These are representative sample records from Science.gov related to your search topic.
For comprehensive and current results, perform a real-time search at Science.gov.
1

Thin conductive diamond films as beam intensity monitors for soft x-ray beamlines  

NASA Astrophysics Data System (ADS)

Quantitative analysis of X-ray absorption and dichroism data requires knowledge of the beamline photon flux during the measurements. We show that thin conductive (B-doped) diamond thin films can be an alternative to the widely used gold meshes for monitoring the beam intensity of soft X-ray beamlines in situ. Limited by the carbon extended x-ray absorption fine structure oscillations, the diamond films become applicable beginning from about 600 eV photon energy, where the important transition metal edges and the rare-earth edges are found. The 100 nm and 250 nm thick free-standing diamond films were grown and tested against standard gold meshes in real-life dichroism experiments performed at beamline ID08 of the European Synchrotron Radiation Facility, Grenoble, France. Quantitative agreement was found between the two experimental data sets. The films feature an extremely high transmission of about 90% and, at the same time, yield a sufficiently strong and clean reference signal. Furthermore, the thin films do not affect the shape of the transmitted beam. X-rays passing mesh-type monitors are subject to diffraction effects, which widen the beam and become particularly disturbing for small beamsizes in the micrometer range.

Kummer, K.; Fondacaro, A.; Yakhou-Harris, F.; Sessi, V.; Pobedinskas, P.; Janssens, S. D.; Haenen, K.; Williams, O. A.; Hees, J.; Brookes, N. B.

2013-03-01

2

Thin conductive diamond films as beam intensity monitors for soft x-ray beamlines  

SciTech Connect

Quantitative analysis of X-ray absorption and dichroism data requires knowledge of the beamline photon flux during the measurements. We show that thin conductive (B-doped) diamond thin films can be an alternative to the widely used gold meshes for monitoring the beam intensity of soft X-ray beamlines in situ. Limited by the carbon extended x-ray absorption fine structure oscillations, the diamond films become applicable beginning from about 600 eV photon energy, where the important transition metal edges and the rare-earth edges are found. The 100 nm and 250 nm thick free-standing diamond films were grown and tested against standard gold meshes in real-life dichroism experiments performed at beamline ID08 of the European Synchrotron Radiation Facility, Grenoble, France. Quantitative agreement was found between the two experimental data sets. The films feature an extremely high transmission of about 90% and, at the same time, yield a sufficiently strong and clean reference signal. Furthermore, the thin films do not affect the shape of the transmitted beam. X-rays passing mesh-type monitors are subject to diffraction effects, which widen the beam and become particularly disturbing for small beamsizes in the micrometer range.

Kummer, K.; Fondacaro, A.; Yakhou-Harris, F.; Sessi, V.; Brookes, N. B. [European Synchrotron Radiation Facility, 6 Rue Jules Horowitz, B.P. 220, F-38043 Grenoble Cedex (France); Pobedinskas, P.; Janssens, S. D.; Haenen, K. [Hasselt University, Institute for Materials Research (IMO), Wetenschapspark 1, B-3590 Diepenbeek (Belgium); IMEC vzw, IMOMEC, Wetenschapspark 1, B-3590 Diepenbeek (Belgium); Williams, O. A. [Fraunhofer Institut Angewandte Festkoerperphysik, Tullastrasse 72, 79108 Freiburg (Germany); School of Physics and Astronomy, Cardiff University, Queens Buildings, The Parade, Cardiff CF24 3AA (United Kingdom); Hees, J. [Fraunhofer Institut Angewandte Festkoerperphysik, Tullastrasse 72, 79108 Freiburg (Germany)

2013-03-15

3

Generating Intense Attosecond X-Ray Pulses Using Ultraviolet-Laser-Induced Microbunching in Electron Beams  

SciTech Connect

We propose a scheme that combines the echo-enabled harmonic generation technique with the bunch compression and allows to generate harmonic numbers of a few hundred in a microbunched beam through up-conversion of the frequency of an ultraviolet seed laser. Sending this beam through a short undulator results in an isolated sub-100 attoseconds pulse of x-ray radiation. Using a representative realistic set of parameters, we show that 1 nm x-ray pulse with peak power exceeding 100 MW and duration as short as 34 attoseconds (FWHM) can be generated from a 200 nm ultraviolet seed laser.

Xiang, D.; Huang, Z.; Stupakov, G.; /SLAC

2009-03-04

4

X-ray beam finder  

DOEpatents

An X-ray beam finder for locating a focal spot of an X-ray tube includes a mass of X-ray opaque material having first and second axially-aligned, parallel-opposed faces connected by a plurality of substantially identical parallel holes perpendicular to the faces and a film holder for holding X-ray sensitive film tightly against one face while the other face is placed in contact with the window of an X-ray head.

Gilbert, H.W.

1983-06-16

5

Quantitative Measurements of X-ray Intensity  

SciTech Connect

This chapter describes the characterization of several X-ray sources and their use in calibrating different types of X-ray cameras at National Security Technologies, LLC (NSTec). The cameras are employed in experimental plasma studies at Lawrence Livermore National Laboratory (LLNL), including the National Ignition Facility (NIF). The sources provide X-rays in the energy range from several hundred eV to 110 keV. The key to this effort is measuring the X-ray beam intensity accurately and traceable to international standards. This is accomplished using photodiodes of several types that are calibrated using radioactive sources and a synchrotron source using methods and materials that are traceable to the U.S. National Institute of Standards and Technology (NIST). The accreditation procedures are described. The chapter begins with an introduction to the fundamental concepts of X-ray physics. The types of X-ray sources that are used for device calibration are described. The next section describes the photodiode types that are used for measuring X-ray intensity: power measuring photodiodes, energy dispersive photodiodes, and cameras comprising photodiodes as pixel elements. Following their description, the methods used to calibrate the primary detectors, the power measuring photodiodes and the energy dispersive photodiodes, as well as the method used to get traceability to international standards are described. The X-ray source beams can then be measured using the primary detectors. The final section then describes the use of the calibrated X-ray beams to calibrate X-ray cameras. Many of the references are web sites that provide databases, explanations of the data and how it was generated, and data calculations for specific cases. Several general reference books related to the major topics are included. Papers expanding some subjects are cited.

Haugh, M. J., Schneider, M.

2011-09-01

6

Time-dependent, x-ray spectral unfolds and brightness temperatures for intense Li + ion beam-driven hohlraums  

NASA Astrophysics Data System (ADS)

X-ray-producing hohlraums are being studied as indirect drives for inertial confinement fusion targets. In a 1994 target series on the PBFAII accelerator, cylindrical hohlraum targets were heated by an intense Li+ ion beam and viewed by an array of 13 time-resolved, filtered x-ray detectors (XRDs). The unfold operator (UFO) code and its suite of auxiliary functions were used extensively in obtaining time-resolved x-ray spectra and radiation temperatures from this diagnostic. The UFO was also used to obtain fitted response functions from calibration data, to simulate data from blackbody x-ray spectra of interest, to determine the suitability of various unfolding parameters (e.g., energy domain, energy partition, smoothing conditions, and basis functions), to interpolate the XRD signal traces, and to unfold experimental data. The simulation capabilities of the code were useful in understanding an anomalous feature in the unfolded spectra at low photon energies (?100 eV). Uncertainties in the differential and energy-integrated unfolded spectra were estimated from uncertainties in the data. The time-history of the radiation temperature agreed well with independent calculations of the wall temperature in the hohlraum.

Fehl, D. L.; Chandler, G. A.; Biggs, F.; Dukart, R. J.; Moats, A. R.; Leeper, R. J.

1997-01-01

7

Apparatus for monitoring X-ray beam alignment  

DOEpatents

A self-contained, hand-held apparatus is provided for minitoring alignment of an X-ray beam in an instrument employing an X-ray source. The apparatus includes a transducer assembly containing a photoresistor for providing a range of electrical signals responsive to a range of X-ray beam intensities from the X-ray beam being aligned. A circuit, powered by a 7.5 VDC power supply and containing an audio frequency pulse generator whose frequency varies with the resistance of the photoresistor, is provided for generating a range of audible sounds. A portion of the audible range corresponds to low X-ray beam intensity. Another portion of the audible range corresponds to high X-ray beam intensity. The transducer assembly may include an a photoresistor, a thin layer of X-ray fluorescent material, and a filter layer transparent to X-rays but opaque to visible light. X-rays from the beam undergoing alignment penetrate the filter layer and excite the layer of fluorescent material. The light emitted from the fluorescent material alters the resistance of the photoresistor which is in the electrical circuit including the audio pulse generator and a speaker. In employing the apparatus, the X-ray beam is aligned to a complete alignment by adjusting the X-ray beam to produce an audible sound of the maximum frequency.

Steinmeyer, Peter A. (Arvada, CO)

1991-10-08

8

Apparatus for monitoring X-ray beam alignment  

DOEpatents

A self-contained, hand-held apparatus is provided for monitoring alignment of an X-ray beam in an instrument employing an X-ray source. The apparatus includes a transducer assembly containing a photoresistor for providing a range of electrical signals responsive to a range of X-ray beam intensities from the X-ray beam being aligned. A circuit, powered by a 7.5 VDC power supply and containing an audio frequency pulse generator whose frequency varies with the resistance of the photoresistor, is provided for generating a range of audible sounds. A portion of the audible range corresponds to low X-ray beam intensity. Another portion of the audible range corresponds to high X-ray beam intensity. The transducer assembly may include an a photoresistor, a thin layer of X-ray fluorescent material, and a filter layer transparent to X-rays but opaque to visible light. X-rays from the beam undergoing alignment penetrate the filter layer and excite the layer of fluorescent material. The light emitted from the fluorescent material alters the resistance of the photoresistor which is in the electrical circuit including the audio pulse generator and a speaker. In employing the apparatus, the X-ray beam is aligned to a complete alignment by adjusting the X-ray beam to produce an audible sound of the maximum frequency. 2 figures.

Steinmeyer, P.A.

1991-10-08

9

Area X-ray or UV camera system for high-intensity beams  

DOEpatents

A system in one embodiment includes a source for directing a beam of radiation at a sample; a multilayer mirror having a face oriented at an angle of less than 90 degrees from an axis of the beam from the source, the mirror reflecting at least a portion of the radiation after the beam encounters a sample; and a pixellated detector for detecting radiation reflected by the mirror. A method in a further embodiment includes directing a beam of radiation at a sample; reflecting at least some of the radiation diffracted by the sample; not reflecting at least a majority of the radiation that is not diffracted by the sample; and detecting at least some of the reflected radiation. A method in yet another embodiment includes directing a beam of radiation at a sample; reflecting at least some of the radiation diffracted by the sample using a multilayer mirror; and detecting at least some of the reflected radiation.

Chapman, Henry N. (Livermore, CA); Bajt, Sasa (Livermore, CA); Spiller, Eberhard A. (Livermore, CA); Hau-Riege, Stefan (Fremont, CA), Marchesini, Stefano (Oakland, CA)

2010-03-02

10

Relativistic self-focusing of ultra-high intensity X-ray laser beams in warm quantum plasma with upward density profile  

SciTech Connect

The results of a numerical study of high-intensity X-ray laser beam interaction with warm quantum plasma (WQP) are presented. By means of an upward ramp density profile combined with quantum factors specially the Fermi velocity, we have demonstrated significant relativistic self-focusing (RSF) of a Gaussian electromagnetic beam in the WQP where the Fermi temperature term in the dielectric function is important. For this purpose, we have considered the quantum hydrodynamics model that modifies refractive index of inhomogeneous WQPs with the inclusion of quantum correction through the quantum statistical and diffraction effects in the relativistic regime. Also, to better illustration of the physical difference between warm and cold quantum plasmas and their effect on the RSF, we have derived the envelope equation governing the spot size of X-ray laser beam in Q-plasmas. In addition to the upward ramp density profile, we have found that the quantum effects would be caused much higher oscillation and better focusing of X-ray laser beam in the WQP compared to that of cold quantum case. Our computational results reveal the importance of the use of electrons density profile and Fermi speed in enhancing self-focusing of laser beam.

Habibi, M., E-mail: habibi.physics@gmail.com [Young Researchers and Elite Club, Shirvan Branch, Islamic Azad University, Shirvan (Iran, Islamic Republic of); Ghamari, F. [Young Researchers and Elite Club, Khorramabad Branch, Islamic Azad University, Khorramabad (Iran, Islamic Republic of)

2014-05-15

11

X-ray beam pointer  

NASA Technical Reports Server (NTRS)

Inexpensive, readily assembled pointer aims X-ray machine for welded assembly radiographs. Plumb bob used for vertical alinement and yardstick used to visualize X-ray paths were inconvenient and inaccurate. Pointer cuts alinement time by one-half and eliminates necessity of retakes. For 3,000 weld radiographs, pointer will save 300 worker-hours and significant materials costs.

Nelson, C. W.

1980-01-01

12

The structural state of epitaxial ZnO layers assessed by measuring the integral intensity of three- and two-beam X-ray diffraction  

NASA Astrophysics Data System (ADS)

Three-beam X-ray diffraction (XRD) has been measured using the Renninger scheme in epitaxial ZnO layers with various thicknesses and degrees of crystal perfection. The integral intensity of three-beam XRD reflections has been analyzed and compared to that of two-beam reflections in the Bragg and Laue geometry. It is established that, for thin ZnO layers grown in the presence of excess oxygen, the integral intensity of three-beam diffraction peaks and Laue reflections is much smaller than that for layers of the same thickness grown in the presence of excess zinc. This fact is explained by the formation of a textured sublayer in the former case.

Kyutt, R. N.; Ivanov, S. V.

2014-10-01

13

Time-dependent, x-ray spectral unfolds and brightness temperatures for intense Li{sup +} ion beam-driven hohlraums  

SciTech Connect

X-ray-producing hohlraums are being studied as indirect drives for Inertial Confinement Fusion targets. In a 1994 target series on the PBFAII accelerator, cylindrical hohlraum targets were heated by an intense Li{sup +} ion beam and viewed by an array of 13 time-resolved, filtered x-ray detectors (XRDs). The UFO unfold code and its suite of auxiliary functions were used extensively in obtaining time- resolved x-ray spectra and radiation temperatures from this diagnostic. UFO was also used to obtain fitted response functions from calibration data, to simulate data from blackbody x-ray spectra of interest, to determine the suitability of various unfolding parameters (e.g., energy domain, energy partition, smoothing conditions, and basis functions), to interpolate the XRD signal traces, and to unfold experimental data. The simulation capabilities of the code were useful in understanding an anomalous feature in the unfolded spectra at low photon energies ({le} 100 eV). Uncertainties in the differential and energy-integrated unfolded spectra were estimated from uncertainties in the data. The time-history of the radiation temperature agreed well with independent calculations of the wall temperature in the hohlraum.

Fehl, D.L.; Chandler, G.A.; Biggs, F.; Dukart, R.J.; Moats, A.R.; Leeper, R.J.

1996-07-01

14

Time-dependent, x-ray spectral unfolds and brightness temperatures for intense Li{sup +} ion beam-driven hohlraums  

SciTech Connect

X-ray-producing hohlraums are being studied as indirect drives for inertial confinement fusion targets. In a 1994 target series on the PBFAII accelerator, cylindrical hohlraum targets were heated by an intense Li{sup +} ion beam and viewed by an array of 13 time-resolved, filtered x-ray detectors (XRDs). The unfold operator (UFO) code and its suite of auxiliary functions were used extensively in obtaining time-resolved x-ray spectra and radiation temperatures from this diagnostic. The UFO was also used to obtain fitted response functions from calibration data, to simulate data from blackbody x-ray spectra of interest, to determine the suitability of various unfolding parameters (e.g., energy domain, energy partition, smoothing conditions, and basis functions), to interpolate the XRD signal traces, and to unfold experimental data. The simulation capabilities of the code were useful in understanding an anomalous feature in the unfolded spectra at low photon energies ({le}100 eV). Uncertainties in the differential and energy-integrated unfolded spectra were estimated from uncertainties in the data. The time{endash}history of the radiation temperature agreed well with independent calculations of the wall temperature in the hohlraum. {copyright} {ital 1997 American Institute of Physics.}

Fehl, D.L.; Chandler, G.A.; Biggs, F.; Dukart, R.J.; Moats, A.R.; Leeper, R.J. [Sandia National Laboratories Albuquerque, New Mexico 87185 (United States)] [Sandia National Laboratories Albuquerque, New Mexico 87185 (United States)

1997-01-01

15

OBSERBATION OF HIGH INTENSITY X-RAYS IN INVERSE COMPTON SCATTERING EXPERIMENT  

E-print Network

OBSERBATION OF HIGH INTENSITY X-RAYS IN INVERSE COMPTON SCATTERING EXPERIMENT S. Kashiwagi, M the first results of high intensity x-ray generation using Inverse Laser Compton scattering. This experiment Facility (ATF) in September 1999.The ATF is an accelerator and beam physics user facility. The 3.5 ps x-ray

16

Proton induced quasi-monochromatic x-ray beams for soft x-ray spectroscopy studies and selective x-ray fluorescence analysis  

SciTech Connect

We present the analytical features and performance of an x-ray spectroscopy end station of moderate energy resolution operating with proton-induced quasi-monochromatic x-ray beams. The apparatus was designed, installed and operated at the 5.5 MV Tandem VdG Accelerator Laboratory of the Institute of Nuclear Physics, N.C.S.R. 'Demokritos,' Athens. The setup includes a two-level ultrahigh vacuum chamber that hosts in the lower level up to six primary targets in a rotatable holder; there, the irradiation of pure element materials-used as primary targets-with few-MeV high current ({approx}{mu}A) proton beams produces intense quasi-monochromatic x-ray beams of selectable energy. In the chamber's upper level, a six-position rotatable sample holder hosts the targets considered for x-ray spectroscopy studies. The proton-induced x-ray beam, after proper collimation, is guided to the sample position whereas various filters can be also inserted along the beam's path to eliminate the backscattered protons or/and to absorb selectively components of the x-ray beam. The apparatus incorporates an ultrathin window Si(Li) spectrometer (FWHM 136 eV at 5.89 keV) coupled with low-noise electronics capable of efficiently detecting photons down to carbon K{alpha}. Exemplary soft x-ray spectroscopy studies and results of selective x-ray fluorescence analysis are presented.

Sokaras, D. [Institute of Nuclear Physics, N.C.S.R. Demokritos, Aghia Paraskevi, 15310 Athens (Greece); Zarkadas, Ch. [PANalytical B.V., 7600 AA Almelo (Netherlands); Fliegauf, R.; Beckhoff, B. [Physikalisch-Technische Bundesanstalt, Abbestrasse 2-12, 10587 Berlin (Germany); Karydas, A. G. [Institute of Nuclear Physics, N.C.S.R. Demokritos, Aghia Paraskevi, 15310 Athens (Greece); Nuclear Spectrometry and Applications Laboratory, IAEA Laboratories, A-2444 Seibersdorf (Austria)

2012-12-15

17

Stripe pattern in the intensity profile of collimated soft x-ray beams caused by surface corrugation of the refocusing mirrors  

NASA Astrophysics Data System (ADS)

The effect of progress in surface finishing of optical components on the collimated-beam properties of soft x-ray beamlines at synchrotron radiation facilities is demonstrated: a stripe pattern, experimentally observed in the 2D intensity profile of beamlines with optical components manufactured 10-15 years ago, would be strongly attenuated if the existing refocusing mirror was replaced by an ultra-precise mirror manufactured with state-of-the-art of today surface finishing techniques. The observed stripe pattern is not caused by diffraction because its period length did not change with photon energy. Instead it can be explained with geometrical optics and is due to the height profile of the refocusing mirror which has been independently measured with a long trace profiler and used as an input in our raytracing simulations.

Schmitz, D.; Siewert, F.; Zeschke, T.

2015-02-01

18

Coherent X-ray Cherenkov radiation produced by microbunched beams  

NASA Astrophysics Data System (ADS)

Analytical and numerical results on the coherent X-ray Cherenkov radiation (CXCR) produced by microbunched beams in the region near the K-, L-edges of materials are obtained. The results show that CXCR can serve as a suitable mechanism for production intense beams of photons in the "water window" region as well as for studying the important microbunching process at FLASH TESLA, LCLS and other FELs.

Aginian, M. A.; Ispirian, K. A.; Ispiryan, M. K.; Ivanyan, M. I.

2014-05-01

19

Intensity measurements of a quasi-monochromatic X-ray beam formed by a spherically bent crystal  

Microsoft Academic Search

A quasi-monochromatic backlighting scheme for the diagnosis of laser-produced plasmas using spherically curved crystals to produce the monochromatic beam is proposed. Comparative flux measurements have been made of a variety of candidate backlighting materials using a spherically bent quartz [1010] crystal as the monochromaticising component. It is demonstrated that very bright quasi-monochromatic beams can be obtained with this crystal in

A. V. Rodé; A. M. Maksimchuk; G. V. Sklizkov; A. Ridgeley; C. Danson; N. Rizvi; R. Bann; E. Forster; I. Uschmann

1990-01-01

20

Calibrating X-ray Imaging Devices for Accurate Intensity Measurement  

SciTech Connect

The purpose of the project presented is to develop methods to accurately calibrate X-ray imaging devices. The approach was to develop X-ray source systems suitable for this endeavor and to develop methods to calibrate solid state detectors to measure source intensity. NSTec X-ray sources used for the absolute calibration of cameras are described, as well as the method of calibrating the source by calibrating the detectors. The work resulted in calibration measurements for several types of X-ray cameras. X-ray camera calibration measured efficiency and efficiency variation over the CCD. Camera types calibrated include: CCD, CID, back thinned (back illuminated), front illuminated.

Haugh, M. J.

2011-07-28

21

Standoff detection of hidden objects using backscattered ultra-intense laser-produced x-rays  

NASA Astrophysics Data System (ADS)

Ultra-intense laser-produced sub-ps X-ray pulses can detect backscattered signals from objects hidden in aluminium containers. Coincident measurements using primary X-rays enable differentiation among acrylic, copper, and lead blocks inside the container. Backscattering reveals the shapes of the objects, while their material composition can be identified from the modification methods of the energy spectra of backscattered X-ray beams. This achievement is an important step toward more effective homeland security.

Kuwabara, H.; Mori, Y.; Kitagawa, Y.

2013-08-01

22

Standoff detection of hidden objects using backscattered ultra-intense laser-produced x-rays  

SciTech Connect

Ultra-intense laser-produced sub-ps X-ray pulses can detect backscattered signals from objects hidden in aluminium containers. Coincident measurements using primary X-rays enable differentiation among acrylic, copper, and lead blocks inside the container. Backscattering reveals the shapes of the objects, while their material composition can be identified from the modification methods of the energy spectra of backscattered X-ray beams. This achievement is an important step toward more effective homeland security.

Kuwabara, H. [IHI Corporation, 1, Shin-Nakahara-cho, Isogo-ku, Yokohama 235-8501 (Japan)] [IHI Corporation, 1, Shin-Nakahara-cho, Isogo-ku, Yokohama 235-8501 (Japan); Mori, Y.; Kitagawa, Y. [The Graduate School for the Creation of New Photonics Industries, 1955-1 Kurematsucho, Nishiku, Hamamatsu, Shizuoka 431-1202 (Japan)] [The Graduate School for the Creation of New Photonics Industries, 1955-1 Kurematsucho, Nishiku, Hamamatsu, Shizuoka 431-1202 (Japan)

2013-08-28

23

1D X-ray Beam Compressing Monochromators  

SciTech Connect

A total beam compression of 5 and 10 corresponding to the asymmetry angles of 9 deg. and 12 deg. is achieved with V-5 and V-10 monochromators, respectively, in standard single crystal pure germanium (220) X-ray beam compressing (V-shaped) monochromators for CuKalpha{sub 1} radiation. A higher 1D compression of X-ray beam is possible using larger angles of asymmetry, however it is achieved at the expense of the total intensity, which is decreased due to the refraction effect. To increase the monochromator intensity, several ways are considered both theoretically and experimentally. Linearly graded germanium rich Ge{sub x}Si{sub (1-x)} single crystal was used to prepare a V-21 single crystal monochromator with 15 deg. asymmetry angles (compression factor of 21). Its temperature gradient version is discussed for CuKalpha{sub 1} radiation. X-ray diffraction measurements on the graded GeSi monochromator showed more than 3-times higher intensity at the output compared with that of a pure Ge monochromator.

Korytar, D.; Dobrocka, E.; Konopka, P.; Zaprazny, Z. [Institute of Electrical Engineering, SAS, Vrbovska cesta 110, SK 92101 Piest'any (Slovakia); Ferrari, C. [CNR IMEM Institute, Parma (Italy); Mikulik, P. [Masaryk University, Brno (Czech Republic); Vagovic, P. [ISS FZK Karlsruhe (Germany); Ac, V. [TnUAD Trencin (Slovakia); Erko, A. [Bessy Berlin (Germany); Abrosimov, N. [IKZ Berlin (Germany)

2010-04-06

24

New X-ray scattering-based beam position monitor for high power synchrotron radiation  

NASA Astrophysics Data System (ADS)

A new method of beam position monitoring for white synchrotron X-ray radiation has been developed. This method utilizes X-rays scattered from a graphite filter originally placed in the beam's path to absorb the low-energy portion of the white beam. The graphite filter acts as an optical source plane for scattered X-rays at the beam's footprint. The scattered X-rays exit the vacuum chamber and an image of the beam footprint is created using a pin-hole camera arrangement in combination with a phosphor screen and a CCD camera. The CCD camera records the image frames of the X-ray footprint from which a centroid position of the intensity is calculated. With proper calibration, the centroid position is easily converted to a beam position in microns. We have found that the intrinsic precision for determining the centroid position of an LED image of the camera system on an optical bench is about 0.06 microns. The new beam position monitor has been tested during a dedicated machine study when the X-ray beam position was changed by small amounts using local positron beam position controls. . The measurement error (standard deviation) of the actual X-ray beam position measurement was about 0.6 microns. In addition to providing beam position information the new device also provides vertical beam intensity profile and total beam intensity.

Revesz, Peter; Temnykh, Alexander B.; Pauling, Alan K.

2010-09-01

25

Experimental investigation of beam heating in a soft X-ray scanning transmission X-ray microscope  

E-print Network

Experimental investigation of beam heating in a soft X-ray scanning transmission X-ray microscope and an accuracy of �1 C has been fabricated for scanning transmission X-ray microscopes (STXM). Here we describe the current generation of soft X-ray (60­2500 eV) scan- ning transmission X-ray microscopes (STXM) to focus

Hitchcock, Adam P.

26

Multiwavelength Anomalous Diffraction at High X-Ray Intensity  

NASA Astrophysics Data System (ADS)

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

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

2011-11-01

27

Intense X-ray machine for penetrating radiography  

NASA Astrophysics Data System (ADS)

Penetrating radiography has been used for many years in the nuclear weapons research programs. Infrequently penetrating radiography has been used in conventional weapons research programs. For example the Los Alamos PHERMEX machine was used to view uranium rods penetrating steel for the GAU-8 program, and the Ector machine was used to see low density regions in forming metal jets. The armor/anti-armor program at Los Alamos has created a need for an intense flash X-ray machine that can be dedicated to conventional weapons research. The Balanced Technology Initiative, through DARPA, has funded the design and construction of such a machine at Los Alamos. It will be an 8- to 10-MeV diode machine capable of delivering a dose of 500 R at 1 m with a spot size of less than 5 mm. The machine used an 87.5-stage low inductance Marx generator that charges up a 7.4-(Omega), 32-ns water line. The water line is discharged through a self-breakdown oil switch into a 12.4-(Omega) water line that rings up the voltage into the high impendance X-ray diode. A long (233-cm) vacuum drift tube is used to separate the large diameter oil-insulated diode region from the X-ray source area that may be exposed to high overpressures by the explosive experiments. The electron beam is selffocused at the target area using a low pressure background gas.

Lucht, Roy A.; Eckhouse, Shimon

28

Thermal deformation of cryogenically cooled silicon crystals under intense X-ray beams: measurement and finite-element predictions of the surface shape  

PubMed Central

X-ray crystal monochromators exposed to white-beam X-rays in third-generation synchrotron light sources are subject to thermal deformations that must be minimized using an adequate cooling system. A new approach was used to measure the crystal shape profile and slope of several cryogenically cooled (liquid nitrogen) silicon monochromators as a function of beam power in situ and under heat load. The method utilizes multiple angular scans across the Bragg peak (rocking curve) at various vertical positions of a narrow-gap slit downstream from the monochromator. When increasing the beam power, the surface of the liquid-nitrogen-cooled silicon crystal deforms from a concave shape at low heat load to a convex shape at high heat load, passing through an approximately flat shape at intermediate heat load. Finite-element analysis is used to calculate the crystal thermal deformations. The simulated crystal profiles and slopes are in excellent agreement with experiments. The parameters used in simulations, such as material properties, absorbed power distribution on the crystal and cooling boundary conditions, are described in detail as they are fundamental for obtaining accurate results. PMID:23765298

Zhang, Lin; Sánchez del Río, Manuel; Monaco, Giulio; Detlefs, Carsten; Roth, Thomas; Chumakov, Aleksandr I.; Glatzel, Pieter

2013-01-01

29

Resonant Auger Effect at High X-Ray Intensity  

SciTech Connect

The resonant Auger effect of atomic neon exposed to high-intensity x-ray radiation in resonance with the 1s {yields} 3p transition is discussed. High intensity here means that the x-ray peak intensity is sufficient ({approx} 10{sup 18} W/cm{sup 2}) to induce Rabi oscillations between the neon ground state and the 1s{sup -1}3p ({sup 1}P) state within the relaxation lifetime of the inner-shell vacancy. For the numerical analysis presented, an effective two-level model, including a description of the resonant Auger decay process, is employed. Both coherent and chaotic x-ray pulses are treated. The latter are used to simulate radiation from x-ray free-electron lasers based on the principle of self-amplified spontaneous emission. Observing x-ray-driven atomic population dynamics in the time domain is challenging for chaotic pulse ensembles. A more practical option for experiments using x-ray free-electron lasers is to measure the line profiles in the kinetic energy distribution of the resonant Auger electron. This provides information on both atomic population dynamics and x-ray pulse properties.

Rohringer, N; Santra, R

2008-03-27

30

Resonant Auger effect at high x-ray intensity.  

SciTech Connect

The resonant Auger effect of atomic neon exposed to high-intensity x-ray radiation in resonance with the 1s {yields} 3p transition is discussed. High intensity here means that the x-ray peak intensity is sufficient ({approx}10{sup 18} W/cm{sup 2}) to induce Rabi oscillations between the neon ground state and the 1s {sup -1}3p ({sup 1}P) state within the relaxation lifetime of the inner-shell vacancy. For the numerical analysis presented, an effective two-level model, including a description of the resonant Auger decay process, is employed. Both coherent and chaotic x-ray pulses are treated. The latter are used to simulate radiation from x-ray free-electron lasers based on the principle of self-amplified spontaneous emission. Observing x-ray-driven atomic population dynamics in the time domain is challenging for chaotic pulse ensembles. A more practical option for experiments using x-ray free-electron lasers is to measure the line profiles in the kinetic energy distribution of the resonant Auger electron. This provides information on both atomic population dynamics and x-ray pulse properties.

Rohringer, N.; Santra, R.; Chemical Sciences and Engineering Division

2008-01-01

31

Intense x-ray machine for penetrating radiography  

SciTech Connect

Penetrating radiography has been used for many years in the nuclear weapons research programs. In frequently penetrating radiography has been used in conventional weapons research programs. For example the Los Alamos PHERMEX machine was used to view uranium rods penetrating steel for the GAU-8 program, and the Ector machine was used to see low-density regions in forming metal jets. The armor/anti-armor program at Los Alamos has created a need for an intense flash x-ray machine that can be dedicated to conventional weapons research. The Balanced Technology Initiative, through DARPA, has funded the design and construction of such a machine at Los Alamos. It will be an 8- to 10-MeV diode machine capable of delivering a dose of 500 R at 1 m with a spot size of less than 5 mm. The machine used an 87.5-stage low-inductance Marx generator that charges up a 7.4-/Omega/, 32-ns water line. The water line is discharged through a self-breakdown oil switch into a 12.4-/Omega/ water line that rings up the voltage into the high-impendance x-ray diode. A long (233-cm) vacuum drift tube is used to separate the large-diameter oil-insulated diode region from the x-ray source area that may be exposed to high overpressures by the explosive experiments. The electron beam is self-focused at the target area using a low-pressure background gas. 15 refs., 11 figs.

Lucht, R.A.; Eckhouse, S.

1989-01-01

32

Saturable absorption of intense hard X-rays in iron  

NASA Astrophysics Data System (ADS)

In 1913, Maurice de Broglie discovered the presence of X-ray absorption bands of silver and bromine in photographic emulsion. Over the following century, X-ray absorption spectroscopy was established as a standard basis for element analysis, and further applied to advanced investigation of the structures and electronic states of complex materials. Here we show the first observation of an X-ray-induced change of absorption spectra of the iron K-edge for 7.1-keV ultra-brilliant X-ray free-electron laser pulses with an extreme intensity of 1020?W?cm?2. The highly excited state yields a shift of the absorption edge and an increase of transparency by a factor of 10 with an improvement of the phase front of the transmitted X-rays. This finding, the saturable absorption of hard X-rays, opens a promising path for future innovations of X-ray science by enabling novel attosecond active optics, such as lasing and dynamical spatiotemporal control of X-rays.

Yoneda, Hitoki; Inubushi, Yuichi; Yabashi, Makina; Katayama, Tetsuo; Ishikawa, Tetsuya; Ohashi, Haruhiko; Yumoto, Hirokatsu; Yamauchi, Kazuto; Mimura, Hidekazu; Kitamura, Hikaru

2014-10-01

33

Saturable absorption of intense hard X-rays in iron.  

PubMed

In 1913, Maurice de Broglie discovered the presence of X-ray absorption bands of silver and bromine in photographic emulsion. Over the following century, X-ray absorption spectroscopy was established as a standard basis for element analysis, and further applied to advanced investigation of the structures and electronic states of complex materials. Here we show the first observation of an X-ray-induced change of absorption spectra of the iron K-edge for 7.1-keV ultra-brilliant X-ray free-electron laser pulses with an extreme intensity of 10(20)?W?cm(-2). The highly excited state yields a shift of the absorption edge and an increase of transparency by a factor of 10 with an improvement of the phase front of the transmitted X-rays. This finding, the saturable absorption of hard X-rays, opens a promising path for future innovations of X-ray science by enabling novel attosecond active optics, such as lasing and dynamical spatiotemporal control of X-rays. PMID:25270525

Yoneda, Hitoki; Inubushi, Yuichi; Yabashi, Makina; Katayama, Tetsuo; Ishikawa, Tetsuya; Ohashi, Haruhiko; Yumoto, Hirokatsu; Yamauchi, Kazuto; Mimura, Hidekazu; Kitamura, Hikaru

2014-01-01

34

Solar Intensity X-ray and particle Spectrometer (SIXS)  

NASA Astrophysics Data System (ADS)

The Solar Intensity X-ray and particle Spectrometer (SIXS) on the BepiColombo Mercury Planetary Orbiter (MPO) will investigate the direct solar X-rays, and energetic protons and electrons which pass the Spacecraft on their way to the surface of Mercury. These measurements are vitally important for understanding quantitatively the processes that make Mercury's surface glow in X-rays, since all X-rays from Mercury are due to interactions of the surface with incoming highly energetic photons and space particles. The X-ray emission of Mercury's surface will be analysed to understand its structure and composition. SIXS data will also be utilised for studies of the solar X-ray corona, flares, solar energetic particles, and the magnetosphere of Mercury, and for providing information on solar eruptions to other BepiColombo instruments. SIXS consists of two detector subsystems. The X-ray detector system includes three identical GaAs PIN detectors which measure the solar spectrum at 1-20 keV energy range, and their combined field-of-view covers ˜1/4 of the whole sky. The particle detector system consists of an assembly including a cubic central CsI(Tl) scintillator detector with five of its six surfaces covered by a thin Si detector, which together perform low-resolution particle spectroscopy with a rough angular resolution over a field-of-view covering ˜1/4 of the whole sky. The energy range of detected particle spectra is 0.1-3 MeV for electrons and 1-30 MeV for protons. A major task for the SIXS instrument is the measurement of solar X-rays on the dayside of Mercury's surface to enable modeling of X-ray fluorescence and scattering on the planet's surface. Since highly energetic particles are expected to also induce a significant amount of X-ray emission via particle-induced X-ray emission (PIXE) and bremsstrahlung when they are absorbed by the solid surface of the planet Mercury, SIXS performs measurements of fluxes and spectra of protons and electrons. SIXS performs particle measurement at all orbital phases of the MPO as the particle radiation can occur also on the night side of Mercury. The energy ranges, resolutions, and timings of X-ray and particle measurements by SIXS have been adjusted to match with the requirements for interpretation of data from Mercury's surface, to be performed by utilising the data of the Mercury Imaging X-ray Spectrometer (MIXS), which will measure X-ray emission from the surface.

Huovelin, J.; Vainio, R.; Andersson, H.; Valtonen, E.; Alha, L.; Mälkki, A.; Grande, M.; Fraser, G. W.; Kato, M.; Koskinen, H.; Muinonen, K.; Näränen, J.; Schmidt, W.; Syrjäsuo, M.; Anttila, M.; Vihavainen, T.; Kiuru, E.; Roos, M.; Peltonen, J.; Lehti, J.; Talvioja, M.; Portin, P.; Prydderch, M.

2010-01-01

35

The low intensity X-ray imaging scope /Lixiscope/  

NASA Technical Reports Server (NTRS)

A fully portable, small-format X-ray imaging system, Lixiscope (low intensity X-ray imaging scope) is described. In the prototype, which has been built to demonstrate the feasibility of the Lixiscope concept, only well-developed and available components have been used. Consideration is given to the principles of operation of the device, some of its performance characteristics as well as possible dental, medical and industrial applications.

Yin, L. I.; Trombka, J. I.; Seltzer, S. M.; Webber, R. L.; Farr, M. R.; Rennie, J.

1978-01-01

36

Laboratory-based micro-X-ray fluorescence setup using a von Hamos crystal spectrometer and a focused beam X-ray tube  

SciTech Connect

The high-resolution von Hamos bent crystal spectrometer of the University of Fribourg was upgraded with a focused X-ray beam source with the aim of performing micro-sized X-ray fluorescence (XRF) measurements in the laboratory. The focused X-ray beam source integrates a collimating optics mounted on a low-power micro-spot X-ray tube and a focusing polycapillary half-lens placed in front of the sample. The performances of the setup were probed in terms of spatial and energy resolution. In particular, the fluorescence intensity and energy resolution of the von Hamos spectrometer equipped with the novel micro-focused X-ray source and a standard high-power water-cooled X-ray tube were compared. The XRF analysis capability of the new setup was assessed by measuring the dopant distribution within the core of Er-doped SiO{sub 2} optical fibers.

Kayser, Y., E-mail: yves.kayser@psi.ch [Department of Physics, University of Fribourg, 1700 Fribourg (Switzerland); Paul Scherrer Institut, 5232 Villigen-PSI (Switzerland); B?achucki, W.; Dousse, J.-Cl.; Hoszowska, J. [Department of Physics, University of Fribourg, 1700 Fribourg (Switzerland)] [Department of Physics, University of Fribourg, 1700 Fribourg (Switzerland); Neff, M.; Romano, V. [Institute of Applied Physics, University of Bern, 3012 Bern (Switzerland)] [Institute of Applied Physics, University of Bern, 3012 Bern (Switzerland)

2014-04-15

37

X-ray beam size measurements on the Advanced Test Accelerator  

SciTech Connect

The electron beam size has been determined on the Advanced Test Accelerator (ATA) by intercepting the beam with a target and measuring the resulting x-ray intensity as a function of time as the target is moved through the beam. Several types of targets have been used. One is a tantalum rod which extends completely across the drift chamber. Another is a tungsten powder filled carbon crucible. Both of these probes are moved from shot to shot so that the x-ray signal intensity varies with probe position. A third is a larger tantalum disk which is inserted on beam axis to allow determining beam size on a one shot basis. The x-ray signals are detected with an MCP photomultiplier tube located at 90/sup 0/ to the beamline. It is sufficiently shielded to reject background x-rays and neutrons. The signals were digitized, recorded and later unfolded to produce plots of x-ray intensity versus probe position for several times during the pulse. The presumption that the x-ray intensity is proportional to beam current density is checked computationally. Details of the probe construction and PMT shielding, as well as sample measurements are given.

Struve, K.W.; Chambers, F.W.; Lauer, E.J.; Slaughter, D.R.

1986-01-01

38

Silicon single crystal as back-reflector for high-intensity hard x-rays  

NASA Astrophysics Data System (ADS)

At the Lawrence Livermore National Laboratory (LLNL) we have engineered a silicon prototype sample that can be used to reflect focused hard x-ray photons at high intensities in back-scattering geometry.1 Our work is motivated by the need for an all-x-ray pump-and-probe capability at X-ray Free Electron Lasers (XFELs) such as the Linac Coherent Light Source (LCSL) at SLAC. In the first phase of our project, we exposed silicon single crystal to the LCLS beam, and quantitatively studied the x-ray induced damage as a function of x-ray fluence. The damage we observed is extensive at fluences typical of pump-and-probe experiments. The conclusions drawn from our data allowed us to design and manufacture a silicon mirror that can limit the local damage, and reflect the incident beam before its single crystal structure is destroyed. In the second phase of this project we tested this prototype back-reflector at the LCLS. Preliminary results suggest that the new mirror geometry yields reproducible Bragg reflectivity at high x-ray fluences, promising a path forward for silicon single crystals as x-ray back-reflectors.

Pardini, Tom; Boutet, Sébastien; Bradley, Joseph; Doeppner, Tilo; Fletcher, Luke B.; Gardner, Dennis F.; Hill, Randy M.; Hunter, Mark S.; Krzywinski, Jacek; Messerschmidt, Marc; Pak, Arthur E.; Quirin, Florian; Sokolowski-Tinten, Klaus; Williams, Garth J.; Hau-Riege, Stefan P.

2014-09-01

39

Ultrafast absorption of intense x rays by nitrogen molecules.  

PubMed

We devise a theoretical description for the response of nitrogen molecules (N(2)) to ultrashort and intense x rays from the free electron laser Linac Coherent Light Source (LCLS). We set out from a rate-equation description for the x-ray absorption by a nitrogen atom. The equations are formulated using all one-x-ray-photon absorption cross sections and the Auger and radiative decay widths of multiply-ionized nitrogen atoms. Cross sections are obtained with a one-electron theory and decay widths are determined from ab initio computations using the Dirac-Hartree-Slater (DHS) method. We also calculate all binding and transition energies of nitrogen atoms in all charge states with the DHS method as the difference of two self-consistent field (SCF) calculations (?SCF method). To describe the interaction with N(2), a detailed investigation of intense x-ray-induced ionization and molecular fragmentation are carried out. As a figure of merit, we calculate ion yields and the average charge state measured in recent experiments at the LCLS. We use a series of phenomenological models of increasing sophistication to unravel the mechanisms of the interaction of x rays with N(2): a single atom, a symmetric-sharing model, and a fragmentation-matrix model are developed. The role of the formation and decay of single and double core holes, the metastable states of N(2)(2+), and molecular fragmentation are explained. PMID:22697546

Buth, Christian; Liu, Ji-Cai; Chen, Mau Hsiung; Cryan, James P; Fang, Li; Glownia, James M; Hoener, Matthias; Coffee, Ryan N; Berrah, Nora

2012-06-01

40

Large-distance refocusing of a submicrometre beam from an X-ray waveguide.  

PubMed

Among the several available X-ray optics for synchrotron radiation producing micrometre and submicrometre beams with high intensity, the X-ray waveguide (WG) can provide the smallest hard X-ray beam in one direction. A drawback of this optics is that, owing to the divergence at the exit, a nanometre-sized spot on the sample can only be obtained if this is within a few micrometres of the WG exit. Another limitation is that in planar WGs the beam is compressed in only one direction. Here, using a dynamically bent elliptical Si/Pt mirror, the guided X-ray beam has been refocused at approximately 1 m from the waveguide exit. The large working distance between the device and the submicrometre focus leaves some space for sample environment (vacuum chamber, furnace, cryostat, magnets, high-pressure device etc.) and allows cross-coupled geometries with two WGs for efficient compression in two directions. PMID:16371712

Lagomarsino, S; Bukreeva, I; Mocella, V; Surpi, A; Bigault, T; Cedola, A

2006-01-01

41

Initial estimation of the dose rates in a polycapillary focused X-ray beam based on determining the beam parameters  

NASA Astrophysics Data System (ADS)

This paper deals with estimating the dose rates achieved in materials irradiated by X-rays from an X-ray tube equipped with polycapillary focusing optics. The proposed method consists of determining the main parameters of the X-ray beam, e.g. the shape of the spectrum, the beam intensity, and the beam profile. All these parameters were obtained with a single spectrometric detector, and they were then employed in evaluating the dose rate. The maximum achievable dose rates in iron and water were determined analytically, and a numeric calculation using the Monte Carlo method provided the depth distribution of the energy deposited in these two materials.

Trojek, Tomáš; Trojková, Darina

2014-11-01

42

High intensity line source for x-ray spectrometer calibration  

SciTech Connect

A high intensity electron-impact x-ray source using a one-dimensional Pierce lens has been built for the purpose of calibrating a bent crystal x-ray spectrometer. This source focuses up to 100 mA of 20-keV electrons to a line on a liquid-cooled anode. The line (which can serve as a virtual slit for the spectrometer) measures approximately 800 ..mu.. x 2 cm. The source is portable and therefore adaptable to numerous types of spectrometer applications. One particular application, the calibration of a high resolution (r = 10/sup 4/) time-resolved cyrstal spectrometer, will be discussed in detail.

Thoe, R.S.

1986-06-01

43

Effect of an electron scattering cloud on X-ray oscillations produced by beaming  

NASA Technical Reports Server (NTRS)

The effect of a scattering cloud on the amplitude of oscillations produced by a rotating beam of X-rays is investigated using analytical and Monte Carlo methods. The scattering cloud was modeled as a uniform density sphere, and the source was represented as an anistropic distribution of radiation emerging from a point at the center of the scattering cloud. The intensity distribution produced by the source beam is examined as a function of optical depth. The relation between electron scattering optical depth and the forward-backward ratio is studied. It is observed that the scattering in a central corona of various optical depths reduces the amplitude of the oscillation. The data suggest that the quasi-periodic oscillations observed in the X-ray intensities of some luminous low-mass X-ray binaries are caused by oscillations in the luminosity of the X-ray star.

Brainerd, J.; Lamb, F. K.

1987-01-01

44

X-ray beam method for displacement measurement in hostile environments  

NASA Technical Reports Server (NTRS)

A new method of extensometry using an X-ray beam was devised, and the results of current testing reveal it to be highly feasible. This technique has been shown to provide a non-contacting system that is immune to problems associated with density variations in gaseous environments, that plague currently available optical methods. This advantage is a result of the non-refracting penetrating nature of X-rays. The method is based on X-ray-induced X-ray fluorescence of targets, which subsequently serve as fudicial markers. Some target materials have melting points over 1600 degrees C which will facilitate measurement at extremely high temperatures. A highly focused intense X-ray beam, which is produced using a Johansen 'bent crystal', is then scanned across the target, which responds by fluorescing X-rays when stimulated by the incident beam. This secondary radiation is monitored using a detector. By carefully measuring beam orientation, change in target edge position can be determined. Many variations on this basic theme are now possible such as two targets demarcating a gage length, or a beam shadowing method using opaque targets.

Jordan, Eric H.; Pease, D. M.; Canistraro, H.; Brew, Dale

1989-01-01

45

Interpretation of nanoparticle X-ray photoelectron intensities  

SciTech Connect

X-ray photoelectron (XPS) intensities have been simulated for spherical core-shell nanoparticles (NPs) in different geometrical arrangements in order to investigate the validity of commonly made assumptions for the interpretation of XPS NP intensities. The single-sphere approximation is valid for a powder sample when all spatial coordinates of the NP positions are uncorrelated. Correlations along either the depth coordinate or the lateral coordinates lead to features in the angular distribution that provide information on these correlations. The XPS intensity is proportional to the surface-to-volume ratio of nanoparticles but only for NP sizes exceeding the inelastic mean free path of the photoelectrons.

Werner, Wolfgang S. M., E-mail: werner@iap.tuwien.ac.at; Chudzicki, Maksymillian; Smekal, Werner [Institute of Applied Physics, Vienna University of Technology, Wiedner Hauptstraße 8-10, A-1040 Vienna (Austria); Powell, Cedric J. [Materials Measurement Science Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8370 (United States)

2014-06-16

46

Interpretation of nanoparticle X-ray photoelectron intensities  

NASA Astrophysics Data System (ADS)

X-ray photoelectron (XPS) intensities have been simulated for spherical core-shell nanoparticles (NPs) in different geometrical arrangements in order to investigate the validity of commonly made assumptions for the interpretation of XPS NP intensities. The single-sphere approximation is valid for a powder sample when all spatial coordinates of the NP positions are uncorrelated. Correlations along either the depth coordinate or the lateral coordinates lead to features in the angular distribution that provide information on these correlations. The XPS intensity is proportional to the surface-to-volume ratio of nanoparticles but only for NP sizes exceeding the inelastic mean free path of the photoelectrons.

Werner, Wolfgang S. M.; Chudzicki, Maksymillian; Smekal, Werner; Powell, Cedric J.

2014-06-01

47

Relationship between x-ray illumination field size and flat field intensity and its impacts on x-ray imaging  

SciTech Connect

Purpose: X-ray cone-beam CT (CBCT) is being increasingly used for various clinical applications, while its performance is still hindered by image artifacts. This work investigates a new source of reconstruction error, which is often overlooked in the current CBCT imaging. The authors find that the x-ray flat field intensity (I{sub 0}) varies significantly as the illumination volume size changes at different collimator settings. A wrong I{sub 0} value leads to inaccurate CT numbers of reconstructed images as well as wrong scatter measurements in the CBCT research. Methods: The authors argue that the finite size of x-ray focal spot together with the detector glare effect cause the I{sub 0} variation at different illumination sizes. Although the focal spot of commercial x-ray tubes typically has a nominal size of less than 1 mm, the off-focal-spot radiation covers an area of several millimeters on the tungsten target. Due to the large magnification factor from the field collimator to the detector, the penumbra effects of the collimator blades result in different I{sub 0} values for different illumination field sizes. Detector glare further increases the variation, since one pencil beam of incident x-ray is scattered into an area of several centimeters on the detector. In this paper, the authors study these two effects by measuring the focal spot distribution with a pinhole assembly and the detector point spread function (PSF) with an edge-spread function method. The authors then derive a formula to estimate the I{sub 0} value for different illumination field sizes, using the measured focal spot distribution and the detector PSF. Phantom studies are carried out to investigate the accuracy of scatter measurements and CT images with and without considering the I{sub 0} variation effects. Results: On our tabletop system with a Varian Paxscan 4030CB flat-panel detector and a Varian RAD-94 x-ray tube as used on a clinical CBCT system, the focal spot distribution has a measured full-width-at-half-maximum (FWHM) of around 0.4 mm, while non-negligible off-focal-spot radiation is observed at a distance of over 2 mm from the center. The measured detector PSF has an FWHM of 0.510 mm, with a shape close to Gaussian. From these two distributions, the author calculate the estimated I{sub 0} values at different collimator settings. The I{sub 0} variation mainly comes from the focal spot effect. The estimation matches well with the measurements at different collimator widths in both horizontal and vertical directions, with an average error of less than 3%. Our method improves the accuracy of conventional scatter measurements, where the scatter is measured as the difference between fan-beam and cone-beam projections. On a uniform water cylinder phantom, more accurate I{sub 0} suppresses the unfaithful high-frequency signals at the object boundaries of the measured scatter, and the SPR estimation error is reduced from 0.158 to 0.014. The proposed I{sub 0} estimation also reduces the reconstruction error from about 20 HU on the Catphan Copyright-Sign 600 phantom in the selected regions of interest to less than 4 HU. Conclusions: The I{sub 0} variation is identified as one additional error source in x-ray imaging. By measuring the focal-spot distribution and detector PSF, the authors propose an accurate method of estimating the I{sub 0} value for different illumination field sizes. The method obtains more accurate scatter measurements and therefore facilitates scatter correction algorithm designs. As correction methods for other CBCT artifacts become more successful, our research is significant in further improving the CBCT imaging accuracy.

Dong Xue; Niu Tianye; Jia Xun; Zhu Lei [Nuclear and Radiological Engineering and Medical Physics Programs, George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States); Department of Radiation Medicine and Applied Sciences, Center for Advanced Radiotherapy Technologies, University of California, San Diego, La Jolla, California 92093 (United States); Nuclear and Radiological Engineering and Medical Physics Programs, George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States)

2012-10-15

48

Generation and application of the soft X-ray laser beam based on capillary discharge  

NASA Astrophysics Data System (ADS)

In this work we report on the generation and characterization of a focused soft X-ray laser beam with intensity and energy density that exceed the threshold for the ablation of PMMA. We demonstrate a feasibility of direct ablation of holes using a focused soft X-ray laser beam. Ablated craters in PMMA/gold-covered-PMMA samples were obtained by focusing the soft X-ray Ar8+ laser pulses generated by a 46.9 nm tabletop capillary-discharge-pumped driver with a spherical Si/Sc multilayer mirror. It was found that the focused beam is capable by one shot to ablate PMMA, even if the focus is significantly influenced by astigmatism. Analysis of the laser beam footprints by atomic force microscope shows that ablated holes have periodic surface structure (similarly as Laser-Induced Periodic Surface Structure) with period ~2,8 ?m and with peak-to-peak depth ~5-10 nm.

Frolov, Oleksandr; Kolacek, Karel; Straus, Jaroslav; Schmidt, Jiri; Prukner, Vaclav; Shukurov, Andrey

2014-05-01

49

X-ray reference-intensity and X-ray fluorescence analyses of Salton Sea core  

Microsoft Academic Search

Quantitative X-ray powder diffraction (XRD) and X-ray transmission (XRT) procedures have been combined with X-ray fluorescence (XRF) and other spectroscopic methods to characterize the mineralogy and chemistry of 33 core samples obtained from the Salton Sea Scientific Drilling Program (SSSDP) well. Major mineral components in the SSSDP samples include quartz, orthoclase, sodic plagioclase, chlorite, epidote, illite, and calcite, with minor

B. L. Davis; C. K. Jr. Shearer; S. B. Simon; M. N. Spilde; J. J. Papike; J. C. Laul

2009-01-01

50

Development of polarized and monochromatic x-ray beams from tube sources  

NASA Astrophysics Data System (ADS)

The development of sources and optics has allowed the migration of techniques originally developed for synchrotron beam lines to field, industrial and clinical applications. For example, monochromatic beams produced with synchrotron sources are known to give higher contrast for mammography than clinical broadband sources. However, clinical sources with very narrow energy bandwidth, produced for example with flat monochromator crystals, tend to have limited intensity and field of view. Doubly curved crystal x-ray optics can provide intense focused monochromatic fan beams from laboratory x-ray tube sources. These optics are routinely employed in crystallography and x-ray fluorescence, however, careful analysis is required to assess whether the focused beam creates unacceptable divergence and hence poor spatial resolution in imaging. The intensity and resolution of the focused beam were measured and compared to simulation results. The measurements and simulations were in good agreement, allowing for system design to provide the required resolution. High efficiency collimating optics coupled with diffracting crystals also can produce relatively high intensity and resolution. For both methods, monochromatization occurs before the patient, resulting in a potential dose reduction as well as significant measured contrast enhancement. If the diffraction angle is chosen at 90 degrees, a polarized monochromatic beam is produced. While synchrotron sources are naturally polarized, polarized beams have been less accessible for field and clinical applications. Development has begun of polarized beam sources using very low power x-ray tubes coupled to polycapillary optics. The choice of the polarizing and analyzing crystals is a tradeoff between intensity and sensitivity to depolarization effects. Intensity and rocking curve measurements have been performed with matched silicon crystals and graphite crystals.

Schmitz, Robert; Bingölbali, Ayhan; Hussain, Abrar; MacDonald, C. A.

2008-08-01

51

Motorized Beam Alignment of a Commercial X-ray Diffractometer  

NASA Technical Reports Server (NTRS)

X-ray diffraction (XRD) is a powerful analysis method that allows researchers to noninvasively probe the crystalline structure of a material. This includes the ability to determine the crystalline phases present, quantify surface residual stresses, and measure the distribution of crystallographic orientations. The Structures and Materials Division at the NASA Glenn Research Center (GRC) heavily uses the on-site XRD lab to characterize advanced metal alloys, ceramics, and polymers. One of the x-ray diffractometers in the XRD lab (Bruker D8 Discover) uses three different x-ray tubes (Cu, Cr, and Mn) for optimal performance over numerous material types and various experimental techniques. This requires that the tubes be switched out and aligned between experiments. This alignment maximizes the x-ray tube s output through an iterative process involving four set screws. However, the output of the x-ray tube cannot be monitored during the adjustment process due to standard radiation safety engineering controls that prevent exposure to the x-ray beam when the diffractometer doors are open. Therefore, the adjustment process is a very tedious series of blind adjustments, each followed by measurement of the output beam using a PIN diode after the enclosure doors are shut. This process can take up to 4 hr to perform. This technical memorandum documents an in-house project to motorize this alignment process. Unlike a human, motors are not harmed by x-ray radiation of the energy range used in this instrument. Therefore, using motors to adjust the set screws will allow the researcher to monitor the x-ray tube s output while making interactive adjustments from outside the diffractometer. The motorized alignment system consists of four motors, a motor controller, and a hand-held user interface module. Our goal was to reduce the alignment time to less than 30 min. The time available was the 10-week span of the Lewis' Educational and Research Collaborative Internship Project (LERCIP) summer internship program and the budget goal was $1200. In this report, we will describe our motorization design and discuss the results of its implementation.

Van Zandt, Noah R.; Myers, James F.; Rogers, Richard B

2013-01-01

52

Photometry of Two Intense Low Mass X-Ray Binaries  

NASA Astrophysics Data System (ADS)

The intense galactic X-ray source GX349+2 (Sco X-2) belongs to the class of persistently bright low-mass X-ray binaries called Z-sources. GX349+2 has only recently been optically identified with a 19th mag star. Of the six known Z-sources, only two (Sco X-1 and Cyg X-2) have been studied in the optical. It has been suggested that Z-sources as a group are characterized by evolved companions and correspondingly long orbital periods (Sco X-1, P=0.8d; Cyg X-2, P=9.8d). Recently Southwell et al. have presented spectroscopic observations of GX349+2 suggesting a 14d orbital period. We have obtained broadband photometry of the system on six consecutive nights in May 1995, and find evidence for a 21.7 +/- 0.3hr period of 0.14 mag half-amplitude, superposed on erratic flickering typical of Sco X-1 type objects. As with other Z-sources, caution will be needed to insure that the variations are truly periodic, and not simply due to chaotic variability observed over a relatively short time span. If our period is confirmed, then the nature of the 14d spectroscopic variation found by Southwell et al. is unclear. GX13+1 is a bright X-ray burst source, located in the galactic bulge. Due to heavy obscuration, no optical counterpart brighter than R ~ 22 has been detected, but an infrared counterpart (K=12) has recently been identified by Naylor et al. (1991) based on spatial coincidence with an accurate radio position. GX13+1 is unusual as there is a disagreement over its classification. Studies of the X-ray time variability place it among the Atoll-sources. However, there is some evidence that the system contains a giant companion (Garcia et al. 1992) which would place it among the Z-sources. In an attempt to determine the period of the system, we observed GX13+1 for 9 days in May -- July 1995. Preliminary photometry confirms variability of ~ 0.4 mag on a timescale of several days, as previously discovered by Charles & Naylor (1992). If GX13+1 is found to have a large orbital period, it would be indicative of a giant companion, and thus challenge the distinction between Atoll- and Z-sources on the basis of orbital and evolutionary characteristics.

Wachter, S.; Margon, B.; Anderson, S.

1995-12-01

53

21 CFR 892.1610 - Diagnostic x-ray beam-limiting device.  

Code of Federal Regulations, 2010 CFR

...Diagnostic x-ray beam-limiting device. (a) Identification. A diagnostic x-ray beam-limiting device is a device such as a collimator, a cone...field by limiting the size of the primary x-ray beam. (b)...

2010-04-01

54

21 CFR 892.1610 - Diagnostic x-ray beam-limiting device.  

Code of Federal Regulations, 2013 CFR

...Diagnostic x-ray beam-limiting device. (a) Identification. A diagnostic x-ray beam-limiting device is a device such as a collimator, a cone...field by limiting the size of the primary x-ray beam. (b)...

2013-04-01

55

21 CFR 892.1610 - Diagnostic x-ray beam-limiting device.  

...Diagnostic x-ray beam-limiting device. (a) Identification. A diagnostic x-ray beam-limiting device is a device such as a collimator, a cone...field by limiting the size of the primary x-ray beam. (b)...

2014-04-01

56

21 CFR 892.1610 - Diagnostic x-ray beam-limiting device.  

Code of Federal Regulations, 2012 CFR

...Diagnostic x-ray beam-limiting device. (a) Identification. A diagnostic x-ray beam-limiting device is a device such as a collimator, a cone...field by limiting the size of the primary x-ray beam. (b)...

2012-04-01

57

21 CFR 892.1610 - Diagnostic x-ray beam-limiting device.  

Code of Federal Regulations, 2011 CFR

...Diagnostic x-ray beam-limiting device. (a) Identification. A diagnostic x-ray beam-limiting device is a device such as a collimator, a cone...field by limiting the size of the primary x-ray beam. (b)...

2011-04-01

58

A compact and portable X-ray beam position monitor using Medipix3  

NASA Astrophysics Data System (ADS)

The present work reports on the design and implementation of a novel portable X-ray beam diagnostics (XBPM) device. The device is transparent to the X-ray beam and provides real-time measurements of beam position, intensity, and size. The measurement principle is based on a pinhole camera which records scattered radiation from a Kapton foil which is placed in the beam path. The use of hybrid detectors (Medipix3) that feature a virtually noiseless readout system with capability of single photon detection and energy resolving power enables the diagnostics with a better resolution and higher sensitivity compared to the use of traditional indirect X-ray detection schemes. We describe the detailed system design, which consists of a vacuum compatible focal plane sensor array, a sensor conditioning and readout board and a heterogeneous data processing unit, which also acts as a network server that handles network communications with clients. The readout protocol for the Medipix3 sensor is implemented using field programmable gate array (FPGA) logic resulting in a versatile and scalable system that is capable of performing advanced functions such as data compression techniques and feature extraction. For the system performance measurements, we equipped the instrument with a single Medipix3 die, bump bonded to a Si sensor, rather than four for which it was designed. Without data compression, it is capable of acquiring magnified images and profiles of synchrotron X-ray beams at a transfer rate through Ethernet of 27 frames/s for one Medipix3 die.

Rico-Alvarez, O.; Kachatkou, A.; Marchal, J.; Willis, B.; Sawhney, K.; Tartoni, N.; van Silfhout, R. G.

2014-12-01

59

Calibration of a gated flat field spectrometer as a function of x-ray intensity  

SciTech Connect

We present an experimental determination of the response of a gated flat-field spectrometer at the Shenguang-II laser facility. X-rays were emitted from a target that was heated by laser beams and then were divided into different intensities with a step aluminum filter and collected by a spectrometer. The transmission of the filter was calibrated using the Beijing Synchrotron Radiation Facility. The response characteristics of the spectrometer were determined by comparing the counts recorded by the spectrometer with the relative intensities of the x-rays transmitted through the step aluminum filter. The response characteristics were used to correct the transmission from two shots of an opacity experiment using the same samples. The transmissions from the two shots are consistent with corrections, but discrepant without corrections.

Xiong, Gang; Yang, Guohong; Li, Hang; Zhang, Jiyan, E-mail: zhangjiyanzjy@sina.com; Zhao, Yang; Hu, Zhimin; Wei, Minxi; Qing, Bo; Yang, Jiamin; Liu, Shenye; Jiang, Shaoen [Research Center of Laser Fusion, China Academy of Engineering Physics, P. O. Box 919-986, Mianyang 621900 (China)] [Research Center of Laser Fusion, China Academy of Engineering Physics, P. O. Box 919-986, Mianyang 621900 (China)

2014-04-15

60

Editorial: Focus on X-ray Beams with High Coherence  

NASA Astrophysics Data System (ADS)

This editorial serves as the preface to a special issue of New Journal of Physics, which collects together solicited papers on a common subject, x-ray beams with high coherence. We summarize the issue's content, and explain why there is so much current interest both in the sources themselves and in the applications to the study of the structure of matter and its fluctuations (both spontaneous and driven). As this collection demonstrates, the field brings together accelerator physics in the design of new sources, particle physics in the design of detectors, and chemical and materials scientists who make use of the coherent beams produced. Focus on X-ray Beams with High Coherence Contents Femtosecond pulse x-ray imaging with a large field of view B Pfau, C M Günther, S Schaffert, R Mitzner, B Siemer, S Roling, H Zacharias, O Kutz, I Rudolph, R Treusch and S Eisebitt The FERMI@Elettra free-electron-laser source for coherent x-ray physics: photon properties, beam transport system and applications E Allaria, C Callegari, D Cocco, W M Fawley, M Kiskinova, C Masciovecchio and F Parmigiani Beyond simple exponential correlation functions and equilibrium dynamics in x-ray photon correlation spectroscopy Anders Madsen, Robert L Leheny, Hongyu Guo, Michael Sprung and Orsolya Czakkel The Coherent X-ray Imaging (CXI) instrument at the Linac Coherent Light Source (LCLS) Sébastien Boutet and Garth J Williams Dynamics and rheology under continuous shear flow studied by x-ray photon correlation spectroscopy Andrei Fluerasu, Pawel Kwasniewski, Chiara Caronna, Fanny Destremaut, Jean-Baptiste Salmon and Anders Madsen Exploration of crystal strains using coherent x-ray diffraction Wonsuk Cha, Sanghoon Song, Nak Cheon Jeong, Ross Harder, Kyung Byung Yoon, Ian K Robinson and Hyunjung Kim Coherence properties of the European XFEL G Geloni, E Saldin, L Samoylova, E Schneidmiller, H Sinn, Th Tschentscher and M Yurkov Fresnel coherent diffractive imaging: treatment and analysis of data G J Williams, H M Quiney, A G Peele and K A Nugent Imaging of complex density in silver nanocubes by coherent x-ray diffraction R Harder, M Liang, Y Sun, Y Xia and I K Robinson Methodology for studying strain inhomogeneities in polycrystalline thin films during in situ thermal loading using coherent x-ray diffraction N Vaxelaire, H Proudhon, S Labat, C Kirchlechner, J Keckes, V Jacques, S Ravy, S Forest and O Thomas Ptychographic coherent diffractive imaging of weakly scattering specimens Martin Dierolf, Pierre Thibault, Andreas Menzel, Cameron M Kewish, Konstantins Jefimovs, Ilme Schlichting, Konstanze von König, Oliver Bunk and Franz Pfeiffer Dose requirements for resolving a given feature in an object by coherent x-ray diffraction imaging Andreas Schropp and Christian G Schroer FLASH: new opportunities for (time-resolved) coherent imaging of nanostructures R Treusch and J Feldhaus Structure of a single particle from scattering by many particles randomly oriented about an axis: toward structure solution without crystallization? D K Saldin, V L Shneerson, M R Howells, S Marchesini, H N Chapman, M Bogan, D Shapiro, R A Kirian, U Weierstall, K E Schmidt and J C H Spence Analysis of strain and stacking faults in single nanowires using Bragg coherent diffraction imaging V Favre-Nicolin, F Mastropietro, J Eymery, D Camacho, Y M Niquet, B M Borg, M E Messing, L-E Wernersson, R E Algra, E P A M Bakkers, T H Metzger, R Harder and I K Robinson Coherent science at the SwissFEL x-ray laser B D Patterson, R Abela, H-H Braun, U Flechsig, R Ganter, Y Kim, E Kirk, A Oppelt, M Pedrozzi, S Reiche, L Rivkin, Th Schmidt, B Schmitt, V N Strocov, S Tsujino and A F Wrulich Energy recovery linac (ERL) coherent hard x-ray sources Donald H Bilderback, Joel D Brock, Darren S Dale, Kenneth D Finkelstein, Mark A Pfeifer and Sol M Gruner Statistical and coherence properties of radiation from x-ray free-electron lasers E L Saldin, E A Schneidmiller and M V Yurkov Microscopic return point memory in Co/Pd multilayer films K A Seu, R Su, S Roy, D Parks, E Shipton, E E Fullerton and S D Kevan Hol

Robinson, Ian; Gruebel, Gerhard; Mochrie, Simon

2010-03-01

61

X-ray pencil beam facility for optics characterization  

NASA Astrophysics Data System (ADS)

The Physikalisch-Technische Bundesanstalt (PTB) has used synchrotron radiation for the characterization of optics and detectors for astrophysical X-ray telescopes for more than 20 years. At a dedicated beamline at BESSY II, a monochromatic pencil beam is used by ESA and cosine Research since the end of 2005 for the characterization of novel silicon pore optics, currently under development for the International X-ray Observatory (IXO). At this beamline, a photon energy of 2.8 keV is selected by a Si channel-cut monochromator. Two apertures at distances of 12.2 m and 30.5 m from the dipole source form a pencil beam with a typical diameter of 100 ?m and a divergence below 1". The optics to be investigated is placed in a vacuum chamber on a hexapod, the angular positioning is controlled by means of autocollimators to below 1". The reflected beam is registered at 5 m distance from the optics with a CCD-based camera system. This contribution presents design and performance of the upgrade of this beamline to cope with the updated design for IXO. The distance between optics and detector can now be 20 m. For double reflection from an X-ray Optical Unit (XOU) and incidence angles up to 1.4°, this corresponds to a vertical translation of the camera by 2 m. To achieve high reflectance at this angle even with uncoated silicon, a lower photon energy of 1 keV is available from a pair of W/B4C multilayers. For coated optics, a high energy option can provide a pencil beam of 7.6 keV radiation.

Krumrey, Michael; Cibik, Levent; Müller, Peter; Bavdaz, Marcos; Wille, Eric; Ackermann, Marcelo; Collon, Maximilien J.

2010-07-01

62

Wavefront aberrations of x-ray dynamical diffraction beams.  

PubMed

The effects of dynamical diffraction in x-ray diffractive optics with large numerical aperture render the wavefront aberrations difficult to describe using the aberration polynomials, yet knowledge of them plays an important role in a vast variety of scientific problems ranging from optical testing to adaptive optics. Although the diffraction theory of optical aberrations was established decades ago, its application in the area of x-ray dynamical diffraction theory (DDT) is still lacking. Here, we conduct a theoretical study on the aberration properties of x-ray dynamical diffraction beams. By treating the modulus of the complex envelope as the amplitude weight function in the orthogonalization procedure, we generalize the nonrecursive matrix method for the determination of orthonormal aberration polynomials, wherein Zernike DDT and Legendre DDT polynomials are proposed. As an example, we investigate the aberration evolution inside a tilted multilayer Laue lens. The corresponding Legendre DDT polynomials are obtained numerically, which represent balanced aberrations yielding minimum variance of the classical aberrations of an anamorphic optical system. The balancing of classical aberrations and their standard deviations are discussed. We also present the Strehl ratio of the primary and secondary balanced aberrations. PMID:25322219

Liao, Keliang; Hong, Youli; Sheng, Weifan

2014-10-01

63

An experimental measurement of metal multilayer x-ray reflectivity degradation due to intense x-ray flux  

SciTech Connect

The degradation of the x-ray reflection characteristics of metal multilayer Bragg diffractors due to intense x-ray flux was investigated. The Z-pinch plasma produced by PROTO II of Sandia National Laboratories, Albuquerque, New Mexico, was used as the source. The plasma generated total x-ray yields of as much as 40 kJ with up to 15 kJ in the neon hydrogen- and helium-like resonance lines in nominal 20-ns pulses. Molybdenum-carbon, palladium-carbon, and tungsten-carbon metal multilayers were placed at 15 and 150 cm from the plasma center. The multilayers were at nominal angles of 5/sup 0/ and 10/sup 0/ to diffract the neon resonance lines. The time-integrated x-ray reflection of the metal multilayers was monitored by x-ray film. A fluorescer-fiber optic-visible streak camera detector system was then used to monitor the time-resolved x-ray reflection characteristics of 135 A- 2d tungsten-carbon multilayers. A large specular component in the reflectivity prevented determination of the rocking curve of the multilayer. For a neon implosion onto a vanadium-doped polyacrylic acid foam target shot, detailed modeling was attempted. The spectral flux was determined with data from 5 XRD channels and deconvolved using the code SHAZAM. The observed decay in reflectivity was assumed to correspond to the melting of the first tungsten layer. A ''conduction factor'' of 82 was required to manipulate the heat loading of the first tungsten layer such that the time of melting corresponded to the observed decay. The power at destruction was 141 MW/cm/sup 2/ and the integrated energy at destruction was 2.0 J/cm/sup 2/. 82 refs., 66 figs., 10 tabs.

Hockaday, M.Y.P.

1987-06-01

64

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

65

Electromagnetic-field distribution measurements in the soft x-ray range: full characterization of a soft x-ray laser beam.  

PubMed

We report direct measurement of the electromagnetic-field spatial distribution in a neonlike Ar capillary discharge-driven soft x-ray laser beam. The wave front was fully characterized in a single shot using a Shack-Hartmann diffractive optics sensor. The wave front was observed to be dependent on the discharge pressure and capillary length, as a result of beam refraction variations in the capillary plasma. The results predict approximately 70% of the laser beam energy can be focused into an area 4 times the size of the diffraction-limited spot, reaching intensities of approximately 4 x 10(13) W/cm(2). PMID:12005683

Le Pape, S; Zeitoun, Ph; Idir, M; Dhez, P; Rocca, J J; François, M

2002-05-01

66

Monte Carlo simulator of realistic x-ray beam for diagnostic applications  

SciTech Connect

Purpose: Monte Carlo simulation is a very useful tool for radiotherapy and diagnostic radiology. Yet even with the latest PCs, simulation of photon spectra emitted by an x-ray tube is a time-consuming task, potentially reducing the possibility to obtain relevant data such as dose evaluations, simulation of geometric settings, or monitor detector efficiency. This study developed and validated a method to generate random numbers for realistic beams in terms of photon spectrum and intensity to simulate x-ray tubes via Monte Carlo algorithms. Methods: Starting from literature data, the most common semiempirical models of bremsstrahlung are analyzed and implemented, adjusting their formulation to describe a large irradiation area (i.e., large field of view) and to take account of the heel effect as in common practice during patient examinations. Results: Simulation results show that Birch and Marshall's model is the fastest and most accurate for the aims of this work. Correction of the geometric size of the beam and validation of the intensity variation (heel effect) yielded excellent results with differences between experimental and simulated data of less than 6%. Conclusions: The results of validation and execution time showed that the tube simulator calculates the x-ray photons quickly and efficiently and is perfectly capable of considering all the phenomena occurring in a real beam (total filtration, focal spot size, and heel effect), so it can be used in a wide range of applications such as industry, medical physics, or quality assurance.

Bontempi, Marco; Andreani, Lucia; Rossi, Pier Luca; Visani, Andrea [Biomechanics Laboratory, Istituto Ortopedico Rizzoli, via di Barbiano 1/10, 40136 Bologna (Italy); Department of Physics, University of Bologna, viale Berti Pichat 6/2, 40137 Bologna (Italy); Biomechanics Laboratory, Istituto Ortopedico Rizzoli, via di Barbiano 1/10, 40136 Bologna (Italy)

2010-08-15

67

Hiresmon: A Fast High Resolution Beam Position Monitor for Medium Hard and Hard X-Rays  

NASA Astrophysics Data System (ADS)

The high-resolution x-ray beam position monitor (XBPM) is based on the principle of a segmented longitudinal ionization chamber with integrated readout and USB2 link. In contrast to traditional transversal ionization chambers here the incident x-rays are parallel to the collecting field which allows absolute intensity measurements with a precision better than 0.3 %. Simultaneously the beam position in vertical and horizontal direction can be measured with a frame rate of one kHz. The precision of position encoding depends only on the SNR of the synchrotron radiation and is in the order of micro meters at one kHz frame rate and 108 photon /sec at 9 KeV.

Menk, Ralf Hendrik; Giuressi, Dario; Arfelli, Fulvia; Rigon, Luigi

2007-01-01

68

A technique for calibrating an electron-beam evaporator x-ray source  

Microsoft Academic Search

An electron-beam metal evaporator was modified to act as an x-ray source for simulating x-ray lithography induced radiation damage in semiconductor devices. Besides x-rays, such a set-up generates secondary and backscattered electrons. Simulation of radiation damage induced during a typical x-ray lithography processing step requires that secondary and backscattered electrons be removed from the incident radiation. A common method to

Robert J. Kinzig

1991-01-01

69

Unveiling and Driving Hidden Resonances with High-Fluence, High-Intensity X-Ray Pulses  

SciTech Connect

We show that high fluence, high-intensity x-ray pulses from the world's first hard x-ray free-electron laser produce nonlinear phenomena that differ dramatically from the linear x-ray-matter interaction processes that are encountered at synchrotron x-ray sources. We use intense x-ray pulses of sub-10-fs duration to first reveal and subsequently drive the 1s{r_reversible}2p resonance in singly ionized neon. This photon-driven cycling of an inner-shell electron modifies the Auger decay process, as evidenced by line shape modification. Our work demonstrates the propensity of high-fluence, femtosecond x-ray pulses to alter the target within a single pulse, i.e., to unveil hidden resonances, by cracking open inner shells energetically inaccessible via single-photon absorption, and to consequently trigger damaging electron cascades at unexpectedly low photon energies.

Kanter, E. P.; Kraessig, B.; Li, Y.; March, A. M.; Ho, P.; Southworth, S. H.; Young, L. [Argonne National Laboratory, Argonne, Illinois 60439 (United States); Rohringer, N. [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States); Max Planck Institute for the Physics of Complex Systems, 01187 Dresden (Germany); Max Planck Advanced Study Group, Center for Free-Electron Laser Science, DESY, Notkestrasse 85, 22607 Hamburg (Germany); Kavli Institute for Theoretical Physics, University of California, Santa Barbara, California 93106 (United States); Santra, R. [Argonne National Laboratory, Argonne, Illinois 60439 (United States); Center for Free-Electron Laser Science, DESY, Notkestrasse 85, 22607 Hamburg (Germany); Department of Physics, University of Hamburg, Jungiusstrasse 9, 20355 Hamburg (Germany); Kavli Institute for Theoretical Physics, University of California, Santa Barbara, California 93106 (United States); DiMauro, L. F.; Doumy, G.; Roedig, C. A. [Ohio State University, Columbus, Ohio 43210 (United States); Berrah, N.; Fang, L.; Hoener, M. [Western Michigan University, Kalamazoo, Michigan 49008 (United States); Bucksbaum, P. H.; Ghimire, S.; Reis, D. A. [PULSE Center, SLAC, Menlo Park, California 94025 (United States); Bozek, J. D.; Bostedt, C. [Linac Coherent Light Source, SLAC, Menlo Park, California 94025 (United States)

2011-12-02

70

Experimental measurement of metal multilayer x-ray reflectivity degradation due to intense x-ray flux  

SciTech Connect

The degradation of the x-ray reflection characteristics of metal multilayer Bragg diffractors due to intense x-ray flux was investigated. The Z-pinch plasma produced by PROTO II of Sandia National Laboratories, Albuquerque, New Mexico, was used as the source. The plasma generated total x-ray yields of as much as 40 kJ with up to 15 kJ in the neon-, hydrogen-, and helium-like resonance lines in nominal 20-ns pulses. Molybdenum-carbon, palladium-carbon, and tungsten-carbon metal multilayers were placed at 50 and 150 cm from the plasma center. The multilayers were at nominal angels of 5/sup 0/ and 10/sup 0/ to diffract the neon resonance lines. The time-integated x-ray reflection of the metal multilayers was monitored by x-ray film. Data for two separate shots were analyzed. For a pure neon gas shot at a power level of 420 TW, the reflectivity of the multilayer at 15 cm decayed rapidly with respect to the still-rising signal of the multilayer at 150 cm. The onset time of the decay corresponded to an integrated dose of 5.27 J/cm/sup 2/. For a neon implosion onto a vanadium-doped polyacrylic acid foam target shot, detailed modeling was attempted. The spectral flux was determined with data from 5 XRD channels and deconvolved using the code SHAZAM. The observed decay in reflectivity was assumed to correspond to the melting of the first tungsten layer.

Hockaday, M.Y.

1986-01-01

71

Asymmetrically cut crystal pair as x-ray magnifier for imaging at high intensity laser facilities  

Microsoft Academic Search

The potential of an x-ray magnifier prepared from a pair of asymmetrically cut crystals is studied to explore high energy x-ray imaging capabilities at high intensity laser facilities. OMEGA-EP and NIF when irradiating mid and high Z targets can be a source of high-energy x-rays whose production mechanisms and use as backlighters are a subject of active research. This paper

C. I. Szabo; U. Feldman; J. F. Seely; J. J. Curry; L. T. Hudson; A. Henins

2010-01-01

72

Fluoroscopic visualization of megavoltage therapeutic x ray beams  

SciTech Connect

A large flat screen-low light level TV-fluoroscopic system having a 43 cm x 43 cm input screen has been used to monitor patients undergoing radiation therapy with megavoltage treatment beams. This article illustrates some preliminary results obtained for /sup 60/Co and 6 Mv x rays. Portals covering the head, the supraclavicular region, the chest, and pelvic regions have been imaged. The live video images clearly show heart, lung, and diaphragm motion. Except in the pelvis, anatomical structures are clearly demonstrated. Permanent recordings are made either on video tape or video disk. The corresponding verification films are shown in each instance. Improved image quality can easily be obtained with improved hardware. The video images are easily enhanced by special analogue circuitry which is available at reasonable cost.

Baily, N.A.; Horn, R.A.; Kampp, T.D.

1980-07-01

73

Time Integrated Soft X-ray Imaging in High Intensity Laser Experiments (thesis)  

SciTech Connect

2009 marks a significant achievement and the dawn of a new era in high intensity laser research with the final commissioning of all 192 beams at the National Ignition Facility (NIF). NIF is a department of energy (DOE) funded project more than 10 years in the making located at the Lawrence Livermore National Laboratory (LLNL). The following research was done as one of many preliminary experiments done to prepare for these historic events. The primary focus of the experimental campaign this paper addresses is to test and develop a thermal x-radiation source using a short pulse laser. This data is hoped to provide information about the thermal transport mechanisms important in the development of prediction models in High Energy Density (HED) science. One of several diagnostics fielded was a soft x-ray imager (SXRI) which is detailed in this paper. The SXRI will be used to measure the relative size of the heated region and also the relative level of specific x-ray emissions among several shot and target configurations. The laser system used was the Titan laser located in the Jupiter Laser Facility (JLF) at Lawrence Livermore National Laboratory (LLNL). Titan uses the JLF Janus Nd:glass laser west frontend system with a Optical Parametric Chirped Pulse Amplification (OPCPA) in place of the nanosecond oscillator. The system is capable of producing laser intensities of over a petawatt with several tens of joules delivered in the beam.

Stafford, D

2009-06-01

74

Divergence measurements of soft x-ray laser beam  

SciTech Connect

The divergence of the CVI 182 A lasing line generated in a rapidly recombining, magnetically confined plasma column was measured using soft x-ray spectrometers equipped with multichannel detectors. In addition to measurements of the relative divergence, an absolute divergence of approx.9 mrad at a magnetic field of 20 kG and approx.5 mrad at a magnetic field of 35 or 50 kG was obtained by a direct scan of the 182 A axial radiation. Based on this data a peak 182 A intensity of approx.100 kW is obtained. Calculations of the spatial distribution of gain in the plasma were in very good agreement with the experimental data.

Suckewer, S.; Skinner, C.H.; Kim, D.; Valeo, E.; Voorhees, D.; Wouters, A.

1986-07-01

75

Studying planetary matter using intense x-ray pulses  

NASA Astrophysics Data System (ADS)

Free-electron laser facilities enable new applications in the field of high-pressure research including planetary materials. The European x-ray Free Electron Laser (European XFEL) in Hamburg, Germany will start user operation in 2017 and will provide photon energies of up to 25 keV. The high-energy density science instrument (HED) is one of the six baseline instruments at the European XFEL. It is dedicated to the study of dense material at strong excitation in a temperature range from eV to keV and pressures >100 GPa which is equivalent to an energy density >100 J mm?3. It will enable studying structural and electronic properties of excited states with hard x-rays. The instrument is currently in its technical design phase and first user experiments are foreseen for summer 2017. In this contribution, we present the x-ray instrumentation and foreseen x-ray techniques at HED and concentrate on prototype hard-condensed matter experiments in the field of planetary research as proposed during recent user consortium meetings for this instrument. These include quasi-isentropic (ramped) compression and shock compression experiments.

Appel, K.; Nakatsutsumi, M.; Pelka, A.; Priebe, G.; Thorpe, I.; Tschentscher, Th

2015-01-01

76

A Experimental Measurement of Metal Multilayer X-Ray Reflectivity Degradation due to Intense X-Ray Flux.  

NASA Astrophysics Data System (ADS)

The degradation of the x-ray reflection characteristics of metal multilayer Bragg diffractors due to intense x -ray flux was investigated. The Z-pinch plasma produced by PROTO II of Sandia National Laboratories, Albuquerque, New Mexico, was used as the source. The plasma generated total x-ray yields of as much as 40 kJ with up to 15 kJ in the neon hydrogen- and helium-like resonance lines in nominal 20-ns pulses. Molybdenum-carbon, paladium-carbon, and tungsten -carbon metal multilayers were placed at 15 and 150 cm from the plasma center. The multilayers were at nominal angles of 5(DEGREES) and 10(DEGREES) to diffract the neon resonance lines. The time-integrated x-ray reflection of the metal multilayers was monitored by x-ray film. A fluorescer -fiber optic-visible streak camera detector system was then used to monitor the time-resolved x-ray reflection characteristics of 135 (ANGSTROM)- 2d tungsten-carbon multilayers. A large specular component in the reflectivity prevented determination of the rocking curve of the multilayer. Data for two separate shots were analyzed. For a pure neon gas shot at a power level of 420 TW, the reflectivity of the multilayer at 15 cm decayed rapidly with respect to the still-rising signal of the multilayer at 150 cm. The onset time of the decay corresponded to an integrated dose of 5.27 J/cm('2). For a neon implosion onto a vanadium-doped polyacrylic acid foam target shot, detailed modeling was attempted. The spectral flux was determined with data from 5 XRD channels and deconvolved using the code SHAZAM. The observed decay in reflectivity was assumed to correspond to the melting of the first tungsten layer. A "conduction factor" of 82 was required to manipulate the heat loading of the first tungsten layer such that the time of melting corresponded to the observed decay. The power at destruction was 141 MW/cm('2) and the integrated energy at destruction was 2.0 J/cm('2).

Hockaday, Mary Yvonne Pottenger

77

Nano-optical elements fabricated by e-beam and x-ray lithography  

Microsoft Academic Search

In this paper we report results obtained in the design and fabrication of diffractive optical elements (DOEs) with minimum feature size down to tens of nanometers by the use of e-beam and x-ray lithography. The DOEs are patterned using e-beam lithography and replicated by x-ray lithography. Since in our days there is an increased interest for extreme ultraviolet and x-ray

Enzo M. Di Fabrizio; Dan Cojoc; Stefano Cabrini; Luca Businaro; Matteo Altissimo; Lisa Vaccari; Filippo Romanato; Radu Malureanu; Burkhard Kaulich; Thomas Wilhein; Jean Susini

2003-01-01

78

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

79

X-ray computed tomography for structural ceramic applications: Beam hardening corrections  

Microsoft Academic Search

Beam hardening (BH), caused by the energy dependence of x-ray attenuation in materials, reduces the reliability of images generated by computed tomographic (CT) when polychromatic x-ray sources are used. The magnitude of the BH effect was calculated, and four different approaches to BH correction for CT imaging of ceramics were investigated: the ''water bag'' approach, prehardening of the beam by

W. A. Ellingson; E. Segal; M. W. Vannier

1987-01-01

80

Thirty-Meter X-Ray Pencil Beam Line at the Institute of Space and Astronautical Science  

Microsoft Academic Search

A 30-m-long X-ray beam line has been built at the Institute of Space and Astronautical Science (ISAS) to evaluate the performance of X-ray optical instruments for space programs, in particular for the X-ray telescope onboard the Astro-D (Asca) satellite. This beam line consists of an X-ray generator, a 30-m-long vacuum duct, and measuring chambers. Strong and stable X-ray pencil beams

Hideyo Kunieda; Yoshiyuki Tsusaka; Hisanori Suzuki; Yasushi Ogasaka; Hisamitsu Awaki; Yuzuru Tawara; Koujun Yamashita; Takashi Yamazaki; Masayuki Itoh; Tsuneo Kii; Fumiyoshi Makino; Yoshiaki Ogawara; Hiroshi Tsunemi; Kiyoshi Hayashida; Susumu Nomoto; Mikio Wada; Emi Miyata; Isamu Hatsukade

1993-01-01

81

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

82

Ion beam induced surface graphitization of CVD diamond for x-ray beam position monitor applications  

SciTech Connect

The Advanced Photon Source at ANL is a third-generation synchrotron facility that generates powerful x-ray beams on its undulator beamlines. It is important to know the position and angle of the x- ray beam during experiments. Due to very high heat flux levels, several patented x-ray beam position monitors (XBPM) exploiting chemical vapor deposition (CVD) diamond have been developed. These XBPMs have a thin layer of low-atomic-mass metallic coating so that photoemission from the x rays generate a minute but measurable current for position determination. Graphitization of the CVD diamond surface creates a very thin, intrinsic and conducting layer that can stand much higher temperatures and minimal x-ray transmission losses compared to the coated metallic layers. In this paper, a laboratory sputter ion source was used to transform selected surfaces of a CVD diamond substrate into graphite. The effect of 1-5 keV argon ion bombardment on CVD diamond surfaces at various target temperatures from 200 to 500 C was studied using Auger electron spectroscopy and in-situ electrical resistivity measurements. Graphitization after the ion bombardment has been confirmed and optimum conditions for graphitization studied. Raman spectroscopy was used to identify the overall diamond structure in the bulk of CVD diamond substrate after the ion bombardments. It was found that target temperature plays an important role in stability and electrical conductivity of the irradiated CVD diamonds.

Liu, Chian; Shu, D.; Kuzay, T.M. [Argonne National Lab, IL (United States). Advanced Photon Source; Wen, L.; Melendres, C.A. [Argonne National Lab., IL (United States). Materials Science Div.]|[Argonne National Lab., IL (United States). Chemical Technology Div.

1996-12-31

83

Combined measurement of X-ray photon correlation spectroscopy and diffracted X-ray tracking using pink beam X-rays.  

PubMed

Combined X-ray photon correlation spectroscopy (XPCS) and diffracted X-ray tracking (DXT) measurements of carbon-black nanocrystals embedded in styrene-butadiene rubber were performed. From the intensity fluctuation of speckle patterns in a small-angle scattering region (XPCS), dynamical information relating to the translational motion can be obtained, and the rotational motion is observed through the changes in the positions of DXT diffraction spots. Graphitized carbon-black nanocrystals in unvulcanized styrene-butadiene rubber showed an apparent discrepancy between their translational and rotational motions; this result seems to support a stress-relaxation model for the origin of super-diffusive particle motion that is widely observed in nanocolloidal systems. Combined measurements using these two techniques will give new insights into nanoscopic dynamics, and will be useful as a microrheology technique. PMID:23955045

Shinohara, Yuya; Watanabe, Akira; Kishimoto, Hiroyuki; Amemiya, Yoshiyuki

2013-09-01

84

Flash imaging of fine structures of cellular organelles by contact x-ray microscopy with a high intensity laser plasma x-ray source  

NASA Astrophysics Data System (ADS)

X-ray flash imaging by contact microscopy with a highly intense laser-plasma x-ray source was achieved for the observation of wet biological cells. The exposure time to obtain a single x-ray image was about 600 ps as determined by the pulse duration of the driving laser pulse. The x-ray flash imaging makes it possible to capture an x-ray image of living biological cells without any artificial treatment such as staining, fixation, freezing, and so on. The biological cells were cultivated directly on the surface of the silicon nitride membranes, which are used for the x-ray microscope. Before exposing the cells to x-rays they were observed by a conventional fluorescent microscope as reference, since the fluorescent microscopes can visualize specific organelles stained with fluorescent dye. Comparing the x-ray images with the fluorescent images of the exact same cells, each cellular organelle observed in the x-ray images was identified one by one and actin filaments and mitochondria were clearly identified in the x-ray images.

Kado, Masataka; Ishino, Masahiko; Kishimoto, Maki; Tamotsu, Satoshi; Yasuda, Keiko; Kinjo, Yasuhito; Shinohara, Kunio

2011-09-01

85

Calibration of X-ray Imaging Devices for Accurate Intensity Measurement  

SciTech Connect

National Security Technologies (NSTec) has developed calibration procedures for X-ray imaging systems using NIST traceable sources. The X-ray sources that are used for calibration are both diode type and diode/fluorescer combinations. Calibrating the X-ray detectors is the key to accurate calibration of the X-ray sources. Both energy dispersive detectors and photodiodes measuring total flux were used. We have developed calibration techniques for the detectors using radioactive sources that are traceable to the National Institute of Standards and Technology (NIST). The German synchrotron at Physikalische Technische Bundestalt (PTB) is used to calibrate silicon photodiodes over the energy range from 50 eV to 60 keV. The measurements on X-ray cameras made using the NSTec X-ray sources have included the quantum efficiency averaged over all pixels, the camera counts per photon per pixel, and response variation across the sensor. The instrumentation required to accomplish the calibrations is described. X-ray energies ranged from 720 eV to 22.7 keV. The X-ray sources produce narrow energy bands, allowing us to determine the properties as a function of X-ray energy. The calibrations were done for several types of imaging devices. There were back illuminated and front illuminated CCD (charge coupled device) sensors, and a CID (charge injection device) type camera. The CCD and CID camera types differ significantly in some of their properties that affect the accuracy of X-ray intensity measurements. All cameras discussed here are silicon based. The measurements of quantum efficiency variation with X-ray energy are compared to models for the sensor structure. Cameras that are not back-thinned are compared to those that are.

Haugh, M. J., Charest, M., Ross, P., Lee, J. Schneider, M., Palmer, N., Teruya,

2012-06-01

86

X-ray acoustic computed tomography with pulsed x-ray beam from a medical linear accelerator  

PubMed Central

Purpose: The feasibility of medical imaging using a medical linear accelerator to generate acoustic waves is investigated. This modality, x-ray acoustic computed tomography (XACT), has the potential to enable deeper tissue penetration in tissue than photoacoustic tomography via laser excitation. Methods: Short pulsed (?s-range) 10 MV x-ray beams with dose-rate of approximately 30 Gy/min were generated from a medical linear accelerator. The acoustic signals were collected with an ultrasound transducer (500 KHz central frequency) positioned around an object. The transducer, driven by a computer-controlled step motor to scan around the object, detected the resulting acoustic signals in the imaging plane at each scanning position. A pulse preamplifier, with a bandwidth of 20 KHz–2 MHz at ?3 dB, and switchable gains of 40 and 60 dB, received the signals from the transducer and delivered the amplified signals to a secondary amplifier. The secondary amplifier had bandwidth of 20 KHz–30 MHz at ?3 dB, and a gain range of 10–60 dB. Signals were recorded and averaged 128 times by an oscilloscope. A sampling rate of 100 MHz was used to record 2500 data points at each view angle. One set of data incorporated 200 positions as the receiver moved 360°. The x-ray generated acoustic image was then reconstructed with the filtered back projection algorithm. Results: The x-ray generated acoustic signals were detected from a lead rod embedded in a chicken breast tissue. The authors found that the acoustic signal was proportional to the x-ray dose deposition, with a correlation of 0.998. The two-dimensional XACT images of the lead rod embedded in chicken breast tissue were found to be in good agreement with the shape of the object. Conclusions: The first x-ray acoustic computed tomography image is presented. The new modality may be useful for a number of applications, such as providing the location of a fiducial, or monitoring x-ray dose distribution during radiation therapy. Although much work is needed to improve the image quality of XACT and to explore its performance in other irradiation energies, the benefits of this modality, as highlighted in this work, encourage further study. PMID:23298069

Xiang, Liangzhong; Han, Bin; Carpenter, Colin; Pratx, Guillem; Kuang, Yu; Xing, Lei

2013-01-01

87

Structured x-ray beams from twisted electrons by inverse Compton scattering of laser light  

E-print Network

The inverse Compton scattering of laser light on high-energetic twisted electrons is investigated with the aim to construct spatially structured x-ray beams. In particular, we analyze how the properties of the twisted electrons, such as the topological charge and aperture angle of the electron Bessel beam, affects the energy and angular distribution of scattered x-rays. We show that with suitably chosen initial twisted electron states one can synthesize tailor-made x-ray beam profiles with a well-defined spatial structure, in a way not possible with ordinary plane-wave electron beams.

D. Seipt; A. Surzhykov; S. Fritzsche

2014-07-28

88

Fluctuation of laser-induced x-rays from electron beam and plasma  

Microsoft Academic Search

There has been a significant progress in the X-ray generation technologies for various laboratory and production application by laser-Compton scheme and laser produced plasma. Femtosecond X-ray generation was performed by Compton scattering through interaction between a 3-ps electron beam and 100-fs laser photons in a 90 degree scattering configuration. The X-ray energy and pulse duration were estimated as 2.3keV and

Akira Endo

2003-01-01

89

In situ micro-focused X-ray beam characterization with a lensless camera using a hybrid pixel detector  

PubMed Central

Results of studies on micro-focused X-ray beam diagnostics using an X-ray beam imaging (XBI) instrument based on the idea of recording radiation scattered from a thin foil of a low-Z material with a lensless camera are reported. The XBI instrument captures magnified images of the scattering region within the foil as illuminated by the incident beam. These images contain information about beam size, beam position and beam intensity that is extracted during dedicated signal processing steps. In this work the use of the device with beams for which the beam size is significantly smaller than that of a single detector pixel is explored. The performance of the XBI device equipped with a state-of-the-art hybrid pixel X-ray imaging sensor is analysed. Compared with traditional methods such as slit edge or wire scanners, the XBI micro-focused beam characterization is significantly faster and does not interfere with on-going experiments. The challenges associated with measuring micrometre-sized beams are described and ways of optimizing the resolution of beam position and size measurements of the XBI instrument are discussed. PMID:24562554

Kachatkou, Anton; Marchal, Julien; van Silfhout, Roelof

2014-01-01

90

An active optics system for EUV/soft x-ray beam shaping  

NASA Astrophysics Data System (ADS)

FERMI@Elettra is a VUV/Soft X-ray Free Electron Laser (FEL) user facility under commissioning in Trieste, Italy. It provides a spatially coherent transform-limited photon beam in the sub-ps regime with high fluence and tunable wavelength. One of the FERMI beamlines, TIMEX, will be dedicated to the study of matter under extreme and metastable conditions, created and probed by the FEL radiation. Moreover, an active optics dedicated to perform the beam shaping at focus is needed in order to provide the necessary flat-top intensity distribution for heating the sample uniformly. In this work the principles of the beam shaping applied to the TIMEX beamline will be discussed as well as the adopted solution. Ray tracing simulations will be shown for theoretical mirror profiles as well as the metrological measurements with an interferometer and the Long Trace Profiler (LTP).

Svetina, C.; Cocco, D.; Di Cicco, A.; Fava, C.; Gerusina, S.; Gobessi, R.; Mahne, N.; Masciovecchio, C.; Principi, E.; Raimondi, L.; Rumiz, L.; Sergo, R.; Sostero, G.; Spiga, D.; Zangrando, M.

2012-10-01

91

Evaluation of a beam-spot camera for megavoltage x rays  

SciTech Connect

A beam-spot camera for measurements of x-ray focal spots of accelerators has been evaluated. The device consists of closely packed 0.25-mm-thick lead and 0.25-mm-thick cardboard strips. It is placed on radiographic film with the lamellae parallel to the beam axis and an exposure made. The images were scanned with a microdensitometer. The results indicate that the broadening of the source intensity profile at half maximum is of the order 1 mm, which permits the use of the beam-spot camera for acceptance testing and quality control. Longer tails in the density profile limit the quantitative information that can be extracted from the images.

Lutz, W.R.; Maleki, N.; Bjaerngard, B.E.

1988-07-01

92

A calculation model for primary intensity distributions from cylindrically symmetric x-ray lenses.  

PubMed

A calculation model for the quantitative prediction of primary intensity fluence distributions obtained by the Bragg diffraction focusing of kilovoltage radiation by cylindrical x-ray lenses is presented. The mathematical formalism describes primary intensity distributions from cylindrically-symmetric x-ray lenses, with a planar isotropic radiation source located in a plane perpendicular to the lens axis. The presence of attenuating medium inserted between the lens and the lens focus is accounted for by energy-dependent attenuation. The influence of radiation scattered within the media is ignored. Intensity patterns are modeled under the assumption that photons that are not interacting with the lens are blocked out at any point of interest. The main characteristics of the proposed calculation procedure are that (i) the application of vector formalism allows universal treatment of all cylindrical lenses without the need of explicit geometric constructs; (ii) intensity distributions resulting from x-ray diffraction are described by a 3D generalization of the mosaic spread concept; (iii) the calculation model can be immediately coupled to x-ray diffraction simulation packages such as XOP and Shadow. Numerical simulations based on this model are to facilitate the design of focused orthovoltage treatment (FOT) systems employing cylindrical x-ray lenses, by providing insight about the influence of the x-ray source and lens parameters on quantities of dosimetric interest to radiation therapy. PMID:18199899

Hristov, Dimitre; Maltz, Jonathan

2008-02-01

93

A calculation model for primary intensity distributions from cylindrically symmetric x-ray lenses  

NASA Astrophysics Data System (ADS)

A calculation model for the quantitative prediction of primary intensity fluence distributions obtained by the Bragg diffraction focusing of kilovoltage radiation by cylindrical x-ray lenses is presented. The mathematical formalism describes primary intensity distributions from cylindrically-symmetric x-ray lenses, with a planar isotropic radiation source located in a plane perpendicular to the lens axis. The presence of attenuating medium inserted between the lens and the lens focus is accounted for by energy-dependent attenuation. The influence of radiation scattered within the media is ignored. Intensity patterns are modeled under the assumption that photons that are not interacting with the lens are blocked out at any point of interest. The main characteristics of the proposed calculation procedure are that (i) the application of vector formalism allows universal treatment of all cylindrical lenses without the need of explicit geometric constructs; (ii) intensity distributions resulting from x-ray diffraction are described by a 3D generalization of the mosaic spread concept; (iii) the calculation model can be immediately coupled to x-ray diffraction simulation packages such as XOP and Shadow. Numerical simulations based on this model are to facilitate the design of focused orthovoltage treatment (FOT) systems employing cylindrical x-ray lenses, by providing insight about the influence of the x-ray source and lens parameters on quantities of dosimetric interest to radiation therapy.

Hristov, Dimitre; Maltz, Jonathan

2008-02-01

94

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

95

Generation and application of a high-average-power polarized soft-x-ray laser beam  

E-print Network

demonstrate the generation of a highly polarized soft-x-ray beam with a compact high-repetition-rate table generated by compact tabletop sources has the potential to affect numerous other applications. © 2001 have also been con- ducted with polarized soft-x-ray radiation from laser- produced plasmas.2

Rocca, Jorge J.

96

The effect of exit beam phase aberrations on parallel beam coherent x-ray reconstructions  

SciTech Connect

Diffraction artifacts from imperfect x-ray windows near the sample are an important consideration in the design of coherent x-ray diffraction measurements. In this study, we used simulated and experimental diffraction patterns in two and three dimensions to explore the effect of phase imperfections in a beryllium window (such as a void or inclusion) on the convergence behavior of phasing algorithms and on the ultimate reconstruction. A predictive relationship between beam wavelength, sample size, and window position was derived to explain the dependence of reconstruction quality on beryllium defect size. Defects corresponding to this prediction cause the most damage to the sample exit wave and induce signature error oscillations during phasing that can be used as a fingerprint of experimental x-ray window artifacts. The relationship between x-ray window imperfection size and coherent x-ray diffractive imaging reconstruction quality explored in this work can play an important role in designing high-resolution in situ coherent imaging instrumentation and will help interpret the phasing behavior of coherent diffraction measured in these in situ environments.

Hruszkewycz, S. O.; Fuoss, P. H. [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Harder, R.; Xiao, X. [X-Ray Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States)

2010-12-15

97

The effect of exit beam phase aberrations on parallel beam coherent x-ray reconstructions.  

SciTech Connect

Diffraction artifacts from imperfect x-ray windows near the sample are an important consideration in the design of coherent x-ray diffraction measurements. In this study, we used simulated and experimental diffraction patterns in two and three dimensions to explore the effect of phase imperfections in a beryllium window (such as a void or inclusion) on the convergence behavior of phasing algorithms and on the ultimate reconstruction. A predictive relationship between beam wavelength, sample size, and window position was derived to explain the dependence of reconstruction quality on beryllium defect size. Defects corresponding to this prediction cause the most damage to the sample exit wave and induce signature error oscillations during phasing that can be used as a fingerprint of experimental x-ray window artifacts. The relationship between x-ray window imperfection size and coherent x-ray diffractive imaging reconstruction quality explored in this work can play an important role in designing high-resolution in situ coherent imaging instrumentation and will help interpret the phasing behavior of coherent diffraction measured in these in situ environments.

Hruszkewycz, S. O.; Harder, R.; Xiao, X.; Fuoss, P. H. (Materials Science Division); ( XSD)

2010-12-01

98

A technique for calibrating an electron-beam evaporator x-ray source  

Microsoft Academic Search

An electron-beam metal evaporator was modified to act as an x-ray source for simulating x-ray lithography induced radiation\\u000a damage in semiconductor devices. Besides x-rays, such a set-up generates secondary and backscattered electrons. Simulation\\u000a of radiation damage induced during a typical x-ray lithography processing step requires that secondary and backscattered electrons\\u000a be removed from the incident radiation. A common method to

Robert J. Kinzig

1991-01-01

99

X-ray QPOs from the Ultra-luminous X-ray Source in M82: Evidence Against Beaming  

NASA Technical Reports Server (NTRS)

We report the discovery with the European Photon Imaging Camera (EPIC) CCD cameras onboard XMM-Newton of a 54 mHz quasiperiodic oscillation (QPO) in the greater than 2 keV X-ray flux from the ultra-luminous X-ray source (ULX) X41.4+60 in the starburst galaxy M82. This is the first detection of a QPO in the X-ray flux from an extra-Galactic ULX, and confirms that the source is a compact object. The QPO is detected in the combined PN and MOS data at the approx. 6sigma level, and separately at lower significances in both the PN and MOS instruments. It had a centroid frequency of 54.3 +/- 0.9 mHz, a coherence Q is identical with nu(sub 0)/Delta nu(sub fwhm) is approx. 5, and an amplitude (rms) in the 2 - 10 keV band of 8.5%. Below about 0.2 Hz the power spectrum can be described by a power-law with index approx. 1, and integrated amplitude (rms) of 13.5%. The X-ray spectrum requires a curving continuum, with a disk-blackbody (diskbb) at T = 3.1 keV providing an acceptable, but not unique, fit. A broad Fe line centered at 6.55 keV is required in all fits, but the equivalent width (EW) of the line is sensitive to the choice of continuum model. There is no evidence of a reflection component. The implied bolometric luminosity is approx. 4 - 5 x 10(exp 40) ergs/s. Data from several archival Rossi X-ray Timing Explorer (RXTE) pointings at M82 also show evidence for QPOs in the 50 - 100 mHz frequency range. Several Galactic black hole candidates (BHCs), including GRS 1915+105, GRO J1655-40, and XTE 1550-564, show QPOs in the same frequency range as the 50 - 100 mHz QPOs in X41.4+60, which at first glance suggests a possible connection with such objects. However, strong, narrow QPOs provide solid evidence for disk emission, and thus present enormous theoretical difficulties for models which rely on either geometrically or relativistically beamed emission to account for the high X-ray luminosities. We discuss the implications of our findings for models of the ULX sources.

Strohmayer, Tod E.; Mushotzky, Richard F.

2003-01-01

100

X-ray lithography source  

DOEpatents

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

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

1991-12-31

101

Modulation of hard x-ray beam profiles by Borrmann pyramid  

SciTech Connect

Spatial modulation of hard x-ray beam profiles is reported, using the 'Borrmann pyramid' formed in dual Bragg diffraction of a single crystal, where a small angular change of the incident beam is magnified to span the entire pyramid base. As an attempt, it is demonstrated using hard x rays by (1) the linear shift of a micrometer sized mask; (2) the partial blockade of a two micron beam; and (3) the millimeter shadow of a nanoscale gold strip, which shows the potential application of Borrmann pyramids in the form of an enlarged x-ray image.

Xu, G. [Materials Science and Engineering, McMaster University, Hamilton, Ontario L8S 4L7 (Canada); Britten, J. [Chemistry Department, McMaster University, Hamilton, Ontario L8S 4L8 (Canada)

2008-01-15

102

77 FR 12226 - Sadex Corp.; Filing of Food Additive Petition (Animal Use); Electron Beam and X-Ray Sources for...  

Federal Register 2010, 2011, 2012, 2013

...Petition (Animal Use); Electron Beam and X-Ray Sources for Irradiation of Poultry Feed...for the safe use of electron beam and x-ray sources for irradiation of poultry feed...for the safe use of electron beam and x- ray sources for irradiation of poultry...

2012-02-29

103

Calculated X-ray Intensities Using Monte Carlo Algorithms: A Comparison to Experimental EPMA Data  

NASA Technical Reports Server (NTRS)

Monte Carlo (MC) modeling has been used extensively to simulate electron scattering and x-ray emission from complex geometries. Here are presented comparisons between MC results and experimental electron-probe microanalysis (EPMA) measurements as well as phi(rhoz) correction algorithms. Experimental EPMA measurements made on NIST SRM 481 (AgAu) and 482 (CuAu) alloys, at a range of accelerating potential and instrument take-off angles, represent a formal microanalysis data set that has been widely used to develop phi(rhoz) correction algorithms. X-ray intensity data produced by MC simulations represents an independent test of both experimental and phi(rhoz) correction algorithms. The alpha-factor method has previously been used to evaluate systematic errors in the analysis of semiconductor and silicate minerals, and is used here to compare the accuracy of experimental and MC-calculated x-ray data. X-ray intensities calculated by MC are used to generate a-factors using the certificated compositions in the CuAu binary relative to pure Cu and Au standards. MC simulations are obtained using the NIST, WinCasino, and WinXray algorithms; derived x-ray intensities have a built-in atomic number correction, and are further corrected for absorption and characteristic fluorescence using the PAP phi(rhoz) correction algorithm. The Penelope code additionally simulates both characteristic and continuum x-ray fluorescence and thus requires no further correction for use in calculating alpha-factors.

Carpenter, P. K.

2005-01-01

104

Spectrum bandwidth narrowing of Thomson scattering X-rays with energy chirped electron beams from laser wakefield acceleration  

SciTech Connect

We study incoherent Thomson scattering between an ultrashort laser pulse and an electron beam accelerated from a laser wakefield. The energy chirp effects of the accelerated electron beam on the final radiation spectrum bandwidth are investigated. It is found that the scattered X-ray radiation has the minimum spectrum width and highest intensity as electrons are accelerated up to around the dephasing point. Furthermore, it is proposed that the electron acceleration process inside the wakefield can be studied by use of 90° Thomson scattering. The dephasing position and beam energy chirp can be deduced from the intensity and bandwidth of the scattered radiation.

Xu, Tong; Chen, Min, E-mail: minchen@sjtu.edu.cn; Li, Fei-Yu; Yu, Lu-Le [Key Laboratory for Laser Plasmas (Ministry of Education), Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China)] [Key Laboratory for Laser Plasmas (Ministry of Education), Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China); Sheng, Zheng-Ming, E-mail: zmsheng@sjtu.edu.cn [Key Laboratory for Laser Plasmas (Ministry of Education), Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China) [Key Laboratory for Laser Plasmas (Ministry of Education), Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China); SUPA, Department of Physics, University of Strathclyde, Glasgow G4 0NG (United Kingdom); Zhang, Jie [Key Laboratory for Laser Plasmas (Ministry of Education), Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China) [Key Laboratory for Laser Plasmas (Ministry of Education), Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China); Beijing National Laboratory of Condensed Matter Physics, Institute of Physics, CAS, Beijing 100190 (China)

2014-01-06

105

Properties of intense quasi-monochromatic X rays produced by resonant transition radiation  

NASA Astrophysics Data System (ADS)

To develop the possibilities of resonant transition radiation (RTR) as an intense quasi-monochromatic X-ray source, we have measured energy spectra and angular distributions of the RTR X rays emitted from Kapton- and silicon-foil stacks by varying the number of foils, foil thickness, and spacing between adjacent foils. The intensity of RTR X rays increases nonlinearly with the number of foils in case of 12.5-?m thick Kapton- and silicon-foil stacks. The energy of the RTR X rays can be tuned by changing only the thickness of the foil and will be defined well when the X rays are sliced at a fixed emission angle. The obtained brilliance of 1.4×1012photons/(s?mrad2?mm2?0.1%b.w.?mA) for the peak energy of 6.7-keV X rays is comparable to those of synchrotron radiation (SR) emitted by using bending magnets in GeV-electron facilities.

Awata, T.; Yajima, K.; Tanaka, T.; Imai, M.; Itoh, A.; Imanishi, N.; Yoshida, K.; Nakayama, K.; Potylitsin, A. P.

1997-02-01

106

Beam based calibration of X-ray pinhole camera in SSRF  

E-print Network

The Shanghai Synchrotron Radiation Facility (SSRF) contains a 3.5-GeV storage ring serving as a national X-ray synchrotron radiation user facility characterized by a low emittance and a low coupling. The stability and quality of the electron beams are monitored continuously by an array of diagnostics. In particular, an X-ray pinhole camera is employed in the diagnostics beamline of the ring to characterize the position, size, and emittance of the beam. The performance of the measurement of the transverse electron beam size is given by the width of the point spread function (PSF) of the X-ray pinhole camera. Typically the point spread function of the X-ray pinhole camera is calculated via analytical or numerical method. In this paper we will introduce a new beam based calibration method to derive the width of the PSF online.

Yong-Bin Leng; Guo-Qing Huang; Man-Zhou Zhang; Zhi-Chu Chen; Jie Chen; Kai-Rong Ye

2011-03-25

107

Beam collimation with polycapillary x-ray optics for high contrast high resolution monochromatic imaging.  

PubMed

Monochromatic imaging can provide better contrast and resolution than conventional broadband radiography. In broadband systems, low energy photons do not contribute to the image, but are merely absorbed, while high energy photons produce scattering that degrades the image. By tuning to the optimal energy, one can eliminate undesirable lower and higher energies. Monochromatization is achieved by diffraction from a single crystal. A crystal oriented to diffract at a particular energy, in this case the characteristic line energy, diffracts only those photons within a narrow range of angles. The resultant beam from a divergent source is nearly parallel, but not very intense. To increase the intensity, collimation was performed with polycapillary x-ray optics, which can collect radiation from a divergent source and redirect it into a quasi parallel beam. Contrast and resolution measurements were performed with diffracting crystals with both high and low angular acceptance. Testing was first done at 8 keV with an intense copper rotating anode x-ray source, then 17.5 keV measurements were made with a low power molybdenum source. At 8 keV, subject contrast was a factor of five higher than for the polychromatic case. At 17.5 keV, monochromatic contrast was two times greater than the conventional polychromatic contrast. The subject contrasts measured at both energies were in good agreement with theory. An additional factor of two increase in contrast, for a total gain of four, is expected at 17.5 keV from the removal of scatter. Scatter might be simply removed using an air gap, which does not degrade resolution with a parallel beam. PMID:15651611

Sugiro, Francisca R; Li, Danhong; MacDonald, C A

2004-12-01

108

Using DCM pitch modulation and feedback to improve long term X-ray beam stability  

NASA Astrophysics Data System (ADS)

In this paper we demonstrate significant improvements to the stability of the monochromatic X-ray beam intensity on several beamlines at Diamond, using a modulation of the pitch axis of the DCM with a piezoelectric actuator. The modulation is detected on an intensity diagnostic (e.g. an ion chamber) using a software lock-in technique. The detected amplitude and phase are used in a feedback to keep the DCM at the peak of the rocking curve, or any arbitrary position 'off-peak' which might be desired to detune the DCM and reject unwanted harmonics. A major advantage of this software based system is the great flexibility offered, using standard, readily available instrumentation. Measurements of the short and long-term performance of the feedback on several beamlines are presented, and the limitations of such a feedback are discussed.

Bloomer, C.; Dent, A.; Diaz-Moreno, S.; Dolbnya, I.; Pedersen, U.; Rehm, G.; Tang, C.; Thomas, C.

2013-03-01

109

Variations in skin dose using 6MV or 18MV x-ray beams  

Microsoft Academic Search

This research aimed to quantitatively evaluate the differences in percentage dose of maximum for 6MV and 18MV x-ray beams\\u000a within the first 1cm of interactions. Thus provide quantitative information regarding the basal, dermal and subcutaneous dose\\u000a differences achievable with these two types of high-energy x-ray beams. Percentage dose of maximum build up curves are measured\\u000a for most clinical field sizes

P. K. N. Yu; T. Cheung; M. J. Butson

2003-01-01

110

Lensless Diffractive Imaging Using Tabletop Coherent High-Harmonic Soft-X-Ray Beams  

SciTech Connect

We present the first experimental demonstration of lensless diffractive imaging using coherent soft x rays generated by a tabletop soft-x-ray source. A 29 nm high harmonic beam illuminates an object, and the subsequent diffraction is collected on an x-ray CCD camera. High dynamic range diffraction patterns are obtained by taking multiple exposures while blocking small-angle diffraction using beam blocks of varying size. These patterns reconstruct to images with 214 nm resolution. This work demonstrates a practical tabletop lensless microscope that promises to find applications in materials science, nanoscience, and biology.

Sandberg, Richard L.; Paul, Ariel; Raymondson, Daisy A.; Haedrich, Steffen; Gaudiosi, David M.; Holtsnider, Jim; Tobey, Ra'anan I.; Cohen, Oren; Murnane, Margaret M.; Kapteyn, Henry C.; Song, Changyong; Miao Jianwei; Liu Yanwei; Salmassi, Farhad [JILA and Department of Physics, University of Colorado and NSF Engineering Research Center in Extreme Ultraviolet Science and Technology, Boulder, Colorado 80309 (United States); Department of Physics and Astronomy, University of California, Los Angeles, California 90095 (United States); Center for X-Ray Optics, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

2007-08-31

111

Palm-top size X-ray microanalyzer using a pyroelectric focused electron beam with 100-micro-meter diameter  

NASA Astrophysics Data System (ADS)

We have developed a palm-top size EPMA (electron probe X-ray microanalyzer), operated by 3 V electric battery except for a rotary vacuum pump. The electron beam was generated by a pyroelectric single crystal, LiTaO3. A needle was used to make a focused electron beam. The smallest beam size was 100 ?m on the sample surface. The X-ray spectra were measured through a Kapton window by a Si-PIN detector for a model specimen containing TiO2 and MnO2 particles, which was an aerosol model specimen, where TiO2 and MnO2 particles of size about 100-200 ?m were separated by a few hundreds micrometers. By moving the sample stage manually, the X-ray spectra were measured for 300 s each by 300 ?m e-beam, and the measured X-ray intensities were strong enough for identification of the major element in individual 100-200 ?m size aerosol particles.

Kawai, Jun; Ohtani, Issei; Imanishi, Akira; Imashuku, Susumu

2014-04-01

112

Z-pinches as intense x-ray sources for high energy density physics applications  

NASA Astrophysics Data System (ADS)

Fast z-pinch implosions can convert more than 10% of the stored electrical energy in a pulsed-power accelerator into x rays. These x rays are produced when an imploding cylindrical plasma, driven by the magnetic field pressure associated with very large axial currents, stagnates upon the cylindrical axis of symmetry. On the Saturn pulsed-power accelerator at Sandia National Laboratories, for example, currents of 6 to 8 MA with a risetime of less than 50 ns are driven through cylindrically-symmetric loads (typically gas jets, arrays of wires, thin foils, or low density foams), producing implosions velocities as high as 100 cm/?s and x-ray energies as high as 500 kJ. The keV component of the resulting x-ray spectrum has been used for many years as a source for material response studies. Alternatively, the x-ray output can be thermalized into a near-Planckian x-ray source by containing it within a large cylindrical radiation case (a hohlraum). These large volume ( 6000 mm^3), long-lived ( 20 ns) radiation sources have recently been used for ICF-relevant ablator physics experiments as well as astrophysical opacity and radiation-material interaction experiments. Magneto-Rayleigh-Taylor instabilities and load symmetry are critical, limiting factors in determining the assembled plasma densities and temperatures, and thus in the x-ray pulsewidths that can be produced on these accelerators. In recent experiments on the Saturn accelerator, these implosion nonuniformities have been minimized by using uniform-fill gas puff loads or by using wire arrays with as many a 192 wires. These techniques produced significant improvements in the pinched plasma quality, reproducibility, and x-ray output power. X-ray pulsewidths of less than 5 ns and peak powers of 75?10 TW have been achieved with arrays of 120 tungsten wires. These powers represent greater than a factor of three in power amplification over the electrical power of the accelerator, and are a record for x-ray powers in the laboratory. When the modification to enable z-pinch implosions on PBFA II is completed, x-ray energies in excess of 1.5 MJ at powers in excess of 150 TW should be reached. These intense x-ray sources offer the potential for performing many new basic physics and fusion-relevant experiments. *This work supported by the U.S. Department of Energy under Contract DE-AC04- 94AL85000.

Matzen, M. Keith

1996-11-01

113

Laboratory Astrophysics Survey of Key X-Ray Diagnostic Lines Using A Microcalorimeter on an Electron Beam Ion Trap  

NASA Astrophysics Data System (ADS)

Cosmic plasma conditions created in an electron beam ion trap (EBIT) make it possible to simulate the dependencies of key diagnostic X-ray lines on density, temperature, and excitation conditions that exist in astrophysical sources. We used a microcalorimeter for such laboratory astrophysics studies because it has a resolving power ~1000, quantum efficiency approaching 100%, and a bandwidth that spans the X-ray energies from 0.2 keV to 10 keV. Our microcalorimeter, coupled with an X-ray optic to increase the effective solid angle, provides a significant new capability for laboratory astrophysics measurements. Broadband spectra obtained from the National Institute of Standards and Technology EBIT with an energy resolution approaching that of a Bragg crystal spectrometer are presented for nitrogen, oxygen, neon, argon, and krypton in various stages of ionization. We have compared the measured line intensities to theoretical predictions for an EBIT plasma.

Silver, E.; Schnopper, H.; Bandler, S.; Brickhouse, N.; Murray, S.; Barbera, M.; Takacs, E.; Gillaspy, J. D.; Porto, J. V.; Kink, I.; Laming, J. M.; Madden, N.; Landis, D.; Beeman, J.; Haller, E. E.

2000-09-01

114

Effect of high-intensity x-ray radiation on Bragg diffraction in silicon and diamond  

SciTech Connect

We simulated the Bragg reflection of high-intensity short x-ray pulses from single-crystal silicon and diamond by coupling tight-binding-molecular dynamics with a simple atomic kinetics model. We found that even when the pulse-averaged Bragg intensity degrades significantly, the reflectivity drops only slightly at the beginning of the pulse until the lattice is disordered by non-thermal melting. These results suggest that Bragg reflectors could produce shortened x-ray pulses through temporal slicing.

Hau-Riege, Stefan P.; Pardini, Tommaso [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)

2012-12-01

115

Influence of X-ray tube spectral distribution on uncertainty of calculated fluorescent radiation intensity  

NASA Astrophysics Data System (ADS)

The relative radiation intensity ( Ri) defined as fluorescent radiation intensity of analyte in specimen to fluorescent radiation intensity of pure element or compound, e.g., oxide is used in calculation in both fundamental parameter methods and in theoretical influence coefficient algorithms. Accuracy of calculated Ri is determined by uncertainties of atomic parameters, spectrometer geometry and also by X-ray tube spectral distribution. This paper presents the differences between Ri calculated using experimental and theoretical X-ray tube spectra evaluated by three different algorithms proposed by Pella et al., Ebel, and Finkelshtein-Pavlova. The calculations are performed for the most common targets, i.e., Cr, Mo, Rh and W. In this study, Ri is calculated for V, Cr, Mn, Fe, Co, Ni, Cu and Mo in steels as an example. The differences between Ri calculated using different X-ray tube spectrum algorithms are presented when pure element standard, multielement standard similar to the analyzed material and one pure element standard for all analytes is used in X-ray fluorescence analysis. The differences between Ri for intermediate-thickness samples (and also for thin films) and for X-ray tube, which ran for many hours, are also evaluated.

Sitko, Rafa?

2007-08-01

116

Asymmetrically cut crystal pair as x-ray magnifier for imaging at high intensity laser facilities.  

PubMed

The potential of an x-ray magnifier prepared from a pair of asymmetrically cut crystals is studied to explore high energy x-ray imaging capabilities at high intensity laser facilities. OMEGA-EP and NIF when irradiating mid and high Z targets can be a source of high-energy x-rays whose production mechanisms and use as backlighters are a subject of active research. This paper studies the properties and potential of existing asymmetric cut crystal pairs from the National Institute of Standards and Technology (NIST) built in a new enclosure for imaging x-ray sources. The technique of the x-ray magnifier has been described previously. This new approach is aimed to find a design that could be used at laser facilities by magnifying the x-ray source into a screen far away from the target chamber center, with fixed magnification defined by the crystals' lattice spacing and the asymmetry angles. The magnified image is monochromatic and the imaging wavelength is set by crystal asymmetry and incidence angles. First laboratory results are presented and discussed. PMID:21034010

Szabo, C I; Feldman, U; Seely, J F; Curry, J J; Hudson, L T; Henins, A

2010-10-01

117

Asymmetrically cut crystal pair as x-ray magnifier for imaging at high intensity laser facilitiesa)  

NASA Astrophysics Data System (ADS)

The potential of an x-ray magnifier prepared from a pair of asymmetrically cut crystals is studied to explore high energy x-ray imaging capabilities at high intensity laser facilities. OMEGA-EP and NIF when irradiating mid and high Z targets can be a source of high-energy x-rays whose production mechanisms and use as backlighters are a subject of active research. This paper studies the properties and potential of existing asymmetric cut crystal pairs from the National Institute of Standards and Technology (NIST) built in a new enclosure for imaging x-ray sources. The technique of the x-ray magnifier has been described previously. This new approach is aimed to find a design that could be used at laser facilities by magnifying the x-ray source into a screen far away from the target chamber center, with fixed magnification defined by the crystals' lattice spacing and the asymmetry angles. The magnified image is monochromatic and the imaging wavelength is set by crystal asymmetry and incidence angles. First laboratory results are presented and discussed.

Szabo, C. I.; Feldman, U.; Seely, J. F.; Curry, J. J.; Hudson, L. T.; Henins, A.

2010-10-01

118

Asymmetrically cut crystal pair as x-ray magnifier for imaging at high intensity laser facilities  

SciTech Connect

The potential of an x-ray magnifier prepared from a pair of asymmetrically cut crystals is studied to explore high energy x-ray imaging capabilities at high intensity laser facilities. OMEGA-EP and NIF when irradiating mid and high Z targets can be a source of high-energy x-rays whose production mechanisms and use as backlighters are a subject of active research. This paper studies the properties and potential of existing asymmetric cut crystal pairs from the National Institute of Standards and Technology (NIST) built in a new enclosure for imaging x-ray sources. The technique of the x-ray magnifier has been described previously. This new approach is aimed to find a design that could be used at laser facilities by magnifying the x-ray source into a screen far away from the target chamber center, with fixed magnification defined by the crystals' lattice spacing and the asymmetry angles. The magnified image is monochromatic and the imaging wavelength is set by crystal asymmetry and incidence angles. First laboratory results are presented and discussed.

Szabo, C. I.; Feldman, U. [Artep Inc., 2922 Excelsior Spring Circle, Ellicott City, Maryland 21042 (United States); Seely, J. F. [Space Science Division, Naval Research Laboratory, Washington, DC 20375-5352 (United States); Curry, J. J.; Hudson, L. T.; Henins, A. [National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States)

2010-10-15

119

Modeling Relativistic Electron Precipitation Bremsstrahlung X-Ray Intensities at 10-100 km Manned Vehicle Altitudes  

NASA Technical Reports Server (NTRS)

Relativisitic electron precipitation (REP) events occur when beams or bunches of relativistic electrons of magnetospheric origin enter the Earth's atmosphere, typically at auroral latitudes. REP events are associated with a variety of space weather effects, including production of transitional and bremsstrahlung radiation, catalytic depletion of stratospheric ozone, and scintillation of transionospheric radio waves. This study examines the intensities of x-rays produced at airliner, manned balloon, and space reuseable launch vehicles (sRLVs). The monoenergetic beam is modeled in cylindrical symetry using the paraxial ray equation. Bremsstrahlung photon production is calculated using the traditional Sauter-Elwert cross-section, providing x-ray emission spectra differential in energy and angle. Attenuation is computed for a plane-stratified standard atmosphere, and the loss processes include photoionization, Rayleigh and Compton scattering, electron-positron pair production, and photonuclear interaction. Peak altitudes of electron energy deposition and bremsstrahlung x-ray production were calculated for beams of energies from 1 MeV through 100 MeV. The altitude peak of bremsstrahlung deposition was consistently and significantly lower that that of the electron deposition due to the longer mean free paths of x-rays compared to electrons within the atmosphere. For example, for a nadir-directed monoenergetic 5 MeV beam, the peak deposition altitude was calculated to be 42 km, but the resulting bremsstrahlung deposition peaked at 25 km. This has implications for crew and passenger safety, especially with the growth of the space tourism industry. A survey of results covering the 1-100 MeV spectrum for the three altitude ranges of interest will be presented.

Krause, L. Habsh; Gilchrist, B. E.; Nishikawa, Ken-Ichi

2013-01-01

120

Modeling Relativistic Electron Precipitation Bremsstrahlung X-Ray Intensities at 10-100 km Manned Vehicle Altitudes  

NASA Astrophysics Data System (ADS)

Relativistic electron precipitation (REP) events occur when beams or bunches of relativistic electrons of magnetospheric origin enter the Earth's atmosphere, typically at auroral latitudes. REP events are associated with a variety of space weather effects, including production of transitional and bremsstrahlung radiation, catalytic depletion of stratospheric ozone, and scintillation of transionospheric radio waves. This study examines the intensities of x-rays produced at airliner, manned balloon, and suborbital Reusable Launch Vehicle (sRLV) altitudes. The monoenergetic beam is modeled in cylindrical symmetry using the paraxial ray equation. Bremsstrahlung photon production is calculated using the traditional Sauter-Elwert cross-section, providing x-ray emission spectra differential in energy and angle. Attenuation is computed for a plane-stratified standard atmosphere, and the loss processes include photoionization, Rayleigh and Compton scattering, electron-positron pair production, and photonuclear interaction. Peak altitudes of electron energy deposition and bremsstrahlung x-ray production were calculated for beams of energies from 1 MeV through 100 MeV. The altitude peak of bremsstrahlung deposition was consistently and significantly lower that that of the electron deposition due to the longer mean free paths of x-rays compared to electrons within the atmosphere. For example, for a nadir-directed monoenergetic 5 MeV beam, the peak deposition altitude was calculated to be 42 km, but the resulting bremmstrahlung deposition peaked at 25 km. This has implications for crew and passenger safety, especially with the growth of the space tourism industry that relies on sRLVs with a nominal apogee of 100 km. A survey of results covering the 1-100 MeV spectrum for the three altitude ranges of interest will be presented.

Habash Krause, L.; Gilchrist, B. E.; Nishikawa, K.; Williams, A.

2013-12-01

121

Superficial dosimetry imaging based on ?erenkov emission for external beam radiotherapy with megavoltage x-ray beam  

SciTech Connect

Purpose: ?erenkov radiation emission occurs in all tissue, when charged particles (either primary or secondary) travel at velocity above the threshold for the ?erenkov effect (about 220 KeV in tissue for electrons). This study presents the first examination of optical ?erenkov emission as a surrogate for the absorbed superficial dose for MV x-ray beams.Methods: In this study, Monte Carlo simulations of flat and curved surfaces were studied to analyze the energy spectra of charged particles produced in different regions near the surfaces when irradiated by MV x-ray beams. ?erenkov emission intensity and radiation dose were directly simulated in voxelized flat and cylindrical phantoms. The sampling region of superficial dosimetry based on ?erenkov radiation was simulated in layered skin models. Angular distributions of optical emission from the surfaces were investigated. Tissue mimicking phantoms with flat and curved surfaces were imaged with a time domain gating system. The beam field sizes (50 × 50–200 × 200 mm{sup 2}), incident angles (0°–70°) and imaging regions were all varied.Results: The entrance or exit region of the tissue has nearly homogeneous energy spectra across the beam, such that their ?erenkov emission is proportional to dose. Directly simulated local intensity of ?erenkov and radiation dose in voxelized flat and cylindrical phantoms further validate that this signal is proportional to radiation dose with absolute average discrepancy within 2%, and the largest within 5% typically at the beam edges. The effective sampling depth could be tuned from near 0 up to 6 mm by spectral filtering. The angular profiles near the theoretical Lambertian emission distribution for a perfect diffusive medium, suggesting that angular correction of ?erenkov images may not be required even for curved surface. The acquisition speed and signal to noise ratio of the time domain gating system were investigated for different acquisition procedures, and the results show there is good potential for real-time superficial dose monitoring. Dose imaging under normal ambient room lighting was validated, using gated detection and a breast phantom.Conclusions: This study indicates that ?erenkov emission imaging might provide a valuable way to superficial dosimetry imaging in real time for external beam radiotherapy with megavoltage x-ray beams.

Zhang, Rongxiao [Department of Physics and Astronomy, Dartmouth College, Hanover, New Hampshire 03755 and Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire 03755 (United States)] [Department of Physics and Astronomy, Dartmouth College, Hanover, New Hampshire 03755 and Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire 03755 (United States); Glaser, Adam K. [Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire 03755 (United States)] [Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire 03755 (United States); Gladstone, David J.; Fox, Colleen J. [Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire 03766 and Department of Medicine, Geisel School of Medicine, Dartmouth College, Hanover, New Hampshire 03755 (United States)] [Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire 03766 and Department of Medicine, Geisel School of Medicine, Dartmouth College, Hanover, New Hampshire 03755 (United States); Pogue, Brian W. [Department of Physics and Astronomy, Dartmouth College, Hanover, New Hampshire 03755 (United States) [Department of Physics and Astronomy, Dartmouth College, Hanover, New Hampshire 03755 (United States); Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire 03766 (United States); Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire 03755 (United States)

2013-10-15

122

Proposal for an x-ray free electron laser oscillator with intermediate energy electron beam.  

PubMed

Harmonic lasing of low-gain free electron laser oscillators has been experimentally demonstrated in the terahertz and infrared regions. Recently, the low-gain oscillator has been reconsidered as a promising candidate for hard x-ray free electron lasers, through the use of high reflectivity, high-resolution x-ray crystals. In this Letter, it is proposed to utilize a crystal-based cavity resonant at a higher harmonic of the undulator radiation, together with phase shifting, to enable harmonic lasing of the x-ray free electron laser oscillator, and hence allow the generation of hard x-ray radiation at a reduced electron beam energy. Results show that fully coherent free electron laser radiation with megawatt peak power, in the spectral region of 10-25 keV, can be generated with a 3.5 GeV electron beam. PMID:22400748

Dai, Jinhua; Deng, Haixiao; Dai, Zhimin

2012-01-20

123

X-ray laser  

DOEpatents

An X-ray laser (10) that lases between the K edges of carbon and oxygen, i.e. between 44 and 23 Angstroms, is provided. The laser comprises a silicon (12) and dysprosium (14) foil combination (16) that is driven by two beams (18, 20) of intense line focused (22, 24) optical laser radiation. Ground state nickel-like dysprosium ions (34) are resonantly photo-pumped to their upper X-ray laser state by line emission from hydrogen-like silicon ions (32). The novel X-ray laser should prove especially useful for the microscopy of biological specimens.

Nilsen, Joseph (Livermore, CA)

1991-01-01

124

X-rays from high-intensity, short-pulse laser interaction with solids  

NASA Astrophysics Data System (ADS)

Laser pulses with high intensity (up to 1018 W/cm2) and short duration (100 fs) were focused on solids. The result was highly ionized material and hot electrons, along with the emission of short pulse x-rays and unicycle electromagnetic pulses with subpicosecond duration.

Falcone, R. W.; Gordon, S. P.; Hamster, H.; Sullivan, A.

1993-10-01

125

Front End X-Ray Beam Position Monitors at the CLS  

SciTech Connect

Front end x-ray beam position monitors (FE XBPM) have been designed and implemented at the Canadian Light Source (CLS, 2.9 GeV, 500 mA) to dynamically provide spatial coordinates of the centre of gravity of the synchrotron radiation intensity profile. At the CLS these fiducialized coordinates are used primarily for beamline performance diagnosis. Currently they are in use on three beamlines: HXMA (06ID-1), CMCF (08ID-1), and XSR (02B2-2) which are sourced by superconducting wiggler, in-vacuum small gap undulator and bending magnet, respectively. The monitors are all based on photoelectric yield detection mechanism by inserting high heat load capacity conducting probes into the periphery of the radiation central cone. The design and commissioning performance of these XBPMs will be discussed.

Smith, S.; Bergstrom, J. [Canadian Light Source, University of Saskatchewan, Saskatoon, SK, S7N 0X4 (Canada); Shu, D. [Advanced Photon Source, Argonne National Laboratory, Argonne IL 60439 (United States); Jiang, D. T. [Canadian Light Source, University of Saskatchewan, Saskatoon, SK, S7N 0X4 (Canada); Department of Physics, University of Guelph, Guelph ON, N1G 2W1 (Canada)

2007-01-19

126

High Gain, Fast Scan, Broad Spectrum, Parallel Beam Wavelength Dispersive X-ray Spectrometer for SEM  

SciTech Connect

Parallax Research, Inc. proposes to produce a new type of x-ray spectrometer for use with Scanning Electron Microscopy (SEM) that would have the energy resolution of WDS and the ease of use of EDS with sufficient gain for lower energies that it can be used at low beam currents as is EDS. Parallax proposes to do this by development of new multiple reflection x-ray collimation optics, new diffractor technology, new detector technology and new scan algorithms.

David OHara; Dr. Eric Lochmer

2003-09-12

127

RadSensor: x-ray detection by direct modulation of an optical probe beam  

Microsoft Academic Search

We present a new x-ray detection technique based on optical measurement of the effects of x-ray absorption and electron hole pair creation in a direct band-gap semiconductor. The electron-hole pairs create a frequency dependent shift in optical refractive index and absorption. This is sensed by simultaneously directing an optical carrier beam through the same volume of semiconducting medium that has

Mark E. Lowry; Corey V. Bennett; Stephen P. Vernon; Tiziana C. Bond; Rebecca Welty; Elaine M. Behymer; Holly E. Petersen; Adam Krey; Richard E. Stewart; Nobuhiko P. Kobayashi; Victor R. Sperry; Phillip L. Stephan; Cathy Reinhardt; Sean Simpson; Paul Stratton; Richard M. Bionta; Mark A. McKernan; Elden Ables; Linda L. Ott; Steven W. Bond; Jay Ayers; Otto L. Landen; Perry M. Bell

2004-01-01

128

Application of a transmission crystal x-ray spectrometer to moderate-intensity laser driven sources  

SciTech Connect

In the pursuit of novel, laser-produced x-ray sources for medical imaging applications, appropriate instrumental diagnostics need to be developed concurrently. A type of transmission crystal spectroscopy has previously been demonstrated as a survey tool for sources produced by high-power and high-energy lasers. The present work demonstrates the extension of this method into the study of medium-intensity laser driven hard x-ray sources with a design that preserves resolving power while maintaining high sensitivity. Specifically, spectroscopic measurements of characteristic K{alpha} and K{beta} emissions were studied from Mo targets irradiated by a 100 fs, 200 mJ, Ti: sapphire laser with intensity of 10{sup 17} W/cm{sup 2} to 10{sup 18} W/cm{sup 2} per shot. Using a transmission curved crystal spectrometer and off-Rowland circle imaging, resolving powers (E/{Delta}E) of around 300 for Mo K{alpha}{sub 2} at 17.37 keV were obtained with an end-to-end spectrometer efficiency of (1.13 {+-} 0.10) x 10{sup -5}. This sensitivity is sufficient for registering x-ray lines with high signal to background from targets following irradiation by a single laser pulse, demonstrating the utility of this method in the study of the development of medium-intensity laser driven x-ray sources.

Mao, J. Y.; Chen, L. M.; Zhang, L.; Sun, Y. Q.; Lin, X. X. [Beijing National Laboratory of Condensed Matter Physics, Institute of Physics, CAS, Beijing 100190 (China); Hudson, L. T. [National Institute of Standards and Technology, 100 Bureau Dr., Gaithersburg, Maryland 20899 (United States); Seely, J. F. [Space Science Division, Naval Research Laboratory, Washington, District of Columbia 20375 (United States); Zhang, J. [Beijing National Laboratory of Condensed Matter Physics, Institute of Physics, CAS, Beijing 100190 (China); Department of Physics, Shanghai Jiao tong University, Shanghai 200240 (China)

2012-04-15

129

An investigation of dose changes for therapeutic kilovoltage X-ray beams with underlying lead shielding.  

PubMed

Kilovoltage x-ray beams are used to treat cancer on or close to the skin surface. Many clinical cases use high atomic number materials as shielding to reduce dose to underlying healthy tissues. In this work, we have investigated the effect on both the surface dose and depth doses in a water phantom with lead shielding at depth in the phantom. The EGSnrc Monte Carlo code was used to simulate the water phantom and to calculate the surface doses and depth doses using primary x-ray beam spectra derived from an analytical model. The x-ray beams were in the energy range of 75-135 kVp with field sizes of 2, 5 and 8 cm diameter. The lead sheet was located beneath the water surface at depths ranging from 0.5-7.5 cm. The surface dose decreased as the lead was positioned closer to the water surface and as the field size was increased. The variation in surface dose as a function of x-ray beam energy was only small but the maximum reduction occurred for the 100 kVp x-ray beam. For the 8 cm diameter field with the lead at 1 cm depth and using the 100 kVp x-ray beam, the surface dose was reduced to 0.898 of the surface dose in the water phantom only. Measured surface dose changes, using a Farmer-type ionization chamber, agreed with the Monte Carlo calculated doses. Calculated depth doses in water with a lead sheet positioned below the surface showed that the dose fall-off increased as the lead was positioned closer to the water surface as compared to the depth dose in the water phantom only. Monte Carlo calculations of the total x-ray beam spectrum at the water surface showed that the total fluence decreased due to a reduction in backscatter from within the water and very little backscatter from the lead. The mean energy of the x-ray spectrum varied less than 1 keV, with the lead at 1 cm beneath the water phantom surface. As the Monte Carlo calculations showed good agreement with the measured results, this method can be used to verify surface dose changes in clinical situations where measurements are difficult. The clinical impact of the use of lead must be considered in the dose prescription for patients being treated with kilovoltage x-ray beams. PMID:17822012

Hill, Robin; Healy, Brendan; Holloway, Lois; Baldock, Clive

2007-07-01

130

Delivery confirmation of bolus electron conformal therapy combined with intensity modulated x-ray therapy  

SciTech Connect

Purpose: The purpose of this study was to demonstrate that a bolus electron conformal therapy (ECT) dose plan and a mixed beam plan, composed of an intensity modulated x-ray therapy (IMXT) dose plan optimized on top of the bolus ECT plan, can be accurately delivered. Methods: Calculated dose distributions were compared with measured dose distributions for parotid and chest wall (CW) bolus ECT and mixed beam plans, each simulated in a cylindrical polystyrene phantom that allowed film dose measurements. Bolus ECT plans were created for both parotid and CW PTVs (planning target volumes) using 20 and 16 MeV beams, respectively, whose 90% dose surface conformed to the PTV. Mixed beam plans consisted of an IMXT dose plan optimized on top of the bolus ECT dose plan. The bolus ECT, IMXT, and mixed beam dose distributions were measured using radiographic films in five transverse and one sagittal planes for a total of 36 measurement conditions. Corrections for film dose response, effects of edge-on photon irradiation, and effects of irregular phantom optical properties on the Cerenkov component of the film signal resulted in high precision measurements. Data set consistency was verified by agreement of depth dose at the intersections of the sagittal plane with the five measured transverse planes. For these same depth doses, results for the mixed beam plan agreed with the sum of the individual depth doses for the bolus ECT and IMXT plans. The six mean measured planar dose distributions were compared with those calculated by the treatment planning system for all modalities. Dose agreement was assessed using the 4% dose difference and 0.2 cm distance to agreement. Results: For the combined high-dose region and low-dose region, pass rates for the parotid and CW plans were 98.7% and 96.2%, respectively, for the bolus ECT plans and 97.9% and 97.4%, respectively, for the mixed beam plans. For the high-dose gradient region, pass rates for the parotid and CW plans were 93.1% and 94.62%, respectively, for the bolus ECT plans and 89.2% and 95.1%, respectively, for the mixed beam plans. For all regions, pass rates for the parotid and CW plans were 98.8% and 97.3%, respectively, for the bolus ECT plans and 97.5% and 95.9%, respectively, for the mixed beam plans. For the IMXT component of the mixed beam plans, pass rates for the parotid and CW plans were 93.7% and 95.8%. Conclusions: Bolus ECT and mixed beam therapy dose delivery to the phantom were more accurate than IMXT delivery, adding confidence to the use of planning, fabrication, and delivery for bolus ECT tools either alone or as part of mixed beam therapy. The methodology reported in this work could serve as a basis for future standardization of the commissioning of bolus ECT or mixed beam therapy. When applying this technology to patients, it is recommended that an electron dose algorithm more accurate than the pencil beam algorithm, e.g., a Monte Carlo algorithm or analytical transport such as the pencil beam redefinition algorithm, be used for planning to ensure the desired accuracy.

Kavanaugh, James A. [Department of Physics and Astronomy, Louisiana State University and Agricultural and Mechanical College, 202 Nicholson Hall, Tower Drive, Baton Rouge, Louisiana 70803-4001 (United States); Hogstrom, Kenneth R.; Fontenot, Jonas P.; Henkelmann, Gregory [Department of Physics and Astronomy, Louisiana State University and Agricultural and Mechanical College, 202 Nicholson Hall, Tower Drive, Baton Rouge, Louisiana 70803-4001 and Mary Bird Perkins Cancer Center, 4950 Essen Lane, Baton Rouge, Louisiana 70809 (United States); Chu, Connel; Carver, Robert A. [Mary Bird Perkins Cancer Center, 4950 Essen Lane, Baton Rouge, Louisiana 70809 (United States)

2013-02-15

131

Enhancing X-Ray Generation by Electron-Beam-Laser Interaction in an Optical Bragg Structure  

NASA Astrophysics Data System (ADS)

We demonstrate that x-ray radiation emitted by relativistic electrons scattered by a counter-propagating laser pulse guided by an adequate Bragg structure surpasses by about 2 orders of magnitude the energy generated by a conventional free-space Gaussian-beam configuration, given the same e beam and injected laser power in both configurations.

Karagodsky, Vadim; Schieber, David; Schächter, Levi

2010-01-01

132

CHARACTERIZATION OF MICROGRAVITY AND GROUND-BASED GROWN CRYSTALS USING SYNCHROTRON WHITE BEAM X-RAY TOPOGRAPHY AND HIGH RESOLUTION TRIPLE AXIS X-RAY DIFFRACTION  

Microsoft Academic Search

The combination of Synchrotron White Beam X-ray Topography (SWBXT) and High Resolution Triple Crystal X-ray Diffractometry (HRTXD) has been used to non-destructively diagnose defect structures in single crystals grown in both microgravity and ground-based environments. Due to the fact that SWBXT is the superior technique for the characterization of defects in highly perfect regions and HRTXD is superior for highly

H. Chung; Y. Guo; J. Su; M. Dudley; H. M. Volz; C. Salles; R. J. Matyi

133

Cone-beam differential phase-contrast laminography with x-ray tube source  

NASA Astrophysics Data System (ADS)

We report on an x-ray cone-beam differential phase-contrast computed laminography (DPC-CL) method for tomographic reconstruction of thin and lamellar objects. We describe the specific scan geometry of DPC-CL, which consists of a Talbot-Lau grating interferometer and a lab-based x-ray tube source, and derive a filtered back-projection (FBP) reconstruction algorithm. The experimental results of a flat sphere phantom and a piece of ham demonstrate the validity of the proposed technique. The existing DPC-CL methods are based on synchrotron sources and the parallel-beam geometry. In contrast, our approach adopts a more accessible x-ray tube source and a cone-beam geometry. Therefore it significantly widens the application range of phase-contrast laminography, particularly in practical laboratory settings, beyond applications at large-scale synchrotron facilities.

Fu, J.; Biernath, T.; Willner, M.; Amberger, M.; Meiser, J.; Kunka, D.; Mohr, J.; Herzen, J.; Bech, M.; Pfeiffer, F.

2014-06-01

134

A framework for 3-D coherent diffraction imaging by focused beam x-ray Bragg ptychography.  

SciTech Connect

We present the framework for convergent beam Bragg ptychography, and, using simulations, we demonstrate that nanocrystals can be ptychographically reconstructed from highly convergent x-ray Bragg diffraction. The ptychographic iterative engine is extended to three dimensions and shown to successfully reconstruct a simulated nanocrystal using overlapping raster scans with a defocused curved beam, the diameter of which matches the crystal size. This object reconstruction strategy can serve as the basis for coherent diffraction imaging experiments at coherent scanning nanoprobe x-ray sources.

Hruszkewycz, S. O.; Holt, M. V.; Tripathi, A.; Maser, J.; Fuoss, P. H. (Center for Nanoscale Materials); ( MSD); (Univ. of California at San Diego)

2011-06-15

135

Characteristics of a tandem system of ionization chambers in X-ray beams, mammography level.  

PubMed

Two parallel plate ionization chambers (inserted in slab phantoms) recently assembled at IPEN were studied in relation to their operational characteristics for use in quality control of X-ray beams, mammography level. The chambers present only one difference: one has an inner collecting electrode made of graphite and the other, of aluminum. These chambers make up a tandem system, which may be employed to verify X-ray beams energy constancy, by the confirmation of half-value layers and effective energies, and to determinate air kerma rates. The chambers presented good results for the operational tests, as recommended internationally. PMID:19910201

Afonso, L C; Vivolo, V; Caldas, L V E

2010-01-01

136

Variations in skin dose using 6MV or 18MV x-ray beams.  

PubMed

This research aimed to quantitatively evaluate the differences in percentage dose of maximum for 6MV and 18MV x-ray beams within the first 1 cm of interactions. Thus provide quantitative information regarding the basal, dermal and subcutaneous dose differences achievable with these two types of high-energy x-ray beams. Percentage dose of maximum build up curves are measured for most clinical field sizes using 6MV and 18MV x-ray beams. Calculations are performed to produce quantitative results highlighting the percentage dose of maximum differences delivered to various depths within the skin and subcutaneous tissue region by these two beams. Results have shown that basal cell layer doses are not significantly different for 6MV and 18MV x-ray beams. At depths beyond the surface and basal cell layer there is a measurable and significant difference in delivered dose. This variation increases to 20% of maximum and 22% of maximum at 1 mm and 1 cm depths respectively. The percentage variations are larger for smaller field sizes where the photon in phantom component of the delivered dose is the most significant contributor to dose. By producing graphs or tables of % dose differences in the build up region we can provide quantitative information to the oncologist for consideration (if skin and subcutaneous tissue doses are of importance) during the beam energy selection process for treatment. PMID:12956189

Yu, P K N; Cheung, T; Butson, M J

2003-06-01

137

Dose estimation and shielding calculation for X-ray hazard at high intensity laser facilities  

NASA Astrophysics Data System (ADS)

An ionizing radiation hazard produced from the interaction between high intensity lasers and solid targets has been observed. Laser-plasma interactions create “hot” electrons, which generate bremsstrahlung X-rays when they interact with ions in the target. However, up to now only limited studies have been conducted on this laser-induced radiological protection issue. In this paper, the physical process and characteristics of the interaction between high intensity lasers and solid targets are analyzed. The parameters of the radiation sources are discussed, including the energy conversion efficiency from laser to hot electrons, hot electron energy spectrum and electron temperature, and the bremsstrahlung X-ray energy spectrum produced by hot electrons. Based on this information, the X-ray dose generated with high-Z targets for laser intensities between 1014 and 1020 W/cm2 is estimated. The shielding effects of common shielding items such as the glass view port, aluminum chamber wall and concrete wall are also studied using the FLUKA Monte Carlo code. This study provides a reference for the dose estimation and the shielding design of high intensity laser facilities.

Qiu, Rui; Zhang, Hui; Yang, Bo; James, C. Liu; Sayed, H. Rokni; Michael, B. Woods; Li, Jun-Li

2014-12-01

138

Generation of Attosecond X-ray Pulses Beyond the Atomic Unit of Time Using Laser Induced Microbunching in Electron Beams  

SciTech Connect

Ever since the discovery of mode-locking, efforts have been devoted to reducing the duration of laser pulses since the ultrashort pulses are critical to explore the dynamics occurred on a ever-shorter timescale. In this paper we describe a scheme that's capable of generating intense attosecond x-ray pulses with duration beyond the atomic unit of time ({approx}24 attoseconds). The scheme combines the echo-enabled harmonic generation technique with the bunch compression which allows one to generate harmonic numbers of a few hundred in a microbunched beam through up-conversion of the frequency of a UV seed laser. A few-cycle intense IR laser is used to generate the required energy chirp in the beam for bunch compression and for selection of an attosecond x-ray pulse. Using a representative realistic set of parameters, we show that 1 nm x-ray pulse with peak power of a few hundred MW and duration as short as 20 attoseconds (FWHM) can be generated from a 200 nm UV seed laser. The proposed scheme may enable the study of electronic dynamics with a resolution beyond the atomic unit of time and may open a new regime of ultrafast sciences.

Xiang, D.; Huang, Z.; Stupakov, G.; /SLAC

2009-12-11

139

Cone beam x-ray luminescence computed tomography: A feasibility study  

SciTech Connect

Purpose: The appearance of x-ray luminescence computed tomography (XLCT) opens new possibilities to perform molecular imaging by x ray. In the previous XLCT system, the sample was irradiated by a sequence of narrow x-ray beams and the x-ray luminescence was measured by a highly sensitive charge coupled device (CCD) camera. This resulted in a relatively long sampling time and relatively low utilization of the x-ray beam. In this paper, a novel cone beam x-ray luminescence computed tomography strategy is proposed, which can fully utilize the x-ray dose and shorten the scanning time. The imaging model and reconstruction method are described. The validity of the imaging strategy has been studied in this paper. Methods: In the cone beam XLCT system, the cone beam x ray was adopted to illuminate the sample and a highly sensitive CCD camera was utilized to acquire luminescent photons emitted from the sample. Photons scattering in biological tissues makes it an ill-posed problem to reconstruct the 3D distribution of the x-ray luminescent sample in the cone beam XLCT. In order to overcome this issue, the authors used the diffusion approximation model to describe the photon propagation in tissues, and employed the sparse regularization method for reconstruction. An incomplete variables truncated conjugate gradient method and permissible region strategy were used for reconstruction. Meanwhile, traditional x-ray CT imaging could also be performed in this system. The x-ray attenuation effect has been considered in their imaging model, which is helpful in improving the reconstruction accuracy. Results: First, simulation experiments with cylinder phantoms were carried out to illustrate the validity of the proposed compensated method. The experimental results showed that the location error of the compensated algorithm was smaller than that of the uncompensated method. The permissible region strategy was applied and reduced the reconstruction error to less than 2 mm. The robustness and stability were then evaluated from different view numbers, different regularization parameters, different measurement noise levels, and optical parameters mismatch. The reconstruction results showed that the settings had a small effect on the reconstruction. The nonhomogeneous phantom simulation was also carried out to simulate a more complex experimental situation and evaluated their proposed method. Second, the physical cylinder phantom experiments further showed similar results in their prototype XLCT system. With the discussion of the above experiments, it was shown that the proposed method is feasible to the general case and actual experiments. Conclusions: Utilizing numerical simulation and physical experiments, the authors demonstrated the validity of the new cone beam XLCT method. Furthermore, compared with the previous narrow beam XLCT, the cone beam XLCT could more fully utilize the x-ray dose and the scanning time would be shortened greatly. The study of both simulation experiments and physical phantom experiments indicated that the proposed method was feasible to the general case and actual experiments.

Chen Dongmei; Zhu Shouping; Yi Huangjian; Zhang Xianghan; Chen Duofang; Liang Jimin [School of Life Sciences and Technology, Xidian University, Xi'an 710071 (China); Tian Jie [School of Life Sciences and Technology, Xidian University, Xi'an 710071 (China); Medical Image Processing Group, Institute of Automation, Chinese Academy of Sciences, Beijing 100190 (China)

2013-03-15

140

X-ray Beaming in the High Magnetic Field Pulsar GX 1+4  

E-print Network

Pulse profiles from X-ray pulsars often exhibit strong energy dependence and both periodic and aperiodic variations with time. The great variety of profiles observed in various sources, and even from individual sources, makes it difficult to separate the numerous factors influencing the phase-dependence of the X-ray emission. These factors include the system geometry and particularly the photon energy and angle dependence of emission about the neutron star poles. Comptonisation may play an important role in determining beam patterns and hence pulse profiles in X-ray pulsars. A Monte Carlo simulation is used to investigate the beaming due to Comptonisation in a simple accretion column geometry. We apply the model to the extremely variable pulse profiles of the high-magnetic field pulsar GX 1+4.

D. K. Galloway; K. Wu

1999-10-29

141

Diamond monochromator for high heat flux synchrotron x-ray beams  

SciTech Connect

Single crystal silicon has been the material of choice for x-ray monochromators for the past several decades. However, the need for suitable monochromators to handle the high heat load of the next generation synchrotron x-ray beams on the one hand and the rapid and on-going advances in synthetic diamond technology on the other make a compelling case for the consideration of a diamond monochromator system. In this paper, we consider various aspects, advantages and disadvantages, and promises and pitfalls of such a system and evaluate the comparative performance of a diamond monochromator subjected to the high heat load of the most powerful x-ray beam that will become available in the next few years. The results of experiments performed to evaluate the diffraction properties of a currently available synthetic single crystal diamond are also presented. Fabrication of a diamond-based monochromator is within present technical means.

Khounsary, A.M.; Smither, R.K.; Davey, S.; Purohit, A.

1993-01-28

142

Studies of LSO:Tb radio-luminescence properties using white beam hard X-ray synchrotron irradiation  

NASA Astrophysics Data System (ADS)

A radio-luminescence set-up was installed at the synchrotron light source ANKA to characterise scintillators under the high X-ray photon flux density of white beam synchrotron radiation. The system allows for investigating the radio-luminescence spectrum of the material under study as well as analysing in situ changes of its scintillation behaviour (e.g. under heat load and/or intensive ionising radiation). In this work we applied the radio-luminescence set-up for investigating the radiation damage effects on the luminescence properties of a new kind of thin single crystal scintillator for high resolution X-ray imaging based on a layer of modified Lu2SiO5 grown by liquid phase epitaxy on a dedicated substrate within the framework of an EC project (SCINTAX).

Cecilia, A.; Rack, A.; Pelliccia, D.; Douissard, P.-A.; Martin, T.; Couchaud, M.; Dupré, K.; Baumbach, T.

143

Linearization beam-hardening correction method for x-ray computed tomographic imaging of structural ceramics  

Microsoft Academic Search

A linearization beam hardening (BH) correction procedure which takes into account the material composition and the x-ray spectrum of the CT scanner being used, can correct for BH effects and reduce it to a level less than 1%. Further reduction of the BH effect to the 0.1% level may not be possible as scattering effects are present. Theoretically, a special

E. Segal; W. A. Ellingson; Y. Segal; I. Zmora

1986-01-01

144

Ultra-thin optical grade scCVD diamond as X-ray beam position monitor.  

PubMed

Results of measurements made at the SIRIUS beamline of the SOLEIL synchrotron for a new X-ray beam position monitor based on a super-thin single crystal of diamond grown by chemical vapor deposition (CVD) are presented. This detector is a quadrant electrode design processed on a 3?µm-thick membrane obtained by argon-oxygen plasma etching the central area of a CVD-grown diamond plate of 60?µm thickness. The membrane transmits more than 50% of the incident 1.3?keV energy X-ray beam. The diamond plate was of moderate purity (?1?p.p.m. nitrogen), but the X-ray beam induced current (XBIC) measurements nevertheless showed a photo-charge collection efficiency approaching 100% for an electric field of 2?V?µm(-1), corresponding to an applied bias voltage of only 6?V. XBIC mapping of the membrane showed an inhomogeneity of more than 10% across the membrane, corresponding to the measured variation in the thickness of the diamond plate before the plasma etching process. The measured XBIC signal-to-dark-current ratio of the device was greater than 10(5), and the X-ray beam position resolution of the device was better than a micrometer for a 1?kHz sampling rate. PMID:25343787

Desjardins, Kewin; Pomorski, Michal; Morse, John

2014-11-01

145

Evidence for beamed electrons in a limb X-ray flare observed by Hard X-Ray Imaging Spectrometer (HXIS)  

NASA Technical Reports Server (NTRS)

The limb flare of November 18, 1980, 14:51 UT, was investigated on the basis of X-ray images taken by the Hard X-ray Imaging Spectrometer (HXIS) and of X-ray spectra from the Hard X-Ray Burst Spectrometer (HXRBS) aboard the Solar Maximum Mission (SMM). The impulsive burst was also recorded at microwave frequencies between 2 and 20 GHz whereas no optical flare and no radio event at frequencies below 1 GHz were reported. The flare occurred directly at the SW limb of the solar disk. Taking advantage of the spatial resolution of HXIS images, the time evolution of the X-radiation originating from relatively small source regions can be studied. Using Monte Carlo computations of the energy distribution of energetic electrons traversing the solar plasma, the bremsstrahlung spectra produced by the electrons were derived.

Haug, Eberhard; Elwert, Gerhard

1986-01-01

146

Radiation beam therapy evolution: From X-rays to hadrons  

SciTech Connect

The history of external radiation beam therapy (radiotherapy)-in particular, proton therapy (PT)-is brietly outlined. Two possible strategies in increasing the efficacy of radiotherapy are considered. The radiotherapy methods and techniques are brietly described. The possibilities of PT in providing effective treatment and the main achievements are demonstrated. The state of the art in the PT development involving the active creation of large clinical PT centers since 1990 is analyzed.

Khoroshkov, V. S. [Institute of Theoretical and Experimental Physics (Russian Federation)], E-mail: khoroshkov@itep.ru

2006-10-15

147

X-ray diffraction imaging of metal-oxide epitaxial tunnel junctions made by optical lithography: use of focused and unfocused X-ray beams.  

PubMed

X-ray diffraction techniques are used in imaging mode in order to characterize micrometre-sized objects. The samples used as models are metal-oxide tunnel junctions made by optical lithography, with lateral sizes ranging from 150 µm down to 10 µm and various shapes: discs, squares and rectangles. Two approaches are described and compared, both using diffraction contrast: full-field imaging (topography) and raster imaging (scanning probe) using a micrometre-sized focused X-ray beam. It is shown that the full-field image gives access to macroscopic distortions (e.g. sample bending), while the local distortions, at the micrometre scale (e.g. tilts of the crystalline planes in the vicinity of the junction edges), can be accurately characterized only using focused X-ray beams. These local defects are dependent on the junction shape and larger by one order of magnitude than the macroscopic curvature of the sample. PMID:23412494

Mocuta, Cristian; Barbier, Antoine; Stanescu, Stefan; Matzen, Sylvia; Moussy, Jean Baptiste; Ziegler, Eric

2013-03-01

148

X-ray diffraction imaging of metal–oxide epitaxial tunnel junctions made by optical lithography: use of focused and unfocused X-ray beams  

PubMed Central

X-ray diffraction techniques are used in imaging mode in order to characterize micrometre-sized objects. The samples used as models are metal–oxide tunnel junctions made by optical lithography, with lateral sizes ranging from 150?µm down to 10?µm and various shapes: discs, squares and rectangles. Two approaches are described and compared, both using diffraction contrast: full-field imaging (topography) and raster imaging (scanning probe) using a micrometre-sized focused X-ray beam. It is shown that the full-field image gives access to macroscopic distortions (e.g. sample bending), while the local distortions, at the micrometre scale (e.g. tilts of the crystalline planes in the vicinity of the junction edges), can be accurately characterized only using focused X-ray beams. These local defects are dependent on the junction shape and larger by one order of magnitude than the macroscopic curvature of the sample. PMID:23412494

Mocuta, Cristian; Barbier, Antoine; Stanescu, Stefan; Matzen, Sylvia; Moussy, Jean-Baptiste; Ziegler, Eric

2013-01-01

149

Measurement of relative K X-ray intensity ratio following radioactive decay and photoionization  

NASA Astrophysics Data System (ADS)

The measurements of the K X-ray intensity ratio I(K ?2/K ?1), I(K ?1/K ?1) and I(K ?/K ?) for elements V, Mn, Zn, Tc, Ru, Cd, Xe, Ba, Cs, Hg and Rn were experimentally determined both by photon excitation, in which 59.5 keV ?-rays from a 241Am and 123.6 keV ?-rays from a 60Co were used, and following the radioactive decay of 51Cr, 55Fe, 67Ga, 99Tc, 111In, 131I, 133Ba, 133Xe, 137Cs, 201Tl and 226Ra. K X-rays emitted by samples were counted by a Si(Li) detector with resolution 160 eV at 5.9 keV. Obtained values were compared with the theoretical values. It was observed that present values agree with the previous theoretical and other experimental results.

Yalç?n, P.

2007-01-01

150

Vagus nerve stimulator stability and interference on radiation oncology x-ray beams  

NASA Astrophysics Data System (ADS)

Five different models of Cyberonics, Inc. vagus nerve stimulation (VNS) therapy pulse generators were investigated for their stability under radiation and their ability to change the absorbed dose from incident radiation. X-ray beams of 6 MV and 18 MV were used to quantify these results up to clinical doses of 68-78 Gy delivered in a single fraction. In the first part, the effect on electronic stimulation signaling of each pulse generator was monitored during and immediately afterwards with computer interrogation. In the second part, the effects of having the pulse generators scatter or attenuate the x-ray beam was also characterized from dose calculations on a treatment planning system as well as from actual radiation measurements. Some device models were found to be susceptible to radiation interference when placed directly in the beam of high energy therapeutic x-ray radiation. While some models exhibited no effect at all, others showed an apparent loss of stimulation output immediately after radiation was experienced. Still, other models were observed to have a cumulative dose effect with a reduced output signal, followed by battery depletion above 49 Gy. Absorbed dose changes on computer underestimated attenuation by nearly half for both energies amongst all pulse generators, although the computer did depict the proper shape of the changed distribution of dose around the device. Measured attenuation ranged from 7.0% to 11.0% at 6 MV and 4.2% to 5.2% at 18 MV for x-rays. Processes of back-scatter and side-scatter were deemed negligible although recorded. Identical results from 6 MV and 18 MV x-ray beams conclude no neutron effect was induced for the 18 MV beam. As there were documented effects identified in this research regarding pulse generation, it emphasizes the importance of caution when considering radiation therapy on patients with implanted VNS devices with observed malfunctions consequential.

Gossman, Michael S.; Ketkar, Amruta; Liu, Arthur K.; Olin, Bryan

2012-10-01

151

Electron Beam-Target Interaction and Spot Size Stabilization in Flash X-Ray Radiography*  

NASA Astrophysics Data System (ADS)

The Dual Axis Radiographic Hydro-Test (DARHT) facility is one of the most important capabilities in science based stockpile stewardship program of the US Department of Energy. DARHT uses an intense relativistic electron beam (20 MeV, 2-4 kA) to provide the necessary dose and a very small radiation spot size ( 1 mm) to achieve the desired optical resolution. Linear induction accelerator technology and electron beam diode technology can produce beams with the desirable characteristics. However, the high current densities at the converter target will cause strong nonlinear effects, which can adversely influence the radiographic performance. Over a time scale of tens of nanoseconds, intense space charge fields of the electron beam will extract positively charged ions from the vaporized target. These ions will partially neutralize the electron beam, reducing its Coulomb self-repulsive force. Initially the beam will pinch near the target, giving a favorable reduction in spot size but possibly degrading the beam quality. The ion column will then propagate upstream, moving the location of the pinch away from the target. The beam will pinch on axis and expand, producing a progressive increase in spot size as the pinch migrates upstream. This phenomenon can severely degrade resolution. In multiple-pulse applications where longer time scale phenomena become important, the expanding plasma plume of the vaporized target material can cause disruption of subsequent electron beam pulses. In this study, we investigate the physics of beam transport and explore methods for mitigating the undesirable effects. Theoretical models have been developed and validated against available experimental data from the Los Alamos Integrated Test Stand (ITS). It is shown that ion propagation can be suppressed by applying a negative bias potential to the target. The ions then become trapped in the target vicinity and actually reduce the spot size rather than increasing it due to the additional ion focusing. The negative bias can be created by inductively isolating the target, by an external voltage source, or most simply by using charge deposition from the electron beam itself to resistively bias the target. An alternative approach utilizes a very thin upstream barrier foil that is transparent to the incoming electron beam but opaque to the lower-velocity ions. Simulations indicate that any of these methods can effectively stabilize the beam spot size. The self-biasing target concept was implemented and tested on the ITS machine and performed as predicted. Computer simulations and data from these experiments allowed us to predict the time scale for ion emission and identify the ion species present. Another key factor is the influence of beam pinch and emittance growth on the radiative output. Results from our beam transport calculations have been linked to a Monte Carlo code to analyze the quantitative impact on the x-ray output spectrum. The presentation will focus on the physics of converter targets and on designs applicable to the DARHT radiographic facility.

Kwan, Thomas J. T.

1999-11-01

152

Long-term stability of beam quality and output of conventional X-ray units.  

PubMed

Conventional diagnostic X-ray units are used for radiographic imaging in many countries. For obtaining entrance surface doses, a numerical dose determination method has been applied in Japan. Although this technique is effective, it has to account for errors, particularly fluctuations, due to the beam quality and output of X-ray tubes. As a part of our quality control procedures, we recorded the entrance surface air kerma, tube voltage, and half-value layer measurements made for four diagnostic X-ray tubes over a 103-week period. The entrance surface air kerma for one of the four X-ray tubes had increased significantly by 11.4 % over 1 year from its initial setting, whereas the tube voltages and half-value layers did not deviate significantly from their initial values. Medical physicists and radiological technologists should be aware of this fluctuation for diagnostic X-ray tubes and take it into consideration when calculating the entrance surface air kerma. PMID:25070378

Fukuda, Atsushi; Matsubara, Kosuke; Miyati, Tosiaki

2015-01-01

153

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

154

X-Ray Spectrum Model  

NSDL National Science Digital Library

TheX-Ray Spectrum Model shows the effect of varying the high voltage (kVp), added filtration and ripple in the high voltage supply to the X-ray tube. The physical mechanisms by which X-rays are produced are Bremsstrahlung (in which collisions of the cathode electrons convert some of their energy into X-ray photons) and characteristic X-rays (in which the cathode electrons kick an inner shell electron out of an atom, and an X-ray photon is release when one of the atom's outer shell electron transitions to the inner shell). Changing the accelerating voltage of the cathode electrons (i.e. changing kVp) affects both mechanisms of X-ray production. Adding filtration to the X-ray beam reduces its intensity, but does not reduce all energy X-rays equally. The X-Ray Spectrum Model was created by Michael Gallis using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. You can examine and modify this compiled EJS model if you run the model (double click on the model's jar file), right-click within a plot, and select "Open Ejs Model" from the pop-up menu. You must, of course, have EJS installed on your computer. 

Gallis, Michael R.

2014-04-16

155

Infrared/X-ray intensity variations and the color of Sgr A*  

NASA Astrophysics Data System (ADS)

We report the frst time-series measurements of Sgr A*-IR's broadband infrared color. Using the newly commissioned laser guide star adaptive optics (LGS AO) system on the Keck II telescope, we imaged Sgr A*-IR, in the broadband liters H (1.6 ?m), K' (2.1 ?m), and L' (3.8 ?m) every 3 minutes over the course of 120 minutes, during which time the Chandra X-ray Observatory was also monitoring the Galactic center. Complementary measurements of Sgr A*'s L'- and Ms (4.7 ?m)-band flux densities were obtained on a separate night with the natural guide star AO system. During our observations, Sgr A*-IR,'s flux density showed a wide range of values (2 to 12 mjy at 2.1 ?m), which are associated with at least 4 peaks in the infrared emission and are among its highest infrared flux density measurements. However, all our near-infrared color measurements are consistent with a constant spectral slope of ? = -0.9 ± 0.2 (F? propto ??), independent of intensity, wavelength, time, or outburst. Assuming that the infrared wavelengths probe synchrotron emission, we interpret the lack of variation in the infrared spectral index as an indication that the acceleration mechanism leaves the distribution of the bulk of the electrons responsible for the infrared emission unchanged. During our coordinated infrared observations, no elevated X-ray emission was detected. While the less frequent X-ray outbursts have shown correlated emission in previous studies, the lack of X-ray variation during the signifbant infrared variations reported here indicates that one may not be able to connect the infrared and X-ray emission to the same electrons. We suggest that while the acceleration mechanism leaves the bulk of the electron energy distribution unchanged, it generates a variable high-energy tail. It is this high-energy tail that gives rise to the less frequent X-ray outbursts.

Hornstein, S. D.; Matthews, K.; Ghez, A. M.; Lu, J. R.; Morris, M.; Becklin, E. E.; Baganoff, F. K.; Rafelski, M.

2006-12-01

156

Kinetic effects and nonlinear heating in intense x-ray-laser-produced carbon plasmas.  

PubMed

The x-ray laser-matter interaction for a low-Z material, carbon, is studied with a particle-in-cell code that solves the photoionization and x-ray transport self-consistently. Photoionization is the dominant absorption mechanism and nonthermal photoelectrons are produced with energy near the x-ray photon energy. The photoelectrons ionize the target rapidly via collisional impact ionization and field ionization, producing a hot plasma column behind the laser pulse. The radial size of the heated region becomes larger than the laser spot size due to the kinetic nature of the photoelectrons. The plasma can have a temperature of more than 10 000 K (>1eV), an energy density greater than 10^{4} J/cm^{3}, an ion-ion Coulomb coupling parameter ??1, and electron degeneracy ??1, i.e., strongly coupled warm dense matter. By increasing the laser intensity, the plasma temperature rises nonlinearly from tens of eV to hundreds of eV, bringing it into the high energy density matter regime. The heating depth and temperature are also controllable by changing the photon energy of the incident laser light. PMID:25493733

Sentoku, Y; Paraschiv, I; Royle, R; Mancini, R C; Johzaki, T

2014-11-01

157

Electron beam stability and beam peak to peak motion data for NSLS X-Ray storage ring  

SciTech Connect

In the past two years, a significant reduction in electron beam motion has been achieved at the NSLS X-Ray storage ring. The implementation of global analog orbit feedbacks, based on a harmonics correction scheme, has reduced the beam motion globally. Implementation of six local analog feedback systems has reduced the beam motion even further at the corresponding beam line straight sections. This paper presents beam motion measurements, showing the improvement due to the feedback systems. Beam motion is measured using a spectrum analyzer and data is presented at various frequencies, where peaks were observed. Finally, some of the beam motion sources are discussed.

Singh, O.

1993-07-01

158

Polychromatic X-ray Micro- and Nano-Beam Science and Instrumentation  

SciTech Connect

Polychromatic x-ray micro- and nano-beam diffraction is an emerging nondestructive tool for the study of local crystalline structure and defect distributions. Both long-standing fundamental materials science issues, and technologically important questions about specific materials systems can be uniquely addressed. Spatial resolution is determined by the beam size at the sample and by a knife-edge technique called differential aperture microscopy that decodes the origin of scattering from along the penetrating x-ray beam. First-generation instrumentation on station 34-ID-E at the Advanced Photon Source (APS) allows for nondestructive automated recovery of the three-dimensional (3D) local crystal phase and orientation. Also recovered are the local elastic-strain and the dislocation tensor distributions. New instrumentation now under development will further extend the applications of polychromatic microdiffraction and will revolutionize materials characterization.

Ice, G. E.; Larson, B. C.; Liu, W.; Barabash, R. I.; Specht, E. D.; Pang, J. W. L.; Budai, J. D.; Tischler, J. Z. [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge TN 37831-6118 (United States); Khounsary, A.; Liu, C.; Macrander, A. T.; Assoufid, L. [Advanced Photon Source, Argonne National Laboratory, 9700 S. Cass Ave. Argonne Il 60439 (United States)

2007-01-19

159

Polychromatic X-ray Micro- and Nano-Beam Science and Instrumentation  

SciTech Connect

Polychromatic x-ray micro- and nano-beam diffraction is an emerging nondestructive tool for the study of local crystalline structure and defect distributions. Both long-standing fundamental materials science issues, and technologically important questions about specific materials systems can be uniquely addressed. Spatial resolution is determined by the beam size at the sample and by a knife-edge technique called differential aperture microscopy that decodes the origin of scattering from along the penetrating x-ray beam. First-generation instrumentation on station 34-ID-E at the Advanced Photon Source (APS) allows for nondestructive automated recovery of the three-dimensional (3D) local crystal phase and orientation. Also recovered are the local elastic-strain and the dislocation tensor distributions. New instrumentation now under development will further extend the applications of polychromatic microdiffraction and will revolutionize materials characterization.

Ice, Gene E [ORNL; Larson, Ben C [ORNL; Liu, Wenjun [ORNL; Barabash, Rozaliya [ORNL; Specht, Eliot D [ORNL; Pang, Judy [ORNL; Budai, John D [ORNL; Tischler, Jonathan Zachary [ORNL; Khounsary, Ali [Argonne National Laboratory (ANL); Liu, Chian [Argonne National Laboratory (ANL); Macrander, Albert T. [Argonne National Laboratory (ANL); Assoufid, Lahsen [Argonne National Laboratory (ANL)

2007-01-01

160

X-RAY IMAGING OF THE APS STORAGE RING BEAM STABILITY EFFECTS: FROM THE ALASKAN EARTHQUAKE TO UNDULATOR FIELD CHANGES  

Microsoft Academic Search

The Advanced Photon Source (APS) 7-GeV storage ring serves as a national x-ray synchrotron radiation user facility. The stability and beam quality of the electron beam, and hence the photon beams, are monitored continuously by an array of diagnostics. In particular, x- ray imaging techniques are employed in the diagnostics EXPERIMENTAL BACKGROUND sector of the ring to characterize beam position,

A. H. Lumpkin; B. X. Yang; C. Y. Yao; L. Emery

2002-01-01

161

Multi-species beam hardening calibration device for x-ray microtomography  

NASA Astrophysics Data System (ADS)

Impact-source X-ray microtomography (XMT) is a widely-used benchtop alternative to synchrotron radiation microtomography. Since X-rays from a tube are polychromatic, however, greyscale `beam hardening' artefacts are produced by the preferential absorption of low-energy photons in the beam path. A multi-material `carousel' test piece was developed to offer a wider range of X-ray attenuations from well-characterised filters than single-material step wedges can produce practically, and optimization software was developed to produce a beam hardening correction by use of the Nelder-Mead optimization method, tuned for specimens composed of other materials (such as hydroxyapatite [HA] or barium for dental applications.) The carousel test piece produced calibration polynomials reliably and with a significantly smaller discrepancy between the calculated and measured attenuations than the calibration step wedge previously in use. An immersion tank was constructed and used to simplify multi-material samples in order to negate the beam hardening effect of low atomic number materials within the specimen when measuring mineral concentration of higher-Z regions. When scanned in water at an acceleration voltage of 90 kV a Scanco AG hydroxyapatite / poly(methyl methacrylate) calibration phantom closely approximates a single-material system, producing accurate hydroxyapatite concentration measurements. This system can then be corrected for beam hardening for the material of interest.

Evershed, Anthony N. Z.; Mills, David; Davis, Graham

2012-10-01

162

Size-dependent ultrafast ionization dynamics of nanoscale samples in intense femtosecond x-ray free-electron-laser pulses.  

PubMed

All matter exposed to intense femtosecond x-ray pulses from the Linac Coherent Light Source free-electron laser is strongly ionized on time scales competing with the inner-shell vacancy lifetimes. We show that for nanoscale objects the environment, i.e., nanoparticle size, is an important parameter for the time-dependent ionization dynamics. The Auger lifetimes of large Ar clusters are found to be increased compared to small clusters and isolated atoms, due to delocalization of the valence electrons in the x-ray-induced nanoplasma. As a consequence, large nanometer-sized samples absorb intense femtosecond x-ray pulses less efficiently than small ones. PMID:23003953

Schorb, Sebastian; Rupp, Daniela; Swiggers, Michelle L; Coffee, Ryan N; Messerschmidt, Marc; Williams, Garth; Bozek, John D; Wada, Shin-Ichi; Kornilov, Oleg; Möller, Thomas; Bostedt, Christoph

2012-06-01

163

LabVIEW control software for scanning micro-beam X-ray fluorescence spectrometer.  

PubMed

Confocal micro-beam X-ray fluorescence microscope was constructed. The system was assembled from commercially available components - a low power X-ray tube source, polycapillary X-ray optics and silicon drift detector - controlled by an in-house developed LabVIEW software. A video camera coupled to optical microscope was utilized to display the area excited by X-ray beam. The camera image calibration and scan area definition software were also based entirely on LabVIEW code. Presently, the main area of application of the newly constructed spectrometer is 2-dimensional mapping of element distribution in environmental, biological and geological samples with micrometer spatial resolution. The hardware and the developed software can already handle volumetric 3-D confocal scans. In this work, a front panel graphical user interface as well as communication protocols between hardware components were described. Two applications of the spectrometer, to homogeneity testing of titanium layers and to imaging of various types of grains in air particulate matter collected on membrane filters, were presented. PMID:22483897

Wrobel, Pawel; Czyzycki, Mateusz; Furman, Leszek; Kolasinski, Krzysztof; Lankosz, Marek; Mrenca, Alina; Samek, Lucyna; Wegrzynek, Dariusz

2012-05-15

164

Copper K-shell x-ray emission induced by the impact of ion beam from an electron cyclotron resonance ion source  

NASA Astrophysics Data System (ADS)

The K-? and K-? x-ray emission (at 8.05 keV and 8.9 keV respectively) produced from a copper target by the impact of 25 keV hydrogen (H+) and nitrogen (N+) ion beams, and 200 keV for argon (Ar+8) beams from an electron cyclotron resonance ion source (ECRIS), has been studied experimentally. The K-? x-ray line intensity exhibited an increase with increasing ion beam energy with a scaling law IK-??E?, where the scaling exponent ? was 4.0, 4.2, and 4.1 for hydrogen, nitrogen, and argon ion beam respectively. The results can be explained by considering the K-shell ionization cross-section for ion impact. The peak to background ratio of x-ray line intensity was observed to increase rapidly with the ion beam energy and highest ratio of 6×105 was observed for hydrogen ions. The study is important for optimizing ECRIS for generating a low cost, long life x-ray source for applications in material science.

Jain, S. K.; Arora, V.; Rathore, R.; Bagchi, S.; Naik, P. A.

2014-11-01

165

Interaction of high intensity laser with non-uniform clusters and enhanced X-ray emission  

SciTech Connect

Laser irradiated clusters with non-uniform density variation are shown to broaden surface plasmon resonance very significantly. As the clusters get heated and expand hydro-dynamically, the Bremsstrahlung X-ray emission yield passes through a maximum in time. The maximum yield decreases with increase in non-uniformity in the electron density inside the clusters. At higher laser intensity, the nonlinearity in laser cluster interaction may arise even prior to electron heating, via the relativistic mass variation and the nonlinear restoration force on electrons. For clusters with radius less than one tenth of the laser wavelength, the restoration force nonlinearity dominates.

Liu, C. S. [Department of Physics, University of Maryland, College Park, Maryland 20742 (United States); Tripathi, V. K.; Kumar, Manoj, E-mail: manojailum@gmail.com [Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016 (India)

2014-10-15

166

Analysis of equatorial x-ray diffraction patterns from muscle fibers: factors that affect the intensities.  

PubMed Central

Previously we have shown that cross-bridge attachment to actin and the radial position of the myosin heads surrounding the thick filament backbone affect the equatorial x-ray diffraction intensities in different ways (Yu, 1989). In the present study, other factors frequently encountered experimentally are analyzed by a simple model of the filament lattice. It is shown that the ordering/disordering of filaments, lattice spacing changes, the azimuthal redistributions of cross-bridges, and variations in the ordered/disordered population of cross-bridges surrounding the thick filaments can distinctly affect the equatorial intensities. Consideration of Fourier transforms of individual components of the unit cell can provide qualitative explanations for the equatorial intensity changes. Criteria are suggested that can be used to distinguish the influence of some factors from others. PMID:7612844

Malinchik, S; Yu, L C

1995-01-01

167

The effects of x-ray beam hardening on detective quantum efficiency and radiation dose  

PubMed Central

The goal of this preliminary study was to investigate the effects of x-ray beam hardening on the detective quantum efficiency (DQE) and the radiation dose of an inline x-ray imaging system. The DQE and the average glandular dose were both calculated under the same experimental conditions for a range of beam hardening levels, corresponding to no added beam hardening and two thicknesses each of Rhodium (Rh) and Molybdenum (Mo) filters. The dose calculation results demonstrate a reduction of 15% to 24% for the range of beam hardening levels. The comparison of all quantities comprising the DQE exhibit very close correlation between the results obtained without added beam hardening to the results corresponding to the range of beam hardening levels. For the specific experimental conditions utilized in this preliminary study, the results are an indication that the use of beam hardening holds the potential to reduce the radiation dose without decreasing the performance of the system. Future studies will seek to apply this method in a clinical environment and perform a comprehensive image quality evaluation, in an effort to further evaluate the potential of beam hardening to balance the tradeoff between dose and image quality. PMID:25214383

Wong, Molly Donovan; Wu, Xizeng; Liu, Hong

2011-01-01

168

Design and characterization of electron beam focusing for X-ray generation in novel medical imaging architecture.  

PubMed

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. PMID:24826066

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

169

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

170

National Synchrotron Light Source users manual: Guide to the VUV and x-ray beam lines  

SciTech Connect

The success of the National Synchrotron Light Source in the years to come will be based, in large part, on the size of the users community and the diversity of the scientific disciplines represented by these users. In order to promote this philosophy, this National Synchrotron Light Source (NSLS) Users Manual: Guide to the VUV and X-Ray Beam Lines, has been published. This manual serves a number of purposes. In an effort to attract new research, it will present to the scientific community-at-large the current and projected architecture and capabilities of the various VUV and x-ray beam lines and storage rings. We anticipate that this publication will be updated periodically in order to keep pace with the constant changes at the NSLS.

Gmuer, N.F.; White-DePace, S.M. (eds.)

1987-08-01

171

Generation of hard X-ray emission by the electron beam in plasma focus facilities  

NASA Astrophysics Data System (ADS)

The results of measurements of the temporal characteristics of hard X-ray emission generated at plasma focus (PF) facilities are presented. Mechanisms of electron beam generation in the PF pinch are analyzed. On the basis of the known mechanisms and experimental data on the measured temporal characteristics of hard X-ray pulses, a mechanism of fast electron generation that takes into account both the effect of the anomalous pinch resistance and the current redistribution in the near-pinch region is proposed. The processes occurring in the pinch plasma are simulated on the basis of the proposed mechanism by using the MicroCap code. It is shown that only a small fraction of the discharge current (1-10%) can be transformed into the electron beam current.

Dulatov, A. K.; Lemeshko, B. D.; Mikhailov, Yu. V.; Prokuratov, I. A.; Selifanov, A. N.

2014-11-01

172

Solar Hard X-Ray Source Sizes in a Beam-heated and Ionized Chromosphere  

NASA Astrophysics Data System (ADS)

Solar flare hard X-rays (HXRs) are produced as bremsstrahlung when an accelerated population of electrons interacts with the dense chromospheric plasma. HXR observations presented by Kontar et al. using the Ramaty High-Energy Solar Spectroscopic Imager have shown that HXR source sizes are three to six times more extended in height than those predicted by the standard collisional thick target model (CTTM). Several possible explanations have been put forward including the multi-threaded nature of flare loops, pitch-angle scattering, and magnetic mirroring. However, the nonuniform ionization (NUI) structure along the path of the electron beam has not been fully explored as a solution to this problem. Ionized plasma is known to be less effective at producing nonthermal bremsstrahlung HXRs when compared to neutral plasma. If the peak HXR emission was produced in a locally ionized region within the chromosphere, the intensity of emission will be preferentially reduced around this peak, resulting in a more extended source. Due to this effect, along with the associated density enhancement in the upper chromosphere, injection of a beam of electrons into a partially ionized plasma should result in an HXR source that is substantially more vertically extended relative to that for a neutral target. Here we present the results of a modification to the CTTM, which takes into account both a localized form of chromospheric NUI and an increased target density. We find 50 keV HXR source widths, with and without the inclusion of a locally ionized region, of ~3 Mm and ~0.7 Mm, respectively. This helps to provide a theoretical solution to the currently open question of overly extended HXR sources.

O'Flannagain, Aidan M.; Brown, John C.; Gallagher, Peter T.

2015-02-01

173

High gain, Fast Scan, Broad Spectrum Parallel Beam Wavelength Dispersive X-ray Spectrometer for SEM  

SciTech Connect

During contract # DE-FG02-ER83545, Parallax Research, Inc. developed a High gain, Fast Scan Broad Spectrum Parallel beam Wavelength Dispersive X-ray Spectrometer for use on Scanning Electron Microscopes (SEM). This new spectrometer allows very fast high resolution elemental analysis of samples in an electron microscope. By comparison to previous WDS spectrometers, it can change from one energy position to another very quickly and has an extended range compared to some similar products.

OHara, David

2009-05-08

174

A Positional X-ray Instrumentation Test Stand For Beam-Line Experiments  

NASA Astrophysics Data System (ADS)

A multi-axis, motion controlled test stand has been built in the PSU 47 m X-ray beam-line for the purpose of testing X-ray instrumentation and mirrors using parallel rays. The test stand is capable of translation along two axes and rotation about two axes with motorized fine position control. The translation stages have a range of motion of 200 mm with a movement accuracy of ± 2.5 microns. Rotation is accomplished with a two-axis gimbal which can rotate 360° about one axis and 240° about another; movement with ± 35 arcsecond accuracy are achieved in both axes. The position and status are monitored using a LabView program. An XCalibr source with multiple target materials is used as an X-ray source and can produce multiple lines between 0.8 and 8 keV. Some sample spectra are shown from a Si-PIN diode detector. This system is well suited for testing X-ray mirror segments which are currently being developed.

Nikoleyczik, Jonathan; Prieskorn, Z.; Burrows, D. N.; Falcone, A.

2014-01-01

175

Imaging single cells in a beam of live cyanobacteria with an X-ray laser.  

PubMed

There exists a conspicuous gap of knowledge about the organization of life at mesoscopic levels. Ultra-fast coherent diffractive imaging with X-ray free-electron lasers can probe structures at the relevant length scales and may reach sub-nanometer resolution on micron-sized living cells. Here we show that we can introduce a beam of aerosolised cyanobacteria into the focus of the Linac Coherent Light Source and record diffraction patterns from individual living cells at very low noise levels and at high hit ratios. We obtain two-dimensional projection images directly from the diffraction patterns, and present the results as synthetic X-ray Nomarski images calculated from the complex-valued reconstructions. We further demonstrate that it is possible to record diffraction data to nanometer resolution on live cells with X-ray lasers. Extension to sub-nanometer resolution is within reach, although improvements in pulse parameters and X-ray area detectors will be necessary to unlock this potential. PMID:25669616

van der Schot, Gijs; Svenda, Martin; Maia, Filipe R N C; Hantke, Max; DePonte, Daniel P; Seibert, M Marvin; Aquila, Andrew; Schulz, Joachim; Kirian, Richard; Liang, Mengning; Stellato, Francesco; Iwan, Bianca; Andreasson, Jakob; Timneanu, Nicusor; Westphal, Daniel; Almeida, F Nunes; Odic, Dusko; Hasse, Dirk; Carlsson, Gunilla H; Larsson, Daniel S D; Barty, Anton; Martin, Andrew V; Schorb, Sebastian; Bostedt, Christoph; Bozek, John D; Rolles, Daniel; Rudenko, Artem; Epp, Sascha; Foucar, Lutz; Rudek, Benedikt; Hartmann, Robert; Kimmel, Nils; Holl, Peter; Englert, Lars; Duane Loh, Ne-Te; Chapman, Henry N; Andersson, Inger; Hajdu, Janos; Ekeberg, Tomas

2015-01-01

176

Mapping of electrical potential distribution with charged particle beams. [using an X-ray source  

NASA Technical Reports Server (NTRS)

Potentials were measured using a beam of soft X-rays in air at 2 x 10 to the -5 power Torr. Ions were detected by a continuous-dynode electron multiplier after they passed through a retarding field. Ultimate resolution depends upon the diameter of the X-ray beam which was 3 mm. When the fields in the region of interest were such to disperse the ions, only a small fraction were detected and the method of measurement was not very reliable. Yet reasonable data could be collected if the ions traveled in parallel paths toward the detector. Development should concentrate on increasing the aperture of the detector from the pinhole which was used to something measured in centimeters. Also increasing the strength of the source would provide a stronger signal and more reliable data. Measurements were made at an estimated ion current to 10 to the -15 power A from a 10 cm length of the X-ray beam, this current being several orders of magnitude below what would have a perturbing effect on the region to be measured. Consequently, the source strength can be increased and prospects for this method of measurement are good.

Robinson, J. W.

1979-01-01

177

Calculation of the parameters of the X-ray diffraction station with adaptive segmented optics on the side beam from the wiggler of the Sibir'-2 storage ring  

SciTech Connect

The mounting of an X-ray diffraction station on the side beam of a 19-pole superconducting wiggler makes it possible not only to use the central synchrotron radiation beam with a wavelength of 0.5 Angstrom-Sign , but also to solve problems requiring softer X rays at a synchrotron radiation (SR) intensity exceeding that for the beams from the bending magnet. A numerical simulation of the formation of photon beams from a source and their transmission through the elements of the station (and through the station as a whole) allows one to calculate the parameters of the station, compare it with the existing analogs, determine its potential and actual efficiency of its elements, and estimate the adjustment quality. A numerical simulation of the SR source on the side beam from the wiggler and the focusing channel (segmented condenser mirror, monochromator with sagittal focusing by the segmented second crystal, and segmented focusing mirror) has been performed. The sizes of the focus and the divergence of rays in it are determined with allowance for the finite sizes of segments. The intensity of radiation with a wavelength {lambda} = 1.0 Angstrom-Sign in the focus is determined taking into account the loss in the SR extraction channel and in the focusing channel. The values of the critical wavelength for the side beam from the wiggler and the wavelength resolution are calculated. The intensities in the X-ray diffraction pattern and its angular resolution are found.

Molodenskii, D. S.; Kheiker, D. M., E-mail: kheiker@ns.crys.ras.ru [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation); Korchuganov, V. N. [National Research Center Kurchatov Institute (Russian Federation); Konoplev, E. E. [NPO Luch (Russian Federation); Dorovatovskii, P. V. [National Research Center Kurchatov Institute (Russian Federation)

2012-05-15

178

EBT2 dosimetry of x-rays produced by the electron beam from a Plasma Focus for medical applications  

SciTech Connect

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 {mu}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.; Mostacci, D.; Sumini, M. [Montecuccolino Nuclear Engineering Laboratory - DIENCA, University of Bologna, via dei Colli 16, I-40136 Bologna (Italy); Rocchi, F. [Montecuccolino Nuclear Engineering Laboratory - DIENCA, University of Bologna, via dei Colli 16, I-40136 Bologna (Italy); UTFISSM-PRONOC, ENEA, via Martiri di Monte Sole 4, I-40129 Bologna (Italy); Tartari, A. [Department of Physics, Ferrara University, via Saragat 1, I-44122 Ferrara (Italy); Mariotti, F. [ENEA, IRP-DOS, via dei Colli 16, I-40136 Bologna (Italy)

2012-09-01

179

Ray-tracing simulations of spherical Johann diffraction spectrometer for in-beam X-ray experiments  

NASA Astrophysics Data System (ADS)

The results of the Monte-Carlo ray-tracing simulations for a Johann-type Bragg spectrometer with spherically curved-crystal designed to detect the X-rays from a fast-moving source are reported. These calculations were performed to optimize the X-ray spectrometer to be used at the gas-target installed at ion storage ring for high-resolution X-ray experiments. In particular, the two-dimensional distributions of detected photons were studied using the Monte-Carlo method both for the stationary and moving X-ray sources, taking into account a detailed description of X-ray source and X-ray diffraction on the crystal as well as a role of the Doppler effect for in-beam experiments. The origin of the asymmetry of observed X-ray profiles was discussed in detail and the procedure to derive a precise (sub-eV) X-ray transition energy for such asymmetric profiles was proposed. The results are important for the investigations of 1s2pP23?1s2sS13 intrashell transition in excited He-like uranium ions in in-beam X-ray experiments.

Jagodzi?ski, P.; Pajek, M.; Bana?, D.; Beyer, H. F.; Trassinelli, M.; Sto¨hlker, Th.

2014-07-01

180

A study of diagnostic x-ray lines in heliumlike neon using an electron beam ion trap  

SciTech Connect

Heliumlike ions play an extremely important role in X-ray astrophysics because of their emissivity and because the relative intensities of their emission lines can be used to infer physical characteristics of X-ray emitting plasmas, including temperature, electron density, and ionization balance. In order to properly apply these diagnostics, accurate atomic data are required, including cross sections for collisional excitation and ionization, radiative rates, and the wavelengths and strengths of satellite lines. Although theoretical atomic models have been created to estimate many of the rates and cross sections involved, very few experimental results are available for comparison with theoretical predictions. This thesis describes an experimental study of heliumlike neon using an electron beam ion trap, a device specifically designed to study X-ray emission from highly charged ions. Using a low-energy X-ray spectrometer designed and built for this experiment, electron impact excitation cross sections and dielectronic satellite strengths were measured for all significant n = 2{yields}1 emission lines in He-like and Li-like Ne over a range of energy extending from well below the direct excitation threshold of the lines to over fourteen times the threshold energy. The cross section for innershell ionization of Li-like Ne, which excites the He-like forbidden line, was also measured. In addition, the radiative and collisional depopulation rates of the metastable ls2s {sup 3}S{sub 1}, state, which form the basis of the He-like Ne density diagnostic, were determined. Experimental results were generally in agreement with theoretical predictions, although some significant differences were noted, particularly for the wavelengths and resonance strengths of dielectronic satellites.

Wargelin, B.J.

1993-10-01

181

Research Into Characteristics of X-Ray Emission Laser Beams from Solid-State Cathode Medium of High-Current Glow Discharge  

NASA Astrophysics Data System (ADS)

X-ray emissions ranging 1.2-3.0 keV with dose rate up to 1.0 Gy/s have been registered in experiments with high-current Glow Discharge. The emissions energy and intensity depend on the cathode material, the kind of plasma-forming gas, and the discharge parameters. The experiments were carried out on the high-current glow discharge device using D2, H2, Kr, and Xe at pressure up to 10 Torr, as well as cathode samples made from Al, Sc, Ti, Ni, Nb, Zr, Mo, Pd, Ta, W, Pt, at current up to 500 mA, and discharge voltage of 500-2500 V. Two emission modes were revealed under the experiments: (1) Diffusion X-rays was observed as separate X-ray bursts (up to 5 × 105 bursts a second and up to 106 X-ray quanta in a burst), (2) X-rays in the form of laser microbeams (up to 104 beams a second and up to 1010 X-ray of quanta in a beam, angular divergence was up to 10-4, the duration of the separate laser beams must be ? = 3 × 10-13-3 × 10-14 s, the separate beam power must be 107-108 W). The emission of the X-ray laser beams occurred when the discharge occurred and within 100 ms after turning off the current. The results of experimental research into the characteristics of secondary penetrating radiation occurring when interacting primary X-ray beams from a solid-state cathode medium with targets made of various materials are reported. It was shown that the secondary radiation consisted of fast electrons. Secondary radiation of two types was observed: (1) The emission with a continuous temporal spectrum in the form of separate bursts with intensity up to 106 fast electrons a burst. (2) The emission with a discrete temporal spectrum and emission rate up to 1010 fast electrons a burst. A third type of the penetrating radiation was observed as well. This type was recorded directly by the photomultiplier placed behind of the target without the scintillator. The abnormal high penetrating ability of this radiation type requires additional research to explain. The obtained results show that creating optically active medium with long-living metastable levels with the energy of 1.0-3.0 keV and more is possible in the solid state.

Karabut, Alexander B.

2006-02-01

182

Normal incidence multilayer telescope for soft X-ray beam expander  

NASA Astrophysics Data System (ADS)

Normal incidence optics have been used with multilayers in EUV region. The 2d of the multilayers has to be equal to the wavelength of interest. At the same time, the reflectivity of the multilayers should decrease with the increase of the interfacial roughness much faster than grazing optics. In general, 2d of 10 nm is the shortest d-spacing available for multilayers in normal incidence. As a challenge of shorter wavelength application, we made NiCr/C multiplayer mirror for the laboratory use at 4.47 nm(carbon K alpha line). The main dish of the Cassegrain optics is 20 cm diameter spherical mirror and the secondary mirror is a reflector in aspherical shape to correct astigmatisms. Its focal point is placed at the X-ray source to create a broad parallel beam of 20 cm in diameter. The flux of the parallel beam is slightly less than the expected value, and gradually decreases of 40% toward the outer region. The measured parallelism is about 25 arcsec, which is a little larger than the designed value. More pricise positioning of the focal point to the X-ray generator may reduce such divergence. The beam profile through a slit shows a core of about 20 arcsec and an extended tail which might be due to scattering tail by the roughness of 0.3 nm. An application of this system is demonstrated with the Astro-E X-ray telescope. The image core is sharper but the scattering tail is considerable. Even after the subtraction of the tail, still some wing is left. This system is bright and parallel enough to examine the optical alignment much faster than previous method, while careful measurements are necessary for quantitative calibration of X-ray telescopes.

Kunieda, Hideyo; Misaki, Kazutami; Haba, Yoshito; Ishida, Manabu; Itoh, Kei; Mori, Hideyuki; Shibata, Ryo

2003-03-01

183

Intensity distribution of the x ray source for the AXAF VETA-I mirror test  

NASA Technical Reports Server (NTRS)

The X-ray generator for the AXAF VETA-I mirror test is an electron impact X-ray source with various anode materials. The source sizes of different anodes and their intensity distributions were measured with a pinhole camera before the VETA-I test. The pinhole camera consists of a 30 micrometers diameter pinhole for imaging the source and a Microchannel Plate Imaging Detector with 25 micrometers FWHM spatial resolution for detecting and recording the image. The camera has a magnification factor of 8.79, which enables measuring the detailed spatial structure of the source. The spot size, the intensity distribution, and the flux level of each source were measured with different operating parameters. During the VETA-I test, microscope pictures were taken for each used anode immediately after it was brought out of the source chamber. The source sizes and the intensity distribution structures are clearly shown in the pictures. They are compared and agree with the results from the pinhole camera measurements. This paper presents the results of the above measurements. The results show that under operating conditions characteristic of the VETA-I test, all the source sizes have a FWHM of less than 0.45 mm. For a source of this size at 528 meters away, the angular size to VETA is less than 0.17 arcsec which is small compared to the on ground VETA angular resolution (0.5 arcsec, required and 0.22 arcsec, measured). Even so, the results show the intensity distributions of the sources have complicated structures. These results were crucial for the VETA data analysis and for obtaining the on ground and predicted in orbit VETA Point Response Function.

Zhao, Ping; Kellogg, Edwin M.; Schwartz, Daniel A.; Shao, Yibo; Fulton, M. Ann

1992-01-01

184

Optimization for Single-Spike X-Ray FELs at LCLS with a Low Charge Beam  

SciTech Connect

The Linac Coherent Light Source is an x-ray free-electron laser at the SLAC National Accelerator Laboratory, which is operating at x-ray wavelengths of 20-1.2 Angstrom with peak brightness nearly ten orders of magnitude beyond conventional synchrotron radiation sources. At the low charge operation mode (20 pC), the x-ray pulse length can be <10 fs. In this paper we report our numerical optimization and simulations to produce even shorter x-ray pulses by optimizing the machine and undulator setup at 20 pC charge. In the soft x-ray regime, with combination of slotted-foil or undulator taper, a single spike x-ray pulse is achievable with peak FEL power of a few 10s GW. Linac Coherent Light Source (LCLS), the world's first hard x-ray Free electron laser (FEL), has started operation since 2009. With nominal operation charge of 250 pC, the generated x-ray pulse length is from 70 fs to a few hundred fs. This marks the beginning of a new era of ultrashort x-ray sciences. In addition, a low charge (20pC) operation mode has also been established. Since the collective effects are reduced at the low charge mode, we can increase the compression factor and still achieve a few kA peak current. The expected electron beam and x-ray pulses are less than 10 fs. There are growing interests in even shorter x-ray pulses, such as fs to sub-fs regime. One of the simple solutions is going to even lower charge. As discussed, single-spike x-ray pulses can be generated using 1 pC charge. However, this charge level is out of the present LCLS diagnostic range. 20 pC is a reasonable operation charge at LCLS, based on the present diagnostic system. At 20 pC in the soft x-ray wavelength regime, we have experimentally demonstrated that FEL can work at undercompression or over-compression mode, such as 1 degree off the full-compression; at full-compression, however, there is almost no lasing. In hard x-ray wavelength regime, we observed that there are reasonable photons generated even at full-compression mode, although the photon number is less than that from under-compression or over-compression mode. Since we cannot measure the x-ray pulse length at this time scale, the machine is typically optimized for generating maximum photons, not minimum pulse length. In this paper, we study the methods of producing femtosecond (or single-spike) x-ray pulses at LCLS with 20 pC charge, based on start-to-end simulations. Figure 1 shows a layout of LCLS. The compression in the second bunch compressor (BC2) determines the final e-beam bunch length. However, the laser heater, dog-leg after the main linac (DL2) and collective effects also affect the final bunch length. To adjust BC2 compression, we can either change the L2 phase or BC2 R{sub 56}. In this paper we only tune L2 phase while keep BC2 R{sub 56} fixed. For the start-to-end simulations, we used IMPACT-T and ELEGANT tracking from the photocathode to the entrance of the undulator, after that the FEL radiation was simulated with GENESIS. IMPACT-T tracks about 10{sup 6} particles in the injector part until 135 MeV, including 3D space charge force. The output particles from IMPACT-T are smoothed and increased to 12 x 10{sup 6} to reduce high-frequency numerical noise for subsequent ELEGANT simulations, which include linear and nonlinear transport effects, a 1D transient model of CSR, and longitudinal space charge effects, as well as geometric and resistive wake fields in the accelerator. In GENESIS part, the longitudinal wake field from undulator chamber and longitudinal space field are also included.

Wang, L.; Ding, Y.; Huang, Z.; /SLAC

2011-12-14

185

The beam-based calibration of an X-ray pinhole camera at SSRF  

NASA Astrophysics Data System (ADS)

A pinhole camera for imaging X-ray synchrotron radiation from a dipole magnet is now in operation at the Shanghai Synchrotron Radiation Facility (SSRF) storage ring. The electron beam size is derived by unfolding the radiation image and the point spread function (PSF) with deconvolution techniques. The performance of the pinhole is determined by the accuracy of the PSF measurement. This article will focus on a beam-based calibration scheme to measure the PSF system by varying the beam images with different quadrupole settings and fitting them with the corresponding theoretical beam sizes. Applying this method at SSRF, the PSF value of the pinhole is revised from 37 to 44 ?m. The deviation in beam size between the theoretical value and the measured value is minimized to 4% after calibration. This optimization allows us to observe the horizontal disturbance due to injection down to as small as 0.5 ?m.

Leng, Yong-Bin; Huang, Guo-Qing; Zhang, Man-Zhou; Chen, Zhi-Chu; Chen, Jie; Ye, Kai-Rong

2012-01-01

186

Measurement of X-ray intensity in mammography by a ferroelectric dosimeter  

NASA Astrophysics Data System (ADS)

Each year in the US over 20 million women undergo mammography, a relatively high dose x-ray examination of the breast, which is relatively sensitive to the carcinogenic effect of ionizing radiation. The radiation risk from mammography is usually expressed in terms of mean glandular dose (MGD) which is calculated as the product of measured entrance exposure (ESE) and a dose conversion factor which is a function of anode material, peak tube voltage (23 to 35 kVp), half-value layer, filtration, compressed breast thickness and breast composition. Mammographic units may have anodes made of molybdenum, rhodium or tungsten and filters of molybdenum, rhodium, or aluminum. In order to accommodate all these parameters, multiple extensive tables of conversion factors are required to cover the range of possibilities. Energy fluence and energy imparted are alternative measures of radiation hazard, which have been used in situations where geometry or filtration is unconventional such as computed tomography or fluoroscopy. Unfortunately, at the present there is no way to directly measure these quantities clinically. In radiation therapy applications, calorimetry has been used to measure energy absorbed. A ferroelectric-based detector has been described that measures energy fluence rate (x-ray intensity) for diagnostic x-ray, 50 to 140 kVp, aluminum filtered tungsten spectrum [Carvalho & Alter: IEEE Transactions 44(6) 1997]. This work explores use of ferroelectric detectors to measure energy fluence, energy fluence rate and energy imparted in mammography. A detector interfaced with a laptop computer was developed to allow measurements on clinical units of five different manufactures having targets of molybdenum, rhodium and tungsten and filters of molybdenum, rhodium, and aluminum of various thicknesses. The measurements provide the first values of energy fluence and energy imparted in mammography. These measurements are compared with conventional parameters such as entrance exposure and mean glandular dose as well as published values of energy imparted for other types of x-ray examinations. Advantage of measuring dose in terms of energy imparted in mammography are simplicity of comparison with other sources of radiation exposure and potential (relative ease) of measurement across a variety of anode and filter combinations.

Alter, Albert J.

2005-07-01

187

Windowless microfluidic platform based on capillary burst valves for high intensity x-ray measurements  

SciTech Connect

We propose and describe a microfluidic system for high intensity x-ray measurements. The required open access to a microfluidic channel is provided by an out-of-plane capillary burst valve (CBV). The functionality of the out-of-plane CBV is characterized with respect to the diameter of the windowless access hole, ranging from 10 to 130 {mu}m. Maximum driving pressures from 22 to 280 mbar corresponding to refresh rates of the exposed sample from 300 Hz to 54 kHz is demonstrated. The microfluidic system is tested at beamline ID09b at the ESRF synchrotron radiation facility in Grenoble, and x-ray scattering measurements are shown to be feasible and to require only very limited amounts of sample, <1 ml/h of measurements without recapturing of sample. With small adjustments of the present chip design, scattering angles up to 30 deg. can be achieved without shadowing effects and integration on-chip mixing and spectroscopy appears straightforward.

Vig, Asger Laurberg; Enevoldsen, Nikolaj; Thilsted, Anil Haraksingh; Eriksen, Johan; Kristensen, Anders [Department of Micro and Nanotechnology, DTU Nanotech, Technical University of Denmark, Building 345east, Orsteds Plads, DK-2800 Kongens Lyngby (Denmark); Haldrup, Kristoffer; Feidenhans'l, Robert; Nielsen, Martin Meedom [Centre for Molecular Movies, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen East (Denmark)

2009-11-15

188

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

PubMed

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

2011-10-11

189

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

190

Beam hardening effects in grating-based x-ray phase-contrast imaging  

SciTech Connect

Purpose: In this work, the authors investigate how beam hardening affects the image formation in x-ray phase-contrast imaging and consecutively develop a correction algorithm based on the results of the analysis. Methods: The authors' approach utilizes a recently developed x-ray imaging technique using a grating interferometer capable of visualizing the differential phase shift of a wave front traversing an object. An analytical description of beam hardening is given, highlighting differences between attenuation and phase-contrast imaging. The authors present exemplary beam hardening artifacts for a number of well-defined samples in measurements at a compact laboratory setup using a polychromatic source. Results: Despite the differences in image formation, the authors show that beam hardening leads to a similar reduction of image quality in phase-contrast imaging as in conventional attenuation-contrast imaging. Additionally, the authors demonstrate that for homogeneous objects, beam hardening artifacts can be corrected by a linearization technique, applicable to all kinds of phase-contrast methods using polychromatic sources. Conclusions: The evaluated correction algorithm is shown to yield good results for a number of simple test objects and can thus be advocated in medical imaging and nondestructive testing.

Chabior, Michael; Donath, Tilman; David, Christian; Bunk, Oliver; Schuster, Manfred; Schroer, Christian; Pfeiffer, Franz [Siemens AG Corporate Technology, 80200 Muenchen (Germany); Paul Scherrer Institut, 5232 Villigen PSI (Switzerland); Siemens AG Corporate Technology, 80200 Muenchen (Germany); Technische Universitaet Dresden, 01062 Dresden (Germany); Technische Universitaet Muenchen, 85748 Garching (Germany)

2011-03-15

191

Effects of electron beam dynamics on resolution of X-ray radiography  

NASA Astrophysics Data System (ADS)

In this study we link particle in cell (PIC) calculations from the code, MERLIN, with electron-photon Monte Carlo calculations using the code, MCNP, to produce synthetic radiographs. The results are used to examine several factors that may have an effect on the resolution of dynamic x-ray radiography such as done at the DARHT (Dual Axis Radiographic Hydro-Test) facility. Three properties are varied in this study, and the results of those variations are examined. First, the electron beam rise time from the accelerator is altered, and the difference on the temporal x-ray production is examined as well as the overall effects on the resolution of the radiographic image. Next, the effects of thermal velocity and energy spread of the electron beam as it exits the accelerator are studied by varying from a cold beam to a more realistic beam that fits with the expected or measured DARHT beam parameters. Finally, the bremsstrahlung conversion target composition is varied, and the effects of target materials and configurations are examined.

Christenson, P. J.; Kwan, T. J. T.

2000-10-01

192

Design of x-ray diagnostic beam line for a synchrotron radiation source and measurement results  

NASA Astrophysics Data System (ADS)

Indus-2 is a 2.5 GeV synchrotron radiation source (SRS) operational at the Raja Ramanna Centre for Advanced Technology (RRCAT) in India. We have designed, developed and commissioned x-ray diagnostic beam line (X-DBL) at the Indus-2. It is based on pinhole array imaging (8-18 keV). We have derived new equations for online measurements of source position and emission angle with pinhole array optics. Measured values are compared with the measurements at an independent x-ray beam position monitor (staggered pair blade monitor) installed in the X-DBL. The measured values are close to the theoretical expected values within ±12 ?m (or ±1.5 ?rad) for sufficiently wide range of the beam movements. So, beside the beam size and the beam emittance, online information for the vertical position and angle is also used in the orbit steering. In this paper, the various design considerations of the X-DBL and online measurement results are presented.

Garg, Akash Deep; Karnewar, A. K.; Ojha, A.; Shrivastava, B. B.; Holikatti, A. C.; Puntambekar, T. A.; Navathe, C. P.

2014-08-01

193

Short-wavelength soft-x-ray laser pumped in double-pulse single-beam non-normal incidence  

SciTech Connect

We demonstrated a 7.36 nm Ni-like samarium soft-x-ray laser, pumped by 36 J of a neodymium:glass chirped-pulse amplification laser. Double-pulse single-beam non-normal-incidence pumping was applied for efficient soft-x-ray laser generation. In this case, the applied technique included a single-optic focusing geometry for large beam diameters, a single-pass grating compressor, traveling-wave tuning capability, and an optimized high-energy laser double pulse. This scheme has the potential for even shorter-wavelength soft-x-ray laser pumping.

Zimmer, D. [LASERIX-CLUPS, LPGP UMR 8578, Universite Paris-Sud 11, F-91405 Orsay (France); GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, D-64291 Darmstadt (Germany); Institut fuer Physik, Johannes Gutenberg-Universitaet Mainz, D-55099 Mainz (Germany); Ros, D.; Guilbaud, O.; Habib, J.; Kazamias, S. [LASERIX-CLUPS, LPGP UMR 8578, Universite Paris-Sud 11, F-91405 Orsay (France); Zielbauer, B. [LASERIX-CLUPS, LPGP UMR 8578, Universite Paris-Sud 11, F-91405 Orsay (France); GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, D-64291 Darmstadt (Germany); Helmholtz Institut Jena, Friedrich-Schiller Universitaet, D-07743 Jena (Germany); Bagnoud, V. [GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, D-64291 Darmstadt (Germany); Helmholtz Institut Jena, Friedrich-Schiller Universitaet, D-07743 Jena (Germany); Ecker, B.; Aurand, B.; Kuehl, T. [GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, D-64291 Darmstadt (Germany); Institut fuer Physik, Johannes Gutenberg-Universitaet Mainz, D-55099 Mainz (Germany); Helmholtz Institut Jena, Friedrich-Schiller Universitaet, D-07743 Jena (Germany); Hochhaus, D. C.; Neumayer, P. [GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, D-64291 Darmstadt (Germany); ExtreMe Matter Institute EMMI, GSI Helmholtzzentrum fuer Schwerionenforschung, D-64291 Darmstadt (Germany); Institut fuer Angewandte Physik, Goethe-Universitaet Frankfurt am Main, D-60438 Frankfurt am Main (Germany)

2010-07-15

194

The Beynon Gabor zone plate: a new tool for de Broglie matter waves and hard X-rays? An off axis and focus intensity investigation.  

PubMed

Optical elements based on Fresnel zones are used in a range of applications, from X-ray telescopy to microscopy and recently also in the manipulation of de Broglie matter waves. In 1992 Beynon and co-workers presented a binary Gabor type zone plate (henceforth referred to as the Beynon Gabor zone plate). Because this zone plate has no higher order foci, it is in principle a very attractive candidate for focusing of de Broglie matter waves and in some cases X-rays. So far the Beynon Gabor zone plate investigations presented in the literature have concentrated on the intensity distribution along the optical axis and in the focal plane. Here we present a detailed numerical investigation of the Beynon Gabor zone plate, including an investigation of the off-optical axis, off focal plane intensity distribution for point source illumination. We show that at integer fractions of the focal length, the beam becomes nearly toroidal (doughnut-shaped). This offers potentially interesting new possibilities for de Broglie matter wave and X-ray optics, for example in STED-like applications. We further show that the increased intensity at the focal point predicted in the literature for a particular Beynon Gabor zone plate transmission function configuration is an artifact due to the lack of sampling nodes. We support our calculations with experimental measurements in the visible light range, using a Beynon Gabor zone plate fabricated with electron beam lithography. PMID:24514360

Greve, Martin M; Vial, Alexandre M; Stamnes, Jakob J; Holst, Bodil

2013-11-18

195

Determination of the energy dependence of the BC-408 plastic scintillation detector in medium energy x-ray beams  

NASA Astrophysics Data System (ADS)

The energy dependence of the response of BC-408 plastic scintillator (PS), an approximately water-equivalent material, has been investigated by employing standardized x-ray beams. IEC RQA and ISO N series x-ray beam qualities, in the range of 40–100?kVp, were calibrated using a PTW-type ionization chamber. The energy response of a thick BC-408 PS detector was measured using the multichannel pulse height analysis method. The response of BC-408 PS increased gradually with increasing energy in the energy range of 40–80?kVp and then showed a flat behavior at about 80 to 120?kVp. This might be due to the self-attenuation of scintillation light by the scintillator itself and may also be partly due to the ionization quenching, leading to a reduction in the intensity of the light output from the scintillator. The results indicated that the sensitivity drop in BC-408 PS material at lower photon energies may be overcome by adding some high-Z elements to its polyvinyltoluene (PVT) base. The material modification may compensate for the drop in the response at lower photon energies. Thus plastic scintillation dosimetry is potentially suitable for applications in diagnostic radiology.

Yücel, H.; Çubukçu, ?.; Uyar, E.; Engin, Y.

2014-11-01

196

Generation of strongly coupled Xe cluster nanoplasmas by low intensive soft x-ray laser irradiation  

SciTech Connect

A seeding gas jet including Xe clusters was irradiated with a laser-driven plasma soft x-ray laser pulse ({lambda}=13.9 nm, {approx}7 ps, {<=}5 Multiplication-Sign 10{sup 9} W/cm{sup 2}), where the laser photon energy is high enough to ionize 4d core electrons. In order to clarify how the innershell ionization followed by the Auger electron emission is affected under the intense laser irradiation, the electron energy distribution was measured. Photoelectron spectra showed that the peak position attributed to 4d hole shifted to lower energy and the spectral width was broadened with increasing cluster size. Moreover, the energy distribution exhibited that a strongly coupled cluster nanoplasma with several eV was generated.

Namba, S.; Hasegawa, N.; Kishimoto, M.; Nishikino, M.; Kawachi, T. [Graduate School of Engineering, Hiroshima University,Kagamiyama 1-4-1, Higashi-Hiroshima, Hiroshima, 739-8527 (Japan); Quantum Beam Science Directorate, Japan Atomic Energy Agency, Umemidai 8-1, Kizugawa, Kyoto, 619-0215 (Japan)

2012-07-11

197

Radiological characterization and water equivalency of genipin gel for x-ray and electron beam dosimetry.  

PubMed

The genipin radiochromic gel offers enormous potential as a three-dimensional dosimeter in advanced radiotherapy techniques. We have used several methods (including Monte Carlo simulation), to investigate the water equivalency of genipin gel by characterizing its radiological properties, including mass and electron densities, photon interaction cross sections, mass energy absorption coefficient, effective atomic number, collisional, radiative and total mass stopping powers and electron mass scattering power. Depth doses were also calculated for clinical kilovoltage and megavoltage x-ray beams as well as megavoltage electron beams. The mass density, electron density and effective atomic number of genipin were found to differ from water by less than 2%. For energies below 150 keV, photoelectric absorption cross sections are more than 3% higher than water due to the strong dependence on atomic number. Compton scattering and pair production interaction cross sections for genipin gel differ from water by less than 1%. The mass energy absorption coefficient is approximately 3% higher than water for energies <60 keV due to the dominance of photoelectric absorption in this energy range. The electron mass stopping power and mass scattering power differ from water by approximately 0.3%. X-ray depth dose curves for genipin gel agree to within 1% with those for water. Our results demonstrate that genipin gel can be considered water equivalent for kilovoltage and megavoltage x-ray beam dosimetry. For megavoltage electron beam dosimetry, however, our results suggest that a correction factor may be needed to convert measured dose in genipin gel to that of water, since differences in some radiological properties of up to 3% compared to water are observed. Our results indicate that genipin gel exhibits greater water equivalency than polymer gels and PRESAGE formulations. PMID:21734335

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

2011-08-01

198

Energy distribution measurement of narrow-band ultrashort x-ray beams via K-edge filters subtraction  

SciTech Connect

The characterization of novel x-ray sources includes the measurement of the photon flux and the energy distribution of the produced beam. The aim of BEATS2 experiment at the SPARC-LAB facility of the INFN National Laboratories of Frascati (Rome, Italy) is to investigate possible medical applications of an x-ray source based on Thomson relativistic back-scattering. This source is expected to produce a pulsed quasi-monochromatic x-ray beam with an instantaneous flux of 10{sup 20} ph/s in pulses 10 ps long and with an average energy of about 20 keV. A direct measurement of energy distribution of this beam is very difficult with traditional detectors because of the extremely high photon flux. In this paper, we present a method for the evaluation of the energy distribution of quasi-monochromatic x-ray beams based on beam filtration with K-edge absorbing foils in the energy range of interest (16-22 keV). The technique was tested measuring the energy distribution of an x-ray beam having a spectrum similar to the expected one (SPARC-LAB Thomson source) by using a tungsten anode x-ray tube properly filtered and powered. The energy distribution obtained has been compared with the one measured with a HPGe detector showing very good agreement.

Cardarelli, Paolo; Di Domenico, Giovanni; Marziani, Michele; Mucollari, Irena; Pupillo, Gaia; Sisini, Francesco; Taibi, Angelo; Gambaccini, Mauro [Dipartimento di Fisica, Universita di Ferrara and INFN - Ferrara, via Saragat 1, I-44122 Ferrara (Italy)

2012-10-01

199

Fluctuation of laser-induced x-rays from electron beam and plasma  

NASA Astrophysics Data System (ADS)

There has been a significant progress in the X-ray generation technologies for various laboratory and production application by laser-Compton scheme and laser produced plasma. Femtosecond X-ray generation was performed by Compton scattering through interaction between a 3-ps electron beam and 100-fs laser photons in a 90 degree scattering configuration. The X-ray energy and pulse duration were estimated as 2.3keV and 280fs from the observed electron and laser beam parameters. The fluctuation of the X-ray output was measured as 25% rms during a 30-min operation, and analyzed as a function of fluctuations of parameters like timing between the electron and laser beam, electron beam charge, laser beam energy, pulse widths, and spatial stability. Further reduction of the fluctuation is possible by improvement of timing stability down to 100fs region. All optical synchronization scheme was proposed and component technologies are under development. The novel scheme employs optical control of linear accelerator and femtosecond lasers by optical locking of lasing between different laser oscillators. Two mode-locked Ti:sapphire lasers of different wavelengths were precisely synchronized by a simple feedback system employing sum frequency generation. The measured rms timing jitter between two lasers was 28fs. Clean EUV light source is strongly demanded for next generation lithography, with 13.5nm, 2%bw, 100W and high pulse stability of less than 1%. The most promising approach is to employ a liquid Xe jet of 10-30 micron-meter diameter as the plasma source with high repetition rate solid state laser. The laser pulse energy usually fluctuates more than a few % and liquid jet fluctuates of the position up to 10% of the diameter. Higher repetition rate plasma generation causes acoustic instability inside the liquid jet. All these obstacles prevent to achieve the desired EUV stability. Discussion will be given on these issues and new architecture is proposed to achieve a clean and stable EUV light source.

Endo, Akira

2003-05-01

200

Dynamics of accelerated electron beams and X rays in solar flares with sub-THz radiation  

NASA Astrophysics Data System (ADS)

Unique measurements by a solar submillimeter radio telescope (SST) have been carried out in the sub-THz radiation at 212 and 405 THz over the past decade. The spectrum of RF radiation in this region increased with frequency for the three flares of November 2 and 4, 2003, and December 6, 2006, and the flux value reached 5 × 103-2 × 104 sfu at 405 GHz (Kaufman et al., 2009). In this work, we consider a set of nonlinear equations for an accelerated electrons beam and the Langmuir wave energy density. The distribution functions of the accelerated electron beam and wave energy density are calculated taking into account Coulomb collisions, electron scattering by waves, and wave scattering by plasma ions. In addition, the source of accelerated particles and the heat level of the Langmuir turbulence are specified. The beam and plasma parameters are chosen based on the aims of a problem. The plasma concentration varies from n = 1013 to 1015 cm-3, the electron plasma frequency f p = (3 × 1010-3 × 1011) Hz in this case. The ratio of plasma and beam concentrations, sufficient to explain the value of the radio flux at a frequency of 300 GHz, is n b/ n = 10-3. The Langmuir turbulence is excited due to the instability of the accelerated electron beam with an initial distribution function of the "bump-in-tail" type. Then, the parameters of radiowaves are calculated in the sub-THz range under the assumption of coalescence of two plasma waves. The calculation results show that a sub-THz radio flux can be obtained under the condition of injection of accelerated electrons. The fine time structure of radio flux observed is easily simulated based on this statement by the pulsed time structure of electron beams and their dynamics in overdense plasma. X-ray and gamma radiation was recorded during the events under study. Hard X-ray radiation is bremsstrahlung radiation from accelerated electron beams.

Vatagin, P. V.; Charikov, Yu. E.; Stepanov, A. V.; Kudryavtsev, I. V.

2012-12-01

201

White Beam Slits and Pink Beam Slits for the Hard X-ray Nanoprobe Beamline at the Advanced Photon Source  

NASA Astrophysics Data System (ADS)

A new type of slit has been designed for use in the hard x-ray nanoprobe beamline at the Advanced Photon Source (APS). The design incorporates monolithic GlidCop slit bodies mounted to commercially available x-y drive systems. Long, tapered apertures with adjacent water-cooling channels intercept the x-ray beam, removing the high heat load produced by two collinear APS undulators. The apertures are L-shaped and provide both horizontal and vertical slits. The beam-defining edges, positioned at the end of the tapered surfaces, consist of two sets of tungsten blades. These blades produce an exit beam with sharp corners and assure a clean cut-off for the white beam edges. The slit assembly is designed to allow overlap of the slit edges to stop the beam. The white beam slit design accommodates 3100 W of total power with a peak power density of 763 W/mm2. The pink beam slit design accommodates 400 W of total power with a peak power density of 180 W/mm2. Detailed thermal analyses were performed to verify the slits' accuracy under full beam loading. The new concept allows beamline operations to 180 mA with a simplified design approach.

Benson, C.; Jaski, Y.; Maser, J.; Powers, T.; Schmidt, O.; Rossi, E.

2007-01-01

202

Wide angle x-ray scattering of proteins : effect of beam exposure on protein integrity.  

SciTech Connect

Wide-angle X-ray scattering patterns from proteins in solution contain information relevant to the determination of protein fold. At relevant scattering angles, however, these data are weak, and the degree to which they might be used to categorize the fold of a protein is unknown. Preliminary work has been performed at the BioCAT insertion-device beamline at the Advanced Photon Source which demonstrates that one can collect X-ray scattering data from proteins in solution to spacings of at least 2.2 {angstrom} (q = 2.8 {angstrom}-1). These data are sensitive to protein conformational states, and are in good agreement with the scattering predicted by the program CRYSOL using the known three-dimensional atomic coordinates of the protein. An important issue in the exploitation of this technique as a tool for structural genomics is the extent to which the high intensity of X-rays available at third-generation synchrotron sources chemically or structurally damage proteins. Various data-collection protocols have been investigated demonstrating conditions under which structural degradation of even sensitive proteins can be minimized, making this technique a viable tool for protein fold categorization, the study of protein folding, unfolding, protein-ligand interactions and domain movement.

Fischetti, R. F.; Rodi, D. J.; Mirza, A.; Makowski, L.; Illinois Inst. of Tech.

2003-01-01

203

High energy X-ray computed tomography for industrial applications  

Microsoft Academic Search

A high-energy X-ray computed tomography system with an electron linear accelerator was developed to image cross-sections of large-scale and high-density materials. An electron linear accelerator is used for the X-ray source. The maximum X-ray energy is 12 MeV and the average energy is around 4 MeV. The intensity of an X-ray fan beam passing through the test object is measured

S. Izumi; S. Kamata; K. Satoh; H. Miyai

1991-01-01

204

High energy X-ray computed tomography for industrial applications  

Microsoft Academic Search

A high energy X-ray computed tomography (CT) system with an electron linear accelerator was developed to image cross-sections of large-scale and high-density materials. An electron linear accelerator is used as the X-ray source. The maximum X-ray energy is 12 MeV, and the average energy is around 4 MeV. The intensity of the X-ray fan beam passing through the test object

S. Izumi; S. Kamata; K. Satoh; H. Miyai

1993-01-01

205

Progress of the APS high heat load X-ray beam position monitor development  

SciTech Connect

Several novel design developments have been established for the Advanced Photon Source (APS) insertion device (ID) X-ray beam position monitor (XBPM) to improve its performance: (1) optimized geometric configuration of the monitor`s sensory blades; (2) smart XBPM system with an intelligent digital signal processor, which provides a self-learning and calibration function; and (3) transmitting XBPM with prefiltering in the commissioning windows for the front end. In this write-up, the authors summarize the recent progress on the XBPM development for the APS ID front ends.

Shu, D.; Barraza, J.; Ding, H.; Kuzay, T.M.; Ramanathan, M.

1997-09-01

206

A portable molecular beam epitaxy system for in situ x-ray investigations at synchrotron beamlines  

SciTech Connect

A portable synchrotron molecular beam epitaxy (MBE) system is designed and applied for in situ investigations. The growth chamber is equipped with all the standard MBE components such as effusion cells with shutters, main shutter, cooling shroud, manipulator, reflection high energy electron diffraction setup, and pressure gauges. The characteristic feature of the system is the beryllium windows which are used for in situ x-ray measurements. An UHV sample transfer case allows in vacuo transfer of samples prepared elsewhere. We describe the system design and demonstrate its performance by investigating the annealing process of buried InGaAs self-organized quantum dots.

Slobodskyy, T. [Institute for Synchrotron Radiation, Karlsruhe Institute of Technology - 76344 Eggenstein-Leopoldshafen (Germany); Institut fuer Angewandte Physik und Zentrum fuer Mikrostrukturforschung, Jungiusstrasse 11, D-20355 Hamburg (Germany); Schroth, P.; Grigoriev, D.; Minkevich, A. A.; Baumbach, T. [Institute for Synchrotron Radiation, Karlsruhe Institute of Technology - 76344 Eggenstein-Leopoldshafen (Germany); Hu, D. Z.; Schaadt, D. M. [Institute for Applied Physics/DFG-Center for Functional Nanostructures, Karlsruhe Institute of Technology (KIT), Karlsruhe (Germany); Institute for Energy Research and Physical Technologies, Technical University Clausthal, Am Stollen 19B, 38640 Goslar (Germany)

2012-10-15

207

X-ray Interferometry with Transmissive Beam Combiners for Ultra-High Angular Resolution Astronomy  

NASA Technical Reports Server (NTRS)

Abstract Interferometry provides one of the possible routes to ultra-high angular resolution for X-ray and gamma-ray astronomy. Sub-micro-arc-second angular resolution, necessary to achieve objectives such as imaging the regions around the event horizon of a super-massive black hole at the center of an active galaxy, can be achieved if beams from parts of the incoming wavefront separated by 100s of meters can be stably and accurately brought together at small angles. One way of achieving this is by using grazing incidence mirrors. We here investigate an alternative approach in which the beams are recombined by optical elements working in transmission. It is shown that the use of diffractive elements is a particularly attractive option. We report experimental results from a simple 2-beam interferometer using a low-cost commercially available profiled film as the diffractive elements. A rotationally symmetric filled (or mostly filled) aperture variant of such an interferometer, equivalent to an X-ray axicon, is shown to offer a much wider bandpass than either a Phase Fresnel Lens (PFL) or a PFL with a refractive lens in an achromatic pair. Simulations of an example system are presented.

Skinner, G. K.; Krismanic, John F.

2009-01-01

208

X-ray beam lines and beam line components for the SLAC Linac Coherent Light Source (LCLS)  

SciTech Connect

The LCLS is a novel high-brightness x-ray source designed to operate in the 300--400 eV range. In contrast to conventional synchrotron radiation sources, its output pulses will be characterized by unprecedented levels of brevity and peak power. In this paper we present recently-developed beam line layouts and design features intended to optimize the delivery of the LCLS photons to various experimental stations.

Tatchyn, R.; Pianetta, P.

1993-04-01

209

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

210

Integral window/photon beam position monitor and beam flux detectors for x-ray beams  

DOEpatents

A monitor/detector assembly in a synchrotron for either monitoring the position of a photon beam or detecting beam flux may additionally function as a vacuum barrier between the front end and downstream segment of the beamline in the synchrotron. A base flange of the monitor/detector assembly is formed of oxygen free copper with a central opening covered by a window foil that is fused thereon. The window foil is made of man-made materials, such as chemical vapor deposition diamond or cubic boron nitrate and in certain configurations includes a central opening through which the beams are transmitted. Sensors of low atomic number materials, such as aluminum or beryllium, are laid on the window foil. The configuration of the sensors on the window foil may be varied depending on the function to be performed. A contact plate of insulating material, such as aluminum oxide, is secured to the base flange and is thereby clamped against the sensor on the window foil. The sensor is coupled to external electronic signal processing devices via a gold or silver lead printed onto the contact plate and a copper post screw or alternatively via a copper screw and a copper spring that can be inserted through the contact plate and coupled to the sensors. In an alternate embodiment of the monitor/detector assembly, the sensors are sandwiched between the window foil of chemical vapor deposition diamond or cubic boron nitrate and a front foil made of similar material.

Shu, Deming (Darien, IL); Kuzay, Tuncer M. (Naperville, IL)

1995-01-01

211

Using an electron beam to produce a bright isotropic subsurface x-ray source for back illumination in landmine detection  

NASA Astrophysics Data System (ADS)

Why is it so difficult to detect concealed shallow buried landmines while it is relatively easy to image and detect cancers within the human body? One reason is that in medical x-ray imaging, the source is on one side of the body and the detectors are on the other. This is back-illumination, the optimal orientation for x-ray imaging. Can back-illumination be used in landmine detection? That is, is it possible to generate sufficient xrays 10 or more cm below the soil surface so that suitable detectors above ground could be used to image shallow buried objects including landmines? In an x-ray tube, high voltage electron beams produce x-rays by electron deceleration (bremsstrahlung) and induced orbital transitions. It may be possible to produce 1000 amp short pulses of electrons at 30 MeV using an electron gun with multiple field emitters. (This is a section of an antiballistic missile device proposed at SPIE Defense and Security 2004.) Electron beams of such energy have range of approximately 100 m in air and 10-15 cm in soil. This 5-10 m tall device could be carried by balloon, helicopter or land vehicle. X-ray production efficiency at 30 MeV is over 50 fold higher compared to medical x-ray tube efficiency. Such a device would produce a bright isotropic source of x-rays in a subsurface plume that might be usable in landmine detection.

Retsky, Michael W.

2005-06-01

212

Characteristics of a high-intensity plasma flash x-ray generator having a double-target radiation tube  

NASA Astrophysics Data System (ADS)

The radiographic characteristics of a high-intensity plasma flash x-ray generator having a solid-target (anode) radiation tube are described. This generator consisted of the following essential components; a high- voltage power supply, a low-impedance coaxial transmission line, a coaxial oil condenser of 0.2 (mu) F, a turbo-molecular pump, a thyratron pulser as a trigger device, and a flash x-ray triode having a rod-shaped long double anode; a 2.0 mm inner tungsten anode was embedded in 3.0 mm copper anode. The high-voltage condenser was charged from 40 to 60 kV by the power supply, and the electric charges in the condenser were discharged to the tube after triggering the cathode electrode. The maximum tube voltage was equivalent to the charged voltage of the main condenser, and the voltage decreased after the triggering. Both the tube voltage and the current displayed damped oscillations, and the maximum tube current was less than 20 kA. The pulse height of the flash x rays substantially increased according to increases in the charged voltage, and the x-ray durations had values of a few microseconds. The plasma x- ray source substantially grew when the charged voltage was increased. The flash x-ray spectra from the plasma x-ray source were measured by a transmission-type spectrometer having a LiF curved crystal of 0.5 mm in thickness. Compared to the intensities of copper K(alpha) 1 and K(alpha) 2 including nondiagram lines increased by using the double target.

Sato, Eiichi; Sagae, Michiaki; Takahashi, Kei; Oizumi, Teiji; Hayasi, Yasuomi; Tamakawa, Yoshiharu; Yanagisawa, Toru

1995-05-01

213

Anomalous intensities of lines observed in RESIK soft X-ray flare spectra  

NASA Astrophysics Data System (ADS)

RESIK was a high-resolution solar X-ray Bragg spectrometer, the most recent ever to be launched, being operational from 2001 to 2003. Its nominal wavelength coverage, 3.3 Å - 6.1 Å, has considerable diagnostic potential. RESIK observed numerous flares as well as non-flaring active regions. During flares, the data gathering intervals were as short as 2 s. Analysis of the data continues to the present time; at the time of writing, data for more than 50 flares have been reduced to science grade (level 2). The spectra include spectral lines formed by H- and He-like ions of various elements as well as continuum. The lines and continua are formed by hot coronal plasma corresponding to temperatures T>2 MK if interpreted thermally. This makes RESIK spectra uniquely suitable for investigations of the physical conditions of the hotter plasma component of flares and active regions. Many spectra were taken during the rise phase of flares. For some events, anomalous line intensity ratios are evident, possibly reflecting the presence of non-equilibrium conditions in flaring plasma -- the observed intensity ratios are not easily explained by isothermal or multi-thermal assumptions. In our presentation, we will show examples of such observations and give possible interpretations.

Sylwester, Barbara; Sylwester, Janusz; Mrozek, Tomasz; Kepa, Anna; Phillips, Kenneth

214

Separation of hard x-ray synchrotron radiation from electron beam slices  

NASA Astrophysics Data System (ADS)

In the electron beam slicing scheme1, 2 considered for National Synchrotron Light Source II (NSLS-II) at Brookhaven National Laboratory, when a low energy electron bunch crosses from top of a high energy storage ring electron bunch, its coulomb force will kick a short slice (slicing bunch) from the core (core bunch) of the storage ring electron bunch. The short slice bunch and the long core bunch when passing through the 3 m long U20 in-vacuum undulator will radiate X-ray pulses with pulse length ~150 fs and 30 ps respectively. To separate the satellite radiation from the core radiation, we propose a conceptual optical scheme allowing for the separation. To get reliable estimates of the separation performances, we apply the Synchrotron Radiation Workshop (SRW) physical optics computer code3, 4 to study the wavefront propagation. As calculations show, at 7.8 keV, the separation signal-to-noise ratio can reach 5~12 and the satellite photon flux per pulse at sample can be 5000~20000 photons/0.1%BW with x-ray pulse length 150 ~ 330 fs depending on the separation method and the crossing angle between the low energy electron bunch and the high energy storage ring bunch. Since the repetition rate of the electron beam slicing system can reach 100 kHz, the average flux per second can reach 5 x 108 ` 2 x 109 photons/sec/0.1%BW.

He, A.; Chubar, O.; Yu, L. H.

2014-09-01

215

Chemical Environment Effects on K[beta]/K[alpha] Intensity Ratio: An X-Ray Fluorescence Experiment on Periodic Trends  

ERIC Educational Resources Information Center

X-ray fluorescence (XRF) data from an energy-dispersive XRF instrument were used to investigate the chlorine K[alpha] and K[beta] peaks in several group 1 salts. The ratio of the peak intensity is sensitive to the local chemical environment of the chlorine atoms studied in this experiment and it shows a periodic trend for these salts. (Contains 1…

Durham, Chaney R.; Chase, Jeffery M.; Nivens, Delana A.; Baird, William H.; Padgett, Clifford W.

2011-01-01

216

Efficiency of capturing a phase image using cone-beam x-ray Talbot interferometry.  

PubMed

We assesses the efficiency of x-ray Talbot interferometry (XTI), a technique based on the Talbot effect for measuring a wavefront gradient, in terms of how quickly it can capture a high-quality phase image with a large signal-to-noise ratio for a given incident photon number. Photon statistics cause errors in the phase of the moiré fringes and impose a detection limit on the wavefront gradient. The relation between the incident photon number and the detection limit is determined, and a figure of merit of XTI for a monochromatic cone beam is then defined. The dependence of the figure of merit on optical system parameters, such as grating pitch and position, is then discussed. The effects of varying the pattern height and linewidth of the second grating are shown for rectangular and trapezoidal teeth. Finally, we show how to design a practical cone-beam Talbot interferometer for certain boundary conditions. PMID:18677365

Yashiro, Wataru; Takeda, Yoshihiro; Momose, Atsushi

2008-08-01

217

Ptychographical imaging of the phase vortices in the x-ray beam formed by nanofocusing lenses  

NASA Astrophysics Data System (ADS)

We present the ptychographical reconstruction of the x-ray beam formed by nanofocusing lenses (NFLs) containing a number of phase singularities (vortices) in the vicinity of the focal plane. As a test object Siemens star pattern was used with the finest features of 50 nm for ptychographical measurements. The extended ptychographical iterative engine (ePIE) algorithm was applied to retrieve both complex illumination and object functions from the set of diffraction patterns. The reconstruction revealed the focus size of 91.4±1.1 nm in horizontal and 70±0.3 nm in vertical direction at full width at half maximum (FWHM). The complex probe function was propagated along the optical axis of the beam revealing the evolution of the phase singularities.

Dzhigaev, D.; Lorenz, U.; Kurta, R. P.; Seiboth, F.; Stankevic, T.; Mickevicius, S.; Singer, A.; Shabalin, A.; Yefanov, O. M.; Strikhanov, M. N.; Falkenberg, G.; Schroer, C. G.; Feidenhans'l, R.; Vartanyants, I. A.

2014-04-01

218

Compact soft x-ray spectrometer for plasma diagnostics at the Heidelberg Electron Beam Ion Trap  

SciTech Connect

A compact flat-field soft x-ray grazing-incidence grating spectrometer equipped with a cryogenically cooled back-illuminated charge-coupled device camera was built and implemented at the Heidelberg Electron Beam Ion Trap. The instrument spans the spectral region from 1 to 37 nm using two different gratings. In slitless operation mode, it directly images a radiation source, in this case ions confined in an electron beam ion trap, with high efficiency and reaching hereby a resolving power of {lambda}/{delta}{lambda} congruent with 130 at 2 nm and of {lambda}/{delta}{lambda} congruent with 600 at 28 nm. Capable of automatized operation, its low noise and excellent stability make it an ideal instrument not only for spectroscopic diagnostics requiring wide spectral coverage but also for precision wavelength measurements.

Lapierre, A.; Crespo Lopez-Urrutia, J. R.; Baumann, T. M.; Epp, S. W.; Gonchar, A.; Gonzalez Martinez, A. J.; Liang, G.; Rohr, A.; Soria Orts, R.; Simon, M. C.; Tawara, H.; Versteegen, R.; Ullrich, J. [Max-Planck Institut fuer Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg (Germany)

2007-12-15

219

Matching X-ray beam and detector properties to protein crystals of different perfection  

PubMed Central

An analysis is given of the effect of different beam and detector parameters on the sharpness of recorded diffraction features for macromolecular crystals of different quality. The crystal quality parameters include crystal strain, crystal or mosaic block size and mosaic block misorientation. Calculations are given for instrument parameters such as angular resolution of the detector, beam divergence and wavelength bandpass to be matched to the intrinsic diffraction properties from these crystals with the aim of obtaining the best possible data out of each crystal. Examples are given using typical crystal imperfections obtained from the literature for both room-temperature and cryo-cooled crystals. Possible implications for the choice of X-ray source, beamline design, detector specifications, instrument set-up and data processing are discussed, together with the limitations of the approach. PMID:24763643

Nave, Colin

2014-01-01

220

Accelerating x-ray data collection using pyramid beam ray casting geometries.  

PubMed

Image reconstruction from its projections is a necessity in many applications such as medical (CT), security, inspection, and others. This paper extends the 2-D Fan-beam method in [2] to 3-D. The algorithm, called Pyramid Beam (PB), is based upon the parallel reconstruction algorithm in [1]. It allows fast capturing of the scanned data, and in 3-D, the reconstructions are based upon the discrete X-ray transform [1]. The PB geometries are reordered to fit parallel projection geometry. The underlying idea is to use the algorithm in [1] by porting the proposed PB geometries to fit the algorithm in [1]. The complexity of the algorithm is comparable with the 3-D FFT. The results show excellent reconstruction qualities while being simple for practical use. PMID:20693110

Averbuch, Amir; Lifschitz, Guy; Shkolnisky, Yoel

2011-02-01

221

Ion-beam sputter deposition of x-ray multilayer optics on large areas  

NASA Astrophysics Data System (ADS)

Most important requirements for the deposition of x-ray optical multilayers are a) using a stable and reproducible deposition technique and b) to find growth conditions where the interfaces between adjacent layers are abrupt (no interdiffusion ? d) and smooth (no roughness ? r). The interface width ? (?2 = ? d 2 + ? r 2) becomes increasingly important for smaller period thicknesses. Furthermore, the kinetic energies of the condensing particles on the substrate surface are of special importance for the interface formation. The ion beam sputter deposition technique (IBSD) provides stable and well adjustable particle energies combined with medium to high deposition rates allowing the fabrication of precise multilayer stacks for x-ray optical applications. We will present our newly installed large area IBSD facility with 400 x 100 mm2 linear ion sources and substrate sizes of up to 200 mm diameter (circular) or 500 x 100 mm 2 (rectangular) and its characteristics concerning thickness homogeneity and process stability. First experimental results of metal/non-metal multilayer depositions with thickness uniformities of 99,9% over the entire substrate area are discussed. Different material combinations (Ni/B4C, Ni/C, Mo/Si) with period thicknesses between 2 nm and 10 nm have been fabricated and characterized by x-ray and EUV reflectometry. Interface widths are typically in the order of 0.3 nm. For the Ni-based multilayers Cu-K? reflectances of R > 80 % can be obtained with period thicknesses dP greater than or equal to 2.5 nm (Ni/B4C) and dP greater than or equal to 3.0 nm (Ni/C). EUV reflectances of the Mo/Si multilayers are as high as R = 68,0 % at ? = 13,5 nm (incidence angle ? = 5 deg).

Gawlitza, Peter; Braun, Stefan; Lipfert, Sebastian; Leson, Andreas

2006-08-01

222

Absolute x-ray dosimetry on a synchrotron medical beam line with a graphite calorimeter  

SciTech Connect

Purpose: The absolute dose rate of the Imaging and Medical Beamline (IMBL) on the Australian Synchrotron was measured with a graphite calorimeter. The calorimetry results were compared to measurements from the existing free-air chamber, to provide a robust determination of the absolute dose in the synchrotron beam and provide confidence in the first implementation of a graphite calorimeter on a synchrotron medical beam line. Methods: The graphite calorimeter has a core which rises in temperature when irradiated by the beam. A collimated x-ray beam from the synchrotron with well-defined edges was used to partially irradiate the core. Two filtration sets were used, one corresponding to an average beam energy of about 80 keV, with dose rate about 50?Gy/s, and the second filtration set corresponding to average beam energy of 90 keV, with dose rate about 20 Gy/s. The temperature rise from this beam was measured by a calibrated thermistor embedded in the core which was then converted to absorbed dose to graphite by multiplying the rise in temperature by the specific heat capacity for graphite and the ratio of cross-sectional areas of the core and beam. Conversion of the measured absorbed dose to graphite to absorbed dose to water was achieved using Monte Carlo calculations with the EGSnrc code. The air kerma measurements from the free-air chamber were converted to absorbed dose to water using the AAPM TG-61 protocol. Results: Absolute measurements of the IMBL dose rate were made using the graphite calorimeter and compared to measurements with the free-air chamber. The measurements were at three different depths in graphite and two different filtrations. The calorimetry measurements at depths in graphite show agreement within 1% with free-air chamber measurements, when converted to absorbed dose to water. The calorimetry at the surface and free-air chamber results show agreement of order 3% when converted to absorbed dose to water. The combined standard uncertainty is 3.9%. Conclusions: The good agreement of the graphite calorimeter and free-air chamber results indicates that both devices are performing as expected. Further investigations at higher dose rates than 50?Gy/s are planned. At higher dose rates, recombination effects for the free-air chamber are much higher and expected to lead to much larger uncertainties. Since the graphite calorimeter does not have problems associated with dose rate, it is an appropriate primary standard detector for the synchrotron IMBL x rays and is the more accurate dosimeter for the higher dose rates expected in radiotherapy applications.

Harty, P. D., E-mail: Peter.Harty@arpansa.gov.au; Ramanathan, G.; Butler, D. J.; Johnston, P. N. [Australian Radiation Protection and Nuclear Safety Agency, Yallambie, Victoria 3085 (Australia)] [Australian Radiation Protection and Nuclear Safety Agency, Yallambie, Victoria 3085 (Australia); Lye, J. E. [Australian Radiation Protection and Nuclear Safety Agency, Yallambie, Victoria 3085, Australia and Australian Clinical Dosimetry Service, Yallambie, Victoria 3085 (Australia)] [Australian Radiation Protection and Nuclear Safety Agency, Yallambie, Victoria 3085, Australia and Australian Clinical Dosimetry Service, Yallambie, Victoria 3085 (Australia); Hall, C. J. [Imaging and Medical Beamline, Australian Synchrotron, Clayton, Victoria 3168 (Australia)] [Imaging and Medical Beamline, Australian Synchrotron, Clayton, Victoria 3168 (Australia); Stevenson, A. W. [Imaging and Medical Beamline, Australian Synchrotron, Clayton, Victoria 3168, Australia and CSIRO, Materials Science and Engineering, Clayton Sth Victoria 3169 (Australia)] [Imaging and Medical Beamline, Australian Synchrotron, Clayton, Victoria 3168, Australia and CSIRO, Materials Science and Engineering, Clayton Sth Victoria 3169 (Australia)

2014-05-15

223

Hot electron and x-ray production from intense laser irradiation of wavelength-scale polystyrene spheres  

SciTech Connect

Hot electron and x-ray production from solid targets coated with polystyrene-spheres which are irradiated with high-contrast, 100 fs, 400 nm light pulses at intensity up to 2x10{sup 17} W/cm{sup 2} have been studied. The peak hard x-ray signal from uncoated fused silica targets is an order of magnitude smaller than the signal from targets coated with submicron sized spheres. The temperature of the x-rays in the case of sphere-coated targets is twice as hot as that of uncoated glass. A sphere-size scan of the x-ray yield and observation of a peak in both the x-ray production and temperature at a sphere diameter of 0.26 {mu}m, indicate that these results are consistent with Mie enhancements of the laser field at the sphere surface and multipass stochastic heating of the hot electrons in the oscillating laser field. These results also match well with particle-in-cell simulations of the interaction.

Sumeruk, H. A.; Kneip, S.; Symes, D. R.; Churina, I. V.; Belolipetski, A. V.; Dyer, G.; Landry, J.; Bansal, G.; Bernstein, A.; Donnelly, T. D.; Karmakar, A.; Pukhov, A.; Ditmire, T. [Texas Center for High Intensity Laser Science, Department of Physics, University of Texas, Austin, Texas 78712 (United States); Department of Physics, Harvey Mudd College, Claremont, California 91711 (United States); Institut fuer Theoretische Physik I, Heinrich-Heine-University of Dusseldorf, 40225 Dusseldorf (Germany); Texas Center for High Intensity Laser Science, Department of Physics, University of Texas, Austin, Texas 78712 (United States)

2007-06-15

224

Low-intensity x-ray and gamma-ray imaging device  

NASA Technical Reports Server (NTRS)

Low-dosage, low-power X-ray system can be made completely self-contained, allowing fluoroscopy and radiography to be carried out in field and remote locations. New device, known as "lixiscope," can be used with conventional X-ray machine turned down to low level, or, it can be operated with radioisotope source for hand-held portable applications. Originally developed for X-ray astronomy, lixiscope obtains high sensitivity by using intermediate stages of photoelectron conversion and electron amplification to generate image suitable for direct viewing or for recording on film.

Yin, L. I.

1978-01-01

225

Commercial CMOS image sensors as X-ray imagers and particle beam monitors  

NASA Astrophysics Data System (ADS)

CMOS image sensors are widely used in several applications such as mobile handsets webcams and digital cameras among others. Furthermore they are available across a wide range of resolutions with excellent spectral and chromatic responses. In order to fulfill the need of cheap systems as beam monitors and high resolution image sensors for scientific applications we exploited the possibility of using commercial CMOS image sensors as X-rays and proton detectors. Two different sensors have been mounted and tested. An Aptina MT9v034, featuring 752 × 480 pixels, 6?m × 6?m pixel size has been mounted and successfully tested as bi-dimensional beam profile monitor, able to take pictures of the incoming proton bunches at the DeFEL beamline (1–6 MeV pulsed proton beam) of the LaBeC of INFN in Florence. The naked sensor is able to successfully detect the interactions of the single protons. The sensor point-spread-function (PSF) has been qualified with 1MeV protons and is equal to one pixel (6 mm) r.m.s. in both directions. A second sensor MT9M032, featuring 1472 × 1096 pixels, 2.2 × 2.2 ?m pixel size has been mounted on a dedicated board as high-resolution imager to be used in X-ray imaging experiments with table-top generators. In order to ease and simplify the data transfer and the image acquisition the system is controlled by a dedicated micro-processor board (DM3730 1GHz SoC ARM Cortex-A8) on which a modified LINUX kernel has been implemented. The paper presents the architecture of the sensor systems and the results of the experimental measurements.

Castoldi, A.; Guazzoni, C.; Maffessanti, S.; Montemurro, G. V.; Carraresi, L.

2015-01-01

226

Automated marker tracking using noisy X-ray images degraded by the treatment beam.  

PubMed

This study demonstrates the feasibility of automated marker tracking for the real-time detection of intrafractional target motion using noisy kilovoltage (kV) x-ray images degraded by the megavoltage (MV) treatment beam. The authors previously introduced the in-line imaging geometry, in which the flat-panel detector (FPD) is mounted directly underneath the treatment head of the linear accelerator. They found that the 121 kVp image quality was severely compromised by the 6 MV beam passing through the FPD at the same time. Specific MV-induced artefacts present a considerable challenge for automated marker detection algorithms. For this study, the authors developed a new imaging geometry by re-positioning the FPD and the x-ray tube. This improved the contrast-to-noise-ratio between 40% and 72% at the 1.2 mAs/image exposure setting. The increase in image quality clearly facilitates the quick and stable detection of motion with the aid of a template matching algorithm. The setup was tested with an anthropomorphic lung phantom (including an artificial lung tumour). In the tumour one or three Calypso(®) beacons were embedded to achieve better contrast during MV radiation. For a single beacon, image acquisition and automated marker detection typically took around 76±6 ms. The success rate was found to be highly dependent on imaging dose and gantry angle. To eliminate possible false detections, the authors implemented a training phase prior to treatment beam irradiation and also introduced speed limits for motion between subsequent images. PMID:25280891

Wisotzky, E; Fast, M F; Oelfke, U; Nill, S

2014-09-30

227

Modeling of heat-bump formation in x-ray optics under SR beams  

NASA Astrophysics Data System (ADS)

We have used a direct optical measurement of the distortion of the first silicon crystal of the CHESS A2 monochromator. The total X-ray power absorbed by the crystal was in the range of 2 to 190 Watts. The X-ray powers measured by a bolometer were in good agreement with the XOP calculations. In-situ optical measurements were used to measure the deformation of the crystal under the heat load between a 3-15° angle of incidence. Simultaneously, ANSYS modeling of the effect of the heat load on the monochromator crystal with the cooling assembly was done. The measured slope error and the surface deformation profiles were in good agreement with the ANSYS simulations. A rocking curve method was used to measure the effect of a heat load on the diffraction properties of the monochromator for a range of beam-defining slit widths. We have found a good correlation between the FWHM of the rocking curves and the slope errors from the optical measurements.

Revesz, Peter; Kazimirov, Alexander; Savino, James J.; Macgahan, Christopher J.; Windisch, Emmett L.

2009-08-01

228

Strict X-ray beam collimation for facial bones examination can increase lens exposure  

PubMed Central

Objectives It is well accepted that collimation is a cost-effective dose-reducing tool for X-ray examinations. This phantom-based study investigated the impact of X-ray beam collimation on radiation dose to the lenses of the eyes and thyroid along with the effect on image quality in facial bone radiography. Methods A three-view series (occipitomental, occipitomental 30 and lateral) was investigated, and radiation doses to the lenses and thyroid were measured using an Unfors dosemeter. Images were assessed by six experienced observers using a visual grading analysis and a total of 5400 observations were made. Results Strict collimation significantly (p<0.0001) reduced the radiation dose to the lenses of the eyes and thyroid when using a fixed projection-specific exposure. With a variable exposure technique (fixed exit dose, to simulate the behaviour of an automatic exposure control), while strict collimation was again shown to reduce thyroid dose, higher lens doses were demonstrated when compared with larger fields of exposure. Image quality was found to significantly improve using strict collimation, with observer preference being demonstrated using visual grading characteristic curves. Conclusion The complexities of optimising radiographic techniques have been shown and the data presented emphasise the importance of examining dose-reducing strategies in a comprehensive way. PMID:22374279

Powys, R; Robinson, J; Kench, P L; Ryan, J; Brennan, P C

2012-01-01

229

Comparison of SOFC Cathode Microstructure Quantified using X-ray Nanotomography and Focused Ion Beam - Scanning Electron Microscopy  

SciTech Connect

X-ray nanotomography and focused ion beam scanning electron microscopy (FIB?SEM) have been applied to investigate the complex 3D microstructure of solid oxide fuel cell (SOFC) electrodes at spatial resolutions of 45 nm and below. The application of near edge differential absorption for x-ray nanotomography and energy selected backscatter detection for FIB–SEM enable elemental mapping within the microstructure. Using these methods, non?destructive 3D x-ray imaging and FIB–SEM serial sectioning have been applied to compare three?dimensional elemental mapping of the LSM, YSZ, and pore phases in the SOFC cathode microstructure. The microstructural characterization of an SOFC cathode is reported based on these measurements. The results presented demonstrate the viability of x-ray nanotomography as a quantitative characterization technique and provide key insights into the SOFC cathode microstructure.

Nelson, George J.; Harris, William H.; Lombardo, Jeffrey J.; Izzo, Jr., John R.; Chiu, W. K. S.; Tanasini, Pietro; cantoni, Marco; Van herle, Jan; Comninellis, Christos; Andrews, Joy C.; Liu, Yijin; Pianetta, Piero; Chu, Yong

2011-01-01

230

Comparison of SOFC Cathode Microstructure Quantified using X-ray Nanotomography and Focused Ioni Beam-scanning Electron Microscopy  

SciTech Connect

X-ray nanotomography and focused ion beam scanning electron microscopy (FIB-SEM) have been applied to investigate the complex 3D microstructure of solid oxide fuel cell (SOFC) electrodes at spatial resolutions of 45 nm and below. The application of near edge differential absorption for x-ray nanotomography and energy selected backscatter detection for FIB-SEM enable elemental mapping within the microstructure. Using these methods, non-destructive 3D x-ray imaging and FIB-SEM serial sectioning have been applied to compare three-dimensional elemental mapping of the LSM, YSZ, and pore phases in the SOFC cathode microstructure. The microstructural characterization of an SOFC cathode is reported based on these measurements. The results presented demonstrate the viability of x-ray nanotomography as a quantitative characterization technique and provide key insights into the SOFC cathode microstructure.

G Nelson; W Harris; J Lombardo; J Izzo Jr.; W Chiu; P Tanasini; M Cantoni; J Van herle; C Comninellis; et al.

2011-12-31

231

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

SciTech Connect

We report an experimental study on the optimization of a laser plasma based x-ray source of ultra-short duration K-? line radiation. The interaction of pulses from a CPA based Ti:sapphire laser (10 TW, 45 fs, 10 Hz) system with magnesium, titanium, iron and copper solid target generates bright 1-8 keV K-? x-ray radiation. The x-ray yield was optimized with the laser pulse duration (at fixed fluence) which is varied in the range of 45 fs to 1.4 ps. It showed a maximum at laser pulse duration of ?740 fs, 420 fs, 350 and 250 fs for Mg (1.3 keV), Ti (4.5 keV), Fe (6.4 keV) and Cu (8.05 keV) respectively. The x-ray yield is observed to be independent of the sign of the chirp. The scaling of the K-? yield (I{sub x} ? I{sub L}{sup ?}) for 45 fs and optimized pulse duration were measured for laser intensities in the region of 3 × 10{sup 14} – 8 × 10{sup 17}. The x-ray yield shows a much faster scaling exponent ? = 1.5, 2.1, 2.4 and 2.6 for Mg, Ti, Fe and Cu respectively at optimized pulse duration compared to scaling exponent of 0.65, 1.3, 1.5, and 1.7 obtained for 45 fs duration laser pulses. The laser to x-ray energy conversion efficiencies obtained for different target materials are ?{sub Mg} = 1.2 × 10{sup ?5}, ?{sub Ti} = 3.1 × 10{sup ?5}, ?{sub Fe} = 2.7 × 10{sup ?5}, ?{sub Cu} = 1.9 × 10{sup ?5}. The results have been explained from the efficient generation of optimal energy hot electrons at longer laser pulse duration. The faster scaling observed at optimal pulse duration indicates that the x-ray source is generated at the target surface and saturation of x-ray emission would appear at larger laser fluence. An example of utilization of the source for measurement of shock-wave profiles in a silicon crystal by time resolved x-ray diffraction is also presented.

Arora, V., E-mail: arora@rrcat.gov.in; Naik, P. A.; Chakera, J. A.; Bagchi, S.; Tayyab, M.; Gupta, P. D. [Laser Plasma Division, Raja Rammana Centre for Advanced Technology, Indore 452 013 (India)] [Laser Plasma Division, Raja Rammana Centre for Advanced Technology, Indore 452 013 (India)

2014-04-15

232

Correlated Intense X-Ray and TEV Activity of Markarian 501 in 1998 June  

Microsoft Academic Search

We present exactly simultaneous X-ray and TeV monitoring with RXTE and HEGRA of the TeV blazar Mrk 501 during 15 days in 1998 June. After an initial period of very low flux at both wavelengths, the source underwent a remarkable flare in the TeV and X-ray energy bands, lasting for about 6 days and with a larger amplitude at TeV

R. M. Sambruna; F. A. Aharonian; H. Krawczynski; A. G. Akhperjanian; J. A. Barrio; K. Bernlöhr; H. Bojahr; I. Calle; J. L. Contreras; J. Cortina; S. Denninghoff; V. Fonseca; J. C. Gonzalez; N. Götting; G. Heinzelmann; M. Hemberger; G. Hermann; A. Heusler; W. Hofmann; D. Horns; A. Ibarra; R. Kankanyan; M. Kestel; J. Kettler; C. Köhler; A. Kohnle; A. Konopelko; H. Kornmeyer; D. Kranich; H. Lampeitl; A. Lindner; E. Lorenz; N. Magnussen; O. Mang; H. Meyer; R. Mirzoyan; A. Moralejo; L. Padilla; M. Panter; R. Plaga; A. Plyasheshnikov; J. Prahl; G. Pühlhofer; G. Rauterberg; A. Röhring; V. Sahakian; M. Samorski; M. Schilling; D. Schmele; F. Schröder; W. Stamm; M. Tluczykont; H. J. Völk; B. Wiebel-Sooth; C. Wiedner; M. Willmer; W. Wittek; L. Chou; P. S. Coppi; R. Rothschild; C. M. Urry

2000-01-01

233

Tests of the APS X-ray transmitting beam position monitors at ESRF  

SciTech Connect

Two different types of synthetic diamond-based X-ray transmitting beam position monitor (XBPM) prototypes have been studied with an undulator white beam at the European Synchrotron Radiation Facility (ESRF) ID-6 beamline. Of particular interest was the possibility of designing an integral window and filter-photon beam position monitor for the Advanced Photon Source (APS) high heat flux insertion device beamlines. The photoelectron-emission type transmitting XBPM prototype uses a 25-mm-diameter, 175-micron-thick CVD-diamond disk with 0.2-micron-thick electrically isolated patterns of aluminum coating on one side of the diamond disk. The photoelectron emission signal was collected from the aluminum-coat surface to provide the beam position information. A novel photoconductive-type transmitting XBPM prototype uses the same CVD-diamond disk, but patterns of aluminum coating were applied on both sides of the diamond disk. A DC bias voltage was used to generate the current signal, which is based on photoconductive properties of the CVD-diamond. Test results are presented in the paper.

Shu, D.; Barraza, J.; Kuzay, T.M. [Argonne National Lab., IL (United States). Advanced Photon Source; Naylor, G.; Elleaume, P. [European Synchrotron Radiation Facility, Grenoble (France)

1997-10-01

234

X-ray and gamma-ray intensity measurements in 131I, 166Ho, 198Au and 199Au decays  

NASA Astrophysics Data System (ADS)

Relative intensities of X- and gamma rays emitted in the decays of 131I, 166Ho, 198Au and 199Au have been measured precisely using a set of five detectors: 96.0 cm 3 and 57.1 cm 3 coaxial HPGe detectors, a 28.27 mm 2 × 5.0 mm vertical planar HPGe detector and two 28.27 mm 2 × 5.5 mm Si(Li) detectors. The measured values of X-ray intensities are, in general, in good agreement with the theoretically calculated values. The intensities of different components of K and L X-rays in the above mentioned decays have been measured for the first time.

Chand, Bakhshish; Goswamy, Jatinder; Mehta, Devinder; Singh, Nirmal; Trehan, P. N.

1989-12-01

235

Image Covariance and Lesion Detectability in Direct Fan-Beam X-Ray Computed Tomography  

PubMed Central

We consider noise in computed tomography images that are reconstructed using the classical direct fan-beam filtered backprojection algorithm, from both full and short-scan data. A new, accurate method for computing image covariance is presented. The utility of the new covariance method is demonstrated by its application to the implementation of a channelized Hotelling observer for a lesion detection task. Results from the new covariance method and its application to the channelized Hotelling observer are compared with results from Monte Carlo Simulations. In addition, the impact of a bowtie filter and x-ray tube current modulation on reconstruction noise and lesion detectability are explored for full-scan reconstruction. PMID:18424878

Wunderlich, Adam; Noo, Frédéric

2009-01-01

236

Integration of a broad beam ion source with a high-temperature x-ray diffraction vacuum chamber  

SciTech Connect

Here, the integration of a low energy, linearly variable ion beam current density, mechanically in situ adjustable broad beam ion source with a high-temperature x-ray diffraction (XRD) vacuum chamber is reported. This allows in situ XRD investigation of phase formation and evolution processes induced by low energy ion implantation. Special care has been taken to an independent adjustment of the ion beam for geometrical directing towards the substrate, a 15 mm small ion source exit aperture to avoid a secondary sputter process of the chamber walls, linearly variable ion current density by using a pulse length modulation (PLM) for the accelerating voltages without changing the ion beam density profile, nearly homogeneous ion beam distribution over the x-ray footprint, together with easily replaceable Kapton{sup Registered-Sign} windows for x-rays entry and exit. By combining a position sensitive x-ray detector with this PLM-modulated ion beam, a fast and efficient time resolved investigation of low energy implantation processes is obtained in a compact experimental setup.

Manova, D.; Bergmann, A.; Maendl, S.; Neumann, H.; Rauschenbach, B. [Leibniz-Institut fuer Oberflaechenmodifizierung e. V., Permoserstr. 15, 04318 Leipzig (Germany)

2012-11-15

237

Dosimetry of x-ray beams: The measure of the problem  

SciTech Connect

This document contains the text of an oral presentation on dosimetry of analytical x-ray equipment presented at the Denver X-Ray Conference. Included are discussions of sources of background radiation, exposure limits from occupational sources, and the relationship of these sources to the high dose source of x-rays found in analytical machines. The mathematical basis of x-ray dosimetry is reviewed in preparation for more detailed notes on personnel dosimetry and the selection of the most appropriate dosimeter for a specific application. The presentation concludes with a discussion common to previous x-ray equipment accidents. 2 refs. (TEM)

de Castro, T.M.

1986-08-01

238

Real-time scanning beam digital x-ray image guidance system for transbronchial needle biopsy  

NASA Astrophysics Data System (ADS)

We investigate a real-time digital tomosynthesis (DTS) imaging modality, based on the scanning beam digital x-ray (SBDX) hardware, used in conjunction with an electromagnetic navigation bronchoscopy (ENB) system to provide improved image guidance for minimally invasive transbronchial needle biopsy (TBNbx). Because the SBDX system source uses electron beams, steered by electromagnets, to generate x-rays, and the ENB system generates an electromagnetic field to localize and track steerable navigation catheters, the two systems will affect each other when operated in proximity. We first investigate the compatibility of the systems by measuring the ENB system localization error as a function of distance between the two systems. The SBDX system reconstructs DTS images, which provide depth information, and so we investigate the improvement in lung nodule visualization using SBDX system DTS images and compare them to fluoroscopic images currently used for biopsy verification. Target localization error remains below 2mm (or virtually error free) if the volume-of-interest (VOI) is at least 50cm away from the SBDX system source and detector. Inside this region, tomographic angle ranges from 3° to 10° depending on the VOI location. Improved lung nodule (<= 20mm diameter) contrast is achieved by imaging the VOI near the SBDX system detector, where the tomographic angle is maximized. The combination of the SBDX image guidance with an ENB system would provide real-time visualization during biopsy with improved localization of the target and needle/biopsy instruments, thereby increasing the average and lowering the variance of the yield for TBNbx.

Yoon, Sungwon; Wilfley, Brian P.; Jasperson, Keith; Krishna, Ganesh; Fahrig, Rebecca

2011-03-01

239

Cluster beam targets for laser plasma extreme ultraviolet and soft x-ray sources  

DOEpatents

Method and apparatus for producing extreme ultraviolet (EUV) and soft x-ray radiation from an ultra-low debris plasma source are disclosed. Targets are produced by the free jet expansion of various gases through a temperature controlled nozzle to form molecular clusters. These target clusters are subsequently irradiated with commercially available lasers of moderate intensity (10{sup 11}--10{sup 12} watts/cm{sup 2}) to produce a plasma radiating in the region of 0.5 to 100 nanometers. By appropriate adjustment of the experimental conditions the laser focus can be moved 10--30 mm from the nozzle thereby eliminating debris produced by plasma erosion of the nozzle. 5 figs.

Kublak, G.D.; Richardson, M.C.

1996-11-19

240

Cluster beam targets for laser plasma extreme ultraviolet and soft x-ray sources  

DOEpatents

Method and apparatus for producing extreme ultra violet (EUV) and soft x-ray radiation from an ultra-low debris plasma source are disclosed. Targets are produced by the free jet expansion of various gases through a temperature controlled nozzle to form molecular clusters. These target clusters are subsequently irradiated with commercially available lasers of moderate intensity (10.sup.11 -10.sup.12 watts/cm.sup.2) to produce a plasma radiating in the region of 0.5 to 100 nanometers. By appropriate adjustment of the experimental conditions the laser focus can be moved 10-30 mm from the nozzle thereby eliminating debris produced by plasma erosion of the nozzle.

Kublak, Glenn D. (124 Turquoise Way, Livermore, Alameda County, CA 94550); Richardson, Martin C. (CREOL

1996-01-01

241

Phase retrieval in x-ray lensless holography by reference beam tuning  

SciTech Connect

We show the ability to determine the relative phase between the object and a reference scatterer by tuning the overall intensity and phase of the reference wave. The proposed reference-guided phase retrieval algorithm uses the relative phase as a constraint to iteratively reconstruct the object and the reference simultaneously, and thus does not require precisely defined reference structures. The algorithm also features rapid and reliable convergence and overcomes the uniqueness problem. The method is demonstrated by a soft-x-ray coherent imaging experiment that utilizes a large micrometer-sized reference structure that can be turned on and off, yielding an object image with resolution close to the reconstruction pixel size of 21 nm.

Zhu, D. L.

2010-02-24

242

X-ray photoelectron and X-ray absorption spectroscopic study on ?-FeSi 2 thin films fabricated by ion beam sputter deposition  

NASA Astrophysics Data System (ADS)

A combination of X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) using synchrotron radiation is applied to clarify surface chemical states of ?-FeSi 2 films fabricated by an ion-beam sputtering deposition method. The differences in the chemical states of the films fabricated at substrate temperatures of 873, 973 and 1173 K are investigated. For the film fabricated at 873 K, Si 2p XPS spectra indicate the formation of a relatively thicker SiO 2 layer. In addition, Fe L-edge XAS spectra exhibit the formation of FeSi 2- X by preferential oxidation of Si or the presence of unreacted Fe. The results for the film fabricated at 1173 K imply the existence of FeSi 2 with ? and ? phases. In contrast, the results for the film fabricated at 973 K indicate the formation of relatively homogeneous ?-FeSi 2. These imply that the relatively excellent crystal property of the film fabricated at 973 K is due to the formation of homogeneous ?-FeSi 2. As a conclusion, the combination of XPS and XAS using synchrotron radiation is a powerful tool to elucidate the surface chemical states of thin films.

Esaka, F.; Yamamoto, H.; Matsubayashi, N.; Yamada, Y.; Sasase, M.; Yamaguchi, K.; Shamoto, S.; Magara, M.; Kimura, T.

2010-03-01

243

Beam Dynamics Study of X-Band Linac Driven X-Ray FELS  

SciTech Connect

Several linac driven X-ray Free Electron Lasers (XFELs) are being developed to provide high brightness photon beams with very short, tunable wavelengths. In this paper, three XFEL configurations are proposed that achieve LCLS-like performance using X-band linac drivers. These linacs are more versatile, efficient and compact than ones using S-band or C-band rf technology. For each of the designs, the overall accelerator layout and the shaping of the bunch longitudinal phase space are described briefly. During the last 40 years, the photon wavelengths from linac driven FELs have been pushed shorter by increasing the electron beam energy and adopting shorter period undulators. Recently, the wavelengths have reached the X-ray range, with FLASH (Free-Electron Laser in Hamburg) and LCLS (Linac Coherent Light Source) successfully providing users with soft and hard X-rays, respectively. FLASH uses a 1.2 GeV L-band (1.3 GHz) superconducting linac driver and can deliver 10-70 fs FWHM long photon pulses in a wavelength range of 44 nm to 4.1 nm. LCLS uses the last third of the SLAC 3 km S-band (2.856 GHz) normal-conducting linac to produce 3.5 GeV to 15 GeV bunches to generate soft and hard X-rays with good spatial coherence at wavelengths from 2.2 nm to 0.12 nm. Newer XFELs (at Spring8 and PSI) use C-band (5.7 GHz) normal-conducting linac drivers, which can sustain higher acceleration gradients, and hence shorten the linac length, and are more efficient at converting rf energy to bunch energy. The X-band (11.4 GHz) rf technology developed for NLC/GLC offers even higher gradients and efficiencies, and the shorter rf wavelength allows more versatility in longitudinal bunch phase space compression and manipulation. In the following sections, three different configurations of X-band linac driven XFELs are described that operate from 6 to 14 GeV. The first (LOW CHARGE DESIGN) has an electron bunch charge of only 10 pC; the second (OPTICS LINEARIZATION DESIGN) is based on optics linearization of the longitudinal phase space in the first stage bunch compressor and can operate with either a high (250 pC) or low (20 pC) bunch charge; and the third (LCLS INJECTOR DESIGN) is similar to LCLS but uses an X-band linac after the first stage bunch compressor at 250 MeV to achieve a final beam energy up to 14 GeV. Compared with LCLS, these X-band linacs are at least a factor of three shorter.

Adolphsen, C.; Limborg-Deprey, C.; Raubenheimer, T.O.; Wu, J.; /SLAC; Sun, Y.; /SLAC

2011-12-13

244

Production of x-rays by the interaction of charged particle beams with periodic structures and crystalline materials  

SciTech Connect

The authors describe their recent experimental study of the production of x-rays by an electron beam interacting with a crystal lattice, i.e. parametric x-ray (PX) generation. In this radiation process, the virtual photon field associated with a relativistic electron traveling in a crystal is diffracted by the crystal lattice in the same way that real x-rays are diffracted by crystals. The radiation produced satisfies the Bragg condition associated with the diffraction of the virtual photons which are nearly parallel to the velocity of the electrons. This phenomenon is associated with a more general class of radiation production mechanisms which include transition radiation (TR), diffraction radiation (DR), and Smith-Purcell radiation. In each case, radiation is produced when the particle`s fields are altered by interacting with a material whose dielectric constant varies along or near the particle`s trajectory. The usual acceleration mechanism for the production of radiation is not involved in these phenomena. In the case of a crystal, the periodic electric susceptibility interacting with the particle`s field produces parametric x-rays. They will also present a theoretical overview of this phenomenon which can be used to generate monochromatic, linearly polarized, directional x-rays. Accelerators with energies ranging from a few MeV to hundreds of MeV may be used as drivers for novel parametrix x-ray generators for various applications requiring the unique properties of these sources.

Rule, D.W.; Fiorito, R.B. [Naval Surface Warfare Center, Silver Spring, MD (United States); Piestrup, M.A.; Gary, C.K. [Adelphi Technologies Inc., Palo Alto, CA (United States); Maruyama, X.K. [Naval Postgraduate School, Monterey, CA (United States). Dept. of Physics

1991-12-31

245

Neutral particle beam intensity controller  

DOEpatents

The neutral beam intensity controller is based on selected magnetic defocusing of the ion beam prior to neutralization. The defocused portion of the beam is dumped onto a beam dump disposed perpendicular to the beam axis. Selective defocusing is accomplished by means of a magnetic field generator disposed about the neutralizer so that the field is transverse to the beam axis. The magnetic field intensity is varied to provide the selected partial beam defocusing of the ions prior to neutralization. The desired focused neutral beam portion passes along the beam path through a defining aperture in the beam dump, thereby controlling the desired fraction of neutral particles transmitted to a utilization device without altering the kinetic energy level of the desired neutral particle fraction. By proper selection of the magnetic field intensity, virtually zero through 100% intensity control of the neutral beam is achieved.

Dagenhart, W.K.

1984-05-29

246

Effects of carbon ion beam on putative colon cancer stem cells and its comparison with X-rays.  

PubMed

Although carbon ion therapy facilities are expensive, the biological effects of carbon ion beam treatment may be better against cancer (and cancer stem cells) than the effects of a photon beam. To investigate whether a carbon ion beam may have a biological advantage over X-rays by targeting cancer stem-like cells, human colon cancer cells were used in vitro and in vivo. The in vitro relative biological effectiveness (RBE) values of a carbon ion beam relative to X-rays at the D10 values were from 1.63 to 1.74. Cancer stem-like CD133(+), CD44(+)/ESA(+) cells had a greater ability for colony and spheroid formation, as well as in vivo tumorigenicity compared with the CD133(-), CD44(-)/ESA(-) cells. FACS (fluorescence-activated cell sorting) data showed that cancer stem-like cells were more highly enriched after irradiation with X-rays than carbon ion at doses that produced the same level of biological efficacy. A colony assay for cancer stem-like cells showed that RBE values calculated by the D10 levels were from 2.05 to 2.28 for the carbon ion beam relative to X-rays. The in vivo xenotransplant assay showed an RBE of 3.05 to 3.25, calculated from the slope of the dose-response curve for tumor growth suppression. Carbon ion irradiation with 15 Gy induced more severe xenograft tumor cell cavitation and fibrosis without significant enhancement of cells with putative cancer stem cell markers, CD133, ESA, and CD44, compared with 30 Gy X-rays, and marker positive cells were significantly decreased following 30 Gy carbon ion irradiation. Taken together, carbon ion beam therapy may have an advantage over photon beam therapy by improved targeting of putative colon cancer stem-like cells. PMID:21454414

Cui, Xing; Oonishi, Kazuhiko; Tsujii, Hirohiko; Yasuda, Takeshi; Matsumoto, Yoshitaka; Furusawa, Yoshiya; Akashi, Makoto; Kamada, Tadashi; Okayasu, Ryuichi

2011-05-15

247

Monte Carlo simulation of X-ray dose distributions for direct aperture optimization of intensity modulated treatment fields  

NASA Astrophysics Data System (ADS)

This thesis investigates methods of reducing radiation dose calculation errors as applied to a specialized x-ray therapy called intensity modulated radiation therapy (IMRT). There are three major areas of investigation. First, limits of the popular 2D pencil beam kernel (PBK) dose calculation algorithm are explored. The ability to resolve high dose gradients is partly related to the shape of the PBK. Improvements to the spatial resolution can be achieved by modifying the dose kernel shapes already present in the clinical treatment planning system. Optimization of the PBK shape based on measured-to-calculated test pattern dose comparisons reduces the impact of some limitations of this algorithm. However, other limitations remain (e.g. assuming spatial invariance, no modeling of extra-focal radiation, and no modeling of lateral electron transport). These limitations directed this thesis towards the second major investigation - Monte Carlo (MC) simulation for IMRT. MC is considered to be the "gold standard" for radiation dose calculation accuracy. This investigation incorporates MC calculated beamlets of dose deposition into a direct aperture optimization (DAO) algorithm for IMRT inverse planning (MC-DAO). The goal is to show that accurate tissue inhomogeneity information and lateral electronic transport information, combined with DAO, will improve the quality/accuracy of the patient treatment plan. MC simulation generates accurate beamlet dose distributions in traditionally difficult-to-calculate regions (e.g. air-tissue interfaces or small (? 5 cm2) x-ray fields). Combining DAO with MC beamlets reduces the required number of radiation units delivered by the linear accelerator by ˜30-50%. The MC method is criticized for having long simulation times (hours). This can be addressed with distributed computing methods and data filtering ('denoising'). The third major investigation describes a practical implementation of the 3D Savitzky-Golay digital filter for MC dose 'denoising'. This thesis concludes that MC-based DAO for IMRT inverse planning is clinically feasible and offers accurate modeling of particle transport and dose deposition in difficult environments where lateral electronic dis-equilibrium exists.

Bergman, Alanah Mary

2007-12-01

248

Microjet formation and hard x-ray production from a liquid metal target irradiated by intense femtosecond laser pulses  

SciTech Connect

By using a liquid metal as a target one may significantly enhance the yield of hard x-rays with a sequence of two intense femtosecond laser pulses. The influence of the time delay between the two pulses is studied experimentally and interpreted with numerical simulations. It was suggested that the first arbitrary weak pulse produces microjets from the target surface, while the second intense pulse provides an efficient electron heating and acceleration along the jet surface. These energetic electrons are the source of x-ray emission while striking the target surface. The microjet formation is explained based on the results given by both optical diagnostics and hydrodynamic modeling by a collision of shocks originated from two distinct zones of laser energy deposition.

Lar'kin, A., E-mail: alexeylarkin@yandex.ru; Uryupina, D.; Ivanov, K.; Savel'ev, A., E-mail: abst@physics.msu.ru [International Laser Center and Faculty of Physics, Lomonosov Moscow State University, Moscow 119991 (Russian Federation); Bonnet, T.; Gobet, F.; Hannachi, F.; Tarisien, M.; Versteegen, M. [Centre d'Études Nucléaires de Bordeaux-Gradignan, University of Bordeaux-CNRS-IN2P3, 33170 Gradignan (France); Spohr, K. [School of Engineering, University of the West of Scotland, Paisley, Scotland PA1 2BE (United Kingdom); Breil, J.; Chimier, B.; Dorchies, F.; Fourment, C.; Leguay, P.-M.; Tikhonchuk, V. T. [Centre Lasers Intenses et Applications, University of Bordeaux-CNRS-CEA, Talence 33405 (France)

2014-09-15

249

Microjet formation and hard x-ray production from a liquid metal target irradiated by intense femtosecond laser pulses  

NASA Astrophysics Data System (ADS)

By using a liquid metal as a target one may significantly enhance the yield of hard x-rays with a sequence of two intense femtosecond laser pulses. The influence of the time delay between the two pulses is studied experimentally and interpreted with numerical simulations. It was suggested that the first arbitrary weak pulse produces microjets from the target surface, while the second intense pulse provides an efficient electron heating and acceleration along the jet surface. These energetic electrons are the source of x-ray emission while striking the target surface. The microjet formation is explained based on the results given by both optical diagnostics and hydrodynamic modeling by a collision of shocks originated from two distinct zones of laser energy deposition.

Lar'kin, A.; Uryupina, D.; Ivanov, K.; Savel'ev, A.; Bonnet, T.; Gobet, F.; Hannachi, F.; Tarisien, M.; Versteegen, M.; Spohr, K.; Breil, J.; Chimier, B.; Dorchies, F.; Fourment, C.; Leguay, P.-M.; Tikhonchuk, V. T.

2014-09-01

250

Ground calibrations of the X-ray detector system of the Solar Intensity X-ray Spectrometer (SIXS) on board BepiColombo  

NASA Astrophysics Data System (ADS)

SIXS includes X-ray and particle detector systems for the BepiColombo Mercury Planetary Orbiter (MPO). Its task is to monitor the direct solar X-rays and energetic particles in a wide field of view in the energy range of 1-20 keV (X-rays), 0.1-3 MeV (electrons) and 1-30 MeV (protons). The main purpose of these measurements is to provide quantitative information on the high energy radiation incident on Mercury's surface which causes the X-ray glow of the planet measured by the MIXS instrument. The X-ray and particle measurements of SIXS are also useful for investigations of the solar corona and the magnetosphere of Mercury. The ground calibrations of the X-ray detectors of the SIXS flight model were carried out in the X-ray laboratory of the Helsinki University during May and June 2012. The aim of the ground calibrations was to characterize the performance of the SIXS instrument's three High-Purity Silicon PIN X-ray detectors and verify that they fulfil their scientific performance requirements. The calibrations included the determination of the beginning of life energy resolution at different operational temperatures, determination of the detector's sensitivity within the field of view as a function of the off-axis and roll angles, pile-up tests for determining the speed of the read out electronics, measurements of the low energy threshold of the energy scale, a cross-calibration with the SMART-1 XSM flight spare detector, and the determination of the temperature dependence of the energy scale. An X-ray tube and the detectors' internal Ti coated 55Fe calibration sources were used as primary X-ray sources. In addition, two external fluorescence sources were used as secondary X-ray sources in the determination of the energy resolutions and in the comparison calibration with the SMART-1 XSM. The calibration results show that the detectors fulfill all of the scientific performance requirements. The ground calibration data combined with the instrument house-keeping data, spacecraft attitude data in relation to the Sun, and the in-flight calibration spectra measured during the operations contain all required information for the final analysis of the solar X-ray data.

Huovelin, Juhani; Lehtolainen, Arto; Genzer, Maria; Korpela, Seppo; Esko, Eero; Andersson, Hans

2014-05-01

251

Operation of beam line facilities for real-time x-ray studies at Sector 7 of the advanced photon source. Final Report  

SciTech Connect

This Final Report documents the research accomplishments achieved in the first phase of operations of a new Advanced Photon Source beam line (7-ID MHATT-CAT) dedicated to real-time x-ray studies. The period covered by this report covers the establishment of a world-class facility for time-dependent x-ray studies of materials. During this period many new and innovative research programs were initiated at Sector 7 with support of this grant, most notably using a combination of ultrafast lasers and pulsed synchrotron radiation. This work initiated a new frontier of materials research: namely, the study of the dynamics of materials under extreme conditions of high intensity impulsive laser irradiation.

Clarke, Roy

2003-09-10

252

Carbon-Ion Beam Irradiation Kills X-Ray-Resistant p53-Null Cancer Cells by Inducing Mitotic Catastrophe  

PubMed Central

Background and Purpose To understand the mechanisms involved in the strong killing effect of carbon-ion beam irradiation on cancer cells with TP53 tumor suppressor gene deficiencies. Materials and Methods DNA damage responses after carbon-ion beam or X-ray irradiation in isogenic HCT116 colorectal cancer cell lines with and without TP53 (p53+/+ and p53-/-, respectively) were analyzed as follows: cell survival by clonogenic assay, cell death modes by morphologic observation of DAPI-stained nuclei, DNA double-strand breaks (DSBs) by immunostaining of phosphorylated H2AX (?H2AX), and cell cycle by flow cytometry and immunostaining of Ser10-phosphorylated histone H3. Results The p53-/- cells were more resistant than the p53+/+ cells to X-ray irradiation, while the sensitivities of the p53+/+ and p53-/- cells to carbon-ion beam irradiation were comparable. X-ray and carbon-ion beam irradiations predominantly induced apoptosis of the p53+/+ cells but not the p53-/- cells. In the p53-/- cells, carbon-ion beam irradiation, but not X-ray irradiation, markedly induced mitotic catastrophe that was associated with premature mitotic entry with harboring long-retained DSBs at 24 h post-irradiation. Conclusions Efficient induction of mitotic catastrophe in apoptosis-resistant p53-deficient cells implies a strong cancer cell-killing effect of carbon-ion beam irradiation that is independent of the p53 status, suggesting its biological advantage over X-ray treatment. PMID:25531293

Amornwichet, Napapat; Oike, Takahiro; Shibata, Atsushi; Ogiwara, Hideaki; Tsuchiya, Naoto; Yamauchi, Motohiro; Saitoh, Yuka; Sekine, Ryota; Isono, Mayu; Yoshida, Yukari; Ohno, Tatsuya; Kohno, Takashi; Nakano, Takashi

2014-01-01

253

SIMULATIONS AND STUDIES OF ELECTRON BEAM DYNAMICS UNDER COMPTON BACK-SCATTERING FOR THE COMPACT X-RAY  

E-print Network

SIMULATIONS AND STUDIES OF ELECTRON BEAM DYNAMICS UNDER COMPTON BACK-SCATTERING FOR THE COMPACT X- tions of a relativistic electron bunch in the compact storage ring ThomX (50 MeV), which is under] is a project of a compact high flux X-ray source based on the Compton scattering of laser photons

Boyer, Edmond

254

Collimator for an x-ray mammography apparatus  

Microsoft Academic Search

A device for generating collimated X-ray beams is described, the device comprising: an X-ray source for emitting an input X-ray beam; a cone arranged in the input X-ray beam to receive the entire input X-ray beam, the cone blocking a portion of the input X-ray beam such that a limited output X-ray beam emerges from the cone, the output X-ray

1989-01-01

255

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

PubMed Central

A dual modality computed mammotomography (CmT) and single photon emission computed tomography (SPECT) system for dedicated 3D breast imaging is in development. Using heavy K-edge filtration, the CmT component narrows the energy spectrum of the cone-shaped x-ray beam incident on the patient’s pendant, uncompressed breast. This quasi-monochromatic beam is expected to improve discrimination of tissue with similar attenuation coefficients while restraining absorbed dose to below that of dual view mammography. Previous simulation studies showed the optimal energy that maximizes dose efficiency for a 50/50% adipose/glandular breast is between 30 and 40 keV. This study experimentally validates these results using pre-breast and post-breast spectral measurements made under tungsten tube voltages between 40 and 100 kVp using filter materials with K-edge values ranging from 15 to 70 keV. Different filter material thicknesses are used, approximately equivalent to the 200th and 500th attenuating value layer (VL) thickness. Cerium (K = 40.4 keV) filtered post-breast spectra for 8–18 cm breasts are measured for a range of breast compositions. Figures of merit include mean beam energy, spectral full-width at tenth-maximum, beam hardening and dose for the range of breast sizes. Measurements corroborate simulation results, indicating that for a given dose, a 200th VL of cerium filtration may have optimal performance in the dedicated mammotomography paradigm. PMID:17228108

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

2012-01-01

256

High-Resolution X-Ray and Light Beam Induced Current (LBIC) Measurements of Multcrystalline Silicon Solar Cells  

SciTech Connect

High-resolution, spatially-resolved x-ray Laue patterns and high-resolution light beam induced current (LBIC) measurements are combined to study two multicrystalline solar cells made from the Heat Exchanger Method (HEM) and the Sting Ribbon Growth technique. The LBIC measurements were made at 4 different wavelengths (488, 633, 780, and 980 nm), resulting in penetration depths ranging from <1 {mu}m to >100 {mu}m. There is a strong correlation between the x-ray and LBIC measurements, showing that some twins and grain boundaries are effective in the reduction of local quantum efficiency, while others are benign.

Jellison Jr, Gerald Earle [ORNL] [ORNL; Budai, John D [ORNL] [ORNL; Bennett, Charlee J C [ORNL] [ORNL; Tischler, Jonathan Zachary [ORNL] [ORNL; Duty, Chad E [ORNL] [ORNL; Yelundur, V. [Georgia Institute of Technology] [Georgia Institute of Technology; Rohatgi, A. [Georgia Institute of Technology] [Georgia Institute of Technology

2010-01-01

257

Design and performance of coded aperture optical elements for the CESR-TA x-ray beam size monitor  

NASA Astrophysics Data System (ADS)

We describe the design and performance of optical elements for an x-ray beam size monitor (xBSM), a device measuring e+ and e- beam sizes in the CESR-TA storage ring. The device can measure vertical beam sizes of 10 - 100 ?m on a turn-by-turn, bunch-by-bunch basis at e± beam energies of ~ 2 - 5 GeV. x-rays produced by a hard-bend magnet pass through a single- or multiple-slit (coded aperture) optical element onto a detector. The coded aperture slit pattern and thickness of masking material forming that pattern can both be tuned for optimal resolving power. We describe several such optical elements and show how well predictions of simple models track measured performances.

Alexander, J. P.; Chatterjee, A.; Conolly, C.; Edwards, E.; Ehrlichman, M. P.; Flanagan, J. W.; Fontes, E.; Heltsley, B. K.; Lyndaker, A.; Peterson, D. P.; Rider, N. T.; Rubin, D. L.; Seeley, R.; Shanks, J.

2014-12-01

258

Generating Ultrashort Coherent Soft X-ray Radiation in Storage Rings Using Angular-modulated Electron Beams  

SciTech Connect

A technique is proposed to generate ultrashort coherent soft x-ray radiation in storage rings using angular-modulated electron beams. In the scheme a laser operating in the TEM01 mode is first used to modulate the angular distribution of the electron beam in an undulator. After passing through a special beam line with non-zero transfer matrix element R{sub 54}, the angular modulation is converted to density modulation which contains considerable higher harmonic contents of the laser. It is found that the harmonic number can be one or two orders of magnitude higher than the standard coherent harmonic generation method which relies on beam energy modulation. The technique has the potential of generating femtosecond coherent soft x-ray radiation directly from an infrared seed laser and may open new research opportunities for ultrafast sciences in storage rings.

Xiang, D.; /SLAC; Wan, W.; /LBL, Berkeley

2010-08-23

259

A simulation-based study on the influence of beam hardening in X-ray computed tomography for dimensional metrology.  

PubMed

X-ray computed tomography (CT) is a radiographic scanning technique for visualising cross-sectional images of an object non-destructively. From these cross-sectional images it is possible to evaluate internal dimensional features of a workpiece which may otherwise be inaccessible to tactile and optical instruments. Beam hardening is a physical process that degrades the quality of CT images and has previously been suggested to influence dimensional measurements. Using a validated simulation tool, the influence of spectrum pre-filtration and beam hardening correction are evaluated for internal and external dimensional measurements. Beam hardening is shown to influence internal and external dimensions in opposition, and to have a greater influence on outer dimensions compared to inner dimensions. The results suggest the combination of spectrum pre-filtration and a local gradient-based surface determination method are able to greatly reduce the influence of beam hardening in X-ray CT for dimensional metrology. PMID:25567408

Lifton, Joseph J; Malcolm, Andrew A; McBride, John W

2015-01-01

260

Ultra-fast and ultra-intense x-ray sciences: first results from the Linac Coherent Light Source free-electron laser  

NASA Astrophysics Data System (ADS)

X-ray free-electron lasers (FELs) produce femtosecond x-ray pulses with unprecedented intensities that are uniquely suited for studying many phenomena in atomic, molecular, and optical (AMO) physics. A compilation of the current developments at the Linac Coherent Light Source (LCLS) and future plans for the LCLS-II and Next Generation Light Source (NGLS) are outlined. The AMO instrumentation at LCLS and its performance parameters are summarized. A few selected experiments representing the rapidly developing field of ultra-fast and peak intensity x-ray AMO sciences are discussed. These examples include fundamental aspects of intense x-ray interaction with atoms, nonlinear atomic physics in the x-ray regime, double core-hole spectroscopy, quantum control experiments with FELs and ultra-fast x-ray induced dynamics in clusters. These experiments illustrate the fundamental aspects of the interaction of intense short pulses of x-rays with atoms, molecules and clusters that are probed by electron and ion spectroscopies as well as ultra-fast x-ray scattering.

Bostedt, C.; Bozek, J. D.; Bucksbaum, P. H.; Coffee, R. N.; Hastings, J. B.; Huang, Z.; Lee, R. W.; Schorb, S.; Corlett, J. N.; Denes, P.; Emma, P.; Falcone, R. W.; Schoenlein, R. W.; Doumy, G.; Kanter, E. P.; Kraessig, B.; Southworth, S.; Young, L.; Fang, L.; Hoener, M.; Berrah, N.; Roedig, C.; DiMauro, L. F.

2013-08-01

261

Electron beam halo monitor for a compact x-ray free-electron laser  

NASA Astrophysics Data System (ADS)

An electron beam halo monitor using diamond-based detectors, which are operated in the ionization mode, has been developed for the SPring-8 Angstrom compact free-electron laser (SACLA) to protect its undulator magnets from radiation damage. Diamond-based detectors are inserted in a beam duct to measure the intensity of the beam halo directly. To suppress the degradation of the electron beam due to the installation of the beam halo monitor, rf fingers with aluminum windows are newly employed. We evaluated the effect of radiation from the Al windows on the output signal both experimentally and by simulation. The operational results of the beam halo monitor employed in SACLA are presented.

Aoyagi, Hideki; Asano, Yoshihiro; Itoga, Toshiro; Nariyama, Nobuteru; Bizen, Teruhiko; Fukami, Kenji; Aoki, Tsuyoshi; Suzuki, Shinsuke; Yamaga, Mitsuhiro; Otake, Takuya; Tanaka, Takashi; Kitamura, Hideo

2013-03-01

262

TOLERANCE OF ARTERIES TO MICROPLANAR X-RAY BEAMS Boudewijn van der Sanden*, PhD, INSERM U836, Institute of Neuroscience Grenoble, France.  

E-print Network

TOLERANCE OF ARTERIES TO MICROPLANAR X-RAY BEAMS Boudewijn van der Sanden*, PhD, INSERM U836.vandersanden@ujf-grenoble.fr Running title: Microplanar X-ray beam irradiation of arteries inserm-00589287,version1-28Apr2011 Author radiation therapy, on the artery wall. In previous studies on animal models, it was shown that capillaries

Paris-Sud XI, Université de

263

Ultra-efficient ionization of heavy atoms by intense X-ray free-electron laser pulses  

NASA Astrophysics Data System (ADS)

X-ray free-electron lasers provide unique opportunities for exploring ultrafast dynamics and for imaging the structures of complex systems. Understanding the response of individual atoms to intense X-rays is essential for most free-electron laser applications. First experiments have shown that, for light atoms, the dominant interaction mechanism is ionization by sequential electron ejection, where the highest charge state produced is defined by the last ionic state that can be ionized with one photon. Here, we report an unprecedentedly high degree of ionization of xenon atoms by 1.5 keV free-electron laser pulses to charge states with ionization energies far exceeding the photon energy. Comparing ion charge-state distributions and fluorescence spectra with state-of-the-art calculations, we find that these surprisingly high charge states are created via excitation of transient resonances in highly charged ions, and predict resonance enhanced absorption to be a general phenomenon in the interaction of intense X-rays with systems containing high-Z constituents.

Rudek, Benedikt; Son, Sang-Kil; Foucar, Lutz; Epp, Sascha W.; Erk, Benjamin; Hartmann, Robert; Adolph, Marcus; Andritschke, Robert; Aquila, Andrew; Berrah, Nora; Bostedt, Christoph; Bozek, John; Coppola, Nicola; Filsinger, Frank; Gorke, Hubert; Gorkhover, Tais; Graafsma, Heinz; Gumprecht, Lars; Hartmann, Andreas; Hauser, Günter; Herrmann, Sven; Hirsemann, Helmut; Holl, Peter; Hömke, André; Journel, Loic; Kaiser, Christian; Kimmel, Nils; Krasniqi, Faton; Kühnel, Kai-Uwe; Matysek, Michael; Messerschmidt, Marc; Miesner, Danilo; Möller, Thomas; Moshammer, Robert; Nagaya, Kiyonobu; Nilsson, Björn; Potdevin, Guillaume; Pietschner, Daniel; Reich, Christian; Rupp, Daniela; Schaller, Gerhard; Schlichting, Ilme; Schmidt, Carlo; Schopper, Florian; Schorb, Sebastian; Schröter, Claus-Dieter; Schulz, Joachim; Simon, Marc; Soltau, Heike; Strüder, Lothar; Ueda, Kiyoshi; Weidenspointner, Georg; Santra, Robin; Ullrich, Joachim; Rudenko, Artem; Rolles, Daniel

2012-12-01

264

Effects of radiation quality on the calibration of kerma-area product meters in x-ray beams  

NASA Astrophysics Data System (ADS)

The calibration coefficients of kerma-area product meters significantly depend on the energy spectrum of the x-ray beam. This effect was examined by measuring the calibration coefficients for several radiation qualities in the range generally used in diagnostic x-ray imaging. The intention was to determine the calibration coefficients for other radiation qualities by interpolation between the measured values, relative to one or more suitable parameters. The x-ray tube voltage, total filtration and half-value thickness were examined as possible specifiers of the energy distribution. No single parameter provided an interpolation of calibration coefficients with the accuracy recommended by the ICRU and IAEA, except for a narrow range of radiation qualities. At least two of the parameters are needed to reliably specify the radiation quality for the interpolation of calibration coefficients.

Toroi, P.; Komppa, T.; Kosunen, A.; Tapiovaara, M.

2008-09-01

265

Beamed and Unbeamed X-ray Emission in FR1 Radio Galaxies  

NASA Technical Reports Server (NTRS)

There is good evidence for X-ray emission associated with AGN jets which are relativistically boosted towards the observer. But to what jet radius does such X-ray emission persist? To attempt to answer this question one can look at radio galaxies; their cores are sufficiently X-ray faint that any unbeamed X-ray emission in the vicinity of the central engine must be obscured. The jets of such sources are at unfavourable angles for relativistic boosting, and so their relatively weak X-ray emission must be carefully separated from the plateau of resolved X-ray emission from a hot interstellar, intragroup, or intracluster medium on which they are expected to sit. This paper presents results arguing that jet X-ray emission is generally detected in radio galaxies, even those of low intrinsic power without hot spots. The levels of emission suggest an extrapolated radio to soft X-ray spectral index, alpha(sub tao x) of about 0.85 at parsec to perhaps kiloparsec distances from the cores.

Worrall, Diana M.

1997-01-01

266

Measurement of coherent x-ray focused beams by phase retrieval with transverse  

E-print Network

ultraviolet (EUV); (110.7440) X-ray imaging. References and links 1. I. McNulty, J. Kirz, C. Jacobsen, E. H. St¨ohr, "Lensless imaging of magnetic nanostructures by x-ray spectro-holography," Nature 432, 885

Fienup, James R.

267

Physiologically gated micro-beam radiation therapy using electronically controlled field emission x-ray source array  

NASA Astrophysics Data System (ADS)

Micro-beam radiation therapy (MRT) uses parallel planes of high dose narrow (10-100 um in width) radiation beams separated by a fraction of a millimeter to treat cancerous tumors. This experimental therapy method based on synchrotron radiation has been shown to spare normal tissue at up to 1000Gy of entrance dose while still being effective in tumor eradication and extending the lifetime of tumor-bearing small animal models. Motion during the treatment can result in significant movement of micro beam positions resulting in broader beam width and lower peak to valley dose ratio (PVDR), and thus can reduce the effectiveness of the MRT. Recently we have developed the first bench-top image guided MRT system for small animal treatment using a high powered carbon nanotube (CNT) x-ray source array. The CNT field emission x-ray source can be electronically synchronized to an external triggering signal to enable physiologically gated firing of x-ray radiation to minimize motion blurring. Here we report the results of phantom study of respiratory gated MRT. A simulation of mouse breathing was performed using a servo motor. Preliminary results show that without gating the micro beam full width at tenth maximum (FWTM) can increase by 70% and PVDR can decrease up to 50%. But with proper gating, both the beam width and PVDR changes can be negligible. Future experiments will involve irradiation of mouse models and comparing histology stains between the controls and the gated irradiation.

Chtcheprov, Pavel; Hadsell, Michael; Burk, Laurel; Ger, Rachel; Zhang, Lei; Yuan, Hong; Lee, Yueh Z.; Chang, Sha; Lu, Jianping; Zhou, Otto

2013-03-01

268

Electron acceleration by laser wakefield and x-ray emission at moderate intensity and density in long plasmas  

SciTech Connect

The dynamics of electron acceleration by laser wakefield and the associated x-rays emission in long plasmas are numerically investigated for parameters close to the threshold of laser self-focusing. The plasma length is set by the use of dielectric capillary tubes that confine the gas and the laser energy. Electrons self-injection and acceleration to the 170 MeVs are obtained for densities as low as 5 x 10{sup 18} cm{sup -3} and a moderate input intensity (0.77 x 10{sup 18} W/cm{sup 2}). The associated x-ray emission at the exit of the capillary tube is shown to be an accurate diagnostic of the electrons self-injection and acceleration process.

Ferrari, H. E. [Consejo Nacional de investigaciones cientificas y tecnicas (CONICET), Bariloche (Argentina); Laboratoire de Physique des Gaz et des Plasmas, CNRS-Universite Paris Sud 11, Orsay (France); Lifschitz, A. F.; Maynard, G.; Cros, B. [Laboratoire de Physique des Gaz et des Plasmas, CNRS-Universite Paris Sud 11, Orsay (France)

2011-08-15

269

MAXI-GSC detection of a sudden drop in X-ray intensity from GX 13+1  

NASA Astrophysics Data System (ADS)

MAXI-GSC detected a sudden drop in X-ray intensity from the low-mass X-ray binary GX 13+1 on August 30, 2014. Base on the on-demand analysis, the 2-10 keV flux once decreased from 0.97+-0.04 photons/s/cm2, which was the average one at 7 scan transits from 01:20 to 10:37 UT on August 30, to 0.31+-0.07 photons/s/cm2 at the scan transit at 12:10, and recovered to 0.87+-0.10 photons/s/cm2 at 13:43.

Negoro, H.; Nakahira, S.; Matsuoka, M.; Ueda, Y.; Kawai, N.; Ueno, S.; Tomida, H.; Kimura, M.; Ishikawa, M.; Nakagawa, Y. E.; Sugizaki, M.; Mihara, T.; Morii, M.; Serino, M.; Sugimoto, J.; Takagi, T.; Yoshikawa, A.; Yoshii, T.; Tachibana, Y.; Yoshida, A.; Sakamoto, T.; Kawakubo, Y.; Ohtsuki, H.; Tsunemi, H.; Uchida, D.; Nakajima, M.; Fukushima, K.; Onodera, T.; Suzuki, K.; Namba, T.; Fujita, M.; Honda, F.; Shidatsu, M.; Kawamuro, T.; Hori, T.; Tsuboi, Y.; Kawagoe, A.; Yamauchi, M.; Itoh, Y. Morooka D.; Yamaoka, K.

2014-09-01

270

All-diamond optical assemblies for a beam-multiplexing X-ray monochromator at the Linac Coherent Light Source  

PubMed Central

A double-crystal diamond (111) monochromator recently implemented at the Linac Coherent Light Source (LCLS) enables splitting of the primary X-ray beam into a pink (transmitted) and a monochromatic (reflected) branch. The first monochromator crystal, with a thickness of ?100?µm, provides sufficient X-ray transmittance to enable simultaneous operation of two beamlines. This article reports the design, fabrication and X-ray characterization of the first and second (300?µm-thick) crystals utilized in the monochromator and the optical assemblies holding these crystals. Each crystal plate has a region of about 5 × 2?mm with low defect concentration, sufficient for use in X-ray optics at the LCLS. The optical assemblies holding the crystals were designed to provide mounting on a rigid substrate and to minimize mounting-induced crystal strain. The induced strain was evaluated using double-crystal X-ray topography and was found to be small over the 5 × 2?mm working regions of the crystals. PMID:25242912

Stoupin, S.; Terentyev, S. A.; Blank, V. D.; Shvyd’ko, Yu. V.; Goetze, K.; Assoufid, L.; Polyakov, S. N.; Kuznetsov, M. S.; Kornilov, N. V.; Katsoudas, J.; Alonso-Mori, R.; Chollet, M.; Feng, Y.; Glownia, J. M.; Lemke, H.; Robert, A.; Sikorski, M.; Song, S.; Zhu, D.

2014-01-01

271

All-diamond optical assemblies for a beam-multiplexing X-ray monochromator at the Linac Coherent Light Source.  

PubMed

A double-crystal diamond (111) monochromator recently implemented at the Linac Coherent Light Source (LCLS) enables splitting of the primary X-ray beam into a pink (transmitted) and a monochromatic (reflected) branch. The first monochromator crystal, with a thickness of ?100?µm, provides sufficient X-ray transmittance to enable simultaneous operation of two beamlines. This article reports the design, fabrication and X-ray characterization of the first and second (300?µm-thick) crystals utilized in the monochromator and the optical assemblies holding these crystals. Each crystal plate has a region of about 5 × 2?mm with low defect concentration, sufficient for use in X-ray optics at the LCLS. The optical assemblies holding the crystals were designed to provide mounting on a rigid substrate and to minimize mounting-induced crystal strain. The induced strain was evaluated using double-crystal X-ray topography and was found to be small over the 5 × 2?mm working regions of the crystals. PMID:25242912

Stoupin, S; Terentyev, S A; Blank, V D; Shvyd'ko, Yu V; Goetze, K; Assoufid, L; Polyakov, S N; Kuznetsov, M S; Kornilov, N V; Katsoudas, J; Alonso-Mori, R; Chollet, M; Feng, Y; Glownia, J M; Lemke, H; Robert, A; Sikorski, M; Song, S; Zhu, D

2014-08-01

272

Analyzing X-Ray Pulsar Profiles: Geometry and Beam Pattern of Her X-1  

E-print Network

We report on our analysis of a large sample of energy dependent pulse profiles of the X-ray binary pulsar Hercules X-1. We find that all data are compatible with the assumption of a slightly distorted magnetic dipole field as sole cause of the asymmetry of the observed pulse profiles. Further the analysis provides evidence that the emission from both poles is equal. We determine an angle of 20 deg between the rotation axis and the local magnetic axis. One pole has an offset of 5 deg from the antipodal position of the other pole. The beam pattern shows structures that can be interpreted as pencil- and fan-beam configurations. Since no assumptions on the polar emission are made, the results can be compared with various emission models. A comparison of results obtained from pulse profiles of different phases of the 35-day cycle indicates different attenuation of the radiation from the poles being responsible for the change of the pulse shape during the main-on state. These results also suggest the resolution of an ambiguity within a previous analysis of pulse profiles of Cen X-3, leading to a unique result for the beam pattern of this pulsar as well. The analysis of pulse profiles of the short-on state indicates that a large fraction of the radiation cannot be attributed to the direct emission from the poles. We give a consistent explanation of both the evolution of the pulse profile and the spectral changes with the 35-day cycle in terms of a warped precessing accretion disk.

S. Blum; U. Kraus

1999-09-27

273

Energy calibration of energy-resolved photon-counting pixel detectors using laboratory polychromatic x-ray beams  

NASA Astrophysics Data System (ADS)

Recently, photon-counting detectors capable of resolving incident x-ray photon energies have been considered for use in spectral x-ray imaging applications. For reliable use of energy-resolved photon-counting detectors (ERPCDs), energy calibration is an essential procedure prior to their use because variations in responses from each pixel of the ERPCD for incident photons, even at the same energy, are inevitable. Energy calibration can be performed using a variety of methods. In all of these methods, the photon spectra with well-defined peak energies are recorded. Every pixel should be calibrated on its own. In this study, we suggest the use of a conventional polychromatic x-ray source (that is typically used in laboratories) for energy calibration. The energy calibration procedure mainly includes the determination of the peak energies in the spectra, flood-field irradiation, determination of peak channels, and determination of calibration curves (i.e., the slopes and intercepts of linear polynomials). We applied a calibration algorithm to a CdTe ERPCD comprised of 128×128 pixels with a pitch of 0.35 mm using highly attenuated polychromatic x-ray beams to reduce the pulse pile-up effect, and to obtain a narrow-shaped spectrum due to beam hardening. The averaged relative error in calibration curves obtained from 16,384 pixels was about 0.56% for 59.6 keV photons from an Americium radioisotope. This pixel-by-pixel energy calibration enhanced the signal- and contrast-to-noise ratios in images, respectively, by a factor of ~5 and 3 due to improvement in image homogeneity, compared to those obtained without energy calibration. One secondary finding of this study was that the x-ray photon spectra obtained using a common algorithm for computing x-ray spectra reasonably described the peaks in the measured spectra, which implies easier peak detection without the direct measurement of spectra using a separate spectrometer. The proposed method will be a useful alternative to conventional approaches using radioisotopes, a synchrotron, or specialized x-ray sources (e.g., characteristic or fluorescent x-rays) by reducing concerns over the beam flux, the irradiation field of view, accessibility, and cost.

Youn, Hanbean; Han, Jong Chul; Kam, Soohwa; Yun, Seungman; Kim, Ho Kyung

2014-10-01

274

Narrowband inverse Compton scattering x-ray sources at high laser intensities  

E-print Network

Narrowband x- and gamma-ray sources based on the inverse Compton scattering of laser pulses suffer from a limitation of the allowed laser intensity due to the onset of nonlinear effects that increase their bandwidth. It has been suggested that laser pulses with a suitable frequency modulation could compensate this ponderomotive broadening and reduce the bandwidth of the spectral lines, which would allow to operate narrowband Compton sources in the high-intensity regime. In this paper we, therefore, present the theory of nonlinear Compton scattering in a frequency modulated intense laser pulse. We systematically derive the optimal frequency modulation of the laser pulse from the scattering matrix element of nonlinear Compton scattering, taking into account the electron spin and recoil. We show that, for some particular scattering angle, an optimized frequency modulation completely cancels the ponderomotive broadening for all harmonics of the backscattered light. We also explore how sensitive this compensation depends on the electron beam energy spread and emittance, as well as the laser focusing.

D. Seipt; S. G. Rykovanov; A. Surzhykov; S. Fritzsche

2014-12-08

275

X-ray photoelectron spectroscopy study of water removal from beryllium at 160 K: Evidence for ion beam induced oxidation  

SciTech Connect

We present data for the ion beam removal of H/sub 2/O from beryllium at 160 K. The removal rate of H/sub 2/O from beryllium is qualitatively slower than that from copper. Evidence from x-ray photoelectron spectroscopic measurements indicates the ion beam causes surface oxidation up to a point where the oxide thickness prohibits further reaction. The mechanism for this ion beam induced surface oxidation is discussed and points toward H/sub 2/O bond breakage by the ion beam as a significant contributing factor.

Lindquist, J.M.; George, P.M.

1989-05-01

276

Enhanced water window x-ray emission from in situ formed carbon clusters irradiated by intense ultra-short laser pulses  

SciTech Connect

Enhanced water window x-ray emission (23–44 Å) from carbon clusters, formed in situ using a pre-pulse, irradiated by intense (I > 10{sup 17} W/cm{sup 2}) ultra-short laser pulse, is demonstrated. An order of magnitude x-ray enhancement over planar graphite target is observed in carbon clusters, formed by a sub-ns pre-pulse, interacting with intense main pulse after a delay. The effect of the delay and the duration of the main pulse is studied for optimizing the x-ray emission in the water window region. This x-ray source has added advantages of being an efficient, high repetition rate, and low debris x-ray source.

Chakravarty, U.; Rao, B. S.; Arora, V.; Upadhyay, A.; Singhal, H.; Naik, P. A.; Chakera, J. A.; Mukherjee, C.; Gupta, P. D. [Raja Ramanna Centre for Advanced Technology, Indore, 452 013 Madhya Pradesh (India)] [Raja Ramanna Centre for Advanced Technology, Indore, 452 013 Madhya Pradesh (India)

2013-07-29

277

Evolution of X-ray calorimeter spectrometers at the Lawrence Livermore Electron Beam Ion Trap  

NASA Astrophysics Data System (ADS)

High-resolution broadband, non-dispersive x-ray calorimeter spectrometers have been under development for spaceflight since 1984. As an offshoot of the significant NASA investment in this technology, we have developed a series of calorimeter instruments for laboratory use and installed them at the Electron Beam Ion Trap (EBIT) facility at the Lawrence Livermore National Laboratory. The calorimeter instruments at EBIT have significantly enhanced the capabilities of our laboratory astrophysics program including broad-band measurements of emission from charge exchange recombination and absolute cross sections for collisional excitation. The first Goddard Space Flight Center (GSFC) calorimeter instrument was installed at the EBIT facility in July of 2000 and has seen two major upgrades. The performance of the instrument has significantly improved from the initial instrument that had a resolving power of ~500 at 6 keV, and essentially no quantum efficiency at energies above 20 keV, to the current instrument that has a resolving power of 1350 and 95% quantum efficiency at 6 keV, and a resolving power of 1800 and 32% quantum efficiency at 60 keV.

Porter, F. S.; Beiersdorfer, P.; Brown, G. V.; Gu, M. F.; Kelley, R. L.; Kahn, S.; Kilbourne, C. A.; Thorn, D. B.

2009-04-01

278

Chirped-beam two-stage free-electron laser for high-power femtosecond x-ray pulse generation  

NASA Astrophysics Data System (ADS)

A method for generating femtosecond-duration x-ray pulses with a free-electron laser is presented. This method uses an energy-chirped electron beam propagating through an undulator to produce a frequency-chirped x-ray pulse by self-amplified spontaneous emission. A short temporal pulse is created by use of a monochromator to select a narrow radiation bandwidth. A second undulator is used to amplify the short-duration radiation. The radiation characteristics produced by a chirped-beam two-stage free-electron laser are calculated, and the performance of the chirped-beam two-stage option for the Linac Coherent Light Source is considered. 2002 Optical Society of America

Schroeder, Carl B.; Pellegrini, Claudio; Reiche, Sven; Arthur, John; Emma, Paul

2002-08-01

279

Grazing-incidence X-ray diffraction of single GaAs nanowires at locations defined by focused ion beams  

PubMed Central

Grazing-incidence X-ray diffraction measurements on single GaAs nanowires (NWs) grown on a (111)-oriented GaAs substrate by molecular beam epitaxy are reported. The positions of the NWs are intentionally determined by a direct implantation of Au with focused ion beams. This controlled arrangement in combination with a nanofocused X-ray beam allows the in-plane lattice parameter of single NWs to be probed, which is not possible for randomly grown NWs. Reciprocal space maps were collected at different heights along the NW to investigate the crystal structure. Simultaneously, substrate areas with different distances from the Au-implantation spots below the NWs were probed. Around the NWs, the data revealed a 0.4% decrease in the lattice spacing in the substrate compared with the expected unstrained value. This suggests the presence of a compressed region due to Au implantation. PMID:24046493

Bussone, Genziana; Schott, Rüdiger; Biermanns, Andreas; Davydok, Anton; Reuter, Dirk; Carbone, Gerardina; Schülli, Tobias U.; Wieck, Andreas D.; Pietsch, Ullrich

2013-01-01

280

Neutron spectral measurements in an intense photon field associated with a high-energy x-ray radiotherapy machine.  

PubMed

High-energy x-ray radiotherapy machines in the supermegavoltage region generate complex neutron energy spectra which make an exact evaluation of neutron shielding difficult. Fast neutrons resulting from photonuclear reactions in the x-ray target and collimators undergo successive collisions in the surrounding materials and are moderated by varying amounts. In order to examine the neutron radiation exposures quantitatively, the neutron energy spectra have been measured inside and outside the treatment room of a Sagittaire medical linear accelerator (25-MV x rays) located at Yale-New Haven Hospital. The measurements were made using a Bonner spectrometer consisting of 2-, 3-, 5-, 8-, 10- and 12-in.-diameter polyethylene spheres with 6Li and 7Li thermoluminescent dosimeter (TLD) chips at the centers, in addition to bare and cadmium-covered chips. The individual TLD chips were calibrated for neutron and photon response. The spectrometer was calibrated using a known PuBe spectrum Spectrometer measurements were made at Yale Electron Accelerator Laboratory and results compared with a neutron time-of-flight spectrometer and an activation technique. The agreement between the results from these independent methods is found to be good, except for the measurements in the direct photon beam. Quality factors have been inferred for the neutron fields inside and outside the treatment room. Values of the inferred quality factors fall primarily between 4 and 8, depending on location. PMID:412048

Holeman, G R; Price, K W; Friedman, L F; Nath, R

1977-01-01

281

X-ray micro-beam characterization of lattice rotations and distortions due to an individual dislocation  

NASA Astrophysics Data System (ADS)

Understanding and controlling the behaviour of dislocations is crucial for a wide range of applications, from nano-electronics and solar cells to structural engineering alloys. Quantitative X-ray diffraction measurements of the strain fields due to individual dislocations, particularly in the bulk, however, have thus far remained elusive. Here we report the first characterization of a single dislocation in a freestanding GaAs/In0.2Ga0.8As/GaAs membrane by synchrotron X-ray micro-beam Laue diffraction. Our experimental X-ray data agrees closely with textbook anisotropic elasticity solutions for dislocations, providing one of few experimental validations of this fundamental theory. On the basis of the experimental uncertainty in our measurements, we predict the X-ray beam size required for three-dimensional measurements of lattice strains and rotations due to individual dislocations in the material bulk. These findings have important implications for the in situ study of dislocation structure formation, self-organization and evolution in the bulk.

Hofmann, Felix; Abbey, Brian; Liu, Wenjun; Xu, Ruqing; Usher, Brian F.; Balaur, Eugeniu; Liu, Yuzi

2013-11-01

282

Generation of focused electron beam and X-rays by the doped LiNbO 3 crystals  

NASA Astrophysics Data System (ADS)

Generation of focused electrons beam with energies up to 100 keV from undoped LiNbO 3 (LN) crystals have been observed [J.D. Brownridge, Nature 358 (1992) 287; J.D. Brownridge, S.M. Shafroth, Appl. Phys. Lett. 79 (2001) 3364] during heating-cooling cycles in a low-pressure environment. This paper reports about similar results that were observed in doped crystals of LN. Generation of electrons by crystals with thicknesses of 1 and 6 mm, was visualized by ZnS screen [ZSS] during heating-cooling cycles in a vacuum chamber ( P = 1-10 mTorr). Generation of X-rays from both thin and thick crystals was evident from registered images from dental X-ray film [DXF]. The possibility of X-ray imaging was demonstrated, using different metal masks. Imaging of X-rays reveals that both focusing and wide-angle scattering modes of operation exist in the electron beams generation pattern during heating-cooling cycles.

Bayssie, M.; Brownridge, J. D.; Kukhtarev, N.; Kukhtarev, T.; Wang, J. C.

2005-12-01

283

Beam halo in high-intensity beams  

SciTech Connect

In space-charge dominated beams the nonlinear space-charge forces produce a filamentation pattern, which in projection to the 2-D phase spaces results in a 2-component beam consisting of an inner core and a diffuse outer halo. The beam-halo is of concern for a next generation of cw, high-power proton linacs that could be applied to intense neutron generators for nuclear materials processing. The author describes what has been learned about beam halo and the evolution of space-charge dominated beams using numerical simulations of initial laminar beams in uniform linear focusing channels. Initial results are presented from a study of beam entropy for an intense space-charge dominated beam.

Wangler, T.P.

1993-01-01

284

Beam halo in high-intensity beams  

SciTech Connect

In space-charge dominated beams the nonlinear space-charge forces produce a filamentation pattern, which in projection to the 2-D phase spaces results in a 2-component beam consisting of an inner core and a diffuse outer halo. The beam-halo is of concern for a next generation of cw, high-power proton linacs that could be applied to intense neutron generators for nuclear materials processing. The author describes what has been learned about beam halo and the evolution of space-charge dominated beams using numerical simulations of initial laminar beams in uniform linear focusing channels. Initial results are presented from a study of beam entropy for an intense space-charge dominated beam.

Wangler, T.P.

1993-06-01

285

Characterization of low-energy photon-emitting brachytherapy sources and kilovoltage x-ray beams using spectrometry  

NASA Astrophysics Data System (ADS)

Low-energy photon sources are used in therapeutic radiation oncology for brachytherapy with low dose-rate (LDR) sources and for superficial and orthovoltage therapy with kilovolt-age x-ray beams. Current dosimetry methods for these sources utilize energy-integrating devices, such as thermoluminescent dosimeters and ionization chambers. This thesis work investigates the dosimetry of LDR brachytherapy sources and kilovoltage x-ray beams using spectrometry, which preserves the energy-specific source output. Several LDR brachytherapy source models were measured with a reverse-electrode germanium (REGe) detector. The measured spectra were corrected for MCNP5-calculated detector response using a deconvolution algorithm (Beach, 2005). The peak areas determined from the corrected spectra were used to calculate the dose-rate constant (Chen and Nath, 2001) and the air-kerma strength. Dose-rate constant results agreed well with the published values (Rivard et al., 2004; Chen and Nath, 2007). Air-kerma strength results were systematically 2%--5% low compared to calibration values and primary air-kerma strength measurements. The spectrometry methods for LDR brachytherapy sources offer a promising alternative to existing experimental techniques, but further work is necessary to improve agreement with the current air-kerma strength standard methodology. Spectra of 20kVp---250kVp x-ray beams were measured with a low-energy germanium detector (LEGe). The LEGe spectrometry system was modeled in MCNP5 to calculate a detector response function. Backward stripping, which showed less variability than deconvolution, was used for correcting the measured x-ray spectra. The corrected experimental spectra were compared to spectra from: (1) Monte Carlo simulations of the full x-ray tube with EGSnrc, (2) the SpekCalc program (Poludniowski et al., 2009), and (3) the Gesellschaft fur Strahlen-und Umweltforschung mbH Munchen (GSF) Report 560. Agreement was best for the UW60-M through UW150-M beams and poorest for the UW20-M and UW-30M beams due to incomplete modeling of tungsten L-shell fluorescence peaks by the EGSnrc code and SpekCalc program. Monte Carlo simulations of thermoluminescent dosimeter and ionization chamber dosimetry demonstrated that variability in response due to the input spectrum was within the limits of accurate geometry simulation. This work has contributed to more accurate x-ray spectra that can be used for future dosimetry investigations with these beams.

Moga, Jacqueline D.

286

Correlation of relative X-ray photoelectron spectroscopy shake-up intensity with CuO particle size  

SciTech Connect

X-ray photoelectron spectroscopy (XPS) analysis of four Cu/SiO{sub 2} catalyst systems of different particle sizes of CuO on the surface showed variation in the relative peak area intensities of the shake-up lines to main core levels of the Cu 2p orbitals. These differences were attributed to various degrees of XPS-induced reduction of CuO initially formed on the surface by spin coating copper(II) acetate {l_brace}Cu-(CH{sub 3}CO{sub 2}){sub 2}{center_dot}H{sub 2}O, Cu(ac){sub 2}{r_brace} solutions of varying concentration. Changes in CuL{sub 3}M{sub 4,5}M{sub 4,5}X-ray excited Auger (XAES) line shapes under time-dependent exposure to the soft Mg K{alpha} X-rays revealed that smaller particle sizes were more susceptible to reduction to Cu(+1) than larger ones. The degree of reduction of Cu(+2) to Cu(+1) correlated with measured atomic force microscopic (AFM) particle heights of CuO on these substrates prior to XPS.

Chusuei, C.C.; Brookshier, M.A.; Goodman, D.W. [Texas A and M Univ., College Station, TX (United States). Dept. of Chemistry] [Texas A and M Univ., College Station, TX (United States). Dept. of Chemistry

1999-04-13

287

X-ray induced electrostatic charging of helium films  

Microsoft Academic Search

It is well known that free electrons can be held onto the free surface of liquid helium through either their own image charges or through the effect of an externally applied electric field. The resultant electrostatic pressure causes films to thin. We have recently measured x-ray reflectivity from static films of isotopic mixtures of helium with an intense x-ray beam

K. Penanen; P. S. Pershan; M. J. Regan; Isaac F. Silvera

1995-01-01

288

Quality indexes based on water measurements for low and medium energy x-ray beams: A theoretical study with PENELOPE  

SciTech Connect

Purpose : To study the use of quality indexes based on ratios of absorbed doses in water at two different depths to characterize x-ray beams of low and medium energies. Methods : A total of 55 x-ray beam spectra were generated with the codes XCOMP5R and SPEKCALC and used as input of a series of Monte Carlo simulations performed with PENELOPE, in which the percentage depth doses in water and thek{sub Q,Q{sub 0}} factors, defined in the TRS-398 protocol, were determined for each beam. Some of these calculations were performed by simulating the ionization chamber PTW 30010. Results : The authors found that the relation betweenk{sub Q,Q{sub 0}} and the ratios of absorbed doses at two depths is almost linear. A set of ratios statistically compatible with that showing the best fit has been determined. Conclusions : The results of this study point out which of these ratios of absorbed doses in water could be used to better characterize x-ray beams of low and medium energies.

Chica, U. [Departamento de Física Atómica, Molecular y Nuclear, Universidad de Granada, E-18071 Granada, Spain and FISRAD S.A.S Carrera 64 a No 22-41, Bogotá D.C. (Colombia)] [Departamento de Física Atómica, Molecular y Nuclear, Universidad de Granada, E-18071 Granada, Spain and FISRAD S.A.S Carrera 64 a No 22-41, Bogotá D.C. (Colombia); Anguiano, M.; Lallena, A. M., E-mail: lallena@ugr.es [Departamento de Física Atómica, Molecular y Nuclear, Universidad de Granada, E-18071 Granada (Spain); Vilches, M. [Servicio de Radiofísica, Hospital Universitario “San Cecilio”, Avda. Dr. Olóriz, 16, E-18012 Granada (Spain)] [Servicio de Radiofísica, Hospital Universitario “San Cecilio”, Avda. Dr. Olóriz, 16, E-18012 Granada (Spain)

2014-01-15

289

Concurrence of monoenergetic electron beams and bright X-rays from an evolving laser-plasma bubble  

PubMed Central

Desktop laser plasma acceleration has proven to be able to generate gigaelectronvolt-level quasi-monoenergetic electron beams. Moreover, such electron beams can oscillate transversely (wiggling motion) in the laser-produced plasma bubble/channel and emit collimated ultrashort X-ray flashes known as betatron radiation with photon energy ranging from kiloelectronvolts to megaelectronvolts. This implies that usually one cannot obtain bright betatron X-rays and high-quality electron beams with low emittance and small energy spread simultaneously in the same accelerating wave bucket. Here, we report the first (to our knowledge) experimental observation of two distinct electron bunches in a single laser shot, one featured with quasi-monoenergetic spectrum and another with continuous spectrum along with large emittance. The latter is able to generate high-flux betatron X-rays. Such is observed only when the laser self-guiding is extended over 4 mm at a fixed plasma density (4 × 1018 cm?3). Numerical simulation reveals that two bunches of electrons are injected at different stages due to the bubble evolution. The first bunch is injected at the beginning to form a stable quasi-monoenergetic electron beam, whereas the second one is injected later due to the oscillation of the bubble size as a result of the change of the laser spot size during the propagation. Due to the inherent temporal synchronization, this unique electron–photon source can be ideal for pump–probe applications with femtosecond time resolution. PMID:24711405

Yan, Wenchao; Chen, Liming; Li, Dazhang; Zhang, Lu; Hafz, Nasr A. M.; Dunn, James; Ma, Yong; Huang, Kai; Su, Luning; Chen, Min; Sheng, Zhengming; Zhang, Jie

2014-01-01

290

Concurrence of monoenergetic electron beams and bright X-rays from an evolving laser-plasma bubble.  

PubMed

Desktop laser plasma acceleration has proven to be able to generate gigaelectronvolt-level quasi-monoenergetic electron beams. Moreover, such electron beams can oscillate transversely (wiggling motion) in the laser-produced plasma bubble/channel and emit collimated ultrashort X-ray flashes known as betatron radiation with photon energy ranging from kiloelectronvolts to megaelectronvolts. This implies that usually one cannot obtain bright betatron X-rays and high-quality electron beams with low emittance and small energy spread simultaneously in the same accelerating wave bucket. Here, we report the first (to our knowledge) experimental observation of two distinct electron bunches in a single laser shot, one featured with quasi-monoenergetic spectrum and another with continuous spectrum along with large emittance. The latter is able to generate high-flux betatron X-rays. Such is observed only when the laser self-guiding is extended over 4 mm at a fixed plasma density (4 × 10(18) cm(-3)). Numerical simulation reveals that two bunches of electrons are injected at different stages due to the bubble evolution. The first bunch is injected at the beginning to form a stable quasi-monoenergetic electron beam, whereas the second one is injected later due to the oscillation of the bubble size as a result of the change of the laser spot size during the propagation. Due to the inherent temporal synchronization, this unique electron-photon source can be ideal for pump-probe applications with femtosecond time resolution. PMID:24711405

Yan, Wenchao; Chen, Liming; Li, Dazhang; Zhang, Lu; Hafz, Nasr A M; Dunn, James; Ma, Yong; Huang, Kai; Su, Luning; Chen, Min; Sheng, Zhengming; Zhang, Jie

2014-04-22

291

Neutral particle beam intensity controller  

DOEpatents

A neutral beam intensity controller is provided for a neutral beam generator in which a neutral beam is established by accelerating ions from an ion source into a gas neutralizer. An amplitude modulated, rotating magnetic field is applied to the accelerated ion beam in the gas neutralizer to defocus the resultant neutral beam in a controlled manner to achieve intensity control of the neutral beam along the beam axis at constant beam energy. The rotating magnetic field alters the orbits of ions in the gas neutralizer before they are neutralized, thereby controlling the fraction of neutral particles transmitted out of the neutralizer along the central beam axis to a fusion device or the like. The altered path or defocused neutral particles are sprayed onto an actively cooled beam dump disposed perpendicular to the neutral beam axis and having a central open for passage of the focused beam at the central axis of the beamline. Virtually zero therough 100% intensity control is achieved by varying the magnetic field strength without altering the ion source beam intensity or its species yield.

Dagenhart, William K. (Oak Ridge, TN)

1986-01-01

292

MOSFET dosimetry with high spatial resolution in intense synchrotron-generated x-ray microbeams  

SciTech Connect

Various dosimeters have been tested for assessing absorbed doses with microscopic spatial resolution in targets irradiated by high-flux, synchrotron-generated, low-energy ({approx}30-300 keV) x-ray microbeams. A MOSFET detector has been used for this study since its radio sensitive element, which is extraordinarily narrow ({approx}1 {mu}m), suits the main applications of interest, microbeam radiation biology and microbeam radiation therapy (MRT). In MRT, micrometer-wide, centimeter-high, and vertically oriented swaths of tissue are irradiated by arrays of rectangular x-ray microbeams produced by a multislit collimator (MSC). We used MOSFETs to measure the dose distribution, produced by arrays of x-ray microbeams shaped by two different MSCs, in a tissue-equivalent phantom. Doses were measured near the center of the arrays and maximum/minimum (peak/valley) dose ratios (PVDRs) were calculated to determine how variations in heights and in widths of the microbeams influenced this for the therapy, potentially important parameter. Monte Carlo (MC) simulations of the absorbed dose distribution in the phantom were also performed. The results show that when the heights of the irradiated swaths were below those applicable to clinical therapy (<1 mm) the MC simulations produce estimates of PVDRs that are up to a factor of 3 higher than the measured values. For arrays of higher microbeams (i.e., 25 {mu}mx1 cm instead of 25x500 {mu}m{sup 2}), this difference between measured and simulated PVDRs becomes less than 50%. Closer agreement was observed between the measured and simulated PVDRs for the Tecomet MSC (current collimator design) than for the Archer MSC. Sources of discrepancies between measured and simulated doses are discussed, of which the energy dependent response of the MOSFET was shown to be among the most important.

Siegbahn, E. A.; Braeuer-Krisch, E.; Bravin, A.; Nettelbeck, H.; Lerch, M. L. F.; Rosenfeld, A. B. [European Synchrotron Radiation Facility (ESRF), 6 Rue Jules Horowitz, 38043 Grenoble (France); Center for Medical Radiation Physics, University of Wollongong, Wollongong, New South Wales 2522 (Australia)

2009-04-15

293

Development of an x-ray beam line at the NSLS for studies in materials science using x-ray absorption spectroscopy  

SciTech Connect

At the time of the submission of the original proposal more than 7 years ago, the X-11 PRT had set as a goal to develop one of the leading and most comprehensive x-ray absorption beam lines in the world. By any measure we have been successful. As is well documented in previous annual progress report and in the NSLS annual reports, our PRT has been extremely productive in a wide range of topics in materials science, solid state physics, chemistry and biology. Well over 100 papers have been published acknowledging the support of this contract and this continues at a rate of about 30 papers per year and about 20 invited presentations per year. Significant in this report are major studies in high T{sub c} compounds, advances in interface studies, new results in premelting phenomena, several pioneering studies in application of XAS to electrochemistry and significant progress in our understanding of the structure of amorphous chalcogenide systems and their photostructural changes.

Sayers, D.E.

1989-01-01

294

Ultra-bright, ultra-broadband hard x-ray driven by laser-produced energetic electron beams  

SciTech Connect

We propose a new method of obtaining a compact ultra-bright, ultra-broadband hard X-ray source. This X-ray source has a high peak brightness in the order of 10{sup 22} photons/(s mm{sup 2} mrad{sup 2} 0.1\\%BW), an ultrashort duration (10 fs), and a broadband spectrum (flat distribution from 0.1 MeV to 4 MeV), and thus has wide-ranging potential applications, such as in ultrafast Laue diffraction experiments. In our scheme, laser-plasma accelerators (LPAs) provide driven electron beams. A foil target is placed oblique to the beam direction so that the target normal sheath field (TNSF) is used to provide a bending force. Using this TNSF-kick scheme, we can fully utilize the advantages of current LPAs, including their high charge, high energy, and low emittance.

Shi, Yin; Shen, Baifei; Zhang, Xiaomei; Wang, Wenpeng; Ji, Liangliang; Zhang, Lingang; Xu, Jiancai; Yu, Yahong; Zhao, Xueyan; Wang, Xiaofeng; Yi, Longqing; Xu, Tongjun; Xu, Zhizhan [State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, P.O. Box 800-211, Shanghai 201800 (China)] [State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, P.O. Box 800-211, Shanghai 201800 (China)

2013-09-15

295

High aspect ratio x-ray waveguide channels fabricated by e-beam lithography and wafer bonding  

NASA Astrophysics Data System (ADS)

We report on the fabrication and characterization of hard x-ray waveguide channels manufactured by e-beam lithography, reactive ion etching and wafer bonding. The guiding layer consists of air or vacuum and the cladding material of silicon, which is favorable in view of minimizing absorption losses. The specifications for waveguide channels which have to be met in the hard x-ray range to achieve a suitable beam confinement in two orthogonal directions are extremely demanding. First, high aspect ratios up to 106 have to be achieved between lateral structure size and length of the guides. Second, the channels have to be deeply embedded in material to warrant the guiding of the desired modes while absorbing all other (radiative) modes in the cladding material. We give a detailed report on device fabrication with the respective protocols and parameter optimization, the inspection and the optical characterization.

Neubauer, H.; Hoffmann, S.; Kanbach, M.; Haber, J.; Kalbfleisch, S.; Krüger, S. P.; Salditt, T.

2014-06-01

296

Strong interference effects in the resonant Auger decay of atoms induced by intense x-ray fields  

SciTech Connect

The theory of resonant Auger decay of atoms in a high-intensity coherent x-ray pulse is presented. The theory includes the coupling between the ground state and the resonance due to an intense x-ray pulse, taking into account the decay of the resonance and the direct photoionization of the ground state, both populating the final ionic states coherently. The theory also considers the impact of the direct photoionization of the resonance state itself which typically populates highly excited ionic states. The combined action of the resonant decay and of the direct ionization of the ground state in the field induces a non-Hermitian time-dependent coupling between the ground and the ''dressed'' resonance stats. The impact of these competing processes on the total electron yield and on the 2s{sup 2}2p{sup 4}({sup 1}D)3p {sup 2}P spectator and 2s{sup 1}2p{sup 6} {sup 2}S participator Auger decay spectra of the Ne 1s{yields}3p resonance is investigated. The role of the direct photoionization of the ground state and of the resonance increases dramatically with the field intensity. This results in strong interference effects with distinct patterns in the electron spectra, which differ for the participator and spectator final states.

Demekhin, Philipp V.; Cederbaum, Lorenz S. [Theoretische Chemie, Physikalisch-Chemisches Institut, Universitaet Heidelberg, Im Neuenheimer Feld 229, D-69120 Heidelberg (Germany)

2011-02-15

297

Research and development of an electron beam focusing system for a high-brightness X-ray generator.  

PubMed

A new type of rotating anticathode X-ray generator, where an electron beam of up to 60 keV irradiates the inner surface of a U-shaped Cu anticathode, has achieved a beam brilliance of 130 kW mm(-2) (at 2.3 kW). A higher-flux electron beam is expected from simulation by optimizing the geometry of a combined-function-type magnet instead of the fringing field of the bending magnet. In order to minimize the size of the X-ray source the electron beam has been focused over a short distance by a new combined-function bending magnet, whose geometrical shape was determined by simulation using the Opera-3D, General Particle Tracer and CST-STUDIO codes. The result of the simulation clearly shows that the role of combined functions in both the bending and the steering magnets is important for focusing the beam to a small size. FWHM sizes of the beam are predicted by simulation to be 0.45 mm (horizontal) and 0.05 mm (vertical) for a 120 keV/75 mA beam, of which the effective brilliance is about 500 kW mm(-2) on the supposition of a two-dimensional Gaussian distribution. High-power tests have begun using a high-voltage 120 kV/75 mA power supply for the X-ray generator instead of 60 kV/100 mA. The beam focus size on the target will be verified in the experiments. PMID:21169692

Sakai, Takeshi; Ohsawa, Satoshi; Sakabe, Noriyoshi; Sugimura, Takashi; Ikeda, Mitsuo

2011-01-01

298

Development of grating-based hard x-ray Talbot interferometry for optics and beam wavefront characterization at the advanced photon source  

NASA Astrophysics Data System (ADS)

Here we report on the effort to develop a hard x-ray grating interferometry technique for application to hard x-ray optics and wavefront characterization at the Advanced Photon Source (APS), Argonne National Laboratory, USA. We will mention the motivation for developing an x-ray interferometer at the APS and discuss the design of the interferometer. We will also describe the efforts in fabricating 2-D gratings and a new type of grating having nanometer periods for high-energy x-ray applications. The preliminary results obtained using x-ray Talbot interferometers built at APS, using a broadband (pink) beam and a monochromatic beam demonstrate the importance of this tool as a metrology instrument for optics and beam wavefront diagnostics.

Marathe, Shashidhara; Wojcik, Michael J.; Kujala, Naresh G.; Macrander, Albert T.; Wen, Han H.; Liu, Chian; Fezzaa, Kamel; Divan, Ralu; Mancini, Derrick C.; Assoufid, Lahsen

2012-09-01

299

Shielding for neutron scattered dose to the fetus in patients treated with 18 MV x-ray beams.  

PubMed

Neutrons are associated with therapeutic high energy x-ray beams as a contaminant that contributes significant unwanted dose to the patient. Measurement of both photon and neutron scattered dose at the position of a fetus from chest irradiation by a large field 18 MV x-ray beam was performed using an ionization chamber and superheated drop detector, respectively. Shielding construction to reduce this scattered dose was investigated using both lead sheet and borated polyethylene slabs. A 7.35 cm lead shield reduced the scattered photon dose by 50% and the scattered neutron dose by 40%. Adding 10 cm of 5% borated polyethylene to this lead shield reduced the scattered neutron dose by a factor of 7.5 from the unshielded value. When the 5% borated polyethylene was replaced by the same thickness of 30% borated polyethylene there was no significant change in the reduction of neutron scatter dose. The most efficient shield studied reduced the neutron scatter dose by a factor of 10. The results indicate that most of the scattered neutrons present at the position of the fetus produced by an 18 MV x-ray beam are of low energy and in the thermal to 0.57 MeV range since lead is almost transparent to neutrons with energies lower than 0.57 MeV. This article constitutes the first report of an effective shield to reduce neutron dose at the fetus when treating a pregnant woman with a high energy x-ray beam. PMID:10984226

Roy, S C; Sandison, G A

2000-08-01

300

Evaluation of some selected vaccines and other biological products irradiated by gamma rays, electron beams and X-rays  

NASA Astrophysics Data System (ADS)

Molecular sizing potency results are presented for irradiated samples of one lot of Haemophilus b conjugate vaccine, pneumococcal polysaccharide type 6B and typhoid vi polysaccharide vaccine. The samples were irradiated (25 kGy) by gamma rays, electron beams and X-rays. IgG and IgM antibody response in mice test results (ELISA) are given for the Hib conjugate vaccine irradiated at 0°C or frozen in liquid nitrogen.

May, J. C.; Rey, L.; Lee, Chi-Jen

2002-03-01

301

Laboratory Astrophysics Survey Of Key X-Ray Diagnostic Lines Using A Microcalorimeter On An Electron Beam Ion Trap  

NASA Astrophysics Data System (ADS)

Cosmic plasma conditions created in an Electron Beam Ion Trap (EBIT) make it possible to simulate the dependencies of key diagnostic x-ray lines on density, temperature, and excitation conditions that exist in astrophysical sources. We used a microcalorimeter to measure broad band spectra obtained from the NIST EBIT with an energy resolution approaching that of a Bragg crystal spectrometer. Spectra are presented for nitrogen, oxygen, neon, argon , and iron in various stages of ionization.

Silver, E.; Schnopper, H.; Bandler, S.; Brickhouse, N.; Murray, S.; Barbera, M.; Takacs, E.; Laming, M.; Kink, I.; Porto, J.; Gillaspy, J. D.; Deslattes, R.; Hudson, L.; Madden, N.; Landis, D.; Beeman, J.; Haller, E. E.

2000-10-01

302

Optimisation of NSLS-II Blade X-ray Beam Position Monitors: from Photoemission type to Diamond Detector  

SciTech Connect

Optimisation of blade type x-ray beam position monitors (XBPM) was performed for NSLS-II undulator IVU20. Blade material, con and #64257;guration and operation principle was analysed in order to improve XBPM performance. Optimisation is based on calculation of the XBPM signal spatial distribution. Along with standard photoemission type XBPM a Diamond Detector Blades (DDB) were analysed as blades for XBPMs. DDB XBPMs can help to overcome drawbacks of the photoemission blade XBPMs.

ILINSKI P.

2012-07-10

303

X-ray beamsplitter  

DOEpatents

An x-ray beamsplitter which splits an x-ray beam into two coherent parts by reflecting and transmitting some fraction of an incident beam has applications for x-ray interferometry, x-ray holography, x-ray beam manipulation, and x-ray laser cavity output couplers. The beamsplitter is formed of a wavelength selective multilayer thin film supported by a very thin x-ray transparent membrane. The beamsplitter resonantly transmits and reflects x-rays through thin film interference effects. A thin film is formed of 5--50 pairs of alternate Mo/Si layers with a period of 20--250 A. The support membrane is 10--200 nm of silicon nitride or boron nitride. The multilayer/support membrane structure is formed across a window in a substrate by first forming the structure on a solid substrate and then forming a window in the substrate to leave a free-standing structure over the window. 6 figs.

Ceglio, N.M.; Stearns, D.G.; Hawryluk, A.M.; Barbee, T.W. Jr.

1987-08-07

304

X-ray beamsplitter  

DOEpatents

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

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

1989-01-01

305

Compton backscattered collimated x-ray source  

DOEpatents

A high-intensity, inexpensive and collimated x-ray source is disclosed for applications such as x-ray lithography is disclosed. An intense pulse from a high power laser, stored in a high-finesse resonator, repetitively collides nearly head-on with and Compton backscatters off a bunched electron beam, having relatively low energy and circulating in a compact storage ring. Both the laser and the electron beams are tightly focused and matched at the interaction region inside the optical resonator. The laser-electron interaction not only gives rise to x-rays at the desired wavelength, but also cools and stabilizes the electrons against intrabeam scattering and Coulomb repulsion with each other in the storage ring. This cooling provides a compact, intense bunch of electrons suitable for many applications. In particular, a sufficient amount of x-rays can be generated by this device to make it an excellent and flexible Compton backscattered x-ray (CBX) source for high throughput x-ray lithography and many other applications. 4 figs.

Ruth, R.D.; Huang, Z.

1998-10-20

306

Compton backscattered collmated X-ray source  

DOEpatents

A high-intensity, inexpensive and collimated x-ray source for applications such as x-ray lithography is disclosed. An intense pulse from a high power laser, stored in a high-finesse resonator, repetitively collides nearly head-on with and Compton backscatters off a bunched electron beam, having relatively low energy and circulating in a compact storage ring. Both the laser and the electron beams are tightly focused and matched at the interaction region inside the optical resonator. The laser-electron interaction not only gives rise to x-rays at the desired wavelength, but also cools and stabilizes the electrons against intrabeam scattering and Coulomb repulsion with each other in the storage ring. This cooling provides a compact, intense bunch of electrons suitable for many applications. In particular, a sufficient amount of x-rays can be generated by this device to make it an excellent and flexible Compton backscattered x-ray (CBX) source for high throughput x-ray lithography and many other applications.

Ruth, Ronald D. (Woodside, CA); Huang, Zhirong (Stanford, CA)

2000-01-01

307

Generation and application of channeling X-rays using a novel, low-emittance electron beam—Status and plans  

NASA Astrophysics Data System (ADS)

We plan to use very small emittance electron beams created from our novel, single tip cathodes to make a channeling-radiation X-ray source for X-ray imaging, especially phase contrast imaging. We calculate that we can preserve the electron emittance from the source to the crystal, and focus to a 40 nm spot on the crystal face for 40 MeV electrons. This yields an X-ray source with good coherence properties. We discuss our plan for experiments at Fermilab with 4.5 MeV electrons at the High Brightness Electron Source Laboratory, and with 40 MeV electrons at the Advanced Superconducting Test Accelerator. We also present the state of our art with cathode construction and testing. Electrons come from the cathodes by field-emission, with the electric field enhanced by geometric properties of a very small, robust diamond tip. This can create an electron beam with very small emittance. We estimate that the normalized emittance of such a beam at the cathode is 3 nm rad. We currently test the cathodes in DC, high-voltage test stands. We will begin experiments placing the cathodes in RF guns in early 2013.

Gabella, W. E.; Brau, C. A.; Choi, B. K.; Ivanov, B.; Jarvis, J. D.; Mendenhall, M. H.; Piot, P.; Mihalcea, D.; Carrigan, R.; Wagner, W.

2013-08-01

308

Using X-ray free-electron lasers for probing of complex interaction dynamics of ultra-intense lasers with solid matter  

SciTech Connect

We demonstrate the potential of X-ray free-electron lasers (XFEL) to advance the understanding of complex plasma dynamics by allowing for the first time nanometer and femtosecond resolution at the same time in plasma diagnostics. Plasma phenomena on such short timescales are of high relevance for many fields of physics, in particular in the ultra-intense ultra-short laser interaction with matter. Highly relevant yet only partially understood phenomena become directly accessible in experiment. These include relativistic laser absorption at solid targets, creation of energetic electrons and electron transport in warm dense matter, including the seeding and development of surface and beam instabilities, ambipolar expansion, shock formation, and dynamics at the surfaces or at buried layers. In this paper, we focus on XFEL plasma probing for high power laser matter interactions based on quantitative calculations using synthesized data and evaluate the feasibility of various imaging and scattering techniques with special focus on the small angle X-ray scattering technique.

Kluge, T., E-mail: t.kluge@hzdr.de; Huang, L. G.; Metzkes, J.; Bussmann, M. [Helmholtz-Zentrum Dresden-Rossendorf e.V., D-01328 Dresden (Germany)] [Helmholtz-Zentrum Dresden-Rossendorf e.V., D-01328 Dresden (Germany); Gutt, C. [Universität Siegen, D-57068 Siegen (Germany)] [Universität Siegen, D-57068 Siegen (Germany); Schramm, U.; Cowan, T. E. [Helmholtz-Zentrum Dresden-Rossendorf e.V., D-01328 Dresden (Germany) [Helmholtz-Zentrum Dresden-Rossendorf e.V., D-01328 Dresden (Germany); Technische Universität Dresden, D-01062 Dresden (Germany)

2014-03-15

309

X-ray multislice computation using the Moodie-Wagenfeld equations: divergent-beam pattern simulation in three-beam and six-beam Laue cases.  

PubMed

Pattern simulations for three-beam and six-beam X-ray diffraction are presented using multislice calculations based on Moodie & Wagenfeld's formulation of the X-ray equations, which factorize Maxwell's equations into Dirac format, using circular-polarization bases. The results are presented in three forms: one-dimensional rocking curves, Pendellösung thickness fringes, and convergent/divergent-beam patterns of single-diffraction orders, using experience gained from CBED (convergent-beam electron diffraction) and LACBED (large-angle CBED) techniques developed for high-voltage electron diffraction transmission patterns. This latter and quite new technique displays the results in the most compact form. The acronym DBXRAD (divergent-beam X-ray diffraction) is used for these patterns. The optics required for these patterns has only recently become available for radiations up to Mo Kalpha(1) in energy and for limited angular divergences, but with capillary focusing currently undergoing rapid development these limits are likely to be extended. However, these simulations define critical angular ranges within reach of current designs. Simulations for light- and heavy-atom structures belonging to the enantiomorphic space-group pair P3(1)21 and P3(2)21 provide clear evidence of chiral interaction between radiation and structure, highlighting divergences from the use in structure analysis of the well studied CBED pattern symmetries. Mo Kalpha(1) and Ta Kalpha(1) wavelengths were used to minimize absorption for the two structures studied, an important factor owing to the large thicknesses (up to 20 mm) required. PMID:10927256

Goodman; Liu

1999-03-01

310

Is low-energy-ion bombardment generated X-ray emission a secondary mutational source to ion-beam-induced genetic mutation?  

NASA Astrophysics Data System (ADS)

Low-energy ion beam biotechnology has achieved tremendous successes in inducing crop mutation and gene transfer. However, mechanisms involved in the related processes are not yet well understood. In ion-beam-induced mutation, ion-bombardment-produced X-ray has been proposed to be one of the secondary mutation sources, but the speculation has not yet been experimentally tested. We carried out this investigation to test whether the low-energy ion-beam-produced X-ray was a source of ion-beam-induced mutation. In the investigation, X-ray emission from 29-keV nitrogen- or argon- ion beam bombarded bacterial Escherichia coli (E. coli) cells held in a metal or plastic sample holder was in situ detected using a highly sensitive X-ray detector. The ion beam bombarded bacterial cells held in different material holders were observed for mutation induction. The results led to a conclusion that secondary X-ray emitted from ion-beam-bombarded biological living materials themselves was not a, or at least a negligible, mutational source, but the ion-beam-induced X-ray emission from the metal that made the sample holder could be a source of mutation.

Thongkumkoon, P.; Prakrajang, K.; Thopan, P.; Yaopromsiri, C.; Suwannakachorn, D.; Yu, L. D.

2013-07-01

311

The application of eigensymmetries of face forms to X-ray diffraction intensities of crystals twinned by 'reticular merohedry'.  

PubMed

This paper is an extension of a previous treatment of `twins by merohedry' with full lattice coincidence [? = 1, Klapper & Hahn (2010). Acta Cryst. A66, 327-346] to `twins by reticular merohedry' with partial lattice coincidence (? > 1). Again, the sets of symmetrically equivalent reflections {hkl} are considered as sets of equivalent faces (face forms) {hkl}, and the behaviour of the oriented eigensymmetries of these forms under the action of a twin operation is used to determine the X-ray reflection sets, the intensities of which are affected or not affected by the twinning. The following cases are treated: rhombohedral obverse/reverse ?3 twins, cubic ?3 (spinel) twins, tetragonal ?5 twins (twin elements m'(120), 2'[ ?210]) and hexagonal ?7 twins (m'(12 ?30), 2'[2 ?10]). For each case the twin laws for all relevant point groups are defined, and the twin diffraction cases A (intensity of twin-related reflection sets not affected), B1 (intensity affected), B2 (intensity affected only by anomalous scattering) and S (single, i.e. non-coincident reflection sets) are derived for all twin laws. A special treatment is provided for the cubic ?3 twins, where the cubic face forms first have to be split into up to four rhombohedral subforms with a threefold axis along one of the four cube <111> directions, here [111]. These subforms exhibit different twin diffraction cases analogous to those derived for the rhombohedral obverse/reverse ?3 twins. A complete list of the split forms and their diffraction cases for all cubic point groups and all ?3 twin elements is given. The application to crystal structure determination of crystals twinned by reticular merohedry and to X-ray topographic mapping of twin domains is discussed. PMID:22186286

Klapper, H; Hahn, Th

2012-01-01

312

Thin film beam splitter multiple short pulse generation for enhanced Ni-like Ag x-ray laser emission.  

PubMed

An alternative, novel multiple pulse generation scheme was implemented directly after the optical compressor output of an x-ray pump laser. The new method uses a polarization sensitive thin film beam splitter and a half-wavelength wave plate for tuning the energy ratio in the multiple short pulses. Based on this method, an extensive study was made of the running parameters for a grazing incidence pumped silver x-ray laser (XRL) pumped with a long pulse of 145 mJ in 6 ns at 532 nm and up to 1.45 J in few picoseconds at 810 nm. Fivefold enhancement in the emission of the silver XRL was demonstrated using the new pump method. PMID:24978964

Cojocaru, Gabriel V; Ungureanu, Razvan G; Banici, Romeo A; Ursescu, Daniel; Delmas, Olivier; Pittman, Moana; Guilbaud, Olivier; Kazamias, Sophie; Cassou, Kevin; Demailly, Julien; Neveu, Olivier; Baynard, Elsa; Ros, David

2014-04-15

313

Probing inhomogeneities in nanoscale organic semiconductor films: Depth profiling using slow positron beam and X-ray reflectivity techniques  

NASA Astrophysics Data System (ADS)

Depth profiling studies in 200 nm organic semiconductor (OSC) films on quartz substrate have been carried out using slow positron beam and X-ray reflectivity (XRR) techniques with the objective of examining structural inhomogeneities in as-deposited film and those annealed at high temperature. Grazing incidence X-ray diffraction and atomic force microscopy measurements are carried out to examine the crystallinity and surface morphology, respectively. In general, annealing is seen to modify the morphology and nanostructure. However, a significant inhomogeneity in nanostructure, marked by a disordered layer with low density region is observed in the film annealed at 200 °C from positron as well as XRR measurements. This study highlights the sensitivity of these techniques to defects and inhomogeneities in nanoscale that may have profound influence on device performance.

Maheshwari, Priya; Bhattacharya, D.; Sharma, S. K.; Mukherjee, S.; Samanta, S.; Basu, S.; Aswal, D. K.; Pujari, P. K.

2014-12-01

314

Diode readout electronics for beam intensity and position monitors for FELs  

NASA Astrophysics Data System (ADS)

LCLS uses Intensity-Position Monitors (IPM) to measure intensity and position of the FEL x-ray pulses. The primary beam passes through a silicon nitride film and four diodes, arranged in quadrants, detect the backscattered x-ray photons. The position is derived from the relative intensity of the four diodes, while the sum provides beam intensity information. In contrast to traditional synchrotron beam monitors, where diodes measure a DC current signal, the LCLS beam monitors have to cope with the pulsed nature of the FEL, which requires a large single shot dynamic range. A key component of these beam monitors is the readout electronics. The first generation of beam monitors showed some limitations. A new scheme with upgraded electronics, firmware and software was implemented resulting in a more robust and reliable measuring tool.

Herrmann, S.; Hart, P.; Freytag, M.; Pines, J.; Weaver, M.; Sapozhnikov, L.; Nelson, S.; Koglin, J.; Carini, G. A.; Tomada, A.; Haller, G.

2014-03-01

315

Optimization of X-ray microplanar beam radiation therapy for deep-seated tumors by a simulation study.  

PubMed

A Monte Carlo simulation was applied to study the energy dependence on the transverse dose distribution of microplanar beam radiation therapy (MRT) for deep-seated tumors. The distribution was found to be the peak (in-beam) dose and the decay from the edge of the beam down to the valley. The area below the same valley dose level (valley region) was decreased with the increase in the energy of X-rays at the same beam separation. To optimize the MRT, we made the following two assumptions: the therapeutic gain may be attributed to the efficient recovery of normal tissue caused by the beam separation; and a key factor for the efficient recovery of normal tissue depends on the area size of the valley region. Based on these assumptions and the results of the simulated dose distribution, we concluded that the optimum X-ray energy was in the range of 100-300 keV depending on the effective peak dose to the target tumors and/or tolerable surface dose. In addition, we proposed parameters to be studied for the optimization of MRT to deep-seated tumors. PMID:24865214

Shinohara, Kunio; Kondoh, Takeshi; Nariyama, Nobuteru; Fujita, Hajime; Washio, Masakazu; Aoki, Yukimasa

2014-01-01

316

Gamma-H2AX foci in cells exposed to a mixed beam of X-rays and alpha particles  

PubMed Central

Background Little is known about the cellular effects of exposure to mixed beams of high and low linear energy transfer radiation. So far, the effects of combined exposures have mainly been assessed with clonogenic survival or cytogenetic methods, and the results are contradictory. The gamma-H2AX assay has up to now not been applied in this context, and it is a promising tool for investigating the early cellular response to mixed beam irradiation. Purpose To determine the dose response and repair kinetics of gamma-H2AX ionizing radiation-induced foci in VH10 human fibroblasts exposed to mixed beams of 241Am alpha particles and X-rays. Results VH10 human fibroblasts were irradiated with each radiation type individually or both in combination at 37°C. Foci were scored for repair kinetics 0.5, 1, 3 and 24 h after irradiation (one dose per irradiation type), and for dose response at the 1 h time point. The dose response effect of mixed beam was additive, and the relative biological effectiveness for alpha particles (as compared to X-rays) was of 0.76 ± 0.52 for the total number of foci, and 2.54 ± 1.11 for large foci. The repair kinetics for total number of foci in cells exposed to mixed beam irradiation was intermediate to that of cells exposed to alpha particles and X-rays. However, for mixed beam-irradiated cells the frequency and area of large foci were initially lower than predicted and increased during the first 3 hours of repair (while the predicted number and area did not). Conclusions The repair kinetics of large foci after mixed beam exposure was significantly different from predicted based on the effect of the single dose components. The formation of large foci was delayed and they did not reach their maximum area until 1 h after irradiation. We hypothesize that the presence of low X-ray-induced damage engages the DNA repair machinery leading to a delayed DNA damage response to the more complex DNA damage induced by alpha particles. PMID:23121736

2012-01-01

317

Deformable motion reconstruction for scanned proton beam therapy using on-line x-ray imaging  

NASA Astrophysics Data System (ADS)

Organ motion is a major problem for any dynamic radiotherapy delivery technique, and is particularly so for spot scanned proton therapy. On the other hand, the use of narrow, magnetically deflected proton pencil beams is potentially an ideal delivery technique for tracking tumour motion on-line. At PSI, our new Gantry is equipped with a Beams Eye View (BEV) imaging system which will be able to acquire 2D x-ray images in fluoroscopy mode during treatment delivery. However, besides precisely tracking motion from BEVs, it is also essential to obtain information on the 3D motion vector throughout the whole region of interest, and any sparsely acquired surrogate motion is generally not sufficient to describe the deformable behaviour of the whole volume in three dimensions. In this study, we propose a method by which 3D deformable motions can be estimated from surrogate motions obtained using this monoscopic imaging system. The method assumes that example motions over a number of breathing cycles can be acquired before treatment for each patient using 4DMRI. In this study, for each of 11 different subjects, 100 continuous breathing cycles have been extracted from extended 4DMRI studies in the liver and then subject specific motion models have been built using principle component analysis (PCA). To simulate treatment conditions, a different set of 30 continuous breathing cycles from the same subjects have then been used to generate a set of simulated 4DCT data sets (so-called 4DCT(MRI) data sets), from which time-resolved digitally reconstructed radiographs (DRRs) were calculated using the BEV geometry for three treatment fields respectively. From these DRRs, surrogate motions from fiducial markers or the diaphragm have been used as a predictor to estimate 3D motions in the liver region for each subject. The prediction results have been directly compared to the ‘ground truth’ motions extracted from the same 30 breath cycles of the originating 4DMRI data set. Averaged over all 11 subjects, and for three field directions, for 99% of predicted positions, median (max) error magnitudes of better than 2.63(5.67) mm can be achieved when fiducial markers was chosen as predictor. Furthermore, three single fields, 4D dose calculations have been performed as a verification tool to evaluate the prediction performance of such a model in the context of scanned proton beam therapy. These show a high similarity between plans considering either PCA predicted motion or ground truth motion, where absolute dose differences of more than 5% (Vdosediff = 5%) occur for the worst field scenarios in only 3.61% (median) or 15.13% (max) of dose calculation points in the irradiated volume. The magnitude of these dose differences were insignificantly dependent on whether surrogate motions were tracked by monoscopic or stereoscopic imaging systems, or whether fiducial markers or diaphragm were chosen as surrogate. This study has demonstrated that on-line deformable motion reconstruction from sparse surrogate motions is feasible, even when using only a monoscopic imaging system. In addition, it has also been found that diaphragm motion can be considered as a good predictor for respiratory deformable liver motion prediction, implying that fiducial markers might not be compulsory if used in conjunction with a patient specific PCA based model.

Zhang, Ye; Knopf, A.; Tanner, C.; Boye, D.; Lomax, A. J.

2013-12-01

318

Deformable motion reconstruction for scanned proton beam therapy using on-line x-ray imaging.  

PubMed

Organ motion is a major problem for any dynamic radiotherapy delivery technique, and is particularly so for spot scanned proton therapy. On the other hand, the use of narrow, magnetically deflected proton pencil beams is potentially an ideal delivery technique for tracking tumour motion on-line. At PSI, our new Gantry is equipped with a Beams Eye View (BEV) imaging system which will be able to acquire 2D x-ray images in fluoroscopy mode during treatment delivery. However, besides precisely tracking motion from BEVs, it is also essential to obtain information on the 3D motion vector throughout the whole region of interest, and any sparsely acquired surrogate motion is generally not sufficient to describe the deformable behaviour of the whole volume in three dimensions. In this study, we propose a method by which 3D deformable motions can be estimated from surrogate motions obtained using this monoscopic imaging system. The method assumes that example motions over a number of breathing cycles can be acquired before treatment for each patient using 4DMRI. In this study, for each of 11 different subjects, 100 continuous breathing cycles have been extracted from extended 4DMRI studies in the liver and then subject specific motion models have been built using principle component analysis (PCA). To simulate treatment conditions, a different set of 30 continuous breathing cycles from the same subjects have then been used to generate a set of simulated 4DCT data sets (so-called 4DCT(MRI) data sets), from which time-resolved digitally reconstructed radiographs (DRRs) were calculated using the BEV geometry for three treatment fields respectively. From these DRRs, surrogate motions from fiducial markers or the diaphragm have been used as a predictor to estimate 3D motions in the liver region for each subject. The prediction results have been directly compared to the 'ground truth' motions extracted from the same 30 breath cycles of the originating 4DMRI data set. Averaged over all 11 subjects, and for three field directions, for 99% of predicted positions, median (max) error magnitudes of better than 2.63(5.67) mm can be achieved when fiducial markers was chosen as predictor. Furthermore, three single fields, 4D dose calculations have been performed as a verification tool to evaluate the prediction performance of such a model in the context of scanned proton beam therapy. These show a high similarity between plans considering either PCA predicted motion or ground truth motion, where absolute dose differences of more than 5% (V(dosediff = 5%)) occur for the worst field scenarios in only 3.61% (median) or 15.13% (max) of dose calculation points in the irradiated volume. The magnitude of these dose differences were insignificantly dependent on whether surrogate motions were tracked by monoscopic or stereoscopic imaging systems, or whether fiducial markers or diaphragm were chosen as surrogate. This study has demonstrated that on-line deformable motion reconstruction from sparse surrogate motions is feasible, even when using only a monoscopic imaging system. In addition, it has also been found that diaphragm motion can be considered as a good predictor for respiratory deformable liver motion prediction, implying that fiducial markers might not be compulsory if used in conjunction with a patient specific PCA based model. PMID:24256693

Zhang, Ye; Knopf, A; Tanner, C; Boye, D; Lomax, A J

2013-12-21

319

High-intensity x-ray holography: an approach to high-resolution snapshot imaging of biological specimens  

SciTech Connect

The crucial physical and technological issues pertaining to the holographic imaging of biological structures with a short-pulse, high-intensity, high-quantum-energy laser were examined. The limitations of x-ray optics are discussed. Alternative holographic techniques were considered, and it was concluded that far-field Fresnel transform holography (Fraunhofer holography) using a photoresist recording surface is most tractable with near term technology. The hydrodynamic expansion of inhomogeneities within the specimen is discussed. It is shown that expansion is the major source of image blurring. Analytic expressions were derived for the explosion of protein concentrations in an x-ray transparent cytoplasm, compared with numerical calculations, and corrections derived to account for the competitive transport processes by which these inhomogeneities lose energy. It is concluded that for the near term Fresnel transform holography, particularly, far-field or Fraunhofer holography, is more practical than Fourier transform holography. Of the alternative fine grain recording media for use with Fresnel transform holography, a photo-resist is most attractive. For best resolution, exposure times must be limited to a few picoseconds, and this calls for investigation of mechanisms to shutter the laser or gate the recording surface. The best contrast ratio between the nitrogen-bearing polymers (protein and the nucleic acids) and water is between the K-edges of oxygen and nitrogen.

Solem, J.C.

1982-08-01

320

Development of an x-ray beam line at the NSLS for studies in materials science using x-ray absorption spectroscopy. Progress report  

SciTech Connect

This has been an exciting year for our PRT, highlighted by the running of the NSLS x-ray ring in an operational mode beginning in May of this year. Our line X-11A was the first to obtain an experimental spectrum and the first to publish a paper with results from the x-ray ring. These early successes have allowed us to run in an operational mode during the entire time that the x-raying ring itself has been operational. In addition to a number of exciting initial scientific results described, the initial results, particularly in the four crystal mode, have verified our original optical design and demonstrated an improved resolution using the four crystals. This will have a significant impact on near edge (XANES) studies.

Sayers, D.E.

1985-10-01

321

Methods for assisting recovery of damaged brain and spinal cord using arrays of X-Ray microplanar beams  

DOEpatents

A method of assisting recovery of an injury site of brain or spinal cord injury includes providing a therapeutic dose of X-ray radiation to the injury site through an array of parallel microplanar beams. The dose at least temporarily removes regeneration inhibitors from the irradiated regions. Substantially unirradiated cells surviving between the microplanar beams migrate to the in-beam irradiated portion and assist in recovery. The dose may be administered in dose fractions over several sessions, separated in time, using angle-variable intersecting microbeam arrays (AVIMA). Additional doses may be administered by varying the orientation of the microplanar beams. The method may be enhanced by injecting stem cells into the injury site.

Dilmanian, F. Avraham (Yaphank, NY); McDonald, III, John W. (Baltimore, MD)

2007-12-04

322

Comparison of beam quality parameters computed from mammographic x-ray spectra measured with different high-resolution semiconductor detectors  

NASA Astrophysics Data System (ADS)

In this work, the x-ray spectra of standard mammographic radiation qualities were measured with Si(Li), SDD and CdTe detectors. The x-ray source was an industrial x-ray tube with an Mo anode, operating at constant tube potentials between 20 and 35 kV, and adapted with filters of Mo and Al, in order to reproduce standard mammographic beam qualities. The measured spectra were corrected by the energy response of each detector, which were determined using Monte Carlo simulation. From the corrected spectra, values of HVL and mean energies were computed. The results show that, after correction by the energy response functions, all detectors provided similar bremsstrahlung spectra, whereas greater differences were observed in the characteristic peaks, due to the different energy resolutions of the detection systems. The comparison between values of HVL and mean energies calculated from the spectra obtained with each detector also show good agreement, with differences up to 5.5%. For most of the conditions studied, the differences between the measured values of HVL and those computed from the corrected spectra are lesser than the experimental uncertainties. Finally, our results show that, although the detectors Si(Li), SDD and CdTe provide similar spectra, the use of the first two detectors, which combine high energy resolution and low spectral distortions, is recommended, since they provide more accurate spectra from which several quality parameters can be determined.

Tomal, A.; Cunha, D. M.; Poletti, M. E.

2014-02-01

323

Benchmarking Charge Exchange Theory with Experiments Using an X-ray Calorimeter at an Electron Beam Ion Trap  

NASA Astrophysics Data System (ADS)

Charge exchange occurs widely throughout the solar system, and also represents a significant contaminating foreground to all observations from low-Earth orbit. With the upcoming 2015 launch of the Astro-H X-ray satellite, which will produce the first high-resolution spectra of extended X-ray sources, it is crucial to improve our understanding of charge exchange spectra. Theoretical models of charge exchange spectra do not always accurately describe observations and require further experimental verification. To this end, we present X-ray spectra from charge exchange experiments performed with the Electron Beam Ion Trap (EBIT) facility at Lawrence Livermore National Laboratory, using the EBIT Calorimeter Spectrometer. We compare the relative strength of the high-n Lyman series emission while varying the ions and neutral gas. We show ion temperature measurements to disentangle the effects of variations in collision velocity. We find that empirical results vary widely with no clear correlation with current theory. We present experimental benchmarks that can be used to develop a more comprehensive and accurate theory.

Betancourt-Martinez, Gabriele; Porter, F. S.; Leutenegger, M. A.; Brown, G. V.; Beiersdorfer, P.

2014-01-01

324

Improvement of image quality by tilted fan beam data acquisition in a helical scan x-ray CT  

SciTech Connect

The helical scan x-ray CT is useful for high speed acquisition of three dimensional image data. In image reconstruction from helical scan data, a set of sequential data is used and the data are interpolated to produce projection data which reconstruct an image of a given cross section. This interpolation sometimes causes artifacts in the reconstructed image. We propose a new data acquisition method which minimizes the effect of scanning slice position in the axial direction. The proposed method inclines an x-ray detector array in the direction of rotation. The tilted angle is defined as arctan ({theta}L/2R{pi} tan {theta}), where L is the moving distance of a table per rotation and R is the radius of rotation of the x-ray source. The angle {theta} is the orthogonal projection of the half of a fan angle onto the parallel beam projection plane. Simulation results showed that our method eliminated the low frequency distortion and slightly improved the spatial resolution in the axial direction.

Ogawa, K.; Yamada, Y.; Uno, T. [Hosei Univ., Tokyo (Japan)

1996-12-31

325

X-RAY RADIATION MECHANISMS AND BEAMING EFFECT OF HOT SPOTS AND KNOTS IN ACTIVE GALACTIC NUCLEAR JETS  

SciTech Connect

The observed radio-optical-X-ray spectral energy distributions (SEDs) of 22 hot spots and 45 knots in the jets of 35 active galactic nuclei are complied from the literature and modeled with single-zone lepton models. It is found that the observed luminosities at 5 GHz (L{sub 5{sub GHz}}) and at 1 keV (L{sub 1{sub keV}}) are tightly correlated, and the two kinds of sources can be roughly separated with a division of L{sub 1{sub keV}} = L{sub 5{sub GHz}}. Our SED fits show that the mechanisms of the X-rays are diverse. While the X-ray emission of a small fraction of the sources is a simple extrapolation of the synchrotron radiation for the radio-to-optical emission, an inverse Compton (IC) scattering component is necessary to model the X-rays for most of the sources. Considering the sources at rest (the Doppler factor delta = 1), the synchrotron-self-Compton (SSC) scattering would dominate the IC process. This model can interpret the X-rays of some hot spots with a magnetic field strength (B {sup delta}{sup =1}{sub ssc}) being consistent with the equipartition magnetic field (B {sup delta}{sup =1}{sub eq}) in 1 order of magnitude, but an unreasonably low B {sup delta}{sup =1}{sub ssc} is required to model the X-rays for all knots. Measuring the deviation between B {sup delta}{sup =1}{sub ssc} and B {sup delta}{sup =1}{sub eq} with ratio R{sub B} {identical_to} B {sup delta}{sup =1}{sub eq}/B {sup delta}{sup =1}{sub ssc}, we find that R{sub B} is greater than 1 and it is tightly anti-correlated with ratio R{sub L} {identical_to} L{sub 1{sub keV}}/L{sub 5{sub GHz}} for both the knots and the hot spots. We propose that the deviation may be due to the neglect of the relativistic bulk motion for these sources. Considering this effect, the IC/cosmic microwave background (CMB) component would dominate the IC process. We show that the IC/CMB model well explains the X-ray emission for most sources under the equipartition condition. Although the derived beaming factor (delta) and co-moving equipartition magnetic field (B'{sub eq}) of some hot spots are comparable to the knots, the delta values of the hot spots tend to be smaller and their B'{sub eq} values tend to be larger than that of the knots, favoring the idea that the hot spots are jet termination and knots are a part of a well-collimated jet. Both B{sub eq}{sup '} and delta are tentatively correlated with R{sub L} . Corrected by the beaming effect, the L'{sub 5{sub GHz}}-L'{sub 1{sub keV}} relations for the two kinds of sources are even tighter than the observed ones. These facts suggest that, under the equipartition condition, the observational differences of the X-rays from the knots and hot spots may be mainly due to the differences on the Doppler boosting effect and the co-moving magnetic field of the two kinds of sources. Our IC scattering models predict a prominent GeV-TeV component in the SEDs for some sources, which are detectable with H.E.S.S. and Fermi/LAT.

Zhang Jin; Bai, J. M.; Chen Liang [National Astronomical Observatories/Yunnan Observatory, Chinese Academy of Sciences, P.O. Box 110, Kunming, Yunnan 650011 (China); Liang Enwei, E-mail: zhang.jin@hotmail.co [Department of Physics, Guangxi University, Nanning 530004 (China)

2010-02-20

326

MICROANALYSIS OF NY/NJ HARBOR SEDIMENTS USING SYNCHROTRON X-RAY BEAMS.  

SciTech Connect

Sediments found in the New York/New Jersey Harbor are widely contaminated with organic and inorganic compounds of anthropogenic origin. As a result, the environmental health of the Harbor has deteriorated and the efficient operation of the Port compromised by difficulties in disposing of sediments resulting from maintenance and improvements of navigational channels. Knowledge of the properties of the sediments on a micro-scale is useful in understanding the transport of contaminants through the environment, for developing effective methods for sediment decontamination, and for subsequent beneficial use of the cleaned sediments. We have investigated several properties of these sediments using synchrotron radiation techniques. These include computed microtomography using absorption and fluorescence contrast mechanisms, x-ray microscopy, microbeam x-ray fluorescence, and Fourier Transform Infrared Spectroscopy (FTIR) for measurements of microstructure, distribution of metals on individual sediment particles, and chemical forms of the contaminants on a micrometer scale. Typical results obtained with these techniques are presented.

JONES,K.W.FENG,H.LANZIROTTI,A.MARINKOVIC,N.ET AL.

2003-12-31

327

Intense Superradiant X Rays from a Compact Source Using a Nanocathode Array and Emittance Exchange  

E-print Network

A novel method of producing intense short wavelength radiation from relativistic electrons is described. The electrons are periodically bunched at the wavelength of interest enabling in-phase superradiant emission that is ...

Graves, William S.

328

Imaging single cells in a beam of live cyanobacteria with an X-ray laser  

DOE Data Explorer

This entry contains ten diffraction patterns, and reconstructions images, of individual living Cyanobium gracile cells, imaged using 517 eV X-rays from the LCLS XFEL. The Hawk software package was used for phasing. The Uppsala aerosol injector was used for sample injection, assuring very low noise levels. The cells come from various stages of the cell cycle, and were imaged in random orientations.

Schot, Gijs, vander

329

Quasimonochromatic x-ray backlighting on the COrnell Beam Research Accelerator (COBRA) pulsed power generator  

Microsoft Academic Search

Monochromatic x-ray backlighting has been employed with great success for imaging of plasmas with strong self-emission such as x-pinches and wire array z-pinches. However, implementation of a monochromatic backlighting system typically requires extremely high quality spherically bent crystals which are difficult to manufacture and can be prohibitively expensive. Furthermore, the crystal must have a direct line of sight to the

P. F. Knapp; J. B. Greenly; P. A. Gourdain; C. L. Hoyt; S. A. Pikuz; T. A. Shelkovenko; D. A. Hammer

2010-01-01

330

Complex aberrations in lymphocytes exposed to mixed beams of (241)Am alpha particles and X-rays.  

PubMed

Modern radiotherapy treatment modalities are associated with undesired out-of-field exposure to complex mixed beams of high and low energy transfer (LET) radiation that can give rise to secondary cancers. The biological effectiveness of mixed beams is not known. The aim of the investigation was the analysis of chromosomal damage in human peripheral blood lymphocytes (PBL) exposed to a mixed beam of X-rays and alpha particles. Using a dedicated exposure facility PBL were exposed to increasing doses of alpha particles (from (241)Am), X-rays and a mixture of both. Chromosomal aberrations were analysed in chromosomes 2, 8 and 14 using fluorescence in situ hybridisation. The found and expected frequencies of simple and complex aberrations were compared. Simple aberrations showed linear dose-response relationships with doses. A higher than expected frequency of simple aberrations was only observed after the highest mixed beam dose. A linear-quadratic dose response curve for complex aberrations was observed after mixed-beam exposure. Higher than expected frequencies of complex aberrations were observed for the two highest doses. Both the linear-quadratic dose-response relationship and the calculation of expected frequencies show that exposure of PBL to mixed beams of high and low LET radiation leads to a higher than expected frequency of complex-type aberrations. Because chromosomal changes are associated with cancer induction this result may imply that the cancer risk of exposure to mixed beams in radiation oncology may be higher than expected based on the additive action of the individual dose components. PMID:23669292

Staaf, Elina; Deperas-Kaminska, Marta; Brehwens, Karl; Haghdoost, Siamak; Czub, Joanna; Wojcik, Andrzej

2013-08-30

331

Dose and energy dependence of response of Gafchromic XR-QA film for kilovoltage x-ray beams.  

PubMed

There is a growing interest in Gafchromic films for patient dosimetry in radiotherapy and in radiology. A new model (XR-QA) with high sensitivity to low dose was tested in this study. The response of the film to different x-ray beam energies (range 28-145 kVp with various filtrations, dose range 0-100 mGy) and to visible light was investigated, together with the after exposure darkening properties. Exposed films were digitized with a commercially available, optical flatbed scanner. A single functional form for dose versus net pixel value variation has been determined for all the obtained calibration curves, with a unique fit parameter different for each of the used x-ray beams. The film response was dependent on beam energy, with higher colour variations for the beams in the range 80-140 kVp. Different sources of uncertainties in dose measurements, governed by the digitalization process, the film response uniformity and the calibration curve fit procedure, have been considered. The overall one-sigma dose measurement uncertainty depended on the beam energy and decreased with increasing absorbed dose. For doses above 10 mGy and beam energies in the range 80-140 kVp the total uncertainty was less than 5%, whereas for the 28 kVp beam the total uncertainty at 10 mGy was about 10%. The post-exposure colour variation was not negligible in the first 24 h after the exposure, with a consequent increase in the calculated dose of about 10%. Results of the analysis of the sensitivity to visible light indicated that a short exposure of this film to ambient and scanner light during the measurements will not have a significant impact on the radiation dosimetry. PMID:16723772

Rampado, O; Garelli, E; Deagostini, S; Ropolo, R

2006-06-01

332

A diffracted-beam monochromator for long linear detectors in X-ray diffractometers with Bragg-Brentano parafocusing geometry  

SciTech Connect

A new diffracted-beam monochromator has been developed for Bragg-Brentano X-ray diffractometers equipped with a linear detector. The monochromator consists of a cone-shaped graphite highly oriented pyrolytic graphite crystal oriented out of the equatorial plane such that the parafocusing geometry is preserved over the whole opening angle of the linear detector. In our standard setup a maximum wavelength discrimination of 3% is achieved with an overall efficiency of 20% and a small decrease in angular resolution of only 0.02 Degree-Sign 2{theta}. In principle, an energy resolution as low as 1.5% can be achieved.

Pers, N. M. van der; Hendrikx, R. W. A.; Delhez, R.; Boettger, A. J. [Department of Material Science and Engineering, Delft University of Technology, Delft (Netherlands)

2013-04-15

333

Patient dose simulations for scanning-beam digital x-ray tomosynthesis of the lungs  

SciTech Connect

Purpose: An improved method of image guidance for lung tumor biopsies could help reduce the high rate of false negatives. The aim of this work is to optimize the geometry of the scanning-beam digital tomography system (SBDX) for providing real-time 3D tomographic reconstructions for target verification. The unique geometry of the system requires trade-offs between patient dose, imaging field of view (FOV), and tomographic angle.Methods: Tomosynthetic angle as a function of tumor-to-detector distance was calculated. Monte Carlo Software (PCXMC) was used to calculate organ doses and effective dose for source-to-detector distances (SDDs) from 90 to 150 cm, patient locations with the tumor at 20 cm from the source to 20 cm from the detector, and FOVs centered on left lung and right lung as well as medial and distal peripheries of the lungs. These calculations were done for two systems, a SBDX system and a GE OEC-9800 C-arm fluoroscopic unit. To evaluate the dose effect of the system geometry, results from PCXMC were calculated using a scan of 300 mAs for both SBDX and fluoroscopy. The Rose Criterion was used to find the fluence required for a tumor SNR of 5, factoring in scatter, air-gap, system geometry, and patient position for all models generated with PCXMC. Using the calculated fluence for constant tumor SNR, the results from PCXMC were used to compare the patient dose for a given SNR between SBDX and fluoroscopy.Results: Tomographic angle changes with SDD only in the region near the detector. Due to their geometry, the source array and detector have a peak tomographic angle for any given SDD at a source to tumor distance that is 69.7% of the SDD assuming constant source and detector size. Changing the patient location in order to increase tomographic angle has a significant effect on organ dose distribution due to geometrical considerations. With SBDX and fluoroscopy geometries, the dose to organs typically changes in an opposing manner with changing patient location. When tumor SNR is held constant (i.e., x-ray fluence is scaled appropriately), SBDX gives 2–10 times less dose than fluoroscopy for the same conditions within the typical range of patient locations. The relative position of the patient (as a percent of SDD) has a much more significant impact on dose than either SDD or patient position. The patient position providing the minimum dose for a given tumor SNR and SDD is approximately the same as the position of maximum tomographic angle.Conclusions: SBDX offers a significant dose advantage over currently used C-arm fluoroscopy. The patient location with lowest dose coincides with the location of maximum tomographic angle. In order to provide adequate space for the patient and for the pulmonologists’ equipment, a SDD of 100 cm is recommended.

Nelson, Geoff; Fahrig, Rebecca [Department of Radiology, Stanford University, Stanford, California 94305 (United States)] [Department of Radiology, Stanford University, Stanford, California 94305 (United States); Yoon, Sungwon [Varian Medical Systems, Palo Alto, California 94304 (United States)] [Varian Medical Systems, Palo Alto, California 94304 (United States); Krishna, Ganesh [Palo Alto Medical Foundation, Mountain View, California 94040 (United States)] [Palo Alto Medical Foundation, Mountain View, California 94040 (United States); Wilfley, Brian [Triple Ring Technologies, Inc., Newark, California 94560 (United States)] [Triple Ring Technologies, Inc., Newark, California 94560 (United States)

2013-11-15

334

Fluorescence detection of white-beam X-ray absorption anisotropy: towards element-sensitive projections of local atomic structure  

PubMed Central

Projections of the atomic structure around Nb atoms in a LiNbO3 single crystal were obtained from a white-beam X-ray absorption anisotropy (XAA) pattern detected using Nb K fluorescence. This kind of anisotropy results from the interference of X-rays inside a sample and, owing to the short coherence length of a white beam, is visible only at small angles around interatomic directions. Consequently, the main features of the recorded XAA corresponded to distorted real-space projections of dense-packed atomic planes and atomic rows. A quantitative analysis of XAA was carried out using a wavelet transform and allowed well resolved projections of Nb atoms to be obtained up to distances of 10?Å. The signal of nearest O atoms was detected indirectly by a comparison with model calculations. The measurement of white-beam XAA using characteristic radiation indicates the possibility of obtaining element-sensitive projections of the local atomic structure in more complex samples. PMID:21997909

Korecki, P.; Tolkiehn, M.; D?browski, K. M.; Novikov, D. V.

2011-01-01

335

Defect characterization and stress analysis by white beam synchrotron X-ray topography in single crystal semiconducting materials  

NASA Astrophysics Data System (ADS)

Semiconductor devices are becoming increasingly more complex as the number of transistors increases in the same Integrated Circuit (IC) area. Due to the complexity in design; processing and packaging of the device plays a crucial role in the IC fabrication. Package induced residual stress are not only detrimental to device performance but can also lead to device failure. We propose a non-destructive method to determine the complete stress state at each point on a packaged Silicon device. Surface and edge defect created as a result of various manufacturing steps were characterized using different techniques, primarily X-ray diffraction topography, optical microscopy, SEM and TEM. Residual stress plays an important role in the performance and lifetime of single crystal device material. Here we present a novel technique using white beam synchrotron X-ray diffraction reticulography, Stress Mapping and Analysis via Ray Tracing (SMART) in order to determine residual stress level at an array of points over the entire crystal area. This method has a unique advantage compared with other stress measurement technique in that it can evaluate all six components of the stress tensor. The underlying experimental technique is based on white beam synchrotron X-ray diffraction topography and ray tracing. An array of X-ray micro-beam is illuminated on the single crystal sample and multiple reflections (reticulographs) are recorded simultaneously on a photographic film. Crystallographic plane normal vector at the location of each micro-beam in the crystal is calculated. The variation of the plane normal vector direction is due to residual strain (both sheer and dilatational) present in the crystal. By considering three different diffracting planes and corresponding reticulograph a complete state of stress is calculated. Principle, applications and limitations are discussed. White beam synchrotron reticulography is used in reflection geometry to evaluate complete residual stress tensor as a function of depth in a single crystal material. This novel technique, an extension of SMART technique is developed to determine stress tensor components at various depths within the crystal. In reflection geometry penetration depth is controlled by manipulating the geometrical parameters such as incident angle. Data is obtained from various penetration depth, which represents exponentially decaying weighted average of actual stress value or in other words this stress profile is Laplace transform of real stress profile. Mathematical procedure is described to determine real stress profile from Laplace profile. To demonstrate this method, a packaged semiconducting Silicon die is used and its complete stress tensor profile is generated. This method has demonstrated the capability of determining all six components of stress as a function of depth in the crystal. Experimental procedure, theoretical basis and mathematical methods along with its application, capability and limitations are discussed. Wafer dicing process results in edge and surface damage. Various characterization tools were used to detect these defects. Surface reflection topographs were taken to probe surface and subsurface defects, primarily scratches and micro cracks. Optical microscopy and SEM were used as a complementary tool for surface characterization. TEM is used for detecting sub-surface nano-cracks and dislocations. X-ray transmission topography is used to detect half loop dislocations resulting from dicing process. In order to study dynamic behavior of defects (dislocations) during thermal processing and operation an environmental chamber (furnace) is designed and built to record in-situ X-ray diffraction topographs during thermal cycling and at high temperature.

Sarkar, Vishwanath

336

A new X-ray fluorescence spectroscopy for extraterrestrial materials using a muon beam.  

PubMed

The recent development of the intense pulsed muon source at J-PARC MUSE, Japan Proton Accelerator Research Complex/MUon Science Establishment (10(6)?s(-1) for a momentum of 60?MeV/c), enabled us to pioneer a new frontier in analytical sciences. Here, we report a non-destructive elemental analysis using µ(-) capture. Controlling muon momentum from 32.5 to 57.5?MeV/c, we successfully demonstrate a depth-profile analysis of light elements (B, C, N, and O) from several mm-thick layered materials and non-destructive bulk analyses of meteorites containing organic materials. Muon beam analysis, enabling a bulk analysis of light to heavy elements without severe radioactivation, is a unique analytical method complementary to other non-destructive analyses. Furthermore, this technology can be used as a powerful tool to identify the content and distribution of organic components in future asteroidal return samples. PMID:24861282

Terada, K; Ninomiya, K; Osawa, T; Tachibana, S; Miyake, Y; Kubo, M K; Kawamura, N; Higemoto, W; Tsuchiyama, A; Ebihara, M; Uesugi, M

2014-01-01

337

A new X-ray fluorescence spectroscopy for extraterrestrial materials using a muon beam  

PubMed Central

The recent development of the intense pulsed muon source at J-PARC MUSE, Japan Proton Accelerator Research Complex/MUon Science Establishment (106?s?1 for a momentum of 60?MeV/c), enabled us to pioneer a new frontier in analytical sciences. Here, we report a non-destructive elemental analysis using µ? capture. Controlling muon momentum from 32.5 to 57.5?MeV/c, we successfully demonstrate a depth-profile analysis of light elements (B, C, N, and O) from several mm-thick layered materials and non-destructive bulk analyses of meteorites containing organic materials. Muon beam analysis, enabling a bulk analysis of light to heavy elements without severe radioactivation, is a unique analytical method complementary to other non-destructive analyses. Furthermore, this technology can be used as a powerful tool to identify the content and distribution of organic components in future asteroidal return samples. PMID:24861282

Terada, K.; Ninomiya, K.; Osawa, T.; Tachibana, S.; Miyake, Y.; Kubo, M. K.; Kawamura, N.; Higemoto, W.; Tsuchiyama, A.; Ebihara, M.; Uesugi, M.

2014-01-01

338

Assessment of flatness and symmetry of megavoltage x-ray beam with an electronic portal imaging device (EPID).  

PubMed

The input/output characteristics of the Wellhofer BIS 710 electronic portal imaging device (EPID) have been investigated to establish its efficacy for periodic quality assurance (QA) applications. Calibration curves have been determined for the energy fluence incident on the detector versus the pixel values. The effect of the charge coupled device (CCD) camera sampling time and beam parameters (such as beam field size, dose rate, photon energy) on the calibration have been investigated for a region of interest (ROI) around the central beam axis. The results demonstrate that the pixel output is a linear function of the incident exposure, as expected for a video-based electronic portal imaging system. The field size effects of the BIS 710 are similar to that of an ion chamber for smaller field sizes up to 10 x 10 cm2. However, for larger field sizes the pixel value increases more rapidly. Furthermore, the system is slightly sensitive to dose rate and is also energy dependent The BIS 710 has been used in the current study to develop a QA procedure for measurements of flatness and symmetry of a linac x-ray beam. As a two-dimensional image of the radiation field is obtained from a single exposure of the BIS 710, a technique has been developed to calculate flatness and symmetry from a defined radiation area. The flatness and symmetry values obtained are different from those calculated conventionally from major axes only (inplane, crossplane). This demonstrates that the technique can pick up the "cold" and "hot" spots in the analysed area, providing thus more information about the radiation beam. When calibrated against the water tank measurements, the BIS 710 can be used as a secondary device to monitor the x-ray beam flatness and symmetry. PMID:12219846

Liu, G; van Doorn, T; Bezak, E

2002-07-01

339

X-Ray Propagation in Tapered Waveguides: Simulation and Optimization  

E-print Network

or to concentrate the beam. The flux density necessary for nanometer-sized beam with high enough intensities by numercial simulation and optimization. The goal of the study is to elucidate how beam concentration can be best achieved in x-ray optical nanostructures. Such optimized waveguides can e.g. be used

Peinke, Joachim

340

X-ray magnetic circular dichroism of ferromagnetic Co4N epitaxial films on SrTiO3(001) substrates grown by molecular beam epitaxy  

NASA Astrophysics Data System (ADS)

5-nm thick Co4N layers capped with 3-nm thick Au layers were grown epitaxially on SrTiO3(001) substrates by molecular beam epitaxy using solid Co and a radio-frequency NH3 plasma. Spin and orbital magnetic moments of the Co4N layers were estimated using x-ray magnetic circular dichroism (XMCD) measurements at 300 K. The site-averaged Co 3d spin magnetic moment is evaluated to be about 1.4 ?B, which is smaller than that predicted theoretically (1.58 ?B). The element-specific XMCD intensities for the Co L3 edge and N K edge show that the magnetic moment is induced at the N atoms.

Ito, Keita; Harada, Kazunori; Toko, Kaoru; Ye, Mao; Kimura, Akio; Takeda, Yukiharu; Saitoh, Yuji; Akinaga, Hiro; Suemasu, Takashi

2011-12-01

341

Development and validation of MCNP4C-based Monte Carlo simulator for fan- and cone-beam x-ray CT  

Microsoft Academic Search

An x-ray computed tomography (CT) simulator based on the Monte Carlo N-particle radiation transport computer code (MCNP4C) was developed for simulation of both fan- and cone-beam CT scanners. A user-friendly interface running under Matlab 6.5.1 creates the scanner geometry at different views as MCNP4C's input file. The full simulation of x-ray tube, phantom and detectors with single-slice, multi-slice and flat

Mohammad Reza Ay; Habib Zaidi

2005-01-01

342

Fast prototyping of high-aspect ratio, high-resolution x-ray masks by gas-assisted focused ion beam  

NASA Technical Reports Server (NTRS)

The capacity of chemically-assisted focused ion beam (fib) etching systems to undertake direct and highly anisotropic erosion of thin and thick gold (or other high atomic number [Z])coatings on x-ray mask membranes/substrates provides new levels of precision, flexibility, simplification and rapidity in the manufacture of mask absorber patterns, allowing the fast prototyping of high aspect ratio, high-resolution masks for deep x-ray lithography.

Hartley, F.; Malek, C.; Neogi, J.

2001-01-01

343

Performance evaluation of diagnostic radiology dosimeters in clinical and calibration x-ray beams.  

PubMed

Diagnostic radiology dosimeters should comply with International Electrotechnical Commission (IEC) 61674 standard in order to perform measurements with sufficient accuracy and reliability. The calibration of a dosimeter is performed under, and pertains to, reference conditions. However, in most cases, dosimeters are used for clinical measurements under non-reference conditions. The performance, in terms of accuracy of dose measurements, of six commercial diagnostic radiology dosimeters was tested at reference calibration and at clinical non-reference conditions. The results showed that all dosimeters being tested exhibited limits of variation within the +/-5% IEC limits. Depending on the detector's physical and operational properties, the dosimeters' energy dependence of response values varied from -4.7% to +4.2%. To address this variation of response, calibration at three radiation qualities (RQR 3, RQR 5, and RQR 9), at least, is recommended. Different irradiation conditions such as air kerma rate, x-ray tube design, x-ray system, and dosimeter operational modes affect the dosimeters' response by less than 3%. A dosimeter that complies with IEC standards and operates according to its specifications could be used at typical clinical irradiation conditions taking into account only corrections for the energy dependence of response. In this case, the error in dose accuracy is expected to be less than 3%. PMID:20386200

Hourdakis, Costantine John; Boziari, Argyro; Manetou, Aggeliki

2010-05-01

344

Dynamic response of CVD monocrystalline diamond to low-energy x-ray beam  

NASA Astrophysics Data System (ADS)

Detectors sensitive to ionizing radiations were assembled from high-purity single-crystal diamond plates with Ti/Au injecting contacts. Spectrally resolved photoconductivity measurements in the range 2-6 eV were used to infer the defect density in the diamond bulk material using silver contacts. The electrical behavior of annealed Ti/Au contacts was analyzed in the dark through current-voltage measurements in the range +/-500V (104 V/cm). Although contacts appear to be ohmic in the dark, two different transport regimes were found under x-ray irradiation as a function of the applied bias voltage. Recombinative regime at low bias and space charge limited injection regime at high bias were evidenced. The analysis of the photocurrent's module and phase under x-ray modulated irradiation allowed us to highlight photoconductive gain phenomena mitigated by a Poole-Frenkel field-assisted detrapping process. Through the analysis of device's impedance under irradiation, a lumped-elements electrical circuit is proposed to explain the detector's dynamic behavior.

Trucchi, D. M.; Allegrini, P.; Spadaro, S.; Conte, G.

2011-05-01

345

Quasimonochromatic x-ray backlighting on the COrnell Beam Research Accelerator (COBRA) pulsed power generator  

SciTech Connect

Monochromatic x-ray backlighting has been employed with great success for imaging of plasmas with strong self-emission such as x-pinches and wire array z-pinches. However, implementation of a monochromatic backlighting system typically requires extremely high quality spherically bent crystals which are difficult to manufacture and can be prohibitively expensive. Furthermore, the crystal must have a direct line of sight to the object, which typically emits copious amounts of radiation and debris. We present a quasimonochromatic x-ray backlighting system which employs an elliptically bent mica crystal as the dispersive element. In this scheme a narrow band of continuum radiation is selected for imaging, instead of line radiation in the case of monochromatic imaging. The flat piece of mica is bent using a simple four-point bending apparatus that allows the curvature of the crystal to be adjusted in situ for imaging in the desired wavelength band. This system has the advantage that it is very cost effective, has a large aperture, and is extremely flexible. The principles of operation of the system are discussed and its performance is analyzed.

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

2010-10-15

346

Dynamics of Hollow Atom Formation in Intense X-Ray Pulses Probed by Partial Covariance Mapping  

NASA Astrophysics Data System (ADS)

When exposed to ultraintense x-radiation sources such as free electron lasers (FELs) the innermost electronic shell can efficiently be emptied, creating a transient hollow atom or molecule. Understanding the femtosecond dynamics of such systems is fundamental to achieving atomic resolution in flash diffraction imaging of noncrystallized complex biological samples. We demonstrate the capacity of a correlation method called “partial covariance mapping” to probe the electron dynamics of neon atoms exposed to intense 8 fs pulses of 1062 eV photons. A complete picture of ionization processes competing in hollow atom formation and decay is visualized with unprecedented ease and the map reveals hitherto unobserved nonlinear sequences of photoionization and Auger events. The technique is particularly well suited to the high counting rate inherent in FEL experiments.

Frasinski, L. J.; Zhaunerchyk, V.; Mucke, M.; Squibb, R. J.; Siano, M.; Eland, J. H. D.; Linusson, P.; v. d. Meulen, P.; Salén, P.; Thomas, R. D.; Larsson, M.; Foucar, L.; Ullrich, J.; Motomura, K.; Mondal, S.; Ueda, K.; Osipov, T.; Fang, L.; Murphy, B. F.; Berrah, N.; Bostedt, C.; Bozek, J. D.; Schorb, S.; Messerschmidt, M.; Glownia, J. M.; Cryan, J. P.; Coffee, R. N.; Takahashi, O.; Wada, S.; Piancastelli, M. N.; Richter, R.; Prince, K. C.; Feifel, R.

2013-08-01

347

Generalized atomic processes for interaction of intense femtosecond XUV- and X-ray radiation with solids  

NASA Astrophysics Data System (ADS)

Generalized atomic processes are proposed to establish a consistent description from the free-atom approach to the heated and even up to the cold solid. It is based on a rigorous introduction of the Fermi-Dirac statistics, Pauli blocking factors and on the respect of the principle of detailed balance via the introduction of direct and inverse processes. A probability formalism driven by the degeneracy of the free electrons enables to establish a link of atomic rates valid from the heated atom up to the cold solid. This allows to describe photoionization processes in atomic population kinetics and subsequent solid matter heating on a femtosecond time scale. The Auger effect is linked to the 3-body recombination via a generalized 3-body recombination that is identified as a key mechanism, along with the collisional ionization, that follows energy deposition by photoionization of inner shells when short, intense and high-energy radiation interacts with matter. Detailed simulations are carried out for aluminum that highlight the importance of the generalized approach.

Deschaud, B.; Peyrusse, O.; Rosmej, F. B.

2014-12-01

348

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

349

X-Ray Spacing  

NSDL National Science Digital Library

This site features a collection of single-phase X-ray powder diffraction patterns for the three most intense D values of an extensive list of minerals. The information is presented in the form of tables of interplanar spacings (D), relative intensities, hkl plane. There are also links to more information about each mineral, such as chemical formula, composition, environment, and name origin.

David Barthelmy

350

Investigation of ion-beam machining methods for replicated x-ray optics  

NASA Technical Reports Server (NTRS)

The final figuring step in the fabrication of an optical component involves imparting a specified contour onto the surface. This can be expensive and time consuming step. The recent development of ion beam figuring provides a method for performing the figuring process with advantages over standard mechanical methods. Ion figuring has proven effective in figuring large optical components. The process of ion beam figuring removes material by transferring kinetic energy from impinging neutral particles. The process utilizes a Kaufman type ion source, where a plasma is generated in a discharge chamber by controlled electric potentials. Charged grids extract and accelerate ions from the chamber. The accelerated ions form a directional beam. A neutralizer outside the accelerator grids supplies electrons to the positive ion beam. It is necessary to neutralize the beam to prevent charging workpieces and to avoid bending the beam with extraneous electro-magnetic fields. When the directed beam strikes the workpiece, material sputters in a predicable manner. The amount and distribution of material sputtered is a function of the energy of the beam, material of the component, distance from the workpiece, and angle of incidence of the beam. The figuring method described here assumes a constant beam removal, so that the process can be represented by a convolution operation. A fixed beam energy maintains a constant sputtering rate. This temporally and spatially stable beam is held perpendicular to the workpiece at a fixed distance. For non-constant removal, corrections would be required to model the process as a convolution operation. Specific figures (contours) are achieved by rastering the beam over the workpiece at varying velocities. A unique deconvolution is performed, using series-derivative solution developed for the system, to determine these velocities.

Drueding, Thomas W.

1996-01-01

351

EXACTRAC x-ray and beam isocenters--What's the difference?  

SciTech Connect

Purpose: To evaluate the geometric accuracy of the isocenter of an image-guidance system, as implemented in the exactrac system from brainlab, relative to the linear accelerator radiation isocenter. Subsequently to correct the x-ray isocenter of the exactrac system for any geometric discrepancies between the two isocenters. Methods: Five Varian linear accelerators all equipped with electronic imaging devices and exactrac with robotics from brainlab were evaluated. A commercially available Winston-Lutz phantom and an in-house made adjustable base were used in the setup. The electronic portal imaging device of the linear accelerators was used to acquire MV-images at various gantry angles. Stereoscopic pairs of x-ray images were acquired using the exactrac system. The deviation between the position of the external laser isocenter and the exactrac isocenter was evaluated using the commercial software of the exactrac system. In-house produced software was used to analyze the MV-images and evaluate the deviation between the external laser isocenter and the radiation isocenter of the linear accelerator. Subsequently, the deviation between the radiation isocenter and the isocenter of the exactrac system was calculated. A new method of calibrating the isocenter of the exactrac system was applied to reduce the deviations between the radiation isocenter and the exactrac isocenter. Results: To evaluate the geometric accuracy a 3D deviation vector was calculated for each relative isocenter position. The 3D deviation between the external laser isocenter and the isocenter of the exactrac system varied from 0.21 to 0.42 mm. The 3D deviation between the external laser isocenter and the linac radiation isocenter ranged from 0.37 to 0.83 mm. The 3D deviation between the radiation isocenter and the isocenter of the exactrac system ranged from 0.31 to 1.07 mm. Using the new method of calibrating the exactrac isocenter the 3D deviation of one linac was reduced from 0.90 to 0.23 mm. The results were complicated due to routine maintenance of the linac, including laser calibration. It was necessary to repeat the measurements in order to perform the calibration of the exactrac isocenter. Conclusions: The deviations between the linac radiation isocenter and the exactrac isocenter were of an order that may have clinical relevance. An alternative method of calibrating the isocenter of the exactrac system was applied and reduced the deviations between the two isocenters.

Tideman Arp, Dennis; Carl, Jesper [Department of Medical Physics, Oncology, Aalborg Hospital, Aarhus University Hospital, Hobrovej 18-22, DK-9100 Aalborg (Denmark)

2012-03-15

352

Realizing in-plane surface diffraction by x-ray multiple-beam diffraction with large incidence angle  

NASA Astrophysics Data System (ADS)

Based on rigorous dynamical-theory calculations, we demonstrate the principle of an x-ray multiple-beam diffraction (MBD) scheme that overcomes the long-lasting difficulties of high-resolution in-plane diffraction from crystal surfaces. This scheme only utilizes symmetric reflection geometry with large incident angles but activates the out-of-plane and in-plane diffraction processes simultaneously and separately in the continuous MBD planes. The in-plane diffraction is realized by detoured MBD, where the intermediate diffracted waves propagate parallel to the surface, which corresponds to an absolute Bragg surface diffraction configuration that is extremely sensitive to surface structures. A series of MBD diffraction and imaging techniques may be developed from this principle to study surface/interface (misfit) strains, lateral nanostructures, and phase transitions of a wide range of (pseudo)cubic crystal structures, including ultrathin epitaxial films and multilayers, quantum dots, strain-engineered semiconductor or (multi)ferroic materials, etc.

Huang, Xian-Rong; Peng, Ru-Wen; Gog, Thomas; Siddons, D. P.; Assoufid, Lahsen

2014-11-01

353

Development and operation of a prototype cone-beam computed tomography system for X-ray medical imaging  

NASA Astrophysics Data System (ADS)

This paper describes the development of a prototype cone-beam computed tomography (CBCT) system for clinical use. The overall system design in terms of physical characteristics, geometric calibration methods, and three-dimensional image reconstruction algorithms are described. Our system consists of an X-ray source and a large-area flat-panel detector with the axial dimension large enough for most clinical applications when acquired in a full gantry rotation mode. Various elaborate methods are applied to measure, analyze and calibrate the system for imaging. The electromechanical and the radiographic subsystems through the synchronized control include: gantry rotation and speed, tube rotor, the high-frequency generator (kVp, mA, exposure time and repetition rate), and the reconstruction server (imaging acquisition and reconstruction). The operator can select between analytic and iterative reconstruction methods. Our prototype system contains the latest hardware and reconstruction algorithms and, thus, represents a step forward in CBCT technology.

Seo, Chang-Woo; Cha, Bo Kyung; Kim, Ryun Kyung; Kim, Cho-Rong; Yang, Keedong; Huh, Young; Jeon, Sungchae; Park, Justin C.; Song, Bongyong; Song, William Y.

2014-01-01

354

MeV single-ion beam irradiation of mammalian cells using the Surrey vertical nanobeam, compared with broad proton beam and X-ray irradiations  

NASA Astrophysics Data System (ADS)

As a part of a systematic study on mechanisms involved in physical cancer therapies, this work investigated response of mammalian cells to ultra-low-dose ion beam irradiation. The ion beam irradiation was performed using the recently completed nanobeam facility at the Surrey Ion Beam Centre. A scanning focused vertical ion nano-beam was applied to irradiate Chinese hamster V79 cells. The V79 cells were irradiated in two different beam modes, namely, focused single ion beam and defocused scanning broad ion beam of 3.8-MeV protons. The single ion beam was capable of irradiating a single cell with a precisely controlled number of the ions to extremely low doses. After irradiation and cell incubation, the number of surviving colonies as a function of the number of the irradiating ions was measured for the cell survival fraction curve. A lower survival for the single ion beam irradiation than that of the broad beam case implied the hypersensitivity and bystander effect. The ion-beam-induced cell survival curves were compared with that from 300-kV X-ray irradiation. Theoretical studies indicated that the cell death in single ion irradiation mainly occurred in the cell cycle phases of cell division and intervals between the cell division and the DNA replication. The success in the experiment demonstrated the Surrey vertical nanobeam successfully completed.

Prakrajang, K.; Jeynes, J. C. G.; Merchant, M. J.; Kirkby, K.; Kirkby, N.; Thopan, P.; Yu, L. D.

2013-07-01

355

X-Ray Diffraction Apparatus  

NASA Technical Reports Server (NTRS)

An x-ray diffraction apparatus for use in analyzing the x-ray diffraction pattern of a sample is introduced. The apparatus includes a beam source for generating a collimated x-ray beam having one or more discrete x-ray energies, a holder for holding the sample to be analyzed in the path of the beam, and a charge-coupled device having an array of pixels for detecting, in one or more selected photon energy ranges, x-ray diffraction photons produced by irradiating such a sample with said beam. The CCD is coupled to an output unit which receives input information relating to the energies of photons striking each pixel in the CCD, and constructs the diffraction pattern of photons within a selected energy range striking the CCD.

Blake, David F. (Inventor); Bryson, Charles (Inventor); Freund, Friedmann (Inventor)

1996-01-01

356

RISK OF SECONDARY MILIGNANT NEOPLASMS FROM PROTON THERAPY AND INTENSITY-MODULATED X-RAY THERAPY FOR EARLY-STAGE PROSTATE CANCER  

PubMed Central

Purpose To assess the risk of a secondary malignant neoplasm (SMN) from proton therapy relative to intensity-modulated radiation therapy (IMRT) using X-rays, taking into account contributions from both primary and secondary sources of radiation, for prostate cancer. Methods and Materials A proton therapy plan and a 6-MV IMRT plan were constructed for 3 patients with early-stage adenocarcinoma of the prostate. Doses from the primary fields delivered to organs at risk of developing an SMN were determined from treatment plans. Secondary doses from the proton therapy and IMRT were determined from Monte Carlo simulations and available measured data, respectively. The risk of an SMN was estimated from primary and secondary doses on an organ-by-organ basis by use of risk models from the Committee on the Biological Effects of Ionizing Radiation. Results Proton therapy reduced the risk of an SMN by 26% to 39% compared with IMRT. The risk of an SMN for both modalities was greatest in the in-field organs. However, the risks from the in-field organs were considerably lower with the proton therapy plan than with the IMRT plan. This reduction was attributed to the substantial sparing of the rectum and bladder from exposure to the therapeutic beam by the proton therapy plan. Conclusions When considering exposure to primary and secondary radiation, proton therapy can reduce the risk of an SMN in prostate patients compared with contemporary IMRT. PMID:19427561

Fontenot, Jonas D.; Lee, Andrew K.; Newhauser, Wayne D.

2014-01-01

357

Risk of Secondary Malignant Neoplasms From Proton Therapy and Intensity-Modulated X-Ray Therapy for Early-Stage Prostate Cancer  

SciTech Connect

Purpose: To assess the risk of a secondary malignant neoplasm (SMN) from proton therapy relative to intensity-modulated radiation therapy (IMRT) using X-rays, taking into account contributions from both primary and secondary sources of radiation, for prostate cancer. Methods and Materials: A proton therapy plan and a 6-MV IMRT plan were constructed for 3 patients with early-stage adenocarcinoma of the prostate. Doses from the primary fields delivered to organs at risk of developing an SMN were determined from treatment plans. Secondary doses from the proton therapy and IMRT were determined from Monte Carlo simulations and available measured data, respectively. The risk of an SMN was estimated from primary and secondary doses on an organ-by-organ basis by use of risk models from the Committee on the Biological Effects of Ionizing Radiation. Results: Proton therapy reduced the risk of an SMN by 26% to 39% compared with IMRT. The risk of an SMN for both modalities was greatest in the in-field organs. However, the risks from the in-field organs were considerably lower with the proton therapy plan than with the IMRT plan. This reduction was attributed to the substantial sparing of the rectum and bladder from exposure to the therapeutic beam by the proton therapy plan. Conclusions: When considering exposure to primary and secondary radiation, proton therapy can reduce the risk of an SMN in prostate patients compared with contemporary IMRT.

Fontenot, Jonas D. [Department of Radiation Physics, University of Texas M. D. Anderson Cancer Center, Houston, TX (United States); Lee, Andrew K. [Department of Radiation Oncology, University of Texas M. D. Anderson Cancer Center, Houston, TX (United States); Newhauser, Wayne D. [Department of Radiation Physics, University of Texas M. D. Anderson Cancer Center, Houston, TX (United States)], E-mail: wnewhaus@mdanderson.org

2009-06-01

358

Accelerating statistical image reconstruction algorithms for fan-beam x-ray CT using cloud computing  

NASA Astrophysics Data System (ADS)

Statistical image reconstruction algorithms potentially offer many advantages to x-ray computed tomography (CT), e.g. lower radiation dose. But, their adoption in practical CT scanners requires extra computation power, which is traditionally provided by incorporating additional computing hardware (e.g. CPU-clusters, GPUs, FPGAs etc.) into a scanner. An alternative solution is to access the required computation power over the internet from a cloud computing service, which is orders-of-magnitude more cost-effective. This is because users only pay a small pay-as-you-go fee for the computation resources used (i.e. CPU time, storage etc.), and completely avoid purchase, maintenance and upgrade costs. In this paper, we investigate the benefits and shortcomings of using cloud computing for statistical image reconstruction. We parallelized the most time-consuming parts of our application, the forward and back projectors, using MapReduce, the standard parallelization library on clouds. From preliminary investigations, we found that a large speedup is possible at a very low cost. But, communication overheads inside MapReduce can limit the maximum speedup, and a better MapReduce implementation might become necessary in the future. All the experiments for this paper, including development and testing, were completed on the Amazon Elastic Compute Cloud (EC2) for less than $20.

Srivastava, Somesh; Rao, A. Ravishankar; Sheinin, Vadim

2011-03-01

359

National Synchrotron Light Source VUV and soft x-ray beam lines: performance characteristics  

SciTech Connect

A total of five beam lines are currently being constructed and commissioned at the NSLS. They involve a 2.75/sup 0/ toroidal grating monochromator, a plane grating grazing monochromator, a large aperture modified Wadsworth monochromator, a Seya-Namioka instrument and a Czerny-Turner instrument. We present details of these beam lines and their anticipated operational characteristics.

Klaffky, R.W.; Howells, M.R.; Williams, G.P.; Takacs, P.Z.; Godel, J.B.

1981-01-01

360

X-ray spectroscopy of a thin foil plasma produced by a short-pulse high-intensity laser  

Microsoft Academic Search

High density and temperature plasmas have been generated by irradiating thin foils of various elements with a high-energy subpicosecond laser pulse. The X-ray emission duration was studied by time-resolved X-ray spectroscopy. Frequency domain interferometry provided a measurement of the hydrodynamic expansion of the back of the foil as a function of time. The effect of longitudinal temperature gradients, i.e., gradients

P. Audebert; V. Nagels; J. P. Geindre; F. Dorchies; O. Peyrusse; S. Gary; F. Girard; R. Shepherd; J. C. Gauthier; C. Chenais-Popovics

2003-01-01

361

Synchrotron X-Ray Diffraction Analysis of Meteorites in Thin Section: Preliminary Results  

NASA Technical Reports Server (NTRS)

X-ray diffraction is the pre-eminent technique for mineral identification and structure determination, but is difficult to apply to grains in thin section, the standard meteorite preparation. Bright focused X-ray beams from synchrotrons have been used extensively in mineralogy and have been applied to extraterrestrial particles. The intensity and small spot size achievable in synchrotron X-ray beams makes them useful for study of materials in thin sections. Here, we describe Synchrotron X-ray Diffraction (SXRD) in thin section as done at the National Synchrotron Light Source, and cite examples of its value for studies of meteorites in thin section.

Treiman, A. H.; Lanzirotti, A.; Xirouchakis, D.

2004-01-01

362

Study of the effect of pyrex and quartz insulators on X-ray intensity in a 4 kJ plasma focus device  

NASA Astrophysics Data System (ADS)

In this paper we study the soft X-ray (SXR) and hard X-ray (HXR) intensity produced in different insulator sleeves by a 4 kJ plasma focus device (APF) using filtered PIN-diodes and a fast scintillation detector. The experiments were performed for a great number of neon filling gas pressures at voltages of 11, 12 and 13 kV. Lengths of 40 and 50 mm look optimal to yield the most SXR intensity for the Pyrex and Quartz insulators respectively. The device appears to optimize much better for Pyrex insulator than the Quartz. For Pyrex and Quartz insulators, the lengths of 40 mm and 50 mm seem optimal to yield maximum HXR intensity, respectively.

Koohestani, Saeedeh; Habibi, Morteza; Amrollahi, Reza

2013-06-01

363

Parametric X-Ray Radiation, Transition Radiation and Bremsstrahlung in X-Ray Region. A Comparative Analysis  

Microsoft Academic Search

\\u000a Intense monochromatic and tunable X-ray beams are extensively exploited in applied investigations, industry and medicine.\\u000a As a rule, these devices are based on a primary powerful radiation source and crystal monochromator. Different radiation mechanisms\\u000a are used — bremsstrahlung from X-ray tube, synchrotron (SR) and an undulator radiation (UR), or, quite recently, bremsstrahlung\\u000a from linac with energy 15 MeV [1].

A. P. Potylitsyn; I. E. Vnukov

364

X-ray Diffraction  

NSDL National Science Digital Library

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

Langan, Shawn

2012-03-08

365

Capillary optics and their applications in x-ray microanalysis  

NASA Astrophysics Data System (ADS)

Capillary-based x-ray optics can provide a small, intense x-ray beam for x-ray microanalysis, including microbeam x-ray fluorescence (MXRF) and microbeam x-ray diffraction (MXRD). Monolithic polycapillary focusing optics and tapered monocapillary optics represent the current state- of-the-art of the technology. The design and the complete x-ray characterizations of such x-ray optics are discussed in this thesis. The application of monolithic polycapillary optics and tapered monocapillary optics for MXRF analysis and the application of tapered monocapillary optics for MXRD analysis are reported. The monolithic polycapillary focusing optic reported in the thesis generated a focused x-ray beam with the sizes of 44 ?m full width of half maximum (FWHM) at the energy of Cu K? line (8.04 keV) and 21 ?m FWHM at Mo K? line (17.4 keV). Using a 16 watt microfocus x-ray source, the average x-ray flux densities over the focal spot were 1.8×105 photons/s//mu m2 for Cu K? and 1.5×105 photon/sec//mu m2 for Mo K/alpha. The obtained flux density at Cu K? was about 4400 times over that of a direct beam at 100 mm away from the x-ray source, and the gain was about 2400 for Mo K? x rays. The optic was applied to a MXRF system to analyze trace elements in various samples. Minimum detection limit in picogram level was achieved for the transition elements (V, Cr, Mn, and Fe). The optic was also used to analyze and map the compositions of different elements in industrial samples. Tapered monocapillary optics were studied and used for MXRF analysis. The beam intensity obtained was 1.5 times over that obtained from a straight monocapillary. Other advantageous features include high energy background suppression and improved output beam stability. Tapered monocapillary optics were also designed and used for MXRD analysis. An optic was designed to fit into an existing micro-diffractometer system. An intensity gain of 3 was achieved compared to a currently used straight monocapillary optic.

Gao, Ning

366

Proton- and x-ray beams generated by ultra-fast CO2 lasers for medical applications  

NASA Astrophysics Data System (ADS)

Recent progress in using picosecond CO2 lasers for Thomson scattering and ion-acceleration experiments underlines their potentials for enabling secondary radiation- and particle- sources. These experiments capitalize on certain advantages of long-wavelength CO2 lasers, such as higher number of photons per energy unit, and favorable scaling of the electrons' ponderomotive energy and critical plasma density. The high-flux x-ray bursts produced by Thomson scattering of the CO2 laser off a counter-propagating electron beam enabled high-contrast, time-resolved imaging of biological objects in the picosecond time frame. In different experiments, the laser, focused on a hydrogen jet, generated monoenergetic proton beams via the radiation-pressure mechanism. The strong power-scaling of this regime promises realization of proton beams suitable for laser-driven proton cancer therapy after upgrading the CO2 laser to sub-PW peak power. This planned improvement includes optimizing the 10-?m ultra-short pulse generation, assuring higher amplification in the CO2 gas under combined isotopic- and power-broadening effects, and shortening the postamplification pulse to a few laser cycles (150-200 fs) via chirping and compression. These developments will move us closer to practical applications of ultra-fast CO2 lasers in medicine and other areas.

Pogorelsky, Igor; Polyanskiy, Mikhail; Yakimenko, Vitaly; Ben-Zvi, Ilan; Shkolnikov, Peter; Najmudin, Zulfikar; Palmer, Charlotte A. J.; Dover, Nicholas P.; Oliva, Piernicola; Carpinelli, Massimo

2011-05-01

367

Proton- and x-ray beams generated by ultra-fast CO(2) lasers for medical applications  

SciTech Connect

Recent progress in using picosecond CO{sub 2} lasers for Thomson scattering and ion-acceleration experiments underlines their potentials for enabling secondary radiation- and particle-sources. These experiments capitalize on certain advantages of long-wavelength CO{sub 2} lasers, such as higher number of photons per energy unit, and favorable scaling of the electrons ponderomotive energy and critical plasma density. The high-flux x-ray bursts produced by Thomson scattering of the CO{sub 2} laser off a counter-propagating electron beam enabled high-contrast, time-resolved imaging of biological objects in the picosecond time frame. In different experiments, the laser, focused on a hydrogen jet, generated monoenergetic proton beams via the radiation-pressure mechanism. The strong power-scaling of this regime promises realization of proton beams suitable for laser-driven proton cancer therapy after upgrading the CO{sub 2} laser to sub-PW peak power. This planned improvement includes optimizing the 10-{mu}m ultra-short pulse generation, assuring higher amplification in the CO{sub 2} gas under combined isotopic- and power-broadening effects, and shortening the postamplification pulse to a few laser cycles (150-200 fs) via chirping and compression. These developments will move us closer to practical applications of ultra-fast CO{sub 2} lasers in medicine and other areas.

Pogorelsky, I.; Polyanskiy, M.; Yakimenko, V.; Ben-Zvi, I.; Shkolnikov, P. Najmudin, Z.; Palmer, C.A.J.; Dover, N.P.; Oliva, P; Carpinelli, M.

2011-07-01

368

X-ray microtomography  

SciTech Connect

In this tutorial, we describe X-ray microtomography as a technique to nondestructively characterize material microstructure in three dimensions at a micron level spatial resolution. While commercially available laboratory scale instrumentation is available, we focus our attention on synchrotron-based systems, where we can exploit a high flux, monochromatic X-ray beam to produce high fidelity three-dimensional images. A brief description of the physics and the mathematical analysis behind the technique is followed by example applications to specific materials characterization problems, with a particular focus on the utilization of three-dimensional image processing that can be used to extract a wide range of useful information.

Landis, Eric N., E-mail: landis@maine.edu [Department of Civil and Environmental Engineering, University of Maine, 5711 Boardman Hall, Orono, Maine 04469 (United States); Keane, Denis T., E-mail: dtkeane@northwestern.edu [Department of Materials Science and Engineering, Northwestern University (United States); DND-CAT, Advanced Photon Source, Argonne National Laboratory, Bldg. 432/A002, 9700 S. Cass Ave, Argonne, Illinois 60439 (United States)

2010-12-15

369

Beam intensity upgrade at Fermilab  

SciTech Connect

The performance of the Fermilab proton accelerator complex is reviewed. The coming into operation of the NuMI neutrino line and the implementation of slip-stacking to increase the anti-proton production rate has pushed the total beam intensity in the Main Injector up to {approx} 3 x 10{sup 13} protons/pulse. A maximum beam power of 270 kW has been delivered on the NuMI target during the first year of operation. A plan is in place to increase it to 350 kW, in parallel with the operation of the Collider program. As more machines of the Fermilab complex become available with the termination of the Collider operation, a set of upgrades are being planned to reach first 700 kW and then 1.2 MW by reducing the Main Injector cycle time and by implementing proton stacking.

Marchionni, A.; /Fermilab

2006-07-01

370

RIS-M-2268 SYNCHROTRON X-RAY DIFFRACTION DSING TRIPLE-AXIS SPECTROMETRY  

E-print Network

The bread wavelength band of intense electromagnetic radiation associated with the centripetal acceleration width of the CuK . line from a conventional X-ray tube, but for identical monochromators at a storage ring (E = 4.3 GeV, I s 50 mA) and at an X-ray tube, the monochromatic beam from the former is more than

371

Diffractive optical elements for differential interference contrast x-ray microscopy  

Microsoft Academic Search

In this paper we introduce phase diffractive optical elements (DOEs) that beside simple focusing, can perform new optical functions in the range of x-rays. In particular, the intensity of the wavefront can be distributed with almost complete freedom. We calculated and fabricated high resolution DOEs that can focus a monochromatic x-ray beam into multiple spots displaced in a single or

Enzo Mario di Fabrizio; Dan Cojoc; Stefano Cabrini; Burkhard Kaulich; Jean Susini; Paolo Facci; Thomas Wilhein

2003-01-01

372

Characterisation of the primary X-ray source of an XPS microprobe Quantum 2000  

E-print Network

The outstanding design feature of an XPS microprobe Quantum 2000 is the double focussing ellipsoidally shaped quartz monochromator of the X-ray source. This device monochromatizes the Alk{\\alpha} radiation and refocuses the X-rays from the Al anode to the sample surface. This way, on one hand a variation of the diameter of the X-ray generating electron beam allows to vary the X-ray beam diameter on the sample surface. On the other hand a scanning of the electron beam across the Al anode scans the X-ray beam across the sample surface. The X-ray source was characterized in detail. The lateral dependency of the primary X-ray intensity and the peaks FWHM were measured as function of the position within the electrostatically rasterable scan area. Additionally, the focussing quality of the monochromator was determined. Therefore the lateral intensity distribution within the primary X-ray beam was estimated far below the 1% intensity level.

Scheithauer, U

2014-01-01

373

Development of an x-ray beam line at the NSLS for studies in materials science using x-ray absorption spectroscopy: Annual progress report  

SciTech Connect

Although only in operation since May, 1985, the X-11 participation research team (PRT) at the NSLS has already demonstrated that it is one of the leading centers of x-ray absorption spectroscopy (XAS). During this time, results have been obtained and programs initiated in a number of areas, for example: interfaces, including deposited metal-metal and metal-semiconductor systems, multilayers and ion implanted layers; electrochemical systems, including Pt electrode fuel cells, Ni oxide battery electrodes, conducting polymers, passivation and corrosion; catalysts, including highly-dispersed supported metal catalysts and zeolite systems; quasi-crystals, heavy fermion systems, uranium and neptunium compounds, rare gas clusters, disordered metals and semiconductors, ferroelectric transition; and, biological systems and related models, including synthetic porphyrins and a number of metalloproteins. In concert with these scientific results have been a number of developments involving the technique itself. These include implementation of unique optical systems on both the A and B lines for optical performance over their designed energy ranges, advances in experimental capability, particular in glancing angle studies, optimization of ion chambers for surface studies, the improvement of electron yield detectors, and improved software for data acquisition and analysis. This report emphasizes some of the research highlights and significant developments of our PRT which occurred during the past year. A detailed bibliography of papers and talks resulting from work done at our beamline and the progress reports for our PRT which were in the 1985 NSLS Annual Report are appended.

Sayers, D.E.

1986-01-01

374

X-Ray Exam: Finger  

MedlinePLUS

What It Is A finger X-ray is a safe and painless test that uses a small amount of radiation to take a picture of one or more fingers. During the examination, an X-ray machine sends a beam of radiation through the ...

375

X-Ray Exam: Wrist  

MedlinePLUS

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

376

X-Ray Exam: Foot  

MedlinePLUS

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

377

X-Ray Exam: Ankle  

MedlinePLUS

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

378

Spectroscopic investigations of hard x-ray emission from 120 ps laser-produced plasmas at intensities near 10{sup 17} W cm{sup {minus}2}  

SciTech Connect

Spectroscopic investigations of the x-ray emission of plasmas heated by 120 ps, frequency doubled pulses from the JANUS Nd: glass laser are presented. High Z K-shell spectra emitted from slab targets heated to near 10{sup 17} W cm{sup {minus}2} intensity are investigated. High resolution ({gamma}/{Delta}{gamma}>5000) x-ray spectra of multicharged ions of H-like Ti, Co, Ni, Cu, and also H-like Sc in the spectral range 1.5--3.0 {angstrom} are obtained in single laser shots using a spherically bent Mica crystal spectrograph with a 186 mm radius of curvature. The spectra- have one dimensional spatial resolution of about 25{mu}m and indicate that the size of the emission zone of the resonance, transitions is <25{mu}m. Simultaneous x-ray images of the plasma from a charge-coupled device pinhole camera confirmed that the plasma x-ray emission is from a similar sized source. Survey spectra {gamma}/{Delta}{gamma}=500--1000) taken with a flat LiF (200) crystal spectrometer with a charge-coupled device detector complement the high resolution data. Two dimensional LASNEX modeling of the laser target conditions indicate that the high K-shell charge states are produced in the hot dense region of the plasma with electron temperature >2 keV and density{approximately}10{sup 22} cm{sup {minus}3}. These experiments demonstrate that with modest laser energy, plasmas heated by high-intensity 120 ps lasers provide a very bright source of hard {approximately}8 keV x-ray emission.

Dunn, J.; Young, B.K.F.; Osterheld, A.L.; Foord, M.E.; Walling, R.S.; Stewart, R.E. [Lawrence Livermore National Lab., CA (United States); Faenov, A.Y. [VINIFTRI, Mendeleevo, Moscow Region (Russian Federation)

1995-11-01

379

Producing X-rays at the APS  

SciTech Connect

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

None

2011-01-01

380

Low dose hard x-ray contact microscopy assisted by a photoelectric conversion layer  

SciTech Connect

Hard x-ray contact microscopy provides images of dense samples at resolutions of tens of nanometers. However, the required beam intensity can only be delivered by synchrotron sources. We report on the use of a gold photoelectric conversion layer to lower the exposure dose by a factor of 40 to 50, allowing hard x-ray contact microscopy to be performed with a compact x-ray tube. We demonstrate the method in imaging the transmission pattern of a type of hard x-ray grating that cannot be fitted into conventional x-ray microscopes due to its size and shape. Generally the method is easy to implement and can record images of samples in the hard x-ray region over a large area in a single exposure, without some of the geometric constraints associated with x-ray microscopes based on zone-plate or other magnifying optics.

Gomella, Andrew; Martin, Eric W.; Lynch, Susanna K.; Wen, Han [Imaging Physics Laboratory, Biophysics and Biochemistry Center, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD, 20892 (United States); Morgan, Nicole Y. [Intramural Research Programs, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD, 20892 (United States)

2013-04-15

381

Measurement of neutron and charged particle contamination in high energy medical therapy x-ray beams using recoil track registration in polycarbonate foils  

SciTech Connect

The production of photoneutrons and high-energy charged particles by betatrons and linear accelerators used in radiotherapy is measured. It is concluded there exists sufficient contamination in high-energy x-ray beams to be a consideration in certain radiotherapy situations. (ACR)

Sanders, M.E.; Morgan, K.Z.; McGinley, P.H.

1980-01-01

382

BONE AND BODY COMPOSITION MEASUREMENTS OF SMALL SUBJECTS: DISCREPANCIES FROM SOFTWARE FOR FAN-BEAM DUAL ENERGY X-RAY ABSORPTIOMETRY  

Technology Transfer Automated Retrieval System (TEKTRAN)

A piglet model was used to determine the variations in measurements from different software algorithms used in the same type of dual energy X ray absorptiometry (DXA) instruments from the same manufacturer. Forty-one piglets (6190 +/- 5856g, mean +/- SD) were scanned in duplicate with a fan-beam den...

383

Lateral spine dual-energy X-ray absorptiometry bone mineral measurement with fan-beam design: effect of osteophytic calcifications on lateral and anteroposterior spine BMD  

Microsoft Academic Search

Recently, fan beam (FB) designs have been made available by several manufacturers (Aloka, Hologic Lunar and Sophar) to measure lumbar spine bone mineral area density (BMD) in both an anteroposterior (AP) and a lateral projection. The present study was performed to evaluate some characteristics of a new dual energy X-ray absorptiometry (DXA) system for supine lateral scans in normals and

H. Franck; M. Munz; M. Scherrer; H. V. Lilienfeld-Toal

1995-01-01

384

X-ray absorption microtomography (microCT) and small beam diffraction mapping of sea urchin teeth  

Microsoft Academic Search

Two noninvasive X-ray techniques, laboratory X-ray absorption microtomography (microCT) and X-ray diffraction mapping, were used to study teeth of the sea urchin Lytechinus variegatus. MicroCT revealed low attenuation regions at near the tooth’s stone part and along the carinar process—central prism boundary; this latter observation appears to be novel. The expected variation of Mg fraction x in the mineral phase

S. R. Stock; J. Barss; T. Dahl; A. Veis; J. D. Almer

2002-01-01

385

Angular distribution and dose measurements of hard x-ray emission from intense laser-plasma interaction  

SciTech Connect

An experimental study on hard x-ray Bremsstrahlung radiation due to fast electron generation from a planar solid copper target irradiated by 150 mJ, 45 fs Ti:sapphire laser pulses at I{approx}10{sup 18} W/cm{sup 2} is reported. Angular distribution of the hard x-ray dose rate (h{nu}{>=}40 keV) is observed to be strongly forward peaked in the direction of target normal with a measured peak value of 40 {mu}Sv/h, at a distance of 500 mm from the target. Two sources of this radiation, one at the laser irradiated target and the other at the chamber wall facing the target, are inferred from the measurements of angular distribution and distance dependence of the x-ray dose rate.

Rao, B. S.; Naik, P. A.; Arora, V.; Khan, R. A.; Gupta, P. D. [Laser Plasma Division, Raja Ramanna Centre for Advanced Technology, Indore 452 013, M.P. (India)

2007-09-15

386

X-ray fluorescence and ion beam analysis of iridescent Art Nouveau glass - authenticity and technology  

NASA Astrophysics Data System (ADS)

EDXRF analysis with subsequent multivariate data analysis proves useful for the determination of the authenticity of iridescent glass artifacts. Thus, clusters of the glass groups investigated were formed which can be associated with the glass manufacturers. By means of ion beam analysis with the external proton beam the producing technology of iridescent glass objects of the Art Nouveau glass manufacturer Loetz/Austria with so-called Papillon pattern was characterised in a non-destructive way. Due to the simultaneous application of PIXE and RBS the glass structure including a sequence of glass layers covered with a SnO 2-layer of approximately 50 nm thickness on the surface could be described.

Jembrih-Simbürger, D.; Neelmeijer, C.; Mäder, M.; Schreiner, M.

2004-11-01

387

Compact x-ray source and panel  

DOEpatents

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

Sampayon, Stephen E. (Manteca, CA)

2008-02-12

388

From X-Rays to Ion Beams: A Short History of Radiation Therapy  

NASA Astrophysics Data System (ADS)

Radiation therapy (RT) developed in several eras. Patients' needs for more effective treatment guided the efforts. The development of ion beam therapy (IBT) can be seen as a corollary in this continuous endeavor to optimize disease control while minimizing normal-tissue damage. It could not have materialized, however, without the curiosity, ingenuity, and perseverance of researchers, engineers, and clinicians who developed important enabling technologies.

Slater, James M.

389

X-ray cone beam tomography with two tilted circular trajectories  

NASA Astrophysics Data System (ADS)

A 3D cone-beam tomograph's performance is presently quantified, and an experimental reconstruction of its implementation is given. It is shown that this double circular-source trajectory system overcomes the problems associated with single circular trajectories. In particular, density resolution is independent of target-area position; the streak artifacts typical of single circular trajectory reconstructions are noted to be suppressed. The method can be implemented without approximation, using the Grangeat (1990) formula.

Rizo, Philippe; Grangeat, Pierre; Sire, Pascal; Le Masson, Patrick; Delageniere, Solange

390

Optics for coherent X-ray applications.  

PubMed

Developments of X-ray optics for full utilization of diffraction-limited storage rings (DLSRs) are presented. The expected performance of DLSRs is introduced using the design parameters of SPring-8?II. To develop optical elements applicable to manipulation of coherent X-rays, advanced technologies on precise processing and metrology were invented. With propagation-based coherent X-rays at the 1?km beamline of SPring-8, a beryllium window fabricated with the physical-vapour-deposition method was found to have ideal speckle-free properties. The elastic emission machining method was utilized for developing reflective mirrors without distortion of the wavefronts. The method was further applied to production of diffraction-limited focusing mirrors generating the smallest spot size in the sub-10?nm regime. To enable production of ultra-intense nanobeams at DLSRs, a low-vibration cooling system for a high-heat-load monochromator and advanced diagnostic systems to characterize X-ray beam properties precisely were developed. Finally, new experimental schemes for combinative nano-analysis and spectroscopy realised with novel X-ray optics are discussed. PMID:25177986

Yabashi, Makina; Tono, Kensuke; Mimura, Hidekazu; Matsuyama, Satoshi; Yamauchi, Kazuto; Tanaka, Takashi; Tanaka, Hitoshi; Tamasaku, Kenji; Ohashi, Haruhiko; Goto, Shunji; Ishikawa, Tetsuya

2014-09-01

391

Determination of the ReA Electron Beam Ion Trap electron beam radius and current density with an X-ray pinhole camera  

NASA Astrophysics Data System (ADS)

The Electron Beam Ion Trap (EBIT) of the National Superconducting Cyclotron Laboratory at Michigan State University is used as a charge booster and injector for the currently commissioned rare isotope re-accelerator facility ReA. This EBIT charge breeder is equipped with a unique superconducting magnet configuration, a combination of a solenoid and a pair of Helmholtz coils, allowing for a direct observation of the ion cloud while maintaining the advantages of a long ion trapping region. The current density of its electron beam is a key factor for efficient capture and fast charge breeding of continuously injected, short-lived isotope beams. It depends on the radius of the magnetically compressed electron beam. This radius is measured by imaging the highly charged ion cloud trapped within the electron beam with a pinhole camera, which is sensitive to X-rays emitted by the ions with photon energies between 2 keV and 10 keV. The 80%-radius of a cylindrical 800 mA electron beam with an energy of 15 keV is determined to be r_{80%}=(212± 19)?m in a 4 T magnetic field. From this, a current density of j = (454 ± 83)A/cm2 is derived. These results are in good agreement with electron beam trajectory simulations performed with TriComp and serve as a test for future electron gun design developments.

Baumann, Thomas M.; Lapierre, Alain; Kittimanapun, Kritsada; Schwarz, Stefan; Leitner, Daniela; Bollen, Georg

2014-07-01

392

Determination of the ReA Electron Beam Ion Trap electron beam radius and current density with an X-ray pinhole camera.  

PubMed

The Electron Beam Ion Trap (EBIT) of the National Superconducting Cyclotron Laboratory at Michigan State University is used as a charge booster and injector for the currently commissioned rare isotope re-accelerator facility ReA. This EBIT charge breeder is equipped with a unique superconducting magnet configuration, a combination of a solenoid and a pair of Helmholtz coils, allowing for a direct observation of the ion cloud while maintaining the advantages of a long ion trapping region. The current density of its electron beam is a key factor for efficient capture and fast charge breeding of continuously injected, short-lived isotope beams. It depends on the radius of the magnetically compressed electron beam. This radius is measured by imaging the highly charged ion cloud trapped within the electron beam with a pinhole camera, which is sensitive to X-rays emitted by the ions with photon energies between 2 keV and 10 keV. The 80%-radius of a cylindrical 800 mA electron beam with an energy of 15 keV is determined to be r(80%) = (212 ± 19)?m in a 4 T magnetic field. From this, a current density of j = (454 ± 83)A/cm(2) is derived. These results are in good agreement with electron beam trajectory simulations performed with TriComp and serve as a test for future electron gun design developments. PMID:25085129

Baumann, Thomas M; Lapierre, Alain; Kittimanapun, Kritsada; Schwarz, Stefan; Leitner, Daniela; Bollen, Georg

2014-07-01

393

Characterization of ion beam sputter deposited W and Si films and W\\/Si interfaces by grazing incidence X-ray reflectivity, atomic force microscopy and spectroscopic ellipsometry  

Microsoft Academic Search

An ion beam sputtering system, which uses a commercial ECR microwave based plasma ion source, has been designed and fabricated in-house for deposition of soft X-ray multilayer mirrors. To begin with, in the ion beam sputtering system W, Si thin films, W\\/Si bi-layer and W\\/Si\\/W tri-layer samples have been deposited on c-Si substrates as precursors to W\\/Si multilayer stack. The

A. Biswas; A. K. Poswal; R. B. Tokas; D. Bhattacharyya

2008-01-01

394

Reflection soft X-ray microscope and method  

DOEpatents

A reflection soft X-ray microscope is provided by generating soft X-ray beams, condensing the X-ray beams to strike a surface of an object at a predetermined angle, and focusing the X-ray beams reflected from the surface onto a detector, for recording an image of the surface or near surface features of the object under observation.

Suckewer, S.; Skinner, C.H.; Rosser, R.

1993-01-05

395

Reflection soft X-ray microscope and method  

DOEpatents

A reflection soft X-ray microscope is provided by generating soft X-ray beams, condensing the X-ray beams to strike a surface of an object at a predetermined angle, and focusing the X-ray beams reflected from the surface onto a detector, for recording an image of the surface or near surface features of the object under observation.

Suckewer, Szymon (Princeton, NJ); Skinner, Charles H. (Lawrenceville, NJ); Rosser, Roy (Princeton, NJ)

1993-01-01

396

Design, optimization and testing of a multi-beam micro-CT scanner based on multi-beam field emission x-ray technology  

NASA Astrophysics Data System (ADS)

As a widely adopted imaging modality for pre-clinical research, micro-CT is constantly facing the need of providing better temporal as well as spatial resolution for a variety of imaging applications. Faster CT scanning speed is also preferred for higher imaging throughput. We recently proposed a gantry-free multi-beam micro-CT (MB?CT) design which has the potential to overcome some of the intrinsic limitations of current rotating-gantry CT technology. To demonstrate its feasibility, we have constructed a testing system with a multi-beam field emission x-ray (MBFEX) source array with a linear array of 20 individually controllable x-ray emitting pixels. Based on simulations of the electron optics and preliminary experimental measurements the design of the MBFEX source has been further optimized. The newly designed imaging system has been characterized and commissioned following our standard imaging protocol. It has clearly shown improved system stability and enhanced imaging capability. As a result of reduced mechanical rotation during imaging acquisition, we are expecting to achieve higher CT scanning speed without significantly sacrificing imaging quality. This prototype MB?CT system, although still in its early development phase, has been proved to be an ideal testing platform for the proposed gantry-free micro-CT scanner.

Peng, R.; Zhang, J.; Calderon-Colon, X.; Wang, S.; Sultana, S.; Wang, P.; Yang, G.; Chang, S.; Lu, J.; Zhou, O.

2010-04-01

397

X-ray shearing interferometer  

DOEpatents

An x-ray interferometer for analyzing high density plasmas and optically opaque materials includes a point-like x-ray source for providing a broadband x-ray source. The x-rays are directed through a target material and then are reflected by a high-quality ellipsoidally-bent imaging crystal to a diffraction grating disposed at 1.times. magnification. A spherically-bent imaging crystal is employed when the x-rays that are incident on the crystal surface are normal to that surface. The diffraction grating produces multiple beams which interfere with one another to produce an interference pattern which contains information about the target. A detector is disposed at the position of the image of the target produced by the interfering beams.

Koch, Jeffrey A. (Livermore, CA)

2003-07-08

398

A feasibility study of dynamic stress analysis inside a running internal combustion engine using synchrotron X-ray beams.  

PubMed

The present investigation establishes the feasibility of using synchrotron-generated X-ray beams for time-resolved in situ imaging and diffraction of the interior components of an internal combustion engine during its operation. The demonstration experiment was carried out on beamline I12 (JEEP) at Diamond Light Source, UK. The external hutch of the JEEP instrument is a large-scale engineering test bed for complex in situ processing and simulation experiments. The hutch incorporates a large capacity translation and rotation table and a selection of detectors for monochromatic and white-beam diffraction and imaging. These capabilities were used to record X-ray movies of a motorcycle internal combustion engine running at 1850 r.p.m. and to measure strain inside the connecting rod via stroboscopic X-ray diffraction measurement. The high penetrating ability and high flux of the X-ray beam at JEEP allowed the observation of inlet and outlet valve motion, as well as that of the piston, connecting rod and the timing chain within the engine. Finally, the dynamic internal strain within the moving connecting rod was evaluated with an accuracy of ~50 × 10(-6). PMID:23412489

Baimpas, Nikolaos; Drakopoulos, Michael; Connolley, Thomas; Song, Xu; Pandazaras, Costas; Korsunsky, Alexander M

2013-03-01

399

X-Ray Lines Close to Kll Auger Electron Energies from Iron, Cobalt, Nickel, and Copper Monocrystals  

NASA Astrophysics Data System (ADS)

By x-ray bombardment of metal monocrystals (Fe, Co, Ni, and Cu), x-rays of KLL radiative Auger electrons (KLL RAE) can be observed on the low energy side of the Kalpha lines. The energies of the x-rays of the KLL RAE of each monocrystal are the same for different lattice planes and when different kinds of x-ray tubes (Mo, W, and Cu) are used. Therefore, the peak energies detected within the KLL Auger electron energy limit are interpreted as KLL RAE x-rays. The measured intensity ratios of KLL/Kalpha are about 0.3%. Additionally, the ratio of I(Kbeta )/I(Kalpha) and I(Si escape peak)/I(Kalpha) are measured. All of these values agree well with theoretical values. The beam shapes of KLL RAE x-rays are studied by taking pictures of x-ray films. The intensity distribution for Ni and Cu are measured by changing the crystal angle with respect to the incident x-ray beam near the Bragg angles of KLL RAE x-rays. It is shown that the KLL RAE x-rays are very sharp and stimulated when the crystal is set at the Bragg angle of the KLL RAE with respect to the incident beam, which contains both the pumping radiation and Bremsstrahlung of the frequencies in the KLL RAE range in which the KLL x-rays stimulation is achieved.

Koo, Yeon Deog

1990-01-01

400