Synchrotron Polychromatic X-ray Research Articles

A theoretical study to focus a polychromatic synchrotron X-ray beam for microbeam radiation therapy

Microbeam radiotherapy (MRT) appears to target tumour cells while sparing normal healthy cells. However, it is in its preclinical stage at present. Clinical trials of MRT can be done in the Imaging and Medical Beamline (IMBL) of the Australian Synchrotron provided that the dose rate deliverable by the X-ray beam in Hutch 3B of the IMBL, where the required patient positioning equipment is located, is sufficiently high for MRT. At present the deliverable dose rate there is only 75Gys−1. However, a deliverable dose rate of between and including 375Gys−1 and 750Gys−1 is required for doing MRT clinical trials in Hutch 3B due to the irradiation profile inherent to MRT. The height of the focused beam in Hutch 3B must also be between and including 1.0 mm and 10 mm. A kinoform compound refractive lens (kinoform CRL) made of [3.5×1018Patomscm−3]-doped Si is proposed to be used in the Scenario where the X-ray beam, produced by a superconducting multipole wiggler source (SCMPW) operating at a maximum magnetic field of 4.000 T, is filtered by 0.6 mm of diamond before reaching the kinoform CRL. This is the Diamond-Optic Scenario. In this Scenario, the dose rate deliverable in Hutch 3B using the optic ranges from 380Gys−1 to 1300Gys−1 with beam heights ranging from 3.55 mm down to 1.0 mm, respectively. Also, the weighted average photon energies of the beam in Hutch 3B in this Scenario are almost entirely suitable for MRT in the IMBL. The X-ray beam in this Scenario can heat the P-doped Si optic to a few hundred degrees Kelvin above the hypothesised melting point of the P-doped Si due to its high power density. Therefore, the optic must be cooled lest it melt. The Diamond-Optic Scenario is not used routinely in the IMBL due to its excessive power. A variation of the Diamond-Optic Scenario, namely that the kinoform CRL be placed before sensitive components instead of after them is proposed for the routine use of this Scenario.

Synchrotron X-ray Laue diffraction study of hydrogen-induced blisters on iron grain boundaries

The effects of grain boundaries (GBs) on the initiation of hydrogen-induced blisters in pure iron were investigated using synchrotron polychromatic X-ray Laue nano-diffraction. It was found that the random GBs were more susceptible to blistering than the coincidence site lattice grain boundaries. High strain levels and severe plastic deformation were observed around the random GBs after hydrogen charging, but not on the coincidence site lattice grain boundaries.

In situ analysis of deformation twins within a magnesium polycrystal: (II) twin growth

The process of twin growth is difficult to be captured instantaneously. Synchrotron polychromatic X-ray microdiffraction (micro-XRD) is applied to in situ study twin growth in extruded Mg-3Al-1Zn polycrystal subjected to uniaxial tension. The micro-XRD data is used to map an area of 396 × 200 μm2 under the loading levels from 12 MPa to 73 MPa. The orientations of seven parents and ten resultant twins are determined by indexing Laue patterns, while their morphologies are mapped by the integrated intensities of particular reflections. {101¯2} twins are detected at 64 MPa. The maximum SF criterion for twin variant selection is invalid here. Twin growth rates are deduced from the variation of integrated intensities between 64 MPa and 68 MPa. It is found that twin growth rates in the HCP material are not proportional to active twin's SF values, though the SF value is related to the magnitude of driving resource. Twin growth rate exhibits obvious anisotropy, either for lengthwise growth rate or thickness growth rate. When two twins within a parent belong to the same twin variant, they exhibit similar growth rates. Meanwhile, when two twins within a parent come across, one can block the other and the latter occur shrinking.

In-situ analysis of grain rotation and lattice strain within a magnesium polycrystal based on synchrotron polychromatic X-ray diffraction technique: (I) prior to twin

Hexagonal-close-packed structure aggregates exhibit complicated deformation behaviors, involving different slips and twinning. Synchrotron polychromatic X-ray microdiffraction (micro-XRD) was utilized to study in situ an extruded Mg-3Al-1Zn strip subjected to uniaxial tension. The evolution of grain rotation and lattice strain was analyzed under the load levels from 12 to 73 MPa. The micro-XRD data was used to map an area of 396 × 200 μm within the region of interest. The experimental set-up and X-ray diffraction microscopy in two dimensions allow the morphology, orientation and strain of the target grain to be determined at the submicron size. Results depict local orientation fluctuation, lattice strain evolution, slips system and elastic modulus within the same grain. As the applied load increases, the grain's rotation is accelerated between 46 MPa and 51 MPa at which level of load the grain-scale plastic deformation is activated. The predominantly slip modes prior to twin are identified as the combination of b1→ = (0002) [112¯0] andb3→ = (0002) [2¯110]. During the inspection, all reflection planes displayed an onset of micro yielding at the macro load level of ∼38 MPa. In this work, we confirm that magnesium is nearly elastic isotropic.

Estimating the absolute flux distribution for a synchrotron X-ray beam using ionization-chamber measurements with various filters.

It is shown that an extensive set of accurate ionization-chamber measurements with a primary polychromatic synchrotron X-ray beam transmitted through various filter combinations/thicknesses can be used to quite effectively estimate the absolute flux distribution. The basic technique is simple but the `inversion' of the raw data to extract the flux distribution is a fundamentally ill-posed problem. It is demonstrated, using data collected at the Imaging and Medical Beamline (IMBL) of the Australian Synchrotron, that the absolute flux can be quickly and reliably estimated if a suitable choice of filters is made. Results are presented as a function of the magnetic field (from 1.40 to 4.00 T) of the superconducting multi-pole wiggler insertion device installed at IMBL. A non-linear least-squares refinement of the data is used to estimate the incident flux distribution and then comparison is made with calculations from the programs SPECTRA, XOP and spec.exe. The technique described is important not only in estimating flux itself but also for a variety of other, derived, X-ray properties such as beam quality, power density and absorbed-dose rate. The applicability of the technique with a monochromatic X-ray beam for which there is significant harmonic contamination is also demonstrated. Whilst absolute results can also be derived in this monochromatic beam case, relative (integrated) flux values are sufficient for our primary aim of establishing reliable determinations of the percentages of the various harmonic components.

In situ synchrotron study of electromigration induced grain rotations in Sn solder joints

Here we report an in situ study of the early stage of microstructure evolution induced by electromigration in a Pb-free β-Sn based solder joint by synchrotron polychromatic X-ray microdiffraction. With this technique, crystal orientation evolution is monitored at intragranular levels with high spatial and angular resolution. During the entire experiment, no crystal growth is detected, and rigid grain rotation is observed only in the two grains within the current crowding region, where high density and divergence of electric current occur. Theoretical calculation indicates that the trend of electrical resistance drop still holds under the present conditions in the grain with high electrical resistivity, while the other grain with low resistivity reorients to align its a-axis more parallel with the ones of its neighboring grains. A detailed study of dislocation densities and subgrain boundaries suggests that grain rotation in β-Sn, unlike grain rotation in high melting temperature metals which undergo displacive deformation, is accomplished via diffusional process mainly, due to the high homologous temperature.

In situ analysis of multi-twin morphology and growth using synchrotron polychromatic X-ray microdiffraction

Synchrotron polychromatic X-ray microdiffraction (micro-XRD) was applied to study in situ deformation twinning of commercially AZ31 (Mg–3Al–1Zn) strip subjected to uniaxial tension. The morphology and growth of twins were analyzed in situ under the load level from 64 to 73 MPa. The X-ray microdiffraction data, collected on beamline 12.3.2 at the Advanced Light Source, were then used to map an area of 396 μm − 200 μm within the region of interest. The experimental set-up and X-ray diffraction microscopy with a depth resolution allow the position and orientation of each illuminated grain to be determined at the submicron size. A list of parent grains sorted by crystallographic orientation were selected to examine their twinning behavior. The results depict twin variant selection, local misorientation fluctuation and mosaic spread for multi-twins within the same parent grain. As load increases, the amplitude of misorientation fluctuation along twin trace keeps increasing. This is attributable to the accumulation of geometrically necessary dislocations.

Ultra-fast in-situ X-ray studies of evolving columnar dendrites in solidifying steel weld pools

High-brilliance polychromatic synchrotron radiation has been used to conduct in-situ studies of the solidification microstructure evolution during simulated welding. The welding simulations were realized by rapidly fusing ∼ 5 mm spot in Fe-Cr-Ni steel. During the solid- liquid-solid phase transformations, a section of the weld pool was placed in an incident 50-150 keV polychromatic synchrotron X-ray beam, in a near-horizontal position at a very low inclination angle. Multiple high-resolution 2D detectors with very high frame rates were utilized to capture time resolved X-ray diffraction data from suitably oriented solid dendrites evolving in the weld pool. Comprehensive analysis of the diffraction data revealed individual and overall dendritic growth characteristics and relevant melt and solid flow dynamics during weld pool solidification, which was completed within 1.5 s. Columnar dendrite tip velocities were estimated from the experimental data and during early stages of solidification were exceeded 4 mm/s. The most remarkable observation revealed through the time-resolved reciprocal space observations are correlated to significant tilting of columnar type dendrites at their root during solidification, presumably caused by convective currents in the weld pool. When the columnar dendrite tilting are transformed to respective metric linear tilting velocities at the dendrite tip; tilting velocities are found to be in the same order of magnitude as the columnar tip growth velocities, suggesting a highly transient nature of growth conditions.

Effect of surface microstructure on electrochemical performance of garnet solid electrolytes.

Cubic garnet phases based on Al-substituted Li7La3Zr2O12 (LLZO) have high ionic conductivities and exhibit good stability versus metallic lithium, making them of particular interest for use in next-generation rechargeable battery systems. However, high interfacial impedances have precluded their successful utilization in such devices until the present. Careful engineering of the surface microstructure, especially the grain boundaries, is critical to achieving low interfacial resistances and enabling long-term stable cycling with lithium metal. This study presents the fabrication of LLZO heterostructured solid electrolytes, which allowed direct correlation of surface microstructure with the electrochemical characteristics of the interface. Grain orientations and grain boundary distributions of samples with differing microstructures were mapped using high-resolution synchrotron polychromatic X-ray Laue microdiffraction. The electrochemical characteristics are strongly dependent upon surface microstructure, with small grained samples exhibiting much lower interfacial resistances and better cycling behavior than those with larger grain sizes. Low area specific resistances of 37 Ω cm(2) were achieved; low enough to ensure stable cycling with minimal polarization losses, thus removing a significant obstacle toward practical implementation of solid electrolytes in high energy density batteries.

Inhomogeneous deformation behavior in intercrystalline regions in polycrystalline Ni

We report on three-dimensional spatially resolved X-ray microdiffraction measurements of inhomogeneous deformation within individual polycrystalline grains. These measurements provide new insights into the role of grain boundaries. Particularly striking is the qualitatively different mechanical behavior of subgrain volumes near grain boundaries and triple junctions compared to bulk-grain mechanical behavior. These differences are studied by characterizing the evolution of the local orientation distribution in a polycrystalline Ni sample using polychromatic synchrotron X-ray microdiffraction. Dependence of deformation on grain boundary types and triple junctions is determined. Quantitative distinctions in deformation behavior between low-angle boundaries, special low-energy high-angle boundaries, general high-angle boundaries and triple junctions are characterized in terms of spatially resolved misorientation development and extensions of grain boundary effects. In general, larger lattice misorientations are observed near boundaries with higher grain boundary energy. Special high-coincidence grain boundaries exhibit smaller deformation misorientations than general high-angle grain boundaries. These observations are consistent with the observed increases in ductility in grain boundary engineered materials.

Residual stresses in Linear Friction Welding of aluminium alloys

In the present study, the residual stresses distribution in the Linear Friction Welded (LFW) pieces were studied using Finite Element (FE) simulation and high energy synchrotron X-ray diffraction. Fully-coupled implicit thermo-mechanical analysis simulation procedure was employed, with semi-automatic re-meshing using Python scripting to accommodate large deformation and output contour tracking methods for extracting deformed configurations. Model validated by the multi-detector polychromatic synchrotron X-ray experimental data were used to study the distribution of residual stresses distribution in the Linear Friction Welded (LFW) pieces to provide a general function to describe the residual stresses distribution. A characteristic length scale was found in the plot.

Assessment of Plastic Deformation Induced by Indentation on a Large Grain on Inconel 600 Using Synchrotron Polychromatic X-ray Microdiffraction

A synchrotron-based three-dimensional (3-D) Laue technique called Differential Aperture X-ray microscopy (DAXM) was used to investigate plastic deformation of Inconel 600 induced by indentation. The DAXM technique is capable of probing up to 60 to 100 μm into the Ni alloy, with micron resolution. A conical indenter was used to generate an indent on a large surface grain on Inconel 600. The DAXM Laue images from the uppermost grain exhibited pronounced streaking and splitting of Laue spots, which increased as the grain boundary was approached. Splitting of the Laue patterns correlates with subgrain or dislocation cell formation. A significant amount of dislocation cell formation was found within the 1-μm voxels probed by DAXM. A change in total angle of 8.79 deg was determined for the uppermost grain from the diffraction data from depths 4 to 28 μm, with an average misorientation angle of 2.15 deg between the dislocation cells. The next grain having a different crystallographic orientation continued to rotate in the same direction as the uppermost grain due to the large plastic deformation.

Deformation twinning and residual stress in calcite studied with synchrotron polychromatic X-ray microdiffraction

Microstructures of deformed calcite in marble from the Bergell Alps are studied by using a microfocused polychromatic synchrotron X-ray beam. The high spatial resolution, together with orientation and strain resolutions, reveals twin plane orientation, multiple twin lamellae, and strain distributions associated with the twins. Single and multiple mechanical twins on $$ e = \left\{ {01\overline{1} 8} \right\} $$ systems are confirmed. Residual stresses are derived from the strain tensor that is derived from Laue diffraction patterns. Average lattice strains from several hundred to over one thousand microstrains are detected in a deformed marble from the Bergell Alps. Such strains suggest 60–120 MPa residual stresses. A detailed study of strain components shows that shear stresses on twin planes are completely released.

A comparative EBSD and micro-XRD study of the intergranular grain structure in CP-Ti

Electron Backscatter Diffraction (EBSD) and scanning polychromatic X-ray micro-diffraction (micro-XRD) have been applied to study the intergranular grain structure in CP-Ti strip. Prior to synchrotron experimentation, a polycrystalline CP-Ti sample was electrochemically polished and a series of fiducial markers were placed on the surface to define a 500 μm×500 μm region of interest. Within this area EBSD was used to obtain an orientation map of the grains at the sample surface. Synchrotron polychromatic X-ray micro-diffraction data, collected on beamline 12.3.2 at the Advanced Light Source, was then used to map an area of 200×60 μm 2 within the region of interest. Comparison of the respective grain maps indicated an average grain size of ∼50 μm. Micro-XRD data was initially used to locate the same surface grains determined by EBSD. Based on comparison of the Euler angles, grain orientation maps from the two data sets were found to be in close agreement. The typical rolling texture found in CP-Ti was identified with the basal pole maxima tilted slightly toward the transverse direction. Subsequent 3D analysis of the Laue pattern intensity distribution of the surface grains revealed that some of the large grains identified by EBSD formed sub-cell structures below the sample surface.

Phase Contrast Microradiography of Mouse Lung Using Synchrotron X-ray: Correlation with Optical Microscopy

PurposeThe purpose of this study is to evaluate the feasibility of phase contrast X-ray microtomography and microradiography, using a polychromatic synchrotron X-ray, for analysis of the mouse lung microstructure.Materials and MethodsNormal mice were used for experiments. Some of the mouse lungs were prepared by the lung fixation-inflation method. The resulting sponge-like inflated lung samples were used for microtomography. The remaining mouse lungs were cut into 10 um sections and were used for microradiography and optical microscopic correlation. The experiments on mouse lung samples were performed at the 7B2 beamline of the Pohang Light Source in Korea.ResultsPhase contrast X-ray microtomography of inflated lung samples showed individual alveolar structure on 3-D reconstruction. Phase contrast microradiographs of thin lung samples showed microstructure of lung, such as alveoli and bronchioles, and were well correlated with optical microscopic images.ConclusionsThe results indicate that the phase contrast X-ray microtomography and microradiography using polychromatic synchrotron X-ray is feasible for evaluation of microstructure of the lung.

Plastic deformation in Al (Cu) interconnects stressed by electromigration and studied by synchrotron polychromatic x-ray microdiffraction

We report here an in-depth synchrotron radiation based white beam x-ray microdiffraction study of plasticity in individual grains of an Al (Cu) interconnect during the early stage of electromigration (EM). The study shows a rearrangement of the geometrically necessary dislocations (GNDs) in bamboo typed grains during that stage. We find that about 90% of the GNDs are oriented so that their line direction is the closest to the current flow direction. In nonbamboo typed grains, the Laue peak positions shift, indicating that the grains rotate. An analysis in terms of force directions has been carried out and is consistent with observed EM induced grain rotation and bending.

D-5 Analysis of Shear Stress Distribution in Al (Cu) Interconnects Induced by Electromigration Based on Schmidt's Law and Studied by Synchrotron Polychromatic X-ray Microdiffraction

D-5 Analysis of Shear Stress Distribution in Al (Cu) Interconnects Induced by Electromigration Based on Schmidt's Law and Studied by Synchrotron Polychromatic X-ray Microdiffraction - Volume 23 Issue 2

In-situ early stage electromigration study in Al line using synchrotron polychromatic X-ray microdiffraction

ABSTRACTElectromigration is a phenomenon that has attracted much attention in the semiconductor industry because of its deleterious effects on electronic devices (such as interconnects) as they become smaller and current density passing through them increases. However, the effect of the electric current on the microstructure of interconnect lines during the very early stage of electromigration is not well documented. In the present report, we used synchrotron radiation based polychromatic X-ray microdiffraction for the in-situ study of the electromigration induced plasticity effects on individual grains of an Al (Cu) interconnect test structure. Dislocation slips which are activated by the electric current stressing are analyzed by the shape change of the diffraction peaks. The study shows polygonization of the grains due to the rearrangement of geometrically necessary dislocations (GND) in the direction of the current. Consequences of these findings are discussed.

Local epitaxy of YBa2Cu3Ox on polycrystalline Ni measured by x-ray microdiffraction

Polychromatic synchrotron x-ray microdiffraction is used to determine the epitaxy of YBa2Cu3Ox (YBCO) films grown on polycrystalline Y.15Zr.85O1.925/CeO2/Y2O3/Ni95W5(Ni) rolling-assisted, biaxially textured substrates (RABiTS). A novel analysis technique is introduced in which the orientation of mosaic films is measured by using a Hough transform to recognize arcs in Laue microdiffraction patterns that correspond to low-index zone axes. While the overall epitaxy is cube-on-cube, grain-by-grain analysis reveals a systematic misorientation of YBCO with respect to Ni: the YBCO [001] rotates toward the direction of the surface normal. The crystal mosaic (for rotation about the rolling direction) measured by a single diffraction pattern sampling a 0.5-μm2 surface area is 0.7° full width at half-maximum for YBCO grown on Ni grains with a low tilt; for more highly tilted grains, the YBCO patterns can no longer be measured, presumably due to the large mosaic. The YBCO mosaic over the entire area of a Ni grain is ∼2.5° and varies with grain size; the mosaic is smaller for larger grains.

X-ray microdiffraction study of growth modes and crystallographic tilts in oxide films on metal substrates.

The crystallographic texture of thin-film coatings plays an essential role in determining such diverse materials properties as wear resistance, recording density in magnetic media and electrical transport in superconductors. Typically, X-ray pole figures provide a macroscopically averaged description of texture, and electron backscattering provides spatially resolved surface measurements. In this study, we have used focused, polychromatic synchrotron X-ray microbeams to penetrate multilayer materials and simultaneously characterize the local structure, orientation and strain tensor of different heteroepitaxial layers with submicrometre resolution. Grain-by-grain microstructural studies of cerium oxide films grown on textured nickel foils reveal two distinct kinetic growth regimes on vicinal surfaces: ledge growth at elevated temperatures and island growth at lower temperatures. In addition, a combinatorial approach reveals that crystallographic tilting associated with these complex interfaces is qualitatively described by a simple geometrical model applicable to brittle films on ductile substrates. The sensitivity of conducting percolation paths to tilt-induced texture improvement is demonstrated.