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

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

Microsoft Academic Search

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

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

2000-01-01

2

Compact integrated X-ray intensity and beam position monitor based on rare gas scintillation  

NASA Astrophysics Data System (ADS)

We have created and tested a compact integrated X-ray beam intensity and position monitor using Ar-gas scintillation. The light generated inside the device's cavity is detected by diametrically opposed PIN diodes located above and below the beam. The intensity is derived from the sum of the top and bottom signals, while the beam position is calculated from the difference-over-sum of the two signals. The device was tested at Cornell High Energy Synchrotron Source with both 17 keV and 59 keV x-rays. For intensity monitoring, the Ar-scintillation monitor performance is comparable to standard ion chambers in terms of precision. As an X-ray beam position monitor the new device response is linear with vertical beam position over a 2 mm span with a precision of 2 ?m.

Revesz, Peter; Ruff, Jacob; Dale, Darren; Krawczyk, Thomas

2013-05-01

3

Compact integrated X-ray intensity and beam position monitor based on rare gas scintillation  

SciTech Connect

We have created and tested a compact integrated X-ray beam intensity and position monitor using Ar-gas scintillation. The light generated inside the device's cavity is detected by diametrically opposed PIN diodes located above and below the beam. The intensity is derived from the sum of the top and bottom signals, while the beam position is calculated from the difference-over-sum of the two signals. The device was tested at Cornell High Energy Synchrotron Source with both 17 keV and 59 keV x-rays. For intensity monitoring, the Ar-scintillation monitor performance is comparable to standard ion chambers in terms of precision. As an X-ray beam position monitor the new device response is linear with vertical beam position over a 2 mm span with a precision of 2 {mu}m.

Revesz, Peter; Ruff, Jacob; Dale, Darren; Krawczyk, Thomas [Cornell University, Cornell High Energy Synchrotron Source, Ithaca, New York 14853 (United States)

2013-05-15

4

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

5

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

PubMed

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. PMID:23556850

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

6

An active beamstop for accurate measurement of high intensity X-ray beams  

NASA Astrophysics Data System (ADS)

In order to accurately measure the X-ray flux and determine the dose absorbed by the sample, we have designed an active beamstop device. Based on the photoelectric effect, the device consists of a beamstop, an insulator, and a concentric photoelectron collector. Tests of this device on the macromolecular crystallography beamline (BL17U1) at the Shanghai Synchrotron Research Facility (SSRF) show that the active beamstop is sufficient for determining the X-ray flux with the relative error smaller than 0.2%. The device can be used as a non-invasive, real-time intensity monitor at the sample during data collection. It can also be used with standard collimated beams or slits and served as a warning when the beam alignment drifts.

Pan, Qiangyan; Wang, Qisheng; Wang, Zhijun; Li, Liang; He, Jianhua

2014-01-01

7

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

8

Multi-concentric-ring open-air ionization chamber for high-intensity X-ray beams  

NASA Astrophysics Data System (ADS)

An ionization chamber with four concentric ring electrodes was used to measure doses of white, 10, 15 and 20 keV synchrotron X-ray beams. The ring-shaped electrodes, which had diameters less than 11.8 mm, collected charges independently only around the beam, excluding strong in-beam charges when the beams passed through a small hole in the electrode centers. As a result, under low saturation voltages, the measured dose rates were confirmed to correlate with the beam intensity when conversion factors calculated with a Monte Carlo code were employed. The influence of the assumed beam sizes and incident positions on the current was almost negligible, with the exception of the incident position dependence at 10 keV.

Nariyama, Nobuteru

2014-11-01

9

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

10

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

11

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

12

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

13

High speed x-ray beam chopper  

DOEpatents

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

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

2002-01-01

14

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

15

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

16

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

17

Hard x-ray nanofocusing with refractive x-ray optics: full beam characterization by ptychographic imaging  

NASA Astrophysics Data System (ADS)

Hard x-ray scanning microscopy relies on small and intensive nanobeams. Refractive x-ray lenses are well suited to generate hard x-ray beams with lateral dimensions of 100 nm and below. The diffraction limited beam size of refractive x-ray lenses mainly depends on the focal length and the attenuation inside the lens material. The numerical aperture of refractive lenses scales with the inverse square root of the focal length until it reaches the critical angle of total reflection. We have used nanofocusing refractive x-ray lenses made of silicon to focus hard x-rays at 8 and 20 keV to (sub-)100 nm dimensions. Using ptychographic scanning coherent diffraction imaging we have characterized these nanobeams with high accuracy and sensitivity, measuring the full complex wave field in the focus. This gives access to the full caustic and aberrations of the x-ray optics.

Schroer, Christian G.; Brack, Florian-Emanuel; Brendler, Roman; Hönig, Susanne; Hoppe, Robert; Patommel, Jens; Ritter, Stephan; Scholz, Maria; Schropp, Andreas; Seiboth, Frank; Nilsson, Daniel; Rahomäki, Jussi; Uhlén, Fredrik; Vogt, Ulrich; Reinhardt, Juliane; Falkenberg, Gerald

2013-09-01

18

Clusters in intense x-ray pulses  

NASA Astrophysics Data System (ADS)

Free-electron lasers can deliver extremely intense, coherent x-ray flashes with femtosecond pulse length, opening the door for imaging single nanoscale objects in a single shot. All matter irradiated by these intense x-ray pulses, however, will be transformed into a highly-excited non-equilibrium plasma within femtoseconds. During the x-ray pulse complex electron dynamics and the onset of atomic disorder will be induced, leading to a time-varying sample. We have performed first experiments about x-ray laser pulse -- cluster interaction with a combined spectroscopy and imaging approach at both, the FLASH free electron laser in Hamburg (Germany) and the LCLS x-ray free-electron laser in Stanford (California). Atomic clusters are ideal for investigating the light - matter interaction because their size can be tuned from the molecular to the bulk regime, thus allowing to distinguish between intra and inter atomic processes. Imaging experiments with xenon clusters show power-density dependent changes in the scattering patterns. Modeling the scattering data indicates that the optical constants of the clusters change during the femtosecond pulse due to the transient creation of high charge states. The results show that ultra fast scattering is a promising approach to study transient states of matter on a femtosecond time scale. Coincident recording of time-of-flight spectra and scattering patterns allows the deconvolution of focal volume and particle size distribution effects. Single-shot single-particle experiments with keV x-rays reveal that for the highest power densities an highly excited and hot cluster plasma is formed for which recombination is suppressed. Time resolved infrared pump -- x-ray probe experiments have started. Here, the clusters are pumped into a nanoplasma state and their time evolution is probed with femtosecond x-ray scattering. The data show strong variations in the scattering patterns stemming from electronic reconfigurations in the cluster plasma. The results will be compared to theoretical predictions and discussed in light of current developments at free-electron laser sources.

Bostedt, Christoph

2012-06-01

19

Intense attosecond radiation from an X-ray FEL - extended version  

SciTech Connect

We propose the use of a ultra-relativistic electron beam interacting with a few-cycle, intense laser pulse and an intense pulse of the coherent x-rays to produce a multi-MW intensity, x-ray pulses {approx}100 attoseconds in duration. Due to a naturally-occurring frequency chirp, these pulses can be further temporally compressed.

Zholents, Alexander A.; Fawley, William M.

2003-12-01

20

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

21

Partially coherent x-ray beam simulations: mirrors and more  

NASA Astrophysics Data System (ADS)

Penetration, micro-resolution, and scattering were the keywords of x-ray analyses in the 20th century. Over the last 15 years, a great class of coherent imaging techniques has emerged as new tools, allowing for low-dose imaging of biological specimen on the nanoscale. Apart from experimental and technical challenges, a better understanding of partially coherent beam propagation is the key for exploiting the new methods' full performance. We present a simulation framework to calculate the mutual intensity and the degree of spatial coherence of typical x-ray focusing and filtering devices used at 3rd generation synchrotron radiation sources. We propose the following modeling scheme: A set of independent point-sources yield independent basic fields, which are superposed in a stochastic manner; by taking the ensemble average, both partially coherent intensity and degree of coherence can be obtained from the mutual intensity. By including real structure effects, like height deviations of focusing mirrors, and vibration of optical components, advanced predictions of x-ray beams can be made. This knowledge is expected to improve reconstruction results from coherent imaging experiments. Coherence simulations of focusing mirrors are presented and validated with analytical results as well as with experimental tests. Coherence filtering by use of x-ray waveguides is shown numerically. We also present first simulations for partially coherent focusing by compound refractive lenses.

Osterhoff, Markus; Salditt, Tim

2011-09-01

22

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

23

An increase of utilization efficiency of X-ray beam  

NASA Astrophysics Data System (ADS)

The features of absorbed dose field formation in objects irradiated with scanned X-ray beams at double—and four-sided irradiation were investigated both analytically and by Monte Carlo methods. An analytical approach uses an angular/spectrum X-ray characteristics calculated with PENELOPE, JEANT 4 and ModeXR codes. It was shown that the special angular orientation of electron beam incidence on the X-ray converter leads to X-ray dose smoothing on the surface of the irradiated object. At the same time, a double-sided irradiation can provide high X-ray beam efficiency at dose uniformity ration (DUR) <1.5 for sizeable object thickness. At four-sided irradiation, the angular orientation of electron beam incidence on the X-ray converter should be changed so as to focus the electrons to the center of the converter. At this mode X-ray beam efficiency is more than 60%.

Lazurik, V. T.; Pismenesky, S. A.; Popov, G. F.; Rudychev, D. V.; Rudychev, V. G.

2007-11-01

24

Initial study of quasimonochromatic X-ray beam performance for X-ray computed mammotomography  

Microsoft Academic Search

We evaluate the feasibility, benefits, and operating parameters of a quasimonochromatic beam for a newly developed X-ray cone beam computed mammotomography application. The value of a near monochromatic X-ray source for a fully 3D tomography application is the expected improved ability to separate tissues with very small differences in attenuation coefficients while maintaining dose level at or below existing dual

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

2003-01-01

25

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

26

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

27

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

28

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

29

X-ray interferometer with an x-ray beam splitter  

NASA Astrophysics Data System (ADS)

We report our examination of a new X-ray interferometer for observation of celestial objects and our recent work for preparation of laboratory experiments. The new X-ray interferometer is consisting of two at mirrors and one at beam splitter which are used as grazing incident optics. The aimed wave length is a O-K band or a C-K band. The beam splitter and the mirrors are fabricated by Mo/Si multilayer. We measured their atness and found that the measured atness is acceptable for the test experiment. A pin hole X-ray source is also preparing for a laboratory experiment in order to demonstrate a X-ray interference. We investigated a possible observation of accretion disks around BHs and nearby stars. With a reasonable size of the base line, we can measure their size and possibly we can obtain an evidence of a black hole shadow.

Kitamoto, S.; Sakata, K.; Murakami, H.; Yoshida, Y.; Seta, H.

2012-09-01

30

Intensive X-ray emission bursts during thunderstorms  

NASA Astrophysics Data System (ADS)

The intensive X-ray emission during thunderstorms was studied at a height of 3340 m above sea level. For the first time, short-time (1-5 min) bursts of X-ray emission were observed. The bursts are highly correlated over a wide space region (about 0.5 km). The main component of X-ray emission in bursts has energies between 50-80 keV. The observed bursts could be attributed to the bremsstrahlung determined by the runaway breakdown (RB) effect in the thundercloud's electric field. Ground-based observations of RB open a wide range of opportunities for the studies of fundamental processes in thunderstorms.

Chubenko, A. P.; Antonova, V. P.; Kryukov, S. Yu.; Piskal, V. V.; Ptitsyn, M. O.; Shepetov, A. L.; Vildanova, L. I.; Zybin, K. P.; Gurevich, A. V.

2000-10-01

31

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

32

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

33

Scattered X-ray beam nondestructive testing  

Microsoft Academic Search

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

G. Harding; J. Kosanetzky

1989-01-01

34

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

35

Beam line for experiments with coherent soft x-rays  

SciTech Connect

The advantages of coherent soft x-rays for three-dimensional imaging of biological specimens are discussed, the x-ray source requirements are described, and the general design of the beam line and its optical system are given. (WHK)

Howells, M.R.; Kirz, J.; Krinsky, S.

1982-12-01

36

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

Microsoft Academic Search

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

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

1990-01-01

37

Characterization of X-ray generator beam profiles.  

SciTech Connect

T to compute the radiography properties of various materials, the flux profiles of X-ray sources must be characterized. This report describes the characterization of X-ray beam profiles from a Kimtron industrial 450 kVp radiography system with a Comet MXC-45 HP/11 bipolar oil-cooled X-ray tube. The empirical method described here uses a detector response function to derive photon flux profiles based on data collected with a small cadmium telluride detector. The flux profiles are then reduced to a simple parametric form that enables computation of beam profiles for arbitrary accelerator energies.

Mitchell, Dean J; Harding, Lee T.; Thoreson, Gregory G.; Theisen, Lisa Anne; Parmeter, John Ethan; Thompson, Kyle Richard

2013-07-01

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  

SciTech Connect

We devise a theoretical description for the response of nitrogen molecules (N{sub 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 ({Delta}SCF method). To describe the interaction with N{sub 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{sub 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{sub 2}{sup 2+}, and molecular fragmentation are explained.

Buth, Christian [Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, 69117 Heidelberg (Germany); PULSE Institute for Ultrafast Energy Science, SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803 (United States); Argonne National Laboratory, Argonne, Illinois 60439 (United States); Liu Jicai [Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, 69117 Heidelberg (Germany); Department of Mathematics and Physics, North China Electric Power University, 102206 Beijing (China); Chen, Mau Hsiung [Physics Division, Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Cryan, James P. [PULSE Institute for Ultrafast Energy Science, SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Department of Physics, Stanford University, Stanford, California 94305 (United States); Fang Li; Hoener, Matthias; Berrah, Nora [Department of Physics, Western Michigan University, Kalamazoo, Michigan 49008 (United States); Glownia, James M. [PULSE Institute for Ultrafast Energy Science, SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Department of Applied Physics, Stanford University, Stanford, California 94305 (United States); Coffee, Ryan N. [PULSE Institute for Ultrafast Energy Science, SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States)

2012-06-07

40

Nonlinear Atomic Response to Intense Ultrashort X Rays  

NASA Astrophysics Data System (ADS)

The nonlinear absorption mechanisms of neon atoms to intense, femtosecond kilovolt x rays are investigated. The production of Ne9+ is observed at x-ray frequencies below the Ne8+, 1s2 absorption edge and demonstrates a clear quadratic dependence on fluence. Theoretical analysis shows that the production is a combination of the two-photon ionization of Ne8+ ground state and a high-order sequential process involving single-photon production and ionization of transient excited states on a time scale faster than the Auger decay. We find that the nonlinear direct two-photon ionization cross section is orders of magnitude higher than expected from previous calculations.

Doumy, G.; Roedig, C.; Son, S.-K.; Blaga, C. I.; Dichiara, A. D.; Santra, R.; Berrah, N.; Bostedt, C.; Bozek, J. D.; Bucksbaum, P. H.; Cryan, J. P.; Fang, L.; Ghimire, S.; Glownia, J. M.; Hoener, M.; Kanter, E. P.; Krässig, B.; Kuebel, M.; Messerschmidt, M.; Paulus, G. G.; Reis, D. A.; Rohringer, N.; Young, L.; Agostini, P.; Dimauro, L. F.

2011-02-01

41

Advances in kilovoltage x-ray beam dosimetry  

NASA Astrophysics Data System (ADS)

This topical review provides an up-to-date overview of the theoretical and practical aspects of therapeutic kilovoltage x-ray beam dosimetry. Kilovoltage x-ray beams have the property that the maximum dose occurs very close to the surface and thus, they are predominantly used in the treatment of skin cancers but also have applications for the treatment of other cancers. In addition, kilovoltage x-ray beams are used in intra operative units, within animal irradiators and in on-board imagers on linear accelerators and kilovoltage dosimetry is important in these applications as well. This review covers both reference and relative dosimetry of kilovoltage x-ray beams and provides recommendations for clinical measurements based on the literature to date. In particular, practical aspects for the selection of dosimeter and phantom material are reviewed to provide suitable advice for medical physicists. An overview is also presented of dosimeters other than ionization chambers which can be used for both relative and in vivo dosimetry. Finally, issues related to the treatment planning and the use of Monte Carlo codes for solving radiation transport problems in kilovoltage x-ray beams are presented.

Hill, Robin; Healy, Brendan; Holloway, Lois; Kuncic, Zdenka; Thwaites, David; Baldock, Clive

2014-03-01

42

X-ray beam method for displacement measurement in hostile environments  

NASA Astrophysics Data System (ADS)

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

43

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

44

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

45

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

PubMed Central

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 (I0) varies significantly as the illumination volume size changes at different collimator settings. A wrong I0 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 I0 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 I0 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 I0 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 I0 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 I0 values at different collimator settings. The I0 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 I0 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 I0 estimation also reduces the reconstruction error from about 20 HU on the Catphan©600 phantom in the selected regions of interest to less than 4 HU. Conclusions: The I0 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 I0 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. PMID:23039629

Dong, Xue; Niu, Tianye; Jia, Xun; Zhu, Lei

2012-01-01

46

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

NASA Astrophysics Data System (ADS)

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

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

2015-03-01

47

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

PubMed

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

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

2015-01-01

48

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

PubMed Central

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

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

2015-01-01

49

Monolithic focused reference beam X-ray holography  

PubMed Central

Fourier transform holography is a highly efficient and robust imaging method, suitable for single-shot imaging at coherent X-ray sources. In its common implementation, the image contrast is limited by the reference signal generated by a small pinhole aperture. Increased pinhole diameters improve the signal, whereas the resolution is diminished. Here we report a new concept to decouple the spatial resolution from the image contrast by employing a Fresnel zone plate to provide the reference beam. Superimposed on-axis images of distinct foci are separated with a novel algorithm. Our method is insensitive to mechanical drift or vibrations and allows for long integration times common at low-flux facilities like high harmonic generation sources. The application of monolithic focused reference beams improves the efficiency of high-resolution X-ray Fourier transform holography beyond all present approaches and paves the path towards sub-10?nm single-shot X-ray imaging. PMID:24394675

Geilhufe, J.; Pfau, B.; Schneider, M.; Büttner, F.; Günther, C. M.; Werner, S.; Schaffert, S.; Guehrs, E.; Frömmel, S.; Kläui, M.; Eisebitt, S.

2014-01-01

50

Nonlinear atomic response to intense, ultrashort x rays  

NASA Astrophysics Data System (ADS)

The nonlinear absorption mechanisms of neon atoms to intense, femtosecond kilovolt x rays are investigated. The production of Ne^9+ is observed at x-ray frequencies below the Ne^8+, 1s^2 absorption edge and demonstrates a clear quadratic dependence on fluence. Theoretical analysis shows that the production is a combination of the 2-photon ionization of Ne^8+ ground state and a high-order sequential process involving single-photon production and ionization of transient excited states on a time-scale faster than the Auger decay. We find that the nonlinear direct two-photon ionization cross-section is orders of magnitude higher than expected from previous calculations.

Doumy, Gilles; Son, Sang-Kil; Roedig, Christoph; Ioan Blaga, Cosmin; Dichiara, Anthony; Santra, Robin; Messerschmidt, Marc; Bostedt, Christoph; Bozek, John; Bucksbaum, Philip; Cryan, James; Glownia, James Mike; Ghimire, Shambhu; Fang, Li; Hoener, Matthias; Berrah, Nora; Kanter, Elliot; Kraessig, Bertold; Reis, David; Rohringer, Nina; Young, Linda; Agostini, Pierre; Dimauro, Louis

2011-06-01

51

Nonlinear atomic response to intense ultrashort x rays.  

PubMed

The nonlinear absorption mechanisms of neon atoms to intense, femtosecond kilovolt x rays are investigated. The production of Ne(9+) is observed at x-ray frequencies below the Ne(8+), 1s(2) absorption edge and demonstrates a clear quadratic dependence on fluence. Theoretical analysis shows that the production is a combination of the two-photon ionization of Ne(8+) ground state and a high-order sequential process involving single-photon production and ionization of transient excited states on a time scale faster than the Auger decay. We find that the nonlinear direct two-photon ionization cross section is orders of magnitude higher than expected from previous calculations. PMID:21405568

Doumy, G; Roedig, C; Son, S-K; Blaga, C I; DiChiara, A D; Santra, R; Berrah, N; Bostedt, C; Bozek, J D; Bucksbaum, P H; Cryan, J P; Fang, L; Ghimire, S; Glownia, J M; Hoener, M; Kanter, E P; Krässig, B; Kuebel, M; Messerschmidt, M; Paulus, G G; Reis, D A; Rohringer, N; Young, L; Agostini, P; DiMauro, L F

2011-02-25

52

The effect of the dc bias voltage on the x-ray bremsstrahlung and beam intensities of medium and highly charged ions of argon  

SciTech Connect

X-ray bremsstrahlung measurements from the 18 GHz High Temperature Superconducting Electron Cyclotron Resonance Ion Source, Pantechnik-Delhi Ion Source were measured as a function of negative dc bias voltage, keeping all other source operating parameters fixed and the extraction voltage in the off condition. The optimization of medium and highly charged ions of argon with similar source operating parameters is described. It is observed that the high temperature component of the electron is altered significantly with the help of bias voltage, and the electron population has to be maximized for obtaining higher current.

Rodrigues, G.; Lakshmy, P. S.; Kanjilal, D.; Roy, A. [Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067 (India); Baskaran, R. [Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, Tamilnadu (India)

2010-02-15

53

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

E-print Network

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

von der Linde, D.

54

A beam hardening correction for X-ray microtomography  

Microsoft Academic Search

We propose a correction of the transmitted intensities in X-ray microscopy allowing improved quantification for polychromatic sources, particularly in tomographic reconstruction. The correction is based on the application of Beer's law for each energy present in the source spectrum. Knowledge of the source spectrum and the average specimen composition are used. The correction is demonstrated on a chemically homogeneous specimen

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

1998-01-01

55

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

56

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

PubMed Central

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

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

2013-01-01

57

Imaging quality assessment of multiplexing x-ray radiography based on multi-beam x-ray source technology  

Microsoft Academic Search

Multiplexing technique has been widely used in telecommunication, magnetic resonance imaging (MRI) and various spectroscopic applications to drastically increase system throughput. In the field of radiology, however, it was just getting started to attract researchers' attention recently due to the development of multi-beam x-ray source technology, especially the emergence of carbon nanotube (CNT) field emission based multi-beam x-ray source. The

J. Zhang; R. Peng; S. Chang; J. P. Lu; O. Zhou

2010-01-01

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

X-ray Intensity Fluctuation Spectroscopy Studies of Near-Atomic-Scale Disorder  

NASA Astrophysics Data System (ADS)

The technique of x-ray intensity fluctuation spectroscopy (XIFS) has been developed and used to make the first observations of the dynamics of critical fluctuations in a binary alloy at equilibrium.( S. Brauer, G.B. Stephenson, M. Sutton, R. Brüning, E. Dufresne, S.G.J. Mochrie, G. Grübel, J. Als-Nielsen, D.L. Abernathy, Phys. Rev. Lett. 74), 2010 (1995). A coherent beam of hard x-rays with 6 × 10^7 photons/second has been formed using a 4 ? m diameter pinhole aperture and a Si(111) crystal monochromator, at undulator beamline 9 (Troika) of the European Synchrotron Radiation Facility. The coherent x-ray beam was used to perform scattering measurements from a single crystal of Fe_3Al near the B2/DO3 order-disorder phase transition (T_c=824.1 K). Below T_c, static speckle patterns were observed near the (1/2 1/2 1/2) superlattice reflection, arising from antiphase domains in the ordered phase. Above Tc however, the scattered intensity was not constant but fluctuated in time. From the intensity time-correlation functions we deduce short-range order correlation times in the range 500-1600 seconds for temperatures 0.15-0.55 K above T_c. These results point the way to future studies of equilibrium dynamics using XIFS techniques.

Brauer, Stephan F.

1996-03-01

60

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

61

Measurements of Fusion Reactions of Low-Intensity Radioactive Carbon Beams on C12 and their Implications for the Understanding of X-Ray Bursts  

NASA Astrophysics Data System (ADS)

The interaction between neutron-rich nuclei plays an important role for understanding the reaction mechanism of the fusion process as well as for the energy production through pycnonuclear reactions in the crust of neutron stars. We have performed the first measurements of the total fusion cross sections in the systems C10,14,15+C12 using a new active target-detector system. In the energy region accessible with existing radioactive beams, a good agreement between the experimental and theoretical cross sections is observed. This gives confidence in our ability to calculate fusion cross sections for systems which are outside the range of today's radioactive beam facilities.

Carnelli, P. F. F.; Almaraz-Calderon, S.; Rehm, K. E.; Albers, M.; Alcorta, M.; Bertone, P. F.; Digiovine, B.; Esbensen, H.; Niello, J. O. Fernández; Henderson, D.; Jiang, C. L.; Lai, J.; Marley, S. T.; Nusair, O.; Palchan-Hazan, T.; Pardo, R. C.; Paul, M.; Ugalde, C.

2014-05-01

62

Low intensity X-ray and gamma-ray spectrometer  

NASA Technical Reports Server (NTRS)

A low intensity X-ray and gamma ray spectrometer for imaging, counting, and energy resolving of single invisible radiation particles is described. The spectrometer includes a converting device for converting single invisible radiation particles to visible light photons. Another converting device converts the visible light photons to photoelectrons. A fiber optics coupling device couples together the two converting devices. An intensifying device intensifies the photoelectrons by an average gain factor of between 10 to the 4th power and 10 to the 7th power. The tensifying device is an anti-ion feedback microchannel plate amplifier which is operated substantially below saturation. A displaying device displays the intensified photoelectrons. The displaying device 32 indicates the spatial position, number, and energy of the incoming single invisible radiation particles.

Yin, L. I. (inventor)

1982-01-01

63

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

64

Conceptual design study of an intense x-ray source for coronary angiography  

SciTech Connect

Calculations are presented for several 1.4 GeV electron storage ring designs which, with an ultra-high field (80 kG) superconducting wiggler magnet and beam current I = 400 mA, will generate a 33.16 keV x-ray beam at 20 m from the wiggler of adequate intensity (6 10{sup 9}/mm{sup {minus}2} sec{sup {minus}1}) and areal size for iodine K-edge coronary dichromography in humans.

Blumberg, L.N.

1992-03-01

65

Tolerance of Arteries to Microplanar X-Ray Beams  

SciTech Connect

Purpose: The purpose is to evaluate effects of a new radiotherapy protocol, microbeam radiation therapy, on the artery wall. In previous studies on animal models, it was shown that capillaries recover well from hectogray doses of X-rays delivered in arrays of narrow ({<=}50 {mu}m) beams with a minimum spacing of 200 {mu}m. Here, short- and long-term effects of comparable microplanar beam configurations on the saphenous artery of the mouse hind leg were analyzed in situ by use of nonlinear optics and compared with histopathologic findings. Methods and Materials: The left hind leg of normal mice including the saphenous artery was irradiated by an array of 26 microbeams of synchrotron X-rays (50 {mu}m wide, spaced 400 {mu}m on center) with peak entrance doses of 312 Gy and 2,000 Gy. Results: The artery remained patent, but narrow arterial smooth muscle cell layer segments that were in the microplanar beam paths became atrophic and fibrotic in a dose-dependent pattern. The wide tunica media segments between those paths hypertrophied, as observed in situ by two-photon microscopy and histopathologically. Conclusions: Clinical risks of long-delayed disruption or occlusion of nontargeted arteries from microbeam radiation therapy will prove less than corresponding risks from broad-beam radiosurgery, especially if peak doses are kept below 3 hectograys.

Sanden, Boudewijn van der, E-mail: Boudewijn.vandersanden@ujf-grenoble.f [INSERM U836, Institute of Neuroscience Grenoble (France); Braeuer-Krisch, Elke [European Synchrotron Radiation Facility, Grenoble (France); Siegbahn, Erik Albert [Department of Oncology and Pathology, Karolinska Institutet, Stockholm (Sweden); Ricard, Clement [INSERM U836, Institute of Neuroscience Grenoble (France); Vial, Jean-Claude [CNRS UMR 5588, Physical Spectroscopy, Grenoble (France); Laissue, Jean [Institute of Pathology, University of Bern (Switzerland)

2010-08-01

66

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

67

X-ray diagnostic for current density profiling relativistic electron beams in vacuum and gas  

SciTech Connect

An x-ray imaging technique has been studied for the purpose of observing the current density profile in a high-current relativistic electron beam (50 MeV, 10 kA). Calculations and measurements of energy spectra and intensities are in good agreement. Results indicate sufficient photon yield for pinhole imaging when the beam deposits a small part of its energy in high-Z gas or a thin high-Z foil. Characteristic L and K x-ray emission is not found not be a reliable technique due to strong L and K shell fluorescence in the presence of intense bremsstrahlung radiation. It is also found that at pressures on the order of one atmosphere, the density of energy deposition in a gas cell is too small to generate sufficient photon yield for time-resolved measurements.

Slaughter, D.; Koppel, L.; Smith, J.

1986-02-15

68

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

69

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

70

High intensity compact Compton X-ray sources: Challenges and potential of applications  

NASA Astrophysics Data System (ADS)

Thanks to the exceptional development of high power femtosecond lasers in the last 15 years, Compton based X-ray sources are in full development over the world in the recent years. Compact Compton sources are able to combine the compactness of the instrument with a beam of high intensity, high quality, tunable in energy. In various fields of applications such as biomedical science, cultural heritage preservation and material science researches, these sources should provide an easy working environment and the methods currently used at synchrotrons could be largely developed in a lab-size environment as hospitals, labs, or museums.

Jacquet, M.

2014-07-01

71

New Techniques For The Measurement of X-Ray Beam or X-Ray Optics Quality  

E-print Network

Proceedings of SPIE Vol. 5197 Soft X-Ray Lasers and Applications V, edited by Ernst E. Fill, Szymon Suckewer or D. Joyeux and co-workers [2], many interferometers have been setting-up (Mach-Zehnder, Fresnel

72

A Bragg beam splitter for hard x-ray free-electron lasers.  

PubMed

We report a Bragg beam splitter developed for utilization of hard x-ray free-electron lasers. The splitter is based on an ultrathin silicon crystal operating in the symmetric Bragg geometry to provide high reflectivity and transmissivity simultaneously. We fabricated frame-shaped Si(511) and (110) crystals with thicknesses below 10 ?m by a reactive dry etching method using atmospheric-pressure plasma. The thickness variation over an illuminated area is less than 300 nm peak-to-valley. High crystalline perfection was verified by topographic and diffractometric measurements. The crystal thickness was evaluated from the period of the Pendellösung beats measured with a highly monochromatic and collimated x-ray probe. The crystals provide two replica pulses with uniform wavefront [(<1/50)?] and low spatial intensity variation (<5%). These Bragg beam splitters will play an important role in innovating XFEL applications. PMID:23481739

Osaka, Taito; Yabashi, Makina; Sano, Yasuhisa; Tono, Kensuke; Inubushi, Yuichi; Sato, Takahiro; Matsuyama, Satoshi; Ishikawa, Tetsuya; Yamauchi, Kazuto

2013-02-11

73

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

NASA Astrophysics Data System (ADS)

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?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.; Krässig, B.; Li, Y.; March, A. M.; Ho, P.; Rohringer, N.; Santra, R.; Southworth, S. H.; Dimauro, L. F.; Doumy, G.; Roedig, C. A.; Berrah, N.; Fang, L.; Hoener, M.; Bucksbaum, P. H.; Ghimire, S.; Reis, D. A.; Bozek, J. D.; Bostedt, C.; Messerschmidt, M.; Young, L.

2011-12-01

74

Interbranch transient beating of X-ray intensities in deformed crystals.  

PubMed

X-ray dynamical diffraction in a deformed crystal is studied using the interbranch resonance concept. It is shown that appreciable beating of the X-ray intensities may be induced by a lattice distortion that produces interbranch transformations of the local dispersion surface. In X-ray plane-wave topography, this effect may be observed as interference fringes arising around the kinematical image of a defect. It is predicted that such interbranch fringes can be induced by edge dislocations. PMID:20555191

Shevchenko, M

2010-07-01

75

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

NASA Astrophysics Data System (ADS)

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

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

2007-07-01

76

Prediction and Measurement of X-Ray Spectral and Intensity Distributions from Low Energy Electron Impact Sources  

NASA Technical Reports Server (NTRS)

In-vacuum electron beam welding is a technology that NASA considered as a joining technique for manufacture of space structures. The interaction of energetic electrons with metal produces x-rays. The radiation exposure to astronauts performing the in-vacuum electron beam welding must be characterized and minimized to insure safe operating conditions. This investigation characterized the x-ray environment due to operation of an in-vacuum electron beam welding tool. NASA, in a joint venture with the Russian Space Agency, was scheduled to perform a series of welding in space experiments on board the United States Space Shuttle. This series of experiments was named the International Space Welding Experiment (ISWE). The hardware associated with the ISWE was leased to NASA, by the Paton Welding Institute (PWI) in Ukraine, for ground based welding experiments in preparation for flight. Two tests were scheduled, using the ISWE electron beam welding tool, to characterize the radiation exposure to an astronaut during the operation of the ISWE. These radiation exposure tests consisted of Thermoluminescence Dosimeters (TLD's) shielded with material currently used by astronauts during Extra Vehicular Activities (EVA) and exposed to x-ray radiation generated by operation of an in-vacuum electron beam welding tool. This investigation was the first known application of TLD's to measure absorbed dose from x-rays of energy less than 10 KeV. The ISWE hardware was returned to Ukraine before the issue of adequate shielding for the astronauts was verified. Therefore, alternate experimental and analytical methods were developed to measure and predict the x-ray spectral and intensity distribution generated by electron impact with metal. These x-ray spectra were used to calculate the absorbed radiation dose to astronauts. These absorbed dose values were compared to TLD measurements obtained during actual operation of the in-vacuum electron beam welding tool. The calculated absorbed dose values were found to be in good agreement with the TLD values.

Edwards, David L.

1999-01-01

77

X-Ray Intensity Fluctuation Spectroscopy Studies of Colloids and Polymers  

NASA Astrophysics Data System (ADS)

X-ray intensity fluctuation spectroscopy (XIFS) using coherent beams available from high brightness synchrotron sources can be used to measure the low-frequency equilibrium dynamics of disordered systems. Conventional techniques using visible light are limited to wavevectors below ~ 4 × 10-3Åfor transparent media. Both colloidal and polymer systems are expected to exhibit slow dynamics for wavevectors q ~ 0.01ÅIn this range the bandpass of the x-ray radiation can be relaxed, producing sufficient intensity in the coherent beam for practical measurements of XIFS. At the Troïka (ID10A) beamline of the European Synchrotron Radiation Facility we have measured the dynamics of colloidal palladium dispersed in glycerol in the time range from 10-4s to 10^2s using a digital autocorrelator. The measured relaxation rates are proportional to q^2 and scale inversely with the viscosity, as expected for a translational diffusion process. XIFS measurements of concentrated polymer micelle liquids composed of polystyrene-polyisoprene block copolymers in a polystyrene homopolymer matrix show that the diffusion coefficient is wavevector dependent. The morphology of the micelles also has significant effects on the equilibrium dynamics of such systems.

Abernathy, Douglas L.

1997-03-01

78

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

79

Propagation of an X-ray beam modified by a photonic crystal.  

PubMed

A method of calculating the transmission of hard X-ray radiation through a perfect and well oriented photonic crystal and the propagation of the X-ray beam modified by a photonic crystal in free space is developed. The method is based on the approximate solution of the paraxial equation at short distances, from which the recurrent formula for X-ray propagation at longer distances is derived. A computer program for numerical simulation of images of photonic crystals at distances just beyond the crystal up to several millimetres was created. Calculations were performed for Ni inverted photonic crystals with the [111] axis of the face-centred-cubic structure for distances up to 0.4?mm with a step size of 4?µm. Since the transverse periods of the X-ray wave modulation are of several hundred nanometres, the intensity distribution of such a wave is changed significantly over the distance of several micrometres. This effect is investigated for the first time. PMID:24971967

Kohn, V G; Snigireva, I; Snigirev, A

2014-07-01

80

Optimization of X-ray beam profilers based on CVD diamond detectors  

NASA Astrophysics Data System (ADS)

A complete beam profiler, based on a CVD diamond pixel detector, has been developed for real-time X-ray source imaging, showing good results in terms of sensitivity and response speed. A dedicated microcontroller-based read-out electronics has been designed to ensure real-time monitoring for a wide range of beam intensities and dose-rates (0.001÷1 Gy/h). The influence of two different metal-diamond interfaces (Ag and Ti/Au) on the X-ray induced photocurrent characteristics has been also investigated, in order to identify which of the two types of contacts can optimize the beam profiler performance in terms of sensitivity and spatial resolution. For this purpose, a set of measurements (X-ray induced photocurrent dependence on bias voltage and dose-rate, specific sensitivity) was carried out with a standard Coolidge tube equipped with a molybdenum target (K? line at 17.5 keV, K? line at 19.6 keV).

Girolami, M.; Conte, G.; Salvatori, S.; Allegrini, P.; Bellucci, A.; Trucchi, D. M.; Ralchenko, V. G.

2012-11-01

81

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

82

Interbranch transient beating of X-ray intensities in deformed crystals  

NASA Astrophysics Data System (ADS)

An appreciable beating of the X-ray intensities may be induced by a lattice distortion that produces interbranch transformations of the local dispersion surface. In X-ray plane-wave topography, this effect may be observed as interference fringes arising around the kinematical image of a defect.

Shevchenko, M.

2010-07-01

83

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

84

Time dependence of X-ray polarizability of a crystal induced by an intense femtosecond X-ray pulse.  

PubMed

The time evolution of the electron density and the resulting time dependence of Fourier components of the X-ray polarizability of a crystal irradiated by highly intense femtosecond pulses of an X-ray free-electron laser (XFEL) is investigated theoretically on the basis of rate equations for bound electrons and the Boltzmann equation for the kinetics of the unbound electron gas. The photoionization, Auger process, electron-impact ionization, electron-electron scattering and three-body recombination have been implemented in the system of rate equations. An algorithm for the numerical solution of the rate equations was simplified by incorporating analytical expressions for the cross sections of all the electron configurations in ions within the framework of the effective charge model. Using this approach, the time dependence of the inner shell populations during the time of XFEL pulse propagation through the crystal was evaluated for photon energies between 4 and 12?keV and a pulse width of 40?fs considering a flux of 10(12)?photons pulse(-1) (focusing on a spot size of ?1?µm). This flux corresponds to a fluence ranging between 0.8 and 2.4?mJ?µm(-2). The time evolution of the X-ray polarizability caused by the change of the atomic scattering factor during the pulse propagation is numerically analyzed for the case of a silicon crystal. The time-integrated polarizability drops dramatically if the fluence of the X-ray pulse exceeds 1.6?mJ?µm(-2). PMID:25485121

Leonov, A; Ksenzov, D; Benediktovitch, A; Feranchuk, I; Pietsch, U

2014-11-01

85

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

SciTech Connect

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

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

2010-07-01

86

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

87

Silicon Mirrors for High-Intensity X-Ray Pump and Probe Experiments  

NASA Astrophysics Data System (ADS)

An all-x-ray pump and probe capability is highly desired for the free-electron laser community. A possible implementation involves the use of an x-ray mirror downstream of the sample to backreflect the pump beam onto itself. We expose silicon single crystals, a candidate for this hard-x-ray mirror, to the hard-x-ray beam of the Linac Coherent Light Source (SLAC National Acceleration Laboratory) to assess its suitability. We find that silicon is an appropriate mirror material, but its reflectivity at high x-ray fluences is somewhat unpredictable. We attribute this behavior to x-ray-induced local damage in the mirror, which we have characterized post mortem via microdiffraction, scanning electron microscopy, and Raman spectroscopy. We demonstrate a strategy to reduce local damage by using a structured silicon-based mirror. Preliminary results suggest that the latter yields reproducible Bragg reflectivity at high x-ray fluences, promising a path forward for silicon single crystals as x-ray backreflectors.

Pardini, Tom; Boutet, Sébastien; Bradley, Joseph; Döppner, 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.

2014-05-01

88

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

89

Preliminary Designs for Modifications to the X-Ray Source and Beam Monitor of the Marshall Space Flight Center's X-Ray Calibration Facility  

NASA Technical Reports Server (NTRS)

Preliminary designs for modifications to the X-ray source and beam monitor of the MSFC X-Ray Calibration Facility to meet requirements for the calibration of the Advanced X-Ray Astrophysics Facility are considered. A rhodium plated copper target and rhodium foil filter are proposed as a source of X-rays of approximately 2.6 keV energy. Bragg scattering of the unpolarized X-ray beam from the present source through an angle of 90 deg by a single crystal placed on the axis of the guide tube is proposed as a source of approximately monoenergetic plane polarized X-rays. A sealed xenon proportional counter with a Beryllium window is proposed as a beam monitor for use between 2.5 and 8 keV to obtain improved detection efficiency.

Croft, W. L.

1983-01-01

90

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. The X-ray sources that are used for calibration are both diode type and diode/fluorescer combinations. Calibrating the X-ray detectors is 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 quantum efficiency averaged over all pixels, 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 R; Ross, P W; Lee, J J; Schneider, M B; Palmer, N E; Teruya, A T

2012-02-16

91

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

92

Synchrotron x-ray radiation from laser wakefield accelerated electron beams in a plasma channel  

NASA Astrophysics Data System (ADS)

Synchrotron x-ray radiation from laser wakefield accelerated electron beams was characterized at the HERCULES facility of the University of Michigan. A mono-energetic electron beam with energy up to 400 MeV was observed in the interaction of an ultra-short laser pulse with a super-sonic gas jet target. The experiments were performed at a peak intensity of 5×1019 W/cm2 by using an adaptive optic. The accelerated electron beam undergoes a so called "betatron" oscillation in an ion channel, where plasma electrons have been expelled by the laser ponderomotive force, and, therefore, emits synchrotron radiation. We observe broad synchrotron x-ray radiation extending up to 30 keV. We find that this radiation is emitted in a beam with a divergence angle as small as 12×4 mrad2 and can have a source size smaller than 3 microns and a peak brightness of 1022 photons/mm2/mrad2/second/0.1% bandwidth, which is comparable to currently existing 3rd generation conventional light sources. This opens up the possibility of using laser-produced "betatron" sources for many applications that currently require conventional synchrotron sources.

Matsuoka, T.; Kneip, S.; McGuffey, C.; Palmer, C.; Schreiber, J.; Huntington, C.; Horovitz, Y.; Dollar, F.; Chvykov, V.; Kalintchenko, G.; Thomas, A. G. R.; Yanovsky, V.; Phuoc, K. Ta; Mangles, S. P. D.; Najmudin, Z.; Maksimchuk, A.; Krushelnick, K.

2010-08-01

93

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

94

X-ray lithography source  

DOEpatents

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

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

1991-01-01

95

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

96

Orbit Feedback Using X-ray Beam Position Monitoring at the Advanced Photon Source (Invited)  

Microsoft Academic Search

The Advanced Photon Source (APS) was commissioned in 1995 as a third-generation x-ray user facility. At that time orbit control was performed exclusively with broadband rf beam position monitors (BPMs). Since then, emphasis has been placed on incorporating x-ray beam position monitors into the orbit control algorithms. This has resulted in an order of magnitude improvement in long-term beam stability

Glenn Decker; Om Singh

2001-01-01

97

Fast Algorithm for X-ray Cone-beam Microtomography and Ping-Chin Cheng1  

E-print Network

). With an X-ray point source and a 2D- detector array, X-rays intersecting a spherical specimen form a cone-beam geometry is beneficial for faster data collection, higher image resolution, better radiation utilization), and generalized the Feldkamp algorithm to allow flexible scanning loci including helical/ helical-like scanning

Virginia Tech

98

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

99

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

100

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

101

Intensity interferometry measurements with hard x-ray FEL pulses at the Linac Coherent Light Source  

NASA Astrophysics Data System (ADS)

Intensity interferometry measurements were carried out to study the spatial coherence properties of a Free-Electron Laser (FEL) in the Self-Amplified Spontaneous Emission (SASE) mode in the hard X-ray regime. Statistical analyses based on ensemble averages of the spatial intensity correlation function were performed on a large number of pulses, overcoming challenges associated with the FEL beam being non-stationary in time and highly collimated. The second-order intensity correlation functions consistently show deviations from unity, reminiscent of the classical Hanbury-Brown and Twiss effect. They also exhibit a slow decaying spatial dependence at length-scales larger than the width of the beam, indicating a high degree of spatial coherence. These measurements are consistent with the behavior of a highly brilliant but chaotic source obeying Gaussian statistics as expected for a SASE FEL. Our study could be used to devise an in-line diagnostic capable of providing quasi real-time feedback for understanding and tuning the FEL process.

Song, Sanghoon; Zhu, Diling; Singer, Andrej; Wu, Juhao; Sikorski, Marcin; Chollet, Matthieu; Lemke, Henrik; Alonso-Mori, Roberto; Glownia, James M.; Krzywinski, Jacek; Lutman, Alberto; Ding, Yuantao; Maxwell, Timothy; Turner, James L.; Gorobtsov, Oleg; Vartanyants, Ivan A.; Robert, Aymeric; Feng, Yiping

2014-09-01

102

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

103

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

104

X-ray beamsplitter  

Microsoft Academic Search

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

Natale M. Ceglio; Daniel S. Stearns; Andrew M. Hawryluk; Barbee Jr. Troy W

1989-01-01

105

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

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

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

Code of Federal Regulations, 2014 CFR

... Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES RADIOLOGY DEVICES Diagnostic Devices § 892.1610 Diagnostic x-ray beam-limiting device. (a) Identification....

2014-04-01

108

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

Code of Federal Regulations, 2013 CFR

... Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES RADIOLOGY DEVICES Diagnostic Devices § 892.1610 Diagnostic x-ray beam-limiting device. (a) Identification....

2013-04-01

109

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

Code of Federal Regulations, 2011 CFR

... Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES RADIOLOGY DEVICES Diagnostic Devices § 892.1610 Diagnostic x-ray beam-limiting device. (a) Identification....

2011-04-01

110

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

Code of Federal Regulations, 2012 CFR

... Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES RADIOLOGY DEVICES Diagnostic Devices § 892.1610 Diagnostic x-ray beam-limiting device. (a) Identification....

2012-04-01

111

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

Code of Federal Regulations, 2010 CFR

... Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES RADIOLOGY DEVICES Diagnostic Devices § 892.1610 Diagnostic x-ray beam-limiting device. (a) Identification....

2010-04-01

112

Diamond X-ray beam-position monitoring using signal readout at the synchrotron radiofrequency.  

PubMed

Single-crystal diamond is a material with great potential for the fabrication of X-ray photon beam-position monitors with submicrometre spatial resolution. Low X-ray absorption combined with radiation hardness and excellent thermal-mechanical properties make possible beam-transmissive diamond devices for monitoring synchrotron and free-electron laser X-ray beams. Tests were made using a white bending-magnet synchrotron X-ray beam at DESY to investigate the performance of a position-sensitive diamond device using radiofrequency readout electronics. The device uniformity and position response were measured in a 25 microm collimated X-ray beam with an I-Tech Libera ;Brilliance' system. This readout system was designed for position measurement and feedback control of the electron beam in the synchrotron storage ring, but, as shown here, it can also be used for accurate position readout of a quadrant-electrode single-crystal diamond sensor. The centre-of-gravity position of the F4 X-ray beam at the DORIS III synchrotron was measured with the diamond signal output digitally sampled at a rate of 130 Msample s(-1) by the Brilliance system. Narrow-band filtering and digital averaging of the position signals resulted in a measured position noise below 50 nm (r.m.s.) for a 10 Hz bandwidth. PMID:20567077

Morse, J; Solar, B; Graafsma, H

2010-07-01

113

The correction of reflection intensities for incomplete absorption of high-energy X-rays in the CCD phosphor  

SciTech Connect

It is shown that incomplete absorption of the X-ray beam in the phosphor of an area detector causes an incident-angle dependence of the recorded X-ray intensities. An energy scan of a SMART-6000 CCD (charge-coupled device) phosphor using synchrotron radiation shows the correction to be of importance above about 17 keV. Intensities of single reflections, each collected several times at different angles of incidence on the phosphor surface, show a pronounced angle-dependence at shorter wavelengths. Both conventional structural refinement and multipole charge density studies confirm that an oblique-incidence correction leads to improved quality of the results. Atomic displacement parameters will be systematically biased when the correction is not applied. For a {lambda} = 0.394 {angstrom} data set, neglecting the correction gives rise to artifacts in the deformation density maps that are likely to lead to misinterpretation of the experimental results.

Wu, G.; Rodrigues, B.L.; Coppens, P. (SUNYB)

2009-03-24

114

The Use of Coherent X-Ray Beams to Study the Dynamics of Soft Condensed Matter Systems  

NASA Astrophysics Data System (ADS)

The study of slow dynamics in soft condensed matter systems has been of interest for many years. One of the most powerful techniques for studying dynamics at these time scales has been Dynamical Light Scattering (DLS). However, it was recognized over twenty years ago that a similar application of X-rays in order to achieve shorter length scales and avoid problems of multiple and stray particle scattering, could open up whole new areas of research. The advent of the high-brilliance third generation synchrotron X-ray sources over a decade ago made it possible for the first time to deliver an intense beam of highly coherent X-rays, enabling many new applications of X-ray scattering, some of which will be discussed. In particular, the technique of X-ray Photon Correlation Spectroscopy (XPCS), the X-ray analog of DLS, has now become an exciting new research area with applications primarily in soft condensed matter. In this talk, we shall trace the development of the use of coherent X-ray beams from the early demonstrations at the NSLS, ESRF and APS synchrotron light sources to current applications which include the study of dynamical fluctuations in colloids and polymers and in particular the study of surface fluctuations in liquid films and membranes. We shall show how XPCS has yielded interesting new results on these systems difficult if not impossible to obtain by other techniques. I wish to acknowledge collaborations with Hyunjung Kim, Larry Lurio, Zhang Jiang, Christian Gutt, Metin Tolan, Tuana Ghaderi, Jyotsana Lal, Simon Mochrie, Miriam Rafailovich, Jonathan Sokolov, Chinhua Li, Tadanori Koga, Xuesong Jiao, Suresh Narayanan.

Sinha, Sunil

2007-03-01

115

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

116

X ray constraints on the beaming hypothesis for BL Lacertae objects  

NASA Technical Reports Server (NTRS)

BL Lacertae objects may be Fanaroff-Riley type I (FR I) galaxies with a relativistic jet roughly parallel to the line of sight. The ratio of parent objects (FR Is) to beamed objects (BL Lacs) depends only on the jet velocity. Recently this ratio become observable. X-ray-flux-limited samples are used to demonstrate the viability of the beaming hypothesis. In the process, the X-ray luminosity functions of FR I galaxies and BL Lac objects are derived. Their respective contributions to the cosmic X-ray background radiation are calculated.

Padovani, P.; Urry, C. M.

1989-01-01

117

Pseudopotential calculations of photoionization of atoms in the x-ray photon energy range and FEL beam monitor development  

NASA Astrophysics Data System (ADS)

A pseudopotential model for calculation of atomic processes under interaction with hard x-ray photons is applied to calculation of Krypton photoionization cross sections by photons with energy in the 20–25 keV range. These cross sections, as well as the mean charge of the resulting ions calculated using the Monte Carlo simulation scheme, are in good agreement with the other theoretical calculations and with the experiment. The obtained results open the doors for new techniques in the design of gas-monitor detectors to control the intensity, coordinates and energy of x-ray free-electron laser (XFEL) beams in the hard x-ray photon energy range. First, Monte Carlo simulations of a scintillation detector application for gas-monitors have been performed.

Chernov, V. E.; Dorofeev, D. L.; Elfimov, S. V.; Zon, B. A.; Gavrilov, G. E.; Naryshkin, Yu G.

2015-03-01

118

Performance Characteristics Of An Intensity Modulated Advanced X-Ray Source (IMAXS) For Homeland Security Applications  

SciTech Connect

X-ray cargo inspection systems for the detection and verification of threats and contraband must address stringent, competitive performance requirements. High x-ray intensity is needed to penetrate dense cargo, while low intensity is desirable to minimize the radiation footprint, i.e. the size of the controlled area, required shielding and the dose to personnel. In a collaborative effort between HESCO/PTSE Inc., XScell Corp., Stangenes Industries, Inc. and Rapiscan Laboratories, Inc., an Intensity Modulated Advanced X-ray Source (IMAXS) was designed and produced. Cargo inspection systems utilizing such a source have been projected to achieve up to 2 inches steel-equivalent greater penetration capability, while on average producing the same or smaller radiation footprint as present fixed-intensity sources. Alternatively, the design can be used to obtain the same penetration capability as with conventional sources, but reducing the radiation footprint by about a factor of three. The key idea is to anticipate the needed intensity for each x-ray pulse by evaluating signal strength in the cargo inspection system detector array for the previous pulse. The IMAXS is therefore capable of changing intensity from one pulse to the next by an electronic signal provided by electronics inside the cargo inspection system detector array, which determine the required source intensity for the next pulse. We report on the completion of a 9 MV S-band (2998 MHz) IMAXS source and comment on its performance.

Langeveld, Willem G. J.; Brown, Craig; Condron, Cathie; Ingle, Mike [Rapiscan Laboratories, Inc., 520 Almanor Ave., Sunnyvale, CA 94085 (United States); Christensen, Phil A.; Johnson, William A.; Owen, Roger D. [HESCO/PTSE Inc., 2501 Monarch St., Alameda, CA 94501 (United States); Hernandez, Michael; Schonberg, Russell G. [XScell Corp., 2134 Old Middlefield Way, Mountain View, CA 94043 (United States); Ross, Randy [Stangenes Industries, Inc., 1052 East Meadow Circle, Palo Alto, CA 94303 (United States)

2011-06-01

119

Soft X-Ray Emission and Charged Particles Beams from a Plasma Focus of Hundreds Joules  

SciTech Connect

In a new stage of characterization of our plasma focus devices of hundred and tens of joules (PF-400J and PF-50J), preliminary series of measurements on soft X-ray and ion beams have been performed in the device PF-400J (176-539 J, 880 nF, T/4 {approx}300 ns). The device was operated in hydrogen to 7 mbar of pressure . The temporal and spatial X-ray characteristics are investigated by means filtered PIN diodes and a multipinhole camera. Graphite collectors, operating in the bias ion collector mode, are used to estimate the characteristic ion energy using the time flight across the probe array. The time of the ion beam emission to be correlated with plasma emission events associated with the soft X-ray pulses detected by the probes. Temporal correlations between soft X-ray signals and ion beams are performed.

Silva, Patricio; Moreno, Jose; Soto, Leopoldo [Comision Chilena de Energia Nuclear, Casilla 188-D, Santiago (Chile); Pavez, Cristian [Comision Chilena de Energia Nuclear, Casilla 188-D, Santiago (Chile); Universidad de Concepcion, Facultad de Ciencias, Departamento de Fisica, Concepcion (Chile); Arancibia, Jaime [Universidad de Chile, Facultad de Ciencias, Departamento de Fisica, Santiago (Chile)

2006-12-04

120

Intensity interferometry of single x-ray pulses from a synchrotron storage ring.  

PubMed

We report on measurements of second-order intensity correlations at the high-brilliance storage ring PETRA III using a prototype of the newly developed adaptive gain integrating pixel detector. The detector records individual synchrotron radiation pulses with an x-ray photon energy of 14.4 keV and repetition rate of about 5 MHz. The second-order intensity correlation function is measured simultaneously at different spatial separations, which allows us to determine the transverse coherence length at these x-ray energies. The measured values are in a good agreement with theoretical simulations based on the Gaussian Schell model. PMID:25148330

Singer, A; Lorenz, U; Marras, A; Klyuev, A; Becker, J; Schlage, K; Skopintsev, P; Gorobtsov, O; Shabalin, A; Wille, H-C; Franz, H; Graafsma, H; Vartanyants, I A

2014-08-01

121

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

122

Femtosecond X-ray-induced explosion of C60 at extreme intensity  

NASA Astrophysics Data System (ADS)

Understanding molecular femtosecond dynamics under intense X-ray exposure is critical to progress in biomolecular imaging and matter under extreme conditions. Imaging viruses and proteins at an atomic spatial scale and on the time scale of atomic motion requires rigorous, quantitative understanding of dynamical effects of intense X-ray exposure. Here we present an experimental and theoretical study of C60 molecules interacting with intense X-ray pulses from a free-electron laser, revealing the influence of processes not previously reported. Our work illustrates the successful use of classical mechanics to describe all moving particles in C60, an approach that scales well to larger systems, for example, biomolecules. Comparisons of the model with experimental data on C60 ion fragmentation show excellent agreement under a variety of laser conditions. The results indicate that this modelling is applicable for X-ray interactions with any extended system, even at higher X-ray dose rates expected with future light sources.

Murphy, B. F.; Osipov, T.; Jurek, Z.; Fang, L.; Son, S.-K.; Mucke, M.; Eland, J. H. D.; Zhaunerchyk, V.; Feifel, R.; Avaldi, L.; Bolognesi, P.; Bostedt, C.; Bozek, J. D.; Grilj, J.; Guehr, M.; Frasinski, L. J.; Glownia, J.; Ha, D. T.; Hoffmann, K.; Kukk, E.; McFarland, B. K.; Miron, C.; Sistrunk, E.; Squibb, R. J.; Ueda, K.; Santra, R.; Berrah, N.

2014-06-01

123

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

124

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

125

High intensity x-ray line emission from aluminum plasmas generated by a 120 TW, 30 fs laser pulse  

NASA Astrophysics Data System (ADS)

The K-shell x-ray spectra from the aluminum plasmas generated by the interaction of the 120TW, 30fs laser with aluminum targets have been measured by defocusing the laser beam. Laser energy-normalized intensity of the He-a line increases with the laser intensity approximately as a power law ? ?IL? with the much smaller exponent of ? =0.062 compared to ? =0.2˜0.5 in the previous experiments, which is caused by the stronger radial thermal diffusivity in the target for the smaller laser spot. Laser-to-He-a line conversion efficiency of up to 1.9×10-3 and as high as about 3×1013 photons/2? Sr aluminum He-a line x-ray source have been achieved for a single shot due to the preplasma effect and relatively large laser spot and energy for the single shot. The x-ray spectra as a function of the laser intensity are also analyzed to get the electron temperature and density.

Yang, Jiamin; Hu, Zhimin; Zhang, Jiyan; Zhu, Tuo; Zhao, Yang; Wen, Tianshu; Wang, Zhebin; Ding, Yaonan; Wei, Mingxi; Yang, Guohong; Zhang, Baohan

2008-11-01

126

Comparison of intensity modulated x-ray therapy and intensity modulated proton therapy for selective subvolume boosting: a phantom study  

NASA Astrophysics Data System (ADS)

Selective subvolume boosting can theoretically improve tumour control probability while maintaining normal tissue complication probabilities similar to those of uniform dose distributions. In this work the abilities of intensity-modulated x-ray therapy (IMXT) and intensity-modulated proton therapy (IMPT) to deliver boosts to multiple subvolumes of varying size and proximities are compared in a thorough phantom study. IMXT plans were created using the step-and-shoot (IMXT-SAS) and helical tomotherapy (IMXT-HT) methods. IMPT plans were created with the spot scanning (IMPT-SS) and distal gradient tracking (IMPT-DGT) methods. IMPT-DGT is a generalization of the distal edge tracking method designed to reduce the number of proton beam spots required to deliver non-uniform dose distributions relative to IMPT-SS. The IMPT methods were delivered over both 180° and 360° arcs. The IMXT-SAS and IMPT-SS methods optimally satisfied the non-uniform dose prescriptions the least and the most, respectively. The IMPT delivery methods reduced the normal tissue integral dose by a factor of about 2 relative to the IMXT delivery methods, regardless of the delivery arc. The IMPT-DGT method reduced the number of proton beam spots by a factor of about 3 relative to the IMPT-SS method.

Flynn, R. T.; Barbee, D. L.; Mackie, T. R.; Jeraj, R.

2007-10-01

127

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

128

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

PubMed Central

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 mm2), 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. PMID:24089916

Zhang, Rongxiao; Glaser, Adam K.; Gladstone, David J.; Fox, Colleen J.; Pogue, Brian W.

2013-01-01

129

Solar Hard X-ray Source Sizes in a Beam-Heated and Ionised Chromosphere  

E-print Network

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 using the Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) have shown that HXR source sizes are 3-6 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 ionisation (NUI) structure along the path of the electron beam has not been fully explored as a solution to this problem. Ionised 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 ionised region within the chromosphere, the intensity of emission will be preferentially reduced around this peak, resulting in a more extended source. Due to...

O'Flannagain, A; Gallagher, P T

2014-01-01

130

Development of the Soft X-ray Intensity Measurement with a Cryogenic Radiometer  

SciTech Connect

A cryogenic radiometer has been revised and examined in order to improve the absolute measurement of soft X-ray intensities. The uncertainty of the temperature rise in the cavity absorber has decreased to 0.2 % through an increase in the thermal responsivity and through the suppression of the fluctuation in the background temperature.

Kato, M.; Nohtomi, A.; Morishita, Y.; Kurosawa, T.; Arai, N.; Suzuki, I. H.; Saito, N. [National Institute of Advanced Industrial Science and Technology (AIST), NMIJ, Tsukuba, Ibaraki 305-8568 (Japan)

2007-01-19

131

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

132

Method for beam hardening correction in quantitative computed X-ray tomography  

NASA Technical Reports Server (NTRS)

Each voxel is assumed to contain exactly two distinct materials, with the volume fraction of each material being iteratively calculated. According to the method, the spectrum of the X-ray beam must be known, and the attenuation spectra of the materials in the object must be known, and be monotonically decreasing with increasing X-ray photon energy. Then, a volume fraction is estimated for the voxel, and the spectrum is iteratively calculated.

Yan, Chye Hwang (Inventor); Whalen, Robert T. (Inventor); Napel, Sandy (Inventor)

2001-01-01

133

Soft X-rays generated by the electron-cyclotron resonance discharge in heavy gases sustained by a high-power microwave beam in a magnetic trap  

Microsoft Academic Search

The soft X-ray line emission from a pulsed electron-cyclotron resonance discharge in argon, maintained by a high-power millimeter-wavelength\\u000a beam in a magnetic mirror trap, was studied using a multilayer mirror X-ray monochromator. The X-ray spectrum was measured,\\u000a and the absolute spectral intensity of emission was determined in a 6–17 nm wavelength range. The discharge can be used as\\u000a an effective

A. V. Vodopyanov; S. V. Golubev; V. G. Zorin; A. Yu. Kryachko; A. Ya. Lopatin; V. I. Luchin; S. V. Razin; A. N. Smirnov

2000-01-01

134

Survey of intensity variability of strong galactic X-ray sources from Uhuru  

NASA Technical Reports Server (NTRS)

X-ray observations made with the Uhuru satellite have been used to study the characteristics of the intensity of 19 strong galactic sources. On a time scale of 0.1-1.0 s, all but two these sources showed variability at a significance level greater than 3 sigmas. On longer time scales - minutes to hours - all but three sources showed variations above the 3-sigma level. In addition to characterizing in a systematic way the broad range of variability of the galactic X-ray sources, the results are applied to specific models of Cygnus X-1 and Cygnus X-3. Comments are also made on the similar nature of the strong galactic-center X-ray sources and the globular-cluster sources.

Forman, W.; Jones, C.; Tananbaum, H.

1976-01-01

135

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

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

136

Investigation into the influence of x-ray scatter on the imaging performance of an x-ray flat-panel imager-based cone-beam volume CT  

NASA Astrophysics Data System (ADS)

The advent of the x-ray flat panel imager (FPI) is making the study of cone beam volume CT (CBVCT) more competitive. Motivated by recent encouraging developments in CBVCT, this paper investigates the influence of x-ray scatter on the imaging performance of an x-ray FPI based CBVCT prototype. The prototype employs a circle-plus-two-arc orbit to meet the data sufficiency condition, and can reconstruct a region of interest within a longitudinally unbounded object using a cone beam filtered back-projection algorithm derived for the data acquisition orbit. First, the humanoid phantom is used to investigate the temporal variation of both scatter intensity and scatter to primary ratio (SPR) in the projection images acquired for CB reconstruction. Second, a 160 mm cylindrical water phantom consisting of four 16 mm rods made up of Acrylic, Polyethelene, Polycarborate and Polystrene respectively is utilized to evaluate the variation of interference caused by x-ray scatter (cupping effect) and signal to noise ratio vs. SPR in projection images. Third, a disc phantom consisting of seven acrylic discs stacked at even intervals is employed to evaluate the influence of x-ray scatter on reconstruction accuracy and the improvement of CBVCT image quality with recourse to an anti-scatter grid. Finally, the alleviation of the cupping effect in the presence of a beam-shaping (bow-tie) attenuator is assessed . The quantitative investigation shows that the influence of x-ray scatter on the SNR and CT number accuracy is a crucial problem to be addressed for the application of x-ray CBVCT.

Tang, Xiangyang; Ning, Ruola; Yu, Rongfeng; Conover, David L.

2001-06-01

137

Radiation damage in protein crystals is reduced with a micron-sized X-ray beam  

PubMed Central

Radiation damage is a major limitation in crystallography of biological macromolecules, even for cryocooled samples, and is particularly acute in microdiffraction. For the X-ray energies most commonly used for protein crystallography at synchrotron sources, photoelectrons are the predominant source of radiation damage. If the beam size is small relative to the photoelectron path length, then the photoelectron may escape the beam footprint, resulting in less damage in the illuminated volume. Thus, it may be possible to exploit this phenomenon to reduce radiation-induced damage during data measurement for techniques such as diffraction, spectroscopy, and imaging that use X-rays to probe both crystalline and noncrystalline biological samples. In a systematic and direct experimental demonstration of reduced radiation damage in protein crystals with small beams, damage was measured as a function of micron-sized X-ray beams of decreasing dimensions. The damage rate normalized for dose was reduced by a factor of three from the largest (15.6 ?m) to the smallest (0.84 ?m) X-ray beam used. Radiation-induced damage to protein crystals was also mapped parallel and perpendicular to the polarization direction of an incident 1-?m X-ray beam. Damage was greatest at the beam center and decreased monotonically to zero at a distance of about 4 ?m, establishing the range of photoelectrons. The observed damage is less anisotropic than photoelectron emission probability, consistent with photoelectron trajectory simulations. These experimental results provide the basis for data collection protocols to mitigate with micron-sized X-ray beams the effects of radiation damage. PMID:21444772

Sanishvili, Ruslan; Yoder, Derek W.; Pothineni, Sudhir Babu; Rosenbaum, Gerd; Xu, Shenglan; Vogt, Stefan; Stepanov, Sergey; Makarov, Oleg A.; Corcoran, Stephen; Benn, Richard; Nagarajan, Venugopalan; Smith, Janet L.; Fischetti, Robert F.

2011-01-01

138

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

139

Transverse Coherence of the LCLS X-Ray Beam  

SciTech Connect

Self-amplifying spontaneous radiation free-electron lasers, such as the LCLS or the European X-FEL, rely on the incoherent, spontaneous radiation as the seed for the amplifying process. Though this method overcomes the need for an external seed source one drawback is the incoherence of the effective seed signal. The FEL process allows for a natural growth of the coherence because the radiation phase information is spread out within the bunch due to slippage and diffraction of the radiation field. However, at short wavelengths this spreading is not sufficient to achieve complete coherence. In this presentation we report on the results of numerical simulations of the LCLS X-ray FEL. From the obtained radiation field distribution the coherence properties are extracted to help to characterize the FEL as a light source.

Not Available

2010-12-01

140

Time-delayed beam splitting with energy separation of x-ray channels  

SciTech Connect

We introduce a time-delayed beam splitting method based on the energy separation of x-ray photon beams. It is implemented and theoretically substantiated on an example of an x-ray optical scheme similar to that of the classical Michelson interferometer. The splitter/mixer uses Bragg-case diffraction from a thin diamond crystal. Another two diamond crystals are used as back-reflectors. Because of energy separation and a minimal number (three) of optical elements, the split-delay line has high efficiency and is simple to operate. Due to the high transparency of diamond crystal, the split-delay line can be used in a beam sharing mode at x-ray free-electron laser facilities.

Stetsko, Yuri P.; Shvyd'ko, Yuri V.; Brian Stephenson, G. [Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439 (United States)] [Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439 (United States)

2013-10-21

141

A simple analytical expression to calculate the backscatter factor for low energy X-ray beams.  

PubMed

A simple analytical expression aiming to calculate the backscatter factor used in dosimetry protocols to determine the absorbed dose in water for low energy X-rays beams is presented. This expression is based on the linear dependence of the backscatter factor with the generating potential, for fixed values of the half-value layer. The results of a recent work in which 74 X-ray beams with different spectroscopic characteristics, generated with the code (xcomp5r) and transported with the Monte Carlo code (penelope) have been used. The expression derived permits to calculate the backscatter factor within 5% accuracy. The predictive power of this expression has been tested for 20 X-ray beams generated with potentials from 50 to 250 kV, for which half-value layers and backscatter factors have been experimentally determined. PMID:20434382

Chica, U; Flórez, G; Anguiano, M; Lallena, A M

2011-04-01

142

Intense X-ray FEL-molecule physics: Highly charged ions  

SciTech Connect

We report on sequential multiphoton ionization of N{sub 2}, H{sub 2}S and SF{sub 6} by intense, femtosecond duration pulses of x-rays from the LCLS free electron laser. Following either K- or L-shell excitation, we observe ionization and fragmentation of the molecule by Auger electron, photoelectron, and ion time-of-flight spectroscopy. Intense excitation of the K-shell leads to depletion and double core hole effects, observed in N{sub 2}. For L-shell excitation, additional relaxation channels suppress depletion, allowing ionization to continue until energetically forbidden. The investigation of multiphoton ionization has produced a better understanding of molecular plasmas created by intense ultrafast x-ray exposure.

Murphy, B. F.; Fang, L.; Osipov, T. Y.; Hoener, M.; Berrah, N. [Western Michigan University, Physics Department, 1903 W. Michigan Avenue, Kalamazoo, MI, 49008 (United States)

2012-05-25

143

A wide-beam X-ray source suitable for diffraction enhanced imaging applications  

NASA Astrophysics Data System (ADS)

Research in diffraction-enhanced imaging (DEI), using a synchrotron source with an X-ray flux of 1.4×10 12 ph/mm 2/s, has shown strong potential in obtaining high-resolution images as compared to conventional radiographs. This research investigates the feasibility of developing a large area circular X-ray source with fluxes comparable to a synchrotron source. The source should be capable of integration into a compact system with peak powers not to exceed 200 kW to be feasible for use in a major medical facility, industrial complex or screening facility (such as cargo or airport). A computational study of a circular concentric filament wide-beam area X-ray source has been investigated in this research. The design features are based on generating electrons from three concentric circular filaments to provide an area electron flux, with a 60 kV accelerating potential and a beam current of up to 3 A. The X-ray target is a grounded stationary oxygen-free copper target with a layer of molybdenum. This target feature differs from standard rotating X-ray targets in conventional X-ray systems. Studies of electron trajectories and their distribution on the target were conducted using the SIMION 3D code. Heat loading and thermal management were studied using heat transfer modules from the coupled FEMLAB multi-physics and MATLAB codes. The Monte Carlo code MCNP 5 was used to obtain the X-ray flux and energy distribution for aluminum and beryllium windows. This computational study shows that this target configuration generates X-rays with photon flux comparable to synchrotron source and sufficient for DEI applications. The maximum target temperature rise is 1357 K after 70 s when cooling the back of the target to liquid nitrogen temperature using cold finger contact, and 325 K for an invaded target, in which liquid nitrogen circulates inside the target.

Kim, Chang H.; Bourham, Mohamed A.; Michael Doster, J.

2006-10-01

144

Investigation of mechanisms leading to precession of intense electron beams  

Microsoft Academic Search

In previous work [I] it was shown that transportation of intense electron beams in vacuum by applied magnetic field leads to precession of the beam concerning the axis of the transport channel. The beam precession was investigated by different diagnostics (Faraday cups, current probes, X-ray detectors). It was found that frequency, amplitude and onset time of the beam precession strongly

Georg Mueller; Vladimir I. Engelko; Vladimir An; Hansjoachim Bluhm; Vladimir S. Kuznetsov; Vladimir G. Kovalev; Galina A. Vyazmenova

2004-01-01

145

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

146

SU-E-I-01: A Fast, Analytical Pencil Beam Based Method for First Order X-Ray Scatter Estimation of Kilovoltage Cone Beam X-Rays  

SciTech Connect

Purpose: To analytically estimate first-order x-ray scatter for kV cone beam x-ray imaging with high computational efficiency. Methods: In calculating first-order scatter using the Klein-Nishina formula, we found that by integrating the point-to-point scatter along an interaction line, a “pencil-beam” scatter kernel (BSK) can be approximated to a quartic expression when the imaging field is small. This BSK model for monoenergetic, 100keV x-rays has been verified on homogeneous cube and cylinder water phantoms by comparing with the exact implementation of KN formula. For heterogeneous medium, the water-equivalent length of a BSK was acquired with an improved Siddon's ray-tracing algorithm, which was also used in calculating pre- and post- scattering attenuation. To include the electron binding effect for scattering of low-kV photons, the mean corresponding scattering angle is determined from the effective point of scattered photons of a BSK. The behavior of polyenergetic x-rays was also investigated for 120kV x-rays incident to a sandwiched infinite heterogeneous slab phantom, with the electron binding effect incorporated. Exact computation and Monte Carlo simulations were performed for comparisons, using the EGSnrc code package. Results: By reducing the 3D volumetric target (o(n{sup 3})) to 2D pencil-beams (o(n{sup 2})), the computation expense can be generally lowered by n times, which our experience verifies. The scatter distribution on a flat detector shows high agreement between the analytic BSK model and exact calculations. The pixel-to-pixel differences are within (-2%, 2%) for the homogeneous cube and cylinder phantoms and within (0, 6%) for the heterogeneous slab phantom. However, the Monte Carlo simulation shows increased deviation of the BSK model toward detector periphery. Conclusion: The proposed BSK model, accommodating polyenergetic x-rays and electron binding effect at low kV, shows great potential in efficiently estimating the first-order scatter from small imaging fields. We are investigating more thoroughly to improve performance and explore applications.

Liu, J; Bourland, J [Wake Forest University, Winston-salem, NC (United States)

2014-06-01

147

Monte Carlo model of the scanning beam digital x-ray (SBDX) source  

PubMed Central

The scanning-beam digital x-ray (SBDX) system has been developed for fluoroscopic imaging using an inverse x-ray imaging geometry. The SBDX system consists of a large-area x-ray source with a multihole collimator and a small detector. The goal of this study was to build a Monte Carlo (MC) model of the SBDX source as a useful tool for optimization of the SBDX imaging system in terms of its hardware components and imaging parameters. The MC model of the source was built in the EGSnrc/BEAMnrc code and validated using the DOSXYZnrc code and Gafchromic film measurements for 80, 100, and 120 kV x-ray source voltages. The MC simulated depth dose curves agreed with measurements to within 5%, and beam profiles at three selected depths generally agreed within 5%. Exposure rates and half-value layers for three voltages were also calculated from the MC simulations. Patient skin-dose per unit detector-dose was quantified as a function of patient size for all three x-ray source voltages. The skin-dose to detector-dose ratio ranged from 5–10 for a 20 cm thick patient to 1 × 103–1 × 105 for a 50 cm patient for the 120 and 80 kV beams, respectively. Simulations of imaging dose for a prostate patient using common imaging parameters revealed that skin-dose per frame was as low as 0.2 mGy. PMID:23093305

Bazalova, M; Weil, MD; Wilfley, B; Graves, EE

2014-01-01

148

Constraints on Off-Axis X-Ray Emission from Beamed GRBs  

E-print Network

We calculate the prompt x-ray emission as a function of viewing angle for beamed Gamma-Ray Burst (GRB) sources. Prompt x-rays are inevitable due to the less highly blueshifted photons emitted at angles greater than 1/gamma relative to the beam symmetry axis, where gamma is the expansion Lorentz factor. The observed flux depends on the combinations (gamma Delta theta) and (gamma theta_v), where (Delta theta) is the beaming angle and theta_v is the viewing angle. We use the observed source counts of gamma-ray-selected GRBs to predict the minimum detection rate of prompt x-ray bursts as a function of limiting sensitivity. We compare our predictions with the results from the Ariel V catalog of fast x-ray transients, and find that Ariel's sensitivity is not great enough to place significant constraints on gamma and (Delta theta). We estimate that a detector with fluence limit ~10^{-7} erg/cm^2 in the 2-10 keV channel will be necessary to distinguish between geometries. Because the x-ray emission is simultaneous with the GRB emission, our predicted constraints do not involve any model assumptions about the emission physics but simply follow from special-relativistic considerations.

Eric Woods; Abraham Loeb

1999-03-24

149

Prospects for compact high-intensity laser synchrotron x-ray and gamma sources  

SciTech Connect

A laser interacting with a relativistic electron beam behaves like a virtual wiggler of an extremely short period equal to half of the laser wavelength. This approach opens a route to relatively compact, high-brightness x-ray sources alternative or complementary to conventional synchrotron light sources. Although not new, the laser synchrotron source (LSS) concept is still waiting for a convincing demonstration. Available at the BNL Accelerator Test Facility (ATF), a high-brightness electron beam and the high-power CO{sub 2} laser may be used as prototype LSS brick stones. In a feasible demonstration experiment, 10-GW, 100-ps CO{sub 2} laser beam will be brought to a head-on collision with a 10-ps, 0.5-nC, 50 MeV electron bunch. Flashes of collimated 4.7 keV (2.6 {angstrom}) x-rays of 10-ps pulse duration, with a flux of {approximately} 10{sup 19} photons/sec, will be produced via linear Compton backscattering. The x-ray spectrum is tunable proportionally to the e-beam energy. A rational short-term extension of the proposed experiment would be further enhancement of the x-ray flux to the 10{sup 22} photons/sec level, after the ongoing ATF CO{sub 2} laser upgrade to 5 TW peak power and electron bunch shortening to 3 ps is realized. In the future, exploiting the promising approach of a high-gradient laser wake field accelerator, a compact ``table-top`` LSS of monochromatic gamma radiation may become feasible.

Pogorelsky, I.V. [Brookhaven National Lab., Upton, NY (United States). Accelerator Test Facility

1996-11-01

150

Prospects for compact high-intensity laser synchrotron x-ray and gamma sources  

NASA Astrophysics Data System (ADS)

A laser interacting with a relativistic electron beam behaves like a virtual wiggler of an extremely short period equal to half of the laser wavelength. This approach opens a route to relatively compact, high-brightness x-ray sources alternative or complementary to conventional synchrotron light sources. Although not new, the laser synchrotron source (LSS) concept is still waiting for a convincing demonstration. Available at the BNL Accelerator Test Facility (ATF), a high-brightness electron beam and the high-power CO2 laser may be used for prototype LSS demonstration. In a feasible demonstration experiment, 10-GW, 100-ps CO2 laser beam will be brought to a head-on collision with a 10-ps, 0.5-nC, 50 MeV electron bunch. Flashes of collimated 4.7 keV (2.6 Å) x-rays of 10-ps pulse duration, with a flux of ˜1019photons/sec, will be produced via linear Compton backscattering. The x-ray spectrum is tunable proportionally to the e-beam energy. A rational short-term extension of the proposed experiment would be further enhancement of the x-ray flux to the 1022 photons/sec level, after the ongoing ATF CO2 laser upgrade to 5 TW peak power and electron bunch shortening to 3 ps is realized. In the future, exploiting the promising approach of a high-gradient laser wake field accelerator, a compact "table-top" LSS of monochromatic gamma radiation may become feasible.

Pogorelsky, I. V.

1997-03-01

151

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

152

Intense Non-Linear Soft X-Ray Emission from a Hydride Target during Pulsed D Bombardment  

Microsoft Academic Search

Radiation emission from low-energy nuclear radiation (LENR) electrodes (both charged-particle and X-rays) represents an important feature of LENR in general. Here, calibration, measurement techniques, and soft X-ray emission results from deuterium bombardment of a Pd target (cathode) placed in a pulsed deuterium glow discharge (PGD) are described. An X-ray intensity of 13.4 mW\\/cm2 and a dose of 3.3 muJ\\/cm2 were

George H. Miley; Yang Yang; Andrei Lipson; Munima Haque; Ian Percel; Michael Romer

2006-01-01

153

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

154

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

155

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

156

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 mollochromator system. In this Paper, we consider various aspects, advantage and disadvantages, and promises and pitfalls of such a system and evaluate the comparative an 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 diamond-based monochromator is within present technical means.

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

1992-12-01

157

Time-Dependent Simulation of Carbon Illuminated by a High Intensity X-Ray Laser  

NASA Astrophysics Data System (ADS)

We simulate a biological cell composed of solid density carbon illuminated by a high intensity X-ray laser with a time-dependent model. This first version is a simple model that neglects inverse bremsstrahlung absorption by free electrons, electron conduction or hydrodynamic effects. Atomic data needed for the simulations can be generated with the flexible atomic code (FAC) or the screened hydrogenic model (SHM).

de la Varga, Alberto G.; Velarde, Pedro; de Gaufridy, François; Cotelo, Manuel; Portillo, David; Zeitoun, Philippe

158

X-ray beam stabilization at BL-17A, the protein microcrystallography beamline of the Photon Factory  

PubMed Central

BL-17A is a new structural biology beamline at the Photon Factory, Japan. The high-brilliance beam, derived from the new short-gap undulator (SGU#17), allows for unique protein crystallographic experiments such as data collection from microcrystals and structural determination using softer X-rays. However, microcrystal experiments require robust beam stability during data collection and minor fluctuations could not be ignored. Initially, significant beam instability was observed at BL-17A. The causes of the beam instability were investigated and its various sources identified. Subsequently, several effective countermeasures have been implemented, and the fluctuation of the beam intensity successfully suppressed to within 1%. Here the instability reduction techniques used at BL-17A are presented. PMID:18421162

Igarashi, Noriyuki; Ikuta, Kazuyuki; Miyoshi, Toshinobu; Matsugaki, Naohiro; Yamada, Yusuke; Yousef, Mohammad S.; Wakatsuki, Soichi

2008-01-01

159

Synchrotron-based coherent scatter x-ray projection imaging using an array of monoenergetic pencil beams  

SciTech Connect

Traditional projection x-ray imaging utilizes only the information from the primary photons. Low-angle coherent scatter images can be acquired simultaneous to the primary images and provide additional information. In medical applications scatter imaging can improve x-ray contrast or reduce dose using information that is currently discarded in radiological images to augment the transmitted radiation information. Other applications include non-destructive testing and security. A system at the Canadian Light Source synchrotron was configured which utilizes multiple pencil beams (up to five) to create both primary and coherent scatter projection images, simultaneously. The sample was scanned through the beams using an automated step-and-shoot setup. Pixels were acquired in a hexagonal lattice to maximize packing efficiency. The typical pitch was between 1.0 and 1.6 mm. A Maximum Likelihood-Expectation Maximization-based iterative method was used to disentangle the overlapping information from the flat panel digital x-ray detector. The pixel value of the coherent scatter image was generated by integrating the radial profile (scatter intensity versus scattering angle) over an angular range. Different angular ranges maximize the contrast between different materials of interest. A five-beam primary and scatter image set (which had a pixel beam time of 990 ms and total scan time of 56 min) of a porcine phantom is included. For comparison a single-beam coherent scatter image of the same phantom is included. The muscle-fat contrast was 0.10 {+-} 0.01 and 1.16 {+-} 0.03 for the five-beam primary and scatter images, respectively. The air kerma was measured free in air using aluminum oxide optically stimulated luminescent dosimeters. The total area-averaged air kerma for the scan was measured to be 7.2 {+-} 0.4 cGy although due to difficulties in small-beam dosimetry this number could be inaccurate.

Landheer, Karl [Ottawa Medical Physics Institute and Ottawa-Carleton Institute for Physics, Department of Physics, Carleton University, 1125 Colonel By Drive, Ottawa K1S 5B6 (Canada); Johns, Paul C. [Ottawa Medical Physics Institute and Ottawa-Carleton Institute for Physics, Department of Physics, Carleton University, 1125 Colonel By Drive, Ottawa K1S 5B6 (Canada); Department of Radiology, University of Ottawa (Canada)

2012-09-15

160

Microfocused X-rays Beams Using Compound Refractive Lenses: Possibilities for Indus-2  

NASA Astrophysics Data System (ADS)

For the generation of micro focused hard x-ray beams on Indus-2, with large depth of focus and large focal lengths, simulation studies have been performed using parabolic Be compound refractive lenses (CRLs). The use of these lenses is expected to open many new experimental possibilities widely used at other synchrotron sources.

Tiwari, M. K.; Lodha, G. S.

2011-07-01

161

Narrow-beam x-ray tests of CCD edge response.  

SciTech Connect

The physical boundaries of a fully-depleted charged-coupled device (CCD) can lead to distorted field lines and non-uniform response. We study this response with a beam of X-rays constrained to a width of less than one pixel, and a system to map the CCD response as a function of transverse position.

Kuhlmann, S.; Spinka, H.; Bernstein, J. P.; Beyer, K. A.; Gades, L.; Kasprzyk, T. E.; Miceli, A.; Spence, R. A.; Talaga, R. (High Energy Physics); ( XSD)

2011-04-01

162

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

SciTech Connect

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

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

1985-01-01

163

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

164

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

Microsoft Academic Search

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

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

2013-01-01

165

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

166

Recent progress on x-ray and pulsed particle beam sources at the Advanced Laser Light Source (ALLS) facility  

NASA Astrophysics Data System (ADS)

The 200TW laser system, (Ti:Sapphire CPA system) delivering 5J in 25fs pulse with a 10Hz repetition rate and a contrast ratio of 1:10^-11 at the fundamental 800nm frequency, is used at the Advanced Laser Light Source (ALLS) facility to develop new generation of x-ray and pulsed particle beam sources (electrons, protons, neutrons). Experimental results on the betatron emission and electron emission from high intensity (<10^19 W/cm2) interactions with gas jet targets (1cm long supersonic nozzle) and on proton generation during high intensity (10^20 W/cm2) laser interaction with thin foil (10nm) and thick (several µm) targets will be presented and discussed. With gas jet targets, very high-resolution single shot phase contrast imaging with 10-20 keV X-rays has been demonstrated, and electrons are currently generated in the GeV range. X-ray source characterization will be presented. With foil targets, the target expansion has been measured on both sides of the target as well as proton generation (15 MeV range) at these relativistic intensities with various diagnostics (folding wave interferometer, time of flight, Thomson parabola...) We will describe the progresses we are doing to move from the laboratory experiments system to the application levels with integrated systems and compact light sources, with a special emphasis on medical applications. We are exploring the use of these high power lasers as a basic tool to image in real time with X-rays (betatron emission) tumors during their irradiation by protons (accelerated by the same laser). + funded by NSERC, CIPI, CFI, FQRNT, MDEIE, INRS, CRC program.

Gnedyuk, S.; Fourmaux, S.; Payeur, S.; Lassonde, P.; MacLean, J. P.; Tchervenkov, C.; Glesser, M.; Marceau, V.; Piché, M.; Fuchs, J.; Krol, A.; Kieffer, J. C.

2012-10-01

167

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

Microsoft Academic Search

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

D J Crotty; R L McKinley; M P Tornai

2007-01-01

168

X-ray spectra of Hercules X-1. 2: Intrinsic beam  

NASA Technical Reports Server (NTRS)

The X-ray spectrum of Hercules X-1 was observed in the energy range 2-24 keV with sufficient temporal resolution to allow detailed study of spectral correlations with the 1.24 sec pulse phase. A region of spectral hardening which extends over approximately the 1/10 pulse phase may be associated with the underlying beam. The pulse shape stability and its asymmetry relative to this intrinsic beam are discussed.

Pravdo, S. H.; Boldt, E. A.; Holt, S. S.; Serlemitsos, P. J.

1977-01-01

169

Study of a new portable x-ray source with micro-beam  

NASA Astrophysics Data System (ADS)

A novel X-ray source with micro-beam has been studied in theory and experiment. The source is composed of three portions: LaB 6 crystal cathode electron gun emitting system, electrostatic focusing system, and permutable metal target system. The electronic current emitted by the electron-gun are controlled by modulating cathode temperature and Wehnelt grid voltage and ratio D w/H, two-equal-radius-cylinder-electrodes focusing system concentrates electron beam, the X-ray photons are irradiated by high energy electron beam bombarding the metal target. The new x-ray source's general-purpose capabilities such as continuous radiation and pulse radiation, focus size and luminance, are also tested. When the temperature of LaB6 cathode is about 1900K and partial pressures being kept below 10 -7 torr, the minimal focus diameter is merely about 10 microns. The new micro focus x-ray source has other lots of advantages such as economy, safety and facility.

Wang, Kaige; Li, Ji; Yang, Qinlao; Guo, Jinchuan; Guo, Baoping; Kuo, Xiaomei; Zhou, Junlan; Niu, Hanben

2006-02-01

170

Thermal Acoustic Sensor for High Pulse Energy X-ray FEL Beams  

SciTech Connect

The pulse energy density of X-ray FELs will saturate or destroy conventional X-ray diagnostics, and the use of large beam attenuation will result in a beam that is dominated by harmonics. We present preliminary results at the LCLS from a pulse energy detector based on the thermal acoustic effect. In this type of detector an X-ray resistant material (boron carbide in this system) intercepts the beam. The pulse heating of the target material produces an acoustic pulse that can be detected with high frequency microphones to produce a signal that is linear in the absorbed energy. The thermal acoustic detector is designed to provide first- and second-order calorimetric measurement of X-ray FEL pulse energy. The first-order calorimetry is a direct temperature measurement of a target designed to absorb all or most of the FEL pulse power with minimal heat leak. The second-order measurement detects the vibration caused by the rapid thermoelastic expansion of the target material each time it absorbs a photon pulse. Both the temperature change and the amplitude of the acoustic signal are directly related to the photon pulse energy.

Smith, T.J.; Frisch, J.C.; Kraft, E.M.; Loos, J.; /SLAC; Bentsen, G.S.; /Rochester U.

2011-12-13

171

Low-exposure scanning-beam x-ray fluoroscopy system  

NASA Astrophysics Data System (ADS)

A prototype scanning-beam digital x-ray system for cardiac fluoroscopy has been constructed. Source-to-detector distance is 94 cm with the subject positioned near the source. The 4-kW source operates at 70-110 kVp and has an electromagnetically-scanned 25-cm-diameter transmission target. The target is at ground potential and is directly liquid cooled for continuous full-power operation. The source collimator has 22,000 holes whose axes are aligned with the center of the detector array. Beam divergence through the 0.38-mm-diameter collimator holes is matched to the 1.8-cm diameter of the detector array. The detector is a 96- element scintillator array optically coupled to a 96-channel photomultiplier tube. A narrow (0.6 degree half-angle) x-ray beam scans the 19-cm-diameter field of view at 30 frames/sec. A two-dimensional shift-and-add reconstruction algorithm produces a narrow-angle classical tomographic view of the subject in real time. The small detector area and large patient- detector distance result in negligible detected x-ray scatter. Signal-to-noise ratio is calculated to be equal to conventional fluoroscopic systems with ten times less patient skin exposure and better than four times less patient integral dose. Exposure reduction is due to the elimination of x-ray scatter and the anti-scatter grid, increased detector DQE, and geometric considerations.

Solomon, Edward G.; Van Lysel, Michael S.; Melen, Robert E.; Moorman, Jack W.; Skillicorn, Brian

1996-04-01

172

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

173

Mapping the continuous reciprocal space intensity distribution of X-ray serial crystallography.  

PubMed

Serial crystallography using X-ray free-electron lasers enables the collection of tens of thousands of measurements from an equal number of individual crystals, each of which can be smaller than 1 µm in size. This manuscript describes an alternative way of handling diffraction data recorded by serial femtosecond crystallography, by mapping the diffracted intensities into three-dimensional reciprocal space rather than integrating each image in two dimensions as in the classical approach. We call this procedure 'three-dimensional merging'. This procedure retains information about asymmetry in Bragg peaks and diffracted intensities between Bragg spots. This intensity distribution can be used to extract reflection intensities for structure determination and opens up novel avenues for post-refinement, while observed intensity between Bragg peaks and peak asymmetry are of potential use in novel direct phasing strategies. PMID:24914160

Yefanov, Oleksandr; Gati, Cornelius; Bourenkov, Gleb; Kirian, Richard A; White, Thomas A; Spence, John C H; Chapman, Henry N; Barty, Anton

2014-07-17

174

Mapping the continuous reciprocal space intensity distribution of X-ray serial crystallography  

PubMed Central

Serial crystallography using X-ray free-electron lasers enables the collection of tens of thousands of measurements from an equal number of individual crystals, each of which can be smaller than 1 µm in size. This manuscript describes an alternative way of handling diffraction data recorded by serial femtosecond crystallography, by mapping the diffracted intensities into three-dimensional reciprocal space rather than integrating each image in two dimensions as in the classical approach. We call this procedure ‘three-dimensional merging’. This procedure retains information about asymmetry in Bragg peaks and diffracted intensities between Bragg spots. This intensity distribution can be used to extract reflection intensities for structure determination and opens up novel avenues for post-refinement, while observed intensity between Bragg peaks and peak asymmetry are of potential use in novel direct phasing strategies. PMID:24914160

Yefanov, Oleksandr; Gati, Cornelius; Bourenkov, Gleb; Kirian, Richard A.; White, Thomas A.; Spence, John C. H.; Chapman, Henry N.; Barty, Anton

2014-01-01

175

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

176

Scanning-beam digital x-ray (SBDX) technology for interventional and diagnostic cardiac angiography  

SciTech Connect

The scanning-beam digital x-ray (SBDX) system is designed for x-ray dose reduction in cardiac angiographic applications. Scatter reduction, efficient detection of primary x-rays, and an inverse beam geometry are the main components of the entrance dose reduction strategy. This paper reports the construction of an SBDX prototype, image reconstruction techniques, and measurements of spatial resolution and x-ray output. The x-ray source has a focal spot that is electronically scanned across a large-area transmission target. A multihole collimator beyond the target defines a series of x-ray beams directed at a distant small-area detector array. The prototype has a 23 cmx23 cm target, 100x100 focal spot positions, and a 5 cmx5 cm CdTe detector positioned 150 cm from the target. With this nonmechanical method of beam scanning, patient images with low detected scatter are generated at up to 30 frame/s. SBDX data acquisition is tomosynthetic. The prototype simultaneously reconstructs 16 planes spaced throughout the cardiac volume using shift-and-add backprojection. Image frames analogous to conventional projection images are generated with a multiplane compositing algorithm. Single-plane versus multiplane reconstruction of contrast-filled coronary arteries is demonstrated with images of the porcine heart. Phantom and porcine imaging studies show multiplane reconstruction is practicable under clinically realistic levels of patient attenuation and cardiac motion. The modulation transfer function for an in-plane slit at mechanical isocenter measured 0.41-0.56 at 1 cycle/mm, depending on the detector element to image pixel interpolation technique. Modeling indicates that desired gains in spatial resolution are achievable by halving the detector element width. The x-ray exposure rate 15 cm below isocenter, without table or patient in the beam, measured 11.5 R/min at 120 kVp, 24.3 kWp and 3.42 R/min at 70 kVp, 14.2 kWp.

Speidel, Michael A.; Wilfley, Brian P.; Star-Lack, Josh M.; Heanue, Joseph A.; Van Lysel, Michael S. [Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); NexRay, Inc., Los Gatos, California 95030 (United States); Department of Medicine and Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin 53792 (United States)

2006-08-15

177

The dosimetry of eye shields for kilovoltage X-ray beams.  

PubMed

The objective of this work was to evaluate the dosimetry of tungsten eye shields for use with kilovoltage X-ray beam treatments. The eye shields, originally designed for megavoltage electron beams, were made of 2 mm tungsten thickness and inside diameters of 11.6 and 15.0 mm with optional aluminium caps of 0.5 and 1 mm thickness. The relative dosimetry of the eye shields were examined by measurement of transmission doses with full scatter conditions, central axis depth doses and beam profiles underneath the eye shield. The X-ray beams used in this study ranged in energy from 50 to 280 kVp. Transmission measurements were performed using an Advanced Markus ionisation chamber located at the surface of an RMI457 Solid Water phantom with a 3 cm diameter applicator flush against the phantom surface. Depth doses and profiles measurements were performed in a PTW MP3 scanning water tank with a PTW diamond detector. Results for transmission doses for the medium size eye shield increased from 1 to 22 % for 50-280 kVp while for the smaller eye shield the percentage dose increased from 3.5 to 30 % for the same energy range. There were minimal differences between using the 0.5 and 1 mm aluminium caps. Central axis depth doses measured with and without the eye shields demonstrated the 125 and 180 kVp beams had higher peak doses behind the eye shields. These results show that these tungsten eye shields are suitable for use with kilovoltage X-ray beams. However, the clinical impact needs to be considered for the higher X-ray beam energies. PMID:23192598

Wang, D; Sobolewski, M; Hill, R

2012-12-01

178

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

179

Intensive X-ray and Radio Monitoring of the Sgr A*/G2 Interaction  

NASA Astrophysics Data System (ADS)

The recent discovery of a dense, cold gas cloud (dubbed “G2”) approaching the supermassive black hole at our Galactic Center (Sgr A*) offers an unprecedented opportunity to test models of black hole accretion and its associated feedback. G2's orbit is eccentric and the cloud already shows signs of tidal disruption by the black hole. High-energy emission from the Sgr A*/G2 encounter will likely rise toward pericenter (Spring 2014) and continue over the next several years as the material circularizes. This encounter may also enhance Sgr A*'s flare activity across the electromagnetic spectrum. I will present intensive multiwavelength campaigns (with an emphasis on X-ray and radio) aimed at studying the radiation properties of Sgr A* as G2 breaks up and feeds the accretion flow, to constrain the rates and emission mechanisms of faint X-ray flares, and to detect G2 itself as it is shocked and heated. This work is supported by Chandra X-ray Observatory Awards GO3-14121X and GO3-14099X and Swift Proposal Number 9120132.

Haggard, Daryl

180

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

181

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

NASA Astrophysics Data System (ADS)

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 (>1 eV ), an energy density greater than 104 J /cm3 , 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.

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

2014-11-01

182

Reproducible radiation-damage processes in proteins irradiated by intense x-ray pulses  

NASA Astrophysics Data System (ADS)

X-ray free-electron lasers have enabled femtosecond protein nanocrystallography, a novel method to determine the structure of proteins. It allows time-resolved imaging of nanocrystals that are too small for conventional crystallography. The short pulse duration helps in overcoming the detrimental effects of radiation damage because x rays are scattered before the sample has been significantly altered. It has been suggested that, fortuitously, the diffraction process self-terminates abruptly once radiation damage destroys the crystalline order. Our calculations show that high-intensity x-ray pulses indeed trigger a cascade of damage processes in ferredoxin crystals, a particular metalloprotein of interest. However, we found that the damage process is initially not completely random. Correlations exist among the protein monomers, so that Bragg diffraction still occurs in the damaged crystals, despite significant atomic displacements. Our results show that the damage process is reproducible to a certain degree, which is potentially beneficial for the orientation step in single-molecule imaging.

Hau-Riege, Stefan P.; Bennion, Brian J.

2015-02-01

183

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

184

Resonant Auger Decay of Molecules in Intense X-Ray Laser Fields: Light-Induced Strong Nonadiabatic Effects  

SciTech Connect

The resonant Auger process is studied in intense x-ray laser fields. It is shown that the dressing of the initial and decaying states by the field leads to coupled complex potential surfaces which, even for diatomic molecules, possess intersections at which the nonadiabatic couplings are singular. HCl is studied as an explicit showcase example. The exact results differ qualitatively from those without rotations. A wealth of nonadiabatic phenomena is expected in decay processes in intense x-ray fields.

Cederbaum, Lorenz S.; Chiang, Ying-Chih; Demekhin, Philipp V. [Theoretische Chemie, Universitaet Heidelberg, Im Neuenheimer Feld 229, 69120 Heidelberg (Germany); Moiseyev, Nimrod [Schulich Faculty of Chemistry and Minerva Center, Technion--Israel Institute of Technology, Haifa 32000 (Israel)

2011-03-25

185

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

186

Optimal X-ray imaging geometry for flat-panel cone-beam computed tomography [prostate radiotherapy application  

Microsoft Academic Search

A theoretical method for identifying optimal X-ray imaging geometry is presented and applied to cone-beam CT (CBCT) using a flat-panel imager (FPI). The method includes the effects of X-ray source distribution, imaging task, X-ray scatter, and detective quantum efficiency (DQE) on the ICRU-recommended figure of merit for image quality-detectability index. Cascaded systems analysis for FPIs is extended to incorporate the

Jeffrey H. Siewerdsen; David A. Jaffray

2000-01-01

187

Performance of X-ray Beam lines at Superconducting Wavelength Shifter  

SciTech Connect

To fully utilize a hard X-ray source generated by a 5-Tesla superconducting wavelength shifter (SWLS) that shifts the critical energy of synchrotron spectrum from 2.1 to 7.5 keV, we have designed and constructed three hard X-ray beamlines, BL01A, BL01B, and BL0IC. BL01A is a white light beamline for phase-contrast X-ray image applications. The spatial resolution of phase-contrast X-ray image is 1 {mu}m. The photon flux can saturate a camera of 700-microns field-of-view within 10 ms. BL01B equipped with a double crystal monochromator (DCM) and a toroidal focusing mirror, which provides photon beams with energies from 5 to 20 keV, is adequate for scattering related experiments and hard X-ray microscopy. The energy-resolution {delta}E/E is 1 x 10-3. The photon flux is optimized to be 4.5 x 1011 photons s-1 with 200 mA ring current, which outcasts the flux of the wiggler beamline BL17B by 110 times at 15 keV. BL01C equipped with a DCM and both collimating and focusing mirrors, covering photon energies from 6 to 33 keV, is ideal for EXAFS and X-ray diffraction (XRD) experiments. The average photon flux is 3 x 1010 photons s-1 with 200 mA ring current. The energy-resolution is between 1.7 x 10-4 and 3.0 x 10-4. In this article, we will present the measured performance of these beamlines.

Song, Y. F.; Chang, C. H.; Liu, C. Y.; Chang, S. H.; Jeng, U.; Lai, Y. H.; Liu, D. G.; Yin, G. C.; Lee, J. F.; Sheu, H. S.; Chung, S. C.; Tsang, K. L.; Liang, K. S. [National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan (China); Hwu, Y. [Institute of Physics, Academia Sinica, Taipei 11529, Taiwan (China)

2007-01-19

188

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

189

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

190

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

NASA Astrophysics Data System (ADS)

A novel electron beam focusing scheme for medical X-ray sources is described in this paper. Most vacuum based medical X-ray sources today employ a tungsten filament operated in temperature limited regime, with electrostatic focusing tabs for limited range beam optics. This paper presents the electron beam optics designed for the first distributed X-ray source in the world for Computed Tomography (CT) applications. This distributed source includes 32 electron beamlets in a common vacuum chamber, with 32 circular dispenser cathodes operated in space charge limited regime, where the initial circular beam is transformed into an elliptical beam before being collected at the anode. The electron beam optics designed and validated here are at the heart of the first Inverse Geometry CT system, with potential benefits in terms of improved image quality and dramatic X-ray dose reduction for the patient.

Bogdan Neculaes, V.; Zou, Yun; Zavodszky, Peter; Inzinna, Louis; Zhang, Xi; Conway, Kenneth; Caiafa, Antonio; Frutschy, Kristopher; Waters, William; De Man, Bruno

2014-05-01

191

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

192

Measurement of the dose deposition characteristics of x-ray fluoroscopy beams in water.  

PubMed

The purpose of this study was to characterize the x-ray dose distribution of fluoroscopy beams by measuring their percent depth dose curves and lateral dose profiles in a water phantom. Percent depth dose curves were measured near the surface with an Attix parallel plate chamber and deep within the water phantom with a Farmer-type cylindrical chamber. Percent depth dose curves were compared to published data where applicable. Lateral dose profiles were measured at depths of 2, 5, 10, and 15 cm in phantom with a Farmer chamber. Pulsed, 50 mA x-ray beams with peak tube potentials of 60, 80, 100, and 120 kV and half value layers of 1.89, 2.52, 3.20, and 4.09 mm Al, respectively, were investigated. PMID:11243345

Fetterly, K A; Gerbi, B J; Alaei, P; Geise, R A

2001-02-01

193

Ion beam lithography for Fresnel zone plates in X-ray microscopy.  

PubMed

Fresnel Zone Plates (FZP) are to date very successful focusing optics for X-rays. Established methods of fabrication are rather complex and based on electron beam lithography (EBL). Here, we show that ion beam lithography (IBL) may advantageously simplify their preparation. A FZP operable from the extreme UV to the limit of the hard X-ray was prepared and tested from 450 eV to 1500 eV. The trapezoidal profile of the FZP favorably activates its 2nd order focus. The FZP with an outermost zone width of 100 nm allows the visualization of features down to 61, 31 and 21 nm in the 1st, 2nd and 3rd order focus respectively. Measured efficiencies in the 1st and 2nd order of diffraction reach the theoretical predictions. PMID:23736396

Keskinbora, Kahraman; Grévent, Corinne; Bechtel, Michael; Weigand, Markus; Goering, Eberhard; Nadzeyka, Achim; Peto, Lloyd; Rehbein, Stefan; Schneider, Gerd; Follath, Rolf; Vila-Comamala, Joan; Yan, Hanfei; Schütz, Gisela

2013-05-20

194

An X-ray calibration facility with a dynamical pencil beam for the post-Astro-E2 telescopes  

NASA Astrophysics Data System (ADS)

We report a new calibration system for large size X-ray optics at ISAS. We adapted a 'dynamical' pencil beam collimated from an X-ray generator, the maximum voltage for which is 50 kV. By combining two stage systems for the X-ray generator and a collimator, the pencil beam dynamically sweeps across a circular region of a telescope with the radius of 60 cm at maximum. In this case, the X-ray telescope and the focal plane detector are both statically fixed. A 4.4~m long rail for detector stage and two positions of the telescope stage provide focal lengths from 4.5 to 12 m, while the previous system can accommodate 4.5 or 4.75 m focal length. The preliminary performance of this system is summarized in this paper. For the post-Astro-EII satellite, a hard X-ray multi-layer supermirror with an unprecedented sensitivity up to 80~keV is strongly expected. This beam facility is of importance because the hard X-ray mirrors always require a long focal length of 8-12 m due to the small reflection angle (about 0.3 degree). Focal length and diameter of future telescopes are always decided by the boundary conditions of the mission at the last moment of the design freeze. Our new X-ray beam facility is designed to match with any kind of X-ray telescope parameters.

Maeda, Yoshitomo; Itoh, Akiharu; Itoh, Kei; Kunieda, Hideyo; Haba, Yoshito; Hayakawa, Akira; Iizuka, Ryo; Inoue, Chiaki; Ishida, Manabu; Misaki, Kazutami; Mori, Hideyuki; Shibata, Ryo

2003-03-01

195

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

196

Measurements of dose distributions in small beams of 6 MV X-rays  

Microsoft Academic Search

Dose distributions produced by small circular beams of 6 MV X-rays have been measured using ionisation chambers of small active volume. Specific quantities measured include tissue maximum ratios (TMR), total scatter correction factors (St), collimator scatter correction factors (Sc) and off-axis ratios (OAR). Field sizes ranged from 12.5 to 30 mm diameter, and were defined by machined auxiliary collimators with

R. K. Rice; J. J. Hansen; G. K. Svensson; R. L. Siddon

1987-01-01

197

Functional characterization of planar sensors with active edges using laser and X-ray beam scans  

NASA Astrophysics Data System (ADS)

We report on the functional characterization of planar sensors with active edges fabricated at Fondazione Bruno Kessler (FBK), Trento, Italy. The measurements here reported were performed by means of laser and X-ray beam scans mainly focusing on the signal efficiency of the edge region of the devices. Results are very encouraging and show very good sensitivity up to few microns away from the device physical edge.

Povoli, M.; Bagolini, A.; Boscardin, M.; Dalla Betta, G.-F.; Giacomini, G.; Hasi, J.; Oh, A.; Zorzi, N.

2013-08-01

198

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

SciTech Connect

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

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

2012-06-15

199

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

200

Scanning-beam digital x-ray (SBDX) system for cardiac angiography  

NASA Astrophysics Data System (ADS)

An advanced Scanning-Beam Digital X-ray (SBDX) system for cardiac angiography has been constructed. The 15-kW source operates at 70 - 120 kVp and has an electron beam that is electromagnetically scanned across a 23-cm X 23-cm transmission target. The target is directly liquid cooled for continuous full-power operation and is located behind a focused source collimator. The collimator is a rectangular grid of 100 X 100 apertures whose axes are aligned with the center of the detector array. X-ray beam divergence through the collimator apertures is matched to the 5.4-cm X 5.4 cm detector, which is 150 cm from the source. The detector is a 48 X 48 element CdZnTe direct-conversion photon-counting detector. A narrow x-ray beam scans the full field of view at up to 30 frames per second. A custom digital processor simultaneously reconstructs sixteen 1,0002 pixel tomographic images in real time. The slices are spaced 1.2 cm apart and cover the entire cardiac anatomy. The small detector area and large patient-detector distance result in negligible detected x-ray scatter. Image signal-to-noise ratio is calculated to be equal to conventional fluoroscopic systems at only 12% of the patient exposure and 25% of the staff exposure. Exposure reduction is achieved by elimination of detected scatter, elimination of the anti-scatter grid, increased detector DQE, and increased patient entrance area.

Solomon, Edward G.; Wilfley, Brian P.; Van Lysel, Michael S.; Joseph, Aaron W.; Heanue, Joseph A.

1999-05-01

201

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

NASA Astrophysics Data System (ADS)

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.

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

2015-02-01

202

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

203

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

204

Common features of particle beams and x-rays generated in a low energy dense plasma focus device  

NASA Astrophysics Data System (ADS)

Features of energetic charged particle beams and x-ray emission in a low energy (1-2 kJ) plasma focus (DPF) device are described and the possible mechanism are explained based on circuit analyses and energy balance in the DPF system. In particular, the resistance and the voltage across the plasma column are estimated to explain the mechanisms of the generation of particle beams and hard x-ray. The analysis shows that the total inductance of a DPF might have played a role for enhancement of the particle beams and x-ray emissions during the phase of anomalous resistance.

Behbahani, R. A.; Xiao, C.

2015-02-01

205

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

NASA Astrophysics Data System (ADS)

The electron beam emitted from the back of Plasma Focus devices is being studied as a radiation source for intraoperative radiation therapy applications. A Plasma Focus device is being developed to this aim, to be utilized as an x-ray source. The electron beam is driven to impinge on 50 ?m brass foil, where conversion x-rays are generated. Measurements with gafchromic film are performed to analyse the attenuation of the x-rays beam and to predict the dose given to the culture cell in radiobiological experiments to follow.

Ceccolini, E.; Rocchi, F.; Mostacci, D.; Sumini, M.; Tartari, A.; Mariotti, F.

2012-09-01

206

Structure in defocused beams of x-ray mirrors: causes and possible solutions  

NASA Astrophysics Data System (ADS)

Grazing incidence mirrors are now a standard optic for focusing X-ray beams. Both bimorph and mechanically bendable mirrors are widely used at Diamond Light Source because they permit a wide choice of focal lengths. They can also be deliberately set out of focus to enlarge the X-ray beam, and indeed many beamline teams now wish to generate uniform beam spots of variable size. However, progress has been slowed by the appearance of fine structure in these defocused beams. Measurements showing the relationship between the medium-frequency polishing error and this structure over a variety of beam sizes will be presented. A theoretical model for the simulations of defocused beams from general mirrors will then be developed. Not only the figure error and its first derivative the slope error, but also the second derivative, the curvature error, must be considered. In conclusion, possible ways to reduce the defocused beam structure by varying the actuators' configuration and settings will be discussed.

Sutter, John P.; Alcock, Simon G.; Rust, Fiona; Wang, Hongchang; Sawhney, Kawal

2014-09-01

207

Optical and x-ray imaging of electron beams using synchrotron emission  

SciTech Connect

In the case of very low eniittance electron and positron storage ring beams, it is impossible to make intrusive measurements of beam properties without increasing the emittance and possibly disrupting the beam. In cases where electron or positron beams have high average power densities (such as free electron laser linacs), intrusive probes such as wires and optical transition radiation screens or Cherenkov emitting screens can be easily damaged or destroyed. The optical and x-ray emissions from the bends in the storage rings and often from linac bending magnets can be used to image the beam profile to obtain emittance information about the beam. The techniques, advantages and limitations of using both optical and x-ray synchrotron emission to measure beam properties are discussed and the possibility of single bunch imaging is considered. The properties of suitable imagers and converters such as phosphors are described. Examples of previous, existing and planned applications are given where available, including a pinhole imaging system currently being designed for the Advanced Photon Source at Argonne National Laboratory.

Wilke, M.D.

1994-12-01

208

EDITORIAL: Intense X-ray science: the first 5 years of FLASH Intense X-ray science: the first 5 years of FLASH  

NASA Astrophysics Data System (ADS)

The Free electron LASer in Hamburg, FLASH at DESY, is the first user facility which has, over the last five years, delivered short (10-50 fs) and intense (up to 1016 W cm-2 peak intensity) light pulses. How big this technological progress really is becomes clear when one realizes that this light source is nine orders of magnitude more brilliant than state-of-the-art third-generation light sources. How does matter behave when illuminated with such pulses? What are the fundamental mechanisms and phenomena? Clearly, this was virgin territory five years ago. The present compilation of results from FLASH is by no means complete but is intended to provide an overview of different types of pioneering experiments, including the highlights and surprises. The contributing authors have explored questions and used targets ranging from physics (condensed matter, plasmas, clusters, atoms and molecules) over chemistry (the quest for the time- and space-resolved visualization of chemical reactions) to biology, driven by the vision of realizing single-shot coherent diffractive imaging of individual species. The goal of tracing structural changes as a function of time and, thus, uncovering the functioning of matter is, in fact, common to all participating disciplines. This extends to the hope, nurtured by upcoming x-ray FELs, to be able to image in the future, nanostructures, large molecules, viruses, cells, etc, on atomic length and time scales, i.e. with Angstrom spatial and attosecond temporal resolution. The articles are kept at a tutorial level in order to be accessible for the non-specialist, with references to original published work for in-depth information. In addition, two articles by Jochen Schneider and Josef Feldhaus describe, respectively, the making of this remarkable new light source and its characteristics and possibilities. We thank all the authors for their contributions and hope that you will enjoy reading them!

Chapman, H.; Ullrich, J.; Rost, J. M.

2010-10-01

209

Ultra hard x rays from krypton clusters heated by intense laser fields R. C. Issac,a)  

E-print Network

Ultra hard x rays from krypton clusters heated by intense laser fields R. C. Issac,a) G. Vieux, B of ultrashort laser pulses with krypton clusters at intensity up to 1.3 1018 Wcm 2 has been investigated. Intense K and K emission from krypton at 12.66 and 14.1 keV, respectively, has been observed using

Strathclyde, University of

210

Model-based inspection of multipackage food products using a twin-beam x-ray system  

NASA Astrophysics Data System (ADS)

A twin-orthogonal-fanbeam x-ray system has been built as part of a six-partner project funded by the Commission of the European Union. The images created by this system represent plan and side views of the object to be inspected. Using such a system, it is possible to locate a point-like feature that creates a significant shadow in both beams, in a 3D space. However, the real value of such a system lies in the fact that it is often possible to see a foreign body, such as a small piece of loose glass, within a jar using one beam, when the same contaminant is invisible to the other beam. Such a situation typically arises when the foreign body is obscured by the x-ray shadow of the neck-shoulder region of a jar. The x-ray system built by our colleagues in this consortium is being used to examine, simultaneously, six jars of semi-fluid savory sauce, held together by shrink-wrapping on a cardboard tray. The inspection algorithm consists of fitting multi-part models of the image intensity function to both the plan and side-view images. Once a model has been fitted, it is possible to use image comparison, in order to highlight any foreign bodies. The pre-processed plan and side-view images are analyzed and correlated together, so that in many cases, a foreign body whose view is obscured in one image can be detected in the other.

Palmer, Stephen C.; Batchelor, Bruce G.

1998-10-01

211

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

Microsoft Academic Search

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

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

1995-01-01

212

Measurements of an optimized beam for x-ray computed mammotomography  

NASA Astrophysics Data System (ADS)

Simulation results from previous studies indicate that a quasi-monochromatic x-ray beam can be produced using a newly developed beam filtration technique. This technique utilizes heavy filtration with novel high Z filter materials having k-edges just above those of CsI, producing a near monochromatic beam with mean energy optimized for detection. The value of a near monochromatic x-ray source for a fully 3D tomography application is the expected improved ability to separate tissues with very small differences in attenuation coefficients for a range of uncompressed breast sizes while maintaining dose levels at or below existing dual view mammography. In this study, we experimentally investigate a set of filter materials (Al, Cu, Ag, Ce, W, and Pb), filter thicknesses (10th, 100th, and 200th VL), and tube potentials (40-80 kVp) using a newly constructed test apparatus. Initial experimental results corroborate simulations and indicate that this approach can improve image quality (SNR) at constant dose. Al, Cu, W, and Pb provide optimal exposure efficiency results at 60 kVp and above. Decreasing relative improvements are observed above 100th VL filter thickness at 78 cm SID. Results are obtained without significant tube heating (except at 40 kVp). In addition, simulations indicate significant reductions in beam hardening. This optimized beam will be incorporated into a novel cone-beam x-ray computed mammotomography sub-system together with an emission tomograph in a dual modality CT/SPECT application specific emission and transmission tomography system for fully 3D uncompressed breast imaging.

McKinley, Randolph L.; Samei, Ehsan; Brzymialkiewicz, Caryl N.; Tornai, Martin P.; Floyd, Carey E., Jr.

2004-05-01

213

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

214

Controlling X-ray beam trajectory with a flexible hollow glass fibre  

PubMed Central

A metre-length flexible hollow glass fibre with 20?µm-bore and 1.5?mm-cladding diameters for transporting a synchrotron X-ray beam and controlling the trajectory has been examined. The large cladding diameter maintains a moderate curvature to satisfy the shallow glancing angle of total reflection. The observed transmission efficiency was more than 20% at 12.4?keV. As a demonstration, a wide-area scan of a synchrotron radiation beam was performed to identify the elements for a fixed metal film through its absorption spectra. PMID:24365917

Tanaka, Yoshihito; Nakatani, Takashi; Onitsuka, Rena; Sawada, Kei; Takahashi, Isao

2014-01-01

215

Experimental characterization of X-ray transverse coherence in the presence of beam transport optics  

NASA Astrophysics Data System (ADS)

A simple Boron fiber based interference scheme [1] and other similar schemes are currently routinely used for X-ray coherence estimation at 3rd generation synchrotron radiation sources. If such a scheme is applied after a perfect monochromator and without any focusing / transport optics in the optical path, the interpretation of the measured interference pattern is relatively straightforward and can be done in terms of the basic parameters of the source [2]. However, if the interference scheme is used after some focusing optics, e.g. close to the X-ray beam waist, the visibility of fringes can be significantly affected by the new shape of the focused beam phase-space. At the same time, optical element imperfections still have a negative impact on the transverse coherence. In such situations, which are frequently encountered in experiments at beamlines, the quantitative interpretation of a measured interference pattern is not straightforward. Here we show that this can nevertheless be done by using partially-coherent synchrotron radiation wavefront propagation simulations. The results obtained from measurements, performed at the 32-ID undulator beamline of the Advanced Photon Source, and wavefront propagation based simulations show, in particular, that new generation 1D Beryllium Compound Refractive Lenses [3, 4] do not reduce the X-ray transverse coherence in any significant manner.

Chubar, O.; Fluerasu, A.; Chu, Y. S.; Berman, L.; Wiegart, L.; Lee, W.-K.; Baltser, J.

2013-03-01

216

Heat transfer issues in high-heat-load synchrotron x-ray beams  

SciTech Connect

In this paper, a short description of the synchrotron radiation x-ray sources and the associated power loads is given, followed by a brief description of typical synchrotron components and their heat load. It is emphasized that the design goals for most of these components is to limit (a) temperature, (b) stresses, or (c) strains in the system. Each design calls for a different geometry, material selection, and cooling scheme. Cooling schemes that have been utilized so far are primarily single phase and include simple macrochannel cooling, microchannel cooling, contact cooling, pin-post cooling, porous-flow cooling, jet cooling, etc. Water, liquid metals, and various cryogenic coolants have been used. Because the trend in x-ray beam development is towards brighter (i.e., more powerful) beams and assuming that no radical changes in the design of x-ray generating machines occurs in the next few years, it is fair to state that the utilization of various effective cooling schemes and, in particular, two-phase flow (e.g., subcooled boiling) warrants further investigation. This, however, requires a thorough examination of stability and reliability of two-phase flows for high-heat-flux components operating in ultrahigh vacuum with stringent reliability requirements.

Khounsary, A.M.; Mills, D.M.

1994-09-01

217

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

218

Point spread function measurement of an X-ray beam focused by a multilayer zone plate with narrow annular aperture.  

PubMed

The experimental procedure for obtaining the point spread function (PSF) of a focusing beam generated using an X-ray multilayer zone plate (MZP) with a narrow annular aperture has been developed. It was possible to reconstruct the PSF by applying the tomographic process to the measured dataset consisting of line spread functions (LSFs) in every radial direction on the focal plane. The LSFs were measured by a knife-edge scanning method of detecting scattered intensity. In the experimental work, quasi-monochromatic undulator radiation with a first harmonic energy of 20?keV was directly focused without a monochromator by the MZP, and the PSF was measured using this procedure. As a result, a near diffraction-limited focused beam size of 46?nm full width at half-maximum was obtained. PMID:24562567

Takano, Hidekazu; Konishi, Shigeki; Koyama, Takahisa; Tsusaka, Yoshiyuki; Ichimaru, Satoshi; Ohchi, Tadayuki; Takenaka, Hisataka; Kagoshima, Yasushi

2014-03-01

219

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

SciTech Connect

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

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

2002-10-14

220

Model independent means of categorizing X-ray binaries - I. Colour-colour-intensity diagrams  

NASA Astrophysics Data System (ADS)

The diverse behaviours displayed by X-ray binaries make it difficult to determine the nature of the underlying compact objects. In particular, identification of systems containing black holes is currently considered robust only if a dynamical mass is obtained. We explore a model-independent means of identifying the central bodies - neutron stars or black holes - of accreting binary systems. We find that four categories of object (classic black holes, GRS 1915-like black holes, pulsars and non-pulsing neutron stars) occupy distinct regions in a 3D colour-colour-intensity (CCI) diagram. Assuming that this clustering effect is due to intrinsic properties of the sources (such as mass-accretion rate, binary separation, mass ratio, magnetic field strength, etc.), we suggest possible physical effects that drive each object to its specific location in the CCI phase space. We also suggest a surface in this space which separates systems that produce jets from those which do not, and demonstrate the use of CCI for identifying X-ray pulsars where a period has not been established. This method can also be used to study subclustering within a category and may prove useful for other classes of objects, such as cataclysmic variables and active galactic nuclei.

Vrtilek, Saeqa Dil; Boroson, Bram Seth

2013-02-01

221

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

222

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

223

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

224

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

225

Line intensity enhancements in stellar coronal X-ray spectra due to opacity effects  

NASA Astrophysics Data System (ADS)

Context: The I(15.01 Å)/I(16.78 Å) emission line intensity ratio in Fe xvii has been reported to deviate from its theoretical value in solar and stellar X-ray spectra. This is attributed to opacity in the 15.01 Å line, leading to a reduction in its intensity, and was interpreted in terms of a geometry in which the emitters and absorbers are spatially distinct. Aims: We study the I(15.01 Å)/I(16.78 Å) intensity ratio for the active cool dwarf EV Lac, in both flare and quiescent spectra. Methods: The observations were obtained with the Reflection Grating Spectrometer on the XMM-Newton satellite. The emission measure distribution versus temperature reconstruction technique is used for our analysis. Results: We find that the 15.01 Å line exhibits a significant enhancement in intensity over the optically thin value. To our knowledge, this is the first time that such an enhancement has been detected on such a sound statistical basis. We interpret this enhancement in terms of a geometry in which the emitters and absorbers are not spatially distinct, and where the geometry is such that resonant pumping of the upper level has a greater effect on the observed line intensity than resonant absorption in the line-of-sight.

Rose, S. J.; Matranga, M.; Mathioudakis, M.; Keenan, F. P.; Wark, J. S.

2008-06-01

226

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

227

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

PubMed

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. PMID:25327627

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

2014-11-21

228

Highly enhanced hard x-ray emission from oriented metal nanorod arrays excited by intense femtosecond laser pulses  

SciTech Connect

We report a 43-fold enhancement in the hard x-ray emission (in the 150-300 keV range) from copper nanorod arrays (compared to a polished Cu surface) when excited by 30-fs, 800-nm laser pulses with an intensity of 10{sup 16} W/cm{sup 2}. The temperature of the hot electrons that emit the x rays is 11 times higher. Significantly, the x-ray yield enhancement is found to depend on both the aspect ratio as well as the cluster size of the nanorods. We show that the higher yield arises from enhanced laser absorption owing to the extremely high local electric fields around the nanorod tips. Particle-in-cell plasma simulations reproduce these observations and provide pointers to further optimization of the x-ray emission.

Mondal, Sudipta; Chakraborty, Indrani; Ahmad, Saima; Carvalho, Daniel; Singh, Prashant; Lad, Amit D.; Narayanan, V.; Ayyub, Pushan; Kumar, G. Ravindra; Zheng, J.; Sheng, Z.M. [Tata Institute of Fundamental Research, 1 Homi Bhabha Road, Mumbai 400 005 (India); Key Laboratory for Laser Plasmas of the Ministry of Education of China and Department of Physics, Shanghai Jiao Tong University, Shanghai (China)

2011-01-15

229

Multiphoton dissociation of H2S by intense x-ray pulses from the Linac Coherent Light Source FEL  

NASA Astrophysics Data System (ADS)

We will report on sequential multiphoton ionization of H2S by intense pulses of x-rays from the LCLS free electron laser. Following L-shell excitation, fragmentation of the molecule is observed by Auger electron, photoelectron, and ion time-of-flight spectroscopy. Intensity dependent features in these spectra shed light on the dynamics of the dissociation process.

Murphy, Brendan; Fang, Li; Hoener, Matthias; Kukk, Edwin; Kanter, Elliot; Bozek, John; Berrah, Nora

2011-06-01

230

Coherence properties of focused X-ray beams at high-brilliance synchrotron sources.  

PubMed

An analytical approach describing properties of focused partially coherent X-ray beams is presented. The method is based on the results of statistical optics and gives both the beam size and transverse coherence length at any distance behind an optical element. In particular, here Gaussian Schell-model beams and thin optical elements are considered. Limiting cases of incoherent and fully coherent illumination of the focusing element are discussed. The effect of the beam-defining aperture, typically used in combination with focusing elements at synchrotron sources to improve transverse coherence, is also analyzed in detail. As an example, the coherence properties in the focal region of compound refractive lenses at the PETRA III synchrotron source are analyzed. PMID:24365911

Singer, Andrej; Vartanyants, Ivan A

2014-01-01

231

Coherence properties of focused X-ray beams at high-brilliance synchrotron sources  

PubMed Central

An analytical approach describing properties of focused partially coherent X-ray beams is presented. The method is based on the results of statistical optics and gives both the beam size and transverse coherence length at any distance behind an optical element. In particular, here Gaussian Schell-model beams and thin optical elements are considered. Limiting cases of incoherent and fully coherent illumination of the focusing element are discussed. The effect of the beam-defining aperture, typically used in combination with focusing elements at synchrotron sources to improve transverse coherence, is also analyzed in detail. As an example, the coherence properties in the focal region of compound refractive lenses at the PETRA III synchrotron source are analyzed. PMID:24365911

Singer, Andrej; Vartanyants, Ivan A.

2014-01-01

232

Hard x-ray production from high intensity laser solid interactions  

SciTech Connect

Intense laser (> 10{sup 21} W/cm{sup 2}) driven hard x-ray sources offer a new alternative to conventional electron accelerator bremsstrahlung sources. These laser driven sources offer considerable simplicity in design and cost advantage for multiple axis views and have the potential for much higher spatial and temporal resolution than is achievable with accelerator sources We have begun a series of experiments using the Petawatt Laser system at LLNL to determine the potential of these sources for radiography applications Absolutely calibrated spectra extending to 20 MeV and high resolution radiographs through a {rho}r{>=}150 gm/cm{sup 2} have been obtained The physics of these sources and the scaling relationships and laser technology required to provide the dose levels necessary for radiography applications will be discussed Diagnostics of the laser produced electrons and photons will be addressed

Sefcik, J. A., LLNL

1998-06-03

233

Beam hardening: Analytical considerations of the effective attenuation coefficient of x-ray tomography  

SciTech Connect

Polychromatic x-ray beams traveling though material are prone to beam hardening, i.e., the high energy part of the incident spectrum gets over represented when traveling farther into the material. This study discusses the concept of a mean attenuation coefficient in a formal way. The total energy fluence is one-to-one related to the traveled distance in case of a polychromatic beam moving through a given, inhomogeneous material. On the basis of this one-to-one relation, it is useful to define a mean attenuation coefficient and study its decrease with depth. Our results are based on a novel parametrization of the energy dependence of the attenuation coefficient that allows for closed form evaluation of certain spectral integrals. This approach underpins the ad hoc semianalytical expressions given in the literature. An analytical model for the average attenuation coefficient is proposed that uses a simple fit of the attenuation coefficient as a function of the photon energy as input. It is shown that a simple extension of this model gives a rather good description of beam hardening for x-rays traveling through water.

Alles, J.; Mudde, R. F. [Kramers Laboratorium voor Fysische Technology, Department of Multi-Scale Physics, Delft University of Technology, Pr. Bernhardlaan 6, 2628 Delft (Netherlands)

2007-07-15

234

Algorithm for X-ray Scatter, Beam-Hardening, and Beam Profile Correction in Diagnostic (Kilovoltage) and Treatment (Megavoltage) Cone Beam CT  

Microsoft Academic Search

Quantitative reconstruction of cone beam X-ray computed tomography (CT) datasets requires accurate modeling of scatter, beam-hardening, beam profile, and detector response. Typically, commercial imaging systems use fast empirical corrections that are designed to reduce visible artifacts due to incomplete modeling of the image formation process. In contrast, Monte Carlo (MC) methods are much more accurate but are relatively slow. Scatter

Jonathan S. Maltz; Bijumon Gangadharan; Supratik Bose; Dimitre H. Hristov; Bruce A. Faddegon; Ajay Paidi; Ali R. Bani-Hashemi

2008-01-01

235

Thermometric- and Acoustic-Based Beam Power Monitor for Ultra-Bright X-Rays  

SciTech Connect

A design for an average beam power monitor for ultra-bright X-ray sources is proposed that makes simultaneous use of calorimetry and radiation acoustics. Radiation incident on a solid target will induce heating and ultrasonic vibrations, both of which may be measured to give a fairly precise value of the beam power. The monitor is intended for measuring ultra-bright Free-Electron Laser (FEL) X-ray beams, for which traditional monitoring technologies such as photo-diodes or scintillators are unsuitable. The monitor consists of a Boron Carbide (B{sub 4}C) target designed to absorb most of the incident beam's energy. Resistance temperature detectors (RTD) and piezoelectric actuators are mounted on the outward faces of the target to measure the temperature changes and ultrasonic vibrations induced by the incident beam. The design was tested using an optical pulsed beam (780 nm, 120 and 360 Hz) from a Ti:sapphire oscillator at several energies between 0.8 and 2.6 mJ. The RTDs measured an increase in temperature of about 10 K over a period of several minutes. The piezoelectric sensors recorded ringing acoustic oscillations at 580 {+-} 40 kHz. Most importantly, the amplitude of the acoustic signals was observed to scale linearly with beam power up to 2 mJ of pulse energy. Above this pulse energy, the vibrational signals became nonlinear. Several causes for this nonlinearity are discussed, including amplifier saturation and piezoelectric saturation. Despite this nonlinearity, these measurements demonstrate the feasibility of such a beam power measurement device. The advantage of two distinct measurements (acoustic and thermometric) provides a useful method of calibration that is unavailable to current LCLS diagnostics tools.

Bentsen, Gregory; /Rochester U. /SLAC

2010-08-25

236

Single-component chemically amplified resist materials for electron-beam and x-ray lithography  

NASA Astrophysics Data System (ADS)

Copolymers of 4-tert-butoxycarbonyloxystyrene (TBS) and sulfur dioxide (SO2) have been found to act as sensitive x-ray ((lambda) equals 14 angstrom) and moderately sensitive electron-beam, single component, chemically amplified, aqueous base soluble positive acting resists. The x-ray and electron-beam response of these materials was a function of copolymer composition, where an increase in the sulfur dioxide content enhanced the resist sensitivity. Initial investigation into the radiation induced reaction mechanism provided evidence that acid formation occurs via polymer main chain scission. It is proposed that at the scission sites radical species are produced which in turn are responsible for the formation of the acidic moieties. Heat treatment of resist films after exposure converted the copolymers to poly(4- hydroxystyrene sulfone) and permitted the exposed film areas to be developed in an aqueous base solution. Preliminary lithographic evaluation has resolved 0.5 micrometers line and space patterns in 0.65 micrometers thick 1.75/1 TBS/SO2 resist films using an x-ray dose of 10 mJ/cm2. For a resist having a composition of 2.1/1 TBS/SO2, 0.25 micrometers line and space features where delineated using an electron-beam dose of 90 (mu) C/cm2 at 30 KV. In addition, minimal surface residue of the exposed areas of the resist film after development was observed when the time interval between the exposure and the post-exposure baking steps was varied from 2-10 minutes.

Novembre, Anthony E.; Tai, Woon W.; Kometani, Janet M.; Hanson, James E.; Nalamasu, Omkaram; Taylor, Gary N.; Reichmanis, Elsa; Thompson, Larry F.

1991-06-01

237

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

238

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

239

Probing the Transverse Coherence of an Undulator X-Ray Beam Using Brownian Particles  

SciTech Connect

We present a novel method to map the two-dimensional transverse coherence of an x-ray beam using the dynamical near-field speckles formed by scattering from colloidal particles. Owing to the statistical nature of the method, the coherence properties of synchrotron radiation from an undulator source is obtained with high accuracy. The two-dimensional complex coherence function is determined at the sample position and the imaging optical scheme further allowed us to evaluate the coherence factor at the undulator output despite the aberrations introduced by the focusing optics.

Alaimo, M. D. [Dipartimento di Fisica, Universita di Milano, I-20133 Milano, CNISM (Italy); European Synchrotron Radiation Facility, BP-220, F-38043 Grenoble (France); Potenza, M. A. C.; Manfredda, M.; Giglio, M. [Dipartimento di Fisica, Universita di Milano, I-20133 Milano, CNISM (Italy); Geloni, G. [Deutsches Elektronen-Synchrotron and European XFEL GmbH, D-22607 Hamburg (Germany); Sztucki, M.; Narayanan, T. [European Synchrotron Radiation Facility, BP-220, F-38043 Grenoble (France)

2009-11-06

240

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

241

X-ray cone-beam computed tomography: principles, applications, challenges and solutions  

NASA Astrophysics Data System (ADS)

In the nineties, x-ray computed tomography, commonly referred to as CT, seemed to be on the track to become old technology, bound to be replaced by more sophisticated techniques such as magnetic resonance imaging, due in particular to the harmful effects of x-ray radiation exposure. Yet, the new century brought with it new technology that allowed a complete change in trends and re-affirmed CT as an essential tool in radiology. For instance, the popularity of CT in 2007 was such that approximately 68.7 million CT examinations were performed in the United States, which was nearly 2.5 times the number of magnetic resonance (MRI) examinations. More than that, CT has expanded beyond its conventional diagnostic role; CT is now used routinely in interventional radiology and also in radiation therapy treatment. The technology advances that allowed the revival of CT are those that made fast, accurate cone-beam data acquisition possible. Nowadays, cone-beam data acquisition allows scanning large volumes with isotropic sub-millimeter spatial resolution in a very fast time, which can be as short as 500ms for cardiac imaging. The principles of cone-beam imaging will be first reviewed. Then a discussion of its applications will be given. Old and new challenges will be presented along the way with current solutions.

Noo, Frederic

2010-03-01

242

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

PubMed Central

Monte Carlo simulations of x-ray beams typically take parameters of the electron beam in the accelerating waveguide to be free parameters. In this paper, a methodology is proposed and implemented to determine the energy, spectral width, and beam divergence of the electron source. All treatment head components were removed from the beam path, leaving only the exit window. With the x-ray target and flattener out of the beam, uncertainties in physical characteristics and relative position of the target and flattening filter, and in spot size, did not contribute to uncertainty in the energy. Beam current was lowered to reduce recombination effects. The measured dose distributions were compared with Monte Carlo simulation of the electron beam through the treatment head to extract the electron source characteristics. For the nominal 6 and 18 MV x-ray beams, the energies were 6.51±0.15 and 13.9±0.2 MeV, respectively, with the uncertainties resulting from uncertainties in the detector position in the measurement and in the stopping power in the simulations. Gaussian spectral distributions were used, with full widths at half maximum ranging from 20±4% at 6 MV to 13±4% at 18 MV required to match the fall-off portion of the percent-depth ionization curve. Profiles at the depth of maximum dose from simulations that used the manufacturer-specified exit window geometry and no beam divergence were 2–3 cm narrower than measured profiles. Two simulation configurations yielding the measured profile width were the manufacturer-specified exit window thickness with electron source divergences of 3.3° at 6 MV and 1.8° at 18 MV and an exit window 40% thicker than the manufacturer’s specification with no beam divergence. With the x-ray target in place (and no flattener), comparison of measured to simulated profiles sets upper limits on the electron source divergences of 0.2° at 6 MV and 0.1° at 18 MV. A method of determining source characteristics without mechanical modification of the treatment head, and therefore feasible in clinics, is presented. The energies and spectral widths determined using this method agree with those determined with only the exit window in the beam path. PMID:19378730

Sawkey, D. L.; Faddegon, B. A.

2009-01-01

243

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

SciTech Connect

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

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

2009-03-15

244

Diffraction-enhanced beam-focusing for X-rays in curved multi-plate crystal cavity.  

PubMed

Unusual x-ray focusing effect is reported for parabolic curved multi-plate x-ray crystal cavities of silicon consisting of compound refractive lenses (CRL). The transmitted beam of the (12 4 0) back reflection near 14.4388 keV from these monolithic silicon crystal devices exhibits extraordinary focusing enhancement, such that the focal length is reduced by as much as 18% for 2-beam and 56% for 24-beam diffraction from the curved crystal cavity. This effect is attributed to the presence of the involved Bragg diffractions, in which the wavevector of the transmitted beam is bent further when traversing several curved crystal surfaces. PMID:20588629

Chang, Y-Y; Chen, S-Y; Wu, H-H; Weng, S-C; Chu, C-H; Lee, Y-R; Tang, M-T; Stetsko, Yu; Shew, B-Y; Yabashi, M; Chang, S-L

2010-04-12

245

Intense nanosecond duration source of x rays for resolving cavitation-induced trauma in human tissue  

Microsoft Academic Search

A pulsed nanosecond x-ray generator based on an actively pumped field emission x-ray tube is described. The x-ray source is based on a high voltage Marx generator that drives a field emission tube without the need for an intermediate energy store. The Marx generator stores 12 Joules in ceramic capacitors and produces a voltage pulse > 380 kilovolts with a

Craig N. Boyer; Glenn E. Holland; John F. Seely

2004-01-01

246

Z pinches as intense x-ray sources for inertial confinement fusion applications  

Microsoft Academic Search

Fast z-pinch implosions can convert more than 10% of the stored electrical energy in a pulsed-power accelerator into x-rays. On the Saturn pulsed-power accelerator at Sandia National Laboratories, currents of 6 to 8 MA with a risetime of less than 50 ns have been used to drive cylindrically-symmetric arrays of wires, producing x-ray energies greater than 400 kJ with x-ray

Matzen

1997-01-01

247

Z pinches as intense X-ray sources for inertial confinement fusion applications  

Microsoft Academic Search

Fast z-pinch implosions can convert more than 10% of the stored electrical energy in a pulsed-power accelerator into X-rays. On the Saturn pulsed-power accelerator at Sandia National Laboratories, currents of 6–8 MA with a risetime of less than 50 ns have been used to drive cylindrically-symmetric arrays of wires, producing X-ray energies greater than 400 kJ with X-ray pulsewidths less

M. Keith Matzen

1999-01-01

248

High contrast femtosecond laser-driven intense hard X-ray source for imaging application  

Microsoft Academic Search

In this report we address the current situation of laser-driven hard X-ray sources for imaging applications, especially the saturation of X-ray conversion efficiency and the serious impact upon imaging quality. By employing high contrast laser pulses, the conversion efficiency to X-rays from solid foil targets is improved and the structure of the spectrum can be optimized with respect to imaging

L. M. Chen; W. M. Wang; M. Kando; L. T. Hudson; F. Liu; X. X. Lin; J. L. Ma; Y. T. Li; S. V. Bulanov; T. Tajima; Y. Kato; Z. M. Sheng; J. Zhang

2010-01-01

249

Measurements of the sensitivity and spatial resolution of radiochromic film using ion beams and X-rays  

NASA Astrophysics Data System (ADS)

Radiochromic film (RCF) is used to study protons and other ions that are accelerated from the rear side of targets illuminated with ultra-intense laser light. An experiment is underway to measure the sensitivity of RCF to protons and alpha particles of various energies using the 1.7 MV tandem Pelletron accelerator at SUNY Geneseo. An ion beam incident on a gold foil is used to expose the RCF to elastically scattered ions in a 28-inch diameter scattering chamber. The film is positioned in a circular arc in the chamber so the scattered ion fluence on the RCF strip varies as a function of the scattering angle. After exposure, the RCF is scanned in color negative transmission mode using an Epson 10000 XL flatbed scanner. The red channel of the resulting scan is used to determine the optical density of the film. The spatial resolution of the film was measured by blocking part of the film with a tantalum knife edge. The sensitivity of RCF to X-rays was also measured by exposing the film to X-rays produced by a biological irradiator. The response of the new Gafchromic HD-V2 radiochromic film is compared with the discontinued Gafchromic HD radiochromic film.

Schepis, M. J.; Shortino, J. P.; Crompton, K. R.; Stillman, C. R.; Freeman, C. G.; Nilson, P. M.; Sorce, C.; Sangster, T. C.

2012-10-01

250

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

251

Simulating cometary and stellar x-ray emission in the laboratory using microcalorimeters and an electron beam ion trap  

SciTech Connect

The mixing of atomic and macroscopic processes taking place in non-terrestrial objects creates complex, dynamic, and intriguing environments. High-resolution x-ray spectra from these sources measured by satellites such as Chandra, XMM-Newton, and the Solar Maximum Mission provide a means for understanding the physics governing these sources. Laboratory measurements of the atomic processes have proved crucial to the interpretation of these spectra. For example using the LLNL electron beam ion traps EBIT-I and EBIT-II a detailed study of the x-ray spectrum of Fe XVII has been conducted addressing the large ratio predicted by theory compared to observations of considerably smaller values of the relative intensity of the 2p-3d {sup 1}P{sub 1} resonant to the {sup 3}D{sub 1} intercombination line. The difference was often attributed to opacity effects. However, laboratory measurements in the optically thin limit agree with observations demonstrating that the prediction is too large and opacity need not be invoked. The laboratory results thus provide a benchmark in the optically thin limit for accurate estimates of opacity effects. To uncover the source of the discrepancy between theory and observation, we have performed a series of experiments that successively uncovered more details about the Fe XVII lines produced in coronal plasmas. Most recently, we used a 32 channel array microcalorimeter from the Astro-E x-ray satellite program to measure the excitation cross section of various Fe XVII lines in the laboratory. These measurements resolve long-standing issues thought to be associated with non-equilibrium processes. We have also used the Astro-E microcalorimeter, and more recently its upgrade from the Astro-E2 project, and the magnetic trapping mode of EBIT-I to accurately measure x-ray emission from charge exchange recombination and to simulate the x-ray line production process in comets. Using only the laboratory measurements, we fit the moderate resolution x-ray spectrum from the comet C/Linear1999 observed by the ACIS-S CCD instrument on the Chandra X-ray Observatory. The good fit to the data shows that we are able to recreate in the laboratory the charge exchange process taking place in comets. With the launch of the Astro-E2 satellite in 2005, whose second generation XRS microcalorimeter array has an energy resolution of 6-7 eV, a factor of 20-30 better than Chandra's ACIS-S CCD, high resolution spectra of comets should become available. These measurements coupled with the laboratory measurements at LLNL using the sister Astro-E2 calorimeter array, will make it possible to accurately diagnose the composition of the solar wind at various locations in the solar system.

Brown, G V; Beiersdorfer, P; Chen, H; Graf, A; May, M; Terracol, S; Thorn, D; Boyce, K R; Cottam, J; Gendreau, K C; Kahn, S M; Kelley, R L; Killbourne, C A; Porter, F S; Szymkowiak, A E

2004-05-06

252

Intense Non-Linear Soft X-Ray Emission from a Hydride Target during Pulsed D Bombardment  

NASA Astrophysics Data System (ADS)

Radiation emission from low-energy nuclear radiation (LENR) electrodes (both charged-particle and X-rays) represents an important feature of LENR in general. Here, calibration, measurement techniques, and soft X-ray emission results from deuterium bombardment of a Pd target (cathode) placed in a pulsed deuterium glow discharge (PGD) are described. An X-ray intensity of 13.4 mW/cm2 and a dose of 3.3 ?J/cm2 were calculated over a 0.5 ms pulse time from AXUV photodiode radiation detector measurements. A most striking feature is that X-ray energies >600 V are observed with a discharge voltage only about half of that value. To further investigate this phenomenon, emission during room temperature D-desorption from electrolytically loaded Pd:Dx cathodes was also studied. The X-ray emission energy observed was quite similar to the PGD case. However, the intensity in this case was almost 13 orders of magnitude lower due to the much lower deuterium fluxes involved.

Miley, George H.; Yang, Yang; Lipson, Andrei; Haque, Munima; Percel, Ian; Romer, Michael

253

Method for matching NBS x-ray beam qualities with a half- or full-wave rectified generator  

Microsoft Academic Search

A method has been devised to enable users of half- and full-wave rectified x-ray sets to match the revised National Bureau of Standards (NBS) x-ray beam qualities obtained with a constant potential generator. The method provides a rapid technique for determining the added filter necessary to attain the same first half-value layers and nearly the same homogeneity coefficients as NBS.

S. J. Goetsch; J. Kamande; F. H. Attix

1985-01-01

254

Beam Damage of Poly(Vinyl Chloride) [PVC] Film as Observed by X-ray Photoelectron Spectroscopy  

SciTech Connect

XPS spectra of a spin-coated film poly(vinyl chloride) (PVC) were collected over a period of 243 minutes at 303 K to determine specimen damage during long exposures to monochromatic Al Ka x-rays. For this PVC film we measured the loss of chlorine as a function of time by rastering a focused 104.6 w 100 um diameter x-ray beam over a 1.4 mm x 0.2 mm area on the sample.

Engelhard, Mark H.; Krishna, Abhilash; Kulkarni, Pranita B.; Lee, Chi-Ying M.; Baer, Donald R.

2003-03-08

255

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

NASA Astrophysics Data System (ADS)

A compact, dual modality computed mammotomography (CmT) and single photon emission computed tomography (SPECT) system for dedicated 3D breast imaging is in development. The CmT component utilizes novel, heavy K-edge filtration to practicably narrow the energy spectrum of the cone-shaped x-ray beam incident on the patient's pendant, uncompressed breast. This quasi-monochromatic beam in CmT is expected to improve discrimination of tissue with very similar attenuation coefficients while restraining dose levels to below that of existing dual view mammography. Our previous extensive simulation studies showed the optimal energy range that provides maximum dose efficiency for a 50/50 adipose/glandular breast is in the 35-40keV range. This current study aims to experimentally validate previous simulation results. Here, experimental pre-breast and post-breast collimated x-ray beam spectral measurements are made under tube operating voltages between 40-100kVp using filter materials from Z=13-74, with K-edge values spanning that of Ce (K=40.4keV), and using different attenuating thicknesses of filter material, approximately equivalent to the 200 th and 500 th attenuating value layer (VL) thickness. Ce-filtered post breast spectra for 8cm to 18cm breasts are measured for a range of breast adipose/glandular compositions. Evaluated figures of merit include mean beam energy, spectral full-width at tenth-maximum, beam hardening and dose for the range of breast sizes. Measurements are shown to corroborate the simulations, and both indicate that for a given dose a 200 th VL of Ce filtration may have the most optimal performance in the dedicated mammotomography paradigm.

Crotty, Dominic J.; McKinley, Randolph L.; Tornai, Martin P.

2006-03-01

256

Calculated L-shell x-ray line intensities for proton and helium ion impact  

SciTech Connect

Theoretical L-shell X-ray line intensities have been calculated for proton and helium bombardment of atoms from nickel (Z/sub 2/ = 28) to curium (Z/sub 2/ = 96). The ionization cross sections for the three L subshells were obtained from the recent calculations by Cohen and Harrigan in the ECPSSR theory, which uses the plane-wave Born approximation (PWBA) with corrections for energy loss (E), Coulomb deflection (C), perturbed-stationary-state (PSS), and relativistic (R) effects. The fluorescence yields and Coster-Kronig transition probabilities were taken from M. O. Krause (Phys. Chem. Ref. Data 8, 307 (1979)) and the L-subshell emission rates from S. I. Salem, S. L. Panosian, and R. A. Krause (Atomic Data and Nuclear Data Tables 14, 91 (1974)). The line intensities Ll, L..cap alpha.., Leta, L..beta../sub 1/ to L..beta../sub 6/, L..beta../sub 9,10/, and L..gamma../sub 1/ to Lgg/sub 6/ are tabulated for selected ion energies from 0.2 to 10 MeV.

Cohen, D.D.; Harrigan, M.

1986-05-01

257

High-intensity flash x-ray apparatus for biomedical radiography  

NASA Astrophysics Data System (ADS)

The construction of a soft flash x-ray (FX) apparatus with a new type of FX tube for biomedical use is described. The FX apparatus may be used for condenser charging voltages of 50-90 kV and peak currents of 20-40 kA. The electric pulse width of the FX waveforms was almost constant and its value was about 0.3 ?s. The effective focal spot varied according to the condenser charging voltage, the anode-cathode (A-C) distance, etc., ranging from 0.2-3.0 mm in diameter. We selected two combinations of electrodes: (a) for normal focusing and a high dose rate; (b) for fine focusing and a low dose rate. The FX intensity was determined by the condenser charging voltage and the A-C distance, while the FX quality (average spectrum distribution) was determined by the average voltage of the FX tube and insertion of metal filters. The average voltage of the FX tube varied according to the condenser charging voltage and the A-C gap impedance. Various clear FX images were obtained by controlling the FX intensity, quality, and the focal spot size. We used Fuji Computed Radiography (FCR) in conjunction with our FX radiography, and by controlling the FX quality and the focal spot size, we obtained some interesting biomedical radiograms.

Sato, E.; Isobe, H.; Hoshino, F.

1986-07-01

258

Negative Resist Material Based on Polysilanes for Electron Beam and X-Ray Lithographies  

NASA Astrophysics Data System (ADS)

In the present paper, we describe the mechanisms of photo- and radiation-induced reactions in silicon based resist materials, polysilanes with Si-branchings and Si-H bondings, candidates for future resist materials. Polysilanes have been previously confirmed to show positive-type resist properties for ultra violet (UV) light, electron beams (EB), and X-rays under all conditions. However, the cross-linking reaction of the polymer became dominant in the polysilane with Si-branchings, upon irradiation with UV light, EB, and ion beams. The efficiency of the cross-linking reaction strongly depended on the ratio of Si-branching producing polymer gels in the polysilane with a higher amount of Si-branching than 5%, even with ?-ray irradiation. Polyhydrosilanes containing vinyl groups were revealed to cause efficient cross-linking reactions in the presence of catalysts for hydrosilylation upon exposure to deep UV or X-rays, leading to high-sensitive negative resist materials for extreme UV lithography.

Seki, Shu; Sakurai, Yusuke; Maeda, Kensaku; Kunimi, Yoshihisa; Tagawa, Seiichi

2000-07-01

259

First Deployment of an Electron Beam Ion Trap at an Advanced Source of Hard X-rays  

NASA Astrophysics Data System (ADS)

We have deployed an Electron Beam Ion Trap (EBIT) at the Advanced Photon Source. The EBIT was cooled to 4K with a cryocooler and mounted on stepper motors to allow precise adjustment relative to the x-ray beam. The electron and x-ray beams crossed at a right angle in the horizontal plane. Spectra of photons emitted off-axis from the incident beams were recorded as Kr26+ and Ar8+ ions were subjected to x-rays up to 18 keV. No heating or other adverse effects on the operation of the cryogenic ion trap were experienced. Spectra and lessons learned for future work will be presented. )

Gillaspy, J. D.; Silver, E.; Kanter, E. P.; Brickhouse, N. S.; Dunford, R. W.; Kirby, K.; Lin, T.; McDonald, J.; Schneider, D.; Seifert, S.; Young, L.

2010-02-01

260

Multiple ionization of atom clusters by intense soft X-rays from a free-electron laser  

Microsoft Academic Search

Intense radiation from lasers has opened up many new areas of research in physics and chemistry, and has revolutionized optical technology. So far, most work in the field of nonlinear processes has been restricted to infrared, visible and ultraviolet light, although progress in the development of X-ray lasers has been made recently. With the advent of a free-electron laser in

H. Wabnitz; L. Bittner; A. R. B. de Castro; R. Döhrmann; P. Gürtler; T. Laarmann; W. Laasch; J. Schulz; A. Swiderski; K. von Haeften; T. Möller; B. Faatz; A. Fateev; J. Feldhaus; C. Gerth; U. Hahn; E. Schneidmiller; K. Sytchev; K. Tiedtke; R. Treusch; M. Yurkov

2002-01-01

261

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

262

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

263

Diffraction with a coherent X-ray beam: dynamics and imaging  

PubMed Central

Methods for carrying out coherent X-ray scattering experiments are reviewed. The brilliance of the available synchrotron sources, the characteristics of the existing optics, the various ways of obtaining a beam of controlled coherence properties and the detectors used are summarized. Applications in the study of the dynamics of speckle patterns are described. In the case of soft condensed matter, the movement of inclusions like fillers in polymers or colloidal particles can be observed and these can reflect polymer or liquid-crystal fluctuations. In hard condensed-matter problems, like phase transitions, charge-density waves or phasons in quasicrystals, the study of speckle fluctuations provides new time-resolved methods. In the domain of lensless imaging, the coherent beam gives the modulus of the sample Fourier transform. If oversampling conditions are fulfilled, the phase can be obtained and the image in the direct space can be reconstructed. The forthcoming improvements of all these techniques are discussed. PMID:17301470

Livet, Frédéric

2007-01-01

264

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

265

Dosimetric application of a special pencil ionization chamber in radiotherapy X-ray beams  

NASA Astrophysics Data System (ADS)

The aim of this work was to study the performance of a pencil ionization chamber with a sensitive volume of only 1.06 cm3 and a length of 3.0 cm, developed at the Calibration Laboratory of the IPEN, in very low-energy radiotherapy X-ray beams. These beams are still used for certain skin cancer treatments due to their rapid attenuation in tissue. The dosimeter performance was evaluated in some tests proposed by the IEC 60731 standard: short- and long-term stability and linearity of response. For a complete analysis of the dosimeter response, the EGSnrc Monte Carlo simulation was utilized to investigate the influence of its different parts on the ionization chamber response. All results of the tests were in accordance with the recommended limits, and this work shows that it is possible to extend the application of this pencil-type ionization chamber developed at the LCI.

Neves, Lucio P.; Perini, Ana P.; Fernández-Varea, José M.; Cassola, Vagner F.; Kramer, Richard; Khoury, Helen J.; Caldas, Linda V. E.

2014-02-01

266

Method for matching NBS x-ray beam qualities with a half- or full-wave rectified generator  

SciTech Connect

A method has been devised to enable users of half- and full-wave rectified x-ray sets to match the revised National Bureau of Standards (NBS) x-ray beam qualities obtained with a constant potential generator. The method provides a rapid technique for determining the added filter necessary to attain the same first half-value layers and nearly the same homogeneity coefficients as NBS. Beam qualities from 100 to 250 kVcp have been duplicated and used to perform blind calibrations at four beam qualities on each of two ion chambers owned by the National Bureau of Standards.

Goetsch, S.J.; Kamande, J.; Attix, F.H.

1985-03-01

267

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

SciTech Connect

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

Tatchyn, Roman; /SLAC

2011-09-01

268

Multiphoton Ionization as a clock to Reveal Molecular Dynamics with Intense Short X-ray Free Electron Laser Pulses  

NASA Astrophysics Data System (ADS)

We investigate molecular dynamics of multiple ionization in N2 through multiple core-level photoabsorption and subsequent Auger decay processes induced by intense, short x-ray free electron laser pulses. The timing dynamics of the photoabsorption and dissociation processes is mapped onto the kinetic energy of the fragments. Measurements of the latter allow us to map out the average internuclear separation for every molecular photoionization sequence step and obtain the average time interval between the photoabsorption events. Using multiphoton ionization as a tool of the multiple-pulse pump-probe scheme, we demonstrate the modification of the ionization dynamics as we vary the x-ray laser pulse duration.

Fang, L.; Osipov, T.; Murphy, B.; Tarantelli, F.; Kukk, E.; Cryan, J. P.; Glownia, M.; Bucksbaum, P. H.; Coffee, R. N.; Chen, M.; Buth, C.; Berrah, N.

2012-12-01

269

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

270

Multiresolution image registration in digital x-ray angiography with intensity variation modeling.  

PubMed

Digital subtraction angiography (DSA) is a widely used technique for visualization of vessel anatomy in diagnosis and treatment. However, due to unavoidable patient motions, both externally and internally, the subtracted angiography images often suffer from motion artifacts that adversely affect the quality of the medical diagnosis. To cope with this problem and improve the quality of DSA images, registration algorithms are often employed before subtraction. In this paper, a novel elastic registration algorithm for registration of digital X-ray angiography images, particularly for the coronary location, is proposed. This algorithm includes a multiresolution search strategy in which a global transformation is calculated iteratively based on local search in coarse and fine sub-image blocks. The local searches are accomplished in a differential multiscale framework which allows us to capture both large and small scale transformations. The local registration transformation also explicitly accounts for local variations in the image intensities which incorporated into our model as a change of local contrast and brightness. These local transformations are then smoothly interpolated using thin-plate spline interpolation function to obtain the global model. Experimental results with several clinical datasets demonstrate the effectiveness of our algorithm in motion artifact reduction. PMID:24469684

Nejati, Mansour; Pourghassem, Hossein

2014-02-01

271

A study on the use of Gafchromic™ EBT3 film for output factor measurements in kilovoltage X-ray beams.  

PubMed

Relative output factors are used in radiation therapy for treatment planning purposes including treatments using kilovoltage X-ray beams. The output factor is the relative dose output for a particular applicator relative to a reference applicator. Due to the differences in the scatter contribution from the inside of an applicator, it is more accurate if output factors are measured for all combinations of X-ray beam energy and applicator. Previously published papers and various kilovoltage X-ray beam dosimetry protocols have discussed the validity of using various cylindrical and parallel plate ionization chambers for relative output factor measurements. In this work, we evaluated the suitability of Gafchromic™ EBT3 film for the determination of output factors for kilovoltage X-ray beams. Output factors were measured with Gafchromic™ EBT3 film for beam qualities of 50, 75, 100 and 125 kVp and applicator sizes of 2, 3, 4 cm diameter, 8 × 8 and 12 × 12 cm(2) square applicators. The film read out was performed with a flatbed EPSON Expression 10000XL scanner. The measured data was compared with benchmark data from measurements using an Advanced Markus ionisation chamber as well as comparing with ratios of published backscatter factor values. The agreement between output factors measured with EBT3 film and the ionisation chamber was generally better than 2 %, with the largest difference of 3.3 % occurring for the 2 cm diameter field with the 50 kVp X-ray beam. These differences were consistent with the estimated total uncertainty in the measurements as calculated by the ISO GUM. The agreement between the output factors measured with film and the published BSFs was generally better than 5 % but differences of up to 12 % occurred for the smallest field size. The results demonstrate that Gafchromic™ EBT3 film is a suitable dosimeter for output factor measurements of kilovoltage X-ray beams. PMID:24264224

Gill, Simran; Hill, Robin

2013-12-01

272

Beam characterization of a lab bench cold cathode ultra-soft X-ray generator  

NASA Astrophysics Data System (ADS)

The aim of this work is to characterize the Ultra Soft X-ray (USX, 1.5 keV, Al K?) photon beam of a customized lab bench cold cathode generator. Within this generator, the electron beam is slowed down in a thin aluminium foil (16 ?m) supported by an easily exchangeable anode. It is shown that the thickness of the foil and the anode configuration determine the spatial distribution and the fluence rate of the photon beam, whereas accelerating voltage determines both fluence rate and energy spectrum feature. It is shown also that under specific operation parameters (i.e. accelerating voltage), a Gaussian energy distribution of the beam can be generated which is centred on the energy of the Al K? line (1.5 keV). Dosimetric films of GAFCHROMIC® HD-810 were used to estimate the photon fluence rate distribution of the beam. Its variation, when the generator acts as a monoenergetic source, was characterized with the two different configurations of the anode assembly. Finally, it is verified that the anode assembly consisting in a flat washer, on which the aluminium foil is set, acts as a simple point-source.

Ounoughi, N.; Mavon, C.; Belafrites, A.; Groetz, J.-E.; Fromm, M.

2013-06-01

273

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

274

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

275

YAP imager and its application with high-energy X-ray beams up to 150 keV  

NASA Astrophysics Data System (ADS)

An X-ray imaging detector called YAP imager has been developed for high-energy X-ray region at the SPring-8 facility. It possesses a [128×128] matrix of YAlO 3:Ce crystals, each element having a volume of 1×1×6 mm 3. A NIM logic module using programmable logic device chip was also developed as a position encoder. The YAP imager has been applied for some applications with a thermal barrier coating material and multi-layer metal sheets targets in the incident X-ray energy region of 70-150 keV. Direct X-ray beam profile at 100 keV was also measured.

Hirota, K.; Toyokawa, H.; Suzuki, M.; Kudo, T.; Nomachi, M.; Sugaya, Y.; Yosoi, M.; Gorin, A.; Manuilov, I.; Riazantsev, A.; Kuroda, K.

2003-09-01

276

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

277

Low-intensity x-ray-imaging scope (Lixiscope)Its applications in sports medicine and orthopaedic surgery  

Microsoft Academic Search

The low-intensity x-ray imaging scope (Lixiscope) is a hand-held, totally portable fluorescopic device utiliz ing a low-energy, low-intensity y source of 125I. The unit was developed at the Goddard Space Flight Cen ter for the National Aeronautics and Space Adminis tration. It has become apparent that there is increasing use of this tool, especially in sports medicine, to diagnose and

William J. Tansey

1981-01-01

278

Materials Discovery: Fine-Grained Classification of X-ray Scattering Images M. Hadi Kiapour Kevin Yager  

E-print Network

of shining an intense and collimated x-ray beam through a sample of interest, and recording the intensity- ate monochromatic, highly collimated and focused beams suitable for demanding x-ray experiments challenge. Modern x-ray detectors include on the order of 1 million 20-bit pixels, and can acquire at 20

Berg, Tamara L.

279

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

280

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

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

281

Characteristic x-ray emission from undermines plasmas irradiated by ultra-intense lasers  

SciTech Connect

Between FY09 and FY11 we have conducted more than a dozen three-week experimental campaigns at high-power laser facilities around the world to investigate laser-channeling through x-ray and optical imaging and the conversion from laser-energy to xrays. We have performed simultaneous two-wavelength x-ray imaging (K-alpha and He-alpha) to distinguish the hot-plasma region (hot-spot) from the laser-produced electrons (K-alpha). In addition, we have initiated a new collaboration with SNL and have performed first shots on the 100 TW beamlet chamber to commission a fast x-ray streak camera to be used to investigate the temporal evolution of our K-alpha sources. We also collaborated on campaigns at the Rutherford Appleton Laboratory (UK) and the LANL Trident laser to employ laser produced x-ray sources for Thomson scattering off dense matter.

Niemann, Christoph

2012-05-05

282

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

283

Precision Measurements of Thulium K X-Ray Relative Intensities Using Bent-Crystal Spectrometry  

Microsoft Academic Search

Measurement of the relative transition rates of various K x-rays has been done in an attempt to clarify the current understanding of the atomic structure of ^{169}Tm as well as to test the structure calculations of Scofield (1975). The data available currently for K x-ray relative transition rates is rather sparse and of varying degrees of precision, especially in the

William Craig Barker

1988-01-01

284

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

285

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

NASA Astrophysics Data System (ADS)

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

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

2007-02-01

286

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

PubMed

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

2007-02-01

287

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

PubMed

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(®) 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. PMID:23206070

Manova, D; Bergmann, A; Mändl, S; Neumann, H; Rauschenbach, B

2012-11-01

288

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

NASA Astrophysics Data System (ADS)

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® 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.; Mändl, S.; Neumann, H.; Rauschenbach, B.

2012-11-01

289

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

290

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

SciTech Connect

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, producing implosions velocities as high as 100 cm/{mu}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 8 a radiation 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. These large volume, long-lived radiation sources have recently been used for ICF-relevant ablator physics experiments as well as astrophysical opacity and radiation-material interaction experiments. Hydromagnetic Rayleigh-Taylor instabilities and cylindrical load symmetry are critical, limiting factors in determining the assembled plasma densities and temperatures, and thus in the x-ray pulse widths 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, Zn reproducibility, and x-ray output power. X-ray pulse widths 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 Saturn n accelerator, and are a record for x-ray powers in the laboratory.

Matzen, M.K.

1997-02-01

291

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

292

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

293

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

294

Glass capillary optics for making x-ray beams of 0.1 to 50 microns diameter  

SciTech Connect

We have fabricated a unique computerized glass puller that can make parabolic or elliptically tapered glass capillaries for microbeam x-ray experiments from hollow glass tubing. We have produced optics that work in a single-bounce imaging mode or in a multi-bounce condensing mode. The imaging-mode capillaries have been used to create 20 to 50 micron diameter x-ray beams at 12 keV that are quite useful for imaging diffraction patterns from tiny bundles of carbon and Kevlar fibers. The condensing-mode capillaries are useful for creating submicron diameter beams and show great promise in x-ray fluorescence applications with femtogram sensitivity for patterned Er and Ti dopants diffused into an optically-active lithium niobate wafer.

Bilderback, Donald H.; Fontes, Ernest [Cornell High Energy Synchrotron Source (CHESS) and School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853 (United States)

1997-07-01

295

Advanced simulations of x-ray beam propagation through CRL transfocators using ray-tracing and wavefront propagation methods  

NASA Astrophysics Data System (ADS)

Compound refractive lenses (CRL) are widely used to manipulate synchrotron radiation beams. Accurate modelling of X-ray beam propagation through individual lenses and through "transfocators" composed of a large number of CRLs is of high importance, since it allows for comprehensive optimization of X-ray beamline designs for particular user experiments. In this work we used the newly developed McXtrace ray-tracing package and the SRW wave-optics code to simulate the beam propagation of X-ray undulator radiation through such a "transfocator" as implemented at ID- 11 at ESRF. By applying two complementary simulation methods, we were able to obtain comparable results (e.g. the beam's focused properties) and also to provide a complete description of X-ray beam propagation through the CRLs and other optical components. However, some discrepancies between the results acquired by both methods (e.g. broader monochromatization degree obtained with the McXtrace code) brought a meaningful insight into further development strategies for the McXtrace package.

Baltser, Jana; Knudsen, Erik; Vickery, Anette; Chubar, Oleg; Snigirev, Anatoly; Vaughan, Gavin; Feidenhans'l, Robert; Lefmann, Kim

2011-09-01

296

Beam hardening correction for X-ray computed tomography of heterogeneous natural materials  

NASA Astrophysics Data System (ADS)

We present a new method for correcting beam hardening artifacts in polychromatic X-ray CT data. On most industrial CT systems, software beam-hardening correction employs some variety of linearization, which attempts to transform the polychromatic attenuation data into its monochromatic equivalent prior to image reconstruction. However, determining optimal coefficients for the transform equation is not straightforward, especially if the material is not well known or characterized, as is the usual case when imaging geological materials. Our method uses an iterative optimization algorithm to find a generalized spline-interpolated transform that minimizes artifacts as defined by an expert user. This generality accesses a richer set of linearization functions that may better accommodate the effects of multiple materials in heterogeneous samples. When multiple materials are present in the scan field, there is no single optimal correction, and the solution can vary depending on which aspects of the beam-hardening and other image artifacts the user wants to minimize. For example, the correction can be optimized to maximize the fidelity of the object outline for solid model creation rather than simply to minimize variation of CT numbers within the material. We demonstrate our method on a range of specimens of varying difficulty and complexity, with consistently positive results.

Ketcham, Richard A.; Hanna, Romy D.

2014-06-01

297

X-Ray Supernovae  

E-print Network

We present a review of X-ray observations of supernovae (SNe). By observing the (~0.1-100 keV) X-ray emission from young SNe, physical key parameters such as the circumstellar matter (CSM) density, mass-loss rate of the progenitor and temperature of the outgoing and reverse shock can be derived as a function of time. Despite intensive search over the last ~25 years, only 15 SNe have been detected in X-rays. We review the individual X-ray observations of these SNe and discuss their implications as to our understanding of the physical processes giving rise to the X-ray emission.

Stefan Immler; Walter H. G. Lewin

2002-03-27

298

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

299

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

300

Quantitative analysis of the x-ray diffraction intensities of undulated smectic phases in bent-core liquid crystals  

SciTech Connect

X-ray diffraction diagrams of undulated smectic phases in bent-core liquid crystals have been theoretically studied. The intensities of the reflections have been obtained for different layer modulations, and a general expression has been deduced for orthogonal cells in terms of the different harmonics of the distortion. The case of sinusoidal modulation is especially simple and has been studied also in oblique cells. High-quality x-ray measurements of three compounds reported in the literature have been analyzed as examples. In all cases it has been deduced that the modulation is sinusoidal and its amplitude has been easily obtained by fitting the experimental intensities. Equatorial (h0) reflections have been also considered to obtain information about the structure of defects at the maxima and minima of the undulation.

Folcia, C. L.; Etxebarria, J. [Departamento de Fisica de la Materia Condensada, Facultad de Ciencia y Tecnologia, Universidad del Pais Vasco, Apartado 644, 48080 Bilbao (Spain); Ortega, J. [Departamento de Fisica Aplicada II, Facultad de Ciencia y Tecnologia, Universidad del Pais Vasco, Apartado 644, 48080 Bilbao (Spain)

2007-07-15

301

3D-CT imaging using characteristic X-rays and visible lights produced by ion micro-beam bombardment  

NASA Astrophysics Data System (ADS)

We improved the spatial resolution of a 3D-CT imaging system consisting of a micro-beam and an X-ray CCD camera of 1 mega pixels (Hamamatsu photonics C8800X), whose element size is 8 ?m × 8 ?m providing an image size of 8 mm × 8 mm. A small ant of ˜6 mm body length was placed in a small tube, rotated by a stepping motor, and a spatial resolution of 4 ?m for X-ray micron-CT using characteristic Ti-K-X-rays (4.558 keV) produced by 3 MeV proton micro-beams was obtained. We applied the X-ray micron-CT to a small ant's head and obtained the fine structures of the head's interior. Because the CCD is sensitive to visible light, we also examined the capability of light micron-CT using visible red light from an Al 2O 3(Cr) ruby scintillator and applied the micron-CT to a small red tick. Though the red tick is highly transparent to Ti-K-X-rays, visible red light does not penetrate through the red tick. The most serious problem was dispersion of lights due to Thomson scattering resulting in obscure projection images.

Ishii, K.; Matsuyama, S.; Yamazaki, H.; Watanabe, Y.; Kawamura, Y.; Yamaguchi, T.; Momose, G.; Kikuchi, Y.; Terakawa, A.; Galster, W.

2006-08-01

302

Anomalous resistivity in beam-return currents and hard-X ray spectra of solar flares  

NASA Astrophysics Data System (ADS)

Context. Observations of hard-X ray (HXR) spectra from solar flares show that there is noncollisional energy loss when energetic beam electrons are transported along the flare loop from their acceleration site above the looptop in the corona to the loop footpoints in the chromosphere. Aims: This paper investigates anomalous (i.e., noncollisional) resistivity due to the effective collision by the wave-particle interaction in the beam-return current system of a flare and its effect on the HXR spectral evolution between the looptop and footpoint sources. Methods: To attribute the noncollisional energy loss to an induced electric field by the beam current, the induced electric field is estimated by the spectral evolution between the looptop and footpoint sources, which is deduced from the standard thin-thick target model. To include collisional and anomalous resistivity caused by the ion-acoustic wave turbulence excited by the return current, the necessary excited level and the excited condition are discussed for the steady-state case in which the return current density driven by the induced electric field in terms of Ohm's law is required to be equal to the beam current density. Results: The results show that including the anomalous resistivity can reasonably remove the discrepancy between observations and predictions. Meanwhile, the necessary excited level for the ion-acoustic turbulence is tens times of the thermal noise of electrostatic fluctuations in the background plasma, which is an ordinary and low excited level that is easily satisfied. Conclusions: This indicates that the microscopic kinetics of plasma particles possibly play an important and critical role in understanding the dynamics of beam-return current systems in the solar atmosphere and in the physics of solar flares.

Xu, L.; Chen, L.; Wu, D. J.

2013-02-01

303

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

304

Systems and methods for detecting an image of an object by use of an X-ray beam having a polychromatic distribution  

DOEpatents

Systems and methods for detecting an image of an object using an X-ray beam having a polychromatic energy distribution are disclosed. According to one aspect, a method can include detecting an image of an object. The method can include generating a first X-ray beam having a polychromatic energy distribution. Further, the method can include positioning a single monochromator crystal in a predetermined position to directly intercept the first X-ray beam such that a second X-ray beam having a predetermined energy level is produced. Further, an object can be positioned in the path of the second X-ray beam for transmission of the second X-ray beam through the object and emission from the object as a transmitted X-ray beam. The transmitted X-ray beam can be directed at an angle of incidence upon a crystal analyzer. Further, an image of the object can be detected from a beam diffracted from the analyzer crystal.

Parham, Christopher; Zhong, Zhong; Pisano, Etta; Connor, Dean; Chapman, Leroy D.

2010-06-22

305

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

306

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

307

Tokamak x ray diagnostic instrumentation  

SciTech Connect

Three classes of x-ray diagnostic instruments enable measurement of a variety of tokamak physics parameters from different features of the x-ray emission spectrum. (1) The soft x-ray (1 to 50 keV) pulse-height-analysis (PHA) diagnostic measures impurity concentrations from characteristic line intensities and the continuum enhancement, and measures the electron temperature from the continuum slope. (2) The Bragg x-ray crystal spectrometer (XCS) measures the ion temperature and neutral-beam-induced toroidal rotation velocity from the Doppler broadening and wavelength shift, respectively, of spectral lines of medium-Z impurity ions. Impurity charge state distributions, precise wavelengths, and inner-shell excitation and recombination rates can also be studied. X rays are diffracted and focused by a bent crystal onto a position-sensitive detector. The spectral resolving power E/..delta..E is greater than 10/sup 4/ and time resolution is 10 ms. (3) The x-ray imaging system (XIS) measures the spatial structure of rapid fluctuations (0.1 to 100 kHZ) providing information on MHD phenomena, impurity transport rates, toroidal rotation velocity, plasma position, and the electron temperature profile. It uses an array of silicon surface-barrier diodes which view different chords of the plasma through a common slot aperture and operate in current (as opposed to counting) mode. The effectiveness of shields to protect detectors from fusion-neutron radiation effects has been studied both theoretically and experimentally.

Hill, K.W.; Beiersdorfer, P.; Bitter, M.; Fredrickson, E.; Von Goeler, S.; Hsuan, H.; Johnson, L.C.; Liew, S.L.; McGuire, K.; Pare, V.

1987-01-01

308

Model for the dynamics of a water cluster in an x-ray free electron laser beam  

Microsoft Academic Search

A microscopic sample placed into a focused x-ray free electron laser beam will explode due to strong ionization on a femtosecond time scale. The dynamics of this Coulomb explosion has been modeled by Neutze et al. [Nature (London) 406, 752 (2000)] for a protein, using computer simulations. The results suggest that by using ultrashort exposures, structural information may be collected

Magnus Bergh; Nicusor Timneanu; David van der Spoel

2004-01-01

309

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

310

An expanded x-ray beam facility (BEaTriX) to test the modular elements of the ATHENA optics  

NASA Astrophysics Data System (ADS)

Future large X-ray observatories like ATHENA will be equipped with very large optics, obtained by assembling modular optical elements, named X-ray Optical Units (XOU) based on the technology of either Silicon Pore Optics or Slumped Glass Optics. In both cases, the final quality of the modular optic (a 5 arcsec HEW requirement for ATHENA) is determined by the accuracy alignment of the XOUs within the assembly, but also by the angular resolution of the individual XOU. This is affected by the mirror shape accuracy, its surface roughness, and the mutual alignment of the mirrors within the XOU itself. Because of the large number of XOUs to be produced, quality tests need to be routinely done to select the most performing stacked blocks, to be integrated into the final optic. In addition to the usual metrology based on profile and roughness measurements, a direct measurement with a broad, parallel, collimated and uniform Xray beam would be the most reliable test, without the need of a focal spot reconstruction as usually done in synchrotron light. To this end, we designed the BEaTriX (Beam Expander Testing X-ray facility) to be realized at INAF-OAB, devoted to the functional tests of the XOUs. A grazing incidence parabolic mirror and an asymmetrically cut crystal will produce a parallel X-ray beam broad enough to illuminate the entire aperture of the focusing elements. An X-ray camera at the focal distance from the mirrors will directly record the image. The selection of different crystals will enable to test the XOUs in the 1 - 5 keV range, included in the X-ray energy band of ATHENA (0.2-12 keV). In this paper we discuss a possible BEaTriX facility implementation. We also show a preliminary performance simulation of the optical system.

Spiga, D.; Pelliciari, C.; Bonnini, E.; Buffagni, E.; Ferrari, C.; Pareschi, G.; Tagliaferri, G.

2014-07-01

311

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

312

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

313

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

314

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

315

Measurement of beam transverse emittance via measurement of the x-ray source size in a wakefield accelerator  

NASA Astrophysics Data System (ADS)

We propose and use a new technique to measure the transverse emittance of a laser-wakefield accelerated beam of relativistic electrons. The technique is based on the simultaneous measurements of the electron beam divergence given by p/p, the measured longitudinal spectrum p and the transverse electron bunch size in the bubble r. The latter is obtained via the measurement of the source size of the x-rays emitted by the accelerating electron bunch in the bubble. These so-called betatron x-rays [ 1 ] have also shown to be spatially coherent and as bright as currently existing 3rd generation Synchrotrons [ 2 ]. We measure a normalized beam transverse emittance as small as 0.6 ? mm:mrad for a monoenergetic electron beam with 400 MeV energy.[ 1 ] A. Rousse, et. al. Phys. Rev. Lett. 93, 135005 (2004)[ 2 ] S. Kneip, et. al. Nature Physics, submitted (2010)

Kneip, S.; Bloom, M.; Mangles, S. P. D.; Najmudin, Z.; McGuffey, C.; Chvykov, V.; Dollar, F.; Kalintchenko, G.; Maksimchuk, A.; Schumaker, W.; Yanovsky, V.; Thomas, A. G. R.; Krushelnick, K.; Martins, J. L.; Fonseca, R.; Silva, L. O.; Phuoc, K. Ta

2010-11-01

316

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

NASA Astrophysics Data System (ADS)

The successful operation of x-ray free-electron lasers (FELs), like the Linac Coherent Light Source or the Free-Electron Laser in Hamburg (FLASH), makes unprecedented research on matter at atomic length and ultrafast time scales possible. However, in order to take advantage of these unique light sources and to meet the strict requirements of many experiments in photon science, FEL photon pulse durations need to be known and tunable. This can be achieved by controlling the FEL driving electron beams, and high-resolution longitudinal electron beam diagnostics can be utilized to provide constraints on the expected FEL photon pulse durations. In this paper, we present comparative measurements of soft x-ray pulse durations and electron bunch lengths at FLASH. The soft x-ray pulse durations were measured by FEL radiation pulse energy statistics and compared to electron bunch lengths determined by frequency-domain spectroscopy of coherent transition radiation in the terahertz range and time-domain longitudinal phase space measurements. The experimental results, theoretical considerations, and simulations show that high-resolution longitudinal electron beam diagnostics provide reasonable constraints on the expected FEL photon pulse durations. In addition, we demonstrated the generation of soft x-ray pulses with durations below 50 fs (FWHM) after the implementation of the new uniform electron bunch compression scheme used at FLASH.

Behrens, C.; Gerasimova, N.; Gerth, Ch.; Schmidt, B.; Schneidmiller, E. A.; Serkez, S.; Wesch, S.; Yurkov, M. V.

2012-03-01

317

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

318

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

319

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

320

Thermal distortion of wavefront in high-intensity-laser system for inverse Compton x-ray generation  

NASA Astrophysics Data System (ADS)

We have developed a stable 7 terawatt (TW) (168 mJ per pulse, 24 fs pulse duration) Ti: sapphire laser system operating at 50 Hz for a generation of femtosecond X-ray pulses by inverse Compton scattering. We corrected the wavefront distortion of these high intensity laser pulses with adaptive optics using a Shack-Hartmann type wavefront sensor and a deformable mirror. We have also started developing a compact all-solid-state Yb: Sr5(PO4)3F (Yb: S-FAP) laser system to realize a practical X-ray pulse generation system. We measured thermal lensing induced in Yb: S-FAP crystal for design of a high-energy regenerative amplifier. In addition, we measured wavefront of the amplified pulses in the Yb: S-FAP regenerative amplifier with the wavefront sensor.

Ishikawa, Hiroki; Ito, Shinji; Endo, Akira; Yanagida, Tatsuya; Torizuka, Kenji; Sakai, Fumio; Washio, Masakazu

2003-06-01

321

High-flux hard X-ray microbeam using a single-bounce capillary with doubly focused undulator beam.  

PubMed

A pre-focused X-ray beam at 12 keV and 9 keV has been used to illuminate a single-bounce capillary in order to generate a high-flux X-ray microbeam. The BioCAT undulator X-ray beamline 18ID at the Advanced Photon Source was used to generate the pre-focused beam containing 1.2 x 10(13) photons s(-1) using a sagittal-focusing double-crystal monochromator and a bimorph mirror. The capillary entrance was aligned with the focal point of the pre-focused beam in order to accept the full flux of the undulator beam. Two alignment configurations were tested: (i) where the center of the capillary was aligned with the pre-focused beam (;in-line') and (ii) where one side of the capillary was aligned with the beam (;off-line'). The latter arrangement delivered more flux (3.3 x 10(12) photons s(-1)) and smaller spot sizes (< or =10 microm FWHM in both directions) for a photon flux density of 4.2 x 10(10) photons s(-1) microm(-2). The combination of the beamline main optics with a large-working-distance (approximately 24 mm) capillary used in this experiment makes it suitable for many microprobe fluorescence applications that require a micrometer-size X-ray beam and high flux density. These features are advantageous for biological samples, where typical metal concentrations are in the range of a few ng cm(-2). Micro-XANES experiments are also feasible using this combined optical arrangement. PMID:19096178

Barrea, Raul A; Huang, Rong; Cornaby, Sterling; Bilderback, Donald H; Irving, Thomas C

2009-01-01

322

High-flux hard X-ray microbeam using a single-bounce capillary with doubly focused undulator beam  

SciTech Connect

A pre-focused X-ray beam at 12 keV and 9 keV has been used to illuminate a single-bounce capillary in order to generate a high-flux X-ray microbeam. The BioCAT undulator X-ray beamline 18ID at the Advanced Photon Source was used to generate the pre-focused beam containing 1.2 x 10{sup 13} photons s{sup -1} using a sagittal-focusing double-crystal monochromator and a bimorph mirror. The capillary entrance was aligned with the focal point of the pre-focused beam in order to accept the full flux of the undulator beam. Two alignment configurations were tested: (i) where the center of the capillary was aligned with the pre-focused beam ('in-line') and (ii) where one side of the capillary was aligned with the beam ('off-line'). The latter arrangement delivered more flux (3.3 x 10{sup 12} photons s{sup -1}) and smaller spot sizes ({le}10 {micro}m FWHM in both directions) for a photon flux density of 4.2 x 10{sup 10} photons s{sup -1} {micro}m{sup -2}. The combination of the beamline main optics with a large-working-distance (approximately 24 mm) capillary used in this experiment makes it suitable for many microprobe fluorescence applications that require a micrometer-size X-ray beam and high flux density. These features are advantageous for biological samples, where typical metal concentrations are in the range of a few ng cm{sup -2}. Micro-XANES experiments are also feasible using this combined optical arrangement.

Barrea, Raul A.; Huang, Rong; Cornaby, Sterling; Bilderback, Donald H.; Irving, Thomas C.; (IIT); (Cornell); (UC)

2009-01-15

323

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

324

Effect of annealing treatment on K{beta}-to-K{alpha} x-ray intensity ratios of 3d transition-metal alloys  

SciTech Connect

The influence of heat annealing treatment on the K{beta}-to-K{alpha} x-ray intensity ratios of 3d transition metal was carried out by x-ray fluorescence studies of various alloy compositions. K{beta}-to-K{alpha} x-ray intensity ratios of Fe, Ni, Ti, Co, and Cu in Fe{sub x}Ni{sub 1-x}, Ti{sub x}Ni{sub 1-x}, and Co{sub x}Cu{sub 1-x} alloys unannealed and thermally annealed at different temperatures have been measured following excitation by 22.69-keV x rays from a 10-mCi {sup 109}Cd radioactive point source. The experimental data obtained after annealing treatment indicate deviations of K{beta}-to-K{alpha} x-ray intensity ratios for 3d transition metals in different alloy compositions from the corresponding ratios for unannealed samples. The present investigation makes it possible to perform reliable interpretation of experimental K{beta}-to-K{alpha} x-ray intensity ratios for various 3d transition metals in their alloys and can also provide quantitative information about the changes of the K{beta}-to-K{alpha} x-ray intensity ratios of these metals with annealing treatment in considered systems.

Han, I. [Faculty of Arts and Sciences, Department of Physics, Agri Ibrahim Cecen University, TR-04100 Agri (Turkey); Demir, L. [Faculty of Sciences, Department of Physics, Atatuerk University, TR-25240 Erzurum (Turkey)

2010-06-15

325

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

326

Time resolved, 2-D hard X-ray imaging of relativistic electron-beam target interactions on ETA-II  

SciTech Connect

Advanced radiographic applications require a constant source size less than 1 mm. To study the time history of a relativistic electron beam as it interacts with a bremsstrahlung converter, one of the diagnostics they use is a multi-frame time-resolved hard x-ray camera. They are performing experiments on the ETA-II accelerator at Lawrence Livermore National Laboratory to investigate details of the electron beam/converter interactions. The camera they are using contains 6 time-resolved images, each image is a 5 ns frame. By starting each successive frame 10 ns after the previous frame, they create a 6-frame movie from the hard x-rays produced from the interaction of the 50-ns electron beam pulse.

Crist, C.E. [Sandia National Labs., Albuquerque, NM (United States); Sampayan, S.; Westenskow, G.; Caporaso, G.; Houck, T.; Weir, J.; Trimble, D. [Lawrence Livermore National Lab., CA (United States); Krogh, M. [AlliedSignal FM and T, Kansas City, MO (United States)

1998-11-01

327

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

NASA Astrophysics Data System (ADS)

Narrowband x- and ? -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 one 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 sensitively this compensation depends on the electron-beam energy spread and emittance, as well as the laser focusing.

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

2015-03-01

328

Plasma focus as intense light source for soft x-ray microscopy  

NASA Astrophysics Data System (ADS)

A plasma focus operating in nitrogen is developed as an x-ray source for the laboratory type x-ray microscope. The radiation has to be emitted into the ``window'' (2.33 nm-4.37 nm) with a reciprocal relative bandwidth (RRB) of ?/???200. The nearly coinciding Lyman-? line of nitrogen VII ?=2.48 nm and the second resonance line of nitrogen VI at ?=2.49 nm are chosen. For the use in the microscope the end on diameter of the source has to be about 200 ?m with a spatial jitter below 100 ?m. A prototype of the source has been examined in its spatial, temporal and spectral properties. The higher ionization cross sections of nitrogen compared to noble gases influences the start of the discharge. First experiments with Fresnel condenser zone plates (CZP) as a tool for plasma soft x-ray emission diagnostics are presented. Experimental results are compared with non LTE modeling of the collapse and pinch phase of the plasma focus.

Lebert, R.; Neff, W.; Holz, R.; Richter, F.

1989-12-01

329

Characteristics of kilovoltage x-ray beams used for cone-beam computed tomography in radiation therapy.  

PubMed

The purpose of this investigation is to characterize the beams produced by a kilovoltage (kV) imager integrated into a linear accelerator (Varian on-board imager integrated into the Trilogy accelerator) for acquiring high resolution volumetric cone-beam computed tomography (CBCT) images of the patient on the treatment table. The x-ray tube is capable of generating photon spectra with kVp values between 40 and 125 kV. The Monte Carlo simulations were used to study the characteristics of kV beams and the properties of imaged target scatters. The Monte Carlo results were benchmarked against measurements, and excellent agreements were obtained. We also studied the effect of including the electron impact ionization (EII), and the simulation showed that the characteristic radiation is increased significantly in the energy spectra when EII is included. Although only slight beam hardening is observed in the spectra of all photons after passing through the phantom target, there is a significant difference in the spectra and angular distributions between scattered and primary photons. The results also show that the photon fluence distributions are significantly altered by adding bow tie filters. The results indicate that a combination of large cone-beam field size and large imaged target significantly increases scatter-to-primary ratios for photons that reach the detector panel. For phantoms 10 cm, 20 cm and 30 cm thick of water placed at the isocentre, the scatter-to-primary ratios are 0.94, 3.0 and 7.6 respectively for an open 125 kVp CBCT beam. The Monte Carlo simulations show that the increase of the scatter is proportional to the increase of the imaged volume, and this also applies to scatter-to-primary ratios. This study shows both the magnitude and the characteristics of scattered x-rays. The knowledge obtained from this investigation may be useful in the future design of the image detector to improve the image quality. PMID:17327651

Ding, George X; Duggan, Dennis M; Coffey, Charles W

2007-03-21

330

In situ X-ray beam imaging using an off-axis magnifying coded aperture camera system  

PubMed Central

An imaging model and an image reconstruction algorithm for a transparent X-ray beam imaging and position measuring instrument are presented. The instrument relies on a coded aperture camera to record magnified images of the footprint of the incident beam on a thin foil placed in the beam at an oblique angle. The imaging model represents the instrument as a linear system whose impulse response takes into account the image blur owing to the finite thickness of the foil, the shape and size of camera’s aperture and detector’s point-spread function. The image reconstruction algorithm first removes the image blur using the modelled impulse response function and then corrects for geometrical distortions caused by the foil tilt. The performance of the image reconstruction algorithm was tested in experiments at synchrotron radiation beamlines. The results show that the proposed imaging system produces images of the X-ray beam cross section with a quality comparable with images obtained using X-ray cameras that are exposed to the direct beam. PMID:23765302

Kachatkou, Anton; Kyele, Nicholas; Scott, Peter; van Silfhout, Roelof

2013-01-01

331

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

332

Rapid prototyping of Fresnel zone plates via direct Ga(+) ion beam lithography for high-resolution X-ray imaging.  

PubMed

A significant challenge to the wide utilization of X-ray microscopy lies in the difficulty in fabricating adequate high-resolution optics. To date, electron beam lithography has been the dominant technique for the fabrication of diffractive focusing optics called Fresnel zone plates (FZP), even though this preparation method is usually very complicated and is composed of many fabrication steps. In this work, we demonstrate an alternative method that allows the direct, simple, and fast fabrication of FZPs using focused Ga(+) beam lithography practically, in a single step. This method enabled us to prepare a high-resolution FZP in less than 13 min. The performance of the FZP was evaluated in a scanning transmission soft X-ray microscope where nanostructures as small as sub-29 nm in width were clearly resolved, with an ultimate cutoff resolution of 24.25 nm, demonstrating the highest first-order resolution for any FZP fabricated by the ion beam lithography technique. This rapid and simple fabrication scheme illustrates the capabilities and the potential of direct ion beam lithography (IBL) and is expected to increase the accessibility of high-resolution optics to a wider community of researchers working on soft X-ray and extreme ultraviolet microscopy using synchrotron radiation and advanced laboratory sources. PMID:24151983

Keskinbora, Kahraman; Grévent, Corinne; Eigenthaler, Ulrike; Weigand, Markus; Schütz, Gisela

2013-11-26

333

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

334

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

335

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

336

Dosimetric properties of high energy current (HEC) detector in keV x-ray beams  

NASA Astrophysics Data System (ADS)

We introduce a new x-ray radiation detector. The detector employs high-energy current (HEC) formed by secondary electrons consisting predominantly of photoelectrons and Auger electrons, to directly convert x-ray energy to detector signal without externally applied power and without amplification. The HEC detector is a multilayer structure composed of thin conducting layers separated by dielectric layers with an overall thickness of less than a millimeter. It can be cut to any size and shape, formed into curvilinear surfaces, and thus can be designed for a variety of QA applications. We present basic dosimetric properties of the detector as function of x-ray energy, depth in the medium, area and aspect ratio of the detector, as well as other parameters. The prototype detectors show similar dosimetric properties to those of a thimble ionization chamber, which operates at high voltage. The initial results obtained for kilovoltage x-rays merit further research and development towards specific medical applications.

Zygmanski, Piotr; Shrestha, Suman; Elshahat, Bassem; Karellas, Andrew; Sajo, Erno

2015-04-01

337

Study of the L3 edges of ion-beam-mixed Pd?Cu alloys by X-ray absorption spectroscopy  

NASA Astrophysics Data System (ADS)

X-ray absorption spectroscopy (XAS) at the L3 edge of Pd is used to investigate the electronic structure of ion-beam-mixed Pd?Cu alloys with a wide composition range (0.1? x?0.9). The formation of chemical bonds between Pd and Cu affects the occupancy and/or hybridization of the d states, and this change is revealed in the white line intensities. It is found that, within ion-beam-mixed Pd?Cu alloys, there is a substantial decrease in the area of the Pd L3 white lines upon increasing the Cu concentration. This result implies that upon alloying with Cu there is a gradual filling of the Pd d band. The amount of d-charge transfer at the Pd site of ion-beam-mixed Pd?Cu alloys has been estimated on the basis of the change within the white line.

Lee, Y. S.; Whang, C. N.; Jeon, Y.; Choi, B. S.; Han, T. J.; Woo, J. J.; Croft, M.

1997-08-01

338

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

E-print Network

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

Feng, Chao; Deng, Haixiao; Zhao, Zhentang

2014-01-01

339

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

340

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

PubMed

Various dosimeters have been tested for assessing absorbed doses with microscopic spatial resolution in targets irradiated by high-flux, synchrotron-generated, low-energy (approximately 30-300 keV) x-ray microbeams. A MOSFET detector has been used for this study since its radio sensitive element, which is extraordinarily narrow (approximately 1 microm), 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 microm x 1 cm instead of 25 x 500 microm2), 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. PMID:19472618

Siegbahn, E A; Bräuer-Krisch, E; Bravin, A; Nettelbeck, H; Lerch, M L F; Rosenfeld, A B

2009-04-01

341

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

342

3D Algebraic Iterative Reconstruction for Cone-Beam X-Ray Differential Phase-Contrast Computed Tomography  

PubMed Central

Due to the potential of compact imaging systems with magnified spatial resolution and contrast, cone-beam x-ray differential phase-contrast computed tomography (DPC-CT) has attracted significant interest. The current proposed FDK reconstruction algorithm with the Hilbert imaginary filter will induce severe cone-beam artifacts when the cone-beam angle becomes large. In this paper, we propose an algebraic iterative reconstruction (AIR) method for cone-beam DPC-CT and report its experiment results. This approach considers the reconstruction process as the optimization of a discrete representation of the object function to satisfy a system of equations that describes the cone-beam DPC-CT imaging modality. Unlike the conventional iterative algorithms for absorption-based CT, it involves the derivative operation to the forward projections of the reconstructed intermediate image to take into account the differential nature of the DPC projections. This method is based on the algebraic reconstruction technique, reconstructs the image ray by ray, and is expected to provide better derivative estimates in iterations. This work comprises a numerical study of the algorithm and its experimental verification using a dataset measured with a three-grating interferometer and a mini-focus x-ray tube source. It is shown that the proposed method can reduce the cone-beam artifacts and performs better than FDK under large cone-beam angles. This algorithm is of interest for future cone-beam DPC-CT applications. PMID:25775480

Fu, Jian; Hu, Xinhua; Velroyen, Astrid; Bech, Martin; Jiang, Ming; Pfeiffer, Franz

2015-01-01

343

3D Algebraic Iterative Reconstruction for Cone-Beam X-Ray Differential Phase-Contrast Computed Tomography.  

PubMed

Due to the potential of compact imaging systems with magnified spatial resolution and contrast, cone-beam x-ray differential phase-contrast computed tomography (DPC-CT) has attracted significant interest. The current proposed FDK reconstruction algorithm with the Hilbert imaginary filter will induce severe cone-beam artifacts when the cone-beam angle becomes large. In this paper, we propose an algebraic iterative reconstruction (AIR) method for cone-beam DPC-CT and report its experiment results. This approach considers the reconstruction process as the optimization of a discrete representation of the object function to satisfy a system of equations that describes the cone-beam DPC-CT imaging modality. Unlike the conventional iterative algorithms for absorption-based CT, it involves the derivative operation to the forward projections of the reconstructed intermediate image to take into account the differential nature of the DPC projections. This method is based on the algebraic reconstruction technique, reconstructs the image ray by ray, and is expected to provide better derivative estimates in iterations. This work comprises a numerical study of the algorithm and its experimental verification using a dataset measured with a three-grating interferometer and a mini-focus x-ray tube source. It is shown that the proposed method can reduce the cone-beam artifacts and performs better than FDK under large cone-beam angles. This algorithm is of interest for future cone-beam DPC-CT applications. PMID:25775480

Fu, Jian; Hu, Xinhua; Velroyen, Astrid; Bech, Martin; Jiang, Ming; Pfeiffer, Franz

2015-01-01

344

Intense X-ray induced formation of silver nanoparticles stabilized by biocompatible polymers  

NASA Astrophysics Data System (ADS)

Colloidal Ag nanoparticles were formed by X-ray irradiation in the presence of a polymer. This new synthesis method is simple, rapid and leads to a high production yield. Compared to the citrate-reduced Ag colloidal, polymer-protected Ag nanoparticles are smaller in size and more stable—and therefore suitable for biomedical application—as verified by TEM observation, XAFS measurement and optical characterization. Ag nanoparticles so produced were also visualized in solution and in real time by a visible light microscope based on dark field light scattering. The color-derived size and distribution of Ag nanoparticles correlates well with the hydrodynamic size data.

Wang, Chang-Hai; Liu, Chi-Jen; Wang, Cheng-Liang; Chien, Chia-Chi; Hwu, Y.; Liu, Ru-Shi; Yang, Chung-Shi; Je, Jung-Ho; Lin, Hong-Ming; Margaritondo, G.

2009-11-01

345

Scanning x-ray microdiffraction with submicron white beam for strain and orientation mapping in thin films  

SciTech Connect

Scanning X-ray Microdiffraction (m-SXRD) combines the use of high brilliance synchrotron sources with the latest achromatic X-ray focusing optics and fast large area 2D-detector technology. Using white beams or a combination of white and monochromatic beams, it allows for orientation and strain/stress mapping of polycrystalline thin films with submicron spatial resolution. The technique is described in detail as applied to the study of thin aluminium and copper blanket films and lines following electromigration testing and/or thermal cycling experiments. It is shown that there are significant orientation and strain/stress variations between grains and inside individual grains. A polycrystalline film when investigated at the granular (micron) level shows a highly mechanically inhomogeneous medium that allows insight into its mesoscopic properties. If the m-SXRD data are averaged over a macroscopic range, results show good agreement with direct macroscopic texture and stress measurements .

Tamura, N.; MacDowell, A.A.; Spolenak, R.; Valek, B.C.; Bravman, J.C.; Brown, W.L.; Celestre, R.S.; Padmore, H.A.; Batterman, B.W.; Patel, J.R.

2003-01-14

346

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

347

Compton backscattered collimated 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)

1998-01-01

348

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

349

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

350

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

351

A controlled radiation source and electron/X-ray flux ratios in an electron beam metal evaporator  

NASA Astrophysics Data System (ADS)

The use of ionizing radiation (X-rays, electrons and ions) in semiconductor processes is becoming more pervasive as device dimensions decrease. One such source of ionizing radiation is an electron beam (EB) metal evaporator. It has, in fact, been used earlier as a mixed X-ray/electron source to simulate ionizing radiation processes in device fab-rication sequences. In those studies, it was not known, however, what fraction of the energy striking a specimen was due to electrons, and what fraction was due to X-rays. In the present paper, application of an electron beam evaporator as a controlled, essen-tially monochromatic ionizing radiation source is described. Using a 0.5 mil thick Be foil, and knowing its mass absorption coefficient for X-rays at the wavelengths involved, the percentage electron and X-ray fluxes as a function of hearth beam current for a set of accelerating voltages was estimated. In addition, the absorption coefficient of an in-expensive, expendable, polymeric foil (pellicle) used in place of Be for actual experi-mental studies was evaluated. The 2.85 ?m thick pellicle was found to transmit 87% of the incident Al K? radiation, and to exhibit a mass absorption coefficient of 303 cm2/ g. The electron flux percentage from an aluminum hearth at a distance of 205 mm, was found to be 26% for a range of hearth electron beam currents between 2.5 x 10-2A and 7.5 x 10-2A, at an accelerating voltage of 6 kV. For a 10 kV accelerating voltage the electron percentage was found to be 35% between 2.5 x 10-2A and 7.5 x 10-2A. X-ray fractions were 74% and 65%, respectively. The radiation system can be used to pro-vide exposures in the 5 x 104 rad(SiO2) to the 2 x 108 rad(SiO2) range for Insulated Gate Field Effect transistors, in about an hour-long experiment.

Bhattacharya, P. K.; Reisman, A.; Chen, M. C.

1988-07-01

352

Radioprotection by DMSO of mammalian cells exposed to X-rays and to heavy charged-particle beams  

Microsoft Academic Search

Summary Populations of G1-phase Chinese hamster cells in stirred suspensions containing various concentrations of DMSO were irradiated with 250 kV X-rays or various heavy charged-particle beams. Chemical radioprotection of cell inactivation was observed for all LET values studied. When cell survival data were resolved into linear and quadratic components, the extent and concentration dependence of DMSO protection were found to

J. D. Chapman; S. D. Doern; A. P. Reuvers; C. J. Gillespie; A. Chatterjee; E. A. Blakely; K. C. Smith; C. A. Tobias

1979-01-01

353

Development of an inspection process for ball-grid-array technology using scanned-beam X-ray laminography  

Microsoft Academic Search

An inspection process based on scanned-beam X-ray laminography (SBXLAM) is proposed herein for quantitatively monitoring the quality of ball-grid-array (BGA) joints. The long-term reliability of the BGA joints depends on the component-assembly process producing joints with sufficient solder volume and proper alignment. Inspection algorithms were developed to measure the critical BGA-joint characteristics, including the alignment between the ball and the

S. M. Rooks; B. Benhabib; K. C. Smith

1995-01-01

354

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

355

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

356

X-ray diffraction imaging with the Multiple Inverse Fan Beam topology: principles, performance and potential for security screening.  

PubMed

The steadily increasing number of explosive threat classes, including home-made explosives (HMEs), liquids, amorphous and gels (LAGs), is forcing up the false-alarm rates of security screening equipment. This development can best be countered by increasing the number of features available for classification. X-ray diffraction intrinsically offers multiple features for both solid and LAGs explosive detection, and is thus becoming increasingly important for false-alarm and cost reduction in both carry-on and checked baggage security screening. Following a brief introduction to X-ray diffraction imaging (XDI), which synthesizes in a single modality the image-forming and material-analysis capabilities of X-rays, the Multiple Inverse Fan Beam (MIFB) XDI topology is described. Physical relationships obtaining in such MIFB XDI components as the radiation source, collimators and room-temperature detectors are presented with experimental performances that have been achieved. Representative X-ray diffraction profiles of threat substances measured with a laboratory MIFB XDI system are displayed. The performance of Next-Generation (MIFB) XDI relative to that of the 2nd Generation XRD 3500TM screener (Morpho Detection Germany GmbH) is assessed. The potential of MIFB XDI, both for reducing the exorbitant cost of false alarms in hold baggage screening (HBS), as well as for combining "in situ" liquid and solid explosive detection in carry-on luggage screening is outlined. PMID:22245364

Harding, G; Fleckenstein, H; Kosciesza, D; Olesinski, S; Strecker, H; Theedt, T; Zienert, G

2012-07-01

357

Synchrotron-induced X-ray microfluorescence on single cells  

NASA Astrophysics Data System (ADS)

Recent improvements in synchrotron X-ray sources (third generation) and in X-ray focusing elements have been realized. This result in delivering highly collimated quasi-monochromatic X-ray beams with tunable energy and beam focused down to sub-micrometer diameter. Preliminary results in the ?-SXRF of single cells were obtained in the hard X-ray range. "Pink"-beam and compound refractive lenses were used resulting in a 1×10 ?m2 (vertical×horizontal) beam size with a flux ˜5×10 10 photon/s/ ?m2. The experiment confirmed that high energy, high intensity X-rays were well suited for microanalysis of sensitive biological specimens such as freeze-dried cells. Results show that the synchrotron microprobe set-up at ESRF allows high sensitivity in trace element measurements for cells treated with pharmacological doses of an iodine-labeled anticancer drug.

Bohic, Sylvain; Simionovici, Alexandre; Ortega, Richard; Heymann, Dominique; Schroer, Christian; Snigirev, Anatoly

2001-07-01

358

Study of the formalism used to determine the absorbed dose for low-energy x-ray beams.  

PubMed

We have studied the procedure commonly recommended by dosimetry protocols for the determination of the absorbed dose in water for low-energy x-rays beams, generated with potentials up to 150 kVp. X-ray beams with different spectra obtained with the XCOMP5R code were transported using the Monte Carlo code PENELOPE in order to calculate backscatter factors and mass-energy absorption coefficients. We have analyzed the uncertainty in the absorbed doses, calculated using the half-value layer to characterize the x-ray beams, due to the uncertainties in both backscatter factors and mass-energy absorption coefficients. We have found that this uncertainty is larger than 5% and can reach values above 11% for some HVL(1) values. The characterization of these doses with the homogeneity coefficient or the generating potential, in addition to the half-value layer is also studied. Using HVL(1) and the kVp, the absorbed dose to water can be reproduced to within 3% for all spectra. PMID:19001702

Chica, U; Anguiano, M; Lallena, A M

2008-12-01

359

Study of the formalism used to determine the absorbed dose for low-energy x-ray beams  

NASA Astrophysics Data System (ADS)

We have studied the procedure commonly recommended by dosimetry protocols for the determination of the absorbed dose in water for low-energy x-rays beams, generated with potentials up to 150 kVp. X-ray beams with different spectra obtained with the XCOMP5R code were transported using the Monte Carlo code PENELOPE in order to calculate backscatter factors and mass-energy absorption coefficients. We have analyzed the uncertainty in the absorbed doses, calculated using the half-value layer to characterize the x-ray beams, due to the uncertainties in both backscatter factors and mass-energy absorption coefficients. We have found that this uncertainty is larger than 5% and can reach values above 11% for some HVL1 values. The characterization of these doses with the homogeneity coefficient or the generating potential, in addition to the half-value layer is also studied. Using HVL1 and the kVp, the absorbed dose to water can be reproduced to within 3% for all spectra.

Chica, U.; Anguiano, M.; Lallena, A. M.

2008-12-01

360

Scanning wire beam position monitor for alignment of a high brightness inverse-Compton x-ray source  

E-print Network

The Free-Electron Laser Laboratory at the University of Hawai`i has constructed and tested a scanning wire beam position monitor to aid the alignment and optimization of a high spectral brightness inverse-Compton scattering x-ray source. X-rays are produced by colliding the 40 MeV electron beam from a pulsed S-band linac with infrared laser pulses from a mode-locked free-electron laser driven by the same electron beam. The electron and laser beams are focused to 60 {\\mu}m diameters at the interaction point to achieve high scattering efficiency. This wire-scanner allows for high resolution measurements of the size and position of both the laser and electron beams at the interaction point to verify spatial coincidence. Time resolved measurements of secondary emission current allow us to monitor the transverse spatial evolution of the e-beam throughout the duration of a 4 {\\mu}s macro-pulse while the laser is simultaneously profiled by pyrometer measurement of the occulted infrared beam. Using this apparatus we ...

Hadmack, Michael R

2013-01-01

361

Beamed and Unbeamed X-Ray Emission in FR1 Radio Galaxies  

NASA Technical Reports Server (NTRS)

The research exploited ROSAT's sensitivity, together with its spatial and spectral resolution, to separate X-ray emission components in the sources. Prior to ROSAT, the dominant X-ray emission mechanism in radio galaxies as a class was unclear, with correlations between the X-ray and radio emission used on one hand to argue for a nuclear origin for the X-rays, and on the other hand for a thermal origin. Our observations (normally between 10 and 25 ks in length) routinely detected the target sources, and demonstrated that both resolved (thermal) and unresolved X-ray emission are typically present. Highlights of our work included two of the first detections of high-power radio galaxies at high redshift, 3C 280 and 3C 220.1. When combined with the work of two other groups, we find that of the 38 radio galaxies at z > 0.6 in the 3CRR sample, 12 were observed in ROSAT pointed observations and 9 were detected with the four most significant detections exhibiting source extent, including 3C 280 and 3C 220.1. Moreover, we discovered extended emission around five 3CRR quasars at redshift greater than about 0.4, one of which is at z > 0.6. Unification predicts that the X-ray environments of powerful radio galaxies and quasars should be similar, and our results show that powerful radio sources are finding some of the highest-redshift X-ray clusters known to date, pointing to deep gravitational potential wells early in the Universe.

Worrall, Diana M.

2000-01-01

362

Spatial structure of a focused X-ray beam diffracted from crystals.  

PubMed

The spatial structure of a beam focused by a planar refractive lens and Bragg diffracted from perfect silicon crystals was experimentally studied at the focal plane using a knife-edge scan and a high-resolution CCD camera. The use of refractive lenses allowed for a detailed comparison with theory. It was shown that diffraction leads to broadening of the focused beam owing to the extinction effect and, for a sufficiently thin crystal, to the appearance of a second peak owing to reflection from the back surface. It was found that the spatial structure of the diffracted beam depends on whether the crystal diffracts strongly (dynamically) or weakly (kinematically). The results help to understand the physical origin of the diffracted intensity recorded in a typical microbeam diffraction experiment. PMID:19713641

Kazimirov, A; Kohn, V G; Snigirev, A; Snigireva, I

2009-09-01

363

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

364

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

Microsoft Academic Search

A linear accelerator based source of coherent radiation, FLASH (Free-electron LASer in Hamburg) provides ultra-intense femtosecond radiation pulses at wavelengths from the extreme ultraviolet (XUV; lambda<100nm) to the soft X-ray (SXR; lambda<30nm) spectral regions. 25-fs pulses of 32-nm FLASH radiation were used to determine the ablation parameters of PMMA - poly (methyl methacrylate). Under these irradiation conditions the attenuation length

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

2007-01-01

365

Characterisation of a MeV Bremsstrahlung x-ray source produced from a high intensity laser for high areal density object radiography  

SciTech Connect

Results of an experiment to characterise a MeV Bremsstrahlung x-ray emission created by a short (<10 ps) pulse, high intensity (1.4 × 10{sup 19} W/cm{sup 2}) laser are presented. X-ray emission is characterized using several diagnostics; nuclear activation measurements, a calibrated hard x-ray spectrometer, and dosimeters. Results from the reconstructed x-ray energy spectra are consistent with numerical simulations using the PIC and Monte Carlo codes between 0.3 and 30 MeV. The intense Bremsstrahlung x-ray source is used to radiograph an image quality indicator (IQI) heavily filtered with thick tungsten absorbers. Observations suggest that internal features of the IQI can be resolved up to an external areal density of 85 g/cm{sup 2}. The x-ray source size, inferred by the radiography of a thick resolution grid, is estimated to be approximately 400 ?m (full width half maximum of the x-ray source Point Spread Function)

Courtois, C.; Compant La Fontaine, A.; Bazzoli, S.; Bourgade, J. L.; Gazave, J.; Lagrange, J. M.; Landoas, O.; Dain, L. Le; Pichoff, N. [CEA, DAM, DIF, F-91297 Arpajon (France)] [CEA, DAM, DIF, F-91297 Arpajon (France); Edwards, R.; Aedy, C. [AWE Plc., Aldermaston, Reading RG7 4PR (United Kingdom)] [AWE Plc., Aldermaston, Reading RG7 4PR (United Kingdom); Mastrosimone, D.; Pien, G.; Stoeckl, C. [Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623 (United States)] [Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623 (United States)

2013-08-15

366

Characterisation of a MeV Bremsstrahlung x-ray source produced from a high intensity laser for high areal density object radiography  

NASA Astrophysics Data System (ADS)

Results of an experiment to characterise a MeV Bremsstrahlung x-ray emission created by a short (<10 ps) pulse, high intensity (1.4 × 1019 W/cm2) laser are presented. X-ray emission is characterized using several diagnostics; nuclear activation measurements, a calibrated hard x-ray spectrometer, and dosimeters. Results from the reconstructed x-ray energy spectra are consistent with numerical simulations using the PIC and Monte Carlo codes between 0.3 and 30 MeV. The intense Bremsstrahlung x-ray source is used to radiograph an image quality indicator (IQI) heavily filtered with thick tungsten absorbers. Observations suggest that internal features of the IQI can be resolved up to an external areal density of 85 g/cm2. The x-ray source size, inferred by the radiography of a thick resolution grid, is estimated to be approximately 400 ?m (full width half maximum of the x-ray source Point Spread Function).

Courtois, C.; Edwards, R.; Compant La Fontaine, A.; Aedy, C.; Bazzoli, S.; Bourgade, J. L.; Gazave, J.; Lagrange, J. M.; Landoas, O.; Dain, L. Le; Mastrosimone, D.; Pichoff, N.; Pien, G.; Stoeckl, C.

2013-08-01

367

Spectral analysis of x-ray emission created by intense laser irradiation of copper materials  

SciTech Connect

We have measured the x-ray emission, primarily from K{sub {alpha}},K{sub {beta}}, and He{sub {alpha}} lines, of elemental copper foil and 'foam' targets irradiated with a mid-10{sup 16} W/cm{sup 2} laser pulse. The copper foam at 0.1 times solid density is observed to produce 50% greater He{sub {alpha}} line emission than copper foil, and the measured signal is well-fit by a sum of three synthetic spectra generated by the atomic physics code FLYCHK. Additionally, spectra from both targets reveal characteristic inner shell K{sub {alpha}} transitions from hot electron interaction with the bulk copper. However, only the larger-volume foam target produced significant K{sub {beta}} radiation, confirming a lower bulk temperature in the higher volume sample.

Huntington, C. M.; Kuranz, C. C.; Drake, R. P. [Atmospheric, Oceanic, Space Science, University of Michigan, Ann Arbor, Michigan 48103 (United States); Malamud, G. [Atmospheric, Oceanic, Space Science, University of Michigan, Ann Arbor, Michigan 48103 (United States); Department of Physics, Nuclear Research Center - Negev, 84190 Beer-Sheva (Israel); Park, H.-S.; Maddox, B. R. [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States)

2012-10-15

368

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

369

An intense soft high-latitude X-ray source H2156-304 - A new BL Lacertae object  

NASA Technical Reports Server (NTRS)

The discovery of an intense high-latitude soft X-ray source (designated H2156-304) detected with the low-energy detectors of the HEAO A-2 experiment is reported. The error box of the source includes a 14th mag starlike object that may be coincident with the radio source PKS 2155-304 and has been suggested as a BL Lac candidate. Intensity variations of H2156-304 on time scales of about 1 sec to 1 day are discussed, along with a probable flare from the source. The derived energy spectrum of the source is shown to be well fitted by either a two-temperature thermal model with temperatures of 16 million and 1.6 million K or a single power-law model with a spectral index of 2.4 + or - 0.3. Hydrogen column densities of approximately 2.5 x 10 to the 20th and 2.0 x 10 to the 20th H atoms/sq cm are obtained for the two-temperature and power-law models, respectively. The emission mechanism of H2156-304 is considered, and the characteristics of this source are compared with those of three known soft X-ray-emitting BL Lac objects.

Agrawal, P. C.; Riegler, G. R.

1979-01-01

370

Effects of X-ray and carbon ion beam irradiation on membrane permeability and integrity in Saccharomyces cerevisiae cells.  

PubMed

Saccharomyces cerevisiae has served as a eukaryotic model in radiation biology studies of cellular responses to ionizing radiation (IR). Research in this field has thus far mainly been focused on DNA strand breaks, DNA base damage, or inhibition of protein activity. However, the effects of IR on S. cerevisiae cell membranes have barely been studied. Here, we investigated the changes in the permeability and integrity of S. cerevisiae cell membranes induced by high-linear energy transfer carbon ion (CI) beam or low-linear energy transfer X-ray. After CI exposure, protein elution and nucleotide diffusion were more pronounced than after X-ray treatment at the same doses, although these features were most prevalent following irradiation doses of 25-175 Gy. Flow cytometry of forward scatter light versus side scatter light and double-staining with fluorescein diacetate and propidium iodide showed that CI and X-ray irradiation significantly affected S. cerevisiae cell membrane integrity and cellular enzyme activity compared with untreated control cells. The extent of lesions in CI-irradiated cells, which exhibited markedly altered morphology and size, was greater than that in X-ray-irradiated cells. The relationships between permeabilized cells, esterase activity, and non-viable cell numbers furthermore indicated that irradiation-induced increases in cell permeabilization and decreases in esterase activity are dependent on the type of radiation and that these parameters correspond well with cell viability. These results also indicate that the patterns of cell inactivity due to X-ray or CI irradiation may be similar in terms of cell membrane damage. PMID:25599994

Cao, Guozhen; Zhang, Miaomiao; Miao, Jianshun; Li, Wenjian; Wang, Jufang; Lu, Dong; Xia, Jiefang

2015-03-01

371

Effects of X-ray and carbon ion beam irradiation on membrane permeability and integrity in Saccharomyces cerevisiae cells  

PubMed Central

Saccharomyces cerevisiae has served as a eukaryotic model in radiation biology studies of cellular responses to ionizing radiation (IR). Research in this field has thus far mainly been focused on DNA strand breaks, DNA base damage, or inhibition of protein activity. However, the effects of IR on S. cerevisiae cell membranes have barely been studied. Here, we investigated the changes in the permeability and integrity of S. cerevisiae cell membranes induced by high–linear energy transfer carbon ion (CI) beam or low–linear energy transfer X-ray. After CI exposure, protein elution and nucleotide diffusion were more pronounced than after X-ray treatment at the same doses, although these features were most prevalent following irradiation doses of 25–175 Gy. Flow cytometry of forward scatter light versus side scatter light and double-staining with fluorescein diacetate and propidium iodide showed that CI and X-ray irradiation significantly affected S. cerevisiae cell membrane integrity and cellular enzyme activity compared with untreated control cells. The extent of lesions in CI-irradiated cells, which exhibited markedly altered morphology and size, was greater than that in X-ray-irradiated cells. The relationships between permeabilized cells, esterase activity, and non-viable cell numbers furthermore indicated that irradiation-induced increases in cell permeabilization and decreases in esterase activity are dependent on the type of radiation and that these parameters correspond well with cell viability. These results also indicate that the patterns of cell inactivity due to X-ray or CI irradiation may be similar in terms of cell membrane damage. PMID:25599994

Cao, Guozhen; Zhang, Miaomiao; Miao, Jianshun; Li, Wenjian; Wang, Jufang; Lu, Dong; Xia, Jiefang

2015-01-01

372

Spatiotemporal focusing dynamics in plasmas at X-ray wavelength  

SciTech Connect

Using a finite curvature beam, we investigate here the spatiotemporal focusing dynamics of a laser pulse in plasmas at X-ray wavelength. We trace the dependence of curvature parameter on the focusing of laser pulse and recognize that the self-focusing in plasma is more intense for the X-ray laser pulse with curved wavefront than with flat wavefront. The simulation results demonstrate that spatiotemporal focusing dynamics in plasmas can be controlled with the appropriate choice of beam-plasma parameters to explore the high intensity effects in X-ray regime.

Sharma, A., E-mail: a-physics2001@yahoo.com; Tibai, Z. [Institute of Physics, University of Pecs, Pecs–7624 (Hungary)] [Institute of Physics, University of Pecs, Pecs–7624 (Hungary); Hebling, J. [Institute of Physics, University of Pecs, Pecs–7624 (Hungary) [Institute of Physics, University of Pecs, Pecs–7624 (Hungary); Szentagothai Research Centre, University of Pecs, Pecs-7624 (Hungary); Mishra, S. K. [Institute for Plasma Research, Gandhinagar (India)] [Institute for Plasma Research, Gandhinagar (India)

2014-03-15

373

Aperiodic W\\/B 4C multilayer systems for X-ray optics: Quantitative determination of layer thickness by HAADF-STEM and X-ray reflectivity  

Microsoft Academic Search

X-ray microanalysis of materials by synchrotron radiation has generated an increasing demand for advanced multilayer based X-ray optical elements that can be used in beam-lines as monochromators of small or large spectral bandwidth, or in components for shaping high-intensity X-ray beams with highest reflectivities. Modern thin film technologies allow the fabrication of appropriate multilayer systems with reproducible control of layer

D. Häussler; Ch. Morawe; U. Roß; B. Ögüt; E. Spiecker; W. Jäger; F. Hertlein; U. Heidorn; J. Wiesmann

2010-01-01

374

Damage study of optical substrates using 1-?m-focusing beam of hard X-ray free-electron laser  

NASA Astrophysics Data System (ADS)

We evaluated the ablation threshold of silicon and synthetic fused silica, which are widely used as optical substrates such as those in X-ray mirrors. A focusing XFEL beam with a beam size of approximately 1 ?m at a photon energy of 10 keV was used. We confirmed that the ablation thresholds of these materials, which were 0.8 ?J/?m2 for the silicon and 4 ?J/?m2 for the synthetic fused silica, approximately agreed with the melting dose.

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

2013-10-01

375

Tunable X-ray source  

DOEpatents

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

Boyce, James R. (Williamsburg, VA)

2011-02-08

376

A wavelet-based single-view reconstruction approach for cone beam x-ray luminescence tomography imaging  

PubMed Central

Single-view x-ray luminescence computed tomography (XLCT) imaging has short data collection time that allows non-invasively and fast resolving the three-dimensional (3-D) distribution of x-ray-excitable nanophosphors within small animal in vivo. However, the single-view reconstruction suffers from a severe ill-posed problem because only one angle data is used in the reconstruction. To alleviate the ill-posedness, in this paper, we propose a wavelet-based reconstruction approach, which is achieved by applying a wavelet transformation to the acquired singe-view measurements. To evaluate the performance of the proposed method, in vivo experiment was performed based on a cone beam XLCT imaging system. The experimental results demonstrate that the proposed method cannot only use the full set of measurements produced by CCD, but also accelerate image reconstruction while preserving the spatial resolution of the reconstruction. Hence, it is suitable for dynamic XLCT imaging study. PMID:25426315

Liu, Xin; Wang, Hongkai; Xu, Mantao; Nie, Shengdong; Lu, Hongbing

2014-01-01

377

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

378

EB-X1: an accurate x-ray mask writer using a variable-shaped beam  

NASA Astrophysics Data System (ADS)

The EB-X1 is an accurate X-ray mask writer with high-throughput that was developed by modifying one of our EB60 variable-shaped E-beam systems. For high resolution, we developed an electron optical system whose 50-nm beam edge sharpness, a 15 A/cm2 beam current density, and 1.0-micrometers X 0.5-micrometers maximum beam size with an acceleration voltage under 30 keV were determined by proximity-effect Monte Carlo simulation. We adopt a three-pronged approach for accurate pattern placement. First, we improve the beam positioning resolution from 20 nm to 5 nm. Because we suppress mechanical vibration, we can attain a 11-nm standard mark detection accuracy, resulting in a 20-nm compensation accuracy in the beam deflection distortion and a 25-nm field stitching accuracy. Second, our new column with its short beam-path and demagnification image of variable-shaped beam optics can attain a beam position stability within 30 nm over two hours. Finally, the use of an electrostatic chuck to firmly hold the mask-substrate with little holding- deformation and large heat transmission reduces mask-substrate deformation to 23 nm during pattern writing. Experiments confirm the EB-X1 can write a 0.2-micrometers minimum-feature sized pattern, has a pattern placement accuracy of 50 nm (3 (sigma) ) and a high throughput approximately ten times higher than that of a conventional point-beam exposure system. Using optimized correction coefficients for a specific layer, an average pattern placement accuracy of 33 nm (3 (sigma) ) can be achieved. The EB-X1 is now being used in the X-ray mask fabrication process line at NTT LSI Laboratories.

Shimazu, Nobuo; Watanabe, Takashi; Morosawa, Tetsuo; Morita, Hirofumi; Kuriyama, Youichi; Kunioka, Tatsuya

1994-11-01

379

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

380

Study of angular width of an X-ray beam fully pumped from quartz single crystal in the presence of temperature gradient  

Microsoft Academic Search

We investigate the cross section of transmitted X-ray beam diffracted by reflecting atomic planes (10–11) of a SiO2 single crystal in Laue geometry for different values of temperature gradient applied to the crystal. It is shown that the\\u000a angular width of a fully pumped X-ray beam depends on the distance between the source and the studied sample and decreases\\u000a with

K. T. Hayrapetyan; S. N. Noreyan; V. V. Margaryan

2010-01-01

381

A Novel High-Resolution Alignment Technique for XFEL Using Undulator X-ray Beams  

E-print Network

, and beamline in an x-ray free-electron laser. Two retractable pinholes at each end of the undulator define on the size of the object. In long stretched objects such as linear accelerators or free-electron lasers (FEL

Kemner, Ken

382

Application of Microfocus X-Ray Beams from Synchrotrons in Heritage Conservation  

Microsoft Academic Search

Synchrotron-based techniques are becoming increasingly important in heritage science and the aim of this article is to describe how recently developed microfocus methods can probe the elemental composition, speciation and structure at the micron level in samples from structures. Firstly an outline is given of the major techniques that are used, namely x-ray fluorescence, diffraction and absorption spectroscopy, and the

Alan V. Chadwick; Aaron Berko; Eleanor J. Schofield; A. Mark Jones; J. Fred W. Mosselmans; Andrew D. Smith

2012-01-01

383

A method for measuring the time structure of synchrotron X-ray beams  

Microsoft Academic Search

We described a method employing a plastic scintillator coupled to a fast photomultiplier tube to generate a timing pulse from the X-ray bursts emitted from a synchrotron radiation source. This technique is useful for performing synchrotron experiments where detailed knowledge of the timing distribution is necessary, such as time-resolved spectroscopy or fluorescence lifetime experiments. By digitizing the time difference between

W. W. Moses; S. E. Derenzo

1990-01-01

384

Dosimetric properties of high energy current (HEC) detector in keV x-ray beams.  

PubMed

We introduce a new x-ray radiation detector. The detector employs high-energy current (HEC) formed by secondary electrons consisting predominantly of photoelectrons and Auger electrons, to directly convert x-ray energy to detector signal without externally applied power and without amplification. The HEC detector is a multilayer structure composed of thin conducting layers separated by dielectric layers with an overall thickness of less than a millimeter. It can be cut to any size and shape, formed into curvilinear surfaces, and thus can be designed for a variety of QA applications. We present basic dosimetric properties of the detector as function of x-ray energy, depth in the medium, area and aspect ratio of the detector, as well as other parameters. The prototype detectors show similar dosimetric properties to those of a thimble ionization chamber, which operates at high voltage. The initial results obtained for kilovoltage x-rays merit further research and development towards specific medical applications. PMID:25789488

Zygmanski, Piotr; Shrestha, Suman; Elshahat, Bassem; Karellas, Andrew; Sajo, Erno

2015-04-01

385

Image formation by continuous writing with multi-beam in X-ray nanolithography  

Microsoft Academic Search

Summary form only given. Difficulties in X-ray lithography are now condensed into mask related matters. Since the exposure mode is basically 1:1, more strict accuracy is requested for mask fabrication than for the final images. Mask fabrication technology has made remarkable progress, and image formation of 70 nm line width was reported recently (Miyatake et al, 2001). Meanwhile, pattern reduction

E. Toyota; M. Washio

2001-01-01

386

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

387

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

388

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

SciTech Connect

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; McDonald III, John W.

2007-01-02

389

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

390

Chirped-Beam Two-Stage SASE-FEL for High Power Femtosceond X-Ray Pulse Generation  

NASA Astrophysics Data System (ADS)

We present a method for generating femtosecond duration x-ray pulses using a single-pass free-electron laser (FEL). This method uses an energy-chirped electron beam to produce a frequency-chirped x-ray pulse through self-amplified spontaneous emission (SASE). After the undulator we consider passing the radiation through a monochromator. The frequency is correlated to the longitudinal position within the pulse, and therefore, by selecting a narrow bandwidth, a short temporal pulse will be transmitted. The short pulse radiation is used to seed a second undulator, where the radiation is amplified to saturation. In addition to short pulse generation, this scheme has the ability to control shot-to-shot fluctuations in the central wavelength due to electron beam energy jitter. We present calculations of the radiation characteristics produced by a chirped beam two-stage SASE-FEL, and consider the performance of the chirped-beam two-stage option for the Linac Coherent Light Source (LCLS).

Schroeder, C. B.; Pellegrini, C.; Reiche, S.; Arthur, J.; Emma, P.

2002-08-01

391

Chirped-beam two-stage SASE-FEL for high power femtosecond X-ray pulse generation  

NASA Astrophysics Data System (ADS)

A method for generating femtosecond duration X-ray pulses using a single-pass free-electron laser (FEL) is presented. This method uses an energy-chirped electron beam propagating through an undulator to produce a frequency-chirped X-ray pulse through self-amplified spontaneous emission (SASE). After the undulator, we consider passing the radiation through a monochromator. The frequency is correlated to the longitudinal position within the pulse; therefore, by selecting a narrow bandwidth, a short temporal pulse will be transmitted. The short pulse radiation is used to seed a second undulator, where the radiation is amplified to saturation. In addition to short pulse generation, this scheme has the ability to control shot-to-shot fluctuations in the central wavelength due to electron beam energy jitter. We present calculations of the radiation characteristics produced by a chirped-beam two-stage SASE-FEL, and consider the performance of the chirped-beam two-stage option for the Linac Coherent Light Source.

Schroeder, C. B.; Pellegrini, C.; Reiche, S.; Arthur, J.; Emma, P.

2002-05-01

392

Quasi-monochromatic field-emission x-ray source  

SciTech Connect

By favoring the L-peak emission over the bremsstrahlung part, direct quasi-monochromatic soft x-ray emission has been obtained with a field emission (FE) x-ray source. The electron impact x-ray setup uses an arrayed cathode of carbon nanopearl FE tips as a stable cold electron source within a vacuum of 10{sup -6}-10{sup -7} Torr. The high brightness of the FE e-beam coupled with the array structure of the cold cathode allows a smoother control of the x-ray emission intensity. The wavelength of the x-ray source can be modified by the choice of target materials. Using Mo as the target material, the x-ray emission shows a peak centered at 2.45 keV with a monochromaticity between 75% and 55% and a FWHM in the range of 450 eV.

Diop, Babacar; Binh, Vu Thien [LPMCN, University of Lyon 1, Villeurbanne 69622 (France)

2012-09-15

393

The intermediate polar GK Persei: An unstable relation of the X-ray and the optical intensities in a series of outbursts  

NASA Astrophysics Data System (ADS)

Context. GK Per is an intermediate polar that has been displaying dwarf nova outbursts since the middle of the twentieth century. Aims: I analyzed a series of such outbursts in the optical and X-ray bands. I pay attention to the relation of intensities of the optical and X-ray emissions, and its reproducibility in a series of these consecutive outbursts. Methods: This analysis uses the data from the BAT/Swift, ASM/RXTE, AAVSO, and AFOEV databases. It investigates the relation of the time evolution of the profiles of outbursts in the individual bands (hard X-ray, medium/hard X-ray, and optical). Results: This analysis shows that the X-ray intensity steeply rises only in the start of the optical outburst and steeply declines only when the optical outburst comes to its end. However, the 1.5-50 keV band intensity saturates and balances on a plateau during the outburst. (The longer the outburst, the longer its plateau.) The peak X-ray intensities of this series display a significantly narrower range than the optical ones (a factor of about two versus a factor of about eight). This implies a discrepancy between the mass flow through the disk and the production of the X-ray emission via bremsstrahlung at the polar caps of the white dwarf. This discrepancy is the largest in the time of the peak optical intensity when the whole disk (or at least its inner part) is in the hot state and the flow of matter through the disk is the greatest. This study shows that a series of outbursts constitutes more general properties of this discrepancy. I argue that the saturation of the X-ray luminosity in outburst cannot be caused by a dominant increase in X-ray absorption. In the interpretation, large structural changes of the accreting regions at the magnetic poles of the white dwarf occur during the outburst. A buried shock proposed by some authors for polars is also promising for explaining the X-ray light curves of outbursts of GK Per. This research made use of the BAT/Swift, ASM/RXTE, AAVSO, and AFOEV databases.

Šimon, V.

2015-03-01

394

Comparison between beam-stop and beam-hole array scatter correction techniques for industrial X-ray cone-beam CT  

NASA Astrophysics Data System (ADS)

In industrial X-ray cone-beam computed tomography, the inspection of large-scale samples is important because of increasing demands on their quality and long-term mechanical resilience. Large-scale samples, for example made of aluminum or iron, are strongly scattering X-rays. Scattered radiation leads to artifacts such as cupping, streaks, and a reduction in contrast in the reconstructed CT-volume. We propose a scatter correction method based on sampling primary signals by employing a beam-hole array (BHA). In this indirect method, a scatter estimate is calculated by subtraction of the sampled primary signal from the total signal, the latter taken from an image where the BHA is absent. This technique is considered complementary to the better known beam-stop array (BSA) method. The two scatter estimation methods are compared here with respect to geometric effects, scatter-to-total ratio and practicability. Scatter estimation with the BHA method yields more accurate scatter estimates in off-centered regions, and a lower scatter-to-total ratio in critical image regions where the primary signal is very low. Scatter correction with the proposed BHA method is then applied to a ceramic specimen from power generation technologies. In the reconstructed CT volume, cupping almost completely vanishes and contrast is enhanced significantly.

Schörner, K.; Goldammer, M.; Stephan, J.

2011-02-01

395

Circular intensity differential scattering measurements in the soft x-ray region of the spectrum (~16 EV to 500 EV)  

NASA Astrophysics Data System (ADS)

We propose the use of recently developed technique of circular intensity differential scattering (CIDS), as extended to the soft x-ray region of the spectrum (16 eV to 500 eV), to study the higher order organization of the eukaryotic chromosome. CIDS is the difference in scattering power of an object when illuminated by right circularly polarized vs. left circularly polarized electromagnetic radiation of arbitrary wavelength. CIDS has been shown to be a very sensitive measure of the helical organization of the scattering object, e.g., the eukaryotic chromosome. Preliminary results of measurements of samples of bacteriophages and octopus sperm done at SRC, Wisconsin, show the technique to be very sensitive to the dimensional parameters of the particles interrogated by circularly polarized light.

Maestre, Marcos F.; Bustamante, Carlos J.; Snyder, Patricia A.; Rowe, Ednor M.; Hansen, Roger W.

1991-11-01

396

[Development of computer code PIETAII, for analysis of exposure dose from portable X-ray in neonatal intensive care unit].  

PubMed

The patients in NICU (Neonatal Intensive Care Unit) are more likely to get portable X-ray often while they are in the hospital. These patients potentially may get relatively more exposure dose in total in a short period of time. We developed a software to analyze the exposure dose for the patients in the incubator, which is called PIETAII (Patient Information of Exposure dose Total Analysis in NICU). Then, we compared the accuracy of PIETAII and SDEC (surface dose evaluation code) based on customary method. Using the 5 cm body thickness with exposure setting of 50 kV, 1 mAs, relative error between the customary method and the calculated dose by PIETAII and SDEC were 1.96% and 32.35%, respectively. PIETAII is a useful software to estimate the entrance surface dose using the exposure setting. PMID:25797661

Shohji, Tomokazu; Kato, Hideki; Katsuki, Youko; Gallagher, Miki

2015-03-01

397

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

398

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.

399

The Broadband and High Sensitivity X-Ray Beam Position Monitor of the IR beamline MIRIAM at Diamond  

NASA Astrophysics Data System (ADS)

A novel X-ray Beam Position Monitor has been designed and implemented on the Multimode InfraRed Imaging And Microspectroscopy (MIRIAM) beamline at Diamond. Installed in the B22 Front End and using no optical elements except for filters, it provides sub-micrometre position sensitivity and sub-microradiant angular sensitivity to Bending Magnet source vertical movements. By sampling at 100 kHz frequency, Fast Fourier Transform analysis is continuously displayed and any periodic components in the Synchrotron Radiation emission are revealed within the exceptional bandwidth of 50 kHz. Long term source drift in position or angle are monitored and recorded every 0.5 seconds.

Cinque, Gianfelice; Howell, George; Cobb, Tom; Tartoni, Nicola

2013-03-01

400

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

401

Damage characterization of SiN x-ray mask membrane caused by electron-beam exposure  

NASA Astrophysics Data System (ADS)

The effects of exposure damage with an electron beam of 20 to 50 kV acceleration voltage on silicon nitride film prepared by LPCVD system have been investigated. It is shown that the optical and mechanical properties of this material are modified and may potentially limit the use as a membrane in an x-ray mask structure for the high density memory devices of GDRAM level. Especially, the optical transmission of films exposed by electron beam with the acceleration voltage of 50 kV and the dosage of 900 (mu) C/cm2 degraded about 17 percent in the wavelength range of 633 +/- 10 nm. The differences in mechanical deflection on the membrane area of 800 X 800 micrometers 2 area which was, before and after, exposed by electron beam of acceleration voltage of 20 kV - 50 kV were shown about 500 angstrom to 100 angstrom. It was measured by the (alpha) -step (Tencor 200) with the stylus force of 19.6 dyne. The distortion of SiN X-ray mask membrane with alignment window was investigated by interferometric phase mapping.

Choi, Sang-Soo; Jeon, Young Jin; Kim, Jong-Soo; Chung, Hai Bin; Lee, Sang-Yun; Lee, Jong-Hyun; Yoo, Hyung Joun

1996-05-01

402

Non-equilibrium Modeling of the Fe XVII 3C/3D Line Ratio in an Intense X-Ray Free-Electron Laser Excited Plasma  

NASA Astrophysics Data System (ADS)

Recent measurements using an X-ray Free Electron Laser (XFEL) and an Electron Beam Ion Trap at the Linac Coherent Light Source facility highlighted large discrepancies between the observed and theoretical values for the Fe xvii 3C/3D line intensity ratio. This result raised the question of whether the theoretical oscillator strengths may be significantly in error, due to insufficiencies in the atomic structure calculations. We present time-dependent spectral modeling of this experiment and show that non-equilibrium effects can dramatically reduce the predicted 3C/3D line intensity ratio, compared with that obtained by simply taking the ratio of oscillator strengths. Once these non-equilibrium effects are accounted for, the measured line intensity ratio can be used to determine a revised value for the 3C/3D oscillator strength ratio, giving a range from 3.0 to 3.5. We also provide a framework to narrow this range further, if more precise information about the pulse parameters can be determined. We discuss the implications of the new results for the use of Fe xvii spectral features as astrophysical diagnostics and investigate the importance of time-dependent effects in interpreting XFEL-excited plasmas.

Loch, S. D.; Ballance, C. P.; Li, Y.; Fogle, M.; Fontes, C. J.

2015-03-01

403

Patient dose simulations for scanning-beam digital x-ray tomosynthesis of the lungs  

PubMed Central

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. PMID:24320450

Nelson, Geoff; Yoon, Sungwon; Krishna, Ganesh; Wilfley, Brian; Fahrig, Rebecca

2013-01-01

404

The feasibility of polychromatic cone-beam x-ray fluorescence computed tomography (XFCT) imaging of gold nanoparticle-loaded objects: a Monte Carlo study  

NASA Astrophysics Data System (ADS)

A recent study investigated the feasibility to develop a bench-top x-ray fluorescence computed tomography (XFCT) system capable of determining the spatial distribution and concentration of gold nanoparticles (GNPs) in vivo using a diagnostic energy range polychromatic (i.e. 110 kVp) pencil-beam source. In this follow-up study, we examined the feasibility of a polychromatic cone-beam implementation of XFCT by Monte Carlo (MC) simulations using the MCNP5 code. In the current MC model, cylindrical columns with various sizes (5-10 mm in diameter) containing water loaded with GNPs (0.1-2% gold by weight) were inserted into a 5 cm diameter cylindrical polymethyl methacrylate phantom. The phantom was then irradiated by a lead-filtered 110 kVp x-ray source, and the resulting gold fluorescence and Compton-scattered photons were collected by a series of energy-sensitive tallies after passing through lead parallel-hole collimators. A maximum-likelihood iterative reconstruction algorithm was implemented to reconstruct the image of GNP-loaded objects within the phantom. The effects of attenuation of both the primary beam through the phantom and the gold fluorescence photons en route to the detector were corrected during the image reconstruction. Accurate images of the GNP-containing phantom were successfully reconstructed for three different phantom configurations, with both spatial distribution and relative concentration of GNPs well identified. The pixel intensity of regions containing GNPs was linearly proportional to the gold concentration. The current MC study strongly suggests the possibility of developing a bench-top, polychromatic, cone-beam XFCT system for in vivo imaging.

Jones, Bernard L.; Cho, Sang Hyun

2011-06-01

405