Dula Parkinson

X-ray micro-tomography at the Advanced Light Source

The X-ray micro-Tomography Facility at the Advanced Light Source has been in operation since 2004. The source is a superconducting bend magnet of critical energy 11.5 keV; photon energy coverage is 8-45 KeV in monochromatic mode, and a filtered white light option yields useful photons up to 50 keV. A user-friendly graphical user interface allows users to collect tomographic and radiographic data sets with options including tiled and time series data sets. We will focus on recent projects that utilize sample environments for in-situ imaging. These environments include a high pressure triaxial flow cell which has allowed study of supercritical CO2 transport through brine-saturated sandstone at pressures typical of in-situ conditions for subsurface CO2 sequestration and water transportation within live plants.

CAMERA: The Center for Advanced Mathematics for Energy Research Applications

Advanced experimental facilities worldwide are probing structure and chemistry, disorder, dynamics and electronic properties, through time, over length scales spanning macroscopic to atomic resolution, in multiple dimensions (e.g., hyperspectral tomography, nano-spectroscopy), under extreme environmental conditions and stimulated reactions. In order to do so, they are collecting more and more data at faster and faster rates. One critical challenge is to build algorithms that can analyze, interpret, and understand the information contained within this experimental data.

Compressive Phase Contrast Tomography

When x-rays penetrate soft matter, their phase changes more rapidly than their amplitude. Interference effects visible with high brightness sources creates higher contrast, edge enhanced images. When the object is piecewise smooth (made of big blocks of a few components), such higher contrast datasets have a sparse solution. We apply basis pursuit solvers to improve SNR, remove ring artifacts, reduce the number of views and radiation dose from phase contrast datasets collected at the Hard X-Ray Micro Tomography Beamline at the Advanced Light Source. We report a GPU code for the most computationally intensive task, the gridding and inverse gridding algorithm (non uniform sampled Fourier transform).

High resolution and fast throughput-time X-ray computed tomography for semiconductor packaging applications

The recent applications of 3D X-ray computed tomography (CT) in microelectronic packages, including nondestructive failure analysis, defect monitoring in solder joints and Cu vias, and progressive reliability study of solder voids, electron migration induced void nucleation in solder joints, and void evolution in Cu vias are reviewed. The high resolution and non-destructive 3D X-ray CT data has proven to be highly valuable in package assembly process development, quality control and reliability risk assessment; however, the field of view of current lab-scale 3D X-ray CT technology is limited to about 1-2mm2 localized area at micron level resolution, due to its low brightness and nonparallel X-ray beam resulting in long data acquisition time. Synchrotron X-ray sources, on the other hand, can provide large area collimated beams with high brightness, which allows imaging within 3-20 minutes an entire 3D package, including Si, underfill, multiple levels of solder joints, and dielectric layers, Cu vias as well as through holes in multiple substrates. The limitation of current 3D X-ray CT techniques as well as directions for next generation 3D X-ray CT techniques provided by the synchrotron X-ray study of 3D packages are discussed in this paper.

Information Technology/Large-Scale Data Handling

The experience of light source users has been transformed in recent years by large increases in flux and brightness, revolutionary new optics and detectors, and automation and advanced sample environments. Beamlines are producing data at rates and volumes that challenge the capabilities of even the most experienced user groups. Meanwhile, the community of synchrotron users continues to grow in size and diversity: researchers come from physics, material science, energy and battery research, geology, biology, chemistry, art history, and more. Almost every natural science domain is being advanced through the techniques employed at these facilities, but a significant fraction of these researchers are first-time or infrequent users of a particular beamline. The combination of an expanding base of new users and increased beamline capabilities is leading to an increase in the amount of “dark data” that is not analyzed fully (or, in some cases, at all).

Coded Aperture Imaging for Fluorescent X-rays

We employ a coded aperture pattern in front of a charge couple device (CCD) pixilated detector to image fluorescent xrays (6-25KeV) from samples irradiated with synchrotron radiation. Coded apertures encode the angular direction of xrays, and given a known source plane, allow for a large Numerical Aperture x-ray imaging system. The algorithm to develop the free standing coded aperture pattern of the Non-Two-Holes-Touching (NTHT) was developed. The algorithms to reconstruct the x-ray image from the encoded pattern recorded are developed by means of modeling and confirmed by experiments on standard samples. Spatial resolution and efficiency are determined for the next development stage whereby an energy resolving pixilated CCD will be deployed allowing for elemental imaging.

Synchrotron X-ray micro-tomography at the Advanced Light Source: Developments in high-temperature in-situ mechanical testing

At the Advanced Light Source (ALS), Beamline 8.3.2 performs hard X-ray micro-tomography under conditions of high temperature, pressure, mechanical loading, and other realistic conditions using environmental test cells. With scan times of 10s–100s of seconds, the microstructural evolution of materials can be directly observed over multiple time steps spanning prescribed changes in the sample environment. This capability enables in-situ quasi-static mechanical testing of materials. We present an overview of our in-situ mechanical testing capabilities and recent hardware developments that enable flexural testing at high temperature and in combination with acoustic emission analysis.

Developments in synchrotron x-ray micro-tomography for in-situ materials analysis at the Advanced Light Source

The Advanced Light Source (ALS) is a third-generation synchrotron X-ray source that operates as a user facility with more than 40 beamlines hosting over 2000 users per year. Synchrotron sources like the ALS provide high quality X-ray beams, with flux that is several orders of magnitude higher than lab-based sources. This is particularly advantageous for dynamic applications because it allows for high-speed, high-resolution imaging and microscale tomography. The hard X-ray beamline 8.3.2 at the Advanced Light Source enables imaging of samples at high temperatures and pressures, with mechanical loading and other realistic conditions using environmental test cells. These test cells enable experimental observation of samples undergoing dynamic microstructural changes in-situ. We present recent instrumentation developments that allow for continuous tomography with scan rates approaching 1 Hz per 3D image. In addition, our use of iterative reconstruction techniques allows for improved image quality despite fewer images and low exposure times used during fast tomography compared to traditional Fourier reconstruction methods.

ALS User Meeting Highlights Accomplishments and Challenges

The 2014 ALS User Meeting, held in Berkeley, California, from October 6-8, 2014, launched with a welcome from UEC Chair Peter Nico and remarks from Associate Lab Director for Energy and Environmental Sciences, Don DePaolo. ALS Director Roger Falcone then addressed the gathering, noting that while the past year has been tough in terms of funding for the ALS, there were also many scientific achievements to highlight and a record number of users with an impressive number of publications.

Reflection on multilayer mirrors: beam profile and coherence properties

The main advantage of Bragg reflection from a multilayer mirror as a monochromator for hard X-rays, is the higher photon flux density because of the larger spectral bandpass compared with crystal lattice reflection. The main disadvantage lies in the strong modulations of the reflected beam profile. This is a major issue for micro-imaging applications, where multilayer-based monochromators are frequently employed to deliver high photon flux density. A subject of particular interest is the origin of the beam profile modifications, namely the irregular stripe patterns, induced by the reflection on a multilayer. For multilayer coatings in general it is known that the substrate and its surface quality significantly influence the performance of mirrors, as the coating reproduces to a certain degree the roughness and shape of the substrate. This proceedings article reviews recent experiments that indicate potential options for producing wave front-preserving multilayer mirrors, as well as new details on the particular mirrors our group has extensively studied in the past.