Measurement and alleviation of subsurface damage in a thick-crystal neutron interferometer

The construction is described of a monolithic thick-crystal perfect silicon neutron interferometer using an ultra-high-precision grinding technique and a combination of annealing and chemical etching that differs from the construction of prior neutron interferometers. The interferometer is the second to have been annealed after machining and the first to be annealed prior to chemical etching. Monitoring the interference signal at each post-fabrication step provides a measurement of subsurface damage and its alleviation. In this case, the strain caused by subsurface damage manifests itself as a spatially varying angular misalignment between the two relevant volumes of the crystal and is reduced from ∼10−5 rad to ∼10−9 rad by way of annealing and chemical etching.

Two-Dimensional Graphene Family Material: Assembly, Biocompatibility and Sensors Applications

Graphene and its chemically exfoliated derivatives—GO and rGO—are the key members of graphene family materials (GFM). The atomically thick crystal structure and the large continuous π conjugate of graphene imparts it with unique electrical, mechanical, optical, thermal, and chemical properties. Although those properties of GO and rGO are compromised, they have better scalability and chemical tunability. All GFMs can be subject to noncovalent modification due to the large basal plane. Besides, they have satisfying biocompatibility. Thus, GFMs are promising materials for biological, chemical and mechanical sensors. The present review summarizes how to incorporate GFMs into different sensing system including fluorescence aptamer-based sensors, field-effect transistors (FET), and electrochemical sensors, as well as, how to covalently and/or non-covalently modify GFMs to achieve various detection purpose. Sensing mechanisms and fabrication strategies that will influence the sensitivity of different sensing system are also reviewed.

Smart Structures and Materials

<p>Piezoelectric crystals are smart materials used in the structures for better performance under vibrations. These crystals act as a vibration damper, which depends upon location, size of crystal and value of shunt resistors. The presented work was carried out to measure the effectiveness of the crystal in reducing the response of the structure. A steel frame was used with three above mentioned parameters. Three (0.5mm. 1.0mm, 1.5mm) thicknesses, four values of shunt resistors (2.2, 10, 33 and 67 ohms) and three locations on the model (Top, Middle, and Bottom). At first, free vibration tests were carried out with these parameters and with no piezoelectric crystals. From this test, it was found that, damping increased from 0.387% (No piezoelectric crystal case) to 4.4% with 1.5mm thickness, 2.2 ohms and bottom position. Further, keeping the 2.2 ohms as constant parameter, 50% Kobe Earthquake excitation was given with other two parameters varying (Total 10 cases). It was found that the peak response reduced from 1.05 g (No piezoelectric case) to 0.83 g (1.5mm thick crystal at bottom). Also, reduction in Arias Intensity was observed. The experimental studies confirmed that the piezoelectric crystals are very effective in reducing the response of the structure with increasing the damping.</p>

Intrinsic Light Yield and Loss Parameter of Y2SiO5:Ce Single Crystal Scintillator

Nowadays, single crystal scintillators play an key role in the scientific researches, high-energy physics and modern medical imaging. In this research, we studied the scintillation response of polished yttrium oxyorthosilicate with Ce-doped (Y2SiO5:Ce, YSO(Ce)) crystals grown by the Czochralski method. The nominal Ce3+ ion is about 0.5% for tested crystals. Energy resolution and photon yield of the scintillator are read out by the photomultiplier tube (XP5200B PMT) under excitation with gamma-rays. The polished YSO:Ce samples (5x5x1 mm3 and 5x5x3 mm3) was tested at room temperature. The 1 mm thick sample shows the better energy resolution than the 3 mm thick crystal. The light yield dependences on the height of crystal were evaluated under excitation with 662 keV gamma ray energy and the intrinsic light yield and loss parameter were also determined.

Polarization control of an X-ray free-electron laser with a diamond phase retarder

A diamond phase retarder was applied to control the polarization states of a hard X-ray free-electron laser (XFEL) in the photon energy range 5–20 keV. The horizontal polarization of the XFEL beam generated from the planar undulators of the SPring-8 Angstrom Compact Free-Electron Laser (SACLA) was converted into vertical or circular polarization of either helicity by adjusting the angular offset of the diamond crystal from the exact Bragg condition. Using a 1.5 mm-thick crystal, a high degree of circular polarization, 97%, was obtained for 11.56 keV monochromatic X-rays, whereas the degree of vertical polarization was 67%, both of which agreed with the estimations including the energy bandwidth of the Si 111 beamline monochromator.