Current Issue : April - June Volume : 2016 Issue Number : 2 Articles : 5 Articles
Hot gas pervades the Universe: about half of the baryonic content in\nthe Universe is expected to be at T > 105 K, and there are as many baryons at T\n> 107 trapped in galaxy clusters as there are locked into stars. There is an\nintimate relation between this hot gas, which delineates the large-scale\nstructure of the Universe, and the most energetic phenomena occurring in the\nimmediate vicinity of super-massive black holes, through a poorly known\nprocess called Cosmic Feedback. Studying the hot and energetic universe\nrequires X-ray observatories in space, whose capabilities greatly exceed those\nof the current workhorse observatories: NASA's Chandra and ESA's XMMNewton.\nAthena has been selected by ESA as the L2 mission (due for launch in\n2028), to address the ââ?¬Å?Hot and Energetic Universeââ?¬Â science theme. It will be a\nlarge X-ray observatory capable of addressing the above topics, and many\nother fundamental questions in contemporary astrophysics. Here we present the\nAthena science objectives, the mission concept and its payload, including the\nX-ray telescope and its two baseline instruments: a Wide Field Imager (WFI)\nand an X-ray Integral Field Unit (X-IFU)....
State of the art X-ray Free Electron Laser facilities currently provide the brightest X-ray pulses\navailable, typically with mJ energy and several hundred femtosecond duration. Here we present\none- and two-dimensional Particle-in-Cell simulations, utilising the process of stimulated Raman\namplification, showing that these pulses are compressed to a temporally coherent, sub-femtosecond\npulse at 8% efficiency. Pulses of this type may pave the way for routine time resolution of electrons\nin nm size potentials. Furthermore, evidence is presented that significant Landau damping and wave breaking\nmay be beneficial in distorting the rear of the interaction and further reducing the final\npulse duration....
A low voltage electropolishing of metal wires is attractive for nanotechnology because it provides centimeter long and micrometer thick probes with the tip radius of tens of nanometers. Using X-ray nanotomography we studied morphological transformations of the surface of tungsten wires in a specially designed electrochemical cell where the wire is vertically submersed into the KOH electrolyte. It is shown that stability and uniformity of the probe span is supported by a porous shell growing at the surface of tungsten oxide and shielding the wire surface from flowing electrolyte. It is discovered that the kinetics of shell growth at the triple line, where meniscus meets the wire, is very different from that of the bulk of electrolyte. Many metals follow similar electrochemical transformations hence the discovered morphological transformations of metal surfaces are expected to play significant role in many natural and technological applications....
X-ray imaging techniques significantly advanced our understanding of materials and biology, among which phase contrast Xray\nmicroscopy has obvious advantages in imaging biological specimens which have low contrast by conventional absorption\ncontrast microscopy. In this paper, three-dimensional microstructure of arthropod with high contrast has been demonstrated by\nsynchrotron X-ray in-line phase contrast tomography. The external morphology and internal structures of an earthworm were\nanalyzed based upon tomographic reconstructions with and without phase retrieval.We also identified and characterized various\nfine structural details such as the musculature system, the digestive system, the nervous system, and the circulatory system. This\nwork exhibited the high efficiency, high precision, and wide potential applications of synchrotron X-ray phase contrast tomography\nin nondestructive investigation of low-density materials and biology...
Ultrafast molecular dynamics can be studied using x-rays from both synchrotrons sources and x-ray free electron lasers. Synchrotron studies are limited by the 10-100 ps duration pulses to processes where the Auger lifetime can be used to probe dynamics initiated by excitation of an inner-shell electron to an antibonding orbital. The short pulses produced by x-ray free electron lasers offer the opportunity to study molecular dynamics directly with pump-probe techniques. A two-mirror x-ray split and delay device has been developed for x- ray pump - x-ray probe experiments at the soft x-ray AMO instrument at the LCLS. The device operates over a photon energy range of 250-1800 eV with a variable delay of up to 200 femtoseconds with 0.1 fs resolution....
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