M. D. de Jonge

The X‐ray Fluorescence Microscopy Beamline at the Australian Synchrotron

A hard x‐ray micro‐nanoprobe has commenced operation at the Australian Synchrotron providing versatile x‐ray fluorescence microscopy across an incident energy range from 4 to 25 keV. Two x‐ray probes are used to collect μ‐XRF and μ‐XANES for elemental and chemical microanalysis: a Kirkpatrick‐Baez mirror microprobe for micron resolution studies and a Fresnel zone plate nanoprobe capable of 60‐nm resolution. Some unique aspects of the beamline design and operation are discussed. An advanced energy dispersive x‐ray fluorescence detection scheme named Maia has been developed for the beamline, which enables ultrafast x‐ray fluorescence microscopy.

The Maia Spectroscopy Detector System: Engineering for Integrated Pulse Capture, Low-Latency Scanning and Real-Time Processing

The Maia detector system is engineered for energy dispersive x‐ray fluorescence spectroscopy and elemental imaging at photon rates exceeding 107/s, integrated scanning of samples for pixel transit times as small as 50μs and high definition images of 108 pixels and real‐time processing of detected events for spectral deconvolution and online display of pure elemental images. The system developed by CSIRO and BNL combines a planar silicon 384 detector array, application‐specific integrated circuits for pulse shaping and peak detection and sampling and optical data transmission to an FPGA‐based pipelined, parallel processor. This paper describes the system and the underpinning engineering solutions.

The New Maia Detector System: Methods For High Definition Trace Element Imaging Of Natural Material

Motivated by the need for megapixel high definition trace element imaging to capture intricate detail in natural material, together with faster acquisition and improved counting statistics in elemental imaging, a large energy‐dispersive detector array called Maia has been developed by CSIRO and BNL for SXRF imaging on the XFM beamline at the Australian Synchrotron. A 96 detector prototype demonstrated the capacity of the system for real‐time deconvolution of complex spectral data using an embedded implementation of the Dynamic Analysis method and acquiring highly detailed images up to 77 M pixels spanning large areas of complex mineral sample sections.

Trends in hard X-ray fluorescence mapping: environmental applications in the age of fast detectors

AbstractEnvironmental samples are extremely diverse but share a tendency for heterogeneity and complexity. This heterogeneity poses methodological challenges when investigating biogeochemical processes. In recent years, the development of analytical tools capable of probing element distribution and speciation at the microscale have allowed this challenge to be addressed. Of these available tools, laterally resolved synchrotron techniques such as X-ray fluorescence mapping are key methods for the in situ investigation of micronutrients and inorganic contaminants in environmental samples. This article demonstrates how recent advances in X-ray fluorescence detector technology are bringing new possibilities to environmental research. Fast detectors are helping to circumvent major issues such as X-ray beam damage of hydrated samples, as dwell times during scanning are reduced. They are also helping to reduce temporal beamtime requirements, making particularly time-consuming techniques such as micro X-ray fluorescence (μXRF) tomography increasingly feasible. This article focuses on μXRF mapping of nutrients and metalloids in environmental samples, and suggests that the current divide between mapping and speciation techniques will be increasingly blurred by the development of combined approaches.n FigureTricolour maps of elemental distributions in a barley grain: Zn (red), Compton (green) and Mn (blue)

Maia X-ray fluorescence imaging: Capturing detail in complex natural samples

Motivated by the challenge of capturing complex hierarchical chemical detail in natural material from a wide range of applications, the Maia detector array and integrated realtime processor have been developed to acquire X-ray fluorescence images using X-ray Fluorescence Microscopy (XFM). Maia has been deployed initially at the XFM beamline at the Australian Synchrotron and more recently, demonstrating improvements in energy resolution, at the P06 beamline at Petra III in Germany. Maia captures fine detail in element images beyond 100 M pixels. It combines a large solid-angle annular energy-dispersive 384 detector array, stage encoder and flux counter inputs and dedicated FPGA-based real-time event processor with embedded spectral deconvolution. This enables high definition imaging and enhanced trace element sensitivity to capture complex trace element textures and place them in a detailed spatial context. Maia hardware and software methods provide per pixel correction for dwell, beam flux variation, dead-time and pileup, as well as off-line parallel processing for enhanced throughput. Methods have been developed for real-time display of deconvoluted SXRF element images, depth mapping of rare particles and the acquisition of 3D datasets for fluorescence tomography and XANES imaging using a spectral deconvolution method that tracks beam energy variation.

Differential phase contrast with a segmented detector in a scanning X-ray microprobe.

Scanning X-ray microprobes are unique tools for the nanoscale investigation of specimens from the life, environmental, materials and other fields of sciences. Typically they utilize absorption and fluorescence as contrast mechanisms. Phase contrast is a complementary technique that can provide strong contrast with reduced radiation dose for weakly absorbing structures in the multi-keV range. In this paper the development of a segmented charge-integrating silicon detector which provides simultaneous absorption and differential phase contrast is reported. The detector can be used together with a fluorescence detector for the simultaneous acquisition of transmission and fluorescence data. It can be used over a wide range of photon energies, photon rates and exposure times at third-generation synchrotron radiation sources, and is currently operating at two beamlines at the Advanced Photon Source. Images obtained at around 2 keV and 10 keV demonstrate the superiority of phase contrast over absorption for specimens composed of light elements.

Reduced As components in highly oxidized environments: Evidence from full spectral XANES imaging using the Maia massively parallel detector

Abstract Synchrotron X-ray fluorescence (SXRF) and X-ray absorption spectroscopy (XAS) have become standard tools to measure element concentration, distribution at micrometer- to nanometer-scale, and speciation (e.g., nature of host phase; oxidation state) in inhomogeneous geomaterials. The new Maia X-ray detector system provides a quantum leap for the method in terms of data acquisition rate. It is now possible to rapidly collect fully quantitative maps of the distribution of major and trace elements at micrometer spatial resolution over areas as large as 1 × 5 cm2. Fast data acquisition rates also open the way to X-ray absorption near-edge structure (XANES) imaging, in which spectroscopic information is available at each pixel in the map. These capabilities are critical for studying inhomogeneous Earth materials. Using a 96-element prototype Maia detector, we imaged thin sections of an oxidized pisolitic regolith (2 × 4.5 mm2 at 2.5 × 2.5 μm2 pixel size) and a metamorphosed, sedimentary exhalative Mn-Fe ore (3.3 × 4 mm2 at 1.25 × 5 μm2). In both cases, As K-edge XANES imaging reveals localized occurrence of reduced As in parts of these oxidized samples, which would have been difficult to recognize using traditional approaches.

Measurement of the x-ray mass attenuation coefficient of silver using the x-ray-extended range technique

We used the x-ray-extended range technique to measure the x-ray mass attenuation coefficients of silver in the 15–50 keV energy range with a level of uncertainty between 0.27% and 0.4% away from the K-edge. The imaginary part of the atomic form factor of silver was derived by subtracting the scattering component from the measured total mass attenuation coefficients. Discrepancies between the measured mass attenuation coefficients and alternative theoretical predictions are discussed.

Systematic functional characterization of putative zinc transport genes and identification of zinc toxicosis phenotypes in Drosophila melanogaster

SUMMARY The heavy metal zinc is an essential component of the human diet and is incorporated as a structural component in up to 10% of all mammalian proteins. The physiological importance of zinc homeostasis at the cellular level and the molecular mechanisms involved in this process have become topics of increasing interest in recent years. We have performed a systematic functional characterization of the majority of the predicted Drosophila Zip (zinc/iron regulated transporter-related protein) and ZnT genes, using the Gal4-UAS system to carry out both ubiquitous and targeted over-expression and suppression studies for 13 of the 17 putative zinc transport genes identified to date. We found that six of these 13 genes may be essential for fly viability and that three of the remaining seven demonstrate over-expression phenotypes. Our findings reaffirm the previously proposed function of dZnT63C (CG17723: FBgn005432) as an important zinc efflux protein and indicate that the fly homolog of hZip1, dZip42C.1 (CG9428: FBgn0033096), is a strong zinc importer in Drosophila. By combining over-expression of dZip42C.1 with suppression of dZnT63C we were able to produce easily identifiable zinc toxicosis phenotypes, which can be rescued or worsened by modifying dietary zinc content. Our findings show that a genetically based zinc toxicosis situation can be therapeutically treated or exacerbated by modifications to the diet, providing a sensitized background for future, more detailed studies of Zip/ZnT function.

A multi-technique investigation of copper and zinc distribution, speciation and potential bioavailability in biosolids

The use of biosolids in agriculture continues to be debated, largely in relation to their metal contents. Our knowledge regarding the speciation and bioavailability of biosolids metals is still far from complete. In this study, a multi-technique approach was used to investigate copper and zinc speciation and partitioning in one contemporary and two historical biosolids used extensively in previous research and field trials. Using wet chemistry and synchrotron spectroscopy techniques it was shown that copper/zinc speciation in the biosolids was largely equivalent despite the biosolids being derived from different countries over a 50 year period. Furthermore, copper speciation was consistently dominated by sorption to organic matter whereas Zn partitioned mainly to iron oxides. These data suggest that the results of historical field trials are still relevant for modern biosolids and that further risk assessment studies should concentrate particularly on Cu as this metal is associated with the mineralisable biosolids fraction.