High-energy X-ray Source Research Articles

Development and Applications of High-Energy X-ray Sources Coupled with High-Power Laser and Electron Accelerator

Development and Applications of High-Energy X-ray Sources Coupled with High-Power Laser and Electron Accelerator

X-ray calibration facility for plasma diagnostics of the MégaJoule laser

The Laser MegaJoule (LMJ) located at CEA-CESTA will be equipped with x-ray plasma diagnostics using different kinds of x-ray components such as filters, mirrors, crystals, detectors and cameras. To guarantee LMJ measurements, detectors such as x-ray cameras need to be regularly calibrated. An x-ray laboratory is devoted to this task and performs absolute x-ray calibrations for similar x-ray cameras running on Laser Integration Line (LIL). This paper presents the x-ray calibration bench with its x-ray tube based High Energy x-ray Source (HEXS) and some calibration results. By mean of an ingenious transposition system under vacuum absolute x-ray calibration of x-ray cameras, like streak and stripline ones, can be carried out. Coupled to a new collimation system with micrometric accuracy on aperture sensitivity quantum efficiency measurements can be achieved with reduced uncertainties.

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

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

Optimizing the operation of a high resolution vertical Johann spectrometer using a high energy fluorescer x-ray source

This paper describes the operation and testing for a vertical Johann spectrometer (VJS) operating in the 13 keV range. The spectrometer is designed to use thin curved mica crystals or thick germanium crystals. The VJS must have a resolution of E/ΔE=3000 or better to measure the Doppler broadening of highly ionized krypton and operate at a small x-ray angle in order to be used as a diagnostic in a laser plasma target chamber. The VJS was aligned, tested, and optimized using a fluorescer type high energy x-ray (HEX) source located at National Security Technologies (NSTec), LLC, in Livermore, CA. The HEX uses a 160 kV x-ray tube to excite fluorescence from various targets. Both rubidium and bismuth fluorescers were used for this effort. This presentation describes the NSTec HEX system and the methods used to optimize and characterize the VJS performance.

Investigation of the domain switching zone near a crack tip in pre-poled lead zirconate titanate ceramic via in situ X-ray diffraction

The domain orientation distributions around the loaded crack tip in a poled piezoelectric ceramic were measured in situ by using a high-energy synchrotron X-ray source. The results show the dynamic domain switching behavior around the switching zone. The relationship between the stress intensity factor and switching zone is revealed. During mechanical loading, the domain switching zone significantly enlarges with an increase in the stress intensity factor. Moreover, the mechanical depoling effect generated by the stress around the crack tip is detected.

The x-ray calibration facility of the laser integration line in the 0.9–10 keV range: The high energy x-ray source and some applications

The laser integration line (LIL) located at CEA-CESTA is equipped with x-ray plasma diagnostics using different kinds of x-ray components such as filters, mirrors, crystals, detectors, and cameras. The CEA-DAM of Arpajon is currently developing x-ray calibration methods and carrying out absolute calibration of LIL x-ray photodetectors. To guarantee LIL measurements, detectors such as x-ray cameras must be regularly calibrated close to the facility. A new x-ray facility is currently available to perform these absolute x-ray calibrations. This paper presents the x-ray tube based high energy x-ray source delivering x-ray energies ranging from 0.9 to 10 keV by means of an anode barrel. The purpose of this source is mainly to calibrate LIL x-ray cameras but it can also be used to measure x-ray filter transmission of plasma diagnostics. Different x-ray absolute calibrations such as x-ray streak and framing camera yields, x-ray charge-coupled device quantum efficiencies, and x-ray filter transmissions are presented in this paper. A x-ray flat photocathode detector sensitivity calibration recently performed for a CEA Z-pinch facility is also presented.

Advantages in the Small-Angle Scattering of X-Ray for Studying Optoelectronic Devices within the Frames of ISTC Projects

The project ISTC “SPECTROMETRIC POSITION SENSITIVE DETECTOR WITH BASE ENERGY SHIFT” is interesting for creation new area semiconductor detector device for EXAFS spectroscopy, for traditional X-ray diffractometry (XRD), as well as Small-Angle X-ray Scattering diffractometry (SASX). Diffractometry methods allow creating original features of position sensitive detector. Crystallography quality of silicon multi layer detector with original photo mask was examined by XRD and SAXS with ordinary scintillation detectors. Grazed incidence SAXS (GISAXS) provides information both about lateral and normal ordering of multilayers at a surface or inside a thin epitaxial film [1]. Using high-energy X-ray source (rotating anode or synchrotron radiation in future) and high adjustment monochromator SAXS rocking curves in transition and reflection mode had been received. It allows obtaining the information of 3D size lamellar or column-like domains. Results of an experimental investigation of the size layer structure are presented.

CHANDRA OBSERVATIONS OF WR 147 REVEAL A DOUBLE X-RAY SOURCE

We report the first results from deep X-ray observations of the Wolf-Rayet binary system WR147 with the Chandra HETG. Analysis of the zeroth order data reveals that WR147 is a double X-ray source. The northern counterpart is likely associated with the colliding wind region, while the southern component is certainly identified with the WN star in this massive binary. The latter is the source of high energy X-rays (including the Fe K_alpha complex at 6.67 keV) whose production mechanism is yet unclear. For the first time, X-rays are observed directly from a WR star in a binary system.

高能X射线源焦斑尺寸的时间分辨诊断

A time-resolved measurement system of spot size for X-ray sources was constructed by coupling a gated CCD camera with a fast scintillator crystal. The spot size of the high-energy pulsed X-ray source from the Dragon-Ⅰ linear induction accelerator was measured at 10 ns intervals, and a curve of spot size versus time was obtained. An LYSO crystal array with a pixel size of 0.78 mm was also designed and tested in X-ray field, and primary experimental results show the array can be used for time-resolved spot size diagnosis of the high energy X-ray source and significantly improve the spatial resolution of X-ray images.

Accelerators and x-rays in cultural heritage investigations

Abstract In the following article a review is given on the use of accelerators in studies connected to our cultural heritage. It focuses on making use of the production and detection of x-rays as a general tool. At “small accelerators”, the proton induced x-ray emission (PIXE), especially when combined with Rutherford backscattering spectroscopy (RBS), has been developed to a very versatile and powerful technique for near-surface investigations. It is well complemented by larger facilities, synchrotron radiation sources as well as medium energy ion accelerators for high energy PIXE. With the development of small compact electron accelerators, a new generation of mono-energetic high-energy high-intensity x-ray sources will add a very comfortable complement in cultural heritage studies. To cite this article: H.-E. Mahnke et al., C. R. Physique 10 (2009).

Phase contrast medical imaging with compact X-ray sources at the Munich-Centre for Advance Photonics (MAP)

In this paper, the excellence cluster “Munich-Centre for Advance Photonics” (MAP) is presented. One of the aims of the project is the development of innovative X-ray-based diagnostics imaging techniques to be implemented at an ultra-compact high-energy and high-brilliance X-ray source. The basis of the project and the developments towards the clinical application of phase contrast imaging applied to mammography and cartilage studies will be presented and discussed.

Interfacial Dipole Measurement of Dielectric/Silicon Interface by X-ray Photoelectron Spectroscopy

Interfacial dipole presented at the interface of dielectric/silicon has been measured with x-ray photoelectron spectroscopy. With a use of high energy x-ray source, the band bending profile of a silicon substrate and the surface potential can be determined. By comparing the potential profile for p+ and n+-Si wafer, a voltage shift can be calculated. Using this method, a large negative potential shift of 0.5 V at La-silicate/silicon interface has been observed. The obtained value of interfacial dipole is consistent with the value obtained from gate leakage current analysis.

Numerical evaluation of the effectiveness of colloidal gold as a contrast agent

Monte Carlo numerical simulations were conducted to evaluate the effectiveness of colloidal gold as a contrast agent. The simulations were conducted using a simple configuration, modeling a phantom to maintain the generality of the results, and the effects of the mass percentage of gold accumulated inside the tumor and the energy of the irradiating X-rays were evaluated, as well as other information, such as the energy spectrum of the photons reaching the detector and the change in the energy deposited inside the phantom. The contrast of the X-ray image due to the layer is calculated from the total energy of photons transmitted to the back surface of the phantom. The simulation revealed that colloidal gold with a mass percentage of 1.0% provided an image for which the contrast was almost 70% of that for bone of the same thickness when X-rays from conventional X-ray tubes were considered. Monochromatic X-rays of 44, 66, and 88 keV, which simulated the Compton scattering monochromatic X-ray source being developed, were also evaluated. X-rays at the first two energies did not have a significant advantage over the rays from the X-ray tubes. For colloidal gold with a mass percentage of 1.0%, the 88 keV monochromatic X-ray produced an image contrast that was about 10% higher than the contrast for bone of the same thickness, as suggested by the K-absorption energy of gold. However, the improvement was not large considering the difficulty involved in making such a high-energy monochromatic X-ray source available.

Development of battery-operated portable high-energy X-ray sources

We have developed a practical portable high-energy X-ray source, which can generate high energy X-rays with energies greater than 100 keV enabling the taking of high-definition X-ray transmission images using an R6(AA) battery as a power source. This result is a consequence of the integration of the compact and energy-saving electron accelerator technologies of AIST and the carbon nanostructure technologies of private companies. In this paper, we discuss these elemental technologies and how to integrate them.

High order reflectivity of highly oriented pyrolytic graphite crystals for x-ray energies up to 22 keV

We used Kr K alpha (12.6 keV), Zr K alpha (15.7 keV), and Ag K alpha (22.2 keV) x-rays, produced by petawatt-class laser pulses, to measure the integrated crystal reflectivity R(int) of flat highly oriented pyrolytic graphite (HOPG) up to the fifth order. The maximum R(int) was observed in first order (3.7 mrad at 12.6 keV), decreasing by a factor of 3-5 for every successive order, and dropping by a factor of 2-2.5 at 22.2 keV. The current study indicates that HOPG crystals are suitable for measuring scattering signals from high energy x-ray sources (E > or = 20 keV). These energies are required to penetrate through the high density plasma conditions encountered in inertial confinement fusion capsule implosions on the National Ignition Facility.

High energy electron generation by the 15 mJ ultrashort pulse laser

We propose a small size high energy X-ray source utilizing ultrashort pulse lasers, and a new scheme for generating quasi-monoenergetic electrons. In this paper, we developed a compact laser electron generator and performed experiment that generated energetic electrons over 1 MeV electrons with only 15 mJ laser energy. The temperatures of emitted electrons were measured to be 0.2 MeV and 0.25 MeV without and with prepulse, respectively.

Abstract 999: Gated Micro Computed Tomography Scanning: An Emerging Tool for Longitudinal Assessment of Murine Cardiac Remodeling.

Background: Recent advances in high energy X-ray source computed tomography (CT) technology have made it possible to accurately image murine cardiac structure and function. We describe the use of a gated Micro CT system to assess cardiac remodeling in a murine model of myocardial infarction (MI). Methods: Adult FVB mice (n = 10) were randomized to surgically induced MI by left coronary artery ligation or sham procedure. Dual gated cardiac and respiratory Micro CT scans were performed pre-operatively and at weeks 4, 8 and 12 post-procedure. End-diastolic and end-systolic images were acquired by gating on the ECG P-and S’-waves, respectively. Post-acquisition analysis was performed using image analysis software and the following parameters were quantified: left ventricular (LV) volume and mass, right ventricular volume and mass, right and left atrial volumes, and ventricular ejection fraction (EF). Results: Images were successfully acquired with a resolution of 100 microns allowing for identification and quantification of key cardiac structures (Fig 1A ). Following MI, animals exhibited left ventricular failure with significantly increased* end systolic and diastolic volumes by week 4. Ventricular dilation continued through week 8, plateauing by week 12. Left ventricular mass increased steadily over 12 weeks*, with a significantly decreased* LVEF of 28.0 ± .05% by week 12 (pre-MI: 66.7 ± .06%,*p < 0.01). Post-MI left ventricular change is detailed in Fig 1B . Conclusions: MicroCT scanning can be successfully used to characterize murine myocardial structure and function, making it a useful tool to assess cardiac phenotypes and models of cardiovascular disease.

In Situ X-Ray Measurements of Defect Generation during PVT Growth of SiC

A standard inductively heated PVT growth furnace modified for diffraction experiments with high energy x-rays in focussing Laue geometry was built. The growth furnace will be placed in front of a tungsten anode high energy x-ray source. The Laue diffraction pattern of the growing crystal can be detected on a CCD camera detector. Evolution of crystalline defects as a function of the growth process parameters will be infered from the diffraction experiments. The furnace design and results of first test measurements serving as proof of concept are reported.

Crack tip process zone domain switching in a soft lead zirconate titanate ceramic

Non-180° domain switching leads to fracture toughness enhancement in ferroelastic materials. Using a high-energy synchrotron X-ray source and a two-dimensional detector in transmission geometry, non-180° domain switching and crystallographic lattice strains were measured in situ around a crack tip in a soft tetragonal lead zirconate titanate ceramic. At K I = 0.71 MPa m 1/2 and below the initiation toughness, the process zone size, spatial distribution of preferred domain orientations, and lattice strains near the crack tip are a strong function of direction within the plane of the compact tension specimen. Deviatoric stresses and strains calculated using a finite element model and projected to the same directions measured in diffraction correlate with the measured spatial distributions and directional dependencies. Some preferred orientations remain in the crack wake after the crack has propagated; within the crack wake, the tetragonal 0 0 1 axis has a preferred orientation both perpendicular to the crack face and toward the crack front.

High energy X-ray CT study on the central void formations and the fuel pin deformations of FBR fuel assemblies

The central void formations and deformations of fuel pins were investigated in fuel assemblies irradiated to high burn-up, using a non-destructive X-ray CT (computer tomography) technique.In this X-ray CT, the effect of strong gamma ray activity could be reduced to a negligible degree by using the pulse of a high energy X-ray source and detecting the intensity of the transmitted X-rays in synchronization with the generated X-rays. Clear cross-sectional images of fuel assemblies irradiated to high burn-up in a fast breeder reactor were successively obtained, in which the wrapping wires, cladding, pellets and central voids could be distinctly seen. The diameter of a typical central void measured by X-ray CT agreed with the one obtained by ceramography within an error of 0.1mm. Based on this result, the dependence of the central void diameter on the linear heating rate was analyzed. In addition, the deformation behavior of a fuel pin along its axial direction could be analyzed from 20 stepwise X-ray cross-sectional images obtained in a small interval, and the results obtained showed a good agreement with the predictions calculated by two computer codes.