopy (STXM) and transmission electron microscopy (TEM) have been employed for a high-resolution morphological and chemical analysis of hair fibers from human, sheep and alpaca. STXM allows optimum contrast imaging of the main hair building blocks due to tuneable photon energy. Chemical similarities and deviations for the human hair building blocks as well as for the three investigated species are discussed on the basis of the local near-edge X-ray absorption fine structure (NEXAFS). The spectra of melanosomes corroborate the state-of-the-art model for the chemical structure of eumelanin. Complementary TEM micrographs reveal the occurrence of cortex sectioning in alpaca hair to some extent. A spectroscopic analysis for human hair cortex indicates low mass loss upon soft X-ray irradiation, but transformation of chemical species with decreasing amount of peptide bonds and increasing NEXAFS signal for unsaturated carbon-carbon bonds. PMID:25553413

Späth, Andreas; Meyer, Markus; Semmler, Sonja; Fink, Rainer H

2015-03-01

54

X-Ray-Diffraction Tests Of Irradiated Electronic Devices: II  

NASA Technical Reports Server (NTRS)

Report describes research on use of x-ray diffraction to measure stresses in metal conductors of complementary metal oxide/semiconductor (CMOS) integrated circuits exposed to ionizing radiation. Expanding upon report summarized in "X-Ray-Diffraction Tests Of Irradiated Electronic Devices: I" (NPO-18803), presenting data further suggesting relationship between electrical performances of circuits and stresses and strains in metal conductors.

Shaw, David C.; Lowry, Lynn E.; Barnes, Charles E.

1993-01-01

55

X-ray tube with magnetic electron steering  

DOEpatents

An X-ray tube uses a magnetic field to steer electrons. The magnetic field urges electrons toward the anode, increasing the proportion of electrons emitted from the cathode that reach desired portions of the anode and consequently contribute to X-ray production. The magnetic field also urges electrons reflected from the anode back to the anode, further increasing the efficiency of the tube.

Reed, Kim W. (Albuquerque, NM); Turman, Bobby N. (Albuquerque, NM); Kaye, Ronald J. (Albuquerque, NM); Schneider, Larry X. (Albuquerque, NM)

2000-01-01

56

Scanning electron microscopy and X-ray diffraction studies in the analysis of medical materials: Gore-Tex versus braided polyester tape for repair of the incompetent cervix.  

PubMed

Cathodoluminescence in the scanning electron microscope and roentgenogram diffraction studies were applied to the analysis of two different medical materials used in cervical cerclage, the treatment of cervical incompetence. Braided polyester tape or Gore-Tex was used as suture material and was analyzed both before and after use in cerclage of the cervix. Results of SEM and X-ray diffraction studies showed distinct differences between the two materials, with the Gore-Tex demonstrating a superior morphological integrity and a decreased likelihood of phagocyte adhesion. These results correlated well with the clinical observations, which also showed Gore-Tex to be a superior medical material. PMID:10568229

Schoenfeld, A; Goverman, J; Barkay, Z; Nitke, S; Rosenberg, Y; Deutscher, G

2000-01-01

57

Growth and texture of spark plasma sintered Al2O3 ceramics: A combined analysis of X-rays and electron back scatter diffraction  

NASA Astrophysics Data System (ADS)

Textured alumina ceramics were obtained by Spark Plasma Sintering of undoped commercial ?-Al2O3 powders. Various parameters (density, grain growth, grain size distribution) of the alumina ceramics, sintered at two typical temperatures 1400 °C and 1700 °C, are investigated. Quantitative textural and structural analysis, carried out using a combination of Electron Back Scattering Diffraction and X-ray diffraction, are represented in the form of mapping and pole figures. The mechanical properties of these textured alumina ceramics include high elastic modulus and hardness values with high anisotropic nature, opening the door for a large range of applications.

Pravarthana, D.; Chateigner, D.; Lutterotti, L.; Lacotte, M.; Marinel, S.; Dubos, P. A.; Hervas, I.; Hug, E.; Salvador, P. A.; Prellier, W.

2013-04-01

58

X-ray framing camera for pulsed, high current, electron beam x-ray sources  

NASA Astrophysics Data System (ADS)

High power x-ray sources built for nuclear weapons effects testing are evolving toward larger overall diameters and smaller anode cathode gaps. We describe a framing camera developed to measure the time-evolution of these 20-50 ns pulsed x-ray sources produced by currents in the 1.5-2.5 MA range and endpoint voltages between 0.2 and 1.5 MV. The camera has up to 4 frames with 5 ns gate widths; the frames are separated by 5 ns. The image data are recorded electronically with a gated intensified CCD camera and the data are available immediately following a shot. A fast plastic scintillator (2.1 ns decay time) converts the x-rays to visible light and, for high sensitivity, a fiber optic imaging bundle carries the light to the CCD input. Examples of image data are shown.

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

2007-07-01

59

Field Emission Scanning Electron Microscopy (FE-SEM) and Energy Dispersive X-Ray (EDX) Spectroscopy  

E-print Network

system with 30 take-off angle for quantitative analysis, digital imaging, and X-ray mapping. The EDAXField Emission Scanning Electron Microscopy (FE-SEM) and Energy Dispersive X-Ray (EDX) Spectroscopy of objective aperture. Dual SE detectors allow versatile imaging. The FE-SEM is equipped with fully digital

Gelfond, Michael

60

SU-E-J-09: A Monte Carlo Analysis of the Relationship Between Cherenkov Light Emission and Dose for Electrons, Protons, and X-Ray Photons  

SciTech Connect

Purpose: A number of recent studies have proposed that light emitted by the Cherenkov effect may be used for a number of radiation therapy dosimetry applications. Here we investigate the fundamental nature and accuracy of the technique for the first time by using a theoretical and Monte Carlo based analysis. Methods: Using the GEANT4 architecture for medically-oriented simulations (GAMOS) and BEAMnrc for phase space file generation, the light yield, material variability, field size and energy dependence, and overall agreement between the Cherenkov light emission and dose deposition for electron, proton, and flattened, unflattened, and parallel opposed x-ray photon beams was explored. Results: Due to the exponential attenuation of x-ray photons, Cherenkov light emission and dose deposition were identical for monoenergetic pencil beams. However, polyenergetic beams exhibited errors with depth due to beam hardening, with the error being inversely related to beam energy. For finite field sizes, the error with depth was inversely proportional to field size, and lateral errors in the umbra were greater for larger field sizes. For opposed beams, the technique was most accurate due to an averaging out of beam hardening in a single beam. The technique was found to be not suitable for measuring electron beams, except for relative dosimetry of a plane at a single depth. Due to a lack of light emission, the technique was found to be unsuitable for proton beams. Conclusions: The results from this exploratory study suggest that optical dosimetry by the Cherenkov effect may be most applicable to near monoenergetic x-ray photon beams (e.g. Co-60), dynamic IMRT and VMAT plans, as well as narrow beams used for SRT and SRS. For electron beams, the technique would be best suited for superficial dosimetry, and for protons the technique is not applicable due to a lack of light emission. NIH R01CA109558 and R21EB017559.

Glaser, A [Thayer School of Engineering, Dartmouth College, NH (United States); Zhang, R [Department of Physics and Astronomy, Dartmouth College, Hanover, NH (United States); Gladstone, D [Dartmouth Hitchcock Medical Center, Lebanon, NH (Lebanon); Pogue, B [Thayer School of Engineering, Dartmouth College, NH (United States); Department of Physics and Astronomy, Dartmouth College, Hanover, NH (United States)

2014-06-01

61

Atmospheric electron-induced x-ray spectrometer development  

NASA Technical Reports Server (NTRS)

This paper extends the work reported at the IEEE Aerospace conference in 2001 and 2003 where the concept and progress in the development of the so called atmospheric Electron X-ray Spectrometer (AEXS) has been described.

Wilcox, Jaroslava Z.; Urgiles, Eduardo; Toda, Risaku; Crisp, Joy

2005-01-01

62

Spectral analysis of X-ray binaries  

E-print Network

In this thesis, I present work from three separate research projects associated with observations of X-ray binaries. Two of those revolve around spectral characteristics of neutron star low-mass X-ray binaries (NS-LMXBs), ...

Fridriksson, Joel Karl

2011-01-01

63

Synchrotron x-ray fluorescence and extended x-ray absorption fine structure analysis  

SciTech Connect

The advent of dedicated synchrotron radiation sources has led to a significant increase in activity in many areas of science dealing with the interaction of x-rays with matter. Synchrotron radiation provides intense, linearly polarized, naturally collimated, continuously tunable photon beams, which are used to determine not only the elemental composition of a complex, polyatomic, dilute material but also the chemical form of the elements with improved accuracy. Examples of the application of synchrotron radiation include experiments in synchrotron x-ray fluorescence (SXRF) analysis and extended x-ray absorption fine structure (EXAFS) analysis. New synchrotron radiation x-ray microprobes for elemental analysis in the parts per billion range are under construction at several laboratories. 76 references, 24 figures.

Chen, J.R.; Gordon, B.M.; Hanson, A.L.; Jones, K.W.; Kraner, H.W.; Chao, E.C.T.; Minkin, J.A.

1984-01-01

64

Functional biocompatible magnetite-cellulose nanocomposite fibrous networks: Characterization by fourier transformed infrared spectroscopy, X-ray powder diffraction and field emission scanning electron microscopy analysis  

NASA Astrophysics Data System (ADS)

The preparation and characterization of functional biocompatible magnetite-cellulose nano-composite fibrous material is described. Magnetite-cellulose nano-composite was prepared by a combination of the solution-based formation of magnetic nano-particles and subsequent coating with amino celluloses. Characterization was accomplished using X-ray powder diffraction (XRD), fourier transformed infrared (FTIR) and field emission scanning electron microscopy (FESEM) analysis. The peaks of Fe3O4 in the XRD pattern of nanocomposite confirm existence of the nanoparticles in the amino cellulose matrix. Magnetite-cellulose particles exhibit an average diameter of roughly 33 nm as demonstrated by field emission scanning electron microscopy. Magnetite nanoparticles were irregular spheres dispersed in the cellulose matrix. The vibration corresponding to the Nsbnd CH3 functional group about 2850 cm-1 is assigned in the FTIR spectra. Functionalized magnetite-cellulose nano-composite polymers have a potential range of application as targeted drug delivery system in biomedical field.

Habibi, Neda

2015-02-01

65

Molecular orbital study of the primary electron donor P700 of photosystem I based on a recent X-ray single crystal structure analysis  

NASA Astrophysics Data System (ADS)

The X-ray structure analysis of photosystem (PS) I single crystals showed that the primary electron donor P700 is a heterodimer formed by one chlorophyll (Chl) a and one Chl a' [Nature 411 (2001) 909]. The electronic structure of the cation radical P700 + rad of the primary donor, which is created in the charge separation process, has been probed by semiempirical molecular orbital calculations including spin polarization effects (RHF-INDO/SP). The calculations, which were based on the X-ray structure, clearly show that P700 is a supermolecule formed by two chlorophyll species. They furthermore predict an asymmetrical charge and spin density distribution in favor of the monomeric Chl a half of this dimer in accordance with results from earlier EPR and ENDOR studies [J. Phys. Chem. B 105 (2000) 1225]. The stepwise inclusion of various electrostatic interactions of the dimer with its nearest surrounding (one threonine forming a hydrogen bond to the keto group of Chl a' and two histidines liganding the Mg atoms of the two chlorophylls) leads to a systematic enhancement of this electronic asymmetry yielding a spin density ratio of almost 5:1 as also found experimentally. A large part of this value is caused by spin polarization effects. This result is only weakly affected by the electrostatic field of more remote amino acid residues and other pigment molecules ('accessory' Chl a molecules) present in PS I. A separate group of calculations involving local geometry optimizations by energy minimization techniques yields a further enhancement of the spin density asymmetry. A particularly strong effect is obtained by allowing for variations of the geometry of the vinyl groups on both chlorophylls of the P700 dimer. Theoretical results for individual isotropic proton and nitrogen hyperfine coupling constants, showing a satisfactory agreement with experimental findings, are also presented.

Plato, Martin; Krauß, Norbert; Fromme, Petra; Lubitz, Wolfgang

2003-11-01

66

Femtosecond all-optical synchronization of an X-ray free-electron laser.  

PubMed

Many advanced applications of X-ray free-electron lasers require pulse durations and time resolutions of only a few femtoseconds. To generate these pulses and to apply them in time-resolved experiments, synchronization techniques that can simultaneously lock all independent components, including all accelerator modules and all external optical lasers, to better than the delivered free-electron laser pulse duration, are needed. Here we achieve all-optical synchronization at the soft X-ray free-electron laser FLASH and demonstrate facility-wide timing to better than 30?fs r.m.s. for 90?fs X-ray photon pulses. Crucially, our analysis indicates that the performance of this optical synchronization is limited primarily by the free-electron laser pulse duration, and should naturally scale to the sub-10 femtosecond level with shorter X-ray pulses. PMID:25600823

Schulz, S; Grguraš, I; Behrens, C; Bromberger, H; Costello, J T; Czwalinna, M K; Felber, M; Hoffmann, M C; Ilchen, M; Liu, H Y; Mazza, T; Meyer, M; Pfeiffer, S; Pr?dki, P; Schefer, S; Schmidt, C; Wegner, U; Schlarb, H; Cavalieri, A L

2015-01-01

67

Femtosecond all-optical synchronization of an X-ray free-electron laser  

NASA Astrophysics Data System (ADS)

Many advanced applications of X-ray free-electron lasers require pulse durations and time resolutions of only a few femtoseconds. To generate these pulses and to apply them in time-resolved experiments, synchronization techniques that can simultaneously lock all independent components, including all accelerator modules and all external optical lasers, to better than the delivered free-electron laser pulse duration, are needed. Here we achieve all-optical synchronization at the soft X-ray free-electron laser FLASH and demonstrate facility-wide timing to better than 30?fs r.m.s. for 90?fs X-ray photon pulses. Crucially, our analysis indicates that the performance of this optical synchronization is limited primarily by the free-electron laser pulse duration, and should naturally scale to the sub-10 femtosecond level with shorter X-ray pulses.

Schulz, S.; Grguraš, I.; Behrens, C.; Bromberger, H.; Costello, J. T.; Czwalinna, M. K.; Felber, M.; Hoffmann, M. C.; Ilchen, M.; Liu, H. Y.; Mazza, T.; Meyer, M.; Pfeiffer, S.; Pr?dki, P.; Schefer, S.; Schmidt, C.; Wegner, U.; Schlarb, H.; Cavalieri, A. L.

2015-01-01

68

Femtosecond all-optical synchronization of an X-ray free-electron laser  

PubMed Central

Many advanced applications of X-ray free-electron lasers require pulse durations and time resolutions of only a few femtoseconds. To generate these pulses and to apply them in time-resolved experiments, synchronization techniques that can simultaneously lock all independent components, including all accelerator modules and all external optical lasers, to better than the delivered free-electron laser pulse duration, are needed. Here we achieve all-optical synchronization at the soft X-ray free-electron laser FLASH and demonstrate facility-wide timing to better than 30?fs r.m.s. for 90?fs X-ray photon pulses. Crucially, our analysis indicates that the performance of this optical synchronization is limited primarily by the free-electron laser pulse duration, and should naturally scale to the sub-10 femtosecond level with shorter X-ray pulses. PMID:25600823

Schulz, S.; Grguraš, I.; Behrens, C.; Bromberger, H.; Costello, J. T.; Czwalinna, M. K.; Felber, M.; Hoffmann, M. C.; Ilchen, M.; Liu, H. Y.; Mazza, T.; Meyer, M.; Pfeiffer, S.; Pr?dki, P.; Schefer, S.; Schmidt, C.; Wegner, U.; Schlarb, H.; Cavalieri, A. L.

2015-01-01

69

The History of X-ray Free-Electron Lasers  

SciTech Connect

The successful lasing at the SLAC National Accelerator Laboratory of the Linear Coherent Light Source (LCLS), the first X-ray free-electron laser (X-ray FEL), in the wavelength range 1.5 to 15 {angstrom}, pulse duration of 60 to few femtoseconds, number of coherent photons per pulse from 10{sup 13} to 10{sup 11}, is a landmark event in the development of coherent electromagnetic radiation sources. Until now electrons traversing an undulator magnet in a synchrotron radiation storage ring provided the best X-ray sources. The LCLS has set a new standard, with a peak X-ray brightness higher by ten orders of magnitudes and pulse duration shorter by three orders of magnitudes. LCLS opens a new window in the exploration of matter at the atomic and molecular scales of length and time. Taking a motion picture of chemical processes in a few femtoseconds or less, unraveling the structure and dynamics of complex molecular systems, like proteins, are some of the exciting experiments made possible by LCLS and the other X-ray FELs now being built in Europe and Asia. In this paper, we describe the history of the many theoretical, experimental and technological discoveries and innovations, starting from the 1960s and 1970s, leading to the development of LCLS.

Pellegrini, C.; /UCLA /SLAC; ,

2012-06-28

70

Electron injectors for next-generation x-ray sources  

Microsoft Academic Search

Next generation x-ray sources require very high-brightness electron beams that are typically at or beyond the present state-of-the-art, and thus place stringent and demanding requirements upon the electron injector parameters. No one electron source concept is suitable for all the diverse applications envisaged, which have operating characteristics ranging from high-average-current, quasi-CW, to high-peak-current, single-pulse electron beams. Advanced Energy Systems, in

Hans P. Bluem; Alan M. M. Todd; Ilan Ben-Zvi; Michael D. Cole; Pat Colestock; Dietmar Janssen; John W. Lewellen; George R. Neil; Dinh C. Nguyen; Larry Phillips; Joe Preble; John Rathke; Tom Schultheiss; Triveni Srinivasan-Rao; Richard L. Wood; Lloyd M. Young

2004-01-01

71

HARD X-RAY OBSERVATIONS OF A JET AND ACCELERATED ELECTRONS IN THE CORONA  

SciTech Connect

We report the first hard X-ray observation of a solar jet on the limb with flare footpoints occulted, so that faint emission from accelerated electrons in the corona can be studied in detail. In this event on 2003 August 21, RHESSI observed a double coronal hard X-ray source in the pre-impulsive phase at both thermal and nonthermal energies. In the impulsive phase, the first of two hard X-ray bursts consists of a single thermal/nonthermal source coinciding with the lower of the two earlier sources, and the second burst shows an additional nonthermal, elongated source, spatially and temporally coincident with the coronal jet. Analysis of the jet hard X-ray source shows that collisional losses by accelerated electrons can deposit enough energy to generate the jet. The hard X-ray time profile above 20 keV matches that of the accompanying Type III and broadband gyrosynchrotron radio emission, indicating both accelerated electrons escaping outward along the jet path and electrons trapped in the flare loop. The double coronal hard X-ray source, the open field lines indicated by Type III bursts, and the presence of a small post-flare loop are consistent with significant electron acceleration in an interchange reconnection geometry.

Glesener, Lindsay; Lin, R. P.; Krucker, Saem, E-mail: glesener@ssl.berkeley.edu [Space Science Laboratory, UC Berkeley, 7 Gauss Way, Berkeley, CA 94720 (United States)

2012-07-20

72

Molecular Imaging Using X-Ray Free-Electron Lasers  

NASA Astrophysics Data System (ADS)

The opening of hard X-ray free-electron laser facilities, such as the Linac Coherent Light Source (LCLS) at SLAC National Accelerator Laboratory in the United States, has ushered in a new era in structural determination. With X-ray pulse durations down to 10 fs or shorter, and up to 1013 transversely coherent photons per pulse in a narrow spectral bandwidth, focused irradiances of 1018 to 1021 W cm-2 or higher can be produced at X-ray energies ranging from 500 eV to 10 keV. New techniques for determining the structure of systems that cannot be crystallized and for studying the time-resolved behavior of irreversible reactions at femtosecond timescales are now available.

Barty, Anton; Küpper, Jochen; Chapman, Henry N.

2013-04-01

73

Molecular imaging using X-ray free-electron lasers.  

PubMed

The opening of hard X-ray free-electron laser facilities, such as the Linac Coherent Light Source (LCLS) at SLAC National Accelerator Laboratory in the United States, has ushered in a new era in structural determination. With X-ray pulse durations down to 10 fs or shorter, and up to 10(13) transversely coherent photons per pulse in a narrow spectral bandwidth, focused irradiances of 10(18) to 10(21) W cm(-2) or higher can be produced at X-ray energies ranging from 500 eV to 10 keV. New techniques for determining the structure of systems that cannot be crystallized and for studying the time-resolved behavior of irreversible reactions at femtosecond timescales are now available. PMID:23331310

Barty, Anton; Küpper, Jochen; Chapman, Henry N

2013-01-01

74

Deducing Electron Properties from Hard X-Ray Observations  

NASA Technical Reports Server (NTRS)

X-radiation from energetic electrons is the prime diagnostic of flare-accelerated electrons. The observed X-ray flux (and polarization state) is fundamentally a convolution of the cross-section for the hard X-ray emission process(es) in question with the electron distribution function, which is in turn a function of energy, direction, spatial location and time. To address the problems of particle propagation and acceleration one needs to infer as much information as possible on this electron distribution function, through a deconvolution of this fundamental relationship. This review presents recent progress toward this goal using spectroscopic, imaging and polarization measurements, primarily from the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). Previous conclusions regarding the energy, angular (pitch angle) and spatial distributions of energetic electrons in solar flares are critically reviewed. We discuss the role and the observational evidence of several radiation processes: free-free electron-ion, free-free electron-electron, free-bound electron-ion, photoelectric absorption and Compton backscatter (albedo), using both spectroscopic and imaging techniques. This unprecedented quality of data allows for the first time inference of the angular distributions of the X-ray-emitting electrons and improved model-independent inference of electron energy spectra and emission measures of thermal plasma. Moreover, imaging spectroscopy has revealed hitherto unknown details of solar flare morphology and detailed spectroscopy of coronal, footpoint and extended sources in flaring regions. Additional attempts to measure hard X-ray polarization were not sufficient to put constraints on the degree of anisotropy of electrons, but point to the importance of obtaining good quality polarization data in the future.

Kontar, E. P.; Brown, J. C.; Emslie, A. G.; Hajdas, W.; Holman, G. D.; Hurford, G. J.; Kasparova, J.; Mallik, P. C. V.; Massone, A. M.; McConnell, M. L.; Piana, M.; Prato, M.; Schmahl, E. J.; Suarez-Garcia, E.

2011-01-01

75

Analysis of electronic structure of amorphous InGaZnO/SiO{sub 2} interface by angle-resolved X-ray photoelectron spectroscopy  

SciTech Connect

The electronic structures of amorphous indium gallium zinc oxide (a-IGZO) on a SiO{sub 2} layers before and after annealing were observed by constant final state X-ray photoelectron spectroscopy (CFS-XPS) and X-ray adsorption near-edge structure spectroscopy (XANES). From the results of angle-resolved CFS-XPS, the change in the electronic state was clearly observed in the a-IGZO bulk rather than in the a-IGZO/SiO{sub 2} interface. This suggests that the electronic structures of the a-IGZO bulk strongly affected the thin-film transistor characteristics. The results of XANES indicated an increase in the number of tail states upon atmospheric annealing (AT). We consider that the increase in the number of tail states decreased the channel mobility of AT samples.

Ueoka, Y.; Ishikawa, Y.; Maejima, N.; Matsui, F.; Matsui, H.; Yamazaki, H.; Urakawa, S.; Horita, M.; Daimon, H.; Uraoka, Y. [Graduate School of Materials Science, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0192 (Japan)] [Graduate School of Materials Science, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0192 (Japan)

2013-10-28

76

Analysis of electronic structure of amorphous InGaZnO/SiO2 interface by angle-resolved X-ray photoelectron spectroscopy  

NASA Astrophysics Data System (ADS)

The electronic structures of amorphous indium gallium zinc oxide (a-IGZO) on a SiO2 layers before and after annealing were observed by constant final state X-ray photoelectron spectroscopy (CFS-XPS) and X-ray adsorption near-edge structure spectroscopy (XANES). From the results of angle-resolved CFS-XPS, the change in the electronic state was clearly observed in the a-IGZO bulk rather than in the a-IGZO/SiO2 interface. This suggests that the electronic structures of the a-IGZO bulk strongly affected the thin-film transistor characteristics. The results of XANES indicated an increase in the number of tail states upon atmospheric annealing (AT). We consider that the increase in the number of tail states decreased the channel mobility of AT samples.

Ueoka, Y.; Ishikawa, Y.; Maejima, N.; Matsui, F.; Matsui, H.; Yamazaki, H.; Urakawa, S.; Horita, M.; Daimon, H.; Uraoka, Y.

2013-10-01

77

Electron injectors for next-generation x-ray sources  

SciTech Connect

Next generation x-ray sources require very high-brightness electron beams that are typically at or beyond the present state-of-the-art, and thus place stringent and demanding requirements upon the electron injector parameters. No one electron source concept is suitable for all the diverse applications envisaged, which have operating characteristics ranging from high-average-current, quasi-CW, to high-peak-current, single-pulse electron beams. Advanced Energy Systems, in collaboration with various partners, is developing several electron injector concepts for these x-ray source applications. The performance and design characteristics of five specific RF injectors, spanning ''L'' to ''X''-band, normal-conducting to superconducting, and low repetition rate to CW, which are presently in various stages of design, construction or testing, is described. We also discuss the status and schedule of each with respect to testing.

Hans P. Bluem; Alan M. M. Todd; Ilan Ben-Zvi; Michael D. Cole; Pat Colestock; Dietmar Janssen; John W. Lewellen; George R. Neil; Dinh C. Nguyen; Larry Phillips; Joe Preble; John Rathke; Tom Schultheiss; Triveni Srinivasan-Rao; Richard L. Wood; Lloyd M. Young

2004-11-01

78

Remote X-Ray Diffraction and X-Ray Fluorescence Analysis on Planetary Surfaces  

NASA Technical Reports Server (NTRS)

The legacy of planetary X-ray Diffraction (XRD) and X-ray Fluorescence (XRF) began in 1960 when W. Parish proposed an XRD instrument for deployment on the moon. The instrument was built and flight qualified, but the Lunar XRD program was cancelled shortly before the first human landing in 1969. XRF chemical data have been collected in situ by surface landers on Mars (Viking 1 & 2, Pathfinder) and Venus (Venera 13 & 14). These highly successful experiments provide critical constraints on our current understanding of surface processes and planetary evolution. However, the mineralogy, which is more critical to planetary surface science than simple chemical analysis, will remain unknown or will at best be imprecisely constrained until X-ray diffraction (XRD) data are collected. Recent progress in X-ray detector technology allows the consideration of simultaneous XRD (mineralogic analysis) and high-precision XRF (elemental analysis) in systems miniaturized to the point where they can be mounted on fixed landers or small robotic rovers. There is a variety of potential targets for XRD/XRF equipped landers within the solar system, the most compelling of which are the poles of the moon, the southern highlands of Mars and Europa.

Blake, David F.; DeVincenzi, D. (Technical Monitor)

1999-01-01

79

Harmonic lasing in x-ray free electron lasers  

NASA Astrophysics Data System (ADS)

Harmonic lasing in a free electron laser with a planar undulator (under the condition that the fundamental frequency is suppressed) might be a cheap and efficient way of extension of wavelength ranges of existing and planned x-ray free electron laser (FEL) facilities. Contrary to nonlinear harmonic generation, harmonic lasing can provide much more intense, stable, and narrow-band FEL beam which is easier to handle due to the suppressed fundamental frequency. In this paper we perform a parametrization of the solution of the eigenvalue equation for lasing at odd harmonics, and present an explicit expression for FEL gain length, taking into account all essential effects. We propose and discuss methods for suppression of the fundamental harmonic. We also suggest a combined use of harmonic lasing and lasing at the retuned fundamental wavelength in order to reduce bandwidth and to increase brilliance of x-ray beam at saturation. Considering 3rd harmonic lasing as a practical example, we come to the conclusion that it is much more robust than usually thought, and can be widely used in the existing or planned x-ray FEL (XFEL) facilities. In particular, Linac Coherent Light Source (LCLS) after a minor modification can lase to saturation at the 3rd harmonic up to the photon energy of 25-30 keV providing multigigawatt power level and narrow bandwidth. As for the European XFEL, harmonic lasing would allow one to extend operating range (ultimately up to 100 keV), to reduce FEL bandwidth and to increase brilliance, to enable two-color operation for pump-probe experiments, and to provide more flexible operation at different electron energies. Similar improvements can be realized in other x-ray FEL facilities with gap-tunable undulators like FLASH II, SACLA, LCLS II, etc. Harmonic lasing can be an attractive option for compact x-ray FELs (driven by electron beams with a relatively low energy), allowing the use of the standard undulator technology instead of small-gap in-vacuum devices. Finally, in this paper we discover that in a part of the parameter space, corresponding to the operating range of soft x-ray beam lines of x-ray FEL facilities (like SASE3 beam line of the European XFEL), harmonics can grow faster than the fundamental wavelength. This feature can be used in some experiments, but might also be an unwanted phenomenon, and we discuss possible measures to diminish it.

Schneidmiller, E. A.; Yurkov, M. V.

2012-08-01

80

Fundamental physics at an X-ray free electron laser  

Microsoft Academic Search

X-ray free electron lasers (FELs) have been proposed to be constructed both at SLAC in the form of the so-called Linac Coherent Light Source as well as at DESY, where the so-called XFEL laboratory is part of the design of the electron-positron linear collider TESLA. In addition to the immediate applications in condensed matter physics, chemistry, material science, and structural

A. Ringwald

2001-01-01

81

X-Ray Diffraction Analysis Program  

NASA Technical Reports Server (NTRS)

SOPAD separates overlapping peaks and analyzes derivatives of X-ray diffraction data. SOPAD helps analyst get most information out of available diffraction data. SOPAD uses Marquardt-type nonlinear regression routine to refine initial estimates of individual peak positions, intensities, shapes, and half-widths.

Wiedemann, K. E.; Unnam, J.; Naidu, S. V. N.; Houska, C. R.

1986-01-01

82

A compact x-ray free electron laser  

SciTech Connect

We present a design concept and simulation of the performance of a compact x-ray, free electron laser driven by ultra-high gradient rf-linacs. The accelerator design is based on recent advances in high gradient technology by a LLNL/SLAC/LBL collaboration and on the development of bright, high current electron sources by BNL and LANL. The GeV electron beams generated with such accelerators can be concerted to soft x-rays in the range from 2--10 nm by passage through short period, high fields strength wigglers as are being designed at Rocketdyne. Linear light sources of this type can produce trains of picosecond (or shorter) pulses of extremely high spectral brilliance suitable for flash holography of biological specimens in vivo and for studies of fast chemical reactions. 12 refs., 8 figs., 4 tabs.

Barletta, W.; Attac, M.; Cline, D.B.; Kolonko, J.; Wang, X.; Bhowmik, A.; Bobbs, B.; Cover, R.A.; Dixon, F.P.; Rakowsky, G.; Gallardo, J.; Pellegrini, C.; Westenskow, G.

1988-09-09

83

Aerosols over the Amazon Rainforest Investigated by Scanning Transmission X-ray Microscopy and Scanning Electron Microscopy  

Microsoft Academic Search

We collected atmospheric aerosols over the central Amazon Basin near Manaus, Brazil, during the wet season in February 2008, as part of the AMAZE-08 (Amazonian Aerosol Characterization Experiment) campaign. Aerosol samples were analyzed by Scanning Transmission X-ray Microscopy (STXM) coupled with Near-Edge X-ray Absorption Fine Structure Spectroscopy (NEXAFS) and Scanning Electron Microscopy (SEM) coupled with Energy-Dispersive X-ray Analysis (EDX). A

M. O. Andreae; P. P. Artaxo; M. K. Gilles; S. T. Martin; E. Mikhailov; R. Moffet; U. Poeschl; B. Sinha; H. Yang

2009-01-01

84

Spectral Analysis of X-Ray Binaries  

NASA Astrophysics Data System (ADS)

In this thesis, I present work from three separate research projects associated with observations of X-ray binaries. Two of those revolve around spectral characteristics of neutron star low-mass X-ray binaries (NS-LMXBs), with a particular source, XTE J1701-462, playing a central role. First, I construct and study color-color and hardness-intensity diagrams (CDs and HIDs) for a large sample of NS-LMXBs using Rossi X-ray Timing Explorer (RXTE) data spanning ~15 years. I study in particular detail three sources whose complicated CDs/HIDs are strongly affected by secular motion -- Cyg X-2, Cir X-1, and GX 13+1 -- and show that Cyg X-2 and Cir X-1 display CD/HID evolution with strong similarities to the transient Z source XTE J1701-462, which was previously shown to have evolved through all subclasses of NS-LMXBs as a result of changes in mass accretion rate. I build on the results for XTE J1701-462, Cyg X-2, and Cir X-1 and rank all the sources in the sample based only on their CD/HID morphology. I speculate that this represents a rough ranking in terms of the relative ranges in mass accretion rate experienced by the sources. Next, I use data from RXTE, Swift, Chandra, and XMM-Newton to study the transition to quiescence and the first ~1200 days of the quiescent phase of XTE J1701-462 following the end of its extraordinarily luminous 19 month outburst in 2006-2007. I find that the crust of the neutron star cooled rapidly during the first ~200 days of quiescence, after having been heated out of thermal equilibrium with the core during the outburst; the source has subsequently shown slower cooling along with sporadic low-level accretion activity. I discuss the implications of the observed cooling behavior and low-level accretion, the former of which yields information on the internal properties of the neutron star. Finally, I use multiple Chandra observations to study the X-ray source populations in the late-type galaxies NGC 6946 and NGC 4485/4490. A particular emphasis is placed on investigating the long-term variability of the sources, several of which are ultraluminous. I present detailed source catalogs and characterize the populations -- which consist primarily of X-ray binaries -- using X-ray luminosity functions and CDs.

Fridriksson, Joel K.

2011-09-01

85

Characterization of AN Electron-Cyclotron - Mirror Plasma as a Soft X-Ray Source for X-Ray Lithography  

NASA Astrophysics Data System (ADS)

There exists an international race to reduce the linewidths of integrated circuits to the sub-micron level. The results of this race are likely to have a strong impact on both the economic and military independence of this country as our society relies more and more heavily on highly sophisticated electronic equipment in our daily lives and in the defense of the country. One of the leading technologies in attaining sub-micron linewidths is x-ray lithography. Results from the ECRIAXS computer code have suggested that a laboratory-sized electron-cyclotron-resonance -heated mirror plasma may be a viable source for x-ray lithography. This work attempts to investigate this suggestion. A foil-filtered x-ray PIN diode and an x-ray pinhole camera have been used to measure x-ray intensities from krypton and neon plasma. The spatially resolved spectral density of the negatives from the x-ray pinhole camera has been measured. A film modeling code (FILM) has been written which predicts the film response. The code includes the integrated spectral response of the film to plasma x-ray emission that has been filtered by a beryllium foil filter. The PIN diode also yields electron temperatures for the plasmas (T_{rm e} ~ 1.3-4.0 keV). The intensity measurements are compared to computations from the ECRIAXS code. The measurements of the spectrally integrated x-ray intensity are supplemented by the measurement of plasma parameters that can be directly compared with some of the ECRIAXS code outputs. It has been found that the plasma densities that are predicted by the code (e.g. 1.75 times 10^{12 } cm^{-3}) are significantly higher than the experimental measurements (e.g. 4.5 times 10^ {11} cm^{-3} ). Modifications to the code can explain some of the discrepancies; however, the results are reliable only to within an order of magnitude.

Goodman, Timothy Paul

86

Aluminum Alloy X-ray Image Classification Using Texture Analysis  

Microsoft Academic Search

This paper presents an automatic classification approach to the X-ray image classification issue of aluminum alloy by image texture analysis methods. Different from the common processing methods, the texture-based approach (XTexture) treats the X-ray image as a special texture image for further processing. By extracting self-correlation moment and wavelet-coefficient moments as the basic classification features based on image texture analysis,

Jun Lu; Qiuqi Ruan

2006-01-01

87

X ray microscope assembly and alignment support and advanced x ray microscope design and analysis  

NASA Technical Reports Server (NTRS)

Considerable efforts have been devoted recently to the design, analysis, fabrication, and testing of spherical Schwarzschild microscopes for soft x ray application in microscopy and projection lithography. The spherical Schwarzschild microscope consists of two concentric spherical mirrors configured such that the third order spherical aberration and coma are zero. Since multilayers are used on the mirror substrates for x ray applications, it is desirable to have only two reflecting surfaces in a microscope. In order to reduce microscope aberrations and increase the field of view, generalized mirror surface profiles have been considered in this investigation. Based on incoherent and sine wave modulation transfer function (MTF) calculations, the object plane resolution of a microscope has been analyzed as a function of the object height and numerical aperture (NA) of the primary for several spherical Schwarzschild, conic, and aspherical head reflecting two mirror microscope configurations.

Shealy, David L.

1991-01-01

88

Elemental analysis and fine structure of mitochondrial granules in growth plate chondrocytes studied by electron energy loss spectroscopy and energy dispersive X-ray microanalysis.  

PubMed

Electron energy loss spectrometry--EELS, and energy dispersive X-ray microanalysis--XRMA, were used to study the elemental composition of mitochondrial dense granules-mdg. The study was performed on dry cut thin sections (80-200 nm) of freeze-dried and low temperature embedded cartilage. Results obtained by means of XRMA clearly showed high phosphorus and calcium content in the mdg. Using EELS at 100 kV primary voltage we found that small concentrations of elements (i.e. below typically 1% atomic weight) are difficult to analyze and map, this especially in sections thicker than 50-60 nm. Surprisingly, analysis of calcium can be successfully performed on thicker sections though the edge lies above the carbon K edge while this is not possible for the phosphorus edge which is located at lower energies. This is likely due to the edge shapes (sharp for calcium and delayed for phosphorus), and to the more intense contribution of multiple low loss scattering in the background for phosphorus between 100 and 130 eV. By means of EELS elemental mapping a centrally located core was found in numerous mdg. In the calcium map the signal was strongest in the middle of mdg which corresponds to the area of reduced carbon signal. We found that carbon maps might be used for high resolution structural studies of chemically unfixed and anhydrously processed biological tissues. As carbon is the main constituent of Lowicryl resin its distribution is reversed to the distribution of biological tissue in which the proportion of carbon is lower, but is proportional to water content in the specimen in vivo. Use of EELS in combination with electron microscope with accelerating voltages in range of 140-200 kV together with anhydrous techniques of the tissue preparation will provide a new type of information which might lead to better understanding of the etiology and function of small structures in the cell. PMID:1808719

Wroblewski, J; Wróblewski, R; Mory, C; Colliex, C

1991-09-01

89

Femtosecond diffractive imaging with a soft-X-ray free-electron laser  

E-print Network

LETTERS Femtosecond diffractive imaging with a soft-X-ray free-electron laser HENRY N. CHAPMAN1 of this principle using the FLASH soft-X-ray free-electron laser. An intense 25 fs, 4 Ã? 1013 W cm-2 pulse by one10 . X-ray free-electron lasers (FELs) are expected to permit diffractive imaging at high

Loss, Daniel

90

Note: Studies on x-ray production in electron cyclotron resonance x-ray source based on ridged cylindrical cavity  

SciTech Connect

A ridged cylindrical cavity has been designed using MICROWAVE STUDIO programme and it is used in the electron cyclotron resonance (ECR) x-ray source. The experimental parameters of the source are optimized for maximizing the x-ray output, and an x-ray dose rate of {approx}1000 {mu}Sv/h was observed at 20 cm from the port, for 500 W of microwave power without using any target. With the molybdenum target located at optimum position of the ridged cavity, the dose rate is found to be increased only by 10%. In order to understand the experimental observation, the electric field pattern of the cavity with the target placed at various radial distances is studied. In this note, the experimental and theoretical studies on ECR x-ray source using the ridged cylindrical cavity are presented.

Selvakumaran, T. S.; Baskaran, R. [Radiological Safety Division, Indira Gandhi Center for Atomic Research, Kalpakkam, Tamilnadu 603102 (India)

2012-02-15

91

Coherent electron beam density modulator for driving X-ray free electron lasers  

NASA Astrophysics Data System (ADS)

We propose a new compact scheme for a Free Electron Laser with more coherent properties for the X-ray beam. Higher FEL performance would be achieved using a train of electron bunches initially accelerated in a linear accelerator. Similar to the RF klystron concept, we propose developing an X-ray FEL which consists of two parts: an X-ray self-seeding electron beam density modulator and an output set of undulators. A density modulator consists of a low-Q X-ray cavity and an undulator, which is placed between the cavity mirrors. We use this undulator as a very high gain amplifier, which compensates the amplitude loss due to monochromatic X-ray reflections from the mirrors. Following the X-ray cavity, the density modulated electron beam is separated from the X-ray beam and then enters the output set of undulators. The frequency spectrum of the final X-ray beam is determined mainly by the bandwidth of the reflected elements in the X-ray cavity.

Novokhatski, A.; Decker, F.-J.; Hettel, B.; Nosochkov, Yu.; Sullivan, M.

2015-02-01

92

Defect Analysis in Crystals using X-ray Topography  

SciTech Connect

A brief review of X-ray topography - a nondestructive method for direct observation and characterization of defects in single crystals - is presented here. The origin and development of this characterization method and the different techniques derived from it are described. Emphasis is placed on synchrotron X-ray topography and its application in studying various crystal imperfections. Mechanisms of contrast formation on X-ray topographs are discussed, with emphasis on contrast associated with dislocations. Determination of Burgers vectors and line directions of dislocations from analysis of X-ray topographs is explained. Contrast from inclusions is illustrated, and their differentiation from dislocations is demonstrated with the aid of simulated topographs. Contrast arising from the deformation fields associated with cracks is also briefly covered.

Raghothamachar,B.; Dhanaraj, G.; Bai, J.; Dudley, M.

2006-01-01

93

Measurement of total calcium in neurons by electron probe X-ray microanalysis.  

PubMed

In this article the tools, techniques, and instruments appropriate for quantitative measurements of intracellular elemental content using the technique known as electron probe microanalysis (EPMA) are described. Intramitochondrial calcium is a particular focus because of the critical role that mitochondrial calcium overload plays in neurodegenerative diseases. The method is based on the analysis of X-rays generated in an electron microscope (EM) by interaction of an electron beam with the specimen. In order to maintain the native distribution of diffusible elements in electron microscopy specimens, EPMA requires "cryofixation" of tissue followed by the preparation of ultrathin cryosections. Rapid freezing of cultured cells or organotypic slice cultures is carried out by plunge freezing in liquid ethane or by slam freezing against a cold metal block, respectively. Cryosections nominally 80 nm thick are cut dry with a diamond knife at ca. -160 °C, mounted on carbon/pioloform-coated copper grids, and cryotransferred into a cryo-EM using a specialized cryospecimen holder. After visual survey and location mapping at ?-160 °C and low electron dose, frozen-hydrated cryosections are freeze-dried at -100 °C for ~30 min. Organelle-level images of dried cryosections are recorded, also at low dose, by means of a slow-scan CCD camera and subcellular regions of interest selected for analysis. X-rays emitted from ROIs by a stationary, focused, high-intensity electron probe are collected by an energy-dispersive X-ray (EDX) spectrometer, processed by associated electronics, and presented as an X-ray spectrum, that is, a plot of X-ray intensity vs. energy. Additional software facilitates: 1) identification of elemental components by their "characteristic" peak energies and fingerprint; and 2) quantitative analysis by extraction of peak areas/background. This paper concludes with two examples that illustrate typical EPMA applications, one in which mitochondrial calcium analysis provided critical insight into mechanisms of excitotoxic injury and another that revealed the basis of ischemia resistance. PMID:24300079

Pivovarova, Natalia B; Andrews, S Brian

2013-01-01

94

Correlated Observations of Auroral Arcs, Electrons, and X Rays from a DMSP Satellite  

Microsoft Academic Search

The first simultaneous observations made from a single DMSP satellite of visible auroral arcs, precipitating primary electrons, and atmospheric bremsstrahlung X rays are presented for a magnetically disturbed auroral event. Measured electron fluxes were used to compute absolute X ray distributions expected at the satellite altitude. The agreement between the calculated and measured X ray spectra is sufficiently good to

P. F. Mizera; J. G. Luhmann; W. A. Kolasinski; J. B. Blake

1978-01-01

95

Probing electronic structure and chemical bonding with x-ray spectroscopy  

NASA Astrophysics Data System (ADS)

The availability of synchrotron sources has expanded significantly the use of x-ray photoelectron (PE) and photoabsorption (PA) spectroscopy to probe the molecular electronic structure and to test the various bonding models the understanding of which is central to all aspects of chemistry. All features observed in x-ray spectra result from electronic transitions within the molecule, which are in turn determined by the molecular electronic structure. For this Ph.D. thesis, x-ray Photoelectron and photoabsorption spectra were measured for a variety of small model molecules. Of particular interest were simple compounds containing nitrogen, oxygen, chlorine and fluorine bound to phosphorus and sulphur wherein these latter elements exist in a highly oxidized valence state, because the state of bonding in these molecules is not well understood. The experiments were conducted at the Canadian Synchrotron Radiation Facility (CSRF) located at the Synchrotron Radiation Center (SRC), University of Wisconsin, Madison, Wisconsin. A synchrotron light source displays several unique features ideal for x-ray spectroscopy. The light produced has a continuous frequency distribution from the ultraviolet to the x-ray region-specific frequencies can be selected with a monochromator, and finally, the light produced is intense, collimated and polarized. An of these properties contribute to the measurement of very high resolution x-ray spectra. The research program involved the collection of experimental spectra of carefully selected compounds in the gas phase, which simplified analysis because all the observed spectral structure results from the electronic structure of the molecule without crystal lattice or intermolecular interaction effects. The experimental spectra were compared with the results of electronic structure calculations done with MS-Xalpha and Gaussian-94 programs. This comparison with experimental results allows the evaluation of the theory and refinement of the bonding model.

Jurgensen, Astrid

1999-11-01

96

Hard x-ray or gamma ray laser by a dense electron beam  

SciTech Connect

A dense electron beam propagating through a laser undulator can radiate a coherent x-ray or gamma ray. This lasing scheme is studied with the Landau damping theory. The analysis suggests that, with currently available physical parameters, coherent gamma rays of up to 50 keV can be generated. The electron quantum diffraction suppresses the free electron laser action, which limits the maximum radiation.

Son, S. [18 Caleb Lane, Princeton, New Jersey 08540 (United States); Joon Moon, Sung [8 Benjamin Rush Ln., Princeton, New Jersey 08540 (United States)

2012-06-15

97

Toward atomic resolution diffractive imaging of isolated molecules with x-ray free-electron lasers  

E-print Network

We give a detailed account of the theoretical analysis and the experimental results of an x-ray-diffraction experiment on quantum-state selected and strongly laser-aligned gas-phase ensembles of the prototypical large asymmetric rotor molecule 2,5-diiodobenzonitrile, performed at the Linac Coherent Light Source [Phys. Rev. Lett. 112, 083002 (2014)]. This experiment is the first step toward coherent diffractive imaging of structures and structural dynamics of isolated molecules at atomic resolution, i. e., picometers and femtoseconds, using x-ray free-electron lasers.

Stern, Stephan; Filsinger, Frank; Rouzée, Arnaud; Rudenko, Artem; Johnsson, Per; Martin, Andrew V; Barty, Anton; Bostedt, Christoph; Bozek, John D; Coffee, Ryan N; Epp, Sascha; Erk, Benjamin; Foucar, Lutz; Hartmann, Robert; Kimmel, Nils; Kühnel, Kai-Uwe; Maurer, Jochen; Messerschmidt, Marc; Rudek, Benedikt; Starodub, Dmitri G; Thøgersen, Jan; Weidenspointner, Georg; White, Thomas A; Stapelfeldt, Henrik; Rolles, Daniel; Chapman, Henry N; Küpper, Jochen

2014-01-01

98

Toward atomic resolution diffractive imaging of isolated molecules with X-ray free-electron lasers.  

PubMed

We give a detailed account of the theoretical analysis and the experimental results of an X-ray-diffraction experiment on quantum-state selected and strongly laser-aligned gas-phase ensembles of the prototypical large asymmetric rotor molecule 2,5-diiodobenzonitrile, performed at the Linac Coherent Light Source [Phys. Rev. Lett.112, 083002 (2014)]. This experiment is the first step toward coherent diffractive imaging of structures and structural dynamics of isolated molecules at atomic resolution, i.e., picometers and femtoseconds, using X-ray free-electron lasers. PMID:25415561

Stern, S; Holmegaard, L; Filsinger, F; Rouzée, A; Rudenko, A; Johnsson, P; Martin, A V; Barty, A; Bostedt, C; Bozek, J; Coffee, R; Epp, S; Erk, B; Foucar, L; Hartmann, R; Kimmel, N; Kühnel, K-U; Maurer, J; Messerschmidt, M; Rudek, B; Starodub, D; Thøgersen, J; Weidenspointner, G; White, T A; Stapelfeldt, H; Rolles, D; Chapman, H N; Küpper, J

2014-01-01

99

European X-Ray Free Electron Laser (EXFEL): local implications  

NASA Astrophysics Data System (ADS)

European X-Ray FEL - free electron laser is under construction in DESY Hamburg. It is scheduled to be operational at 2015/16 at a cost more than 1 billion Euro. The laser uses SASE method to generate x-ray light. It is propelled by an electron linac of 17,5GeV energy and more than 2km in length. The linac uses superconducting SRF TESLA technology working at 1,3 GHz in frequency. The prototype of EXFEL is FLASH Laser (200 m in length), where the "proof of principle" was checked, and from the technologies were transferred to the bigger machine. The project was stared in the nineties by building a TTF Laboratory -Tesla Test Facility. The EXFEL laser is a child of a much bigger teraelectronovolt collider project TESLA (now abandoned in Germany but undertaken by international community in a form the ILC). A number of experts and young researchers from Poland participate in the design, construction and research of the FLASH and EXFEL lasers.

Romaniuk, Ryszard S.

2013-10-01

100

Note: Studies on target placement in TE111 cylindrical cavity of electron cyclotron resonance x-ray source for the enhancement of x-ray dose  

NASA Astrophysics Data System (ADS)

X-ray source based on electron cyclotron resonance principle has been constructed using TE111 cylindrical cavity. At present the device is used to provide low energy x-ray field for thermoluminescent dosimeter badge calibration. Theoretical and experimental studies on the effect of target placement inside the TE111 cylindrical cavity for enhancing the x-ray output are carried out and the results are presented in this note. Optimum target location is identified by theoretical analysis on the electric field distribution inside the cavity using MICROWAVE STUDIO program. By modifying the magnetic field configuration, the resonance region is shifted to the optimum target location. The microwave transmission line is upgraded with a three stub tuner which improves the microwave coupling from the source to the target loaded cavity. Molybdenum target is located at a radial distance of 2.5 cm from the cavity center and the x-ray dose rate is measured at 20 cm from the exit port for different microwave power. With the introduction of the target, the x-ray output has improved nearly from 70% to 160% in the microwave power of 150-500 W.

Selvakumaran, T. S.; Baskaran, R.; Singh, A. K.; Sista, V. L. S. Rao

2010-03-01

101

Note: Studies on target placement in TE{sub 111} cylindrical cavity of electron cyclotron resonance x-ray source for the enhancement of x-ray dose  

SciTech Connect

X-ray source based on electron cyclotron resonance principle has been constructed using TE{sub 111} cylindrical cavity. At present the device is used to provide low energy x-ray field for thermoluminescent dosimeter badge calibration. Theoretical and experimental studies on the effect of target placement inside the TE{sub 111} cylindrical cavity for enhancing the x-ray output are carried out and the results are presented in this note. Optimum target location is identified by theoretical analysis on the electric field distribution inside the cavity using MICROWAVE STUDIO program. By modifying the magnetic field configuration, the resonance region is shifted to the optimum target location. The microwave transmission line is upgraded with a three stub tuner which improves the microwave coupling from the source to the target loaded cavity. Molybdenum target is located at a radial distance of 2.5 cm from the cavity center and the x-ray dose rate is measured at 20 cm from the exit port for different microwave power. With the introduction of the target, the x-ray output has improved nearly from 70% to 160% in the microwave power of 150-500 W.

Selvakumaran, T. S.; Baskaran, R.; Singh, A. K. [Safety Group, Radiological Safety Division, Indira Gandhi Center for Atomic Research, Kalpakkam 603102 (India); Sista, V. L. S. Rao [Nuclear Physics Division, Bhabha Atomic Research Center, Mumbai 400085 (India)

2010-03-15

102

Food Irradiation Using Electron Beams and X-Rays  

NASA Astrophysics Data System (ADS)

In this presentation we will discuss the technology of food irradiation using electron accelerators. Food irradiation has generally come to describe the use of ionizing radiation to decrease the population of, or prevent the growth of, undesirable biological organisms in food. The many beneficial applications include insect disinfestation, sprouting inhibition, delayed ripening, and the enhanced safety and sterilization of fresh and frozen meat products, seafood, and eggs. With special regard to food safety, bacteria such as Salmonella enteridis, Listeria monocytogenes, Campylobacter jejuni and Escherichia coli serotype O157:H7 are the primary causes of food poisoning in industrialized countries. Ionizing doses in the range of only 1-5 kilogray (kGy) can virtually eliminate these organisms from food, without affecting the food's sensory and nutritional qualities, and without inducing radioactivity. The key elements of an accelerator-based irradiation facility include the accelerator system, a scanning system, and a material handling system that moves the product through the beam in a precisely controlled manner. Extensive radiation shielding is necessary to reduce the external dose to acceptable levels, and a safety system is necessary to prevent accidental exposure of personnel during accelerator operation. Parameters that affect the dose distribution must be continuously monitored and controlled with process control software. The choice of electron beam vs x-ray depends on the areal density (density times thickness) of the product and the anticipated mass throughput. To eliminate nuclear activation concerns, the maximum kinetic energy of the accelerator is limited by regulation to 10 MeV for electron beams, and 5 MeV for x-rays. From penetration considerations, the largest areal density that can be treated by double-sided electron irradiation at 10 MeV is about 8.8 g/cm2. Products having greater areal densities must be processed using more penetrating x-rays. The mass throughput (dM/dt in kg/s) of an accelerator-based system is proportional to the average beam power (P in kW), and inversely proportional to the minimum required dose (Dm in kGy, with 1 kGy = 1 kJ/kg). The constant of proportionality is the mass throughput efficiency. Throughput efficiencies of 0.4 or better are typical of electron beam installations, but are only 0.025-0.035 for x-ray installations, primarily because of the inefficiency of bremsstrahlung generation at 5 MeV (about 8an axially-coupled, standing-wave, L-band linac with an average power in excess of 100 kW to achieve reasonable throughput rates with x-ray processing. Various design aspects of this new machine will be presented.

Miller, Bruce

2003-04-01

103

Fourier Analysis and Structure Determination--Part III: X-ray Crystal Structure Analysis.  

ERIC Educational Resources Information Center

Discussed is single crystal X-ray crystal structure analysis. A common link between the NMR imaging and the traditional X-ray crystal structure analysis is reported. Claims that comparisons aid in the understanding of both techniques. (MVL)

Chesick, John P.

1989-01-01

104

Electron probe X-ray analysis on human hepatocellular lysosomes with copper deposits: copper binding to a thiol-protein in lysosomes  

SciTech Connect

Livers of eight patients with chronic liver diseases were investigated by energy dispersive x-ray analysis. First, three kinds of preparations (osmium-Epon sections, glutaraldehyde-frozen sections, and unfixed-frozen sections) were compared for element detectability at a subcellular level. The glutaraldehyde-frozen sections were satisfactory as far as copper, sulfur, and phosphorus were concerned. Five patients (one patient with Wilson's disease, one chronic cholestasis, one chronic hepatitis, and two asymptomatic primary biliary cirrhosis) yielded x-ray images of copper and sulfur consistent with hepatocellular lysosomes. Second, the glutaraldehyde-frozen sections were utilized for a study of copper deposits in the patients' livers. There was a significant correlation between copper and sulfur contents in the lysosomes of all patients studied but no correlation in the remainder of the cytoplasm. Zinc was not detected in the lysosomes. Whatever the content of copper in the lysosomes, the ratio of delta copper to phosphorus (weight/weight) to delta sulfur to phosphorus was 0.60. These data indicate that most lysosomal copper binds to a thiol protein, probably metallothionein, in the liver.

Hanaichi, T.; Kidokoro, R.; Hayashi, H.; Sakamoto, N.

1984-11-01

105

Electron and proton induced x-ray spectrometry: Two complementary spatially resolved analytical techniques in mineralogy  

Microsoft Academic Search

Spatially resolved quantitative analysis by means of the electron probe micro analyzer (EPMA) is now well-established as a routine analytical method for point chemical analysis of a variety of mineral materials. Modern computer controlled EPMA are most often equipped with wavelength dispersive spectrometers (WDS). Quantitative analysis are generally carried out according to a standard based approached, i.e. the x-ray intensities

G. Remond; C. Gilles; D. Isabelle; C. Choi; M. Azahra; O. Rouer; F. Cesbron

1995-01-01

106

Estimation of lattice strain in ZnO nanoparticles: X-ray peak profile analysis  

NASA Astrophysics Data System (ADS)

ZnO nanoparticles were synthesized from chitosan and zinc chloride by a precipitation method. The synthesized ZnO nanoparticles were characterized by Fourier transform infrared spectroscopy, X-ray diffraction peak profile analysis, Scanning electron microscopy, Transmission electron microscopy and Photoluminescence. The X-ray diffraction results revealed that the sample was crystalline with a hexagonal wurtzite phase. We have investigated the crystallite development in ZnO nanoparticles by X-ray peak profile analysis. The Williamson-Hall analysis and size-strain plot were used to study the individual contributions of crystallite sizes and lattice strain ? on the peak broadening of ZnO nanoparticles. The parameters including strain, stress and energy density value were calculated for all the reflection peaks of X-ray diffraction corresponding to wurtzite hexagonal phase of ZnO lying in the range 20°-80° using the modified form of Williamson-Hall plots and size-strain plot. The results showed that the crystallite size estimated from Scherrer's formula, Williamson-Hall plots and size-strain plot, and the particle size estimated from Transmission electron microscopy analysis are very much inter-correlated. Both methods, the X-ray diffraction and Transmission electron microscopy, provide less deviation between crystallite size and particle size in the present case.

Bindu, P.; Thomas, Sabu

2014-07-01

107

Development of a quantification method for x-ray microanalysis with an electron microscope  

NASA Astrophysics Data System (ADS)

The overview of the history of quantitative x-ray microanalysis shows the efficiency of the use of standards to achieve the most reliable quantification. State-of-the-art cold field emission gun scanning electron microscopes offer excellent resolution but lack a sufficient level of beam current stability essential for reliable quantitative microanalysis. The purpose of this work is to develop a new method for quantitative x-ray microanalysis adapted to unstable beam current conditions. In the Cliff and Lorimer method, which was developed for the analytical transmission electron microscope, the composition was calculated from the ratio of the characteristic x-ray intensities of two elements in the same spectrum. In this work, this ratio method is applied to bulk specimens in a scanning electron microscope (SEM). In order to reduce the amplitude of error propagation, the proposed ratio for SEM quantitative microanalysis is the intensity of a x-ray divided by the sum of intensities of one or more characteristic lines of each of tire elements found in the specimen. Moreover, the calculated x-ray intensities are corrected for the effects of absorption, fluorescence and Coster-Kronig yields, and other physical factors normally considered in microbeam analysis. Uncertainties in physical parameters and models, clue to the lack of exhaustive measurements as well as their scattering, revealed by a disaggrement between the measured and calculated ratios, are minimized by the use of a calibration factor inserted into the ratio. This calibration factor is determined using a standard for a given element. It can be used as often as needed and allows for the correction of uncertainties in the x-ray detector efficiency. In order to quantify the specimen, the measured experimental ratio is compared to a simulated ratio with the appropriate calibration factor. The composition is interpolated from the theoretical ratio curves. Two methods of calculation of emitted x-ray intensity are proposed, by analytical calculations using the Pouchou and Pichoir model or by an in-house developed Monte Carlo simulation program. Two sets of National Bureau of Standards (NBS) microanalysis standard reference materials, AuCu (SRM 482) and AuAg (SRM 481), are used to validate this method. The comparison of calculated composition with the nominal one underlines the need for a beam-energy-dependent calibration factor, particularly because of ionization cross-section uncertainties. The use of high energy characteristic x-ray lines (above 5 keV) permits accuracy around 3% with a beam-energy-dependent calibration factor. The effects of beam energy, ionization cross-section models, mass-absorption coefficients and x-ray generation methods are compensated by the appropriate calibration factor. The change of the family of characteristic lines affects the accuracy. Finally, as in any quantitative microanalysis, the use of a filter to extract the characteristic intensity causes errors for low energy peaks. The analysis of the effect of calibration factors and mass-absorption coefficient enhances the need for refining the x-ray generation and emission parameters. The error propagation is less important than if using the classical Cliff and Lorimer method in a SEM. However, the use of appropriate calibration factors and pair of lines offers promising accuracy in almost any conditions. This method is independent of the beam current, which is the purpose of this work. Despite many uncertainties of physical parameters, this method offers an efficient and reliable alternative to quantitative x-ray microanalysis with any electron microscope. Although developed for a binary material, the method can be extended to heterogeneous, rough, multiple-component materials, inasmuch as it can be simulated with a Monte Carlo program or any other method that computes characteristic x-ray lines intensities.

Horny, Paula

108

Pair Creation and an X-ray Free Electron Laser  

E-print Network

Using a quantum kinetic equation coupled to Maxwell's equation we study the possibility that focused beams at proposed X-ray free electron laser facilities can generate electric field strengths large enough to cause spontaneous electron-positron pair production from the QED vacuum. Our approach yields the time and momentum dependence of the single particle distribution function. Under conditions reckoned achievable at planned facilities, repeated cycles of particle creation and annihilation take place in tune with the laser frequency. However, the peak particle number density is insensitive to this frequency and one can anticipate the production of a few hundred particle pairs per laser period. Field-current feedback and quantum statistical effects are small and can be neglected in this application of non-equilibrium quantum mean field theory.

R. Alkofer; M. B. Hecht; C. D. Roberts; S. M. Schmidt; D. V. Vinnik

2001-08-17

109

Terawatt x-ray free-electron-laser optimization by transverse electron distribution shaping  

NASA Astrophysics Data System (ADS)

We study the dependence of the peak power of a 1.5 Å Terawatt (TW), tapered x-ray free-electron laser (FEL) on the transverse electron density distribution. Multidimensional optimization schemes for TW hard x-ray free-electron lasers are applied to the cases of transversely uniform and parabolic electron beam distributions and compared to a Gaussian distribution. The optimizations are performed for a 200 m undulator and a resonant wavelength of ?r=1.5 Å using the fully three-dimensional FEL particle code genesis. The study shows that the flatter transverse electron distributions enhance optical guiding in the tapered section of the undulator and increase the maximum radiation power from a maximum of 1.56 TW for a transversely Gaussian beam to 2.26 TW for the parabolic case and 2.63 TW for the uniform case. Spectral data also shows a 30%-70% reduction in energy deposited in the sidebands for the uniform and parabolic beams compared with a Gaussian. An analysis of the transverse coherence of the radiation shows the coherence area to be much larger than the beam spotsize for all three distributions, making coherent diffraction imaging experiments possible.

Emma, C.; Wu, J.; Fang, K.; Chen, S.; Serkez, S.; Pellegrini, C.

2014-11-01

110

Hard-X-ray magnetic microscopy and local magnetization analysis using synchrotron radiation.  

PubMed

X-ray measurement offers several useful features that are unavailable from other microscopic means including electron-based techniques. By using X-rays, one can observe the internal parts of a thick sample. This technique basically requires no high vacuum environment such that measurements are feasible for wet specimens as well as under strong electric and magnetic fields and even at a high pressure. X-ray spectroscopy using core excitation provides element-selectivity with significant sensitivities to the chemical states and atomic magnetic moments in the matter. Synchrotron radiation sources produce a small and low-divergent X-ray beam, which can be converged to a spot with the size of a micrometer or less using X-ray focusing optics. The recent development in the focusing optics has been driving X-ray microscopy, which has already gone into the era of X-ray nanoscopy. With the use of the most sophisticated focusing devices, an X-ray beam of 7-nm size has successfully been achieved [1]. X-ray microscopy maintains above-mentioned unique features of X-ray technique, being a perfect complement to electron microscopy.In this paper, we present recent studies on magnetic microscopy and local magnetic analysis using hard X-rays. The relevant instrumentation developments are also described. The X-ray nanospectroscopy station of BL39XU at SPring-8 is equipped with a focusing optics consisting of two elliptic mirrors, and a focused X-ray beam with the size of 100 × 100 nm(2) is available [2]. Researchers can perform X-ray absorption spectroscopy: nano-XAFS (X-ray absorption fine structure) using the X-ray beam as small as 100 nm. The available X-ray energy is from 5 to 16 keV, which allows nano-XAFS study at the K edges of 3d transition metals, L edges of rare-earth elements and 5d noble metals. Another useful capability of the nanoprobe is X-ray polarization tunability, enabling magnetic circular dichroism (XMCD) spectroscopy with a sub-micrometer resolution. Scanning XMCD imaging, XMCD measurement in local areas, and element-specific magnetometry for magnetic particles/magnetic devices as small as 100 nm can be performed. Nano-XAFS application includes visualization of the chemical state in a particle catalyst [3] and phase-change memory devices [4]. For magnetic microscopic study, magnetization reversal processes of an individual magnetic CoPt dot in bit-patterned media have directly been observed [2]. Imaging of the chemical distribution and magnetic domain evolution in a Nd-Fe-B sintered magnet in demagnetization processes is presented. PMID:25359804

Suzuki, Motohiro

2014-11-01

111

Full spatial characterization of a nanofocused x-ray free-electron laser beam by ptychographic imaging  

PubMed Central

The emergence of hard X-ray free electron lasers (XFELs) enables new insights into many fields of science. These new sources provide short, highly intense, and coherent X-ray pulses. In a variety of scientific applications these pulses need to be strongly focused. In this article, we demonstrate focusing of hard X-ray FEL pulses to 125?nm using refractive x-ray optics. For a quantitative analysis of most experiments, the wave field or at least the intensity distribution illuminating the sample is needed. We report on the full characterization of a nanofocused XFEL beam by ptychographic imaging, giving access to the complex wave field in the nanofocus. From these data, we obtain the full caustic of the beam, identify the aberrations of the optic, and determine the wave field for individual pulses. This information is for example crucial for high-resolution imaging, creating matter in extreme conditions, and nonlinear x-ray optics. PMID:23567281

Schropp, Andreas; Hoppe, Robert; Meier, Vivienne; Patommel, Jens; Seiboth, Frank; Lee, Hae Ja; Nagler, Bob; Galtier, Eric C.; Arnold, Brice; Zastrau, Ulf; Hastings, Jerome B.; Nilsson, Daniel; Uhlén, Fredrik; Vogt, Ulrich; Hertz, Hans M.; Schroer, Christian G.

2013-01-01

112

X-Ray Free Electron Laser Interaction With Matter  

SciTech Connect

X-ray free electron lasers (XFELs) will enable studying new areas of laser-matter interaction. We summarize the current understanding of the interaction of XFEL pulses with matter and describe some of the simulation approaches that are used to design experiments on future XFEL sources. Modified versions of these models have been successful in guiding and analyzing experiments performed at the extreme-ultraviolet FEL FLASH at wavelengths of 6 nm and longer. For photon energies of several keV, no XFEL-matter interaction experiments have been performed yet but data is anticipated to become available in the near future, which will allow to test our understanding of the interaction physics in this wavelength regime.

Hau-Riege, S

2009-05-12

113

Focusing mirror for x-ray free-electron lasers.  

PubMed

We present the design, fabrication, and evaluation of a large total-reflection mirror for focusing x-ray free-electron laser beams to nanometer dimensions. We used an elliptical focusing mirror made of silicon that was 400 mm long and had a focal length of 550 mm. Electrolytic in-process dressing grinding was used for initial-step figuring and elastic emission machining was employed for final figuring and surface smoothing. A figure accuracy with a peak-to-valley height of 2 nm was achieved across the entire area. Characterization of the focused beam was performed at BL29XUL of SPring-8. The focused beam size was 75 nm at 15 keV, which is almost equal to the theoretical size. PMID:19044333

Mimura, Hidekazu; Morita, Shinya; Kimura, Takashi; Yamakawa, Daisuke; Lin, Weimin; Uehara, Yoshihiro; Matsuyama, Satoshi; Yumoto, Hirokatsu; Ohashi, Haruhiko; Tamasaku, Kenji; Nishino, Yoshinori; Yabashi, Makina; Ishikawa, Tetsuya; Ohmori, Hitoshi; Yamauchi, Kazuto

2008-08-01

114

Chemical bonding effects in X-ray spectral analysis  

Microsoft Academic Search

In this review we examine the use of chemical bonding effects apparent in x-ray spectra (chemical shift, change in shape and intensity of the lines) for qualitative and quantitative analysis of the chemical state of elements (charge state, valency, coordination number, chemical bond type, etc.), and also for direct identification of chemical compounds. In this connection, we examine methods of

L. N. Mazalov; B. A. Treiger

1983-01-01

115

X-RAY EMISSION ANALYSIS: SAMPLE LOSSES DURING EXCITATION  

EPA Science Inventory

Many samples of atmospheric aerosols and biological materials containing volatile or unstable species are now being examined by X-ray emission analysis, and loss of these species by sample heating is a critical consideration. The amount of heat energy deposited in a sample by the...

116

RF Phase Stability and Electron Beam Characterization for the PLEIADES Thomson X-Ray Source  

SciTech Connect

We report on the performance of an S-band RF photocathode electron gun and accelerator for operation with the PLEIADES Thomson x-ray source at LLNL. To produce picosecond, high brightness x-ray pulses, picosecond timing, terahertz bandwidth diagnostics, and RF phase control are required. Planned optical, RF, x-ray and electron beam measurements to characterize the dependence of electron beam parameters and synchronization on RF phase stability are presented.

Brown, W J; Hartemann, F V; Tremaine, A M; Springer, P T; Le Sage, G P; Barty, C P J; Rosenzweig, J B; Crane, J K; Cross, R R; Fittinghoff, D N; Gibson, D J; Slaughter, D R; Anderson, S

2002-10-16

117

In Situ X-Ray Analysis of Protein Crystals in Low-Birefringent And X-Ray Transmissive Plastic Microchannels  

SciTech Connect

Plastic microchannel crystallization template designs made from inexpensive cyclic olefin copolymers have been shown to be low-birefringent, X-ray transmissive and compatible with microfluidic fabrication in restricted geometry. The model proteins thaumatin, lysozyme and bacteriorhodopsin demonstrated the feasibility of conducting counter-diffusion equilibration within the new plastic configuration. Crystals of each of these proteins were directly evaluated in situ using synchrotron radiation and their diffraction quality was evaluated without invasive manipulation or cryofreezing. Protein crystals able to produce complete X-ray data sets were used to calculate electron-density maps for structure determination. Fluidic crystallization in the plastic platform was also coupled with a commercialized automated imager and an in situ X-ray scanner that allowed optical and X-ray inspection of crystallization hits. The results demonstrate the feasibility of rapid nanovolume counter-diffusion crystallization experiments without the need for additional instrumentation.

Ng, J.D.; Clark, P.J.; Stevens, R.C.; Kuhn, P.

2009-05-22

118

Manganese Binding Properties of Human Calprotectin under Conditions of High and Low Calcium: X-ray Crystallographic and Advanced Electron Paramagnetic Resonance Spectroscopic Analysis.  

PubMed

The antimicrobial protein calprotectin (CP), a hetero-oligomer of the S100 family members S100A8 and S100A9, is the only identified mammalian Mn(II)-sequestering protein. Human CP uses Ca(II) ions to tune its Mn(II) affinity at a biologically unprecedented hexahistidine site that forms at the S100A8/S100A9 interface, and the molecular basis for this phenomenon requires elucidation. Herein, we investigate the remarkable Mn(II) coordination chemistry of human CP using X-ray crystallography as well as continuous-wave (CW) and pulse electron paramagnetic resonance (EPR) spectroscopies. An X-ray crystallographic structure of Mn(II)-CP containing one Mn(II), two Ca(II), and two Na(I) ions per CP heterodimer is reported. The CW EPR spectrum of Ca(II)- and Mn(II)-bound CP prepared with a 10:0.9:1 Ca(II):Mn(II):CP ratio is characterized by an unusually low zero-field splitting of 485 MHz (E/D = 0.30) for the S = 5/2 Mn(II) ion, consistent with the high symmetry of the His6 binding site observed crystallographically. Results from electron spin-echo envelope modulation and electron-nuclear double resonance experiments reveal that the six Mn(II)-coordinating histidine residues of Ca(II)- and Mn(II)-bound CP are spectroscopically equivalent. The observed (15)N (I = 1/2) hyperfine couplings (A) arise from two distinct classes of nitrogen atoms: the coordinating ?-nitrogen of the imidazole ring of each histidine ligand (A = [3.45, 3.71, 5.91] MHz) and the distal ?-nitrogen (A = [0.11, 0.18, 0.42] MHz). In the absence of Ca(II), the binding affinity of CP for Mn(II) drops by two to three orders of magnitude and coincides with Mn(II) binding at the His6 site as well as other sites. This study demonstrates the role of Ca(II) in enabling high-affinity and specific binding of Mn(II) to the His6 site of human calprotectin. PMID:25597447

Gagnon, Derek M; Brophy, Megan Brunjes; Bowman, Sarah E J; Stich, Troy A; Drennan, Catherine L; Britt, R David; Nolan, Elizabeth M

2015-03-01

119

Analysis of urinary stone components by x-ray coherent scatter: characterizing composition beyond laboratory x-ray diffractometry  

Microsoft Academic Search

Monoenergetic x-ray diffraction (XRD) analysis is an established standard for the assessment of urinary stone composition. The inherent low energy of x-rays used (8 keV), however, restricts penetration depth and imposes a requirement for small powdered samples. A technique capable of producing detailed information regarding component structural arrangements in calculi non-destructively would provide clearer insights into causes of formation and

Melanie T M Davidson; Deidre L Batchelar; Sujeevan Velupillai; John D Denstedt; Ian A Cunningham

2005-01-01

120

Correlative analysis of hard and soft x ray observations of solar flares  

NASA Technical Reports Server (NTRS)

We have developed a promising new technique for jointly analyzing BATSE hard X-ray observations of solar flares with simultaneous soft X-ray observations. The technique is based upon a model in which electric currents and associated electric fields are responsible for the respective heating and particle acceleration that occur in solar flares. A useful by-product of this technique is the strength and evolution of the coronal electric field. The latter permits one to derive important flare parameters such as the current density, the number of current filaments composing the loop, and ultimately the hard X-ray spectrum produced by the runaway electrons. We are continuing to explore the technique by applying it to additional flares for which we have joint BATSE/Yohkoh observations. A central assumption of our analysis is the constant of proportionality alpha relating the hard X-ray flux above 50 keV and the rate of electron acceleration. For a thick-target model of hard X-ray production, it can be shown that cv is in fact related to the spectral index and low-energy cutoff of precipitating electrons. The next step in our analysis is to place observational constraints on the latter parameters using the joint BATSE/Yohkoh data.

Zarro, Dominic M.

1994-01-01

121

Few-femtosecond time-resolved measurements of X-ray free-electron lasers  

NASA Astrophysics Data System (ADS)

X-ray free-electron lasers, with pulse durations ranging from a few to several hundred femtoseconds, are uniquely suited for studying atomic, molecular, chemical and biological systems. Characterizing the temporal profiles of these femtosecond X-ray pulses that vary from shot to shot is not only challenging but also important for data interpretation. Here we report the time-resolved measurements of X-ray free-electron lasers by using an X-band radiofrequency transverse deflector at the Linac Coherent Light Source. We demonstrate this method to be a simple, non-invasive technique with a large dynamic range for single-shot electron and X-ray temporal characterization. A resolution of less than 1?fs root mean square has been achieved for soft X-ray pulses. The lasing evolution along the undulator has been studied with the electron trapping being observed as the X-ray peak power approaches 100?GW.

Behrens, C.; Decker, F.-J.; Ding, Y.; Dolgashev, V. A.; Frisch, J.; Huang, Z.; Krejcik, P.; Loos, H.; Lutman, A.; Maxwell, T. J.; Turner, J.; Wang, J.; Wang, M.-H.; Welch, J.; Wu, J.

2014-04-01

122

Few-femtosecond time-resolved measurements of X-ray free-electron lasers.  

PubMed

X-ray free-electron lasers, with pulse durations ranging from a few to several hundred femtoseconds, are uniquely suited for studying atomic, molecular, chemical and biological systems. Characterizing the temporal profiles of these femtosecond X-ray pulses that vary from shot to shot is not only challenging but also important for data interpretation. Here we report the time-resolved measurements of X-ray free-electron lasers by using an X-band radiofrequency transverse deflector at the Linac Coherent Light Source. We demonstrate this method to be a simple, non-invasive technique with a large dynamic range for single-shot electron and X-ray temporal characterization. A resolution of less than 1 fs root mean square has been achieved for soft X-ray pulses. The lasing evolution along the undulator has been studied with the electron trapping being observed as the X-ray peak power approaches 100 GW. PMID:24781868

Behrens, C; Decker, F-J; Ding, Y; Dolgashev, V A; Frisch, J; Huang, Z; Krejcik, P; Loos, H; Lutman, A; Maxwell, T J; Turner, J; Wang, J; Wang, M-H; Welch, J; Wu, J

2014-01-01

123

Portable total reflection x-ray fluorescence analysis in the identification of unknown laboratory hazards  

SciTech Connect

In this study, a portable total reflection x-ray fluorescence (TXRF) spectrometer was used to analyze unknown laboratory hazards that precipitated on exterior surfaces of cooling pipes and fume hood pipes in chemical laboratories. With the aim to examine the accuracy of TXRF analysis for the determination of elemental composition, analytical results were compared with those of wavelength-dispersive x-ray fluorescence spectrometry, scanning electron microscope and energy-dispersive x-ray spectrometry, energy-dispersive x-ray fluorescence spectrometry, inductively coupled plasma atomic emission spectrometry, x-ray diffraction spectrometry (XRD), and x-ray photoelectron spectroscopy (XPS). Detailed comparison of data confirmed that the TXRF method itself was not sufficient to determine all the elements (Z?>?11) contained in the samples. In addition, results suggest that XRD should be combined with XPS in order to accurately determine compound composition. This study demonstrates that at least two analytical methods should be used in order to analyze the composition of unknown real samples.

Liu, Ying, E-mail: liu.ying.48r@st.kyoto-u.ac.jp; Imashuku, Susumu; Sasaki, Nobuharu; Ze, Long; Kawai, Jun [Department of Materials Science and Engineering, Kyoto University, Yoshida-Honmachi, Sakyo-ku, Kyoto 606-8501 (Japan); Takano, Shotaro; Sohrin, Yoshiki [Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Seki, Hiroko; Miyauchi, Hiroya [Kyoto Prefectural Technology Center for Small and Medium Enterprises, Chudojiminami machi, Shimogyo-ku, Kyoto 600-8813 (Japan)

2014-05-15

124

Wavelength dispersive analysis with the synchrotron x ray fluorescence microprobe  

NASA Technical Reports Server (NTRS)

A wavelength dispersive spectrometer (WDS) was tested on the synchrotron x ray fluorescence microprobe at Brookhaven National Laboratory. Compared to WDS spectra using an electron microprobe, the synchrotron WDS spectra have much better sensitivity and, due to the absence of bremsstrahlung radiation, lower backgrounds. The WDS spectrometer was successfully used to resolve REE L fluorescence spectra from standard glasses and transition metal K fluorescence spectra from kamacite.

Rivers, M. L.; Thorn, K. S.; Sutton, S. R.; Jones, K. W.; Bajt, S.

1993-01-01

125

Accuracy evaluation of a Compton X-ray spectrometer with bremsstrahlung X-rays generated by a 6 MeV electron bunch  

SciTech Connect

A Compton-scattering-based X-ray spectrometer is developed to obtain the energy distribution of fast electrons produced by intense laser and matter interactions. Bremsstrahlung X-rays generated by fast electrons in a material are used to measure fast electrons’ energy distribution in matter. In the Compton X-ray spectrometer, X-rays are converted into recoil electrons by Compton scattering in a converter made from fused silica glass, and a magnet-based electron energy analyzer is used to measure the energy distribution of the electrons that recoil in the direction of the incident X-rays. The spectrum of the incident X-rays is reconstructed from the energy distribution of the recoil electrons. The accuracy of this spectrometer is evaluated using a quasi-monoenergetic 6 MeV electron bunch that emanates from a linear accelerator. An electron bunch is injected into a 1.5 mm thick tungsten plate to produce bremsstrahlung X-rays. The spectrum of these bremsstrahlung X-rays is obtained in the range from 1 to 9 MeV. The energy of the electrons in the bunch is estimated using a Monte Carlo simulation of particle-matter interactions. The result shows that the spectrometer's energy accuracy is ±0.5 MeV for 6.0 MeV electrons.

Kojima, Sadaoki, E-mail: kojima-s@ile.osaka-u.ac.jp; Arikawa, Yasunobu; Zhang, Zhe; Ikenouchi, Takahito; Morace, Alessio; Nagai, Takahiro; Abe, Yuki; Sakata, Shouhei; Inoue, Hiroaki; Utsugi, Masaru; Nakai, Mitsuo; Nishimura, Hiroaki; Shiraga, Hiroyuki; Fujioka, Shinsuke; Azechi, Hiroshi [Institute of Laser Engineering, Osaka University, 2-6 Yamada-oka, Suita, Osaka 565-0871 (Japan); Nishimura, Yasuhiko; Togawa, Hiromi [Toyota Technical Development Corporation, 1-21 Imae, Hanamoto-cho, Toyota, Aichi 470-0334 (Japan); Ozaki, Tetsuo [National Institute for Fusion Science, 322-6 Oroshicho, Toki, Gifu 509-5292 (Japan); Kato, Ryukou [The Institute of Science and Industrial Research, Osaka University, 2-6 Yamada-oka, Suita, Osaka (Japan)

2014-11-15

126

Accuracy evaluation of a Compton X-ray spectrometer with bremsstrahlung X-rays generated by a 6 MeV electron buncha)  

NASA Astrophysics Data System (ADS)

A Compton-scattering-based X-ray spectrometer is developed to obtain the energy distribution of fast electrons produced by intense laser and matter interactions. Bremsstrahlung X-rays generated by fast electrons in a material are used to measure fast electrons' energy distribution in matter. In the Compton X-ray spectrometer, X-rays are converted into recoil electrons by Compton scattering in a converter made from fused silica glass, and a magnet-based electron energy analyzer is used to measure the energy distribution of the electrons that recoil in the direction of the incident X-rays. The spectrum of the incident X-rays is reconstructed from the energy distribution of the recoil electrons. The accuracy of this spectrometer is evaluated using a quasi-monoenergetic 6 MeV electron bunch that emanates from a linear accelerator. An electron bunch is injected into a 1.5 mm thick tungsten plate to produce bremsstrahlung X-rays. The spectrum of these bremsstrahlung X-rays is obtained in the range from 1 to 9 MeV. The energy of the electrons in the bunch is estimated using a Monte Carlo simulation of particle-matter interactions. The result shows that the spectrometer's energy accuracy is ±0.5 MeV for 6.0 MeV electrons.

Kojima, Sadaoki; Arikawa, Yasunobu; Nishimura, Yasuhiko; Togawa, Hiromi; Zhang, Zhe; Ikenouchi, Takahito; Ozaki, Tetsuo; Morace, Alessio; Nagai, Takahiro; Abe, Yuki; Sakata, Shouhei; Inoue, Hiroaki; Utsugi, Masaru; Nakai, Mitsuo; Nishimura, Hiroaki; Shiraga, Hiroyuki; Kato, Ryukou; Fujioka, Shinsuke; Azechi, Hiroshi

2014-11-01

127

Accuracy evaluation of a Compton X-ray spectrometer with bremsstrahlung X-rays generated by a 6 MeV electron bunch.  

PubMed

A Compton-scattering-based X-ray spectrometer is developed to obtain the energy distribution of fast electrons produced by intense laser and matter interactions. Bremsstrahlung X-rays generated by fast electrons in a material are used to measure fast electrons' energy distribution in matter. In the Compton X-ray spectrometer, X-rays are converted into recoil electrons by Compton scattering in a converter made from fused silica glass, and a magnet-based electron energy analyzer is used to measure the energy distribution of the electrons that recoil in the direction of the incident X-rays. The spectrum of the incident X-rays is reconstructed from the energy distribution of the recoil electrons. The accuracy of this spectrometer is evaluated using a quasi-monoenergetic 6 MeV electron bunch that emanates from a linear accelerator. An electron bunch is injected into a 1.5 mm thick tungsten plate to produce bremsstrahlung X-rays. The spectrum of these bremsstrahlung X-rays is obtained in the range from 1 to 9 MeV. The energy of the electrons in the bunch is estimated using a Monte Carlo simulation of particle-matter interactions. The result shows that the spectrometer's energy accuracy is ±0.5 MeV for 6.0 MeV electrons. PMID:25430210

Kojima, Sadaoki; Arikawa, Yasunobu; Nishimura, Yasuhiko; Togawa, Hiromi; Zhang, Zhe; Ikenouchi, Takahito; Ozaki, Tetsuo; Morace, Alessio; Nagai, Takahiro; Abe, Yuki; Sakata, Shouhei; Inoue, Hiroaki; Utsugi, Masaru; Nakai, Mitsuo; Nishimura, Hiroaki; Shiraga, Hiroyuki; Kato, Ryukou; Fujioka, Shinsuke; Azechi, Hiroshi

2014-11-01

128

Intravenous coronary angiography utilizing K-emission and bremsstrahlung X-rays produced by electron bombardment  

SciTech Connect

The screening of the general population for coronary artery disease would be practical if a method existed for visualizing the extent of occlusion after an intravenous injection of contrast agent. Measurements performed with synchrotron radiation at SSRL and NSLS have shown that such an intravenous angiography procedure would be possible with an intense source of monochromatic X-rays. Because of the high cost of an electron synchrotron, theoretical analysis and experiments using inanimate phantoms has been undertaken to demonstrate the feasibility of using the spectrum produced by two appropriately chosen anode materials when bombarded with electrons in the 100--500 keV energy range for angiography. By using the X-rays emitted at 120{degree} to the incident electron direction, about 20--30% of the X-ray intensity would be due to K-emission lines. Calculations using the TIGERP Monte Carlo Code, have shown that high quality angiograms of human coronary arteries should be possible with a contrast agent containing ytterbium, if an electron beam pulses of 16 kJ were used for each anode target. The experimental program supported in part by the DOE has consisted of these theoretical calculations and experiments at the Dynamitron Electron Accelerator Facility at BNL.

NONE

1992-12-31

129

Macromolecular structures probed by combining single-shot free-electron laser diffraction with synchrotron coherent X-ray imaging.  

PubMed

Nanostructures formed from biological macromolecular complexes utilizing the self-assembly properties of smaller building blocks such as DNA and RNA hold promise for many applications, including sensing and drug delivery. New tools are required for their structural characterization. Intense, femtosecond X-ray pulses from X-ray free-electron lasers enable single-shot imaging allowing for instantaneous views of nanostructures at ambient temperatures. When combined judiciously with synchrotron X-rays of a complimentary nature, suitable for observing steady-state features, it is possible to perform ab initio structural investigation. Here we demonstrate a successful combination of femtosecond X-ray single-shot diffraction with an X-ray free-electron laser and coherent diffraction imaging with synchrotron X-rays to provide an insight into the nanostructure formation of a biological macromolecular complex: RNA interference microsponges. This newly introduced multimodal analysis with coherent X-rays can be applied to unveil nano-scale structural motifs from functional nanomaterials or biological nanocomplexes, without requiring a priori knowledge. PMID:24786694

Gallagher-Jones, Marcus; Bessho, Yoshitaka; Kim, Sunam; Park, Jaehyun; Kim, Sangsoo; Nam, Daewoong; Kim, Chan; Kim, Yoonhee; Noh, Do Young; Miyashita, Osamu; Tama, Florence; Joti, Yasumasa; Kameshima, Takashi; Hatsui, Takaki; Tono, Kensuke; Kohmura, Yoshiki; Yabashi, Makina; Hasnain, S Samar; Ishikawa, Tetsuya; Song, Changyong

2014-01-01

130

The amorphous Zn biomineralization at Naracauli stream, Sardinia: electron microscopy and X-ray absorption spectroscopy.  

PubMed

An amorphous Zn biomineralization ("white mud"), occurring at Naracauli stream, Sardinia, in association with cyanobacteria Leptolyngbya frigida and diatoms, was investigated by electron microscopy and X-ray absorption spectroscopy. Preliminary diffraction analysis shows that the precipitate sampled on Naracauli stream bed is mainly amorphous, with some peaks ascribable to quartz and phyllosilicates, plus few minor unattributed peaks. Scanning electron microscopy analysis shows that the white mud, precipitated in association with a seasonal biofilm, is made of sheaths rich in Zn, Si, and O, plus filaments likely made of organic matter. Transmission electron microscopy analysis shows that the sheaths are made of smaller units having a size in the range between 100 and 200 nm. X-ray absorption near-edge structure and extended X-ray absorption fine structure data collected at the Zn K-edge indicate that the biomineral has a local structure similar to hemimorphite, a zinc sorosilicate. The differences of this biomineral with respect to the hydrozincite biomineralization documented about 3 km upstream in the same Naracauli stream may be related to either variations in the physicochemical parameters and/or different metabolic behavior of the involved biota. PMID:23832800

Medas, D; Lattanzi, P; Podda, F; Meneghini, C; Trapananti, A; Sprocati, A; Casu, M A; Musu, E; De Giudici, G

2014-06-01

131

Coherence Properties of Individual Femtosecond Pulses of an X-ray Free-Electron Laser  

SciTech Connect

Measurements of the spatial and temporal coherence of single, femtosecond x-ray pulses generated by the first hard x-ray free-electron laser, the Linac Coherent Light Source, are presented. Single-shot measurements were performed at 780 eV x-ray photon energy using apertures containing double pinholes in 'diffract-and-destroy' mode. We determined a coherence length of 17 {micro}m in the vertical direction, which is approximately the size of the focused Linac Coherent Light Source beam in the same direction. The analysis of the diffraction patterns produced by the pinholes with the largest separation yields an estimate of the temporal coherence time of 0.55 fs. We find that the total degree of transverse coherence is 56% and that the x-ray pulses are adequately described by two transverse coherent modes in each direction. This leads us to the conclusion that 78% of the total power is contained in the dominant mode.

Vartanyants, I.A.; /DESY /Moscow Phys. Eng. Inst.; Singer, A.; Mancuso, A.P.; Yefanov, O.M.; /DESY; Sakdinawat, A.; Liu, Y.; Bang, E.; /UC, Berkeley; Williams, G.J.; /SLAC; Cadenazzi, G.; Abbey, B.; /Melbourne U.; Sinn, H.; /European XFEL, Hamburg; Attwood, D.; /UC, Berkeley; Nugent, K.A.; /Melbourne U.; Weckert, E.; /DESY; Wang, T.; Zhu, D.; Wu, B.; Graves, C.; Scherz, A.; Turner, J.J.; Schlotter, W.F.; /SLAC /LERMA, Ivry /Zurich, ETH /LBL, Berkeley /ANL, APS /Argonne /SLAC /LLNL, Livermore /Latrobe U. /SLAC /SLAC /European XFEL, Hamburg /SLAC /Hamburg U.

2012-06-06

132

ANALYSIS OF THE MICROBIOLOGICAL PARTICULATES IN MUNICIPAL DRINKING-WATER BY SCANNING ELECTRON MICROSCOPY/X-RAY ENERGY SPECTROSCOPY (ANALYSE VON BIOLOGISCHEN PARTIKELN IM TRINKWASSER DURCH RASTERELEKTRONEN-MIKROSKOPIE UND ELEKTRONENSTRAHLMIKROANALYSE)  

EPA Science Inventory

Scanning electron microscopy and X-ray energy spectroscopy (SEM/XES) were used to survey the biological and nonbiological particles in two different municipal drinking-water systems. Microbiological particles could be differentiated from nonbiological by their qualitative element...

133

Chemical selective microstructural analysis of thin film using resonant x-ray reflectivity  

SciTech Connect

Strong modulations of the reflected x-ray intensities near the respective absorption edges of the constituent materials promise to determine layer composition of thin film structures along with spectroscopic like information. Near the absorption edge, the orders of magnitude more contrast beyond the pure electron density distributions of materials find an approach to overcome the low density difficulty of the conventional x-ray reflectivity technique. These aspects are explained by experimental studies on partially decomposed boron nitride thin films. Chemical composition profile is determined from free surface to the embedded buried layer with depth resolution in nanometer scale. The results of resonant reflectivity for chemical analysis are correlated with depth dependent x-ray photo electron spectroscopy.

Nayak, Maheswar; Lodha, G. S. [X-ray Optics Section, Indus Synchrotrons Utilization Division, Raja Ramanna Centre for Advanced Technology, Indore 452013, Madhya Pradesh (India)

2013-07-14

134

Feasibility considerations of a soft-x-ray distributed feedback laser pumped by an x-ray free electron laser  

NASA Astrophysics Data System (ADS)

We discuss the feasibility of a soft-x-ray distributed feedback laser (DFL) pumped by an x-ray free electron laser (X-FEL). The DFL under consideration is a Mg/SiC bi-layered Bragg reflector pumped by a single X-FEL bunch at 57.4?eV, stimulating the Mg L2,3 emission at 49?eV corresponding to the 3s–3d ?2p1/2,3/2 transition. Based on a model developed by Yariv and Yeh and an extended coupled-wave theory, we show that it would be possible to obtain a threshold gain compatible with the pumping provided by available X-FEL facilities.

André, Jean-Michel; Le Guen, Karine; Jonnard, Philippe

2014-08-01

135

Feasibility considerations of a soft-x-ray distributed feedback laser pumped by an x-ray free electron laser  

E-print Network

We discuss the feasibility of a soft-x-ray distributed feedback laser (DFL) pumped by an x-ray free electron laser (X-FEL). The DFL under consideration is a Mg/SiC bi-layered Bragg reflector pumped by a single X-FEL bunch at 57.4 eV, stimulating the Mg L2,3 emission at 49 eV corresponding to the 3s-3d â??2p1/2,3/2 transition. Based on a model developed by Yariv and Yeh and an extended coupled-wave theory, we show that it would be possible to obtain a threshold gain compatible with the pumping provided by available X-FEL facilities.

André, Jean-Michel; Jonnard, Philippe

2014-01-01

136

X-ray fluorescence analysis with synchrotron radiation  

NASA Astrophysics Data System (ADS)

The method of trace element analysis by X-ray fluorescence detection has been improved to an especially efficient multielement method for the ng to pg range in matrices containing light elements by the use of synchrotron radiation for excitation. It was necessary to determine the intensity and polarisation of the synchrotron radiation quantitatively. Inclusion of the vertical electron beam diameter and the divergence into the calculation, and definition of an effective vertical beam diameter by fitting the calculated polarisation spectrum leads to quantitative agreement between experimental and calculated absolute intensity spectra of scattered and fluorescent radiation of well-defined samples. This means that absolute mass determinations are in principle possible. The physical limits of detection calculated with these data agree very well with the experimental results. The limits of detection for special elements can be optimised by using different absorbers in the primary beam. They range from 0.05 to 0.2 ?g for organic matrix. This implies an absolute physical detection limit of 0.1 to 0.4 pg for a diameter of the primary beam of 0.5 mm and a sample of 1 mg/cm 2.

Knöchel, A.; Petersen, W.; Tolkiehn, G.

1983-04-01

137

Nuclear Resonance Energy Analysis of Inelastic X-Ray Scattering  

Microsoft Academic Search

Inelastic scattering of x rays by gaseous, liquid, and solid samples was measured using a nuclear transition as a reference for the energy analysis of the scattered radiation. The samples were irradiated by a beam of synchrotron radiation with a bandwidth of 6.4 meV. The scattered radiation was analyzed using a resonance detector with a bandpass of 0.5 mueV. These

A. I. Chumakov; A. Q. R. Baron; R. Rüffer; H. Grünsteudel; A. Meyer

1996-01-01

138

Image Analysis in X-ray Computed Tomography  

Microsoft Academic Search

Computed Tomography (CT) is a powerful nondestructive evaluation method for producing 2-D or 3-D cross-sectional image of body tissues and organs. X-ray scans furnish detailed images of an object such as dimensions, shape, internal defects and density for diagnostic and research purposes. The image-analysis technique includes: image acquisition, image processing, measurements, data processing, and interpretation. Statistical functions enable to analyze

Emilia Dana

139

X-ray emission from relativistically moving electron density cusps  

SciTech Connect

We report on novel methods to generate ultra-short, coherent, X-rays using a laserplasma interaction. Nonlinear interaction of intense laser pulses with plasma creates stable, specific structures such as electron cusps. For example, wake waves excited in an underdense plasma by an intense, short-pulse laser become dense and propagate along with the laser pulse. This is called a relativistic flying mirror. The flying mirror can reflect a counter-propagating laser pulse and directly convert it into high-frequency radiation, with a frequency multiplication factor of {approx} 4{gamma}{sup 2} and pulse shortening with the same factor. After the proof-of-principle experiments, we observed that the photon number generated in the flying mirror is close to the theoretical estimate. We present the details of the experiment in which a 9 TW laser pulse focused into a He gas jet generated the Flying Mirror, which partly reflected a 1 TW pulse, giving up to {approx} 10{sup 10} photons, 60 nJ (1.4 Multiplication-Sign 10{sup 12} photons/sr) in the XUV spectral region (12.8-22 nm).

Kando, M.; Pirozhkov, A. S.; Nakamura, T.; Hayashi, Y.; Kotaki, H.; Kawase, K.; Esirkepov, T. Zh.; Fukuda, Y.; Kiriyama, H.; Okada, H.; Daito, I.; Kameshima, T.; Mori, M.; Koga, J. K.; Daido, H.; Faenov, A. Ya.; Pikuz, T.; Ma, J.; Chen, L.-M.; Ragozin, E. N. [Japan Atomic Energy Agency (Japan); Osaka University (Japan); Joint Institute for High Temperature of the Russian Academy of Science, Moscow (Russian Federation); Institute of Physics, Chinese Academy of Sciences, Beijing (China); P. N. Lebedev Physical Institute of the Russian Academy of Sciences, Leninsky prospekt 53, 119991 Moscow (Russian Federation); Japan Atomic Energy Agency and Graduate School for the Creation of New Photonics Industries (Japan); Ludwig-Maximilians-University (Germany); and others

2012-07-11

140

X-ray source assembly having enhanced output stability, and fluid stream analysis applications thereof  

DOEpatents

An x-ray source assembly and method of operation are provided having enhanced output stability. The assembly includes an anode having a source spot upon which electrons impinge and a control system for controlling position of the anode source spot relative to an output structure. The control system can maintain the anode source spot location relative to the output structure notwithstanding a change in one or more operating conditions of the x-ray source assembly. One aspect of the disclosed invention is most amenable to the analysis of sulfur in petroleum-based fuels.

Radley, Ian (Glenmont, NY); Bievenue, Thomas J. (Delmar, NY); Burdett, John H. (Charlton, NY); Gallagher, Brian W. (Guilderland, NY); Shakshober, Stuart M. (Hudson, NY); Chen, Zewu (Schenectady, NY); Moore, Michael D. (Alplaus, NY)

2008-06-08

141

X-ray source assembly having enhanced output stability, and fluid stream analysis applications thereof  

DOEpatents

An x-ray source assembly (2700) and method of operation are provided having enhanced output stability. The assembly includes an anode (2125) having a source spot upon which electrons (2120) impinge and a control system (2715/2720) for controlling position of the anode source spot relative to an output structure. The control system can maintain the anode source spot location relative to the output structure (2710) notwithstanding a change in one or more operating conditions of the x-ray source assembly. One aspect of the disclosed invention is most amenable to the analysis of sulfur in petroleum-based fuels.

Radley, Ian; Bievenue, Thomas J.; Burdett Jr., John H.; Gallagher, Brian W.; Shakshober, Stuart M.; Chen, Zewu; Moore, Michael D.

2007-04-24

142

Crystallization, preliminary X-ray crystallographic and cryo-electron microscopy analysis of a bifunctional enzyme fucokinase/L-fucose-1-P-guanylyltransferase from Bacteroides fragilis.  

PubMed

Fucokinase/L-fucose-1-P-guanylyltransferase (FKP) is a bifunctional enzyme which converts L-fucose to Fuc-1-P and thence to GDP-L-fucose through a salvage pathway. The molecular weights of full-length FKP (F-FKP) and C-terminally truncated FKP (C-FKP, residues 300-949) are 105.7 and 71.7?kDa, respectively. In this study, both recombinant F-FKP and C-FKP were expressed and purified. Size-exclusion chromatography experiments and analytical ultracentrifugation results showed that both F-FKP and C-FKP are trimers. Native F-FKP protein was crystallized by the vapour-diffusion method and the crystals belonged to space group P212121 and diffracted synchrotron X-rays to 3.7?Å resolution. The crystal unit-cell parameters are a = 91.36, b = 172.03, c = 358.86?Å, ? = ? = ? = 90.00°. The three-dimensional features of the F-FKP molecule were observed by cryo-EM (cryo-electron microscopy). The preliminary cryo-EM experiments showed the F-FKP molecules as two parallel disc-shaped objects stacking together. Combining all results together, it is assumed that there are six FKP molecules in one asymmetric unit, which corresponds to a calculated Matthews coefficient of 2.19?Å(3)?Da(-1) with 43.83% solvent content. These preliminary crystallographic and cryo-EM microscopy analyses provide basic structural information on FKP. PMID:25195892

Cheng, Chongyun; Gu, Jianhua; Su, Jing; Ding, Wei; Yin, Jie; Liang, Wenguang; Yu, Xiaoxia; Ma, Jun; Wang, Peng George; Xiao, Zhicheng; Liu, Zhi-Jie

2014-09-01

143

Three-dimensional manipulation of electron beam phase space for seeding soft x-ray free-electron lasers  

E-print Network

In this letter, a simple technique is proposed to induce strong density modulation into the electron beam with small energy modulation. By using the combination of a transversely dispersed electron beam and a wave-front tilted seed laser, three-dimensional manipulation of the electron beam phase space can be utilized to significantly enhance the micro-bunching of seeded free-electron laser schemes, which will improve the performance and extend the short-wavelength range of a single-stage seeded free-electron laser. Theoretical analysis and numerical simulations demonstrate the capability of the proposed technique in a soft x-ray free-electron laser.

Feng, Chao; Deng, Haixiao; Zhao, Zhentang

2014-01-01

144

Three-dimensional manipulation of electron beam phase space for seeding soft x-ray free-electron lasers  

NASA Astrophysics Data System (ADS)

In this paper, a simple technique is proposed to induce strong density modulation into the electron beam with small energy modulation. By using the combination of a transversely dispersed electron beam and a wave-front tilted seed laser, three-dimensional manipulation of the electron beam phase space can be utilized to significantly enhance the microbunching of seeded free-electron laser schemes, which will improve the performance and extend the short-wavelength range of a single-stage seeded free-electron laser. Theoretical analysis and numerical simulations demonstrate the capability of the proposed technique in a soft x-ray free-electron laser.

Feng, Chao; Zhang, Tong; Deng, Haixiao; Zhao, Zhentang

2014-07-01

145

Enabling membrane protein structure and dynamics with X-ray free electron lasers.  

PubMed

Determining the three-dimensional structures and dynamics of membrane proteins remains one of the great challenges of modern biology. The recent availability of X-ray free electron laser (XFEL) light sources has opened the door to a new and revolutionary approach to performing X-ray analysis of these important biomolecules. Recent advances in sample delivery, data reduction, and phasing have enabled the high-resolution structural probing of membrane proteins at room temperature. While considerable challenges remain, the recent developments described in this review may ultimately provide structural biologists with powerful tools for obtaining unprecedented atomic-scale and dynamic visualization of membrane proteins at near-physiological conditions. PMID:24930119

Feld, Geoffrey K; Frank, Matthias

2014-08-01

146

Laboratory-size three-dimensional x-ray microscope with Wolter type I mirror optics and an electron-impact water window x-ray source  

NASA Astrophysics Data System (ADS)

We constructed a laboratory-size three-dimensional water window x-ray microscope that combines wide-field transmission x-ray microscopy with tomographic reconstruction techniques, and observed bio-medical samples to evaluate its applicability to life science research fields. It consists of a condenser and an objective grazing incidence Wolter type I mirror, an electron-impact type oxygen K? x-ray source, and a back-illuminated CCD for x-ray imaging. A spatial resolution limit of around 1.0 line pairs per micrometer was obtained for two-dimensional transmission images, and 1-?m scale three-dimensional fine structures were resolved.

Ohsuka, Shinji; Ohba, Akira; Onoda, Shinobu; Nakamoto, Katsuhiro; Nakano, Tomoyasu; Miyoshi, Motosuke; Soda, Keita; Hamakubo, Takao

2014-09-01

147

Boron Doped diamond films as electron donors in photovoltaics: An X-ray absorption and hard X-ray photoemission study  

SciTech Connect

Highly boron-doped diamond films are investigated for their potential as transparent electron donors in solar cells. Specifically, the valence band offset between a diamond film (as electron donor) and Cu(In,Ga)Se{sub 2} (CIGS) as light absorber is determined by a combination of soft X-ray absorption spectroscopy and hard X-ray photoelectron spectroscopy, which is more depth-penetrating than standard soft X-ray photoelectron spectroscopy. In addition, a theoretical analysis of the valence band is performed, based on GW quasiparticle band calculations. The valence band offset is found to be small: VBO?=?VBM{sub CIGS} – VBM{sub diamond}?=?0.3?eV?±?0.1?eV at the CIGS/Diamond interface and 0.0?eV?±?0.1?eV from CIGS to bulk diamond. These results provide a promising starting point for optimizing the band offset by choosing absorber materials with a slightly lower valence band maximum.

Kapilashrami, M.; Zegkinoglou, I. [Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Department of Physics, University of Wisconsin Madison, Madison, Wisconsin 53706 (United States); Conti, G.; Nemšák, S.; Conlon, C. S.; Fadley, C. S. [Department of Physics, University of California, Davis, California 95616 (United States); Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Törndahl, T.; Fjällström, V. [Ångström Solar Center, Uppsala University, Box 534, SE-751 21 Uppsala (Sweden); Lischner, J. [Department of Physics, University of California, Berkeley, California 94720 (United States); Louie, Steven G. [Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Department of Physics, University of California, Berkeley, California 94720 (United States); Hamers, R. J.; Zhang, L. [Department of Chemistry, University of Wisconsin Madison, Madison, Wisconsin 53706 (United States); Guo, J.-H. [Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Himpsel, F. J., E-mail: fhimpsel@wisc.edu [Department of Physics, University of Wisconsin Madison, Madison, Wisconsin 53706 (United States)

2014-10-14

148

Reabsorption of Soft X-Ray Emission at High X-Ray Free-Electron Laser Fluences  

NASA Astrophysics Data System (ADS)

We report on oxygen K-edge soft x-ray emission spectroscopy from a liquid water jet at the Linac Coherent Light Source. We observe significant changes in the spectral content when tuning over a wide range of incident x-ray fluences. In addition the total emission yield decreases at high fluences. These modifications result from reabsorption of x-ray emission by valence-excited molecules generated by the Auger cascade. Our observations have major implications for future x-ray emission studies at intense x-ray sources. We highlight the importance of the x-ray pulse length with respect to the core-hole lifetime.

Schreck, Simon; Beye, Martin; Sellberg, Jonas A.; McQueen, Trevor; Laksmono, Hartawan; Kennedy, Brian; Eckert, Sebastian; Schlesinger, Daniel; Nordlund, Dennis; Ogasawara, Hirohito; Sierra, Raymond G.; Segtnan, Vegard H.; Kubicek, Katharina; Schlotter, William F.; Dakovski, Georgi L.; Moeller, Stefan P.; Bergmann, Uwe; Techert, Simone; Pettersson, Lars G. M.; Wernet, Philippe; Bogan, Michael J.; Harada, Yoshihisa; Nilsson, Anders; Föhlisch, Alexander

2014-10-01

149

Reabsorption of soft x-ray emission at high x-ray free-electron laser fluences.  

PubMed

We report on oxygen K-edge soft x-ray emission spectroscopy from a liquid water jet at the Linac Coherent Light Source. We observe significant changes in the spectral content when tuning over a wide range of incident x-ray fluences. In addition the total emission yield decreases at high fluences. These modifications result from reabsorption of x-ray emission by valence-excited molecules generated by the Auger cascade. Our observations have major implications for future x-ray emission studies at intense x-ray sources. We highlight the importance of the x-ray pulse length with respect to the core-hole lifetime. PMID:25375708

Schreck, Simon; Beye, Martin; Sellberg, Jonas A; McQueen, Trevor; Laksmono, Hartawan; Kennedy, Brian; Eckert, Sebastian; Schlesinger, Daniel; Nordlund, Dennis; Ogasawara, Hirohito; Sierra, Raymond G; Segtnan, Vegard H; Kubicek, Katharina; Schlotter, William F; Dakovski, Georgi L; Moeller, Stefan P; Bergmann, Uwe; Techert, Simone; Pettersson, Lars G M; Wernet, Philippe; Bogan, Michael J; Harada, Yoshihisa; Nilsson, Anders; Föhlisch, Alexander

2014-10-10

150

Phase contrast: the frontier of x-ray and electron imaging  

NASA Astrophysics Data System (ADS)

Phase contrast has been a fundamental component of microscopy since the early 1940s. In broad terms, it refers to the formation of images using not the combination of wave intensities but their amplitudes with the corresponding phase factors. The impact on visible microscopy of biological specimens has been major. This contrast mechanism is now playing an increasingly important role in other kinds of microscopy, notably those based on electrons or x-rays. It notably solves the background problem of weak absorption contrast. New breakthroughs and new techniques are continuously produced, unfortunately unknown to most of the scientists that could exploit them. The present special cluster issue of reviews was inspired by this situation. The case of x-rays is very interesting. Phase contrast requires a high degree of longitudinal and lateral coherence. But conventional x-ray sources are not coherent. The progress of synchrotron sources yielded high coherence as a key byproduct—and started a rapid expansion of phase contrast radiology. No review—or cluster of reviews—can possibly cover all the facets of the recent progress. Without trying to be absolutely comprehensive, the present special cluster issue touches a variety of issues, giving a very broad picture. Liu et al review in general terms the different phase-based hard-x-ray techniques, with an interesting variety of examples. Then, Suortti et al and Wang et al present more specialized overviews of crystal and grating based x-ray imaging techniques, very powerful in the analysis of biological specimens. Mokso et al discuss the many facets of tomography using phase effects, expanding the picture of tomographic reconstruction of the three previous reviews. Wu et al treat the rapid progress in hard-x-ray focusing and its impact on radiology and tomography for materials science and biomedical research. The next two reviews deal with special and very interesting classes of applications. Specifically, Lee et al discuss the use of the new radiology techniques in the study of liquids, and Coan et al present the progress in phase-contrast radiology analysis of real patients. Although x-ray imaging is the main focus of the special cluster issue, the picture would not be complete without a view on the parallel and very exciting developments in electron microscopy. The last review, by Wu et al , is dedicated indeed to this broader picture, presenting recent progress in Zernike-related electron phase contrast. We trust that the special cluster issue will not only update readers on the evolution of a very important class of experimental techniques, but also prepare them for the forthcoming developments. We are indeed at the threshold of another revolution. The recently inaugurated first x-ray free electron lasers bring, together with many other record performances, full lateral coherence and excellent longitudinal coherence. The first imaging experiments show in practice their impact, and indicate that this field, far from saturating its progress, is ready for new major breakthroughs.

Hwu, Y.; Margaritondo, G.

2013-12-01

151

Plasma X-ray Spectra Analysis Using Genetic Algorithms Igor E. Golovkin  

E-print Network

Plasma X-ray Spectra Analysis Using Genetic Algorithms Igor E. Golovkin Department of Physics for plasma diagnostics. We use genetic algorithms to automatically analyze experi- mental X-ray line spectra-ray line spectra. 1 INTRODUCTION X-ray spectroscopic analysis is a widely used method for hot dense plasma

Louis, Sushil J.

152

Comparative X-ray Standing Wave Analysis of Metal-Phosphonate Multilayer Films of Dodecane and Porphyrin Molecular Square  

E-print Network

Comparative X-ray Standing Wave Analysis of Metal-Phosphonate Multilayer Films of Dodecane specular X-ray reflectivity (XRR), X-ray fluorescence, and long-period X-ray standing wave (XSW) analysis- deposited structural nature of the films. Herein we report a study using long period X-ray standing wave

153

X-Ray-Diffraction Tests Of Irradiated Electronic Devices: I  

NASA Technical Reports Server (NTRS)

X-ray-diffraction tests performed on aluminum conductors in commercial HI1-507A complementary metal oxide/semiconductor (CMOS) integrated-circuit analog multiplexers, both before and after circuits exposed to ionizing radiation from Co(60) source, and after postirradiation annealing at ambient and elevated temperatures. Tests in addition to electrical tests performed to determine effects of irradiation and of postirradiation annealing on electrical operating characteristics of circuits. Investigators sought to determine whether relationship between effects of irradiation on devices and physical stresses within devices. X-ray diffraction potentially useful for nondestructive measurement of stresses.

Shaw, David C.; Lowry, Lynn E.; Barnes, Charles E.

1993-01-01

154

The First Angstrom X-Ray Free-Electron Laser  

SciTech Connect

The Linac Coherent Light Source produced its first x-ray laser beam on 10 April 2009. Today it is routinely producing x-ray pulses with energy >2 mJ across the operating range from 820-8,200 eV. The facility has begun operating for atomic/molecular/optical science experiments. Performance of the facility in its first user run (1 October - 21 December) and current machine development activities will be presented. Early results from the preparations for the start of the second user run is also reported.

Galayda, John; /SLAC

2012-08-24

155

Win X-ray: A New Monte Carlo Program that Computes X-ray Spectra Obtained with a Scanning Electron Microscope  

NASA Astrophysics Data System (ADS)

A new Monte Carlo program, Win X-ray, is presented that predicts X-ray spectra measured with an energy dispersive spectrometer (EDS) attached to a scanning electron microscope (SEM) operating between 10 and 40 keV. All the underlying equations of the Monte Carlo simulation model are included. By simulating X-ray spectra, it is possible to establish the optimum conditions to perform a specific analysis as well as establish detection limits or explore possible peak overlaps. Examples of simulations are also presented to demonstrate the utility of this new program. Although this article concentrates on the simulation of spectra obtained from what are considered conventional thick samples routinely explored by conventional microanalysis techniques, its real power will be in future refinements to address the analysis of sample classifications that include rough surfaces, fine structures, thin films, and inclined surfaces because many of these can be best characterized by Monte Carlo methods. The first step, however, is to develop, refine, and validate a viable Monte Carlo program for simulating spectra from conventional samples.

Gauvin, Raynald; Lifshin, Eric; Demers, Hendrix; Horny, Paula; Campbell, Helen

2006-02-01

156

Win X-ray: a new Monte Carlo program that computes X-ray spectra obtained with a scanning electron microscope.  

PubMed

A new Monte Carlo program, Win X-ray, is presented that predicts X-ray spectra measured with an energy dispersive spectrometer (EDS) attached to a scanning electron microscope (SEM) operating between 10 and 40 keV. All the underlying equations of the Monte Carlo simulation model are included. By simulating X-ray spectra, it is possible to establish the optimum conditions to perform a specific analysis as well as establish detection limits or explore possible peak overlaps. Examples of simulations are also presented to demonstrate the utility of this new program. Although this article concentrates on the simulation of spectra obtained from what are considered conventional thick samples routinely explored by conventional microanalysis techniques, its real power will be in future refinements to address the analysis of sample classifications that include rough surfaces, fine structures, thin films, and inclined surfaces because many of these can be best characterized by Monte Carlo methods. The first step, however, is to develop, refine, and validate a viable Monte Carlo program for simulating spectra from conventional samples. PMID:17481341

Gauvin, Raynald; Lifshin, Eric; Demers, Hendrix; Horny, Paula; Campbell, Helen

2006-02-01

157

Calculation of x-ray spectra emerging from an x-ray tube. Part I. Electron penetration characteristics in x-ray targets  

SciTech Connect

The penetration characteristics of electron beams into x-ray targets are investigated for incident electron kinetic energies in the range 50-150 keV. The frequency densities of electrons penetrating to a depth x in a target, with a fraction of initial kinetic energy, u, are calculated using Monte Carlo methods for beam energies of 50, 80, 100, 120 and 150 keV in a tungsten target. The frequency densities for 100 keV electrons in Al, Mo and Re targets are also calculated. A mixture of simple modeling with equations and interpolation from data is used to generalize the calculations in tungsten. Where possible, parameters derived from the Monte Carlo data are compared to experimental measurements. Previous electron transport approximations in the semiempirical models of other authors are discussed and related to this work. In particular, the crudity of the use of the Thomson-Whiddington law to describe electron penetration and energy loss is highlighted. The results presented here may be used towards calculating the target self-attenuation correction for bremsstrahlung photons emitted within a tungsten target.

Poludniowski, Gavin G.; Evans, Philip M. [Joint Department of Physics, Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, Downs Road, Sutton, Surrey SM2 5PT (United Kingdom)

2007-06-15

158

X-ray analysis of poly(vinyl fluoride)  

SciTech Connect

Three different X-ray analysis technique were used to investigate the chain defect content present in the crystalline regions of poly(vinyl fluoride). The techniques used were a fiber pattern analysis, a powder pattern analysis, and a meridional intensity analysis. The fiber pattern analysis proved unable to determine either the tacticity or regic defect content in PVF. However, it was found that the refinement favored a statistical packing of the chains in the crystalline regions. This packing arrangement was supported by the powder pattern analysis and molecular modeling calculations. The meridional intensity analysis proved to be sensitive to the regic defect content of the sample. The results of this analysis correlated well with previous DSC work.

Lando, J.B. [Case Western Reserve Univ., Cleveland, OH (United States). Dept. of Macromolecular Science; Hanes, M.D. [Phillips Petroleum, Bartlesville, OK (United States)

1995-02-13

159

The soft x-ray instrument for materials studies at the linac coherent light source x-ray free-electron laser  

SciTech Connect

The soft x-ray materials science instrument is the second operational beamline at the linac coherent light source x-ray free electron laser. The instrument operates with a photon energy range of 480-2000 eV and features a grating monochromator as well as bendable refocusing mirrors. A broad range of experimental stations may be installed to study diverse scientific topics such as: ultrafast chemistry, surface science, highly correlated electron systems, matter under extreme conditions, and laboratory astrophysics. Preliminary commissioning results are presented including the first soft x-ray single-shot energy spectrum from a free electron laser.

Schlotter, W. F.; Turner, J. J.; Rowen, M.; Holmes, M.; Messerschmidt, M.; Moeller, S.; Krzywinski, J.; Lee, S.; Coffee, R.; Hays, G. [LCLS, SLAC National Accelerator Laboratory, 2575 Sand Hill Rd., Menlo Park, California 94025 (United States); Heimann, P. [LCLS, SLAC National Accelerator Laboratory, 2575 Sand Hill Rd., Menlo Park, California 94025 (United States); Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Krupin, O. [LCLS, SLAC National Accelerator Laboratory, 2575 Sand Hill Rd., Menlo Park, California 94025 (United States); European XFEL GmbH, Albert-Einstein-Ring 19, 22761 Hamburg (Germany); Soufli, R.; Fernandez-Perea, M.; Hau-Riege, S. [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550 (United States); Kelez, N. [Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Beye, M.; Gerken, N.; Sorgenfrei, F.; Wurth, W. [Institute for Experimental Physics and CFEL, University of Hamburg, Luruper Chaussee 149, 22761 Hamburg (Germany); and others

2012-04-15

160

Proposal for a pulse-compression scheme in x-ray free-electron lasers to generate a multiterawatt, attosecond x-ray pulse.  

PubMed

A novel scheme to compress the radiation pulse in x-ray free electron lasers is proposed not only to shorten the pulse length but also to enhance the peak power of the radiation, by inducing a periodic current enhancement with an optical laser and applying a temporal shift between the optical and electron beams. Calculations show that a 10-keV x-ray pulse with a peak power of 5 TW and a pulse length of 50 asec can be generated by applying this scheme to an existing x-ray free electron laser facility. PMID:23473154

Tanaka, Takashi

2013-02-22

161

Near-monochromatic X-ray beams produced by the free electron laser and Compton backscatter  

Microsoft Academic Search

The intense photon output of a free electron laser may be made to collide with its own high energy electron beam to create nearly monochromatic x-rays using Compton backscatter techniques. These x-rays can be used for imaging and non-imaging diagnostic and therapeutic experiments. The initial configuration of the Vanderbilt Medical Free Electron Laser (Sierra Laser Systems, Sunnyvale, CA) produces intense

FRANK E. CARROLL; JAMES W. WATERS; RON R. PRICE; CHARLES A. BRAU; CARLTON F. ROOS; NORMAN H. TOLK; DAVID R. PICKENS; W. HOYT STEPHENS

1990-01-01

162

Femtosecond electronic response of atoms to ultra-intense x-rays.  

SciTech Connect

An era of exploring the interactions of high-intensity, hard X-rays with matter has begun with the start-up of a hard-X-ray free-electron laser, the Linac Coherent Light Source (LCLS). Understanding how electrons in matter respond to ultra-intense X-ray radiation is essential for all applications. Here we reveal the nature of the electronic response in a free atom to unprecedented high-intensity, short-wavelength, high-fluence radiation (respectively 10{sup 18} W cm{sup -2}, 1.5-0.6 nm, {approx}10{sup 5} X-ray photons per {angstrom}{sup 2}). At this fluence, the neon target inevitably changes during the course of a single femtosecond-duration X-ray pulse - by sequentially ejecting electrons - to produce fully-stripped neon through absorption of six photons. Rapid photoejection of inner-shell electrons produces 'hollow' atoms and an intensity-induced X-ray transparency. Such transparency, due to the presence of inner-shell vacancies, can be induced in all atomic, molecular and condensed matter systems at high intensity. Quantitative comparison with theory allows us to extract LCLS fluence and pulse duration. Our successful modelling of X-ray/atom interactions using a straightforward rate equation approach augurs favourably for extension to complex systems.

Young, L.; Kanter, E .P.; Li, Y.; March, A.-M.; Pratt, S. T.; Santra, R.; Southworth, S. H.; Rohringer, N.; DiMauro, L. F.; Doumy, G.; Roedig, C. A.; Berrah, N.; Fang, L.; Hoener, M.; Bucksbaum, P. H.; Cryan, J. P .; Ghimire, S.; Glownia, J. M.; Reis, D. A.; Bozek, J. D.; Bostedt, C.; Messerschmidt, M.; Western Michigan Univ.; SLAC National Accelerator Lab.; The Ohio State Univ.; LLNL; Univ. of Chicago

2010-07-01

163

New event analysis method with the x-ray CCD camera XIS for ASTRO-E  

Microsoft Academic Search

We introduce a new method of event analysis with the x-ray CCD camera (XIS) on board the next Japanese X-ray astronomical satellite, Astro-E. In the ordinary method, we used 'grade' classification; we distinguished the x-ray events from background events by referring the shape and the extent of the charge-split pixels, because non x-ray events spread to many pixels. However, at

Hiroshi Murakami; Takeshi G. Tsuru; Hisamitsu Awaki; Masaaki Sakano; Mamiko Nishiuchi; Kenji Hamaguchi; Katsuji Koyama; Hiroshi Tsunemi

1999-01-01

164

Inferring the Energy Distribution of Accelerated Electrons in Solar Flares from X-ray Observations  

NASA Technical Reports Server (NTRS)

Knowledge of the energy distribution of electrons accelerated in solar flares is important for constraining possible acceleration mechanisms and for understanding the relationships between flare X-ray sources, radio sources, and particles observed in space. Solar flare hard X-rays are primarily emitted from dense, thick-target regions in the lower atmosphere, but the electrons are understood to be accelerated higher in the corona. Various processes can distort the X-ray spectrum or the energy distribution of electrons before they reach the thick-target region. After briefly reviewing the processes that affect the X-ray spectrum and the electron distribution, I will describe recent results from a study of flare spectra from RHESSI to determine the importance of these processes in inferring the energy distribution of accelerated electrons.

Holman, Gordon D.; Sui, Linhui; Su, Yang

2008-01-01

165

Methods development for diffraction and spectroscopy studies of metalloenzymes at X-ray free-electron lasers.  

PubMed

X-ray free-electron lasers (XFELs) open up new possibilities for X-ray crystallographic and spectroscopic studies of radiation-sensitive biological samples under close to physiological conditions. To facilitate these new X-ray sources, tailored experimental methods and data-processing protocols have to be developed. The highly radiation-sensitive photosystem II (PSII) protein complex is a prime target for XFEL experiments aiming to study the mechanism of light-induced water oxidation taking place at a Mn cluster in this complex. We developed a set of tools for the study of PSII at XFELs, including a new liquid jet based on electrofocusing, an energy dispersive von Hamos X-ray emission spectrometer for the hard X-ray range and a high-throughput soft X-ray spectrometer based on a reflection zone plate. While our immediate focus is on PSII, the methods we describe here are applicable to a wide range of metalloenzymes. These experimental developments were complemented by a new software suite, cctbx.xfel. This software suite allows for near-real-time monitoring of the experimental parameters and detector signals and the detailed analysis of the diffraction and spectroscopy data collected by us at the Linac Coherent Light Source, taking into account the specific characteristics of data measured at an XFEL. PMID:24914169

Kern, Jan; Hattne, Johan; Tran, Rosalie; Alonso-Mori, Roberto; Laksmono, Hartawan; Gul, Sheraz; Sierra, Raymond G; Rehanek, Jens; Erko, Alexei; Mitzner, Rolf; Wernet, Phillip; Bergmann, Uwe; Sauter, Nicholas K; Yachandra, Vittal; Yano, Junko

2014-07-17

166

Investigation of surface structure with X-ray absorption and electron emission spectroscopies  

NASA Astrophysics Data System (ADS)

The use of electron spectromicroscopy for the study of the chemical composition and electronic properties of surfaces, overlayers, and interfaces has become widely accepted. Improvements to the optics of instruments such as the X-ray photo electron emission microscope have pushed spectroscopic microscopies into the realm of very high spatial resolution, at and below 1 micrometer [1]. Coupled with the high spectral resolution available from third generation synchrotron sources, this spatial resolution allows the measurement of micro-X-ray absorption near-edge spectra in addition to the more typical electron emission spectra and diffraction patterns. Complementary to the experimental developments is the development of improved theoretical methods for computational modeling of X-ray absorption and emission spectroscopies. In the field of tribochemistry, zinc dialkyl dithiophosphate (ZDDP) has long been a topic of much study. ZDDP is widely used as an anti-wear additive in engine oils and there is interest in determining the decomposition products of ZDDP that provide this protection against friction. An analysis of X-ray absorption near-edge spectra of thermal films from ZDDP samples is presented, including a comparison of the Zinc L-edge spectra with model calculations [2]. It was found essential to carry out self-consistent calculations of the electronic structure for the modeling. For the techniques of electron diffraction, a new method for a full multiple-scattering calculation of diffraction patterns from crystals with two-dimensional periodicity parallel to the surface is presented [3]. The calculation makes use of Helmholtz's reciprocity principle to compute the path-reversed process of the back propagation of a photoelectron from the position of a distant detector to that of the emitting atom. Early application is demonstrated with simulations of 64 eV M2,3VV and 914 eV L 2,3VV Auger electron diffraction from a Cu(001) surface. The functionality of the path-reversed calculation is greatly increased by extension to photoelectron diffraction for crystal surfaces with many atoms per unit cell [4]. The results are essentially indistinguishable from those of a conventional forward-path calculation. Application to photoelectron diffraction for 955 eV O 1s emission from a MgO(001) surface shows good agreement with experiment.

Pauli, Mark Daniel

167

Femtosecond X-Ray Free Electron Laser Pulse Duration Measurement from Spectral Correlation Function  

SciTech Connect

We present a novel method for measuring the duration of femtosecond x-ray pulses from self-amplified spontaneous emission free electron lasers by performing statistical analysis in the spectral domain. Analytical expressions of the spectral correlation function were derived in the linear regime to extract both the pulse duration and the spectrometer resolution. Numerical simulations confirmed that the method can be also used in the nonlinear regime. The method was demonstrated experimentally at the Linac Coherent Light Source by measuring pulse durations down to 13 fs FWHM.

Lutman, A. A

2012-04-17

168

Damage threshold investigation using grazing incidence irradiation by hard x-ray free electron laser  

NASA Astrophysics Data System (ADS)

X-ray free electron lasers (XFELs) with intense and ultra-short pulse X-rays possibly induce damage to optical elements. We investigated the damage thresholds of optical materials by using focusing XFEL beams with sufficient power density for studying ablation phenomena. 1-?m focusing beams with 10 keV photon energy were produced at the XFEL facility SACLA (SPring-8 Angstrom Compact free electron LAser). The focusing beams irradiated samples of rhodium-coated substrate, which is used in X-ray mirror optics, under grazing incident condition.

Koyama, T.; Yumoto, H.; Tono, K.; Sato, T.; Togashi, T.; Inubushi, Y.; Katayama, T.; Kim, J.; Matsuyama, S.; Mimura, H.; Yabashi, M.; Yamauchi, K.; Ohashi, H.

2013-09-01

169

Combining Electron Microscopic with X-Ray Crystallographic Structures  

Microsoft Academic Search

Analgorithm has been developed for placing three-dimensional atomic structures into appropriately scaled cryoelectron microscopy maps. The first stage in this process is to conduct a three-dimensional angular search in which the center of gravity of an X-ray crystallographically determined structure is placed on a selected position in the cryoelectron microscopy map. The quality of the fit is measured by the

Michael G. Rossmann; Ricardo Bernal; Sergei V. Pletnev

2001-01-01

170

Surface roughness analysis of multilayer x-ray optics  

NASA Astrophysics Data System (ADS)

Rigaku Innovative Technologies (RIT) produces x-ray optics based on multilayer mirrors. A multilayer mirror is deposited on a wafer and mounted on a solid backing plate in an elliptical shape to focus x-rays. The wafer surface imperfections, defects from the multilayer deposition, and figure errors induced by the mounting process result in some focal spot widening for the final optics. An AFM is used in the spatial period range 0.1 - 10 microns, and a "ZYGO" interferometric microscope is used in the spatial period range 1 micron - 5 mm, to study these imperfections determining the influence of each technological step on the focal spot quality. AFM analysis shows dramatically different roughness between 1 x 1 micron and 20 x 20 micron field of view on super-polished substrates from some suppliers and only a little difference from others. A smoothing effect of a multilayer coating at spatial periods less than one micron as well as defects in multilayer coatings have been observed with power spectral density analysis. Machining marks on the surface of wafers are clearly seen at ZYGO microscope pictures. Ray-tracing simulations based on the ZYGO data show the focal spot shape changes due to the figure errors introduced at the step of a multilayer coated wafer mounting and only background scattering with no focal spot widening from defects induced at the step of multilayer deposition.

Martynov, Vladimir V.; Platonov, Yuriy Y.

2008-08-01

171

A simulation of X-ray shielding for a superconducting electron cyclotron resonance ion source  

SciTech Connect

It is generally assumed that large amounts of x-rays are emitted from the ion source of an Electron Cyclotron Resonance (ECR) instrument. The total amount of x-rays should be strictly limited to avoid the extra heat load to the cryostat of the superconducting ECR ion source, since they are partly absorbed by the cold mass into the cryostat. A simulation of x-ray shielding was carried out to determine the effective thickness of the x-ray shield needed via the use of Geant4. X-ray spectra of the 10 GHz Nanogan ECR ion source were measured as a function of the thickness variation in the x-ray shield. The experimental results were compared with Geant4 results to verify the effectiveness of the x-ray shield. Based on the validity in the case of the 10 GHz ECR ion source, the x-ray shielding results are presented by assuming the spectral temperature of the 28 GHz ECR ion source.

Park, Jin Yong; Won, Mi-Sook; Lee, Byoung-Seob; Yoon, Jang-Hee; Choi, Seyong; Ok, Jung-Woo [Busan Center, Korea Basic Science Institute, Busan 609-735 (Korea, Republic of)] [Busan Center, Korea Basic Science Institute, Busan 609-735 (Korea, Republic of); Choi, Jeong-Sik [Hydrogen Energy Department, Dong-shin University, Naju, Jeonnam 520-714 (Korea, Republic of)] [Hydrogen Energy Department, Dong-shin University, Naju, Jeonnam 520-714 (Korea, Republic of); Kim, Byoung-Chul, E-mail: bchkim@kriss.re.kr [Center for Ionizing Radiation, Korea Research Institute of Standards and Science, Daejeon 305-340 (Korea, Republic of)] [Center for Ionizing Radiation, Korea Research Institute of Standards and Science, Daejeon 305-340 (Korea, Republic of)

2014-02-15

172

A simulation of X-ray shielding for a superconducting electron cyclotron resonance ion source.  

PubMed

It is generally assumed that large amounts of x-rays are emitted from the ion source of an Electron Cyclotron Resonance (ECR) instrument. The total amount of x-rays should be strictly limited to avoid the extra heat load to the cryostat of the superconducting ECR ion source, since they are partly absorbed by the cold mass into the cryostat. A simulation of x-ray shielding was carried out to determine the effective thickness of the x-ray shield needed via the use of Geant4. X-ray spectra of the 10 GHz Nanogan ECR ion source were measured as a function of the thickness variation in the x-ray shield. The experimental results were compared with Geant4 results to verify the effectiveness of the x-ray shield. Based on the validity in the case of the 10 GHz ECR ion source, the x-ray shielding results are presented by assuming the spectral temperature of the 28 GHz ECR ion source. PMID:24593527

Park, Jin Yong; Won, Mi-Sook; Lee, Byoung-Seob; Yoon, Jang-Hee; Choi, Seyong; Ok, Jung-Woo; Choi, Jeong-Sik; Kim, Byoung-Chul

2014-02-01

173

A simulation of X-ray shielding for a superconducting electron cyclotron resonance ion source  

NASA Astrophysics Data System (ADS)

It is generally assumed that large amounts of x-rays are emitted from the ion source of an Electron Cyclotron Resonance (ECR) instrument. The total amount of x-rays should be strictly limited to avoid the extra heat load to the cryostat of the superconducting ECR ion source, since they are partly absorbed by the cold mass into the cryostat. A simulation of x-ray shielding was carried out to determine the effective thickness of the x-ray shield needed via the use of Geant4. X-ray spectra of the 10 GHz Nanogan ECR ion source were measured as a function of the thickness variation in the x-ray shield. The experimental results were compared with Geant4 results to verify the effectiveness of the x-ray shield. Based on the validity in the case of the 10 GHz ECR ion source, the x-ray shielding results are presented by assuming the spectral temperature of the 28 GHz ECR ion source.

Park, Jin Yong; Won, Mi-Sook; Lee, Byoung-Seob; Yoon, Jang-Hee; Choi, Seyong; Ok, Jung-Woo; Choi, Jeong-Sik; Kim, Byoung-Chul

2014-02-01

174

Artificial neural networks for plasma x-ray spectroscopic analysis  

SciTech Connect

Modern diagnostic instrumentation produces a vast amount of data that often requires substantial analysis efforts. New methods are needed to improve the efficiency of the analysis process. Artificial neural networks have been applied to a variety of signal processing and image recognition problems. The feed-forward, back-propagation technique is well suited for the analysis of scientific laboratory data, which is viewed as a pattern-matching problem. We summarize the concepts and algorithms as implemented on a personal computer, and illustrate the method using a nonlocal thermodynamic equilibrium theoretical atomic physics model for {ital k}-shell x-ray spectroscopy of a high density, high temperature aluminum plasma. Extensions to other types of spectroscopy data analysis are discussed.

Larsen, J.T. (Cascade Applied Sciences, Inc., P. O. Box 4477, Boulder, Colorado 80306 (United States)); Morgan, W.L. (Kinema Research, 18720 Autumn Way, Monument, Colorado 80132 (United States)); Goldstein, W.H. (Lawrence Livermore National Laboratory, Livermore, California 94550 (United States))

1992-10-01

175

Pair production from vacuum at the focus of an X-ray free electron laser  

Microsoft Academic Search

There are definite plans for the construction of X-ray free electron lasers (FEL), both at DESY, where the so-called XFEL is part of the design of the electron–positron linear collider TESLA, as well as at SLAC, where the so-called Linac Coherent Light Source (LCLS) has been proposed. Such an X-ray laser would allow for high-field science applications: one could make

A. Ringwald

2001-01-01

176

Electronic Structure of KH2PO4 Single Crystal Studied by Soft-X-Ray Spectroscopy  

Microsoft Academic Search

The problem of resolving molecular components of the electronic structure of KH2PO4 single crystal with respect to its chemical and orbital character has been approached by X-ray absorption spectroscopy (XAS) and soft X-ray emission spectroscopy (SXES). XAS around K-absorption edge of O atom was carried out in order to the existence of relation between the electronic structure and ferroelectric phase

Tetsuya Nishina; Tohru Higuchi; Eisuke Magome; Poul Olade Velasco; Jeng Long Chen; Wang Li Yang; Jinghua Guo; Masanori Fukunaga; Masaru Komukae

2011-01-01

177

X-ray diagnostics of runaway electrons in fast gas discharges  

Microsoft Academic Search

Results from experimental studies of x-ray emission during gas discharges are reported. They confirm experimentally the presence of runaway electrons in short, high-pressure discharges under highly overvolted conditions. These electrons, when stopped at the anode, produce x-ray radiation. A high-energy component above 3 keV was measured. The effects of the type of gas, its pressure, electrode separation, and applied voltage

W. W. Byszewski; G. Reinhold

1982-01-01

178

2014 9 30 XFEL: X-ray Free Electron LaserSACLA[1] X [2  

E-print Network

1 2014 9 30 X SACLA X X X X X XFEL: X-ray Free Electron LaserSACLA[1] X [2-5841-6550 FAX : 03-5841-6550 E-mailmimura@edm.t.u-tokyo.ac.jp TEL075-753-3750 FAX075-753-3819 E-753-2094 [1] X XFEL: X-ray Free Electron LaserSACLA XFEL 5 1 2006 5 2011 3 SPring-8 Angstrom Compact

Yamamoto, Hirosuke

179

Hard X-ray Spectra and Positions of Solar Flares observed by RHESSI: photospheric albedo, directivity and electron spectra  

E-print Network

We investigate the signature of the photospheric albedo contribution in solar flare hard X-ray spectra, the effect of low energy cutoffs in electron spectra, and the directivity of hard X-ray emission. Using Ramaty High Energy Solar Spectroscopic Imager (RHESSI) flare data we perform a statistical analysis of spatially integrated spectra and positions of solar flares. We demonstrate clear centre-to-limb variation of photon spectral indices in the 15-20 keV energy range and a weaker dependency in the 20-50 keV range which is consistent with photospheric albedo as the cause. The results also suggest that low-energy cutoffs sometimes inferred in mean electron spectra are an artefact of albedo. We also derive the anisotropy (ratio of downward/observer directed photons) of hard X-ray emission in the 15-20 keV range for various heliocentric angles.

J. Kasparova; E. P. Kontar; J. C. Brown

2007-01-30

180

X-ray observations of MeV electron precipitation with a balloon-borne germanium spectrometer  

E-print Network

X-ray observations of MeV electron precipitation with a balloon-borne germanium spectrometer R. M-resolution germanium detector aboard the MAXIS (MeV Auroral X-ray Imaging and Spectroscopy) balloon payload detected, and M. P. McCarthy, X-ray observations of MeV electron precipitation with a balloon-borne germanium

California at Berkeley, University of

181

Fractal analysis of powder X-ray diffraction patterns  

NASA Astrophysics Data System (ADS)

X-ray diffraction (XRD) patterns with broad background are commonly found in the characterization of materials with a certain degree of amorphicity, so the sharp intensity peaks associated with material phases are not well defined. This work used rescaled range (denoted by R/S) analysis, a method intended for fractal analysis of noisy signals, to characterize XRD patterns with broad background. It is found that XRD patterns with broad background are not random at all, but contain information on regularities expressed as autocorrelations of the intensity signal. Sol-gel alumina fired at different temperatures was used as an example to illustrate the applicability of the method. It is shown that fractal R/S analysis is able to locate angular regions that can be associated to ideal International Centre for Diffraction Data Powder Diffraction File (ICDD PDF) lines of diverse alumina phases.

Ortiz-Cruz, A.; Santolalla, C.; Moreno, E.; de los Reyes-Heredia, J. A.; Alvarez-Ramirez, J.

2012-02-01

182

X-ray free-electron lasers--present and future capabilities [Invited  

SciTech Connect

The Linac Coherent Light Source is now in operation as an X-ray free-electron laser (FEL) user facility. It produces coherent pulses of 550-10,000 eV X-rays of duration adjustable from <10 fs to 500 fs. Typical peak power is in excess of 20 GW. The facility will soon be joined by several X-ray FELs under construction around the world. This article will provide an abridged history of free-electron lasers, a description of some basic physics regarding free-electron laser light amplification, and an overview of the rapidly growing list of examples in which lasers will be used in the control and operation of X-ray FELs.

Galayda, John N.; Arthur, John; Ratner, Daniel F.; White, William E. [SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025 (United States)

2010-11-15

183

X-ray Free-Electron Lasers - Present and Future Capabilities [Invited  

SciTech Connect

The Linac Coherent Light Source is now in operation as an X-ray free-electron laser (FEL) user facility. It produces coherent pulses of 550-10,000 eV X-rays of duration adjustable from <10 fsto500 fs. Typical peak power is in excess of 20 GW. The facility will soon be joined by several X-ray FELs under construction around the world. This article will provide an abridged history of free-electron lasers, a description of some basic physics regarding free-electron laser light amplification, and an overview of the rapidly growing list of examples in which lasers will be used in the control and operation of X-ray FELs.

Galayda, John; Ratner, John Arthur:a Daniel F.; White, William E.; /SLAC

2011-11-16

184

Observation of pulsed x-ray trains produced by laser-electron Compton scatterings  

SciTech Connect

X-ray generation based on laser-electron Compton scattering is one attractive method to achieve a compact laboratory-sized high-brightness x-ray source. We have designed, built, and tested such a source; it combines a 50 MeV multibunch electron linac with a mode-locked 1064 nm laser stored and amplified in a Fabry-Perot optical cavity. We directly observed trains of pulsed x rays using a microchannel plate detector; the resultant yield was found to be 1.2x10{sup 5} Hz in good agreement with prediction. We believe that the result has demonstrated good feasibility of linac-based compact x-ray sources via laser-electron Compton scatterings.

Sakaue, Kazuyuki; Washio, Masakazu [Research Institute for Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555 (Japan); Araki, Sakae; Fukuda, Masafumi; Higashi, Yasuo; Honda, Yosuke; Omori, Tsunehiko; Taniguchi, Takashi; Terunuma, Nobuhiro; Urakawa, Junji [KEK (High Energy Accelerator Research Organization), 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan); Sasao, Noboru [Department of Physics, Kyoto University, Sakyo, Kyoto 606-8502 (Japan)

2009-12-15

185

MESSENGER X-RAY SPECTROMETER DETECTION OF ELECTRON-INDUCED X-RAY FLUORESCENCE FROM MERCURY'S SURFACE. Richard D. Starr (richard.d.starr@nasa.gov)1,2  

E-print Network

spacecraft measures ele- mental abundances on the surface of Mercury by de- tecting fluorescent X-rayMESSENGER X-RAY SPECTROMETER DETECTION OF ELECTRON-INDUCED X-RAY FLUORESCENCE FROM MERCURY, University of California, Los Angeles, CA 90095, USA. Introduction: X-ray emission from solar system bodies

Nittler, Larry R.

186

X-Ray Diffraction Analysis of NLO Crystals: Traditional Applications and More New Opportunities  

NASA Technical Reports Server (NTRS)

Single crystal X-ray diffraction analysis is one of the more important methods for the molecular and crystal structure determination of matter and therefore it has a great importance in material science including design and engineering of different compounds with non-linear optical (NLO) properties. It was shown in our previous publications that this method provides unique information about molecular structure of NLO compounds, their crystal symmetry and crystal packing arrays, molecular conformation and geometries and many other structural and electronic characteristics that are important for understanding the nature of NLO properties of solids. A very new application of the X-ray diffraction method is related to analysis of the electron density distribution p(r) in crystals and some of its characteristics (atomic and group charges, dipole and higher multipole moments, etc.), that may be obtained directly form the diffraction measurements. In the present work, we will discuss our preliminary low temperature high-resolution X-ray data for the m-nitroaniline (mNA) single crystal (VI). This is one of the "classical" organic NLO materials and electron density distribution analysis in this simple compound has a great scientific interest.

Antipin, Mikhail Yu.; Clark, Ronald D.; Nesterov, Vladimir N.

1998-01-01

187

X-ray Microtomographic Imaging and Analysis for Basic Research  

Microsoft Academic Search

For research facilities with access to synchrotron X-ray sources, X-ray absorption microtomography (XMT) has evolved from an experimental imaging method to a specialized, if not yet routine, microscopy for imaging the three-dimensional (3D) distribution of linear attenuation coefficients and, in some cases, elemental concentration with micron spatial resolution. Recent advances in source and detector design have produced conventional X-ray source

J. Dunsmuir; S. Bennett; L. Fareria; A. Mingino; M. Sansone

2007-01-01

188

A Sealed, UHV Compatible, Soft X-ray Detector Utilizing Gas Electron Multipliers  

SciTech Connect

An advanced soft X-ray detector has been designed and fabricated for use in synchrotron experiments that utilize X-ray absorption spectroscopy in the study a wide range of materials properties. Fluorescence X-rays, in particular C{sub K} at 277eV, are converted in a low pressure gas medium, and charge multiplication occurs in two gas electron multipliers, fabricated in-house from glass reinforced laminate, to enable single photon counting. The detector satisfies a number of demanding characteristics often required in synchrotron environments, such as UHV compatibility compactness, long-term stability, and energy resolving capability.

Schaknowski, N.A.; Smith, G.

2009-10-25

189

Influence of Bernstein modes on the efficiency of electron cyclotron resonance x-ray source  

Microsoft Academic Search

The article considers the factors influencing the temperature of hot electron component in an electron cyclotron resonance (ECR) x-ray source. In such sources the electron heating occurs often due to extraordinary electromagnetic wave propagating perpendicularly to the magnetic field. In this case the possibility of the absorption of Bernstein modes is regarded as an additional mechanism of electron heating. The

V. V. Andreev; G. V. Nikitin; V. Yu. Savanovich; A. M. Umnov; L. I. Elizarov; K. S. Serebrennikov; E. A. Vostrikova

2006-01-01

190

High-intensity double-pulse X-ray free-electron laser  

NASA Astrophysics Data System (ADS)

The X-ray free-electron laser has opened a new era for photon science, improving the X-ray brightness by ten orders of magnitude over previously available sources. Similar to an optical laser, the spectral and temporal structure of the radiation pulses can be tailored to the specific needs of many experiments by accurately manipulating the lasing medium, that is, the electron beam. Here we report the generation of mJ-level two-colour hard X-ray pulses of few femtoseconds duration with an XFEL driven by twin electron bunches at the Linac Coherent Light Source. This performance represents an improvement of over an order of magnitude in peak power over state-of-the-art two-colour XFELs. The unprecedented intensity and temporal coherence of this new two-colour X-ray free-electron laser enable an entirely new set of scientific applications, ranging from X-ray pump/X-ray probe experiments to the imaging of complex biological samples with multiple wavelength anomalous dispersion.

Marinelli, A.; Ratner, D.; Lutman, A. A.; Turner, J.; Welch, J.; Decker, F.-J.; Loos, H.; Behrens, C.; Gilevich, S.; Miahnahri, A. A.; Vetter, S.; Maxwell, T. J.; Ding, Y.; Coffee, R.; Wakatsuki, S.; Huang, Z.

2015-03-01

191

High-intensity double-pulse X-ray free-electron laser.  

PubMed

The X-ray free-electron laser has opened a new era for photon science, improving the X-ray brightness by ten orders of magnitude over previously available sources. Similar to an optical laser, the spectral and temporal structure of the radiation pulses can be tailored to the specific needs of many experiments by accurately manipulating the lasing medium, that is, the electron beam. Here we report the generation of mJ-level two-colour hard X-ray pulses of few femtoseconds duration with an XFEL driven by twin electron bunches at the Linac Coherent Light Source. This performance represents an improvement of over an order of magnitude in peak power over state-of-the-art two-colour XFELs. The unprecedented intensity and temporal coherence of this new two-colour X-ray free-electron laser enable an entirely new set of scientific applications, ranging from X-ray pump/X-ray probe experiments to the imaging of complex biological samples with multiple wavelength anomalous dispersion. PMID:25744344

Marinelli, A; Ratner, D; Lutman, A A; Turner, J; Welch, J; Decker, F-J; Loos, H; Behrens, C; Gilevich, S; Miahnahri, A A; Vetter, S; Maxwell, T J; Ding, Y; Coffee, R; Wakatsuki, S; Huang, Z

2015-01-01

192

High-intensity double-pulse X-ray free-electron laser  

PubMed Central

The X-ray free-electron laser has opened a new era for photon science, improving the X-ray brightness by ten orders of magnitude over previously available sources. Similar to an optical laser, the spectral and temporal structure of the radiation pulses can be tailored to the specific needs of many experiments by accurately manipulating the lasing medium, that is, the electron beam. Here we report the generation of mJ-level two-colour hard X-ray pulses of few femtoseconds duration with an XFEL driven by twin electron bunches at the Linac Coherent Light Source. This performance represents an improvement of over an order of magnitude in peak power over state-of-the-art two-colour XFELs. The unprecedented intensity and temporal coherence of this new two-colour X-ray free-electron laser enable an entirely new set of scientific applications, ranging from X-ray pump/X-ray probe experiments to the imaging of complex biological samples with multiple wavelength anomalous dispersion. PMID:25744344

Marinelli, A.; Ratner, D.; Lutman, A. A.; Turner, J.; Welch, J.; Decker, F.-J.; Loos, H.; Behrens, C.; Gilevich, S.; Miahnahri, A. A.; Vetter, S.; Maxwell, T.J.; Ding, Y.; Coffee, R.; Wakatsuki, S.; Huang, Z.

2015-01-01

193

X-RAY NONLINEAR OPTICAL PROCESSES IN ATOMS USING A SELF-AMPLIFIED SPONTANEOUS EMISSION FREE-ELECTRON LASER  

SciTech Connect

X-ray free electron lasers (xFEL) will open new avenues to the virtually unexplored territory of non-linear interactions of x rays with matter. Initially xFELs will be based on the principle of self-amplified spontaneous emission (SASE). Each SASE pulse consists of a number of coherent intensity spikes of random amplitude, i.e. the process is chaotic and pulses are irreproducible. The coherence time of SASE xFELs will be a few femtoseconds for a photon energy near 1 keV. The importance of coherence properties of light in non-linear optical processes was theoretically discovered in the early 1960s. In this contribution we will illustrate the impact of field chaoticity on x-ray non-linear optical processes on neon for photon energies around 1 keV and intensities up to 10{sup 18} W/cm{sup 2}. Resonant and non-resonant processes are discussed. The first process to be addressed is the formation of a double-core hole in neon by photoionization with x rays above 1.25 keV energy. In contrast to the long-wavelength regime, non-linear optical processes in the x-ray regime are characterized in general by sequential single-photon single-electron interactions. Despite this fact, the sequential absorption of multiple x-ray photons depends on the statistical properties of the radiation field. Treating the x rays generated by a SASE FEL as fully chaotic, a quantum-mechanical analysis of inner-shell two-photon absorption is performed. By solving a system of time-dependent rate equations, we demonstrate that double-core hole formation in neon via x-ray two-photon absorption is enhanced by chaotic photon statistics. At an intensity of 10{sup 16} W/cm{sup 2}, the statistical enhancement is about 30%, much smaller than typical values in the optical regime. The second part of this presentation discusses the resonant Auger effect of atomic neon at the 1s-3p transition (at 867.1 eV). For low X-ray intensity, the excitation process 1s {yields} 3p in Neon can be treated perturbatively. The core-hole excited 1s{sup -1} 3p state is embedded in the continuum and decays via Auger-process on the timescale of approximately 5 fs. Increasing the x-ray intensity above 1.5 x 10{sup 18} W/cm{sup 2}, a peak intensity accessible with xFEL sources in the near future, x-ray induced emission from 3p back to 1s becomes possible, i.e. Rabi oscillations between these two levels can be induced. For the numerical analysis of this process, an effective two-level model, including a description of the resonant Auger decay process, is employed. The observation of x-ray-driven atomic populations dynamics in the time domain is challenging for chaotic xFEL pulses. In addition to requiring single-shot measurements, sub-femtosecond temporal resolution would be needed. The Rabi oscillations will, however, be imprinted on the kinetic energy distribution of the resonant Auger electron (see Fig. 1). Measuring the resonant Auger-electron line profile will provide information on both atomic population dynamics and x-ray pulse properties.

Rohringer, N

2008-08-08

194

Visualizing a protein quake with time resolved X-ray scattering at a free electron laser  

PubMed Central

A ‘protein quake’ describes the hypothesis that proteins rapidly dissipate energy through quake like structural motions. Here we measure ultrafast structural changes in the Blastochloris viridis photosynthetic reaction center following multi-photon excitation using time-resolved wide angle X-ray scattering at an X-ray free electron laser. A global conformational change arises within picoseconds, which precedes the propagation of heat through the protein. This motion is damped within a hundred picoseconds. PMID:25108686

Arnlund, David; Johansson, Linda C.; Wickstrand, Cecilia; Barty, Anton; Williams, Garth J.; Malmerberg, Erik; Davidsson, Jan; Milathianaki, Despina; DePonte, Daniel P.; Shoeman, Robert L.; Wang, Dingjie; James, Daniel; Katona, Gergely; Westenhoff, Sebastian; White, Thomas A.; Aquila, Andrew; Bari, Sadia; Berntsen, Peter; Bogan, Mike; van Driel, Tim Brandt; Doak, R. Bruce; Kjær, Kasper Skov; Frank, Matthias; Fromme, Raimund; Grotjohann, Ingo; Henning, Robert; Hunter, Mark S.; Kirian, Richard A.; Kosheleva, Irina; Kupitz, Christopher; Liang, Mengning; Martin, Andrew V.; Nielsen, Martin Meedom; Messerschmidt, Marc; Seibert, M. Marvin; Sjöhamn, Jennie; Stellato, Francesco; Weierstall, Uwe; Zatsepin, Nadia A.; Spence, John C. H.; Fromme, Petra; Schlichting, Ilme; Boutet, Sébastien; Groenhof, Gerrit; Chapman, Henry N.; Neutze, Richard

2014-01-01

195

Femtosecond Diffractive Imaging with a Soft-X-Ray Free-Electron Laser  

Microsoft Academic Search

Theory predicts that with an ultrashort and extremely bright coherent X-ray pulse, a single diffraction pattern may be recorded from a large macromolecule, a virus, or a cell before the sample explodes and turns into a plasma. Here we report the first experimental demonstration of this principle using the FLASH soft X-ray free-electron laser. An intense 25 fs, 4 x

Bogan; Michael James

2010-01-01

196

XPCS at the European X-ray free electron laser facility  

Microsoft Academic Search

The European X-ray free electron laser source (XFEL) will provide highly brilliant (B>1033ph\\/s\\/mm2\\/mrad2\\/0.1% bw) and coherent X-ray beams. The pulse structure and the unprecedented brightness will allow one for the first time to study fast dynamics in the time domain, thus giving direct access to the dynamic response function S(Q,t), instead of S(Q,?), which is of central importance for a

G. Grübel; G. B. Stephenson; C. Gutt; H. Sinn; Th. Tschentscher; Hasylab

2007-01-01

197

Femtosecond diffractive imaging with a soft-X-ray free-electron laser  

Microsoft Academic Search

Theory predicts that, with an ultrashort and extremely bright coherent X-ray pulse, a single diffraction pattern may be recorded from a large macromolecule, a virus or a cell before the sample explodes and turns into a plasma. Here we report the first experimental demonstration of this principle using the FLASH soft-X-ray free-electron laser. An intense 25fs, 4×1013Wcm-2 pulse, containing 1012

Henry N. Chapman; Anton Barty; Michael J. Bogan; Sébastien Boutet; Matthias Frank; Stefan P. Hau-Riege; Stefano Marchesini; Bruce W. Woods; Sasa Bajt; W. Henry Benner; Richard A. London; Elke Plönjes; Marion Kuhlmann; Rolf Treusch; Stefan Düsterer; Thomas Tschentscher; Jochen R. Schneider; Eberhard Spiller; Thomas Möller; Christoph Bostedt; Matthias Hoener; David A. Shapiro; Keith O. Hodgson; David van der Spoel; Florian Burmeister; Magnus Bergh; Carl Caleman; Gösta Huldt; M. Marvin Seibert; Filipe R. N. C. Maia; Richard W. Lee; Abraham Szöke; Nicusor Timneanu; Janos Hajdu

2006-01-01

198

Progress in rod pinch electron beam diodes as intense x-ray radiography sources  

Microsoft Academic Search

Rod-pinch electron beam diodes were reintroduced at BEAMS'98 as small-diameter intense x-ray sources after a twenty-year hiatus. Much progress has been made recently in both analytical and particle-in-cell numerical modeling of the diode behavior and in obtaining intense x-ray sources for pulsed radiography. Rod-pinch diodes utilize a thin annular cathode surrounding a small-diameter anode rod extending through and beyond the

G. Cooperstein; R. J. Commisso; D. D. Hinshelwood; D. Mosher; P. F. Ottinger; S. J. Stephanakis; J. W. Schumer; S. B. Swanekamp; B. V. Weber; F. C. Young; J. E. Maenchen; P. R. Menge; C. L. Olson; B. V. Oliver; D. V. Rose; D. R. Welch; R. Carlson; D. Oro; D. Fulton; E. Hunt; D. Droemer; W. J. DeHope

2000-01-01

199

Accurate macromolecular structures using minimal measurements from X-ray free-electron lasers.  

PubMed

X-ray free-electron laser (XFEL) sources enable the use of crystallography to solve three-dimensional macromolecular structures under native conditions and without radiation damage. Results to date, however, have been limited by the challenge of deriving accurate Bragg intensities from a heterogeneous population of microcrystals, while at the same time modeling the X-ray spectrum and detector geometry. Here we present a computational approach designed to extract meaningful high-resolution signals from fewer diffraction measurements. PMID:24633409

Hattne, Johan; Echols, Nathaniel; Tran, Rosalie; Kern, Jan; Gildea, Richard J; Brewster, Aaron S; Alonso-Mori, Roberto; Glöckner, Carina; Hellmich, Julia; Laksmono, Hartawan; Sierra, Raymond G; Lassalle-Kaiser, Benedikt; Lampe, Alyssa; Han, Guangye; Gul, Sheraz; DiFiore, Dörte; Milathianaki, Despina; Fry, Alan R; Miahnahri, Alan; White, William E; Schafer, Donald W; Seibert, M Marvin; Koglin, Jason E; Sokaras, Dimosthenis; Weng, Tsu-Chien; Sellberg, Jonas; Latimer, Matthew J; Glatzel, Pieter; Zwart, Petrus H; Grosse-Kunstleve, Ralf W; Bogan, Michael J; Messerschmidt, Marc; Williams, Garth J; Boutet, Sébastien; Messinger, Johannes; Zouni, Athina; Yano, Junko; Bergmann, Uwe; Yachandra, Vittal K; Adams, Paul D; Sauter, Nicholas K

2014-05-01

200

Time-resolved structural studies at synchrotrons and X-ray free electron lasers: opportunities and challenges  

PubMed Central

X-ray free electron lasers (XFELs) are potentially revolutionary X-ray sources because of their very short pulse duration, extreme peak brilliance and high spatial coherence, features that distinguish them from today’s synchrotron sources. We review recent time-resolved Laue diffraction and time-resolved wide angle X-ray scattering (WAXS) studies at synchrotron sources, and initial static studies at XFELs. XFELs have the potential to transform the field of time-resolved structural biology, yet many challenges arise in devising and adapting hardware, experimental design and data analysis strategies to exploit their unusual properties. Despite these challenges, we are confident that XFEL sources are poised to shed new light on ultrafast protein reaction dynamics. PMID:23021004

Neutze, Richard; Moffat, Keith

2012-01-01

201

Time-resolved structural studies at synchrotrons and X-ray free electron lasers: opportunities and challenges.  

PubMed

X-ray free electron lasers (XFELs) are potentially revolutionary X-ray sources because of their very short pulse duration, extreme peak brilliance and high spatial coherence, features that distinguish them from today's synchrotron sources. We review recent time-resolved Laue diffraction and time-resolved wide angle X-ray scattering (WAXS) studies at synchrotron sources, and initial static studies at XFELs. XFELs have the potential to transform the field of time-resolved structural biology, yet many challenges arise in devising and adapting hardware, experimental design and data analysis strategies to exploit their unusual properties. Despite these challenges, we are confident that XFEL sources are poised to shed new light on ultrafast protein reaction dynamics. PMID:23021004

Neutze, Richard; Moffat, Keith

2012-10-01

202

Solar Flare X-ray Source Motion as a Response to Electron Spectral Hardening  

E-print Network

Context: Solar flare hard X-rays (HXRs) are thought to be produced by nonthermal coronal electrons stopping in the chromosphere, or remaining trapped in the corona. The collisional thick target model (CTTM) predicts that sources produced by harder power-law injection spectra should appear further down the legs or footpoints of a flare loop. Therefore, hardening of the injected power-law electron spectrum during flare onset should be concurrent with a descending hard X-ray source. Aims: To test this implication of the CTTM by comparing its predicted HXR source locations with those derived from observations of a solar flare which exhibits a nonthermally-dominated spectrum before the peak in HXRs, known as an early impulsive event. Methods: HXR images and spectra of an early impulsive C-class flare were obtained using the Ramaty High-Energy Solar Spectroscopic Imager (RHESSI). Images were reconstructed to produce HXR source height evolutions for three energy bands. Spatially-integrated spectral analysis was perf...

O'Flannagain, A; Brown, J; Milligan, R; Holman, G

2013-01-01

203

Field-emission scanning electron microscopy and energy-dispersive x-ray analysis to understand the role of tannin-based dyes in the degradation of historical wool textiles.  

PubMed

An innovative approach, combining field-emission scanning electron microscopy (FESEM) with energy dispersive X-ray spectroscopy (EDX) analysis, is presented to investigate the degradation mechanisms affecting tannin-dyed wool. In fact, tannin-dyed textiles are more sensitive to degradation then those dyed with other dyestuffs, even in the same conservation conditions. FESEM-EDX was first used to study a set of 48 wool specimens (artificially aged) dyed with several raw materials and mordants, and prepared according to historical dyeing recipes. EDX analysis was performed on the surface of wool threads and on their cross-sections. In addition, in order to validate the model formulated by the analysis of reference materials, several samples collected from historical and archaeological textiles were subjected to FESEM-EDX analysis. FESEM-EDX investigations enabled us to reveal the correlation between elemental composition and morphological changes. In addition, aging processes were clarified by studying changes in the elemental composition of wool from the protective cuticle to the fiber core in cross-sections. Morphological and elemental analysis of wool specimens and of archaeological and historical textiles showed that the presence of tannins increases wool damage, primarily by causing a sulfur decrease and fiber oxidation. PMID:24983911

Restivo, Annalaura; Degano, Ilaria; Ribechini, Erika; Pérez-Arantegui, Josefina; Colombini, Maria Perla

2014-10-01

204

Note: theoretical study on the gas pressure dependence of x-ray yield in TE(111) cavity based electron cyclotron resonance x-ray source.  

PubMed

Adopting Langevin methodology, a pressure dependent frictional force term which represents the collisional effect is added to the Lorentz equation. The electrons are assumed to be starting from the uniformly distributed co-ordinates on the central plane. The trajectory of each electron is numerically simulated by solving the modified Lorentz equation for a given pressure. The Bremsstrahlung x-ray energy spectrum for each electron crossing the cavity wall boundary is obtained using the Duane-Hunt law. The total x-ray yield is estimated by adding the spectral contribution of each electron. The calculated yields are compared with the experimental results and a good agreement is found. PMID:25430155

Selvakumaran, T S; Sen, Soubhadra; Baskaran, R

2014-11-01

205

Note: Theoretical study on the gas pressure dependence of x-ray yield in TE111 cavity based electron cyclotron resonance x-ray source  

NASA Astrophysics Data System (ADS)

Adopting Langevin methodology, a pressure dependent frictional force term which represents the collisional effect is added to the Lorentz equation. The electrons are assumed to be starting from the uniformly distributed co-ordinates on the central plane. The trajectory of each electron is numerically simulated by solving the modified Lorentz equation for a given pressure. The Bremsstrahlung x-ray energy spectrum for each electron crossing the cavity wall boundary is obtained using the Duane-Hunt law. The total x-ray yield is estimated by adding the spectral contribution of each electron. The calculated yields are compared with the experimental results and a good agreement is found.

Selvakumaran, T. S.; Sen, Soubhadra; Baskaran, R.

2014-11-01

206

Prevailing features of x-ray-induced molecular electron spectra revealed with fullerenes.  

PubMed

X-ray photoabsorption from intense short pulses by a molecule triggers complicated electron and subsequently ion dynamics, leading to photoelectron spectra, which are difficult to interpret. Illuminating fullerenes offers a way to separate out the electron dynamics since the cage structure confines spatially the origin of photo- and Auger electrons. Together with the sequential nature of the photoprocesses at intensities available at x-ray free-electron lasers, this allows for a remarkably detailed interpretation of the photoelectron spectra, as we will demonstrate. The general features derived can serve as a paradigm for less well-defined situations in other large molecules or clusters. PMID:25192093

Camacho Garibay, Abraham; Saalmann, Ulf; Rost, Jan M

2014-08-22

207

Prevailing Features of X-Ray-Induced Molecular Electron Spectra Revealed with Fullerenes  

NASA Astrophysics Data System (ADS)

X-ray photoabsorption from intense short pulses by a molecule triggers complicated electron and subsequently ion dynamics, leading to photoelectron spectra, which are difficult to interpret. Illuminating fullerenes offers a way to separate out the electron dynamics since the cage structure confines spatially the origin of photo- and Auger electrons. Together with the sequential nature of the photoprocesses at intensities available at x-ray free-electron lasers, this allows for a remarkably detailed interpretation of the photoelectron spectra, as we will demonstrate. The general features derived can serve as a paradigm for less well-defined situations in other large molecules or clusters.

Camacho Garibay, Abraham; Saalmann, Ulf; Rost, Jan M.

2014-08-01

208

Influence of Bernstein modes on the efficiency of electron cyclotron resonance x-ray source  

NASA Astrophysics Data System (ADS)

The article considers the factors influencing the temperature of hot electron component in an electron cyclotron resonance (ECR) x-ray source. In such sources the electron heating occurs often due to extraordinary electromagnetic wave propagating perpendicularly to the magnetic field. In this case the possibility of the absorption of Bernstein modes is regarded as an additional mechanism of electron heating. The Bernstein modes in an ECR x-ray source can arise due to either linear transformation or parametric instability of external transversal wave. The article briefly reviews also the further experiments which will be carried out to study the influence of Bernstein modes on the increase of hot electron temperature and consequently of x-ray emission.

Andreev, V. V.; Nikitin, G. V.; Savanovich, V. Yu.; Umnov, A. M.; Elizarov, L. I.; Serebrennikov, K. S.; Vostrikova, E. A.

2006-03-01

209

Calculating the X-Ray Fluorescence from the Planet Mercury Due to High-Energy Electrons  

NASA Technical Reports Server (NTRS)

The least-studied terrestrial planet is Mercury due to its proximity to the Sun, which makes telescopic observations and spacecraft encounters difficult. Our lack of knowledge about Mercury should change in the near future due to the recent launching of MESSENGER, a Mercury orbiter. Another mission (BepiColombo) is currently being planned. The x-ray spectrometer on MESSENGER (and planned for BepiColombo) can characterize the elemental composition of a planetary surface by measuring emitted fluorescent x-rays. If electrons are ejected from an atom s inner shell by interaction with energetic particles such as photons, electrons, or ions, electrons from an outer shell can transfer to the inner shell. Characteristic x-rays are then emitted with energies that are the difference between the binding energy of the ion in its excited state and that of the ion in its ground state. Because each element has a unique set of energy levels, each element emits x-rays at a unique set of energies. Electrons and ions usually do not have the needed flux at high energies to cause significant x-ray fluorescence on most planetary bodies. This is not the case for Mercury where high-energy particles were detected during the Mariner 10 flybys. Mercury has an intrinsic magnetic field that deflects the solar wind, resulting in a bow shock in the solar wind and a magnetospheric cavity. Electrons and ions accelerated in the magnetosphere tend to follow its magnetic field lines and can impact the surface on Mercury s dark side Modeling has been done to determine if x-ray fluorescence resulting from the impact of high-energy electrons accelerated in Mercury's magnetosphere can be detected by MESSENGER. Our goal is to understand how much bulk chemical information can be obtained from x-ray fluorescence measurements on the dark side of Mercury.

Burbine, T. H.; Trombka, J. I.; Bergstrom, P. M., Jr.; Christon, S. P.

2005-01-01

210

Development of an X-ray pixel detector with multi-port charge-coupled device for X-ray free-electron laser experiments  

SciTech Connect

This paper presents development of an X-ray pixel detector with a multi-port charge-coupled device (MPCCD) for X-ray Free-Electron laser experiments. The fabrication process of the CCD was selected based on the X-ray radiation hardness against the estimated annual dose of 1.6 × 10{sup 14} photon/mm{sup 2}. The sensor device was optimized by maximizing the full well capacity as high as 5 Me- within 50 ?m square pixels while keeping the single photon detection capability for X-ray photons higher than 6 keV and a readout speed of 60 frames/s. The system development also included a detector system for the MPCCD sensor. This paper summarizes the performance, calibration methods, and operation status.

Kameshima, Takashi [JASRI, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan)] [JASRI, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan); Ono, Shun; Kudo, Togo; Ozaki, Kyosuke; Kirihara, Yoichi; Kobayashi, Kazuo; Inubushi, Yuichi [RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148 (Japan)] [RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148 (Japan); Yabashi, Makina; Hatsui, Takaki, E-mail: hatsui@spring8.or.jp [JASRI, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan) [JASRI, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan); RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148 (Japan); Horigome, Toshio [Institute for Molecular Science, Myodaiji, Okazaki 444-8585 (Japan)] [Institute for Molecular Science, Myodaiji, Okazaki 444-8585 (Japan); Holland, Andrew; Holland, Karen [XCam, Ltd, 2 Stone Circle Road, Round Spinney Industrial Estate, Northampton NN3 8RF (United Kingdom)] [XCam, Ltd, 2 Stone Circle Road, Round Spinney Industrial Estate, Northampton NN3 8RF (United Kingdom); Burt, David [e2v, 106 Waterhouse Lane, Chelmsford, Essex CM1 2QU (United Kingdom)] [e2v, 106 Waterhouse Lane, Chelmsford, Essex CM1 2QU (United Kingdom); Murao, Hajime [Meisei Electric Co. Ltd, Naganuma 2223, Isesaki, Gunma 372-8585 (Japan)] [Meisei Electric Co. Ltd, Naganuma 2223, Isesaki, Gunma 372-8585 (Japan)

2014-03-15

211

Industrial x-ray fluorescence analysis new applications and challenges for cryogenic detectors  

SciTech Connect

Cryogenic, high-resolution X-ray detectors have potential applications in industrial X-ray fluorescence (XRF) analysis. We discuss various XRF analysis techniques currently used in the semiconductor industry, problems encountered due to limitations of current detectors and the potential benefits of using cryogenic detectors in these applications. We give examples of demonstration experiments, compare the performance of current conventional and cryogenic X-ray spectrometers and present an outlook.

Frank, M.

1997-08-01

212

Experimental demonstration of femtosecond two-color x-ray free-electron lasers.  

PubMed

With an eye toward extending optical wave-mixing techniques to the x-ray regime, we present the first experimental demonstration of a two-color x-ray free-electron laser at the Linac Coherent Light Source. We combine the emittance-spoiler technique with a magnetic chicane in the undulator section to control the pulse duration and relative delay between two intense x-ray pulses and we use differently tuned canted pole undulators such that the two pulses have different wavelengths as well. Two schemes are shown to produce two-color soft x-ray pulses with a wavelength separation up to ?1.9% and a controllable relative delay up to 40 fs. PMID:23581326

Lutman, A A; Coffee, R; Ding, Y; Huang, Z; Krzywinski, J; Maxwell, T; Messerschmidt, M; Nuhn, H-D

2013-03-29

213

Development of a Sub-Picosecond Tunable X-Ray Source at the LLNL Electron Linac  

SciTech Connect

The use of ultrafast laser pulses to generate very high brightness, ultra short (fs to ps) pulses of x-rays is a topic of great interest to the x-ray user community. In principle, femtosecond-scale pump-probe experiments can be used to temporally resolve structural dynamics of materials on the time scale of atomic motion. The development of sub-ps x-ray pulses will make possible a wide range of materials and plasma physics studies with unprecedented time resolution. A current project at LLNL will provide such a novel x-ray source based on Thomson scattering of high power, short laser pulses with a high peak brightness, relativistic electron bunch. The system is based on a 5 mm-mrad normalized emittance photoinjector, a 100 MeV electron RF linac, and a 300 mJ, 35 fs solid-state laser system. The Thomson x-ray source produces ultra fast pulses with x-ray energies capable of probing into high-Z metals, and a high flux per pulse enabling single shot experiments. The system will also operate at a high repetition rate ({approx} 10 Hz).

Slaughter, D; Springer, P; Le Sage, G; Crane, J; Ditmire, T; Cowan, T; Anderson, S G; Rosenzweig, J B

2001-08-31

214

X-ray microprobe system for XRF analysis and spectroscopy at SPring-8 BL39XU.  

PubMed

An X-ray microprobe system for X-ray fluorescence (XRF) analysis and spectroscopy has been developed at SPring-8 BL39XU; it comprises an X-ray focusing or collimation system, energy-dispersive (ED) and wavelength-dispersive (WD) XRF spectrometers, and a sample-scanning system. The conventional ED spectrometer will be utilized for qualitative and quantitative trace-element analysis, and the WD spectrometer will be used both for trace-element analysis and XRF spectroscopy. A combination of monochromated undulator radiation and the WD spectrometer will enable resonant XRF spectroscopy using brilliant hard X-ray undulator radiation. PMID:15263763

Hayakawa, S; Goto, S; Shoji, T; Yamada, E; Gohshi, Y

1998-05-01

215

Clinical applications of scanning electron microscopy and X-ray microanalysis in dermatology  

SciTech Connect

Scanning electron microscopy is frequently applied to dermatological problems, as is evident from a review of the recent literature. In this paper, preparation methods and new techniques allowing experimental studies on the integumentary system are emphasized. Quantitative analysis in the electron microscope by use of energy-dispersive X-ray microanalysis (EDX) has become an important accessory technique. EDX can, for instance, be used to study problems involving physiological changes induced in skin by agents causing contact reactions. Recently, it has been shown that treatment with DNCB, chromate and nickel causes changes in elemental distribution in guinea-pig skin. In addition, elemental uptake in the integumentary system and in pathological inclusions in skin can be analyzed.

Forslind, B.

1984-01-01

216

Infrared Line Emission from Molecular Gas Heated by X-Rays and Energetic Electrons  

NASA Technical Reports Server (NTRS)

"I propose to carry out a detailed study using infrared observations (and in some cases, optical and ultraviolet observations) of dense interstellar gas exposed to intense fluxes of X-rays and/or energetic electrons. This is undoubtedly the dominant source of line emission for clouds exposed to X-rays from active galactic nuclei, supernova shocks, or embedded X-ray sources (e.g., X-ray binaries), or to high-temperature or relativistic electrons in galaxy clusters, near powerful radio sources, or supernova remnants. Detailed physical and chemical models of such clouds will be used to analyze infrared observations of the Great Annihilator X-ray source in the Galactic Center, cD galaxies in massive cooling flows, and the nuclei of Seyfert galaxies which will be obtained with the Infrared Space Observatory (ISO), UV and optical observations of the Crab Nebula obtained with the Hubble Space Telescope, and ground-based near-infrared observations of Seyfert nuclei. Results from this work will also be of great relevance to observations obtained with the Submillimeter Wave Astronomical Satellite (SWAS). In the first year of funding of this proposal, my chief collaborators (D.J. Hollenbach and A.G.G.M. Tielens, both of NASA Ames Research Center) and I concentrated on completing our models of the physical conditions in, and the resulting line emission from, dense gas irradiated by X-rays. As noted in the original proposal, some important physical processes were not yet thoroughly incorporated into our models at the time of submission. We completed our modeling of the physical conditions and line emission for essentially the entire range of parameter space (five orders of magnitude in X-ray flux to gas density ratio) occupied by typical dense interstellar clouds in which the gas is mostly neutral and X-rays are important for the ionization, chemistry, and thermal balance.

Maloney, Philip R.

1997-01-01

217

Direct observation of unstained wet biological samples by scanning-electron generation X-ray microscopy  

SciTech Connect

Analytical tools of nanometre-scale resolution are indispensable in the fields of biology, physics and chemistry. One suitable tool, the soft X-ray microscope, provides high spatial resolution of visible light for wet specimens. For biological specimens, X-rays of water-window wavelength between carbon (284 eV; 4.3 nm) and oxygen (540 eV; 2.3 nm) absorption edges provide high-contrast imaging of biological samples in water. Among types of X-ray microscope, the transmission X-ray microscope using a synchrotron radiation source with diffractive zone plates offers the highest spatial resolution, approaching 15-10 nm. However, even higher resolution is required to measure proteins and protein complexes in biological specimens; therefore, a new type of X-ray microscope with higher resolution that uses a simple light source is desirable. Here we report a novel scanning-electron generation X-ray microscope (SGXM) that demonstrates direct imaging of unstained wet biological specimens. We deposited wet yeasts in the space between two silicon nitride (Si{sub 3}N{sub 4}) films. A scanning electron beam of accelerating voltage 5 keV and current 1.6 nA irradiates the titanium (Ti)-coated Si{sub 3}N{sub 4} film, and the soft X-ray signal from it is detected by an X-ray photodiode (PD) placed below the sample. The SGXM can theoretically achieve better than 5 nm resolution. Our method can be utilized easily for various wet biological samples of bacteria, viruses, and protein complexes.

Ogura, Toshihiko, E-mail: t-ogura@aist.go.jp [Neuroscience Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Central 2, Umezono, Tsukuba, Ibaraki 305-8568 (Japan)] [Neuroscience Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Central 2, Umezono, Tsukuba, Ibaraki 305-8568 (Japan)

2010-01-01

218

Combined x-ray/electron/optical Monte Carlo code based on PENELOPE and DETECT-II  

NASA Astrophysics Data System (ADS)

We describe MANTIS (Monte carlo x-rAy electroN opTical Imaging Simulation), a tool for simulating imaging systems that tracks x rays, electrons, and optical photons in the same geometric model. The x-ray and electron transport and involved physics models are from the PENELOPE package and include elastic and inelastic scattering, and bremsstrahlung from 100 eV to 1 GeV. The optical transport and corresponding physics models are from DETECT-II and include Fresnel refraction and reflection at material boundaries, bulk absorption and scattering. X rays are generated using the flexible source description from PENELOPE. When x rays or electrons interact and deposit energy in the scintillator, the code generates a number of optical quanta at that location, according to a model for the conversion process. The optical photons are then tracked until they reach an absorption event that in some cases contributes to the electronic signal. We demonstrate the capabilities of the new tool with respect to x-ray source, object to be imaged, and detector models. Of particular importance is the improved geometric description of structured phosphors that can handle tilted columns in needle-like phosphor screens. Examples of the simulation output with respect to signal blur and pulse-height distributions of the scintillation light are discussed and compared with previously published experimental results.

Badano, Aldo; Sempau, Josep; Boswell, Jonathan S.

2005-04-01

219

High-gain X-ray free electron laser by beat-wave terahertz undulator  

SciTech Connect

The THz undulator has a higher gain to realize a much brighter X-ray at saturation, compared with the optical undulator under the same undulator strength and beam quality. In order to fill the high-power THz gap and realize the THz undulator, two superimposed laser pulses at normal incidence to the electron-beam moving direction form an equivalent high-field THz undulator by the frequency difference to realize the high-gain X-ray Free electron laser. The pulse front tilt of lateral fed lasers is used to realize the electron-laser synchronic interaction. By PIC simulation, a higher gain and a larger X-ray radiation power by the beat wave THz undulator could be realized, compared with the optical undulator for the same electron beam parameters.

Chang, Chao; Hei, DongWei [Science and Technology on High Power Microwave Laboratory, Northwest Institute of Nuclear Technology, Xi'an City 710024 (China) [Science and Technology on High Power Microwave Laboratory, Northwest Institute of Nuclear Technology, Xi'an City 710024 (China); Institute of Energy, Tsinghua University, Beijing 100084 (China); Pellegrin, Claudio; Tantawi, Sami [SLAC National Accelerator Laboratory, Stanford University, Stanford, California 94309 (United States)] [SLAC National Accelerator Laboratory, Stanford University, Stanford, California 94309 (United States)

2013-12-15

220

Femtosecond X-ray Pulse Temporal Characterization in Free-Electron Lasers Using a Transverse Deflector  

SciTech Connect

We propose a novel method to characterize the temporal duration and shape of femtosecond x-ray pulses in a free-electron laser (FEL) by measuring the time-resolved electron-beam energy loss and energy spread induced by the FEL process, with a transverse radio-frequency deflector located after the undulator. Its merits are simplicity, high resolution, wide diagnostic range, and non-invasive to user operation. When the system is applied to the Linac Coherent Light Source, the first hard x-ray free-electron laser in the world, it can provide single-shot measurements on the electron beam and x-ray pulses with a resolution on the order of 1-2 femtoseconds rms.

Ding, Y.; /SLAC; Behrens, C.; /DESY; Emma, P.; Frisch, J.; Huang, Z.; Loos, H.; Krejcik, P.; Wang, M-H.; /SLAC

2011-12-13

221

Characterization of AlInN/AlN/GaN FET structures using x-ray diffraction, x-ray reflectometry and grazing incidence x-ray fluorescence analysis  

NASA Astrophysics Data System (ADS)

The structural parameters of AlInN/AlN/GaN high mobility field effect transistors (FETs) determine their electrical properties. The AlN-interlayer (spacer) thickness especially plays an important role to enhance the mobility and the density of the two dimensional electron gas (2DEG). However, structural characterization of this ultra-thin AlN-interlayer is ambiguous when only high resolution x-ray diffraction (HRXRD) and x-ray reflectometry (XRR) are taken into account. Here a combined layer analysis was performed using HRXRD, XRR and grazing incidence x-ray fluorescence (GIXRF) for the determination of the AlN-interlayer thickness. A sample series of AlInN/AlN/GaN FETs on Si(1?1?1) has been grown and analysed. The growth time of the AlN-interlayer was changed from 0 to 12 s and the AlInN barrier was grown nearly lattice matched to GaN with a nominal thickness of 5 nm. By the combination of HRXRD, XRR, GIXRF and simultaneous simulation of the data the determination of the spacer thickness was successfully performed.

Lesnik, Andreas; Bläsing, Jürgen; Hennig, Jonas; Dadgar, Armin; Krost, Alois

2014-09-01

222

Uranium Analysis with X-ray Microscopy Research Team: Andrew Duffin, Jesse Ward, Gregory Eiden, Steven Smith, Bruce McNamara, Edgar Buck  

E-print Network

Uranium Analysis with X-ray Microscopy Research Team: Andrew Duffin, Jesse Ward, Gregory Eiden Chemical fingerprinting of anthropogenic and mineral uranium leading to chemical age dating of reactive uranium samples Develop x-ray and/or electron microscopy protocol for non- destructive uranium sample

223

The effect of turbulent density perturbations on solar flare electron transport and X-ray spectrum  

NASA Astrophysics Data System (ADS)

RHESSI solar flare hard X-ray observations sometimes cannot be adequately interpreted in terms of purely collisional electron transport. We instead present numerical simulations where we consider the energetic electron-beam interactions in the presence of low frequency den-sity perturbations. We demonstrate how the turbulent density perturbations affect the high frequency Langmuir waves and in turn, the flare accelerated electron distribution. The conse-quences of this self-consistent treatment are discussed for the observable X-ray spectrum.

Hannah, Iain; Kontar, Eduard

224

A simplified description of X-ray free-electron lasers  

PubMed Central

It is shown that an elementary semi-quantitative approach explains essential features of the X-ray free-electron laser mechanism, in particular those of the gain and saturation lengths. Using mathematical methods and derivations simpler than complete theories, this treatment reveals the basic physics that dominates the mechanism and makes it difficult to realise free-electron lasers for short wavelengths. This approach can be specifically useful for teachers at different levels and for colleagues interested in presenting X-ray free-electron lasers to non-specialized audiences. PMID:21335894

Margaritondo, G.; Rebernik Ribic, Primoz

2011-01-01

225

A simplified description of X-ray free-electron lasers.  

PubMed

It is shown that an elementary semi-quantitative approach explains essential features of the X-ray free-electron laser mechanism, in particular those of the gain and saturation lengths. Using mathematical methods and derivations simpler than complete theories, this treatment reveals the basic physics that dominates the mechanism and makes it difficult to realise free-electron lasers for short wavelengths. This approach can be specifically useful for teachers at different levels and for colleagues interested in presenting X-ray free-electron lasers to non-specialized audiences. PMID:21335894

Margaritondo, G; Rebernik Ribic, Primoz

2011-03-01

226

Efficiency calibration of an HPGe X-ray detector for quantitative PIXE analysis  

NASA Astrophysics Data System (ADS)

Particle Induced X-ray Emission (PIXE) is an analytical technique, which provides reliably and accurately quantitative results without the need of standards when the efficiency of the X-ray detection system is calibrated. The ion beam microprobe of the Ion Beam Modification and Analysis Laboratory at the University of North Texas is equipped with a 100 mm2 high purity germanium X-ray detector (Canberra GUL0110 Ultra-LEGe). In order to calibrate the efficiency of the detector for standard less PIXE analysis we have measured the X-ray yield of a set of commercially available X-ray fluorescence standards. The set contained elements from low atomic number Z = 11 (sodium) to higher atomic numbers to cover the X-ray energy region from 1.25 keV to about 20 keV where the detector is most efficient. The effective charge was obtained from the proton backscattering yield of a calibrated particle detector.

Mulware, Stephen J.; Baxley, Jacob D.; Rout, Bibhudutta; Reinert, Tilo

2014-08-01

227

The use of combined three-dimensional electron backscatter diffraction and energy dispersive X-ray analysis to assess the characteristics of the gamma/gamma-prime microstructure in alloy 720Li.  

PubMed

Multiple three-dimensional reconstructions of a ?/?' phase structure in Alloy 720Li have been carried out by employing a serial milling technique with simultaneous electron backscatter diffraction (EBSD) and energy dispersive x-ray (EDX) analysis data collection. Combining EBSD data with EDX is critical in obtaining maps to distinguish between the chemically differing, but crystallographically similar ? and ?' phases present in the alloy studied. EDX is shown to allow the differentiation of ? and ?' phases, with EBSD providing increased grain shape accuracy. The combination of data sources also allowed identification of coherent ?/?' phase interfaces that would not be identified using solely EBSD or EDX. The study identifies a region of grain banding within the alloy, which provides the basis for a three-dimensional comparison and discussion of ?' phase size between coarse and fine grain regions, whilst also identifying coherent ?' phase interfaces, possible only using both EDX and EBSD systems simultaneously. The majority of the ?' phase lies in the range of 1-10 ?m in non-banded regions, with a detectable particle size limit of 500 nm being established. The validity of the reconstruction has been demonstrated using an electron interaction volumes model, and an assessment of the validity of EBSD and EDX data sources is discussed showing ?' phase connectivity in all dimensions. PMID:22343666

Child, D J; West, G D; Thomson, R C

2012-03-01

228

The analysis and interpretation of solar X-ray photographs  

NASA Technical Reports Server (NTRS)

The paper examines methods of analyzing and interpreting solar X-ray photographs obtained by soft X-ray telescopes such as those used during the Skylab mission, to obtain information on the physical conditions that give rise to coronal X-ray emitting features revealed by inspection or microdensitometry of the X-ray photographs. First, the differential emission measure function is defined. By choosing models for this function and calculating the integral for the irradiance at the film for each filter, one calculates the effective temperature and emission measure. This method gives correct results only when applied to isothermal regions. For heterothermal regions, a modeling approach which predicts the run of temperature and density, and thus the form of the differential measure function, is used.

Underwood, J. H.; Mckenzie, D. L.

1977-01-01

229

Copyright The Discussion Group of X-Ray Analysis,  

E-print Network

HAYASHI, Shuji MATSUO, Yoshihiro MORI and Takashi WATANABE #12;#12;37 25 2005 X Adv. X-Ray. Chem. Anal and authored by Jun KAWAI 1 , Kenji SAKURAI 2 , Kouichi TSUJI 3 , Hisashi HAYASHI 4 , Shuji MATSUO 5

Jun, Kawai

230

IPC two-color analysis of x ray galaxy clusters  

NASA Technical Reports Server (NTRS)

The mass distributions were determined of several clusters of galaxies by using X ray surface brightness data from the Einstein Observatory Imaging Proportional Counter (IPC). Determining cluster mass distributions is important for constraining the nature of the dark matter which dominates the mass of galaxies, galaxy clusters, and the Universe. Galaxy clusters are permeated with hot gas in hydrostatic equilibrium with the gravitational potentials of the clusters. Cluster mass distributions can be determined from x ray observations of cluster gas by using the equation of hydrostatic equilibrium and knowledge of the density and temperature structure of the gas. The x ray surface brightness at some distance from the cluster is the result of the volume x ray emissivity being integrated along the line of sight in the cluster.

White, Raymond E., III

1990-01-01

231

A statistical analysis of hard X-Ray solar flares  

NASA Technical Reports Server (NTRS)

In this study we perform a statistical study on, 8319 X-Ray solar flares observed with the Hard X-Ray Spectrometer (HXRBS) on the Solar Maximum Mission satellite (SMM). The events are examined in terms of the durations, maximum intensities, and intensity profiles. It is concluded that there is no evidence for a correlation between flare intensity, flare duration, and flare asymmetry. However, we do find evidence for a rapid fall-of in the number of short-duration events.

Pearce, G.; Rowe, A. K.; Yeung, J.

1993-01-01

232

High-Performance X-ray Detection in a New Analytical Electron Microscope  

NASA Technical Reports Server (NTRS)

X-ray detection by energy-dispersive spectrometry in the analytical electron microscope (AEM) is often limited by low collected X-ray intensity (P), modest peak-to-background (P/B) ratios, and limitations on total counting time (tau) due to specimen drift and contamination. A new AFM has been designed with maximization of P. P/B, and tau as the primary considerations. Maximization of P has been accomplished by employing a field-emission electron gun, X-ray detectors with high collection angles, high-speed beam blanking to allow only one photon into the detector at a time, and simultaneous collection from two detectors. P/B has been maximized by reducing extraneous background signals generated at the specimen holder, the polepieces and the detector collimator. The maximum practical tau has been increased by reducing specimen contamination and employing electronic drift correction. Performance improvments have been measured using the NIST standard Cr thin film. The 0-3 steradian solid angle of X-ray collection is the highest value available. The beam blanking scheme for X-ray detection provides 3-4 times greater throughput of X-rays at high count rates into a recorded spectrum than normal systems employing pulse-pileup rejection circuits. Simultaneous X-ray collection from two detectors allows the highest X-ray intensity yet recorded to be collected from the NIST Cr thin film. The measured P/B of 6300 is the highest level recorded for an AEM. In addition to collected X-ray intensity (cps/nA) and P/B measured on the standard Cr film, the product of these can be used as a figure-of-merit to evaluate instruments. Estimated minimum mass fraction (MMF) for Cr measured on the standard NIST Cr thin film is also proposed as a figure-of-merit for comparing X-ray detection in AEMs. Determinations here of the MMF of Cr detectable show at least a threefold improvement over previous instruments.

Lyman, C. E.; Goldstein, J. I.; Williams, D. B.; Ackland, D. W.; vonHarrach, S.; Nicholls, A. W.; Statham, P. J.

1994-01-01

233

Time-resolved protein nanocrystallography using an X-ray free-electron laser  

PubMed Central

We demonstrate the use of an X-ray free electron laser synchronized with an optical pump laser to obtain X-ray diffraction snapshots from the photoactivated states of large membrane protein complexes in the form of nanocrystals flowing in a liquid jet. Light-induced changes of Photosystem I-Ferredoxin co-crystals were observed at time delays of 5 to 10 µs after excitation. The result correlates with the microsecond kinetics of electron transfer from Photosystem I to ferredoxin. The undocking process that follows the electron transfer leads to large rearrangements in the crystals that will terminally lead to the disintegration of the crystals. We describe the experimental setup and obtain the first time-resolved femtosecond serial X-ray crystallography results from an irreversible photo-chemical reaction at the Linac Coherent Light Source. This technique opens the door to time-resolved structural studies of reaction dynamics in biological systems. PMID:22330507

Aquila, Andrew; Hunter, Mark S.; Doak, R. Bruce; Kirian, Richard A.; Fromme, Petra; White, Thomas A.; Andreasson, Jakob; Arnlund, David; Bajt, Saša; Barends, Thomas R. M.; Barthelmess, Miriam; Bogan, Michael J.; Bostedt, Christoph; Bottin, Hervé; Bozek, John D.; Caleman, Carl; Coppola, Nicola; Davidsson, Jan; DePonte, Daniel P.; Elser, Veit; Epp, Sascha W.; Erk, Benjamin; Fleckenstein, Holger; Foucar, Lutz; Frank, Matthias; Fromme, Raimund; Graafsma, Heinz; Grotjohann, Ingo; Gumprecht, Lars; Hajdu, Janos; Hampton, Christina Y.; Hartmann, Andreas; Hartmann, Robert; Hau-Riege, Stefan; Hauser, Günter; Hirsemann, Helmut; Holl, Peter; Holton, James M.; Hömke, André; Johansson, Linda; Kimmel, Nils; Kassemeyer, Stephan; Krasniqi, Faton; Kühnel, Kai-Uwe; Liang, Mengning; Lomb, Lukas; Malmerberg, Erik; Marchesini, Stefano; Martin, Andrew V.; Maia, Filipe R.N.C.; Messerschmidt, Marc; Nass, Karol; Reich, Christian; Neutze, Richard; Rolles, Daniel; Rudek, Benedikt; Rudenko, Artem; Schlichting, Ilme; Schmidt, Carlo; Schmidt, Kevin E.; Schulz, Joachim; Seibert, M. Marvin; Shoeman, Robert L.; Sierra, Raymond; Soltau, Heike; Starodub, Dmitri; Stellato, Francesco; Stern, Stephan; Strüder, Lothar; Timneanu, Nicusor; Ullrich, Joachim; Wang, Xiaoyu; Williams, Garth J.; Weidenspointner, Georg; Weierstall, Uwe; Wunderer, Cornelia; Barty, Anton; Spence, John C. H.; Chapman, Henry N.

2012-01-01

234

Time-resolved protein nanocrystallography using an X-ray free-electron laser.  

PubMed

We demonstrate the use of an X-ray free electron laser synchronized with an optical pump laser to obtain X-ray diffraction snapshots from the photoactivated states of large membrane protein complexes in the form of nanocrystals flowing in a liquid jet. Light-induced changes of Photosystem I-Ferredoxin co-crystals were observed at time delays of 5 to 10 µs after excitation. The result correlates with the microsecond kinetics of electron transfer from Photosystem I to ferredoxin. The undocking process that follows the electron transfer leads to large rearrangements in the crystals that will terminally lead to the disintegration of the crystals. We describe the experimental setup and obtain the first time-resolved femtosecond serial X-ray crystallography results from an irreversible photo-chemical reaction at the Linac Coherent Light Source. This technique opens the door to time-resolved structural studies of reaction dynamics in biological systems. PMID:22330507

Aquila, Andrew; Hunter, Mark S; Doak, R Bruce; Kirian, Richard A; Fromme, Petra; White, Thomas A; Andreasson, Jakob; Arnlund, David; Bajt, Saša; Barends, Thomas R M; Barthelmess, Miriam; Bogan, Michael J; Bostedt, Christoph; Bottin, Hervé; Bozek, John D; Caleman, Carl; Coppola, Nicola; Davidsson, Jan; DePonte, Daniel P; Elser, Veit; Epp, Sascha W; Erk, Benjamin; Fleckenstein, Holger; Foucar, Lutz; Frank, Matthias; Fromme, Raimund; Graafsma, Heinz; Grotjohann, Ingo; Gumprecht, Lars; Hajdu, Janos; Hampton, Christina Y; Hartmann, Andreas; Hartmann, Robert; Hau-Riege, Stefan; Hauser, Günter; Hirsemann, Helmut; Holl, Peter; Holton, James M; Hömke, André; Johansson, Linda; Kimmel, Nils; Kassemeyer, Stephan; Krasniqi, Faton; Kühnel, Kai-Uwe; Liang, Mengning; Lomb, Lukas; Malmerberg, Erik; Marchesini, Stefano; Martin, Andrew V; Maia, Filipe R N C; Messerschmidt, Marc; Nass, Karol; Reich, Christian; Neutze, Richard; Rolles, Daniel; Rudek, Benedikt; Rudenko, Artem; Schlichting, Ilme; Schmidt, Carlo; Schmidt, Kevin E; Schulz, Joachim; Seibert, M Marvin; Shoeman, Robert L; Sierra, Raymond; Soltau, Heike; Starodub, Dmitri; Stellato, Francesco; Stern, Stephan; Strüder, Lothar; Timneanu, Nicusor; Ullrich, Joachim; Wang, Xiaoyu; Williams, Garth J; Weidenspointner, Georg; Weierstall, Uwe; Wunderer, Cornelia; Barty, Anton; Spence, John C H; Chapman, Henry N

2012-01-30

235

Micro-column Scanning Electron Microscope and X-ray Spectrometer (MSEMS) for Planetary Exploration  

NASA Astrophysics Data System (ADS)

Scanning Electron Microscopy combined with electron-induced X-ray Fluorescence Spectroscopy (SEM-EDX) is one of the most powerful techniques for characterizing sub-µm surface morphology and composition. In terrestrial laboratories, SEM-EDX is used to elucidate natural processes such as low-temperature diagenesis, thermal or pressure induced metamorphism, volcanism/magmatism, atmosphere/crust interaction and biological activity. Such information would be highly useful for investigating the natural history of the terrestrial planets, satellites and primitive bodies, providing morphological and elemental information that is 2 orders of magnitude higher in resolution than optical techniques. Below we describe the development of a Micro-column Scanning Electron Microscope and X-ray Spectrometer (MSEMS) for flight. The enabling technology of the MSEMS is a carbon nanotube field emission (CNTFE) electron source that is integrated with micro-electro-mechanical-systems (MEMS) - based electron gun and electron optical structures. A hallmark of CNTFE electron sources is their low chromatic aberration, which reduces the need for high accelerating voltages to obtain small spot size. The CNTFE also offers exceptional brightness and nanometer source size, eliminating the need for condenser lenses, making simple electrostatic focusing optics possible. Moreover, the CNT field emission gun (CFEG) at low operating voltage dissipates 103 less power than thermally-assisted Schottky emitters. A key feature of the MSEMS design is the lack of scanning coils. Rather, a piezoelectric sample stage capable of sub-nanometer resolution scans the sample past the fixed crossover of the MSEMS electron beam. We will describe a MEMS-based templating technique for fabricating mechanically and electrically stable miniature CFEGs. Using existing silicon (Si) technology, we fabricated highly controlled and precise MEMS structures for both the CNT cathode and focusing optics for the micro-column. The reproducibility of anisotropic wet etching enables precise alignment of the CNT tip with the electron extracting first anode in a gun configuration by using an interlocking templating technique. The CFEG can be fully integrated with a MEMS-based microcolumn. Extensive electron trajectory analysis using Lorentz 2D/3D software demonstrates that 10-nm imaging resolution at 5 keV is achievable with a 10-mm working distance from a column measuring just 16 mm in length. We will present the design of the microcolumn as well as the MEMS fabrication process. We have also tested a piezoelectric scanning stage inside a laboratory SEM with a fixed electron beam. Additional, we implemented our own LabVIEW software interface for controlling the stage and for enabling communication with the secondary electron detector for image formation. SEM micrographs obtained employing this novel technique will be presented.

Ribaya, B.; Niemann, D.; Makarewicz, J.; Clevenson, H.; McKenzie, C.; Nguyen, C.; Blake, D. F.

2009-12-01

236

Design optimization for an X-ray free electron laser driven by SLAC linac  

Microsoft Academic Search

I present a design study for an X-ray Free Electron Laser (FEL) driven by the SLAC linac. The study assumes the FEL is based on Self-Amplified Spontaneous Emission (SASE) and lasing is achieved in a single pass of a high current, high brightness electron beam through a long wiggler. Following a brief review of the fundamentals of SASE, I provide

Ming Xie

1995-01-01

237

Study of runaway electrons with Hard X-ray spectrometry of tokamak plasmas  

NASA Astrophysics Data System (ADS)

Hard-X-ray spectrometry is a tool widely used for diagnostic of runaway electrons in existing tokamaks. In future machines, ITER and DEMO, HXR spectrometry will be useful providing information on runaway electron energy, runaway beam current and its profile during disruption.

Shevelev, A.; Kiptily, V.; Chugunov, I.; Khilkevitch, E.; Gin, D.; Doinikov, D.; Naidenov, V.; Plyusnin, V.; EFDA-JET contributors

2014-08-01

238

Consequences of Electron Precipitation at Mercury: X-ray Aurorae and Heavy Ion Production  

NASA Astrophysics Data System (ADS)

Observations from the MESSENGER spacecraft in orbit around Mercury have established that a quasi-trapped population of ions and electrons with 1-10 keV energies exists at about 1.5 RM radial distance from the planet center (where RM is Mercury's radius) around much of the planet. Additionally, measurements from MESSENGER's X-Ray Spectrometer (XRS) have documented numerous cases of nightside X-ray fluorescence, which is likely due to the precipitation of 1-10 keV electrons onto the surface of Mercury. Since Mercury has virtually no ionosphere or atmosphere, particles that precipitate impact the planet's surface directly. Using results from a global kinetic transport model of Mercury's magnetosphere, we find that an auroral oval type of electron precipitation pattern forms at latitudes above and below the geomagnetic equator, which is offset to the north of the geographic equator by about 0.2 RM. The locations of X-ray fluorescence on the planet map almost directly to where the nightside electron precipitation is seen in the global kinetic model, leading to the conclusion that the precipitating 1-10 keV electrons indeed result in an X-ray "aurora" at Mercury. Another consequence of electron precipitation at Mercury is the production of heavy ions, in particular sodium and potassium, through electron-stimulated desorption (ESD). Estimated electron precipitation fluxes and ESD yield rates suggest that this process may be a significant contributor to the exosphere and heavy ion cloud observed around Mercury.

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

2012-12-01

239

Sequential electronic and structural transitions in VO2 observed using X-ray absorption spectromicroscopy.  

PubMed

The popular dual electronic and structural transitions in VO2 are explored using X-ray absorption spectromicroscopy with high spatial and spectral resolutions. It is found that during both heating and cooling, the electronic transition always precedes the structural Peierls transition. Between the two transitions, there are intermediate states that are spectrally isolated here. PMID:25319233

Kumar, Suhas; Strachan, John Paul; Pickett, Matthew D; Bratkovsky, Alexander; Nishi, Yoshio; Williams, R Stanley

2014-11-26

240

X-ray spectra from the Cornell Electron-Beam Ion Source (CEBIS I)  

SciTech Connect

Radiation emitted from the Cornell electron beam ion source (CEBIS I) has been surveyed with a Si(Li) x-ray detector. These spectra can be used to estimate backgrounds from electron bremsstrahlung and to evaluate the feasibility of atomic physics experiments using the CEBIS I source in this configuration. 1 ref., 2 figs.

Johnson, B.M.; Jones, K.W.; Kostroun, V.O.; Ghanbari, E.; Janson, S.W.

1985-01-01

241

Characteristics of focused soft X-ray free-electron laser beam determined by ablation  

E-print Network

Characteristics of focused soft X-ray free-electron laser beam determined by ablation of organic. Dyer, "Excimer laser polymer ablation: twenty years on," Appl. Phys. A77, 167-173 (2003) and references of coherent radiation, FLASH (Free-electron LASer in Hamburg) provides ultra-intense femtosecond radiation

von der Linde, D.

242

Analysis of particles produced during airbag deployment by scanning electron microscopy with energy dispersive x-ray spectroscopy and their deposition on surrounding surfaces: a mid-research summary  

NASA Astrophysics Data System (ADS)

Airbags can be encountered in forensic work when investigating a car crash and are typically constructed with primerlike material to begin the deployment apparatus. The mechanisms of airbag deployment can produce particles ideal for scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDS) analysis. A recent study published by Berk studied airbags with vents and showed that it is possible for particles generated from the deployment of these airbags to deposit on surfaces in the vehicle as the airbags deflate.1 Another paper published by Berk reported particles similar in morphology and composition to primer gunshot residue (GSR) are produced by side impact airbags.2 This paper's aim will be to show mid-point results of a study still in progress in which non-vented airbags were analyzed to determine if they exhibited the same particle depositing features as their vented airbag counterparts. Further investigation in this study is being performed to find more airbags which produce primer gunshot residue-like particles containing lead, barium, and antimony from airbag deployment. To date, the study has resulted in (1) non-vented airbags exhibiting deposition of particles suitable for SEM/EDS analysis and (2) no gunshot residue-like particles being detected from the airbag residues studied thus far.

Wyatt, J. Matney

2011-06-01

243

Three-dimensional Radio and X-Ray Modeling and Data Analysis Software: Revealing Flare Complexity  

NASA Astrophysics Data System (ADS)

Many problems in solar physics require analysis of imaging data obtained in multiple wavelength domains with differing spatial resolution in a framework supplied by advanced three-dimensional (3D) physical models. To facilitate this goal, we have undertaken a major enhancement of our IDL-based simulation tools developed earlier for modeling microwave and X-ray emission. The enhanced software architecture allows the user to (1) import photospheric magnetic field maps and perform magnetic field extrapolations to generate 3D magnetic field models; (2) investigate the magnetic topology by interactively creating field lines and associated flux tubes; (3) populate the flux tubes with user-defined nonuniform thermal plasma and anisotropic, nonuniform, nonthermal electron distributions; (4) investigate the spatial and spectral properties of radio and X-ray emission calculated from the model; and (5) compare the model-derived images and spectra with observational data. The package integrates shared-object libraries containing fast gyrosynchrotron emission codes, IDL-based soft and hard X-ray codes, and potential and linear force-free field extrapolation routines. The package accepts user-defined radiation and magnetic field extrapolation plug-ins. We use this tool to analyze a relatively simple single-loop flare and use the model to constrain the magnetic 3D structure and spatial distribution of the fast electrons inside this loop. We iteratively compute multi-frequency microwave and multi-energy X-ray images from realistic magnetic flux tubes obtained from pre-flare extrapolations, and compare them with imaging data obtained by SDO, NoRH, and RHESSI. We use this event to illustrate the tool's use for the general interpretation of solar flares to address disparate problems in solar physics.

Nita, Gelu M.; Fleishman, Gregory D.; Kuznetsov, Alexey A.; Kontar, Eduard P.; Gary, Dale E.

2015-02-01

244

The identification of the pigments used to paint statues of Feixiange Cliff in China in late 19th century by micro-Raman spectroscopy and scanning electron microscopy\\/energy dispersive X-ray analysis  

Microsoft Academic Search

The application of micro-Raman spectroscopy (?-RS) and scanning electron microscopy (SEM)\\/energy dispersive X-ray spectrometer (EDS) to the research of pigments collected from Statues of Feixiange Cliff No. 67 and No. 69 niche of Tang Dynasty in China is reported. Five kinds of pigments were found in the experimental data, including black (carbon), white (gypsum+quartz), blue (lapis lazuli) and green (Paris

Pu-jun Jin; Wei Huang; Jianhua-Wang; Gang Zhao; Xiao-ling Wang

2010-01-01

245

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

246

Electron beam-based sources of ultrashort x-ray pulses.  

SciTech Connect

A review of various methods for generation of ultrashort x-ray pulses using relativistic electron beam from conventional accelerators is presented. Both spontaneous and coherent emission of electrons is considered. The importance of the time-resolved studies of matter at picosecond (ps), femtosecond (fs), and atttosecond (as) time scales using x-rays has been widely recognized including by award of a Nobel Prize in 1999 [Zewa]. Extensive reviews of scientific drivers can be found in [BES1, BES2, BES3, Lawr, Whit]. Several laser-based techniques have been used to generate ultrashort x-ray pulses including laser-driven plasmas [Murn, Alte, Risc, Rose, Zamp], high-order harmonic generation [Schn, Rund, Wang, Arpi], and laser-driven anode sources [Ande]. In addition, ultrafast streak-camera detectors have been applied at synchrotron sources to achieve temporal resolution on the picosecond time scale [Wulf, Lind1]. In this paper, we focus on a different group of techniques that are based on the use of the relativistic electron beam produced in conventional accelerators. In the first part we review several techniques that utilize spontaneous emission of electrons and show how solitary sub-ps x-ray pulses can be obtained at existing storage ring based synchrotron light sources and linacs. In the second part we consider coherent emission of electrons in the free-electron lasers (FELs) and review several techniques for a generation of solitary sub-fs x-ray pulses. Remarkably, the x-ray pulses that can be obtained with the FELs are not only significantly shorter than the ones considered in Part 1, but also carry more photons per pulse by many orders of magnitude.

Zholents, A.; Accelerator Systems Division (APS)

2010-09-30

247

Study of runaway electrons using dosimetry of hard x-ray radiations in Damavand tokamak  

SciTech Connect

In this work several studies have been conducted on hard x-ray emissions of Damavand tokamak based on radiation dosimetry using the Thermoluminescence method. The goal was to understand interactions of runaway electrons with plasma particles, vessel wall, and plasma facing components. Total of 354 GR-200 (LiF:Mg,Cu,P) thermoluminescence dosimeter (TLD) crystals have been placed on 118 points – three TLDs per point – to map hard x-ray radiation doses on the exterior of the vacuum vessel. Results show two distinctive levels of x-ray radiations doses on the exterior of the vessel. The low-dose area on which measured dose is about 0.5 mSv/shot. In the low-dose area there is no particular component inside the vessel. On the contrary, on high-dose area of the vessel, x-ray radiations dose exceeds 30 mSv/shot. The high-dose area coincides with the position of limiters, magnetic probe ducts, and vacuum vessel intersections. Among the high-dose areas, the highest level of dose is measured in the position of the limiter, which could be due to its direct contact with the plasma column and with runaway electrons. Direct collisions of runaway electrons with the vessel wall and plasma facing components make a major contribution for production of hard x-ray photons in Damavand tokamak.

Rasouli, C.; Pourshahab, B.; Rasouli, H. [Plasma Physics and Nuclear Fusion Research School, Nuclear Science and Technology Research Institute, AEOI, PO Box 14155-1339, Tehran (Iran, Islamic Republic of)] [Plasma Physics and Nuclear Fusion Research School, Nuclear Science and Technology Research Institute, AEOI, PO Box 14155-1339, Tehran (Iran, Islamic Republic of); Hosseini Pooya, S. M.; Orouji, T. [Radiation Application Research School, Nuclear Science and Technology Research Institute, AEOI, PO Box 14155-1339, Tehran (Iran, Islamic Republic of)] [Radiation Application Research School, Nuclear Science and Technology Research Institute, AEOI, PO Box 14155-1339, Tehran (Iran, Islamic Republic of)

2014-05-15

248

UltraShort Electron Bunch and X-Ray Temporal Diagnostics with an X-Band Transverse Deflector  

Microsoft Academic Search

The measurement of ultra-short electron bunches on the femtosecond time scale constitutes a very challenging problem. In X-ray free-electron laser facilities such as the Linac Coherent Light Source (LCLS), generation of sub-ten femtosecond X-ray pulses is possible, and some efforts have been put into both ultra-short electron and X-ray beam diagnostics. Here we propose a single-shot method using a transverse

Yuantao

2011-01-01

249

Ablation of Organic Molecular Solids by Focused Soft X-Ray Free-Electron Laser Radiation  

NASA Astrophysics Data System (ADS)

The first soft X-ray free-electron laser has recently been put into operation at DESY in Hamburg. Tunable soft X-ray coherent radiation can be generated at the FLASH (Free-electron LASer in Hamburg; formerly known as VUV FEL or TTF2 FEL). In the interaction experiments reported here, the laser system provided ~ 25-fs, ~ 10-? J pulses of 32-nm radiation. We irradiated thin (500 nm) layers of poly (methyl methacrylate) - PMMA deposited on a silicon substrate by single, focused FLASH pulses. The pulse energy was adjusted using a gas attenuator.

Chalupský, J.; Juha, L.; Kuba, J.; Cihelka, J.; Hájková, V.; Bergh, M.; Bionta, R. M.; Caleman, C.; Chapman, H.; Hajdu, J.; Hau-Riege, S.; Jurek, M.; Koptyaev, S.; Krása, J.; Krenz-Tronnier, A.; Krzywinski, J.; London, R.; Meyer-ter-Vehn, J.; Nietubyc, R.; Pelka, J. B.; Sobierajski, R.; Sokolowski-Tinten, K.; Stojanovic, N.; Tiedtke, K.; Toleikis, S.; Tschentscher, T.; Velyhan, A.; Wabnitz, H.; Zastrau, U.

250

Macroporous silicon membranes as electron and x-ray transmissive windows  

SciTech Connect

Macroporous silicon membranes are fabricated whose pores are terminated with 60 nm thin silicon dioxide shells. The transmission of electrons with energies of 5 kV-25 kV through these membranes was investigated reaching a maximum of 22% for 25 kV. Furthermore, the transmission of electromagnetic radiation ranging from the far-infrared to the x-ray region was determined. The results suggest the application of the membrane as window material for electron optics and energy dispersive x-ray detectors.

Schilling, J.; Scherer, A.; Goesele, U.; Kolbe, M. [California Institute of Technology, 391 S. Holliston Avenue, Pasadena, California, 91125 (United States); Max Planck Institute of Microstructure Physics, Halle (Germany); Physikalisch-Technische Bundesanstalt, Berlin (Germany)

2004-08-16

251

Femtosecond x-ray pulse characterization in free-electron lasers using a cross-correlation technique.  

PubMed

We report the first measurements of x-ray single-pulse duration and two-pulse separation at the Linac Coherent Light Source using a cross-correlation technique involving x rays and electrons. An emittance-spoiling foil is adopted as a very simple and effective method to control the output x-ray pulse. A minimum pulse duration of about 3 fs full width at half maximum has been measured together with a controllable pulse separation (delay) between two pulses. This technique provides critical temporal diagnostics for x-ray experiments such as x-ray pump-probe studies. PMID:23368472

Ding, Y; Decker, F-J; Emma, P; Feng, C; Field, C; Frisch, J; Huang, Z; Krzywinski, J; Loos, H; Welch, J; Wu, J; Zhou, F

2012-12-21

252

Automated Chemical Analysis of Internally Mixed Aerosol Particles Using X-ray Spectromicroscopy at the Carbon K-Edge  

SciTech Connect

We have developed an automated data analysis method for atmospheric particles using scanning transmission X-ray microscopy coupled with near edge X-ray fine structure spectroscopy (STXM/NEXAFS). This method is applied to complex internally mixed submicrometer particles containing organic and inorganic material. Several algorithms were developed to exploit NEXAFS spectral features in the energy range from 278 to 320 eV for quantitative mapping of the spatial distribution of elemental carbon, organic carbon, potassium, and noncarbonaceous elements in particles of mixed composition. This energy range encompasses the carbon K-edge and potassium L2 and L3 edges. STXM/NEXAFS maps of different chemical components were complemented with a subsequent analysis using elemental maps obtained by scanning electron microscopy coupled with energy dispersive X-ray analysis (SEM/EDX). We demonstrate the application of the automated mapping algorithms for data analysis and the statistical classification of particles.

Gilles, Mary K; Moffet, R.C.; Henn, T.; Laskin, A.

2011-01-20

253

Development of a new quantitative X-ray microanalysis method for electron microscopy.  

PubMed

Quantitative X-ray microanalysis of thick samples is usually performed by measuring the characteristic X-ray intensities of each element in a sample and in corresponding standards. The ratio of the measured intensities from the unknown material to that from the standard is related to the concentration using the ZAF or ?(?z) equations. Under optimal conditions, accuracies approaching 1% are possible. However, all the experimental conditions must remain the same during the sample and standard measurements. This is not possible with cold field emission scanning electron microscopes (FE-SEMs) where beam current can fluctuate around 5% in its stable regime. Very little work has been done on variable beam current conditions (Griffin, B.J. & Nockolds, C.E., Scanning 13, 307-312, 1991), and none relating to cold FE-SEM applications. To address this issue, a new method was developed using a single spectral measurement. It is similar in approach to the Cliff-Lorimer method developed for the analytical transmission electron microscope. However, corrections are made for X rays generated from thick specimens using the ratio of the characteristic X-ray intensities of two elements in the same material. The proposed method utilizes the ratio of the intensity of a characteristic X-ray normalized by the sum of X-ray intensities of all the elements measured for the sample, which should also reduce the amplitude of error propagation. Uncertainties in the physical parameters of X-ray generation are corrected using a calibration factor that must be previously acquired or calculated. As an example, when this method was applied to the calculation of the composition of Au-Cu National Institute of Standards and Technology standards measured with a cold field emission source SEM, relative accuracies better than 5% were obtained. PMID:20961482

Horny, Paula; Lifshin, Eric; Campbell, Helen; Gauvin, Raynald

2010-12-01

254

Structure studies of the R-phase using the X-ray and electron diffraction method  

NASA Astrophysics Data System (ADS)

The R-phase was induced in polycrystalline 50.6at% Ni-Ti and 51.2at% Ni-Ti alloys by deformation of \\varepsilon=5% and annealing at 350°C for 70 hours. This procedure allowed for a good separation of transformations: B2{to}R and R{to}B19'. The X-ray diffraction patterns were refined with Rietveld method for three structure models of the following space groups: P3, P{-}3 and P31m. The atomic positions were calculated from the Patterson maps determined from the LeBail method. The comparable lowest value of reliability factors was obtained from the Rietveld refinement for P3 and P{-}3 space groups. Electron diffraction patterns registered for basics zones were compared with kinematically calculated models. Profile line analysis was done in rows with significant differences. All results supported the P{-}3 model.

Goryczka, T.; Morawiec, H.

2003-10-01

255

Performance of the x-ray free-electron laser oscillator with crystal cavity  

NASA Astrophysics Data System (ADS)

Simulations of the x-ray free-electron laser (FEL) oscillator are presented that include the frequency-dependent Bragg crystal reflectivity and the transverse diffraction and focusing using the two-dimensional FEL code GINGER. A review of the physics of Bragg crystal reflectors and the x-ray FEL oscillator is made, followed by a discussion of its numerical implementation in GINGER. The simulation results for a two-crystal cavity and realistic FEL parameters indicate ˜109 photons in a nearly Fourier-limited, ps pulse. Compressing the electron beam to 100 A and 100 fs results in comparable x-ray characteristics for relaxed beam emittance, energy spread, and/or undulator parameters, albeit in a larger radiation bandwidth. Finally, preliminary simulation results indicate that the four-crystal FEL cavity can be tuned in energy over a range of a few percent.

Lindberg, R. R.; Kim, K.-J.; Shvyd'Ko, Yu.; Fawley, W. M.

2011-01-01

256

AMPHIBOLE FIBER CONCENTRATION DETERMINATION FOR A SERIES OF COMMUNITY AIR SAMPLES: USE OF X-RAY DIFFRACTION TO SUPPLEMENT ELECTRON MICROSCOPE ANALYSIS  

EPA Science Inventory

The accurate measurement of annual average mineral fiber concentrations at various air sampling sites provides the best index of non-occupational inhalation exposure to fibers in a community located near an industrial source of airborne amphibole fibers. The transmission electron...

257

Resonance fluorescence in ultrafast and intense x-ray free-electron-laser pulses  

NASA Astrophysics Data System (ADS)

The spectrum of resonance fluorescence is calculated for a two-level system excited by an intense, ultrashort x-ray pulse made available, for instance, by free-electron lasers such as the Linac Coherent Light Source. We allow for inner-shell hole decay widths and destruction of the system by further photoionization. This two-level description is employed to model neon cations strongly driven by x rays tuned to the 1s2p-1?1s-12p transition at 848eV; the x rays induce Rabi oscillations which are so fast that they compete with Ne 1s-hole decay. We predict resonance fluorescence spectra for two different scenarios: first, chaotic pulses based on the self-amplified spontaneous emission principle, like those presently generated at x-ray free-electron-laser facilities and, second, Gaussian pulses which will become available in the foreseeable future with self-seeding techniques. As an example of the exciting opportunities derived from the use of seeding methods, we predict, in spite of the above obstacles, the possibility to distinguish at x-ray frequencies a clear signature of Rabi flopping in the spectrum of resonance fluorescence.

Cavaletto, Stefano M.; Buth, Christian; Harman, Zoltán; Kanter, Elliot P.; Southworth, Stephen H.; Young, Linda; Keitel, Christoph H.

2012-09-01

258

Dual x-ray fluorescence spectrometer and method for fluid analysis  

DOEpatents

Disclosed are an X-ray fluorescence (SRF) spectrometer and method for on-site and in-line determination of contaminant elements in lubricating oils and in fuel oils on board a marine vessel. An XRF source block 13 contains two radionuclide sources 16, 17 (e.g. Cd 109 and Fe 55), each oriented 180 degrees from the other to excite separate targets. The Cd 109 source 16 excites sample lube oil flowing through a low molecular weight sample line 18. The Fe 55 source 17 excites fuel oil manually presented to the source beam inside a low molecular weight vial 26 or other container. Two separate detectors A and B are arranged to detect the fluorescent x-rays from the targets, photons from the analyte atoms in the lube oil for example, and sulfur identifying x-rays from bunker fuel oil for example. The system allows both automated in-line and manual on-site analysis using one set of signal processing and multi-channel analyzer electronics 34, 37 as well as one computer 39 and user interface 43.

Wilson, Bary W.; Shepard, Chester L.

2005-02-22

259

Challenges to quantitative multivariate statistical analysis of atomic-resolution X-ray spectral.  

PubMed

A new aberration-corrected scanning transmission electron microscope equipped with an array of Si-drift energy-dispersive X-ray spectrometers has been utilized to acquire spectral image data at atomic resolution. The resulting noisy data were subjected to multivariate statistical analysis to noise filter, remove an unwanted and partially overlapping non-sample-specific X-ray signal, and extract the relevant correlated X-ray signals (e.g., channels with L and K lines). As an example, the Y?Ti?O? pyrochlore-structured oxide (assumed here to be ideal) was interrogated at the [011] projection. In addition to pure columns of Y and Ti, at this projection, there are also mixed 50-50 at. % Y-Ti columns. An attempt at atomic-resolution quantification is presented. The method proposed here is to subtract the non-column-specific signal from the elemental components and then quantify the data based upon an internally derived k-factor. However, a theoretical basis to predict this non-column-specific signal is needed to make this generally applicable. PMID:22849798

Kotula, Paul G; Klenov, Dmitri O; von Harrach, H Sebastian

2012-08-01

260

X-ray analysis of fully depleted CCDs with small pixel size  

NASA Astrophysics Data System (ADS)

X-rays frames offer a lot of information about CCD. 55Fe sources are traditionally being used for CCD gain and charge transfer efficiency (CTE) measurements. The pixel size of modern scientific CCDs is getting smaller. The charge diffusion causes the charge spread among neighboring pixels especially in thick fully depleted sensors. This enables measurement of the charge diffusion using 55Fe X-rays. On the other hand, the usual CTE char- acterization method based on single pixel X-ray events becomes statistically deficient. A new way of measuring CTE using shape and amplitude analysis of X-ray clusters is presented and discussed. This method requires high statistical samples. Advances in test automation and express analysis technique allows for acquiring such statistical samples in a short period of time. The details of our measurement procedure are presented. The lateral diffusion measured using e2v CCD250 is presented and implications for X-ray cluster size and expected cluster shape are discussed. The CTE analysis using total X-ray cluster amplitude is presented. This analysis can reveal CTE problems for certain conditions. The statistical analysis of average X-ray cluster shape is presented. Characteristics X-rays can be used for the whole system absolute calibration. We demonstrate how spectral features of 55Fe and 241Am rad. sources are used for system linearity measurements.

Kotov, I. V.; Haupt, J.; Kubánek, P.; O'Connor, P.; Takacs, P.

2014-07-01

261

Phase distinction in semi-insulating polycrystalline silicon by pattern recognition of X-ray photoelectron spectroscopy/X-ray-induced Auger electron spectroscopy data  

NASA Astrophysics Data System (ADS)

X-ray photoelectron spectroscopy (XPS) and X-ray-induced Auger electron spectroscopy (XAES) supported with the lineshape analysis by the pattern recognition (PR) method and the fuzzy k-nearest neighbor rule ( kNN FR) were applied to study semiinsulating polycrystalline silicon layers (SIPOS). The aim of the present work was to obtain the qualitative and quantitative information about the surface region of as-received SIPOS layers. For the purpose of qualitative analysis the binding energies (BE), binding energy shifts (?BE), the half widths (FWHM) and the lineshapes of the Si 2p, O 1s and O KLL lines were analysed. The quantitative analysis was performed on the basis of the XPS using sensitivity factor method, multiline (ML) approach and the kNN FR. The performance of the kNN rule is possible after selecting the proper set of reference standard materials to which the rule refers during identification of an ambiguous chemical state. By selecting the reference samples supplying the information about the chemical state of Si, SiO x and SiO 2, the kNN rule allowed to distinguish qualitatively these three different phases in SIPOS samples. The particular application of the kNN FR makes possible the quantitative analysis by referring the fuzzy probability of classification for the given chemical state to the concentration of particular constituents in the investigated SIPOS. All the methods applied are consistent in revealing the quantitative results and show that SIPOS is a deeply non-homogeneous material, consisting of two phases: silicon and silicon oxide.

Lesiak, Beata; Zemek, Jozef; Jozwik, Adam

1998-09-01

262

Multicomponent Signal Unmixing from Nanoheterostructures: Overcoming the Traditional Challenges of Nanoscale X-ray Analysis via Machine Learning.  

PubMed

The chemical composition of core-shell nanoparticle clusters have been determined through principal component analysis (PCA) and independent component analysis (ICA) of an energy-dispersive X-ray (EDX) spectrum image (SI) acquired in a scanning transmission electron microscope (STEM). The method blindly decomposes the SI into three components, which are found to accurately represent the isolated and unmixed X-ray signals originating from the supporting carbon film, the shell, and the bimetallic core. The composition of the latter is verified by and is in excellent agreement with the separate quantification of bare bimetallic seed nanoparticles. PMID:25760234

Rossouw, David; Burdet, Pierre; de la Peña, Francisco; Ducati, Caterina; Knappett, Benjamin R; Wheatley, Andrew E H; Midgley, Paul A

2015-04-01

263

A Computer Program for Calculation of Calibration Curves for Quantitative X-Ray Diffraction Analysis.  

ERIC Educational Resources Information Center

Describes a FORTRAN IV program written to supplement a laboratory exercise dealing with quantitative x-ray diffraction analysis of mixtures of polycrystalline phases in an introductory course in x-ray diffraction. Gives an example of the use of the program and compares calculated and observed calibration data. (Author/GS)

Blanchard, Frank N.

1980-01-01

264

RADIOCHEMICAL ANALYSIS BY HIGH SENSITIVITY DUAL-OPTIC MICRO X-RAY FLUORESCENCE  

EPA Science Inventory

A novel dual-optic micro X-ray fluorescence instrument will be developed to do radiochemical analysis of high-level radioactive wastes at DOE sites such as Savannah River Site and Hanford. This concept incorporates new X-ray optical elements such as monolithic polycapillaries and...

265

New method of comparison for electron temperature measurements in plasmas using X-ray spectra of heavy elements  

SciTech Connect

Conditions and applicability limits of a new X-ray spectroscopy method for electron temperature measurements in plasmas of heavy elements are considered. The method is based on comparison of spectra under study with those of well diagnosed laser-produced plasmas. To apply the method for diagnosing tungsten plasmas a thorough analysis of laser-produced plasma spectra has been performed. The analysis included investigation of spectrum peculiarities and determination of electron temperatures. Quantitative data were obtained for determining electron temperatures in tungsten plasmas using relative intensities of spectral peaks in the spectral range {lambda} = 3 - 6 nm. (laser plasma)

Shevelko, A P [P N Lebedev Physical Institute, Russian Academy of Sciences, Moscow (Russian Federation)

2011-08-31

266

Ancient administrative handwritten documents: X-ray analysis and imaging.  

PubMed

Handwritten characters in administrative antique documents from three centuries have been detected using different synchrotron X-ray imaging techniques. Heavy elements in ancient inks, present even for everyday administrative manuscripts as shown by X-ray fluorescence spectra, produce attenuation contrast. In most cases the image quality is good enough for tomography reconstruction in view of future applications to virtual page-by-page `reading'. When attenuation is too low, differential phase contrast imaging can reveal the characters from refractive index effects. The results are potentially important for new information harvesting strategies, for example from the huge Archivio di Stato collection, objective of the Venice Time Machine project. PMID:25723946

Albertin, F; Astolfo, A; Stampanoni, M; Peccenini, Eva; Hwu, Y; Kaplan, F; Margaritondo, G

2015-03-01

267

XSPEC12: Object-Oriented X-Ray Analysis  

NASA Astrophysics Data System (ADS)

XSPEC was designed to be a mission-independent general purpose X-ray data analysis program. In order for XSPEC to keep fulfilling this role well into the 21st Century we have re-implemented its code base in ANSI C++ using object oriented programming techniques. The abstract programming formulation used for XSPEC12 gives considerable advantages for the future. It will be possible to implement new data formats, table model formats, fitting and statistical techniques by loading ``add-in'' modules without the necessity of recompiling existing code. As the first examples, we have written modules that (a) read INTEGRAL/SPI data and responses and (b) implement the CERN/MINUIT optimization library. The new code can also solve problems with source confusion (multiple sources can be modeled and fit from a single spectrum). As for efficiency, the new code achieves similar performance in double precision arithmetic than XSPEC11 gives in single precision. For the cases of analysis with simple analytical models and large spectral arrays, and time series analyses (multiple spectra with the same response matrices) XSPEC12 should give a considerable speed advantage over previous versions. XSPEC12 will have a very similar, but enhanced, syntax over previous releases. It will continue to support user models in Fortran77, but will also support user models in C and C++. The I/O streams designed for XSPEC12 can support either a command line user interface or, in future, a GUI. Additionally, the plotting interface has been written to be independent of the plotting library: future releases will be able to implement newer user graphics packages. XSPEC12 should be available as an alpha release in the late Spring of 2003. We encourage readers to join the testing program that we will be announcing once the release date has been set.

Dorman, B.; Arnaud, K. A.; Gordon, Craig A.

2003-03-01

268

X-ray irradiation induced changes in electron transport in stabilized a-Se photoconductors  

SciTech Connect

We have examined the effect of high-dose x-ray irradiation on electron transport in stabilized amorphous selenium (a-Se) x-ray photoconductive films (of the type used in x-ray image detectors) by measuring the electron lifetime ?{sub e} through interrupted-field time-of-flight experiments. X-ray induced effects have been examined through two types of experiments. In recovery experiments, the a-Se was preirradiated with and without an applied field (5 V/?m) during irradiation with sufficient dose (typically ?20 Gy at 21 °C) to significantly reduce the electron lifetime by ?50%, and then the recovery of the lifetime was monitored as a function of time at three different temperatures, 10 °C, 21 °C, and 35 °C. The lifetime recovery kinetics was exponential with a relaxation time ?{sub r} that is thermally activated with an activation energy of 1.66 eV. ?{sub r} is a few hours at 21 °C and only a few minutes at 35 °C. In experiments examining the irradiation induced effects, the a-Se film was repeatedly exposed to x-ray radiation and the changes in the drift mobility and lifetime were monitored as a function of accumulated dose D. There was no observable change in the drift mobility. At 21 °C, the concentration of x-ray induced deep traps (or capture centers), N{sub d}, increases linearly with D (N{sub d} ? D) whereas at 35 °C, the recovery process prevents a linear increase in N{sub d} with D, and N{sub d} saturates. In all cases, even under high dose irradiation (?50 Gy), the lifetime was recoverable to its original equilibrium (pre-exposure) value within a few relaxation times.

Walornyj, M.; Kasap, S. O. [Department of Electrical and Computer Engineering, University of Saskatchewan, 57 Campus Drive, Saskatoon, Saskatchewan S7N 5A9 (Canada)] [Department of Electrical and Computer Engineering, University of Saskatchewan, 57 Campus Drive, Saskatoon, Saskatchewan S7N 5A9 (Canada)

2013-12-07

269

Investigation of magnetic field manipulated electrons produced from laser-driven ultrafast x-ray sources using x-ray emission spectroscopy  

NASA Astrophysics Data System (ADS)

We used x-ray emission spectroscopy to study energetic electrons (10–100?keV) generated at the laser focus of an intense ultrafast laser interacting with a primary thin film tape target. The electrons penetrated the tape and reached a secondary target of thin metal foils as the probe. The trajectories of these electrons were manipulated with an external magnetic field generated from a home-made Halbach magnet. The interaction of these energetic electrons with the probe produced characteristic x-rays, which were used to infer the flux and temperature of the electrons emitted from the laser focus at the primary tape target. A potential application using these energetic electrons is discussed.

Lee, Changju; Davidson, R. Andrew; Guo, Ting

2015-03-01

270

Prevailing features of X-ray induced molecular electron spectra revealed with fullerenes  

E-print Network

Intense X-ray photo-absorption from short and intense pulses by a molecule triggers complicated electron and subsequently ion dynamics leading to photo-electron spectra which are difficult to interpret. Illuminating fullerenes offers a way to separate out the electron dynamics. Moreover, the fullerene cage confines spatially the origin of photo and Auger electrons. Together with the sequential nature of the photo processes at intensities available at X-ray free electron lasers, this allows for a remarkably detailed interpretation of the photo-electron spectra as we will demonstrate. The general features derived can serve as a paradigm for less well-defined situations in other large molecules or clusters.

Garibay, Abraham Camacho; Rost, Jan M

2014-01-01

271

Making use of x-ray optical effects in photoelectron-, Auger electron-, and x-ray emission spectroscopies: Total reflection, standing-wave excitation, and resonant effects  

SciTech Connect

We present a general theoretical methodology and related open-access computer program for carrying out the calculation of photoelectron, Auger electron, and x-ray emission intensities in the presence of several x-ray optical effects, including total reflection at grazing incidence, excitation with standing-waves produced by reflection from synthetic multilayers and at core-level resonance conditions, and the use of variable polarization to produce magnetic circular dichroism. Calculations illustrating all of these effects are presented, including in some cases comparisons to experimental results. Sample types include both semi-infinite flat surfaces and arbitrary multilayer configurations, with interdiffusion/roughness at their interfaces. These x-ray optical effects can significantly alter observed photoelectron, Auger, and x-ray intensities, and in fact lead to several generally useful techniques for enhancing surface and buried-layer sensitivity, including layer-resolved densities of states and depth profiles of element-specific magnetization. The computer program used in this study should thus be useful for a broad range of studies in which x-ray optical effects are involved or are to be exploited in next-generation surface and interface studies of nanoscale systems.

Yang, S.-H. [IBM Almaden Research Center, San Jose, California 95120 (United States); Gray, A. X. [Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94740 (United States); Department of Physics, University of California at Davis, Davis, California 95616 (United States); Stanford Institute for Materials and Energy Science, Stanford University and SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Kaiser, A. M. [Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94740 (United States); Department of Physics, University of California at Davis, Davis, California 95616 (United States); Peter Grunberg Institute, PGI-6, Forschungszentrum Juelich, 52425 Juelich (Germany); Mun, B. S. [Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Department of Applied Physics, Hanyang University, Ansan, Gyeonggi 426-791 (Korea, Republic of); Sell, B. C. [Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94740 (United States); Department of Physics, University of California at Davis, Davis, California 95616 (United States); Department of Physics, Otterbein College, Westerville, Ohio 43081 (United States); Kortright, J. B. [Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94740 (United States); Fadley, C. S. [Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94740 (United States); Department of Physics, University of California at Davis, Davis, California 95616 (United States)

2013-02-21

272

Soft x-ray spectroscopic studies of the electronic structure of organic semiconductors  

NASA Astrophysics Data System (ADS)

Organic semiconductors have several unique properties, different from traditional inorganic semiconductors, such as flexibility and low cost production on a large scale. Potentially, they can be used in several new optoelectronic devices, such as organic solar cells, and organic light-emitting devices (OLEDs) Phthalocyanines (Pc's) are one important type of molecular organic semiconductor. The ease with which a diverse set of cations can bond to the phthalocyanine ligand leads to Pc-based thin films that display a wide variety of optical and electrical properties. In these materials, the ligand has a complex electronic structure in itself, and the introduction of metal cations adds further complexity to the states near the Fermi level (EF) due to the overlap of metal d states with carbon and nitrogen 2p states. In this thesis, the electronic structure of several Pc's has been studied by soft x-ray spectroscopies, such as x-ray photoemission spectroscopy (XPS), x-ray absorption spectroscopy (XAS), and x-ray emission spectroscopy (XES). To avoid potential contamination and beam damage, the large area thin film samples have been prepared in situ by using organic molecular beam deposition (OMBD). The structure of samples were characterized ex situ by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The soft x-ray spectra recorded from stationary samples are found to represent the electronic structure from damaged molecules, which is caused by intense x-ray beams. Continuously translating samples during measurement overcomes this problem. Element, chemical, and symmetry specific occupied and unoccupied partial density of states (PDOS) from Pc's were observed. They show good agreement with density functional theory (DFT) calculations. Studies of potassium doping non-transition metal Pc, fluorinated metal Pc, and metal oxide Pc's show several interesting phenomena, such as variation of molecular symmetry, and charge transfer and d-d* resonant inelastic x-ray scattering (RIXS) features. These observations and comparisons with other organic semiconductors, such as Tri (8-hydroxyquinoline) aluminum (Alq3), and metal oxides, such as V2O3, not only help to deepen our understanding of the optical and electrical properties of Pc's, but also provide valuable information for the studies of other materials.

Zhang, Yufeng

273

A Review of X-ray Free-Electron Laser Theory  

SciTech Connect

High-gain free-electron lasers (FELs) are being developed as extremely bright sources for a next-generation x-ray facility. In this paper, we review the basic theory of the startup, the exponential growth, and the saturation of the high-gain process, emphasizing the self-amplified spontaneous emission (SASE). The radiation characteristics of an x-ray FEL, including its transverse coherence, temporal characteristics, and harmonic content, are discussed. FEL performance in the presence of machine errors and undulator wakefields is examined. Various enhancement schemes through seeding and beam manipulations are summarized.

Huang, Zhirong; /SLAC; Kim, Kwang-Je; /ANL, APS

2006-12-18

274

Accurate macromolecular structures using minimal measurements from X-ray free-electron lasers  

PubMed Central

X-ray free-electron laser (XFEL) sources enable the use of crystallography to solve three-dimensional macromolecular structures under native conditions and free from radiation damage. Results to date, however, have been limited by the challenge of deriving accurate Bragg intensities from a heterogeneous population of microcrystals, while at the same time modeling the X-ray spectrum and detector geometry. Here we present a computational approach designed to extract statistically significant high-resolution signals from fewer diffraction measurements. PMID:24633409

Hattne, Johan; Echols, Nathaniel; Tran, Rosalie; Kern, Jan; Gildea, Richard J.; Brewster, Aaron S.; Alonso-Mori, Roberto; Glöckner, Carina; Hellmich, Julia; Laksmono, Hartawan; Sierra, Raymond G.; Lassalle-Kaiser, Benedikt; Lampe, Alyssa; Han, Guangye; Gul, Sheraz; DiFiore, Dörte; Milathianaki, Despina; Fry, Alan R.; Miahnahri, Alan; White, William E.; Schafer, Donald W.; Seibert, M. Marvin; Koglin, Jason E.; Sokaras, Dimosthenis; Weng, Tsu-Chien; Sellberg, Jonas; Latimer, Matthew J.; Glatzel, Pieter; Zwart, Petrus H.; Grosse-Kunstleve, Ralf W.; Bogan, Michael J.; Messerschmidt, Marc; Williams, Garth J.; Boutet, Sébastien; Messinger, Johannes; Zouni, Athina; Yano, Junko; Bergmann, Uwe; Yachandra, Vittal K.; Adams, Paul D.; Sauter, Nicholas K.

2014-01-01

275

Thermal conduction and heating by nonthermal electrons in the X-ray halo of M87  

NASA Technical Reports Server (NTRS)

A hydrostatic model for the X-ray halo around the giant elliptical galaxy M87 is presented. It is shown that by taking into account the processes of thermal conduction, and nonthermal heating by relativistic electrons in the radio lobes, a self-consistent hydrostatic model can be constructed. There is no need to invoke radiative accretion or the suppression of thermal conductivity.

Tucker, W. H.; Rosner, R.

1983-01-01

276

Imaging X-ray multilayer structures using cross-sectional high resolution electron microscopy  

Microsoft Academic Search

Mo\\/Si soft X-ray multilayer films have been imaged in cross section by high resolution electron microscopy, and the dependence of important multilayer parameters on imaging conditions has been investigated. The layer thicknesses were found to be insensitive to the focus setting near the Scherzer defocus value (+160 to -800 A). At larger defocus conditions, however, additional Mo fringes were visible

Yuanda Cheng; David J. Smith; Mary B. Stearns; Daniel G. Stearns

1992-01-01

277

SCANNING ELECTRON MICROSCOPY/X-RAY FLUORESCENCE CHARACTERIZATION OF POST-ABATEMENT DUST  

EPA Science Inventory

Scanning electron microscopy (SEM) and laboratory X-ray fluorescence (XRF) were used to characterize post-abatement dust collected with a HEPA filtered vacuum. hree size fractions of resuspended dust (0-30 pm, 2.5-15 pm, and ...

278

Implications of X-Ray Observations for Electron Acceleration and Propagation in Solar Flares  

NASA Technical Reports Server (NTRS)

High-energy X-rays and gamma-rays from solar flares were discovered just over fifty years ago. Since that time, the standard for the interpretation of spatially integrated flare X-ray spectra at energies above several tens of keV has been the collisional thick-target model. After the launch of the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) in early 2002, X-ray spectra and images have been of sufficient quality to allow a greater focus on the energetic electrons responsible for the X-ray emission, including their origin and their interactions with the flare plasma and magnetic field. The result has been new insights into the flaring process, as well as more quantitative models for both electron acceleration and propagation, and for the flare environment with which the electrons interact. In this article we review our current understanding of electron acceleration, energy loss, and propagation in flares. Implications of these new results for the collisional thick-target model, for general flare models, and for future flare studies are discussed.

Holman, G. D.; Aschwanden, M. J.; Aurass, H.; Battaglia, M.; Grigis, P. C.; Kontar, E. P.; Liu, W.; Saint-Hilaire, P.; Zharkova, V. V.

2011-01-01

279

Characterization of calcium crystals in Abelia using x-ray diffraction and electron microscopes  

Technology Transfer Automated Retrieval System (TEKTRAN)

Localization, chemical composition, and morphology of calcium crystals in leaves and stems of Abelia mosanensis and A. ×grandiflora were analyzed with a variable pressure scanning electron microscope (VP-SEM) equipped with an X-ray diffraction system, low temperature SEM (LT-SEM) and a transmission ...

280

Serial femtosecond X-ray diffraction of 30S ribosomal subunit microcrystals in liquid suspension at ambient temperature using an X-ray free-electron laser  

PubMed Central

High-resolution ribosome structures determined by X-ray crystallography have provided important insights into the mechanism of translation. Such studies have thus far relied on large ribosome crystals kept at cryogenic temperatures to reduce radiation damage. Here, the application of serial femtosecond X-ray crystallography (SFX) using an X-ray free-electron laser (XFEL) to obtain diffraction data from ribosome microcrystals in liquid suspension at ambient temperature is described. 30S ribosomal subunit microcrystals diffracted to beyond 6?Å resolution, demonstrating the feasibility of using SFX for ribosome structural studies. The ability to collect diffraction data at near-physiological temperatures promises to provide fundamental insights into the structural dynamics of the ribosome and its functional complexes. PMID:23989164

Demirci, Hasan; Sierra, Raymond G.; Laksmono, Hartawan; Shoeman, Robert L.; Botha, Sabine; Barends, Thomas R. M.; Nass, Karol; Schlichting, Ilme; Doak, R. Bruce; Gati, Cornelius; Williams, Garth J.; Boutet, Sébastien; Messerschmidt, Marc; Jogl, Gerwald; Dahlberg, Albert E.; Gregory, Steven T.; Bogan, Michael J.

2013-01-01

281

Non-destructive surface characterization of float glass: X-ray reflectivity and grazing incidence X-ray fluorescence analysis  

Microsoft Academic Search

In the present study we have carried out non-destructive surface characterization of a float glass using total reflection X-ray fluorescence (TXRF) technique and X-ray reflectivity (XRR). The in-depth distribution of Sn and Fe impurities has been determined by TXRF where as X-ray optical properties such as r.m.s surface roughness, refractive index, etc., have been derived by XRR. The results obtained

M. K. Tiwari; M. H. Modi; G. S. Lodha; A. K. Sinha; K. J. S. Sawhney; R. V. Nandedkar

2005-01-01

282

Anisotropic x ray magnetic linear dichroism - Its importance for the analysis of soft x ray spectra of magnetic oxides  

SciTech Connect

Using spectroscopic information for x ray magnetometry and magnetic microscopy requires detailed theoretical understanding of spectral shape and magnitude of dichroism signals. We have shown unambiguously that--contrary to common belief--spectral shape and magnitude of x ray magnetic linear dichroism (XMLD) are not only determined by the relative orientation of magnetic moments and x ray polarization, but also their orientations relative to the crystallographic axes must be taken into account for accurate interpretation of XMLD data.

van der Laan, G.; Arenholz, Elke

2008-07-02

283

X-ray evidence for electron-ion equilibrium and ionization nonequilibrium in young supernova remnants  

NASA Technical Reports Server (NTRS)

The A-2 spectroscopy experiment on HEAO 1 detected X-ray emission up to 25 keV from the supernova remnants Cas A and Tycho. The spectra must include continuum components with effective temperature equivalent or 10 to the 8th power K which could arise from optically thin plasmas in the collisionless shock fronts. This is the first indication of electron-ion temperature equilibrium in the expanding shell of young remnants. Measurements of the equivalent widths of the K alpha and K beta iron line blends in Cas A, show that their ratio is not compatible with the measured X-ray temperature in the collisional ionization equilibrium model. The search for hard X-ray pulsars in both remnants was unsuccessful.

Pravdo, S. H.; Smith, B. W.

1979-01-01

284

Spectrometer for hard X-ray free-electron laser based on diffraction focusing.  

PubMed

X-ray free-electron lasers (XFELs) generate sequences of ultra-short spatially coherent pulses of X-ray radiation. A diffraction focusing spectrometer (DFS), which is able to measure the whole energy spectrum of the radiation of a single XFEL pulse with an energy resolution of ?E/E 2 × 10(-6), is proposed. This is much better than for most modern X-ray spectrometers. Such resolution allows one to resolve the fine spectral structure of the XFEL pulse. The effect of diffraction focusing occurs in a single-crystal plate due to dynamical scattering, and is similar to focusing in a Pendry lens made from a metamaterial with a negative refraction index. Such a spectrometer is easier to operate than those based on bent crystals. It is shown that the DFS can be used in a wide energy range from 5 keV to 20 keV. PMID:23412482

Kohn, V G; Gorobtsov, O Y; Vartanyants, I A

2013-03-01

285

Nanofocusing of hard X-ray free electron laser pulses using diamond based Fresnel zone plates  

PubMed Central

A growing number of X-ray sources based on the free-electron laser (XFEL) principle are presently under construction or have recently started operation. The intense, ultrashort pulses of these sources will enable new insights in many different fields of science. A key problem is to provide x-ray optical elements capable of collecting the largest possible fraction of the radiation and to focus into the smallest possible focus. As a key step towards this goal, we demonstrate here the first nanofocusing of hard XFEL pulses. We developed diamond based Fresnel zone plates capable of withstanding the full beam of the world's most powerful x-ray laser. Using an imprint technique, we measured the focal spot size, which was limited to 320?nm FWHM by the spectral band width of the source. A peak power density in the focal spot of 4×1017?W/cm2 was obtained at 70 fs pulse length. PMID:22355576

David, C.; Gorelick, S.; Rutishauser, S.; Krzywinski, J.; Vila-Comamala, J.; Guzenko, V. A.; Bunk, O.; Färm, E.; Ritala, M.; Cammarata, M.; Fritz, D. M.; Barrett, R.; Samoylova, L.; Grünert, J.; Sinn, H.

2011-01-01

286

Electron-positron pairs, Compton reflection, and the X-ray spectra of active galactic nuclei  

NASA Technical Reports Server (NTRS)

It is shown here that reprocessing of radiation fron nonthermal pair cascades by cold material in the central parts of active galactic nuclei (AGN) gives rise to X-ray and gamma-ray spectra that satisfy current observational constraints. An average 1-30 keV X-ray spectral index alpha(x) of about 0.7 in the compact range 30-300 is obtained for a wide range of Lorentz factors of the injected electrons. The gamma-ray spectra are steep, with alpha(gamma) about two, and satisfy the observational constraints. Radiation from pair cascades exhibits steep power law decreases in soft X-rays similar to those observed in AGN. The overall picture is consistent with AGN having an accretion disk which intercepts and reprocesses a substantial fraction of the nonthermal continuum incident upon it from above and below.

Zdziarski, Andrzej A.; Ghisellini, Gabriele; George, Ian M.; Fabian, A. C.; Svensson, Roland; Done, Chris

1990-01-01

287

Emerging opportunities in structural biology with X-ray free-electron lasers  

PubMed Central

X-ray free-electron lasers (X-FELs) produce X-ray pulses with extremely brilliant peak intensity and ultrashort pulse duration. It has been proposed that radiation damage can be “outrun” by using an ultra intense and short X-FEL pulse that passes a biological sample before the onset of significant radiation damage. The concept of “diffraction-before-destruction” has been demonstrated recently at the Linac Coherent Light Source, the first operational hard X-ray FEL, for protein nanocrystals and giant virus particles. The continuous diffraction patterns from single particles allow solving the classical “phase problem” by the oversampling method with iterative algorithms. If enough data are collected from many identical copies of a (biological) particle, its three-dimensional structure can be reconstructed. We review the current status and future prospects of serial femtosecond crystallography (SFX) and single-particle coherent diffraction imaging (CDI) with X-FELs. PMID:22922042

Schlichting, Ilme; Miao, Jianwei

2012-01-01

288

Emerging opportunities in structural biology with X-ray free-electron lasers.  

PubMed

X-ray free-electron lasers (X-FELs) produce X-ray pulses with extremely brilliant peak intensity and ultrashort pulse duration. It has been proposed that radiation damage can be 'outrun' by using an ultra intense and short X-FEL pulse that passes a biological sample before the onset of significant radiation damage. The concept of 'diffraction-before-destruction' has been demonstrated recently at the Linac Coherent Light Source, the first operational hard X-ray FEL, for protein nanocrystals and giant virus particles. The continuous diffraction patterns from single particles allow solving the classical 'phase problem' by the oversampling method with iterative algorithms. If enough data are collected from many identical copies of a (biological) particle, its three-dimensional structure can be reconstructed. We review the current status and future prospects of serial femtosecond crystallography (SFX) and single-particle coherent diffraction imaging (CDI) with X-FELs. PMID:22922042

Schlichting, Ilme; Miao, Jianwei

2012-10-01

289

[Proposal of a cloud chamber experiment using diagnostic X-ray apparatus and an analysis assisted by a simulation code].  

PubMed

A cloud chamber is a radiation detector that can visualize the tracks of charged particles. In this study, we developed a middle-type cloud chamber for use in practical training using a diagnostic X-ray apparatus. Because our cloud chamber has a heater to vaporize ethanol and features antifogging glass, it is possible to observe the vapor trails for a long time without the need for fine adjustments. X-rays with a tube voltage of 40 kV or of 120 kV (with a 21-mm aluminum filter) were irradiated at the chamber and the various phenomena were observed. We explain these phenomena in terms of the range of electrons and/or interactions between X-rays and matter and conclude that our analysis is consistent with analysis using the Monte Carlo simulation code EGS5. PMID:23609860

Hayashi, Hiroaki; Hanamitsu, Hiroki; Nishihara, Sadamitsu; Ueno, Junji; Miyoshi, Hirokazu

2013-04-01

290

Electron Spectroscopy: Ultraviolet and X-Ray Excitation.  

ERIC Educational Resources Information Center

Reviews recent growth in electron spectroscopy (54 papers cited). Emphasizes advances in instrumentation and interpretation (52); photoionization, cross-sections and angular distributions (22); studies of atoms and small molecules (35); transition, lanthanide and actinide metal complexes (50); organometallic (12) and inorganic compounds (2);…

Baker, A. D.; And Others

1980-01-01

291

X-ray imaging of chemically active valence electrons during a pericyclic reaction  

PubMed Central

Time-resolved imaging of chemically active valence electron densities is a long-sought goal, as these electrons dictate the course of chemical reactions. However, X-ray scattering is always dominated by the core and inert valence electrons, making time-resolved X-ray imaging of chemically active valence electron densities extremely challenging. Here we demonstrate an effective and robust method, which emphasizes the information encoded in weakly scattered photons, to image chemically active valence electron densities. The degenerate Cope rearrangement of semibullvalene, a pericyclic reaction, is used as an example to visually illustrate our approach. Our work also provides experimental access to the long-standing problem of synchronous versus asynchronous bond formation and breaking during pericyclic reactions. PMID:25424639

Bredtmann, Timm; Ivanov, Misha; Dixit, Gopal

2014-01-01

292

Comparison of the decameric structure of peroxiredoxin-II by transmission electron microscopy and X-ray crystallography.  

PubMed

The decameric human erythrocyte protein torin is identical to the thiol-specific antioxidant protein-II (TSA-II), also termed peroxiredoxin-II (Prx-II). Single particle analysis from electron micrographs of Prx-II molecules homogeneously orientated across holes in the presence of a thin film of ammonium molybdate and trehalose has facilitated the production of a >/=20 A 3-D reconstruction by angular reconstitution that emphasises the D5 symmetry of the ring-like decamer. The X-ray structure for Prx-II was fitted into the transmission electron microscopic reconstruction by molecular replacement. The surface-rendered transmission electron microscopy (TEM) reconstruction correlates well with the solvent-excluded surface of the X-ray structure of the Prx-II molecule. This provides confirmation that transmission electron microscopy of negatively stained specimens, despite limited resolution, has the potential to reveal a valid representation of surface features of protein molecules. 2-D crystallisation of the Prx-II protein on mica as part of a TEM study resulted in the formation of a p2 crystal form with parallel linear arrays of stacked rings. This latter 2-D form correlates well with that observed from the 2.7 A X-ray structure of Prx-II solved from a new orthorhombic 3-D crystal form. PMID:11410278

Harris, J R; Schröder, E; Isupov, M N; Scheffler, D; Kristensen, P; Littlechild, J A; Vagin, A A; Meissner, U

2001-06-11

293

Investigation of electron trajectories of an x-ray tube in magnetic fields of MR scanners  

SciTech Connect

A hybrid x-ray/MR system combining an x-ray fluoroscopic system and an open-bore magnetic resonance (MR) system offers advantages from both powerful imaging modalities and thus can benefit numerous image-guided interventional procedures. In our hybrid system configurations, the x-ray tube and detector are placed in the MR magnet and therefore experience a strong magnetic field. The electron beam inside the x-ray tube can be deflected by a misaligned magnetic field, which may damage the tube. Understanding the deflection process is crucial to predicting the electron beam deflection and avoiding potential damage to the x-ray tube. For this purpose, the motion of an electron in combined electric (E) and magnetic (B) fields was analyzed theoretically to provide general solutions that can be applied to different geometries. For two specific cases, a slightly misaligned strong field and a perpendicular weak field, computer simulations were performed with a finite-element method program. In addition, experiments were conducted using an open MRI magnet and an inserted electromagnet to quantitatively verify the relationship between the deflections and the field misalignment. In a strong (B>>E/c; c: speed of light) and slightly misaligned magnetic field, the deflection in the plane of E and B caused by electrons following the magnetic field lines is the dominant component compared to the deflection in the ExB direction due to the drift of electrons. In a weak magnetic field (B{<=}E/c), the main deflection is in the ExB direction and is caused by the perpendicular component of the magnetic field.

Wen Zhifei; Fahrig, Rebecca; Conolly, Steven; Pelc, Norbert J. [Departments of Radiology and Physics, Stanford University, Stanford, California 94305 (United States); Departments of Radiology, Stanford University, Stanford, California 94305 (United States); Department of Bioengineering, University of California, Berkeley, California 94720 (United States); Departments of Radiology and Bioengineering, Stanford University, Stanford, California 94305 (United States)

2007-06-15

294

Investigation of electron trajectories of an x-ray tube in magnetic fields of MR scanners.  

PubMed

A hybrid x-ray/MR system combining an x-ray fluoroscopic system and an open-bore magnetic resonance (MR) system offers advantages from both powerful imaging modalities and thus can benefit numerous image-guided interventional procedures. In our hybrid system configurations, the x-ray tube and detector are placed in the MR magnet and therefore experience a strong magnetic field. The electron beam inside the x-ray tube can be deflected by a misaligned magnetic field, which may damage the tube. Understanding the deflection process is crucial to predicting the electron beam deflection and avoiding potential damage to the x-ray tube. For this purpose, the motion of an electron in combined electric (E) and magnetic (B) fields was analyzed theoretically to provide general solutions that can be applied to different geometries. For two specific cases, a slightly misaligned strong field and a perpendicular weak field, computer simulations were performed with a finite-element method program. In addition, experiments were conducted using an open MRI magnet and an inserted electromagnet to quantitatively verify the relationship between the deflections and the field misalignment. In a strong (B > E/c; c: speed of light) and slightly misaligned magnetic field, the deflection in the plane of E and B caused by electrons following the magnetic field lines is the dominant component compared to the deflection in the E X B direction due to the drift of electrons. In a weak magnetic field (B < or = E/c), the main deflection is in the E x B direction and is caused by the perpendicular component of the magnetic field. PMID:17654908

Wen, Zhifei; Fahrig, Rebecca; Conolly, Steven; Pelc, Norbert J

2007-06-01

295

ANALYSIS AND MITIGATION OF X-RAY HAZARD GENERATED FROM HIGH INTENSITY LASER-TARGET INTERACTIONS  

SciTech Connect

Interaction of a high intensity laser with matter may generate an ionizing radiation hazard. Very limited studies have been made, however, on the laser-induced radiation protection issue. This work reviews available literature on the physics and characteristics of laser-induced X-ray hazards. Important aspects include the laser-to-electron energy conversion efficiency, electron angular distribution, electron energy spectrum and effective temperature, and bremsstrahlung production of X-rays in the target. The possible X-ray dose rates for several femtosecond Ti:sapphire laser systems used at SLAC, including the short pulse laser system for the Matter in Extreme Conditions Instrument (peak power 4 TW and peak intensity 2.4 x 10{sup 18} W/cm{sup 2}) were analysed. A graded approach to mitigate the laser-induced X-ray hazard with a combination of engineered and administrative controls is also proposed.

Qiu, R.; Liu, J.C.; Prinz, A.A.; Rokni, S.H.; Woods, M.; Xia, Z.; /SLAC; ,

2011-03-21

296

Tomographic analysis of the nonthermal x-ray bursts during disruption instability in the T-10 tokamak  

SciTech Connect

Non-thermal x-ray radiation (E{sub ?} up to 150 keV) is measured in the T-10 tokamaks during disruption instability using two sets of CdTe detectors (10 vertical and 7 horizontal view detectors). Special narrow cupper tubes collimators with lead screening and CdTe detectors integrated with amplifiers inside metallic containers provides enhanced spatial resolution of the system (r ? 3 cm) and assures protection from the parasitic hard x-ray (E{sub ?} up to 1.5 MeV) and electromagnetic loads during disruption. Spatial localization of the nonthermal x-ray emissivity is reconstructed using tomographic Cormack technique with SVD matrix inversion. Analysis indicated appearance of an intensive non-thermal x-ray bursts during initial stage of the disruptions at high density. The bursts are characterized by repetitive spikes (2–3 kHz) of the x-ray emissivity from the plasma core area. Analysis indicated that the spikes can be connected with acceleration of the non-thermal electrons in enhanced longitudinal electric fields induced during energy quench at the disruption instability.

Savrukhin, P. V., E-mail: p.savrukhin@iterrf.ru [National Research Center “Kurchatov Institute”, 123182 Moscow (Russian Federation); ITER RF Domestic Agency, Institution Project Center ITER” 123182 Moscow (Russian Federation); Ermolaeva, A. I.; Shestakov, E. A.; Khramenkov, A. V. [National Research Center “Kurchatov Institute”, 123182 Moscow (Russian Federation)

2014-10-15

297

Tomographic analysis of the nonthermal x-ray bursts during disruption instability in the T-10 tokamak  

NASA Astrophysics Data System (ADS)

Non-thermal x-ray radiation (E? up to 150 keV) is measured in the T-10 tokamaks during disruption instability using two sets of CdTe detectors (10 vertical and 7 horizontal view detectors). Special narrow cupper tubes collimators with lead screening and CdTe detectors integrated with amplifiers inside metallic containers provides enhanced spatial resolution of the system (r ˜ 3 cm) and assures protection from the parasitic hard x-ray (E? up to 1.5 MeV) and electromagnetic loads during disruption. Spatial localization of the nonthermal x-ray emissivity is reconstructed using tomographic Cormack technique with SVD matrix inversion. Analysis indicated appearance of an intensive non-thermal x-ray bursts during initial stage of the disruptions at high density. The bursts are characterized by repetitive spikes (2-3 kHz) of the x-ray emissivity from the plasma core area. Analysis indicated that the spikes can be connected with acceleration of the non-thermal electrons in enhanced longitudinal electric fields induced during energy quench at the disruption instability.

Savrukhin, P. V.; Ermolaeva, A. I.; Shestakov, E. A.; Khramenkov, A. V.

2014-10-01

298

Tomographic analysis of the nonthermal x-ray bursts during disruption instability in the T-10 tokamak.  

PubMed

Non-thermal x-ray radiation (E? up to 150 keV) is measured in the T-10 tokamaks during disruption instability using two sets of CdTe detectors (10 vertical and 7 horizontal view detectors). Special narrow cupper tubes collimators with lead screening and CdTe detectors integrated with amplifiers inside metallic containers provides enhanced spatial resolution of the system (r ? 3 cm) and assures protection from the parasitic hard x-ray (E? up to 1.5 MeV) and electromagnetic loads during disruption. Spatial localization of the nonthermal x-ray emissivity is reconstructed using tomographic Cormack technique with SVD matrix inversion. Analysis indicated appearance of an intensive non-thermal x-ray bursts during initial stage of the disruptions at high density. The bursts are characterized by repetitive spikes (2-3 kHz) of the x-ray emissivity from the plasma core area. Analysis indicated that the spikes can be connected with acceleration of the non-thermal electrons in enhanced longitudinal electric fields induced during energy quench at the disruption instability. PMID:25362394

Savrukhin, P V; Ermolaeva, A I; Shestakov, E A; Khramenkov, A V

2014-10-01

299

IDENTIFICATION OF SELECTED SILICATE MINERALS AND THEIR ASBESTIFORM VARIETIES BY ELECTRON OPTICAL AND X-RAY TECHNIQUES  

EPA Science Inventory

Illustrations of electron micrographs showing morphology, electron diffraction patterns, energy dispersive X-ray spectra, and X-ray diffraction patterns of selected silicates and their asbestiform varieties are presented as an aid in their identification. A method for preparing r...

300

Electronic structure of Fe/MgO/Fe multilayer stack by X-ray magnetic circular dichroism  

SciTech Connect

The interface properties of Fe/MgO/Fe multilayer stack were investigated by using X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD). The magnetic multilayers were deposited by electron beam evaporation method, which exhibits the attributes of perpendicular magnetic anisotropy (PMA). XAS analysis shows that Fe-layer forms a Fe-O-rich interface region with MgO-layer and a sum-rule analysis of the XMCD estimates the average magnetic moment of 2.31?±?0.1 ?{sub B} per Fe-atom. XAS and XMCD studies indicate the formation of a heterostructure (Fe/FeO/Fe{sub 2}O{sub 3}) on the interface. A phase transition in Fe-O stoichiometry at interface is also observed at low temperature (90?K), which may be useful in magnetic storage technology.

Gautam, Sanjeev, E-mail: sgautam71@kist.re.kr; Hwa Chae, Keun, E-mail: khchae@kist.re.kr [Advanced Analysis Center, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of); Asokan, Kandasami; Pal Singh, Jitendra [Materials Science Division, Inter-University Accelerator Centre, New Delhi 110-067 (India); Chang, Fan-Hsiu; Lin, Hong-Ji [National Synchrotron Radiation Research Center, Hsinchu 30 076, Taiwan (China)

2014-05-07

301

Soft-x-ray harmonic comb from relativistic electron spikes.  

PubMed

We demonstrate a new high-order harmonic generation mechanism reaching the "water window" spectral region in experiments with multiterawatt femtosecond lasers irradiating gas jets. A few hundred harmonic orders are resolved, giving ?J/sr pulses. Harmonics are collectively emitted by an oscillating electron spike formed at the joint of the boundaries of a cavity and bow wave created by a relativistically self-focusing laser in underdense plasma. The spike sharpness and stability are explained by catastrophe theory. The mechanism is corroborated by particle-in-cell simulations. PMID:22540709

Pirozhkov, A S; Kando, M; Esirkepov, T Zh; Gallegos, P; Ahmed, H; Ragozin, E N; Faenov, A Ya; Pikuz, T A; Kawachi, T; Sagisaka, A; Koga, J K; Coury, M; Green, J; Foster, P; Brenner, C; Dromey, B; Symes, D R; Mori, M; Kawase, K; Kameshima, T; Fukuda, Y; Chen, L; Daito, I; Ogura, K; Hayashi, Y; Kotaki, H; Kiriyama, H; Okada, H; Nishimori, N; Imazono, T; Kondo, K; Kimura, T; Tajima, T; Daido, H; Rajeev, P; McKenna, P; Borghesi, M; Neely, D; Kato, Y; Bulanov, S V

2012-03-30

302

Empirical studies of solar flares: Comparison of X-ray and H alpha filtergrams and analysis of the energy balance of the X-ray plasma  

NASA Technical Reports Server (NTRS)

The physics of solar flares was investigated through a combined analysis of X-ray filtergrams of the high temperature coronal component of flares and H alpha filtergrams of the low temperature chromospheric component. The data were used to study the magnetic field configuration and its changes in solar flares, and to examine the chromospheric location and structure of X-ray bright points (XPB) and XPB flares. Each topic and the germane data are discussed. The energy balance of the thermal X-ray plasma in flares, while not studied, is addressed.

Moore, R. L.

1979-01-01

303

Copyright The Discussion Group of X-Ray Analysis,  

E-print Network

analysis for eutectic Pb-Sn solder has been carried out. [Key words] SEM-EDX, Scanning electron microscope, Silicon drift detector, Line analysis, Eutectic Pb-Sn solder 2 SEM- EDX Pb-Sn EDX SEM-EDX Pb-Sn 1. SEM X X.6 SEM image and line analysis for eutectic Pb-Sn solder on Cu. The line analysis has been carried

Jun, Kawai

304

Laser Assisted Emittance Exchange: Downsizing the X-ray Free Electron Laser  

SciTech Connect

A technique is proposed to generate electron beam with ultralow transverse emittance through laser assisted transverse-to-longitudinal emittance exchange. In the scheme a laser operating in the TEM10 mode is used to interact with the electron beam in a dispersive region and to initiate the emittance exchange. It is shown that with the proposed technique one can significantly downsize an x-ray free electron laser (FEL), which may greatly extend the availability of these light sources. A hard x-ray FEL operating at 1.5 {angstrom} with a saturation length within 30 meters using a 3.8 GeV electron beam is shown to be practically feasible.

Xiang, Dao; /SLAC

2009-12-11

305

Double-core-hole spectroscopy for chemical analysis with an intense X-ray femtosecond laser  

PubMed Central

Theory predicts that double-core-hole (DCH) spectroscopy can provide a new powerful means of differentiating between similar chemical systems with a sensitivity not hitherto possible. Although DCH ionization on a single site in molecules was recently measured with double- and single-photon absorption, double-core holes with single vacancies on two different sites, allowing unambiguous chemical analysis, have remained elusive. Here we report that direct observation of double-core holes with single vacancies on two different sites produced via sequential two-photon absorption, using short, intense X-ray pulses from the Linac Coherent Light Source free-electron laser and compare it with theoretical modeling. The observation of DCH states, which exhibit a unique signature, and agreement with theory proves the feasibility of the method. Our findings exploit the ultrashort pulse duration of the free-electron laser to eject two core electrons on a time scale comparable to that of Auger decay and demonstrate possible future X-ray control of physical inner-shell processes. PMID:21969540

Berrah, Nora; Fang, Li; Murphy, Brendan; Osipov, Timur; Ueda, Kiyoshi; Kukk, Edwin; Feifel, Raimund; van der Meulen, Peter; Salen, Peter; Schmidt, Henning T.; Thomas, Richard D.; Larsson, Mats; Richter, Robert; Prince, Kevin C.; Bozek, John D.; Bostedt, Christoph; Wada, Shin-ichi; Piancastelli, Maria N.; Tashiro, Motomichi; Ehara, Masahiro

2011-01-01

306

Duplex multiwire proportional x-ray detector for multichord time-resolved soft x-ray and electron temperature measurements on T-10 tokamak.  

PubMed

Compact 64-channel multiwire proportional chamber is successfully used on T-10 and TCV tokamaks as a continuous-current soft x-ray detectors. The duplex multiwire proportional x-ray detector is a new generation of these detectors. It has been designed for simultaneous multichord measurement of plasma soft x-ray emissivity in a two spectral ranges and determination of the electron temperature by the two-absorber method. The detector consists of two identical multiwire proportional chambers filled by 90%Kr+10%CH(4) gas mixture at atmospheric pressure. The first multiwire chamber has 64 channels. The second multiwire chamber (installed behind the first one) has 32 channels. Both chambers view the plasma through the one helium-filled slot-hole camera. Thus, the first multiwire chamber serves as an absorber filter for the second one. Such construction of the detector allows us in addition to soft x-ray measurements to provide measurement of the plasma core electron temperature with spatial resolution of about 2 cm and a time resolution of less than 50 mus. The construction of the detector and experimental results illustrating the potential of the diagnostic are presented. PMID:19044481

Sushkov, A V; Andreev, V F; Kravtsov, D E

2008-10-01

307

Duplex multiwire proportional x-ray detector for multichord time-resolved soft x-ray and electron temperature measurements on T-10 tokamaka)  

NASA Astrophysics Data System (ADS)

Compact 64-channel multiwire proportional chamber is successfully used on T-10 and TCV tokamaks as a continuous-current soft x-ray detectors. The duplex multiwire proportional x-ray detector is a new generation of these detectors. It has been designed for simultaneous multichord measurement of plasma soft x-ray emissivity in a two spectral ranges and determination of the electron temperature by the two-absorber method. The detector consists of two identical multiwire proportional chambers filled by 90%Kr+10%CH4 gas mixture at atmospheric pressure. The first multiwire chamber has 64 channels. The second multiwire chamber (installed behind the first one) has 32 channels. Both chambers view the plasma through the one helium-filled slot-hole camera. Thus, the first multiwire chamber serves as an absorber filter for the second one. Such construction of the detector allows us in addition to soft x-ray measurements to provide measurement of the plasma core electron temperature with spatial resolution of about 2cm and a time resolution of less than 50?s. The construction of the detector and experimental results illustrating the potential of the diagnostic are presented.

Sushkov, A. V.; Andreev, V. F.; Kravtsov, D. E.

2008-10-01

308

Large format imaging detectors for x-ray free-electron-lasers  

NASA Astrophysics Data System (ADS)

New generation synchrotron light sources, the X-ray free electron lasers, require a two dimensional focal plane instrumentation to perform X-ray imaging from below 100eV up to 25keV. The instruments have to face the accelerator bunch structure and energy bandwidth which is different for existing (FLASH, Hamburg and LCLS, Menlo Park) and future photon sources (SACLA, Harima and XFEL, Hamburg). Within the frame of the Center for Free Electron Laser Science (CFEL), a joint effort of the Max-Planck Society, DESY and the University of Hamburg, the MPI semiconductor laboratory developed, produced and operated large area X-ray CCD detectors with a format of nearly 60cm2 image area. They show outstanding characteristics: a high readout speed due to a complete parallel signal processing, high and homogeneous quantum efficiency, low signal noise, radiation hardness and a high pixel charge handling capacitance. We will present measurement results which demonstrate the X-ray spectroscopic and imaging capabilities of the fabricated devices. We will also report on the concept and the anticipated properties of the full, large scale system. The implementation of the detector into an experimental chamber to perform measurements e.g. of macromolecules in order to determine their structure at atomic resolutions will be shown.

Hartmann, Robert; Epp, Sascha; Gorke, Hubert; Hartmann, Andreas; Hauser, Günther; Herrmann, Sven; Holl, Peter; Kimmel, Nils; Meidinger, Norbert; Reich, Christian; Rolles, Daniel; Soltau, Heike; Strüder, Lothar; Ullrich, Joachim; Weidenspointner, Georg

2011-06-01

309

Fabrication, measurement, and analysis of multilayer x- ray diffraction gratings  

NASA Astrophysics Data System (ADS)

I examine the theory and fabrication of lamellar multilayer x-ray diffraction gratings. I use current theory based on the Kirchoff Integral for amplitude gratings and a new equation for phase gratings to analyze current technology multilayer grating performance (where the period/? exceeds 10). I examine the possible fabrication methods and define two general categories (additive: multilayer added to patterned substrate, subtractive: grating etched into multilayer). I conclude the additive approach is superior, leading to x-ray analogues to binary optics and holographic optical elements. I define an additive process in detail and demonstrate the serviceability of the key processes: thermal growth of silicon dioxide on silicon, lithography, a combined plasma-etch and wet-etch. Multilayer fabrication difficulties on patterned substrates are identified, including: mushroom cap growth, and filleting in the grooves. Measurements done at NSLS on 2 amplitude gratings and 1 phase grating are reported. The data is shown to be compatible with the Kirchoff theory.

Hansen, Douglas P.

1997-12-01

310

Liberation of Neutrons from Beryllium by X-Rays: Radioactivity Induced by Means of Electron Tubes  

Microsoft Academic Search

IT has been recently reported1 that neutrons are liberated from beryllium by gamma-rays of radium and that these are able to induce radioactivity in iodine. Following up this work, we have attempted to liberate neutrons from beryllium by means of hard X-rays, produced by high-voltage electron tubes. An electron tube, which could conveniently be operated by a high-voltage impulse generator

A. Brasch; F. Lange; A. Waly; T. E. Banks; T. A. Chalmers; Leo Szilard; F. L. Hopwood

1934-01-01

311

Constraints on photon pulse duration from longitudinal electron beam diagnostics at a soft X-ray free-electron laser  

E-print Network

-ray free-electron laser C. Behrens1 , N. Gerasimova1 , Ch. Gerth1 , B. Schmidt1 , E.A. Schneidmiller1 , S, Ukraine (Dated: February 28, 2012) The successful operation of X-ray free-electron lasers (FELs), like the Linac Coherent Light Source or the Free-Electron Laser in Hamburg (FLASH), makes unprecedented research

312

Laterally graded multilayer optics for x-ray analysis  

NASA Astrophysics Data System (ADS)

Periodic multilayers are well known as Bragg reflectors for X- rays. A high reflectivity and a wide reflection width are their outstanding features. However, if multilayers shall be used as reflective coating for X-ray optics, especially for wide acceptance angles, uniform layer thicknesses cause chromatic aberrations. These aberrations can be overcome by laterally graded multilayer optics. Their Bragg angle is matched laterally to the incidence angle so that for all points on the reflector, Bragg reflection is obtained for the same wavelength. Three major types of laterally graded multilayer mirrors ('Gobel Mirrors') are applied in X-ray diffractometry: (1) parabolic, (2) elliptic and (3) planar. In this paper, we give design criteria and formulae for these mirrors. Furthermore, we discuss the requirements on the dimensions and the fabrication process. Two different processes suitable for the fabrication, sputter coating and pulsed laser deposition (PLD), are described. The X-ray optical parameters and their characterization are presented for various mirrors designed for Cu K(alpha) , Mo K(alpha) and Cr K(alpha) radiation. From Ni/C and Ni/B4C multilayers, high-photon-flux monochromators with a Cu K(beta) /K(alpha) intensity ratio of about 1:1000 have been realized. The divergence of the 'parallel' beam reflected from parabolic mirrors is about 0.02 degrees, which is one order of magnitude lower than the divergence of polycapillary optics, monocapillary optics and waveguides. Comparing the photon flux density in a high resolution diffraction setup with and without mirror optics a gain factor of 16 was achieved for parabolic Ni/B4C multilayer mirrors.

Schuster, Manfred R.; Goebel, H.; Bruegemann, Lutz; Bahr, D.; Burgaezy, F.; Michaelsen, Carsten; Stoermer, Michael; Ricardo, P.; Dietsch, Reiner; Holz, Thomas; Mai, Hermann

1999-11-01

313

New approach to breast tumor detection based on fluorescence x-ray analysis  

PubMed Central

A new technical approach to breast-tumor detection is proposed. The technique is based on fluorescence x-ray analysis, and can identify a miniature malignant tumor within the breast. The primary beam intensity needed in fluorescence x-ray analysis is on a lower order of magnitude than that used in mammography. Thus, the newly-proposed technique would enable detection of a still tiny breast cancer while dramatically lowering the radiation dose. Field-emission x-ray sources might be a key for translating this concept into a medical technique. PMID:20930932

Hayashi, Yasuhiko; Okuyama, Fumio

2010-01-01

314

Cluster of galaxies & Cosmology - X-ray analysis of fossil group RXJ1720.1+2360  

NASA Astrophysics Data System (ADS)

We present the results on the X-ray analysis of fossil group of galaxies RXJ1720.1+2360. Fossil Groups are systems associated to extended emission in X-rays with one single central elliptical galaxy surrounded by very faint companions. This unusual lack of bright galaxies in the group is presumably due to galactic cannibalism. In this study we present for the first time the imaging and spectral analysis of the XMM-Newton data of RXJ1720.1+2360. This work is part of a systematic study to determine the X-ray properties of fossil groups.

Lozada, Monica

2012-09-01

315

Conservation of Moroccan manuscript papers aged 150, 200 and 800 years. Analysis by infrared spectroscopy (ATR-FTIR), X-ray diffraction (XRD), and scanning electron microscopy energy dispersive spectrometry (SEM-EDS).  

PubMed

The preservation of manuscripts and archive materials is a serious problem for librarians and restorers. Paper manuscript is subjected to numerous degradation factors affecting their conservation state. This research represents an attempt to evaluate the conservation restoration process applied in Moroccan libraries, especially the alkaline treatment for strengthening weakened paper. In this study, we focused on six samples of degraded and restored paper taken from three different Moroccan manuscripts aged 150, 200 and 800 years. In addition, the Japanese paper used in restoration has been characterized. A modern paper was also analyzed as reference. A three-step analytical methodology based on infrared spectroscopy (ATR-FTIR), X-ray diffraction (XRD) and scanning electron microscopy coupled to energy dispersive spectrometry (SEM-EDS) analysis was developed before and after restoration in order to determine the effect of the consolidation treatment on the paper structure. The results obtained by XRD and ATR-FTIR disclosed the presence of barium sulfate (BaSO4) in all restored paper manuscripts. The presence of calcium carbonate (CaCO3) in all considered samples was confirmed by FTIR spectroscopy. The application of de-acidification treatment causes significant changes connected with the increase of intensity mostly in the region 1426 cm(-1), assigned to the asymmetric and symmetric CO stretching mode of calcite, indicating the effectiveness of de-acidification procedure proved by the rise of the alkaline reserve content allowing the long term preservation of paper. Observations performed by SEM magnify the typical paper morphology and the structure of fibbers, highlighting the effect of the restoration process, manifested by the reduction of impurities. PMID:25459630

Hajji, Latifa; Boukir, Abdellatif; Assouik, Jamal; Lakhiari, Hamid; Kerbal, Abdelali; Doumenq, Pierre; Mille, Gilbert; De Carvalho, Maria Luisa

2015-02-01

316

Conservation of Moroccan manuscript papers aged 150, 200 and 800 years. Analysis by infrared spectroscopy (ATR-FTIR), X-ray diffraction (XRD), and scanning electron microscopy energy dispersive spectrometry (SEM-EDS)  

NASA Astrophysics Data System (ADS)

The preservation of manuscripts and archive materials is a serious problem for librarians and restorers. Paper manuscript is subjected to numerous degradation factors affecting their conservation state. This research represents an attempt to evaluate the conservation restoration process applied in Moroccan libraries, especially the alkaline treatment for strengthening weakened paper. In this study, we focused on six samples of degraded and restored paper taken from three different Moroccan manuscripts aged 150, 200 and 800 years. In addition, the Japanese paper used in restoration has been characterized. A modern paper was also analyzed as reference. A three-step analytical methodology based on infrared spectroscopy (ATR-FTIR), X-ray diffraction (XRD) and scanning electron microscopy coupled to energy dispersive spectrometry (SEM-EDS) analysis was developed before and after restoration in order to determine the effect of the consolidation treatment on the paper structure. The results obtained by XRD and ATR-FTIR disclosed the presence of barium sulfate (BaSO4) in all restored paper manuscripts. The presence of calcium carbonate (CaCO3) in all considered samples was confirmed by FTIR spectroscopy. The application of de-acidification treatment causes significant changes connected with the increase of intensity mostly in the region 1426 cm-1, assigned to the asymmetric and symmetric Csbnd O stretching mode of calcite, indicating the effectiveness of de-acidification procedure proved by the rise of the alkaline reserve content allowing the long term preservation of paper. Observations performed by SEM magnify the typical paper morphology and the structure of fibbers, highlighting the effect of the restoration process, manifested by the reduction of impurities.

Hajji, Latifa; Boukir, Abdellatif; Assouik, Jamal; Lakhiari, Hamid; Kerbal, Abdelali; Doumenq, Pierre; Mille, Gilbert; De Carvalho, Maria Luisa

2015-02-01

317

X-ray photoelectron spectroscopy and X-ray-excited Auger electron spectroscopy studies of diamondlike carbon films deposited using unbalanced magnetron sputtering  

NASA Astrophysics Data System (ADS)

The electronic structure of diamondlike carbon (DLC) films deposited using unbalanced magnetron sputtering is examined using Electron Energy-Loss, X-ray photoelectron and X-ray-excited Auger spectroscopies. The characteristics of DLC films are discussed as functions of deposition conditions, e.g. argon gas pressure and substrate bias voltage. As the substrate bias voltage is increased, the films show the evidence of graphite and carbide formation as revealed in the C 1s and valance band spectra. However, with increasing argon gas pressure, the electron spectra of the films show diamondlike structure. ^1 Soon-Cheon Seo, David C. Ingram, and Hugh H. Richardson, J. Vac. Sci. Technol. A 13 Nov/Dec (1995).

Seo, Soon-Cheon; Ingram, David C.

1996-03-01

318

Electron Beam Production and Characterization for the PLEIADES Thomson X-ray Source  

SciTech Connect

We report on the performance of an S-band RF photocathode electron gun and accelerator for operation with the PLEIADES Thomson x-ray source at LLNL. Simulations of beam production, transport, and focus are presented. It is shown that a 1 ps, 500 pC electron bunch with a normalized emittance of less than 5 {pi}mm-mrad can be delivered to the interaction point. Initial electron measurements are presented. Calculations of expected x-ray flux are also performed, demonstrating an expected peak spectral brightness of 10{sup 20} photons/s/mm{sup 2}/mrad{sup 2}/0.1% bandwidth. Effects of RF phase jitter are also presented, and planned phase measurements and control methods are discussed.

Brown, W J; Hartemann, F V; Tremaine, A M; Springer, P T; Le Sage, G P; Barty, C P J; Rosenzweig, J B; Crane, J K; Cross, R R; Fittinghoff, D B; Gibson, D J; Slaughter, D R; Anderson, S

2002-10-14

319

Boiling the Vacuum with an X-Ray Free Electron Laser  

E-print Network

X-ray free electron lasers will be constructed in this decade, both at SLAC in the form of the so-called Linac Coherent Light Source as well as at DESY, where the so-called TESLA XFEL laboratory uses techniques developed for the design of the TeV energy superconducting electron-positron linear accelerator TESLA. Such X-ray lasers may allow also for high-field science applications by exploiting the possibility to focus their beams to a spot with a small radius, hopefully in the range of the laser wavelength. Along this route one obtains very large electric fields, much larger than those obtainable with any optical laser of the same power. We consider here the possibility of obtaining an electric field so high that electron-positron pairs are spontaneously produced in vacuum (Schwinger pair production) and review the prospects to verify this non-perturbative production mechanism for the first time in the laboratory.

A. Ringwald

2003-04-15

320

X-Ray Analysis of Ribosomes: the Static of the Dynamic  

Microsoft Academic Search

This review considers a brief history, comments, and consequences of recent remarkable achievements: X-ray analysis on the level of atomic resolution of structures of bacterial ribosomes, their subunits, and functional complexes.

A. M. Kopylov

2002-01-01

321

Purification, crystallization and preliminary X-ray analysis of struthiocalcin 1 from ostrich (Struthio camelus) eggshell  

PubMed Central

The purification, crystallization and preliminary X-ray analysis of struthiocalcin 1 (SCA-1), a protein obtained from the intramineral part of ostrich (Struthio camelus) eggshell, is reported. PMID:18007058

Reyes-Grajeda, Juan Pablo; Marín-García, Liliana; Stojanoff, Vivian; Moreno, Abel

2007-01-01

322

X-ray analysis of Pt?Sn catalysts supported on zinc-aluminium spinel  

Microsoft Academic Search

An x-ray diffraction analysis of Pt?Sn catalysts supported on zinc-aluminium spinel has shown that, after testing in paraffin dehydrogenation, they contain a tin-platinum solid solution with a face-centered cubic cell.

E. M. Moroz; N. A. Pakhomov; G. R. Kotelnikov; R. A. Buyanov; V. A. Patanov

1977-01-01

323

Theoretical study of Raman chirped adiabatic passage by X-ray absorption spectroscopy: Highly excited electronic states and rotational effects  

NASA Astrophysics Data System (ADS)

Raman Chirped Adiabatic Passage (RCAP) is an efficient method to climb the vibrational ladder of molecules. It was shown on the example of fixed-in-space HCl molecule that selective vibrational excitation can thus be achieved by RCAP and that population transfer can be followed by X-ray Photoelectron spectroscopy [S. Engin, N. Sisourat, P. Selles, R. Taïeb, and S. Carniato, Chem. Phys. Lett. 535, 192-195 (2012)]. Here, in a more detailed analysis of the process, we investigate the effects of highly excited electronic states and of molecular rotation on the efficiency of RCAP. Furthermore, we propose an alternative spectroscopic way to monitor the transfer by means of X-ray absorption spectra.

Engin, Selma; Sisourat, Nicolas; Selles, Patricia; Taïeb, Richard; Carniato, Stéphane

2014-06-01

324

THE XMM-NEWTON/EPIC X-RAY LIGHT CURVE ANALYSIS OF WR 6  

SciTech Connect

We obtained four pointings of over 100 ks each of the well-studied Wolf-Rayet star WR 6 with the XMM-Newton satellite. With a first paper emphasizing the results of spectral analysis, this follow-up highlights the X-ray variability clearly detected in all four pointings. However, phased light curves fail to confirm obvious cyclic behavior on the well-established 3.766 day period widely found at longer wavelengths. The data are of such quality that we were able to conduct a search for event clustering in the arrival times of X-ray photons. However, we fail to detect any such clustering. One possibility is that X-rays are generated in a stationary shock structure. In this context we favor a corotating interaction region (CIR) and present a phenomenological model for X-rays from a CIR structure. We show that a CIR has the potential to account simultaneously for the X-ray variability and constraints provided by the spectral analysis. Ultimately, the viability of the CIR model will require both intermittent long-term X-ray monitoring of WR 6 and better physical models of CIR X-ray production at large radii in stellar winds.

Ignace, R. [Department of Physics and Astronomy, East Tennessee State University, Johnson City, TN 37663 (United States); Gayley, K. G. [Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52245 (United States); Hamann, W.-R.; Oskinova, L. M. [Institute for Physics and Astronomy, University Potsdam, D-14476 Potsdam (Germany); Huenemoerder, D. P. [Massachusetts Institute of Technology, Kavli Institute for Astrophysics and Space Research, 70 Vassar Street, Cambridge, MA 02139 (United States); Pollock, A. M. T. [European Space Agency XMM-Newton Science Operations Centre, European Space Astronomy Centre, Apartado 78, Villanueva de la Cañada, E-28691 Madrid (Spain); McFall, M., E-mail: ignace@etsu.edu [Department of Physics, 191 W. Woodruff Avenue, Ohio State University, Columbus, OH 43210 (United States)

2013-09-20

325

X-ray and photoelectron spectroscopy of the structure, reactivity, and electronic structure of semiconductor nanocrystals  

SciTech Connect

Semiconductor nanocrystals are a system which has been the focus of interest due to their size dependent properties and their possible use in technological applications. Many chemical and physical properties vary systematically with the size of the nanocrystal and thus their study enables the investigation of scaling laws. Due to the increasing surface to volume ratio as size is decreased, the surfaces of nanocrystals are expected to have a large influence on their electronic, thermodynamic, and chemical behavior. In spite of their importance, nanocrystal surfaces are still relatively uncharacterized in terms of their structure, electronic properties, bonding, and reactivity. Investigation of nanocrystal surfaces is currently limited by what techniques to use, and which methods are suitable for nanocrystals is still being determined. This work presents experiments using x-ray and electronic spectroscopies to explore the structure, reactivity, and electronic properties of semiconductor (CdSe, InAs) nanocrystals and how they vary with size. Specifically, x-ray absorption near edge spectroscopy (XANES) in conjunction with multiple scattering simulations affords information about the structural disorder present at the surface of the nanocrystal. X-ray photoelectron spectroscopy (XPS) and ultra-violet photoelectron spectroscopy (UPS) probe the electronic structure in terms of hole screening, and also give information about band lineups when the nanocrystal is placed in electric contact with a substrate. XPS of the core levels of the nanocrystal as a function of photo-oxidation time yields kinetic data on the oxidation reaction occurring at the surface of the nanocrystal.

Hamad, K.S.

2000-05-01

326

Electron Energy Partition in the Above-the-looptop Solar Hard X-Ray Sources  

NASA Astrophysics Data System (ADS)

Solar flares produce non-thermal electrons with energies up to tens of MeVs. To understand the origin of energetic electrons, coronal hard X-ray (HXR) sources, in particular above-the-looptop sources, have been studied extensively. However, it still remains unclear how energies are partitioned between thermal and non-thermal electrons within the above-the-looptop source. Here we show that the kappa distribution, when compared to conventional spectral models, can better characterize the above-the-looptop HXRs (gsim15 keV) observed in four different cases. The widely used conventional model (i.e., the combined thermal plus power-law distribution) can also fit the data, but it returns unreasonable parameter values due to a non-physical sharp lower-energy cutoff Ec. In two cases, extreme-ultraviolet data were available from SDO/AIA and the kappa distribution was still consistent with the analysis of differential emission measure. Based on the kappa distribution model, we found that the 2012 July 19 flare showed the largest non-thermal fraction of electron energies about 50%, suggesting equipartition of energies. Considering the results of particle-in-cell simulations, as well as density estimates of the four cases studied, we propose a scenario in which electron acceleration is achieved primarily by collisionless magnetic reconnection, but the electron energy partition in the above-the-looptop source depends on the source density. In low-density above-the-looptop regions (few times 109 cm-3), the enhanced non-thermal tail can remain and a prominent HXR source is created, whereas in higher-densities (>1010 cm-3), the non-thermal tail is suppressed or thermalized by Coulomb collisions.

Oka, Mitsuo; Krucker, Säm; Hudson, Hugh S.; Saint-Hilaire, Pascal

2015-02-01

327

Use Of An Axisymmetric Microscope With Electronic Readout For Collecting Soft X-Ray Images  

NASA Astrophysics Data System (ADS)

The axisymmetric microscope, first discussed by Wolter1-2, provides high resolution and sensitivity for investigating the soft X-ray emission of laser-driven plasmas3-4. Such a device having a 10 X magnification has been constructed. Its resolution has been evaluated empirically using several grids backlighted by either an X-ray or a visible light source. Due to surface roughness and departure from theoretical contours, the X-ray resolution was found to be near 25 µm whereas the visible light image of the 12 tim grids was still good. We present a comparison between the images of laser-driven plasmas given by this microscope and by a 10 X pinhole camera. Until now these images were recorded on X-ray film. We have shown5 that film could be replaced by C.C.D. in a pinhole camera when the photon energy lies within the 1-10 keV range. Below 1 keV the quantum yield is too low so we have used an image converter tube made by RTC. It is a diode-inverter tube with a soft X-ray photocathode and a P20 phosphor deposited on an optic fiber plate. The electronic image appearing on the screen is read by a C.C.D. working in the visible spectral fields. An electronic image readout chain, which is identical to those associated with streak cameras6, then processes automatically and immediately the images given by the microscope.

Cavailler, C.; Henry, Ph.; Launspach, J.; De Mascureau, J.; Millerioux, M.; Rostaing, M.; Sauneuf, R.

1985-02-01

328

Bayesian analysis of X-ray jet features of the high redshift quasar jets observed with Chandra  

NASA Astrophysics Data System (ADS)

X-ray emission of powerful quasar jets may be a result of the inverse Compton (IC) process in which the Cosmic Microwave Background (CMB) photons gain energy by interactions with the jet's relativistic electrons. However, there is no definite evidence that IC/CMB process is responsible for the observed X-ray emission of large scale jets. A step toward understanding the X-ray emission process is to study the Radio and X-ray morphologies of the jet. Results from Chandra X-ray and multi-frequency VLA imaging observations of a sample of 11 high- redshift (z > 2) quasars with kilo-parsec scale radio jets are reported. The sample consists of a set of four z ? 3.6 flat-spectrum radio quasars, and seven intermediate redshift (z = 2.1 - 2.9) quasars comprised of four sources with integrated steep radio spectra and three with flat radio spectra.We implement a Bayesian image analysis program, Low-count Image Reconstruction and Analysis (LIRA) , to analyze jet features in the X-ray images of the high redshift quasars. Out of the 36 regions where knots are visible in the radio jets, nine showed detectable X-ray emission. Significant detections are based on the upper bound p-value test based on LIRA simulations. The X-ray and radio properties of this sample combined are examined and compared to lower-redshift samples.This work is supported in part by the National Science Foundation REU and the Department of Defense ASSURE programs under NSF Grant no.1262851 and by the Smithsonian Institution, and by NASA Contract NAS8-39073 to the Chandra X-ray Center (CXC). This research has made use of data obtained from the Chandra Data Archive and Chandra Source Catalog, and software provided by the CXC in the application packages CIAO, ChIPS, and Sherpa. Work is also supported by the Chandra grant GO4-15099X.

McKeough, Kathryn; Siemiginowska, Aneta; Kashyap, Vinay; Stein, Nathan; Cheung, Chi C.

2015-01-01

329

X-ray structural analysis of molten PbCl2  

NASA Astrophysics Data System (ADS)

The structure of molten PbCl2 was investigated by using high temperature X-ray diffraction(XRD) and X-ray absorption fine structure (XAFS) analysis techniques. It is concluded from the Fourier transformation and Debye scattering analyses of the XRD data and the curve fitting analysis of the XAFS function that the nearest Pb2+ Cl- pair consists of relatively rigid 4-fold coordination and additional loose 2&3 coordination structures.

Okamoto, Y.; Iwadate, Y.; Fukushima, K.; Matsuura, H.; Minato, K.

2005-02-01

330

Hard x-ray tomographic studies of the destruction of an energetic electron ring.  

PubMed

A tomography system was designed and built at the Large Plasma Device to measure the spatial distribution of hard x-ray (100 KeV-3 MeV) emissivity. The x-rays were generated when a hot electron ring was significantly disrupted by a shear Alfvén wave. The plasma is pulsed at 1 Hz (1 shot/s). A lead shielded scintillator detector with an acceptance angle defined by a lead pinhole is mounted on a rotary gimbal and used to detect the x-rays. The system measures one chord per plasma shot using only one detector. A data plane usually consists of several hundred chords. A novel Dot by Dot Reconstruction (DDR) method is introduced to calculate the emissivity profile from the line integrated data. In the experiments, there are often physical obstructions, which make measurements at certain angles impossible. The DDR method works well even in this situation. The method was tested with simulated data, and was found to be more effective than previously published methods for the specific geometry of this experiment. The reconstructed x-ray emissivity from experimental data by this method is shown. PMID:23742547

Wang, Y; Gekelman, W; Pribyl, P

2013-05-01

331

Hard x-ray tomographic studies of the destruction of an energetic electron ring  

NASA Astrophysics Data System (ADS)

A tomography system was designed and built at the Large Plasma Device to measure the spatial distribution of hard x-ray (100 KeV-3 MeV) emissivity. The x-rays were generated when a hot electron ring was significantly disrupted by a shear Alfvén wave. The plasma is pulsed at 1 Hz (1 shot/s). A lead shielded scintillator detector with an acceptance angle defined by a lead pinhole is mounted on a rotary gimbal and used to detect the x-rays. The system measures one chord per plasma shot using only one detector. A data plane usually consists of several hundred chords. A novel Dot by Dot Reconstruction (DDR) method is introduced to calculate the emissivity profile from the line integrated data. In the experiments, there are often physical obstructions, which make measurements at certain angles impossible. The DDR method works well even in this situation. The method was tested with simulated data, and was found to be more effective than previously published methods for the specific geometry of this experiment. The reconstructed x-ray emissivity from experimental data by this method is shown.

Wang, Y.; Gekelman, W.; Pribyl, P.

2013-05-01

332

Femtosecond time-resolved powder diffraction experiments using hard X-ray free-electron lasers.  

PubMed

In the next decade the scientific community expects a strong impact in physics, chemistry, biology, material research and life sciences by the availability of high-brilliance X-ray radiation from free-electron laser (FEL) sources. In particular, in the field of ultrafast science these new sources will allow new types of experiments, enabling new phenomena to be discovered. Whereas today ultrafast X-ray diffraction experiments are strongly restricted by the limited X-ray flux of current sources of sub-picosecond X-ray pulses, FELs will provide short pulses of typically 10(12) photons with a duration of the order of 100 fs and monochromaticity of 10(-3). Here, the feasibility of time-resolved single-shot powder diffraction experiments using these intense pulses, and the requirements of these experiments, are discussed. The detector count rates are estimated for diffraction from a model compound in a wide q-regime under the special consideration of high resolving power. In the case of LCLS radiation parameters, single-shot experiments will be feasible although high-resolution powder diffraction will require a reduction of the intrinsic FEL radiation bandwidth. PMID:16239753

Blome, C; Tschentscher, Th; Davaasambuu, J; Durand, P; Techert, S

2005-11-01

333

Auger Electrons via K? X-Ray Lines of Platinum Compounds for Nanotechnological Applications  

NASA Astrophysics Data System (ADS)

We will report study on the K? X-ray lines of platinum. Pt compounds, such as cisplatin, are common in biomedical applications. The active element Pt can emit or absorb hard X-rays. We have obtained the photoionization cross sections from the oscillator strengths of 1s-2p (K?) transitions in Pt ions. We find that these transitions appear as resonances in photoionization in the hard X-ray energy range of 64 - 71 keV (0.18 - 0.17 Å) below the K-shell ionization and with a strength orders of magnitude higher compared to that at the K-shell ionization. This is the focus of our study for possible initiation of an emission cascade of Auger electrons at the resonant energy. We will present the oscillator strengths and attenuation coefficients per unit mass for all the K? transitions in the event platinum cascades through various, namely from fluorine-like to hydrogen like, ionic states. The study is motivated by uur proposed method, Resonant Theranosticsb,C (RT) for biomedical appliations, which aims to find narrow band X-ray energy that corresponds to resonant photo-absorption and leads to emission of Auger electrons. As the next step of the RT method we will also report on experimental results on producing monochromatic X-rays, targeted to the resonant energy, from the wide band Bremstruhlung radiation of a conventional X-ray source. Partially support: DOE, Computational Facility: Ohio Supercomputer Center, Columbus, Ohio. "Resonant X-Ray Enhancement of the Auger Effect in High-Z atoms, molecules, and Nanoparticles: Biomedical Applications", A.K. Pradhan, S.N. Nahar, M. Montenegro, Yan Yu, H.L. Zhang, C. Sur, M. Mrozik, R.M. Pitzer, J. of Phys. Chem. A, 113 (2009), 12356. "Monte Carlo Simulations and Atomic Calculations for Auger Processes in Biomedical Nanotheranostics", M. Montenegro, S. N. Nahar, A. K. Pradhan, Ke Huang, Yan Yu, J. of Phys. Chem. A, 113 (2009), 12364.

Nahar, Sultana N.; Lim, Sara; Pradhan, A. K.; Pitzer, R. M.

2011-06-01

334

Compact X-ray Free Electron Laser from a Laser-plasma Accelerator using a Transverse Gradient Undulator  

SciTech Connect

Compact laser-plasma accelerators can produce high energy electron beams with low emittance, high peak current but a rather large energy spread. The large energy spread hinders the potential applications for coherent FEL radiation generation. In this paper, we discuss a method to compensate the effects of beam energy spread by introducing a transverse field variation into the FEL undulator. Such a transverse gradient undulator together with a properly dispersed beam can greatly reduce the effects of electron energy spread and jitter on FEL performance. We present theoretical analysis and numerical simulations for SASE and seeded extreme ultraviolet and soft x-ray FELs based on laser plasma accelerators.

Huang, Zhirong; Ding, Yuantao; /SLAC; Schroeder, Carl B.; /LBL, Berkeley

2012-09-13

335

An Introduction to the Scope, Potential and Applications of X-ray Analysis  

NSDL National Science Digital Library

This site from Michael Laing at the University of Natal provides an introduction to X-ray crystallography and the applications of various techniques. A discussion of basic crystallography leads into X-ray diffraction and a variety of X-ray techniques, including Laue, powder, and single crystal methods. Other topics include difffractometers, the reciprocal lattice explorer, and moving crystal and moving film methods such as the rotation, precession and Weissenberg methods. A section on applications and analysis of these methods is also included. Diagrams, tables and graphs support the text.

Michael Laing

336

Transverse pulse shaping and optimization of a tapered hard X-ray free electron laser  

E-print Network

Multidimensional optimization schemes for TW hard X-Ray free electron lasers are applied to the cases of transversely uniform and parabolic electron beam distributions and compared to examples of transversely Gaussian beams. The optimizations are performed for a $200$m undulator and a resonant wavelength of $\\lambda_r=1.5\\AA $ using the fully 3-dimensional FEL particle code GENESIS. Time dependent simulations showed that the maximum radiation power is larger for flatter transverse distributions due to enhanced optical guiding in the tapered section of the undulator. For a transversely Gaussian beam the maximum output power was found to be $\\text{P}_{max}$=$1.56$ TW compared to $2.26$ TW for the parabolic case and $2.63$ TW for the uniform case. Spectral data also showed a 30-70$\\%$ reduction in energy deposited in the sidebands for the uniform and parabolic beams compared with a Gaussian. An analysis of the maximum power as a function of detuning from resonance shows that redshifting the central wavelength by...

Emma, Claudio; Wu, Juhao

2014-01-01

337

X-ray absorption spectroscopic investigation of the electronic structure differences in solution and crystalline oxyhemoglobin  

PubMed Central

Hemoglobin (Hb) is the heme-containing O2 transport protein essential for life in all vertebrates. The resting high-spin (S = 2) ferrous form, deoxy-Hb, combines with triplet O2, forming diamagnetic (S = 0) oxy-Hb. Understanding this electronic structure is the key first step in understanding transition metal–O2 interaction. However, despite intense spectroscopic and theoretical studies, the electronic structure description of oxy-Hb remains elusive, with at least three different descriptions proposed by Pauling, Weiss, and McClure-Goddard, based on theory, spectroscopy, and crystallography. Here, a combination of X-ray absorption spectroscopy and extended X-ray absorption fine structure, supported by density functional theory calculations, help resolve this debate. X-ray absorption spectroscopy data on solution and crystalline oxy-Hb indicate both geometric and electronic structure differences suggesting that two of the previous descriptions are correct for the Fe–O2 center in oxy-Hb. These results support the multiconfigurational nature of the ground state developed by theoretical results. Additionally, it is shown here that small differences in hydrogen bonding and solvation effects can tune the ground state, tipping it into one of the two probable configurations. These data underscore the importance of solution spectroscopy and show that the electronic structure in the crystalline form may not always reflect the true ground-state description in solution. PMID:24062465

Wilson, Samuel A.; Green, Evan; Mathews, Irimpan I.; Benfatto, Maurizio; Hodgson, Keith O.; Hedman, Britt; Sarangi, Ritimukta

2013-01-01

338

REVIEW ARTICLE: Perturbation effects in dosimetry: Part I. Kilovoltage x-rays and electrons  

NASA Astrophysics Data System (ADS)

Perturbation effects are defined as departures from ideal large-detector or Bragg - Gray cavity behaviour. Such effects are central to the use of practical dosimeters for accurate dose determination, as is required in external-beam radiotherapy. A theoretical framework for treating perturbation effects is established. In this first part of the review, perturbation in kilovoltage x-ray and megavoltage electron beams are treated in detail, with the emphasis on ionization chambers. The displacement factor for ion chambers in kilovoltage x-ray beams is discussed, starting with the early, pioneering work of Lamerton and Lidén. The evidence for the large values of the perturbation factor in medium-energy x-ray beams (between 100 and 300 kV) recommended in the 1987 IAEA dosimetry code is critically examined and revised, smaller values are given. In electron beams the theoretical approaches to the correction for the in-scattering correction in gas-filled cavities is discussed in detail. The evidence for negligible perturbation in low-energy electron beams in plane-parallel chambers with adequate guard-ring widths is critically reviewed, including the suggested correction for perturbation due to backscattering differences between the chamber-wall material and the medium. The various models for the response of thermoluminescent dosimeters in electron beams are discussed. It is concluded that Monte Carlo simulation of dosimeter response is likely to play an even bigger role in the future.

Nahum, A. E.

1996-09-01

339

Accelerated electrons and hard X-ray emission from X-pinches  

NASA Astrophysics Data System (ADS)

The generation of accelerated electrons in the X-pinch minidiode is studied experimentally. It is well known that the explosion of an X-pinch consisting of two or more wires is accompanied by the formation of a minidiode, in which electrons are accelerated. The subsequent slowing down of electrons in the products of wire explosion causes the generation of hard X-ray (HXR) emission with photon energies higher than 10 keV. In this work, the spatial and temporal characteristics of X-pinch HXR emission are studied, the specific features of HXR generation are discussed, and the capability of applying this radiation to point-projection X-ray imaging of various plasma and biological objects is considered. The parameters of the electron beam produced in the X-pinch are measured using a Faraday cup and X-ray diagnostics. The experiments were performed with the XP generator (550 kA, 100 ns) at Cornell University (United States) and the BIN generator (270 kA, 150 ns) at the Lebedev Physical Institute (Russia).

Shelkovenko, T. A.; Pikuz, S. A.; Mingaleev, A. R.; Agafonov, A. V.; Romanova, V. M.; Ter-Oganes'yan, A. E.; Tkachenko, S. I.; Blesener, I. C.; Mitchell, M. D.; Chandler, K. M.; Kusse, B. R.; Hammer, D. A.

2008-09-01

340

The cyclotron spectrum of anisotropic ultrarelativistic electrons: interpretation of X-ray pulsar spectra  

E-print Network

The spectrum of cyclotron radiation produced by electrons with a strongly anisotropic velocity distribution is calculated taking into account higher harmonics. The motion of the electrons is assumed to be ultrarelativistic along the magnetic field and nonrelativistic across the field. One characteristic feature of the resulting spectrum is that harmonics of various orders are not equally spaced. The physical properties and observed spectra of four X-ray pulsars displaying higher cyclotron harmonics are analyzed. The cyclotron features in the spectra of all four pulsars can be interpreted only as emission lines. Moreover, the observed harmonics are not equidistant, and display certain other properties characteristic of emission by strongly anisotropic ultrarelativistic electrons. In addition, there are indirect theoretical arguments that the electrons giving rise to cyclotron features in the spectra of X-ray pulsars are ultrarelativistic and characterized by strongly anisotropic distributions. As a result, estimates of the magnetic fields of X-ray pulsars (which are usually derived from the energies of cyclotron lines) and certain other physical parameters require substantial revision.

A. N. Baushev

2008-04-10

341

MANTIS: combined x-ray, electron and optical Monte Carlo simulations of indirect radiation imaging systems  

NASA Astrophysics Data System (ADS)

We describe MANTIS (Monte carlo x-rAy electroN opTical Imaging Simulation), a tool for simulating imaging systems that tracks x-rays, electrons and optical photons in arbitrary materials and complex geometries. The x-ray and electron transport and involved physics models are from the PENELOPE package, and the optical transport and corresponding physics models are from DETECT-II and include Fresnel refraction and reflection at material boundaries, bulk absorption and scattering. Complex geometries can be handled with the aid of the geometry routines included in PENELOPE. When x-rays or electrons interact and deposit energy in the scintillator, the code generates a number of optical quanta according to a user-selected model for the conversion process. The optical photons are then tracked until they reach an absorption event, which in some cases contributes to the output signal, or escape from the geometry. We demonstrate the capabilities of this new tool with respect to the statistics of the optical signal detected and to the three-dimensional point-response functions corresponding to columnar phosphor screens.

Badano, Aldo; Sempau, Josep

2006-03-01

342

Analysis and interpretation of X-ray pulsars  

NASA Technical Reports Server (NTRS)

By careful measurements of the fluctuations in pulsar pulse periods on time scales of days and longer, researchers determined that these fluctuations are caused by changes in the rotation rate of the stellar crust apparently arising from matter accretion. The study of these fluctuations is a particularly promising way to determine the properties of accreting pulsars, because stellar rotation is relatively simple in comparison to much other X-ray source physics and can be investigated in detail. Rotation rates can be determined precisely.

Boynton, Paul E.; Deeter, John E.

1987-01-01

343

Quantitative Evaluation of Radiation Damage to Polyethylene Terephthalate by Soft X-rays and High-energy Electrons  

E-print Network

Quantitative Evaluation of Radiation Damage to Polyethylene Terephthalate by Soft X-rays and High to polyethylene terephthalate (PET) caused by soft X-rays and energetic electrons have been measured using to polyethylene terephalate (PET) by TEM-EELS versus nonspatially resolved NEXAFS.5 That study also reported

Hitchcock, Adam P.

344

Design and analysis of x-ray microscope of four mirrors working at grazing incidence  

NASA Astrophysics Data System (ADS)

In the latest 20 years, x-ray imaging technology has developed fast in order to meet the need of x-ray photo-etching, spatial exploration technology, high-energy physics, procedure diagnosis of inertial confinement fusion (ICF) etc. But, Since refractive index of materials in the x-ray region is lower than 1, and x-ray is strongly absorbed by the materials, it is very difficult to image objects in the x ray region. Conventional imaging methods are hardly suitable to x-ray range. Generally, grazing reflective imaging and coding aperture imaging methods have been adopted more and more. In this paper, non-coaxial grazing reflective imaging KB and KBA microscope systems are discussed in detail, and an x-ray microscope consisting of four mirrors working at grazing incidence is designed. It is an anastigmatic system, and the oblique angle of the image is evidently decreased. The resolution of 5-7 can be obtained within 2 field of view. And finally we also make analysis of the key problems that are met in the processing of manufacturing this system are analyzed.

Hu, Jiasheng; Zhao, Lingling; Li, Xiang

2006-01-01

345

Quantitative Analysis of Mt. St. Helens Ash by X-Ray Diffraction and X-Ray Fluorescence Spectrometry  

Microsoft Academic Search

A quantitative study by x-ray diffraction, optical polarizing microscopy, and x-ray fluorescence spectrometry of fallout and ambient ash from three Mt. St. Helens eruptions has revealed a consistent picture of the mineralogical and elemental composition. The major components observed are amorphous glass, plagioclase of about An50 composition, minor amounts of quartz and other SiO2 polymorphs, as well as ferromagnesian constituents

Briant L. Davis; L. Ronald Johnson; Dana T. Griffen; William Revell Phillips; Robert K. Stevens; David Maughan

1981-01-01

346

Polarization control of an X-ray free-electron laser with a diamond phase retarder.  

PubMed

A diamond phase retarder was applied to control the polarization states of a hard X-ray free-electron laser (XFEL) in the photon energy range 5-20 keV. The horizontal polarization of the XFEL beam generated from the planar undulators of the SPring-8 Angstrom Compact Free-Electron Laser (SACLA) was converted into vertical or circular polarization of either helicity by adjusting the angular offset of the diamond crystal from the exact Bragg condition. Using a 1.5 mm-thick crystal, a high degree of circular polarization, 97%, was obtained for 11.56 keV monochromatic X-rays, whereas the degree of vertical polarization was 67%, both of which agreed with the estimations including the energy bandwidth of the Si 111 beamline monochromator. PMID:24763633

Suzuki, Motohiro; Inubushi, Yuichi; Yabashi, Makina; Ishikawa, Tetsuya

2014-05-01

347

X-ray absorption study of the electronic structure of Mn-doped amorphous Si  

SciTech Connect

The electronic structure of Mn in amorphous Si (a-Mn{sub x}Si{sub 1?x}) is studied by X-ray absorption spectroscopy at the Mn L{sub 3,2} edges for x = 0.005-0.18. Except the x = 0.005 sample, which shows a slight signature of Mn{sup 2+} atomic multiplets associated with a local Mn moment, all samples have broad and featureless L{sub 3,2} absorption peaks, corresponding to an itinerant state for all 3d electrons. The broad X-ray absorption spectra exclude the possibility of a localized 3d moment and explain the unexpectedly quenched Mn moment in this magnetically-doped amorphous semiconductor. Such a fully delocalized d state of Mn dopant in Si has not been previously suggested.

Arenholz, Elke; Zeng, Li; Huegel, A.; Helgren, E.; Hellman, F.; Piamonteze, C.; Arenholz, E.

2008-03-08

348

ELECTRON MICROSCOPY AND X-RAY SCANNING MICROANALYSIS OF NEEDLE BIOPSY MATERIAL FROM HUMAN LIVER  

PubMed Central

A study has been made of the fine structure of hepatic parenchymal cells of human biopsy material in a case of pancreatic tumor with obstructive jaundice. Dense particles about 60 A in diameter have been found in the cytoplasm, which are considered to be ferritin molecules by electron microscopy. They are encountered throughout the cytoplasmic matrix and are often aggregated in electron-transparent areas, most of which are enclosed by an apparently single-layered membrane. Identification of the elemental iron has been pursued by the application of the x-ray scanning microanalyser which reveals a quantitative value within 1.0 per cent of the pure iron sample. The use of x-ray scanning microanalysis enables one to obtain accurate data from extremely small and precisely defined volumes of biological specimens. PMID:14002530

Yasuzumi, G.

1962-01-01

349

X-ray photoemission electron microscopy, a tool for the investigation of complex magnetic structures.  

SciTech Connect

X-ray Photoemission Electron Microscopy unites the chemical specificity and magnetic sensitivity of soft x-ray absorption techniques with the high spatial resolution of electron microscopy. The discussed instrument possesses a spatial resolution of better than 50 nm and is located at a bending magnet beamline at the Advanced Light Source, providing linearly and circularly polarized radiation between 250 and 1300 eV. We will present examples which demonstrate the power of this technique applied to problems in the field of thin film magnetism. The chemical and elemental specificity is of particular importance for the study of magnetic exchange coupling because it allows separating the signal of the different layers and interfaces in complex multi-layered structures.

Scholl, Andreas; Ohldag, Hendrik; Nolting, Frithjof; Stohr, Joachim; Padmore, Howard A.

2001-08-30

350

Attosecond Thomson-scattering x-ray source driven by laser-based electron acceleration  

SciTech Connect

The possibility of producing attosecond x-rays through Thomson scattering of laser light off laser-driven relativistic electron beams is investigated. For a ?200-as, tens-MeV electron bunch produced with laser ponderomotive-force acceleration in a plasma wire, exceeding 10{sup 6} photons/s in the form of ?160 as pulses in the range of 3–300 keV are predicted, with a peak brightness of ?5 × 10{sup 20} photons/(s mm{sup 2} mrad{sup 2} 0.1% bandwidth). Our study suggests that the physical scheme discussed in this work can be used for an ultrafast (attosecond) x-ray source, which is the most beneficial for time-resolved atomic physics, dubbed “attosecond physics.”.

Luo, W. [School of Nuclear Science and Technology, University of South China, Hengyang 421001 (China) [School of Nuclear Science and Technology, University of South China, Hengyang 421001 (China); College of Science, National University of Defense Technology, Changsha 410073 (China); Zhuo, H. B.; Yu, T. P. [College of Science, National University of Defense Technology, Changsha 410073 (China)] [College of Science, National University of Defense Technology, Changsha 410073 (China); Ma, Y. Y. [College of Science, National University of Defense Technology, Changsha 410073 (China) [College of Science, National University of Defense Technology, Changsha 410073 (China); Applied Ion Beam Physics Laboratory, Institute of Modern Physics, Fudan University, Shanghai 200433 (China); Song, Y. M.; Zhu, Z. C. [School of Nuclear Science and Technology, University of South China, Hengyang 421001 (China)] [School of Nuclear Science and Technology, University of South China, Hengyang 421001 (China); Yu, M. Y. [Department of Physics, Institute for Fusion Theory and Simulation, Zhejiang University, Hangzhou 310027 (China) [Department of Physics, Institute for Fusion Theory and Simulation, Zhejiang University, Hangzhou 310027 (China); Theoretical Physics I, Ruhr University, D-44801 Bochum (Germany)

2013-10-21

351

Constraints on photon pulse duration from longitudinal electron beam diagnostics at a soft x-ray free-electron laser  

NASA Astrophysics Data System (ADS)

The successful operation of x-ray free-electron lasers (FELs), like the Linac Coherent Light Source or the Free-Electron Laser in Hamburg (FLASH), makes unprecedented research on matter at atomic length and ultrafast time scales possible. However, in order to take advantage of these unique light sources and to meet the strict requirements of many experiments in photon science, FEL photon pulse durations need to be known and tunable. This can be achieved by controlling the FEL driving electron beams, and high-resolution longitudinal electron beam diagnostics can be utilized to provide constraints on the expected FEL photon pulse durations. In this paper, we present comparative measurements of soft x-ray pulse durations and electron bunch lengths at FLASH. The soft x-ray pulse durations were measured by FEL radiation pulse energy statistics and compared to electron bunch lengths determined by frequency-domain spectroscopy of coherent transition radiation in the terahertz range and time-domain longitudinal phase space measurements. The experimental results, theoretical considerations, and simulations show that high-resolution longitudinal electron beam diagnostics provide reasonable constraints on the expected FEL photon pulse durations. In addition, we demonstrated the generation of soft x-ray pulses with durations below 50 fs (FWHM) after the implementation of the new uniform electron bunch compression scheme used at FLASH.

Behrens, C.; Gerasimova, N.; Gerth, Ch.; Schmidt, B.; Schneidmiller, E. A.; Serkez, S.; Wesch, S.; Yurkov, M. V.

2012-03-01

352

[Study on spectrum analysis of X-ray based on rotational mass effect in special relativity].  

PubMed

Based on special relativity, the formation mechanism of characteristic X-ray has been studied, and the influence of rotational mass effect on X-ray spectrum has been given. A calculation formula of the X-ray wavelength based upon special relativity was derived. Error analysis was carried out systematically for the calculation values of characteristic wavelength, and the rules of relative error were obtained. It is shown that the values of the calculation are very close to the experimental values, and the effect of rotational mass effect on the characteristic wavelength becomes more evident as the atomic number increases. The result of the study has some reference meaning for the spectrum analysis of characteristic X-ray in application. PMID:20545180

Yu, Zhi-Qiang; Xie, Quan; Xiao, Qing-Quan

2010-04-01

353

State-of-the-art and problems of X-ray diffraction analysis of biomacromolecules  

SciTech Connect

The state-of-the-art of X-ray diffraction studies of biomacromolecules is briefly characterized, and the challenge imposed by science is discussed. These studies are characterized by a wide scope and extensive use. This field of science is of great interest and is developed in many countries. The main purpose is to solve practical problems in medicine consisting in the design of drugs against various diseases. X-ray diffraction analysis of enzymes brought the pharmaceutical industry to a new level, thus allowing the rational design of drugs against formerly untreatable diseases. Modern X-ray diffraction studies of biomacromolecules laid the basis for a new science called structural biology. This method allows one to solve fundamental problems of physical chemistry for a new state of matter existing in living systems. Here, science poses numerous problems in analysis of X-ray diffraction data on biological macromolecules. Many of theses problems are in their infancy.

Andreeva, N. S. [Russian Academy of Sciences, Engelhardt Institute of Molecular Biology (Russian Federation)], E-mail: andreeva@eimb.ru

2006-12-15

354

Contemporary X-ray electron-density studies using synchrotron radiation.  

PubMed

Synchrotron radiation has many compelling advantages over conventional radiation sources in the measurement of accurate Bragg diffraction data. The variable photon energy and much higher flux may help to minimize critical systematic effects such as absorption, extinction and anomalous scattering. Based on a survey of selected published results from the last decade, the benefits of using synchrotron radiation in the determination of X-ray electron densities are discussed, and possible future directions of this field are examined. PMID:25295169

Jørgensen, Mads R V; Hathwar, Venkatesha R; Bindzus, Niels; Wahlberg, Nanna; Chen, Yu-Sheng; Overgaard, Jacob; Iversen, Bo B

2014-09-01

355

X-ray measurement of the electron static structure factor in LiF  

Microsoft Academic Search

The x-ray incoherent cross section has been measured in crystalline LiF. The static structure factor and the exchange and correlation energy of valence electrons in LiF have been obtained. Making use of the results of a recent Hartree-Fock calculation in solid LiF, the correlation contribution to the ground-state energy has been determined. The static structure factor data have been analyzed

G. Calzuola; C. Petrillo; F. Sacchetti

1999-01-01

356

Design optimization for an X-ray free electron laser driven by SLAC LINAC  

Microsoft Academic Search

I present a design study for an X-ray Free Electron Laser (FEL)driven by the SLAC linac. The study assumes the FEL is basedon Self-Amplified Spontaneous Emission (SASE) and lasing isachieved in a single pass of a high current, high brightness electronbeam through a long wiggler. Following a brief review ofthe fundamentals of SASE, I will provide without derivation acollection of

Ming Xie; Lawrence Berkeley

1996-01-01

357

Parametric x-ray radiation along the velocity of relativistic electron in a Bragg scattering geometry  

Microsoft Academic Search

Based on the dynamic scattering theory, forward parametric x-ray radiation (FPXR) of a relativistic electron is investigated\\u000a in a single crystal plate in a Bragg scattering geometry. Analytical expressions for the spectral-angular distribution of\\u000a FPXR and transition radiation (TR) including the crystal surface orientation with respect to a system of diffracting atomic\\u000a planes are derived, which allow one to identify

S. V. Blazhevich; A. V. Noskov

2007-01-01

358

Imaging x-ray multilayer structures using cross-sectional high resolution electron microscopy  

Microsoft Academic Search

Mo\\/Si soft x-ray multilayer films have been imaged in cross section by high resolution electron microscopy and the dependence of important multilayer parameters on imaging conditions has been investigated. Multiple measurements of the widths of the Mo crystalline layers were made from images recorded as part of a through-focal series. The layer thicknesses were found to be insensitive to the

Yuanda Cheng; David J. Smith; Mary Beth Stearns; Daniel G. Stearns

1992-01-01

359

Contemporary X-ray electron-density studies using synchrotron radiation  

PubMed Central

Synchrotron radiation has many compelling advantages over conventional radiation sources in the measurement of accurate Bragg diffraction data. The variable photon energy and much higher flux may help to minimize critical systematic effects such as absorption, extinction and anomalous scattering. Based on a survey of selected published results from the last decade, the benefits of using synchrotron radiation in the determination of X-ray electron densities are discussed, and possible future directions of this field are examined. PMID:25295169

Jørgensen, Mads R. V.; Hathwar, Venkatesha R.; Bindzus, Niels; Wahlberg, Nanna; Chen, Yu-Sheng; Overgaard, Jacob; Iversen, Bo B.

2014-01-01

360

Confinement of hot, hard x-ray producing electrons in solar flares  

Microsoft Academic Search

Possible thermal models for solar, hard X-ray emission, consisting of small volumes in which the electrons are rapidly heated to 4 x 10⁸ K, are examined to determine under what conditions such models can be more efficient than nonthermal models. The primary energy-loss mechanism in these models is source expansion due to heat conduction which deviates from its classical value

D. F. Smith; C. G. Lilliequist

1979-01-01

361

Aerosols over the Amazon Rainforest Investigated by Scanning Transmission X-ray Microscopy and Scanning Electron Microscopy  

NASA Astrophysics Data System (ADS)

We collected atmospheric aerosols over the central Amazon Basin near Manaus, Brazil, during the wet season in February 2008, as part of the AMAZE-08 (Amazonian Aerosol Characterization Experiment) campaign. Aerosol samples were analyzed by Scanning Transmission X-ray Microscopy (STXM) coupled with Near-Edge X-ray Absorption Fine Structure Spectroscopy (NEXAFS) and Scanning Electron Microscopy (SEM) coupled with Energy-Dispersive X-ray Analysis (EDX). A newly developed electron microscopic technique revealed the presence of liquid organic material in aerosol particles, which we interpret as secondary organic aerosol (SOA). In the coarse fraction, mineral dust particles of transatlantic origin were common, and sometimes were coated with secondary organic aerosol (SOA). Many of these particles showed chemical and morphological evidence of cloud processing. Primary biogenic aerosols in the supermicron size range could be identified by their morphological characteristics. They were quite abundant, and were frequently coated with SOA. NEXAFS revealed characteristic X-ray absorption spectra showing multiple carbon functionalities in these particles. In the fine fraction of the Amazonian aerosol, these SOA particles are the most abundant particle type. They are frequently (but not always) found internally mixed with very small seasalt, dust, and carbonaceous particles. STXM-NEXAFS yielded characteristic spectra for these particles, including alkyl, carbonyl, and carboxyl functionalities. Double-bonded carbon was present at significant, but variable abundance in these particles. A surprising result is the presence of carbonate in many particles of all size classes, even in particle types where carbonates from mineral dust are not expected to be present.

Andreae, M. O.; Artaxo, P. P.; Gilles, M. K.; Martin, S. T.; Mikhailov, E.; Moffet, R.; Poeschl, U.; Sinha, B.; Yang, H.

2009-12-01

362

Atomic holography with electrons and x-rays: Theoretical and experimental studies  

SciTech Connect

Gabor first proposed holography in 1948 as a means to experimentally record the amplitude and phase of scattered wavefronts, relative to a direct unscattered wave, and to use such a {open_quotes}hologram{close_quotes} to directly image atomic structure. But imaging at atomic resolution has not yet been possible in the way he proposed. Much more recently, Szoeke in 1986 noted that photoexcited atoms can emit photoelectron of fluorescent x-ray wavefronts that are scattered by neighboring atoms, thus yielding the direct and scattered wavefronts as detected in the far field that can then be interpreted as holographic in nature. By now, several algorithms for directly reconstructing three-dimensional atomic images from electron holograms have been proposed (e.g. by Barton) and successfully tested against experiment and theory. Very recently, Tegze and Faigel, and Grog et al. have recorded experimental x-ray fluorescence holograms, and these are found to yield atomic images that are more free of the kinds of aberrations caused by the non-ideal emission or scattering of electrons. The basic principles of these holographic atomic imaging methods are reviewed, including illustrative applications of the reconstruction algorithms to both theoretical and experimental electron and x-ray holograms. The author also discusses the prospects and limitations of these newly emerging atomic structural probes.

Len, P M [Univ. of California, Davis, CA (United States). Dept. of Physics

1997-06-01

363

Computerized X-ray tomography analysis of sandbox models: Examples of thin-skinned thrust systems  

Microsoft Academic Search

Computerized X-ray tomography applied to analog sandbox experiments performed in a normal gravity field makes possible the analysis of the kinematic evolution, as well as the three-dimensional geometry, of models that simulate tectonic deformations. Most of the plastic or viscous analog materials generally used in a normal gravity field for such models have X-ray attenuations compatible with medical scanner images.

Bernard Colletta; Jean Letouzey; Roberto Pinedo; Jean François Ballard; Pascal Balé

1991-01-01

364

Diffuse Hard X-Ray Emission in Starburst Galaxies as Synchrotron from Very High Energy Electrons  

NASA Astrophysics Data System (ADS)

The origin of the diffuse hard X-ray (2-10 keV) emission from starburst galaxies is a long-standing problem. We suggest that synchrotron emission of 10-100 TeV electrons and positrons (e ±) can contribute to this emission, because starbursts have strong magnetic fields. We consider three sources of e ± at these energies: (1) primary electrons directly accelerated by supernova remnants, (2) pionic secondary e ± created by inelastic collisions between cosmic ray (CR) protons and gas nuclei in the dense interstellar medium of starbursts, and (3) pair e ± produced between the interactions between 10 and 100 TeV ?-rays and the intense far-infrared (FIR) radiation fields of starbursts. We create one-zone steady-state models of the CR population in the Galactic center (R <= 112 pc), NGC 253, M82, and Arp 220's nuclei, assuming a power-law injection spectrum for electrons and protons. We consider different injection spectral slopes, magnetic field strengths, CR acceleration efficiencies, and diffusive escape times, and include advective escape, radiative cooling processes, and secondary and pair e ±. We compare these models to extant radio and GeV and TeV ?-ray data for these starbursts, and calculate the diffuse synchrotron X-ray and inverse Compton (IC) luminosities of these starbursts in the models which satisfy multiwavelength constraints. If the primary electron spectrum extends to ~PeV energies and has a proton/electron injection ratio similar to the Galactic value, we find that synchrotron emission contributes 2%-20% of their unresolved, diffuse hard X-ray emission. However, there is great uncertainty in this conclusion because of the limited information on the CR electron spectrum at these high energies. IC emission is likewise a minority of the unresolved X-ray emission in these starbursts, from 0.1% in the Galactic center to 10% in Arp 220's nuclei, with the main uncertainty being the starbursts' magnetic field. We also model generic starbursts, including submillimeter galaxies, in the context of the FIR-X-ray relation, finding that anywhere between 0% and 16% of the total hard X-ray emission is synchrotron for different parameters, and up to 2% in the densest starbursts assuming an E -2.2 injection spectrum and a diffusive escape time of 10 Myr (E/3 GeV)-1/2 (h/100 pc). Neutrino observations by IceCube and TeV ?-ray data from HESS, VERITAS, and CTA can further constrain the synchrotron X-ray emission of starbursts. Our models do not constrain the possibility of hard, second components of primary e ± from sources like pulsars in starbursts, which could enhance the synchrotron X-ray emission further.

Lacki, Brian C.; Thompson, Todd A.

2013-01-01

365

Atmospheric Electron-induced X-Ray Spectrometer (AEXS) Instrument Development  

NASA Technical Reports Server (NTRS)

Introduction: This paper describes the progress in data acquisition and establishing the observational capability of the AEXS instrument. The AEXS is a miniature instrument[1-4] based on the excitation of characteristic X-Ray Fluorescence (XRF) and luminescence spectra using a focused electron beam which enables nondestructive evaluation of sample surfaces in planetary ambient atmospheres. In situ operation is obtained through the use of a thin electron transmissive membrane to isolate the vacuum of the AEXS source from the outside ambient atmosphere. Thus eliminating the need for a vacuum pumped sample chamber as is common in all laboratory SEM s. The transmitted electrons impinge on the sample exciting XRF spectra from the irradiated spot on in-situ or collected samples with sub-mm to cm-scale spatial resolution at Mars atmospheric pressure. The AEXS system (Fig 1) consists of a high-energy (>10keV) electron gun encapsulated by the isolation membrane, an XRF detection and analyzer system, and a high voltage power supply. The XRF data are analyzed to determine the elemental abundance for the irradiated spots. The approach to demonstrating a proof of concept of the AEXS has been through 1) demonstrating the viability of microfabricated membranes, 2) assembling AEXS setups with increasingly integrated functional components, and 3) simulating the AEXS observational capabilities. The development of the instrument is described in detail in the poster paper[4] at this conference. This paper focuses on describing the progress of the AEXS instrument to acquire XRF data and using commercially available software to analyze the data streams and determine the accuracy, precision and resolution of the analysis compared to the certified elemental abundance.

Urgiles, E.; Wilcox, J. Z.; Toda, R.; Crisp, J.; George, T.

2005-01-01

366

Resonant X-ray Scattering Experiments on the Ordering of Electronic Degrees of Freedom  

NASA Astrophysics Data System (ADS)

Resonant X-ray scattering (RXS) has been developed as a powerful technique for observing orderings of electronic degrees of freedom: charge, spin, orbital, and multipoles. After a brief introduction of the RXS technique, we review some RXS experiments on the orderings in d and f electron systems with a strong correlation between electrons. The basic concept of RXS and the recent developments of the technique are described in this review paper. We also present future prospects of the studies using RXS for users.

Matsumura, Takeshi; Nakao, Hironori; Murakami, Youichi

2013-02-01

367

Disentangling atomic-layer-specific x-ray absorption spectra by Auger electron diffraction spectroscopy  

NASA Astrophysics Data System (ADS)

In order to investigate the electronic and magnetic structures of each atomic layer at subsurface, we have proposed a new method, Auger electron diffraction spectroscopy, which is the combination of x-ray absorption spectroscopy (XAS) and Auger electron diffraction (AED) techniques. We have measured a series of Ni LMM AED patterns of the Ni film grown on Cu(001) surface for various thicknesses. Then we deduced a set of atomic-layer-specific AED patterns in a numerical way. Furthermore, we developed an algorithm to disentangle XANES spectra from different atomic layers using these atomic-layer-specific AED patterns. Surface and subsurface core level shift were determined for each atomic layer.

Matsui, Fumihiko; Matsushita, Tomohiro; Kato, Yukako; Hashimoto, Mie; Daimon, Hiroshi

2009-11-01

368

fLasHThe Free-Electron Laser new technologies for new science: Soon X-ray free-electron lasers  

E-print Network

fLasHªThe Free-Electron Laser in Hamburg new technologies for new science: Soon X-ray free-electron to you a new research facility of unprecedented features ­ FLASH, the Free-Electron Laser in Hamburg. Time to explore the femtosecond dynamics of nature Soon X-ray free-electron lasers will enable us

369

Quantitative description of microstructure defects in hexagonal boron nitrides using X-ray diffraction analysis  

SciTech Connect

A routine for simultaneous quantification of turbostratic disorder, amount of puckering and the dislocation and stacking fault density in hexagonal materials was proposed and tested on boron nitride powder samples that were synthesised using different methods. The routine allows the individual microstructure defects to be recognised according to their effect on the anisotropy of the X-ray diffraction line broadening. For quantification of the microstructure defects, the total line broadening is regarded as a linear combination of the contributions from the particular defects. The total line broadening is obtained from the line profile fitting. As testing material, graphitic boron nitride (h-BN) was employed in the form of hot-isostatically pressed h-BN, pyrolytic h-BN or a h-BN, which was chemically vapour deposited at a low temperature. The kind of the dominant microstructure defects determined from the broadening of the X-ray diffraction lines was verified by high resolution transmission electron microscopy. Their amount was attempted to be verified by alternative methods. - Highlights: • Reliable method for quantification of microstructure defects in BN was suggested. • The method is based on the analysis of anisotropic XRD line broadening. • This XRD line broadening is unique and characteristic of the respective defect. • Thus, the quantification of coexistent microstructure defects is possible. • The method was tested on hexagonal BN, which was produced by different techniques.

Schimpf, C., E-mail: schimpf@iww.tu-freiberg.de; Motylenko, M.; Rafaja, D.

2013-12-15

370

Reflection electron-energy-loss spectroscopy, x-ray-absorption spectroscopy, and x-ray photoelectron spectroscopy studies of a new type of layer compound CrPS4  

NASA Astrophysics Data System (ADS)

A new type of layer compound, CrPS4, has been investigated by means of reflection electron-energy-loss spectroscopy (REELS), x-ray-absorption spectroscopy (XAS), and x-ray photoelectron spectroscopy (XPS). Information on the bonding states of the compositional atoms and the occupied energy states has been deduced from the core- and valence-electron XPS results. The binding energies and the multiplet structures of core levels have been discussed in detail. Information on the unoccupied energy states has been deduced from the XAS results. On the basis of the REELS results, energy positions and the joint density of states have been discussed. The optical properties have been investigated through the Kramers-Kronig analysis of the REELS spectrum. We have made an attempt to derive the depth profile of the localized energy states from the incident-energy dependence. A schematic energy-band model has been proposed.

Ohno, Youichi; Mineo, Ayako; Matsubara, Ichiro

1989-11-01

371

X-ray analysis of nonMaxwellian distributions (current drive)  

SciTech Connect

The plasma bremsstrahlung emission is utilized to determine the shape of the electron velocity distribution in situations where it deviates strongly from a Maxwellian distribution. The instrumentation used to measure the hard x-ray emission is briefly discussed. Model calculations show that polarization measurements give best results for unrelativistic tails with tail temperatures T/sub b/ < 50 keV, whereas measurements of the angular distribution of the x-ray emission based on the forward scattering of bremsstrahlung for relativistic electrons yields the best information for T/sub b/ > 50 keV. The techniques were originally developed in order to analyze runaway discharges. Recently, they found new interest because of the formation of energetic electron tails during current drive. The first x-ray results from the current drive during LH heating on PLT are discussed.

von Goeler, S.; Stevens, J.; Stodiek, W.

1983-06-01

372

X-ray diagnostic for current density profiling relativistic electron beams in vacuum and gas  

SciTech Connect

An x-ray imaging technique has been studied for the purpose of observing the current density profile in a high-current relativistic electron beam (50 MeV, 10 kA). Calculations and measurements of energy spectra and intensities are in good agreement. Results indicate sufficient photon yield for pinhole imaging when the beam deposits a small part of its energy in high-Z gas or a thin high-Z foil. Characteristic L and K x-ray emission is not found not be a reliable technique due to strong L and K shell fluorescence in the presence of intense bremsstrahlung radiation. It is also found that at pressures on the order of one atmosphere, the density of energy deposition in a gas cell is too small to generate sufficient photon yield for time-resolved measurements.

Slaughter, D.; Koppel, L.; Smith, J.

1986-02-15

373

Simulation Studies of the X-Ray Free-Electron Laser Oscillator  

SciTech Connect

Simulations of the x-ray free-electron laser (FEL) oscillator are presented that include transverse effects and realistic Bragg crystal properties with the two-dimensional code GINGER. In the present cases considered the radiation divergence is much narrower than the crystal acceptance, and the numerical algorithm can be simplified by ignoring the finite angular bandwidth of the crystal. In this regime GINGER shows that the saturated x-ray pulses have 109 photons and are nearly Fourier-limited with peak powers in excess of 1 MW. Wealso include preliminary results for a four-mirror cavity that can be tuned in wavelength over a few percent, with future plans to incorporate the full transverse response of the Bragg crystals into GINGER to more accurately model this tunable source.

Lindberg, R. R.; Shyd'ko, Y.; Kim, K.-J; Fawley, W. M.

2009-08-14

374

A single-shot transmissive spectrometer for hard x-ray free electron lasers  

SciTech Connect

We report hard x-ray single-shot spectral measurements of the Linac Coherent Light Source. The spectrometer is based on a 10 {mu}m thick cylindrically bent Si single crystal operating in the symmetric Bragg geometry to provide dispersion and high transmission simultaneously. It covers a spectral range >1% using the Si(111) reflection. Using the Si(333) reflection, it reaches a resolving power of better than 42 000 and transmits >83% of the incident flux at 8.3 keV. The high resolution enabled the observation of individual spectral spikes characteristic of a self-amplified spontaneous emission x-ray free electron laser source. Potential applications of the device are discussed.

Zhu Diling; Cammarata, Marco; Feldkamp, Jan M.; Fritz, David M.; Hastings, Jerome B.; Lee, Sooheyong; Lemke, Henrik T.; Robert, Aymeric; Turner, James L.; Feng Yiping [Linac Coherent Light Source, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025 (United States)

2012-07-16

375

Sensing the wavefront of x-ray free-electron lasers using aerosol spheres  

SciTech Connect

Characterizing intense, focused x-ray free electron laser (FEL) pulses is crucial for their use in diffractive imaging. We describe how the distribution of average phase tilts and intensities on hard x-ray pulses with peak intensities of 10 21 W/m2 can be retrieved from an ensemble of diffraction patterns produced by 70 nm-radius polystyrene spheres, in a manner that mimics wave-front sensors. Besides showing that an adaptive geometric correction may be necessary for diffraction data from randomly injected sample sources, the paper demonstrates the possibility of collecting statistics on structured pulses using only the diffraction patterns they generate and highlights the imperative to study its impact on single-particle diffractive imaging.

Loh, N.Duane; Starodub, Dimitri; Lomb, Lukas; Hampton, Christina Y.; Martin, Andrew V.; Sierra, Raymond G.; Barty, Anton; Aquila, Andrew; Schulz, Joachim; Steinbrener, Jan; Shoeman, Robert L.; Kassemeyer, Stephan; Bostedt, Christoph; Bozek, John; Epp, Sascha W.; Erk, Benjamin; Hartmann, Robert; Rolles, Daniel; Rudenko, Artem; Rudek, Benedikt; Foucar, Lutz

2014-04-22

376

Ultrafast myoglobin structural dynamics observed with an X-ray free-electron laser.  

PubMed

Light absorption can trigger biologically relevant protein conformational changes. The light-induced structural rearrangement at the level of a photoexcited chromophore is known to occur in the femtosecond timescale and is expected to propagate through the protein as a quake-like intramolecular motion. Here we report direct experimental evidence of such 'proteinquake' observed in myoglobin through femtosecond X-ray solution scattering measurements performed at the Linac Coherent Light Source X-ray free-electron laser. An ultrafast increase of myoglobin radius of gyration occurs within 1 picosecond and is followed by a delayed protein expansion. As the system approaches equilibrium it undergoes damped oscillations with a ~3.6-picosecond time period. Our results unambiguously show how initially localized chemical changes can propagate at the level of the global protein conformation in the picosecond timescale. PMID:25832715

Levantino, Matteo; Schirò, Giorgio; Lemke, Henrik Till; Cottone, Grazia; Glownia, James Michael; Zhu, Diling; Chollet, Mathieu; Ihee, Hyotcherl; Cupane, Antonio; Cammarata, Marco

2015-01-01

377

Sensing the wavefront of x-ray free-electron lasers using aerosol spheres.  

PubMed

Characterizing intense, focused x-ray free electron laser (FEL) pulses is crucial for their use in diffractive imaging. We describe how the distribution of average phase tilts and intensities on hard x-ray pulses with peak intensities of 10(21) W/m(2) can be retrieved from an ensemble of diffraction patterns produced by 70 nm-radius polystyrene spheres, in a manner that mimics wavefront sensors. Besides showing that an adaptive geometric correction may be necessary for diffraction data from randomly injected sample sources, our paper demonstrates the possibility of collecting statistics on structured pulses using only the diffraction patterns they generate and highlights the imperative to study its impact on single-particle diffractive imaging. PMID:23736456

Loh, N Duane; Starodub, Dmitri; Lomb, Lukas; Hampton, Christina Y; Martin, Andrew V; Sierra, Raymond G; Barty, Anton; Aquila, Andrew; Schulz, Joachim; Steinbrener, Jan; Shoeman, Robert L; Kassemeyer, Stephan; Bostedt, Christoph; Bozek, John; Epp, Sascha W; Erk, Benjamin; Hartmann, Robert; Rolles, Daniel; Rudenko, Artem; Rudek, Benedikt; Foucar, Lutz; Kimmel, Nils; Weidenspointner, Georg; Hauser, Guenter; Holl, Peter; Pedersoli, Emanuele; Liang, Mengning; Hunter, Mark S; Gumprecht, Lars; Coppola, Nicola; Wunderer, Cornelia; Graafsma, Heinz; Maia, Filipe R N C; Ekeberg, Tomas; Hantke, Max; Fleckenstein, Holger; Hirsemann, Helmut; Nass, Karol; White, Thomas A; Tobias, Herbert J; Farquar, George R; Benner, W Henry; Hau-Riege, Stefan; Reich, Christian; Hartmann, Andreas; Soltau, Heike; Marchesini, Stefano; Bajt, Sasa; Barthelmess, Miriam; Strueder, Lothar; Ullrich, Joachim; Bucksbaum, Philip; Frank, Matthias; Schlichting, Ilme; Chapman, Henry N; Bogan, Michael J

2013-05-20

378

A Bragg beam splitter for hard x-ray free-electron lasers.  

PubMed

We report a Bragg beam splitter developed for utilization of hard x-ray free-electron lasers. The splitter is based on an ultrathin silicon crystal operating in the symmetric Bragg geometry to provide high reflectivity and transmissivity simultaneously. We fabricated frame-shaped Si(511) and (110) crystals with thicknesses below 10 ?m by a reactive dry etching method using atmospheric-pressure plasma. The thickness variation over an illuminated area is less than 300 nm peak-to-valley. High crystalline perfection was verified by topographic and diffractometric measurements. The crystal thickness was evaluated from the period of the Pendellösung beats measured with a highly monochromatic and collimated x-ray probe. The crystals provide two replica pulses with uniform wavefront [(<1/50)?] and low spatial intensity variation (<5%). These Bragg beam splitters will play an important role in innovating XFEL applications. PMID:23481739

Osaka, Taito; Yabashi, Makina; Sano, Yasuhisa; Tono, Kensuke; Inubushi, Yuichi; Sato, Takahiro; Matsuyama, Satoshi; Ishikawa, Tetsuya; Yamauchi, Kazuto

2013-02-11

379

Synchrotron radiation based micro X-ray fluorescence analysis of the calibration samples used in surface sensitive total reflection and grazing emission X-ray fluorescence techniques  

NASA Astrophysics Data System (ADS)

Total reflection X-ray fluorescence (TXRF) and grazing emission X-ray fluorescence (GEXRF) are surface sensitive techniques and can be used for detailed surface studies of different materials, including ultra-low concentration contamination or the lateral and depth distributions of elements. The calibration procedure typically used involves placing a micro-droplet (˜?l) of the standard solution onto a silicon wafer (or quartz backing). After evaporation of the solvent, the residual amount of elements is used as a reference standard. Knowledge of the distribution of residue material on the substrate surface is crucial for precise quantification. In the present work the investigation of the lateral distribution of elements in the multielemental calibrating samples, containing the 23 most commonly studied elements, by using the synchrotron radiation based micro X-ray fluorescence is presented. The goal of this project was the study of a uniformity of the elemental distributions and determination of the residual elements morphology depending on the temperature of the drying process. The X-ray images were compared with optical and SEM images. Paper presents in details the experimental setup, sample preparation procedures, measurements and results. In the analysis of the X-ray images of the sample dried in high temperature the censoring approach was applied improving the quality of statistical analysis. The information on the elements distribution in the calibrating samples can be useful for developing more accurate calibration procedures applied in quantitative analysis of surface sensitive TXRF and GEXRF techniques.

Kubala-Kuku?, A.; Bana?, D.; Pajek, M.; Szlachetko, J.; Jagodzi?ski, P.; Susini, J.; Salomé, M.

2013-12-01

380

The vacuum system of the European X-ray free electron laser XFEL  

NASA Astrophysics Data System (ADS)

The European X-ray Free Electron Laser XFEL, a new international research facility, will be built at DESY/Hamburg. The XFEL will generate extremely brilliant and ultra short pulses of spatially coherent X-rays with tuneable wavelengths down to 0.1 nm, and exploit them for revolutionary scientific experiments at various disciplines. The basic process adopted to produce the X-ray pulses is SASE (Self-Amplified Spontaneous Emission). Therefore electron bunches are produced in a high-brightness gun, brought to high energy of about 20 GeV through a superconducting linear accelerator, and transported to up to 250 m long undulators, where the X-rays are generated. The beam vacuum system of the accelerator contains sections operated at room temperature as well as at 2 K in the areas of the superconducting accelerating structures, thus requiring an insulating vacuum system. In addition to standard UHV requirements, the vacuum system for this facility needs to preserve the cleanliness of the superconducting cavity surfaces. Therefore the preparation of all vacuum components for the 1.6 km long main linac includes cleaning of the components in a clean room to remove particles, installation into the accelerator in local clean rooms, and special procedures for pump down and venting. Further challenges are the undulator vacuum chambers filling more than 700 m, where a high surface quality with respect to surface roughness and thickness of oxide layers is mandatory to reduce wake field effects, and the vacuum systems for the various beam dumps, where exit windows acting as vacuum barriers of sufficient reliability need to be developed. In addition, a large amount of about 1.7 km of transport beam lines is required. The layout of the various vacuum sections as well as experience with prototype components will be described.

Zapfe, K.; Böhnert, M.; Hensler, O.; Hoppe, D.; Mildner, N.; Nagorny, B.; Rehlich, K.; Remde, H.; Wagner, A.; Wohlenberg, T.; Wojtkiewicz, J.

2008-03-01

381

Transformation of nanodiamond into carbon onions: A comparative study by high-resolution transmission electron microscopy, electron energy-loss spectroscopy, x-ray diffraction, small-angle x-ray scattering, and ultraviolet Raman spectroscopy  

Microsoft Academic Search

The structural properties of both nanodiamond particles synthesized by detonation and the products of their transformation into carbon onions via vacuum annealing at 1000 and 1500 °C have been studied using high-resolution transmission electron microscopy (HRTEM), electron energy-loss spectroscopy, x-ray diffraction (XRD), small-angle x-ray scattering (SAXS), and Raman spectroscopy. The advantages of UV Raman spectroscopy over visible Raman spectroscopy for

Oleksandr O. Mykhaylyk; Yurii M. Solonin; David N. Batchelder; Rik Brydson

2005-01-01

382

The identification of the pigments used to paint statues of Feixiange Cliff in China in late 19th century by micro-Raman spectroscopy and scanning electron microscopy/energy dispersive X-ray analysis  

NASA Astrophysics Data System (ADS)

The application of micro-Raman spectroscopy (?-RS) and scanning electron microscopy (SEM)/energy dispersive X-ray spectrometer (EDS) to the research of pigments collected from Statues of Feixiange Cliff No. 67 and No. 69 niche of Tang Dynasty in China is reported. Five kinds of pigments were found in the experimental data, including black (carbon), white (gypsum + quartz), blue (lapis lazuli) and green (Paris green + Barium sulphate). After synthesized in 1814, Paris green was reported for a large import as a light and bright green pigment to paint architectures in China from the late 19th century. The analyzed blue pigment demonstrated the similar Raman spectra to the Lâjvardina blue glazed ceramics, which indicated lapis lazuli was an artificial product. This confirmed the painting of Feixiange Cliff in the early Republic of China as the historical record, and also reveals that some pigments were imported from abroad.

Jin, Pu-jun; Huang, Wei; Jianhua-Wang; Zhao, Gang; Wang, Xiao-ling

2010-11-01

383

X-ray free-electron lasers: Scientific goals and machine implications  

NASA Astrophysics Data System (ADS)

Free electron lasers are now being designed which will operate at wavelengths down to about 1. [1] The physics of the high-gain, single pass FEL process requires extremely bright electron pulses in the 10-20 GeV range. This electron brightness should be achievable using an RF-photocathode source and a linear accelerator, such as the initial acceleration stage of a TeV-range linear electron-positron collider. The x-ray FEL radiation produced will have unique properties. In particular: • The FEL peak intensity and peak brightness will be many orders of magnitude higher than can be produced by any other source. • The pulse length will be less than 1 picosecond, orders of magnitude shorter than can be achieved with any other bright source such as a synchrotron. • The FEL radiation will have full transverse coherence and a degeneracy parameter (photons/coherence volume) equal to 109 or more. No other source can produce hard x-radiation with a degeneracy parameter significantly greater than 1. These properties offer the chance to study chemical, biological, and condensed matter dynamical processes with sub-picosecond time resolution and angstrom spatial resolution. [2] The high peak power of the FEL radiation (greater than 1014W/cm2) could be used to create precisely-controlled chemical and structural modifications inside samples. There is also the possibility that nonlinear x-ray interactions could be used to give increased resolution for spectroscopic studies, to greatly expand the parameter space for atomic physics studies, and to permit new fundamental tests of quantum mechanics. The exploration of these new x-ray techniques will require considerable development, not only in technical areas such as optics and detectors, but also in understanding the basic physics of the interaction of very intense x-radiation with matter. A large collaboration of US institutions is now conducting preliminary research and development in these areas, with the intention of creating an FEL operating at 1.5 in about the year 2006. [3] Germany also has a strong short-wavelength FEL research program, with a soft x-ray FEL under construction and a proposal for a future large facility based at the TESLA linear collider, [4] which would produce a variety of hard and soft x-ray laser beams. This work was supported by the US Department of Energy, Office of Basic Energy Sciences, under contract DE-AC03-76SF00515.

Arthur, John

2001-07-01

384

First spin-resolved electron distributions in crystals from combined polarized neutron and X-ray diffraction experiments  

PubMed Central

Since the 1980s it has been possible to probe crystallized matter, thanks to X-ray or neutron scattering techniques, to obtain an accurate charge density or spin distribution at the atomic scale. Despite the description of the same physical quantity (electron density) and tremendous development of sources, detectors, data treatment software etc., these different techniques evolved separately with one model per experiment. However, a breakthrough was recently made by the development of a common model in order to combine information coming from all these different experiments. Here we report the first experimental determination of spin-resolved electron density obtained by a combined treatment of X-ray, neutron and polarized neutron diffraction data. These experimental spin up and spin down densities compare very well with density functional theory (DFT) calculations and also confirm a theoretical prediction made in 1985 which claims that majority spin electrons should have a more contracted distribution around the nucleus than minority spin electrons. Topological analysis of the resulting experimental spin-resolved electron density is also briefly discussed. PMID:25075338

Deutsch, Maxime; Gillon, Béatrice; Claiser, Nicolas; Gillet, Jean-Michel; Lecomte, Claude; Souhassou, Mohamed

2014-01-01

385

Measurement of the unstained biological sample by a novel scanning electron generation X-ray microscope based on SEM  

SciTech Connect

We introduced a novel X-ray microscope system based on scanning electron microscopy using thin film, which enables the measurement of unstained biological samples without damage. An unstained yeast sample was adsorbed under a titanium (Ti)-coated silicon nitride (Si{sub 3}N{sub 4}) film 90 nm thick. The X-ray signal from the film was detected by an X-ray photodiode (PD) placed below the sample. With an electron beam at 2.6 kV acceleration and 6.75 nA current, the yeast image is obtained using the X-ray PD. The image is created by soft X-rays from the Ti layer. The Ti layer is effective in generating the characteristic 2.7-nm wavelength X-rays by the irradiation of electrons. Furthermore, we investigated the electron trajectory and the generation of the characteristic X-rays within the Ti-coated Si{sub 3}N{sub 4} film by Monte Carlo simulation. Our system can be easily utilized to observe various unstained biological samples of cells, bacteria, and viruses.

Ogura, Toshihiko, E-mail: t-ogura@aist.go.jp [Neuroscience Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Central 2, Umezono, Tsukuba, Ibaraki 305-8568 (Japan)] [Neuroscience Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Central 2, Umezono, Tsukuba, Ibaraki 305-8568 (Japan)

2009-08-07

386

Analysis of medieval glass by X-ray spectrometric methods  

NASA Astrophysics Data System (ADS)

Systematic investigation of the 16th century glasses of Ljubljana is motivated by the spread of Italian glass-working technology into central Europe. The glass was probed using the external beam PIXE technique due to its non-destructiveness. Initial test measurements were performed by the methods of PIGE, XRF, electron probe microanalysis, and LA-ICP-MS. The PIXE data were evaluated statistically using the principal component analysis and minimizing the stress function. The manufacturing procedures were indicated by the Rb/Sr content in the glass: the investigated glasses were mainly produced with the ash (not potash) of halophitic plants.

Šmit, Ž.; Pelicon, P.; Vidmar, G.; Zorko, B.; Budnar, M.; Demortier, G.; Gratuze, B.; Šturm, S.; Ne?emer, M.; Kump, P.; Kos, M.

2000-03-01

387

[X-ray tubes with ionic indemnification of negative space electronic charge].  

PubMed

How to increase anode current in the fine-focus diagnostic X-ray tubes (XTs) is analyzed. It has been found that there are new three-class XTs that have advantages of both ionic and electronic tubes. The specific feature of the new class XTs is the gaseous atmosphere available in the working volume. Ionizing the gaseous atmosphere with a emission electron flow in the path from the cathode to the anode yields a dot volumetric positively charged ion grid that closely approaches the cathode and can pay a big bonus in anode current output. PMID:11534285

Kanikovski?, V B

2001-01-01

388

Angular distribution of K-shell X-rays produced by 29 keV electrons incident on Ag  

NASA Astrophysics Data System (ADS)

The absolute intensities of the K? and K? X-rays produced by 29 keV electrons incident on a thick Ag target at forward angles in the range 0° to 55° relative to incident electrons have been measured. When corrections are made for attenuation within the target material, the results indicate that the K-shell X-rays are emitted isotropically. The experimental K-shell X-ray and bremsstrahlung production probability densities are compared to the results simulated by the Monte Carlo program, PENELOPE, and are found to be in good agreement.

Gonzales, D.; Requena, S.; Davis, S.; Williams, S.

2011-06-01

389

EBT2 dosimetry of x-rays produced by the electron beam from a Plasma Focus for medical applications  

NASA Astrophysics Data System (ADS)

The electron beam emitted from the back of Plasma Focus devices is being studied as a radiation source for intraoperative radiation therapy applications. A Plasma Focus device is being developed to this aim, to be utilized as an x-ray source. The electron beam is driven to impinge on 50 ?m brass foil, where conversion x-rays are generated. Measurements with gafchromic film are performed to analyse the attenuation of the x-rays beam and to predict the dose given to the culture cell in radiobiological experiments to follow.

Ceccolini, E.; Rocchi, F.; Mostacci, D.; Sumini, M.; Tartari, A.; Mariotti, F.

2012-09-01

390

Electronic Properties of Hydrogen Storage Materials with Photon-in/Photon-out Soft-X-Ray Spectroscopy  

SciTech Connect

The applications of resonant soft X-ray emission spectroscopy on a variety of carbon systems have yielded characteristic fingerprints. With high-resolution monochromatized synchrotron radiation excitation, resonant inelastic X-ray scattering has emerged as a new source of information about electronic structure and excitation dynamics. Photon-in/photon-out soft-X-ray spectroscopy is used to study the electronic properties of fundamental materials, nanostructure, and complex hydrides and will offer potential in-depth understanding of chemisorption and/or physisorption mechanisms of hydrogen adsorption/desorption capacity and kinetics.

Guo, Jinghua

2008-09-22

391

Variable soft X-ray excesses in active galactic nuclei from nonthermal electron-positron pair cascades  

NASA Technical Reports Server (NTRS)

In the present study of the formation of steep soft X-ray excesses that are superposed on flatter, hard X-ray power-law spectra in nonthermal electron-positron pair cascade sources, the soft excess in pair-cascade AGN models appears as a steep power law superposed on the tail of the UV bump and the flat nonthermal (hard X-ray) power law. The model-parameter space in which an excess in soft X-rays is visible is ascertained, and the time-variability of soft excesses in pair cascade models is examined. It is established that the parameter space in which soft excesses appear encompasses the range of preferred input parameters for a recently development Compton reflection model of UV and X-ray emission from the central engine of an AGN.

Zdziarski, Andrzej A.; Coppi, Paolo S.

1991-01-01

392

Femtosecond X-ray induced electron kinetics in dielectrics: application for FEL-pulse-duration monitor  

NASA Astrophysics Data System (ADS)

Modern X-ray free-electron lasers (FELs) provide pulses with photon energies from a few tens of eV up to the tens of keV and durations as short as only a few femtoseconds. Experimental pump-probe scheme with a FEL pump and a visible light probe of a solid-state target can be used for the pulse-duration monitor on a shot-to-shot basis. To study the electron cascading in different materials used for pulse-duration monitor, XCASCADE, a Monte Carlo model of the X-ray-induced electron cascading within an irradiated target is developed. It is shown here that the electron cascade duration is sensitive to a choice of material. An appropriately selected target can significantly shorten the electron relaxation times. The grounds, upon which such a choice of the material can be made, are discussed. The results suggest that for photon energies of 24 keV, one could achieve direct monitoring of the pulse duration of 40 fs. Further deconvolution of the electron density into the contribution from the pulse itself and from the secondary cascading can increase the resolution up to a scale of a femtosecond.

Medvedev, Nikita

2015-03-01

393

Design and characterization of electron beam focusing for X-ray generation in novel medical imaging architecture  

SciTech Connect

A novel electron beam focusing scheme for medical X-ray sources is described in this paper. Most vacuum based medical X-ray sources today employ a tungsten filament operated in temperature limited regime, with electrostatic focusing tabs for limited range beam optics. This paper presents the electron beam optics designed for the first distributed X-ray source in the world for Computed Tomography (CT) applications. This distributed source includes 32 electron beamlets in a common vacuum chamber, with 32 circular dispenser cathodes operated in space charge limited regime, where the initial circular beam is transformed into an elliptical beam before being collected at the anode. The electron beam optics designed and validated here are at the heart of the first Inverse Geometry CT system, with potential benefits in terms of improved image quality and dramatic X-ray dose reduction for the patient.

Bogdan Neculaes, V., E-mail: neculaes@research.ge.com; Zou, Yun; Zavodszky, Peter; Inzinna, Louis; Zhang, Xi; Conway, Kenneth; Caiafa, Antonio; Frutschy, Kristopher; Waters, William; De Man, Bruno [GE Global Research, Niskayuna, New York 12309 (United States)] [GE Global Research, Niskayuna, New York 12309 (United States)

2014-05-15

394

Design and characterization of electron beam focusing for X-ray generation in novel medical imaging architecturea)  

NASA Astrophysics Data System (ADS)

A novel electron beam focusing scheme for medical X-ray sources is described in this paper. Most vacuum based medical X-ray sources today employ a tungsten filament operated in temperature limited regime, with electrostatic focusing tabs for limited range beam optics. This paper presents the electron beam optics designed for the first distributed X-ray source in the world for Computed Tomography (CT) applications. This distributed source includes 32 electron beamlets in a common vacuum chamber, with 32 circular dispenser cathodes operated in space charge limited regime, where the initial circular beam is transformed into an elliptical beam before being collected at the anode. The electron beam optics designed and validated here are at the heart of the first Inverse Geometry CT system, with potential benefits in terms of improved image quality and dramatic X-ray dose reduction for the patient.

Bogdan Neculaes, V.; Zou, Yun; Zavodszky, Peter; Inzinna, Louis; Zhang, Xi; Conway, Kenneth; Caiafa, Antonio; Frutschy, Kristopher; Waters, William; De Man, Bruno

2014-05-01

395

Prospects for higher spatial resolution quantitative X-ray analysis using transition element L-lines  

NASA Astrophysics Data System (ADS)

Lowering electron beam kV reduces electron scattering and improves spatial resolution of X-ray analysis. However, a previous round robin analysis of steels at 5 - 6 kV using L?-lines for the first row transition elements gave poor accuracies. Our experiments on SS63 steel using L?-lines show similar biases in Cr and Ni that cannot be corrected with changes to self-absorption coefficients or carbon coating. The inaccuracy may be caused by different probabilities for emission and anomalous self-absorption for the La-line between specimen and pure element standard. Analysis using Ll(L3-M1)-lines gives more accurate results for SS63 plausibly because the M1-shell is not so vulnerable to the atomic environment as the unfilled M4,5-shell. However, Ll-intensities are very weak and WDS analysis may be impractical for some applications. EDS with large area SDD offers orders of magnitude faster analysis and achieves similar results to WDS analysis with L?-lines but poorer energy resolution precludes the use of Ll-lines in most situations. EDS analysis of K-lines at low overvoltage is an alternative strategy for improving spatial resolution that could give higher accuracy. The trade-off between low kV versus low overvoltage is explored in terms of sensitivity for element detection for different elements.

Statham, P.; Holland, J.

2014-03-01

396

Femtosecond Diffractive Imaging with a Soft-X-Ray Free-Electron Laser  

SciTech Connect

Theory predicts that with an ultrashort and extremely bright coherent X-ray pulse, a single diffraction pattern may be recorded from a large macromolecule, a virus, or a cell before the sample explodes and turns into a plasma. Here we report the first experimental demonstration of this principle using the FLASH soft X-ray free-electron laser. An intense 25 fs, 4 x 10{sup 13} W/cm{sup 2} pulse, containing 10{sup 12} photons at 32 nm wavelength, produced a coherent diffraction pattern from a nano-structured non-periodic object, before destroying it at 60,000 K. A novel X-ray camera assured single photon detection sensitivity by filtering out parasitic scattering and plasma radiation. The reconstructed image, obtained directly from the coherent pattern by phase retrieval through oversampling, shows no measurable damage, and extends to diffraction-limited resolution. A three-dimensional data set may be assembled from such images when copies of a reproducible sample are exposed to the beam one by one.

Chapman, H.N.; Barty, A.; Bogan, M.J.; Boutet, S.; Frank, M.; Hau-Riege, S.P.; Marchesini, S.; Woods, B.W.; Bajt, S.; Benner, H.; London, R.A.; Plonjes, E.; Kuhlmann, M.; Treusch, R.; Dusterer, S.; Tschentscher, T.; Schneider, J.R.; Spiller, E.; Moller, T.; Bostedt, C.; Hoener, M.; /LLNL, Livermore /UC, Davis /SLAC, SSRL /Uppsala U. /DESY /Berlin, Tech. U.; ,

2010-10-07

397

Femtosecond Diffractive Imaging with a Soft-X-ray Free-Electron Laser  

E-print Network

Theory predicts that with an ultrashort and extremely bright coherent X-ray pulse, a single diffraction pattern may be recorded from a large macromolecule, a virus, or a cell before the sample explodes and turns into a plasma. Here we report the first experimental demonstration of this principle using the FLASH soft X-ray free-electron laser. An intense 25 fs, 4 10^13 W/cm^2 pulse, containing 10^12 photons at 32 nm wavelength, produced a coherent diffraction pattern from a nano-structured non-periodic object, before destroying it at 60,000 K. A novel X-ray camera assured single photon detection sensitivity by filtering out parasitic scattering and plasma radiation. The reconstructed image, obtained directly from the coherent pattern by phase retrieval through oversampling, shows no measurable damage, and extends to diffraction-limited resolution. A three-dimensional data set may be assembled from such images when copies of a reproducible sample are exposed to the beam one by one.

Chapman, H N; Barty, A; Benner, W H; Bergh, M; Bogan, M J; Bostedt, C; Boutet, S; Burmeister, F; Caleman, C; Düsterer, S; Frank, M; Hajdu, J; Hau-Riege, S P; Hodgson, K O; Hoener, M; Huldt, G; Kuhlmann, M; Lee, R W; London, R A; Maia, F R N C; Marchesini, S; Möller, T; Plonjes, E; Schneider, J R; Seibert, M M; Shapiro, D A; Spiller, E; Szoke, A; Timneanu, N; Treusch, R; Tschentscher, T; Van der Spoel, D; Woods, B W; Bajt, Sasa; Barty, Anton; Bergh, Magnus; Bogan, Michael J.; Bostedt, Christoph; Boutet, Sebastien; Burmeister, Florian; Caleman, Carl; Chapman, Henry N.; Dusterer, Stefan; Frank, Matthias; Hajdu, Janos; Hau-Riege, Stefan P.; Hodgson, Keith O.; Hoener, Matthias; Huldt, Gosta; Kuhlmann, Marion; Lee, Richard W.; London, Richard A.; Maia, Filipe R.N.C.; Marchesini, Stefano; Moller, Thomas; Plonjes, Elke; Schneider, Jochen R.; Shapiro, David A.; Spiller, Eberhard; Spoel, David van der; Szoke, Abraham; Timneanu, Nicusor; Treusch, Rolf; Tschentscher, Thomas; Woods, Bruce W.

2006-01-01

398

Structural biology at the European X-ray free-electron laser facility.  

PubMed

The European X-ray free-electron laser (XFEL) facility, under construction in the Hamburg region, will provide high-peak brilliance (greater than 10(33) photons s(-1) mm(-2) mrad(-2) per 0.1% BW), ultrashort pulses (approx. 10 fs) of X-rays, with a high repetition rate (up to 27 000 pulses s(-1)) from 2016 onwards. The main features of this exceptional X-ray source, and the instrumentation developments necessary to exploit them fully, for application to a variety of scientific disciplines, are briefly summarized. In the case of structural biology, that has a central role in the scientific case of this new facility, the instruments and ancillary laboratories that are being planned and built within the baseline programme of the European XFEL and by consortia of users are also discussed. It is expected that the unique features of the source and the advanced features of the instrumentation will allow operation modes with more efficient use of sample materials, faster acquisition times, and conditions better approaching feasibility of single molecule imaging. PMID:24914145

Altarelli, Massimo; Mancuso, Adrian P

2014-07-17

399

Feasibility Study of Gas Electron Multiplier Detector as an X-Ray Image Sensor  

E-print Network

For its ease manufacturing, flexible geometry, and cheap manufacturing cost, the gas electron multiplier (GEM) detector can be used as an x-ray image sensor. For this purpose, we acquired relative detection efficiencies and suggested a method to increase the detection efficiency in order to study the possibility of GEM detector as an x-ray image sensor. The GEM detector system is composed of GEM foils, the instrument system, the gas system, and the negative power supply. The instrument system consists of the A225 charge sensitive preamp, A206 discriminator, and MCA8000D multichannel analyzer. For the gas system, Argon gas was mixed with CO2 to the ratio of 8:2, and for the negative 2,000 volts, the 3106D power supply was used. The CsI-coated GEM foil was used to increase the detection efficiency. Fe-55 was used as an x-ray source and the relative efficiency was acquired by using the ratio of GEM detector to the CdTe detector. The total count method and the energy spectrum method were used to calculate the rel...

Shin, Sukyoung; Lee, Soonhyouk

2015-01-01

400

Bulk electronic structure of K3C60 as revealed by soft x-rays  

NASA Astrophysics Data System (ADS)

We present C1s x-ray absorption, x-ray emission, and resonant inelastic x-ray scattering (RIXS) spectra of single-phase crystalline K3C60 . The comparison to valence-band photoelectron spectra from the same sample facilitates identification of the contribution from surface and bulk electronic states in the latter. Bulk-sensitive techniques show that the valence bands of K3C60 and pure C60 are characterized by spectral features of similar width, in agreement with the predictions of band-structure calculations. Symmetry selectivity in the RIXS process allows us to assign peaks in the C1s absorption spectrum, demonstrating a close correspondence with pure C60 also in the conduction band. The symmetry selectivity is as pronounced in K3C60 as in pure C60 , indicating that the local C60 symmetry is not appreciably affected by the K doping, either in the ground state or intermediate state, on the time scale of 6fs .

Käämbre, Tanel; Schiessling, Joachim; Kjeldgaard, Lisbeth; Qian, Limin; Marenne, Ingrid; O'Shea, James N.; Schnadt, Joachim; Nordlund, Dennis; Glover, Chris J.; Rubensson, Jan-Erik; Rudolf, Petra; Mårtensson, Nils; Nordgren, Joseph; Brühwiler, Paul A.

2007-05-01

401

Sub-femtosecond precision measurement of relative X-ray arrival time for free-electron lasers  

NASA Astrophysics Data System (ADS)

Today's brightest coherent X-ray sources, X-ray free-electron lasers, produce ultrafast X-ray pulses for which full-width at half-maximum durations as short as 3?fs have been measured. There has been a marked increase in the popularity of such short pulses now that optical timing techniques have begun to report an X-ray/optical delay below ?10?fs r.m.s. errors. As a result, sub-10?fs optical pulses have been implemented at the Linac Coherent Light Source (LCLS) X-ray beamlines, thus warranting a push to reduce the error in X-ray/optical delay measurements to the 1?fs level. Here, we report a unique two-dimensional spectrogram measurement of the relative X-ray/optical delay. This easily scalable relative delay measurement already surpasses previous techniques by an order of magnitude with its sub-1?fs temporal resolution and opens up the prospect of time-resolved X-ray measurements to the attosecond community.

Hartmann, N.; Helml, W.; Galler, A.; Bionta, M. R.; Grünert, J.; L. Molodtsov, S.; Ferguson, K. R.; Schorb, S.; Swiggers, M. L.; Carron, S.; Bostedt, C.; Castagna, J.-C.; Bozek, J.; Glownia, J. M.; Kane, D. J.; Fry, A. R.; White, W. E.; Hauri, C. P.; Feurer, T.; Coffee, R. N.

2014-09-01

402

Feasibility Study of Gas Electron Multiplier Detector as an X-Ray Image Sensor  

E-print Network

For its ease manufacturing, flexible geometry, and cheap manufacturing cost, the gas electron multiplier (GEM) detector can be used as an x-ray image sensor. For this purpose, we acquired relative detection efficiencies and suggested a method to increase the detection efficiency in order to study the possibility of GEM detector as an x-ray image sensor. The GEM detector system is composed of GEM foils, the instrument system, the gas system, and the negative power supply. The instrument system consists of the A225 charge sensitive preamp, A206 discriminator, and MCA8000D multichannel analyzer. For the gas system, Argon gas was mixed with CO2 to the ratio of 8:2, and for the negative 2,000 volts, the 3106D power supply was used. The CsI-coated GEM foil was used to increase the detection efficiency. Fe-55 was used as an x-ray source and the relative efficiency was acquired by using the ratio of GEM detector to the CdTe detector. The total count method and the energy spectrum method were used to calculate the relative efficiency. The relative detection efficiency of GEM detector for Fe-55 by using total count method was 32 % and by using energy spectrum method, the relative efficiencies were 5, 43, 33, 37, 35, and 36 % respectively according to the energy spectrum of 2, 3, 4, 5, 6, and 7 KeV. In conclusion, we found that the detection efficiency of the two layered GEM detector is insufficient for the x-ray image sensor, so we suggested a CsI coated GEM foil to increase the efficiency rate and the result value was increased to 41 %.

Sukyoung Shin; Jaehoon Jung; Soonhyouk Lee

2015-03-12

403

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

PubMed

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

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

2013-09-27

404

Eigen analysis for classifying chest x-ray images  

NASA Astrophysics Data System (ADS)

A method first employed for face recognition has been employed to analyse a set of chest x-ray images. After marking certain common features on the images, they are registered by means of an affine transformation. The differences between each registered image and the mean of all images in the set are computed and the first K principal components are found, where K is less than or equal to the number of images in the set. These form eigenimages (we have coined the term 'eigenchests') from which an approximation to any one of the original images can be reconstructed. Since the method effectively treats each pixel as a dimension in a hyperspace, the matrices concerned are huge; we employ the method developed by Turk and Pentland for face recognition to make the computations tractable. The K coefficients for the eigenimages encode the variation between images and form the basis for discriminating normal from abnormal. Preliminary results have been obtained for a set of eigenimages formed from a set of normal chests and tested on separate sets of normals and patients with pneumonia. The distributions of coefficients have been observed to be different for the two test sets and work is continuing to determine the most sensitive method for detecting the differences.

Bones, Philip J.; Butler, Anthony P. H.

2004-10-01

405

On the Statistical Analysis of X-ray Polarization Measurements  

NASA Technical Reports Server (NTRS)

In many polarimetry applications, including observations in the X-ray band, the measurement of a polarization signal can be reduced to the detection and quantification of a deviation from uniformity of a distribution of measured angles of the form alpha plus beta cosine (exp 2)(phi - phi(sub 0) (0 (is) less than phi is less than pi). We explore the statistics of such polarization measurements using both Monte Carlo simulations as well as analytic calculations based on the appropriate probability distributions. We derive relations for the number of counts required to reach a given detection level (parameterized by beta the "number of sigma's" of the measurement) appropriate for measuring the modulation amplitude alpha by itself (single interesting parameter case) or jointly with the position angle phi (two interesting parameters case). We show that for the former case when the intrinsic amplitude is equal to the well known minimum detectable polarization (MDP) it is, on average, detected at the 3sigma level. For the latter case, when one requires a joint measurement at the same confidence level, then more counts are needed, by a factor of approximately equal to 2.2, than that required to achieve the MDP level. We find that the position angle uncertainty at 1sigma confidence is well described by the relation sigma(sub pi) equals 28.5(degrees) divided by beta.

Strohmayer, T. E.; Kallman, T. R.

2013-01-01

406

On the Statistical Analysis of X-Ray Polarization Measurements  

NASA Astrophysics Data System (ADS)

In many polarimetry applications, including observations in the X-ray band, the measurement of a polarization signal can be reduced to the detection and quantification of a deviation from uniformity of a distribution of measured angles of the form A + Bcos 2(phi - phi0) (0 < phi < ?). We explore the statistics of such polarization measurements using Monte Carlo simulations and ?2 fitting methods. We compare our results to those derived using the traditional probability density used to characterize polarization measurements and quantify how they deviate as the intrinsic modulation amplitude grows. We derive relations for the number of counts required to reach a given detection level (parameterized by ? the "number of ?'s" of the measurement) appropriate for measuring the modulation amplitude a by itself (single interesting parameter case) or jointly with the position angle phi (two interesting parameters case). We show that for the former case, when the intrinsic amplitude is equal to the well-known minimum detectable polarization, (MDP) it is, on average, detected at the 3? level. For the latter case, when one requires a joint measurement at the same confidence level, then more counts are needed than what was required to achieve the MDP level. This additional factor is amplitude-dependent, but is ?2.2 for intrinsic amplitudes less than about 20%. It decreases slowly with amplitude and is ?1.8 when the amplitude is 50%. We find that the position angle uncertainty at 1? confidence is well described by the relation ?phi = 28.°5/?.

Strohmayer, T. E.; Kallman, T. R.

2013-08-01

407

Location of Calcium Within Bacillus Spores by Electron Probe X-Ray Microanalysis1  

PubMed Central

Spectroscopic microanalysis of the element-characteristic X rays produced by a scanning electron microprobe was employed to detect calcium and carbon in both intact and thin-sectioned spores of Bacillus cereus T and B. megaterium QM B1551. Linear scan profiles and multilinear scan images of the X-ray emissions for calcium (CaK?) were compared with those for carbon (CK?) as an index of mass. Location was accomplished by stereological comparisons with secondary electron images and conventional transmission electron micrographs. Although the elements could be detected at the attogram level theoretically, spatial resolution was limited to ?500 to 1,000 nm in an intact spore, e.g., by the primary electron beam diameter, the electron-excited spore microvolume, and the type of specimen support. The resolution was improved to ?100 to 200 nm by use of thin-sectioned spores, with precautions to prevent calcium leakage from the specimen during preparations. In both intact and sectioned spores, calcium was distributed throughout the spore, similarly to carbon, and concentrated mainly in a central region corresponding to the spore protoplast. Images PMID:4627927

Scherrer, René; Gerhardt, Philipp

1972-01-01

408

Radio and Hard X-Ray Images of High-Energy Electrons in an X-Class Solar Flare  

NASA Technical Reports Server (NTRS)

We present the first comparison between radio images of high-energy electrons accelerated by a solar flare and images of hard X-rays produced by the same electrons at photon energies above 100 keV. The images indicate that the high-energy X-rays originate at the footpoints of the loops dominating the radio emission. The radio and hard X-ray light curves match each other well and are quantitatively consistent with an origin in a single population of nonthermal electrons with a power-law index of around 4.5-5. The high-frequency radio spectral index suggests a flatter energy spectrum, but this is ruled out by the X-ray spectrum up to 8 MeV.

White, S. M.; Krucker, S.; Shibasaki, K.; Yokoyama, T.; Shimojo, M.; Kundu, Mukul R.

2003-01-01

409

SAVLOC, computer program for automatic control and analysis of X-ray fluorescence experiments  

NASA Technical Reports Server (NTRS)

A program for a PDP-15 computer is presented which provides for control and analysis of trace element determinations by using X-ray fluorescence. The program simultaneously handles data accumulation for one sample and analysis of data from previous samples. Data accumulation consists of sample changing, timing, and data storage. Analysis requires the locating of peaks in X-ray spectra, determination of intensities of peaks, identification of origins of peaks, and determination of a real density of the element responsible for each peak. The program may be run in either a manual (supervised) mode or an automatic (unsupervised) mode.

Leonard, R. F.

1977-01-01

410

Radiation from laser accelerated electron bunches: Coherent terahertz and femtosecond X-rays  

SciTech Connect

Electron beam based radiation sources provide electromagnetic radiation for countless applications. The properties of the radiation are primarily determined by the properties of the electron beam. Compact laser driven accelerators are being developed that can provide ultra-short electron bunches (femtosecond duration) with relativistic energies reaching towards a GeV. The electron bunches are produced when an intense laser interacts with a dense plasma and excites a large amplitude plasma density modulation (wakefield) that can trap background electrons and accelerate them to high energies. The short pulse nature of the accelerated bunches and high particle energy offer the possibility of generating radiation from one compact source that ranges from coherent terahertz to gamma rays. The intrinsic synchronization to a laser pulse and unique character of the radiation offers a wide range of possibilities for scientific applications. Two particular radiation source regimes are discussed: Coherent terahertz emission and x-ray emission based on betatron oscillations and Thomson scattering.

Leemans, W.P.; Esarey, E.; van Tilborg, J.; Michel, P.A.; Schroeder, C.B.; Toth, Cs.; Geddes, C.G.R.; Shadwick, B.A.

2004-10-01

411

Analysis of strain/stress inhomogeneities contributing to x-ray strain/stress analysis  

NASA Astrophysics Data System (ADS)

X-ray strain/stress analysis has been widely used in the determination of applied and residual stresses in the surface layers of crystalline materials. However, it is shown that further development and clarification are certainly needed to enhance the applicability of the x-ray strain/stress analysis method. In this work, the basic theory of x-ray strain/stress analysis is reviewed and discussed. Homogeneous continuum analysis is extended to polycrystalline materials in a rigorous fashion based on the assumptions of constant stress or constant strain in all grains. Numerical simulation is used to study the definition of the allowable crystallographic coordinate systems for the grains diffracting at a Psi-tilt. These grains are then used in the mesh definition of the finite element model (FEM). The variation of local and average elastic constants with Psi and Xi angles in the sample coordinate system for different Psi-tilts and reflections are obtained through both numerical simulation and analytical solutions. The results show that this variation causes an elastic incompatibility and local inhomogeneous strain/stress distribution, which in turn can cause deviations from the linear deformation theory. Analysis of sampling volumes is then applied to better understand the local inhomogeneous strain/stress distribution and the inhomogeneity of mechanical response in polycrystalline materials. Finite element modeling is then used to determine the x-ray representative volume. Finally, experiments are used to test the concepts obtained from numerical simulation and analytical solutions for local and average elastic constants, local and average elastic strains and the relationships between them.

Song, Yongchu

412

Nanopaleomagnetism of meteoritic Fe-Ni studied using X-ray photoemission electron microscopy  

NASA Astrophysics Data System (ADS)

X-ray photoemission electron microscopy (XPEEM) enables natural remanent magnetisation to be imaged with ˜30 nm resolution across a field of view of 5-20 ?m. The method is applied to structural features typical of the Widmanstätten microstructure (kamacite - tetrataenite rim - cloudy zone - plessite) in the Tazewell IIICD iron meteorite. Kamacite lamellae and the tetrataenite rim are multidomain, whereas plessite consists of laths of different phases displaying a range of stable magnetisation directions. The cloudy zone (CZ) displays a complex interlocking domain pattern resulting from nanoscale islands of tetrataenite with easy axes distributed along three possible crystallographic directions. Quantitative analysis of the coarse and intermediate CZ was achieved using a combination of image simulations and histogram profile matching. Remanence information was extracted from individual regions of interest ˜400 nm wide, demonstrating for the first time the capability of XPEEM to perform quantitative paleomagnetic analysis at sub-micron length scales. The three tetrataenite easy axis orientations occur with equal probability in the coarse and intermediate CZ, suggesting that spinodal decomposition in these regions was not strongly influenced by internal interaction fields, and that they are suitable candidates for future paleomagnetic studies. The fine CZ shows a strong dominance of one easy axis. This effect is attributed to island-island exchange interactions that render the fine CZ unsuitable for paleomagnetic study. Variations in the relative strength (proportion of dominant easy axis) and direction (direction of dominant easy axis) of a paleomagnetic field can be resolved from different regions of the CZ using XPEEM, raising the prospect of obtaining a time-resolved measurement of the active dynamo period in meteorites originating from the upper unmelted regions of differentiated asteroids (e.g. chondrites, pallasites, mesosiderites).

Bryson, James F. J.; Herrero-Albillos, Julia; Kronast, Florian; Ghidini, Massimo; Redfern, Simon A. T.; van der Laan, Gerrit; Harrison, Richard J.

2014-06-01

413

A controlled radiation source and electron/X-ray flux ratios in an electron beam metal evaporator  

NASA Astrophysics Data System (ADS)

The use of ionizing radiation (X-rays, electrons and ions) in semiconductor processes is becoming more pervasive as device dimensions decrease. One such source of ionizing radiation is an electron beam (EB) metal evaporator. It has, in fact, been used earlier as a mixed X-ray/electron source to simulate ionizing radiation processes in device fab-rication sequences. In those studies, it was not known, however, what fraction of the energy striking a specimen was due to electrons, and what fraction was due to X-rays. In the present paper, application of an electron beam evaporator as a controlled, essen-tially monochromatic ionizing radiation source is described. Using a 0.5 mil thick Be foil, and knowing its mass absorption coefficient for X-rays at the wavelengths involved, the percentage electron and X-ray fluxes as a function of hearth beam current for a set of accelerating voltages was estimated. In addition, the absorption coefficient of an in-expensive, expendable, polymeric foil (pellicle) used in place of Be for actual experi-mental studies was evaluated. The 2.85 ?m thick pellicle was found to transmit 87% of the incident Al K? radiation, and to exhibit a mass absorption coefficient of 303 cm2/ g. The electron flux percentage from an aluminum hearth at a distance of 205 mm, was found to be 26% for a range of hearth electron beam currents between 2.5 x 10-2A and 7.5 x 10-2A, at an accelerating voltage of 6 kV. For a 10 kV accelerating voltage the electron percentage was found to be 35% between 2.5 x 10-2A and 7.5 x 10-2A. X-ray fractions were 74% and 65%, respectively. The radiation system can be used to pro-vide exposures in the 5 x 104 rad(SiO2) to the 2 x 108 rad(SiO2) range for Insulated Gate Field Effect transistors, in about an hour-long experiment.

Bhattacharya, P. K.; Reisman, A.; Chen, M. C.

1988-07-01

414

Monte Carlo simulation of characteristic x-ray emission from thick samples bombarded by kiloelectronvolt electrons  

NASA Astrophysics Data System (ADS)

We describe systematic Monte Carlo (MC) calculations of characteristic K and L x-ray emission from thick samples bombarded by kiloelectronvolt electrons. The simulations were performed using the general-purpose MC code PENELOPE, which was modified by introducing a new database of electron-impact ionization cross sections calculated from the distorted-wave Born approximation (DWBA). The calculated yields, defined as the number of photons emerging from the target per unit solid angle and per incident electron, are compared with experimental measurements available from the literature, which pertain to single-element materials with atomic numbers ranging from Z = 6 up to Z = 82 and electron beam energies from a few kiloelectronvolts up to 40 keV. To reveal the dependence of the characteristic x-ray yields on the adopted ionization cross sections, simulations were also performed using cross sections based on the plane-wave Born approximation (PWBA). Our calculations confirm that, in the considered energy range, the DWBA is considerably more accurate than the PWBA.

Bote, D.; Llovet, X.; Salvat, F.

2008-05-01

415

Synchrotron x-ray radiation from laser wakefield accelerated electron beams in a plasma channel  

NASA Astrophysics Data System (ADS)

Synchrotron x-ray radiation from laser wakefield accelerated electron beams was characterized at the HERCULES facility of the University of Michigan. A mono-energetic electron beam with energy up to 400 MeV was observed in the interaction of an ultra-short laser pulse with a super-sonic gas jet target. The experiments were performed at a peak intensity of 5×1019 W/cm2 by using an adaptive optic. The accelerated electron beam undergoes a so called "betatron" oscillation in an ion channel, where plasma electrons have been expelled by the laser ponderomotive force, and, therefore, emits synchrotron radiation. We observe broad synchrotron x-ray radiation extending up to 30 keV. We find that this radiation is emitted in a beam with a divergence angle as small as 12×4 mrad2 and can have a source size smaller than 3 microns and a peak brightness of 1022 photons/mm2/mrad2/second/0.1% bandwidth, which is comparable to currently existing 3rd generation conventional light sources. This opens up the possibility of using laser-produced "betatron" sources for many applications that currently require conventional synchrotron sources.

Matsuoka, T.; Kneip, S.; McGuffey, C.; Palmer, C.; Schreiber, J.; Huntington, C.; Horovitz, Y.; Dollar, F.; Chvykov, V.; Kalintchenko, G.; Thomas, A. G. R.; Yanovsky, V.; Phuoc, K. Ta; Mangles, S. P. D.; Najmudin, Z.; Maksimchuk, A.; Krushelnick, K.

2010-08-01

416

Single-component chemically amplified resist materials for electron-beam and x-ray lithography  

NASA Astrophysics Data System (ADS)

Copolymers of 4-tert-butoxycarbonyloxystyrene (TBS) and sulfur dioxide (SO2) have been found to act as sensitive x-ray ((lambda) equals 14 angstrom) and moderately sensitive electron-beam, single component, chemically amplified, aqueous base soluble positive acting resists. The x-ray and electron-beam response of these materials was a function of copolymer composition, where an increase in the sulfur dioxide content enhanced the resist sensitivity. Initial investigation into the radiation induced reaction mechanism provided evidence that acid formation occurs via polymer main chain scission. It is proposed that at the scission sites radical species are produced which in turn are responsible for the formation of the acidic moieties. Heat treatment of resist films after exposure converted the copolymers to poly(4- hydroxystyrene sulfone) and permitted the exposed film areas to be developed in an aqueous base solution. Preliminary lithographic evaluation has resolved 0.5 micrometers line and space patterns in 0.65 micrometers thick 1.75/1 TBS/SO2 resist films using an x-ray dose of 10 mJ/cm2. For a resist having a composition of 2.1/1 TBS/SO2, 0.25 micrometers line and space features where delineated using an electron-beam dose of 90 (mu) C/cm2 at 30 KV. In addition, minimal surface residue of the exposed areas of the resist film after development was observed when the time interval between the exposure and the post-exposure baking steps was varied from 2-10 minutes.

Novembre, Anthony E.; Tai, Woon W.; Kometani, Janet M.; Hanson, James E.; Nalamasu, Omkaram; Taylor, Gary N.; Reichmanis, Elsa; Thompson, Larry F.

1991-06-01

417

Using Lasers and X-rays to Reveal the Motion of Atoms and Electrons  

ScienceCinema

July 7, 2009 Berkeley Lab summer lecture: The ultrafast motion of atoms and electrons lies at the heart of chemical reactions, advanced materials with exotic properties, and biological processes such as the first event in vision. Bob Schoenlein, Deputy Director for Science at the Advanced Light Source, will discuss how such processes are revealed by using laser pulses spanning a millionth of a billionth of a second, and how a new generation of light sources will bring the penetrating power of x-rays to the world of ultrafast science

Bob Schoenlein

2010-01-08

418

Radiation damage in protein serial femtosecond crystallography using an x-ray free-electron laser.  

PubMed

X-ray free-electron lasers deliver intense femtosecond pulses that promise to yield high resolution diffraction data of nanocrystals before the destruction of the sample by radiation damage. Diffraction intensities of lysozyme nanocrystals collected at the Linac Coherent Light Source using 2 keV photons were used for structure determination by molecular replacement and analyzed for radiation damage as a function of pulse length and fluence. Signatures of radiation damage are observed for pulses as short as 70 fs. Parametric scaling used in conventional crystallography does not account for the observed effects. PMID:24089594

Lomb, Lukas; Barends, Thomas R M; Kassemeyer, Stephan; Aquila, Andrew; Epp, Sascha W; Erk, Benjamin; Foucar, Lutz; Hartmann, Robert; Rudek, Benedikt; Rolles, Daniel; Rudenko, Artem; Shoeman, Robert L; Andreasson, Jakob; Bajt, Sasa; Barthelmess, Miriam; Barty, Anton; Bogan, Michael J; Bostedt, Christoph; Bozek, John D; Caleman, Carl; Coffee, Ryan; Coppola, Nicola; Deponte, Daniel P; Doak, R Bruce; Ekeberg, Tomas; Fleckenstein, Holger; Fromme, Petra; Gebhardt, Maike; Graafsma, Heinz; Gumprecht, Lars; Hampton, Christina Y; Hartmann, Andreas; Hauser, Günter; Hirsemann, Helmut; Holl, Peter; Holton, James M; Hunter, Mark S; Kabsch, Wolfgang; Kimmel, Nils; Kirian, Richard A; Liang, Mengning; Maia, Filipe R N C; Meinhart, Anton; Marchesini, Stefano; Martin, Andrew V; Nass, Karol; Reich, Christian; Schulz, Joachim; Seibert, M Marvin; Sierra, Raymond; Soltau, Heike; Spence, John C H; Steinbrener, Jan; Stellato, Francesco; Stern, Stephan; Timneanu, Nicusor; Wang, Xiaoyu; Weidenspointner, Georg; Weierstall, Uwe; White, Thomas A; Wunderer, Cornelia; Chapman, Henry N; Ullrich, Joachim; Strüder, Lothar; Schlichting, Ilme

2011-12-01

419

Generation of harmonics via multiphoton resonant excitation of hydrogenlike ions in an x-ray free-electron-laser field  

NASA Astrophysics Data System (ADS)

The coherent radiation spectrum of highly charged hydrogenlike ions in an intense x-ray free-electron-laser field is considered. The spectrum corresponding to harmonic generation in the resonant multiphoton excitation regime is investigated both analytically and numerically, arising from the Dirac Hamiltonian. The obtained analytical results are based on the generalized rotating wave approximation and are in good agreement with performed numerical calculations. Estimations show that one can achieve efficient generation of coherent hard x-ray radiation using multiphoton resonant excitation by appropriate x-ray pulses.

Avetissian, H. K.; Avchyan, B. R.; Mkrtchian, G. F.

2014-11-01

420

The soft X-ray properties of AGN from the CJF sample. A correlation analysis between soft X-ray and VLBI properties  

NASA Astrophysics Data System (ADS)

Context: We present the soft X-ray properties obtained in the ROSAT All-Sky survey and from pointed PSPC observations for the AGN in the complete flux-density limited Caltech-Jodrell Bank flat spectrum sample (hereafter CJF). CJF is a VLBI survey (VLBA observations at 5 GHz) of 293 AGN with detailed information on jet component motion. Aims: We investigate and discuss the soft X-ray properties of this AGN sample and examine the correlations between X-ray and VLBI properties, test beaming scenarios, and search for the discriminating properties between the sub-samples detected and not detected by ROSAT. Methods: Comparing the observed and the predicted X-ray fluxes by assuming an Inverse Compton (IC) origin for the observed X-rays, we compute the beaming or Doppler factor, ?_IC, for the CJF sources and compare it with the equipartition Doppler factor, ?_EQ. We further contrast the Doppler factors with other beaming indicators derived from the VLBI observations, such as the value of the expansion velocity, and the observed and intrinsic brightness temperature. We calculate two different core dominance parameters (R): the ratio of total VLBI flux to single-dish flux, R_V, and the ratio of the VLBI core-component flux to single-dish flux, R_C. In addition, we investigate the large-scale radio structure of the AGN and the difference between the pc- and kpc-scale structure (misalignment) with regard to the X-ray observations. Results: We find a nearly linear relation between X-ray and radio luminosities, and a similar but less stringent behaviour for the relation between optical and X-ray luminosities. The CJF-quasars show faster apparent motions and larger values of ?_IC than the radio galaxies do. The quasars detected by ROSAT have a different ?_app-redshift relationship compared to the non-detected ones. We find no significant difference in R between the quasars detected and not detected by ROSAT. We find evidence that R is larger for quasars and BL Lac objects than it is for radio galaxies, in accordance with unification scenarios. ROSAT-detected sources tend to reveal extended large-scale radio structures more often. Conclusions: We conclude that beaming alone cannot explain the observed dichotomy of ROSAT detection or non-detection and assume that the large-scale jet structure plays a decisive role. Tables 3-6 are only available in electronic form at http://www.aanda.org

Britzen, S.; Brinkmann, W.; Campbell, R. M.; Gliozzi, M.; Readhead, A. C. S.; Browne, I. W. A.; Wilkinson, P.

2007-12-01

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