May 2010 Archives

A Chinese group led by Professor J. Zhang (President of Shanghai Jiao Tong University) recently published a report on the generation of X-ray pulses of around 3 keV by using an Ar clustering gas jet target (~3mm dia.) and a Ti:sapphire laser (power 800 mJ, pulse width 28 fs, wavelength 800 nm, frequency 10 Hz). The intensity of the Ar K-shell emissions in the forward direction was found to be around 10⁴ photons/mrad²/pulse. The group emphasized the significance of laser contrast, which is a ratio of the main pulse and pre-pulse, and found that X-ray flux is reduced by 2 orders of magnitude if the laser pulse contrast decreases from 10⁹ to 10⁷ with constant laser pulse energy. For more information, see the paper, "Intense High-Contrast Femtosecond K-Shell X-Ray Source from Laser-Driven Ar Clusters", L. M. Chen et al., Phys. Rev. Lett. 104, 215004 (2010).

An international team of paleontologists, geochemists and physicists led by Dr. R. A. Wogelius (University of Manchester, UK) recently employed X-ray fluorescence imaging to analyze a 150 million year old fossil of Archaeopteryx, which had dinosaur-like teeth and bird-like feathers. For many years, it was believed that the fossil contained nothing but bone and rock. However, the use of a brilliant synchrotron X-ray beam enabled the detection of chemical elements hidden within. It was found that the fossil still had elemental compositions that were completely different from the embedding geological matrix. The researchers completed the chemical map of the dinobird for 12 elements for the first time. Some phosphor and sulfur were found in soft tissue, as well as trace zinc and copper in bone. The experiment was done at wiggler beam line 6-2 at Stanford Synchrotron Radiation Lightsource (SSRL, California, USA). For more information, see the paper, "Archaeopteryx feathers and bone chemistry fully revealed via synchrotron imaging", U. Bergmann et al., Proc. Nat. Aca. Sci., 107, 9060 (2010).

Professor P. Dutta (University of Chicago) and his colleagues recently clarified that the surface density profile acquires layered structures at 0.2 T_c; T_c is the liquid-gas critical temperature. The present research was for dielectric liquids, pentaphenyl trimethyl trisiloxane, and pentavinyl pentamethyl cyclopentasiloxane. The X-ray reflectivity technique was employed to determine the surface profile experimentally. The research group had previously found similar phenomena for other liquid dielectric liquids as well as liquid metals. The present studies could strengthen their series of work. For more information, see the paper, "Surface order in cold liquids: X-ray reflectivity studies of dielectric liquids and comparison to liquid metals", S. Chattopadhyay et al., Phys. Rev, B81, 184206 (2010).

Dr. C. H. Chen (National Taiwan University, Taiwan) and his colleagues recently published a report on ultra high resolution element mapping. The research group employed a scanning transmission electron microscope (STEM) with specially enhanced spherical aberration correction. The beam size was nearly 1 Å. A silicon drift detector (Bruker XFlash-5030) was employed and set with a solid angle of 0.13 steradian. The group studied InGaAs/InAlAs superlattices, and discussed the 1.47 Å dumbbell structure using both structural imaging and mapping of characteristic X-rays (In L, Ga K and As K). For more information, see the paper, "Emergent Chemical Mapping at Atomic-Column Resolution by Energy-Dispersive X-Ray Spectroscopy in an Aberration-Corrected Electron Microscope", M.-W. Chu et al., Phys. Rev. Lett. 104, 196101 (2010).

Combinatorial materials synthesis is a promising new way of developing and finding novel functional materials. By the use of sophisticated thin film technology, it is possible to create compositionally graded samples on the same single substrate. To analyze this combinatorial library, some novel technique is required. A UK research group led by Professor K. D. Rogers (Cranfield University, UK) recently reported on high-throughput data collection and analysis using an X-ray diffraction (XRD) probe. In the research, an extended X-ray beam was used to illuminate the libraries, and a large area detector was used to collect the data. A new algorithm was employed to analyze the collected data and extract the crystallographic information. For more information, see the paper, "High Throughput X-ray Diffraction Analysis of Combinatorial Polycrystalline Thin Film Libraries", S. Roncallo et al., Anal. Chem., 82, 4564 (2010).

The Advanced Photon Source has received approval from the U.S. Department of Energy (DOE) for the first stage of an upgrade to the facility. Details of the upgrade program can be found in a downloadable movie, http://www.aps.anl.gov/Upgrade/CDR

In the May 2010 issue of Nature Materials, Joerg Heber interviewed Professor G. Materlik, CEO of the Diamond Light Source, UK. The article features his answers to 7 wide-ranging questions that would be of particular interest to readers, such as "What is the future of synchrotrons?", "How about free-electron lasers?" and "Are you worried about the general science budget in the UK and about Diamond's funding?" For more information, see the article, "Coherence comes full circle", Nature Materials 9, 375 (2010).