Current Issue : July - September Volume : 2016 Issue Number : 3 Articles : 4 Articles
We report on the development of a new experimental instrument for time-resolved x-ray scattering\n(TRXS) at the Pohang Light Source (PLS-II). It operates with a photon energy ranging from 5 to\n18 keV. It is equipped with an amplified Ti:sappahire femto second laser, optical diagnostics, and\nlaser beam delivery for pump-probe experiments. A high-speed single-element detector and high\ntrigger-rate oscilloscope are used for rapid data acquisition. While this instrument is capable of\nmeasuring sub-nanosecond dynamics using standard laser pump/x-ray probe techniques, it also takes\nadvantage of the dense 500 MHz standard fill pattern in the PLS-II storage ring to efficiently record\nnano-to-micro-second dynamics simultaneously. We demonstrate this capability by measuring both\nthe (fast) impulsive strain and (slower) thermal recovery dynamics of a crystalline InSb sample\nfollowing intense ultra fast laser excitation. Exploiting the full repetition rate of the storage ring\nresults in a significant improvement in data collection rates compared to conventional bunch-tagging\nmethods....
We report development of micro-focusing optics for high-energy x-rays by combining a sagittally bent Laue crystal monchromator with Kirkpatrick-Baez (K-B) X-ray focusing mirrors. The optical system is able to provide a clean, high-flux X-ray beam suitable for pair distribution function (PDF) measurements at high pressure using a diamond anvil cell (DAC). A focused beam of moderate size (10-15 �¼m) has been achieved at energies of 66 and 81 keV. PDF data for nanocrystalline platinum (n-Pt) were collected at 12.5 GPa with a single 5 s X-ray exposure, showing that the in-situ compression, decompression, and relaxation behavior of samples in the DAC can be investigated with this technique. PDFs of n-Pt and nano Au (n-Au) under quasi-hydrostatic loading to as high as 71 GPa indicate the existence of substantial reduction of grain or domain size for Pt and Au nanoparticles at pressures below 10â��GPa. The coupling of sagittally bent Laue crystals with K-B mirrors provides a useful means to focus high-energy synchrotron X-rays from a bending magnet or wiggler source....
After drawbacks and shortages of using conventional kV or MV imaging mode were analyzed, this\nstudy proposes a new position verification mode with using the energy larger than 15 MeV or nominal\naccelerating potential greater than 25 MV X-Ray. The new position verification mode is\nnamed HMV imaging mode. Along with the comparison of theoretical analyses, phantom experiments\nand clinical results to the original imaging modes, this report is going to demonstrate the\nHMV imaging mode is superior to traditional kV and MV imaging modes. This report first theoretically\nanalyzed three main effects of X-ray interacting with medium by numerous equations and\ncompared their mass attenuation coefficient with different types of tissue. X-ray irradiated on a\nââ?¬Å?Catphan 500ââ?¬Â cylinder phantom with different energies to verify these theoretical results. Furthermore,\nbased on phantom experimentsââ?¬â?¢ results, we have done numerous clinical trials and\ncomparisons with patientââ?¬â?¢s clinical results. The theoretical and experimental results illustrate that\nthe scanned images from HMV mode have a good quality and have ability to identify different tissue\ncomponents clearly. HMV imaging mode overcomes drawbacks of position verification from\nboth kV and MV level imaging mode as well as keeping advantages of kV and MV imaging mode.\nThe result indicates that HMV is a good position verification mode in radiotherapy...
The compositions of diverse planetary bodies are of fundamental interest to planetary science, providing clues to the\nformation and evolutionary history of the target bodies and the solar system as a whole. Utilizing the X-ray fluorescence\nunique to each atomic element, X-ray imaging spectroscopy is a powerful diagnostic tool of the chemical and\nmineralogical compositions of diverse planetary bodies. Until now the mass and volume of focusing X-ray optics\nhave been too large for resource-limited in situ missions, so near-target X-ray observations of planetary bodies have\nbeen limited to simple collimator-type X-ray instruments. We introduce a new Miniature lightweight Wolter-I focusing\nX-ray Optics (MiXO) using metal-ceramic hybrid X-ray mirrors based on electroformed nickel replication and\nplasma thermal spray processes. MiXO can enable compact, powerful imaging X-ray telescopes suitable for future\nplanetary missions. We illustrate the need for focusing X-ray optics in observing relatively small planetary bodies such\nas asteroids and comet nuclei. We present a few example configurations of MiXO telescopes and demonstrate their\nsuperior performance in comparison to an alternative approach, micro-pore optics, which is being employed for the\nfirst planetary focusing X-ray telescope, the Mercury Imaging X-ray Spectrometer-T on board Bepicolumbo. X-ray imaging\nspectroscopy using MiXO will open a large new discovery space in planetary science and will greatly enhance our\nunderstanding of the nature and origin of diverse planetary bodies....
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