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

Study on fundamental processes of laser welded metals observed with intense x-ray beams  

NASA Astrophysics Data System (ADS)

With use of photon techniques including visible light, soft and hard x-rays, precise fundamental laser welding processes in the repair and maintenance of nuclear plant engineering were reviewed mechanistically. We make discussions centered on the usefulness of an intense soft x-ray beams for evaluations of spatial residual strain distribution and welded metal convection behavior including the surface morphology. Numerical results obtained with a general purpose three-dimensional code SPLICE for the simulation of the welding and solidifying phenomena. Then it is concluded that the x-ray beam would be useful as one of the powerful tools for understanding the mechanisms of various complex phenomena with higher accuracy and higher resolution.

Muramatsu, T.; Daido, H.; Shobu, T.; Takase, K.; Tsukimori, K.; Kureta, M.; Segawa, M.; Nishimura, A.; Suzuki, Y.; Kawachi, T.

2

X-ray beam finder  

DOEpatents

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

Gilbert, H.W.

1983-06-16

3

Development of ionization chamber for in-line intensity monitoring of large profile parametric X-ray beam  

NASA Astrophysics Data System (ADS)

An in-line ionization chamber has been developed for the real-time measurement of the absolute intensity of the pulsed parametric X-ray (PXR) beam during irradiation experiments. The quasi-monochromatic PXR generating system was developed at the Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University. In contrast to typical narrow X-ray beams in synchrotron radiation facilities, the PXR beam profile is as large as approximately 100 mm in diameter with rather uniform flux distribution at the X-ray output port in the experimental hall. The energy of the PXR beam ranges from 5 to 34 keV, which is specified by the PXR target crystal plane and its geometrical condition. The ionization chamber is of a plane parallel type employing 6-?m thick double-sided aluminum vapor-deposited polyester films for the plane electrodes through which the X-ray beam passes. The plane bias electrode has been placed at an equal distance of 25 mm from the two plane earth electrodes that act as the beam windows with an aperture diameter of 120 mm. Due to the pulsed property of the PXR beam and the geometrical configuration of the ionization chamber, the charge-sensitive preamplifier output pulse height represents an integral of the fast electron current, corresponding to a half of the total ionization charge produced by the beam. The intensity of the PXR beam has been measured for various X-ray energies by using nitrogen and argon, respectively, as the filling gas.

Tanaka, T.; Kuwada, T.; Takahashi, Y.; Hayakawa, K.; Hayakawa, Y.; Sakai, T.; Nogami, K.; Nakao, K.; Inagaki, M.; Sato, I.

2013-03-01

4

Modelling properties of hard x-rays generated by the interaction between relativistic electrons and very intense laser beams  

NASA Astrophysics Data System (ADS)

In a previous paper we presented a calculation model for high harmonic generation by relativistic Thomson scattering of the electromagnetic radiation by free electrons. In this paper we present a similar model for the calculation of the energies of hard x-rays (20- 200 keV) resulted from the interaction between relativistic electrons (20-100 MeV) and very intense laser beams. Starting from the relativistic equations of motion of an electron in the electromagnetic field we show that the Liènard-Wiechert equation leads to electromagnetic waves whose frequencies are in the domain of hard x-rays. When the relativistic parameter of the laser beam is greater than unity, the model predicts the existence of harmonics of the above frequencies. Our theoretical values are in good agreement with experimental values of the x-ray energies from the literature and predict accurately their angular distribution.

Popa, Alexandru

2009-01-01

5

Results of a search for paraphotons with intense X-ray beams at SPring-8  

NASA Astrophysics Data System (ADS)

A search for paraphotons, or hidden U(1) gauge bosons, is performed using an intense X-ray beamline at SPring-8. “Light Shining through a Wall” technique is used in this search. No excess of events above background is observed. A stringent constraint is obtained on the photon-paraphoton mixing angle, ?<8.06×10-5 (95% C.L.) for 0.04 eV

Inada, T.; Namba, T.; Asai, S.; Kobayashi, T.; Tanaka, Y.; Tamasaku, K.; Sawada, K.; Ishikawa, T.

2013-05-01

6

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

7

Cryo-protection of protein crystals in intense x-ray beams  

SciTech Connect

A focused white beam from existing synchrotrons has an intensity comparable with the monochromatic beams available from future undulator beamlines. The beam from station 9.5 on the SRS has therefore been used to examine the radiation damage caused within a protein crystal, cooled to near liquid nitrogen temperature. It was found that observable radiation damage occurred at doses comparable with those which have been observed in cryo-electron microscopy. It would be possible to collect many data sets from the test lysozyme crystal before radiation damage occurred under these conditions. However, it would not be possible to collect a good quality data set from a single protein crystal of a few tens of microns in size, even at liquid nitrogen temperature.

Gonzalez, A.; Thompson, A.W.; Nave, C. (SERC Daresbury Laboratory, Warrington WA4 4AD (United Kingdom))

1992-01-01

8

Diffraction of real and virtual photons in a pyrolytic graphite crystal as source of intensive quasimonochromatic X-ray beam  

NASA Astrophysics Data System (ADS)

A series of experiments on the parametric X-rays radiation (PXR) generation and radiation soft component diffraction of relativistic electrons in pyrolytic graphite (PG) crystals have been carried out at the Tomsk synchrotron. It is shown that the experimental results with PG crystals are explained by the kinematic PXR theory if we take into account a contribution of the real photons diffraction (transition radiation, bremsstrahlung and PXR photons as well). The measurements of the emission spectrum of channeled electrons in the photon energy range much smaller than the characteristic energy of channeling radiation have been performed with a crystal-diffraction spectrometer. For electrons incident along the <1 1 0> axis of a silicon crystal, the radiation intensity in the energy range 30? ??360 keV exceeds the bremsstrahlung one almost by an order of magnitude. Different possibilities to create an effective source of the monochromatic X-ray beam based on the real and virtual photons diffraction in the PG crystals have been considered.

Bogomazova, E. A.; Kalinin, B. N.; Naumenko, G. A.; Padalko, D. V.; Potylitsyn, A. P.; Sharafutdinov, A. F.; Vnukov, I. E.

2003-01-01

9

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

10

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

NASA Astrophysics Data System (ADS)

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.; Ghamari, F.

2014-05-01

11

Parametric X-ray radiation for calibration of X-ray space telescopes and generation of several X-ray beams  

NASA Astrophysics Data System (ADS)

The setup based on a moderate energy linear accelerator (linac) is proposed to provide users with a tunable, quasi-monochromatic, linearly polarized X-ray beam. The effect of parametric X-ray radiation (PXR) from relativistic electrons in a crystal is used in an X-ray source. The application of the setup for calibration of X-ray space telescopes and other equipment is considered. The setup allows calibration of angular, spectral, polarization parameters of telescopes with smooth tuning of X-ray energy from several keV to hundreds of keV. Estimates of X-ray flux intensities and spectral line widths on the telescope aperture at a distance of several hundred meters are presented. Besides, the PXR-based facility for simultaneous generation of several X-ray beams is proposed.

Shchagin, A. V.; Khizhnyak, N. A.; Fiorito, R. B.; Rule, D. W.; Artru, X.

2001-01-01

12

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

13

Exotic X-ray Sources from Intermediate Energy Electron Beams  

NASA Astrophysics Data System (ADS)

High intensity x-ray beams are used in a wide variety of applications in solid-state physics, medicine, biology and material sciences. Synchrotron radiation (SR) is currently the primary, high-quality x-ray source that satisfies both brilliance and tunability. The high cost, large size and low x-ray energies of SR facilities, however, are serious limitations. Alternatively, "novel" x-ray sources are now possible due to new small linear accelerator (LINAC) technology, such as improved beam emittance, low background, sub-Picosecond beam pulses, high beam stability and higher repetition rate. These sources all stem from processes that produce Radiation from relativistic Electron beams in (crystalline) Periodic Structures (REPS), or the periodic "structure" of laser light. REPS x-ray sources are serious candidates for bright, compact, portable, monochromatic, and tunable x-ray sources with varying degrees of polarization and coherence. Despite the discovery and early research into these sources over the past 25 years, these sources are still in their infancy. Experimental and theoretical research are still urgently needed to answer fundamental questions about the practical and ultimate limits of their brightness, mono-chromaticity etc. We present experimental results and theoretical comparisons for three exotic REPS sources. These are Laser-Compton Scattering (LCS), Channeling Radiation (CR) and Parametric X-Radiation (PXR).

Chouffani, K.; Wells, D.; Harmon, F.; Jones, J. L.; Lancaster, G.

2003-08-01

14

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

SciTech Connect

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

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

2012-12-15

15

Very intense source of flash x rays  

NASA Astrophysics Data System (ADS)

This article describes the design of a very intense source of flash x rays using the HERMES III electron accelerator that delivers a measured peak dose and peak dose rate of (370±58) krad(CaF2) and (3.5±0.7)×1013 rad(CaF2)/s, respectively, over a useful area of 80 cm2, without target destruction. Measured electron and photon source distributions agree with those generated from a numerical model. The quality of the agreement gives credibility to both and validates the main assumptions of the model.

Sanford, T. W. L.; Halbleib, J. A.; Poukey, J. W.; Welch, D. R.; McAtee, W. H.; Mock, R. C.

1992-11-01

16

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

17

Fast Soft X-ray Beam Shutter  

SciTech Connect

Most biological or polymer samples are radiation sensitive materials. A study of these materials at synchrotron radiation sources is challenging in order to minimize and systematically quantify exposure to the period of actual measurements. Since damage can occur on a scale of milliseconds there is a requirement for a beam shutter which can close and open in sub-millisecond times. At the Advanced Light Source two scanning transmission X-ray microscopes (STXM) have been equipped with innovative shutters.

Kilcoyne, A.L.D. [Department of Physics, North Carolina State University, Raleigh, NC 27695 (United States); Tyliszczak, T. [Brockhouse Institute for Material Research, McMaster University, Hamilton, ON L8S 4M1 (Canada)

2004-05-12

18

Coherent X-ray Cherenkov radiation produced by microbunched beams  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

19

Intensity correlation measurement system by picosecond single shot soft x-ray laser.  

PubMed

We developed a new soft x-ray speckle intensity correlation spectroscopy system by use of a single shot high brilliant plasma soft x-ray laser. The plasma soft x-ray laser is characterized by several picoseconds in pulse width, more than 90% special coherence, and 10(11) soft x-ray photons within a single pulse. We developed a Michelson type delay pulse generator using a soft x-ray beam splitter to measure the intensity correlation of x-ray speckles from materials and succeeded in generating double coherent x-ray pulses with picosecond delay times. Moreover, we employed a high-speed soft x-ray streak camera for the picosecond time-resolved measurement of x-ray speckles caused by double coherent x-ray pulse illumination. We performed the x-ray speckle intensity correlation measurements for probing the relaxation phenomena of polarizations in polarization clusters in the paraelectric phase of the ferroelectric material BaTiO(3) near its Curie temperature and verified its performance. PMID:20113111

Kishimoto, Maki; Namikawa, Kazumichi; Sukegawa, Kouta; Yamatani, Hiroshi; Hasegawa, Noboru; Tanaka, Momoko

2010-01-01

20

1D X-ray Beam Compressing Monochromators  

SciTech Connect

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

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

2010-04-06

21

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

E-print Network

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

Hitchcock, Adam P.

22

Effects of intense x-ray radiation on polycapillary fiber performance  

Microsoft Academic Search

Several applications of Kumakhov polycapillary optics require extended exposure to intense x- ray radiation. No degradation of performance has been observed when using polycapillary x- ray optics with laboratory sources. As part of an ongoing study to develop an understanding of damage mechanisms and performance limitations, borosilicate glass polycapillaries have been exposed to white beam bending magnet synchrotron radiation with

Bimal K. Rath; D. C. Aloisi; Donald H. Bilderback; N. Gao; Walter M. Gibson; F. A. Hofmann; B. E. Homan; Chris J. Jezewski; I. L. Klotzko; J. M. Mitchell; S. M. Owens; Johannes B. Ullrich; Lei Wang; Gregory M. Wells; Qi Fan Xiao; Carolyn A. MacDonald

1995-01-01

23

X-Ray Radiation from Nonlinear Thomson Scattering of an Intense Femtosecond Laser on Relativistic Electrons in a Helium Plasma  

E-print Network

X-Ray Radiation from Nonlinear Thomson Scattering of an Intense Femtosecond Laser on Relativistic November 2003) We have generated x-ray radiation from the nonlinear Thomson scattering of a 30 fs=1:5 J laser beam on plasma electrons. A collimated x-ray radiation with a broad continuous spectrum peaked

Umstadter, Donald

24

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

PubMed

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

2013-07-01

25

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

26

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

27

Intense x-ray machine for penetrating radiography  

SciTech Connect

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

Lucht, R.A.; Eckhouse, S.

1989-01-01

28

High-intensity laser synchrotron x-ray source  

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 Light Source (LSLS) concept is still waiting for a convincing demonstration. Available at the BNL`s Accelerator Test Facility (ATF), a high-brightness electron beam and the high-power C0{sub 2} laser may be used as prototype LSLS brick stones. In a feasible demonstration experiment, 10-GW, 100-ps C0{sub 2} laser beam will be brought to a head-on collision with a 10-ps, 0.5-nC, 70 MeV electron bunch. Flashes of well-collimated, up to 9.36-keV ({approximately}{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 a variable e-beam energy. A natural short-term extension of the proposed experiment would be further enhancement of the x-ray flux to a 10{sup 21}{minus}10{sup 22} photons/sec level, after the ongoing ATF CO{sub 2} laser upgrade to 1 TW peak power and electron bunch shortening to 3 ps. The ATF LSLS x-ray beamline, exceeding by orders of magnitude the peak fluxes attained at the National Synchrotron Light Source (NSLS) x-ray storage ring, may become attractive for certain users, e.g., for biological x-ray microscopy. In addition, a terawatt CO{sub 2} laser will enable harmonic multiplication of the x-ray spectrum via nonlinear Compton scattering.

Pogorelsky, I.V.

1995-10-01

29

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

PubMed

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 SiO2 optical fibers. PMID:24784587

Kayser, Y; B?achucki, W; Dousse, J-Cl; Hoszowska, J; Neff, M; Romano, V

2014-04-01

30

Use of active-edge silicon detectors as X-ray beam monitors  

NASA Astrophysics Data System (ADS)

Silicon detectors have been developed which are active to within several microns of the physical edge of the detector. These active-edge devices can be placed near an intense X-ray beam to accurately measure the X-ray beam properties. In addition, they can be fabricated in a variety of geometries that will be useful for monitoring the intensity, profile, and position of synchrotron X-ray beams. One shape is a detector with a through hole surrounded by four active elements. The hole allows the intense X-ray beam to go through the center while the four elements can detect any change in the position or dispersion of the beam. Another shape is a rectangular 5 mm long×0.5 mm wide device with a set of four elements that are 100 ?m wide. These devices could be mounted on the upstream side of the jaws of an x- y collimating slit to measure the intensity profile of the beam that each jaw of the slit is stopping. Small detectors could also be mounted in a cylindrical beam stop to give on-line beam intensity measurements. A variety of different geometries were tested at beamline 10.3.1 of the Advanced Light Source using a 12.5 keV X-ray beam. They have wide dynamic range, excellent position sensitivity and low sensitivity to radiation damage.

Kenney, C. J.; Hasi, J.; Parker, Sherwood; Thompson, A. C.; Westbrook, E.

2007-11-01

31

Potential applications of polycapillary optics to polarized beam X-ray fluorescence analysis  

Microsoft Academic Search

The Polarized beam X-ray fluorescence (XRF) technique has potential applications in elemental analysis in materials analysis and in-vivo. In this work, first micro X-ray fluorescence (MXRF) measurements were done using a focusing lens. Polarization can be used to reduce the background, to give a better minimum detection limit. Polarizing the beam, using scattering has a disadvantage of low intensity and

Abrar M. Hussain

2006-01-01

32

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

33

An ultra fast electron beam x-ray tomography scanner  

Microsoft Academic Search

This paper introduces the design of an ultra fast x-ray tomography scanner based on electron beam technology. The scanner has been developed for two-phase flow studies where frame rates of 1 kHz and higher are required. Its functional principle is similar to that of the electron beam x-ray CT scanners used in cardiac imaging. Thus, the scanner comprises an electron

F. Fischer; D. Hoppe; E. Schleicher; G. Mattausch; H. Flaske; R. Bartel; U. Hampel

2008-01-01

34

An ultra fast electron beam x-ray tomography scanner  

Microsoft Academic Search

This paper introduces the design of an ultra fast x-ray tomography scanner based on electron beam technology. The scanner has been developed for two-phase flow studies where frame rates of 1 kHz and higher are required. Its functional principle is similar to that of the electron beam x-ray CT scanners used in cardiac imaging. Thus, the scanner comprises an electron

35

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

36

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

37

Ultrafast absorption of intense x rays by nitrogen molecules  

NASA Astrophysics Data System (ADS)

We devise a theoretical description for the response of nitrogen molecules (N2) to ultrashort and intense x rays from the free electron laser Linac Coherent Light Source (LCLS). We set out from a rate-equation description for the x-ray absorption by a nitrogen atom. The equations are formulated using all one-x-ray-photon absorption cross sections and the Auger and radiative decay widths of multiply-ionized nitrogen atoms. Cross sections are obtained with a one-electron theory and decay widths are determined from ab initio computations using the Dirac-Hartree-Slater (DHS) method. We also calculate all binding and transition energies of nitrogen atoms in all charge states with the DHS method as the difference of two self-consistent field (SCF) calculations (?SCF method). To describe the interaction with N2, 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 N2: 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 N22+, and molecular fragmentation are explained.

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

2012-06-01

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

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

NASA Astrophysics Data System (ADS)

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

Trojek, Tomáš; Trojková, Darina

2014-11-01

40

Research on temperature measurement by X-ray transmission intensity  

NASA Astrophysics Data System (ADS)

The relationship between temperature and X-ray transmission intensity was researched and analyzed by inspecting material density change, which is caused by thermal expansion. A digital radiographic system was employed to obtain the images. On this basis, we deduced the temperature formula based on the average gray level of the captured images. The measured temperatures were obtained from the experiments and the errors were analyzed. We concluded that when X-rays pass through an object, the X-ray strength and the gray level of the image under high temperatures are greater than those under lower temperatures and the image gray level error has great impact on the accuracy of the measured temperature. The presented approach allowed the non-contact temperature measurement of material.

Chen, Shuyue; Cheng, Rong

2013-02-01

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

Quantitative measurement of hard x-ray spectra for high intensity laser produced plasma  

SciTech Connect

X-ray line spectra ranging from 17 to 77 keV were quantitatively measured with a Laue spectrometer, composed of a cylindrically curved crystal and a detector. Either a visible CCD detector coupled with a CsI phosphor screen or an imaging plate can be chosen, depending on the signal intensities and exposure times. The absolute sensitivity of the spectrometer system was calibrated using pre-characterized laser-produced x-ray sources and radioisotopes. The integrated reflectivity for the crystal is in good agreement with predictions by an open code for x-ray diffraction. The energy transfer efficiency from incident laser beams to hot electrons, as the energy transfer agency for specific x-ray line emissions, is derived as a consequence of this work.

Zhang, Z.; Nishimura, H.; Namimoto, T.; Fujioka, S.; Arikawa, Y.; Hosoda, H.; Azechi, H. [Institute of Laser Engineering, Osaka University, 2-6 Yamada-oka, Suita, Osaka 565-0871 (Japan); Nishikino, M.; Kawachi, T.; Sagisaka, A.; Orimo, S.; Ogura, K.; Pirozhkov, A.; Yogo, A.; Kiriyama, H.; Kondo, K. [Quantum Beam Science Directorate, Kansai Photon Science Institute, JAEA, Kyoto 619-0215 (Japan); Okano, Y. [Laser Research Center for Molecular Science, Institute for Molecular Science, National Institute of Natural Science 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585 (Japan); Ohshima, S. [Institute of Laser Engineering, Osaka University, 2-6 Yamada-oka, Suita, Osaka 565-0871 (Japan); Pioneering Research Unit for Next Generation, Kyoto University, Uji 611-0011 (Japan)

2012-05-15

43

X-ray diffraction tomography employing an annular beam.  

PubMed

We demonstrate depth-resolved materials characterization by scanning a sample through an annular beam of X-rays. We measure Bragg X-ray diffraction from a sample with a planar detector positioned centrally in a circular dark field defined by the annular beam. The diffraction maxima are optically encoded with the position of crystalline phases along this beam. Depth-resolved material phase images are recovered via tomosynthesis. We demonstrate our technique using a heterogeneous three-dimensional object comprising three different phases; cyclotetramethylene - tetranitramine, copper and nickel, distributed in a low density medium. Our technique has wide applicability in analytical imaging and is scalable with respect to both scan size and X-ray energy. PMID:24921314

Evans, Paul; Rogers, Keith; Dicken, Anthony; Godber, Simon; Prokopiou, Danae

2014-05-19

44

Monochromators for small cross-section x-ray beams from high heat flux synchrotron sources  

SciTech Connect

For some x-ray experiments, only a fraction of the intense central cone of x-rays generated by high-power undulator sources can be used; the x-ray source emittance is larger than the useful emittance for the experiment. For example with microfocusing optics, or for coherence experiments, x-ray beams with cross sections less than 0.1 mm{sup 2} are desirable. With such small beams, the total thermal load is small even though the heat flux density is high. Analyses indicate that under these conditions, rather simple crystal cooling techniques can be used. We illustrate the advantages of a small beam monochromator, with a simple x-ray monochromator optimized for x-ray microdiffraction. This monochromator is designed to achieve negligible distortion when subjected to a narrow (0.1 mm wide) beam from an APS undulator operating at 100 mA. It also allows for rapid and repeatable energy scans and rapid cycling between monochromatic and white beam conditions.

Ice, G.; Riemer, B. [Oak Ridge National Lab., TN (United States); Khounsary, A. [Argonne National Lab., IL (United States)

1996-10-01

45

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

46

Interpretation of nanoparticle X-ray photoelectron intensities  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

47

Muonic Lyman x-ray intensities in pure elements  

Microsoft Academic Search

Muonic x-ray intensity ratios (I(Ki)\\/I(K..cap alpha..)) have been measured for 21 pure elements in the range 4< or =Z< or =48. The cyclic variation of these ratios with Z is clearly seen to follow the pattern of the periodic table of the elements over this range. The product of I(K..beta..)\\/I(K..cap alpha..) and nearest-neighbor distance in the pure-element lattices varies approximately

C. J. Orth; M. E. Schillaci; J. D. Knight; L. F. Mausner; R. A. Naumann; G. Schmidt; H. Daniel

1982-01-01

48

Muonic Lyman x-ray intensities in pure elements  

Microsoft Academic Search

Muonic x-ray intensity ratios [I(Ki)I(Kalpha)] have been measured for 21 pure elements in the range 4<=Z<=48. The cyclic variation of these ratios with Z is clearly seen to follow the pattern of the periodic table of the elements over this range. The product of I(Kbeta)I(Kalpha) and nearest-neighbor distance in the pure-element lattices varies approximately linearly with Z within each period.

C. J. Orth; M. E. Schillaci; J. D. Knight; L. F. Mausner; R. A. Naumann; G. Schmidt; H. Daniel

1982-01-01

49

Monolithic focused reference beam X-ray holography.  

PubMed

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

Editorial: Focus on X-ray Beams with High Coherence  

Microsoft Academic Search

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

Ian Robinson; Gerhard Gruebel; Simon Mochrie

2010-01-01

51

X-ray topography on the VEPP-3 and VEPP-4 SR beams and X-ray imaging techniques  

Microsoft Academic Search

X-ray topography studies performed using the VEPP-3 and VEPP-4 storage rings SR beams as well as ones concerning X-ray imaging techniques using TV and charge-coupled (CCD) devices are briefly reviewed. The main parameters of these devices and the prospects for their application and development are discussed.

V. E. Panchenko

1987-01-01

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

Bessel spatial profile of a soft x-ray laser beam  

SciTech Connect

We report far-field profile measurements of an optical-field-ionized high-order harmonic-seeded soft x-ray laser. We show that the beam transverse profile can be controlled between a regular Gaussian shape and a Bessel profile exhibiting several rings via the infrared laser pump intensity. These experimental data are supported by a complete numerical modeling including a two-dimensional plasma amplifier simulation and a two-level soft x-ray amplification using a Maxwell-Bloch treatment. This model takes into account the experimental high-order harmonic wavefront and intensity before it is numerically amplified.

Tissandier, F.; Sebban, S.; Ribiere, M.; Gautier, J.; Zeitoun, Ph.; Lambert, G.; Goddet, J.-Ph.; Burgy, F.; Valentin, C.; Rousse, A. [Laboratoire d'Optique Appliquee, ENSTA Paristech/Ecole Polytechnique/CNRS, UMR 7639, F-91761 Palaiseau Cedex (France); Nejdl, J.; Mocek, T. [Institute of Physics, ASCR, Na Slovance 2, CZ-182 21 Prague 8 (Czech Republic); Maynard, G. [Laboratoire de Physique des Gaz et des Plasmas, Universite Paris Sud/CNRS, UMR 8578, F-91405 Orsay Cedex (France)

2010-12-06

54

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

55

Coherent Cone-Beam X-ray Microscopy  

SciTech Connect

A novel full-field imaging method using the (111) Bragg diffraction of a sub-micron gold crystal as the divergent cone-beam for sample illumination is reported. The divergence of the illumination allows for very high magnification, limited only by the achievable ratio of the crystal-to-sample and sample-to-detector distances. In this case an x-ray magnification of approximately 115 was achieved.

Harder, R.; Xiao, X. [Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439 (United States)

2011-09-09

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

Grazing incidence parametric X-ray radiation from the relativistic electron beam moving in parallel to the superlattice surface  

NASA Astrophysics Data System (ADS)

New configuration for generation of the parametric X-ray radiation (PXR) by an ultrarelativistic electron beam is considered. The beam propagates along the external surface of periodical multilayer structure (superlattice) while the photons are emitted under the condition of grazing incidence diffraction. PXR spectral intensity is calculated for this case. It is shown that this specific configuration of the electron beam and target radiator can be used for the PXR generation in a storage ring. It can allow one to obtain the monochromatic X-ray beams with the smoothly tuned frequency and the spectral intensity exceeding intensity of the synchrotron radiation in the narrow spectral ranges.

Feranchuk, I. D.; Feranchuk, S. I.

2007-05-01

58

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

59

X-ray pencil beam facility for optics characterization  

NASA Astrophysics Data System (ADS)

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

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

2010-07-01

60

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

61

A simple specimen holder for low temperature X-ray intensity studies using a General Electric diffractometer  

Microsoft Academic Search

A simple device is described which is suitable for X-ray diffraction intensity studies at temperatures near that of liquid nitrogen. The device enables one to make such a study with little or no loss in beam intensity and with a specimen which is free of frost.

J H Brady; E C van Reuth

1966-01-01

62

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

Code of Federal Regulations, 2010 CFR

A diagnostic x-ray beam-limiting device is a device such as a collimator, a cone, or an aperture intended to restrict the dimensions of a diagnostic x-ray field by limiting the size of the primary x-ray beam. (b) Classification. Class...

2010-04-01

63

Multi-beam X-ray source breast tomosynthesis reconstruction with different algorithms  

E-print Network

Multi-beam X-ray source breast tomosynthesis reconstruction with different algorithms Weihua Zhou ABSTRACT Digital breast tomosynthesis is a new technique to improve the early detection of breast cancer multi-beam X-ray sources breast tomosynthesis system. Carbon nanotube technology based X-ray tubes were

Chen, Ying "Ada"

64

Two-Dimensional X-Ray Beam Phase Sensing  

NASA Astrophysics Data System (ADS)

We present a new method to analyze quantitatively the wave front of a partially coherent x-ray beam. The technique is based on the use of two-dimensional speckle patterns combined with digital image correlation algorithms and offers a pixel size resolution, a high accuracy, and a reduced sensitivity to mechanical vibrations thanks to a very simple setup. The requirements on transverse and longitudinal coherence are also low. Finally, we show how the method can be used for phase contrast imaging applications by a single sample exposure process.

Bérujon, Sébastien; Ziegler, Eric; Cerbino, Roberto; Peverini, Luca

2012-04-01

65

Two-dimensional x-ray beam phase sensing.  

PubMed

We present a new method to analyze quantitatively the wave front of a partially coherent x-ray beam. The technique is based on the use of two-dimensional speckle patterns combined with digital image correlation algorithms and offers a pixel size resolution, a high accuracy, and a reduced sensitivity to mechanical vibrations thanks to a very simple setup. The requirements on transverse and longitudinal coherence are also low. Finally, we show how the method can be used for phase contrast imaging applications by a single sample exposure process. PMID:22587288

Bérujon, Sébastien; Ziegler, Eric; Cerbino, Roberto; Peverini, Luca

2012-04-13

66

X-ray emission as a diagnostic from pseudospark-sourced electron beams  

NASA Astrophysics Data System (ADS)

X-ray emission has been achieved using an electron beam generated by a pseudospark low-pressure discharge and utilised as a diagnostic for beam detection. A 300 A, 34 kV PS-sourced electron beam pulse of 3 mm diameter impacting on a 0.1 mm-thick molybdenum target generated X-rays which were detected via the use of a small, portable X-ray detector. Clear X-ray images of a micro-sized object were captured using an X-ray photodetector. This demonstrates the inducement of proton induced X-ray emission (PIXE) not only as an indicator of beam presence but also as a future X-ray source for small-spot X-ray imaging of materials.

Bowes, D.; Yin, H.; He, W.; Zhang, L.; Cross, A. W.; Ronald, K.; Phelps, A. D. R.; Chen, D.; Zhang, P.; Chen, X.; Li, D.

2014-09-01

67

Hard X-ray Imaging Microscopy using X-ray Guide Tube as Beam Condenser for Field Illumination  

NASA Astrophysics Data System (ADS)

An optical system for illumination of object in x-ray imaging microscopy is developed. The optical system is a beam condenser consisting of a single-bounce conical-shape mono-capillary (x-ray guide tube: XGT) made of Pyrex glass. The XGT condenser was tested at the beam line 47XU of SPring-8 using a Fresnel zone plate as an objective lens. Comparing with the microscope without beam condenser, the flux density is improved by a factor of 12-20 in the x-ray energy range of 6-8 keV. Test patterns with a 50 nm-structure are clearly resolved at 8 keV with an exposure time less than 1 s.

Suzuki, Yoshio; Takeuchi, Akihisa; Uesugi, Kentaro; Terada, Yasuko; Nakazawa, Hiromoto; Ohzawa, Sumito; Aoyama, Tomoki; Nii, Hajime; Handa, Katsumi

2013-10-01

68

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

69

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

70

Two-dimensional x-ray magnification based on a monolithic beam conditioner  

Microsoft Academic Search

In x-ray imaging and beam conditioning it is useful to magnify or demagnify the x-ray beam, or an image, approaching (sub)micrometre resolution or the (sub)micrometre illuminated region. Using an asymmetric diffractor it is possible to expand or compress the x-ray beam in one direction. Combining two such diffractors with mutually perpendicular planes of diffraction even two-dimensional beam expansion or compression

D. Korytár; P. Mikulík; C. Ferrari; J. Hrdý; T. Baumbach; A. Freund; A. Kubena

2003-01-01

71

Chemical-effect variation of K ?\\/K ? X-ray intensity ratios in 3d elements  

Microsoft Academic Search

Chemical effects on K?\\/K? X-ray intensity ratios for some Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn compounds are studied experimentally. The X-ray spectra were measured by using a Si (Li) solid state detector with high resolution. The vacancies were produced by heavily filtered 241Am gamma rays. It is found that the K?\\/K? X-ray intensity ratios measured with

Omer Sogut; Erdo?an Büyükkasap; Hasan Erdo?an

2002-01-01

72

Grazing incident asymmetric X-ray diffraction of ?-FeSi 2 layers, produced by ion beam synthesis  

Microsoft Academic Search

The crystal structure of ?-FeSi2 phase, prepared by ion beam synthesis (IBS) method, followed by rapid thermal annealing (RTA) is investigated by grazing incident asymmetric X-ray diffraction (GIAXRD). The X-ray spectra, obtained at different grazing angles, indicated that the ?-FeSi2 phase is formed in the whole implantation range. From the comparison of the reflections intensities ratios, it is found that

A. Atanassov; M. Baleva; V. Darakchieva; E. Goranova

2004-01-01

73

Tomosynthesis reconstruction from multi-beam X-ray sources  

Microsoft Academic Search

We investigate methods for reconstructing tomosynthesis data using arrays of microfabricated X-ray sources and area CCD detectors. Tomosynthesis is a 3D imaging technique for limited-angle tomography that uses multiple radiographic images taken from an X-ray source placed at several positions to estimate a 3D distribution of X-ray attenuation. In our implementation, the moving X-ray source is replaced with multiple carbon

David S. Lalush; Enzhuo Quan; Ramya Rajaram; Jian Zhang; Jianping Lu; Otto Zhou

2006-01-01

74

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

75

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

Microsoft Academic Search

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

Robert J. Kinzig

1991-01-01

76

Constancy check of beam quality in conventional diagnostic X-ray equipment.  

PubMed

A tandem ionization chamber was developed for quality control programs of X-ray equipment used in conventional radiography and mammography. A methodology for the use of the tandem chamber in the constancy check of diagnostic X-ray beam qualities was established. The application at a medical X-ray imaging facility of this established methodology is presented. The use of the tandem chamber in the constancy check of diagnostic X-ray beam qualities is a useful method to control the performance of the X-ray equipment. PMID:18434171

Costa, Alessandro M; Badin, Rômulo S; Leite, Marina S; Caldas, Linda V E

2008-10-01

77

Divergence measurements of soft x-ray laser beam  

SciTech Connect

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

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

1986-07-01

78

Quantitative X-Ray Imaging of Density Distributions in High-Intensity Discharge Lamps  

Microsoft Academic Search

Summary form only given. Development of a table-top X-ray absorption imaging apparatus for determination of Hg densities in high-intensity discharge lamps is described. The apparatus is based on a commercial X-ray tube source and detection of X-rays with a phosphor and optical charge-coupled device (CCD). This type of system has the apparent disadvantages, relative to a synchrotron based system, of

J. J. Curry; B. Lafitte

2007-01-01

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

Characterization of the 46.9-nm soft X-ray laser beam from a capillary discharge  

NASA Astrophysics Data System (ADS)

Intense lasing had been obtained from argon plasma in the soft X-ray region from a capillary discharge plasma system. Different diagnostics have been used to characterize the lasing properties by recording the temporal, spatial, and spectral profiles of the emission. The divergence measurement indicates that the soft X-ray laser beam has good directionality with a divergence of 3.5 mrad. The spectrum of the laser beam measured using a transmission grating showed intense lasing line at 46.9 nm. Diffraction orders as high as 10th orders were observed. The temporal profile recorded with a vacuum diode showed a distinct laser peak with a pulse width ~1.2 ns (FWHM). In addition, the coherence of the X-ray laser beam was also confirmed from the high-contrast interference fringes (visibility ~85 %) recorded using double slits.

Barnwal, S.; Prasad, Y. B. S. R.; Nigam, S.; Aneesh, K.; Sharma, M. L.; Kushwaha, R. P.; Tripathi, P. K.; Naik, P. A.; Chakera, J. A.; Navathe, C. P.; Gupta, P. D.

2014-10-01

81

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

NASA Astrophysics Data System (ADS)

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

Hockaday, Mary Yvonne Pottenger

82

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

83

Efficient Monte Carlo simulations in kilovoltage x-ray beams  

NASA Astrophysics Data System (ADS)

Kilovoltage x-ray systems are modeled with BEAMnrc using directional bremsstrahlung splitting, which is five to six orders of magnitude more efficient than a simulation without splitting and 60 times more efficient than uniform bremsstrahlung splitting. Optimum splitting numbers are between 2 and 3 orders of magnitude larger than for megavoltage beams A self-consistent approach for the calculation of free-air chamber correction factors with the EGSnrc Monte Carlo system is introduced. In addition to the traditional factors employed to correct for attenuation (A att), photon scatter (Ascat) and electron energy loss (Aeloss), correction factors for aperture leakage (Aap) and backscatter (A b) are defined. Excellent agreement is obtained between calculated and measured Ascat and Aeloss values. Computed Aatt values for medium-energy and mammography beams reproduce the measurements well. For low-energy lightly-filtered beams, Aatt values show significant differences with the experiment. Scaling the tungsten L-shell EII cross-sections by a factor of 2 eliminate these differences. The inconsistency of the evacuated-tube technique for measuring Aatt is negligible for medium-energy and mammography beams, and 0.2% for low-energy lightly-filtered beams The aperture correction Aap becomes significant in the medium-energy range with increasing energy. The newly introduced backscatter correction Ab becomes as high as 0.4% in the low-energy range. In the medium-energy range, calculations reproduce experimental half-value layer values to better than 2.3%. For mammography beams a difference of 0.5% and 2.5% with experiment is obtained with and without a scaling of the tungsten L-shell EII cross-sections respectively. For low-energy lightly-filtered beams a scaling factor of 2.1 gives the best agreement (˜ 3%) with the experiment, significantly worsening to 8% for a scaling factor of 1.8, which gives the best match for Aatt. The fast algorithm for calculating the scatter contribution to cone beam computed tomography scans increases the efficiency by more than 3 orders of magnitude. Smoothing the scatter distribution pushes the efficiency gain over four orders of magnitude. The iterative correction algorithm removes the scatter from the measured scans improving the accuracy of the reconstructed image. The dependence of image reconstruction accuracy on the sophistication of the photon interaction models is investigated. No significant difference is observed when using models including coherent and incoherent scattering. Considering only incoherent scattering for free electrons shows a significant bias.

Mainegra-Hing, Ernesto

84

Computed tomography for light materials using a monochromatic X-ray beam produced by parametric X-ray radiation  

NASA Astrophysics Data System (ADS)

Computed tomography (CT) for light materials such as soft biological tissues was performed using a monochromatic X-ray beam provided by a parametric X-ray radiation (PXR) source at the Laboratory for Electron Beam Research and Application (LEBRA) of Nihon University. Using a high-efficiency flat panel detector (FPD), each projection image for CT was taken with exposure times of 5 or 10 s, and 60-360 projection images in each run were obtained with total measurement time of 5 min to 1 h. CT images were obtained from the projection images using the conventional calculation method. The typical tomograms obtained had sharp outlines, which are likely attributable to the propagation-based phase contrast.

Hayakawa, Y.; Hayakawa, K.; Inagaki, M.; Kaneda, T.; Nakao, K.; Nogami, K.; Sakae, T.; Sakai, T.; Sato, I.; Takahashi, Y.; Tanaka, T.

2013-08-01

85

Signal-to-noise ratio of intensity interferometry experiments with highly asymmetric x-ray sources  

SciTech Connect

The authors discuss the signal-to-noise ratio of an intensity interferometry experiment for a highly asymmetric x-ray source using different aperture shapes in front of the photodetectors. It is argued that, under ideal conditions using noiseless detectors and electronics, the use of slit-shaped apertures, whose widths are smaller but whose lengths are much greater than the transverse coherence widths of the beam in the corresponding directions, provides no signal-to-noise advantage over the use of pinhole apertures equal to or smaller than the coherence area. As with pinholes, the signal-to-noise ratio is determined solely by the count degeneracy parameter and the degree of coherence of the beam. This contrasts with the signal-to-noise ratio enhancement achievable using slit-shaped apertures with an asymmetric source in a Young`s experiment.

Feng, Y.P.; McNulty, I.; Xu, Z.; Gluskin, E. [Argonne National Lab., IL (United States). Experimental Facilities Div.

1995-06-23

86

Signal-to-noise ratio of intensity interferometry experiments with highly asymmetric x-ray sources  

SciTech Connect

We discuss the signal-to-noise ratio of an intensity interferometry experiment for a highly asymmetric x-ray source using different aperture shapes in front of the photodetectors. It is argued that, under ideal conditions using noiseless detectors and electronics, the use of slit-shaped apertures, whose widths are smaller but whose lengths are much greater than the transverse coherence widths of the beam in the corresponding directions, provides no signal-to-noise advantage over the use of pinhole apertures equal to or smaller than the coherence area. As with pinholes, the signal-to-noise ratio is determined solely by the count degeneracy parameter and the degree of coherence of the beam. This contrasts with the signal-to-noise ratio enhancement achievable using slit-shaped apertures with an asymmetric source in a Young`s experiment.

Feng, Y.P.; McNulty, I.; Xu, Z.; Gluskin, E.

1997-02-11

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

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

SciTech Connect

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

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

1996-12-31

89

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

90

The VANILLA sensor as a beam monitoring device for X-ray radiation therapy.  

PubMed

Cancer treatments such as intensity-modulated radiotherapy (IMRT) require increasingly complex methods to verify the accuracy and precision of the treatment delivery. In vivo dosimetry based on measurements made in an electronic portal imaging device (EPID) has been demonstrated. The distorting effect of the patient anatomy on the beam intensity means it is difficult to separate changes in patient anatomy from changes in the beam intensity profile. Alternatively, upstream detectors scatter and attenuate the beam, changing the energy spectrum of the beam, and generate contaminant radiation such as electrons. We used the VANILLA device, a Monolithic Active Pixel Sensor (MAPS), to measure the 2D beam profile of a 6 MV X-ray beam at Bristol Hospital in real-time in an upstream position to the patient without clinically significant disturbance of the beam (0.1% attenuation). MAPSs can be made very thin (~20 ?m) with still a very good signal-to-noise performance. The VANILLA can reconstruct the collimated beam edge with approximately 64 ?m precision. PMID:24215812

Velthuis, J J; Hugtenburg, R P; Cussans, D; Perry, M; Hall, C; Stevens, P; Lawrence, H; McKenzie, A

2014-01-01

91

X-ray photoelectron spectroscopy analysis of organic materials irradiated with gas cluster ion beam  

SciTech Connect

Irradiation effect of gas cluster ion beams (GCIB) on organic materials were studied with X-ray photoelectron spectroscopy by comparison to that with Ar-monomer ions. In the case of polyimide, the intensity of both N-C = O and -C-O- bond decreased with 500 eV Ar monomer ion irradiation. On the other hand, there was no significant change in the XPS spectra after Ar-GCIB irradiation. From the size-selected GCIB irradiation study, the damages in polyimide decreased with increasing the cluster size owing to the reduction of energy per atoms.

Nakagiri, Motohiro; Toyoda, Noriaki; Yamada, Isao [Incubation center, Graduate school of engineering, University of Hyogo, 2167 Shosha, Himeji, Hyogo, 671-2280 (Japan)

2011-01-07

92

The energy calibration of x-ray absorption spectra using multiple-beam diffraction  

SciTech Connect

A new method for calibrating the energy scale of x-ray absorption spectra from an energy dispersive spectrometer has been developed. Distinct features in the diffracted intensity of the curved silicon crystal monochromator have been assigned to multiple-beam diffraction. The photon energies of these structures can be calculated if the precise spacing of the diffracting planes and the orientation of the crystal relative to the incident synchrotron radiation are known. The evaluation of Miller indices of operative reflections and the calculation of the corresponding photon energy is presented. The assignment of operative reflexes is simplified if the monochromator crystal can be rotated around the main diffracting vector {bold H}.

Hagelstein, M.; Cunis, S. (Fachhochschule Ostfriesland, Constantiaplatz 4, D-2970 Emden (Germany)); Frahm, R. (Hamburger Synchrotronstrahlungslabor HASYLAB at DESY, Notkestrasse 85, D-2000 Hamburg 52 (Germany)); Rabe, P. (Fachhochschule Ostfriesland, Constantiaplatz 4, D-2970 Emden (Germany))

1992-01-01

93

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

NASA Astrophysics Data System (ADS)

The degradation of the X-ray reflection characteristics of metal multilayer Bragg diffractors due to intense X-ray flux was investigated. Molybdenum-carbon, paladium-carbon, and tungsten-carbon metal multilayers were used. Data for two separate shots were analyzed. For a pure neon gas shot at 420 TW, the reflectivity of the multilayer at 15 cm decayed rapidly with respect to the still-rising signal of the multilayer at 150 cm. The onset time of the decay corresponded to an integrated dose of 5.27 J/sq cm. 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 8.9 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/sq cm and the integrated energy at destruction was 2.0 J/sq cm.

Hockaday, Mary Yvonne Pottenger

1987-06-01

94

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

PubMed

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

2014-03-01

95

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

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

96

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

Microsoft Academic Search

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

Robert J. Kinzig

1991-01-01

97

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

SciTech Connect

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

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

2010-12-01

98

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

99

High-intensity, subkolovolt x-ray calibration facility using a Cockroft--Walton proton accelerator  

Microsoft Academic Search

Considerable need has arisen for the development of well-calibrated x-ray detectors capable of detecting photons with energies between 100 and 1000 electron-volts. This energy region is of significant interest since the x-ray emission from high-temperature (kT approximately 1.0 keV), laser-produced plasmas is predominantly in this range. A high-intensity, subkilovolt x-ray calibration source was developed which utilizes proton-induced inner-shell atomic fluorescence

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

1976-01-01

100

Increase of parametric X-ray intensity due to the Borrmann effect  

NASA Astrophysics Data System (ADS)

Parametric X-ray radiation (PXR) from relativistic electrons in a crystal with a thickness larger than the X-ray absorption length is considered. The characteristics of this radiation are analysed in detail taking into account the dynamical diffraction theory. It is shown that the PXR intensity increases and its dependence on the electron energy changes when the X-ray quanta are emitted under conditions of anomalous absorption (the Borrmann effect). The details of the PXR angular distribution and its comparison with the experimental data are also discussed.

Ahmadi, Abbas; Feranchuk, Ilya

2013-09-01

101

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

Microsoft Academic Search

The relative radiation intensity (Ri) defined as fluorescent radiation intensity of analyte in specimen to fluorescent radiation intensity of pure element or compound, e.g., oxide is used in calculation in both fundamental parameter methods and in theoretical influence coefficient algorithms. Accuracy of calculated Ri is determined by uncertainties of atomic parameters, spectrometer geometry and also by X-ray tube spectral distribution.

Rafal Sitko

2007-01-01

102

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

103

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

104

Whitebeam X-ray topography  

Microsoft Academic Search

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

Moreton Moore

2012-01-01

105

Production of intense, tunable, quasi-monochromatic X-rays using the RPI linear accelerator  

NASA Astrophysics Data System (ADS)

This research investigated the production of parametric X-rays (PXR) using the 60-MeV electron linear accelerator at Rensselaer Polytechnic Institute. PXR is an intense, energy tunable, and polarized X-ray source derived from the interaction of relativistic electrons and the periodic structure of crystal materials. In this work, PXR photon yields and the associated bremsstrahlung background were characterized for graphite, LiF, Si, Ge, Cu, and W target crystals. A model that considers the experimental geometry and crystal mosaicity was employed to predict PXR energy broadening. Measured energy linewidths consistently agreed with predicted values except in cases using poor quality graphite in which the mosaicity was greater than the PXR characteristic angle, 8.5 mrad for 60 MeV electrons. When the predicted energy linewidth was more narrow than our Si X-ray detector resolution, a near-absorption edge transmission technique was used to measure the PXR energy linewidth for Si(400) FWHM of 134 eV at 9.0 keV (2%) and Si(220) FWHM of 540 eV at 17.7 keV (3%). An experimental study was conducted to select PXR target crystals most appropriate for X-ray production at typical mammography energies (17--20 keV). Low Z materials like graphite and LiF were most suitable for PXR production because of their low Bremsstrahlung production, electron scattering, and photon absorption. Graphite was most efficient at producing PXR photons while the LiF energy linewidth was narrower. A theoretical model that considers electron multiple scattering, electron divergence, and crystal mosaicity was used to broaden the PXR photon distribution in order to calculate predicted PXR photon yield. This approach, proposed by A. P. Potylitsin, was allowed comparison of measured and predicted PXR yields. The relative error was typically below 0.5. In some cases with LiF, the differences between predicted and measured values were as low as 2% for LiF(400) and 13% for LiF(220). Finally, this work reports for the first time PXR imaging. This was achieved using LiF(220) interacting with 56 MeV electrons with electron beam currents up to 6 muA.

Sones, Bryndol A.

106

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

NASA Technical Reports Server (NTRS)

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

Carpenter, P. K.

2005-01-01

107

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 require high x-ray energy and high x-ray intensity to penetrate dense cargo. On the other hand, low intensity is desirable to minimize the radiation footprint. A collaboration between HESCO/PTSE Inc., Schonberg Research Corporation and Rapiscan Laboratories, Inc. has been formed in order to design and build an Intensity-Modulated Advanced X-ray Source (IMAXS). Such a source would allow cargo inspection systems to achieve up to two inches greater imaging penetration capability, while retaining the same average radiation footprint as present fixed-intensity sources. Alternatively, the same penetration capability can be obtained as with conventional sources with a reduction of the average radiation footprint by about a factor of three. The key idea is to change the intensity of the source for each x-ray pulse based on the signal strengths in the inspection system detector array during the previous pulse. In this paper we describe methods to accomplish pulse-to-pulse intensity modulation in both S-band (2998 MHz) and X-band (9303 MHz) linac sources, with diode or triode (gridded) electron guns. The feasibility of these methods has been demonstrated. Additionally, we describe a study of a shielding design that would allow a 6 MV X-band source to be used in mobile applications.

Langeveld, Willem G. J. [Rapiscan Laboratories, Inc., Sunnyvale, CA 94085 (United States); Johnson, William A.; Owen, Roger D. [HESCO/PTSE Inc., Alameda, CA 94501 (United States); Schonberg, Russell G. [Schonberg Research Corporation, Los Altos, CA 94023 (United States)

2009-03-10

108

Intensity-Modulated Advanced X-ray Source (IMAXS) for Homeland Security Applications  

NASA Astrophysics Data System (ADS)

X-ray cargo inspection systems for the detection and verification of threats and contraband require high x-ray energy and high x-ray intensity to penetrate dense cargo. On the other hand, low intensity is desirable to minimize the radiation footprint. A collaboration between HESCO/PTSE Inc., Schonberg Research Corporation and Rapiscan Laboratories, Inc. has been formed in order to design and build an Intensity-Modulated Advanced X-ray Source (IMAXS). Such a source would allow cargo inspection systems to achieve up to two inches greater imaging penetration capability, while retaining the same average radiation footprint as present fixed-intensity sources. Alternatively, the same penetration capability can be obtained as with conventional sources with a reduction of the average radiation footprint by about a factor of three. The key idea is to change the intensity of the source for each x-ray pulse based on the signal strengths in the inspection system detector array during the previous pulse. In this paper we describe methods to accomplish pulse-to-pulse intensity modulation in both S-band (2998 MHz) and X-band (9303 MHz) linac sources, with diode or triode (gridded) electron guns. The feasibility of these methods has been demonstrated. Additionally, we describe a study of a shielding design that would allow a 6 MV X-band source to be used in mobile applications.

Langeveld, Willem G. J.; Johnson, William A.; Owen, Roger D.; Schonberg, Russell G.

2009-03-01

109

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

110

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

... 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

111

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

112

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

113

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

114

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

115

X-ray scattering intensities of water at extreme pressure and temperature  

SciTech Connect

We have calculated the coherent x-ray scattering intensity of several phases of water at 1500 and 2000 K under high pressure, using ab initio Density Functional Theory (DFT). Our calculations span the molecular liquid, ice VII, and superionic solid phases, including the recently predicted symmetrically hydrogen bonded region of the superionic phase. We show that wide angle x-ray scattering intensity could be used to determine phase boundaries between these high pressure phases, and we compare the results for ice VII and superionic water. We compute simulated spectra and provide new atomic scattering form factors for water at extreme conditions, which take into account frequently neglected changes in ionic charge and electron delocalization. We show that our modifed atomic form factors allow for a nearly exact comaprison to the total x-ray scattering intensities calculated from DFT. Finally, we analyze the effect our new form factors have on determination of the oxygen-oxygen radial distribution function.

Goldman, N; Fried, L E

2007-01-03

116

Monitoring x-ray beam damage on lipid films by an integrated Brewster angle microscope/x-ray diffractometer  

E-print Network

Polyunsaturated lipids with conjugated tails are easily dam- aged by x-ray irradiation in the presence of oxygen samples and thin films has been detected since the beginning of x-ray studies. Dam- age to lipid samples

Lee, Ka Yee C.

117

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

118

Enhancement of x-ray line emission from plasmas produced by short high-intensity laser double pulses  

E-print Network

Enhancement of x-ray line emission from plasmas produced by short high-intensity laser double laser-produced plasmas are bright ultrafast line x-ray sources potentially suitable for different onto a solid target into the x-ray emission is significantly enhanced when a laser prepulse precedes

Limpouch, Jiri

119

Coherent x-ray scatter projection imaging using an array of monoenergetic pencil beams  

NASA Astrophysics Data System (ADS)

Traditional projection x-ray imaging utilizes only the information from the primary photons. Low-angle coherent scatter images can be made simultaneous to the primary images and provide additional information. To speed up acquisition time for coherent scatter projection imaging, we developed disentangling algorithms for the overlapping scatter patterns generated by multi pencil-beam geometries. A system at the Canadian Light Source synchrotron was configured which utilizes a custom collimator designed to convert a 33.17 keV monoenergetic fan beam from a Laue monochromator into multiple pencil beams by using 3 mm thick tungsten alloy stoppers. The pencil beams then travel through the sample and are absorbed by a tungsten bar. A digital flat panel detector records the superimposed scatter patterns from the beams. The sample is scanned through the beams using an automated step-and-shoot setup. The pixel value of the coherent scatter image is generated by integrating the radial profile (scatter intensity versus scattering angle) over an angular range. An MLEM-based iterative method and a least-squares method were developed to disentangle the scatter patterns. Although past work has primarily been applied to medicine, other applications include non-destructive testing and security.

Landheer, Karl; Johns, Paul C.

2012-06-01

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

Intensity Interferometry of Single X-Ray Pulses from a Synchrotron Storage Ring  

NASA Astrophysics Data System (ADS)

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.

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

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

Possible evidence for beaming in flares from microwave and hard X-ray imaging and spectra  

NASA Technical Reports Server (NTRS)

The magnetic field strength and number of burst-producing energetic electrons are presently deduced for the impulsive phase of a solar flare at microwave wavelengths, with the VLA, and hard X-rays, with the SMM Hard X-ray Burst Spectrometer. The combined data indicate that the number of microwave-emitting electrons is at least three orders of magnitude smaller than the number of thick target electrons producing the hard X-rays; this is suggested to be due to the high beaming and inefficient radiation of gyrosynchrotron emission by comparison with isotropically distributed electrons.

Schmahl, E. J.; Kundu, M. R.; Dennis, B. R.

1986-01-01

124

X-ray enhancement in a nanohole target irradiated by intense ultrashort laser pulses  

SciTech Connect

In this paper, we present a comparative study of the laser energy absorption, soft x-ray emission (in the water window region: 2.3-4.4 nm) and hard x-ray emission (in the 2-20 keV range) from planar aluminum and nanohole alumina of 40 nm average diameter, when irradiated by Ti:sapphire laser pulses. The laser pulse duration was varied from 45 to 500 fs, and the focused intensity on the target ranged from {approx}3 x 10{sup 16} W/cm{sup 2} to 3x10{sup 17} W/cm{sup 2}. The x-ray yield enhancement from the nanoholes shows an increased coupling of the laser energy to the target. The effect of laser pulse duration on the x-ray emission was also studied, where a resonance like phenomenon was observed. The laser energy absorption measurements in the nanoholes showed a marginal enhancement in absorption as compared to planar Al. The integrated keV x-ray yield, from nanohole alumina and planar Al, at an intensity of 3 x 10{sup 17} W/cm{sup 2}, was 25 and 3.5 {mu}J, respectively. The results can be explained by considering the hydrodynamic expansion of the laser irradiated structure and field enhancement in the nanoholes.

Chakravarty, U.; Arora, V.; Chakera, J. A.; Naik, P. A.; Srivastava, H.; Tiwari, P.; Srivastava, A.; Gupta, P. D [Raja Ramanna Centre for Advanced Technology, Indore 452013 (India)

2011-03-01

125

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

126

Evaluation of a ventricular assist device: stability under x-rays and therapeutic beam attenuation.  

PubMed

Improved outcomes and quality of life of heart failure patients have been reported with the use of left ventricular assist devices (LVADs). However, little information exists regarding devices in patients undergoing radiation cancer treatment. Two HeartWare Ventricular Assist Device (HVAD) pumps were repeatedly irradiated with high intensity 18 MV x-rays to a dosage range of 64-75 Gy at a rate of 6 Gy/min from a radiation oncology particle accelerator to determine operational stability. Pump parameter data was collected through a data acquisition system. Second, a computerized tomography (CT) scan was taken of the device, and a treatment planning computer estimated characteristics of dose scattering and attenuation. Results were then compared with actual radiation measurements. The devices exhibited no changes in pump operation during the procedure, though the titanium components of the HVAD markedly attenuate the therapy beam. Computer modeling indicated an 11.8% dose change in the absorbed dosage that was distinctly less than the 84% dose change measured with detectors. Simulated and measured scattering processes were negligible. Computer modeling underestimates pretreatment dose to patients when the device is in the field of radiation. Future x-ray radiation dosimetry and treatment planning in HVAD patients should be carefully managed by radiation oncology specialists. PMID:22236626

Gossman, Michael S; Graham, Joel D; Tamez, Dan; Voskoboynikov, Neil; Larose, Jeffrey A

2012-01-01

127

Electron-beam and x-ray lithographic characteristics of the optical resist ARCH  

Microsoft Academic Search

The multi-component, positive acting, chemically amplified deep-UV ((lambda) equals 248 nm) resist ARCH, has been evaluated for use in proximity x-ray and electron-beam lithography. Characterization of the x-ray lithographic response of ARCH resist using a pulsed laser point source ((lambda) equals 1.4 nm) proximity print stepper resulted in a process producing sub-0.20 micrometers features at a dose of 22 mJ\\/cm2.

Anthony E. Novembre; Regine G. Tarascon; Omkaram Nalamasu; Linus A. Fetter; Kevin J. Bolan; Chester S. Knurek; Norbert Muenzel; Heinz E. Holzwarth

1995-01-01

128

Ultra fast electron beam X-ray computed tomography for two-phase flow measurement  

Microsoft Academic Search

Electron beam X-ray CT is a new technique for a fast measurement of multiphase flows with frame rates of 1000 images per second and more. It gives, in principle, quantitatively accurate images of the flow at high spatial resolution and it is non-intrusive since moderately radiation absorbing vessel walls can be penetrated by X-rays. However, on the road to a

F. Fischer; U. Hampel

2010-01-01

129

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

130

Diamond monochromator for high heat flux synchrotron x-ray beams  

Microsoft Academic Search

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

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

1992-01-01

131

Diamond monochromator for high heat flux synchrotron x-ray beams  

Microsoft Academic Search

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

Ali M. Khounsary; Robert K. Smither; Steve Davey; Ankor Purohit

1993-01-01

132

Focused ion beam sample preparation for high spatial resolution X-ray microanalysis  

Microsoft Academic Search

Thin slices of Si integrated circuit samples of about 100 nm to a couple of hundred nanometers containing process related defects have been prepared by focused ion beam (FIB) for high spatial resolution X-ray microanalysis. The X-ray signals from the bulk are minimised to enhance the signal-to-background ratio of the defects which are in the sub-micron range. The experimental results

K. L. Pey; Alan J Leslie

1995-01-01

133

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

134

Relative X-ray line intensities and their application to a single standard procedure for quantitative X-ray microanalysis of bulk samples and thin films  

Microsoft Academic Search

X-ray spectra collected by an energy dispersive spectrometer on an electron microprobe analyzer were fitted to determine relative line intensities between elements for a wide range of atomic numbers. The relative line intensities within spectral series for K, L and M lines were also obtained. In the case of Kalpha lines an empirical formula is proposed for the prediction of

Michael S. Hatzistergos

2007-01-01

135

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

136

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

137

Conceptual Design of Dielectric Accelerating Structures for Intense Neutron and Monochromatic X-ray Sources  

Microsoft Academic Search

Bright compact photon sources, which utilize electron beam interaction with periodic structures, may benefit a broad range of medical, industrial and scientific applications. A class of dielectric-loaded periodic structures for hard and soft X-ray production has been proposed that would provide a high accelerating gradient when excited by an external RF and\\/or primary electron beam. Target-distributed accelerators (TDA), in which

Anatoly Blanovsky; Anatoly

2004-01-01

138

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

139

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

PubMed Central

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 least and most optimally satisfied the non-uniform dose prescriptions, respectively. The IMPT delivery methods reduced normal tissue integral dose by a factor of about two 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 three relative to the IMPT-SS method. PMID:17921573

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

2009-01-01

140

Absorption and x-ray measurements from ultra-intense laser-plasma interactions  

NASA Astrophysics Data System (ADS)

The interaction of subpicosecond 1.06 micrometers laser light at intensities up to 1018 W/cm2 with dense preformed plasmas is investigated by measurements of the absorption of the laser light in the plasma and by measurements of the production of bremsstrahlung x- rays. Absorption measurements are made by collecting the scattered light in an Ulbricht sphere. Light scattered in the backward and specular directions is collected separately. Measurements are presented for both high and low Z targets. X-ray production is measured using a nine channel filter/scintillator spectrometer.

Klem, Daniel E.; Darrow, Christopher B.; Lane, Stephen M.; Perry, Michael D.

1993-07-01

141

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

PubMed

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

2011-04-12

142

Deep inner-shell multiphoton ionization by intense x-ray free-electron laser pulses.  

PubMed

We have investigated multiphoton multiple ionization dynamics of xenon atoms using a new x-ray free-electron laser facility, SPring-8 Angstrom Compact free electron LAser (SACLA) in Japan, and identified that Xe(n+) with n up to 26 is produced at a photon energy of 5.5 keV. The observed high charge states (n?24) are produced via five-photon absorption, evidencing the occurrence of multiphoton absorption involving deep inner shells. A newly developed theoretical model, which shows good agreement with the experiment, elucidates the complex pathways of sequential electronic decay cascades accessible in heavy atoms. The present study of heavy-atom ionization dynamics in high-intensity hard-x-ray pulses makes a step forward towards molecular structure determination with x-ray free-electron lasers. PMID:23679721

Fukuzawa, H; Son, S-K; Motomura, K; Mondal, S; Nagaya, K; Wada, S; Liu, X-J; Feifel, R; Tachibana, T; Ito, Y; Kimura, M; Sakai, T; Matsunami, K; Hayashita, H; Kajikawa, J; Johnsson, P; Siano, M; Kukk, E; Rudek, B; Erk, B; Foucar, L; Robert, E; Miron, C; Tono, K; Inubushi, Y; Hatsui, T; Yabashi, M; Yao, M; Santra, R; Ueda, K

2013-04-26

143

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

144

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

Microsoft Academic Search

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

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

145

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

SciTech Connect

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

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

2012-04-15

146

Chemical-effect variation of Kbeta\\/Kalpha X-ray intensity ratios in 3d elements  

Microsoft Academic Search

Chemical effects on Kbeta\\/Kalpha X-ray intensity ratios for some Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn compounds are studied experimentally. The X-ray spectra were measured by using a Si (Li) solid state detector with high resolution. The vacancies were produced by heavily filtered 241Am gamma rays. It is found that the Kbeta\\/Kalpha X-ray intensity ratios measured with

Omer Sogut; Erdogan Büyükkasap; Hasan Erdogan

2002-01-01

147

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

148

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

NASA Astrophysics Data System (ADS)

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.

2013-10-01

149

Scanned-beam x-ray source technology for photon backscatter imaging technique of mine detection: advanced technology research  

Microsoft Academic Search

A very high power, state-of-the-art, scanning x-ray source has been developed for use with an x-ray backscatter system that detects and images buried land mines. This paper describes the distinctive qualities of the x-ray source technology necessary to prove the feasibility of the mine detection technique in the field. The imaging system requires that an x-ray beam, having a nominal

Charlotte M. Burchanowski; Robert B. Moler; Steve L. Shope

1995-01-01

150

X-ray beam-shaping via deformable mirrors: Analytical computation of the required mirror profile  

NASA Astrophysics Data System (ADS)

X-ray mirrors with high focusing performances are in use in both mirror modules for X-ray telescopes and in synchrotron and FEL (Free Electron Laser) beamlines. A degradation of the focus sharpness arises in general from geometrical deformations and surface roughness, the former usually described by geometrical optics and the latter by physical optics. In general, technological developments are aimed at a very tight focusing, which requires the mirror profile to comply with the nominal shape as much as possible and to keep the roughness at a negligible level. However, a deliberate deformation of the mirror can be made to endow the focus with a desired size and distribution, via piezo actuators as done at the EIS-TIMEX beamline of FERMI@Elettra. The resulting profile can be characterized with a Long Trace Profilometer and correlated with the expected optical quality via a wavefront propagation code. However, if the roughness contribution can be neglected, the computation can be performed via a ray-tracing routine, and, under opportune assumptions, the focal spot profile (the Point Spread Function, PSF) can even be predicted analytically. The advantage of this approach is that the analytical relation can be reversed; i.e., from the desired PSF the required mirror profile can be computed easily, thereby avoiding the use of complex and time-consuming numerical codes. The method can also be suited in the case of spatially inhomogeneous beam intensities, as commonly experienced at synchrotrons and FELs. In this work we expose the analytical method and the application to the beam shaping problem.

Spiga, Daniele; Raimondi, Lorenzo; Svetina, Cristian; Zangrando, Marco

2013-05-01

151

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

152

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

153

Origin-independent calculation of quadrupole intensities in X-ray spectroscopy.  

PubMed

For electronic excitations in the ultraviolet and visible range of the electromagnetic spectrum, the intensities are usually calculated within the dipole approximation, which assumes that the oscillating electric field is constant over the length scale of the transition. For the short wavelengths used in hard X-ray spectroscopy, the dipole approximation may not be adequate. In particular, for metal K-edge X-ray absorption spectroscopy (XAS), it becomes necessary to include higher-order contributions. In quantum-chemical approaches to X-ray spectroscopy, these so-called quadrupole intensities have so far been calculated by including contributions depending on the square of the electric-quadrupole and magnetic-dipole transition moments. However, the resulting quadrupole intensities depend on the choice of the origin of the coordinate system. Here, we show that for obtaining an origin-independent theory, one has to include all contributions that are of the same order in the wave vector consistently. This leads to two additional contributions depending on products of the electric-dipole and electric-octupole and of the electric-dipole and magnetic-quadrupole transition moments, respectively. We have implemented such an origin-independent calculation of quadrupole intensities in XAS within time-dependent density-functional theory, and demonstrate its usefulness for the calculation of metal and ligand K-edge XAS spectra of transition metal complexes. PMID:23205980

Bernadotte, Stephan; Atkins, Andrew J; Jacob, Christoph R

2012-11-28

154

Ultrafast imaging of nanoclusters with intense x-ray laser pulses  

NASA Astrophysics Data System (ADS)

Ultrafast x-ray scattering opens the door for unprecedented insight into the structure and dynamics of matter with atomic resolution. Any sample in an x-ray laser flash, however, will be converted into a highly excited, non-equilibrium plasma during the pulse. The scatter signal itself is sensitive to changes in the electronic structure of the sample leading to distortions of the signal intensities with respect to the ground state configuration. On the other hand, the information about the electronic structure carried by the scatter signal can be exploited to gain insight into transient electronic states on the femtosecond time scale of the x-ray pulse. We have performed single shot -- single particle scattering experiments on clusters to investigate the interplay between excitation and scattering in nanoscale objects with x-ray pulses from both, the FLASH and LCLS free electron lasers. Atomic clusters have been proven ideal to investigate the interaction between intense light pulses and matter in a wide spectral regime from the infrared to x-rays due to their finite size and simple electronic structure. Spectroscopy data recorded in coincidence with the scattering patterns revealed strong power-density dependent ionization dynamics of the clusters. The scattering patterns themselves provide information on the 2-dim as well as 3-dim structure of clusters and of cluster ensembles. Modeling the scattering patterns indicates that the optical constants of the clusters, which are inherently coupled to its electronic structure and thus charge states, change during the femtosecond pulse. Time resolved experiments with pump -- probe techniques have started which allow following the time evolution of cluster ionization up to several ps.

Bostedt, Christoph

2011-03-01

155

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

156

X-ray luminescence of ZnSCdS:Au,Cu phosphor using X-ray beams for medical applications  

Microsoft Academic Search

The purpose of the present study was to evaluate the X-ray luminescence and imaging performance of phosphor screens prepared from ZnSCdS:Au,Cu. Absolute efficiency, X-ray luminescence efficiency, detector optical gain, and gain transfer function were experimentally determined. Theoretical models were also employed to fit experimental data and to determine optical properties of the phosphor material. Additionally, the emission spectrum of ZnSCdS:Au,Cu

I. Kandarakis; D. Cavouras; C. D. Nomicos; G. S. Panayiotakis

2001-01-01

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

Investigation of tomosynthetic perfusion measurements using the scanning-beam digital x-ray (SBDX) system  

NASA Astrophysics Data System (ADS)

The feasibility of making regional perfusion measurements using a tomosynthetic digital subtraction angiography (TDSA) acquisition has been demonstrated. The study of tomosynthetic perfusion measurements was motivated by the clinical desire for perfusion measurements in an interventional angiography suite. These pilot studies were performed using the scanning-beam digital x-ray (SBDX) system which is an inverse-geometry imaging device which utilizes an electromagnetically-scanned x-ray source, and a small CdTe direct conversion photon counting detector. The scanning electron source was used to acquire planar-tomographic images of a 12.5 x 12.5 cm field of view at a frame rate of 15 frames/sec during dynamic contrast injection. A beagle animal model was used to evaluate the tomosynthetic perfusion measurements. A manual bolus injection of iodinated contrast solution was used in order to resolve the parameters of the contrast pass curve. The acquired planar tomosynthetic dataset was reconstructed with a simple back-projection algorithm. Digital subtraction techniques were used to visualize the change in contrast agent intensity in each reconstructed plane. Given the TDSA images, region of interest based analysis was used in the selection of the image pixels corresponding to the artery and tissue bed. The mean transit time (MTT), regional cerebral blood volume (rCBV) and regional cerebral blood flow (rCBF) were extracted from the tomosynthetic data for selected regions in each of the desired reconstructed planes. For the purpose of this study, the arterial contrast enhancement curve was fit with a combination of gamma variate terms, and the MTT was calculated using a deconvolution based on the singular value decomposition (SVD). The results of the contrast pass curves derived with TDSA were consistent with the results from perfusion measurements as implemented with CT acquisition.

Nett, Brian E.; Chen, Guang-Hong; Van Lysel, Michael S.; Betts, Timothy; Speidel, Michael; Rowley, Howard A.; Aagaard Kienitz, Beverly D.; Mistretta, Charles A.

2004-10-01

159

THE X-RAY DETECTABILITY OF ELECTRON BEAMS ESCAPING FROM THE SUN  

SciTech Connect

We study the detectability and characterization of electron beams as they leave their acceleration site in the low corona toward interplanetary space through their nonthermal X-ray bremsstrahlung emission. We demonstrate that the largest interplanetary electron beams ({approx}>10{sup 35} electrons above 10 keV) can be detected in X-rays with current and future instrumentation, such as RHESSI or the X-Ray Telescope (XRT) onboard Hinode. We make a list of optimal observing conditions and beam characteristics. Amongst others, good imaging (as opposed to mere localization or detection in spatially integrated data) is required for proper characterization, putting the requirement on the number of escaping electrons (above 10 keV) to {approx}>3 x 10{sup 36} for RHESSI, {approx}>3 x 10{sup 35} for Hinode/XRT, and {approx}>10{sup 33} electrons for the FOXSI sounding rocket scheduled to fly in 2011. Moreover, we have found that simple modeling hints at the possibility that coronal soft X-ray jets could be the result of local heating by propagating electron beams.

Saint-Hilaire, Pascal; Krucker, Saem; Christe, Steven; Lin, Robert P. [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States)], E-mail: shilaire@ssl.berkeley.edu

2009-05-01

160

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

PubMed

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

Desjardins, Kewin; Pomorski, Michal; Morse, John

2014-11-01

161

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

162

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

NASA Astrophysics Data System (ADS)

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; Johns, Paul C.

2012-09-01

163

Dense laser-driven electron sheets as relativistic mirrors for coherent production of brilliant X-ray and ?-ray beams  

NASA Astrophysics Data System (ADS)

Several techniques exist to obtain brilliant X-ray beams by coherent reflection from relativistic electrons ( E e= ? mc 2) with Doppler frequency upshift of 4 ? 2. We describe a new approach starting with an ultra-thin solid target. Larger ‘driver’-laser intensities with high contrast are required to produce dense electron sheets. Their acceleration in vacuum results in a transverse momentum component besides the dominant longitudinal momentum component. The counter-propagating ‘production’ laser for optimum Doppler boost in X-ray production by reflection has to be injected opposite to the electron direction and not opposite to the driver laser. Different measures to increase the reflectivity of the electron sheet via laser trapping or free-electron-laser-like micro-bunching are discussed, extending the photon energy into the MeV range. Here, first-order estimates are given.

Habs, D.; Hegelich, M.; Schreiber, J.; Gross, M.; Henig, A.; Kiefer, D.; Jung, D.

2008-11-01

164

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

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

165

The effect of beam-driven return current instability on solar hard X-ray bursts  

NASA Technical Reports Server (NTRS)

The problem of electrostatic wave generation by a return current driven by a small area electron beam during solar hard X-ray bursts is discussed. The marginal stability method is used to solve numerically the electron and ion heating equations for a prescribed beam current evolution. When ion-acoustic waves are considered, the method appears satisfactory and, following an initial phase of Coulomb resistivity in which T sub e/T sub i rise, predicts a rapid heating of substantial plasma volumes by anomalous ohmic dissipation. This hot plasma emits so much thermal bremsstrahlung that, contrary to previous expectations, the unstable beam-plasma system actually emits more hard X-rays than does the beam in the purely collisional thick target regime relevant to larger injection areas. Inclusion of ion-cyclotron waves results in ion-acoustic wave onset at lower T sub e/T sub i and a marginal stability treatment yields unphysical results.

Cromwell, D.; Mcquillan, P.; Brown, J. C.

1986-01-01

166

Generation of femtosecond electron bunches and hard-X-rays by ultra-intense laser wake field acceleration in a gas jet  

Microsoft Academic Search

Summary form only given. Femtosecond electron beams and hard X-rays with ??0.1 nm may find various applications in biology, chemistry, and molecular electronics giving a new time-scale probe analysis. Such short electron beams can be produced in the wake field acceleration by short relativistically intense laser pulses and then Thomson scattering of a second laser pulse can serve for efficient

A. Zhidkov; M. Uesaka; T. Hosokai; K. Kinoshita

2004-01-01

167

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

168

Measurement of high energy x-ray beam penumbra with Gafchromic EBT radiochromic film.  

PubMed

High energy x-ray beam penumbra are measured using Gafchromic EBT film. Gafchromic EBT, due to its limited energy dependence and high spatial resolution provide a high level of accuracy for dose assessment in penumbral regions. The spatial resolution of film detector systems is normally limited by the scanning resolution of the densitometer. Penumbral widths (80%/20%) measured at Dmax were found to be 2.8, 3.0, 3.2, and 3.4 mm (+/- 0.2 mm) using 5, 10, 20, and 30 cm square field sizes, respectively, for a 6 MV linear accelerator produced x-ray beam. This is compared to 3.2 mm +/- 0.2 mm (Kodak EDR2) and 3.6 mm +/- 0.2 mm (Kodak X-Omat V) at 10 cm x 10 cm measured using radiographic film. Using a zero volume extrapolation technique for ionization chamber measurements, the 10 cm X 10 cm field penumbra at Dmax was measured to be 3.1 mm, a close match to Gafchromic EBT results. Penumbral measurements can also be made at other depths, including the surface, as the film does not suffer significantly from dosimetric variations caused by changing x-ray energy spectra. Gafchromic EBT film provides an adequate measure of penumbral dose for high energy x-ray beams. PMID:16964868

Cheung, Tsang; Butson, Martin J; Yu, Peter K N

2006-08-01

169

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

170

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

171

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

172

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

173

Effect of vacancy de-excitation parameters on L X-rays of Pb using H + beam  

NASA Astrophysics Data System (ADS)

The collision progression including ionization of an inner-shell by an energetic proton and decay of vacancy is a motivating theme in ion-beam analysis. To explore measured vacancy de-excitation parameters for Pb, intensity ratios are experimentally determined from L X-rays with proton impact in the energy range 225-400 keV. Predictions of UAECPSSR theory are employed for ionization cross-sections. For atomic parameters such as transition rates, fluorescence, Auger and Coster-Kronig (CK) yields, various databases are used. In this paper, significance of these features and current progress are discussed.

Jain, Arvind Kumar; Mohan, Harsh; Sharma, Sunita

2010-06-01

174

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

PubMed

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 × 10(3)-1 × 10(5) 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, M D; Wilfley, B; Graves, E E

2012-11-21

175

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

176

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

Microsoft Academic Search

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

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

2002-01-01

177

Applications of pixellated GaAs X-ray detectors in a synchrotron radiation beam  

NASA Astrophysics Data System (ADS)

Hybrid semiconductor pixel detectors are being investigated as imaging devices for radiography and synchrotron radiation beam applications. Based on previous work in the CERN RD19 and the UK IMPACT collaborations, a photon counting GaAs pixel detector (PCD) has been used in an X-ray powder diffraction experiment. The device consists of a 200 ?m thick SI-LEC GaAs detector patterned in a 64×64 array of 170 ?m pitch square pixels, bump-bonded to readout electronics operating in single photon counting mode. Intensity peaks in the powder diffraction pattern of KNbO 3 have been resolved and compared with results using the standard scintillator, and a PCD predecessor (the ?3). The PCD shows improved speed, dynamic range, 2-D information and comparable spatial resolution to the standard scintillator based systems. It also overcomes the severe dead time limitations of the ?3 by using a shutter based acquisition mode. A brief demonstration of the possibilities of the system for dental radiography and image processing are given, showing a marked reduction in patient dose and dead time compared with film.

Watt, J.; Bates, R.; Campbell, M.; Mathieson, K.; Mikulec, B.; O'Shea, V.; Passmore, M.-S.; Schwarz, C.; Smith, K. M.; Whitehill, C.; XIMAGE Project

2001-03-01

178

Conceptual Design of Dielectric Accelerating Structures for Intense Neutron and Monochromatic X-ray Sources  

NASA Astrophysics Data System (ADS)

Bright compact photon sources, which utilize electron beam interaction with periodic structures, may benefit a broad range of medical, industrial and scientific applications. A class of dielectric-loaded periodic structures for hard and soft X-ray production has been proposed that would provide a high accelerating gradient when excited by an external RF and/or primary electron beam. Target-distributed accelerators (TDA), in which an additional electric field compensates for lost beam energy in internal targets, have been shown to provide the necessary means to drive a high flux subcritical reactor (HFSR) for nuclear waste transmutation. The TDA may also be suitable for positron and nuclear isomer production, X-ray lithography and monochromatic computer tomography. One of the early assumptions of the theory of dielectric wake-field acceleration was that, in electrodynamics, the vector potential was proportional to the scalar potential. The analysis takes into consideration a wide range of TDA design aspects including the wave model of observed phenomena, a layered compound separated by a Van der Waals gap and a compact energy source based on fission electric cells (FEC) with a multistage collector. The FEC is a high-voltage power source that directly converts the kinetic energy of the fission fragments into electrical potential of about 2MV.

Blanovsky, Anatoly

2004-12-01

179

Conceptual Design of Dielectric Accelerating Structures for Intense Neutron and Monochromatic X-ray Sources  

SciTech Connect

Bright compact photon sources, which utilize electron beam interaction with periodic structures, may benefit a broad range of medical, industrial and scientific applications. A class of dielectric-loaded periodic structures for hard and soft X-ray production has been proposed that would provide a high accelerating gradient when excited by an external RF and/or primary electron beam. Target-distributed accelerators (TDA), in which an additional electric field compensates for lost beam energy in internal targets, have been shown to provide the necessary means to drive a high flux subcritical reactor (HFSR) for nuclear waste transmutation. The TDA may also be suitable for positron and nuclear isomer production, X-ray lithography and monochromatic computer tomography. One of the early assumptions of the theory of dielectric wake-field acceleration was that, in electrodynamics, the vector potential was proportional to the scalar potential. The analysis takes into consideration a wide range of TDA design aspects including the wave model of observed phenomena, a layered compound separated by a Van der Waals gap and a compact energy source based on fission electric cells (FEC) with a multistage collector. The FEC is a high-voltage power source that directly converts the kinetic energy of the fission fragments into electrical potential of about 2MV.

Blanovsky, Anatoly [Teacher Technology Center, 7850 Melrose Ave., Los Angeles, CA 90046 (United States)

2004-12-07

180

Size-Dependent Ultrafast Ionization Dynamics of Nanoscale Samples in Intense Femtosecond X-Ray Free-Electron-Laser Pulses  

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

181

Comparison of neutron and high-energy X-ray dual-beam radiography for air cargo inspection.  

PubMed

Dual-beam radiography techniques utilising various combinations of high-energy X-rays and neutrons are attractive for screening bulk cargo for contraband such as narcotics and explosives. Dual-beam radiography is an important enhancement to conventional single-beam X-ray radiography systems in that it provides additional information on the composition of the object being imaged. By comparing the attenuations of transmitted dual high-energy beams, it is possible to build a 2D image, colour coded to indicate material. Only high-energy X-rays, gamma-rays and neutrons have the required penetration to screen cargo containers. This paper reviews recent developments and applications of dual-beam radiography for air cargo inspection. These developments include dual high-energy X-ray techniques as well as fast neutron and gamma-ray (or X-ray) radiography systems. High-energy X-ray systems have the advantage of generally better penetration than neutron systems, depending on the material being interrogated. However, neutron systems have the advantage of much better sensitivity to material composition compared to dual high-energy X-ray techniques. In particular, fast neutron radiography offers the potential to discriminate between various classes of organic material, unlike dual energy X-ray techniques that realistically only offer the ability to discriminate between organic and metal objects. PMID:18054493

Liu, Y; Sowerby, B D; Tickner, J R

2008-04-01

182

Valence electronic structure of Ni in Ni–Si alloys from relative K X-ray intensity studies  

Microsoft Academic Search

The K?-to-K? X-ray intensity ratio of Ni in Ni3Si, Ni2Si and NiSi has been determined by energy dispersive X-ray fluorescence technique. It is found that the intensity ratio of Ni decreases from pure Ni to Ni2Si and then increases from Ni2Si to NiSi, in good agreement with the electronic structure calculations cited in the literature. We have also performed band

Y. Kalayci; A. Aydinuraz; B. Tugluoglu; R. H. Mutlu

2007-01-01

183

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

NASA Astrophysics Data System (ADS)

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. A system at the Canadian Light Source synchrotron was configured which utilizes multiple 33.17 keV 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. An MLEM-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. For a five-beam porcine phantom image the muscle-fat contrast was 0.10 +/- 0.01 and 1.16 +/- 0.03 for the primary and scatter images, respectively. The air kerma was measured using Al2O3:C 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

184

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

NASA Astrophysics Data System (ADS)

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.; Tripathi, V. K.; Kumar, Manoj

2014-10-01

185

Measurement of L alpha/L iota X-ray intensity ratios  

NASA Astrophysics Data System (ADS)

L alpha/L iota X-ray intensity ratios of La2O3, CeO2, Sm, Eu, Ho, Er, YbO2, Hf, Ta, W, Re, Pt, Au, HgO, Tl, Pb, Bi, ThO2, and U have been measured using the 59.5 keV incident photon energy. The LX-rays emitted from the samples were counted using a Si(Li) detector with a resolution 155eV at 5.96 keV.

Sogut, O.; Buyukkasap, E.; Kucukonder, A.

2005-09-01

186

Studying ATHENA optics with divergent and collimated x-ray beams  

NASA Astrophysics Data System (ADS)

An open question in the measurement of X-ray optics for satellite experiments is what the PSF (point spread function) looks like in orbit and what the focal length for a source at infinite distance is. In order to measure segmented optics as proposed for ATHENA a collimated X-ray beam with a size of several square centimeters is necessary. We showed that by using a zone plate such a collimated beam can be achieved. We discuss here the requirements such a zone plate collimator has to comply in order to characterize with this collimator an ATHENA type optic. Additional we can present results obtained with a first version of such a collimator and can show so the proof of principle.

Menz, Benedikt; Bräuninger, Heinrich; Burwitz, Vadim; Hartner, Gisela; Predehl, Peter

2014-07-01

187

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

188

Proposal for Generating Brilliant X-Ray Beams Carrying Orbital Angular Momentum  

SciTech Connect

We consider use of a variable polarizing undulator for generating brilliant x-ray beams carrying orbital angular momentum. We find that higher harmonics of the radiation correspond to Laguerre-Gaussian modes with azimuthal mode indices l equal to one less than the harmonic number when the undulator is operated to produce circularly polarized light. Beams with nonzero l carry orbital angular momentum quantized in units of l({Dirac_h}/2{pi}) per photon. When operated to produce linear polarization, the harmonics correspond to Hermite-Gaussian modes. Selection of these modes with conventional monochromator optics opens the door for new research with x-ray synchrotron and free-electron laser sources.

Sasaki, Shigemi; McNulty, Ian [Advanced Photon Source, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439 (United States)

2008-03-28

189

Photoionization and Photoemission by the Standing - Intensity of Dynamical X-Ray Diffraction.  

NASA Astrophysics Data System (ADS)

This thesis contains theoretical studies of nonrelativistic, inner-shell photoionization, and angle-resolved, photoelectron ejection by the standing-wave intensity of dynamical x -ray diffraction in the Bragg reflection geometry. These studies are carried out for two purposes: (1) to put the yield formulae of the X-Ray Standing Wave Technique (XSWT) in the differential form most appropriate for the application of photoelectron spectroscopy, and (2) to answer a lingering question on the adequacy of the dipole approximation for describing the photoeffect spectra of XSWT via investigating the effects of quadrupole retardation on the determination of the coherent fraction and the coherent position. In the dipole approximation, electron photoejection by the standing-wave intensity of XSWT has been found to differ from corresponding fluorescence and Auger emissions in that it proceeds at rate not proportional to the standing -wave intensity unless the dynamical diffraction field is in the sigma polarization geometry, or otherwise the XSWT experiment is performed at small Bragg angles or near-normal incidence conditions. It has also been found that the coherent position is by no means sensitive to effects owing to quadrupole retardation, whereas numerical results calculated for a Si adsorbate on a Ge substrate have exhibited changes exceeding 10% in the magnitude of the coherent fraction, but only for unfavorable experimental conditions. This observation has led to concluding the dipole approximation sound and accurate for most practical XSWT experiments.

Kayed, Mohammad Ahmad

190

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

191

Resonant photo-pumping x-ray-laser scheme using intense characteristic x rays for water-window radiation generation  

SciTech Connect

A line pair for a resonant photo-pumping x-ray-laser scheme is proposed in which the wavelength matching between the aluminum K{alpha}{sub 2} line ({lambda}= 0.833 95 nm) and the 2p{sup 6}-(2p{sub 1/2},4d{sub 3/2}){sub 1} transition of the neonlike zinc ions ({lambda}= 0.834 00 nm) is used. The population kinetics code of the neonlike zinc ions in plasma under irradiation of the aluminum K{alpha} line shows that substantial amplification gain can be generated in the transition of (2p{sub 1/2},3p{sub 1/2}){sub 0}-(2p{sub 1/2},4d{sub 3/2}){sub 1} at a wavelength of 3.5 nm. We also investigate the experimental arrangement of this scheme, which implies that this scheme is feasible with the present ultra-short-pulse-laser technology.

Kawachi, Tetsuya [Quantum Beam Science Directorate, Japan Atomic Energy Agency (JAEA) 8-1-7, Umemidai, Kizugawa, Kyoto 619-0215 (Japan); Kato, Yoshiaki [Graduate School for the Creation of New Photonics Industries 1955-1, Kurematsu, Hamamatsu, Shizuoka 431-1202 (Japan)

2011-12-15

192

X-ray diffraction on spider silk during controlled extrusion under a synchrotron radiation X-ray beam.  

PubMed

The structure of a single thread of Nephila edulis silk has been studied by in situ X-ray diffraction from a living spider. A systematic increase of orientational order with increasing silking speed up to 40 mm s-1 was observed. Within a few mm from the spinnerets exit, crystalline domains with a beta-poly(L-alanine) structure were observed. The data also suggest an increase in crystalline fraction in the immediate vicinity of the spigot exit. PMID:11710191

Riekel, C; Madsen, B; Knight, D; Vollrath, F

2000-01-01

193

Evaluation of x-ray scatter properties in a dedicated cone-beam breast CT scanner  

Microsoft Academic Search

The magnitude of scatter contamination on a first-generation prototype breast computed tomography (CT) scanner was evaluated using the scatter-to-primary ratio (SPR) metric. The SPR was measured and characterized over a wide range of parameters relevant to breast CT imaging, including x-ray beam energy, breast diameter, breast composition, isocenter-to-detector distance, collimated slot thickness, and grid ratio. The results demonstrated that in

Nikula Shah; John M. Boone; Alexander L. C. Kwan

2005-01-01

194

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

195

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

196

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

197

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

198

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

NASA Technical Reports Server (NTRS)

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

Robinson, J. W.

1979-01-01

199

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

200

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

201

Beryllium window and acoustic delay line design for x-ray lithography beam lines at the University of Wisconsin Center for X-ray Lithography  

SciTech Connect

X-ray lithography systems require sample chambers that can perform exposures in helium gas at atmospheric pressure. The interface between the experimental chamber and the beamline is critical for x-ray lithography and the storage ring. It must allow a high x-ray flux throughput while providing a vacuum barrier so that helium gas does not leak into the beam line and the storage ring. The beam line must also be designed to have protection in the case that a window does fail in order to minimize adverse effects to the ring and other systems. The details of the design for the vacuum system used on beam lines for the Center for X-ray Lithography at the University of Wisconsin Synchrotron Radiation Center 1-GeV electron storage ring are reported. Curved beryllium windows with a 1{times}5-cm{sup 2} aperture and 13 {mu}m thick that have a leak rate less than 10{sup {minus}10} Torr l/s have been successfully used at the experimental chamber beam-line interface. This thin flat beryllium foil is mounted in a curved housing with a wire seal to minimize helium leakage. The window assembly is designed and has been tested to withstand substantial overpressure before failure. If the beryllium window does fail, the beamline has an acoustic delay line that is designed to delay the incoming shock wave of helium gas so that a fast valve at the end of the beam line will close and minimize leakage of helium into the storage ring. The acoustic delay line is designed with baffles to slow the shock front and a secondary thin window to protect against molecular diffusion into the storage ring. The acoustic delay line has been tested to determine the effect of baffle design on delay of the shock wave. A theoretical model that provides a good description of the acoustic delay has also been developed.

Brodsky, E.L. (Center for X-ray Lithography, University of Wisconsin, 3731 Schneider Drive, Stoughton, Wisconsin 53589 (United States)); Hamilton, W. (Nuclear Engineering and Engineering Physics, University of Wisconsin, 153 Engineering Research Building, Madison, Wisconsin 53705 (United States)); Wells, G.; Cerrina, F. (Center for X-ray Lithography, University of Wisconsin, 3731 Schneider Drive, Stoughton, Wisconsin 53589 (United States)); Corradini, M. (Nuclear Engineering and Engineering Physics, University of Wisconsin, 153 Engineering Research Building, Madison, Wisconsin 53705 (United States))

1992-01-01

202

Breast tomosynthesis reconstruction with a multi-beam x-ray source Ying Chen *a,b  

E-print Network

Breast tomosynthesis reconstruction with a multi-beam x-ray source Ying Chen *a,b , Weihua Zhou-dimensional breast imaging technique, breast tomosynthesis allows the reconstruction of an arbitrary set of planes in the breast from a limited-angle series of x-ray projection images. The breast tomosynthesis technique has

Chen, Ying "Ada"

203

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

SciTech Connect

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

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

2012-09-01

204

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

205

Limitations of coherent diffractive imaging of single objects due to their damage by intense x-ray radiation  

NASA Astrophysics Data System (ADS)

During the coherent diffraction imaging (CDI) of a single object with an intense x-ray free-electron laser (FEL) pulse, the structure of the object changes due to the progressing radiation damage. Electrons are released from atoms and ions during photo-, Auger- and collisional ionization processes. More and more ions appear in the sample. The repulsive force between ions makes them move apart. Form factors of the created ions are reduced when compared with the atomic form factors. Additional scattering of energetic photons from the free electrons confined within the beam focus deteriorates the obtained diffractive signal. Here, we consider pulses short enough to neglect ionic movement and investigate how (i) the decrease of atomic form factors due to the progressing ionization of the sample and (ii) the scattering from the free electrons influence the signal obtained during the CDI. We quantify the loss of structural information about the object due to these effects with hydrodynamic simulations. Our study has implications for the experiments planned on high-resolution three-dimensional imaging of single reproducible particles with x-ray FELs.

Ziaja, B.; Chapman, H. N.; Fäustlin, R.; Hau-Riege, S.; Jurek, Z.; Martin, A. V.; Toleikis, S.; Wang, F.; Weckert, E.; Santra, R.

2012-11-01

206

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

SciTech Connect

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

Wargelin, B.J.

1993-10-01

207

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

208

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

SciTech Connect

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

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

2011-12-14

209

Conceptual design of a novel instrument for producing intense pulses of 10 ps X-rays for ultra-fast fluorescence measurements  

SciTech Connect

A novel bench-top device for producing intense, fast pulses of x-rays has been designed with 10 ps fwhm (full-width at half-maximum) x-ray pulse width, 120 keV maximum energy, 100 kHz repetition rate, and 1 A peak current onto the x-ray anode. The device includes three sections: (1) an electron gun that generates 5 ns wide pulses of 120 keV electrons at 100 kHz; (2) solenoidal magnetic lenses and deflection plates that focus the electrons onto an aperture plate and sweep the pulsed beam past the aperture, respectively; and (3) a tungsten anode onto which the post-aperture electrons are focused, producing pulses of x-rays. At a sweeping rate of 10{sup 13} V/s, the electron pulses and resulting x-ray pulses are reduced to about 10 ps. The design process used EGUN (an electron optics and gun design program) electron trajectory simulations, including calculation of important space charge effects. When built, this instrument will be used to excite new, fast, bright scintillator samples in crystal or powdered form, allowing fluorescent lifetimes and spectra to be measured with a microchannel PMT. The very narrow 10 ps x-ray pulse width is necessary for accurate measurements of the risetimes of very fast scintillators (e.g., BaF{sub 2}). In addition, the large x-ray flux (1 A peak current) is advantageous when using a reflection grating monochromator to measure decay times at different wavelengths.

Gruber, G.J.

1996-05-01

210

Spatial properties of $?-?$ conjugated network in semicrystalline polymer thin films studied by intensity x-ray cross-correlation functions  

E-print Network

We present results of x-ray study of spatial properties of $\\pi-\\pi$ conjugated networks in polymer thin films. We applied the x-ray cross-correlation analysis to x-ray scattering data from blends of poly(3-hexylthiophene) (P3HT) and gold nanoparticles. The Fourier spectra of the intensity cross-correlation functions for different films contain non-zero components of orders $n=2,4$ and $6$ measuring the degree of structural order in the system.

R. P. Kurta; L. Grodd; E. Mikayelyan; O. Y. Gorobtsov; I. Fratoddi; I. Venditti; M. Sprung; S. Grigorian; I. A. Vartanyants

2013-11-06

211

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

SciTech Connect

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

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

2012-05-15

212

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

213

Soft X-Ray Magnetic Imaging of Focused Ion Beam Lithographically Patterned Fe Thin Films  

SciTech Connect

We illustrate the potential of modifying the magnetic behavior and structural properties of ferromagnetic thin films using focused ion beam 'direct-write' lithography. Patterns inspired by the split-ring resonators often used as components in meta-materials were defined upon 15 nm Fe films using a 30 keV Ga{sup +} focused ion beam at a dose of 2 x 10{sup 16} ions cm{sup -2}. Structural, chemical and magnetic changes to the Fe were studied using transmission soft X-ray microscopy at the ALS, Berkeley CA. X-ray absorption spectra showed a 23% reduction in the thickness of the film in the Ga irradiated areas, but no change to the chemical environment of Fe was evident. X-ray images of the magnetic reversal process show domain wall pinning around the implanted areas, resulting in an overall increase in the coercivity of the film. Transmission electron microscopy showed significant grain growth in the implanted regions.

Cook, Paul J.; Shen, Tichan H.; Grundy, PhilJ.; Im, Mi Young; Fischer, Peter; Morton, Simon A.; Kilcoyne, Arthur D.L.

2008-11-09

214

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

215

A mechanical chopper with continuously adjustable duty cycle for a wide X-ray beam  

NASA Astrophysics Data System (ADS)

The prototype of a fast beam chopper for hard X-rays, with a continuously variable duty cycle from less than 10 to more than 90% has been successfully developed, built and tested. The apparatus consists in 12 planetary stainless-steel blades that are 100 mm wide and are mounted on two large discs. All blades are kept permanently parallel to each other, thanks to a gear system, which also allows changing their orientation. The two main parameters of the chopper (duty cycle and chopping frequency) are controlled independently and remotely. In the present design, the device allows chopping frequencies ranging from 0 to 300 Hz. The principle of operation, preliminary results of the instrument's performance and an example demonstrating the capacity of the system for image quality improvement and X-ray dose reduction at the specimen are presented.

Renier, M.; Fiedler, S.; Nemoz, C.; Gonzalez, H.; Berruyer, G.; Bravin, A.

2005-08-01

216

Tunable, monochromatic x rays using the internal beam of a betatron  

NASA Astrophysics Data System (ADS)

Tunable, monochromatic x rays from thin radiators mounted inside a betatron have been observed. Parametric x-ray radiation (PXR) was generated by 33-MeV electrons passing multiple times through three radiators: a 43-?m-thick Si crystal, a 400-?m-thick graphite crystal, or a 310-layered-pair (W and B4C, d=14.86 Å) multilayer. The pulse-height spectrum of the radiation (5 to 30 keV) was obtained and was tuned by rocking the crystal or multilayer relative to the electron-beam direction. The experimental results appear to follow theoretical predictions for PXR emission with some modification required for the curved trajectory of the electrons.

Kaplin, V. V.; Uglov, S. R.; Bulaev, O. F.; Goncharov, V. J.; Voronin, A. A.; Piestrup, M. A.; Gary, C. K.; Nasonov, N. N.; Fuller, M. K.

2002-05-01

217

Hard X-ray and Hot Electron Production from Intense Laser Irradiation of Wavelength-Scale Droplets  

Microsoft Academic Search

We have examined the production of hard x-rays from the irradiation of 1 mum diameter water droplets with a 35 fs laser at intensity up to 7 x 10^17 W\\/cm^2. We observe substantial x-ray production in the photon energy range above 100 keV and find that the implied hot electron temperatures from these micron scale targets is significantly higher than

T. Ditmire; S. Wilks; J. Zweiback; T. E. Cowan; T. D. Donnelly; M. Rust; I. Weiner; M. Allen; R. A. Smith

2000-01-01

218

Hard x-ray and hot electron production from intense laser irradiation of wavelength-scale particles  

Microsoft Academic Search

We have examined the production of hard x-rays from the irradiation of ?1 µm diameter water droplets with a 35 fs laser at an intensity of up to 7×1017 Wc m?2. We observe substantial x-ray production in the photon energy range above 100 keV and find that the implied hot electron temperatures from these micron- scale targets are significantly higher

T D Donnelly; M Rust; I Weiner; M Allen; R A Smith; C A Steinke; S Wilks; J Zweiback; T Ditmire

2001-01-01

219

MIT\\/OSO 7 catalog of x-ray sources: intensities, spectra, and long-term variability  

Microsoft Academic Search

This paper is a summary of the observations of the cosmic X-ray sky performed by the MIT 1--40 KeV X-ray detectors on the OSO 7 between 1971 October and 1973 May. Specifically, we have computed the mean intensities or upper limits of all third Uhuru or OSO 7 cataloged sources (185 sources) in the 3--10 KeV range. For those sources

T. H. Markert; P. F. Winkler; F. N. Laird; G. W. Clark; D. R. Hearn; G. F. Sprott; F. K. Li; H. V. Bradt; W. H. G. Lewin; H. W. Schnopper

1979-01-01

220

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

221

Size dependent ionization dynamics of argon clusters in intense x-ray pulses  

NASA Astrophysics Data System (ADS)

Free Electron Lasers open the door for novel experiments in many science areas ranging from ultrafast chemical dynamics to single shot imaging of molecules. For the success of virtually all experiments with free electron lasers a detailed understanding of the light - matter interaction in the x-ray regime is pivotal. The Linac Coherent Light Source (LCLS) free electron laser in Stanford allows for the first time to study innershell ionization dynamics of intense x-ray pulses on a femtosecond time scale. We performed experiments on the ionization dynamics of Argon clusters at different pulse length using the slotted spoiler foil in the second LCLS bunch compressor [1]. The Auger rate of argon clusters is predicted to be size dependent and lower than in atoms due to delocalization of the valence electrons [2]. We observe a dependence of the ionization dynamics on pulse length and cluster size. The results are discussed and also compared to recent atomic and molecular data from LCLS.[4pt] [1] P. Emma et al. PRL 92, 074801 (2004)[0pt] [2] U. Saalmann, JM Rost PRL 89, 14 (2002)

Schorb, Sebastian; Swiggers, M.; Coffee, R.; Messerschmidt, M.; Moeller, S.; Williams, G.; Bozek, J.; Osipov, T.; Wada, S.; Rupp, D.; Moeller, T.; Bostedt, C.

2011-03-01

222

Size dependent ionization dynamics of argon clusters in intense x-ray pulses  

NASA Astrophysics Data System (ADS)

Free Electron Lasers open the door for novel experiments in many science areas ranging from ultrafast chemical dynamics to single shot imaging of molecules. For the success of virtually all experiments with free electron lasers a detailed understanding of the light - matter interaction in the x-ray regime is pivotal. The Linac Coherent Light Source (LCLS) free electron laser in Stanford allows for the first time to study innershell ionization dynamics of intense x-ray pulses on a femtosecond time scale. We performed experiments on the ionization dynamics of Argon clusters at different pulse length using the slotted spoiler foil in the second LCLS bunch compressor [1]. The Auger rate of argon clusters is predicted to be size dependent and lower than in atoms due to delocalization of the valence electrons [2]. We observe a dependence of the ionization dynamics on pulse length and cluster size. The results are discussed and also compared to recent atomic and molecular data from LCLS.[4pt] [1] P. Emma et al. PRL 92, 074801 (2004)[0pt] [2] U. Saalmann, JM Rost PRL 89, 14 (2002)

Schorb, Sebastian; Rupp, D.; Swiggers, M.; Coffee, R. N.; Messerschmidt, M.; Williams, G.; Bozek, J. D.; Wada, S.-I.; Möller, T.; Bostedt, C.

2012-06-01

223

Size dependent ionization dynamics of argon clusters in intense x-ray pulses  

NASA Astrophysics Data System (ADS)

Free Electron Lasers open the door for novel experiments in many science areas ranging from ultrafast chemical dynamics to single shot imaging of molecules. For the success of virtually all experiments with free electron lasers a detailed understanding of the light - matter interaction in the x-ray regime is pivotal. The Linac Coherent Light Source (LCLS) free electron laser in Stanford allows for the first time to study inner shell ionization dynamics of intense x-ray pulses on a femtosecond time scale. We performed experiments on the ionization dynamics of Argon clusters at different pulse length using the slotted spoiler foil in the second LCLS bunch compressor [1]. The Auger rate of argon clusters is predicted to be size dependent and lower than in atoms due to delocalization of the valence electrons [2]. We observe a dependence of the ionization dynamics on pulse length and cluster size. The results are discussed and also compared to recent atomic and molecular data from LCLS.[4pt] [1] P. Emma et al. PRL 92, 074801 (2004)[0pt] [2] U. Saalmann, JM Rost, PRL 89, 14 (2002)

Schorb, Sebastian; Swiggers, M.; Rupp, D.; Coffee, R.; Messerschmidt, M.; Möller, S.; Williams, G.; Bozek, J.; Osipov, T.; Wada, S.; Kornilov, O.; Möller, T.; Bostedt, C.

2011-11-01

224

Strain field and scattered intensity profiling with energy dispersive x-ray scattering  

NASA Astrophysics Data System (ADS)

Two powerful synchrotron x-ray scattering techniques for residual strain depth-profiling and tomography-like scatter-intensity profiling of materials are presented. The techniques utilize energy dispersive x-ray scattering, from a fixed microvolume, with microscanning of the specimen being used to profile its interior. The tomography-like profiles exploit scattering-cross-section variations, and can be contrast enhanced by separately monitoring scattering from different crystal structures. The strain profiling technique is shown to finely chronicle the internal strain variation over several mm of steel. Detailed strain profiling for a cantilever spring demonstrates the interplay of residual and external stresses in elastic/plastic deformation. Since surface compression, by shot peening, is a classic method to fortify against fatigue failure, the strain profile for a shot-peened, surface-toughened material is determined and discussed in terms of a simple elastic-plastic stress/strain model. Finally the lattice strains in a WC/Co coated steel composite material are discussed.

Croft, M.; Zakharchenko, I.; Zhong, Z.; Gurlak, Y.; Hastings, J.; Hu, J.; Holtz, R.; DaSilva, M.; Tsakalakos, T.

2002-07-01

225

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

226

Electron beams and X ray radiation generated by laser wakefield in capillary tubes  

NASA Astrophysics Data System (ADS)

Laser wakefield is generated inside capillary tubes in order to study the conditions for self-injection of plasma electrons and their acceleration inside a large domain of parameters. Dielectric capillary tubes are employed to guide the laser pulse and collect laser energy around the central focal spot to favor laser propagation. Electrons are observed to be self-injected and accelerated to the 200 MeV range when a peak laser intensity as low as 5×1017 W/cm2 is used. X-rays emitted by betatron radiation constitute a precise diagnostic of the electron acceleration process. Furthermore, the peak brightness of X-rays is increased to 1021 ph/s/mm2/mrad2/0.1%BW when the laser pulse is focused to 5×1018 W/cm2, which is about 30 times higher than the value obtained by using a 2 mm gas jet.

Cros, B.; Ju, J.; Döpp, A.; Cassou, K.; Ferrari, H. E.; Maynard, G.; Genoud, G.; Wojda, F.; Svensson, K.; Burza, M.; Lundh, O.; Persson, A.; Wahlström, C.-G.

2012-12-01

227

Effects of Surface Processing on the Response of CZT Gamma Detectors: Studies with a Collimated Synchrotron X-Ray Beam  

Microsoft Academic Search

Using a microscale X-ray mapping technique incorporating a synchrotron beam, we are able to reveal the fine details of the\\u000a surface properties in cadmium zinc telluride (CZT) semiconductor detectors. A detector, with various degrees of surface roughness,\\u000a was irradiated by a high-spatial-resolution X-ray beam. The detector’s response was analyzed and displayed as a two-dimensional\\u000a (2-D) map, and the charge collection

A. Hossain; A. E. Bolotnikov; G. S. Camarda; Y. Cui; S. Babalola; A. Burger; R. B. James

2008-01-01

228

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

229

Masses, beaming and Eddington ratios in ultraluminous X-ray sources  

NASA Astrophysics Data System (ADS)

I suggest that the beaming factor in bright ultraluminous X-ray sources (ULXs) varies as , where is the Eddington ratio for accretion. This is required by the observed universal Lsoft ~ T-4 relation between soft-excess luminosity and temperature, and is reasonable on general physical grounds. The beam scaling means that all observable properties of bright ULXs depend essentially only on the Eddington ratio , and that these systems vary mainly because the beaming is sensitive to the Eddington ratio. This suggests that bright ULXs are stellar-mass systems accreting at Eddington ratios of the order of 10-30, with beaming factors b >~ 0.1. Lower luminosity ULXs follow bolometric (not soft-excess) L ~ T4 correlations and probably represent sub-Eddington accretion on to black holes with masses ~10Msolar. High-mass X-ray binaries containing black holes or neutron stars and undergoing rapid thermal- or nuclear-time-scale mass transfer are excellent candidates for explaining both types. If the scaling for bright ULXs can be extrapolated to the Eddington ratios found in SS433, some objects currently identified as active galactic nuclei at modest redshifts might actually be ULXs (`pseudo-blazars'). This may explain cases where the active source does not coincide with the centre of the host galaxy.

King, A. R.

2009-02-01

230

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; Cubukçu, S; Uyar, E; Engin, Y

2014-11-21

231

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

232

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

NASA Astrophysics Data System (ADS)

A seeding gas jet including Xe clusters was irradiated with a laser-driven plasma soft x-ray laser pulse (?=13.9 nm, ~7 ps, <=5×109 W/cm2), where the laser photon energy is high enough to ionize 4d core electrons. In order to clarify how the innershell ionization followed by the Auger electron emission is affected under the intense laser irradiation, the electron energy distribution was measured. Photoelectron spectra showed that the peak position attributed to 4d hole shifted to lower energy and the spectral width was broadened with increasing cluster size. Moreover, the energy distribution exhibited that a strongly coupled cluster nanoplasma with several eV was generated.

Namba, S.; Hasegawa, N.; Kishimoto, M.; Nishikino, M.; Kawachi, T.

2012-07-01

233

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

234

X-ray emission study of ion beam mixed Cu\\/Al films on polyimide  

Microsoft Academic Search

Cu (40 nm)\\/Al\\/polyimide\\/Si was mixed with 80 keV Ar{sup +} and Nâ{sup +} from 5.0Ã10¹⁵ to 15Ã10¹⁵ ions\\/cm². Ultrasoft x-ray emission valence spectra (XES) of Cu, C, N and O excited by electron and photon radiation were used for study of chemical reactions in Cu\\/Al\\/PI\\/Si and PI\\/Si systems induced by ion beam mixing in dependence of type of ions and

Ernst Z. Kurmaev; D. A. Zatsepin; Robert P. Winarski; Shane Stadler; David L. Ederer; Alexander P. Moewes; V. V. Fedorenko; S. N. Shamin; V. R. Galakhov; G. S. Chang; C. N. Whang

1999-01-01

235

Characterization of growth defects in piezoelectric single crystals by synchrotron white beam X-ray topography  

Microsoft Academic Search

Growth defects in piezoelectric single crystals, langasite (La3 Ga5SiO14 or LGS) and its two isomorphs langanite (La3Ga5.5Nb0.5O14 or LGN) and langatate (La3Ga5.5Ta0.5O14 or LGT), along with quartz, were characterized by synchrotron white beam X-ray topography (SWBXT) and complemented by optical microscopy and other characterization techniques. A systematic study of LGS, LGN and LGT crystals, grown by Czochralski technique, at different

Huaibin Chen

2005-01-01

236

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

237

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

NASA Technical Reports Server (NTRS)

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

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

2009-01-01

238

Intense Super-radiant X-rays from a Compact Source using a Nanocathode Array and Emittance Exchange  

SciTech Connect

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 super-radiant emission that is far more intense than from unbunched electrons. The periodic bunching is achieved in steps beginning with an array of beamlets emitted from a nanoengineered field emission array. The beamlets are then manipulated and converted to a longitudinal density modulation via a transverse to longitudinal emittance exchange. Periodic bunching at short wavelength is shown to be possible, and the partially coherent x-ray properties produced by Inverse Compton scattering from an intense laser are estimated. The proposed method increases the efficiency of x-ray production by several orders of magnitude, potentially enabling compact x-ray sources to produce brilliance and flux similar to major synchrotron facilities.

Graves, W.S.; /MIT, LNS; Kaertner, F.X.; /MIT, LNS /CFEL, Hamburg; Moncton, D.E.; /MIT, LNS; Piot, P.; /Northern Illinois U. /Fermilab

2012-02-01

239

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

NASA Astrophysics Data System (ADS)

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

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

2007-01-01

240

An empirical model of diagnostic x-ray attenuation under narrow-beam geometry  

SciTech Connect

Purpose: The purpose of this study was to develop and validate a mathematical model to describe narrow-beam attenuation of kilovoltage x-ray beams for the intended applications of half-value layer (HVL) and quarter-value layer (QVL) estimations, patient organ shielding, and computer modeling. Methods: An empirical model, which uses the Lambert W function and represents a generalized Lambert-Beer law, was developed. To validate this model, transmission of diagnostic energy x-ray beams was measured over a wide range of attenuator thicknesses [0.49-33.03 mm Al on a computed tomography (CT) scanner, 0.09-1.93 mm Al on two mammography systems, and 0.1-0.45 mm Cu and 0.49-14.87 mm Al using general radiography]. Exposure measurements were acquired under narrow-beam geometry using standard methods, including the appropriate ionization chamber, for each radiographic system. Nonlinear regression was used to find the best-fit curve of the proposed Lambert W model to each measured transmission versus attenuator thickness data set. In addition to validating the Lambert W model, we also assessed the performance of two-point Lambert W interpolation compared to traditional methods for estimating the HVL and QVL [i.e., semilogarithmic (exponential) and linear interpolation]. Results: The Lambert W model was validated for modeling attenuation versus attenuator thickness with respect to the data collected in this study (R{sup 2} > 0.99). Furthermore, Lambert W interpolation was more accurate and less sensitive to the choice of interpolation points used to estimate the HVL and/or QVL than the traditional methods of semilogarithmic and linear interpolation. Conclusions: The proposed Lambert W model accurately describes attenuation of both monoenergetic radiation and (kilovoltage) polyenergetic beams (under narrow-beam geometry).

Mathieu, Kelsey B.; Kappadath, S. Cheenu; White, R. Allen; Atkinson, E. Neely; Cody, Dianna D. [Department of Bioengineering, Rice University, Houston, Texas 77005 (United States); Division of Diagnostic Imaging, University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030 (United States); Division of Bioinformatics and Computational Biology, University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030 (United States); Department of Statistics, Rice University, Houston, Texas 77005 (United States); Division of Diagnostic Imaging, University of Texas MD Anderson Cancer Center, Houston, Texas 77030 (United States)

2011-08-15

241

An empirical model of diagnostic x-ray attenuation under narrow-beam geometry  

PubMed Central

Purpose: The purpose of this study was to develop and validate a mathematical model to describe narrow-beam attenuation of kilovoltage x-ray beams for the intended applications of half-value layer (HVL) and quarter-value layer (QVL) estimations, patient organ shielding, and computer modeling. Methods: An empirical model, which uses the Lambert W function and represents a generalized Lambert-Beer law, was developed. To validate this model, transmission of diagnostic energy x-ray beams was measured over a wide range of attenuator thicknesses [0.49–33.03 mm Al on a computed tomography (CT) scanner, 0.09–1.93 mm Al on two mammography systems, and 0.1–0.45 mm Cu and 0.49–14.87 mm Al using general radiography]. Exposure measurements were acquired under narrow-beam geometry using standard methods, including the appropriate ionization chamber, for each radiographic system. Nonlinear regression was used to find the best-fit curve of the proposed Lambert W model to each measured transmission versus attenuator thickness data set. In addition to validating the Lambert W model, we also assessed the performance of two-point Lambert W interpolation compared to traditional methods for estimating the HVL and QVL [i.e., semilogarithmic (exponential) and linear interpolation]. Results: The Lambert W model was validated for modeling attenuation versus attenuator thickness with respect to the data collected in this study (R2?>?0.99). Furthermore, Lambert W interpolation was more accurate and less sensitive to the choice of interpolation points used to estimate the HVL and?or QVL than the traditional methods of semilogarithmic and linear interpolation. Conclusions: The proposed Lambert W model accurately describes attenuation of both monoenergetic radiation and (kilovoltage) polyenergetic beams (under narrow-beam geometry). PMID:21928626

Mathieu, Kelsey B.; Kappadath, S. Cheenu; White, R. Allen; Atkinson, E. Neely; Cody, Dianna D.

2011-01-01

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

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

NASA Astrophysics Data System (ADS)

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

Retsky, Michael W.

2005-06-01

244

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

245

Synchrotron white-beam X-ray topography of ferroelectric domains in a BaTiO3 single crystal  

Microsoft Academic Search

Ferroelectric domains and strains in a barium titanate (BaTiO3) single crystal, grown by the top-seeded solution growth technique, have been investigated by synchrotron white-beam X-ray topography (SWBXT) and optical microscopy. Conventional radiation X-ray topography studies in this system had previously been hampered by the presence of internal strain fields which made it difficult to observe the overall domain structures. SWBXT

Bong Mo Park; Su Jin Chung; Hyung Soon Kim; Weimin Si; Michael Dudley

1997-01-01

246

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

247

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

248

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

SciTech Connect

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

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

2007-12-15

249

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

250

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

251

X-ray amplification in intense ultrashort KrF laser-Xe cluster interactions  

NASA Astrophysics Data System (ADS)

In earlier work, a time-dependent, ionization dynamic model of a cluster of xenon atoms was constructed [2,3] in an effort to determine conditions under which the X-ray line amplification data that was observed experimentally at wavelengths between 2.71 and 2.88 Å[1] could be replicated. Model calculations showed that, at laser intensities greater than 1019 W/cm2, the outermost N-shell electrons of xenon would be stripped away by tunnel ionization in less than a femtosecond. They also showed that L-shell electrons within the resulting cluster of Ni-like ions could be photoionized at a sufficient rate as to generate population inversions between these hole states and the states they radiatively decayed into. These inversions only lasted for several femtoseconds, and they were generated early in time when the cluster was being rapidly heated and the cluster's density was rapidly evolving, but was still high. They were seen to depend on the heating and expansion dynamics of the cluster, which had not been modeled in detail in this early work. In this paper, molecular dynamics calculations are described in which the rapidly evolving temperatures and ion densities of an intensely laser-heated cluster are calculated for different peak laser intensities and for two different sized xenon nano-clusters. This data is then used as an input to the ionization dynamic calculations in order to determine the influence of cluster size and of peak laser intensity on the gain coefficient calculations. In these calculations, inner-shell photoionization rates are shaped by the temperature and density dependence of the bremsstrahlung emissions under the assumption that these emissions drive the photoionizations. This shaping produces calculated gain coefficients that agree well with the measured ones.

Petrova, Tz. B.; Davis, J.; Whitney, K. G.; Petrov, G. M.

2012-09-01

252

Improved Scatter Correction in X-Ray Cone Beam CT with Moving Beam Stop Array Using Johns' Equation  

E-print Network

In this paper, an improved scatter correction with moving beam stop array (BSA) for x-ray cone beam (CB) CT is proposed. Firstly, correlation between neighboring CB views is deduced based on John's Equation. Then, correlation-based algorithm is presented to complement the incomplete views by using the redundancy (over-determined information) in CB projections. Finally, combining the algorithm with scatter correction method using moving BSA, where part of primary radiation is blocked and incomplete projections are acquired, an improved correction method is proposed. Effectiveness and robustness is validated by Monte Carlo (MC) simulation with EGSnrc on humanoid phantom.

Yan, Hao; Tang, Shaojie; Xu, Qiong

2014-01-01

253

Intensity modulated x-ray (IMXT) vs. proton (IMPT) therapy for theragnostic hypoxia-based dose painting  

PubMed Central

In this work the abilities of intensity modulated x-ray therapy (IMXT) and intensity modulated proton therapy (IMPT) to deliver boosts based on theragnostic imaging were assessed. Theragnostic imaging is the use of functional or molecular imaging data for prescribing radiation dose distributions. Distal gradient tracking, a new IMPT method designed for the delivery of non-uniform dose distributions, was assessed. Dose prescriptions for a hypoxic region in a head and neck squamous cell carcinoma patient were designed to either uniformly boost the region or redistribute the dose based on positron emission tomography (PET) images of the 61Cu(II)-diacetyl-bis(N4-methylthiosemicarbazone) (61Cu-ATSM) hypoxia surrogate. Treatment plans for the prescriptions were created for four different delivery methods: IMXT delivered with step-and-shoot and with helical tomotherapy, and IMPT delivered with spot scanning and distal gradient tracking. IMXT and IMPT delivered comparable dose distributions within the boost region for both uniform and redistributed theragnostic boosts. Normal tissue integral dose was lower by a factor of up to three for IMPT relative to the IMXT. For all delivery methods, the mean dose to the nearby organs at risk changed by less than 2 Gy for redistributed versus uniform boosts. The distal gradient tracking method resulted in comparable plans to the spot scanning method while reducing the number of proton beam spots by a factor of over three. PMID:18635895

Flynn, Ryan T; Bowen, Stephen R; Bentzen, Soren M; Mackie, T Rockwell; Jeraj, Robert

2009-01-01

254

Upgrade of the thirty-meter x-ray pencil beam line at the Institute of Space and Astronautical Science  

NASA Astrophysics Data System (ADS)

The thirty-meter X-ray pencil beam line at the Institute of Space and Astronautical Science (ISAS) was utilized for ground-based calibrations of X-ray telescopes (XRTs) onboard the ASTRO-D, the ASTRO-E and the ASTRO- E2 satellites. Recent upsizing or downsizing of XRT required upgrade of the ISAS beam line. We replaced a vacuum chamber in which the stages had been installed by a new cylindrical chamber whose diameter and length are 1.8 m and 11.3 m, respectively. Stages on which a telescope and detectors had been mounted were also replaced. At same time, a new CCD consists of 1240×1152 pixels whose size are 22.5×22.5 ?m was introduced. The detector stage can be moved along the X-ray beam in the vacuum chamber, which allows us to change the distance between the sample and the detectors from 0.7 m to 9 m. The two stages can move in at least 500×500 mm2 of square in the plane normal to the X-ray beam. The pitching of some moving axes are measured at 60 arcsec at most. The others are no more than about 30 arcsec. From April 2013, the ASTRO-H Soft X-ray telescopes (SXTs) have been calibrated at the new ISAS beam line.

Hayashi, Takayuki; Sato, Toshiki; Tomikawa, Kazuki; Kikuchi, Naomichi; Sato, Takuro; Iizuka, Ryo; Maeda, Yoshitomo; Ishida, Manabu

2014-07-01

255

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

256

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

257

Calculated valence electronic structure of 3d metals for use in the X-ray intensity ratio studies  

Microsoft Academic Search

3d occupation numbers of the transition elements corresponding to various types of atomic configurations are calculated by means of the linear muffin-tin orbital (LMTO) method. This data is used with the multiconfiguration Dirac–Fock (MCDF) X-ray intensity ratios to estimate the electron populations of the 3d metals in alloys.

H. Dagistanli; Y. Kalayci; R. H. Mutlu

2010-01-01

258

A novel ultrafast and intense keV X-ray source from laser-plasma interactions  

Microsoft Academic Search

We have produced polychromatic x-ray radiation by linear and non-linear Thomson scattering of an intense femtosecond laser on relativistic electrons accelerated in a helium plasma. The principle is the following. When relativistic electrons are submitted to a strong femtosecond laser pulse they experience strong accelerations and emit a femtosecond burst of nonlinear Thomson scattering radiation. This was demonstrated in the

Kim Ta Phuoc; Antoine Rousse; Frederic Burgy; Jean-Philippe Rousseau; Rahul Shah; Victor Malka; Donald Umstadter; Daniele Hulin

2003-01-01

259

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

SciTech Connect

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

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

1986-05-01

260

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

NASA Astrophysics Data System (ADS)

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 rise time of < 4 nanoseconds from an equivalent generator-impedance of 52 W. A numerical model is used in which the x-ray tube's cathode width and anode-cathode gap (AK) are permitted to change with time while electron current between the cathode and anode is treated as non relativistic and space-charge-limited (SCL). By coupling this model to an equivalent circuit representation of the Marx generator a calculation of the cathode current, anode-cathode potential and the output x-ray spectrum can be made. The radiation dose is 55 millirems at 30.4 cm from the anode of the x-ray tube and is Gaussian in shape with a 35 nanosecond (full width at half maximum) FWHM. The measured x-ray dose, pulse shape and width are consistent with model predictions. The source was successfully used to study high-velocity projectile induced cavatation in human tissue.

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

2004-11-01

261

Air Cavity Effects on the Absorbed Dose for 4-, 6- and 10MV X-ray Beams : Larynx Model  

Microsoft Academic Search

Purpose : When an x-ray beam of small field size is irradiated to target area containing an air cavity, such as larynx, the underdosing effect is observed in the region near the interfaces of air and soft tissue. With a larynx model, air cavity embedded in tissue-equivalent material, this study is intended for examining parameters, such as beam quality, field

Chang-Seon Kim; Dae-Sik Yang; Chul-Yong Kim; Myung-Sun Choi

1997-01-01

262

Scattering Theory When an x-ray beam (or neutron or light) passes through a material with  

E-print Network

Scattering Theory When an x-ray beam (or neutron or light) passes through a material radiation is scattered in directions that differ from that of the incident beam. Scattering arises since x of scattered radiation resulting from this process bears a direct relationship to the structure (the pattern

Beaucage, Gregory

263

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

PubMed Central

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

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

2012-01-01

264

Investigation of GEM-Micromegas detector on X-ray beam of synchrotron radiation  

NASA Astrophysics Data System (ADS)

To reduce the discharge of the standard bulk Micromegas and GEM detectors, a GEM-Micromegas detector was developed at the Institute of High Energy Physics. Taking into account the advantages of the two detectors, one GEM foil was set as a preamplifier on the mesh of Micromegas in the structure and the GEM preamplification decreased the working voltage of Micromegas to significantly reduce the effect of the discharge. At the same gain, the spark probability of the GEM-Micromegas detector can be reduced to a factor 0.01 compared to the standard Micromegas detector, and an even higher gain could be obtained. This paper describes the performance of the X-ray beam detector that was studied at 1W2B Laboratory of Beijing Synchrotron Radiation Facility. Finally, the result of the energy resolution under various X-ray energies was given in different working gases. This indicates that the GEM-Micromegas detector has an energy response capability in an energy range from 6 keV to 20 keV and it could work better than the standard bulk-Micromegas.

Zhang, Yu-Lian; Qi, Hui-Rong; Hu, Bi-Tao; Fan, Sheng-Nan; Wang, Bo; Liu, Mei; Zhang, Jian; Liu, Rong-Guang; Chang, Guang-Cai; Liu, Peng; Ouyang, Qun; Chen, Yuan-Bo; Yi, Fu-Ting

2014-04-01

265

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

E-print Network

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 multiple-pulse pump-probe scheme, we demonstrate the modi?cation of the ionization dynamics as we vary the x-ray laser pulse duration.

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

2013-01-01

266

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

267

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

268

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

NASA Astrophysics Data System (ADS)

Hot electron and x-ray production from solid targets coated with polystyrene-spheres which are irradiated with high-contrast, 100fs, 400nm light pulses at intensity up to 2×1017W/cm2 have been studied. The peak hard x-ray signal from uncoated fused silica targets is an order of magnitude smaller than the signal from targets coated with submicron sized spheres. The temperature of the x-rays in the case of sphere-coated targets is twice as hot as that of uncoated glass. A sphere-size scan of the x-ray yield and observation of a peak in both the x-ray production and temperature at a sphere diameter of 0.26?m, indicate that these results are consistent with Mie enhancements of the laser field at the sphere surface and multipass stochastic heating of the hot electrons in the oscillating laser field. These results also match well with particle-in-cell simulations of the interaction.

Sumeruk, H. A.; Kneip, S.; Symes, D. R.; Churina, I. V.; Belolipetski, A. V.; Dyer, G.; Landry, J.; Bansal, G.; Bernstein, A.; Donnelly, T. D.; Karmakar, A.; Pukhov, A.; Ditmire, T.

2007-06-01

269

Bremsstrahlung X ray mappings of an intense, widespread, and pulsating electron precipitation event following a sudden commencement  

SciTech Connect

For the first time, remote bremsstrahlung X ray spatial, temporal, and spectral mappings from a satellite are presented for a strong energetic electron precipitation event following a sudden commencement. After the sudden commencement of July 13, 1982, and at the beginning of a magnetospheric substorm, X rays were observed over a period of more than 4 min from the P78-1 spacecraft at 600-km altitude. The X rays above 21 keV were emitted over a magnetic local time (MLT) interval spanning 6 hours. Five precipitating temporal spikes were observed with coherency over wide longitude intervals of 3 hours or more in MLT near midnight. The energy spectra over broad longitude intervals tended to be harder simultaneously at the times of greatest X ray intensity. The power input to the atmosphere from precipitating electrons that produced the X rays emitted within 2200--2230 MLT is estimated to have reached values of 5 x 10/sup 16/ ergs/s over an area of about 3 x 10/sup 4/ km/sup 2/, leading to an average energy deposition rate of about 160 ergs/cm/sup 2/ s. The precipitation inputs at other magnetic local times displayed nearly simultaneous sharp maxima in time but with lower power inputs. copyright American Geophysical Union 1987

Imhof, W.L.; Voss, H.D.; Mobilia, J.; Datlowe, D.W.

1987-02-01

270

Method and apparatus for reducing x-ray grid images  

SciTech Connect

This patent describes a diagnostic x-ray machine for producing a radiographic image of a body, the image received by an x-ray sensitive medium. It comprises an x-ray source for producing a beam of x-ray radiation along a major axis directed through the body and toward the x-ray sensitive medium; a grid means positioned relative to the x-ray source, within the beam of x-rays after they pass through the body but prior to their reaching the x-ray sensitive medium for rejecting the x-rays scattered by the body; a reciprocating means for moving the grid means along an axis perpendicular to the major axis between a first limit and a second limit; a modulator means for controlling the intensity of the x-ray beam from the x-ray source; and a signal means for synchronizing the modulator means with the motion of the grid means between the first and second limit so as to control x-ray intensity as a function of grid velocity.

Scheid, C.C.

1991-08-13

271

Intense X-ray flares from active stellar systems - EV Lacertae and HD 8357  

NASA Technical Reports Server (NTRS)

The HEAO A-1 Sky Survey Experiment included X-ray data used to define light curves for the flare star EV Lac and for X-ray flares observed in the binary system HD 8357. The data were taken during flare events and were detailed enough to calculate the flare rates and flaring luminosities. The peak luminosities during flares were several times the luminosities in normal X-ray flares emitted by the objects. Peak luminosities reached 30-50 times the normal variations and were associated with an order of magnitude increase in energy output. EV Lac was sufficiently active to be recommended for inclusion in future X-ray monitoring programs.

Ambruster, C.; Snyder, W. A.; Wood, K. S.

1984-01-01

272

A Vlasov Solver for Longitudinal Dynamics in Beam Delivery Systems for X-Ray FELs  

SciTech Connect

Direct numerical methods for solving the Vlasov equationoffer some advantages over macroparticle simulations, as they do notsuffer from the consequences of the statistical fluctuations inherent inusing a number of macroparticles smaller than thebunch population.Unfortunately these methods are more time-consuming and generallyconsidered impractical in a full 6D phase space. However, in alower-dimension phase space they may become attractive if the beamdynamics is sensitive to the presence of small charge-densityfluctuations and a high resolution is needed. In this paper we present a2D Vlasov solverfor studying the longitudinal beam dynamics insingle-pass systems of interest for X-Ray FELs, where characterization ofthe microbunching instability stemming from self-field amplified noise isof particular relevance.

Venturini, Marco; Warnock, Robert; Zholents, Alexander

2007-05-09

273

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

274

Beam monitor system for an x-ray free electron laser and compact laser  

NASA Astrophysics Data System (ADS)

A beam-monitor system for XFEL/SPring 8, “SACLA,” has been constructed. In order to maintain a stable self-amplified spontaneous emission (SASE) interaction, the straightness and overlap of the axes to within 3?m between the electron beams and the radiated x rays for an undulator section of about 100 m length is necessary. This straightness means relative alignment to an experimental target sample. Furthermore, a temporal stability of 30 fs in order to maintain a constant peak beam current is also necessary to conduct stable SASE lasing. The monitor system was developed to satisfy these spatial and temporal stability and resolution criteria. The system comprises spatial monitors, such as cavity-type beam-position monitors and screen monitors, as well as temporal measurement instruments, such as current monitors, waveguide spectrometers, coherent synchrotron-radiation detectors, a streak camera, and an rf deflector. Commissioning of SACLA started from March 2011, and the monitors performed sufficient roles to tune the beams for lasing. The achieved overall performances of the system, including data acquisition, are: the beam position monitor has a spatial resolution of 600 nm in rms; the bunch-length monitors show ability to observe bunch lengths from 1 ns in an injector with velocity bunching to less than 30 fs after three-stage bunch compressors. The less than 3?m spatial resolution of the screen monitor was also confirmed during practical beam operation. Owing to these fulfilled performances, such as the high spatial and temporal resolutions, stable lasing of SACLA has been achieved.

Otake, Y.; Maesaka, H.; Matsubara, S.; Inoue, S.; Yanagida, K.; Ego, H.; Kondo, C.; Sakurai, T.; Matsumoto, T.; Tomizawa, H.

2013-04-01

275

Theoretical polarization-dependent X-ray spectra of Be-like Fe calculated for different electron beam densities  

NASA Astrophysics Data System (ADS)

We study theoretically the polarization properties of X-ray spectra of Be-like Fe ions excited through resonant capture by an electron beam with different electron densities. Our previous work in this area was related to the study of polarization of dielectronic satellite lines of Fe ions excited by a low-density electron beam. (A.S. Shlyaptseva, R.C. Mancini, P. Neill, P. Beiersdorfer, J.R. Crespo López-Urrutia, and K. Widmann, Phys. Rev. A, 57), 888 (1998) Here we extend our work to the case of higher-density electron beams. As the density of the electron beam increases, new channels of electron capture appear. Thus the atomic and polarization characteristics of the satellite lines change. Moreover, additional X-ray satellite lines will appear. Using the density matrix formalism, we calculate the polarization characteristics and polarization-dependent spectra of dielectronic satellite lines of Be-like Fe produced at different energies and densities of the electron beam. We compare the results of the present work with our previous ones for low-density electron beams. These results are relevant to the identification of X-ray polarization-dependent spectral features and for X-ray line polarization spectroscopy.

Shlyaptseva, Alla; Mancini, Roberto

1998-05-01

276

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

277

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

SciTech Connect

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

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

2012-11-15

278

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

279

Scanned-beam x-ray source technology for photon backscatter imaging technique of mine detection: advanced technology research  

NASA Astrophysics Data System (ADS)

A very high power, state-of-the-art, scanning x-ray source has been developed for use with an x-ray backscatter system that detects and images buried land mines. This paper describes the distinctive qualities of the x-ray source technology necessary to prove the feasibility of the mine detection technique in the field. The imaging system requires that an x-ray beam, having a nominal illumination area on the ground of two centimeters by two centimeters, sweeps across a width of three meters in a time of 15 milliseconds or less. The source must produce an integrated flux of 106 x-rays (min) at 120 kVp (min) for each pixel. The source technology is based on a plasma-focused electrom beam operating up to 140 kilovolts with a current of 0.7 ampere. The electrom beam is magnetically shaped to form a thin ellipse with dimensions of approximately one millimeter by ten millimeters. The scanner is designed to run continuously with target temperature of 160 degrees F (max). The overall design allows the scanner to run with operational and auxilary power generators in the field. A unique 400 hertz, 440 volt, 3-phase, SCR-controlled, low energy storage DC source, with low ripple and 1% voltage regulation, supplies the scanner with 100 kilowatts of power at up to 160 kilovolts. The uniqueness of the mine detection technique and scanner design limits radiation hazards: 1) focusing and tight collimation minimizes stray x-rays; 2) the x-rays travel directly into the ground and are mostly absorbed; 3) radiation leakage from the source is not permitted; and 4) backscatter radiation is strongly localized around the irradiation area, is directed upward, and has a small angular distribution.

Burchanowski, Charlotte M.; Moler, Robert B.; Shope, Steve L.

1995-06-01

280

Evaluation of X-Ray Beam Quality Based on Measurements and Estimations Using SpekCalc and Ipem78 Models  

PubMed Central

Background: Different computational methods have been used for the prediction of X-ray spectra and beam quality in diagnostic radiology. The purpose of this study was to compare X-ray beam qualities based on half-value layers (HVLs) determined through measurements and computational model estimations. Methods: The HVL estimations calculated by IPEM78 (Spectrum Processor of the Institute of Physics and Engineering in Medicine’s Report 78) and SpekCalc software were compared with those determined through measurements. In this study, the HVLs of both Philips (Phil) (Philips Healthcare, Best, NL) and General Electric Company (GE) (GE Global Research, Niskayuna, US) diagnostic range X-ray machines (50 kVp to 125 kVp) were evaluated. Results: In the HVL estimations, SpekCalc and IPEM78 showed maximum differences of 10% and 9%, respectively, compared with direct measurements. Both models provided means and SDs of HVLs that were within 5% of the HVL measurements of GE and Phil machines. Conclusion: Both computational models provide an alternative method for estimating the HVL of diagnostic range X-ray. These models are user-friendly in predicting HVLs, which are used to characterise the quality of the X-ray beam, and these models provide predictions almost instantly compared with experimental measurements. PMID:23610546

Chen, Suk Chiang; Jong, Wei Loong; Harun, Ahmad Zaky

2012-01-01

281

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

282

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

283

Experimental Investigation of a Pseudospark-Produced High-Brightness Electron Beam for X-ray Applications  

NASA Astrophysics Data System (ADS)

This paper presents the progress in the experimental investigation of pseudospark-produced electron beams to drive x-ray emission for medical devices. Experiments are performed to determine the discharge behaviors (breakdown characteristics, electron beam generation efficiency) and the qualities of electron beams (peak current, energy spread, and transverse emittance) produced by a thirty-gap pseudospark device. The system is operated at 70kV. The breakdown voltage and discharge current are measured by a high voltage probe and Rogowski coil. A movable multi-probe array consists of 4 electrostatic probes to measure the beam currents profile at different radial and axial locations. Thus the energy spread and rms emittance of electron beams can be determined radially and axially. A discussion of the measured discharge characteristics and beam parameters to drive x-ray emission are also presented.

Hu, Jing; Rovey, Joshua

2010-11-01

284

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

285

XLVII. The effect of discontinuities of the background on the evaluation of the intensities of X-ray reflexions from crystalline powders  

Microsoft Academic Search

The paper relates to the measurement of X-ray intensities ; it discusses in particular the discontinuous character of the background of white radiation and its effect on the evaluation of the intensities of X-ray reflexions. Discontinuities of two types are considered arising from absorption steps and from sudden sensitivity changes of the photographic emulsion for certain wavelengths. Means of avoiding

A. Baxter; J. C. M. Brentano

1937-01-01

286

Testing the beamed inverse-Compton model for jet X-ray emission: velocity structure and deceleration?  

E-print Network

By considering a small sample of core-dominated radio-loud quasars with X-ray jets, I show, as has been argued previously by others, that the observations require bulk jet deceleration if all of the X-ray emission is to be explained using the widely adopted beamed inverse-Compton model, and argue that jets even in these powerful objects must have velocity structure in order to reconcile their radio and X-ray properties. I then argue that the deceleration model has several serious weaknesses, and discuss the viability of alternative models for the decline in X-ray/radio ratio as a function of position. Although inverse-Compton scattering from the jets is a required process and must come to dominate at high redshifts, adopting an alternative model for the X-ray emission of some nearby, well-studied objects can greatly alleviate some of the problems posed by these observations for the beamed inverse-Compton model.

M. J. Hardcastle

2005-11-17

287

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

Microsoft Academic Search

The Linac Coherent Light Source is an x-ray free-electron laser at the SLAC National Accelerator Laboratory, which is operating at x-ray wavelengths of 20-1.2 Angstrom with peak brightness nearly ten orders of magnitude beyond conventional synchrotron radiation sources. At the low charge operation mode (20 pC), the x-ray pulse length can be <10 fs. In this paper we report our

Lanfa

2011-01-01

288

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

289

A simple, direct method for x-ray scatter estimation and correction in digital radiography and cone-beam CT  

Microsoft Academic Search

X-ray scatter poses a significant limitation to image quality in cone-beam CT (CBCT), resulting in contrast reduction, image artifacts, and lack of CT number accuracy. We report the performance of a simple scatter correction method in which scatter fluence is estimated directly in each projection from pixel values near the edge of the detector behind the collimator leaves. The algorithm

J. H. Siewerdsen; M. J. Daly; B. Bakhtiar; D. J. Moseley; S. Richard; H. Keller; D. A. Jaffray

2006-01-01

290

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

E-print Network

-ray radiation from laser­plasma interactions (15­ 20), betatron radiation is straightforward and able to deliverConcurrence of monoenergetic electron beams and bright X-rays from an evolving laser-plasma bubble for Laser Plasmas (Ministry of Education), Department of Physics and Astronomy, Shanghai Jiao Tong

Wang, Wei Hua

291

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

292

Interlaced x-ray microplanar beams: A radiosurgery approach with clinical potential  

PubMed Central

Studies have shown that x-rays delivered as arrays of parallel microplanar beams (microbeams), 25- to 90-?m thick and spaced 100–300 ?m on-center, respectively, spare normal tissues including the central nervous system (CNS) and preferentially damage tumors. However, such thin microbeams can only be produced by synchrotron sources and have other practical limitations to clinical implementation. To approach this problem, we first studied CNS tolerance to much thicker beams. Three of four rats whose spinal cords were exposed transaxially to four 400-Gy, 0.68-mm microbeams, spaced 4 mm, and all four rats irradiated to their brains with large, 170-Gy arrays of such beams spaced 1.36 mm, all observed for 7 months, showed no paralysis or behavioral changes. We then used an interlacing geometry in which two such arrays at a 90° angle produced the equivalent of a contiguous beam in the target volume only. By using this approach, we produced 90-, 120-, and 150-Gy 3.4 × 3.4 × 3.4 mm3 exposures in the rat brain. MRIs performed 6 months later revealed focal damage within the target volume at the 120- and 150-Gy doses but no apparent damage elsewhere at 120 Gy. Monte Carlo calculations indicated a 30-?m dose falloff (80–20%) at the edge of the target, which is much less than the 2- to 5-mm value for conventional radiotherapy and radiosurgery. These findings strongly suggest potential application of interlaced microbeams to treat tumors or to ablate nontumorous abnormalities with minimal damage to surrounding normal tissue. PMID:16760251

Dilmanian, F. Avraham; Zhong, Zhong; Bacarian, Tigran; Benveniste, Helene; Romanelli, Pantaleo; Wang, Ruiliang; Welwart, Jeremy; Yuasa, Tetsuya; Rosen, Eliot M.; Anschel, David J.

2006-01-01

293

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

294

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

295

Spectral energetic properties of the X-ray-boosted photoionization by an intense few-cycle laser  

NASA Astrophysics Data System (ADS)

We report a discovery that an intense few-cycle laser pulse passing through gas leaves a fingerprint of its field envelope on the photoelectron energy spectrum, which involves continuous X-ray radiations. The spectrum resulting from the photoionization processes includes significant quantum enhancement and interference and exhibits interesting energetic properties. The spectral cut-off energies reflect the strength, time, and interference of the laser field modulation on the photoelectron energy. These energetic properties suggest a new method for precise intense-laser-pulse measurement in situ. The method has the advantages of accuracy, simplicity, speed, and large dynamic ranges (up to many orders of intensity).

Ge, Yu-Cheng; He, Hai-Ping

2014-07-01

296

An intensity correction for pole figure measurements by grazing incident and grazing exit angle X-ray diffraction  

SciTech Connect

In pole figure measurement by X-ray diffraction, the intensity must be corrected for geometric factors entering into the intensity. For the grazing (often, also called glancing) angle diffraction mode, the irradiated area changes with the grazing angle. A theoretical analysis of this effect was made and compared with measured data from a texture-free silver sample. An intensity correction factor is given as the ratio of the detector slit width and the width of the irradiated sample area as seen from the detector. As an application, the texture of thin copper film was studied.

Njeh, Anouar; Wieder, Thomas; Ghozlen, Mohamed Hedi Ben; Fuess, Hartmut

2004-05-15

297

Scanning X-ray microscope  

US Patent & Trademark Office Database

A scanning X-ray microscope including an X-ray source capable of emitting a beam of X-rays, a collimator positioned to receive the beam of X-rays and, to collimate this beam, a focusing cone means to focus the beam of X-rays, directed by the collimator, onto a focal plane, a specimen mount for supporting a specimen in the focal plane to receive the focused beam of X-rays, and X-ray beam scanning means to relatively move the specimen and the focusing cone means and collimator to scan the focused X-ray beam across the specimen, a detector disposed adjacent the specimen to detect flourescent photons emitted by the specimen upon exposure to the focused beam of X-rays to provide an electrical output representative of this detection, means for displaying and/or recording the information provided by the output from the detector, means for providing information to the recording and/or display means representative of the scan rate and position of the focused X-ray beam relative to the specimen whereby the recording and/or display means can correlate the information received to record and/or display quantitive and distributive information as to the quantity and distribution of elements detected in the specimen. Preferably there is provided an X-ray beam modulation means upstream, relative to the direction of emission of the X-ray beam, of the focusing cone means.

1982-02-23

298

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

299

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

SciTech Connect

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

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

2010-08-23

300

Beamed and Unbeamed X-ray Emission in FR1 Radio Galaxies  

NASA Technical Reports Server (NTRS)

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

Worrall, Diana M.

1997-01-01

301

Proton therapy versus intensity modulated x-ray therapy in the treatment of prostate cancer: Estimating secondary cancer risks  

NASA Astrophysics Data System (ADS)

External beam radiation therapy is used to treat nearly half of the more than 200,000 new cases of prostate cancer diagnosed in the United States each year. During a radiation therapy treatment, healthy tissues in the path of the therapeutic beam are exposed to high doses. In addition, the whole body is exposed to a low-dose bath of unwanted scatter radiation from the pelvis and leakage radiation from the treatment unit. As a result, survivors of radiation therapy for prostate cancer face an elevated risk of developing a radiogenic second cancer. Recently, proton therapy has been shown to reduce the dose delivered by the therapeutic beam to normal tissues during treatment compared to intensity modulated x-ray therapy (IMXT, the current standard of care). However, the magnitude of stray radiation doses from proton therapy, and their impact on this incidence of radiogenic second cancers, was not known. The risk of a radiogenic second cancer following proton therapy for prostate cancer relative to IMXT was determined for 3 patients of large, median, and small anatomical stature. Doses delivered to healthy tissues from the therapeutic beam were obtained from treatment planning system calculations. Stray doses from IMXT were taken from the literature, while stray doses from proton therapy were simulated using a Monte Carlo model of a passive scattering treatment unit and an anthropomorphic phantom. Baseline risk models were taken from the Biological Effects of Ionizing Radiation VII report. A sensitivity analysis was conducted to characterize the uncertainty of risk calculations to uncertainties in the risk model, the relative biological effectiveness (RBE) of neutrons for carcinogenesis, and inter-patient anatomical variations. The risk projections revealed that proton therapy carries a lower risk for radiogenic second cancer incidence following prostate irradiation compared to IMXT. The sensitivity analysis revealed that the results of the risk analysis depended only weakly on uncertainties in the risk model and inter-patient variations. Second cancer risks were sensitive to changes in the RBE of neutrons. However, the findings of the study were qualitatively consistent for all patient sizes and risk models considered, and for all neutron RBE values less than 100.

Fontenot, Jonas David

302

Characteristics of orthovoltage x-ray therapy beams at extended SSD for applicators with end plates.  

PubMed

The effects of extended SSD (ESSD) on orthovoltage x-ray therapy dosimetry have been studied for a Therapax DXT300 treatment unit with several open- and close-ended cones. For the open-ended cones, the beam output and percentage depth dose (PDD) at ESSD can be accurately estimated from the measured data at the nominal SSD (NSSD) by an inverse square law (ISL) and a divergence factor for gaps (distance from cone end to point of interest) up to 15 cm. In the case of close-ended applicators (with an end plate of 3.2 mm thick PMMA), extending SSD results in significant changes in output and in PDDs, but has little effect on beam penumbra and flatness for gaps up to 15 cm. The output at ESSD calculated by applying the ISL with the NSSD is found to be as much as 9% different from the measurement for the close-ended cone. The output at ESSD can, however, be calculated accurately by applying the ISL with an effective SSD or using a measured gap factor. The change in the PDDs with SSD can be calculated from a geometric divergence using a pseudo SSD which is approximately equal to 60% of the effective SSD determined in air. The calculated PDD curves at ESSD using this divergence factor agree well with measurements (within +/- 1% for beams of 100-300 kVp with cone size ranging from 10 x 10 to 20 x 20 cm2 and gap distance up to 15 cm). PMID:9044418

Li, X A; Salhani, D; Ma, C M

1997-02-01

303

Characteristics of orthovoltage x-ray therapy beams at extended SSD for applicators with end plates  

NASA Astrophysics Data System (ADS)

The effects of extended SSD (ESSD) on orthovoltage x-ray therapy dosimetry have been studied for a Therapax DXT300 treatment unit with several open- and close-ended cones. For the open-ended cones, the beam output and percentage depth dose (PDD) at ESSD can be accurately estimated from the measured data at the nominal SSD (NSSD) by an inverse square law (ISL) and a divergence factor for gaps (distance from cone end to point of interest) up to 15 cm. In the case of close-ended applicators (with an end plate of 3.2 mm thick PMMA), extending SSD results in significant changes in output and in PDDs, but has little effect on beam penumbra and flatness for gaps up to 15 cm. The output at ESSD calculated by applying the ISL with the NSSD is found to be as much as 9% different from the measurement for the close-ended cone. The output at ESSD can, however, be calculated accurately by applying the ISL with an effective SSD or using a measured gap factor. The change in the PDDs with SSD can be calculated from a geometric divergence using a pseudo SSD which is approximately equal to 60% of the effective SSD determined in air. The calculated PDD curves at ESSD using this divergence factor agree well with measurements (within for beams of 100 - 300 kVp with cone size ranging from to and gap distance up to 15 cm).

Li, X. Allen; Salhani, D.; Ma, C.-M.

1997-02-01

304

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

305

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

E-print Network

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 um provides sufficient X-ray transmittance to enable simultaneous operation of two beamlines. Here we report on the design, fabrication, and X-ray characterization of the first and second (300-um-thick) crystals utilized in the monochromator and the optical assemblies holding these crystals. Each crystal plate has a region of about 5 X 2 mm2 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 X 2 mm2 working regions of the crystals.

Stoupin, S; 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; Song, S; Sikorski, M; Zhu, D

2014-01-01

306

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

307

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

308

A tetrahedron beam computed tomography benchtop system with a multiple pixel field emission x-ray tube  

PubMed Central

Purpose: To demonstrate the feasibility of Tetrahedron Beam Computed Tomography (TBCT) using a carbon nanotube (CNT) multiple pixel field emission x-ray (MPFEX) tube. Methods: A multiple pixel x-ray source facilitates the creation of novel x-ray imaging modalities. In a previous publication, the authors proposed a Tetrahedron Beam Computed Tomography (TBCT) imaging system which comprises a linear source array and a linear detector array that are orthogonal to each other. TBCT is expected to reduce scatter compared with Cone Beam Computed Tomography (CBCT) and to have better detector performance. Therefore, it may produce improved image quality for image guided radiotherapy. In this study, a TBCT benchtop system has been developed with an MPFEX tube. The tube has 75 CNT cold cathodes, which generate 75 x-ray focal spots on an elongated anode, and has 4 mm pixel spacing. An in-house-developed, 5-row CT detector array using silicon photodiodes and CdWO4 scintillators was employed in the system. Hardware and software were developed for tube control and detector data acquisition. The raw data were preprocessed for beam hardening and detector response linearity and were reconstructed with an FDK-based image reconstruction algorithm. Results: The focal spots were measured at about 1?×?2 mm2 using a star phantom. Each cathode generates around 3 mA cathode current with 2190 V gate voltage. The benchtop system is able to perform TBCT scans with a prolonged scanning time. Images of a commercial CT phantom were successfully acquired. Conclusions: A prototype system was developed, and preliminary phantom images were successfully acquired. MPFEX is a promising x-ray source for TBCT. Further improvement of tube output is needed in order for it to be used in clinical TBCT systems. PMID:21992368

Xu, Xiaochao; Kim, Joshua; Laganis, Philip; Schulze, Derek; Liang, Yongguang; Zhang, Tiezhi

2011-01-01

309

A tetrahedron beam computed tomography benchtop system with a multiple pixel field emission x-ray tube  

SciTech Connect

Purpose: To demonstrate the feasibility of Tetrahedron Beam Computed Tomography (TBCT) using a carbon nanotube (CNT) multiple pixel field emission x-ray (MPFEX) tube. Methods: A multiple pixel x-ray source facilitates the creation of novel x-ray imaging modalities. In a previous publication, the authors proposed a Tetrahedron Beam Computed Tomography (TBCT) imaging system which comprises a linear source array and a linear detector array that are orthogonal to each other. TBCT is expected to reduce scatter compared with Cone Beam Computed Tomography (CBCT) and to have better detector performance. Therefore, it may produce improved image quality for image guided radiotherapy. In this study, a TBCT benchtop system has been developed with an MPFEX tube. The tube has 75 CNT cold cathodes, which generate 75 x-ray focal spots on an elongated anode, and has 4 mm pixel spacing. An in-house-developed, 5-row CT detector array using silicon photodiodes and CdWO{sub 4} scintillators was employed in the system. Hardware and software were developed for tube control and detector data acquisition. The raw data were preprocessed for beam hardening and detector response linearity and were reconstructed with an FDK-based image reconstruction algorithm. Results: The focal spots were measured at about 1 x 2 mm{sup 2} using a star phantom. Each cathode generates around 3 mA cathode current with 2190 V gate voltage. The benchtop system is able to perform TBCT scans with a prolonged scanning time. Images of a commercial CT phantom were successfully acquired. Conclusions: A prototype system was developed, and preliminary phantom images were successfully acquired. MPFEX is a promising x-ray source for TBCT. Further improvement of tube output is needed in order for it to be used in clinical TBCT systems.

Xu, Xiaochao; Kim, Joshua; Laganis, Philip; Schulze, Derek; Liang, Yongguang; Zhang, Tiezhi [Department of Radiation Oncology, William Beaumont Hospital, Royal Oak, Michigan 48073 (United States); Department of Radiation Oncology, William Beaumont Hospital, Royal Oak, Michigan 48073and Department of Physics, Oakland University, Rochester, Michigan 48309 (United States); Xinray Systems LLC, Research Triangle Park, North Carolina 27709 (United States); Department of Radiation Oncology, William Beaumont Hospital, Royal Oak, Michigan 48073 and Department of Medical Physics, Wayne State University, Detroit, Michigan 48201 (United States); Department of Radiology, William Beaumont Hospital, Royal Oak, Michigan 48073 (United States); Department of Radiation Oncology, William Beaumont Hospital, Royal Oak, Michigan 48073 (United States)

2011-10-15

310

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

311

Transmission grating streaked spectrometer for the diagnosis of soft x-ray emission from ultrahigh intensity laser heated targets  

SciTech Connect

A free-standing gold transmission grating with a period of 5000 A has been coupled to a soft x-ray sensitive streak camera with a limiting temporal resolution of 10 ps. The streak camera is equipped with a caesium iodide transmission photocathode and observations have been made in the 10-100 A regime. For a small source (200 {mu}m diameter) the spectral resolution is predicted to be around 2.5 A. This has been confirmed by examination of the Lyman-{alpha} line in hydrogen-like laser heated boron. A recorded linewidth of 2.44 A is demonstrated. The instrument has been used to diagnose the soft x-ray emission from a plastic (CH) foil target heated by an ultra-intense (2x10{sup 20} W cm{sup -2}) laser pulse.

Eagleton, R.T.; James, S.F. [AWE Aldermaston, Reading, Berkshire, RG7 4PR (United Kingdom)

2004-10-01

312

X-ray spectroscopic studies of hot, dense iron plasma formed by subpicosecond high intensity KrF laser irradiation  

SciTech Connect

The time-integrated x-ray emission from a hot, dense iron plasma has been recorded. The iron plasma was created when a target with a 1000-A-thick iron layer buried beneath 1000 A of plastic was irradiated by a 300 fs pulse of 249 nm laser light at an intensity of approximately 10{sup 17} Wcm{sup {minus}2}. Two models have been used to construct a synthetic x-ray spectrum. The first employs detailed, spectroscopically accurate atomic data and the second uses a local thermodynamic equilibrium opacity model. The detailed model shows fairly good agreement with experiment whereas the opacity model only shows agreement in the gross features. {copyright} {ital 1996 American Institute of Physics.}

Nazir, K.; Rose, S.J. [Department of Physics and Space Science, University of Birmingham, Edgbaston, Birmingham, B15 2TT (United Kingdom)] [Department of Physics and Space Science, University of Birmingham, Edgbaston, Birmingham, B15 2TT (United Kingdom); Djaoui, A. [Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 OQX (United Kingdom)] [Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 OQX (United Kingdom); Tallents, G.J.; Holden, M.G. [Department of Physics, University of Essex, Colchester CO4 3SQ (United Kingdom)] [Department of Physics, University of Essex, Colchester CO4 3SQ (United Kingdom); Norreys, P.A. [Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 OQX (United Kingdom)] [Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 OQX (United Kingdom); Fews, P. [Department of Physics, University of Bristol, Bristol BS8 1TL (United Kingdom)] [Department of Physics, University of Bristol, Bristol BS8 1TL (United Kingdom); Zhang, J. [Clarendon Laboratory, Parks Road, Oxford OX1 3PU (United Kingdom)] [Clarendon Laboratory, Parks Road, Oxford OX1 3PU (United Kingdom); Failles, F. [Department of Physics and Space Science, University of Birmingham, Edgbaston, Birmingham, B15 2TT (United Kingdom)] [Department of Physics and Space Science, University of Birmingham, Edgbaston, Birmingham, B15 2TT (United Kingdom)

1996-12-01

313

Multiphoton ionization as a clock to reveal molecular dynamics with intense short x-ray free electron laser pulses.  

PubMed

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. PMID:23368555

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

2012-12-28

314

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

SciTech Connect

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

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

2011-08-15

315

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

NASA Astrophysics Data System (ADS)

The dynamics of electron acceleration by laser wakefield and the associated x-rays emission in long plasmas are numerically investigated for parameters close to the threshold of laser self-focusing. The plasma length is set by the use of dielectric capillary tubes that confine the gas and the laser energy. Electrons self-injection and acceleration to the 170 MeVs are obtained for densities as low as 5 × 1018 cm-3 and a moderate input intensity (0.77 × 1018 W/cm2). The associated x-ray emission at the exit of the capillary tube is shown to be an accurate diagnostic of the electrons self-injection and acceleration process.

Ferrari, H. E.; Lifschitz, A. F.; Maynard, G.; Cros, B.

2011-08-01

316

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

SciTech Connect

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

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

1994-09-01

317

The Effect of Valence Electrons and Electron Cloud Distortion upon Intensities in Electron and X-Ray Scattering (Applied to Zinc Oxide)  

Microsoft Academic Search

An extensive investigation of electron scattering by zinc oxide has been carried out by Lark-Horovitz and Yearian. The intensity distribution, determined by photographic methods, showed marked anomalies with respect to the intensity distribution of the corresponding x-ray pattern. The visually estimated x-ray intensities seem to be in general agreement with values calculated from approximate Fermi or Pauling-Sherman wave functions, and

Vivian A. Johnson

1940-01-01

318

Phase-contrast x-ray imaging with intense Ar K{alpha} radiation from femtosecond-laser-driven gas target  

SciTech Connect

Intense Ar K{alpha} x ray with very little continuum background has been generated using a dense Ar gas irradiated with an intense femtosecond laser, with the measured flux of 1.2x10{sup 3} photons/mrad{sup 2}/pulse. This compact quasimonochromatic x-ray source, with a source size of only 12 {mu}m, has been applied to x-ray radiographic imaging of a biological specimen, resulting in high-resolution, high quality phase-contrast images. Correlation between this intense K{alpha} emission with the laser channeling in the Ar gas is discussed.

Chen, L. M.; Kando, M.; Ma, J.; Kotaki, H.; Fukuda, Y.; Hayashi, Y.; Daito, I.; Homma, T.; Ogura, K.; Mori, M.; Pirozhkov, A. S.; Koga, J.; Daido, H.; Bulanov, S. V.; Kimura, T.; Tajima, T.; Kato, Y. [Advanced Photon Research Center, Japan Atomic Energy Agency, 8-1 Umemidai Kizugawa, Kyoto 619-0215 (Japan)

2007-05-21

319

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

NASA Astrophysics Data System (ADS)

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

Moga, Jacqueline D.

320

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

321

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

322

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

323

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

324

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

325

Generation of high-intensity coherent radition in the soft-x-ray and vacuum-ultraviolet region  

SciTech Connect

An electron beam can be made to interact with an undulator magnet so that a collective unstable mode is excited. In this mode, the beam generates coherent radiation whose wavelength is detemined by the undulator period and the electron energy. By proper choice of the electron-beam energy, energy dispersion, and density, one can obtain coherent radiation in the soft-x-ray region with peak and average power of the order of hundreds of megawatts and hundreds of milliwatts, respectively. Larger peak powers, of the order of a gigawatt, can be expected for UV radiation with lambda in the range of 500--2000 A. We discuss the physical principles of these systems and give examples of how they might be built.

Murphy, J.B.; Pellegrini, C.

1985-01-01

326

X-ray beam filtration, dosimetry phantom size and CT patient dose conversion factors  

NASA Astrophysics Data System (ADS)

We examine how the choice of CT x-ray beam filtration and phantom size influences patient dose (D) to computed tomography dose index (CTDI) conversion factors (i.e. D/CTDI). The ratio of head to body phantom CTDIw for a defined scan technique is ?, and the ratio of organ dose when the body filter is changed to the head filter is ?. CTDI and organ doses were obtained using the ImPACT CT patient dosimetry calculator, and values of ? and ? were determined for 39 CT scanners. The average value of ? for the 39 CT scanners covering a 20 year period was 1.99 ± 0.23, but 30% of scanners had ? values that differed by more than 10% from the average. For GE, the value of ? has been approximately constant at ~2.0. Both Philips and Siemens show a definite upward trend from values well below 2.0 in the early 1990s to well over 2.0 for their latest models. The data for Toshiba show no overall trend with time with half the data points below 2.0 and the remainder above this value. The average value of ? was 1.09 ± 0.25. All vendors showed a downward trend in the ? parameter, and where the most recent scanners from each vendor had a ? value close to unity. Our results show that average D/CTDI conversion factors for a body phantom/filter combination are typically double those appropriate for a head phantom/filter combination.

Huda, Walter; Sterzik, Alexander; Tipnis, Sameer

2010-01-01

327

Novel correction method for X-ray beam energy fluctuation of high energy DR system with a linear detector  

NASA Astrophysics Data System (ADS)

A high energy digital radiography (DR) testing system has generated diverse scientific and technological interest in the field of industrial non-destructive testing. However, due to the limitations of manufacturing technology for accelerators, an energy fluctuation of the X-ray beam exists and leads to bright and dark streak artifacts in the DR image. Here we report the utilization of a new software-based method to correct the fluctuation artifacts. The correction method is performed using a high pass filtering operation to extract the high frequency information that reflects the X-ray beam energy fluctuation, and then subtracting it from the original image. Our experimental results show that this method is able to rule out the artifacts effectively and is readily implemented on a practical scanning system.

Yang, Min; Chen, Hao; Meng, Fan-Yong; Wei, Dong-Bo

2011-11-01

328

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

329

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

330

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

NASA Astrophysics Data System (ADS)

We propose a new method of obtaining a compact ultra-bright, ultra-broadband hard X-ray source. This X-ray source has a high peak brightness in the order of 1022 photons/(s mm2 mrad2 0.1%BW), an ultrashort duration (10 fs), and a broadband spectrum (flat distribution from 0.1 MeV to 4 MeV), and thus has wide-ranging potential applications, such as in ultrafast Laue diffraction experiments. In our scheme, laser-plasma accelerators (LPAs) provide driven electron beams. A foil target is placed oblique to the beam direction so that the target normal sheath field (TNSF) is used to provide a bending force. Using this TNSF-kick scheme, we can fully utilize the advantages of current LPAs, including their high charge, high energy, and low emittance.

Shi, Yin; Shen, Baifei; Zhang, Xiaomei; Wang, Wenpeng; Ji, Liangliang; Zhang, Lingang; Xu, Jiancai; Yu, Yahong; Zhao, Xueyan; Wang, Xiaofeng; Yi, Longqing; Xu, Tongjun; Xu, Zhizhan

2013-09-01

331

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

SciTech Connect

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

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

2013-09-15

332

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

PubMed Central

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

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

2011-01-01

333

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

334

Method of calibrating dosimeters in scattered x-rays  

Microsoft Academic Search

Existing methods of calibrating dosimeters for monitoring x-ray protection have various disadvantages that prevent one from raising the accuracy [i]~ A major disadvantage in methods in which one compares readings of the test and standard instruments in a direct beam arises from the high values of :the radiation intensity. The minimum dose rate provided by an x-ray tube as adjusted

F. I. Glezin; L. V. Kleimenova; T. L. Skomorokhova; A. V. Frolova; E. V. Shirmer

1982-01-01

335

Valence-electron configuration of Ti and Ni in Ti x Ni 1? x alloys from K?-to- K? X-ray intensity ratio studies  

Microsoft Academic Search

K?-to-K? X-ray intensity ratios of Ti and Ni have been measured in pure metals and in alloys of TixNi1?x (x=0.7, 0.6, 0.5, 0.4 and 0.3) following excitation by 22.69keV X-rays from a 10mCi 109Cd radioactive point source. The valence-electron configurations of these metals were determined by corporation of measured K?-to-K? X-ray intensity ratios with the results of multiconfiguration Dirac–Fock calculation

I. Han; L. Demir

2010-01-01

336

Dislocation analysis for heat-exchanger method grown sapphire with white beam synchrotron X-ray topography  

Microsoft Academic Search

Dislocations in high quality Heat-Exchanger Method (HEM) produced sapphire were analyzed with the white beam large area transmission synchrotron X-ray topography technique. After analysis the dislocations for different Laue spots, i.e. different diffraction vectors, in one recorded film, three kinds of dislocations, i.e. screw, edge and mixed dislocations were identified in the studied HEM sapphire, but most are mixed type,

W. M. Chen; P. J. McNally; Yu. V. Shvyd’ko; T. Tuomi; A. N. Danilewsky; M. Lerche

2003-01-01

337

Study of defect structures in MLEK grown InP single crystals by synchrotron white beam X-ray topography  

SciTech Connect

The application of Synchrotron White Beam X-ray Topography (SWBXT) as a non-destructive diagnostic technique to the characterization of defect structures in large size InP single crystals was presented. Various kinds of defect configurations, including slip bands, micro-twin lamellae, growth striations, individual dislocations, and precipitates, were revealed. The relationship between defect formation and growth conditions was briefly discussed.

Si, W.; Chung, H.; Dudley, M.; Prasad, V. [State Univ. of New York, Stony Brook, NY (United States); Anselmo, A.; Bliss, D.F. [RL/ERXE, Hanscom AFB, MA (United States)

1996-12-31

338

Impulsive solar X-ray bursts: Bremsstrahlung radiation from a beam of electrons in the solar chromosphere and the total energy of solar flares  

NASA Technical Reports Server (NTRS)

Analysis of various aspects of impulsive X-ray bursts (IXB's) has lead to the consideration of a model where the X-rays are produced by bremsstrahlung radiation from a beam of electrons directed toward the photosphere. It was found that in general the X-ray spectrum from such a beam will fall off more rapidly than when the effect of the beaming of radiation is neglected. Furthermore, the spectral index of the resulting X-rays appears to increase by about unity for X-ray energies 100 kev, a fact which may explain the observed cutoff in the spectrum of the IXB's. It is also shown that in such a model there is sufficient energy in the form of nonthermal electrons to explain the total energy (approximately 10 to the 32nd power ergs) of a flare.

Petrosian, V.

1973-01-01

339

Valence electronic structure of Mn in undoped and doped lanthanum manganites from relative K X-ray intensity studies  

Microsoft Academic Search

Relative K X-ray intensities of Mn in Mn, MnO2, LaMnO3 and La0.7B0.3MnO3 (B = Ca, Sr and Ce) systems have been measured following excitation by 59.54 keV ?-rays from a 200 mCi 241Am point-source. The measured results for the compounds deviate significantly from the results of pure Mn. Comparison of the experimental data with the multi-configuration Dirac–Fock (MCDF) effective atomic

S. Raj; H. C. Padhi; P. Raychaudhury; A. K. Nigam; R. Pinto; M. Polasik; F. Pawlowski; D. K. Basa

2001-01-01

340

Wavelet analysis of white beam x-ray fluorescence holograms: determination of lattice sites and imaging of local atomic structure  

NASA Astrophysics Data System (ADS)

The prospects of atomic structure imaging with the continuous spherical wavelet transform (CSWT) as applied to white beam x-ray fluorescence holograms (XFH) are discussed. Recording of XFH with a white x-ray beam eliminates holographic twin images and minimizes extinction effects. However, the lack of these parasitic effects is accompanied by a limited radial resolution. In this work, by introducing an approximation of the white x-ray spectrum based on the Gumbel distribution, we propose an improvement both in generation of white beam XFH and in data analysis. Using approximate analytical models and realistic numerical simulations, we give a detailed description of the properties and resolution of local structure projections directly obtained from XFH by using wavelet analysis. It is demonstrated that the CSWT and, in particular, its windowed inversion can be effectively used to enhance and speed up reliability factor (R-factor) analysis of the data, which enables precise fully three-dimensional localization of multiple lattice sites of dopants. For this, an exact analytic formula for the inversion is given, enabling its fast calculation in a single step. As an example system, we consider magnetic ions in wurtzite GaN.

Dul, D. T.; Korecki, P.

2012-11-01

341

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

342

The MIT/OSO 7 catalog of X-ray sources - Intensities, spectra, and long-term variability  

NASA Technical Reports Server (NTRS)

This paper is a summary of the observations of the cosmic X-ray sky performed by the MIT 1-40-keV X-ray detectors on OSO 7 between October 1971 and May 1973. Specifically, mean intensities or upper limits of all third Uhuru or OSO 7 cataloged sources (185 sources) in the 3-10-keV range are computed. For those sources for which a statistically significant (greater than 20) intensity was found in the 3-10-keV band (138 sources), further intensity determinations were made in the 1-15-keV, 1-6-keV, and 15-40-keV energy bands. Graphs and other simple techniques are provided to aid the user in converting the observed counting rates to convenient units and in determining spectral parameters. Long-term light curves (counting rates in one or more energy bands as a function of time) are plotted for 86 of the brighter sources.

Markert, T. H.; Laird, F. N.; Clark, G. W.; Hearn, D. R.; Sprott, G. F.; Li, F. K.; Bradt, H. V.; Lewin, W. H. G.; Schnopper, H. W.; Winkler, P. F.

1979-01-01

343

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

344

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

345

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

346

Characterization of oxide scale on Alloy 446 by x-ray nano-beam analysis.  

SciTech Connect

To understand the potential degradation of metallic interconnects, tubes of alloy 446 were exposed to air/hydrogen dual atmosphere at elevated temperatures for 1030 h. The scale developed on the air side consisted of two layers. Because the two sublayers in the oxide scale were too thin for evaluation by regular X-ray diffraction, nanobeam X-ray diffraction was used to study the phase compositions in the scales that formed on both the air and hydrogen sides of alloy 446. The results indicate that Mn{sub 1-x}Cr{sub 2-x}O{sub 4} spinel is the major phase in the oxide scale on alloy 446. The valence of manganese in the oxide scale was also evaluated by X-ray near-edge absorption.

Zeng, Z; Natesan, K; Cai, S; Nuclear Engineering Division; IMSA

2008-01-01

347

EBT2 Dosimetry of X-rays produced by the electron beam from PFMA-3, a Plasma Focus for medical applications  

E-print Network

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

Elisa Ceccolini; Federico Rocchi; Domiziano Mostacci; Marco Sumini; Agostino Tartari

2011-12-09

348

EBT2 Dosimetry of X-rays produced by the electron beam from PFMA-3, a Plasma Focus for medical applications  

E-print Network

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

Ceccolini, Elisa; Mostacci, Domiziano; Sumini, Marco; Tartari, Agostino

2011-01-01

349

X-ray Polarization Spectroscopy to Study Hot Electron Transport in High Intensity Laser Produced Plasma  

NASA Astrophysics Data System (ADS)

X-ray polarization spectroscopy was used to study anisotropy of hot electron velocity distribution functions (VDFs) in a plasma generated at 10^18W/cm^2. Chlorinated triple-layer targets were irradiated and polarization degree of Cl Hea line was measured as a function of overcoat thickness. The polarization degree, nearly zero at the surface, becomes negative then positive, and finally becomes zero with increase in the thickness. This result indicate that VDF in under-dens region is affected with laser field, and that in over-dense region is with acceleration along the laser propagation. Depolarization seen in the surface and dense region is consistent with predictions with a time-dependent atomic kinetics code [1]. [1] T. Kawamura, et al., PRL 99, 115003 (2007)

Nishimura, H.; Inubushi, Y.; Okano, Y.; Fujioka, S.; Kai, T.; Kawamura, T.; Batani, D.; Morace, A.; Redaelli, R.; Fourment, C.; Santos, J.; Malka, G.; Boscheron, A.; Casner, A.; Koenig, M.; Jhozaki, T.; Nagatomo, H.; Mima, K.

2008-11-01

350

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

351

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

352

Ultrashort x-ray pulse generation by electron beam slicing in storage rings  

NASA Astrophysics Data System (ADS)

We propose a new method to generate ultrashort x-ray pulses using focused short low energy (˜20 MeV) electron bunches to create short slices of electrons from the circulating electron bunches in a synchrotron radiation storage ring. When a low energy electron bunch crosses from the top of a high energy storage ring electron bunch, its Coulomb force will kick a short slice from the core of the storage ring electron bunch. The separated slices, when passing through an undulator, will radiate ultrashort x-ray pulses at about 160 fs. We discuss the advantages, challenges, and provide data which confirm the feasibility of this new method.

He, A.; Willeke, F.; Yu, L. H.

2014-04-01

353

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

354

X-ray micro-CT with a displaced detector array: application to helical cone-beam reconstruction.  

PubMed

In x-ray micro-CT applications, it is useful to increase the field of view by offsetting a two-dimensional (2D) detector array. In this technical note, we briefly review the methods for image reconstruction with an asymmetric 2D detector array, elaborate on the use of an associated weighting scheme in the case of helical/spiral cone-beam scanning, and perform a series of numerical tests to demonstrate helical cone-beam image reconstruction with such an arrangement. PMID:14596314

Liu, Vinson; Lariviere, Nicholas R; Wang, Ge

2003-10-01

355

Efficient low debris hard x-ray source based on intense femtosecond laser irradiation on multiwalled carbon nanotubes  

NASA Astrophysics Data System (ADS)

Efficient coupling of laser energy is one of the primary concerns for devising laser based photon and charged particle sources with potential applications in a wide field of research interests. We report a two orders of magnitude efficient moderately hard x-ray (50 - 300 keV) source based on multi-walled carbon nanotubes (MWNT) irradiated by moderately intense (1015 - 1017 Wcm-2) ultra-short laser pulses. This is also accompanied by a three orders of magnitude reduction in ion debris in comparison with conventional metallic targets making these sources operationally safe. The bremsstrahlung measurement reveals a two orders of magnitude increment in x-ray flux from MWNT. Contrary to expectation that the rise in "hot" electron temperature leads to an increment of emitted ion energies form the plasma, a monotonic reduction of ion energies with increasing laser intensity for MWNT is noticed. Angle resolved ion flux measurement reveals an extremely divergent ion emission from MWNT with an evident three orders of magnitude reduction in ion flux. Based on the scaling laws for resonance absorption, our experimental data remarkably matches with theoretical predictions based on electrostatic calculations. This confirms the localized enhancement of the laser electric field near the tip of the MWNTs yield localized hot spots in the expanding plasma sheath layer leading to a non-planar expansion. This is characterized by a decrease in ion accelerating potential as well as a divergent ion emission, as observed in experiments.

Prem Kiran, P.; Bagchi, Suman; Bhuyan, M. K.; Krishnamurthy, M.; Yang, K.; Rao, A. M.; Ravindra Kumar, G.

2010-05-01

356

Coherent Compton X-ray sources  

SciTech Connect

Coherent X-Rays can be produced by scattering of laser light by a beam of relativistic electrons, provided that the electron beam is density modulated or the scattering is done at, or near 90{degree}. Since the coherent scattering is proportional to N{sup 2}, where N is the number of electrons, and the incoherent scattering is proportional to N, also a modest degree of coherence can substantially increase the X-Ray yield. The theory of laser-electron beam scattering is reviewed and compared with the emission of radiation by an electron beam in an undulator. Examples of the practical implementation of an intense source of coherent X-Rays are discussed.

Luccio, A.; Miceli, L.

1993-12-31

357

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

358

A simple concept shutter for high energy X-ray beams  

Microsoft Academic Search

A new design of a high speed shutter system which provides a uniform exposure is described in this paper. The elements of the system are specified. The material for the shutter plates are chosen so that when the system is shut down no X-ray transmission will occur. The mathematical model of the system is derived. The dynamic performance of the

Hossein Moini; Chang-Lin Kuo; John C. Bilello

1989-01-01

359

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

360

Application of X-ray reflection interface microscopy to thin-film materials  

Microsoft Academic Search

New X-ray imaging techniques with excellent spatial resolution are under development for investigating surface and interface structures. X-ray reflection imaging microscopy (XRIM) applies full-field imaging to a specularly reflected X-ray beam from a surface or interface. This technique uses a zone plate objective lens to spatially resolve the reflected X-ray intensity and, by exploiting phase contrast, allows steps or terraces

Zhan Zhang; Paul Zschack; Paul Fenter

2011-01-01

361

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

362

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

363

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.

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

2014-01-01

364

Synchrotron white beam X-ray topography analysis of MBE grown CdTe/CdTe (111)B  

SciTech Connect

The structural quality of CdTe(111)B substrates and MBE grown CdTe epilayers is examined with synchrotron white beam x-ray topography (SWBXT). Reflection SWBXT indicates that CdTe substrates with comparable x-ray double crystal rocking curve full width at half maximum values can have radically different defect microstructures, i.e. dislocation densities and the presence of inclusions. Dislocation mosaic structures delineated by SWBXT are consistent with the distribution of etch pits revealed by destructive chemical etch pit analysis. Direct one-to-one correspondence between distinct features of the topographic image and individual etch pits is demonstrated. Clearly resolved images of individual dislocations are obtained by carrying out transmission SWBXT. Our investigation demonstrates how the extent of twinning in a CdTe epilayer is strongly influenced by the quality of the defect microstructure, and how dislocations propagate from an inclusion. 11 refs., 8 figs., 1 tab.

Fanning, T.; Dudley, M. (SUNY, Stony Brook, NY (United States)); Lee, M.B.; Casagrande, L.G.; Di Marzio, D. (Grumman Corporate Research Center, Bethpage, NY (United States))

1993-08-01

365

X-ray monochromator  

NASA Technical Reports Server (NTRS)

An x-ray monochromator is described, wherin a housing supports a plurality of mirrors forming a plurality of opposed mirror faces in parallel with each other and having thereon multilayer coatings, with each of said pairs of mirror faces being provided with identical coatings which are different from the coatings on the other pairs of mirror faces such that each pair of mirror faces has a peak x-ray reflection at a different wavelength regime. The housing is moveable to bring into a polychromatic x-ray beam that pair of mirror faces having the best x-ray reflection for the desired wavelength, with the mirrors being pivotable to move the mirror faces to that angle of incidence at which the peak reflectivity of the desired wavelength x-rays occurs.

Hoover, Richard B. (inventor)

1992-01-01

366

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

367

Combined total body X-ray irradiation and total skin electron beam radiotherapy with an improved technique for mycosis fungoides  

SciTech Connect

Twelve consecutive patients with advanced stage mycosis fungoides (MF) were treated with combined total body X ray irradiation (TBI) and total skin electron beam radiotherapy (EBRT). Six had generalized plaque disease and dermatopathic nodes, three had tumor stage disease and node biopsy positive for mycosis fungoides, and three had erythroderma/Sezary syndrome. The treatment regimen consisted of split course total body X ray irradiation, given in twice weekly 15 cGy fractions to 75 cGy, then total skin electron beam radiation therapy given in once weekly 400 cGy fractions to a total dose of 2400 cGy. Underdosed areas and areas of greatest initial involvement were boosted 400 cGy twice weekly for an additional 1200 cGy. This was followed by a second course of total body X ray irradiation, to a total dose of 150 cGy. The total skin electron beam radiotherapy technique is a modification of an established six position EBRT technique for mycosis fungoides. Measurements to characterize the beam with and without a lexan scattering plate, demonstrated that the combination of no-plate beams produced better dose uniformity with a much higher dose rate. This improved technique is particularly advantageous for elderly and/or frail patients. Nine (75%) of the 12 patients achieved complete response (CR). The other three had significant improvement with greater than 80% clearing of their disease and resolution of symptoms. All six patients with generalized plaque disease achieved complete response and remained free of disease from 2 to 16 months. Two of three node positive patients also achieved complete response; one, with massive biopsy-documented mycosis fungoides nodal disease and deep open tumors, remained relapse-free over 2 years. Only one of the three patients with erythroderma/Sezary syndrome achieved a complete response, which was short lived.

Halberg, F.E.; Fu, K.K.; Weaver, K.A.; Zackheim, H.S.; Epstein, E.H. Jr.; Wintroub, B.U.

1989-08-01

368

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

PubMed

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

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

2014-01-01

369

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

370

STUDIES ON PURE ELEMENT INTENSITIES, MASS ABSORPTION COEFFICIENTS AND PARAMETERS (n AND no FOR ENERGY-DISPERSIVE X-RAY FLUORESCENCE ANALYSIS  

Microsoft Academic Search

Determination of pure element intensities is important in EDS (energy-dispersive X-ray fluorescence analysis) analysis. In a previous paper, we have studied three determination methods of pure element intensities: the pure thick metal foil, oxide, and low concentration methods. The pure element intensities of Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Br, Rb, Sr, Y, Zr, Nb, and

Hua Younan

2001-01-01

371

XPAD X-ray hybrid pixel detector for charge density quality diffracted intensities on laboratory equipment.  

PubMed

The new generation of X-ray detectors, the hybrid pixel area detectors or `pixel detectors', is based on direct detection and single-photon counting processes. A large linearity range, high dynamic and extremely low noise leading to an unprecedented high signal-to-noise ratio, fast readout time (high frame rates) and an electronic shutter are among their intrinsic characteristics which render them very attractive. First used on synchrotron beamlines, these detectors are also promising in the laboratory, in particular for pump-probe or quasi-static experiments and accurate electron density measurements, as explained in this paper. An original laboratory diffractometer made from a Nonius Mach3 goniometer equipped with an Incoatec Mo microsource and an XPAD pixel area detector has been developed at the CRM2 laboratory. Mo K? accurate charge density quality data up to 1.21?Å(-1) resolution have been collected on a sodium nitroprusside crystal using this home-made diffractometer. Data quality for charge density analysis based on multipolar modelling are discussed in this paper. Deformation electron densities are compared to those already published (based on data collected with CCD APEXII and CAD4 diffractometers). PMID:25274511

Wenger, Emmanuel; Dahaoui, Slimane; Alle, Paul; Parois, Pascal; Palin, Cyril; Lecomte, Claude; Schaniel, Dominik

2014-10-01

372

LETTER TO THE EDITOR: Hard x-ray and hot electron production from intense laser irradiation of wavelength-scale particles  

Microsoft Academic Search

We have examined the production of hard x-rays from the irradiation of ~1 µm diameter water droplets with a 35 fs laser at an intensity of up to 7×1017 W cm-2. We observe substantial x-ray production in the photon energy range above 100 keV and find that the implied hot electron temperatures from these micron-scale targets are significantly higher than

T. D. Donnelly; M. Rust; I. Weiner; M. Allen; R. A. Smith; C. A. Steinke; S. Wilks; J. Zweiback; T. E. Cowan; T. Ditmire

2001-01-01

373

X-ray-based measurement of composition during electron beam melting of AISI 316 stainless steel: Part I. Experimental setup and processing of spectra  

Microsoft Academic Search

An energy dispersive X-ray (EDX) detector mounted on a laboratory scale electron beam furnace (30 kW) was employed to assess\\u000a the potential use of X-rays as a means of on-line liquid alloy composition monitoring during electron beam (EB) melting of\\u000a alloys. The design and construction of the collimation and protection systems used for the EDX are described in Part I.

M. Ritchie; S. L. Cockcroft; A. Mitchell; P. D. Lee; T. Wang

2003-01-01

374

Desktop repetitive sources of powerful electron beams, X-ray and microwaves for lab investigations in radiation chemistry, physics and biology  

Microsoft Academic Search

We present results of the research and development work that has made it possible to create compact repetitive sources of high-power electron beams, X-rays, and microwaves. Laboratory investigations require that specific parameters of the e-beam, X-rays, and microwaves be high. It is energetically more advantageous to increase average power by using repetitive devices. The basic unit of such devices represents

V. G. Shpak; M. I. Yalandin; S. A. Shunailov

1996-01-01

375

Spatially resolved X-ray emission of heavy ion beam interaction with solid matter.  

NASA Astrophysics Data System (ADS)

We have been investigated K-shell radiation of projectile ions and solid media during its interaction. The main advantage of the method consists in that the media is transparent for radiation applied for diagnostics, which provides the data acquisition directly from the interaction volume. The projectile and target spectra in the energy range of 1.5^ -^ 8 keV were registered by means of spherically bend crystal spectrometers (FSSR) with a high spatial resolution along the beam propagation. The Ni, Ca and Mg ions accelerated in GSI UNILAC facility to the energies of 11.4 and 5.9 MeV/u were slowed down in solid quartz, quartz aerogels and aluminum media. Low-density (up to 0.02 g/cc) aerogel targets allowed expanding the interaction volume up to 100 times and, accordingly, to resolve the evolution of ion beam velocity and charge states inside the media. Simultaneously, the wavelengths and relative intensities of Ka satellite lines radiated by Si and Al target ions with different charges were measured. This has been provided us to investigate the excited media of the heavy ion track on a timescale of radiation transitions lifetimes (˜20 fs after excitation). Low beam current of 1 uA allowed us to consider the excitation process as a number of statistically independent acts of single heavy ion energy deposition to the media.

Pikuz, Sergey, Jr.; Rosmej, Olga; Faenov, Anatoly; Efremov, Vladimir P.; Korostiy, Svitlana; Blazevic, Abel; Fertman, Alexander; Skobelev, Igor; Norman, Henry E.; Hoffmann, Dieter H. H.

2006-04-01

376

Design and characterization of a multi-beam micro-CT scanner based on carbon nanotube field emission x-ray technology  

NASA Astrophysics Data System (ADS)

In this dissertation, I will present the results for my Ph.D. research for the past five years. My project mainly focuses on advanced imaging applications with a multi-beam x-ray source array based on carbon nanotube field emission technology. In the past few years, research in carbon nanotubes gradually changed from the raw material science to its application. Field emission x-ray application is one of the hottest research areas for carbon nanotube. Compared to traditional thermionic x-ray sources, the carbon nanotube field emission x-ray source has some natural advantages over traditional thermionic x-ray sources such as instantaneous x-ray generation, programmability and miniaturization. For the past few years, the research and development of carbon nanotube field emission x-ray has shifted from single x-ray beam applications to spatially distributed multi-beam x-ray sources. Previously in Zhou group, we have already built a gated micro-CT system with single beam micro-focus x-ray tube for higher spatial and temporal resolution as required in live animal imaging and a multi-beam tomosynthesis system targeting for faster and more stable breast imaging. Now my project mainly focused on the design, characterization and optimization of a multi-beam micro-CT imaging system. With the increase of gantry rotation speed approaching the mechanical limit, it is getting more and more difficult to further speed up the CT scanning. My new system promises a potential solution for the problem, and it serves as a great test platform for truly stationary micro-CT geometry. The potential capabilities it showed during the characterization and imaging measurements was promising. The dissertation is composed of five chapters. In Chapter 1, I will generally review the physics principles of x-ray generation and interaction with matter. Then the discovery of carbon nanotube and its great potential to serve as an excellent field emission electron source will be introduced in the second chapter, also the synthesis and technique of carbon nanotube field emission x-ray source fabrication demonstrated. Chapter 3 will be mainly describing the design of the multi-beam micro-CT system. Afterwards characterization, optimization and results from imaging measurements will be discussed in Chapter 4. Finally the conclusion and future work of this field will be given in Chapter 5.

Peng, Rui

377

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

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

378

Sub-pixel resolution of a pnCCD for X-ray white beam applications  

NASA Astrophysics Data System (ADS)

A new approach to achieve sub-pixel spatial resolution in a pnCCD detector with 75 × 75 ?m2 pixel size is proposed for X-ray applications in single photon counting mode. The approach considers the energy dependence of the charge cloud created by a single photon and its split probabilities between neighboring pixels of the detector based on a rectangular model for the charge cloud density. For cases where the charge of this cloud becomes distributed over three or four pixels the center position of photon impact can be reconstructed with a precision better than 2 ?m. The predicted charge cloud sizes are tested at selected X-ray fluorescence lines emitting energies between 6.4 keV and 17.4 keV and forming charge clouds with size (rms) varying between 8 ?m and 10 ?m respectively. The 2 ?m enhanced spatial resolution of the pnCCD is verified by means of an x-ray transmission experiment throughout an optical grating.

Abboud, A.; Send, S.; Pashniak, N.; Leitenberger, W.; Ihle, S.; Huth, M.; Hartmann, R.; Strüder, L.; Pietsch, U.

2013-05-01

379

X-ray ferromagnetic resonance spectroscopy  

SciTech Connect

We present a method to measure continuous-wave ferromagnetic resonance (FMR) spectra based on the core-level absorption of circularly polarized x rays. The technique is demonstrated by using a monochromatic x-ray beam incident on an yttrium-iron-garnet sample excited by a microwave field at 2.47 GHz. FMR spectra are obtained by monitoring the x-ray absorption intensity at the photon energy corresponding to the maximum of the magnetic circular dichroism effect at the iron L{sub 2,3} edges as a function of applied magnetic field. The x-ray FMR signal is shown to be energy dependent, which makes the technique element sensitive and opens up new possibilities to perform element-resolved FMR in magnetic alloys and multilayers.

Boero, G.; Rusponi, S.; Bencok, P.; Popovic, R.S.; Brune, H.; Gambardella, P. [Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne (Switzerland); European Synchrotron Radiation Facility (ESRF), F-38043 Grenoble (France); Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne (Switzerland)

2005-10-10

380

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

381

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

382

Cooper-minimum-type structure in proton-induced L1 - and L3 -subshell x-ray line intensities of Pd measured with high-resolution x-ray spectroscopy  

Microsoft Academic Search

We report on high-resolution measurements of the L1 - and L3 -subshell x-ray lines of Pd induced by 0.5-3.0 MeV proton bombardment. The experimental results for the relative intensities of the Lbeta3 (L1-M3) , Lbeta4 (L1-M2) , and Lbeta6 (L3-N1) lines are compared to the theoretically predicted values employing L -subshell ionization cross sections calculated within the semiclassical approximation and

M. Kavcic; Z. Smit

2009-01-01

383

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

SciTech Connect

Purpose: An improved method of image guidance for lung tumor biopsies could help reduce the high rate of false negatives. The aim of this work is to optimize the geometry of the scanning-beam digital tomography system (SBDX) for providing real-time 3D tomographic reconstructions for target verification. The unique geometry of the system requires trade-offs between patient dose, imaging field of view (FOV), and tomographic angle.Methods: Tomosynthetic angle as a function of tumor-to-detector distance was calculated. Monte Carlo Software (PCXMC) was used to calculate organ doses and effective dose for source-to-detector distances (SDDs) from 90 to 150 cm, patient locations with the tumor at 20 cm from the source to 20 cm from the detector, and FOVs centered on left lung and right lung as well as medial and distal peripheries of the lungs. These calculations were done for two systems, a SBDX system and a GE OEC-9800 C-arm fluoroscopic unit. To evaluate the dose effect of the system geometry, results from PCXMC were calculated using a scan of 300 mAs for both SBDX and fluoroscopy. The Rose Criterion was used to find the fluence required for a tumor SNR of 5, factoring in scatter, air-gap, system geometry, and patient position for all models generated with PCXMC. Using the calculated fluence for constant tumor SNR, the results from PCXMC were used to compare the patient dose for a given SNR between SBDX and fluoroscopy.Results: Tomographic angle changes with SDD only in the region near the detector. Due to their geometry, the source array and detector have a peak tomographic angle for any given SDD at a source to tumor distance that is 69.7% of the SDD assuming constant source and detector size. Changing the patient location in order to increase tomographic angle has a significant effect on organ dose distribution due to geometrical considerations. With SBDX and fluoroscopy geometries, the dose to organs typically changes in an opposing manner with changing patient location. When tumor SNR is held constant (i.e., x-ray fluence is scaled appropriately), SBDX gives 2–10 times less dose than fluoroscopy for the same conditions within the typical range of patient locations. The relative position of the patient (as a percent of SDD) has a much more significant impact on dose than either SDD or patient position. The patient position providing the minimum dose for a given tumor SNR and SDD is approximately the same as the position of maximum tomographic angle.Conclusions: SBDX offers a significant dose advantage over currently used C-arm fluoroscopy. The patient location with lowest dose coincides with the location of maximum tomographic angle. In order to provide adequate space for the patient and for the pulmonologists’ equipment, a SDD of 100 cm is recommended.

Nelson, Geoff; Fahrig, Rebecca [Department of Radiology, Stanford University, Stanford, California 94305 (United States)] [Department of Radiology, Stanford University, Stanford, California 94305 (United States); Yoon, Sungwon [Varian Medical Systems, Palo Alto, California 94304 (United States)] [Varian Medical Systems, Palo Alto, California 94304 (United States); Krishna, Ganesh [Palo Alto Medical Foundation, Mountain View, California 94040 (United States)] [Palo Alto Medical Foundation, Mountain View, California 94040 (United States); Wilfley, Brian [Triple Ring Technologies, Inc., Newark, California 94560 (United States)] [Triple Ring Technologies, Inc., Newark, California 94560 (United States)

2013-11-15

384

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

385

Complex aberrations in lymphocytes exposed to mixed beams of (241)Am alpha particles and X-rays.  

PubMed

Modern radiotherapy treatment modalities are associated with undesired out-of-field exposure to complex mixed beams of high and low energy transfer (LET) radiation that can give rise to secondary cancers. The biological effectiveness of mixed beams is not known. The aim of the investigation was the analysis of chromosomal damage in human peripheral blood lymphocytes (PBL) exposed to a mixed beam of X-rays and alpha particles. Using a dedicated exposure facility PBL were exposed to increasing doses of alpha particles (from (241)Am), X-rays and a mixture of both. Chromosomal aberrations were analysed in chromosomes 2, 8 and 14 using fluorescence in situ hybridisation. The found and expected frequencies of simple and complex aberrations were compared. Simple aberrations showed linear dose-response relationships with doses. A higher than expected frequency of simple aberrations was only observed after the highest mixed beam dose. A linear-quadratic dose response curve for complex aberrations was observed after mixed-beam exposure. Higher than expected frequencies of complex aberrations were observed for the two highest doses. Both the linear-quadratic dose-response relationship and the calculation of expected frequencies show that exposure of PBL to mixed beams of high and low LET radiation leads to a higher than expected frequency of complex-type aberrations. Because chromosomal changes are associated with cancer induction this result may imply that the cancer risk of exposure to mixed beams in radiation oncology may be higher than expected based on the additive action of the individual dose components. PMID:23669292

Staaf, Elina; Deperas-Kaminska, Marta; Brehwens, Karl; Haghdoost, Siamak; Czub, Joanna; Wojcik, Andrzej

2013-08-30

386

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.

387

Identification of twinned gas phase clusters by single-shot scattering with intense soft x-ray pulses  

NASA Astrophysics Data System (ADS)

Scattering experiments on xenon nanoclusters with high-intensity soft x-ray laser pulses from the Free-Electron LASer in Hamburg (FLASH) are performed to investigate different cluster morphologies in the gas phase. Three different types of scattering patterns can be identified. The most frequent pattern of concentric rings reflects the event of a single spherical cluster in focus. Fine interference rings similar to Newton rings appear when two clusters are illuminated at ?m distance, revealing three-dimensional information about the location of the clusters. Between 10 and 30% of all hits show a previously unknown twin cluster configuration with two clusters in direct contact. Simulations of scattering patterns for twin clusters with different sizes of the two particles, degree of fusion and orientation in space allow us to explain all the observed patterns.

Rupp, D.; Adolph, M.; Gorkhover, T.; Schorb, S.; Wolter, D.; Hartmann, R.; Kimmel, N.; Reich, C.; Feigl, T.; de Castro, A. R. B.; Treusch, R.; Strüder, L.; Möller, T.; Bostedt, C.

2012-05-01

388

Fluorescence detection of white-beam X-ray absorption anisotropy: towards element-sensitive projections of local atomic structure  

PubMed Central

Projections of the atomic structure around Nb atoms in a LiNbO3 single crystal were obtained from a white-beam X-ray absorption anisotropy (XAA) pattern detected using Nb K fluorescence. This kind of anisotropy results from the interference of X-rays inside a sample and, owing to the short coherence length of a white beam, is visible only at small angles around interatomic directions. Consequently, the main features of the recorded XAA corresponded to distorted real-space projections of dense-packed atomic planes and atomic rows. A quantitative analysis of XAA was carried out using a wavelet transform and allowed well resolved projections of Nb atoms to be obtained up to distances of 10?Å. The signal of nearest O atoms was detected indirectly by a comparison with model calculations. The measurement of white-beam XAA using characteristic radiation indicates the possibility of obtaining element-sensitive projections of the local atomic structure in more complex samples. PMID:21997909

Korecki, P.; Tolkiehn, M.; Dabrowski, K. M.; Novikov, D. V.

2011-01-01

389

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

NASA Astrophysics Data System (ADS)

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

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

2010-09-01

390

A new X-ray fluorescence spectroscopy for extraterrestrial materials using a muon beam.  

PubMed

The recent development of the intense pulsed muon source at J-PARC MUSE, Japan Proton Accelerator Research Complex/MUon Science Establishment (10(6)?s(-1) for a momentum of 60?MeV/c), enabled us to pioneer a new frontier in analytical sciences. Here, we report a non-destructive elemental analysis using µ(-) capture. Controlling muon momentum from 32.5 to 57.5?MeV/c, we successfully demonstrate a depth-profile analysis of light elements (B, C, N, and O) from several mm-thick layered materials and non-destructive bulk analyses of meteorites containing organic materials. Muon beam analysis, enabling a bulk analysis of light to heavy elements without severe radioactivation, is a unique analytical method complementary to other non-destructive analyses. Furthermore, this technology can be used as a powerful tool to identify the content and distribution of organic components in future asteroidal return samples. PMID:24861282

Terada, K; Ninomiya, K; Osawa, T; Tachibana, S; Miyake, Y; Kubo, M K; Kawamura, N; Higemoto, W; Tsuchiyama, A; Ebihara, M; Uesugi, M

2014-01-01

391

A new X-ray fluorescence spectroscopy for extraterrestrial materials using a muon beam  

NASA Astrophysics Data System (ADS)

The recent development of the intense pulsed muon source at J-PARC MUSE, Japan Proton Accelerator Research Complex/MUon Science Establishment (106 s-1 for a momentum of 60 MeV/c), enabled us to pioneer a new frontier in analytical sciences. Here, we report a non-destructive elemental analysis using µ- capture. Controlling muon momentum from 32.5 to 57.5 MeV/c, we successfully demonstrate a depth-profile analysis of light elements (B, C, N, and O) from several mm-thick layered materials and non-destructive bulk analyses of meteorites containing organic materials. Muon beam analysis, enabling a bulk analysis of light to heavy elements without severe radioactivation, is a unique analytical method complementary to other non-destructive analyses. Furthermore, this technology can be used as a powerful tool to identify the content and distribution of organic components in future asteroidal return samples.

Terada, K.; Ninomiya, K.; Osawa, T.; Tachibana, S.; Miyake, Y.; Kubo, M. K.; Kawamura, N.; Higemoto, W.; Tsuchiyama, A.; Ebihara, M.; Uesugi, M.

2014-05-01

392

Neutral particle beam intensity controller  

DOEpatents

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

Dagenhart, William K. (Oak Ridge, TN)

1986-01-01

393

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

394

X-ray production by 500 MeV electron beam in a periodically structured monocrystalline target of GaAs  

NASA Astrophysics Data System (ADS)

The experiment at the Tomsk synchrotron on generation of 27 keV X-rays by 500 MeV electrons in a new type of a periodical crystalline target is presented. The target has been made on the surface of a GaAs crystal plate by means of microlithography. The etched microstructure is a system of about 300 strips, 14 ?m thick, 100 ?m high and the gaps between the strips are 29 ?m. The measured spectra and orientational dependences of the X-rays emitted at a Bragg angle are discussed. The generated radiation consists of parametric X-ray radiation (PXR) and diffracted X-ray transition radiation (DTR). It is shown that the intensity of the DTR component of generated X-rays is much higher than that of the PXR.

Kaplin, V. V.; Kuznetsov, S. I.; Timchenko, N. A.; Uglov, S. R.; Zabaev, V. N.

2001-01-01

395

Diamond X-ray Photodiode for White and Monochromatic SR beams  

PubMed Central

High purity, single crystal CVD diamond plates are screened for quality and instrumented into a sensor assembly for quantitative characterization of flux and position sensitivity. Initial investigations have yielded encouraging results and have led to further development. Several limiting complications are observed and discussed, as well as mitigations thereof. For example, diamond quality requirements for x-ray diodes include low nitrogen impurity and crystallographic defectivity. Thin electrode windows and electronic readout performance are ultimately also critical to device performance. Promising features observed so far from prototype devices include calculable responsivity, flux linearity, position sensitivity and timing performance. Recent results from testing in high flux and high speed applications are described. PMID:21822344

Keister, Jeffrey W.; Smedley, John; Muller, Erik M.; Bohon, Jen; Heroux, Annie

2011-01-01

396

STUDY AND DETERMINATION OF PURE ELEMENT INTENSITIES FOR ENERGY-DISPERSIVE X-RAY FLUORESCENCE ANALYSIS  

Microsoft Academic Search

Among the methods for determining pure element intensities, here we have used pure bulk samples, oxide samples, and low concentration samples. Commercial pure thick metal foils have been used with Fe, Co, Ni, Cu, Zn, Ge, Y, Zr, Nb, and Mo. For those elements for which pure metal foils are not available, such as Mn, Ga, As, Se, and Sr,

Hua Younan

2001-01-01

397

Soft X-Ray Beam line for Industry Application in Saga  

SciTech Connect

The varied line spacing plane grating monochromator (VLS-PGM) has been constructed for an industry application beamline using soft x-rays from the 1.4 GeV storage ring in Saga, which is the first synchrotron in Kyushu Island. The design aim of the VLS-PGM is to cover the wide-energy range from 40-1,000 eV and also to have medium resolving power, high throughput, better reproducibility and suppression of higher-order light. In order to cover the wide energy range with suppressing higher-order light, a set of three focusing mirrors and one grating is installed. The resolving power expected from the ray-tracing calculation using SHADOW is more than 5,000 with 10 micron slits. The conventional photoelectron spectrometer is installed with an ion gun, a flood gun and a twin-anode x-ray source. The instrument for XAFS measurement is also attached to the main chamber.

Kamada, M.; Azuma, J.; Takahashi, K.; Kondo, Y. [Synchrotron Light Application Center, Saga University, Saga 840-8502 (Japan); Miyata, H.; Tsuji, J.; Hashimoto, H. [Toray Research Center Inc., Shiga 520-8567 (Japan); Yamashige, H. [Synchrotron Light Application Center, Saga University, Saga 840-8502 (Japan); Faculty of Science, Fukuoka University, Fukuoka 814-0180 (Japan); Kurisaki, S.; Wakita, H. [Faculty of Science, Fukuoka University, Fukuoka 814-0180 (Japan); Furuya, K.; Harata, A.; Tochihara, H. [Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Fukuoka 816-8580 (Japan); Matsuo, S.; Watanabe, T.; Inaba, M. [Faculty of Science, Fukuoka University, Fukuoka 814-0180 (Japan); Kobelco Research Inc., Hyogo 651-0073 (Japan); Okajima, T.; Setoyama, H.; Yoshimura, D. [Saga Light Source, Saga 841-0005 (Japan); Fujimoto, H. [Faculty of Science, Kumamoto University, Kumamoto 860-8555 (Japan)

2007-01-19

398

Cone beam x-ray luminescence computed tomography reconstruction with a priori anatomical information  

NASA Astrophysics Data System (ADS)

X-ray luminescence computed tomography (XLCT) is a novel molecular imaging modality that reconstructs the optical distribution of x-ray-excited phosphor particles with prior informational of anatomical CT image. The prior information improves the accuracy of image reconstruction. The system can also present anatomical CT image. The optical system based on a high sensitive charge coupled device (CCD) is perpendicular with a CT system. In the XLCT system, the xray was adopted to excite the phosphor of the sample and CCD camera was utilized to acquire luminescence emitted from the sample in 360 degrees projection free-space. In this study, the fluorescence diffuse optical tomography (FDOT)-like algorithm was used for image reconstruction, the structural prior information was incorporated in the reconstruction by adding a penalty term to the minimization function. The phosphor used in this study is Gd2O2S:Tb. For the simulation and experiments, the data was collected from 16 projections. The cylinder phantom was 40 mm in diameter and contains 8 mm diameter inclusion; the phosphor in the in vivo study was 5 mm in diameter at a depth of 3 mm. Both the errors were no more than 5%. Based on the results from these simulation and experimental studies, the novel XLCT method has demonstrated the feasibility for in vivo animal model studies.

Lo, Pei-An; Lin, Meng-Lung; Jin, Shih-Chun; Chen, Jyh-Cheng; Lin, Syue-Liang; Chang, C. Allen; Chiang, Huihua Kenny

2014-09-01

399

Quasimonochromatic x-ray backlighting on the COrnell Beam Research Accelerator (COBRA) pulsed power generatora)  

NASA Astrophysics Data System (ADS)

Monochromatic x-ray backlighting has been employed with great success for imaging of plasmas with strong self-emission such as x-pinches and wire array z-pinches. However, implementation of a monochromatic backlighting system typically requires extremely high quality spherically bent crystals which are difficult to manufacture and can be prohibitively expensive. Furthermore, the crystal must have a direct line of sight to the object, which typically emits copious amounts of radiation and debris. We present a quasimonochromatic x-ray backlighting system which employs an elliptically bent mica crystal as the dispersive element. In this scheme a narrow band of continuum radiation is selected for imaging, instead of line radiation in the case of monochromatic imaging. The flat piece of mica is bent using a simple four-point bending apparatus that allows the curvature of the crystal to be adjusted in situ for imaging in the desired wavelength band. This system has the advantage that it is very cost effective, has a large aperture, and is extremely flexible. The principles of operation of the system are discussed and its performance is analyzed.

Knapp, P. F.; Greenly, J. B.; Gourdain, P. A.; Hoyt, C. L.; Pikuz, S. A.; Shelkovenko, T. A.; Hammer, D. A.

2010-10-01

400

Quasimonochromatic x-ray backlighting on the COrnell Beam Research Accelerator (COBRA) pulsed power generator  

SciTech Connect

Monochromatic x-ray backlighting has been employed with great success for imaging of plasmas with strong self-emission such as x-pinches and wire array z-pinches. However, implementation of a monochromatic backlighting system typically requires extremely high quality spherically bent crystals which are difficult to manufacture and can be prohibitively expensive. Furthermore, the crystal must have a direct line of sight to the object, which typically emits copious amounts of radiation and debris. We present a quasimonochromatic x-ray backlighting system which employs an elliptically bent mica crystal as the dispersive element. In this scheme a narrow band of continuum radiation is selected for imaging, instead of line radiation in the case of monochromatic imaging. The flat piece of mica is bent using a simple four-point bending apparatus that allows the curvature of the crystal to be adjusted in situ for imaging in the desired wavelength band. This system has the advantage that it is very cost effective, has a large aperture, and is extremely flexible. The principles of operation of the system are discussed and its performance is analyzed.

Knapp, P. F.; Greenly, J. B.; Gourdain, P. A.; Hoyt, C. L.; Pikuz, S. A.; Shelkovenko, T. A.; Hammer, D. A. [Laboratory of Plasma Studies, Cornell University, 439 Rhodes Hall, Ithaca, New York 14853 (United States)

2010-10-15

401

Determining X-Ray Source Intensity and Confidence Bounds in Crowded Fields  

NASA Astrophysics Data System (ADS)

We present a rigorous description of the general problem of aperture photometry in high-energy astrophysics photon-count images, in which the statistical noise model is Poisson, not Gaussian. We compute the full posterior probability density function for the expected source intensity for various cases of interest, including the important cases in which both source and background apertures contain contributions from the source, and when multiple source apertures partially overlap. A Bayesian approach offers the advantages of allowing one to (1) include explicit prior information on source intensities, (2) propagate posterior distributions as priors for future observations, and (3) use Poisson likelihoods, making the treatment valid in the low-counts regime. Elements of this approach have been implemented in the Chandra Source Catalog.

Primini, F. A.; Kashyap, V. L.

2014-11-01

402

Determining X-Ray Source Intensity and Confidence Bounds in Crowded Fields  

E-print Network

We present a rigorous description of the general problem of aperture photometry in high energy astrophysics photon-count images, in which the statistical noise model is Poisson, not Gaussian. We compute the full posterior probability density function for the expected source intensity for various cases of interest, including the important cases in which both source and background apertures contain contributions from the source, and when multiple source apertures partially overlap. A Bayesian approach offers the advantages that it allows one to (a) include explicit prior information on source intensities, (b) propagate posterior distributions as priors for future observations, and (c) use Poisson likelihoods, making the treatment valid in the low counts regime. Elements of this approach have been implemented in the Chandra Source Catalog.

Primini, F A

2014-01-01

403

Increasing X-ray Intensity of XTE J1752-223  

NASA Astrophysics Data System (ADS)

Observations of XTE J1752-223 (ATEL #2258) with the RXTE All-Sky Monitor show increasing intensity, with one-day averages (2-12 keV) of 57(11) mCrab on MJD 55128, 86(12) on 55129, and 145(23) on 55130 (partial day). The spectrum appear softer in the most recent measurements, suggesting a transition to the thermal state (see ATEL #2261) if the source is a black hole binary system.

Remillard, R. A.; ASM Team at MIT

2009-10-01

404

A synthetic diamond probe for both low-energy mammography X-rays and high-energy electron therapy beams  

NASA Astrophysics Data System (ADS)

Although diamond has been studied for dosimetry principally due to its near-tissue equivalence, its use in both low-energy X-rays and high-energy electron beams has not been reported. This report is based on dosimetric studies of a synthetic diamond probe when subjected to diagnostic mammography X-ray photons and megavoltage electron therapy beams. The probe, constructed using entirely tissue-equivalent Perspex body, was configured for radiation dose measurement in either 'edge-on' or 'flat-on' exposure geometry without having first to re-orient the diamond within the body of the detector, and it was designed to be compatible with commercial electrometer systems. The radiation response of the diamond tested showed negligible energy dependence; its minimal background signal, high sensitivity (547.52 nC Gy -1 mm -3) and suitability for measurements in small radiation fields of steep dose gradients due to its small size make it suitable for clinical dosimetry. The presented probe has the potential advantage of replacing conventional radiation dosimeters.

Ade, N.; Nam, T. L.; Assiamah, M.

2012-03-01

405

Reduction in the intensity of solar X-ray emission in the 2- to 15-keV photon energy range and heating of the solar corona  

SciTech Connect

The time profiles of the energy spectra of low-intensity flares and the structure of the thermal background of the soft X-ray component of solar corona emission over the period of January-February, 2003, are investigated using the data of the RHESSI project. A reduction in the intensity of X-ray emission of the solar flares and the corona thermal background in the 2- to 15-keV photon energy range is revealed. The RHESSI data are compared with the data from the Interball-Geotail project. A new mechanism of solar corona heating is proposed on the basis of the results obtained.

Mirzoeva, I. K., E-mail: colombo2006@mail.ru [Russian Academy of Sciences, Space Research Institute (Russian Federation)

2013-04-15

406

Studies of defect generation in CdZnTe and InP single crystals using synchrotron white beam x-ray topography  

Microsoft Academic Search

Synchrotron White Beam X-ray Topography (SWBXT), along with Lang topography, chemical etching analysis, TEM and Nomarski optical microscopy have been used for the characterization of defect structures in large CdZnTe and InP single crystals and for the determination of the nature of growth striations and the contrast formation mechanism in the images of growth striations in X-ray topography. In the

Hua Chung

1997-01-01

407

A constrained, total-variation minimization algorithm for low-intensity x-ray CT  

SciTech Connect

Purpose: The authors developed an iterative image-reconstruction algorithm for application to low-intensity computed tomography projection data, which is based on constrained, total-variation (TV) minimization. The algorithm design focuses on recovering structure on length scales comparable to a detector bin width. Methods: Recovering the resolution on the scale of a detector bin requires that pixel size be much smaller than the bin width. The resulting image array contains many more pixels than data, and this undersampling is overcome with a combination of Fourier upsampling of each projection and the use of constrained, TV minimization, as suggested by compressive sensing. The presented pseudocode for solving constrained, TV minimization is designed to yield an accurate solution to this optimization problem within 100 iterations. Results: The proposed image-reconstruction algorithm is applied to a low-intensity scan of a rabbit with a thin wire to test the resolution. The proposed algorithm is compared to filtered backprojection (FBP). Conclusions: The algorithm may have some advantage over FBP in that the resulting noise level is lowered at equivalent contrast levels of the wire.

Sidky, Emil Y.; Duchin, Yuval; Pan, Xiaochuan; Ullberg, Christer [Department of Radiology, University of Chicago, 5841 S. Maryland Avenue, Chicago, Illinois 60637 (United States); XCounter AB, Svaerdvaegen 11, SE-182 33 Danderyd (Sweden)

2011-05-15

408