Recently in Others Category

A very interesting idea that proposes the use of a motor in a hard disk drive as an X-ray chopper has been recently published. It can produce X-ray pulses of ms width and few μs rise time. In the research, the system was used to test the response of X-ray detectors such as ionization chambers and photo diodes. For more information, see the paper, "Hard disk drive based microsecond x-ray chopper for characterization of ionization chambers and photodiodes", O. Muller et al., Rev. Sci. Instrum. 86, 035105 (2015).

Optical tweezers are widely used because they are capable of trapping small materials by highly-focused laser beams. They are highly useful for manipulating single fragile objects. Recently compact optical tweezers have been designed and developed specifically for synchrotron X-ray diffraction experiments. Samples of a few micrometers up to a few tens of micrometers size can be trapped easily. The selection and positioning of single objects out of a batch of many can be performed semi-automatically by software routines. For more information, see the paper, "Optical Tweezers for Synchrotron Radiation Probing of Trapped Biological and Soft Matter Objects in Aqueous Environments", S. C. Santucci et al., Anal. Chem., Article ASAP (DOI: 10.1021/ac200515x Publication Date (Web) May 4, 2011).

So far, it has been understood that the only way to realize hard-X-ray mirrors with near 100% reflectivity is the use of total external reflection at grazing incidence to a surface. Dr. Y. V. Shvyd'ko (Argonne National Lab, USA) and his colleagues have recently proposed to use Bragg reflections from synthetic diamond crystal. They discussed how it shows an unprecedented reflecting power at normal incidence with meV order narrow bandwidths for hard X-rays. The optics might be a good candidate for X-ray free-electron laser oscillators (X-FELO). For more information, see the paper, "High-reflectivity high-resolution X-ray crystal optics with diamonds", Y. V. Shvyd'ko et al., Nature Physics, doi:10.1038/nphys1506; published online, 17 January 2010.

Professors T. Narayanan (ESRF, Grenoble, France), M. Giglio (XFEL, Hamburg, Germany) and their collaborators have recently published an interesting paper on a novel method to map the two-dimensional transverse coherence of an X-ray beam. The technique uses the dynamical near-field speckles formed by scattering from colloidal particles, which are executing Brownian motions. It is possible to measure the change of the interference fringes, and consequently the fluctuation of speckles. It was found that the coherence properties of synchrotron radiation from an undulator source are obtained with high accuracy. For more information, see the paper, "Probing the transverse coherence of an undulator X-ray beam using Brownian particles", M. D. Alaimo et al., Phys. Rev. Lett., 103, 194805 (2009).

It is well known that nanoparticles often enhance catalytic activity. However, it is still an open question as to whether the metallic or the oxidized state of the particle is the catalytically more active phase. It is therefore significant to study the oxidation/reduction process of metallic nanoparticles. A group led by Professor H. Dosh (Max-Planck-Institut für Metallforschung, Germany) recently reported on some very interesting XRD and GISAXS studies on the oxygen-induced shape transformation of Rh nanoparticles. The experiments were done in-situ, during the oxidation/reduction cycle at high temperature. The group found that shape transformation is driven by the formation of a surface oxide O-Rh-O trilayer, which can stabilize Rh nanoparticles with low-index facets. For more information, see the paper, "Shape Changes of Supported Rh Nanoparticles During Oxidation and Reduction Cycles", P. Nolte et al., Science, 321, 1654-1658 (2008).

Super conducting devices are promising as high energy-resolution detectors for soft X-ray and/or mass spectrometry. As the device size is quite small, e.g., several hundred microns squared, arraying has been one of the most important technical targets for enhancing detection efficiency. So far, it has been difficult to increase the number of arrays, because of the incoming heat problem when connecting wires from devices operated at 0.3 K to electronic circuits at normal temperature. Dr. M. Ohkubo and his colleagues at the National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan recently succeeded in developing a novel technology using thin co-axis wires of 0.33mm in dia. They also attached great importance to material selection. As a result, it has become possible to connect more than 100 arrays, yet the incoming heat is extremely small at 5.4 x 10^-6 W. The increase in temperature has effectively been suppressed to 15 mK. For more information, contact Dr. M. Ohkubo, Phone, +81-29-861-5685, Fax +81-29-861-5730, m.ohkubo@aist.go.jp, http://unit.aist.go.jp/riif/srg/index.htm

A miniworkshop on Pixel Array Detector: Status and Applications was held at the National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan. The contributors were M.O.Lampert (Canberra-EURYSIS), H.Oyanagi (AIST), G.Foran (ASRP), S.Muto (NIFS), T.Satoh (JAERI), H.Takahashi (Univ of Tokyo), and M.Okubo (AIST). The requirements and solutions for pixel array detectors with high energy-resolution were discussed with particular emphasis on applications in X-ray spectrometry and plasma physics. The abstract booklet is available from Professor Hiroyuki Oyanagi, AIST, Phone: +81-29-8615072, Fax: +81-29-8615085, h.oyanagi@aist.go.jp