X-ray treatment at 5 MeV and above

There is agreement in the scientific community that X-ray treatment of food at 7.5 MeV can be safe. Possible process improvements for treating at higher than 5 MeV X-rays have been re-visited. Monte Carlo methods have been applied to simulate the X-ray conversion process and to calculate dose distributions in homogeneous phantoms. Experimental data obtained using X-rays produced with a Rhodotron TT200 at 5 and 10 MeV verifies a representative set of data which is calculated with the presented method.

With this qualified Monte Carlo tool, calculations at 7.5 MeV incident electron energy were performed. The analysis gives special attention to higher photon yield, improved product penetration, as well as surface and edge effects.     

Material modifications induced by swift heavy ions in NbTi superconducting wires

The Facility for Antiproton and Ion Research (FAIR) to be built at GSI in Darmstadt will be equipped with superconducting magnets. Due to the high ion beam intensities and related beam losses, radiation damage of the Cu/NbTi superconducting wires used in the magnet coils has to be considered. Here we report first experimental results on NbTi multifilament wires exposed to 2.6 GeV U ions at room temperature. Radiation-induced effects were examined using X-ray diffraction and transmission electron microscopy. With increasing ion fluence the amount of the α-Ti phase decreases. This is crucial because α-Ti precipitates are the main flux-pinning centres in the Nb–Ti superconducting alloy. The equilibrium hcp α-Ti transforms into the hexagonal ω-Ti phase.     

P-T diagram in the As-S system

Abstract

Chalcogenide glasses in the system As-S are candidates for very low loss fiber-optic materials. In order to modulate physical properties of such glassese by wellaimed pressure variation the knowledge of the P-T diagram is a precondition. Therefore the aim of this investigation was to cheque the energy-dispersive X-ray diffraction method for low symmetry materials like Realgar (AsS) in order to elaborate P-T diagrams in a time reducing technique.     

In situ mapping of high-pressure fluids using hydrothermal diamond anvil cells

We present new results combining high pressures and temperatures attainable in a diamond anvil cell with in situ synchrotron radiation induced micro-X-ray fluorescence measurements. Hydrothermal diamond anvil cells experiments have been performed by measuring the partitioning of Pb between aqueous fluids (pure water or NaCl-enriched water) and hydrous silicate melts of haplogranite composition using synchrotron X-ray fluorescence. The in situ measurements were performed in the range 0.3–1.2 GPa and 730–850 ^°C both in the aqueous fluid and in the silicate melts being in equilibrium. Pb is strongly partitioned into high-pressure–temperature hydrous melts when Cl is present in either the hydrous melt or the aqueous fluid. Moreover, our comparisons of in situ results with post-mortem results show that significant changes take place during rapid quenching especially when samples are small (few hundred of microns in diameter). Water exsolution is induced by the quench in the silicate melt showing the high mobility of Pb which immediately partitions into the water vapor phase during the quench. The current in situ approach offers thus a pertinent complementary method to the classical experimental petrology investigations.     

Multiscale modeling of irradiated polycrystalline FCC metals

We propose a set of models for the post-irradiation deformation response of polycrystalline FCC metals. First, a defect- and dislocation-density based evolution model is developed to capture the features of irradiation-induced hardening as well as intra-granular softening. The proposed hardening model is incorporated within a rate-independent single crystal plasticity model. The result is a non-homogeneous deformation model that accounts for defect absorption on the active slip planes during plastic loading. The macroscopic non-linear constitutive response of the polycrystalline aggregate of the single crystal grains is then obtained using a micro–macro transition scheme, which is realized within a Jacobian-free multiscale method (JFMM). The Jacobian-free approach circumvents explicit computation of the tangent matrix at the macroscale by using a Newton–Krylov process. This has a major advantage in terms of storage requirements and computational cost over existing approaches based on homogenized material coefficients in which explicit Jacobian computation is required at every Newton step. The mechanical response of neutron-irradiated single and polycrystalline OFHC copper is studied and it is shown to capture experimentally observed grain-level phenomena.     

Evaluation of X-ray sources for quantitative two- and three-dimensional imaging of liquid mass distribution in atomizing sprays

Quantitative measurement of liquid mass distribution is demonstrated in an impinging-jet atomizing spray using a broadband, ∼80 keV X-ray tube source for 2-D radiography and 3-D computed tomography (CT). The accuracy, precision, and sensitivity of these data are evaluated using narrowband, ∼10 keV, synchrotron radiation from the Argonne National Laboratory Advanced Photon Source (APS) at the same flow conditions. It is found that the broadband X-ray tube source can be used for 2-D measurement of the equivalent path length (EPL) and 3-D CT imaging of liquid mass distribution with typical error of 5–10%. Data are compared for cases with and without the use of potassium iodide (KI), which at 15% concentration by mass increases the attenuation coefficient eightfold and enables 2-D and 3-D measurement of EPL with a signal-to-noise ratio (SNR) of 5:1 down to 15 μm. At this concentration, the effects of energy-dependent attenuation (i.e., spectral beam hardening) are negligible for EPL up to 5 mm. Hence, the use of broadband X-ray tube sources is feasible for many practical engineering sprays with a dynamic range in EPL of ∼330:1. The advantages and limitations of using broadband and narrowband X-ray sources are discussed, and recommendations for improving performance are presented.     

Development and trends in synchrotron studies of ancient and historical materials

Synchrotron photon-based methods are increasingly being used for the physico-chemical study of ancient and historical materials (archaeology, palaeontology, conservation sciences, palaeo-environments). In particular, parameters such as the high photon flux, the small source size and the low divergence attained at the synchrotron make it a very efficient source for a range of advanced spectroscopy and imaging techniques, adapted to the heterogeneity and great complexity of the materials under study. The continuous tunability of the source — its very extended energy distribution over wide energy domains (meV to keV) with a high intensity — is an essential parameter for techniques based on a very fine tuning of the probing energy to reach high chemical sensitivity such as XANES, EXAFS, STXM, UV/VIS spectrometry, etc. The small source size attained (a few micrometres) at least in the vertical plane leads to spatial coherence of the photon beams, giving rise in turn to a series of imaging methods already crucial to the field. This review of the existing literature shows that microfocused hard X-ray spectroscopy (absorption, fluorescence, diffraction), full-field X-ray tomography and infrared spectroscopy are the leading synchrotron techniques in the field, and presents illustrative examples of the study of ancient and historical materials for the various methods. Fast developing analytical modalities in scanning spectroscopy (STXM, macro-XRF scanning) and novel analytical strategies regarding optics, detectors and other instrumental developments are expected to provide major contributions in the years to come. Other energy domains are increasingly being used or considered such as far-infrared and ultraviolet/visible for spectroscopy and imaging. We discuss the main instrumental developments and perspectives, and their impact for the science being made on ancient materials using synchrotron techniques.     

Informatics methods to enable sharing of quantitative imaging research data

Introduction

The National Cancer Institute Quantitative Research Network (QIN) is a collaborative research network whose goal is to share data, algorithms and research tools to accelerate quantitative imaging research. A challenge is the variability in tools and analysis platforms used in quantitative imaging. Our goal was to understand the extent of this variation and to develop an approach to enable sharing data and to promote reuse of quantitative imaging data in the community.

Methods

We performed a survey of the current tools in use by the QIN member sites for representation and storage of their QIN research data including images, image meta-data and clinical data. We identified existing systems and standards for data sharing and their gaps for the QIN use case. We then proposed a system architecture to enable data sharing and collaborative experimentation within the QIN.

Results

There are a variety of tools currently used by each QIN institution. We developed a general information system architecture to support the QIN goals. We also describe the remaining architecture gaps we are developing to enable members to share research images and image meta-data across the network.

Conclusions

As a research network, the QIN will stimulate quantitative imaging research by pooling data, algorithms and research tools. However, there are gaps in current functional requirements that will need to be met by future informatics development. Special attention must be given to the technical requirements needed to translate these methods into the clinical research workflow to enable validation and qualification of these novel imaging biomarkers.     

Synthesis and luminescence in some fluoro-silicates for the possible applications in OSL dosimetry

Various fluoro-silicates, viz. M₂SiF₆ (M=Li, Na, K) were synthesized by reacting the mixture of corresponding salt and silicic acid with Hydrofluoric acid. The thermal analysis of these materials was performed. These materials were doped with ions Ce³⁺, Cu⁺, Ag⁺ and photoluminescence, TL, OSL properties were studied. Intense TL and OSL was observed from these materials. Due to decomposition during heating, these materials may not be suitable as TL Phosphors, but will be good phosphors for radiation dosimetry using OSL.